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Geology of the country around Goole, Doncaster and the Isle of Axholme Memoir for one-inch sheets 79 and 88 (England and Wales)

By G D Gaunt

Bibliographical reference: Gaunt, G D. 1994. Geology of the country around Goole, Doncaster and the Isle of Axholme. Memoir of the British Geological Survey, sheets 79 and 88 (England and Wales).

• Author: G D Gaunt
• Contributors:
• Stratigraphy; C G Godwin E G Smith
• Economic geology; P M Harris
• Geophysics; J D Cornwell
• Structure; M C G Clarke, G A Kirby, P W Swallow
• Palaeontology; M A Calver, M Mitchell, B Owens, J Pattison, W H C Ramsbottom, N J Riley, G Warrington

British Geological Survey

Geology of the country around Goole, Doncaster and the Isle of Axholme Memoir for one-inch sheets 79 and 88 (England and Wales)

First published 1994. British Geological Survey, Keyworth. Printed in the UK for HMSO. Dd 292031 C8 2/94 ISBN 0 11 884488 1.

Author: G D Gaunt, BSc, PhD; formerly British Geological Survey. Contributors: M A Calver, MA, PhD; M C G Clarke, BSc, PhD; C G Godwin, BSc, MSc; M Mitchell, MA; W H C Ramsbottom, MA, PhD; E G Smith, BSc; P W Swallow, formerly British Geological Survey; J D Cornwell, MSc, PhD; P M Harris; G A Kirby, BSc, PhD; B Owens, BSc, PhD, DSc; J Pattison, MSc; N J Riley, BSc, PhD; G Warrington, BSc, PhD.

(Front cover) Cover photograph Hatfield Main Colliery, South Yorkshire. Photo: A A Jackson.

(Back cover)

Other publications of the Survey dealing with this and adjoining districts

Books

• Memoirs
• Geology of the district north and east of Leeds (sheet 70), 1950
• Geology of the country around Wakefield (sheet 78), 1940
• Geology of the country around Kingston upon Hull and Brigg (sheets 80 & 89), 1992
• Geology of the country around Barnsley (sheet 87), 1947
• Geology of the country around Sheffield (sheet 100), 1957
• Geology of the country around East Retford, Worksop and Gainsborough (sheet 101), 1973
• British Regional Geology
• Eastern England from the Tees to the Wash (2nd edition), 1980
• The Pennines and adjacent areas (3rd edition), 1954
• Mineral Assessment Reports
• No. 22 Scunthorpe, north-west SK 81, 1976
• No. 29 Scunthorpe, south-west SK 80, 1977
• No. 33 Gainsborough, north SK 89, 1978
• No. 37 Bawtry SK 69, 1979
• No. 43 Misterton SK 79, 1979
• No. 92 Armthorpe SE 60, 1982

Maps

• 1:625 000
• Solid geology (south sheet)
• Quaternary geology (south sheet)
• Aeromagnetic (south sheet)
• Bouguer anomaly (south sheet)
• 1:250 000
• Solid geology, Humber–Trent 1983
• Aeromagnetic anomaly, Humber–Trent 1977
• Bouguer gravity anomaly, Humber–Trent 1977
• 1:50 000 or 1:63 360
• Sheet 70 (Leeds) Solid and Drift (separate editions) 1974
• Sheet 71 (Selby) Solid and Drift 1973
• Sheet 72 (Beverley) Drift 1968
• Sheet 78 (Wakefield) Solid and Drift 1978
• Sheet 80 (Kingston upon Hull) Solid and Drift (separate editions) 1983
• Sheet 87 (Barnsley) Solid and Drift 1976
• Sheet 89 (Brigg) Solid and Drift (separate editions) 1982
• Sheet 100 (Sheffield) Solid and Drift 1974
• Sheet 101 (East Retford) Solid and Drift 1967

Preface

The area described in this memoir forms the southern part of the Vale of York, a low-lying, largely drift-covered, rather featureless tract. However, its lack of scenic attractiveness does not detract from its considerable geological interest and economic importance.

The district includes the deep concealed eastern extension of the Yorkshire Coalfield, and the mining of coal remains the principal resource-based industry. Data from the many colliery workings and exploratory boreholes have provided the basis for detailed correlations of the Coal Measures sequences and for establishing the distribution of individual coals. The widespread occurrence of sand and gravel within the Drift deposits, which have been identified in mineral assessment surveys, provides the basis of another major extractive industry, which underpins the construction industry. Extensive spreads of peat have been delimited; they are presently exploited for use in a variety of horticultural applications. Some hydrocarbon potential has been identified in the district, but at present production is restricted to the Hatfield Moors Gasfield.

Deep boreholes and geophysical data have made it possible to recognise a major, extensively faulted pre-Permian anticlinal structure (Askern–Spital Structure) traversing the district, and a pronounced gravity low in the north-east has been interpreted as a secondary cupola of an inferred Market Weighton granite, previously thought to be located to the north of the district.

A detailed appraisal of the complex late Quaternary sequence reveals evidence of rapid climatic and sea-level changes, and constantly changing depositional regimes. On at least one occasion the district was completely glaciated; on another it was largely occupied by Lake Humber. This memoir includes an account of the late Quaternary history of the district, interpreting the sequence of depositional environments from the character and disposition of the deposits, and dating them as far as practicable from the evidence of diagnostic pollen and radiocarbon assays. Not only does the memoir provide some fascinating insights into the impact of climate change in the past but it also documents the very significant impact that man has had on the landscape of the region.

Peter J Cook, DSc. Director, British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham. NG12 5GG October 1993

History of survey of the Goole and Doncaster sheets

The country around Goole and Doncaster was originally surveyed on a scale of six inches to one mile in Yorkshire and one inch to one mile in Lincolnshire and Nottinghamshire (as the county boundaries were defined prior to 1974) and published on parts of several hand-coloured Old Series one-inch geological sheets. The western half of the district, west of approximately National Grid line 700, was surveyed by W T Aveline; its southernmost part was included on OS Sheet 82 NE (published in 1861, revised in 1875 and incorporating additions in 1897, with an explanatory memoir by Aveline published in 1861 and 1880); the area farther north was included on OS sheets 87 SE (published in 1863, with additions in 1870 and 1876) and 87 NE (published in 1863). The eastern half of the district was surveyed by A G C Cameron and W A E Ussher; its southernmost part was included on OS Sheet 83 (Solid and Drift editions, each published in 1886, with an explanatory memoir by Ussher et al., published in 1888); the area farther north was included on OS Sheet 86 (Solid and Drift editions, both published in 1887, with an explanatory memoir by Ussher, published in 1890).

A narrow strip of ground along the western edge of the district was resurveyed by W Edwards and G H Mitchell between 1929 and 1935, and the southernmost part of the district was resurveyed by E G Smith between 1957 and 1960, both on the six-inch scale. The main part of the district was resurveyed on the same scale by G D Gaunt, G H Rhys and E G Smith, under the supervision of D R A Ponsford, between 1962 and 1968. The district is covered by Solid and Drift editions at the one-inch scale of the Goole (79) and Doncaster (88) geological sheets, published in 1971 and 1969 respectively.

Six-inch geological maps included wholly or in part within the district are listed below, together with the names of the surveyors and dates of survey. The surveyors were R A Eden, W Edwards, G D Gaunt, R F Goossens, G H Mitchell, G H Rhys and E G Smith.

Copies of the fair-drawn National Grid maps are deposited for public reference in the library of the British Geological Survey at Keyworth. Copies may be purchased from BGS either as uncoloured dyeline sheets or, where printed stocks are held, as * published sheets. + Incompletely surveyed sheets.

A narrow strip of ground along the western margin of the district from Walden Stubbs southwards, west of National Grid Line 550, is included on six-inch geological maps based on the Yorkshire Country Series. These maps are 250 (NE, SE), surveyed by W Edwards in 1933; 264 (NE, SE), 276 (NE, SE), 284 (NE, SE) and 290 (NE), surveyed by G H Mitchell in 1929–32. Manuscript copies of these maps are deposited for public reference in the library of the British Geological Survey at Keyworth, from whom black and white photographs of them can be ordered.

Notes

• Throughout the memoir the word 'district' refers to the area covered by the 1:63 360 geological sheets 79 (Goole) and 88 (Doncaster).
• National Grid references are given in square brackets. They are not generally given in the text for boreholes which are included in Appendix 1.
• The authorship of fossil species is given in the fossil index.
• Publication of this memoir, compiled in 1985–88, has unavoidably been delayed and it does not incorporate the most recent published work.

Acknowledgements

Most of this memoir has been written by G D Gaunt. An account of the Coal Measures prepared by C G Godwin in the early 1970s has been extensively used in the preparation of the relevant part of the Carboniferous chapter. Contributions by E G Smith are incorporated into the Permian and Triassic chapter, and the Quaternary chapter. The structure chapter includes a contribution on gravity and aeromagnetic evidence by J D Cornwell, and some of the figures in that chapter are based partly on maps prepared by M C G Clarke, G A Kirby and P W Swallow. The economic geology chapter was compiled by P M Harris. Carboniferous fossils referred to in the memoir were identified by M A Calver, M Mitchell, B Owens, W H C Ramsbottom and N J Riley; the Permian fossils were identified by J Pattison, and comments on Triassic correlation are based on palynomorph identifications by G Warrington. The memoir was edited by J W Baldock, A J Wadge and J I Chisholm.

Grateful acknowledgement is made to numerous individuals and organisations for generous help, advice and information. In particular, British Coal, BP Petroleum Development (UK) Limited, Candecca Resources Limited, the Department of Energy, Esso Exploration and Production UK Limited, RTZ Oil and Gas Limited, and Taylor Woodrow Energy Limited are thanked for permission to publish certain information.

Geology of the country around Goole, Doncaster and the Isle of Axholme—summary

The area described in this memoir forms the southern part of the Vale of York, a low-lying, largely drift-covered tract with little relief and lying mostly at less than 10 m above OD. A few more elevated tracts, including the Isle of Axholme, rise to heights of 20 to 50 m. Exposures of Permo-Triassic rocks are largely restricted to the western margin of the district where they reach 85 m above OD and form the foothills of the Pennines.

Palaeozoic rocks have been proved at depth below Permo-Triassic rocks in boreholes and colliery workings. The oldest of them, the Carboniferous Limestone, was deposited mainly in a warm, shallow shelf sea. The overlying Millstone Grit is the product of large deltas, and the succeeding Coal Measures were laid down on an extensive swampy coastal plain.

The Carboniferous rocks were uplifted, faulted and folded during the Hercynian Orogeny and then eroded, after which the Permo-Triassic aeolian, marine, lacustrine, fluvial and evaporitic deposits were laid down in a large intracontinental basin under hot, arid conditions. There is no further depositional record of events in the district between the late Triassic and late Quaternary.

The extensive and varied late Quaternary Drift deposits include sediments formed in glacial, periglacial, lacustrine, fluvial, estuarine and aeolian environments. The deposits reflect a history of climatic and sea-level changes during which the district suffered at least one major glaciation, a partial glaciation, and a blockage of the Humber Gap which led to the formation of the vast Lake Humber. In historical times, man has diverted some of the rivers and has also produced extensive spreads of artificially induced alluvium (warp).

The district includes the concealed eastern extension of the Yorkshire Coalfield, in which the Barnsley Coal is the principal worked seam. Sand and gravel deposits are widespread and are worked for use mainly in the construction industry. Peat extraction is also an important industry. The only currently operating onshore gasfield in the UK is located in the district, at Hatfield Moors.

(Geological sequence) Summary of geological sequence. Drift deposits not necessarily in chronostratigraphical order within stage. 1 Included in Glacial Sand and Gravel on published maps. 2 Shown as Boulder Clay on published maps.

Chapter 1 Introduction

Physiographical and geological setting

This memoir describes the geology of the district covered by the Goole (79) and Doncaster (88) one-inch geological maps of England and Wales (Figure 1).

Topographically, the district (Figure 2) is virtually coincident with the southern part of the Vale of York, that wide tract of low ground between the Pennines to the west and the hills of eastern Yorkshire and Lincolnshire to the east. Much of the district is less than 10 m above OD; extensive areas in the east and north are less than 3m above OD and are, therefore, below high-tide level in the rivers which traverse them. The highest ground, in the south-west, rises to about 85 m above OD near Stainton, and relatively high ground along the western edge of the district northwards to Askern reaches 30 m above OD. These westernmost hills consist of Permian rocks and form the lowest foothills of the Pennines. Triassic strata rest on the Permian across the rest of the district. The Sherwood Sandstone outcrop rises to 33 m above OD in Bawtry Forest, with a ridge descending from it northwards to Rossington, and the outcrop of the overlying Mercia Mudstone reaches 21 m above OD south of Misterton; these localities are the northernmost extensions of the undulating hills of central Nottinghamshire.

Four other areas of elevated ground occur within the district, three of which are formed of Sherwood Sandstone: Brayton Barff (up to 51 m above OD) and adjacent ground in the north-west, a ridge (up to 22 m above OD) running eastwards through Snaith, and a ridge (up to 23 m above OD) running north-eastwards through Doncaster. The fourth elevated area, formed of Mercia Mudstone, is the Isle of Axholme, which rises to 40 m above OD. The hills of eastern Yorkshire and Lincolnshire, comprising Jurassic and Cretaceous rocks, lie only a few kilometres to the east of the district. The extensive low-lying parts of the district are a veritable land of rivers, notably the Derwent, Ouse, Aire, Went, Don, Torne, Idle and Trent, within which the drainage of one fifth of England flows towards the Humber Estuary, a short distance farther east (Figure 2).

At depth, the Permian rocks unconformably overlie Upper Carboniferous Coal Measures, which pass downwards into Millstone Grit and Carboniferous Limestone, the last being the oldest rocks proved by boreholes in the district.

All the low-lying areas and much of the elevated ground are mantled by Quaternary deposits, or 'Drift'. These deposits, and the Permian and Triassic rocks where they crop out, produce a wide variety of soils: heavy clays on the Mercia Mudstone and Quaternary lacustrine and alluvial deposits; well-drained, light soils on the Sherwood Sandstone, Quaternary sands and gravels and on much of the 'warped' ground (see p.130). In addition, there are limy soils on the Permian rocks in the south-west, and acidic soils on peat deposits in some central and southern areas, including the two largest remaining expanses of lowland raised bog in Britain, Thorne Moors and Hatfield Moors.

The oldest evidence of man in the district is the Lower Palaeolithic 'Rossington Hand Axe' (p.106). Remains of artifacts from younger stone ages and from the Bronze Age and Iron Age have also been found. Doncaster (Danum), situated on a major strategic route to the north (perpetuated as the Al trunk road), is the best known of several Roman sites. The Humber Estuary facilitated deep penetration of the district by Anglian, and later by Danish, immigrants, and most of the small towns and villages owe their origins to these settlers. Some of the earliest efforts towards more effective drainage of the low-lying ground may date from Anglo-Danish or even Roman times, and certainly some similar land improvement was undertaken in later Medieval times on large estates established by various ecclesiastical houses. The most important of the major drainage operations, however, were the river diversions carried out in the 1620s by Cornelius Vermuyden (Figure 2) and, subsequently, by others including John Smeaton, which produced marked changes in the landscape (Cory, 1985). Such operations, together with the large-scale warping carried out since the mid-18th century (see p.130), transformed thousands of acres of poor-quality land into some of the best arable land in Britain. The construction of canals, and later the railways, improved communications considerably across the district. The development of Goole in the mid-19th century provided a port for sea-going ships, and today three motorways, constructed in the 1960s and 1970s, cross the district.

Outline of geological history

The pre-Carboniferous geology of the district, known only in outline from geophysical evidence, includes part of a broad, deep-seated belt of magnetic rocks that trends south-eastwards from the Lake District to The Wash. A gravity low, centred in the Market Weighton area, just to the north-east of the district, can perhaps best be interpreted as a granitic 'batholith', elongated south-westwards; the alternative interpretation, of a deep trough of Lower Carboniferous sediments along this axis, cannot be entirely discounted, however. Farther south, a thickened sequence of Lower Carboniferous, and possibly older arenaceous strata, can be deduced with more confidence to underlie the Gainsborough Trough. This is flanked by higher density rocks to the north, beneath the Askern–Spital Structure, underlain either by a major ridge in the magnetic 'basement' or by igneous rocks, perhaps of Carboniferous age.

In early Carboniferous (Dinantian) times the whole district was covered by a tropical sea in which mainly calcareous sediments were deposited. The resulting Carboniferous Limestone, probably several hundred metres thick, accumulated at rates which generally kept pace with subsidence, so that shallow-water conditions were maintained. Subsidence in northern and central parts of the district was slow, but in the Gainsborough Trough, which extended east-south-eastwards across the southern part of the district, it was more rapid; there, at least towards the end of Dinantian times, some thin mudstones were laid down.

By early Upper Carboniferous (Namurian) times deposition of grey mud and silt dominated the entire district, but, as deltaic and eventually fluvial conditions became established, periodic incursions of sand occurred. The resulting Millstone Grit sequence is predominantly of brackish and freshwater origin, although some of the lowest, largely argillaceous, strata are marine. At higher levels the presence of thin marine bands indicates periodic transient incursions of the sea. Subsidence continued to be more rapid in the Gainsborough Trough than farther north, but this differential effect diminished later in the Namurian and subsequently became insignificant. Nevertheless, the Millstone Grit in the trough is locally over 800m thick, compared with little more than 300 m farther north. A cyclic pattern of sedimentation became established towards the end of the Namurian. Each cycle, where complete, contains a thin basal marine mudstone and continues upwards through coarser, brackish and freshwater mudstone and siltstone to deltaic and/or fluvial sandstone, coarse grained and even conglomeratic in places, and locally topped by a thin coal and/or seatearth, signifying emergence.

During the later Upper Carboniferous (Westphalian), the district formed part of an extensive coastal plain on which the Coal Measures were laid down, mainly as fluvial, lacustrine and swamp deposits. These strata consist largely of grey mudstones and siltstones but include numerous thin, fine-grained sandstones and coals. Cyclic sedimentation continued but there are few marine bands, except near the base of the Coal Measures and in certain other parts of the sequence, although several 'Estheria' bands imply brackish incursions. Most cycles, however, terminate upwards in a coal seam. Despite subsequent erosion, a thickness of more than 1440 m of Coal Measures survives in the south-western part of the district. Variations within the sequence show an overall easterly thinning and also a thinning across a belt of country running from near Askern east-south-eastwards across the middle of the district, and corresponding closely to the northern edge of the old Gainsborough Trough. The topmost surviving Coal Measures are in places stained red and other colours, the results of weathering and oxidation in pre-late Permian times.

During the Hercynian Orogeny, in latest Carboniferous and earliest Permian times, the Carboniferous rocks in the district were uplifted, faulted and gently folded, and then subjected to prolonged erosion. Both the tectonic effects and the erosion were most marked along the Askern–Spital Structure (p.90).

From early Permian times until almost the end of the Triassic, the district lay in the south-western marginal part of a vast intracontinental depression with a fairly arid, hot, low-latitude climate. Aeolian conditions, with deposition of the thin and impersistent Basal (Permian) Sands, continued until the middle of the Permian. Throughout late Permian times, however, the basin was occupied by the shallow inland 'Zechstein Sea', which periodically inundated even the marginal parts of the depression. The resulting deposits comprise a broadly cyclic sequence, locally over 200 m thick in the district, and form the Don to Eskdale groups. During the more extensive transgressions, limestones that are largely dolomite rich were formed, notably the Lower Magnesian Limestone and the Upper Magnesian Limestone. During partial regressions the Zechstein Sea became hypersaline; anhydrite and, to a lesser extent, other evaporites were deposited, partly in peritidal sabkha conditions and partly by subsequent replacive and displacive mineralisation. Between incursions, however, deposition in marginal areas was predominantly of red, desert-derived, fluvial, lacustrine and peritidal mudstones and siltstones, of which the Middle Marl and Upper Marl are typical.

Following the final regression of the Zechstein Sea at the end of the Permian, thick spreads of red fluvial sands accumulated in early Triassic times, forming the Sherwood Sandstone Group, which is up to 400 m thick in the district. Later in the Trias, however, another periodically hypersaline shallow inland sea became established in more central parts of the basin; thick red, fluvial, lagoonal and peritidal mudstones and siltstones, locally dolomitic and gypsiferous, were deposited in marginal areas. These strata,- comprising the Mercia Mudstone Group, are up to about 200 m thick in the district but are incomplete, the highest 60 m of the group being present a short distance farther east.

No depositional evidence of geological history between latest Triassic times and the late Quaternary has survived in the district, although some generalised assumptions can be made from consideration of the sequence farther east. For much of the Jurassic the district was probably covered by shallow open seas, with mudstone and at times limestone deposition, but it is possible that in the middle part of the period, northern and western areas experienced brackish and freshwater depositional conditions, with transient emergence and erosion. Similar mainly nonmarine and periodically emergent conditions probably continued during much of the early Cretaceous. In the late Cretaceous, however, the sea in which the Chalk was deposited almost certainly covered the entire district. During the Tertiary, differential uplift and the imposition of an overall easterly dip produced prolonged denudation which removed all the post-Triassic rocks from the district and exposed Permian rocks in the extreme west. The westerly and northerly flowing drainage pattern evolved during this time.

Denudation probably continued for much of the Quaternary, until less than 500 000 years ago. Subsequently, throughout at least one major glaciation, a thick ice sheet extended across the entire district. Subglacial erosion cut deep channels into bedrock and then filled them with deposits ranging from laminated clay to gravel; some clay till was deposited and, during deglaciation, meltwater from the south and west transported fluvioglacial sand and gravel into the district. In the early part of the Ipswichian (or last) Interglacial Stage, with sea level still glacioeustatically well below present OD, the rivers incised courses to at least 13 m below OD in places, but with the ensuing sea-level rise to just above OD they eventually deposited extensive spreads of sand and gravel. Organic remains in these deposits indicate a climate at least as warm as that prevailing at present.

When sea level fell again during the early and middle Devensian (or last) Glacial Stage, the rivers crossing the district incised wide valleys down to nearly 20 m below OD in places; both cryoturbation structures and ventifacts formed during times of severe periglacial conditions. In the late Devensian, glacial blockage of the Humber Gap by ice from the North Sea created a vast lake (Lake Humber) in the Vale of York. Ice flowing south down the Vale of York temporarily re-entered north-eastern parts of the district and deposited sand and gravel along its edges into the lake. Lake Humber initially rose to about 30 m above OD and sand and gravel were deposited around its margins, but it soon fell, for a time to at least 4 m below OD, before establishing a longer-lasting level at about 9 m above OD, when sand was deposited around its margins and thick laminated clay accumulated in more central areas. The lake finally disappeared, apparently by filling with sediment; the rivers then deposited sandy levees across the emergent lacustrine plain until the glacial blockage in the Humber Gap was finally breached, when they again incised their courses down to nearly 20 m below OD in response to the prevailing low sea level. In latest Devensian times, blown sand accumulated in places and more cryoturbation structures and ventifacts are thought to have formed. As the sea rose to its present level during the Flandrian ('post-glaciar’) Stage, the rivers crossing the district filled their incised channels with alluvium and eventually spread these deposits thinly but widely beyond the channel confines; peat accumulated extensively in the more low-lying waterlogged areas. In historical times, man has diverted some of the rivers and has also produced extensive spreads of artificially induced alluvium, or warp.

Chapter 2 Carboniferous

The oldest rocks proved within the district are of Carboniferous age, but they are entirely concealed beneath Permian and younger strata. Direct knowledge of their stratigraphy, lithology and fossils is therefore limited to evidence from boreholes, colliery shafts and workings. Even the deepest boreholes, however, do not reach the base of the Carboniferous sequence; probably a substantial thickness of strata comprising all but the topmost part of the Carboniferous Limestone lies, as yet unproved, at greater depths. More than half of the known succession, up to and including approximately the lowest quarter of the Coal Measures, has been penetrated only by the few hydrocarbon boreholes drilled in and closely adjacent to the district. Few of the boreholes were cored and the available evidence is largely limited to lithological logs based on chipping samples, supplemented by geophysical logs. In contrast, information about the rest of the Coal Measures is derived from more than 100, mainly cored, surface boreholes as well as from shafts, cored underground boreholes and workings in several collieries, six of which are centred within the district. Consequently, the relevant part of this account is necessarily selective and includes only the most important details, principally those concerned with thickness, lithologies and faunas. Except for unverified fossil names, which are given in quotes, the faunas referred to in this chapter were identified by M A Calver, M Mitchell, W H C Ramsbottom and N J Riley, and the palynomorphs, mainly miospores, were identified by B Owens.

The Carboniferous succession in the district is similar to that of the Pennines, where a lithostratigraphical classification consisting of Carboniferous Limestone, Millstone Grit and Coal Measures, in ascending order, was developed early in the 19th century. These terms were also used chronostratigraphically by adding 'Series' to each, but it is now recognised generally that lithostratigraphical and chronostratigraphical subdivisions should be separately defined (Ramsbottom et al., 1978, pp. 5–6 fig. 1). An international chronostratigraphical classification is shown in (Figure 3). The three original names can, therefore, revert to their former usage and they are applied here as informal lithostratigraphical terms of group status, with the proviso that, by present convention, the base of the Coal Measures is taken at the base of the Subcrenatum Marine Band. The Cravenoceras leion Marine Band is not proved in the district, and the base of the Millstone Grit is drawn at the top of the limestone sequence (Figure 4).

British Carboniferous rocks contain abundant and various fossils and the many biostratigraphical correlation schemes which are based on them have been reviewed by George et al. (1976, pp. 2–4) and Ramsbottom et al., (1978, pp. 2–5). Certain marine taxa have an extensive geographical distribution and a restricted stratal range, which makes them particularly useful for chronostratigraphical correlation. The base of each Silesian stage, up to and including Westphalian C (Figure 3), is defined with respect to a specific goniatite-bearing marine band, each with an informal name. Within the Westphalian stages, many species of nonmarine bivalves or mussels occur in characteristic assemblages which provide a basis for recognising chronozones. More tightly defined assemblages of mussel species or faunal belts (Calver, 1956) permit more detailed correlation within these chronozones.

The Carboniferous has been shown radiometrically to span the period between about 365 and 290 million years ago (Forster and Warrington, 1985). During this time, British Carboniferous sediments were deposited in equatorial latitudes (Smith et al., 1981). The Carboniferous palaeogeography of northern England is imperfectly known, but much of the clastic sediment is thought to have come from the long-denuded mountains of the Caledonides to the north. To the south, the London–Brabant Massif of the southern Midlands formed high ground against which the Carboniferous sequences thinned and wedged out. Within northern England there are differing types of depositional facies and marked thickness variations, which show that tectonic effects produced fairly well-defined 'basins', 'troughs' and 'gulfs' in which subsidence was much more rapid than on adjacent 'blocks', particularly during parts of Dinantian and Namurian times. One such rapidly subsiding area, the Gainsborough Trough, lies south-west of a line approximately between Askern and Owston Ferry.

The topmost part of the Carboniferous Limestone, the oldest rocks proved in the district, consists largely of limestone containing corals and other fauna which suggest deposition on a warm, shallow, open-marine, carbonate platform. In the Gainsborough Trough, however, the sediments were mainly impure limestones interbedded with mudstones, as in the Scaftworth No. 2 Oil Borehole just south of the present district; these suggest a different depositional environment marked by deeper water and a plentiful supply of fine sediment.

Much of the Millstone Grit is argillaceous, mainly mudstones but with some siltstone; although marine faunas are present, they are largely confined to thin marine bands. The included sandstones or 'grits', from which this part of the Carboniferous succession derived its name, are locally coarse grained and conglomeratic, the pebbles being mainly of quartz. Large-scale cross-bedding and other sedimentological features, together with the nature of the detrital minerals in the sandstones, imply that most of them are deltaic accumulations, largely derived from the north. Thin and probably impersistent coals and seatearths, mainly in the upper part of the Millstone Grit, indicate transient emergence and the growth of vegetation. There is increasing evidence upwards through the Millstone Grit of repetitive deposition, resulting in cyclic rock sequences. A complete cycle comprises:

• Seatearth and/or coal, indicating emergence
• Sandstones, locally thick and suggestive of fluviodeltaic deposition
• Argillaceous strata, commonly coarsening upward (generally devoid of fossils which might indicate the depositional environment, but with scattered plant debris suggesting proximity to land)
• A thin argillaceous marine band, signifying marine transgression.

The Millstone Grit is more than twice as thick in the Gainsborough Trough as it is on parts of the block to the north, demonstrating the marked difference in rates of subsidence between the two areas. Thickness variations become less pronounced towards the top of the sequence, as the subsidence of the Gainsborough Trough waned in the late Namurian.

The Coal Measures successions are generally similar in lithology to the Millstone Grit sequences and consist largely of mudstones and siltstones with subsidiary sandstones. Cyclical sequences occur throughout. Few of the numerous cycles contain basal marine bands; some possess 'Estheria' bands suggesting brackish-water incursions, but most either contain mussel-rich layers near their bases, implying freshwater inundations, or are unfossiliferous except for scattered plant debris. The sandstones are generally thin and fine-grained, and have sedimentary features and distribution patterns suggesting mainly fluvial origins. They are commonly impersistent, and are absent in some cycles, but some locally expand enormously in thickness, becoming medium to coarse grained and conglomeratic, and containing worn fragments of siltstone, mudstone, 'ironstone' and coal. Some clearly occupy deep channels incised into the underlying strata and may therefore indicate appreciable variations in drainage base level. Coals are common, and in the middle part of the Coal Measures their thicknesses are substantial, several seams exceeding 1.5 m.

The stratigraphical and sedimentological characteristics of the Coal Measures indicate mainly lacustrine, fluvial and swamp deposition on an extensive coastal plain, with little or no relief except during temporary lowerings of drainage base level. The influence of the Gainsborough Trough was insignificant during early Westphalian times and was not discernible thereafter. Instead, a new but less-marked pattern of differential subsidence became established, producing an overall westerly thickening, especially towards the south-west and, to a lesser extent, the north-west. The relatively thin sequences found in an elongate area running east-south-east from near Askern and in places coinciding with the northern margin of the earlier Gainsborough Trough reflect initial movement along the Askern–Spital Structure (pp. 90–91). In the north-west of the district some sequences vary appreciably in thickness in a north-westerly direction, suggesting contemporaneous movement along north-east-trending structures aligned parallel to the Don Monocline (pp. 91, 94). The full extent of Coal Measures deposition in the district is uncertain; substantial erosion, accompanying and following the Hercynian orogenic movements, removed an unknown thickness of Coal Measures strata prior to late Permian times. As a result, at least 600 m of Coal Measures strata were removed in the north-west which are still present in the south-east, assuming a constant original thickness.

Carboniferous limestone

The limestones and associated rocks of Dinantian age underlying the district are probably several hundred metres thick, on evidence from boreholes farther south (Edwards, 1967, pp. 14–23) and from outcrops in the Pennines to the west. However, only the highest part of the sequence has been proved, in Belton, Trumfleet No. 1 and Askern oil boreholes (Figure 4). Scaftworth No. 2 Oil Borehole also penetrated the highest part of the Carboniferous Limestone and, although situated just south of the district, summary details are included here because it postdates the relevant memoir (Smith et al., 1973, see pp. 8–11); as it lies in the middle of the Gainsborough Trough it highlights some of the facies variations between trough and block.

In Belton Oil Borehole, which proved 53.3 m of limestone, the lowest strata are pale creamy white, with some slightly darker beds above. The middle and upper beds are white, cream and fawn, becoming brownish grey near the top. Most of them are described as 'flakey', which probably implies thin bedding. Specimens of core from 1.2 to 2.7 m below the top are of crinoidal limestone containing Amplexizaphrentis cf. enniskilleni, Rotiphyllum sp., a pustulose productoid and Paladin sp. ex gr. of the barkeri–maillieuxi group. Although not diagnostic, these taxa suggest a Brigantian age.

Trumfleet No. 1 Oil Borehole proved 55.8 m of limestone. Approximately the lowest 5.8 m, which were cored, are described as 'darker, fractured, finely crystalline' limestone. The overlying 42 m comprise 'brownish' to white crystalline (in places coarsely) limestone with some white 'soft' and 'chalky' beds. Unidentified foraminifera were reported from these strata and, from some brownish beds, two 'thin coaly smuts'. Most of the topmost 8 m were cored and are described as 'whitish-brown crystalline limestone with black pyritic shale breaks' and, 5.5 m below the top, 'fetid bitumastic limestone'. This core yielded Cynthaxonia cornu, zaphrentoids including Fasciculophyllum cf. densum and Rotiphyllum sp., Tetralasma sp. nov., Antiquatonia hindi, A. cf. insculpta, Athyris?, Brachythyris integricostata, Buxtonia sp. nov., Gigantoproductus sp., Productus sp., Spinier bisulcatus, an indeterminate gastropod, a trilobite pygidium and abundant crinoid debris. The corals were found in the more finely crystalline parts of the core; they suggest a Brigantian age. The record of Tetralasma (cf. Schindewolf, 1942, p.92, pl. 21, fig. 6 a–c) is the first in Britain (Mitchell, 1958).

Askern Oil Borehole penetrated only 14 m into the limestone, which is described as 'brown crystalline limestone, silicified in parts', overlain by 'white saccharoidal limestone with some black shale'. Although about 5.5 m of core were taken and some corals and crinoids were reported, no other details are available.

In Scaftworth No. 2 Oil Borehole, which proved 79 m of limestone and associated strata, the lowest 18 m are medium to dark grey, slightly pyritic, subfissile mudstones which become more calcareous upwards. They are succeeded, above an apparently sharp junction, by about 15 m of pale to medium grey, 'speckled', blocky argillaceous limestones with a few thin layers of medium to dark grey mudstone. These mudstone layers increase in number and thickness upwards, producing a gradation into the upper 46 m of interbedded pale to medium grey, argillaceous limestones, with thinner, medium to dark grey calcareous mudstones. The only fossils recorded are palynomorphs, the details of which are not available, and some derived late Silurian to early Devonian acritarchs.

Although the available evidence is limited to the uppermost Carboniferous Limestone strata, it does suggest that the argillaceous content decreases from Scaftworth No. 2 Oil Borehole, in the middle of the Gainsborough Trough, to Trumfleet No. 1 and Askern oil boreholes on its northeastern margins and to Belton Oil Borehole on the block beyond. The sequence proved in Scaftworth No. 2 Oil Borehole appears to be basinal and is not unlike that reported in parts of the Widmerpool Gulf to the south (Falcon and Kent, 1960, p.20). This supports the suggestion by Smith et al., (1973, p.10) that a basinal facies may exist in the middle of the Gainsborough Trough.

Millstone Grit

Thirteen boreholes have proved parts of the Millstone Grit within the district. Seven of them are shown on (Figure 4), the others being Axholme No. 2, Hatfield No. 2, Trumfleet Nos. 2, 3 and 5 and Moss oil boreholes. Warmsworth and Scaftworth No. 2 oil boreholes are included in this account and in (Figure 4) and (Figure 5); although situated just outside the district, they provide important relevant information. Scaftworth No. 2 Oil Borehole proved 813 m of Millstone Grit, the thickest known complete sequence in the Gainsborough Trough. This contrasts markedly with the 315 m-thick sequence in Belton Oil Borehole on the block to the north-east, and proves the much greater contemporaneous subsidence within the trough. The four complete thicknesses proved in the district and those known farther east (Gaunt et al., 1992, fig. 3) show that the Millstone Grit thickens westwards both in the Gainsborough Trough and on the block to the north-east, as suggested by the conjectured isopachs on the location plan of (Figure 4).

Because few cores were taken in these boreholes there is macrofaunal evidence of only the three youngest Namurian stages. This evidence is limited to five boreholes, but the geophysical logs, and especially the gamma-ray logs, provide correlations with equivalent strata in most of the other boreholes (Figure 5). The only available information from Moss Oil Borehole is a suite of fossils in the BGS collections, but these fossils allow a good correlation with the nearby Trumfleet No. 1 Oil Borehole (Figure 6). Below the Bilinguites gracilis Marine Band, however, there is little chronostratigraphical evidence, and inter-borehole lithostratigraphical correlation is somewhat tentative.

Beds below the Bilinguites gracilis Marine Band

For descriptive purposes the beds below the Bilinguites gracilis Marine Band may be subdivided into four informal lithostratigraphical units, in ascending order the lower mudstones, the lower sandstones, the upper mudstones and the upper sandstones. As (Figure 4) shows, these strata form more than half of the total Millstone Grit succession and they encompass most of the thinning between the Gainsborough Trough and the block to the north-east.

The lower mudstones thin from 225 to 23 m between Scaftworth No. 2 and Belton oil boreholes. They are mainly medium grey to black, variably blocky or fissile and locally pyritic mudstones, which are largely noncalcareous except near the base. Some medium to dark grey and brownish grey siltstones are present near the top of the sequence and ironstone nodules occur in places. A few, generally thin, white to brown, fine- to medium-grained, calcareous and locally micaceous sandstones are present also. In Hatfield No. 1 Oil Borehole the lowest sandstone proved was recorded as dolomitic; it is overlain by coarse-grained sandstone. In Askern Oil Borehole some of the sandstones are berthierinitic; there are also a few thin, cream to brown and dark grey, finely crystalline, silty or sandy, micaceous and locally pyritic limestones. In Scaftworth No. 2 Oil Borehole some of the latter are recorded as dolomitic. (These descriptions are based on chipping samples, so the recorded distinction between calcareous sandstones and silty and sandy limestones may not be firmly based). Traces of coal were noted in Askern and Trumfleet No. 1 oil boreholes, with subjacent mudstone seatearths in the latter. Indeterminate fragments of fossils were recorded at 1423 m in Trumfleet No. 1 Oil Borehole, just above one of the coals. Calcite noted in chipping samples elsewhere in these strata, although attributed to veins in the borehole logs, may be derived from shelly fossils. Some derived late Silurian to early Devonian acritarchs were found in the lower part of the mudstones in Scaftworth No. 2 Oil Borehole. Although miospores from 1448 m in Trumfleet No. 1 Oil Borehole and from 1604 m and 1524 m in Hatfield No. 1 Oil Borehole contain Crassipora kosankei in sufficient numbers to suggest a Kinderscoutian or younger age, the presence of certain other taxa, including some typical of the Westphalian, indicates contamination by caving. Perhaps a better, though indirect, indication of age is given by the high gamma-ray response of the lowest 48 m, 43 m and 58 m of mudstones in Scaftworth No. 2, Askern and Trumfleet No. 1 oil boreholes respectively, a feature that is characteristic of lithologically similar mudstones of Pendleian and early Arnsbergian age in the Ashover area (Ramsbottom et al., 1962, p.119; Cosgrove, 1962, p.164, pl. VIII). If this evidence is reliable it shows that, in the Gainsborough Trough at least, the base of the Namurian is in effect coincident with the Millstone Grit/Carboniferous Limestone boundary as drawn on (Figure 4). The lithology of the lower mudstones reflects quiescent deposition, possibly in basinal conditions, with periodic input of turbiditic sand; however, the presence of coals and seatearths implies transient emergence. To the east of the district the lower mudstones are represented by 19 m of dark siltstones with thin limestones in Corringham No. 7 Oil Borehole (Gaunt et al., 1992, fig. 3); they are also recognised in several boreholes south of the Gainsborough Trough (Smith et al., 1973, pl. II).

The lower sandstones comprise 20 to 45 m of sandstones containing thin interbedded siltstones, mudstones and locally a few limestones. Most of the sandstones are white to pale grey and brown, fine-grained and well sorted, with angular to subangular grains; some medium-grained, poorly sorted sandstone was noted in Hatfield No. 1 Oil Borehole and some subrounded grains were recorded in Axholme No. 1 Oil Borehole. The sandstones are variably calcareous and locally pyritic and carbonaceous; some glauconitic grains were noted in Axholme No. 1 Oil Borehole. The interbedded siltstones and mudstones vary from medium grey to black and are poorly to noncalcareous; they are locally micaceous and pyritic, and they include a silty seatearth-mudstone in Askern Oil Borehole. A thin, dark grey, silty limestone is present in Trumfleet No. 1 Oil Borehole and a thin, white to brown, crystalline dolomitic limestone or dolomite occurs at the base of the thickest sandstone in Scaftworth No. 2 Oil Borehole. Although no miospore identifications are available, the miospores from the lower sandstones in Scaftworth No. 2 Oil Borehole are recorded as being more numerous and less corroded than those in the underlying strata. This suggests increasing proximity to land and, with the dominance of arenaceous sediment, deposition along the distal edge of a deltaic environment. The lower sandstones cannot be clearly delineated in boreholes to the east of the district, although in Corringham No. 7 Oil Borehole (Gaunt et al., 1992, fig. 3) they are certainly present and may exceed 100 m in thickness. They can be recognised in several boreholes on the block south of the Gainsborough Trough (Smith et al., 1973, pl. II), where, however, they tend to be siltstones rather than sandstones.

The upper mudstones thin from 266 m in Scaftworth No. 2 Oil Borehole to about 155 m in Axholme No. 1 and Belton oil boreholes. They largely comprise mudstones, silty mudstones and, mainly in the upper part, siltstones that are medium grey to black, though locally greyish brown; the siltstones are variably blocky or fissile, poorly or noncalcareous (but recorded as partly dolomitic in Hatfield No. 1 Oil Borehole) and in places micaceous, carbonaceous or pyritic. They contain some ironstone nodules. The upper mudstones also include some generally thin, white to pale grey and brown, fine- to medium-grained, well-sorted, variably calcareous and locally pyritic sandstones. A few thin, pale to dark grey and brown, silty and sandy, finely crystalline and locally sideritic, carbonaceous limestones are present also. Those in Askern Oil Borehole may be berthierinitic. Traces of coal were recorded from the middle of the upper mudstones in Hatfield No. 1 and Belton oil boreholes, with a subjacent seatearth mudstone in the former; coal was also present near or at the top of the sequence in Trumfleet Nos. 1 and 3, and Hatfield Nos. 1 and 2 oil boreholes, with a subjacent seatearth in places. A scale of Rhizodopsis sp. was found at 1524 m in Belton Oil Borehole, and 'Lingula' and 'Posidonia' were recorded from about 1202 m in Trumfleet No. 1 Oil Borehole, but BGS has no fossils from the latter occurrence. Miospores from 1295 m and 1240 m in Trumfleet No. 1 Oil Borehole and from 1449 m, 1372 m and 1284 m in Hatfield No. 1 Oil Borehole contain C. kosankei, accompanied by Raistrickia fulva in the last two of these occurrences. These assemblages indicate a Kinderscoutian or younger age, but some other taxa suggest a degree of contamination. The most prominent gamma-ray peaks in the upper mudstones are near the base and top (Figure 5). The Ethology of these strata implies fairly quiescent deposition, but with some transient emergence, and the considerable amount of plant debris noted in miospore preparations suggests that land was not too distant. The upper mudstones may correlate eastwards with the strata between the lowest seatearth and the lowest proven marine band in Blyton and Coning-ham No. 7 oil boreholes, (Gaunt et al., 1992, fig. 3), and southwards with at least some of the argillaceous strata underlying the Kinderscout Grit in the East Retford district (Smith et al., 1973, pl. II).

The upper sandstones, which thin from 70 to about 12 m between Scaftworth No. 2 and Axholme No. 1 oil boreholes, consist mainly of sandstones with interbedded siltstones and mudstones which continue up to the base of the B. gracilis Marine Band. Most of the sandstones are fairly thin, white to pale grey and brown, fine to medium grained, moderately sorted, variably calcareous and locally carbonaceous, with berthierine in Askern Oil Borehole. Thick sandstones occur in Scaftworth No. 2 and Warmsworth oil boreholes; coarse grains are present in the latter and also in a thin sandstone, possibly at the same stratigraphical level, in Crowle Oil Borehole. The interbedded and overlying mudstones and siltstones are medium grey to black and variously micaceous, carbonaceous and pyritic. Traces of coal and mudstone or sandstone seatearths occur within the upper sandstones in Askern and Trumfleet Nos. 1 and 3 oil boreholes. There is evidence of a Lingula band immediately above, with Lingula mytilloides, cf. Anthraconeilo sp., Sanguinolites v-scriptus and, attached to a plant fragment, Spirorbis sp. in black mudstone and siltstone in Trumfleet No. 1 Oil Borehole; Planolites ophthalmoides, L. mytilloides, Palaeoneilo sp., Sanguinolites sp. and 'fish debris' occur at a similar stratigraphical level in Moss Oil Borehole (Figure 6), and 'Lingula' and 'fish remains' are found in the equivalent beds in Askern Oil Borehole, although BGS has no fossils from the last occurrence. A minor gamma-ray peak at this level in Trumfleet No. 1 Oil Borehole (Figure 5) can be matched with peaks in several other boreholes. In Trumfleet No. 1 Oil Borehole, black pyritic mudstone only 1.83 m below the B. gracilis Marine Band yielded Reticuloceras sp. of the R coreticulatum group, according to BGS correspondence with the relevant oil company, although BGS has no fossils from this position. R. coreticulatum occurs between the lower and upper divisions of the Kinderscout Grit in Pennine outcrops (Bisat and Hudson, 1943; Hudson, 1945), so its reported presence in the present district suggests that most, if not all of the upper sandstones are of Kinderscoutian age and that the sandstone bands equate with the Lower Kinderscout Grit. L. mytilloides and Retispira sp. occur at the same stratigraphical level in Moss Oil Borehole (Figure 6). A thin dark grey 'shelly' limestone immediately below the B. gracilis Marine Band in Trumfleet No. 1 Oil Borehole may equate with a thin limestone and thin calcareous siltstone at a similar stratigraphical level in Tickhill No. 1 and Ranskill No. 1 oil boreholes to the south of the district (Smith et al., 1973, p.19). The thicker and more massive sandstones in Scaftworth No. 2 and Warmsworth oil boreholes suggest deltaic accumulations, but those elsewhere may be partly of fluvial origin. They equate with the sandstones between the lowest proven marine band and the B. gracilis Marine Band to the east of the district (Gaunt et al., 1992, fig. 3), and with the locally thick Kinderscout Grit recognised in the Gainsborough Trough to the south (Smith et al., 1973, pl. II).

Bilinguites gracilis Marine Band

The only faunal evidence of the B. gracilis Marine Band, which marks the base of the Marsdenian Stage, is from Trumfleet No. 1 and Moss oil boreholes. In the former, 3.96 m of grey to black silty mudstone at 1105.8 m yielded Dunbarella sp., Pseudocatastroboceras cf. rawsoni, Anthracoceratites sp. (which ranged upwards for a further 3.96 m), Bilinguites gracilis, Idiognathodus sp., hindeodelloid bar and Ozarkodina cf. deliculata. The presence of Idiognathodus is consistent with the earliest appearance of this genus at the base of the Marsdenian Stage. The fauna from Moss Oil Borehole (Figure 6) comprises L. mytilloides, Dunbarella sp., Anthraconeilo sp., Posidonia sp., Anthracoceratites sp., B. gracilis and B. gracilis (early form); it ranges through 11.04 m, and such a thick accumulation suggests a near-coastal location. In the Askern Borehole the B. gracilis Marine Band can be placed with some precision within a similar lithostratigraphical sequence, and the gamma-ray peak coinciding with the marine band in Trumfleet No. 1 Oil Borehole can be correlated with peaks in several other boreholes (Figure 4) and (Figure 5). Similar faunas have been found in the B. gracilis Marine Band in some of the Corringham oil boreholes to the east of the district (Gaunt et al., 1992, p.7, fig 3); although the marine band is only tentatively recognised immediately south of the district, it has been proved farther to the south (Edwards, 1967, pp. 35–49).

Beds between the Bilinguites gracilis and B. bilinguis marine bands

These beds, which form the lower part of the Marsdenian Stage, thin north-eastwards from 109 to 28 m between Scaftworth No. 2 and Axholme No. 1 oil boreholes. However, their thickness varies considerably even over short distances; it is, for example, 37 m, 67 m and possibly more than 80 m in Trumfleet Nos. 5, 1 and 3 oil boreholes respectively. There is also considerable lithostratigraphical variation within the sequence, with up to three groups of locally prominent sandstones.

The lower strata, which in most boreholes comprise between one third and two thirds of the interval, consist of mudstones passing up into siltstones. They range from medium grey to black and are variously slightly calcareous, micaceous, pyritic and carbonaceous, with some ironstone nodules. A few thin, fine-grained, silty, calcareous sandstones are present locally within these strata; a thin brown, sandy, ferruginous limestone was recorded in Trumfleet Nos. 1 and 3 oil boreholes, and seatearth-mudstones were noted near the base and top of these sequences in Trumfleet Nos. 5 and 3 oil boreholes respectively. In some boreholes a minor gamma-ray peak occurs about 10 m above the B. gracilis Marine Band peak.

In Askern and the Trumfleet oil boreholes most of the upper part of the sequence comprises white to brown, massive, fine- to coarse-grained and locally pebbly, moderately to poorly sorted, feldspathic sandstone; it is suggestive of deltaic accumulation. Sandstone also occupies much of the upper part in Scaftworth No. 2 and the Axholme oil boreholes, but it is white to pale grey, fine to medium grained, well sorted and thinly interbedded with siltstone and silty mudstone. Although these sandstones are similar in their main lithological characteristics, the thick accumulation in Scaftworth No. 2 Oil Borehole is possibly of distal deltaic origin, whereas the much thinner accumulations in the Axholme oil boreholes may be partly fluvial. Hatfield No.1 Oil Borehole contains two such thin sets of interbedded, fine-grained sandstones and argillaceous rocks, one in the middle of the sequence and another near the top, the latter with a marked gamma-ray peak at its base which correlates with a similarly placed peak in Axholme No. 1 Oil Borehole. A peak is also clearly identifiable in Hatfield No. 2 Oil Borehole at 1272 m (Figure 5), but here neither the lithological nor gamma-ray log indicates sandstone immediately above. The nearest sandstone in the sequence lies some 12 m below and consists of about 40 m of white, massive, medium-grained, pebbly sandstone. The only comparable sandstone to this elsewhere in the district is in Warmsworth Oil Borehole, where three sandstones occur between the B. gracilis and B. bilinguis marine bands. The lowest, less than 5 m above the former, is 10 m thick and partly coarse grained, the middle and upper sandstones being fine-grained and locally carbonaceous. Prominent gamma-ray peaks occur between the three sandstones and a coal is recorded above the middle sandstone (Figure 5). In Crowle Oil Borehole some pebbly sandstones and partly coarse-grained sandstones may be correlatives.

The variation in number, thickness and lithology of these sandstones suggests depositional environments ranging from fluvial to distal deltaic, apparently over short distances, marginal to the Gainsborough Trough. The sandstones can be correlated south-eastwards with similar beds in the Gainsborough and Corringham oil boreholes (Smith et al., 1973, pp. 16, 18–20, pl. II; Gaunt et al., 1992, fig. 3). However, their correlation westwards is in some doubt because of uncertainties about the overlying B. bilinguis Marine Band (see below). Some or all of them may equate with the East Carlton Grit of the Leeds–Bradford area (Edwards et al., 1950, pp. 8–15, fig. 4; Stephens et al., 1953, pp. 46–57, fig. 10), which lies below the B. bilinguis sensu stricto Marine Band. Alternatively some or all of them may equate with the Woodhouse or Brandon Grit of the same area, and with the Heyden Rock/Pule Hill Grit, north-west of Sheffield (Eden et al., 1957, pp. 16–19, fig. 4; Stevenson and Gaunt, 1971, pp. 179–180, 231, 232, pl. XIX); these occur above the B. bilinguis s.s.and below the B. bilinguis late form marine bands.

The highest strata below the B. bilinguis Marine Band, not more than 9 m thick except in Scaftworth No. 2 and apparently in Hatfield No. 2 oil boreholes, are medium grey to black, and locally brown, silty mudstones and siltstones containing ironstone nodules, with a thin sandstone locally. Traces of coal or seatearth were recorded from these strata in Scaftworth No. 2, Warmsworth, Hatfield No. 1 and most of the Trumfleet oil boreholes although, as summarised below, in at least one of these boreholes there is evidence that the coal and seatearth may lie between two B. bilinguis Marine Bands

Bilinguites bilinguis Marine Band(s)

Two, possibly three, boreholes within the district provide faunal evidence of the Bilinguites bilinguis Marine Band. In Askern Oil Borehole about 2 m of cored mudstone at 996.4 m are recorded as marine and labelled 'R. reticulatum mut. B marine band' (this being the former name for the marine band), but neither confirmatory identifications nor fossils are available in the BGS archives. In Trumfleet No. 2 Oil Borehole the following sequence was recorded from core above 1034.8 m, where it rests on thick, fine- to coarse-grained, feldspathic sandstones (this depth, and the thicknesses, are from a small-scale diagrammatic section and are therefore approximate).

The lower marine band contains juvenile specimens consistent with Bilinguites bilinguis. The strata equivalent to this section can be identified with some precision in the other Trumfleet oil boreholes, where there is evidence of at least one seatearth and traces of coal (as shown with respect to Trumfleet No. 1 Oil Borehole on (Figure 4). In Trumfleet Nos. 1 and 5 oil boreholes there is a marked gamma-ray peak at this horizon that can be correlated, with varying degrees of confidence, with peaks in other gamma-ray logs, including that for Barlow Oil Borehole (Figure 5).

It is possible that the two marine layers recorded in Trumfleet No. 2 Oil Borehole relate to two separate B. bilinguis marine bands. Up to three marine bands characterised by Bilinguites bilinguis are known in various parts of northern England, the lowest and highest of these bands containing early and late forms of the species respectively. The B. bilinguis early form Marine Band is little known east of the Pennines where it is probably not widespread, but it is proved in boreholes in the Ashover area of Derbyshire lying only 6 to 7 m above the B. gracilis Marine Band and with no intervening sandstones (Ramsbottom et al., 1962, pp. 120–121, pl. VII). Within the district it may be represented by a minor gamma-ray peak recorded about 10 m above the presumed B. gracilis Marine Band in some of the boreholes, most obviously in Scaftworth No. 2 Oil Borehole. The B. bilinguis sensu stricto Marine Band (but not the late form band) is also proved in the Ashover boreholes, 23 to 33 m above the early form band, again with no intervening sandstones. However, farther north, from north-west of Sheffield to the Leeds–Bradford area (as summarised above) locally thick sandstones are present, both below and above the sensu stricto band. The faunal evidence from the Trumfleet No. 2 and Askern oil boreholes, together with the gamma-ray correlations on (Figure 5), almost certainly indicate the B. bilinguis sensu stricto and late form marine bands. The late form band may also be represented by L. mytilloides, only 7.46 m below the Bilinguites superbilinguis Marine Band in Moss Oil Borehole (Figure 6).

Beds between the Bilinguites bilinguis and B. superbilinguis marine bands

In contrast to the lower part of the Millstone Grit, the beds between the B. bilinguis and superbilinguis marine bands, in the middle part of the Marsdenian Stage, exhibit less marked northerly or north-easterly thinning, being 45 m thick in Scaftworth No. 2 Oil Borehole and between 22 and 31 m in boreholes along and beyond the north-eastern margin of the Gainsborough Trough. Except in Scaftworth No. 2 and Warmsworth oil boreholes, these beds consist of mainly argillaceous rocks below, with some sandstones in the upper part.

The argillaceous strata comprise some fissile mudstones near the base, and silty mudstones interbedded with siltstones above. They are medium grey to black, appreciably micaceous and contain a few ironstone nodules. In Askern Oil Borehole there is a thin sandstone in the upper part and a seatearth at the top of these strata, which may equate with two fairly thin, fine-grained sandstones and a thin coal respectively in Warmsworth Oil Borehole. A mudstone seatearth occurs at the same stratigraphical level in Trumfleet No. 5 Oil Borehole.

The overlying sandstones are mainly fine to medium grained and moderately to well sorted, and are interbedded with thin silty mudstones and/or siltstones; in the Trumfleet oil boreholes they are more massive and contain some coarse-grained varieties. The lower of the two fairly thin sandstones at approximately the same stratigraphical level in Barlow Oil Borehole also contains some coarse grains. Some of these sandstones are poorly cemented, but siliceous or calcareous matrices are reported in others. Mixed fluviodeltaic origins are envisaged.

In contrast, most of the beds between the B. bilinguis and B. superbilinguis marine bands in the slightly thicker sequence within Scaftworth No. 2 Oil Borehole consist of sandstones. Those in the lower and middle parts of the sequence are white to pale grey, fine to coarse grained, moderately to well sorted, regularly cross-bedded and massive, whereas those in the upper part, as in the other boreholes, are mainly white, fine-grained, well sorted and contain thin interbedded siltstones. They suggest an upward passage from essentially deltaic to fluvial deposition. All these sandstones lie at the same stratigraphical level as the Guiseley Grit of the Leeds–Bradford area (Edwards et al., 1950, pp. 8, 15, fig. 4; Stephens et al., 1953, pp. 50 and 58, fig. 10) and the Ashover Grit of Derbyshire (Smith et al., 1967, p.68, 70–71, figs. 6 and 7). The continuations to the south of the district are referred to as 'Ashover Grit' by Smith et al. (1973, p.16, 20–21, fig. 5, pl. II).

The top of the sandstones forms a seatearth in Trumfleet Nos. 1 and 2 oil boreholes, and in some other boreholes there are mudstone seatearths and traces of coal in the medium grey to black, locally micaceous, carbonaceous and pyritic, silty mudstones and siltstones which overlie the sandstones and continue up to the B. superbilinguis Marine Band. Except in the Hatfield oil boreholes these argillaceous strata are not more than 5 m thick and, in places, they may include the Lingula-bearing basal part of the B. superbilinguis Marine Band at their top.

Bilinguites superbilinguis Marine Band

Faunas from the Superbilinguis Marine Band have been found in five boreholes and possibly also in a sixth. In Askern Oil Borehole 0.3 m of black mudstone at 963.47 m yielded Anthracoceras or Dimorphoceras sp., Bilinguites superbilinguis, Caneyella sp. and a palaeoniscid scale. In Moss Oil Borehole (Figure 6) L. mytilloides, Orbiculoidea nitida, productoid fragment, B. superbilinguis, an ostracod and a palaeoniscid scale were found in 4.60 m of strata. In the Trumfleet No.1 Oil Borehole 0.3 m of black mudstone at the same stratigraphical level yielded B. superbilinguis in abundance; the underlying black silty mudstone, apparently about 6 m thick according to the borehole section, contains two Lingula-bearing bands. In Trumfleet No. 2 Oil Borehole Lingula mytilloides, Crurithyris sp., B. superbilinguis, Cancelloceras sp. and Verneuilites sigma were found in 0.9 m of dark grey to black carbonaceous mudstone, with Eingula' apparently ranging through about 1 m of similar strata both below and above. Although Trumfleet No. 3 Oil Borehole was apparently not cored at the appropriate part of the sequence, 'goniatites' and 'fossil ghosts' are recorded from there in the borehole log. The marine band may be just as thick farther east: in Belton Oil Borehole, 3.0 m of micaceous mudstone and siltstone at 1321 m yielded L. mytilloides, Orbiculoidea cf. nitida, B. cf. superbilinguis, Idiognathoides sulcatus sulcatus, hindeodellid bars and indeterminate fish debris. L. mytilloides and ammonoid spat were found in the underlying 3 m of strata. A layer of phosphatised bioclastic debris is reported from the base of the marine band in this borehole. In Trumfleet No. 1 Oil Borehole there is a distinct, although not very marked, gamma-ray peak at the level of the main part of the marine band, with two smaller peaks corresponding to the Lingula-bearing layers in the underlying 4 m. A comparable, distinct, but not particularly large gamma-ray peak, with or without one or two closely underlying subsidiary peaks, is discernible in most of the other boreholes for which geophysical logs are available (Figure 5), and in Trumfleet No. 5 Oil Borehole the peak is virtually coincident with a thin white crystalline limestone.

Beds between the Bilinguites superbilinguis and Cancelloceras cancellatum marine bands

The beds between the B. superbilinguis and C. cancellatum marine bands, which lie within the upper part of the Marsdenian Stage, are from 17 m to 35 m thick, except in Belton Oil Borehole, where they are only about 5.5 m thick. In contrast with the underlying parts of the Millstone Grit succession, however, the thicknesses in Scaftworth No. 2 and Warmsworth oil boreholes in the middle of the Gainsborough Trough are similar to, or even less than those in most of the boreholes to the north. The lower beds are predominantly argillaceous, but, with the apparent exception of Hatfield No. 2 Oil Borehole, much of the upper part consists of sandstone.

The lower strata, in some boreholes forming more than two thirds of the sequence, consist of mudstones and silty mudstones, with some siltstones near the top. They are medium grey to black, locally carbonaceous and pyritic, but apparently not particularly micaceous. Some ironstone nodules are present and, in a few bes, there are either one or two thin sandstones near the top. In Hatfield No. 1 and some of the Trumfleet oil boreholes there is evidence of one or more mudstone or sandstone seatearths and traces of coal, either near the top of the argillaceous strata or in the lower part of the overlying sandstones. In Moss Oil Borehole (Figure 6) the argillaceous strata include three layers containing Carbonicola sp. and two intervening layers containing L. mytilloides, the higher of which also yielded an orthocone nautiloid. A thin black mudstone about 4 m above a coal and seatearth in Trumfleet No.1 Oil Borehole is recorded as containing abundant 'Lingula' and may equate with the higher Lingula layers in Moss Oil Borehole. A similar 'Lingula'-bearing black mudstone was reported from a comparable stratigraphical level in Askern Oil Borehole, but BGS has neither identification records nor fossils from either occurrence. This Lingula band may equate with the Verneuilites sigma Marine Band occurring west of Sheffield (Davies, 1941, pp. 241–243; Stevenson and Gaunt, 1971, pp. 178–184, 232–234, fig. 15, pl. XIX). The Carbonicola-bearing strata above it in Moss Oil Borehole, which are 5.75 m thick, contain C. deansi, C. lenicurvata and C. pseudacuta.

The sandstones in the upper part of this interval are mainly white to pale grey and brown, fine-grained and less commonly medium grained, silty and locally micaceous or slightly calcareous, and also reportedly feldspathic in some boreholes. Only in Trumfleet No. 5 Oil Borehole have any coarse-grained, poorly sorted varieties been noted. In some boreholes the sandstones are interbedded with silty mudstones and siltstones. Their general characteristics suggest fluvial deposition. These sandstones occur at the same stratigraphical level as the Huddersfield White Rock of western Yorkshire (Bromehead et al., 1933, pp. 18–19, 65–68), the Rivelin Grit west of Sheffield (Eden et al., 1957, pp. 18–20, fig. 4) and the Chatsworth Grit of Derbyshire (Smith et al., 1967, pp. 68–69, 73–74, figs. 6 and 7). They continue as thin and insignificant sandstones immediately south of the district, but farther south thicken to at least 70 m and become locally coarse grained (Smith et al., 1973, pp. 16, 22, fig. 5, pl. II).

The overlying strata, up to the C. cancellatum Marine Band, are less than 6 m thick, except in Hatfield No. 2 Oil Borehole, and consist mainly of medium grey to black, variously micaceous, pyritic and carbonaceous mudstones, silty mudstones and siltstones containing some 'ironstone' nodules and locally a thin sandstone. In the Trumfleet oil boreholes, a mudstone or sandstone seatearth and traces of coal occur within these strata with, in the No. 1 borehole, a 'Lingula' band recorded immediately below (Figure 6), at a level that corresponds with a minor gamma-ray peak in both the No. 1 and No. 5 boreholes. A similar minor peak, close below the more marked peak indicating the C. cancellatum Marine Band, is discernible in the geophysical logs of several other boreholes. In contrast, a 'Lingula' band is recorded from above a thin coal and subjacent sandstone seatearth in Askern Oil Borehole. BGS has no identifications or fossils from either occurrence, but in Moss Oil Borehole (Figure 6) L. mytilloides occurs between 1.35 and 1.20 m below the C. cancellatum Marine Band. There are several records of Lingula-bearing strata in the beds below the C. cancellatum Marine Band to the south of the district, in Derbyshire (Smith et al., 1973, p.22, pl. II; Smith et al., 1967, pp. 69, 74–75) and west of Sheffield (Eden et al., 1957, pp. 18, 20–21, fig. 4; see also Stevenson and Gaunt, 1971, pp. 182–183, 239, pl. XIX).

Cancelloceras cancellatum Marine Band

Faunal evidence of the C. cancellatum Marine Band, which lies at the base of the Yeadonian Stage, was found in four boreholes. In Trumfleet No.1 Oil Borehole Lingula sp., Dunbarella cf. elegans, Anthroceratites sp., Agastrioceras carinatum, Cancelloceras cancellatum, C. crencellatum, an indeterminate ostracod and Elonichthys sp. were recovered from 2.7 m of dark grey fissile mudstone at a level corresponding to a distinct, although not very high peak on the gamma-ray log. A similar fauna, but without C. cancellatum, ranges through 3.25 m of strata in Moss Oil Borehole. The Askern Oil Borehole yielded A. carinatum and C. crencellatum from 1.8 m of black 'fetid' mudstone at the equivalent stratigraphical level. In Belton Oil Borehole echinoderm debris, Serpuloides stubblefieldi, a turreted gastropod, Lingula mytilloides, Orbiculoidea sp., Productus carbonarius, Cancelloceras crencellatum, Dithyrocaris sp. (carapace and telson) and indeterminate fish debris were found in 3.1 m of strata which passed up from grey, slightly micaceous siliceous limestone and/or calcareous siltstone into black micaceous mudstone. The gamma-ray peak at the level of the C. cancellatum Marine Band in Trumfleet No. 1 Oil Borehole can be matched with similar and, in some places, more strongly marked peaks recorded in several other boreholes. However, the presence of a strong peak intermediate between those marking the C. cancellatum and Cancelloceras cumbriense marine bands in Trumfleet Nos. 1 and 5 oil boreholes (see below) casts doubt on the precision of these gamma-ray correlations in certain boreholes. The C. cancellatum Marine Band has been widely recognised to the south of the district (Smith et al., 1973, pp. 16, 23–24, pl. II), and comparable faunas found to the east of the district are also presumed to indicate the band (Gaunt et al., 1992, p. 7, fig. 3).

Beds between the Cancelloceras cancellatum and C. cumbriense marine bands

The beds between the C. cancellatum and C. cumbriense marine bands, which form the lowest part of the Yeadonian Stage, vary from only 6 m to 13 m in thickness, apparently randomly, and consist largely of medium-grey to black, partly silty and locally pyritic mudstones. A thin but marked gamma-ray trough, immediately above the peak signifying the C. cancellatum Marine Band, is shown as a thin sandstone, a thin coal and a thin siltstone on the lithological logs of Scaftworth No. 2, Warmsworth and Hatfield No. 2 oil boreholes. In Axholme No. 1 and less obviously No. 2 oil boreholes the thickness of this trough suggests the presence of some siltstone or sandstone. Thin sandstones were also noted at this stratigraphical level in Walkeringham No. 1 and Ranskill No. 1 oil boreholes in the middle of the Gainsborough Trough immediately south of the district (Smith et al., 1973, p.25), but they are rare or absent elsewhere.

Approximately half way between the gamma-ray peaks corresponding to the C. cancellatum and C. cumbriense marine bands in Trumfleet No. 1 Oil Borehole, there is an even stronger peak, but the only difference recorded from the cores at this level is the slightly calcareous nature of the black mudstones. A similar strong peak is recorded at the same level in Trumfleet No. 5 Oil Borehole, and its possible presence elsewhere throws doubt upon the precise gamma-ray correlations of the C. cancellatum Marine Band in certain boreholes. In Moss Oil Borehole Carbonicola pseudacuta, Naiadites sp. cf. productus and Geisina arcuata were found in 2.42 m of strata which range up to 0.76 m below the C. cumbriense Marine Band. The log of Askern Oil Borehole indicates a 'Lingula'-bearing layer close below the C. cumbriense Marine Band, but BGS has no further information on, or fossils from this layer. 'Lingula'-bearing beds are recorded from, a comparable stratigraphical level in Tickhill No. 1, Walkeringham No. 1 and possibly several of the Gainsborough oil boreholes in the middle of the Gainsborough Trough immediately south of the district (Smith et al., 1973, pp. 23, 25, pl. II).

Cancelloceras cumbriense Marine Band

Three boreholes in the district provide faunal evidence of the C. cumbriense Marine Band. The thickest sequence, 2.20 m in Moss Oil Borehole, contains L. mytilloides, Dunbarella sp., Anthracoceratites sp., C. crenulatum, C. cumbriense and fish debris. In Trumfleet No. 1 Oil Borehole, 0.6 m of grey mudstone yielded Caneyella multirugata, an indeterminate costate pectinoid, Posidonia sp. Anthracoceratites sp., Cancelloceras crenulatum, C. cumbriense and cf. Homoceratoides, and are marked by a distinct but not very high gamma-ray peak. At the same stratigraphical level in Askern Oil Borehole, Posidonia sp., an indeterminate mollusc spat, Anthracoceratites sp., C. cumbriense and 'Guilielmites' were found in about 0.15 m of black mudstone; the diagrammatic section of this borehole suggests that the marine band was somewhat thicker than the depth range of these fossils implies. The position of the C. cumbriense Marine Band can be identified in some other boreholes by a minor but fairly distinct peak on their gamma-ray logs, but in the comparable logs of certain boreholes, including Scaftworth No. 2, Warmsworth and the Axholme oil boreholes, its position is less certain.

Beds between the Cancelloceras cumbriense and Subcrenatum marine bands

The beds between the C. cumbriense and Subcrenatum marine bands, which form the upper part of the Yeadonian Stage, range in thickness from less than 10 m in Belton Oil Borehole to 26 m in Askern Oil Borehole, but no clear pattern of thickness variation is discernible. The lower part of the sequence is dominantly argillaceous, but sandstones occupy much of the upper part, except in the Hatfield oil boreholes.

The lower strata, generally forming not more than half of the sequence, are pale grey to black, locally micaceous and commonly silty mudstones, containing ironstone nodules. Some thin micaceous siltstones, and locally one or two thin fine-grained sandstones, are present near the top, apparently forming an interbedded passage into the overlying sandstones.

The upper sandstones are mainly white to pale grey (but with widespread brown staining), fine to medium grained, moderately to poorly sorted, locally micaceous and with some siliceous or calcareous cement. Some coarse-grained varieties occur in Trumfleet Nos. 1 and 5 and Barlow oil boreholes, and some poorly cemented layers are reported from several boreholes. Although much of the sandstone appears to be massive, a thin siltstone or mudstone, which in Scaftworth No. 2 Oil Borehole is 3 m thick, occurs in the middle or upper part in places; in Askern and Trumfleet No. 3 oil boreholes a mudstone seatearth is reported at this level. The sandstones, probably of fluviodeltaic origin, continue to the south and east of the district (Smith et al., 1973, pp. 16, 25, fig. 5, pl. II; Gaunt et al., 1992, p.7, fig. 3) and lie at the same strati-graphical level as the locally thicker Rough Rock of the central and southern Pennines. In Hatfield Nos. 1 and 2 oil boreholes, the equivalent strata are reported to be interbedded grey micaceous siltstones and silty mudstones, and this is supported by the gamma-ray logs.

The strata between the sandstones and the Subcrenatum Marine Band are not more than 4 m thick and consist of medium grey to black, locally silty mudstones and siltstones with, in some places, thin sandy layers. Some borehole records indicate the presence of a mudstone or sandstone seatearth and traces of coal, the latter presumably equivalent to the Pot Clay Coal of the eastern Pennines and adjacent areas.

Coal Measures

More than 130 boreholes and colliery shafts have proved Coal Measures strata within the district, and additional information about the succession is available from colliery workings and underground boreholes. However, fewer than 20 boreholes penetrated to the base of the Coal Measures, and most of these are concentrated near the centre of the district, so that the thickness variations of these beds are not known in detail. Moreover, these variations depend on both the original depositional thicknesses and the extent of subsequent erosion of the highest Coal Measures prior to the late Permian. In order to distinguish these two effects clearly, the thickness variations for two separate parts of the Coal Measures are given here. The Coal Measures up to the Aegiranum Marine Band (top of Westphalian B) are estimated to be more than 930 m in the south-west of the district and just under 700 m in the north-west. The sequence thins somewhat between these western areas, and there is also an overall easterly thinning, probably to less than 500 m in places. These variations are mainly attributable to original depositional differences in thickness. The Coal Measures above the Aegiranum Marine Band are locally at least 510 m thick in the south-west, but probably not more than 150 m and 100 m in the south-east and north-east; they are entirely absent in parts of the north-west, where prelate Permian erosion has in places removed at least 100 m of strata below the Aegiranum Marine Band.

For descriptive purposes the sequence is divided into three parts corresponding to the Westphalian stages A, B and C/D (Figure 7). The relationship of these units to the Lower, Middle and Upper divisions of the Coal Measures used on the published maps (sheets 79 and 88) is also shown in (Figure 7).

Certain broad lithostratigraphical differences are apparent within the Coal Measures; they can be distinguished, in particular stratal ranges, by aspects such as the characteristics of sandstones, the incidence and thickness of coals, and the presence or absence of marine and/or 'Estheria' bands. These essentially lithostratigraphical considerations are summarised, with some interpretative comments in places, within the framework of the Westphalian stages. The principal coals, marine bands, 'Estheria' bands and sandstones are shown on (Figure 7).

Westphalian A strata

Westphalian A strata extend from the base of the Subcrenatum (Pot Clay) Marine Band to the base of the Vanderbeckei (Clay Cross) Marine Band, corresponding to the Lower Coal Measures of the published maps (sheets 79 and 88). They thin north-eastwards across the district from more than 550 to probably less than 300 m (Figure 9) and (Figure 10), and comprise three sequences differing considerably in cyclic development. The lowest sequence (Figure 7) and (Figure 8), up to and including what is probably the Burton Joyce Marine Band, is 135 m thick in Warmsworth Oil Borehole, but probably only about half as thick in the north-east. It contains up to eleven well-defined cycles, most of which have a marine band at the base; a few have locally thick sandstones and several have a thin coal or seatearth at the top. The cycles are in many respects similar to those in the upper part of the Millstone Grit and suggest a similar depositional environment.

The middle sequence (Figure 7) and (Figure 9), which continues up to the base of the Top Beeston Coal, thins northeastwards from nearly 240 to less than 140 m. Although at least 13 cycles are probably present, they are poorly defined, except near the top. No marine bands are known; the few coals are thin and at least some are impersistent. Thick sandstones, especially in the lower half of the sequence, suggest fluvial deposition beyond the reach of marine transgressions.

The highest sequence (Figure 7) and (Figure 10) thins generally north-eastwards from approximately 200 m probably to about 100 m, but expands locally in the north-west to just over 150 m. It contains up to 25 cycles, most of them with a coal at the top. Of the thicker coals the Top Beeston, Thorncliff, Parkgate and Flockton Thick are potentially valuable, but the Top Silkstone or Blocking Coal has too many partings to be workable. No marine bands are known, but the Low 'Estheria' Band in the lower part of the sequence may result from a slightly brackish incursion. Sandstones are generally thin and impersistent, but a few of them, notably the Slack Bank Rock and the Parkgate Rock, expand markedly in places and locally cut down considerably into the underlying strata, either as channel-fill or major scour deposits. Although deposition on a low-lying swampy plain is envisaged, it appears that at times there may have been appreciable variations in drainage base level. Substantial thickness changes in individual cycles, in places over short distances laterally, may be due partly to drainage base-level variations or to differential compaction, but some may mark minor contemporaneous tectonic activity, notably slight thinning across the northern margin of the Gainsborough Trough and marked variations on a north-easterly trend in northwestern areas (Figure 10).

Evidence of the lowest and middle sequences comes almost entirely from oil boreholes, which were rarely cored; thus the lithological successions are deduced mainly from chippings and gamma-ray logs. In contrast, the highest sequence has been proved by numerous cored boreholes for coal, so that there is much more palaeontological data, especially concerning the non-marine mussel faunas.

Subcrenatum (Pot Clay) Marine Band

The Subcrenatum (Pot Clay) Marine Band is recognisable on most gamma-ray logs by a distinct, but not necessarily large peak. In Warmsworth Oil Borehole, for example, the strata coinciding with the peak are described from chippings as dark grey to black, fissile, laminated and partly silty 'shale'. The gamma-ray-based identifications of the marine band in (Figure 8) correlate with the position of the marine band in Tickhill No. 1 and Ranskill No. 1 boreholes, just south of the district, where diagnostic faunas were proved (Smith et al., 1973, p.48, pl. III). In Moss Oil Borehole, however, a fauna typical of the Subcrenatum Marine Band, comprising Planolites ophthalmoides, Serpulites?, L. mytilloides, Homoceratoides sp., Gastrioceras subcrenatum, Hindeodella sp. and platformed conodonts, occurs in 1.77 m of strata lying at least 12 m above where this marine band would be expected by comparison with Trumfleet No. 1 (Figure 6) and other nearby oil boreholes, and it is possible that the above fauna is from the Honley Marine Band.

The beds between the Subcrenatum and Honley marine bands

The beds between the Subcrenatum and Honley marine bandsthin north-eastwards from almost 45 m in Warmsworth Oil Borehole to 19 m and 13 m in Axholme No. 1 and Barlow oil boreholes respectively; they may be largely faulted out in Askern Oil Borehole. They contain at least four cycles: above relatively thick argillaceous strata, which in places comprise more than half the sequence, the principal components are, in ascending order, the Crawshaw Sandstone, Soft Bed Coal, Soft Bed faunal bands, Springwood Marine Band and Clay Coal.

Crawshaw Sandstone

The Crawshaw Sandstone is mainly white, but with some brown staining, fine-grained, well cemented and locally slightly calcareous. It thins generally north-eastwards.

Soft Bed Coal

The Soft Bed Coal, at the top of the lowest cycle, was detected in chippings from Hatfield No. 2, and by a sharp gamma-ray trough in Scaftworth No. 2 and Warmsworth oil boreholes; it may also be represented by coal chippings from about the same horizon in some of the Trumfleet oil boreholes. No coal was found in a short length of core through these beds in Hatfield No. 1 Oil Borehole, but the top of the siltstone-seatearth at 1127.7 m probably indicates its position.

Soft Bed faunal bands and Springwood Marine Band

The three Soft Bed faunal bands (Eagar, 1947, 1952) and the Springwood Marine Band are probably included in the core from Hatfield No. 1 Oil Borehole, logged by N Aitkenhead. Dark grey silty mudstone, 0.6 m thick at 1127.7 m, contains Carbonicola including C. rectilinearis?, Spirorbis sp., G. arcuata and fish debris including acanthodian spines, Elonichthys sp. scale, palaeoniscid scales, Rhabdoderma sp. and Rhizodopsis sp., and probably represents the lowest Soft Bed faunal band. The overlying sandy siltstones with a seatearth top are succeeded at 1123.5 m by 0.6 m of dark grey silty mudstone reportedly containing a 'polyzoa' fragment, ?shell fragment, ?ostracod and fish debris. BGS collections include ?mussel fragment, Spirorbis sp., ostracods and fish debris, with conflicting depth records of 1114.0 m and 1123.2 m. Whether these fossils are from the mudstone at 1123.5 m or not, the probability is that they represent the middle Soft Bed faunal band, the basal part of which, in some adjacent districts, contains Lingula and is differentiated as the Holbrook Marine Band. At 1120.4 m, above further sandy siltstones with a seatearth top, the lower part of 1.7 m of dark grey mudstone contains abundant Lingula mytilloides and fish debris including Rhadinichthys sp. This is probably the Springwood Marine Band, which in places is associated with the highest Soft Bed faunal band. Gamma-ray peaks in some of the other boreholes may indicate one or more of these faunal bands. The entire sequence is similar to, but thinner than, that proved in Tickhill No. 1 Oil Borehole just south of the present district (Smith et al., 1973, p.49, pl. III).

Clay Coal

The Clay Coal at the top of the fourth cycle was detected in chippings from several oil boreholes and, although not present in the core from Hatfield No. 1 Oil Borehole, it can be placed in the section at about 1115 m, where a sharp gamma-ray trough occurs just above a mudstone-seatearth in the core.

Honley Marine Band

The Honley Marine Band is represented in the core from Hatfield No. 1 Oil Borehole by grey mudstone containing Posidonia sp. nov., G. arcuata and fish debris including Rhizodopsis sp. and palaeoniscid scales at 1114.0 m. It may also be marked in Trumfleet No. 1 Oil Borehole by the occurrence of 'Lingula' at about 930 m. Both occurrences coincide with a small but distinct gamma-ray peak which can be correlated across several other boreholes (Figure 8). The position of the Honley Marine Band in Moss Oil Borehole (Figure 6) is uncertain. It may be represented by a fauna given above which, although typical of the Subcrenatum Marine Band, lies at least 12 m above where this marine band would be expected. Alternatively, the Honley Marine Band may be represented in Moss Oil Borehole by P. ophthalmoides and L. mytilloides at a level less than 6 m below the Listeri Marine Band.

The beds between the Honley and Listeri marine bands

The beds between the Honley and Listeri marine bands are up to 18 m thick in the Trumfleet, Hatfield and Axholme oil boreholes but thin to just under 10 m in Scaftworth No. 2 and Barlow oil boreholes to the north and south respectively. They apparently contain only one cycle, comprising argillaceous beds, which in places comprise more than half the sequence, overlain by the Sub-Alton Sandstone and Ganister Coal.

Sub-Alton Sandstone

The Sub-Alton Sandstone is generally thicker in the east and north, and may split westwards towards Warmsworth Oil Borehole. It varies from white to brown and is fine-grained, silty, micaceous, partly calcareous and locally feldspathic, and in Warmsworth Oil Borehole is described as laminated.

Ganister Coal

The Ganister Coal was proved by chippings from several oil boreholes and is indicated by troughs on the gamma-ray logs from other boreholes. The chippings are variously described as vitreous, pyritic, lignitic and bright. The horizon is probably represented in Moss Oil Borehole by the seatearth lying about 3 m below the Listeri Marine Band.

Listeri Marine Band

The Listeri Marine Band is clearly recognisable in most gamma-ray logs (Figure 8) by its characteristically high peak (Ponsford, 1955, pp. 34–35; Knowles, 1964). In Scaftworth No. 2 Oil Borehole, chipping samples from the marine band are described as dark grey, pyritic, carbonaceous mudstone, and the same beds in Trumfleet No. 1 Oil Borehole seem to be particularly pyritic. In the nearby Moss Oil Borehole (Figure 6) the marine band is at least 1.14 m thick and yielded an indeterminate gastropod, Caneyella multirugata, Dunbarella papyracea, Posidonia gibsoni, Posidonia sp. nov., orthocone nautloid, Anthracoceratites sp. and Gastrioceras listeri.

The beds between the Listeri and Meadow Farm marine bands

The beds between the Listeri and Meadow Farm marine bands thin northwards and eastwards from almost 34 m in the Warmsworth Oil Borehole to between 17 and 25 m in the other oil boreholes, and contain at least two cycles. Much of the sequence is argillaceous and is interbedded, in ascending order, with impersistent sandstones, the Parkhouse Marine Band, the Loxley Edge Rock and the Forty-Yards Coal.

The sandstones in the lower part of the sequence in Scaftworth No. 2 and Warmsworth oil boreholes are brown stained, moderately sorted, coarse grained and poorly cemented, and occur at the same stratigraphical level as sandstones recorded farther south and south-west (Smith et al., 1973, p.54, pl. III; Smith et al., 1967, pp. 111–112, fig. 9; Eden et al., 1957, pp. 44–45, fig. 6). These sandstones are thin or absent in the other oil boreholes. Carbonicola sp., Curvirimula sp., Geisina arcuata and fish debris were present in Moss Oil Borehole (Figure 6) in the 1.29 m of argillaceous strata which overlie the Listeri Marine Band.

Parkhouse Marine Band

The Parkhouse Marine Band (Smith et al., 1967, pp. 111–112, fig. 9; see also Eden et al., 1957, pp. 44–45, fig. 6) is traceable by either one or two closely spaced, distinct gamma-ray peaks in most of the oil boreholes (Figure 8). Chippings from this horizon in Warmsworth Oil Borehole are of medium to dark grey, laminated silty 'shale'. Although no gamma-ray peak is discernible in Trumfleet No. 5 Borehole, traces of mudstone-seatearth are recorded from about the same level, which presumably mark the top of the lowest cycle in this sequence. In Moss Oil Borehole (Figure 6) two thin layers, each containing foraminifera and L. mytilloides, are separated by a parting containing Carbonicola sp. and G. arcuata. Similarly, there is a thin sandstone between the two peaks in Scaftworth No. 2 Oil Borehole. These occurrences suggest that, in places, the Parkhouse Marine Band is split and an incipient cycle is developed between them. In Moss Oil Borehole (Figure 6) P. ophthalmoides found slightly higher in the sequence may relate to either the Parkhouse or Meadow Farm Marine Band.

The Loxley Edge Rock is generally thin and locally absent in the areas proved by the oil boreholes. It is white or grey with some brown staining, fine-grained, commonly silty and micaceous, well cemented, calcareous in places and locally carbonaceous and sideritic.

The Forty-Yards Coal was detected in chippings from Hatfield Nos. 1 and 2 oil boreholes and by a marked gamma-ray trough in Warmsworth and Scaftworth No. 2 oil boreholes. The lithological log based on the chippings from the latter borehole suggests that there is also an impersistent lower leaf of coal.

The Meadow Farm Marine Band is recognisable by a distinct gamma-ray peak and is correlated as shown in (Figure 8). Under its former name of the Forty-Yards Marine Band (see Smith et al., 1967, p.114), it can be traced to the south of the district (Smith et al., 1973, p.53, pl. III). In the Moss Oil Borehole (Figure 6) the band is thin and contains L. mytilloides.

The beds between the Meadow Farm and Amaliae marine bands

The beds between the Meadow Farm and Amaliae marine bandsthin north-eastwards from about 20 m in Scaftworth No. 2 Oil Borehole to only about 4 m in Barlow and Axholme oil boreholes. Two cycles may be present; the junction between the two is suggested by chippings of mudstone-seatearth in Askern and some of the Trumfleet oil boreholes, and by a low but distinct gamma-ray peak in several other boreholes, to lie in mudstones no more than 5 m above the Meadow Farm Marine Band. The rest of the sequence is mainly argillaceous, but with impersistent sandstones in the upper part and the Norton Coal at the top.

The sandstones in the sequence were proved in Scaftworth No. 2 and Warmsworth oil boreholes to be white, pale brown and grey, fine to medium grained, silty, partly laminated and calcareous. They are also recorded to the south-west of the district (Smith et al., 1967, pp. 113–114, fig. 9). The Norton Coal was detected in chippings from most of the Trunifleet and Hatfield oil boreholes and by its gamma-ray trough in the Scaftworth No. 2 and, with less certainty, in Warmsworth oil boreholes.

The Amaliae Marine Band can be recognised in most gamma-ray logs (Figure 8) by a distinct peak, although of varying magnitude; in Trumfleet No. 1 Oil Borehole the peak coincides with chippings of black coaly 'shale'. The same horizon in Moss Oil Borehole (Figure 6) lies in the lower part of a thick sequence rich in fish debris, including platysomids and palaeoniscids. In Warmsworth Oil Borehole, both the gamma-ray log and the chippings suggest that the marine band may be washed out by the Wharncliffe Rock.

The beds between the Amaliae and Langley marine bands

The beds between the Amaliae and Langley marine bandsthin slightly northwards and eastwards from about 18 m in Warmsworth Oil Borehole to between 7 and 15 m in the other boreholes, and they apparently contain only one cycle. In some oil boreholes almost the entire sequence is argillaceous, but in others the Wharncliffe Rock is present and the Upper Band Coal occurs at least locally at the top of the cycle. The Wharncliffe Rock, where present, lies generally within the upper part of the sequence, but in the Warmsworth and Askern oil boreholes it comprises almost all of the succession. It is variously white, buff, pale grey and brown, fine to medium grained, poorly to well cemented and locally slightly calcareous. In Trumfleet No. 5 and possibly in some of the other oil boreholes, the seatearth of the Upper Band Coal is developed at its top.The coal was detected in chippings from the Trumfleet No. 1 and Hatfield No. 2 oil boreholes. The Langley Marine Band, formerly the Upper Band Marine Band (Godwin, 1960), is proved in most oil boreholes as a generally distinct peak which varies considerably in magnitude, possibly due to the band not being fully marine in parts of the district. In Hatfield No. 1 Oil Borehole the peak coincides with chippings of dark grey to black mudstone, and in Moss Oil Borehole the band lies in the middle of a thick sequence rich in fish debris, including platysomids and palaeoniscids.

The beds between the Langley and Burton Joyce marine bands

The beds between the Langley and Burton Joyce marine bands are 4 to 7 m thick, a range compatible with thicknesses of 5.9 m and 7.6 m noted elsewhere (Eden, 1954, p.101 and Smith et al., 1967, p.116, fig. 9, respectively) between the Upper Band seatearth and the Burton Joyce Marine Band. Only one cycle is discernible and the sequence is entirely argillaceous, except for a thin silty sandstone in its upper part in Warmsworth Oil Borehole and traces of inferior coal and mudstone-seatearth in chippings from near the top in Trumfleet No. 1 and Askern oil boreholes.

The Burton Joyce Marine Band is tentatively placed at a minor, and in some oil boreholes ill-defined, gamma-ray peak occurring 4 to 7 m above the Langley Marine Band peak. In view of the low magnitude and poor resolution of this peak, the bed may not be fully marine. In Moss Oil Borehole it lies near the top of a thick sequence rich in fish debris, including platysomids and palaeoniscids.

The beds between the Burton Joyce Marine Band and the Better Bed Coal

The beds between the Burton Joyce Marine Band and the Better Bed Coalthin eastwards and northwards from 127 m in Warmsworth Oil Borehole to about 85 m in Axholme No. 1 and possibly only 65 m in Barlow Oil Borehole. Thin coals or seatearths locally suggest up to six cycles, but generally there is little cyclic evidence. Thick sandstones in the middle and upper parts of the sequence are shown on the Goole (79) and Doncaster (88) geological sheets as equivalent to the Elland Flags of western Yorkshire, but a correlation with, in ascending order, the Greenmoor Rock and Grenoside Sandstone of south Yorkshire (Mitchell et al., 1947, p.12, fig. 4; Eden et al., 1957, pp. 49–52, fig. 6) is now considered more valid.

The argillaceous strata underlying the Greenmoor Rock comprise, on the evidence of chippings and gamma-ray logs, an upwards-coarsening sequence from mudstones to siltstones, although the occurrence of a thin coal or seatearth near their top in some oil boreholes suggests that two cycles are present.

Greenmoor Rock

The Greenmoor Rock apparently continues the upwards-coarsening sequence. Its lower part is generally silty, 'muddy' and micaceous, with interbedded siltstones, whereas the upper part is thicker bedded, more massive and locally feldspathic and calcareous. It is generally a white to pale grey and locally brown, fine-grained, well-sorted sandstone, with some medium-grained sandstone in Belton and Crowle oil boreholes in the east. Large white, brown and green micas were noted in Hatfield No. 1, Axholme No. 2 and Crowle oil boreholes, as they have been in comparable strata farther south near East Retford (Smith et al., 1973, p.55). A thin coal or seatearth commonly occurs near or at the top of the Greenmoor Rock.

The strata between the Greenmoor Rock and the Grenoside Sandstone are mainly argillaceous, ranging from black and locally carbonaceous mudstones to micaceous siltstones, but they also contain some impersistent, thin, white to pale grey and brown, fine-grained silty sandstones. Two distinct seatearths in Trumfleet No. 1 Oil Borehole suggest that parts of at least three cycles are present, and fragments of Rhabdoderma sp. and Rhizodopsis sauroides at 1228 m in Belton Oil Borehole appear to mark the base of the highest of these cycles. The 'Kilburn Marker', a distinctive thin, black, berthierinitic siltstone occurring in the upper part of these strata farther south (Strong, in Falcon and Kent, 1960, p.52) may be represented by thin, black, carbonaceous 'shale' at 797 m in Trumfleet No. 1 Oil Borehole, by several thin, greenish grey, berthierinitic siltstones within 6 m of mudstone at 808 m in Trumfleet No. 5 Oil, Borehole and by thin, black, pyritic, carbonaceous 'shale' at 1216 m in Crowle Oil Borehole, although the last of these occurrences seems to lie within the Grenoside Sandstone.

Grenoside Sandstone

The Grenoside Sandstone consists of sandstone with interbedded siltstone and silty mudstone. The sandstone is white to pale grey, locally greenish or brownish, and fine to medium grained, though there are coarse-grained layers in Axholme No. 1 Oil Borehole; it is locally feldspathic and calcareous. Large white, brown, bronze and green micas, apparently concentrated on laminations, were noted in most of the boreholes, as they have been in comparable strata further south (Smith et al., 1973, p.55; Hewitt and Brunstrom, 1966, p.553). Ripple bedding was seen in core from the highest sandstone in Axholme No. 2 Oil Borehole. Two thin coals in Warmsworth Oil Borehole and a thin coal or seatearth elsewhere suggest that parts of two, and possibly three, cycles are present. Where a thin coal or seatearth lies close to the top of the Grenoside Sandstone, as in Trumfleet Nos. 1 and 3 oil boreholes, it is probably a lower leaf of the Better Bed Coal, which is commonly split in this way.

Better Bed Coal

Argillaceous strata up to 7 m thick lie between the Grenoside Sandstone and the Better Bed Coal in some oil boreholes. The Better Bed Coal, known as the Kilburn farther south, was proved in most oil boreholes but was absent from core through the appropriate horizon in Axholme No. 2 Oil Borehole, although its seatearth was present. In several of the oil boreholes there is evidence of two distinct leaves, as in the equivalent Grenoside Sandstone Coal in parts of the Sheffield district (Eden et al., 1957, p.53).

The beds between the Better Bed and Top Beeston coals

The beds between the Better Bed and Top Beeston coalsthin north-eastwards from just over 110 m in Warmsworth and Scaftworth No. 2 oil boreholes to between 72 and 75 m in Axholme No. 1, Crowle and Barlow oil boreholes. The presence of thin coals and seatearths suggest up to seven cycles, but they are difficult to correlate except near the top. Some of the coals in the middle of the sequence may correspond to the Black Bed and Crow coals of west Yorkshire but only the Low Beeston Coal near the top is readily identifiable.

The argillaceous strata overlying the Better Bed seatearth in cores from the Axholme No. 2 Oil Borehole were 2.5 m of grey, bioturbated mudstone with Carbonicola aff. communis, Carbonicola aff. martini, Curvirimula aff. trapeziforma and Naiadites sp. in the lowest 0.4 m and thin interbedded siltstone near the top. Indeterminate mussels occurred 2.75 m higher in a ripple-bedded layer within pale grey, fine-grained, well-sorted, micaceous sandstones containing small-scale cross-bedding and bioturbation, the latter suggesting the presence of cf. Planolites.

Most of the argillaceous strata at higher levels are silty mudstones and siltstones, and are commonly micaceous. They contain ironstones, apparently nodular, that are noted mainly near the supposed Black Bed and Crow coals in the middle of the sequence and also towards the top of the sequence, locally associated with another thin coal. The interbedded sandstones are variously white, buff, grey and pale brown, fine-grained and commonly silty and micaceous; some in the lower part of the sequence contain large white and coloured micas.

Two of the cored boreholes for coal penetrated this sequence. In Pollington No. 1 Borehole (Edwards, 1951, pp. 223–225) about 60 m of strata below the Top Beeston Coal are similar in several respects to their correlatives in Crowle Oil Borehole; the thin coals and seatearths suggest that there are five cycles. Hemingbrough Borehole passed through a fault below the supposed Top Silkstone and penetrated a further 43 m of partly faulted strata containing two thin coals which may be the Better Bed (0.25 m) and Crow (0.46 m) coals (Figure 10). Mussels and Spirorbis sp. are present above the lower coal, and Planolites sp. occurs above the higher coal and also about 15 m higher, not far above a thin seatearth. Mussels were also found in mudstones about 3.5 to 7.9 m below the Low Beeston Coal at the bottom of Pollington No. 2 Borehole.

Low Beeston Coal

The Low Beeston Coal forms a poor-quality lower leaf to the Top Beeston at Kellingley Colliery, west of Kellington and just outside the district. In the north-west of the district it is indistinguishable from the Top Beeston, possibly being represented in the coaly seatearth of the latter in the West Haddlesey No. 1, Rawcliffe No. 2, Drax No. 2 and Great Heck boreholes. In other local boreholes, however, such as Camblesforth No. 3, Eskholme, Fenwick and Chapel Haddlesey, the Low Beeston is recognisable as up to 0.63 m of inferior quality and locally pyritic coal with 'dirt' layers, separated from the Top Beeston Coal by up to 11.5 m of beds. This local gap may increase and become general to the south and south-east where thin coal or 'coaly streaks' were detected about 5 m below the Top Beeston in Askern, Trumfleet No. 5 and Axholme No. 1 oil boreholes (Figure 9). In North Carr Borehole in the south-east of the district, a thin coal 3.60 m below the Top Beeston may be the Low Beeston.

The strata between the Low and Top Beeston coals consist of silty mudstone and siltstone with, in the south, some thin sandstones. The Top Beeston Coal commonly has the Beeston Rider Coal lying just above it. Both are thickest in the north-west, where they are over 1 m thick and up to 0.6 m thick respectively. Where the two coals are close together or united, the potentially workable thicknesses are substantial, reaching 2.34 m of coal within 2.56 m of strata in Gowdall Borehole. Where the Low and Top Beeston seams are close together, similarly thick coal sequences can result as, for example, in Pollington No. 2 Borehole where 2.0 m of coal lies within 2.29 m of beds. The gap between the Top Beeston and Beeston Rider is generally not more than 1 m, but reaches 2.65 m in Camblesforth No. 3 Borehole (Figure 10). Both coals thin to the east, being only 0.86 m and 0.01 m thick respectively, and separated by 1.33 m of mudstone in Airmyn Grange Borehole. In Drax No. 3 Borehole they are both cut out by a thick sandstone (see below). About 1.6 m of coal were proved in the Eskholme and Fenwick boreholes, although appreciable splitting occurs in the latter; in Trumfleet Borehole for coal, a short distance farther south, only 0.61 m of coal was found. Chippings and gamma-ray logs from the oil boreholes (Figure 9) suggest that the Top Beeston continues through the southern part of the district, and in the north-east Blyton Carr (Figure 10) and North Carr boreholes proved 0.76 m and 0.80 m of coal respectively. The Beeston Rider may be cut out by locally sandy siltstones in much of the south.

The Top Beeston commonly contains one or more layers of dull coal, which apparently increase in number and thickness southwards, but there is little evidence of the persistent 'hards' which occur farther west (Wandless et al., 1935). Pyritic coal, with a sulphur content of more than 5 per cent in places, is recorded from the highest part of the Top Beeston and from the Beeston Rider, and solid pyrite occurs locally; for example, 0.025 m of pyrite is present in the Top Beeston in Camblesforth No. 2 Borehole.

The beds between the Top Beeston and Beeston Rider coals and the Low 'Estheria' Band

The beds between the Top Beeston and Beeston Rider coals and the Low 'Estheria' Band are generally more than 18 m thick in the north-west and as far south as Trumfleet Borehole. They reach 32.16 m in Gowdall Borehole but thin eastwards to 15.18 m in Rawcliffe No. 2 Borehole (Figure 10); thicknesses farther south are largely uncertain. The expanded sequence between the Top Beeston and the Top Silkstone coals in Warmsworth Oil Borehole (Figure 9) suggests a thickness of about 45 m in the south-west, but only 13.19 m were proved in Blyton Carr Borehole in the south-east (Figure 10). Thin coals and seatearths are present, the highest coal being the Low Silkstone; they suggest up to five cycles, each consisting mainly of basal, locally fossiliferous mudstone succeeded by silty mudstone and siltstone with, in places, thin fine-grained sandstones near the top. In Drax No. 3 Borehole, however, 29.70 m of pale grey, medium-grained, cross-bedded sandstone with a conglomeratic base cuts down through all the Beeston coals. Planolites ophthalmoides is common near the base of the lowest cycle and occurs, with Anthracosphaerium? sp., Carbonicola cf. polmontensis, Curvirimula candela, Naiadites sp., Spirorbis sp., Geisina arcuata and fish debris, in some of the higher cycles; the uncommonly elongate Anthraconaia potoriba was found 7.20 m below the Low 'Estheria' Band in Ash Hill Borehole. The Low Silkstone Coal is up to 0.30 m thick in a few boreholes as far apart as Drax No. 2 and Blyton Carr, but it is generally less than 0.10 m thick and is absent in many boreholes.

The strata between the Low Silkstone Coal or its seatearth and the Low 'Estheria' Band are up to 1.5 m thick in the north-west, for example in Weeland Road Borehole, but they thin southwards and are absent in Blyton Carr and East Stockwith boreholes, as they are farther south (Smith et al., 1973, p.57). They range from mudstones to siltstones and locally contain ostracods and fish debris.

The Low 'Estheria' Band varies considerably in thickness, even across short distances, and reaches 3.65 m in Blyton Carr Borehole. In many boreholes it can be divided into a lower, dark grey to black, shaly mudstone only rarely more than 1 m thick and an upper, paler and silty mudstone containing ironstone layers and nodules; the latter is generally the thicker where the entire band is itself thick. In some boreholes, such as Lee Lane and Pincheon Green, the lower part of the band is absent. In others, the upper part has clearly been cut out, the most extreme example being in Barlow No. 2 Borehole where all but 0.15 m of the lower part is cut out by the Slack Bank Rock. The diagnostic 'Estheria' sp. nov. is more abundant in the lower part but associated Carbonicola sp., Curvirimula sp., ostracods and fish debris are generally more common in the upper part. In Selby No. 1 Borehole, 'Scaldia minuta' from about 829 m may be 'Estheria' and indicate the Low 'Estheria' Band (Edwards, 1951, p.232). Some old records of 'Naiadites', for example from 855.2 m in Lindholme Borehole, are now recognised as Estheria sp. nov. and it is possible that references to 'Naiadites' in relevant strata in some recent boreholes may also require revision.

The beds between the Low 'Estheria' Band and the Top Silkstone or Blocking Coal

The beds between the Low 'Estheria' Band and the Top Silkstone or Blocking Coal are 10.78 m thick in East Stock-with Borehole, and elsewhere generally exceed 4 m; in some areas there seems to be an inverse relationship between their thickness and that of the Low 'Estheria' Band. The 1.18 m proved in Camblesforth No. 2 Borehole may be reduced by faulting within the mudstones, which are described as soft; only one cycle is discernible. The basal strata are commonly thin silty mudstones, locally containing Curvirimula candela and C. subovata, and much of the upper part consists of siltstones with, in places, some thin fine-grained sandstones containing ripple bedding, contorted layers and bioturbation.

Top Silkstone or Blocking Coal

The Top Silkstone or Blocking Coal is commonly split into three, and locally up to six leaves with a maximum leaf thickness of 0.65 m and a maximum total coal thickness in Misson Borehole of 1.52 m. Except in the south, the leaves are spread within less than 3 m of strata. In the north-west, the lowest one or two and, in Camblesforth No. 2 Borehole, the lowest three leaves are partly or entirely of cannel coal and are generally less than 0.20 m in total, although locally they are almost up to 0.60 m; fish debris occurs in the mudstones between them. The middle one or two leaves, above up to 0.84 m of intervening mudstone-seatearth, have a maximum coal thickness in Roall Ings Borehole of 0.65 m and any mudstone-seatearth between them is generally less than 0.20 m. The highest one or two leaves, overlying up to 1.70 m of intervening mudstone-seatearth, may equate with the Silkstone or Blocking Rider Coal of areas to the west. These leaves comprise mainly inferior quality coal not more than 0.13 m thick in total. To the east, the lowest leaves pass into coaly streaks within seatearth, the middle leaves unite to only 0.24 m in Airmyn Grange Borehole and the upper leaves are represented only by seatearth. A similar pattern is apparent southwards towards Doncaster, with two leaves totalling 0.43 m of coal within 0.68 m of strata in Eskholme Borehole (Figure 10), although a 0.10 m lower leaf of cannel coal is present in Trumfleet Borehole. Appreciable thickness variations and localised splitting occur near the southern edge of the district. Wilsic Hall Borehole proved a single leaf 0.59 m thick, the upper part being cannel coal, but in Spital Croft Borehole nearby, three leaves comprise 0.78 m of coal within 1.12 m of strata, the lowest and highest being thin cannel bands. In Misson Borehole three leaves comprising 1.00 m of coal within 1.98 m of strata are separated by 3.65 m of strata from a higher 0.52 m leaf, the upper part of which is cannel coal; this sequence is reminiscent of that farther south where the Top Silkstone splits widely into the Blackshale and Yard coals (Smith et al., 1967, p.84, fig. 8, pl. VI). In Blyton Carr and East Stockwith boreholes, however, four leaves comprising 0.67 m and 0.85 m of coal occur within only 1.02 and 1.08 m of strata respectively, so that differentiation into the Blackshale and Yard is apparently confined to the Misson area.

The beds between the Top Silkstone or Blocking Coal and the Thorncliff Coal

The beds between the Top Silkstone or Blocking Coal and the Thorncliff Coal thin northwards from about 45 m in the south to between 15 m and 24 m in the area between Askern and Thorne, and farther north. Where the Slack Bank Rock is present, however, the sequence is generally much thicker. This sandstone in places cuts down through the Top Silkstone or Blocking to produce up to 52.64 m of coeval strata. Three cycles are discernible, with the Middleton Eleven Yards and probably the Threequarters coals at the top of the middle cycle.

Dark grey to black fissile mudstones, locally with fish debris and mussels, commonly rest on the Top Silkstone or Blocking, but they are cut out by thin sandstones in Rawcliffe Nos. 1 and 2 boreholes. A coal of inferior quality, not more than 0.20 m thick, or just a seatearth, marks the top of the lowest cycle in places. Mussels occur locally in mudstones at the base of the middle cycle, as in Trumfleet Borehole, but in many areas much of this cycle comprises siltstones with locally thick, conglomeratic sandstones which in boreholes as far apart as Eggborough No. 3 and Idle may cut out the underlying thin coal or seatearth.

Middleton Eleven Yards Coal

The Middleton Eleven Yards Coal, recognisable in northern and central parts of the district, is commonly split into two or three, and locally up to five leaves. A maximum total coal thickness of 0.69 m was proved in Pollington No. 2 Borehole, where four leaves lie within 2.11 m of strata. The overall thickness of the entire seam, however, is generally less than 1 m. To the south, between Askern and Crowle, the seam is reduced to one or two thin leaves, mainly of inferior quality. In Bentley Colliery No. 2 Shaft (Figure 10) it comprises either one thin leaf or includes another thin leaf 3.78 m below, and in Brier Hills Borehole it consists of a single leaf 0.52 m thick. It may well continue farther south into the Threequarters Coal, although exact correlation is uncertain.

Threequarters Coal

The Threequarters Coal is recognisable in the south of the district and consists of one or two closely spaced, thin leaves. It reaches 0.46 m in Misson Borehole and thins to 0.02 m and 0.05 m in Wilsic Hall and Blyton Carr boreholes respectively.

The strata between the Middleton Eleven Yards or Threequarters and the Thorncliff vary greatly in thickness, being over 20 m in those northern locations where the Slack Bank Rock is thickest, and less than 3 m northeast of Askern (Figure 11) where the thinnest proving is 0.80 m in Eskholme Borehole (Figure 10). In most boreholes only one cycle is discernible, although in Camblesforth No. 1 Borehole two cycles are suggested by a thin seatearth near the top.The basal mudstones in these strata, which locally contain mussels, pass up into siltstones with one or more generally thin sandstones which in the extreme north coalesce and thicken into the Slack Bank Rock.

Slack Bank Rock

The Slack Bank Rock (Edwards et al., 1950, pp. 29–30) is thickest in Barlow No. 2 and Burn Airfield No. 1 boreholes, 46.74 m and 42.70 m respectively, where it cuts down to the Low 'Estheria' Band, but it is thin or absent in most boreholes farther south. Only its basal part is coarse grained, but it contains several conglomeratic beds. It is conceivable that in some localities where it is thickest, the Slack Bank Rock incorporates some of the locally thick sandstones occurring in the cycle below the Middleton Eleven Yards.

Thorncliff Coal

The Thorncliff Coal complex is subject to two major southward splits (Figure 11), which increase its total thickness from 0.22 m in Barlow No. 2 Borehole to over 13 m in Misson (Figure 10) and adjacent boreholes. The lowest coal produced by these splits is the Wheatley Lime. To the north-west of a line from Askern to Drax, and apparently also in Booth Ferry Borehole (Figure 11), the Thorncliff consists of up to four leaves, the uppermost being the thickest, with a total coal thickness in Pollington No. 2 Borehole reaching 2.03 m within 2.36 m of strata.

Wheatley Lime Coal

The Wheatley Lime Coal is probably represented north of the Askern–Drax–Booth Ferry Borehole line by all but the uppermost of the closely spaced leaves of the Thorncliff; if so, it is represented in Eggborough No. 3 Borehole by 0.89 m of coal in up to three leaves, the lower two being thin and of inferior quality, and separated from the uppermost leaf by less than 0.5 m of strata. In central areas, the Wheatley Lime consists mainly of two, but locally of up to four leaves with a maximum total coal thickness in Eskholme Borehole of 0.87 m within 1.18 m of strata and a maximum interleaf separation, in Pincheon Green Borehole, of 1.88 m. East of Doncaster, however, only a single leaf no more than 0.15 m thick and, in places, only a seatearth have been proved. Farther south the Wheatley Lime is still present, although impersistent, as a single leaf not more than 0.20 m thick, which rises to only 0.07 m below the Thorncliff in Wilsic Hall Borehole. The Wheatley Lime generally has a high sulphur content, especially near its base, and it produced 9 per cent ash from Pincheon Green Borehole. In only a few western boreholes is there any evidence of the durain layer near the base, which is widespread farther west (Wandless and Macrae, 1935, p.74).

The strata between the Wheatley Lime and the Thorn-cliff are over 8 m thick in a narrow south-west-trending area south of Askern (Figure 11), with a maximum of 9.50 m in Fenwick Hall Borehole, but they thin to less than 0.5 m to the north and south-west, and to 1.26 m in Blyton Carr Borehole in the south-east. The basal mudstones contain Spirorbis sp., Carbonicola spp., C. rhomboidalis, Naiadites flexuosus and Geisina arcuata, and are succeeded mainly by silty mudstones and siltstones, but sandstones up to 8 m thick are present locally between Bentley, Askern and Thorne.

In the extreme north, the Thorncliff Coal is less than 0.22 m and 0.45 m thick in Barlow No. 2 and Hemingbrough boreholes respectively; locally, these thicknesses may also include the Wheatley Lime Coal. The impoverishment may relate to the presence of thick Slack Bank Rock in the vicinity. Elsewhere north of the Askern Drax–Booth Ferry Borehole line, the Thorncliff is generally more than 0.70 m thick and reaches 1.35 m in Pollington No. 2 Borehole. In central areas it splits into several leaves, six being present in Eskholme Borehole, and the maximum total coal thicknesses recorded are 1.64 m in Markham Main Colliery No. 7 Underground Borehole [SE 6168 0453] and 1.50 m in Bentley Colliery No. 2 Shaft, but two leaves totalling only 0.24 m and a single 0.47 m-thick leaf in Brier Hills and Crowle Common boreholes respectively show that it is thinner in the east. Somewhere in these central areas a split occurs in the lower part of the Thorncliff which widens to the south. The split leaf is probably the impersistent thin coal lying as much as 6 m below the main coal in Bentley Colliery No. 2 Shaft and Gate Farm and Brier Hills boreholes; farther south, the Thorncliff is in two or more widely separated leaves occupying 12 m of strata. The thickest total coal recorded in the south is 1.73 m from Spital Croft Borehole, where higher leaves may be cut out by sandstone, but individual leaves are generally less than 0.60 m thick, commonly less than 0.20 m and in places are represented only by seatearths. In Misson Borehole interleaf mudstones yielded Spirorbis sp., Carbonicola cristagalli, C. oslancis, C. rhomboidalis, C. robusta, Naiadites sp., G. arcuata and fish debris. Much of the Thorncliff Coal, especially in the west, is of good quality, with less than 1 per cent sulphur, although near Askern up to 12 per cent sulphur is recorded from its basal part. It consists mainly of bright coal in the west, with increases in dull coal near the base and locally near the top towards the south and east.

The beds between the Thorncliff and Parkgate coals

The beds between the Thorncliff and Parkgate coalsare 37.54 m thick in Pollington No. 2 Borehole, but thin generally and irregularly south-eastwards to 14.20 m inLaughton Borehole. Thin coals or seatearths locally indicate up to four cycles, with a fifth near the top in some north-western boreholes such as Burn Airfield No. 2, Eggborough No. 3 and Great Heck, possibly due to a split from the Parkgate Coal above. Dark grey to black mudstones in the lower part of the lowest cycle contain Spirorbis sp., Anthracosphaerium sp. nov. cf. dawsoni, C. cristagalli, C. oslancis, Naiadites sp. and fish debris. Similar faunas occur in the lower part of the succeeding cycles, some preserved in ironstone. Those faunas in the middle cycles lie at approximately the same stratigraphical horizon as the Cockleshell shell bed of Derbyshire. Siltstones and sandstones occurring in places in the higher parts of some cycles appear to cut down locally into the underlying beds, notably those in the second and fourth cycle up from the base.

Parkgate Coal

The Parkgate Coal complex is generally less than 2.5 m thick. Its subdivisions, with their correlations, are:

The Hards provide the best coal, with commonly less than 1 per cent sulphur and, notably in the south, a low ash content. In the extreme south-west (Figure 12) only one seam, up to 1.60 m thick in Wilsic Lodge Borehole, is present; in Spital Croft Borehole it comprises bright coal 0.50 m (probably Bottom Softs), dull coal 0.22 m (probably part or all of Hards) and bright coal 0.79 m (possibly some of the Hards, all of the Top Softs and possibly the Parkgate Roof Coal). If the Parkgate Roof is not present in this section, it is completely absent because there is no trace of coal or seatearth in the thick mudstones above.

The Parkgate Coal is more than 1 m thick in the south and east, except where it is partly or wholly washed out by the Parkgate Rock (Figure 12). However, it is thinner in the north-west, being only 0.4 m and 1.0 m thick hereabouts. The seam is 1.21 m thick in Wood Close Borehole, where it is directly overlain, and perhaps cut into, by the Parkgate Rock. The same situation exists in Westwoodside Borehole where the coal comprises Bottom Softs 0.37 m, Hards about 0.49 m and Top Softs about 0.33 m. In Martin Common and Piper Wood boreholes, 0.34 m to 0.42 m of cannel coal lie 0.25 m to 0.28 m below the main seam and may be a split of the Bottom Softs. The entire Parkgate Coal is preserved locally in the south-east, being a single seam 1.08 m thick in North Carr Borehole. In the nearby East Stockwith Borehole, the section reads: dirty pyritic coal 0.12 m (probably all Bottom Softs), mudstone-seatearth 0.41 m, mainly bright coal 0.30 m, cannel coal 0.24 m.

In central areas the thickest fully preserved Parkgate Coal, from Bentley Colliery No. 2 Shaft, is: Bottom Softs 0.53 m, Hards 0.56 m, Top Softs (including thin 'dirt' in the middle) 0.43 m. Farther east, Gate Farm Borehole proved: Bottom Softs 0.25 m, Hards 0.54 m, Top Softs (including thin cannel coal at the top) 0.51 m; and Crowle Common Borehole proved pyritic coal 0.37 m (probably all Bottom Softs), mudstone-seatearth 0.08 m, coal 0.35 m (probably most or all of Hards), mudstone seatearth 0.12 m, inferior pyritic coal 0.26 m (probably mainly Top Softs). Farther north, Quay Lane Borehole proved a single seam 1.42 m thick, but to the west, between Thorne and Askern, full provings of coal are only 0.51 m to 1.00 m thick, although 1.12 m are preserved beneath Parkgate Rock in Trumfleet Borehole. In Fenwick and Cross Hill boreholes, part at least of the Bottom Softs have split away, forming up to 0.08 m of cannel or inferior quality coal lying 0.08 m below the main seam, and no Bottom Softs are recorded in Pincheon Green Borehole, where the single seam comprises Hards 0.44 m and Top Softs 0.35 m.

An irregular westward thinning of the Parkgate Coal occurs across northern areas. Booth Ferry Borehole proved: coal 0.30 m (probably all Bottom Softs), mudstone with seatearth 0.67 m, coal 1.00 m. Between Rawcliffe, Pollington and Selby the total coal section is only 0.34 to 0.70 m thick, and farther north-west it is 0.33 to 0.57 m thick, although exceptionally it reaches 0.84 m in West Haddlesey No. 1 Borehole (Figure 10). In the north-west the Bottom Softs is generally less than 0.15 m thick, inferior and pyritic, and may be absent altogether; the Hards too are thin, generally less than 0.10 m, but the Top Softs remains fairly thick, being 0.43 m in Camblesforth No. 1 Borehole for example, although their top is commonly inferior, with pyrite or cannel. Hemingbrough Borehole, in the far north, proved 0.94 m of coal in which the lowest 0.15 m is the Bottom Softs but the rest is 'dirty', suggesting that both the Hards and Top Softs deteriorate in this direction.

The strata between the Parkgate and Parkgate Roof coals thin irregularly eastwards across most northern and central parts of the district from 1.02 m and 0.46 m in Pale Lane Borehole and Bentley Colliery No. 2 Shaft respectively to apparently less than 0.10 m in Booth Ferry and Crowle Common boreholes. But they expand to 0.86 m in North Carr Borehole in the south-east. They are largely argillaceous and contain Naiadites sp. in the incomplete sequence in Gate Farm Borehole.

Parkgate Roof Coal

The Parkgate Roof Coal is more than 0.5 m thick in an elongate area stretching north-east from Askern (Figure 12) and reaches 0.69 m in Gowdall Borehole, but elsewhere it thins to as little as 0.10 m and it is largely washed out by the Parkgate Rock in the south. Much of the coal is bright, although some thin dull layers are present in places and in the north-west, at least, it is generally of inferior quality and locally pyritic. In an elongate area from Great Heck to Booth Ferry, which partly coincides with its greatest thickness (Figure 12), it lies close below the Lower Fenton Coal, and is locally difficult to distinguish from it.

The beds between the Parkgate and Flockton Thick coals

The beds between the Parkgate and Flockton Thick coalsthicken westwards from about 21 m to about 45 m across the north of the district and are generally over 50 m in the south, especially where the Parkgate Rock is thick, reaching 77.19 m in Spital Croft Borehole. There is evidence of up to six cycles, the Parkgate Rock lying within the lowest. The main seams, in ascending order, are the Low and Top Fenton coals, which seem to correlate southwards with the Deep Hard coals, then one or more unnamed coals and the Flockton Thin, which probably correlate with the Deep Soft coals. Most of these seams are thin and widely split into two or more leaves, which commonly makes correlation between boreholes uncertain.

The strata between the Parkgate and Fenton–Deep Hard coals are up to 9 m thick in the extreme north and north-west, where they consist mainly of thin mudstones, locally with mussels, passing up into siltstones with impersistent thin sandstones. They thin south-eastwards to less than 1 m of mudstone, partly seatearth, in an elongate area (Figure 12) between Great Heck and Drax and possibly farther east. The beds are only 1.30 and 1.69 m thick in Kellington Common and Lee Lane boreholes respectively, to the west. Farther south, between Askern and Thorne, and possibly farther east, they expand to between 6 and 16 m; they are generally thicker in the west and again are mainly argillaceous, with mussels locally near the base, but in places they include thin sandstones at higher levels. In the south-west of the district, the beds expand locally to more than 30 m, and consist mainly of the Parkgate Rock; but in those few boreholes where the sandstone has not cut down to the Parkgate Coal, the latter is directly overlain by argillaceous strata, as it is farther north.

Parkgate Rock

The Parkgate Rock, thin or absent north-east of a line from Askern to Belton, is commonly over 15 m thick farther south-west and reaches 36.50 m in Bentley Colliery No. 2 Shaft, although it is possible that hereabouts it may be combined with siltstones from above the Low Fenton Coal which apparently have washed out the coal. The borehole sections through the Parkgate Rock show sandstones passing up into siltstones, or interbedded sandstones and siltstones, or just siltstones; conglomeratic layers occur in the lower part of the Rock in several sections. The base of the Parkgate Rock can be strongly transgressive downwards, cutting out the entire Parkgate Coal sequence in sections as far apart as Askern Colliery No. 1 Shaft and Idle and Blyton Carr boreholes.

Low Fenton Coal

The Low Fenton Coal is recognisable in most northern and central boreholes west of a line from Goole to Wroot, but it apparently dies out farther east. The thickest provings are in the north-west, where three, and locally four leaves occur within up to 1.86 m of strata; the lowest leaf is the thickest and reaches 0.72 m in West Haddlesey No. 1 Borehole (Figure 10), the thickest total coal being 0.91 m in Chapel Haddlesey Borehole. The Low Fenton thins eastwards to one leaf of 0.18 m in Hemingbrough Borehole. Where the Low Fenton lies less than 1 m above the Parkgate Coal (Figure 12) the former, in so far as it can be distinguished from the latter, comprises two or three leaves with a total coal thickness of generally not more than 0.60 m within less than 1.00 m of strata, and here also the seam thins eastwards. In central areas the seam contains up to 0.66 m of coal, generally in three leaves within up to 1.16 m of strata. Eskholme Borehole (Figure 10) provides an exception with 0.76 m of coal in five leaves within 0.99 m of strata, but here, as in Cross Hill and Pincheon Green boreholes nearby, the Low and Top Fenton coals may have come together. Southwards, the Low Fenton almost certainly becomes the lowest of the Deep Hard coals.

The strata between the Low and Top Fenton are up to 12 m thick in that area (Figure 12) where the Low Fenton lies close above the Parkgate Coal, but elsewhere they are generally not more than 8 m thick and may be less than 1 m locally south of Pollington. They consist largely of mudstones except in areas where they are more than 8 m thick, when siltstones and sandstones are commonly present, as in Great Heck Borehole. Fossils in the basal strata include Spirorbis sp., Anthracosia regularis, Naiadites sp., N. sp. nov. and fish debris.

Top Fenton Coal

The Top Fenton Coal is recognisable in most northern and central areas west of a line from Goole to Wroot, except locally around Drax and Rawcliffe, and is generally absent farther east. In Lee Lane Borehole four leaves totalling 0.76 m of coal lie within 2.16 m of strata, and in several other boreholes nearby there are two leaves. The upper is generally the thicker and is 0.95 m in Eggborough No. 3 Borehole; the beds between the leaves are generally thin but reach 3.06 m in Camblesforth No. 2 Borehole and 2.90 m in Bentley Colliery No. 2 Shaft. The majority of provings, however, are of one leaf less than 0.36 m thick and commonly less than half this thickness, especially in the east and south. The Top Fenton lies at approximately the same stratigraphical horizon as the highest part of the Deep Hard Coals farther south, but as it is thin or absent around and east of Doncaster, it is difficult to demonstrate direct continuity.

The Deep Hard coals, recognisable across the south of the district, consist generally of two seams separated by up to 13 m of strata. In Wilsic Hall and Blyton Carr boreholes the lower coal is split into four leaves totalling 0.36 m and three leaves totalling 0.26 m, whilst the upper coal in these boreholes comprises two leaves totalling 0.09 m and one leaf of 0.27 m. Much of the intervening strata are mudstones and siltstones, locally with mussels near the base and in places interbedded with thin coals or seatearths, but some sandstones are present, mainly in the east. It is possible that the upper seam is the Deep Hard Roof Coal of the area east of Chesterfield (Smith et al., 1967, pp. 141–146; Smith et al., 1973, p.65).

The beds between the Top Fenton and Flockton Thin coals, which are generally present in the northern and central parts of the district, reach a maximum of 22.41 m in Eskholme Borehole and more than 15 m are proved in several adjacent boreholes, but they thin to only 4 m locally to the north and east and 8 m to the south. They include at least two cycles, most noticeably in the west where one and sometimes two thin coals or seatearths may occur, generally near the top and possibly having split off the Flockton Thin above. Mudstones commonly form much of the lower cycle, although siltstones and locally some thin sandstones are not uncommon. The upper cycle consists largely of mudstone but locally thick sandstones appear to have cut down through the lower cycle to rest on the Top Fenton Coal in Eggborough No. 3 and Gowdall boreholes.

The strata between the Deep Hard and Deep Soft coals in the south of the district thin generally eastwards from nearly 20 to 7 m. A thin coal or seatearth near the top, possibly a split off the Deep Soft above, divides the sequence into two cycles in some western boreholes. The beds are mainly argillaceous, with fossils near their base in places, but sandstones occur locally near the top, for example in Bank End Borehole. The fauna from the strata overlying the Top Fenton and Deep Hard coals includes Spirorbis sp., Anthracosia regularis, Carbonicola oslancis, C. cf. rhomboidalis, C. cf. venusta, Naiadites sp., N. sp. nov., G. arcuata and fish debris.

Flockton Thin Coal

The Flockton Thin Coal, present in most northern and central areas, is commonly split into two, and locally into five leaves. The thickest total coal and the most splits are in the north-west, where West Haddlesey No. 1 Borehole proved 0.94 m of coal in five leaves within 3.38 m of strata. However, there is no trace of coal or seatearth in Hemingbrough or Booth Ferry boreholes, although Quay Lane Borehole proved 0.38 m of coal in four thin leaves within 1.61 m of strata. Coming southwards, the seam is generally less than 0.30 m of coal within one or two thin leaves in central areas, although there is a possibility that one or more thin coals lying as much as 10 m below the Flockton Thin may have split off from it. In some sections there is no coal, as in Trumfleet Borehole, and in others just a seatearth, for example in Askern Colliery No. 1 Shaft. Farther south, the Flockton Thin almost certainly passes into the higher of the Deep Soft coals.

The Deep Soft coals in the south of the district consist generally of two coals separated by nearly 17 m of strata. The lower coal is up to 0.57 m thick but, especially in the east, it is represented only by a seatearth or is apparently cut out by overlying sandstones or siltstone. In most boreholes where the two coals are present, the intervening 10 to 17 m of beds commonly contain ripple-bedded, bioturbated and locally conglomeratic sandstones below, with siltstones and some mudstones above. In Idle and Newington boreholes, however, only 1 m and 2 m of argillaceous beds, mainly seatearths, are present respectively. The higher coal splits in places into two or three closely spaced leaves, as in Wilsic Hall Borehole where three leaves contain 0.42 m of coal within 0.77 m of strata. Elsewhere, however, a single seam, other than thin dirt layers, is up to 1.26 m thick, and in Misterton Borehole a seam, presumably the upper coal, contains more than 2.00 m of coal in 2.87 m of strata. In Misson and Blyton Carr boreholes both the Deep Soft coals are washed out by sandstones and siltstones. Northwards, the lower of the Deep Soft coals may pass into one or more of the thin coals locally lying between the Top Fenton and Flockton Thin, and which may have split off the latter seam.

The strata between the Flockton Thin or Deep Soft coals and the Flockton Thick Coal reach a maximum of 15.66 m in West Haddlesey No. 1 Borehole (Figure 10), but thin to between 4 and 6 m in places between Egg-borough and Snaith. Elsewhere in northern and central areas, they are generally less than 10 m thick, but reach 14.28 m in Idle Borehole. In a few widely spaced boreholes a thin coal or seatearth, possibly split from the Flockton Thick, suggests two cycles; fossiliferous mudstones in the lower parts of both cycles contain Spirorbis sp., Anthraconaia aff. salteri, Anthracosia regularis, Anthracosphaerium cf. cycloquadratum, Carbonicola cf. venusta, Naiadites cf. subtruncatus, N. sp. nov., G. arcuata and fish debris. The higher parts of the cycles are mainly siltstones with locally thick sandstones that in places, as in Eskholme Borehole (Figure 10), cut down to the Flockton Thin, and elsewhere, as in Camblesforth No. 3, Hemingbrough and Blyton Carr boreholes, cut out the underlying Flockton Thin or Deep Soft coals altogether.

Flockton Thick Coal

The Flockton Thick Coal generally comprises an impersistent lower coal not more than 0.30 m thick, mainly of inferior quality and locally of cannel, and an upper coal commonly more than 0.80 m thick and locally in two or three leaves. The two coals are separated in some northern and central areas by more than 3 m of mainly argillaceous strata; in some sections the coals may be so widely spaced that the lower one is mistaken for the thin coal lying just above the Flockton Thin. The thickest upper coal in the north is in Drax No. 4 Borehole where approximately 1.34 m of coal, including a 1.16 m-thick leaf, lie within 2.34 m of strata. The thickest occurrence in central sections is in Gate Farm Borehole (Figure 10) where at least 2.35 m of coal, including a 1.42 m-thick leaf, lie within 3.44 m of strata, although in this and in Westwoodside boreholes, and possibly other boreholes nearby, the total coal thickness may include the lower coal and also an unnamed coal which locally lies close above the Flockton Thick. In northern and central areas generally, the upper coal is normally more than 0.40 m thick and is more than 1 m thick in several boreholes. In the south it is 1.15 m thick in Pipers Wood Borehole and 0.98 m thick in Misterton Borehole; elsewhere it is mainly 0.50 to 0.90 m thick. Much of the upper coal is of good quality with ash and sulphur contents being lowest in the north-west and its thickest leaf is largely of bright coal. A small area of Flockton Thick Coal has been worked from Askern Colliery.

The beds between the Flockton Thick Coal and the Vanderbeckei Marine Band

The beds between the Flockton Thick Coal and the Vanderbeckei Marine Band appear to be thickest in an elongate area from Fenwick Borehole (18.24 m) (Figure 10) south-eastwards to Brier Hills (18.35 m). They thin north-eastwards to between 3 and 9 m in Hemingbrough, Booth Ferry, Quay Lane and Crowle Common boreholes. Farther south they are mainly 5 to 12 m, but thicken in the extreme south-west to 16.56 m in Wilsic Hall Borehole, although in the extreme south-east they are little more than 1 m thick in Blyton Carr Borehole (Figure 10). Thin coals or seatearths suggest three or four cycles in northern and central areas, but only two cycles in the south. The only widespread coal is the Joan, lying close below the Vanderbeckei Marine Band. Darkish grey, fossiliferous mudstones are widely present in the lowest cycle and, most notably in the north-west, in the lower parts of the two higher cycles; the fauna includes Spirorbis sp., A. regularis, C. oslancis, C. venusta, Naiadites sp., N. sp. nov. and G. arcuata. The upper parts of the cycles are commonly siltstones, with sandstones being widely but irregularly distributed in one or more cycles, notably in Camblesforth No. 1, Eggborough Nos. 1 to 3, Pollington No. 3 and Snaith boreholes, and in places, as in Misson Borehole (Figure 10), the siltstone or sandstone has washed out the thin coals or seatearths to obscure the cycle boundaries.

Joan Coal

The Joan Coal is thickest in Gate Farm Borehole (Figure 10) where 0.71 m of coal in two leaves occur within 1.12 m of strata. Comparable thicknesses in up to three leaves are proved also in Bentley Colliery No. 2 Shaft (0.56 m), Markham Main Colliery No. 1 Shaft (0.55 m) and Misterton Borehole (0.69 m including thin 'dirt' layers). Elsewhere in the south-east the Joan Coal is locally difficult to distinguish from closely underlying thin coals and even, in Blyton Carr Borehole, from the closely underlying Flockton Thick. Farther west the Joan is up to 0.40 m thick, generally in a single leaf with thin 'dirt' layers, but in Misson Borehole it is marked only by a seatearth. To the north, Fenwick Grange Borehole proved five leaves totalling 0.17 m of coal within 0.50 m of strata, but farther north the Joan is largely confined to the Great Heck–Gowdall–Pollington area where a single leaf reaches 0.28 m in Great Heck Borehole. Outside this area the seam is represented by only a seatearth or is absent. The Joan is everywhere of inferior quality and generally comprises 'dirty' coal.

The strata between the Joan Coal and the Vanderbeckei Marine Band, which are virtually all mudstone, only rarely exceed 1 m; they are generally less than 0.3 m and in many places are absent. In Trumfleet Borehole the coal and marine band are represented by only a seatearth and a fish debris-bearing black mudstone respectively, and the 0.30 m of intervening strata include a fragmental clayrock (Richardson and Francis, 1971).

Westphalian B strata

Westphalian B strata extend from the base of the Vanderbeckei Marine Band to the base of the Aegiranum Marine Band and encompass approximately the lower two-thirds of the Middle Coal Measures of the published maps (sheets 79 and 88). The succession is thickest in the south-west where it probably reaches 380 m (see isopach diagrams on (Figure 13) and (Figure 16)); it is also locally thick, possibly up to 330 m, in the north-west between Camblesforth and Chapel Haddlesey, and may originally have been thick farther to the north-west, although this is uncertain because the highest strata were removed by prelate Permian erosion. Near Askern, less than 300 m are present, and a zone of thinner strata extends from there in an east-south-easterly direction. Only about 230 m are present in the south-east and possibly less in the northeast. Between 32 and 46 cycles are commonly discernible, and although there are no major differences in cyclic development, three sequences contrasting in certain respects can be recognised.

The lowest and thinnest sequence, up to the Haigh Moor Coal (Figure 13), is characterised by a fairly uniform stratigraphical succession and thickness across most of the district. Deposition seems to have occurred across extremely flat terrain which prevailed during and for some time after the marine incursion marked by the basal marine band. No marked variations in drainage base level are detectable.

The middle sequence extends from the Haigh Moor Coal to the Two-Foot Coal (Figure 13) and (Figure 16) and is much the thickest. Its principal features are extensive and wide splits in most of the coals and large variations in inter-coal thicknesses, producing complicated seam patterns such as those of the Barnsley and Hatfield High Hazel coals and their correlatives. These features suggest small variations in relief, differential compaction and, where locally thick sandstones such as the Horbury Rock and Abdy Rock cut down through pre-existing strata, periodic drainage base-level variations, but slight contemporaneous tectonic activity may also have been a contributory factor. The sequence also contains the thickest coals; the Dunsil, Barnsley and its correlatives, and Hatfield High Hazel are extensively mined.

The upper sequence, above the Two-Foot Coal, contains several marine bands and several 'Estheria' bands, the latter possibly resulting from brackish depositional conditions. Most of these marine and 'Estheria' bands are of restricted lateral extent, suggesting incursions limited by relief. Across much of the district, however, the stratigraphical succession is fairly uniform and, except along its southern margin, the thickness shows little variation, suggesting that any relief was minor. The presence of locally thick sandstones with erosive bases, such as the Woolley Edge Rock and the Oaks Rock, however, again implies periodic variations in drainage base-level.

Westphalian B strata have been cored in most parts of the district, providing much palaeontological information. The Vanderbeckei (formerly Clay Cross) Marine Band consists of black mudstone or siltstone in which, in the absence of goniatites and pectinoids, the presence of Lingula is diagnostic. The thickest provings of the band range from about 0.45 to 0.73 m, between Austerfield and Misterton and northwards to Gate Farm Borehole. Similar thicknesses occur in the adjacent district to the south (Smith et al., 1973, pp. 70–72, fig. 16). The abnormally thick 1.60 m recorded from Austerfield Borehole may not all have contained Lingula. In Crowle Common and Quay Lane boreholes to the north-east, the marine band is 0.47 m and 0.49 m thick respectively. But in more central and north-western areas, other than possibly being up to 0.53 m in Ash Hill Borehole, it is no more than 0.30 m and is commonly less than 0.15 m. Even Lingula has not been proved in Trumfleet Borehole. Thicknesses of 0.25 m and 0.20 m in Great Heck and Pollington No. 3 boreholes are compatible with those from sections just to the west of this part of the district but, except for Barlow No. 2 (0.08 m) and Hemingbrough (up to 0.30 m) boreholes, there are no provings of Lingula north of a line from West Haddlesey to Goole. Other fossils found in the marine band include fish debris, 'fucoids', burrows and plant fragments, some of them pyritic, and 'Estheria' is recorded from the base in Quay Lane Borehole. Except in Misson Borehole, where Spirorbis sp. and Anthracosia sp. are present, and possibly also in Wood Close Borehole, there is no evidence of mussels within the marine band, in contrast to such occurrences farther south (Smith et al., 1973, pp. 70–72, fig. 16).

The beds between the Vanderbeckei Marine Band and the Haigh Moor Coal

The beds between the Vanderbeckei Marine Band and the Haigh Moor Coal are generally 45 to 60 m thick, except in the Great Heck–Pollington–Askern area where locally they expand to almost 68 m, and in the south-east where they decrease to about 42 m in places. At least seven cycles are marked by thin coals or seatearths, but the incidence of mussels suggests that up to nine cycles are present in places. The only laterally extensive coal is the Lidget, although one or more thin coals at a lower level may represent the Second Ell Coal of areas to the south (Smith et al., 1973, p.72). Sandstones are present locally in most, if not all of the cycles, but they are mainly less than 8 m thick. The sandstone in the lowest cycle is equivalent to the Thornhill Rock of west Yorkshire and is generally the thickest and most persistent, being found in boreholes as far apart as West Haddlesey No. 1, Quay Lane and Misterton.

The dark grey and commonly silty mudstones overlying the Vanderbeckei Marine Band are richly fossiliferous and in places include shelly ironstone layers; they have yielded Spirorbis sp., Anthraconaia williamsoni, Anthracosia cf. beaniana, A. aff. phrygiana, A. sp. ovum/phrygiana, Naiadites cf. triangularis, N. quadratus and fish debris including Megalichthys sp. The faunas found in the higher mussel bands below the Lidget Coal are much the same as those found between the Lidget and the Haigh Moor coals, and include Spirorbis sp. Anthraconaia curtata, A. modiolaris, Anthracosia aquilina, A. 'carissima', A. ovum, A. phrygiana, A. subrecta, A. sp. ovum/phrygiana, Anthracosphaerium affine, A. turgidum, Naiadites quadratus and N. cf. triangularis.

Lidget Coal

The Lidget Coal is thickest in the west and is commonly split into two or more leaves in the north-west. It has a similar structure near Austerfield, being 0.77 m in three leaves and 0.69 m in three leaves in West Haddlesey No. 2 and Roall Ings boreholes respectively, and 0.76 m in one leaf and 0.90 m in three leaves in Rossington Colliery No. 17 Underground [SK 6022 9837] and Martin Common boreholes respectively. The seam thins eastwards so that in the north-east the Lidget is represented by only a seatearth in Airmyn Grange Borehole and is absent in Booth Ferry Borehole (Figure 13), but one or two thin leaves persist in most easterly areas farther south.

The dark grey mudstones overlying the Lidget Coal are widely fossiliferous and locally contain shelly ironstone layers; they have yielded Spirorbis sp., A. Carissima, A. ovum, A. aff. phrygiana, A. sp. phrygiana/ovum, Anthracosphaerium? and Naiadites sp.

Haigh Moor Coal

The Haigh Moor Coal consists in the north of one or two closely spaced leaves with a maximum coal thickness of 1.17 m in Roall Ings Borehole, and also locally one or two thin leaves in the underlying 1 to 3 m of strata. In West Haddlesey No. 1 Borehole, for example, the coal consists of two leaves of 0.40 m and a third leaf 0.62 m thick, just above. In Barlow No. 2 Borehole it is 0.93 m thick, but in Booth Ferry Borehole it is only 0.54 m thick. In these northern sections much of the coal is bright, but dull layers are recorded from middle and upper parts in places, and from the base in Hemingbrough Borehole, and thin cannel coal occurs locally at the top. There is an appreciable thinning of the seam into central areas of the district, where a main leaf from 0.13 m in Fenwick Borehole and Bentley Colliery No. 2 Shaft to possibly as much as 0.50 m thick in Eskholme Borehole, is locally accompanied by up to three underlying, and up to two overlying thin leaves. In Gate Farm Borehole, however, the entire Haigh Moor Coal is cut out by the Haigh Moor Rock. In southern parts of the district, the Haigh Moor Coal consists of three closely spaced thick leaves with, locally, impersistent thin leaves. The thickest individual leaf is 0.70 m in Misterton Borehole and the thickest total coal is 1.24 m in Newington Borehole, although the thickest seam including coal and intervening strata is 2.03 m in Brancroft Borehole. The lowest of the three main leaves is mainly bright coal, with thin dull layers near the top.The middle leaf, although also largely bright coal, contains one or more dull layers of which one, near the middle of the leaf, persists across much of the southern areas. The upper leaf is generally the thinnest of the three main leaves and is partly of inferior quality coal, locally pyritic and prone to splitting in places. Towards the extreme southeast, the leaves are reduced to two in North Carr Borehole (1.14 m of coal in 1.32 m of strata) and to one (0.50 m and 0.69 m thick) in Laughton and Blyton Carr boreholes respectively.

The beds between the Haigh Moor and Swallow Wood coals

The beds between the Haigh Moor and Swallow Wood coals are difficult to characterise because it seems that an upper leaf of the Haigh Moor diverges widely from section to section and may be confused with the Swallow Wood Floor Coal in some areas. However, the beds between the main parts of the Haigh Moor and Swallow Wood coals are fairly distinct and range in thickness generally from about 13 m to about 19 m in the north. In central areas, the succession varies from about 19 to only 8.63 m in Crowle Common Borehole, and in the south from nearly 16 to 14.48 m in North Carr Borehole. Thin coals and seatearths suggest two, and locally three cycles in northern and central areas but only one cycle in the south, although there the top of a sandstone occurring widely in the middle of the sequence may mark the junction between the two cycles delineated farther north. In the north, an impersistent coal, which is partly cannel in places, separates the two cycles and lies in the upper part of the sequence, but R F Goossens and C G Godwin have traced it westwards beyond the district into the Castleford area where it apparently correlates with the highest leaf of the Haigh Moor Coal. Where it is not separately recognisable, this coal may have thinned out, been cut out or passed into the Swallow Wood Floor Coal. In central parts of the district it lies generally in the middle of the sequence and may be split locally, but it is not traceable farther south. The mudstones overlying the main part of the Haigh Moor Coal and also those succeeding its divergent upper leaf are locally fossiliferous in northern and central areas and have yielded Anthraconaia sp., A. phrygiana, N. quadratus, N. triangularis, N. sp. quadratus/productus, ostracods and fish debris. Impersistent sandstones occur in both cycles in northern and central areas, being generally more widespread and thicker in the lower cycle, and they are present also in the middle of the single-cycle sequence in the south. In some localities they seem to expand and join with the Haigh Moor Rock.

Haigh Moor Rock

The name Haigh Moor Rock refers to locally thick sandstones and associated siltstones lying generally above the Haigh Moor Coal. They are up to about 55 m in Markham Main Colliery No. 1 Shaft (Figure 13), where they rest on the main part of the Haigh Moor Coal and cut out the Swallow Wood Coal. They are 38.40 m thick in Gate Farm Borehole, where they cut out all the Haigh Moor seam, and thicknesses of over 20 m are recorded from Brind Common, Gowdall, Snaith and some of the Eggborough and Camblesforth boreholes, and from Thorne Colliery No. 1 Shaft, where the Haigh Moor and/or Swallow Wood coals are thin or cut out. The sandstones in the Haigh Moor Rock are virtually all fine-grained but locally contain conglomeratic layers. Ripple bedding is common and convoluted layers have been noted. Most of the associated siltstones occur in the upper part. In some localities the Haigh Moor Rock clearly includes sandstones that lie between the Swallow Wood and Dunsil coals, and locally it probably incorporates the sandstones lying below the upper leaf of the Haigh Moor, so in places it encompasses a wider stratigraphical range than it does in its type area farther west.

Swallow Wood Coal

The Swallow Wood Coal is a workable seam in the south-west of the district; in Harworth Colliery No. 22 A Underground Borehole [SK 6511 9398], it is 2.06 m thick, and although five or more 'dirt' layers are present, they are very thin. Elsewhere in the south-west, three principal leaves are distinguishable; the ascending sequence in Wilsic Hall Borehole (Figure 13), for example, reads: inferior coal 0.28 m, seatearth 0.73 m, coal 0.65 m including 0.05 m seatearth near top, seatearth 0.20 m, coal 0.81 m. These three leaves, the Floor Coal, Bottom Bed and Main Bed, diverge, thin and deteriorate eastwards and northwards across the district.

The Floor Coal is identifiable with certainty only in south-western and central southern areas, consisting of about 0.30 m of mainly bright coal in the south-west towards Maltby Colliery but thinning, deteriorating and splitting locally to the east and north. It may be represented by 0.19 m of coal lying 1.73 m below the main Swallow Wood in East Stockwith Borehole (Figure 13) in the south-east, and it lies more than 2 m below the Bottom Bed in parts of the Rossington Colliery take. It has not been recorded around and east of Doncaster, being cut out by the Haigh Moor Rock in Markham Main Colliery No. 1 Shaft (Figure 13).

The Bottom Bed consists entirely of bright coal in the south-west of the district within the Maltby Colliery take, but it develops dull layers to the north-east. In south-western and central southern areas generally, it ranges from 0.42 m to a maximum, in Idle Borehole, of 0.79 m. In Piper's Wood and Partridge Hill boreholes, the coal contains a thin 'dirt' layer and its basal and topmost layers are of inferior quality in several boreholes. Farther east, it thins to 0.48 m in Misterton Borehole, and in East Stockwith Borehole (Figure 13) it has split into four leaves totalling 0.37 m of coal within 0.62 m of strata, its top in both localities being cannel coal. The strata separating it from the Main Bed expand to 2.63 m and 2.72 m respectively in these boreholes. The Bottom Bed thins also to the north, being 0.53 m, 0.28 m and 0.60 m in Bentley Colliery No. 2 Shaft, Gate Farm and Brier Hills boreholes respectively, and in these sections the overlying strata expand eastwards, being 0.25 m, 0.66 m and 3.20 m thick respectively. These beds yielded mussels including 'Anthracosia' and fish debris in Brier Hills Borehole. Recognition of the Bottom Bed is uncertain farther north. Where the Swallow Wood is represented by only one leaf, as in Askern Colliery No. 1 Shaft (0.63 m) and Eskholme Borehole (0.40 m), the Bottom Bed and the Main Bed may be united, but farther east, as in Pincheon Green and Quay Lane boreholes, the former may be represented by a seatearth 3.73 m and 2.37 m respectively below the latter. Again, these beds thicken eastwards. The Bottom Bed and Main Bed may also combine in parts of the north-west, but in some boreholes, such as West Haddlesey No. 1, the Bottom Bed may be a thin 0.07 m to 0.19 m leaf as much as 3.48 m below the Main Bed. There is no easterly divergence between the two coals in the north as there is farther south, for in Booth Ferry Borehole they appear to be combined as a 0.30 m-thick seam and in Fir Tree Borehole, just beyond the district to the north, the Bottom Bed may be a 0.26 m leaf lying only 0.20 m below the Main Bed.

The Main Bed is up to 0.91 m thick in south-western and central southern areas, but is split by as many as three argillaceous seatearth layers, the thickest being 0.26 m. It largely comprises bright coal, but contains one dull band in the lower part and one or two dull layers near the top, the uppermost dull layer being called 'jabez'. The Main Bed thins eastwards to 0.30 m and 0.33 m in East Stockwith (Figure 13) and Misterton boreholes respectively, and northwards to 0.38 m and 0.33 m (with a 0.03 m dirt layer) in Brier Hills (Figure 13) and Gate Farm boreholes respectively; however, in Bentley Colliery No. 2 Shaft it is apparently represented by 0.91 m of pyritic coal. Farther north, and especially towards the north-west, the Main Bed is probably united with the Bottom Bed, but where it is thought to be separate it is 0.20 m, 0.24 m, 0.40 m and 0.14 m thick in Pincheon Green, Quay Lane, West Haddlesey No. 1 (Figure 13) and Fir Tree boreholes respectively; the thickest record in the north is 0.75 m in Burn Airfield No. 2 Borehole. The Main Bed deteriorates in quality northwards across the district, with increasing amounts of 'dirty', inferior or pyritic coal and some cannel layers near its base and top.

The beds between the Swallow Wood and Dunsil coals

The beds between the Swallow Wood and Dunsil coalsrange from possibly little more than 8 m to nearly 22 m in thickness across most of the northern half of the district, but Quay Lane and Crowle Common (Figure 13) boreholes indicate a marked expansion east of Thorne to 36.99 m in the latter borehole, due to the thickening of two sandstones in the sequence. These sandstones, which occur at approximately the same stratigraphical position as the Woodhouse Rock near Sheffield, are apparently united at Thorne Colliery where a borehole at the bottom of No. 1 Shaft proved a mudstone-seatearth that probably represents the Swallow Wood at a depth of 30.25 m below the Dunsil, and immediately under 23.09 m of sandstone. Farther south, where the sandstones are generally thinner, the beds between the two coals increase in thickness westwards from 22.55 m in Brier Hills Borehole (Figure 13) to 27.06 m in Bentley Colliery No. 2 Shaft, but they cannot be delineated in Markham Main No. 1 Shaft (Figure 13), where thick Haigh Moor Rock cuts down through the Swallow Wood. This westward increase in the sequence continues into southern parts of the district, where East Stockwith and Spital Croft boreholes proved thicknesses of not more than 21.80 m, and 40.64 m respectively, and Harworth Colliery 9A Underground Borehole [SK 6448 9320], only a few metres south of the district, proved about 47 m. Thin coals, including the Waterloo Marker and the First Waterloo, seatearths and mussel bands suggest between three and six cycles. Where mudstones succeed the Swallow Wood, they commonly contain ironstones and a fauna in which Spirorbis sp. is abundant and persistent, as it is above the equivalent Second Waterloo Coal farther south (Smith et al., 1973, p.76; Edwards, 1967, p.95; Calver in Smith et al., 1967, p.165). The associated mussels are principally Anthracosia spp., and ostracods and fish debris have also been recorded.

The Waterloo Marker Coal lies generally 4 to 10 m above the Swallow Wood, but the intervening thickness reaches 12.38 m in Spital Croft Borehole. The thickest proving of the Waterloo Marker Coal is 0.63 m in Rossington Colliery No. 26 Underground Borehole [SK 6187 9901], but in most places it is less than 0.20 m. In the west and south it is split into two or three leaves and, elsewhere, it is either absent or marked by only a seatearth. In a few places, a seatearth occurs about 3 m below the Waterloo Marker and is locally separated from it by a thin sandstone and an overlying mussel layer; the seatearth may, by analogy with farther south (Smith et al., 1973, p.76), represent a diverging lower leaf of the Waterloo Marker.

Mudstones overlying the Waterloo Marker contain widespread Spirorbis sp., and the associated mussels, commonly preserved in ironstone, include Anthraconaia cf. pumila, Anthracosia beaniana, A. disjuncta, A. nitida, A. ovum, A. phrygiana, A. sp. disjuncta/phrygiana, A. sp. nov. cf. phrygiana, Anthracospherium turgidum, Naiadites quadratus and N. triangularis.

First Waterloo Coal

The First Waterloo Coal is highly variable in terms of its position in the sequence, thickness of coal, number of leaves and thickness of intervening strata; as a result it is difficult to correlate in some sections. It occurs in the middle to upper parts of the Swallow Wood/Dunsil interval. In some southern and north-western boreholes, a thin coal close below the Dunsil and, in the south, possibly uniting with it locally, may be a diverging upper leaf of the First Waterloo. Where two or three leaves are present, the upper or middle is generally the thickest; in Misson Borehole (Figure 13) the middle leaf is as much as 0.55 m thick. In this borehole the highest and lowest leaves are 4.13 m apart, the latter being the more divergent, and it is possible that in Harworth Colliery No. 22A Underground Borehole [SK 6511 9398] they are about 14 m apart. In the northern half of the district there is less evidence of splitting, but a coal up to 0.22 m thick varies considerably in position within the sequence, suggesting that it may be different impersistent leaves of the First Waterloo. Mussels are recorded from above the lowest leaf in Brier Hills, Misson and Piper's Wood boreholes, and fish debris occurs above the middle leaf in Harworth Colliery No. 22A Underground Borehole.

The strata above the First Waterloo are locally fossiliferous, notably in Bands End, Brier Hills, Misson and Westwoodside boreholes, where Spirorbis sp., A. cf. phrygiana, Naiadites sp. and fish debris have been found.

Dunsil Coal

The Dunsil Coal varies considerably in thickness, being up to 1.70 m locally, but in some areas it lies very close to, or is united with, the Barnsley Coal so that it cannot be separately distinguished. In the extreme north-west the Dunsil comprises, in West Haddlesey No. 1 Borehole (Figure 13), a main leaf 1.19 m thick with locally one or two leaves each less than 0.10 m thick close below it, which may partly relate to the First Waterloo; more commonly another leaf up to 0.36 m thick lies close above it. In a narrow, elongate area running east-north-eastwards from Kellington and Whitley through Camblesforth and to the north of Howden, however, the Dunsil is very thin or absent. Some of this attenuation is due to the coal being partly or entirely cut out by the Horbury Rock, as in Eggborough Nos. 1 and 3, Drax No. 3 (Figure 13), Brind Common and Fir Tree boreholes. In other sections, however, such as Roall Ings, Lee Lane and Camblesforth No. 3 boreholes, where the Dunsil is overlain by mudstones, its attenuation and inferior quality may be depositional. Further to the south-east, its main leaf reaches 1.26 m in Drax No. 2 Borehole, where it lies only 0.42 m below the lowest part of the Low Barnsley Coal, but a slight southerly thinning reduces its main leaf to 0.66 m in Pincheon Green Borehole and not more than 0.60 m between Askern and Crowle generally. The Dunsil increases in thickness southwards across the area around Doncaster, and is associated with fewer split leaves and better quality coal. It is 1.70 m thick in Bentley Colliery No. 1 East Underground Borehole [SE 5849 1039], 1.34 m in Hatfield Colliery No. 35 Underground Borehole [SE 6746 1061] and 1.17 m in Markham Main Colliery No. 1 Shaft (Figure 13). In the last two sections, the Dunsil lies less than 1 m below the Barnsley.

The close association of the Dunsil and Barnsley coals continues through much of the central southern part of the district, producing coal in Partridge Hill Borehole up to 3.85 m thick with thin 'dirt' layers. The Dunsil is distinct, however, from the Barnsley in the extreme southwest, being only 0.40 m thick in Wilsic Hall Borehole. In the south-east, two closely spaced leaves total 1.64 m of coal; here the Dunsil is thought to be closely associated with the Blidworth Coal above (here included with the Barnsley) and possibly also with a high leaf of the First Waterloo below. Much of the Dunsil is bright coal, but layers of 'hards' occur throughout. Most of the 'hards' are impersistent, but one near the middle of the seam is widely recognisable and contains a bright coal layer within it in places. In Bentley Colliery workings this 'hards' layer combines with others to form a bed of dull coal up to 0.76 m thick; the deterioration northwards is largely confined to the upper part of the seam. Southwards the seam deteriorates by splitting mainly in the lower part, as in Yorkshire Main Colliery workings. The Dunsil has been worked in small areas at Askern, Bentley, Hatfield, Markham Main, Rossington and Yorkshire Main collieries and more extensively in conjunction with the Barnsley at Harworth Colliery, but its exploitation is restricted by variations in thickness and quality and by locally unsatisfactory roof conditions.

The beds between the Dunsil and Barnsley coals

The beds between the Dunsil and Barnsley coalsare thickest along the western edge of the district, being 25.65 m and 24.69 m in Lee Lane Borehole and Askern Colliery No. 1 Shaft respectively. Although they are only 14.58 m in Bentley Colliery No. 2 Shaft, they expand southwards to 16.20 m in Wilsic Hall Borehole (Figure 13). There is an irregular easterly thinning across the north of the district to possibly as little as 4.51 m in Rawcliffe No. 2 Borehole and 6.82 m in Crowle Common Borehole, but in Drax Nos. 2 and 4 and Airmyn Grange boreholes, the Dunsil and the widely diverging lowest part of the Low Barnsley Coal are less than 0.5 m apart and are locally united. From Hatfield Colliery No. 1 Shaft and adjacent workings southwards past Markham Main Colliery No. 1 Shaft and workings, and across central southern parts of the district, the Dunsil and Barnsley are generally less than 0.5 m apart and locally come together. In the southeast, the Dunsil, although separated from the Barnsley by up to 13 m of strata, is thought to be united with or closely overlain by the Blidworth Coal. In the west and north, where the beds between the Dunsil and Barnsley are of appreciable thickness, two or three cycles are marked by thin coals or seatearths. Much of the sequence commonly consists of siltstone. Where sandstone is present, it is generally in the lower part, and in a few boreholes as far apart as Percy Lodge and Wilsic Hall it rests directly on the Dunsil. Where mudstones overlie the coal, however, they locally contain Spirorbis sp., A. phrygiana and N. quadratus, and in a few northern boreholes such as Camblesforth No. 1 and Great Heck, mudstones containing Spirorbis sp. and Naiadites sp. occur above a seatearth in the middle part of the sequence.

Barnsley Coal

The Barnsley Coal complex, which in this account includes the Blidworth Coal and its north-western correlative, is subject to several widely divergent splits but contains considerable thicknesses of coal, especially where closely associated or united with the Dunsil. It is the most extensively worked seam in the district and has been exploited in extensive workings in Askern, Bentley, Brodsworth, Bullcroft, Cadeby, Harworth, Hatfield, Maltby, Markham Main, Rossington and Yorkshire Main collieries. The subdivisions of the seam, based on those recognised farther south (Smith et al., 1973, p.80) are:

(Figure 14) and (Figure 15) illustrate these subdivisions and the various splits.

Two splits occur in the north. One develops northwards within the Low Barnsley, probably by expansion of the impersistent strata within the Bottom Softs, and increases to over 15 m in Drax No. 4 and Airmyn Grange (Figure 14) boreholes where the intervening strata consist mainly of siltstones with some thin sandstones. In these sections and also in Drax No. 2 Borehole the lower part of the Low Barnsley lies within 0.5 m of, and is locally united with, the Dunsil. This split is less pronounced north-eastwards near the northern edge of the district, but it is apparently well developed to the north-west where at least the lowest part of the Bottom Softs continues beyond the district as a separate thin coal probably correlating with the Blidworth Coal of Nottinghamshire (Edwards, 1967, pp. 95–96). Largely superimposed on this split is the 'Warren House Split', between the Low Barnsley and Warren House coals, which is as much as 9 to 11 m thick in Burn Airfield No. 1, Barlow No. 2 (Figure 14) and Drax No. 4 boreholes, where the intervening beds are mainly siltstones with thin sandstones locally. Between Eggborough and Howden these sandstones and siltstones thicken markedly to form the Horbury Rock which, as in Camblesforth Nos. 1 (Figure 14) and 3 and Drax No. 3 boreholes (Figure 13) cuts down through the Low Barnsley and in places also through the Dunsil. Cross-bedding and ripple-bedding are widespread in the Horbury Rock and conglomeratic layers are present locally.

Around Hatfield Colliery No. 1 Shaft (Figure 14) in the centre of the district and southwards, the main part of the Barnsley Coal lies within 0.5 m of, or joins with, the Dunsil. The two diverge westwards and also to the east, but in the latter direction, the Blidworth Coal splits south-eastwards from the rest of the Barnsley and remains close to the Dunsil. The strata within this split are up to 13 m thick and consist largely of siltstones, locally with sandstones; mudstones occur widely in the middle of the sequence, however, and in Langholme and Blyton Carr boreholes they contain mussels. Along an underground drift about 700 m south from Hatfield Colliery No. 1 Shaft, the Day Bed Softs and Barnsley Rider diverge markedly to lie more than 15 m above the main part of the Barnsley. Farther south, as in Gate Farm and Brancroft boreholes (Figure 14), this interval is more than 20 m wide, but in several sections, such as Markham Main Colliery No. 1 Shaft (Figure 13), the Day Bed Softs and Barnsley Rider are not recognisable and may be cut out by siltstones and sandstones. Both seams probably converge eastwards with the main part of the Barnsley Coal near Grove House and Westwoodside boreholes. The Day Bed Softs apparently converge westwards also, being closely associated with the main part of the Barnsley in Maltby Colliery (Smith et al., 1973, pp. 78–80), but the Barnsley Rider continues westwards to lie 7 to 11 m above the main part of the Barnsley (Mitchell et al., 1947, p.63, figs. 15 and 18). Where these two seams lie more than about 5 m above the Barnsley, the intervening beds commonly include siltstones, locally some sandstones, in places one or two thin coals or seatearths and, in Harworth Colliery 22A Underground [SK 6511 9398] and Misson boreholes, some mussels.

Bottom Softs

The Bottom Softs are mainly good quality bright coal but the basal part is locally inferior and 0.27 m of cannel coal is present in Misson Borehole (Figure 15). They are more than 0.75 m thick locally, reaching 0.97 m in Rossington Colliery B 77 workings, and the intervening partings are generally not more than 0.05 m thick in the south of the district.

Hards

The Hards are widely sub-divisible only in the south of the district, although the Gees, and more noticeably the Clay Coal, are impersistent. The greatest thickness of the Hards is 0.94 m in Rossington B 20 workings but their sulphur content increases upwards and may be high at the top. In the north the Hards are generally thin and locally cannot be distinguished; a thin argillaceous layer occurs in the lower part of the Hards in some places. The argillaceous layer above the Hards, although impersistent, is generally between 0.03 and 0.15 m thick; in the north it is more widespread and widens into the 'Warren House Split'.

Top Softs

The Top Softs consist largely or entirely of bright coal. In the north the Low and Middle Bed Softs are generally united and up to 0.85 m thick. The impersistent mudstone partings between them are up to 0.15 m thick in the south-west and slightly thicker eastwards. The Day Bed Softs are generally of inferior quality. They are united with the Middle and Low Bed Softs in places from Askern northwards and also locally in Bentley and Hatfield collieries; these united Top Softs in some northwestern areas expand to 1.24 m, although their basal part is generally inferior. Except in the north-west, the Barnsley Rider is separated from the rest of the Top Softs, although the intervening beds are less than 0.30 m thick in most northern areas. The Rider consists mainly of bright coal but contains some dull layers in the north. It is of good quality in Askern, Bentley and Markham Main collieries but it becomes pyritic farther north, and although in the south it increases locally to 0.69 m thick in Harworth Colliery No. 22A Underground Borehole [SK 6511 9398], it includes much 'dirty' coal and some 'dirt' layers hereabouts.

The beds between the Barnsley Coal and the Kent's Thick Coal

The beds between the Barnsley Coal and the Kent's Thick Coal vary across northern and central parts of the district, from more than 40 m thick in West Haddlesey No. 1 Borehole (Figure 13) and Bentley Colliery No. 2 Shaft in the west, to less than 20 m in Drax No. 2, Brind Common and Percy Lodge boreholes farther east. In addition they are less than 30 m thick in the area between Whitley and Camblesforth. In some central sections such as Markham Main Colliery No. 1 Shaft (Figure 13) and in more southerly areas, these beds cannot be accurately measured since the Barnsley Rider cannot be identified with certainty. In the south-west, where this coal is probably cut out, the strata between the main part of the Barnsley Coal and the Kent's Thick Coal are about 53 m thick, as in Wilsic Hall Borehole (Figure 13). Three cycles are widely discernible, with the Dull Coal at the top of the lowest, but in a few places at least one higher cycle is suggested by an impersistent seatearth which may have split off the base of the Kent's Thick. Siltstones and sandstones are common in all three cycles, though sandstones are thickest in the lowest and highest cycles. In some areas, notably in the south-west, the siltstones and sandstones coalesce to obliterate the cycles and locally to cut down through the Barnsley Rider. Thin mudstones at the base of the first cycle yield traces of mussels in only a few places, but plant debris is particularly common at this level.

Dull or 'Main Smut' Coal

The Dull or 'Main Smut' Coal at the top of the first cycle, although locally impersistent, contains over 0.60 m of coal in places. It is generally in one leaf, but in a few sections is in two or three leaves and is characterised by a prominent durain layer.

Mudstones at the base of the second cycle are commonly mussel bearing, especially in the north, and in the Ash Hill, Cross Hill and Fenwick boreholes they also contain sparse 'Estheria' sp. Mudstones at the base of the third cycle also contain mussels, apparently more abundantly in the south. 'Estheria' sp. recorded from Bank End and Harworth Colliery No. 22A Underground [SK 6511 9398] boreholes appears to be from this horizon. The fauna from the entire sequence includes Spirorbis sp., Anthraconaia pulchella, Anthracosia spp. including A. cf. aquilinoides and A. sp. nov. cf. planitumida, Anthracosphaerium propinquum, A. cf. turgidum, Naiadites cf. angustus, N productus, 'Estheria' sp. and fish debris including palaeoniscid scales.

Kent's Thick Coal

The Kent's Thick Coal is split into two closely spaced leaves across much of the district, but in eastern sections in the Hemingbrough, Misson (Figure 13) and Westwoodside boreholes and at Thorne Colliery, the seam is united; in western sections in the Yorkshire Main Colliery No. 18 Underground Borehole [SK 571 999], Askern Colliery No. 1 Shaft and West Haddlesey No. 1 Borehole, the two leaves have diverged markedly, being 9.00 m apart in the last section. Where the split is more than about 4 m wide, the intervening strata consist mainly of siltstones or sandstones. The lower leaf of the Kent's Thick is generally 0.25 to 0.80 m thick and largely comprises bright coal, but locally its base and top is of inferior coal; cannel coal occurs at the base in Camblesforth No. 1 and Bank End boreholes. The upper leaf, locally impersistent but generally up to 0.75 m thick, commonly contains one or more layers of dull coal, of which the most widely developed lies near the middle of the leaf, and in Hatfield Colliery No. 35 Underground Borehole [SE 6746 1061] the highest 0.30 m is cannel coal. This leaf generally has a low sulphur content. From Hatfield Colliery south-westwards, the upper leaf splits in places into up to four thin coals, as in Markham Main Colliery No. 1 Shaft (Figure 13), where the thickest intervening 'dirt' layer is 1.12 m thick.

The beds between the Kent's Thick Coal and the Hatfield High Hazel Coal

The beds between the Kent's Thick Coal and the Hatfield High Hazel Coal(and its correlatives) vary from 23 m to apparently just over 41 m thick. Most of the sections in which they exceed 36 m are south and south-east of Doncaster, as in Misson Borehole (Figure 16) where they are 37.13 m thick. But in Rawcliffe No. 1 Borehole, where thick sandstones occur in the lower part, they reach 38.33 m, whilst in Eskholme Borehole, where sandstones occur at several levels, they are 36.99 m and in Hatfield Colliery No. 1 Shaft they are 41.02 m, although here the abnormal thickness appears to be due to an appreciable dip, for elsewhere in the colliery these beds are not more than 33 m thick. Up to four cycles are indicated locally by the incidence of impersistent thin coals, seatearths and mussel bands. The Kent's Thin Coal lies at the top of the third cycle up, and it is possible that some of the lower seatearths represent splits from this coal.

Up to 14 m of mudstone overlie the Kent's Thick Coal, with abundant plant debris locally at the base and thin ironstone beds and several mussel-bearing layers, especially in the lower part, which have yielded Spirorbis sp., Anthracosia spp. including A. caledonica?, A. planitumida and A. sp. cf. fulva, Naiadites aff. productus and sineoid markings. In several places, notably around Rawcliffe and in southern sections such as Misson (Figure 16) and Martin Common boreholes, these mudstones are succeeded by thick and locally conglomeratic sandstones. Where distinguishable, the next two cycles, up to the Kent's Thin Coal, are generally thin but consist largely of siltstones with thin sandstones in places, although mudstones at their bases have yielded Anthracosia simulans and Anthracosphaerium turgidum.

Kent's Thin Coal

The Kent's Thin Coal occurs as up to three closely spaced thin leaves in Fir Tree, Brind Common (Figure 16), Hemingbrough and Selby No. 2 boreholes in the north of the district, and also in some north-western boreholes, but elsewhere in the north it is marked generally by only a seatearth. In southern areas, although absent in Misson Borehole, it consists generally of up to three closely spaced leaves containing locally more than 0.50 m of coal, as in Austerfield and Brancroft boreholes. In Wilsic Lodge and Wilsic Hall boreholes in the southwest, although the seam was not cored, it is estimated to be 0.80 m thick. To the south of the district the Kent's Thin equates with the bottom bed of the two widely split parts of the High Hazles Coal of the East Midlands (Smith et al., 1973, p.81).

Mudstones in the lower part of the cycle above the Kent's Thin contain Spirorbis sp., Anthraconaia aff. pulchella, Anthracosia spp. including A. caledonica, A. aff. fulva and A. simulans, and N. productus. The succeeding strata are mainly siltstones with thin impersistent sandstones, but thicker sandstones occur in Fenwick, Fosterhouses (Figure 16), Eckholme and Pincheon Green boreholes. In Hatfield Colliery North-east Return Drift the beds reach 14.45 m in thickness, although this may be an overestimate of their stratigraphical thickness. These sandstones and siltstones are probably responsible for cutting out the Kent's Thin in some areas, and in sections such as Bentley Colliery No. 2 Shaft (Figure 16) they merge with similar underlying beds to obliterate the cycles.

Hatfield High Hazel Coal

The Hatfield High Hazel Coal (not to be confused with the High Hazles Coal of the East Midlands) is distinct in central and north-eastern parts of the district. To the north-west and west, however, it splits into the lower and upper parts of the Stanley Main Coal, which farther west converge to form the thick seam of that name around Wakefield (Edwards et al., 1940, pp. 71–74, figs. 42, 43). The Hatfield High Hazel also splits southwards, its lower part becoming the top bed of the High Hazles Coal and its upper part becoming the Kilnhurst Coal (Smith et al., 1973, pp. 81–82, pl. VI), locally with one or two thin coals between them. To the south-west, at least the lower part of the Hatfield High Hazel becomes the Beamshaw Coal of the Barnsley district (Mitchell et al., 1947, pp. 66–67).

In Hatfield Colliery No. 1 and Thorne Colliery No. 1 shafts, the Hatfield High Hazel is a single seam 1.78 m and 1.60 m thick respectively, and it reaches 1.95 m in the south-eastern part of Hatfield Colliery workings. To the north and north-east it remains unified and up to 1.49 m thick in boreholes as far apart as Eskholme, Quay Lane and Booth Ferry. In other directions, however, even within Hatfield Colliery workings, the coal splits into as many as four leaves separated by the lower, middle and upper 'dirts'. Although in the northern and western part of these workings only the upper 'dirt' is apparent, lying 0.15 to 0.30 m below the top of the coal, farther to the north and west the main split occurs at the level of the middle 'dirt'. In the north, from Brind Common Borehole (Figure 16) to as far west as Hemingbrough Borehole, the split is less than 0.5 m wide, but it increases markedly westwards to 15.98 m in Selby No. 2 Borehole and is still 10.93 m in Eggborough No. 1 Borehole, there separating the two parts of the Stanley Main Coal. Mussels and fish debris are recorded locally in the mudstones in the lower part of the interval and there are siltstones and sandstones above it in some sections, as in Eggborough No. 1 Borehole. This wide split persists along the western edge of the district as far south as Fenwick and Shaftholme Grange boreholes, but in Bentley Colliery No. 2 Shaft the lower and probably also the upper of the Stanley Main seams appear to be missing within a thick siltstone and sandstone sequence. In the north-west of the district, even as close to Hatfield Colliery as Fosterhouses Borehole (Figure 16), the upper 'dirt' of the Hatfield High Hazel persists and continues to split the upper part of the Stanley Main farther in this direction, as in Camblesforth No. 1 and Eggborough No. 1 boreholes.

In the southern and eastern parts of Hatfield Colliery workings, the lower and middle 'dirts' separate the three closely spaced leaves in Crowle Common and Brier Hills boreholes (Figure 16). The two splits widen southwards, each being more than 2 m thick in Markham Main Colliery No. 1 Shaft and Gate Farm Borehole. Farther in this direction, across the south of the district, the seam below the expanded lower 'dirt' continues as the top bed of the High Hazles, estimated to be 0.84 m thick in Wilsic Lodge Borehole, but apparently only 0.03 m in Misson Borehole. The seam between the expanded lower and middle 'dirty' becomes impersistent southwards, being commonly represented only by a seatearth. The seam above the expanded middle 'dirt' becomes the Kilnhurst Coal, 1.02 m thick (in two closely spaced leaves) and 0.61 m thick in Westwoodside and Misson boreholes respectively, and commonly lying more than 12 m above the top bed of the High Hazles Coal. Mussels are recorded from the higher of these expanded splits as far north as Gate Farm Borehole and they were found in strata equivalent to both splits in Misson Borehole. Siltstones and locally some sandstones occur in this interval. Thick sandstones are present in Blyton Carr Borehole in the south-east, apparently between the top bed of the High Hazles and the Kilnhurst, but the correlation is uncertain here, especially as in the nearby East Stockwith Borehole about 40 m of locally conglomeratic sandstone occur between the Meltonfield and High Hazles coals, cutting out all the intervening seams including the Kilnhurst.

The Hatfield High Hazel is mainly bright coal, but dull coal layers are common in its lowest part and just above the upper 'dirt', and they occur locally elsewhere. The coal is generally of a highly volatile and weakly coking type, with moderate to low ash and sulphur contents, but commonly a high chlorine content. In the north-west, the lower part of the split Stanley Main is mainly bright coal, with one or two dull layers near the base; the upper part, however, consists largely of dirty coal, particularly where further splits develop, although it also contains bands of bright coal, especially near the top. In the south, much of the top bed of the High Hazles is also bright coal, but in the Bank End Borehole the lower half is largely of inferior quality; in Rossington Colliery No. 1 Shaft, 0.15 m of the 0.48 m seam is cannel coal. The Kilnhurst Coal is also largely bright coal, but has dull layers near the base and locally in the middle and near the top.

The beds between the Hatfield High Hazel Coal (and its correlatives) and the Two-Foot Coal

The beds between the Hatfield High Hazel Coal (and its correlatives) and the Two-Foot Coal are mainly between 17 and 34 m thick, but reach up to 38 m in some western sections. The maximum recorded thickness of 41.56 m in Hatfield Colliery No. 1 Shaft includes 6.68 m of 'conglomerate' and 2.03 m of 'dolomitic limestone and copper pyrites', and is thought not to be a true stratigraphical thickness since it may be faulted. Seatearths and impersistent coals commonly indicate that between two and five cycles are present. In most sections only one coal, the Winter or Abdy, is present, but its cyclic position is not consistent and it may be a composite of at least two split and impersistent leaves occurring in different parts of the district. Mudstones occur generally at the bases of most cycles and some contain mussels and related fossils, notably at the base of the lowest cycle where Spirorbis sp., Anthraconaia cf. pulchella, Anthracosia aff. faba, Naiadites alatus and fish debris are recorded. Siltstones are present in all the cycles; they are more common in the higher cycles where, with impersistent but locally thick sandstones, they form the Abdy Rock.

Winter or Abdy Coal

The Winter or Abdy Coal (the latter name being used south-west and south of the district) lies in the lower part of the Hatfield High Hazel/Two-Foot interval and apparently at the top of the first or second cycles in western and north-western sections, such as Eggborough No. 1 and Camblesforth No. 1 boreholes (Figure 16). Farther east and south-east, however, it occurs higher up, apparently at the top of the third cycle, as in Fenwick and Crowle Common boreholes (Figure 16), and similar variations are apparent in more southerly parts of the district. In a few boreholes, such as Brind Common, Fosterhouses and Brier Hills, two coals are present at this horizon. It appears probable that the Winter Coal is widely split across much of the district, except in the west and north-west, and that where the seam occurs high in the sequence it is only the upper split of the coal that persists. This view is supported by the variations in thickness, for in several north-western boreholes, such as Thorpe Hall, West Haddlesey No. 2, Chapel Haddlesey and Selby No. 2, more than 1.00 m of coal is proved either as a single seam or as one or two thin leaves close below a thick one. In contrast, there is a general thinning to the south-east, especially in the lower split where two are present. Much of the Winter in the north-west is good quality bright coal with one or two dull layers in the middle, but to the south-east a 'dirt' layer appears just above the middle and the two resulting leaves become progressively more dirty in this direction.

Abdy Rock

The Abdy Rock, overlying the Winter Coal but not shown in (Figure 16), comprises sandstones, locally with interbedded and suprajacent siltstones. In the north the Rock is thin and impersistent, and consists mainly of siltstones, the thickest proving being in Cross Hill Borehole where it is 7.77 m thick and includes 6.10 m of sandstone. Farther south, it is locally thicker but consists mainly or entirely of siltstone in most sections. Around Austerfield, however, boreholes such as Martin Common and Lady Galway proved more than 20 m of sandstone cutting out the Winter Coal and locally the Kilnhurst.

Two-Foot Coal

The Two-Foot Coal is at a maximum of 1.12 m in Bentley Colliery No. 2 Shaft (Figure 16), and elsewhere it is generally 0.30 to 0.80 m thick. Although in many areas it is a single seam, it splits locally into two leaves separated by up to nearly 5 m of strata which in a few sections include thin sandstones. The lower leaf does not contain more than 0.30 m of coal, and is itself split into two or three leaves in places and is generally of inferior quality. In several sections including Bentley Colliery No. 2 Shaft the lower leaf is probably only a seatearth. Much of the upper leaf, especially near its top, is also inferior coal and some of the thicker provings, including that in Bentley Colliery No. 2 Shaft, are largely or entirely of cannel coal. In Trumfleet Borehole, where the upper leaf comprises 0.53 m of cannel and the lower leaf is represented by seatearth, the two are separated by 0.46 m of black 'shale' containing 'Estheria' sp. and fish debris.

The beds between the Two-Foot and Meltonfield coals

The beds between the Two-Foot and Meltonfield coalsare 5.5 m thick to possibly more than 30 m near Austerfield, but otherwise are generally not more than 15 m thick. Only one cycle is present, assuming that a thin coal or seatearth occurring locally in the upper part of the interval, as in Crowle Common and Misson boreholes, is a split from the Meltonfield. The Maltby Marine Band occurs at the base of the cycle, with mussel-bearing mudstones, siltstones and then thin sandstones at successively higher levels, although the sandstones are much thicker and conglomeratic near Austerfield.

Maltby (formerly Two-Foot) Marine Band

The Maltby (formerly Two-Foot) Marine Band has been proved in most places, although in some southern sections it is cut out by overlying sandstones; in the core from Lady Galway Borehole the fossiliferous mudstone was only 0.01 m thick and was probably a derived fragment occurring within thick conglomeratic sandstones. Elsewhere, the marine band generally lies directly on the Two-Foot Coal, although in a few places up to 0.03 m of carbonaceous or canneloid mudstone intervenes. The marine band consists of dark grey or black, commonly silty mudstone that in most sections is less than 0.10 m thick, but which expands considerably near the western edge of the district between Whitley and Doncaster, reaching 1.68 m in Trumfleet Borehole. The increased thickness may be present farther south but evidence from cored boreholes is lacking. Where the marine band is thin its fauna is largely limited to small fragments of Lingula mytilloides and fish debris, but in the thicker provings at Fenwick and Trumfleet boreholes and in Bentley Colliery No. 2 Shaft, the lower part of the marine band in particular yields a more diverse fauna, including Posidoniella laevis (Culpin, 1909).

These thick and richly fossiliferous provings of the marine band are comparable to those at Bullcroft and Brodsworth collieries to the west of the district (Culpin 1909; Edwards, 1951, pp. 137, 144) and at Maltby Colliery to the south (Smith et al., 1973, p.83). It is noticeable that they overlie the Two-Foot Coal where it consists largely or entirely of cannel.

In Barlow No. 2, Hemingbrough, Fenwick, Cross Hill and Trumfleet boreholes, up to 0.5 m of dark grey or black mudstone resting on the Maltby Marine Band contains Estheria, probably all Lioestheria vinti, and fish debris. The overlying mudstones, which in most other boreholes lie directly on the marine band, are nearly 5 m thick and have yielded an abundant fauna including Spirorbis sp., Anthraconaia aff. cymbula, A. librata, Anthracosia acutella, A. cf. aquilina, A. aquilinoides, A. atra, A. concinna, A. lateralis, A. planitumida, Anthracosphaerium aff. propinquum, A. radiatum, Curoirimula? Naiadites alatus, N. obliquus, N. productus? and fish debris including aconthodian spines, Elonichthys sp., Rhabdoderma sp. and Rhizodopsis sp. In some northern sections, such as Camblesforth No. 1 Borehole (Figure 16), a thin mudstone closer to the Meltonfield Coal has yielded Spirorbis sp. and a few of the mussel species listed above.

Meltonfield Coal

The Meltonfield Coal, although recorded as a single seam in several widely scattered sections, consists more commonly of two leaves. The upper is generally the thicker, and in most areas they are less than 0.5 m apart. In a few provings, however, especially between Selby and Camblesforth, the intervening strata expand to 6.30 m and include siltstones and sandstones. The lower leaf itself splits into two or more thin leaves locally, especially in the east, as in Crowle Common and Brier Hills boreholes, and a thin leaf splits away from the main part of the upper leaf in some eastern and southern locations. The thickest total coal proved is 1.82 m in Snaith Borehole, and thicknesses between 0.70 m and 1.22 m are widespread. In some localities, however, particularly in the north-west, the Meltonfield is thin or absent where it is cut out, partly or wholly, by the Woolley Edge Rock or equivalent strata. The lower leaf is generally not more than 0.60 m thick, but reaches 0.85 m in Snaith Borehole. It commonly consists partly, and locally entirely, of inferior quality coal. The upper leaf is 1.08 m and 1.06 m thick in Fenwick Hall and Pollington No. 3 boreholes respectively and contains some bright coal in places, but argillaceous partings are not uncommon and its upper part in particular consists widely of cannel coal. In Pollington No. 2 Borehole, where a single seam 1.14 m thick is proved, all but 0.19 m of it is cannel coal.

The beds between the Meltonfield and Newhill coals

The beds between the Meltonfield and Newhill coalsare mainly between 9 and 20 m thick, except in the northwest, where they reach 25.94 m in Barlow No. 2 Borehole; they are even thicker farther west where the Woolley Edge Rock, which lies in this part of the succession, is thickly developed. However, as the rock commonly cuts out part or all of the Meltonfield Coal, as in Eggborough No. 1 Borehole (Figure 16), its full thickness cannot always be determined. At least two cycles are readily discernible across much of the district from the occurrence of a widespread seatearth lying in or above the middle of the sequence, which locally supports a thin coal and in places the overlying Manton 'Estheria' Band. In a few sections, however, seatearths at higher levels suggest one or more additional cycles, although they may only be localised splits from the Newhill Coal. There is some geophysical evidence suggesting that the Clown Tonstein lies close below the Newhill in the south.

In at least eleven boreholes, widely scattered but mainly in the north and east, including Camblesforth No. 1, Brind Common, Crowle Common and Misson boreholes, the mudstones resting directly on the Meltonfield or lying up to 3 m above the seam have yielded 'Estheria' sp., some of which have been confirmed as Lioestheria they are associated with fish debris. Mudstones slightly higher in the sequence have yielded mussels including Anthracosia acutella, A. atra, A. cf. planitumida and Naiadites obliquus. In many sections this lower cycle consists partly of silty mudstones, and although elsewhere some siltstones are present, there are only a few provings of sandstone, mainly as thin bands. In Barlow No. 2 and Gate Farm boreholes, and apparently in several other sections including East Stockwith Borehole, a thin ironstone layer containing white ooliths is associated with the seatearth below the Manton 'Estheria' Band. X-ray analysis by K S Siddiqui showed that the principal mineral in the ooliths in a specimen (RFG 296a) from a depth of 450.37 m in Barlow No. 2 Borehole is calcite, with subordinate limonite.

Manton 'Estheria' Band

The Manton 'Estheria' Band, characterised by the presence of Lioestheria vinti, is widely present in the north, as in Camblesforth No. 1 and Fenwick boreholes (Figure 16), but in the far north-west it is cut out by the Woolley Edge Rock; its maximum recorded thickness is 1.69 m in Barlow No. 2 Borehole. It thins southwards and is commonly absent in the south of the district, where it is confirmed only at Bank End Borehole; it is only 0.05 m thick here. Equivalent beds in Misson and Fosterhouses boreholes are rich in fish debris. The band generally consists of black, silty, carbonaceous mudstone and contains L. vinti and fish debris, together with Naiadites sp. in some sections.

Woolley Edge Rock

The overlying mudstones commonly contain mussels. Siltstones are common below the Newhill Coal, locally with thin sandstones, but in the north-west these arenaceous strata expand to form the Woolley Edge Rock. The rock is more than 40 m thick in Chapel Haddlesey and Eggborough No. 2 boreholes and exceeds 30 m in several adjacent boreholes including Eggborough No. 1 (Figure 16). It consists mainly of medium- to coarse-grained sandstones with conglomeratic layers in the lower part, but also includes some siltstones in the upper part and at the top, which commonly lies close below the seatearth of the Newhill. The Meltonfield Coal is partly or entirely cut out by its lower part in some areas.

The Clown Tonstein (Eden et al., 1963; see also Smith et al., 1973, p.84) is probably indicated by the distinct gamma-ray peak in the mudstones close below the Newhill Coal in some southern sections, such as Wilsic Lodge (Figure 16) and Lady Galway boreholes.

Newhill Coal

The Newhill Coal is equivalent to the Clown Coal of the East Midlands and is thickest in western central parts of the district, where it reaches 1.33 m, including 0.06 m of mudstone near the base, in Shaftholme Grange Borehole. It is generally more than 0.80 m thick in the area of the Askern, Hatfield, Markham Main and Bentley collieries, although some dirty coal or thin mudstone partings are commonly present near the base. In the north, the coal is not more than 0.25 m thick and several sections proved only a seatearth. This thinning is particularly marked in the north-west, where the Woolley Edge Rock is thick, as in Eggborough No. 1 Borehole where only 0.02 m of coal is present. In the far north-west the Newhill was removed by pre-late Permian erosion. The seam also thins to the east and south-east, although two closely spaced leaves are locally present. In the southwest, in Wilsic Lodge Borehole (Figure 16), the coal is estimated to be 0.60 m thick. In the east and south-east the coal is generally of inferior quality and in some boreholes such as Gate Farm and Bank End its upper part is cannel.

The beds between the Newhill and Swinton Pottery coals

The beds between the Newhill and Swinton Pottery coalsare mainly between 12 and 20 m thick, but are thicker in some central northern and south-western sections, reaching 28.37 and 24.9 m in Camblesforth No. 1 and Wilsic Lodge boreholes respectively. The interval is only 5.41 m in Blyton Carr Borehole in the south-east. The thickness cannot be accurately measured in some eastern boreholes, such as Crowle Common, Gate Farm and Brier Hills, because the Oaks Rock has cut out the Swinton Pottery Coal hereabouts. A widespread seatearth, locally supporting a thin coal, divides the sequence into two cycles, with the Clown Marine Band near the base of the lower cycle. In some sections a thin coal or seatearth close below the Swinton Pottery Coal suggests a third cycle, but it may only be a split from this coal.

Clown Marine Band

The Clown Marine Band has been proved only to the south of the Armthorpe (Wilson, 1926, p.30), Brier Hills and Gate Farm boreholes; it reaches 0.41 m in thickness in Misson Borehole (Figure 16). This distribution coincides with an area where the Newhill Coal is largely impoverished and its upper part is commonly cannel coal. Grey mudstones up to 1.85 m thick and locally containing plant debris, 'fucoids' and fish debris underlie the marine band, which consists of black shaly mudstone containing L. mytilloides and fish debris including acanthodian spines, Rhadinichthys sp. and Strepsodus sp. In some uncored southern boreholes such as Wilsic Lodge, a pronounced gamma-ray peak close above the Newhill Coal almost certainly marks the marine band.

North of the area where the Clown Marine Band is proved, the beds equivalent to it yield mussels, ostracods and fish debris, and mussels also occur in the overlying mudstones. The rest of the cycle above the Newhill largely comprises mudstones, although siltstones and thin sandstones are present locally. The thickness of the cycle decreases northwards and in some areas it seems to consist only of the seatearth at its top; this lies directly on the Newhill Coal in Camblesforth No. 1 Borehole (Figure 16). In such areas the succeeding cycle is abnormally thick and commonly includes substantial siltstones and some sandstones. The mudstones at its base have yielded Anthracosia atra, Naiadites angustus and fish debris, with '?Estheria' being reported from this level in Misson Borehole. Both A. atra and N. angustus are also recorded from the incipient cycle close below the Swinton Pottery Coal.

Swinton Pottery Coal

The Swinton Pottery Coal is thickest in the north-west, reaching 0.90 m in Burn Airfield No. 2 Borehole. It maintains similar thicknesses towards the east and south, being 0.75 m in Percy Lodge Borehole and 0.61 m in Bentley Colliery No. 2 Shaft, but it thins farther to the east and south where it is generally less than 0.40 m thick and in some sections is less than 0.20 m, although generally persistent. An impersistent thin coal or seatearth lying about 6 m below the Swinton Pottery in some areas may be a split from that coal, but generally the coal is a single seam consisting either of bright coal, as at Askern Colliery, or interlayered bright and dull coal, as at Bentley Colliery. In some north-western and western sections, however, parts of the seam are of inferior coal.

The beds between the Swinton Pottery and Wheatworth coals

The beds between the Swinton Pottery and Wheatworth coalsare 49.99 m thick in Rossington Colliery No. 1 Shaft, where they consist largely of Oaks Rock. They exceed 30 m in several other provings where the sandstone is thick, but elsewhere they range mainly between 16 and 26 m.

Although commonly only three or four cycles are apparent in any one section, the detailed correlation of thin coals, seatearths and fossil bands suggests that five cycles are present. The Houghton Marine Band lies at or near the base of the next to the lowest cycle and the Sutton Marine Band is in the lower part of the highest cycle. In a few sections, thin coals or seatearths suggesting one or two additional cycles close below the Wheatworth Coal are probably local splits from that seam.

The cycle above the Swinton Pottery contains mudstones in its lower part, which yield N. angustus and fish debris. The cycle is commonly less than 2 m thick but reaches 8.26 m in Barlow No. 2 Borehole. Where the cycle is expanded, as in Brind Common Borehole and Bentley Colliery No. 2 Shaft, it includes siltstones and locally some sandstones. An impersistent seatearth and rarely a thin coal, as in the Armthorpe Borehole, mark its top.

Haughton Marine Band

The Haughton Marine Band was first recorded in the district by Culpin (1909) in Bentley Colliery No. 2 Shaft (Figure 16), it presumably being his 'fifth marine band'. It is 7.32 m thick in Lady Galway Borehole and more than 4 m thick in several western, central and southern boreholes. It is generally thick where the underlying cycle is thin and vice versa, but it is cut out by the Oaks Rock in places, most notably in a belt about 8 km wide stretching south-south-westwards from Thorne Colliery and covering Hatfield and Rossington collieries. The marine band consists of dark grey to black, silty mudstone which in places includes thin layers or lenses of siltstone; thin ironstone occurs locally in the south. The marine fauna is largely benthonic and includes the distinctive trace fossil cf. Tomaculum sp.; 'fucoid' markings are widespread. Some northern boreholes, such as Barlow No. 1, Hemingbrough and Brind Common (Figure 16), yielded only Lingula sp. Also in the north, mussels have been found underlying the marine band in Brind Common Borehole and are present in its upper part in Bar low No. 2, Ash Hill and Pollington No. 2 boreholes. The full fauna comprises: foraminifera including Ammodiscus sp., Glomospira sp. and Tolypammina sp., Serpuloides stubblefieldi, Lingula elongata, L. mytilloides, Orbiculoidea cf. nitida, coiled gastropod, pleurotomariid, Anthracosia acutella, A. cf. atra, Curvirimula sp., Myalina?, Naiadites alatus, Cypridina? Geisina sp., Holinella sp., cf. Shansiella, fish debris, cf. Tomaculum sp., 'fucoids' and pyritic burrows.

Where the Haughton Marine Band is thick, the overlying part of its cycle commonly consists only of mudstone seatearth extending up to the fairly persistent thin coal at the top, which reaches a thickness of 0.41 m in Hemingbrough Borehole. However, in northern and some eastern boreholes, where the marine band is thin, it is succeeded by generally silty mudstones containing mussels which include A. cf. acutella and Naiadites sp., associated in Barlow No. 2 Borehole with Carbonita humilis and 'Estheria' sp., and in Westwoodside Borehole with 'fucoids'. In a few widely scattered boreholes such as Camblesforth No. 1 and Misson, the upper part of this cycle contains thin siltstones and sandstones.

Mudstones forming much or all of the succeeding cycle contain mussels in the lower beds, including Anthracosia rubida, A. simulans and Naiadites angustus. Again, thin siltstones occur in a few places near the top of the cycle, which is marked locally by a thin impersistent coal, but more widely by only a seatearth.

The overlying cycle is not well defined because the mudstones in it are apparently unfossiliferous and there are only impersistent traces of coal or seatearth at its top. In some of the few sections where the Sutton Marine Band at the base of the next cycle can be identified, a thin sandstone occurs just below the marine band. It seems likely that this sandstone expands in some areas to form the Oaks Rock, although it is possible that sandstones and siltstones above the Sutton Marine Band also contribute to the Oaks Rock in some sections.

Oaks Rock

The Oaks Rock is thickest in a large area between Drax, Crowle and the south-western corner of the district. It reaches a maximum thickness of 42.64 m in Rossington Colliery No. 1 Shaft where its base lies close above the Newhill Coal. Where it is thick the lower part of the sandstone is commonly medium to coarse grained and locally conglomeratic, with fine-grained sandstones at higher levels and siltstones near the top.

Sutton Marine Band

The Sutton Marine Band occurs in the lower part of the cycle below the Wheatworth Coal, but it has been recorded from only a few locations, all in the north-west, such as Eggborough No. 1 Borehole; its most south-easterly proving is in Ash Hill Borehole. It comprises less than 0.5 m of black shaly mudstone containing L. mytilloides and 'fucoids'.

Where the Sutton Marine Band is present the higher part of its cycle consists of mudstones, locally silty and with thin siltstones; elsewhere, there are impersistent thin siltstones and sandstones close below the Wheatworth Coal, which thicken locally to make up part of the Oaks Rock. In a few sections, such as Pollington No. 2 Borehole, thin seatearths suggest splits from the lower part of the Wheatworth Coal, especially where this is itself represented only by a seatearth.

Wheatworth Coal

The Wheatworth Coal is thickest around Rawcliffe, reaching 1.87 m in Rawcliffe No. 2 Borehole. Several adjacent boreholes prove more than 1.50 m of coal, locally split into two or more leaves. Elsewhere, it is generally about 0.80 m thick or less; for example, Eggborough No. 1 Borehole proved 0.83 m in two leaves and Hatfield Colliery No. 1 Shaft and the nearby Fosterhouses and Wood End boreholes all encountered 0.81 m of coal in one or more leaves. There are considerable local variations in thickness, especially in the north and east where the coal is locally split into as many as six leaves. Although fairly persistent laterally, the coal is absent in the boreholes at Brind Common, Snaith and Lady Galway. Seatearths mark its position in some of these sections, but in others both coal and seatearth are absent.

The beds between the Wheatworth Coal and the Aegiranum Marine Band

The beds between the Wheatworth Coal and the, Aegiranum Marine Bandare 15.59 m thick in Hatfield Colliery No. 1 Shaft and more than 10 m in several scattered boreholes such as Fosterhouses, Crowle Common and Wilsic Lodge, but over large areas of the district they are only 5 to 8 m thick. Only one cycle is generally discernible. Where mudstones occur in the lower part of the cycle they contain mussels, locally associated with ostracods and fish debris, but the record of Hemicycloleaia minima from Barlow No. 2 Borehole is unique to this stratigraphical horizon. Siltstones and sandstones occur widely in the upper part of the cycle and commonly occupy much of the cycle where it is more than about 8 m thick. A thin coal or seatearth commonly marks the top of the cycle. The coal is 0.49 m, 0.43 m and 0.40 m thick in Booth Ferry, Barlow No. 2 and Camblesforth No. 2 boreholes respectively, but in most other sections it is less than 0.30 m. In Hemingbrough Borehole 7 mm of dark grey tonstein with coal streaks in its middle were recorded from near the top of the coal, here 0.33 m thick. In some boreholes the Aegiranum Marine Band rests directly on this coal or, in its absence, on its seatearth. In other boreholes, however, thin dark grey or black mudstone, locally shaly or silty, intervenes and reaches 0.74 m thick in Great Heck Borehole. Although generally identical lithologically to the overlying marine band, it is devoid of marine fossils, but in a few places it has yielded Spirorbis sp., mussels including Naiadites cf. obliquus and fish and plant debris.

Westphalian C and ?D strata

The Coal Measures above the base of the Aegiranum Marine Band are probably all referable to the Westphalian C Stage, with the possible exception of not more than about the highest 80 m near the south-western corner of the district which could be of Westphalian D age but from which fossil evidence is lacking. The thickness of these Coal Measures at any locality depends on variations in pre-late Permian structural activity (pp. 87–91) and consequent differential erosion. At least 510 m have survived this erosion locally in the south-west, but in parts of the north-west no Wesphalian C strata are preserved. Between 21 and 23 cycles are widely recognisable up to the level of the Cambriense Marine Band and a further 35 are locally discernible in the higher strata. The top of the Cambriense Marine Band, which forms the base of the Upper Coal Measures as shown on the published maps (sheets 79 and 88), serves also to separate two sequences contrasting slightly in several respects.

The lower sequence (Figure 17) is similar to the underlying upper part of the Westphalian B strata in containing several marine and several 'Estheria' bands, but differs in that all the marine bands, the Aegiranum, Edmondia, Shafton and Cambriense, appear within the limits of preservation of appropriate strata to be wide ranging, suggesting extensive transgressions. Several locally thick sandstones with erosive bases, notably the Glasshoughton Rock and the Mexborough Rock, imply appreciable variations in drainage base level between the marine incursions. Most of the coals are thin and of inferior quality, but the Houghton Thin, Sharlston Low, Sharlston Top and Shafton coals, and also possibly the unnamed coal underlying the Shafton Marine Band, locally exceed 1.00 m in total coal thickness; these coals split into two or more leaves in places and some of them are locally at least partly canneloid.

The higher sequence (Figure 18), lying above the Cambriense Marine Band and subdivided into, in ascending order, the Ackworth, Brierley, Hemsworth and Badsworth divisions by Goossens and Smith (1973); see also (Figure 7), is imperfectly known because of extensive pre-late Permian erosion and lack of coring of its upper part. There are no marine bands, but 'Estheria' is known locally at two stratigraphical levels and suspected at two more, suggesting brackish depositional conditions that may have been of restricted extent due to varied relief. At least two sandstones, the Ackworth Rock and the Brierley Rock, expand considerably in thickness in places and apparently have erosive bases, again implying drainage base-level variations. Although an appreciable number of coals are present, at least in the lowest 200 m or so of these strata that have been cored, most of the seams are less than 0.40 m thick and are of inferior quality. Only the Brierley Coal locally exceeds 1.00 m in thickness.

The strata up to the Cambriense Marine Band have been sufficiently cored to provide appreciable palaeontological information, but there is little comparable information from the strata above this marine band, partly because of the restricted preservation of these strata and partly because of paucity of cored boreholes.

Aegiranum (formerly Mansfield) Marine Band

The Aegiranum (formerly Mansfield) Marine Band is widely proved. It is generally more than 4 m thick and locally exceeds 10 m, the thickest continuously marine sequence being 10.14 m in Fosterhouses Borehole (Figure 17). In the Hemingbrough and Booth Ferry boreholes, and in a few others mainly in the north, foraminifera are recorded up to 14 m above the base of the band, but in these sections the middle part of the band is devoid of fossils. Erosion at the base of the Ackton Rock has reduced the marine band to less than 1 m in the Grove House, Crowle Common and Pollington No. 2 boreholes. In several uncored boreholes such as Shaftholme Grange and Wilsic Hall (Figure 17), the marine band is indicated by high gamma-ray values. The band is mainly of dark grey, locally silty mudstone; thin siltstones occur in the lower part and near the top in some provings, and in Blyton Carr Borehole in the south-east all but 0.70 m at the top of the 8.96 m-thick marine band are siltstones with sandstone laminae. The Mansfield 'Cank', a layer or band of nodules of calcareous siltstone near the base of the marine band, has been proved in several sections; it is generally less than 0.30 m thick but is recorded as 1.37 m in Hatfield Colliery No. 1 Shaft.

The beds between the Aegiranum Marine Band and the Houghton Thin Coal

The beds between the Aegiranum Marine Band and the Houghton Thin Coalare generally thicker in the north and west, being 29.98 m in Gowdall Borehole but only 2.49 m in Langholme Borehole (Figure 17), although the latter value is thin even by comparison with other south-eastern boreholes. To a certain extent the thickness of these beds varies inversely with that of the Aegiranum Marine Band, and the combined thickness of the two is between 18 and 32 m across all but the south-east of the district. Only one cycle is present, except possibly in the northern boreholes at Whitley Bridge, Camblesforth No. 1 and Hemingbrough, where mussels recorded 3 to 5 m below the Houghton Thin suggest the incipient development of a second cycle near the top of the sequence, above the Ackton Rock. In some central and southern sections the mudstones succeeding the Aegiranum Marine Band are fossiliferous and, notably in Brier Hills (Figure 17) and Westwoodside boreholes, they have yielded Anthraconaia adamsii, Naiadites sp. cf. productus, fish debris including platysomid scales, Planolites ophthalmoides and 'fucoids'.

Ackton Rock

The Ackton Rock includes the siltstones and sandstones which largely comprise the rest of the sequence up to the Houghton Thin Coal. Across much of the district these strata are dominantly massive siltstones with thin interbedded sandstones in places. In more easterly boreholes, however, at Fir Tree, Brind Common, Crowle Common, Grove House and Gate Farm (Figure 17), thick and locally conglomeratic sandstones are present. In some of these eastern boreholes, for example at Bank End, the Ackton Rock merges with the Glasshoughton Rock above.

Houghton Thin Coal

The Houghton Thin Coal is largely split in the north into two leaves, separated generally by mudstone but in places by siltstones and sandstones; the interval in Camblesforth No. 3 Borehole is 5.20 m and the beds in a few boreholes contain mussels and fish debris. In central and southern areas a single seam is generally present, although thin 'dirt' partings are recorded in places. The thickest total coal is 1.00 m and 0.83 m in Langholme and Brier Hills boreholes respectively; the two leaves in Gowdall Borehole in the north-west total 0.80 m (Figure 17).

The beds between the Houghton Thin and Sharlston Low coals

The beds between the Houghton Thin and Sharlston Low coals are usually 20 to 35 m thick, except in the far southeast where the Glasshoughton Rock and a higher sandstone merge in Langholme Borehole (Figure 17) or where there is a condensed argillaceous sequence, as in Blyton Carr Borehole. The beds are obviously much thinner in these sections but their thickness cannot be determined accurately. At least two cycles are present, with the Sharlston Yard Coal at the top of the lower, theGlasshoughton Rock in the upper, and a higher, impersistent, thin coal suggesting the local development of a thin third cycle. Except where the Glasshoughton Rock has cut down to the Houghton Thin, this coal is generally succeeded by thin mudstones from which Spirorbis sp., mussels and fish debris have been reported. The higher part of the lowest cycle is not more than 5 m thick and largely comprises siltstones, with thin sandstones in a few sections.

Sharlston Yard Coal

The Sharlston Yard Coal is a single seam in some provings; it is 0.64 m thick in Gowdall Borehole (Figure 17). In contrast, many widely scattered sections show the Sharlston Yard to consist of several thin coal seams, seatearths and partings spread through as much as 6 m of strata. In many of the boreholes where neither coal nor seatearth is recorded, the Glasshoughton Rock has cut down through the horizon of the seam.

The mudstones above the Sharlston Yard have yielded mussels and fish debris in a few sections, including Gowdall Borehole. In some areas they pass up into siltstones, which continue up to the Sharlston Low Coal; elsewhere they are overlain by the Glasshoughton Rock.

Glasshoughton Rock

The Glasshoughton Rock lies between the Sharlston Yard and Sharlston Low coals around Glasshoughton, to the west of the present district (Edwards et al., 1940, p.85), but within local sections the name has been loosely applied to include sandstones occurring at lower levels, including the Ackton Rock, and at higher horizons. Where such sandstones merge, they are no longer the Glasshoughton Rock, although the name has been widely misused in this way. Merged sandstones form a sequence 70 m thick in Quay Lane Borehole. The Glasshoughton Rock itself is up to 30 m thick and consists largely of variably fine- to coarse-grained sandstone that is locally conglomeratic at the base and in its middle part. Clasts of ironstone and siltstone are common and the rock in places contains large-scale cross-bedding. Interbedded siltstones are common at higher levels, and in some sections the upper part of the unit is entirely siltstone.

Sharlston Low Coal

The Sharlston Low Coal is generally a single seam or two closely spaced leaves. The thickest cored coal is 1.01 m in two leaves in Gate Farm Borehole (Figure 17). Gamma-ray logs of some northern boreholes suggest greater thicknesses, however, such as 1.15 m (in two leaves) and 1.60 m in New Bridge and Camblesforth No. 3 boreholes respectively. The occurrence of 3.06 m of coal in several leaves within 4.12 m of strata at a depth of 410.54 m in Gowdall Borehole (Figure 17) is difficult to correlate, but the sequence probably includes at least part of the Sharlston Low, the Sharlston Muck and possibly part of the Sharlston Top coals.

The beds between the Sharlston Low and Sharlston Top coals

The beds between the Sharlston Low and Sharlston Top coalsare generally 14 to 24 m thick. At least three cycles are present; the Sharlston Muck Coal lies in the upper part of the lowest cycle, which commonly consists of siltstones with some thin sandstones.

Sharlston Muck Coal

The Sharlston Muck Coal includes several thin, poor-quality coals and seatearths lying about 8 m above the Sharlston Low. A hard, pale brown and grey mottled ton-stein 0.05 m thick occurs between these thin coals in Hemingbrough, Bank End, Brier Hills and possibly Misson boreholes and may be indicated by a high gamma-ray value at a similar horizon in Martin Common Borehole. The tonstein probably correlates with that recorded in Ranskill and Stone boreholes farther south (Smith et al., 1973, p.89) and with that occurring beneath the High Main Coal of Nottinghamshire (Eden et al., 1963, pp. 54–56). Mudstone within and above the leaves of the Sharlston Muck have yielded mussels including Naiadites hindi, ostracods and fish debris in a few sections.

The strata between the Sharlston Muck and Sharlston Top coals are predominantly siltstones, with locally one or two closely spaced thin coals. In central areas sandstones are present, which thicken to merge with the Glasshoughton Rock in a few localities, as in Bentley Colliery No. 2 Shaft, Thorne Colliery No. 1 Shaft, Quay Lane Borehole and, with only thin siltstones intervening, Fosterhouses Borehole.

A 2.10 m-thick tonstein is recorded from the uncored Wilsic Hall Borehole (Figure 17), immediately below a coal tentatively correlated with the Sharlston Top. High gamma-ray values from beds below the same coal in Shaftholme Grange Borehole probably also indicate the tonstein (Figure 17).

Sharlston Top Coal

The Sharlston Top Coal is locally split into five leaves, the highest being generally the thickest. The total coal is thickest in central and north-western areas, culminating in a total of more than 1.60 m in three leaves, 1.48 m in four leaves and 1.12 m in one seam in Pollington Nos. 2 and 3 and Cross Hill boreholes respectively. In the south and east, although the coal is widely proved, it is mainly less than 0.4 m thick, except in Grove House Borehole where 0.53 m occurs in three leaves.

The beds between the Sharlston Top and the Edmondia Marine Band

The beds between the Sharlston Top and the Edmondia Marine Band are 10 to 30 m thick in most parts except the south-east, where in boreholes at Langholme (Figure 17) and Blyton Carr they are much thinner. Thin coals, seatearths and mussel-bearing layers show that four cycles are present locally. Much of the sequence is siltstone, with thin sandstones in places. As many as four mussel-bearing bands are recognisable in some boreholes, for example at Gate Farm (Figure 17). They occur at the base of the first, second and fourth cycles and also at the top of the fourth cycle, immediately beneath the coal which underlies the Edmondia Marine Band. The fauna from these bands includes Spirorbis sp., Anthraconaia sp. cf. adamsii, Naiadites cf. daviesi, N. melvillei, Carbonita humilis and fish debris. There are unconfirmed records of ?'Estheria' from the base of the second cycle in Grove House Borehole and also from the bases of the two cycles discernible in Austerfield Borehole. The coal underlying the Edmondia Marine Band is less than 0.50 m thick, except in Bank End Borehole where two closely spaced leaves total 0.69 m. Both leaves are of cannel coal and, elsewhere, this coal is partly or entirely cannel.

Edmondia Marine Band

The Edmondia Marine Band is widely proved across the district either by its fauna or by high gamma-ray values. The fossils occur within a maximum thickness of 6 m, although not all of them are fully marine. The gamma-ray values extend through 10.80 m of strata in Shaftholme Grange Borehole (Figure 17). The band consists of dark grey mudstone near the base, becoming paler and more silty above and locally containing laminae and thin beds of siltstone. Thin seams and small nodules of ironstone are widely present. Foraminifera including Agathamminoides sp., Ammodiscus sp., Glomospira sp. and Glomospirella sp. have been identified; Lingula sp., Edmondia sp., Planolites ophthalmoides, 'fucoids' and fish debris are also present. In several sections the Edmondia Marine Band cannot be identified and has probably been cut out by erosion at the base of the Mexborough Rock.

The beds between the Edmondia Marine Band and the Shafton Coal

The beds between the Edmondia Marine Band and the Shafton Coal are difficult to delineate in the many boreholes where the top of the Edmondia Marine Band is not accurately fixed. If the marine band is assumed to be about 5 m thick, however, the succeeding strata up to the Shafton are 15 to 26 m thick in the north and in most central and western areas north of Doncaster. They are locally less than 10 m, as in Grove House and Brier Hills boreholes (Figure 17), but in Gate Farm Borehole and across the southern part of the district they are much thicker, reaching 53.71 m in Langholme Borehole. This southerly expansion is due to the presence of the thick Mexborough Rock in these areas. Between three and five cycles are locally discernible, with thin, impersistent, poor quality, canneloid coals in the higher cycles. Where not cut out by the Mexborough Rock, thin mudstones succeed the Edmondia Marine Band and in Grove House Borehole they contain mussel traces. They pass up into siltstones with thin sandstones in places; a seatearth also occurs within the sequence, and the thin overlying mudstone contains mussels in Cross Hill, Fosterhouses (Figure 17) and Austerfield boreholes. In these sections there are therefore two cycles, and another slightly higher seatearth suggests a third cycle in a few places. The two highest cycles each have mudstones in their lower parts that are widely fossiliferous; they contain mussels and Estheria, the latter being more extensive in the upper cycle. The full fauna is Spirorbis sp., Naiadites aff. daviesi, Geisina subarcuata, Lioestheria vinti and fish debris.

Mexborough Rock

The Mexborough Rock occurs across the southern part of the district, in places exceeding 40 m in thickness. It consists mainly of fine- to medium-grained sandstone; locally, as in Langholme Borehole (Figure 17), the sandstone is partly coarse grained and in some localities contains conglomeratic layers at the base and in the middle. Siltstone is interbedded with the upper part of the sandstone in places and also commonly succeeds the sandstone, extending up to the Shafton Coal, as in Misson Borehole (Figure 17). The Mexborough Rock is not always attributable to a particular cycle. Boreholes such as Langholme suggest that it originates not lower than the third cycle above the base of the Edmondia Marine Band. In northern and central areas, however, where the Mexborough Rock is not recognisable, most of the sandstones occurring between the Edmondia Marine Band and the Shafton Coal lie in the two lower cycles. In southern areas where the Mexborough Rock is thickly developed, it either extends up to the Shafton Coal or is separated from it by siltstones with no cyclic indicators. On this evidence it seems probable that the Mexborough Rock is referable to one of the two higher cycles and that it does not extend widely into central and northern areas, even as a thin sandstone. To the south of the district (Smith et al., 1973, p.90), the name Mexborough Rock is used to include sandstones lying below the Edmondia Marine Band or above the Shafton Coal, but which have merged with the Mexborough Rock.

Shafton Coal

The Shafton Coal is thickest in the western central part of the district. It is commonly split into several closely spaced leaves and an appreciable part of the coal is of inferior quality or 'dirty'. Hatfield Colliery No. 1 Shaft proved four leaves with a total of 1.52 m of coal in 2.35 m of strata, and in Sun Inn Borehole only 0.41 m out of 1.57 m in three leaves is clean coal. The coal thins northwards and eastwards, only 0.28 m and 0.10 m being found in Pollington No. 2 and Brier Hills (Figure 17) boreholes respectively, but in the south up to 0.98 m of coal is recorded, as in the Langholme Borehole.

The beds between the Shafton Coal and the Shafton Marine Band

The beds between the Shafton Coal and the Shafton Marine Bandare mainly 8 to 16 m thick, but they decrease to between 4 and 6 m in widely scattered sections such as Sun Inn, Gate Farm and Langholme boreholes, and they expand to between 19 and 20 m in New Bridge and Drax No. 1 (Newland) boreholes in the north-east. In most sections there are two cycles, the lower being the thicker. They are generally separated by a thin coal or a seatearth, even where the sequence is thin, as in Gate Farm Borehole, but in a few boreholes, such as Grove House (Figure 17), there are several closely spaced seatearths. The mudstones which succeed the Shafton are locally interbedded with thin siltstones; they contain a widespread fauna which in places ranges up to 6 m above the coal and includes Naiadites daviesi, N. melvillei, Carbonita humilis, Geisina subarcuata, Hemicycloleaia minima, Lioestheria vinti, platysomid scales, Rhizodopsis sp. and other fish debris. More persistent siltstones and locally a thin sandstone occur near the top of the lower cycle. The thin upper cycle has yielded few fossils, except in Fish-lake Borehole, where mussels and ostracods are recorded. It mainly comprises mudstone and siltstone and culminates upwards in many boreholes in a coal which, although variously 'dirty', pyritic and canneloid in places, is 1.09 m thick (including a 0.12 m 'dirt' layer) in Langholme Borehole and between 0.63 and 0.74 m in central localities such as Carr Head Lane, Grove House and Gate Farm boreholes (Figure 17). In a few localities, such as Sun Inn and Shaftholme Grange boreholes, as much as 0.25 m of mudstone overlying the coal has yielded mussels, Estheria sp.' and fish debris, but not the accompanying marine fossils indicative of the succeeding Shafton Marine Band.

Shafton Marine Band

The Shafton Marine Band has been proved in most cored boreholes and has been identified in several uncored boreholes, such as Gowdall and Wilsic Hall, by high gamma-ray values on the geophysical logs. To the west of the district, marine fossils are commonly limited to two layers separated by up to 10 m of barren strata, including siltstones and sandstones in places, the entire sequence ranging up to 15 m. The marine band is similarly split and is more than 13.50 m thick in Sun Inn Borehole near the western edge of the district, where the lower marine layer is 6.58 m thick. Elsewhere in the district, however, marine fossils are limited to less than 5 m of strata which are considered to equate only with the lower part of the marine band farther west. The marine fossils occur mainly in dark grey mudstones, locally with thin layers or nodules of ironstone, which pass up into medium grey mudstones in places.

The beds between the Shafton and Cambriense marine bands

The beds between the Shafton and Cambriense marine bands thin southwards from 47.63 m in Pincheon Green Borehole to 22.12 m in Misson Borehole (Figure 17). Farther east the thickness of 37.55 m in Grove House Borehole (Figure 17) enhances the belief (Gaunt et al., 1992, p. 14, fig. 6) that the two highest and closely spaced 'marine bands' proved in Crosby Borehole (Edwards, 1951, pp. 161–162), just east of the district, are not the Shafton and Cambriense marine bands but that both are derived from the Shafton Marine Band, the lower occurrence being debris which caved from the side of the borehole and was cored out of sequence.

The coals, seatearths and faunal layers in the succession indicate up to six cycles in most boreholes and possibly, in view of the number of seatearths, seven cycles in Grove House Borehole. The lowest cycle is generally the thickest and has the most persistent and thickest coal at its top (0.51 m, 0.43 m and 0.38 m in Hatfield Colliery No. 1 and Askern Colliery No. 1 shafts and Pincheon Green Borehole respectively).

The mudstones succeeding the Shafton Marine Band have yielded Spirorbis sp., Anthraconaia persulcata, Anthraconaia cf. spathulata, Naiadites ? 'Geisina?, Estheria sp.', ostracods and fish debris. They pass up into siltstones in most sections, but in a few boreholes, such as Ox Carr Wood and Gate Farm, up to 16.30 m of sandstones occupy much of the lowest cycle. A thin layer of coal recorded in the latter borehole may well be a derived fragment within the basal part of the sandstone.

The five higher cycles each consist mainly of mudstones, in places passing up into siltstones with thin sandstones. Naiadites sp. and Lioestheria sp. are present in the lower part of each in some sections. All five of these faunal layers were proved in Sun Inn Borehole, and Pincheon Green and Ox Carr Wood boreholes (Figure 17) together proved all but the highest of them. Spirorbis sp., Geisina subarcuata, ostracods and fish debris also occur in these faunal layers. In Mill Field Road Borehole the basal part of the third cycle, below the layer with Lioestheria sp. and mussels, consists of 0.10 m of dark grey siltstone and silty mudstone with 'fragmented clay rock' at the base, a similar lithology to that described by Richardson and Francis (1971).

In Ox Carr Wood Borehole, 2.74 m of mudstone lies between the coal at the top of the highest cycle and the Cambriense Marine Band. It is black at the base and grey above, and yielded 'Estheria' sp. in the lowest 0.05 m and mussels above. It is possible that equivalent strata have been included within the Cambriense Marine Band in other boreholes.

Cambriense (formerly Top) Marine Band

The Cambriense (formerly Top) Marine Band is recorded as being 5.03 m, 3.66 m and 2.77 m thick in Holme Wood Lane, Ox Carr Wood and Grove House (Figure 18) boreholes respectively, but elsewhere it is apparently less than 2 m. In the south it is partly or entirely cut out beneath the Ackworth Rock; only 0.69 m was preserved in Misson Borehole and it was absent in Langholme and Wilsic Hall boreholes (Figure 18). In a few sections, such as Shaftholme Grange Borehole, it is marked by high gamma-ray values. In some northern and central sections, such as Brier Hills Borehole (Figure 17), it was removed by pre-late Permian erosion. The lower part of the marine band generally comprises dark grey, locally silty mudstone up to 1 m thick, which passes into medium grey mudstone, in places containing thin layers and nodules of ironstone. Some siltstones and sandstones are recorded within the marine band in Grove House Borehole (Figure 18), but these may well be fragments which have slipped down the borehole because the log also notes slipped, disturbed and crushed core. The lower part of the marine band contains most of the fauna, although 'fucoids' are recorded elsewhere.

Ackworth Division

Boreholes in the south show that the beds between the Cambriense Marine Band and the Brierley Coal thin steadily eastwards, from at least 74.78 m at Wilsic Hall, to about 60 m at Austerfield and Misson, and to not more than 50.45 m at Langholme (Figure 18). There may be a similar eastward thinning in central boreholes if the suggested positions of the Brierley Coal in Thorne Colliery No. 1 Shaft, Sun Inn and Ox Carr Wood boreholes are correct. Up to ten cycles are locally discernible in Ox Carr Wood Borehole. The Ackworth Rock is probably referable to one of the lower cycles. Several thin coals occur locally in the higher cycles.

In central boreholes such as Pincheon Green, Grove House, Ox Carr Wood (Figure 18), Holme Wood Lane, Stainforth and Woodhouse Green, the lowest cycle consists of silty mudstones passing up into siltstones, with sandstone limited to thin bands in a few places and with a seatearth at the top. The thin impersistent sandstones may be vestigial lateral equivalents of the Ackworth Rock, but the section in Grove House Borehole (Figure 18) suggests that the rock belongs, at least in part, only to the second cycle. Here the seatearth at the top of the lowest cycle is overlain by nearly 5 m of coarse-grained, massive sandstone lying immediately below the sub-Permian unconformity.

The Ackworth Rock is generally 20 to 30 m thick across the south of the district and reaches 31.32 m in Sun Inn Borehole (Figure 18), but farther north and east it is generally thin or absent. Where thickly developed the sandstone is fine to medium grained, and locally coarse grained. It is massive and in places shows large-scale cross-bedding; there are conglomeratic layers at the base and in its lower part in some sections, which contain angular to subrounded fragments of siltstone, mudstone, ironstone and coal. The upper part of the Ackworth Rock contains sandstone interbedded with siltstone in most places and its top is commonly siltstone. The sandstone–seatearth 6.32 m above the base of the unit in Misson Borehole and a persistent conglomeratic layer at approximately the same level in several nearby boreholes (Figure 18) suggest that the Ackworth Rock, at least in some areas, may be formed by the thickening and merging of sandstones in two or more adjacent cycles.

The coals above the Ackworth Rock are not easy to correlate, but the one or more closely spaced seams just above it in Bank End, Langholme, Misson and Austerfield boreholes may correlate with the unnamed coal which Goossens and Smith (1973, p.496) refer to as lying about 35 m above the base of the Cambriense Marine Band; the highest coal below the Brierley in Misson and other boreholes may be their Elmsall Coal. 'Estheria' occurring in mudstone above the unnamed coal in Bank End Borehole is compatible with this correlation, since the only other fossils recorded from the succession are all from the basal part of the second cycle below the Brierley Coal. These are mainly fish debris, but mussels in Ox Carr Wood Borehole, 'ostracods' in Bank End Borehole and supposed 'fucoid markings' in Sun Inn Borehole are also present. Only in Wilsic Hall Borehole is there evidence of a substantial thickness of sandstone close below the Brierley Coal; this may be the Newstead Rock described by Goossens and Smith in the Wakefield district (1973, pp. 494–497, fig. 2) or the Dalton Rock of the Sheffield area (Eden et al., 1957, p.126, fig. 26).

Brierley Division

The Brierley Coal, equivalent to the Blyth Coal of areas further south (Smith et al., 1973, pp. 95–96, pl. IX), is recognisable with certainty only in southern and centre-west parts of the present district; elsewhere it is either cut out by the Brierley Rock as in Bank End Borehole (Figure 18) or removed by pre-late Permian erosion as in most northern and eastern central areas. It forms a single seam 1.09 m thick in Misson Borehole and is 1.12 m thick in Austerfield Borehole, where it includes two dirt layers totalling 0.12 m. The coals proved in Rossington Colliery No. 1 Shaft and Wilsic Hall Borehole are only slightly thinner. The distinctive black, coal-free mudstone-seatearth which overlies the Brierley Coal farther west (Goossens and Smith, 1973, p.498) is not discernible in the present sections.

The beds between the Brierley Coal and the Fourth Cherry Tree Marker are 51 to 58 m thick in the south, if identifications of the Fourth Cherry Tree Marker in Misson and Austerfield boreholes and Rossington Colliery No. 1 Shaft (Figure 18) are correct. Farther north, these beds were largely or entirely removed by pre-late Permian erosion. In the Misson section there are at least eleven cycles, although several of them are thin and incomplete, as is the case farther to the north-west (Goossens and Smith, 1973, p.498). The Brierley Rock has cut down through the lower cycles in the Austerfield and Wilsic Hall boreholes, and may be referable to one of the middle cycles in the sequence, possibly the fifth cycle up in Misson Borehole where 2.64 m of sandstone are recorded. Coals are present at the top of several cycles, especially in Misson Borehole, but all of them are thin and correlation between boreholes is uncertain. Mudstones at the base of the lowest cycle in Wilsic Hall Borehole contain shell fragments, but the rest of the cycle is here cut out by the Brierley Rock. Where the cycle is preserved, however, as in Rossington Colliery No. 1 Shaft and Misson Borehole, the mudstones pass up into siltstones, locally with thin sandstones as in Ox Carr Wood Borehole. The three succeeding cycles are thin, probably incomplete and locally impersistent.

The Brierley Rock, probably equivalent to the Wickersley Rock of the Sheffield and East Retford districts (Eden et al., 1957, pp. 126–127, fig. 26; Smith et al., 1973, p.96, pl. IX respectively), is 41.51 m thick in south-western sections in the Martin Common and Austerfield boreholes (Figure 18). The Brierley Rock is thin or absent in sections north-east of Bank End Borehole (Figure 18). It is mainly fine- to medium-grained sandstone and is locally coarse, with conglomeratic layers in places at the base and in its lower part; some sections show large-scale cross-bedding. In some boreholes a few thin siltstones are present in its middle and upper parts, and in places close above it; in Wilsic Hall Borehole 0.01 m of coal recorded in the middle of the Brierley Rock within partly coarse-grained sandstone containing 'ironstone pebbles' may be a derived fragment. The beds overlying the rock yielded ostracods in Wilsic Hall Borehole and mussels, '?Estheria' and fish debris in Austerfield Borehole, apparently from the lowest part of the succeeding cycle. The mussels recorded from a depth of 101.50 m in Sun Inn Borehole are possibly from the same stratigraphical level. Shell debris observed in Misson Borehole at 528.36 m probably lies at a higher strati-graphical level and may equate with mussels recorded from 92.96 m in Sun Inn Borehole. The few sections available show that thin sandstones are present in the four cycles below the presumed Fourth Cherry Tree Marker.

Hemsworth and Badsworth divisions

The Fourth Cherry Tree Marker is a prominent musselestheriid band first recognised in Cherry Tree Borehole east of South Elmsall (Goossens and Smith, 1973, p.492). It has not been recognised with certainty within the district, but may be represented by certain faunal layers. For example, at 509.11 m in Misson Borehole, black mudstone 0.11 m thick contains 'Spirorbis' and ?Estheria; the overlying beds are grey mudstone 0.04 m, 'ironstone' with thin 'shale' layers 0.18 m, and grey mudstone with thin 'ironstone' near the base and becoming silty near the top, 0.86 m. This sequence resembles that of the Fourth Cherry Tree Marker in Cherry Tree Borehole. In Austerfield Borehole, 0.40 m of dark grey mudstone yielded abundant '?Estheria' near the base and mussels above, and in Rossington Colliery No. 1 Shaft, 0.53 m of black 'shale' containing 'ironstone' layers also yielded mussels; both bands correlate with that in Misson Borehole (Figure 18).

The beds between the Fourth Cherry Tree Marker and the Upton Coal were removed by pre-late Permian erosion across most of the district. Only in the south and south-west are they preserved, where they are 47 to 54 m thick. Eight cycles are present in Misson Borehole (Figure 18), each consisting largely of mudstones and siltstones, with thin sandstones in a few cycles. In contrast, fairly thick sandstones occur in the Austerfield Borehole farther west, within one or more of the middle cycles. These sandstones are tentatively correlated with the Houghton Common Rock (Green et al., 1878, p.468) of the Barnsley district.

The sandstone here called Houghton Common Rock is 24.00 m and 27.37 m thick in Wilsic Hall Borehole and Rossington Colliery No. 1 Shaft respectively, thinning eastwards to only 10.20 m in Austerfield Borehole; it is absent in Misson Borehole (Figure 18). It consists mainly of fine-grained sandstone, with a conglomeratic base in Rossington Colliery No. 1 Shaft and possibly also in Austerfield Borehole. Thin siltstone bands and laminae occur in places and ripple bedding has been recorded. Although in thickness and lithology these sandstones resemble the Houghton Common Rock of Houghton Common, in the Austerfield and Rossington sections they are separated from the presumed Upton Coal by two or three thin cycles of mudstone and siltstone with a coal and, at Austerfield, a mussel layer. This contrasts with the situation between Houghton and Hemsworth, west of the present district, where the Houghton Common Rock either lies immediately under the Upton Coal or is separated from it by thin siltstones and sandy siltstones (Goossens and Smith, 1973, pp. 502–503, fig. 2, pl. 22). In addition, Misson Borehole yielded abundant 'Estheria' at a depth of 473.51 m, which may indicate the Third Cherry Tree Marker. On cyclic evidence and depth below the presumed seatearth of the Upton Coal, this faunal band appears to lie above rather than below the Houghton Common Rock. It may be, therefore, that the Houghton Common Rock of this account is not the Houghton Common Rock of the Barnsley district, but rather a locally thickened sandstone lying between the Fourth and Third Cherry Tree markers.

The Upton Coal, although not identified with certainty, is thought to be the 0.58 m-thick seam proved in Rossington Colliery No. 1 Shaft and the 0.53 m-thick seam in Austerfield Borehole (Figure 18), each of these being the thickest seams proved above the Brierley Coal in these sections. The correlative in Misson Borehole is taken as a coal-free seatearth, but this is very uncertain. In Wilsic Hall Borehole uncored provings of coal recorded as 0.40 m thick, with possibly a 0.20 m-thick coal 1.20 m below, are thought to be the Upton.

The beds above the Upton Coal are present only in the south-west, 110.20 m and 109.90 m being proved in Wilsic Lodge and Wilsic Hall boreholes respectively. Elsewhere, pre-late Permian erosion has removed them entirely. The number of cycles present in the fullest sequence at Wilsic is unknown because the boreholes here were not cored, but six cycles are discernible from the thin coals and seatearths in the 53.29 m of beds in Rossington Colliery No. 1 Shaft. Both the Rossington and Austerfield sections show that the lowest five cycles each consist mainly of thin mudstones passing up into siltstones. The thin mudstones overlying the Upton Coal in Austerfield Borehole yielded mussels, and in Misson Borehole mudstones above the same horizon yielded 'Spirorbis sp.', mussels, ostracods and fish debris. The only fauna recorded from higher strata are mussels, including 'cf. Anthraconauta phillipsii' according to Edwards (1951, p.226), which occur in 1.09 m of 'dark bind with ironstone bands' at the base of the fourth cycle above the Upton Coal in Rossington Colliery No. 1 Shaft. These mussels may come from the First Cherry Tree Marker because the 82.27 m of strata between them and the Fourth Cherry Tree Marker in this shaft are only slightly thinner than the comparable sequences in Badsworth No. 3 and Cherry Tree boreholes (93.35 m and 88.77 m thick respectively) in the district to the west (Goossens and Smith, 1973, p.500).

The First Cherry Tree Marker has not been identified in Wilsic Hall or any other borehole in the south-west, but comparison with its conjectured position in Rossington Colliery No. 1 Shaft suggests that it may lie between about 150 m and 170 m in Wilsic Hall Borehole; if so, the thin sandstones lying between about 115 m and 129 m in Wilsic Hall Borehole may correlate with the Badsworth Rock (Goossens and Smith, 1973, p.506) of the Wakefield district.

Primary red Coal Measures, whose reddish and purplish colours resulted from oxidising conditions during deposition, cannot be proved with any confidence in the district. The only likely candidates are the uppermost 26.50 m in the Wilsic Lodge Borehole; these comprise mudstones, overlain by siltstones and then sandstones. The beds are variously described as grey, purple, red and brown. By comparison with the nearby Wilsic Hall Borehole, these strata overlie the sandstones which possibly correlate with the Badsworth Rock. Primary red strata were also recorded down to the base of, and locally below the Badsworth Rock to the west of the present district (Goossens and Smith, 1973, p.505) and to slightly lower in the succession in the East Retford district (Smith et al., 1973, pp. 46–47, 98, pl. IX). However, the purple, red and brown beds in Wilsic Lodge Borehole may owe their abnormal colours to secondary oxidation as described below.

Red-stained Coal Measures

In places, beds lying close below the sub-Permian unconformity are variably and commonly mottled red, brown, purple, blue, green and yellow. The rocks were originally deposited as grey beds but were weathered under oxidising conditions near the pre-late Permian land surface. This was a secondary effect occurring many millions of years after the rocks were laid down. As a result of gentle folding, faulting (pp. 94, 95) and erosion before the onset of late Permian sedimentation, the Coal Measures within the weathered reddened zone vary considerably in stratigraphical horizon across the district. The effect is seen at about the Two-Foot Coal in Pale Lane and West Haddlesey No. 1 boreholes in the north; in the southwest, however, in Wilsic Hall and nearby boreholes, red colours do not come in until well above the Upton Coal and staining may not be distinguishable from primary colouration. Within the zone of secondary oxidation, mudstones and finer grained siltstones are generally purple, in some sections becoming red immediately below the unconformity, and they pass down locally through blue and green to their normal grey colours. Sandstones and coarser grained siltstones are commonly red, reddish brown and yellow near the unconformity and pass down through paler brown and locally greenish hues. Ironstones are mainly red, and in some boreholes are described as hematite; they are commonly the lowest beds in a borehole to be reddened. Many borehole logs do not record reddened Coal Measures, especially where no cores were taken. In many of those that do, the descriptions are so generalised that the depth of staining cannot be accurately determined. Nevertheless, some overall assessment of the effect is possible. Of 48 boreholes and shafts recording reddening, nine show a depth of oxidation of less than 7 m and another 29 of less than 17 m. The greatest depths of reddening are 30.33 m in Markham Main Colliery No. 1 Shaft (if 'mottled marl' in the original log indicates oxidation), 28.88 m in Woodhouse Green Borehole, where faulting may have facilitated deep weathering, and just under 24 m in Grove House and Lady Galway Plantation boreholes. In a few boreholes where the descriptions are sufficiently detailed, it is apparent that the red colour is missing in a zone about 1 m thick immediately below the sub-Permian unconformity. The beds below remain reddened, but within this narrow band mudstones or siltstones are grey and sandstones are white. The effect is particularly noticeable in Sun Inn and Bank End boreholes, to depths below the unconformity of 1.07 m and 0.51 m respectively. The loss of the red colours is believed to be due to the reducing and leaching effects of groundwater percolating down following the initial, late Permian marine transgression (Smith and Francis, 1967, p.18).

Other possible evidence of pre-late Permian weathering includes 'broken' or 'soft' strata immediately beneath the unconformity. Many boreholes record 'clunch' in this position, a term which normally denotes an argillaceous seatearth but which also seems to have been used for a highly weathered surface layer. A few boreholes, such as Westwoodside, record cracks, some filled with sand, which are probably desiccation cracks. Pyrite is usually common in the Coal Measures close below the unconformity, and is associated not only with ironstones but also with other rock types, including sandstones. The mineral probably results from downward-percolating groundwater following the initial late Permian marine transgression.

Chapter 3 Permian and Triassic

Strata of Permian and Triassic age are described together in this chapter because they have many common features, notably red sediments and evaporites, and because the position of their mutual boundary is uncertain. They form rockhead throughout the district, with successively younger beds to the east in response to the gentle easterly dip. Except in some western areas and in the Isle of Axholme they are largely concealed by Quaternary deposits, and most of the information on these rocks comes from boreholes which, although numerous, include only a few cored sequences.

The lithostratigraphical divisions of the Permian and Triassic strata present within the district are shown in (Figure 19). The traditional terminology was used on the Goole (sheet 79) and Doncaster (sheet 88) maps, published in 1972 and 1969 respectively, but a later nomenclature, proposed by Smith et al. (1974) and Warrington et al. (1980), is adopted in the following description. (Figure 19) also shows the revised nomenclature for the Upper Permian strata proposed by Smith et al. (1986). The youngest Triassic rocks are absent in the district but occur farther east (Gaunt et al., 1992, pp.24–28), where they comprise the uppermost 60 m of the Mercia Mudstone Group, the Penarth Group (c.12 to 19 m thick) and that basal part (c.5 to 7 m thick) of the Lias Group which is of Triassic age.

Except for scattered traces of indeterminate plant debris the only macrofossils of Permian or Triassic age in the district are sparse marine faunas in the Marl Slate, the Lower Marl, the Lower Magnesian Limestone and the Upper Magnesian Limestone. These faunas, identified by J Pattison, comprise assemblages characteristic of Zechstein strata across north-central Europe and are referable to the Upper Permian. Palynomorphs indicate a late Permian (Kazanian/Tatarian) age (Warrington in Smith et al., 1974).

The exact position of the boundary between the Permian and Triassic is unknown. In Germany it is defined purely on a lithostratigraphical basis and is placed arbitrarily at the base of the Brockelschiefer, the lowest subdivision of the Buntsandstein. The equivalent stratigraphical level in eastern England is thought to lie at the base of, or within, the Saliferous Marl (Warrington et al., 1980, pp.9–10). However, the junction between the Saliferous Marl (now known as the Roxby Formation) and the overlying Sherwood Sandstone Group is gradational and markedly diachronous; consequently, it is possible that in some areas the Permian–Triassic boundary lies within the lower part of the latter group. In western Europe, including Britain, the absence of Tethyan ammonites renders the identification of Triassic stages particularly difficult. Nevertheless, the presence of palynomorphs, principally miospores, in parts of the Mercia Mudstone Group provides some correlative evidence, and the relevant comments in this chapter are based on work by G Warrington.

The Permian and Triassic periods, spanning some 40 and 45 million years respectively, together lasted from about 290 to about 205 million years ago (Forster and Warrington, 1985). During this time, that part of the earth's crust on which the British Permian and Triassic rocks were formed was drifting northwards from a few degrees north of the equator to just over 30 degrees north (Smith et al., 1981). By early Permian times the hot humid paralic environment of the late Carboniferous had moderated and Hercynian earth movements, with the resulting substantial denudation, had produced an intracontinental landscape of uplands and basins which had a hot, but mainly arid, climate. The largest of these basins, here referred to as the Southern North Sea Basin, stretched from eastern England into central Europe; it continued to subside intermittently for much of the later Permian and Triassic. The rate of subsidence and the periodic establishment of restricted oceanic connections controlled the depositional environment, so that the basin was variously the focus of aeolian, fluvial, lacustrine, epitidal and shallow marine sedimentation.

In eastern England terrestrial conditions prevailed throughout the early Permian, so that only the largely aeolian Basal (Permian) Sands and thin breccias were deposited. For much of the late Permian the basin was occupied by the shallow epeiric Zechstein Sea, which underwent five major and several minor cycles of transgression and regression, resulting in the deposition of repeated sequences of carbonates, evaporites and clastics. In eastern England these sequences comprise the Don, Aislaby, Teesside, Staintondale and Eskdale groups. The five major cycles, designated EZ1 to EZ5 by Smith (1970), correspond at least approximately with the five groups, and also with the Z1 to Z5 cycles of Germany. Following the final regression of the Zechstein Sea, fluvial deposition, which produced the Sherwood Sandstone Group, took place over much of eastern England during the latest Permian and early part of the Trias. The overlying Mercia Mudstone Group resulted from varied fluvial, lagoonal, epitidal and shallow marine deposition, marginal to a hypersaline sea that developed in central parts of the basin, to the east.

The district lies in the south-western marginal part of the former Southern North Sea Basin, which was flanked to the west by uplands in the region of the present Pennines and to the south by the so-called London–Brabant Massif. Between these two uplands there was a gap, probably to the south-east of Nottingham, through which clastics from the present Midlands, and possibly from farther south, reached the depositional basin in eastern England at certain times. The three principal components of the Permian and Triassic rocks in the district, namely reddish coloured clastics, dolomitic carbonates and evaporites, and their thickness variations, clearly reflect deposition around the margin of a fairly arid intracontinental basin situated in low tropical latitudes.

Basal (Permian) Sands

In much of central and eastern Yorkshire (and adjacent parts of Nottinghamshire and Lincolnshire) the denuded and weathered top of the Carboniferous sequence is covered unconformably by a friable and locally incohesive sandstone, the Basal (Permian) Sands, which varies from 0 to 30 m in thickness. Certain characteristics, notably rounded grains, imply an aeolian origin, but there is also some evidence of partial subaqueous reworking (Versey, 1925; Pryor, 1971). Towards its northern and southern margins the Basal Sands become discontinuous and locally contain layers of breccia and/or conglomerate, as in the East Retford district (Smith et al., 1973, pp.107–112). To the west, along the Permian outcrop, the sandstone is also discontinuous, although locally extensive and about 6 m thick. To the east it continues under the North Sea and is equivalent to the Rotliegendes of Germany. Like the latter, the Basal Sands are mostly of early Permian age, but parts were reworked during the initial transgression of the Zechstein Sea in the late Permian.

Within the district the Basal Sands form a nearly continuous spread, but some boreholes, mainly in the south and west, failed to prove the deposit (Figure 20a). In many of the boreholes the sandstone is less than 3 m thick, except in the north-west where, despite its absence in some boreholes, it is commonly more than 5 m thick; this increase evidently continues westwards to the outcrops between Kippax and Pontefract (Edwards et al., 1940, fig. 54). The thickest proved sequence (12.95 m) is in Pincheon Green Borehole. Thicker sequences may be present in four uncored boreholes–Fenwick Grange (20.8 m), Fir Tree, just north of the district (19.6 m), Burn Airfield No. 2 (15.9 m) and Crowle Oil (13.7 m) (Figure 21)–but the available descriptions are ambiguous and they may include some Coal Measures sandstone. It is uncertain whether the thickness variations mainly reflect irregularities in the surface on which the sandstone was deposited or an undulating top to the sandstone. In Barlow No. 2 and Brier Hills boreholes the basal surface is irregular within the limits of the core, but this does not necessarily imply larger-scale relief; on the other hand, the isolation of some of the thicker sequences suggests that deposition may have been in localised dune fields.

The sandstone is predominantly pale to medium grey and, more commonly in its upper part, bluish grey. In a few borehole records it is described variously as white or brown, and pink or green tinges have been noted near the base in places. It is mainly fine to medium grained, fairly well sorted and dominantly composed of quartz; coarse grains, occurring both scattered and in thin layers, are present locally. Grain shapes range from subangular to rounded; the latter are sufficiently common to have been noted in the samples from many uncored boreholes, and imply an aeolian component. However, several boreholes prove thin clayey or silty layers, or an argillaceous matrix, mainly near the top of the sandstone, suggesting some subaqueous reworking. A matrix of calcite/dolomite or gypsum is recorded in a few boreholes throughout the sequence, in places forming small nodular masses. The majority of borehole records, however, refer to the sandstone as 'soft', and several indicate poor core recovery, presumably due to the friable nature of the rock. Accessory minerals include pyrite, which occurs in disseminated form in several boreholes, and mica and feldspar in White Cross Borehole [SK 5684 9785]. The mica, rare elsewhere in the Basal Sands, may indicate subaqueous reworking, an interpretation supported by the level laminations and traces of graded bedding in White Cross Borehole, where poikilitic gypsum cement is present. Five cored boreholes prove cross-bedding, four of them in the north-west and one (Lady Galway Borehole) in the south, where cross-bedded dips of up to 18° were recorded.

The presence of breccia or, less commonly, conglomerate, generally at or near the base of the sandstone, has been proved in several boreholes, mostly those near the southern edge of the district and in the Trumfleet–Fosterhouses area north of Doncaster (Figure 20a). The angular fragments in the breccias consist of sandstone, siltstone and mudstone, some with red and purple hues comparable to those in the topmost part of the underlying Coal Measures; the pebbles in the conglomerates comprise similar rocks and quartz.

Don Group (EZ1)

Marl Slate and Lower Marl

In this account the Marl Slate Formation is described with the Lower Marl Member of the Lower Magnesian Limestone because in some parts of the district these units cannot be separated.

The Marl Slate of central and eastern Yorkshire comprises up to 5 m of dark grey to black, laminated, fissile, dolomitic mudstone and/or argillaceous dolomite with a characteristically flecked appearance. It contains a restricted fossil assemblage consisting mainly of carbonaceous plant debris, Lingula and fish debris, and it produces an abnormally high gamma-ray peak on borehole geophysical logs. In these and other respects it is similar to the Marl Slate of Durham and to the Kupferschiefer of Germany. It evidently does not extend westwards to the Permian outcrop in Yorkshire, but rocks of similar lithology continue southward into the East Retford district (Smith et al., 1973, pp.112–120). The Marl Slate was deposited during the initial (EZ1) transgression of the Zechstein Sea. In places it mantles high ridges of the Basal Sands, so the transgression may have been rapid and substantial, with water depths locally in excess of 60 m (Smith, 1979). The marked sapropelic and bituminous nature of the Marl Slate suggests oxygen-poor, reducing depositional conditions with poor circulation, and its high metallic-ion concentrations may result from abnormally large amounts of phytoplankton or from high salinity.

The Lower Marl is largely confined to southern Yorkshire and adjacent parts of Nottinghamshire and Lincolnshire, where it consists of pale or, more rarely, dark grey, flaggy to massive, calcareous and/or dolomitic, variably silty mudstone and siltstone, with thin beds and lenses of argillaceous dolomitic limestone in places. It contains fossils similar to those in the Marl Slate with, in addition, foraminifera and a locally abundant calcareous macrofauna, notably of bryozoa and brachiopods. It is about 55 m thick in the East Retford area, south of the present district, where it includes a thin Marl Slate facies (Smith et al., 1973, pp.112–120), but it thins markedly northwards, largely by gradational or interdigitating lateral passage into Lower Magnesian Limestone, and becomes thin and impersistent in central Yorkshire. The Lower Marl was deposited during the first (EZ1) Zechstein transgression and has been interpreted variously as estuarine and deposited in a wide embayment, the Nottingham Bight (Smith, 1970), or as lagoonal (Harwood, 1981). In either case, it can be considered as a marginal facies variant of the lower subdivision of the Lower Magnesian Limestone, i.e. as the Kimberley facies of the Wetherby Member of the Cadeby Formation (see below and Smith et al., 1986).

Within the district a thin argillaceous sequence occurs between the Basal Sands and the Lower Magnesian Limestone; it contains strata suggestive of the Marl Slate and/or the Lower Marl, depending on the locality. In northern and eastern areas the sequence is less than 2 m thick and in some places along the western edge of the district it appears to be absent. In some western, central and southern parts it reaches a thickness of 4 m or more (Figure 20b). For example, near the southern edge of the district, the Idle and Newington boreholes record 6.4 m and 5.1 m respectively; in the west, Bentley Colliery No. 1 Shaft [SE 5698 0749] and the Shaftholme Grange Borehole (Figure 21) intersected 6.3 m and 5.7 m respectively; and the Crowle Common Borehole shows 7.5 m of 'grey marl with limestone bands', which probably include part of the overlying Lower Magnesian Limestone, because no argillaceous unit of comparable thickness is known within 15 km.

The thin argillaceous sequence in the north and east consists largely of flecked, dark grey to black, hard, shaly mudstone, locally silty and micaceous, and containing sparse carbonaceous plant debris, Lingula credneri and fish debris (mainly palaeoniscoid scales with a few teeth and bones). In Wressle Borehole the conifers Pseudovoltzia liebeana and Ullmannia sp., and the fish Pygopterus? were recorded. In several boreholes, mainly in the northwest, including Great Heck and Selby No. 2 boreholes (Figure 21), the sequence includes a basal layer, up to 0.5 m thick, of sandy or silty limestone; in more easterly localities, this is a calcareous siltstone containing dark grey to black shell casts, which in Fenwick Common Borehole are recognised as Bakevellia binneyi and Permophorus costatus. Of the available geophysical logs from northerly and easterly boreholes, those from Crowle Oil and the three Axholme oil boreholes show a strong signal, whereas that from Barlow Oil Borehole is nondiagnostic. The lithological, palaeontological and geophysical characters suggest that the thin argillaceous sequence in northern and eastern parts of the district consists of Marl Slate with little or no Lower Marl (Figure 20b).

In those western, central and southern areas where the argillaceous sequence is generally over 2 m thick (Figure 20b), similar dark-coloured mudstone is widely present and several boreholes prove basal carbonate-rich strata containing black shell casts. In Dadsley Well Borehole [SK 5898 9429] (Figure 21) the core of this basal stratum, examined by D B Smith, comprises 0.34 m of grey dolomite on 0.10 m of grey, finely crystalline limestone containing abundant rounded sand grains, with B. binneyi and P. costatus in both layers. Interbedded very shelly limestones higher in the sequence, up to 0.3 m thick, suggest gradation upwards into the Lower Magnesian Limestone. Their more diverse macrofauna includes not only the fossils mentioned above, but also 'Schizodus' (in an old log of Bentley Colliery No. 1 Shaft but not present in the BGS collections), Discina sp. (Pincheon Green Borehole), D. konincki (Ash Hill Borehole), Fenestella geinitzi near the top of the argillaceous sequence, and Platysomus cf. striatus (Misson Borehole). A high gamma-ray peak characteristic of the Marl Slate was recorded in geophysical logs of the Hatfield oil boreholes and in the lower part of the thicker sequence in the Idle Borehole, but the response in the Trumfleet oil boreholes was not diagnostic. This argillaceous sequence includes: scattered sand grains and thin sand layers, some with rounded grains, near the base; contorted bedding in Trumfleet No. 2 Oil Borehole, similar to that in the Marl Slate of Durham (Smith and Francis, 1967, p.102); and possible glauconite grains in Brier Hills Borehole. Thus the sequence in most western, central and southern parts of the district includes the Marl Slate, locally with carbonate-rich basal B. binneyi/P. costatus shell layers which are probably littoral in origin. It also widely includes the Lower Marl, locally interbedded with, but generally overlying, the Marl Slate; the Lower Marl facies thins northwards and eastwards by passage into the Lower Magnesian Limestone. Miospore assemblages from the 'Lower Permian Marl' between 501.40 and 530.35 m in Axholme Borehole (and from the 'Middle Permian Marl' at 454.15 m in that borehole) were examined by the late R F A Clarke (unpublished report to BGS). They are dominated by specimens of Lueckisporites virkkiae, Lunatisporites spp., Illinites spp., Klausipollenites schaubergeri and Falcisporites zapfei, with Protohaploxypinus spp. and sporadic Vittatina hiltonensis, Perisaccus granulosus and Nuskoisporites spp.They are comparable with assemblages from the Zechstein sequence elsewhere in England (Clarke, 1965; Pattison et al., 1973; Warrington, in Smith et al., 1973) and are indicative of a late Permian (Kazanian to Tatarian) age.

The 'Lower Permian Marl' at 306.63 m in the Ash Hill Borehole, near Sykehouse, yielded palynomorph assemblages that include miospores but which are dominated by acritarchs of the genus Baltisphaeridium, with representatives of the genera Micrhystridium, Veryhachium and Leiofusa. The acritarchs, documented by Wall and Downie (1963), are not age-diagnostic, but indicate a marine environment. Wall and Downie (1963, p.775) regard the assemblage as reflecting sedimentation farther from the margin of the Zechstein basin than one examined by them from the 'Lower Permian Marl' at Conisborough, farther west in the adjacent Barnsley (Sheet 87) district, where smaller, shorter spined acritarchs, predominantly Veryhachium spp., are associated with larger numbers of miospores.

Lower Magnesian Limestone (excluding the Lower Marl Member)

The Lower Magnesian Limestone (Cadeby Formation of Smith et al., 1986) comprises a white to grey, calcitic and dolomitic carbonate sequence, locally more than 100 m thick. It is present throughout central and eastern Yorkshire and adjacent parts of the East Midlands. It correlates with the combined Lower and Middle Magnesian Limestone of County Durham, now known as the Raisby and Ford formations respectively (Smith et al., 1986), and with the Zechsteinkalk and Werradolomit of Germany. The formation makes the main topographical feature along the Permian outcrop to the west and, in exposures there, a lower and an upper subdivision have long been recognised (Sedgwick, 1829; Mitchell, 1932; Edwards et al., 1940, pp.122–126; Mitchell et al., 1947, pp.113–115). The lower subdivision (Wetherby Member of Smith et al., 1986) consists mainly of fine-grained to coarsely granular limestone and oolite, appreciably dolomitised and generally forming thick parallel beds, although small-scale cross-bedding and ripple-bedding are present locally. It is quite fossiliferous and reefs occur in places. The upper subdivision (Sprotbrough Member of Smith et al., 1986) consists mainly of finely or, less commonly, coarsely crystalline dolomite, some of it minutely cellular due to recrystallised ooliths, with some less altered oolite locally. It commonly exhibits large-scale cross-bedding; fossils are scarce and reefs are absent. The two subdivisions are separated by the Hampole Discontinuity, recognised locally at outcrop as a minor erosional surface (Smith, 1968). This is overlain by the Hampole Beds, a sequence up to 1.5 m thick, comprising three thin, greenish, shaly mudstones separated by two cream, finely oolitic and partly laminated calcitic dolomites. The interval suggests a transient regression, followed by epitidal deposition. The Lower Magnesian Limestone as a whole includes littoral, shelf, slope and basin facies (Smith, 1974, pp.124–130) and was deposited in the Zechstein Basin during the transgressive phase of the EZ1 cycle. Much of the dolomitisation was early diagenetic (Harwood, 1982).

Details

The higher part of the Lower Magnesian Limestone forms rockhead, much of it at outcrop, in several places along the western edge of the district, south-west of Doncaster. Farther east, the formation is present across the whole area, thickening in this direction to more than 80 m, and locally to over 100 m (Figure 20c). In Wressle and Drax boreholes, where the previously recorded thicknesses were 116 m and 107 m respectively, the highest 15 to 20 m are now shown, by comparison with adjacent boreholes, to belong to the Hayton Anhydrite; amended thicknesses were used to construct (Figure 20c). The thickest proving in the district is 100.6 m in Hemingbrough Borehole, with 108.4 m in Fir Tree Borehole, just north of the district. In view of the 139 m recorded in Crosby Borehole [SE 8745 1225], east of the district (Gaunt et al., 1992, figs. 7, 8a), it is possible that thicknesses of more than 100 m extend westward into the Keadby–Luddington area within the district. However, as South Cliffe Oil Borehole [SE 8791 3522], just north-east of the district, proved only 10 m of Lower Magnesian Limestone (Gaunt et al., 1992, figs. 7, 8a), a marked north-eastward thinning probably occurs in the north-eastern corner of the district, representing the change from thick carbonate facies deposition on the shelf to thin carbonate/thick evaporite formation in the basin. The apparent thickness irregularities in more western parts of the district may be due partly to inaccurate borehole records and partly to local variations in the passage of Lower Marl marginal facies into limestone. Some isolated thickenings, notably two in the Doncaster–Bentley area and two in the Whitley–Kellington area, may be relict hills of limestone that survived penecontemporaneous erosion, as there are complementary thinnings of Middle Marl above them (Figure 20c) and (Figure 23a).

The Lower Magnesian Limestone has been extensively worked around Stainton, and 12.2 m of cross-bedded dolomitic limestone were formerly seen in one quarry [SK 551 941]. There are small exposures of white, yellow and grey limestone, much of it dolomite, including granular, oolitic and cellular varieties, in and around Edlington Wood [SK 550 980] and in a small inlier [SK 553 967] to the south-east. Numerous swallow holes exist along and just beyond the limestone outcrops in these areas.

Farther north, in Alverley Hall Quarry [SK 5535 9915], E G Smith recorded details of one of the most southerly of the reefs in the limestone; this is the only known reef and the only undoubted exposure of the lower subdivision of the Lower Magnesian Limestone within the district. The reef consists of hard, dense, buff dolomite rising 15 m above the quarry floor; it comprises a highly fossiliferous bryozoan core, 4.5 m high, containing irregular thin red mudstone layers within a thick stromatolite mantle, the top of which, when previously observed by Mitchell (1932), was slightly brecciated and recemented. The reef fauna, most if not all of it from the bryozoan core, includes Agathammina pusilla, Geinitzina sp., Hemigordius?, Acanthocladia anceps, A. anceps laxa, Batostomella columnaris, Thamniscus dubius, Dielasma elongatum, Yunnania? cf. helicina, Bakevellia binneyi, Liebea squamosa, Parallelodon striatus, Schizodus obscurus and ostracods. The strata above the reef, in descending order, are:

Although the Hampole Discontinuity was not recognisable, the higher dolomite layers (2, 4 and 6 above) are considered to represent the lower dolomite of the Hampole Beds, which would place the discontinuity at the base of layer 2.

Most of the limestone at rockhead farther north is concealed by Quaternary deposits. The Lower Magnesian Limestone just east of the outcrops described above was cored in three boreholes (Dadsley Well [SK 5898 9429], Stainton Little Wood [SK 5549 9428] and White Cross [SK 5684 9785]), examined by D B Smith and summarised together here.

At the base is a pale to dark grey, thin-bedded, fine-grained, argillaceous dolomite, up to 3 m thick, with mudstone laminae and scattered carbonaceous plant debris. The abundant fauna includes (from Dadsley Well Borehole) Acanthocladia anceps, Batostomella columnaris, B. crassa, Fenestella cf. geinitzi, Protoretepora ehrenbergi, Cleiothyridina pectinifera, Horridonia horrida, Lingula credneri, Pterospirifer alatus and Stenoscisma sp., suggesting well-circulated open-sea conditions with virtually normal salinity. Above lie several metres of grey to brownish grey, fine-grained, locally fetid dolomite; this has variably undulating, and locally irregular, thin bedding and laminae, mudstone partings and traces of carbonaceous plant debris, as well as scattered small masses of galena, possibly resulting from poorer circulation in more euxinic conditions. The succeeding grey to buff, fine-grained dolomite, apparently about 13 m thick in Dadsley Well Borehole but only 1 to 2 m thick in the other two boreholes, is characterised by an irregularly nodular or patchy texture, irregular stylolitic bedding planes, numerous small cavities and local autobrecciation; it is interpreted as a slope deposit. The overlying strata, only 2 m thick in Dadsley Well Borehole but about 18 m thick in the other two boreholes, consist of pale grey, apparently thick-bedded, fine- to medium-grained locally 'saccharoidal', lustre-mottled dolomite; abundant minute cavities, traces of small-scale cross-bedding and ripple-bedding, localised patches suggestive of bioturbation, burrow-like structures and a few small shell fragments were noted. Although few traces of ooliths were recorded, these strata may be altered shelf and/or littoral oolites. If so, the large thickness variations within this sequence, and in the underlying supposed slope deposits, suggest that the upward growth and basinward migration of the carbonate shelf was by no means uniform, even across distances of less than 4 km.

The succeeding 0.5 m-thick, pale buff-grey, pisolitic dolomite containing carbonate intraclasts in Stainton Little Wood Borehole could have resulted from transient regression and may approximate to the Hampole Discontinuity; unfortunately some core was missing at this stratigraphical level in White Cross Borehole. The overlying pale buff, fine- to medium-grained, lustre-mottled dolomite is 1.7 m thick in Stainton Little Wood Borehole and has abundant minute cavities, small-scale cross-bedding, traces of altered ooliths and a few shells; it represents a shelf facies, similar to the Hampole Beds, as does the equivalent, but coarser-grained dolomite above the missing core in White Cross Borehole. The grey, thin-bedded and laminated, fine-grained dolomite in Dadsley Well Borehole at this strati-graphical level is undiagnostic.

If these interpretations are correct, the lower subdivision of the Lower Magnesian Limestone ranges from 18 to 25 m thick in these boreholes; the upper subdivision is about 29 m thick in Dadsley Well Borehole, but only about 12.7 m and 8.4 m thick in Stainton Little Wood and White Cross boreholes respectively. The last two reduced thicknesses suggest the possibility of penecontemporaneous erosion.

The higher part of the Lower Magnesian Limestone in the three boreholes comprises white to buff and pale grey, fine-to medium-grained, abundantly cellular and lustre-mottled dolomite; ophitic gypsum, acicular cavities perhaps due to sulphate solution, some small masses of anhydrite and galena, and traces of algal laminae are recorded. Cross-bedding with dips up to 10° and, in White Cross Borehole, traces of bivalves and gastropods are present also. Although only sparse remains of ooliths survive, much of this higher dolomite is possibly an altered oolite of shelf and/or littoral derivation.

Farther north, along the western edge of the district, a similar carbonate sequence is discernible in Coalite No. 3 Borehole [SE 5596 1357] at Askern (Figure 21). D B Smith, who examined the core, estimated that the borehole reached to within a metre or two of the base of the Lower Magnesian Limestone. He divided the sequence into lower and upper subdivisions, 15.9 m (incomplete) and 28.4 m thick respectively, separated by 1.2 m of 'Transitional beds'. The lowest 3.9 m comprise grey to greyish brown, argillaceous, shaly dolomite, with thin grey mudstone layers. The abundant fauna includes Agathammina milioloides, A. pusilla, Calcitornella? minutissima, Cyclogyra kinkelini, nodosariids (including Geinitzina sp.), Acanthocladia sp., Fenestella geinitzi, Penniretepora waltheri, Protoretepora sp., trepostome bryozoa, Horridonia horrida, Pterospinfer alatus, indeterminate strophalosiids, Astartella? Bakevellia binneyi and ostracods. The fauna decreases markedly in the highest 0.7 m of these beds, which become irregularly laminated and contain dark carbonaceous partings with ?plant debris, suggesting more euxinic conditions. The succeeding 5.6 m of strata consist of pale grey dolomite, with undulating and locally irregular bedding, giving the nodular appearance of a slope deposit, and they contain numerous cavities, small masses of gypsum, pyrite and sphalerite, and a scattered fauna including Agathammina milioloides, A. pusilla, Acanthocladia anceps, Aviculopinna?, Bakevellia binneyi, Schizodus sp. and ostracods. There is an upward gradation into the highest 6.4 m of the lower subdivision, which comprise greyish cream, interbedded finely granular and finely oolitic dolomite, with traces of small-scale cross-bedding. The scattered fauna includes Calcinema? (or productoid spines), Agathammina milioloides, A. pusilla, Cyclogyra kinkelini, Thamniscus?, nodosariids, gastropods, Bakevellia binneyi, Schizodus obscurus and ostracods. The 'Transition beds' consist of greyish cream, finely granular dolomite; near the top this is finely oolitic and contains Agathammina pusilla, Yunnania cf. tunstallensis, Bakevellia? and Schizodus sp.

The lowest 10.7 m of the upper subdivision are mainly cream to buff, fine- to medium-grained oolites with upward-thickening cross-bedding. They are succeeded by 3.0 m of coarse-grained oolites, which contain several thin pisolitic layers, one of them at the base, and irregular undulating laminae, presumed to be of algal origin. This coarse oolitic-pisolitic sequence (Figure 21) is reminiscent of the oncolithic and pisolitic layers in Dadsley Well and Stainton Little Wood boreholes, respectively, and suggests a possible regressive phase and an alternative position for the Hampole Discontinuity. The highest 14.7 m of Lower Magnesian limestone in Coalite No. 3 Borehole are cream, medium to coarse, granular dolomites, with two thin shelly pisolitic layers near the base and scattered relict ooliths at higher levels, as well as abundant minute cavities and cross-bedding with dips up to 26°. The fauna, largely concentrated in certain layers, including the pisolitic and coarser oolitic layers, includes Calcinema? (or productoid spines), Agathammina pusilla, gastropods, Bakevellia including B. binneyi, Schizodus sp. and ostracods. The pisolitic and coarser oolitic layers may be of regressive littoral origin, with some epitidal algal growth, but the rest of the upper 14.7 m are probably shelf deposits.

Farther east in the district, detailed core descriptions of most or all of the Lower Magnesian Limestone are available from five boreholes–Misson (in the south), Thorne Colliery Centre (in the middle) and Camblesforth No. 1, Barlow No. 2 and Hemingbrough (in the north). The first three of these boreholes are summarised here, in descending order.

Misson Borehole (examined by R A Eden and E G Smith)

In view of the southerly location of Misson Borehole, the upward persistence of 'marl' layers through more than 33 m of strata is compatible with the 'marl'-rich Lower Magnesian Limestone farther south (Smith et al., 1973, pp.122–124, fig. 23). There is no evidence of the Hampole Discontinuity. By comparison with boreholes farther west, 'limestones' 1 and 2 are referable to the lower subdivision, but the correlation of 'limestone' 3 is uncertain.

Thorne Colliery Centre Borehole (examined by M Robinson, British Coal) (Figure 21)

Items 1 to 4 in this borehole are not unlike items 1 and 2 in Misson borehole and suggest a change from well-circulated open-sea to slope deposition. (Differing descriptive styles may mask other similarities at higher levels).

Camblesforth No. 1 Borehole (examined independently by R F Goossens, British Coal and L M Fuzesy (1980) (Figure 21)

Fuzesy (1980) divided the sequence in this borehole into a lower, partly dolomitised limestone unit and an upper dolomite unit, with the junction 3.2 m below the top of item 2 above. He correlated the two units with the lower and upper subdivisions respectively of the outcrop to the west, although no reason for this correlation is given. The partly dolomitised limestone unit is interpreted as a semi-restricted subtidal deposit (with the nodular structures in item 2 forming as concretions, soon after deposition, by mineral segregation initiated by the release of ammonia from decomposing organic matter). The dolomite unit, except for the highest 5.2 m (item 5 above) is regarded as a more restricted subtidal deposit (in which the contained nodular sulphates are interpreted as having formed in semi-consolidated, slightly lithified sediments, by direct precipitation from refluxing heavy, hypersaline brines and also as a by-product of the conversion of aragonite and/or calcite to dolomite). The highest dolomite (item 5 above) is considered to be a supratidal sabkha deposit in view of the flattened, enterolithic and 'chicken-wire' structure of the contained sulphates.

The detailed core descriptions of Barlow No. 2 and Hemingbrough boreholes, by R F Goossens of British Coal, show many similarities to that of the nearby Camblesforth No. 1 Borehole, the wavy- and nodular-bedded strata being particularly noticeable (Goossens, 1973, p.242).

Summary

From the nine cored boreholes reviewed above and from other borehole evidence, comprising sparse descriptions from old cored boreholes, recent partial corings (mainly of the lowest strata) and chipping samples, it is apparent that although no clearly delineated stratigraphical classification of the Lower Magnesian Limestone is recognisable across the district, certain broad conclusions can be drawn.

A. In approximately the lower half of the limestone there is a generalised sequence comprising, in upward order:

1. Darkish grey, thin-bedded and laminated, argillaceous, dolomitic limestone at the base, with thin dark grey mudstone layers, scattered plant debris and a diverse and locally abundant fauna consisting mainly of fischerinid and some nodosariid foraminifera, bryozoa (notably retiform taxa) and brachiopods, with some bivalves and fish debris. Upward passage, mainly gradational, into
2. Interbedded pale to dark grey, dolomitic limestone, partly argillaceous (especially in the south), with thin dark grey mudstone layers, stylolitic bedding planes, irregular wavy bedding, scattered plant debris and a sparse and restricted fauna. Upward passage, mainly by locally thick alternations, into
3. Pale to medium grey, dolomitic limestone with a nodular appearance, scattered small masses of gypsum and/or anhydrite, traces of brecciation and only rare traces of plant debris and shells. Upward gradational and/or alternating passage into
4. Pale grey dolomitic limestone, variously fine-grained, finely crystalline or saccharoidal, with locally scattered shell debris.

In addition to the fauna from this sequence listed from Dadsley Well, Coalite No. 3 and Misson boreholes, the fossils recovered from Axholme, Fenwick, Fenwick Common, Fishlake and Wressle boreholes and Bentley Colliery No. 2 Shaft include Crurithyris clannyana, Dasyalosia goldfussi?, Dielasma sp. including D. elongatum, Discina konincki, Orthothrix excavata, O. cf. lezvisiana, Stenoscisma cf. humbletonensis, S. schlotheimi, Streptorhynchus pelargonatus and Streblochondria? pusilla. The upward decrease in abundance and diversity of the brachiopod fauna as a whole through the sequence, with H. horrida and S. morrisiana being apparently the most durable species (J Pattison, unpublished report), implies increasingly hostile conditions, probably due to poorer circulation and possibly to increasing salinity. The lithological variations within the sequence suggest that the depositional environment changed from open sea with increasingly restricted conditions to shallow-water shelf, with one or more slope-deposition phases as the shelf extended basinwards and upwards.

B. There is no direct evidence of the Hampole Discontinuity, nor of any clear distinction into lower and upper subdivisions, in central and eastern parts of the district, and it is possible that shelf deposition continued without any regressive interruptions in these areas. However, in some of the more westerly boreholes, such as Great Heck (Figure 21), there is a thin pisolitic or oncolithic bed in or just above the middle of the Lower Magnesian Limestone, which is reminiscent of comparable beds in Daley Well, Stainton Little Wood, Coalite No. 3 and Camblesforth No. 1 (item 3) boreholes that suggest the possibility of transient regression. At approximately the same stratigraphical level in several more easterly boreholes, such as Bank End, Belton, Crowle Oil (Figure 21) and Trumfleet No. 1 and No. 2 Oil, and also apparently in Bentley Colliery No. 1 Shaft, there is evidence of a gypsum and/or anhydrite-rich layer which, like the comparable item 7 in Thorne Colliery Centre Borehole, is suggestive of the temporary establishment of supratidal sabkha conditions following a transient regression. A comparable sulphate-rich layer occurs in boreholes east of the district, where it raises the possibility 'that some of the lower part of the Hayton Anhydrite may interdigitate with, and so be coeval with, the middle, locally anhydritic, part of the Lower Magnesian Limestone' (Gaunt et al., 1992, p.20, fig. 7).

C. Much of the upper part of the Lower Magnesian Limestone is pale grey, fine-grained or finely crystalline dolomitic limestone or dolomite. Only a few boreholes such as Coalite No. 3, Thorne Colliery Centre and Crowle Oil prove oolites (Figure 21) and there is little evidence of granular or cellular textures suggestive of recrystallised oolites. Traces of large-scale cross-bedding, admittedly difficult to detect in boreholes, are limited to a few western boreholes, such as Sun Inn. Small gypsum and/or anhydrite masses, apparently nodular, appear to be widespread and to increase in abundance upwards. Fossils are scarce and generally comprise shell debris, indeterminate except for those from Misson Borehole. These rather nondescript upper strata suggest a thick and extensive, largely nonoolitic, shelf accumulation saturated by highly saline groundwater.

D. Numerous boreholes including Great Heck, Thorne Colliery Centre, Camblesforth No.1 and Hatfield No. 1 Oil (Figure 21) show that the highest few metres of the Lower Magnesian Limestone are rich in gypsum and/or anhydrite in both nodular and layered form, and that they also commonly contain thin reddish mudstone layers. Where cores were taken, the host dolomite is thoroughly recrystallised and in places there is evidence of autobrecciation and algal growth. Following Fuzesy (1980), these strata are considered to result from the widespread establishment of supratidal sabkha conditions, presumably at the beginning of the regressive phase of the EZ1 cycle.

'Marl' between Lower Magnesian Limestone and ?Hayton Anhydrite

Although the ?Hayton Anhydrite, which occurs in northeastern parts of the district, generally rests directly on Lower Magnesian Limestone, in eight boreholes and in Hatfield Colliery No. 1 Shaft (Figure 20d), it rests on intervening, mainly reddish, argillaceous strata. The latter are recorded as 'marl', except in Hatfield No. 1 Oil and Crowle Oil boreholes where they are designated as mudstone. In five of these sections the argillaceous strata contain anhydrite or gypsum. The thickest sequence recorded is in North Ewster Borehole (14.3 m) (Figure 22), and the thinnest is in Hemingbrough Borehole (2.1 m) (Figure 22). In Fenwick Hall Borehole the thickness is unrecorded, but evidently small. The appreciable thickness in most of the sections presumably precludes an origin entirely as a solution residue. Except for that in Hemingbrough Borehole, the occurrences all lie close to the south-western limit of the overlying ?Hayton Anhydrite, which suggests that the argillaceous strata may be largely, if not entirely, part of a basal leaf of the Middle Marl extending locally under the anhydrite. The isolated thin occurrence in Hemingbrough Borehole could conceivably be due entirely to solution residue.

?Hayton Anhydrite

The Hayton Anhydrite, a correlative of the Hartlepool Anhydrite of County Durham and the Werraanhydrit of Germany, overlies the Lower Magnesian Limestone in eastern Yorkshire and northern Lincolnshire. It is thickest, up to 145 m, along the basinward slope, beyond the limestone shelf, but then thins markedly towards the centre of the basin. In the opposite direction it extends thinly on to the limestone shelf in places. Two subdivisions are commonly discernible, the lower and thicker one comprising mainly anhydrite, and the upper one containing appreciable amounts of dolomite. The Hayton Anhydrite and the Hartlepool Anhydrite have both been interpreted by Taylor and Colter (1975), Taylor (1980) and Smith (1980a) as intertidal to supratidal sabkha deposits, formed around the margins of the Zechstein Sea at a time of hypersalinity.

Within approximately the north-eastern half of the district anhydrite overlies the Lower Magnesian Limestone, although locally thin 'marls' intervene, as described above. The anhydrite thickens north-eastwards (Figure 20d), reaching 39 m in Brind Common Borehole and, just north of the district, 49.5 m in Fir Tree Borehole (Figure 22); it is known to extend farther in that direction (Wilcockson, 1950; Edwards, 1951, pp.101–102, fig. 38; Goossens, 1973, p. 242, fig. 4). Core descriptions from Camblesforth No. 1 Borehole (examined independently by R F Goossens of British Coal and D B Smith) and Thorne Colliery Centre Borehole (examined by M Robinson of British Coal) show the anhydrite to be 7.2 m and 13.0 m thick respectively (Figure 22). It is pale to medium reddish and bluish grey, with some darker grey and purple patches, and fine-grained; it locally has a flattened nodular or 'pillow' structure, in places within a framework of reddish brown and greenish grey mudstone partings. In Camblesforth No. 1 Borehole some flow structures may be present. Locally, numerous laminae and thin wispy lenses of reddish brown and greenish grey mudstone and siltstone are present; some are contorted in a manner suggesting load casts and some apparently contain anhydrite masses, suggesting autobrecciation. Thin layers and lenses of pale grey dolomite occur near the base. In some oil boreholes, where chippings have been examined microscopically, the anhydrite is described as clear, translucent and white, though locally red stained; it is generally fine to medium crystalline, but fibrous in places, possibly after gypsum, and with small amounts of gypsum apparently as thin layers or veins. There is an increase in reddish brown and greenish grey mudstone, within the anhydrite, to the south-west. This increase is particularly marked between the 10 m and 0 m isopachs (Figure 20d), showing that the anhydrite passes laterally by interdigitation into the lower, but in places clearly not the lowest, part of the Middle Marl. Thin anhydrite layers continue extensively farther southwest within the Middle Marl, and several borehole records also imply an interbedded passage from the anhydrite into that part of the Middle Marl extending above it.

The considerable thicknesses of anhydrite above the basinward slope of the Lower Magnesian Limestone in the Brind Common and Fir Tree boreholes are comparable with those of the Hayton Anhydrite in Burton upon Stather Oil (66 m) [SE 8787 1883] and South Cliffe Oil (133 m) [SE 8791 3522] boreholes farther east (Gaunt et al., 1992, figs. 7, 8b). Consequently most, though not necessarily all, of the thick anhydrite in the north-eastern corner of the district is considered to be Hayton Anhydrite. However, the absence of associated dolomite in the upper part of the anhydrite presumes that the upper subdivision of the Hayton Anhydrite either does not extend westward into the district or loses its dolomite content laterally in that direction.

Farther south-west the anhydrite thins more gradually above the Lower Magnesian Limestone shelf; the apparently irregular pattern of thinning (Figure 20d) superficially resembles a dendritic drainage system. If this analogy is valid, the irregularities might partly reflect the varying intensity of sabkha deposition, associated with a system of shallow tidal creeks converging and draining north-eastwards. However, where the argillaceous content is increasing south-westwards and the anhydrite is passing laterally into Middle Marl, it is thought that at least some of the irregularities are due to variations in the reliability of uncored borehole records, resulting from the difficulty of assessing the relative amounts of anhydrite and 'marl' present. This thinner anhydrite is probably also equivalent to the Hayton Anhydrite, although its passage into the Middle Marl is apparently at variance with the situation in the adjacent region, where the Hayton Anhydrite either does not extend as far as the Middle Marl or wedges out below it (Smith, 1974, fig. 38; Taylor and Colter, 1975, fig. 2; Harwood et al., 1982, fig. Y2).

Along part of the eastern edge of the district it is also difficult to reconcile the thicknesses of anhydrite in Crowle Common (11.0 m), the three Axholme Oil (up to 15.2 m) and North Ewster (17.5 m) boreholes with its virtual absence, other than as thin layers within mudstone, in the nearby Crosby and Butterwick Oil boreholes to the east (Gaunt et al., 1992, fig. 7). In Crosby Borehole some anhydrite may have been included within the upper part of the Lower Magnesian Limestone, as happened in other old boreholes such as Wressle and Drax. However, the equivalent stratigraphical position of the anhydrite in North Ewster Borehole is occupied by dolomitic limestone of the Kirkham Abbey Formation in Butterwick Borehole, [SE 8421 0563] within otherwise similar sequences and across a distance of less than 2 km (Figure 22). These circumstances raise the possibility that some of the anhydrite within the district may have formed as epitidal sabkha deposits, while the shallow marine carbonates of the Kirkham Abbey Formation accumulated offshore to the north and east during the EZ2 cycle. Taylor and Colter (1975, p.254) noted that 'the Kirkham Abbey Formation .... interdigitate (s) landwards with sabkha anhydrites and eventually mudstones .... of the Middle Marls'. Similar lateral changes, with attendant difficulties in nomenclature, were noted by Taylor (1980, pp.96–99, fig. 4). Thus, although the anhydrite in the district includes the Hayton Anhydrite, it may also include a distinct, younger, thin but widespread, deposit attributable to the Aislaby Group in more south-westerly areas.

Aislaby Group (EZ2)

Kirkham Abbey Formation

In eastern Yorkshire and the adjacent part of Lincolnshire a thick dolomitic limestone, the Kirkham Abbey Formation, originated mainly as a shelf deposit during the transgressive phase of the EZ2 cycle. Unlike its correlatives in County Durham (the Hartlepool and Roker Dolomites) and Germany (the Hauptdolomit) it does not crop out, except possibly near Ripon (Harwood et al., 1982, p. 33). The formation is present just east of the district and is known to thicken northwards from 16 m in Butterwick Oil Borehole (Figure 22) to 68 m in South Cliffe Oil Borehole (Gaunt et al., 1992, p.20, figs. 7, 8c). It therefore certainly extends westwards into the district, but has not yet been proved. A few thin 'limestones' are recorded from within the Middle Marl in certain old boreholes such as Wressle, Drax and Axholme but, with one exception, none has been proved in more recent adjacent boreholes, which record anhydrite and gypsum layers at comparable stratigraphical levels. The exception is 1.0 m of 'grey limestone' within the lower part of the Middle Marl, some distance above the 20 m of ?Hayton Anhydrite in Percy Lodge Borehole (Figure 22). This thin limestone could represent the western edge of the Kirkham Abbey Formation, and is so interpreted in (Figure 23a). The formation may pass laterally westwards into anhydrite (see above).

'Marl' Between ?Hayton Anhydrite and ?Fordon Evaporites

The ?Fordon Evaporites in the northern part of the district generally rest directly on the ?Hayton Anhydrite. However, in four boreholes and in Thorne Colliery No. 1 Shaft (Figure 23a) the two formations are separated by grey and 'blue' argillaceous strata, which are recorded as 'marl' or, in Camblesforth No. 1 Borehole, as laminated mudstone and siltstone containing lenses of anhydrite. The thickest sequence, 7.2 m, is in Snaith Borehole, and three others, 3.1 m in Barlow No. 2, 3.0 m in Brind Common and 2.7 m in Camblesforth No. 1 boreholes (Figure 22) are sufficiently thick to imply origins other than as solution residues. These argillaceous strata could be relics of a depositionally distinct, intermediate leaf of the Middle Marl.

However, the five proved occurrences are widely separated within the limits of the overlying ?Fordon Evaporites (Figure 23a), which are conjectured to have a displacive/replacive origin (see below). The 'marls' may, therefore, be a part of the Middle Marl that lay marginally under the zone of growth of the ?Fordon Evaporites.

?Fordon Evaporites

The Fordon Evaporites and their German equivalents, the Stassfurt Evaporites, are thick, halite-rich evaporites which originated in the Zechstein Basin during the regressive phase of the EZ2 cycle. They extend into eastern Yorkshire and north-eastern Lincolnshire, but thin markedly south-westwards and do not reach rockhead. In South Cliffe Oil Borehole, just north-east of the district, the beds consist merely of 3 m of anhydrite and anhydritic dolomite (Gaunt et al., 1992, figs. 7, 8d) and they were not found in Burton upon Stather Oil or more southerly boreholes.

Halite closely associated with the Middle Marl has been proved in the north of the district in 18 boreholes and in Thorne Colliery No. 1 Shaft (Figure 23a). The thickest provings are 17.0 m in Selby No. 2 (Figure 21) and Burn Airfield No. 1 boreholes, but the thickness variations have no meaningful pattern and could, at least partly, result from minor salt movement. Most of the halite is grey, with some pink and brown layers and nodular masses, and it is medium to coarsely crystalline. Even in uncored boreholes the presence of associated grey and subordinate red mudstone, and also of anhydrite, is generally apparent. The relationship of these impurities to the halite was seen in the cores of Barlow No. 2 Borehole (examined by R F Goossens of British Coal) and Camblesforth No. 1 Borehole (examined independently by R F Goossens and D B Smith) (Figure 22), where irregular wispy lenses of silty mudstone up to 0.3 m thick, and nodular masses or layers of anhydrite up to 0.1 m thick, form a 'corroded ragged mesh' within the halite. Some of the halite contains up to 40 per cent of these impurities and Goossens (1973, p. 243) estimates that the halite as a whole is about 75 per cent pure.

According to Smith (1974, pp.131–132) these structures suggest a secondary, partly displacive (of mudstone) and partly replacive (of anhydrite) origin of the halite, by precipitation from interstitial, hypersaline groundwater within the Middle Marl.

In view of the virtual absence of halite within the EZ1cycle rocks generally (Taylor and Colter, 1975, p. 254), the halite associated with the Middle Marl in the district may well be genetically related to the halite-rich Fordon Evaporites deposited in basinal areas. However, considering both the evidence from South Cliffe Oil and more southerly boreholes, and its absence from boreholes such as Fir Tree (Figure 22), Booth Ferry and Quay Lane, it is clear that the halite does not continue directly eastwards from the district into the Fordon Evaporites. Although the two may be in continuity farther north, within the district there remains some uncertainty concerning their correlation. Nevertheless, the halite within the district probably resulted from the same hypersaline phase that produced the Fordon Evaporites.

Middle Marl

The Middle Marl (Edlington Formation of Smith et al., 1986) comprises a sequence of red, and subordinate greyish green, locally dolomitic mudstones and siltstones, which separates the Lower Magnesian Limestone from the Upper Magnesian Limestone along the outcrop in Yorkshire. It contains small nodular layers of gypsum which increase in abundance northwards; towards the south there is an increasing proportion of interbedded sandy strata and some thin conglomerates and breccias occur locally, mainly in the upper part of the sequence, as described by Smith et al., (1973, pp.139–153). East and particularly north-east of the outcrop, the Middle Marl includes increasing amounts of nodular and layered anhydrite, concentrated at certain stratigraphical levels. Farther in these directions the Kirkham Abbey Formation and Fordon Evaporites develop within its middle part and ultimately replace it entirely; some of the lower argillaceous strata also evidently pass laterally into the higher part of the Hayton Anhydrite (Figure 21). Hence, deposition of the Middle Marl may have commenced during the regressive phase of the EZ1 cycle and, in view of the restricted range of the succeeding Zechstein transgression, it continued throughout much or, in more westerly areas, all of the EZ2 cycle. The Middle Marl is interpreted as terrigenous sediment derived from a fairly low-lying and largely arid hinterland to the west and south, and deposited on a wide coastal plain containing transient lagoons and playas and subject to periodic tidal incursion.

Within the district the Middle Marl reaches rockhead in several places south-west of Doncaster and also at Askern (Figure 23a), but although much of it crops out in these localities, virtually the only exposures are of red-weathered mudstone, locally with gypsum, in ditches. However, the highest strata, directly beneath the Upper Magnesian Limestone, are seen in an old quarry [SE 5604 1342] at Askern. They comprise 1.2 m of yellowish brown siltstone with thin beds of cream, fine-grained limestone in the highest 0.3 m, resting on 1.2 m of alternating, variably red and grey siltstone and mudstone.

The Middle Marl continues eastwards at depth throughout the district and its thickness variations (Figure 22) and (Figure 23a) reflect its relationship to the contiguous formations. Localised thinning in the Doncaster–Bentley and Whitley–Kellington areas coincides with thicker underlying Lower Magnesian Limestone. Wilson (1926) attributed this complementary relationship to the Middle Marl occupying hollows on the limestone surface. With the more numerous borehole records now available it appears that the thicker limestone occurs where it was preserved as isolated low hills, which suggests some erosion of the surrounding limestone surface prior to Middle Marl deposition. The Middle Marl thickens irregularly eastwards to more than 40 m between the north-western and south-eastern corners of the district (Figure 23a), reaching 58.6 m in Blyton Carr Borehole (Figure 22). It then thins irregularly north-eastwards, partly by the development within its lower part of the ?Hayton Anhydrite, Kirkham Abbey Formation and ?Fordon Evaporites. The limits of the last two show a clear relationship to the thinning (Figure 23a). The upper part of the Middle Marl continues north-eastwards above these formations, but is reduced to 5.9 m in Fir Tree Borehole (Figure 22).

Most borehole records refer to the Middle Marl merely as red and greyish green 'marl' with thin gypsum, locally thin anhydrite and, in some old records, thin 'limestone'. Most of the sequence is evidently red; greyish green strata occur in the basal and topmost parts and are thinly interbedded elsewhere, notably where anhydrite and/or halite is present. However, a few cored boreholes, some geophysical logs and several boreholes where the chipping samples were carefully examined, show that the Middle Marl changes laterally as it is traced northeastwards.

Details

In the south-west of the district the Middle Marl in the White Cross Borehole, examined by D B Smith, is 44.73 m thick. It contains several, mainly pale greenish grey, locally gypsiferous or carbonate-cemented, fine-grained, silty sandstones up to 0.53 m thick, as well as greenish grey to reddish brown, locally anhydritic or dolomitic micaceous siltstones up to 1.67 m thick, mainly in the lowest and highest parts. Some of the sandstones exhibit small-scale cross-bedding and, less commonly, ripple-bedding; one thin bed about 18 m above the base contains medium and coarse grains, some rounded and 'frosted', and small subangular to rounded pebbles. Gypsum, both nodular and in layers up to 0.43 m thick, occurs throughout, but is more common in the lower part, and the only anhydrite, a layer 0.15 m thick, overlies one of the lowest gypsum layers. Carbonaceous plant debris, the only known macrofossil material from the Middle Marl within the district, was noted in interbedded siltstone and mudstone near the base. D B Smith also noted fragments of pale, slightly greenish grey, fine- to medium-grained, weakly carbonate-cemented sandstone from the uncored Middle Marl in nearby Stainton Little Wood Borehole. To the east the only equivalent sandstone in Rossington Colliery No. 1 Shaft (Figure 22) is 1.32 m thick and underlies 0.89 m of 'sandy mottled marl' at the top of the Middle Marl. Farther east, in the cored Bank End Borehole (Figure 22), examined by R F Goossens (British Coal), some of the basal 5.0 m of 'marl' are sandy and contain thin limestones, and some of the highest 2.4 m of 'marl' are silty and contain distinct thin siltstones and limestones. Anhydrite, as nodules and layers up to 0.15 m thick, is more common than in the west, and numerous thin gypsum layers are present. To the north-west, cored Middle Marl in Sun Inn Borehole, north-west of Doncaster, also examined by R F Goossens, contains three pale grey limestones up to 0.15 m thick in the basal 1.0 m of grey and red 'marl'. This record enhances the impression from several old uncored boreholes in southerly and westerly locations of an interbedded passage up from the Lower Magnesian Limestone into the Middle Marl, which in some areas at least has survived any approximately coeval local erosion or displacive sulphate mineralisation.

Towards the north-east there is much less evidence of sandy or carbonate-rich strata, but there is an increase in the amount of nodular and layered anhydrite, which appears to be concentrated at three levels: one at or near the base, one in the middle and a less significant one near, or locally at, the top of the sequence. The three anhydrite-rich 'marl' layers are distinct, for example in the geophysical logs of Hatfield Moors No. 1 and No. 2 Oil boreholes and in the cores from Cross Hill Borehole, examined by R F Goossens (British Coal), where the Middle Marl comprises: 'marl' 10.4 m, on anhydrite with 'marl' layers 1.1 m, on 'marl' with anhydrite layers 17.5 m, on anhydrite with 'marl' partings 3.0 m, on 'marl' with anhydrite layers 7.8 m, on anhydrite 0.6 m. In the nearby Pollington No. 3 Borehole the lower and middle anhydrite-rich 'marl' layers were noted from chipping samples to be 5.2 m and 7.6 m thick respectively. The lower anhydrite-rich 'marl' layer in particular is distinguishable in chipping samples from several boreholes, such as Kellington No. 3 and Grove House, where it is 7.3 m and 9.4 m thick respectively. The proximity of these and other boreholes, where the lower anhydrite-rich 'marl' is most distinct, to the south-western limit of the ?Hayton Anhydrite enhances the view that the latter passes laterally into the lower part of the Middle Marl.

The middle anhydrite-rich 'marl' layer is traceable for some distance north-eastwards over the ?Hayton Anhydrite and is separated from the latter by several metres of 'marl', as seen in the cores from Thorne Colliery Centre Borehole (Figure 22), examined by M Robinson (British Coal), where the Middle Marl may be summarised, in descending order, as:

Item 2 above is the middle anhydrite-rich marl layer. In Thorne Colliery No. 1 Shaft, only a few metres away, the underlying item 1 is represented by: blue and brown 'marl' 6.66 m, on 'marl' and 'salt' 0.08 m, on blue 'marl' 0.43. This occurrence of 'salt' is on the southern limit of the ?Fordon Evaporites. The implications, as illustrated on (Figure 22), are that these evaporites develop well below, and are unrelated to, the middle anhydrite-rich 'marl' layer. This view is enhanced by the core from Camblesforth No. 1 Borehole (Figure 22), examined independently by R F Goossens and D B Smith, in which the Middle Marl may be summarised, in descending order as:

The middle anhydrite-rich 'marl' layer, the upper part of bed 1 above, becomes less distinct northwards, and neither it nor the upper anhydrite-rich layer, item 3 above, were distinguished in the cored Barlow No. 2 Borehole.

Teesside Group (EZ3)

Upper Magnesian Limestone

The Upper Magnesian Limestone of the Yorkshire Province (the Brotherton Formation of Smith et al., 1986) correlates with the Seaham Formation of the Durham Province. It is a relatively uniform sequence of white to grey, mainly dolomitic carbonate up to at least 65 m thick and extends across central and eastern Yorkshire into adjacent parts of Nottinghamshire and Lincolnshire, producing a minor feature along much of the outcrop. The formation represents the shelf facies formed during the transgressive phase of the EZ3 cycle and is approximately equivalent to the Plattendolomit in Germany. Much of the sequence is finely crystalline, and small-scale cross-bedding, ripple-bedding and channel cut-and-fill structures testify to shallow-water deposition. Oolites are present in some western locations, including the area west of Doncaster (Mitchell, 1932), and are considered to be near-shore sediments. In more eastern areas the highest strata are locally algal-laminated, suggesting an epitidal environment.

Within the district the Upper Magnesian Limestone reaches rockhead, much of it at outcrop, in several places along and adjacent to the western edge, as far north as Askern and Norton [SE 555 153]. Farther east it is present throughout, thickening north-eastwards from about 10 m in the Rossington–Austerfield area to just over 30 m locally in the north-east (Figure 23b). The apparently thick provings in the old Wressle and Drax boreholes probably include the overlying Billingham Main Anhydrite and intervening 'marl', but the 33.2 m of limestone proved in the old Selby Borehole appears valid in this respect. There is also an isolated thickening, reaching 33.8 m in Laughton Borehole [SK 8185 9674], near the south-eastern corner of the district.

Where exposed, mainly in old small quarries, the limestone is cream, yellow or buff, thin bedded and flaggy, commonly with grey and some red mudstone partings. Much of the rock is finely crystalline but oolites occur in several places and some cellular-textured limestone has been noted. The fossils are concentrated in particular beds and restricted to a few euryhaline taxa, principally the alga Calcinema permiana and the small bivalves Liebea squamosa and Schizodus obscurus. Gastropods including Yunnania tunstallensis and Mourlonia? are also present.

Details

One quarry [SK 5765 9486] near the southern edge of the district reveals 3.7 m of flaggy dolomitic limestone, and in another [SK 5815 9477], nearby to the east, 0.6 m of yellow, flaggy, oolitic dolomitic limestone was noted. Of the several quarries around Wadworth, one [SK 5638 9680] exposes 6.1 m of yellow, thin-bedded, fine-grained and oolitic limestone, another [SK 5755 9738] reveals 3.7 m of pale brown, thin-bedded limestone containing a 0.61 m-thick nodular band, and in a third [SK 5853 9708] some wavy bedding was noted in 1.8 m of yellow, cellular and close-grained, locally shelly limestone. Red and grey mudstone partings were seen in 6.1 m of yellow and grey, thin-bedded limestone in a quarry [SK 5603 9855] at Stump Cross. At Balby, fossiliferous oolites occur in one quarry [SE 5627 0192] and cellular-textured limestone was formerly seen in other nearby exposures. Several closely adjacent quarries in an area [SE 554 027] west of Newton expose a sequence of buff and pink oolitic limestone with red mudstone partings, at least 3.7 m thick, on cream, pink and grey, thin-bedded limestone with shells in the highest 0.6 m, at least 6.7 m thick. Similar lithologies were noted in quarries at Scawsby [SE 552 049] and near Owston [SE 552 110]. Cream and grey, thin-bedded, finely crystalline dolomitic limestone, some of it with a porcellanous appearance, was noted in several quarries at Askern, the thickest occurrences being 7.0 m in that quarry [SE 5604 1342] where the limestone is seen resting on Middle Marl (p. 66), and 6.7 m in Askern Quarry [SE 5603 1398]. Up to 2.4 m of red-stained limestone is visible at an exposure [SE 5606 1355] on Askern Hill. The limestone seen in several old quarries in Park Plantation [SE 551 140], north-west of Askern, is thicker bedded than elsewhere in the area; it was thought to be Lower Magnesian Limestone when the adjacent part of the Wakefield (78) geological sheet was mapped. However, the presence of C. permiana shows the rock to be Upper Magnesian Limestone. The most northerly exposure in the district is in a quarry [SE 5572 1546] in Norton where 3.0 m of cream and grey thin-bedded limestone were noted.

In the few boreholes within the district which provide any details, the Upper Magnesian Limestone is described as grey or buff, locally red-stained, flaggy or thin-bedded limestone or dolomite, in places with gypsum and/or anhydrite, mainly near the base and/or top. Several boreholes as widely spaced as Bank End in the south and Drax No. 3 in the north, and including Thorne Colliery Centre, Camblesforth No. 1, Hatfield No. 1 Oil and Crowle Oil boreholes (Figure 21), record a grey 'marl', generally not more than 2 m thick, at between 3 m and 8 m from the top. Some boreholes in the north-west, such as Pollington No. 2, Rawcliffe No. 1 and Burn Airfield No. 1, record two 'marl' layers in the highest 8 m. More detailed descriptions refer to the limestone as mainly fine-grained or finely crystalline and, in some oil borehole records, microcrystalline, with bedding, laminae and 'marl' or mudstone partings that are commonly wavy or irregular. Where ooliths have been noted they are mainly in the upper part of the limestone. In some south-western boreholes, such as Edlington Nos. 1 and 2 [SK 5542 9868] and [SK 5552 9865] respectively and Bentley No. 1, and in a few elsewhere, such as Hatfield No. 1 Oil (Figure 21) and Belton Oil, the basal beds are 'sandy'; quartz grains, some rounded, were noted near the top of the limestone in Hatfield Nos. 1 and 2 oil boreholes. Small-scale cross- and ripple-bedding have been noted in a few widely spaced boreholes. Much of the contained gypsum occurs as thin veins; anhydrite is present both interstitially and as small nodular masses and thin layers, mainly near the top, as in Thorne Colliery Centre and Camblesforth No. 1 boreholes (Figure 22). Finely disseminated pyrite and, in Misson Borehole, some galena have been noted. The only fossils recorded are scattered to locally numerous Calcinema permiana, Liebea squamosa and Schizodus obscurus, with a few gastropods; scattered carbonaceous plant debris occurs in some of the darker and more argillaceous partings.

The original extent of oolith deposition is difficult to ascertain, partly because of considerable recrystallization. In the south-west, where ooliths are more apparent, D B Smith recorded porous coarse-grained dolomite, presumed to be altered oolite, in fragments from Dadsley Well Borehole (Figure 21). In the core from White Cross Borehole he noted some finely mottled porous dolomite, also presumably altered oolite, in the lower beds, as well as in some layers up to 0.3 m thick of fine to, less commonly, coarse oolites, with a finely granular matrix, in the upper part. The spread of at least some thin oolite layers farther north-east is attested by traces of recrystallised 'ghost' ooliths in Hatfield Nos. 1 and 2 Oil, Hatfield West Oil, Axholme Nos. 1 and 2 Oil and Crowle Oil boreholes, mainly in the upper part of the limestone. Finely cellular textures were noted by M Robinson (British Coal) in the core from Thorne Colliery Borehole (Figure 21). Farther north, although there is little other evidence of ooliths in the area, the core from Camblesforth No. 1 Borehole (Figure 21), examined independently by R F Goossens (British Coal) and D B Smith, shows that ooliths are present in the middle and upper parts of the limestone, as the following summary in descending order, shows:

In this and other boreholes in the district the irregular and wavy bedding and laminae in the upper part of the limestone are possibly of algal origin. Together with the thin mudstone and 'marl' layers also in the upper part, these features may signify shallowing to an epitidal environment, which culminated in the establishment of supratidal sabkha conditions, as shown by the widespread layered, nodular, interstitial and poikilitic anhydrite in the topmost strata.

'Marl' between Upper Magnesian Limestone and Billingham Main Anhydrite

The Billingham Main Anhydrite rests directly on Upper Magnesian Limestone in most north-eastern parts of the district, but in three northerly boreholes (Selby, Barlow Oil and Fir Tree) and in nearly all provings in western, central and southern areas, the two formations are separated by argillaceous strata (Figure 23c) which, with three exceptions, are not more than 4.0 m thick and have no discernible thickness-distribution pattern. The three exceptions are Axholme Borehole (6.1 m), Barlow Oil Borehole (c. 6 m, based on geophysical log) and Trumfleet No. 3 Oil Borehole (4.9 m, a figure at variance with those in nearby boreholes).

The argillaceous strata are mainly recorded as 'marl', which is generally grey or greenish grey, with some red and brown hues, mainly in more southerly and westerly locations; in places they are silty and commonly contain gypsum. In a few boreholes they are referred to as mudstone, locally silty, or siltstone. R F Goossens (British Coal) noted a thin irregular grey limestone near the top of the 0.46 m-thick argillaceous strata in Bank End Borehole. In the core from Thorne Colliery Centre Borehole, examined by M Robinson (British Coal), the equivalent strata (Figure 21) comprise reddish brown silty marl 1.52 m, on bluish grey marl 1.02 m, and contain gypsum veins and layers up to 30 mm thick throughout. In the south-west of the district these strata appear to comprise a basal leaf of the Upper Marl, extending some distance north-eastwards beneath the Billingham Main Anhydrite. The isolated occurrences of similar strata in Selby, Barlow Oil and Fir Tree boreholes may be relict lenses of such a leaf or may, at least partly, be solution residues, as also may the only comparable proving east of the district, where approximately 5 m of silty mudstone containing at least one thin dolomite layer occur in Brigg Oil Borehole (Gaunt et al., 1992, p. 21).

Billingham Main Anhydrite

In north-eastern Yorkshire the Billingham Main Anhydrite is up to 15 m thick in places, but thins gradually southwards and westwards. It thickens greatly eastwards towards the basin, where it is considerably affected by halokinesis. The formation includes nodular anhydrite with a (possibly stromatolitic) dolomite matrix, thinly layered and laminated anhydrite and, less commonly, thin brecciated anhydrite. These components suggest, respectively, supratidal sabkhas, shallow water deposition (possibly intertidal or in residual pools) and penecontemporaneous reworking, probably early in the regressive phase of the EZ3 cycle. It is equivalent to the German Hauptanhydrit.

Within the district the Billingham Main Anhydrite extends south-westwards and may reach the southern edge near Austerfield (Figure 23c). However, the formation has not been recorded in many boreholes within the area, which suggests some local impersistence. Its thickness does not exceed 4 m, except in an elongate area between West Haddlesey No. 1 and Drax No. 4 boreholes (5.0 m and 6.0 m respectively), a small area east of Askern where both Eskholme and Wood End Borehole prove 4.6 m, and further south in the isolated Bank End Borehole (4.14 m). The anhydrite is grey and is commonly accompanied by grey and white gypsum. Associated grey and red 'marl' is widespread also, especially in more westerly locations, but also around Thorne Colliery and in Bank End Borehole. This suggests that the anhydrite passes laterally, possibly by interdigitation, into Upper Marl around its margins and may produce some of the apparently thicker provings. In Fenwick Hall Borehole, for example, 0.5 m of reddish brown 'marl' intervenes in the middle of 3.3 m of anhydrite (Figure 24).

Details

Limestone or dolomite has been noted with the anhydrite in several boreholes, including Selby and Wood End. In the core from Camblesforth No.1 Borehole, examined independently by R F Goossens (British Coal) and D B Smith, the anhydrite, 1.65 m thick, is mainly dark grey, finely crystalline and commonly nodular, with traces of flow structure in the upper part. Gypsum is present as thin layers and individual crystals; grey, fine-grained dolomite is widespread as laminae, thin layers and lenses, which are generally irregular and wavy and which in some places form a 'reticulate mesh'. The core from Thorne Colliery Centre Borehole (Figure 24), examined by M Robinson (British Coal), may be summarised as: white to grey 'inferior' anhydrite with some irregular red 'marl' layers, especially in the lower part, 0.48 m; on reddish brown 'marl' with thin gypsum layers at top and base, 0.16 m; on irregularly interlayered anhydrite, gypsum, 'limestone' and red 'marl', 0.49 m. The 4.14 m-thick anhydrite cored in Bank End Borehole and examined by R F Goossens (British Coal) is described as grey and red, with bands of gypsum and partings of red and grey 'marl'.

Elsewhere in southern and south-western parts of the district the identity of the Billingham Main Anhydrite is less distinct, possibly in places because of splitting or lateral lithological changes, but partly because thinning of the overlying Carnallitic Marl brings it closer to the Upper Anhydrite. In some uncored boreholes the two anhydrite formations have not been differentiated, and in some places the two deposits may merge. In Shaftholme Grange Borehole (Figure 24) the Billingham Main Anhydrite is only 1.4 m thick; a short distance to the south, in Bentley Colliery No. 1 Shaft, it appears to be represented by 0.36 m of 'bastard limestone'; and farther south-east in Armthorpe Borehole (Figure 24) it is recorded as 0.91 m of 'manly gypsum'. Near the southern edge of the district the Billingham Main Anhydrite was recorded in Austerfield and Partridge Hill boreholes as only 0.6 m and 0.8 m thick respectively; it may be represented by 0.4 m of gypsum, the lowest of numerous gypsum layers proved, in Newington Borehole. Although not recorded in any of the boreholes farther east, near the southern edge of the district, the Billingham Main Anhydrite may be impersistently present, in view of its reported occurrence near Gainsborough (Smith et al., 1973, pp.157, 160).

'Marl' between Billingham Main Anhydrite and ?Boulby Halite

The ?Boulby Halite, which occurs only in the north-eastern part of the district, is separated from the Billingham Main Anhydrite by argillaceous strata described as grey and, in Quay Lane Borehole, red 'marl' containing some gypsum and/or anhydrite. The thickness of the 'marl' varies from 8.5 m in Quay Lane Borehole to 4.5 m in Fir Tree Borehole, just north of the district (Figure 24). These substantial thicknesses preclude origins as solution residues; added to those of the Carnallitic Marl, they approximate to the total thickness of marl between the Billingham Main and Upper anhydrites where no ?Boulby Halite is present. This suggests that the 'marl' below the halite is part of the Carnallitic Marl that has been separated by the displacive growth of the halite. On the evidence from South Cliffe and Risby Oil boreholes farther north-east (Gaunt et al., 1992, fig. 7), the 'marl' below the halite probably dies out in that direction.

?Boulby Halite

Near Whitby the Boulby Halite is up to 90 m thick and includes potash minerals and some apparently relict anhydrite. Thicker sequences, appreciably affected by salt movements, occur farther east. The deposit is equivalent to the German Leine Halit. There is a marked southwestward thinning across Yorkshire, and the formation fails to reach rockhead. The Boulby Halite represents the main evaporitic part of the EZ3 cycle in basinal areas. It is thought to have originated at least partly from supratidal sabkha deposition, but possibly partly also by direct precipitation from shallow hypersaline water; it was subjected to considerable later replacive and displacive mineral changes. In South Cliffe Oil Borehole, just northeast of the district, the Boulby Halite rests directly on Billingham Main Anhydrite and comprises 12 m of halite with minor partings of red and green 'marl'. It is not distinguishable farther south in the logs of Burton upon Stather Oil and Crosby boreholes, although both logs imply the presence of small amounts of halite within argillaceous strata at the equivalent stratigraphical level (Gaunt et al., 1992, p. 22, fig. 7).

Within the district, halite above the Billingham Main Anhydrite occurs in only two boreholes, both in the north-east (Figure 23c). In Quay Lane Borehole it comprises 10.0 m of 'halite with some red and grey marl'; in Brind Common Borehole it is 16.7 m of 'salt with some red and grey marl' (Figure 24). Just north of the district, the nearby Fir Tree Borehole proved 12.0 m of 'salt with some grey and red marl', on 3.5 m of 'salt and anhydrite' at the same stratigraphical level (Figure 24). The halite appears to have developed within the marl possibly by displacement and, to some extent, by lateral migration. However, beyond the district, to the north-east, the main part of the Boulby Halite is nowhere underlain by 'marl'. Conceivably, therefore, the halite within the district could be a distinct lenticular mass at a slightly higher stratigraphical level, so it is referred to here as ?Boulby Halite.

Staintondale Group (EZ4)

Carnallitic Marl

The Carnallitic Marl is a sequence of red and subsidiary greyish green mudstones and siltstones. As defined in north-east Yorkshire, the Carnallitic Marl refers to the argillaceous unit overlying the Boulby Halite, thus constituting the lowest subdivision of the Staintondale Group and the equivalent of the German Roter Salzton. In this district it is also used informally for the entire marl sequence between the Upper Magnesian Limestone and the Upper Anhydrite, or Upgang Formation where present, in those areas where intervening evaporite formations are absent. It is, in effect, the lower part of the Upper Marl (Roxby Formation of Smith et al., 1986) of the Permian outcrop. In central Yorkshire the Carnallitic Marl is 5 to 8 m thick, but it increases to 20 m or more to the east and south-east, in Lincolnshire, where it apparently includes some sandstone (Gaunt et al., 1992, p. 22, fig. 7). It is considered to comprise terrigenous sediment derived from a fairly low-lying and largely arid hinterland to the west and south. It was deposited mainly by anastomosing streams, but possibly also in ephemeral lagoons and playas, on a wide coastal plain that may have experienced periodic tidal incursion during the transition from the EZ3 to the EZ4 cycle.

The thickest recorded Carnallitic Marl, 21.95 m, is in Axholme Borehole, but this figure is at variance with thicknesses in adjacent localities and the record of this old borehole is open to re-interpretation. The thinnest sequences, under 5 m and possibly down to 2.5 m, are in the Austerfield area and possibly at Rossington Colliery. The greatest thickness variations occur mainly in the west and south (Figure 23c), which may reflect original fluvial deposition patterns of channels and interfluvial areas on the more landward part of the coastal plain. Most borehole records merely refer to the sequence as red 'marl', generally with gypsum. Some subsidiary grey strata occur in places, mainly in more westerly locations and, in Brier Hills and Cross Hill boreholes, specifically near the base. Certain records indicate that the gypsum is present as 'bands', partings or veins, and in Fenwick Hall (Figure 24) and Wood End boreholes a 1.22 m-thick gypsum layer is differentiated in the middle part of the sequence. Similar gypsum thicknesses are suggested in some of the geophysical logs from oil boreholes. In Hatfield Main No. 1 Shaft some of the gypsum is contorted and associated with 'bastard limestone'.

Details

Where greater detail is available, much of it from microscopic examination of chipping samples from oil boreholes, the argillaceous strata are described as mudstone or shale and siltstone, locally qualified as fissile, calcareous or dolomitic. Sandy 'marl' or mudstone, and distinct sandstones, are referred to in records from more southerly and westerly locations, including Hatfield West Oil, Axholme Nos. 1 and 2 Oil, Langholme, Haxey and Martin Common boreholes, and also the shafts and boreholes at Bentley and Rossington Collieries. The relevant core from Camblesforth No. 1 Borehole, examined independently by R F Goossens (British Coal) and D B Smith, may be summarised as mainly red silty mudstone, with greenish grey lenses near the top, impregnated with anhydrite in the middle, and with some grey dolomitic and anhydritic layers and lenses in the lower part (Figure 24); gypsum is present locally as irregular fibrous veins and scattered crystals. In Thorne Colliery Centre Borehole the core, examined by M Robinson (British Coal), comprises mainly reddish brown 'marl' with some thin grey layers in the lower part, slightly silty in the middle and with some gypsum veins up to 20 mm thick. Farther south in Bank End Borehole the equivalent strata, examined by R F Goossens (British Coal), consist mainly of red interbedded 'marl' and silty 'marl', passing upwards into thin, greyish green siltstone at the top, and containing gypsum bands throughout and some nodular anhydrite in the lower part.

Upgang Formation

A lithologically distinct but laterally variable layer, the Upgang Formation, which is generally not more than 0.6 m thick, caps the Carnallitic Marl in parts of central Yorkshire. It comprises grey, sandy, partly oolitic dolomite, but in the Whitby area it consists mainly of magnesite. In places it is laminated and contains traces of small-scale cross-bedding. Although its stratigraphical position suggests deposition during the transgressive phase of the EZ4 cycle, there is some doubt whether it is a true marine carbonate.

Within the district the Upgang Formation was first recognised in Camblesforth No. 1 Borehole (Smith, 1974, p.137) where it comprises 0.23 m of patchy grey and brown, finely crystalline, partly laminated and locally anhydritic dolomite, containing undulating lensoid veins of fibrous gypsum at the base and near the top (Figure 24). A search of the borehole records reveals only one other occurrence, of 0.46 m of 'limestone with traces of gypsum' at the same stratigraphical level in Drax Borehole. However, in view of the location of these two boreholes (Figure 23d), it seems likely that the Upgang Formation is present in more northerly and north-easterly parts of the district, but undetected because of its thinness and the paucity of coring. It may conceivably be present in places farther south, in view of the records of the Gainsborough Oil boreholes (Smith et al., 1973, p. 160).

Upper Anhydrite

Although apparently not more than about 9 m thick, the Upper Anhydrite (Sherburn Formation of Smith et al., 1986) is remarkably widespread across central and eastern Yorkshire, and adjacent parts of northern Lincolnshire; it continues farther eastwards into the Pegmatitanhydrit of Germany. In places it contains small-scale cross-bedding and ripple-bedding, and also some magnesitic laminae. It is considered to have been deposited in an extensive, but shallow hypersaline sea and was possibly then subjected to appreciable mineralogical changes which produced the included halite and potash-mineral crystals and pseudomorphs after them.

Within the district the Upper Anhydrite extends westwards to about 5 km from its theoretical outcrop position. In the Askern–Whitley area it is up to, 5 m thick, but in Shaftholme Grange Borehole (Figure 24), near its western limit, it is reduced to 1.1 m. It increases to over 6 m in several areas farther east (Figure 23d), the thickest proving (excluding the record of 9.14 m from Kellington No. 7 Borehole, which is totally at variance with thicknesses in adjacent boreholes) being 7.5 m in Percy Lodge Borehole.

Details

In most boreholes which include any details the anhydrite is described merely as white or, less commonly, white and pink. A few records refer to its massive character and several, mainly in the western half of the district, refer to associated gypsum which evidently occurs mainly at the top of the anhydrite. In the Hatfield Moors Nos. 1 and 2 oil boreholes the anhydrite is described as white, clear, translucent and finely crystalline to microcrystalline. The cored Barlow No. 2 Borehole, examined by R F Goossens (British Coal), proved 5.97 m of pink anhydrite with some grey bands of gypsum in the middle and lower parts, and some gypsum and red 'marl' streaks in the topmost 0.15 m. The 7.26 m of cored anhydrite in the nearby Camblesforth No. 1 Borehole, examined independently by R F Goossens and D B Smith, are mainly pale bluish grey to bluish white and partly translucent, fine-grained to finely crystalline and partly massive; red silty mudstone and siltstone occur interstitially and in small patches and, in the upper part, there are patches and veins of gypsum. In the cored Thorne Colliery Centre Borehole, examined by M Robinson (British Coal), the 5.40 m-thick anhydrite is pearly grey and contains 80 mm and 40 mm-thick red 'marl' layers (Figure 24). In some more westerly boreholes there is evidence that the anhydrite is split locally, for example in Burn Airfield No. 2 Borehole, where 3.80 m of anhydrite, on 1.00 m of 'marl', on 2.60 m of anhydrite were proved (Figure 24). This local splitting of the Upper Anhydrite should not be confused with the existence of an unnamed anhydrite and/or gypsum up to 3 m thick which occurs several metres lower in the sequence in a few places, for example in Camblesforth No. 3 Borehole.

In the southern part of the district the cored Upper Anhydrite in Bank End Borehole, examined by R F Goossens (British Coal), is 5.23 m thick and comprises, in ascending order: reddish grey, pale grey and pale pink anhydrite with red 'marl' interstitially near the base and forming inclusions in the upper part, and with gypsum streaks in the upper part. If present in Rossington Colliery No. 1 Shaft the Upper Anhydrite is probably represented only by 0.04 m of 'limestone'.

Eskdale Group (EZ5)

Saliferous Marl

In eastern Yorkshire and adjacent parts of Lincolnshire the Upper Anhydrite is overlain by the Sleights Siltstone, which comprises up to 13 m of reddish brown to greenish grey siltstone and silty mudstone, which are sandy in places, with traces of small-scale cross-bedding, and which contain anhydrite and halite, both interstitially and as scattered crystals, lenses and veins. The siltstone is interpreted as terrigenous fluvial and lagoonal sediment, deposited on a wide coastal plain during the interval between the EZ4 and EZ5 cycles. Where the Top Anhydrite (now the Littlebeck Formation) is absent, the Sleights Siltstone cannot be distinguished from the overlying Saliferous Marl.

In eastern Yorkshire the Saliferous Marl, which overlies the Top Anhydrite, is up to 150 m thick. It thins progressively westwards, where it becomes in effect the upper part of the Upper Marl along the Permian outcrop, and south-westwards where successively lower strata pass laterally into, or interdigitate with, the Sherwood Sandstone. The name Roxby Formation has been proposed for both the Saliferous Marl of east Yorkshire and the Upper Marl of the Permian outcrop (Smith et al., 1986). The Saliferous Marl consists mainly of reddish mudstone and siltstone, but commonly includes layers and lenses of sandstone, especially towards the top. Anhydrite and gypsum are present in places, interstitially and as veins, and some disseminated halite occurs also. Small-scale cross-bedding, ripple-bedding, desiccation cracks (some filled with sand) and thin breccias containing rolled mudstone fragments (also the result of desiccation), are widespread. Fluvial and lagoonal deposition on a wide coastal plain throughout most or all of the EZ5 cycle is envisaged.

The Saliferous Marl is partly equivalent to the Bunter Shale Formation of the North Sea region (Rhys, 1974), in which the slightly more silty Bröckelschiefer Member is commonly distinguishable at the base. In Germany the base of the Triassic System is placed arbitrarily at the base of the Bröckelschiefer; however, in eastern England the Permo-Triassic transition may be represented by the lateral passage into Sherwood Sandstone and the actual boundary may lie in the basal part of the Sandstone.

In the absence of evidence of the Top Anhydrite, which is only about 1 m thick in South Cliffe Oil Borehole to the north-east (Gaunt et al., 1992, fig. 7), the Sleights Siltstone cannot be distinguished within the district. All the mainly argillaceous strata between the Upper Anhydrite and the Sherwood Sandstone are therefore here referred to as Saliferous Marl.

Three trends are evident in the thickness variations of the Saliferous Marl (Figure 23d). An irregular, but general south-westerly thinning, except in the extreme southeast, is probably due to lateral passage of the upper part of the sequence into Sherwood Sandstone in that direction. The irregularities, which show a marked east-northeast alignment, may also result from this lateral passage; the areas of thinner strata, down to about 9 m locally, may coincide with places where westerly derived fans of Sherwood Sandstone replace the upper argillaceous strata. Alternatively, these irregularities may reflect original fluvial deposition patterns of channels and interfluvial areas. The increase in thickness in the south-east, up to 37.8 m in North Carr Borehole, continues farther south, where the Saliferous Marl forms much of the exposed Upper Marl (Smith et al., 1973, pp.157–160). This increase could be due to the persistence of quiescent argillaceous lagoonal sedimentation, with deposition of any incoming sand being limited to marginal localities.

In most borehole records the Saliferous Marl is referred to merely as red 'marl'. Some greyish 'marl' and gypsum (in streaks or veins) or anhydrite apparently occur near the base. Some of the 'marl' is qualified as silty or sandy, and a few records describe the sequence in terms of mudstone and siltstone. White, greyish or red sandstone, which is fine to medium grained and locally calcareous, is widely interbedded with the argillaceous strata; it occurs mainly in the upper part, being reported from boreholes as far apart as Barlow, Cross Hill, Crowle Oil, Hatfield Nos. 1 and 2 Oil, Hatfield West Oil and East Stockwith. Much of the sandstone is clearly thin and possibly discontinuous, but sandstones with a thickness of 4 m or more are present in Bentley Colliery No. 1 Shaft in the west and Martin Common Borehole in the south.

In the core from Barlow No. 2 Borehole, examined by R F Goossens (British Coal), the Saliferous Marl comprises 11.66 m of red silty and sandy 'marl' containing grey streaks and patches, ripple-bedding and 'sun-cracks'; gypsum streaks occur near the base, thin red siltstone in the middle and two pale grey sandstones, up to 0.46 m thick and containing small-scale cross-bedding, in the upper part. A similar sequence was recorded from Camblesforth No. 1 Borehole (Figure 24), examined independently by R F Goossens and D B Smith, where the Saliferous Marl, 16.38 m thick, contains one 0.61 m-thick sandstone in its upper part, 'sun-cracks' on at least two stratigraphical levels and minute gypsum masses in the middle part. No equivalent sandstones were seen in the 13.55 m-thick cored sequence at Thorne Colliery Borehole, examined by M Robinson (British Coal), but thin, greyish, silty and irregular sandy layers were noted in the upper part, and the contained gypsum occurs in inclined veins up to 5 mm thick. Small-scale cross-bedding, ripple-bedding, contorted bedding, 'sun-cracks' on at least two levels and scattered large 'wind-rounded' sand grains were noted by R F Goossens in the 9.02 m-thick Saliferous Marl core from Bank End Borehole; the sequence there comprises interbedded silty or sandy 'marl' and siltstone, mainly red but with greyish green streaks, patches and mottling.

If the 0.04 m-thick 'limestone' in Rossington Colliery No. 1 Shaft is equivalent to the Upper Anhydrite (p. 73), there is no Saliferous Marl at this locality. The overlying strata, some of which were included in 'Upper Permian Marl' by Edwards (1951, p. 226), comprise grey and red sandstones, at least 4.5 m thick, separated by red and grey 'marl' layers not more than 1.3 m thick; these strata are included here in the Sherwood Sandstone.

Upper Marl

The name Upper Marl is applicable along the Permian outcrop zone in Yorkshire and north Nottinghamshire to largely argillaceous strata between the Upper Magnesian Limestone and the Sherwood Sandstone. It is referred to the Roxby Formation by Smith et al. (1986). The sequence comprises reddish and subsidiary greenish grey mudstone and siltstone, containing thin lenses of anhydrite and/or gypsum in places. It is more than 30 m thick in parts of central Yorkshire but thins southwards and ultimately passes laterally into Sherwood Sandstone in that direction (Smith et al., 1973, pp.157–159). Lithologically it is closely comparable to its individual components farther east (Figure 19); like them it originated mainly as terrigenous fluvial and lagoonal sediment, deposited on a wide coastal plain during the closing part of the EZ3 cycle and throughout much or all of the EZ4 and EZ5 cycles.

Within the district the thickness of Upper Marl decreases along the outcrop from 28 m or more near Askern, to between 15 and 20 m around Bentley Colliery and about 14 m in Doncaster. If the 0.04 m of. 'limestone' in Rossington Colliery No. 1 Shaft is the Upper Anhydrite (p.73), the Upper Marl farther west and southwest may be less than 5 m thick in places. Upper Marl crops out from Tickhill northwards almost to Wadworth and in two outliers farther west, but it is exposed, as 'red clay', only in ditch bottoms and road cuttings. To the west of Doncaster, where it crops out between Balby and Hexthorpe, 'red clay' was seen overlying Upper Magnesian Limestone at an old quarry [SE 5577 0145], in a railway cutting [SE 5595 0173] and in a temporary exposure [SE 5633 0187]; red mudstone with a 'grey band' was noted in another railway cutting [SE 5650 0219]. The most northerly outcrops of Upper Marl are west of Askern, where 'marl' pits [SE 551 134] provide several exposures of red and subsidiary greyish-green-banded silty mudstone and siltstone, which contain a few layers, up to 0.25 m thick, of powdery white dolomitic siltstone, with red wavy laminae of mudstone. Graves at the northern end of the Askern Burial Ground [SE 5535 1400] are excavated into stiff red 'clay'. G H Mitchell previously noted 3.05 m of 'red marl' in 'marl' pits [SE 5555 1418], said to have been 7.6 m deep, but now concealed beneath colliery tips.

Sherwood Sandstone Group

In eastern England, the thick sequence of dominantly arenaceous rocks which overlies the Saliferous Marl (or, where the latter is absent, successively lower formations in a southward direction) was formerly subdivided into Lower Mottled Sandstone and overlying Bunter Pebble Beds in southern areas, and Bunter Sandstone succeeded by Keuper Sandstone farther north. However, the prefixes Bunter and Keuper have chronostratigraphical implications in Germany, where they originated. Palynomorphs (mainly miospores) show that in many parts of Britain, including eastern England, the lithostratigraphical and chronostratigraphical boundaries are not coincident. This arenaceous sequence in eastern England is, therefore, now renamed the Sherwood Sandstone Group (Warrington et al., 1980). Around Nottingham the group is divisible into the pebble-free Lenton Sandstone Formation (formerly Lower Mottled Sandstone) and the overlying pebble-bearing Nottingham Castle Formation (formerly Bunter Pebble beds). These formations are traceable northwards into the East Retford district (Smith et al., 1973, pp.161–177) but farther north, because of the paucity of pebbles, only local informal subdivisions of the group can be recognised.

The Sherwood Sandstone in the district consists mainly of red, brown and, in a few places, greenish grey, moderately hard to friable, well to poorly sorted, fine- to medium-and, less commonly, coarse-grained sandstone. Thin layers and lenses of brownish red and greenish grey mudstone and siltstone are present. Some beds contain scattered, but locally numerous, rolled fragments of reddish and greyish mudstone and siltstone, possibly the product of desiccation and reworking of the thin argillaceous layers and lenses. Rounded quartzite pebbles are common in the middle and upper parts of the sandstone in southern areas, but they become increasingly rare, and smaller, to the north. The lithologies of these pebbles suggest a derivation from the south (Smith, 1963). Some of the sandstone is parallel bedded and, locally, evenly laminated, with micaceous partings; ripple-bedding occurs in places, but a substantial part of the sequence is cross-bedded. In the southern half of the district, cross-bedding dips are largely to the east throughout much of the sequence, whereas in the northern half they are more variable, at least in the middle part of the sequence, where they range in direction from north-west clockwise to east (Figure 25). Although subangular to subrounded grain shapes predominate in the sandstone, the localised occurrences of rounded grains, and also of ventifacts and desiccation cracks, testify to some degree of aridity.

The Sherwood Sandstone is interpreted (Warrington, 1974) as a sequence of mainly fluvial sediments deposited along the western margin of the intracontinental Southern North Sea Basin. The initial incoming of these sandy deposits and the subsequent appearance of quartzite pebbles part-way up the sequence both imply increasingly high-energy transport, due to steeper gradients and possibly to higher rainfall in the source areas, and suggest continuing, but spasmodic, uplift of the London–Brabant Massif. The succession is unfossiliferous.

Sherwood Sandstone forms rockhead in most western and central parts of the district, but much of it is concealed beneath Quaternary deposits. Farther east, where it dips beneath Mercia Mudstone, the total thickness increases northwards from about 275 m to over 400 m (Figure 25). The thinnest proving is 276.0 m in Misterton Borehole. In Haxey Borehole the abnormally thick sequence, as recorded by Edwards (1951, p.183), compared with that in adjacent boreholes, is probably due to the erroneous inclusion of 15 to 20 m of Saliferous Marl, and a corrected thickness is shown on (Figure 26). The abnormally thin sequence, 287 to 303 m, recorded in the old Axholme, Axholme Nos. 1, 2 and 3 Oil and Blyton Carr boreholes may be the result of tectonic effects, perhaps along faulting associated with the Askern–Spital Structure (p.90). In the north, just beyond the district, Fir Tree Borehole proved the Sherwood Sandstone to be 418.50 m thick.

The Sherwood Sandstone forms the Rossington, Doncaster and Snaith ridges and the hills of Hambleton Hough and Brayton Barff. Except for small areas east and north of Tickhill, where the lowest strata (shown on the geological maps as Lower Mottled Sandstone) crop out, these ridges and hills provide the largest outcrops, forming pale brown, light, sandy soil. Actual exposures are mainly of strata from a quarter to half way up the sequence.

Details

The widest stratigraphical range of exposure occurs near the southern edge of the district. A roadside exposure [SK 5826 9509] of 0.91 m of argillaceous sandstone lies near the base of the Sherwood Sandstone, which forms the small outlier of Gallow Hill to the west. Just to the east and south-east, 1.83 m of red sandstone with greenish bands and 4.57 m of red sandstone were seen in excavations [SK 5919 9512] and [SK 5989 9375] respectively for the A1M Motorway. Both exposures probably lie within the lowest 15m of the Sherwood Sandstone. Farther east, on the Rossington Ridge, a pathside bank [SK 6310 9532] reveals red sandstone with cross-bedded dips mainly to the east; an old quarry [SK 6573 9409] exposes 3.66 m of cross-bedded sandstone containing layers of pebbles; and, in a railway cutting [SK 6519 9465] nearby, scattered pebbles occur in 3.66 m of pale brown cross-bedded sandstone. The last two pebble-bearing exposures lie approximately 150 m above the base of the Sherwood Sandstone. Farther east, near Misson, an extensive pit [SK 700 954] reveals 1.22 m of variegated red, grey and yellow sandstone, which contains red and greyish green, rolled mudstone fragments and exhibits cross-bedded dip directions ranging from north-east clockwise to south-east. These strata lie about 270 m above the base of the Sherwood Sandstone; in that area, therefore, they are probably only about 10 m below the top of the sequence. Farther north, along the eastern side of the Rossington Ridge, 1.22 m of red sandstone containing rolled mudstone fragments were seen in an old pit [SK 6556 9581], and cross-bedding dips directed mainly to the east occur in red sandstone observed in a drain [SK 6494 9947] south of Auckley. At three exposures in Bessacarr, on the northern end of the ridge, cross-bedded dips directed to the east, east-south-east (at up to 20°) and from east-north-east clockwise to east-south-east, were recorded in fine-grained red sandstone in a railway cutting [SE 6220 0027], an old pit in a private garden [SE 6077 0194], and another railway cutting [SE 6025 0220] respectively. In the first of these exposures a 0.61 m-thick bed contains small quartzitic pebbles and rolled mudstone fragments.

At Balby, on the southern side of the south-western end of the Doncaster Ridge, red sandstone formerly seen in several places at the bottom of extensive clay pits [SE 561 005] shows that Sherwood Sandstone continues to the western edge of the district in that locality, confined within a graben. About 6 m of red cross-bedded sandstone were formerly seen in each of three pits [SE 5631 0089]; [SE 5690 0092]; [SE 5581 0095] nearby to the north-east. On the ridge to the north, 4.57 m of red cross-bedded sandstone is exposed in a railway cutting [SE 5715 0243]; this is stratigraphically the lowest cross-bedding in the Sherwood Sandstone recorded in the district, lying only 15 to 18 m above the base of the sequence. Red sandstone, 4.57 m thick, was formerly exposed in an adjacent pit [SE 5712 0221]. Sandstone, generally red, has been proved in many temporary excavations in Doncaster. The most exotic of these was 'Sand House', originally a drift mine excavated as a source of sand early in the nineteenth century in the vicinity of, and apparently extending partly below, Green Dyke Cemetery [SE 575 023]. Exquisite carvings of kings and queens, animals and other items were fashioned from the Sherwood Sandstone in the walls of the mine galleries, which after gas lighting was installed in about 1860 were open to the public for a fee of sixpence (21/2p). 'Sand House' was inhabited until the 1930s, but is now inaccessible.

Farther north on the Doncaster Ridge a railway cutting [SE 6145 0480], near Markham Main Colliery, exposes 5.79 m of red cross-bedded sandstone. An old quarry [SE 6051 0554] near Whitley Hills formerly revealed at least 1.83 m of red sandstone containing a few rolled mudstone fragments and quartzite pebbles. These inclusions occur at the bases of cross-bedded layers which vary from 0.23 to 0.91 m in thickness and have cross-bedded dips up to 28° directed mainly to the east-south-east. The railway cutting [SE 6114 0771] near Kirk Sandall exposes 2.13 m of red sandstone containing a few quartzite pebbles and rolled mudstone fragments, and with cross-bedding dips to the east-north-east. Grey sandstone, 1.22 m thick, occurs in a stream bank [SE 6460 1053] south of Stainforth, and 5.49 m of pale yellowish brown, fine-grained sandstone recorded in a pit [SE 6467 0842] north of Dunsville contains a few small quartzite pebbles and red and greyish green rolled mudstone fragments that are limited to the bases of certain beds; cross-bedding at this exposure dips mainly to the east. To the north of Hatfield Woodhouse there is an area [SE 676 089] about 500 by 300 m in size containing stiff red clay soil on a surface which inclines gently to the east. Augering in this area reveals red and greyish green mudstone at depths down to 1.2 m; fragments of red mudstone were dug up at a locality [SE 6748 0921] just to the north. This area is thought to be the dip-slope outcrop of one of the thicker mudstone layers within the Sherwood Sandstone; it lies about 200 m above the base of the sequence. At Thorne, farther north-east, 1.52 m of red sandstone were seen in the banks of Thorne Gyme [SE 6781 1400], and notes made by W T Aveline during the primary geological survey (c. 1859–60) suggest that it may also have been seen at the bottom of one or two sand pits in the town.

There are no undoubted exposures of Sherwood Sandstone near Askern, but 0.76 m of red sand observed at the bottom of a ditch [SE 5612 1279] may be weathered sandstone; if so, it lies less than 10 m above the base of the sequence. Near Whitley, up to 2.44 m of red sandstone are exposed in two pits [SE 556 208]; the rock contains numerous micaceous laminae, a few small quartzite pebbles and scattered rolled mudstone fragments, and its cross-bedding dips are mainly to the north-east. Similar observations were previously made by W Edwards in a pit [SE 556 220] farther north.

On the Snaith Ridge a trench running from Kellington south-westwards just beyond the district revealed red sandstone with cross-bedded dips mainly to the north. A deep quarry [SE 5823 2380] north-west of Hensall reveals 12.19 m of red, fine-grained sandstone containing a few rolled red mudstone fragments, even fewer small quartzite pebbles, and several thin lenses of dark red mudstone; cross-bedding dips range from north-west clockwise to east. Identical sandstone up to 10.67 m thick occurs in quarries [SE 578 232] south-west of Hensall. In quarries [SE 590 230] south of this village there are 4.57 m of sandstone containing several beds, up to 0.38 m thick, of dark red mudstone containing yellowish grey layers. Red sandstone has been seen in numerous excavations between Low Eggborough and Great Heck. In one pit [SE 5859 2223] the rock is more thinly bedded and micaceous than normal, and cross-bedding dips range from north-west clockwise to north-east. Quarries [SE 599 213] north-east of Great Heck reveal up to 13.72 m of pale reddish brown, fine- to medium-grained sandstone. The rock contains a few small quartzite pebbles, layers of rolled fragments of red mudstone, and thin but extensive layers of red mudstone; in places, these accentuate units of cross-bedding, in which dips range from north-west clockwise to south, but are predominantly to the north-east. Several exposures of sandstone have been seen around Pollington. In one pit [SE 6120 2013] the sandstone, although mainly red, includes impersistent thin yellow beds; a few rolled mudstone fragments and even fewer small quartzite pebbles are present and the cross-bedding ranges from north-north-west clockwise to east. In another pit [SE 6177 1977] to the south-east, the cross-bedding in 3.66 m of red sandstone is confined to directions from north-east clockwise to east. Large excavations [SE 613 205] to the north reveal up to 4.57 m of red sandstone with cross-bedding dips from north-west clockwise to north-east, and farther north, in pits [SE 623 220] near Gowdall, the cross-bedding dips in 0.91 m of red sandstone are mainly to the north-east. The only sandstone exposure seen farther east on the Snaith Ridge is in a pit [SE 6483 2206] which reveals up to 4.88 m of the rock. In a temporary excavation [SE 6550 2433] east of Carlton, north of the Snaith Ridge, the cross-bedding dips in pale red sandstone range from north clockwise to south-east.

In the north-western corner of the district, excavations [SE 585 305] on the summit of Brayton Barff revealed red sandstone with cross-bedding dips mainly between north-east and east, but in trenches radiating to the north-east, south-west and west from the summit, the dominant directions were seen to be between north and north-east. The sandstone in these trenches is mainly pale red, thin bedded and medium grained, but with some darker red, fine-grained, silty sandstone beds containing abundant micaceous laminae, and some thin lenses of dark red mudstone. Scattered small rolled fragments of red and grey-green mudstone occur locally in the sandstone, but there are virtually no quartzite pebbles. An old excavation [SE 5741 2971] to the south-west reveals 1.52 m of pale reddish brown sandstone with cross-bedding dips between north and northeast. Similar rock was seen in several nearby pits along the Brayton to Gateforth road, although in one of these [SE 5767 2957] the cross-bedding dips were atypically to the south-west.

With the paucity of coring, few of the deep coal and oil boreholes provide any details of the Sherwood Sandstone, but some information, especially on the incidence of argillaceous layers, rolled argillaceous fragments and quartzite pebbles, is available from the large number of water boreholes, some of them cored. The following summary is derived largely from these water boreholes, a selection of which is included on (Figure 26), which shows that for descriptive purposes an informal threefold subdivision of the sandstone is recognisable.

Approximately the lowest 40 m of Sherwood Sandstone are characterised by an abundance of thin argillaceous layers and a virtual absence of quartzite pebbles. In some boreholes the sandstone is brown or red from the base upwards, but elsewhere, especially where numerous argillaceous layers and laminae provide an interbedded passage up from the Saliferous Marl, up to 2 m of the basal sandstone is greenish grey, albeit streaked with brown in places. At higher levels the sandstone is brownish red, except in places where up to 0.3 m of greenish grey sandstone commonly occurs immediately below and/or above an argillaceous layer. The sandstone in this lower part of the sequence is mainly fine to medium grained, partly micaceous, generally thin bedded and locally laminated. There is little evidence of cross-bedding, except in water boreholes at Roall and Eggborough, but ripple-bedding was noted about 6 m and 10 m above the base in Hatfield Woodhouse No. 1 [SE 6842 0972] and Hatfield Lane (Armthorpe) [SE 6306 0597] water boreholes respectively. Where grain shape has been noted it is largely subangular, but scattered rounded grains occur in several boreholes, for example in the basal 1.37 m of sandstone in Warning Tongue Lane (Cantley) No. 1 Water Borehole [SK 6308 9990]. The argillaceous layers and laminae are mainly dark red, but a few are greyish green either entirely or in their middle part. They range from mudstone to, less commonly, siltstone. Most are less than 0.5 m thick but a few, for example in Rawcliffe Bridge [SE 7015 2124] and Selby [SE 620 321] water boreholes (Figure 26) are up to about 2 m thick. Load casts occur on the base of some of these argillaceous layers, a few of which, for example a 0.10 m-thick siltstone in Hatfield Woodhouse No. 1 Water Borehole, are internally contorted. The only pebbles recorded from the lower part of the sequence are a few in Hatfield Woodhouse No. 1 Borehole, but the presence of rolled argillaceous fragments, although not common, is attested by the records of several boreholes and colliery shafts (Figure 26).

The middle, and thickest, part of the Sherwood Sandstone, from about 40 m above the base up to 200 m in the south and up to 250 m in the north, is characterised by fewer argillaceous layers than the underlying strata and, except apparently near the northern edge of the district, by the presence of a few quartzite pebbles. The sandstone in this part of the sequence is almost entirely red, except for some greenish grey beds associated with argillaceous layers. Much of it is medium grained and well sorted; some finer- grained varieties, which are generally micaceous, thin bedded and locally laminated, are present, as also are somewhat more poorly sorted, medium- and coarse-grained beds. However, no correlations can be established between the coarser-grained occurrences in boreholes. As with the lower strata, some scattered rounded grains have been noted. Cross-bedding, with dips up to 20°, is recorded from several boreholes, but again no correlations are possible. The argillaceous layers have the same characteristics as those in the lower strata, but occur less frequently. Rolled argillaceous fragments are, in contrast, more abundant, occurring both widely scattered and locally concentrated into thin 'marl conglomerate' layers. They are generally pale to dark red, but with some greyish green varieties in places; their maximum recorded size is 75 mm, although most are less than half this length. Some of the fragments occur in the fine- and medium-grained sandstones, as do single and scattered occurrences of quartzite pebbles, but where these pebbles are more concentrated, generally at the base of a bed, the host sandstone is recorded in several boreholes as coarse grained, and in places as cross-bedded. These pebble concentrations cannot be firmly correlated between boreholes, although they are more common at certain stratigraphical levels. The largest pebbles recorded are 50 mm across, but most are well under half this size, especially in northern areas. Other than quartzite, the only lithology recorded from pebbles is brown 'Magnesian Limestone' in the middle part of Warning Tongue Lane (Cantley) No. 1 Borehole. Sand-filled desiccation cracks, although apparently not common, have been noted in a few places, mainly in the argillaceous layers. Some of the oil boreholes prove minute, but apparently widely scattered occurrences of gypsum, which may also have been derived from the argillaceous layers.

The upper part of the Sherwood Sandstone, less than 100 m thick in the south but possibly more than 150 m in the north, is poorly known due to the paucity of cored boreholes and absence of shafts through it. The highest 78.33 m of the sandstone in Westwoodside Borehole, the cores from which were examined by C G Godwin and G H Rhys, provide the only detailed evidence. The sandstone is mainly fine to medium grained, locally micaceous, thin bedded and laminated, but also with appreciable cross-bedding, to within 1.5 m of its top in this borehole. Thin argillaceous layers are also present, but apparently not as numerous as in the higher part of the sandstone farther east (Gaunt et al., 1992, p. 23). Rolled argillaceous fragments are present too, but in upward-decreasing abundance. Small quartzite pebbles were very rarely noted and no other pebbles are recorded from the upper part of the sandstone elsewhere in the district. The Westwoodside Borehole also shows carbonaceous partings in the sandstone, small-scale cross-bedding, slump structures in the argillaceous layers and sand-filled wedges in an argillaceous layer 35.5 m from the top of the sandstone. The uppermost 0.10 m of sandstone, immediately below the Mercia Mudstone, is 'broken up' and 'soft', possibly due to desiccation and weathering; this is the only evidence known in the district of a suggested erosion surface at the top of the Sherwood Sandstone; it may equate with the Hardegsen Disconformity of mid-Scythian age within the Buntsandstein of Germany (Geiger and Hopping, 1968; Warrington, 1970; 1974).

The most obvious variation in the upper part of the Sherwood Sandstone is its colour. Borehole records show that the concept of a consistent thickness of greyish sandstone in the upper part, the 'Keuper Sandstone' of the primary geological survey and some old accounts, is invalid. In some boreholes, such as Axholme and Lindholme, only the highest few metres, if any, below the Mercia Mudstone are greyish. In others, the highest Sherwood Sandstone present, whether occurring beneath Mercia Mudstone or at rockhead beneath Quaternary deposits, is greyish to considerable depths: for example, to 24 m beneath Quaternary deposits in Bank End Borehole, to 73 m (but with some brownish layers or patches) beneath Mercia Mudstone in Westwoodside Borehole, to 23 m beneath Quaternary deposits in Hatfield Peat Works Borehole [SE 7124 0839], to 39 m beneath Quaternary deposits in a water borehole at Red House [SE 7290 1084] and to 78 m (but with some red patches) beneath Quaternary deposits in Wressle Borehole. The distribution of thick greyish sandstone shows that it forms broadly basin-shaped masses separated by areas where the sandstone is red almost, or entirely to its top. Some of the grey masses lie under thick peat, for example that on Hatfield Moors. Here, acidic groundwater with a pH of 5.6 was found at a depth of 36.5 m below ground level, well below the base of the peat, in a borehole [SE 7079 0630] at Lindholme Hall. The acidity is almost certainly due to the overlying peat, and may well have produced the local thick greyish sequence in the underlying sandstone by prolonged leaching. However, other thick grey masses, for example in the Hemingbrough–Wressle–Newsholme area, occur where there is no peat. It is suggested (Gaunt, 1976a, pp.154–157, fig. 18) that at least some of these grey masses may owe their leaching to the former existence above them of thick peat deposits during the latter part of the Ipswichian (last) Interglacial Stage.

Mercia Mudstone Group

The thick sequence of mainly reddish mudstones and siltstones that succeeds the Sherwood Sandstone Group, formerly called Keuper Marl, is now renamed the Mercia Mudstone Group (Warrington et al., 1980). Some parts of the sequence have been locally subdivided lithostratigraphically, for example around Nottingham (Elliott, 1961) and in the East Retford district (Smith et al., 1973). In chronostratigraphical terms the group ranges from late Scythian to early Rhaetian in age. The sequence has yielded no fossils other than spores and pollen derived from land plants (Smith and Warrington, 1971).

The Mercia Mudstone mainly comprises red and subsidiary greenish grey, locally dolomitic and variably gypsiferous mudstones with some siltstones. They are interpreted as coastal-plain fluvial, lagoonal (playa), epitidal and shallow-marine sediments, deposited around the western margin of the Southern North Sea Basin at a time when the basin contained a hypersaline sea with periodic restricted oceanic connections. A marked lowering of the hinterland relief from that previously existing is presumed from the low-energy, argillaceous nature of the sediments, but the dominant red colour implies a continuing hot and intracontinental environment.

Marine influence is indicated by sparse Lingula recorded near Eakring by Rose and Kent (1955) and by the slightly dolomitic nature of some parts of the sequence; the contained gypsum may have originated in shallow playas or in localised sabkhas. In Germany the marine influence reached its maximum with deposition of the dolomitic and halitic Muschelkalk, and a comparable facies, traceable across the North Sea, was recognised in Tetney Lock Borehole, near Grimsby (Geiger and Hopping, 1968).

Within the district the Mercia Mudstone forms rock-head over approximately the eastern third of the area, as illustrated in (Figure 25)^‡1 . However, it is entirely concealed by Quaternary deposits except near Misson, around Misterton, on the Isle of Axholme and on Crowle Hill, where it produces stiff reddish brown clay soil. Its thickness increases with the easterly dip and is estimated to be just over 200 m along the eastern edge of the district south of West Butterwick, the thickest proving being 189 m in Laughton Borehole. Approximately the highest 60 m of Mercia Mudstone are absent from the district, but are present in South Cliffe, Corringham Oil (Figure 27) and Burton upon Stather boreholes a short distance farther east (Gaunt et al., 1992, fig. 9).

At outcrop, the only recognisable lithostratigraphical differentiation is of the Clarborough Formation (Smith and Warrington, 1971), a thin sequence of closely interbedded gypsiferous and dolomitic mudstones, siltstones and fine-grained sandstones which, being more resistant than the underlying and overlying strata, has produced the higher ground around Misterton and on the Isle of Axholme. Although not traceable with any certainty at outcrop north of Belton, the Clarborough Formation probably continues for some distance in this direction, on the evidence of boreholes (p. 83, (Figure 27). Several thin lenses of locally gypsiferous siltstone and, to a lesser extent, fine-grained sandstone, called skerries, are traceable by their resistant features and by fragments in the soil on outcrops below, within and above the Clarborough Formation, especially south of Low Burnham. A few individual gypsum layers are traceable by fragments in the soil on the Clarborough Formation outcrop south of Misterton.

Details

The base of the Mercia Mudstone was proved by augering across an area [SK 707 954] east of Misson, but the nearest exposures, of interbedded red and greyish green mudstones containing a few thin grey siltstones, are around flooded excavations [SK 714 960] to the north-east. Farther north, over 6 m of interbedded red and greyish green mudstone was seen along the Snow Sewer [SK 7060 9842] to [SK 7111 9833] east of Newlands Farm. Both of these exposures lie between approximately 12 and 20 m above the base of the Mercia Mudstone. To the east, strata below the Clarborough Formation are visible, generally in a weathered state as red 'clay', in several ditches west of Misterton, but 0.61 m of red mudstone on 0.30 m of green mudstone was observed at one locality [SK 7498 9390]. These lower strata are similarly poorly exposed where they crop out on the western slopes of the Isle of Axholme. A 0.61 m section, including thin skerries, was seen in one ditch [SE 7630 0158]; about 30 m of red silty mudstone with subsidiary greyish green layers and, towards the top, some thin grey siltstones, were recorded in a trench, from [SE 7722 0281] to the base of the Clarborough Formation at [SE 7823 0299] south of Epworth. An old excavation [SE 7788 0515] north-west of that village revealed 1.22 m of red silty mudstone, also lying close below the Clarborough Formation.

The Clarborough Formation is present around Misterton, on the evidence of hard skerries and also of gypsum. An old pit [SK 7547 9335] revealed 2.44 m of red mudstone containing thin skerries and gypsum layers in the lower and middle parts, lying just above the base of the formation; 2.13 m of red mudstone containing many thin skerries, seen in another exposure [SK 7670 9425], occurs near its top. Farther north, at Craiselound, a temporary excavation [SK 7722 9872] revealed 1.07 m of red mudstone containing thin gypsum layers and, near the base, a thin gypsiferous skerry, which probably lies less than 1 m above the base of the Clarborough Formation. Near Cliff Hill, north of Haxey, 3.86 m of interbedded red and grey mudstone containing thin gypsiferous skerries and cut by thin gypsum veins are exposed in a railway cutting [SE 7711 0117]; a nearby pit [SE 7706 0123] reveals 3.51 m of virtually identical strata. A sparse miospore assemblage froth this exposure suggests an age near the Ladinian–Carnian stage boundary (Smith and Warrington, 1971, p. 217, pl. 14).

The entire Clarborough Formation, here about 15 m thick and comprising hard, red and greyish green, silty mudstone and siltstone, some of it gypsiferous and containing fibrous gypsum layers, was seen in a trench [SE 7823 0299] to [SE 7881 0308] south of Epworth. The graveyard [SE 7848 0404] east of St Andrews Church in Epworth revealed 0.61 m of hard grey silty mudstone and gypsiferous siltstone, and similar strata crop out along the path west of the church. Farther north, several exposures of hard gypsiferous siltstone, some of it with poikilitic anhydrite, occur in an old railway cutting [SE 7764 0471] to [SE 7775 0493], and other exposures near old sidings [SE 781 052] reveal interbedded red and grey mudstone and partly gypsiferous, flaggy siltstone.

Almost the full thickness of the Clarborough Formation, here about 11 m thick, is exposed in a large pit [SE 785 054], which reveals interbedded red and greyish green silty mudstone and siltstone containing two lenticular layers of gypsiferous siltstone cut by fibrous gypsum veins; the lower of these layers is up to 3.0 m thick and the upper about 1.5 m thick. Similar strata are visible in another pit [SE 787 055] nearby. The Clarborough Formation cannot be traced with any certainty at outcrop north of these exposures.

The strata above the Clarborough Formation are poorly exposed in the district. A temporary excavation [SE 8002 0199] north-west of Owston Ferry revealed 5.18 m of red and green mudstone with thin skerries near the base and top. Some skerries can be mapped west and north of Owston Ferry on the evidence of fragments in the soil; some of these fragments contain pseudomorphs after halite. Red siltstones and thin (<0.05 m), fine-grained, silty sandstones were seen above the Clarborough Formation in a trench [SE 7881 0308] to [SE 8051 0355] south of Epworth; in the pit [SE 787 055] north of Epworth, referred to previously, 6.40 m of the strata immediately above the Clarborough Formation are exposed.

From the Belton area northwards the Mercia Mudstone is undivided at the surface because the Clarborough Formation is not traceable with any certainty. A prominent feature [SE 775 070] associated with fragments of greyish green, flaggy siltstone and less commonly of fine-grained silty sandstone in the soil, indicates a hard skerry west of Belton. A less prominent feature, also with skerry fragments, runs around the southern and eastern sides of the circular depression [SE 790 065] east of the village; either could be a northerly continuation of the Clarborough Formation. Farther east, grey siltstone fragments are present at a locality [SE 812 061] south of Beltoft, where the rock has been quarried (in old 'gravel pits'). Several sections showing up to 3.66 m of red mudstone with subsidiary interbedded greyish green bands, and silty mudstone containing a few thin grey siltstones and bedded layers of fibrous gypsum up to 0.13 m thick, occur in extensive excavations [SE 778 116] south of Crowle, where at least 10 m of the Mercia Mudstone were formerly worked. These strata, lying about 70 m above the base of the mudstone, are below the stratigraphical level of the Clarborough Formation, as also is the outcrop forming Crowle Hill [SE 777 133]. This hill owes its prominence to a hard skerry; siltstone fragments are abundant in the soil around its summit, and an exposure [SE 7753 1336] reveals 0.61 m of hard grey siltstone. Records show that 8.53 m of alternating red and green 'beds' containing two 0.10 m-thick gypsum layers in the lower part were cut through when the railway cutting [SE 775 133] nearby to the west was excavated in 1901. The most northerly exposure of Mercia Mudstone is in Paupers' Drain [SE 7860 1415] to [SE 7885 1419], which reveals 2.44 m of grey mudstones with thin red silty mudstones and a few thin grey siltstones.

Although only a few boreholes in the district provide any details of the Mercia Mudstone, there is sufficient information to identify certain lithological variations (Figure 27), which can be related to the lithostratigraphical subdivisions recognised farther south (Smith et al., 1973, pp.177–196) and also to the lower five (A–E) of the seven informal descriptive units, largely based on borehole-geophysical evidence, established farther east (Gaunt et al., 1992, p.25, fig.9).

A. Except for 1.22 m of 'Blue stone' in Reedness Borehole [SE 7914 2329], which may be the greyish top of the otherwise red underlying Sherwood Sandstone, the lowest part of the Mercia Mudstone comprises mudstone or 'marl', which is red in colour, in contrast to the overlying strata. This red mudstone is a northerly continuation of that at the base of the 'Green Beds sensu lato' of Smith and Warrington (1971, pp.204–206). On the basis largely of a high gamma-ray response, it approximates closely to unit A in boreholes farther east and is also identified in Axholme No. 1 and Crowle oil boreholes within the district; like unit A, it thickens slightly northwards (Figure 27). Farther in this direction it may correspond to the Seaton Carew Formation (Smith, 1980 b). In Westwoodside Borehole, where the cores were examined by C G Godwin and G H Rhys, and in Eastoft Hall Borehole [SE 804 163], where they were examined by G H Mitchell, the red strata were seen to contain grey and greyish green patches, mottling and spots; in the former borehole, red 'marl' fragments in a basal siltstone suggest penecontemporaneous reworking, and 'suncracks' in the overlying mudstone imply desiccation.

B. The succeeding 30 m or so of strata are characterised by an abundance of siltstone, by a predominantly grey to green colour and by an appreciable content of sulphate minerals. Correlation with the 'Green Beds sensu stricto' occurring farther south (Smith and Warrington, 1971, pp.203–206; Warrington et al., 1980) is suggested by the grey and green colours; the lowest 13.72 m in Haxey Borehole were recognised as Green Beds by Smith (1912). These strata approximate to unit B, which is based largely on geophysical records of Crowle and Axholme No.1 oil boreholes, and boreholes to the east of the district; they too apparently have the same slight northerly thickening (Figure 27). Siltstones are recorded in some boreholes, such as Westwoodside and Eastoft Hall; in others their presence is implied by terms such as 'stone', 'sandy marl' and 'hard marl'. Most of the siltstones are grey and individually not more than about 2 m thick, and are interbedded with silty mudstones. A 0.30 m thick grey sandstone was recorded from the upper part in Haxey Borehole. In the lower half of these strata, the interbedded silty mudstones are green, grey or 'blue' in the upper half they display greyish green and red colour banding and mottling. The dominant grey to green colour is noted in several other boreholes, such as Crowle Common, Quay Lane and Fir Tree, in which the Mercia Mudstone is otherwise undifferentiated. In Westwoodside and Eastoft Hall boreholes some of the mudstones are micaceous and fissile.

The greatest concentration of sulphate minerals lies at or near the base of these strata and produces the relatively low gamma-ray response typical of the lowest part of unit B in boreholes within and east of the district. In Westwoodside Borehole this concentration comprises 0.51 m of anhydrite containing gypsum veins and 'stringers', and a thin grey mudstone in its middle; elsewhere it is recorded as gypsum. Most of the sulphate in the overlying strata in Westwoodside and the other boreholes is recorded as gypsum, occurring as interbedded layers, cross-cutting veins and discrete, probably nodular, masses, although in Westwoodside Borehole some of the siltstones have an anhydritic matrix. In this borehole also, pseudomorphs after halite were noted in several places. The 0.46 m of 'grey limestone' in the upper part in Haxey Borehole may conceivably be sulphate-rich siltstone.

The only evidence of age of these grey to green siltstone and sulphate-rich strata comes from Westwoodside Borehole, where miospores indicate a late Scythian age (Smith and Warrington, 1971). This dating, and the concentration of sulphates, invites correlation with the Esk Evaporite Formation farther north (Warrington et al., 1980, p. 57) and with the Rot Halite Member of the Dowsing Dolomite Formation offshore to the east (Rhys, 1974).

C. The overlying 40 to 50 m of mudstone contain fewer siltstones than the beds below and above, except near the top. They equate with the lower part of the former 'Keuper Marl' of areas to the south (Smith and Warrington, 1971, pp.208–210; Smith et al., 1973, fig. 20, pp.184 et seq.). On the basis largely of geophysical records, they approximate to unit C in boreholes farther east, and apparently show the same slight northerly thickening (Figure 27); they are also partly recognised in Axholme No. 1 and Crowle oil boreholes. The mudstone, recorded as 'marl' in most boreholes, is predominantly red but with some minor green, grey and blue layers, mottling and spots; some of it is silty. In the upper part of these mudstones, interbedded thin grey to greyish brown siltstones were seen in the cores from Eastoft Hall Borehole and in chippings from Crowle Oil Borehole; the thin, pale greyish green, hard sandstones recorded from chippings from Belton Oil Borehole at a comparable stratigraphical level are probably siltstones. Elsewhere, thin beds of 'grey stone' and 'hard stone' betray the presence of siltstones, as also may 'gravel' at a similar stratigraphical level in Axholme Borehole (where no gravel occurs in the Quaternary deposits). Ripple-bedding was seen in the siltstones and associated 'marl' from Eastoft Hall Borehole. These thin siltstones increase in abundance upwards and reflect an interbedded passage into the beds above. Gypsum occurs widely in this part of the sequence as thin layers (less than 0.08 m), veins and small nodular masses, but it is not abundant. Miospores recorded by Smith and Warrington (1971, p. 217, fig. 2) in the upper part of Westwoodside Borehole suggest a late Scythian age.

D. At least 40 m of the overlying strata are interbedded mudstones and siltstones, appreciably gypsiferous and locally hard. They are lithologically suggestive of the Clarborough Formation (Smith and Warrington, 1971, p. 210) and approximate to unit D, based largely on geophysical records of boreholes farther east. The base of unit D is apparent in the gamma-ray log of Axholme No. 1 Oil Borehole, as also is the 'regional gamma-ray marker' (Balchin and Ridd, 1970), which occurs in or just above the middle of the unit (Figure 27). The coarser strata in this borehole are recorded as slightly calcareous, greyish green siltstone with, above the 'regional gamma-ray marker', some slightly calcareous, reddish brown sandstone, both with associated gypsum. In the nearby Epworth Water Tower Borehole [SE 7824 0475], the bottom of which is at about the stratigraphical level of the top of Axholme No.1 Borehole (Figure 27), 1.14 m of 'very hard grey siltstone' was proved at a depth of 9.6 m. North Moor Water Borehole [SE 803 090], commencing at a similar stratigraphical level, penetrated numerous layers of mainly grey or blue, hard, 'waterstone' and 'stone' interbedded with red and blue 'clay'; one 'very hard blue stone', 1.22 m thick, took five and a half days to drill through. Gypsum is abundant, individual occurrences being up to 0.46 m thick. The highest part of Eastoft Hall Water Borehole, also starting at a comparable stratigraphical level, consists of interbedded grey siltstone up to 2.44 m thick and red 'marl', 'clay' and shale up to 3.2 m thick, with several occurrences of gypsum. In the comparable part of Oak Nurseries (Gilberdyke) Water Borehole [SE 8407 2967], which records the entire Mercia Mudstone as 'marl', the presence of a green and three grey layers (Figure 27), as distinct from red elsewhere, may indicate the continuation of siltstones into the north-eastern part of the district.

Although the lithology of this 40 m-thick gypsiferous siltstone-rich sequence is suggestive of the Clarborough Formation, it is clear from the lesser thickness of the latter, and its approximate height above the base of the Mercia Mudstone, that in the Haxey–Epworth area the Clarborough Formation equates only with the upper part of this sequence (Figure 27). The more resistant beds of this upper part produce the topographical feature which enabled the Clarborough Formation to be mapped; it may be due to a greater interstitial calcareous and/or dolomitic content. Such a concentration of carbonates may result from solution, in the weathering zone, of calcite and/or dolomite that was originally more widely distributed through the range of strata, and subsequent recrystallization within the coarser upper layers. The same process was invoked with respect to certain parts of the Lias, which are lime-rich only near the surface (Gaunt et al., 1992, p.30).

Thin silty dolomitic limestones occur within the gypsiferous siltstone-rich strata farther north-east beyond the district, for example in South Cliffe Oil Borehole (Figure 27), suggesting a marine influence on deposition in this direction and a correlation, partly suggested by the 'regional gamma-ray marker', with the Muschelkalk Halite Member and/or immediately overlying beds in the upper part of the Dowsing Dolomitic Formation of the North Sea region (Rhys, 1974). The only chronostratigraphical evidence from these strata within the district is supplied by miospores from the Clarborough Formation exposure [SE 7706 0123] near Haxey (p. 80), which suggest an age close to the Ladinian–Carnian stage boundary (Smith and Warrington, 1971, p. 217, fig.2, pl. 14).

E. The overlying strata, up to the top of that part of the Mercia Mudstone present in the district, as indicated in (Figure 27), are described in boreholes as mainly red mudstone or 'marl', with some gypsum in places. They approximate to the lower part of unit E, which is based largely on geophysical records from boreholes such as Corringham and South Cliffe (Figure 27), and others farther east, but have not been subject to this type of investigation within the district.

Chapter 4 Structure

Little is known of the structure of rocks underlying the Coal Measures in the district. Some deductions can be made from Bouguer gravity anomaly and aeromagnetic surveys (Institute of Geological Sciences, 1977a, 1977b) and, with respect to the Millstone Grit, from limited seismic evidence in the south-east, interpreted by comparison with a few deep boreholes. In contrast, structures in the Coal Measures (most notably the Askern–Spital Structure) are known in considerable detail, particularly where the measures were mined (mainly in the south-west of the district); elsewhere, they can be reconstructed with varying degrees of probability from borehole results and seismic evidence. The simpler structures affecting the Permian and Triassic rocks can also be deduced from borehole data.

Geophysical evidence of deep-seated (sub-Coal Measures) structures

The Bouguer gravity anomaly and aeromagnetic survey maps for the district both indicate the presence of several significant anomalies which are largely indicative of structures affecting pre-Coal Measures rocks (Figure 28a) and (Figure 28c).

The gravity data (Figure 28a) are regionally influenced by the effect of the varying thicknesses of low-density sedimentary rocks of Triassic, Permian and Upper Carboniferous age. However, these variations are known from borehole and seismic information, except, critically, for sequences in the north and north-east of the region, see (Figure 30), and so their gravity effect can be calculated. In (Figure 28b) this contribution has been removed and the remaining gravity anomalies are largely due to pre-Namurian rocks. The aeromagnetic anomalies (Figure 28c) are mainly due to deep basement rocks, although the possible existence of magnetic volcanic or intrusive rocks within the Carboniferous sequence cannot be excluded. The major gravity and aeromagnetic anomalies have been interpreted along the profile AA' (Figure 28d), (Figure 29e). Datum level -12 mGal." data-name="images/P947285.jpg">(Figure 29a), (Figure 29e)." data-name="images/P947286.jpg">(Figure 29b), (Figure 29c), (Figure 29d) and (Figure 29e).

One of the principal features which give an indication of the deep, sub-Coal Measures structure is a pronounced Bouguer gravity anomaly low, in and beyond the north-east corner of the district (Figure 28a) and (Figure 28b). This gravity low indicates the presence of relatively low-density rocks beneath the area and was interpreted by Bott et al. (1978) as reflecting a batholith, the 'Market Weighton granite', intruded into pre-Carboniferous strata. The main part of the supposed granite lies outside the district, but a subsidiary low, in the Reedness area south-east of Goole, could represent a secondary cupola of the batholith, which is postulated to be elongated south-westwards (Figure 28d).

The partial overlap of the gravity low with a pronounced positive aeromagnetic anomaly, centred some 8 km further south, east of Crowle, A on (Figure 28c), suggests that the postulated granite intruded magnetic basement rocks occurring at an interpreted depth of only about 3 km. In this respect the geophysical signature of the suspected granite is similar to that of the Wensleydale Granite beneath the Askrigg Block (Wilson and Cornwell, 1982).

Bott et al. (1978) also suggested that the possible presence of a granite batholith in the 'Market Weighton' area could explain the existence of the concealed stable block there in Carboniferous, Jurassic and early Cretaceous times (Kent, 1980), though the interrelationship between uplift and sedimentation is complex in the area.

However, the interpretation of the Bouguer gravity anomaly low as granite has been challenged by Arveschough (1986), who suggested, on the basis of seismic reflection and scanty borehole evidence, that a thick sequence of Lower Carboniferous strata, in a deep graben structure, could account for the observed gravity data. Nevertheless, it is more difficult to reproduce some of the characteristics of the gravity anomaly, particularly its amplitude, with a graben model, as Bott (1988) has pointed out.

The comments made by Bott et al. (1978) and Bott (1988) concerning the main Market Weighton anomaly apply also to the subsidiary gravity low within the district. Its form can best be interpreted as a granite intrusion extending from a depth of about 3.5 km down to about 10 km. Interpretation as a sedimentary trough is less satisfactory and requires sedimentary rock densities that are less than those regarded as typical for Lower Carboniferous sequences. The principal aeromagnetic anomaly, A on (Figure 28c) can be satisfactorily interpreted as magnetic rocks intruded by and flanking the supposed concealed granite, although it seems necessary to postulate that the granite itself also has a moderate magnetisation: in this respect it differs from the concealed granites of Weardale and Wensleydale, samples of which do not contain significant amounts of magnetite.

This pronounced aeromagnetic anomaly in the east of the district, A on (Figure 28c) is in fact superimposed on a regional north-west to south-east zone of magnetic highs, part of which is also seen in the northern part of the district, B on (Figure 28c). This zone is interpreted as reflecting a broad, deep-seated belt of pre-Carboniferous magnetic rocks extending from the Lake District to The Wash; the nature of this magnetic basement remains conjectural, but a Precambrian age seems most likely.

Geophysical anomalies associated with the Askern–Spital Structure at sub-Coal Measures levels are evident on both the Bouguer gravity anomaly and aeromagnetic maps (Figure 28a), (Figure 28b) and (Figure 28c). The structure coincides with a significant, elongate gravity high, which is well defined on its southern side by a steep gradient zone over the edge of the Gainsborough Trough. Its northern margin is less well defined (Figure 29e). Datum level -12 mGal." data-name="images/P947285.jpg">(Figure 29a), except where it coincides with the edge of the Market Weighton anomaly low. The associated aeromagnetic anomaly, a weak high, C–C′ on (Figure 28c), is not particularly clear in the district, but can be traced as a more pronounced magnetic high for a further 40 km to the west-north-west into the Bradford area. The decrease in Bouguer gravity values on the southern side of the Askern–Spital Structure can be partly ascribed to an increase in thickness of low-density Millstone Grit (and older?) rocks in the Gainsborough Trough (Figure 30). However, postulation of additional interpretative features is necessary in order to reproduce the form of the observed gravity field (Figure 29c). On the northern side of the Bouguer anomaly profile, values are reduced by the effect of the Market Weighton anomaly low, though it is unlikely that the postulated granite would extend at depth so far south-west. Beyond the end of the southern part of the profile (Figure 29e). Datum level -12 mGal." data-name="images/P947285.jpg">(Figure 29a) another low-density body, either a granite or a Lower Carboniferous sedimentary basin, is required to explain the low gravity values. More significantly within the district, the assumed structure of the rocks below the Millstone Grit has to be modified in order to reproduce the form of the Askern–Spital gravity high. Alternative interpretations for these have been discussed for the district to the east (Gaunt et al., 1992). The preferred interpretative profile (Figure 29c) suggests a thick Lower Carboniferous limestone sequence and, at greater depth, localised basins of Lower Carboniferous or older arenaceous rocks. This interpretation would be modified if high density pre-Carboniferous rocks exist beneath the Askern–Spital Structure.

The associated weak aeromagnetic high, trending east-south-east, C–C′ on (Figure 28c), indicates that magnetic rocks, probably igneous in origin, are also associated with the deeper part of the Askern–Spital Structure. The depth to the source of this anomaly could be as little as 2 to 3 km. This interpretation indicates that the magnetic rocks might occur within, or just below, the Lower Carboniferous sequence. Two alternative, interpretative profiles postulate either (i) a pronounced ridge of rocks with moderate magnetic susceptibility, rising from a more deep-seated (faulted?) block of magnetic basement (Figure 29d), or (ii) igneous rocks, either lavas or intrusions of possible Carboniferous age, along the crest of the structure (Figure 29e). The highest part of the supposed ridge is postulated to lie directly beneath the Askern–Spital Structure and to have a steep, northward-facing slope. Similarly, the igneous rocks would be interpreted as having their maximum development beneath that structure (Figure 28d) and (Figure 29e).

Other Bouguer gravity anomalies with smaller amplitudes appear to be related to structures affecting the Coal Measures: they include a low over the Finningley Syncline (Figure 28d) and (Figure 31). Although the faults in the south-western part of the district are not associated with discrete anomalies, the Bouguer anomaly contours are parallel to the north-easterly trending structures. Most of the major faults associated with the Askern–Spital Structure occur on the southern side of the Bouguer gravity high (Figure 28d) and it is also noticeable that the Hatfield Moors Dome occurs where that structure is inter- sected by the south-westerly trending Market Weighton Structure.

Seismic evidence in the south-eastern part of the district allows the construction of generalised structure contours on the base of the Millstone Grit and shows some related faulting. These structure contours can be extrapolated westwards using data from a few deep boreholes. The resulting interpretation (Figure 30) outlines the Gainsborough Trough, with an amplitude in excess of 800 m, in the central southern part of the district. No structural interpretation can be made for this stratigraphical level in either the northern or south-western parts of the district.

Structure of the Coal Measures

The Barnsley/Warren House Coal provides the best stratigraphical level on which to illustrate Coal Measures structure. Depths to this coal are well documented in the southwest of the district, where it is mined, and they can readily be extrapolated in those central areas where the Hatfield High Hazel Coal is mined. Elsewhere, they are recorded from most of the boreholes which reach the Coal Measures, and in some north-western and south-eastern areas they are discernible from seismic evidence. The resulting compilation (Figure 31) clearly shows the Askern–Spital Structure, essentially a well-faulted anticline running east-south-eastwards across the middle of the district, and also a general, though irregular, eastward component to the dip in most parts of the district. This generalised eastward tilt also affects the Permo-Triassic succession, imposed during later Mesozoic and/or Tertiary times. Removal of the post-Triassic eastward dip from the structural configuration of the Barnsley/Warren House Coal shows the structure of the Coal Measures in early Permian times (Figure 32). The Askern–Spital Structure is readily discernible, but the structural patterns both to the north and south are appreciably different from those now in existence.

Coal Measures structure can be summarised in terms of northern and southern areas, and the intervening Askern–Spital Structure. Since the accuracy of the evidence varies widely, comments on the reliability of the structural reconstructions are included where necessary. Faults that are believed to intersect give no clear indication of offsetting effects and are shown without displacement (Figure 31) and (Figure 32).

Northern area

North of the Askern–Spital Structure the principal structures (Figure 31) are the generalised easterly dip, with cross faulting aligned to the north-east and, apparently less commonly, to the south-east. Three minor flexures are present: the small upfold around Ash Hill Borehole [SE 6213 1615] is more evident on the early Permian structure contours (Figure 32) than on the existing configuration (Figure 31); both it and another upfold in the area north-west of Thorne [SE 670 150] are short anticlinal spurs running off the Trumfleet Dome (described below). A small dome is recognisable, mainly on seismic evidence, farther east near Crowle [SE 776 116].

The Carleton, Knottingley, Stubbs Lane and Kellington faults extend north-eastwards into the district. All have south-easterly downthrows, which only in a few localities exceed 50 m.

The Bowers House Fault trends south-east, throwing the Barnsley/Warren House Coal up to 100 m down to the south-west. It is the continuation of the Lumby Fault on the adjoining Wakefield (78) Geological Sheet. Recent seismic data have provided more precision in the location of this fault than was possible when the Goole (79) Geological Sheet was being compiled. At that time the existence of the fault was postulated to account for the substantial variations in the Barnsley/Warren House Coal levels in numerous boreholes. The north-eastward continuation of the Rockley Lane Fault is largely conjectural, being the simplest explanation for the high level of the Barnsley Coal in the Ash Hill Borehole compared to boreholes farther south and east, without resorting to uncommonly steep dips. The north-eastward continuation of the South Don Fault, though not proved in Hatfield Colliery, is located in several places in Thorne Colliery workings of the Hatfield High Hazel Coal, although its throw there does not appear to exceed about 12 m. Farther south-east in both of these collieries there is clear evidence of several other faults running parallel to the South Don Fault, with a few associated cross faults aligned to the east-south-east; displacements are generally small, the largest known being a southerly downthrow of 30 m in a fault aligned east-south-east, close to Thorne Colliery shafts. All the faults shown farther east, in the area around the minor dome near Crowle (Figure 32), are invoked on seismic evidence.

The Askern–Spital Structure

Previously referred to as a 'Fold-Belt' (Edwards, 1951, p.114, fig. 39, pl. IV), a 'High' (Kent, 1966; Howitt and Brunstrom, 1966) and an 'Anticline' (Kent, 1974, fig. 5), the Askern–Spital Structure is essentially an irregular, well-faulted anticline, which runs east-south-eastwards across the middle of the district, plunging in that direction (Figure 31). The irregularities result from localised changes in trend and variations in amplitude (in excess of 150 m in places), which produce several distinct domes, the largest of which are the Trumfleet and Hatfield Moors domes (Figure 31). Removal of the post-Triassic eastward dip shows that in early Permian times there was no east-south-eastward plunge and the configurations of some of the domes were slightly different (Figure 32). The northern extension of the Trumfleet Dome to encompass Ash Hill Borehole is particularly clear on (Figure 32); it led Kent (1966, p.345, pl. 20) to refer to it as the Trumfleet Anticline. Two other spurs run off the Trumfleet Dome, one to the north-east (referred to previously) and one to the south-south-east, the latter bearing a minor dome near Barnby Dun (Figure 31). The culmination of the Hatfield Moors Dome appears to have been slightly farther east in early Permian times (Figure 32) than at present (Figure 31), and it is possible that minor domes exist even farther east; however, in the absence of mining information and the paucity of borehole data they cannot be delineated, the structure contours in this eastern area being drawn largely on seismic evidence. Several minor domes are certainly present to the west, in Askern Colliery, where they are generally separated from each other by complex faulting. The two most marked of these domes are around the colliery shafts [SE 558 138] and at a locality [SE 557 133] to the south, across a reversed fault (see below).

Three extensive faults run parallel or subparallel to the Askern–Spital Structure: all throw down to the south, except where one of them is locally reversed. The Stainforth Fault, on the northern flank of the structure, has measured throws of up to 93 m on the Warren House Coal in Askern Colliery, and of up to 90 m on the Hatfield High Hazel Coal in Hatfield Colliery. Extrapolated structure contours indicate considerably larger throws just beyond the north-western edge of workings in the latter colliery. Seismic evidence suggests that the Stainforth Fault dies out eastwards under the southern part of Hatfield Chase.

The Askern Fault, which cuts across the middle of the Trumfleet Dome, generally appears to have throws of less than 80 m, except towards its western end where displacements of up to 119 m are known on the Warren House Coal in Askern Colliery. Farther west in these workings, the throw decreases markedly within about 1 km; the fault turns sharply south-westwards (south of the colliery shafts), and reverses its throw shortly before terminating against another south-easterly aligned fault which has a south-westerly downthrow of up to 65 m (Figure 31). In these workings also, a branch off the Askern Fault runs north of the colliery shafts and has a south-westerly downthrow of up to 77 m; this branch may be related to the Wentbridge Fault farther to the north-west (Goossens and Smith, 1973, p.510, pl. 21). The Askern Fault was formerly thought to continue east-south-eastwards across the southern part of Hatfield Moors; this continuation was included on the Doncaster (88) Geological Sheet, partly on borehole evidence relating to the Permo-Triassic succession and partly on geophysical evidence, which suggested a displacement of the western edge of the Mercia Mudstone near Tunnel Pits Farm. Recent seismic surveys, however, show no trace of this east-south-easterly continuation of the Askern Fault, but confirm the existence of the Hatfield Woodhouse Fault, at least as far east as Sandtoft. The Hatfield Woodhouse Fault, at its western end lying at or close to the junction of the Askern and Armthorpe faults (the latter described below), cuts the Askern–Spital Structure obliquely across the northern part of the Hatfield Moors Dome, but then continues south-eastwards along the northern edge of the Askern–Spital Structure, thus in effect replacing the function of the Stainforth Fault in this direction.

There is also seismic evidence for discontinuous faults with northerly downthrows running parallel to, and on the southern side of, the Hatfield Woodhouse Fault, forming narrow grabens across the northern part of the Hatfield Moors Dome (Figure 31). Farther south-east across the Isle of Axholme the seismic evidence is inconclusive, but the simplest interpretation of data from the Axholme oil boreholes, near Epworth, is a continuation of the Hatfield Woodhouse Fault with an accompanying graben on its southern side (Figure 31). There is also seismic evidence of a south-westerly downthrowing fault aligned with, and probably forming the continuation of, the Hatfield Woodhouse Fault at Susworth, near the eastern edge of the district.

Two small, north-eastward-trending faults cross the Askern-Spital Structure between the Stainforth Fault and a northerly branch of the Askern Fault in Askern Colliery, and both the Rockley Lane and South Don faults are presumed to cross the structure farther south-east, although direct evidence is lacking. It is possible that one or more faults cross the Trumfleet Dome, and there is seismic evidence for several faults on the flanks of the Hatfield Moors Dome.

Southern area

The dominant structural feature in the area south of the Askern–Spital Structure is the Finningley Syncline, which has an amplitude of generally more than 150 m and plunges gently east-south-eastwards (Figure 31), separating the Askern–Spital Structure from the Maltby–Tickhill and Walkeringham–Gainsborough anticlines, which lie to the south of the district (Smith et al., 1973, pp.207–210, figs. 32 and 33). In the west a minor syncline branches north-westwards off the Finningley Syncline and passes through Shaftholme, north of Bentley. Removal of the post-Triassic eastward dip shows that in early Permian times (Figure 32) the Finningley Syncline plunged westward, heading in this direction towards the northern part of the Maltby Basin (Kent, 1966, pl. 20). This westward plunge closely reflects that of the Gainsborough Trough in the underlying older Carboniferous rocks (Figure 30), suggesting that the Finningley Syncline is in effect the final manifestation of the Gainsborough Trough in the Carboniferous rocks.

In the south-west the main faults are aligned either to the north-east or the east-south-east, as they are in more northerly parts of the district. The north-easterly trending faults are more prominent, probably because they are an extension of the Don Monocline, which produces such marked swings in outcrops in the exposed coalfield to the south-west (Mitchell et al., 1947, pp.126–130, pl. I, fig. 30; Eden et al., 1957, p.148, pl. VI).

The Rockley Lane Fault, with measured south-easterly downthrows of up to 36 m on the Barnsley Coal, north of Bentley, and displacements of structure contours of up to 46 m farther north-east, is approximately in line with the North Don Fault, which lies to the south-west (Mitchell et al., 1947; Eden et al., 1957, p.150, pl. VI); but whether the two faults are continuous in this direction is uncertain. A parallel fault downthrowing in the opposite direction produces a narrow, shallow graben on the south-eastern side of the Rockley Lane Fault. The South Don Fault almost certainly continues north-eastwards into the district and, with closely associated parallel faults, displaces structure contours in the Barnsley Coal, north-east of Bentley, by up to 30 m. Farther south, although two north-easterly aligned faults produce a well-defined graben in the Permo-Triassic rocks at Balby (as summarised below), there is insufficient evidence within the district to locate, or assess the magnitude of, these faults in the Coal Measures; fault lines in this vicinity on (Figure 31) are therefore largely conjectural. The Armthorpe Fault to the east is extensively proved in the Barnsley Coal workings at Markham Main Colliery and has a measured south-easterly downthrow of 116 m. It, too, has an associated fault with an opposing downthrow, producing a shallow graben on its south-eastern side.

The most notable faults with east-south-easterly alignments are those proved in Yorkshire Main and Rossington collieries, forming shallow grabens almost along the axis of the Finningley Syncline. Throws of up to 20 m are recorded in the Barnsley Coal near the western edge of the district, but in most places these faults have displacements of less than 12 m. All the short faults shown farther east on (Figure 31) and (Figure 32) are implied by seismic evidence.

Structure of the Permian and Triassic rocks

Structure contours on the base of the Permian rocks (Figure 33) and on the bases of the Sherwood Sandstone and Mercia Mudstone (Figure 34), drawn entirely on the abundant borehole data available, reflect the fairly uniform eastward dip and minor, localised variations of strike. They also show, by comparison with structure contours on the Barnsley/Warren House Coal (Figure 31), the marked nature of the unconformity between the Coal Measures and the Permo-Triassic rocks. (Figure 32), showing structure contours on the Barnsley/Warren House Coal as they were in early Permian times, gives some idea of the variation in magnitude of the unconformity in different parts of the district. The faults shown cutting the Permian and Triassic rocks on (Figure 33) and (Figure 34) are justified either by rockhead configurations, in areas near the western edge of the district, or by offsets in the structure contours, the fault positions being calculated from their locations in the Coal Measures.

Those elements of Coal Measures structure that are discernible in the Permian and Triassic rocks show considerably decreased magnitudes; this implies slight, posthumous movements on structures already in existence in early Permian times. In the north, the Carleton, Knottingley, Stubbs Lane, Kellington and Bowers House faults persist through the Permian and Triassic sequence; however, there was no rejuvenation of the minor flexures in the Coal Measures. The Askern–Spital Structure is clearly recognisable, although in subdued form, by a dome at Askern, (which manifests itself topographically as the hill on which the town is situated), by another dome at Trumfleet, by a gentle anticline above the Hatfield Moors Dome and by the Stainforth, Askern and Hatfield Woodhouse faults. On the evidence of rockhead configurations in the south-west and structure contours farther north-east, the Rockley Lane, South Don and Armthorpe faults, and some of their associated faults, also persist across the central part of the district. To the south, a slight westward swing in the basal Permian structure contours (Figure 33) suggests minor rejuvenation of the Finningley Syncline, but the more ac centuated swing of the structure contours on the base of the Sherwood Sandstone (Figure 34) results from the southward passage of the upper part of the Upper Marl into Sherwood Sandstone; it is therefore not a true reflection of structure at this stratigraphical level. In the south-west, rockhead configurations clearly delineate the two east-south-easterly aligned faults forming the graben in which Loversall is situated. The north-easterly aligned graben at Balby is also similarly delineated; the south-westward extension of Sherwood Sandstone at rockhead suggests that this graben has a magnitude of about 50 m. However, basal Permian structure contours (Figure 33) imply that the bounding faults have throws of less than half of this magnitude. A possible explanation may be that one or more faults cross the graben and downthrow to the south–west, thus extending Sherwood Sandstone at rockhead in this direction. The fault on the northern side of the graben at Loversall may be one of these. There is some mining evidence, just west of the district, which suggests that south-westerly down-throwing faults in the Coal Measures also extend southeastwards towards the graben; these may cross the graben and persist up into the Permian and Triassic succession.

Synopsis of structural history

Geophysical evidence regarding the structural history of pre-Coal Measures strata is scanty. A pronounced Bouguer gravity anomaly low in the north-east is perhaps best interpreted as a south-westward elongation of the supposed Market Weighton granite, intruded into pre-Carboniferous rocks and probably of Caledonian age. Partial overlap with a strong aeromagnetic high suggests that the pre-Carboniferous strata there are magnetic and may be part of a distinct south-eastward trending belt of magnetic basement rocks, the nature, origin and age of which remain conjectural. The postulated presence of a major granitoid batholith in the Market Weighton area has been invoked as an explanation for the concealed stable block there in the Carboniferous and Mesozoic.

Gravity and aeromagnetic anomalies are also evident over the Askern–Spital Structure. One interpretation suggests that a thick Lower Carboniferous limestone sequence and more localised basins of Lower Carboniferous or older arenaceous rocks flank that feature. Magnetic rocks, either lavas or intrusions that are possibly of Carboniferous age, or a deep-seated (faulted?) block of moderately magnetic rocks, may occur beneath the crest of the structure.

Seismic evidence outlines the Gainsborough Trough; structure contours on the base of the Millstone Grit show this feature to have an amplitude of more than 800 m, but no structural interpretation of Namurian (or older) rocks is possible over much of the district.

Nevertheless, for much of the Carboniferous, at least until early Westphalian times, extensional tectonics led to considerable differences between the rapidly subsiding Gainsborough Trough across the southern part of the district (Figure 30) and the slowly subsiding 'block' area to the north. This differential vertical movement decreased markedly in the late Namurian. The Coal Measures are consistently thickest in the south-west, suggesting that the same relationships continued on a reduced scale during much of the Westphalian.

However, the thicknesses of coals and of intercoal sequences, and the patterns of coal-seam splits, indicate that during late Westphalian A, and certainly in Westphalian B times, other structural elements operated. A subsidiary thickening of the Coal Measures in the northwest implies somewhat greater subsidence towards a developing basin there, probably controlled by incipient faults trending north-eastwards and therefore tangential to the developing basin farther north-west. Between that basin and the deeper one in the south-west, in the region of the old Gainsborough Trough, intercoal sequences are generally thinnest in an elongate area extending east-south-eastwards from north of Askern across the southern part of Hatfield Chase; this zone is virtually coincident with the southern edge of the block that had previously formed the northern flank of the Gainsborough Trough.

During the hiatus between Coal Measures deposition and the renewal of sedimentation in the late Permian Zechstein Sea, the Hercynian Orogeny produced gentle folding, extensive faulting, uplift and consequent erosion in the district. The principal fold, a multidomed anticline running east-south-east from Askern, forms the core of the Askern–Spital Structure, which was flanked to the north by cross faulted minor flexures and to the south by the Finningley Syncline, which at that time plunged westwards (Figure 32). The faults are mainly aligned to the north-east or east-south-east, and most throw down towards the south; they are therefore closely comparable to faults in the exposed coalfield to the west. Two other similarities with the area to the west are notable: the Stainforth, Askern and Hatfield Woodhouse faults, associated with the Askern–Spital Structure, form an eastward continuation of the Morley–Campsall Fault Belt (Edwards et al., 1940, p.142, fig. 58); and the Rock-ley Lane, South Don and Armthorpe faults are in effect structural continuations of the Don Monocline (Mitchell et al., 1947, pp.126–130, pl. 1, fig. 30; Eden et al., 1957, p.148, pl. VI). The consistency of the southerly component of downthrow on the main faults, and the presence of grabens associated with many of them, implies widespread tension in a north-south direction. The tension appears to have been greatest in the west and could suggest an element of rotation in the fault pattern, as it does elsewhere in the Coal Measures of western Yorkshire. Alternatively, the greater intensity of movement apparent in the west may result from concentration of movement where two prominent structures cross, namely the 'Morley–Campsall–Askern–Spitar Structure and the Don Monocline with its associated faults; both are probably rejuvenated older structures, possibly Caledonian or earlier.

However, the Askern–Spital Structure, whatever its deep-seated precursor, cannot be attributed solely to regional tension; it’s essentially anticlinal nature, position and alignment suggest upward movement along the south-western margin of the block which flanked the northern side of the Gainsborough Trough. The early Permian westward-plunging Finningley Syncline (Figure 32) also suggests continued movement compatible with the former 'block' and trough distribution. This renewal of upward movement along the south-western margin of the old block may have been in response to the block beginning to tilt down to the north-east, in a phase of differential uplift and tilting which eventually, after considerable denudation, produced the intracontinental basin inundated by the late Permian Zechstein Sea.

There is only sparse evidence, in the district, of the age or nature of the post-Triassic movements that produced the general eastward dip, some late activity along faults, and slight rejuvenation of the Askern–Spital Structure. The eastward dip of the Permian and Triassic rocks may reflect increasing subsidence in that direction towards the Southern North Sea Basin, but evidence from later Mesozoic rocks east of the district implies that the dip is a composite feature resulting from more than one phase of movement. The Jurassic rocks to the east have an eastward dip virtually identical with that of the Mercia Mudstone in the district (Figure 34), whereas the late Cretaceous Chalk, resting with major unconformity on the Jurassic, dips to the north-east. If, however, this post-Cretaceous north-eastward dip is removed from the existing eastward Jurassic dip, the Jurassic rocks are shown to have had an original south-south-easterly dip (Gaunt et al., 1992, pp.105–106, fig. 38 i–iii), possibly reflecting the effects of the Market Weighton Structure. This structure was active intermittently from early Jurassic to early Cretaceous times. The inference is that this south-south-eastward dip of the Jurassic strata resulted from tilting prior to deposition of the Chalk, but that the dip was changed to its present, generally eastward direction during a further phase of tilting in post-Cretaceous times. These variations in direction of dip probably reflect movements of the locus of epeirogenic subsidence in the North Sea region throughout Mesozoic and later times.

Evidence from farther east also suggests the possibility of late movement along some faults, and on the Askern–Spital Structure. Both the Brough and Flixborough faults have the typical east-south-east alignment of many faults in the Coal Measures (the latter being aligned with faults proved in Thorne Colliery) and may well have resulted from renewed movement on original Hercynian fractures. The Brough faults appear to have been active intermittently in middle Jurassic times, and movement on the Flixborough faults may also have occurred at various times in the Jurassic. Similarly, there are suggestions that intermittent arching over the south-eastern continuation of the Askern–Spital Structure took place in Jurassic times (Kent, 1980, pp.116–117; Gaunt et al., 1992, pp.105–106). These suggestions of renewed, intra-Jurassic movement on structures farther east, and therefore by implication within the district also, do not preclude the possibility of even later movement along faults and on the Askern–Spital Structure, especially during the Tertiary phase of uplift and tilting.

Chapter 5 Quaternary

Quaternary deposits, referred to as 'Drift' on the geological maps, cover 90 per cent of the district, generally being most extensive and thickest in the low-lying areas. They range lithologically from peat and clay to gravel, and were deposited in glacial, periglacial, lacustrine, fluvial, aeolian and estuarine conditions.

The Quaternary Period, which commenced between about 1.6 and 2.4 million years ago, encompassed major climatic fluctuations, which form the basis for chronostratigraphical classification. In Britain a sequence of alternating temperate and cold stages, with glacial episodes in some of the cold stages, has been formulated (Mitchell et al., 1973). The study of oceanic sediments, however, shows that there were considerably more climatic changes than can be deduced from the incomplete evidence on land (e.g. Bowen, 1978, pp.198–199, table 10–1), but until means of dating and correlation improve, the land-based sequence of stages must be used provisionally as a descriptive framework.

Resumé of Quaternary history

Within the district there are deposits attributable to the last three British Quaternary stages (the Ipswichian, Devensian and Flandrian), and also to an older, pre-Ipswichian, glacial stage. The Quaternary history of the district, as far as it is known, is summarised below and illustrated in (Figure 35); a more detailed history is published elsewhere (Gaunt, 1981).

There is no evidence that deposits of Cromerian age (about 500 000 years ago) or older are preserved. Consequently, the long, early part of the Quaternary appears to represent a continuation of the denudational regime which had persisted during Tertiary times. The oldest deposits, of pre-Ipswichian glacial origin, indicate the existence of a thick cover of ice derived from the north and north-west, beneath which deep subglacial incision and deposition took place; fluvioglacial meltwater deposits entered the district from the south and west during deglaciation.

Subsequent fluvial incision occurred just prior to the temperate Ipswichian Stage as a result of the sea level being at or more than 13 m below OD, which suggests retarded glacioeustatic effects. As sea level rose to about, or just above, OD during this interglacial, estuarine deposits formed in the incised drainage courses, as at Langham. Somewhat later, the rivers Don and Idle deposited extensive spreads of older river gravel.

In the cold Devensian Stage, which apparently began about 120 000 years ago, sea level fell to more than 20 m below OD, again reflecting glacioeustatic effects, and rivers crossing the district incised wide valleys directed towards the Humber Gap to the east. Periglacial conditions, indicated mainly by cryoturbation structures and ventifacts, prevailed during at least part of this long incision phase. However, except possibly for some ?fluvial sand and gravel now deeply concealed beneath 25-Foot Drift, and also possibly some head, there is no evidence of deposition until late in the Devensian. Then, probably about 18 000 radiocarbon years ago, glacial blockage of the Humber Gap (Gaunt et al., 1992, pp.109, 121) impounded a large lake (Lake Humber) across much of the district and adjacent areas. The lake rose initially to about 30 m above OD, sand and gravel being deposited around its margins. During this high-level lacustrine phase a tongue of ice surged southwards down the Vale of York and into northern and eastern parts of the district, depositing sand and gravel into the lake. The ice soon melted and the lake level fell, apparently transiently to as low as 4 m below OD, before establishing a longer lasting level at about 9 m above OD. Lake Humber finally disappeared, apparently by filling up with sediments, which are known as the 25-Foot Drift. Rivers then deposited sandy levees as they initiated courses across the emergent lacustrine plain. In the last millennium of the Devensian (which by definition terminated 10 000 radiocarbon years ago), blown sand accumulated in places, and some ventifacts and cryoturbation structures at the top of the Devensian glacial and lacustrine deposits may have formed at this time.

At the beginning of the Flandrian or slightly earlier, breaching of the glacial deposits in the Humber Gap allowed the rivers crossing the district to incise their courses down almost to 20 m below OD, again in response to the continuing eustatically low sea level. As the sea rose to its present level later in the Flandrian, alluvium eventually filled these incised courses and spread thinly but widely beyond them, locally covering peat that had developed in the prevailing wetter climate and more waterlogged conditions. In historic times some river diversions and some deposition of alluvium, known as warp, have been effected by man.

The stratigraphical and altimetric relationships of the Quaternary deposits are shown schematically in (Figure 36). More extensive local details of the Quaternary geology than can be included in this account are available in an unpublished thesis (Gaunt, 1976a).

Pre-Ipswichian glacial deposits

Deposits of pre-Ipswichian glacial origin are largely confined to western parts of the district.

Clay till

Clay till (shown as boulder clay on geological maps) consists of bluish grey to reddish brown silty and locally sandy clay with scattered erratics up to boulder size; it is more reddish or yellowish where weathered. The erratics are mainly of Carboniferous sandstone, siltstone and coal, and Permian limestone, with smaller numbers of Carboniferous limestone and chert, forming an 'east Pennine' erratic suite. A few erratics of igneous rocks, some recognisably from the Lake District, are also present. On the evidence of these erratics, the ice which deposited the clay till in the district had traversed the eastern Pennine slopes, and some of it had originated or passed close to the Lake District. The stone orientations on Brayton Barff and at Balby (see below), analysis of coal erratics from Balby, and distribution of Permian erratics west of the Permian outcrops beyond the district show that most, if not necessarily all, of the ice which entered the district from the north and north-west had flowed south down the Vale of York after crossing the Pennines, presumably via Stainmore (as it did later, in the Devensian), not via the Aire Gap (Gaunt, 1981, pp.83–85, fig. 2).

The sparsity of clay till, its isolation either on elevated locations or in sheltered low-lying areas, and the absence of associated glacial landforms, suggests a glaciation of considerable antiquity. The presence, locally above the clay till, of older river gravel, for which there is fossil evidence of an Ipswichian interglacial age (summarised below), confirms the glaciation as pre-Ipswichian. However, the two small patches of supposed till east of Beltoft on the Isle of Axholme could conceivably be exceptions, for on the evidence of Devensian glacial sand and gravel, summarised below, they lie within the area that was briefly covered by a surge of Devensian ice, and may have formed during this episode.

Details

Quaternary deposits on the summit of Brayton Barff [SE 585 305] (Plate 1), south-west of Selby, are described by Sheppard (1915), Kendall and Wroot (1924, p.680) and Melmore (1934), but clay till was not previously recorded there. The sand at the base of the sequence (Figure 37) is reddish brown and mainly level bedded, and contains a few pebbles of quartz, quartzite, chert and Permian limestone near its base and top. Above a sharp level contact at 46.3 m above OD, there is grey to reddish brown laminated clay, which includes laminae of silt and fine-grained sand containing coal particles. Small-scale intraformational folds, faults and thrusts are present in the laminated clay which, except on the northern part of the summit, passes gradually up into pale reddish brown sandy clay till, with many of its erratics concentrated into distinct layers. This till is succeeded, above a sharp contact, by pale greyish brown clay till with less pronounced erratic layering; this oversteps the lower till on the northern part of the summit to rest on the laminated clay, the top of which is here severely crumpled. Both varieties of till contain almost identical 'east Pennine' erratic suites, and both possess remarkably concentrated stone orientations (Figure 37).

At a locality [SE 588 280] near Burn a small patch of pale brown sandy clay, which contains a few Carboniferous sandstone pebbles and rests on Sherwood Sandstone, is suggestive of sandy clay till. Although no till was found on the Snaith Ridge within the district, a trench south-west of Kellington (section A to C on (Figure 38) proved reddish brown variably sandy clay till containing irregular masses of grey clay and 'east Pennine' erratics, largely concealed by lacustrine sand and gravel. Some clay till occurs within glacial channel deposits in the Arksey Channel (see below).

At Edenthorpe, on the Doncaster Ridge, up to 3.0 m of brown silty and locally sandy clay till were proved by excavations and boreholes to rest partly on Sherwood Sandstone and partly on a basal clayey gravel, and to pass eastwards beneath the older river gravel. Elsewhere on the Doncaster Ridge thin clay till may transgress across the top of glacial channel deposits in the Barnby Dun Station, Armthorpe and Wheatley Park channels (summarised below).

The lower part of the clay till formerly exposed to depths of nearly 11 m in large pits [SE 562 003] at Balby, which rests mainly on Sherwood Sandstone, is dark bluish grey clay containing thin level steaks of reddish slightly sandy clay. The upper part, locally above a greyish brown colour-banded clay layer up to 1.2 m thick, varies from greyish to reddish brown clay, but weathers in the top 3 m or so to yellowish brown. The erratics throughout are a typical 'east Pennine' assemblage with the addition of a few of igneous rocks, including Shap Granite (Corbett and Kendall, 1896), Ennerdale 'granite', 'quarry porphyry' from the Vale of St John, augite andesite from Borrow-dale, 'diabase' from Eycott Hill, and Whin Sill (Corbett, 1903). Kendall and Wroot (1924, p.923) noted a trail of gypsum fragments which 'rose nearly vertically in the clay [till] and turned over in a loop 18 feet high'. Stone orientations (Figure 39) are concentrated between west–east and NNW–SSE.

On the eastern side of a pit [SE 569 009] to the north-east, 2.1 m of brown silty clay till pass down into red and dark brown sand, resting on Sherwood Sandstone, and in another pit [SK 5506 9959] to the south-west, 1.8 m of brown clay till resting on Sherwood Sandstone pass laterally westwards into 0.6 m of sand. The clay till continues south-eastwards past Loversall, resting partly on Permian rocks and apparently partly on glacial channel deposits (summarised below), and borehole logs describe it as reddish to greyish brown clay with 'limestone' and coal erratics. Motorway excavations showed that the brown clay till resting partly on Permian rocks, but mainly on Sherwood Sandstone, south-east of Wadworth contains pockets of sand up to 3.0 m thick and 6.1 m wide, and also apparently more erratics of Carboniferous limestone than occur elsewhere in the district. One excavation [SK 5837 9602] proved 3.0 m of red clay till, and another [SK 5915 9517] revealed up to 1.2 m of brown clayey sand till, both rich in Permian limestone erratics. The small patch of clay till [SK 578 953] near Gallow Hill, and others farther south-west, were mapped on soil evidence. Farther east in the Torne Valley, reddish to greyish brown clay till [SK 610 966] rich in Permian limestone erratics rests at least partly on Sherwood Sandstone and partly on glacial channel deposits, and it is locally overlain by older river gravel.

On the northern part of the Rossington Ridge an excavation [SE 6309 0033] proved 0.61 m of grey clay till resting on Sher wood Sandstone and passing eastwards under older river gravel. Small clay outcrops farther west are probably glacial channel deposits. Brownish grey clay in several places farther south on the Rossington Ridge is largely unexposed; boreholes prove some of it to be a glacial channel deposit at depth, but its wide extent both at the surface and beneath fluvioglacial sand and gravel, coupled with the presence of fragments of Carboniferous sandstone and other 'east Pennine' erratics at the surface, suggest that some of it is clay till.

Small mounds protruding through alluvium in the southeastern part of Misterton Carr were mapped as clay till on the evidence of red, brown and grey pebbly clay soil.

On the Isle of Axholme, two small patches [SE 804 070]; [SE 817 070] of reddish brown to pale brown variably sandy clay east of Beltoft, with pebbles of Carboniferous sandstone, Permian limestone, 'Bunter quartzite' and 'skerry' from the subjacent Mercia Mudstone, are suggestive of clay till.

Glacial channel deposits

Boreholes and some excavations show that several narrow, steep-sided channels which, with one exception, are deeply incised into bedrock, mainly Sherwood Sandstone, occur in the western part of the district and farther west. The deposits filling the channels (shown as boulder clay on geological maps) consist largely of virtually stoneless and commonly laminated greyish clay, although clay till is present in at least one channel. Sand, with or without gravel and commonly containing coal particles, occurs in several channels, mainly in their lower parts and towards their eastern ends. Where pebbles are present they are mainly of Carboniferous sandstone, limestone and associated rocks, and of Permian limestone; they are commonly grooved and scratched.

The channels are unrelated to the present or any known pre-existing valleys; they are, moreover, closed channels with undulating long profiles which, in the Banby Dun Station Channel, cut down to about twice the depth of rockhead in the Humber Gap. A subaerial origin is, therefore, precluded. So also is ice gouging, in view of the depth, narrowness and general shape of the channels, which are quite unlike fiords, for example. The channels are, however, closely comparable to the 'tunnel-dale' of Denmark and 'rinnentaler' of Germany and, like them, they are believed to have been cut by powerful sub-glacial drainage, such as has been detected under existing ice sheets, for example in Alaska (Russell, 1893) and Greenland (Wright, 1911, p.82). An abrasive sediment load may have contributed to the incising power of these subglacial streams. The easterly or south-easterly trend of the channels, and the obviously Pennine derivation of some of the contained deposits, suggest that they probably flowed under enormous hydrostatic pressure from sources, possibly glacial lakes, high in the Pennines. Most of the channels in the district are aligned with gaps through the Permian scarp to the west, for example the Ferrybridge 'gap', Went 'gorge', Hampole Beck 'gap' and the Don 'gap'. Most of the channels in the Doncaster area also point eastwards to the Haxey Gap south of the Isle of Axholme, so that a genetic relationship between the channels and these gaps is possible.

The deposits in the channels are believed to have formed subglacially also, for several reasons. If they had been deposited subaerially when thick ice melted over and around the channels they would have been markedly heterogeneous, ill-sorted and poorly stratified sediments, probably mainly ablation and flow tills. They have not been proved outside the channel confines, where they might be expected if deposition had been subaerial. The evidence of two or more cycles of incision and deposition would, if deposition had been subaerial, have required two or more episodes of ice advance and deglaciation, each with identical local patterns of subglacial flow. The presence of thick sand and/or gravel at the eastern ends of at least the Barnby Dun Station and Hunster Grange channels suggests that the flows occasionally choked themselves at their downstream ends, an event that could occur only while a high hydrostatic head was maintained under ice. Increasing water pressure may at times have demolished such blockages, allowing another cycle of incision and deposition. Engineering tests have shown that clays from several channels are markedly over-consolidated, to a degree commensurate with the weight of several hundred metres of ice.

The glacial channel deposits are referable to a pre-Ipswichian glaciation for the same reasons as those applied above to the clay till and, in view of their common depositional environment and intimate association, the two categories of sediment presumably formed during the same glacial episode. The nearest pre-Ipswichian glacial channel deposits to those summarised above are in the Immingham Channel east of the Lincolnshire Wolds, which are provisionally correlated by Gaunt et al. (1992, pp.109–112) with the Anglian (anti-penultimate cold) Stage sensu Mitchell et al. (1973).

Details

On the Snaith Ridge, several glacial channels were proved in the trench running south-west from Kellington and in the railway cutting to Eggborough Power Station (sections A to C and D to F respectively on (Figure 38), including one cut into clayey gravel associated with clay till. A few large irregular masses of red sand are present in the laminated clay. The disposition of deposits at the southern end of the railway cutting, where some pebbles of igneous rocks were found, and at the north-eastern end of the trench, suggest more than one cycle of incision and deposition. There are other suspected channel deposits in two small clayey hollows east of Kellington, in Kellington No. 2 Borehole [SE 5551 2431] which proved 12.3 m of grey clay resting on Sherwood Sandstone, in pylon foundations [SE 5520 2407] and another excavation [SE 5626 2397] which both proved grey clay beneath sand and gravel, and under part of St Edmund's Church, Kellington, which is slightly tilted. Three of the clay-filled channels in the railway cutting are traceable for short distances to the south-east, the only evidence of channel alignment in the area. A trench [SE 4994 1414] to [SE 4979 1369] north-east of Wrangbrook, outside the district west of Askern, exposed four steep-sided channels up to 26m wide cut into Lower Magnesian Limestone and filled with reddish brown laminated clayey silt.

All the channels in the Doncaster area (Figure 40) are cut into Sherwood Sandstone except the Loversall Channel, which is cut into Permian rocks. The deposits in the Moss Channel, completely concealed beneath 25-Foot Drift, consist entirely of clay in the north-western part, but towards the south-east they include sand, 'stones' and gravel, including a basal 'limestone gravel'.

Similarly, the deposits in the western part of the Barnby Dun Station Channel are predominantly of clay. They include 60.3 m of clay in a borehole [SE 6188 0833] recorded by Corbett (1903), who noted its likeness to laminated clay in a brick pit (Corbett, 1897) farther south-west, referred to below. This remarkable thickness of clay was doubted by some subsequent commentators but validated by another borehole [SE 6183 0831] which, beneath thin older river gravel, proved clay with thin layers of sand and gravel to 65.5 m, resting on Sherwood Sandstone. The amount of sand and gravel in this channel, mainly near its base, increases south-eastwards, and near its known limit in this direction a borehole c. [SE 6787 0534] proved running sand to the bottom of the borehole at 28.2 m; samples proved that the sand was not incohesive Sherwood Sandstone. A borehole [SE 5523 0920] into the concealed deposits in the Arksey Channel passed through alternations of laminated clay and silty clay till, also slightly laminated and containing a typical 'east Pennine' erratic assemblage. In this channel also a south-eastward increase in sand and gravel at depth is noticeable. In the Armthorpe Channel, Corbett (1897) noted 'fine bluish laminated clay ... to all appearance a warp clay' to a depth of 9.1 m in a pit [SE 610 057], and G H Mitchell recorded 'blue boulder clay', which he also suspected to be 'warp', in a trench, from [SE 6043 0630] south-westwards.

The deposits in the Wheatley Park Channel were exposed in excavations at the ICI works [SE 585 052], where 4.6 m of clay were seen, and at the extension to Doncaster Infirmary [SE 592 042], where weathered yellowish brown locally sandy clay, with traces of laminations, was noted. Boreholes there proved thick, bluish grey, laminated clay and silt with thin layers of red sand and a few boulders. Old deep clay pits [SE 614 027] east of Doncaster Race Course probably mark the south-eastern limit of this deposit. Other boreholes into the channels in the Doncaster area are recorded by Price and Best (1982). An old excavation [SE 2613 0053] in the Bessacarr Channel, on the Rossington Ridge, exposed 5.5 m of grey clay, which boreholes show to be laminated at depth, with silt beds and, near the base, some gravel.

Bluish grey clay in the Rossington Channel was formerly worked in pits north-west of Rossington. This channel continues eastwards at least as far as Finningley Airfield, near which boreholes [SK 654 984] prove 9.5 m of stoneless laminated clay without reaching rockhead; farther east it may be responsible for an ill-drained area [SK 678 985] in which shallow excavations revealed the older river gravel to be abnormally clayey. Shallow boreholes into the clay till which stretches south-eastwards past Loversall show that it contains few stones below the surface and continues down to more than 1 m below OD, implying the presence of a channel which, farther east, may continue into the Hunster Grange Channel. In a trench into the latter, near the Rossington–Tickhill road, G H Mitchell noted 'blue clay probably laminated', and a nearby borehole [SK 6230 9670] proved sand to 1.8 m, on clay to 30.5 m, on sand and gravel to the bottom of the borehole at 39.3 m. This channel continues eastwards to the north of Austerfield, where a deep excavation [SK 6577 9502] exposed nearly 3 m of coarse, unsorted, unbedded, boulder-bearing gravel derived from Carboniferous and Permian rocks and with a clayey sand matrix, below several metres of the lithologically and texturally quite distinct fluvioglacial sand and gravel capping the Rossington Ridge (summarised below). The two deposits are separated by 0.16 m of laminated silty clay; the presence of water at the bottom of the excavation suggested clay at greater depth.

The Limpool Farm Channel was discovered by a borehole [SK 6200 9479] (Clayton, 1979, p.56) which, below fluvioglacial sand and gravel, proved silt and laminated clay to the bottom of the borehole at 18 m. Another channel is believed to exist south of the district at Harworth (Smith et al., 1973, pp.217, 220), containing clay which Aveline (1880, pp.25–26) noticed to be largely devoid of pebbles.

Sandy boulder clay

Two small deposits [SK 642 932]; [SK 650 950] west of Austerfield, mapped as sandy boulder clay, were regarded by Smith et al. (1973, p.217) as 'locally derived ground moraine' consisting essentially of reworked material from the Sherwood Sandstone. The boundary between the more southerly patch and the fluvioglacial sand and gravel to the north is an arbitrary line. The more northerly patch is exposed in a railway cutting [SK 6500 9477], which reveals brown sandy clay with pebbles.

Glacial sand and gravel

The characteristics of four small sand and gravel deposits suggest a common origin with the clay till.

Unbedded and poorly sorted gravel containing cobbles, and with a sand matrix, on the summit of Brayton Barff [SE 585 305] rests with a gradational and locally channelled contact on clay till (Figure 37). In addition to the 'east Pennine' pebble assemblage, a few pebbles of igneous rocks including 'Cheviot porphyrites and Hornblende Rock from the Lake District' (Sheppard, 1915) are present. Sand and gravel with a similar composition occurs on the nearby summit of Hambleton Hough [SE 557 299] at about 46 m above OD. The clay till revealed in the trench running south-west from Kellington (Figure 38) passes south-westwards into clayey gravel and then into gravel with a sand matrix. The gravel throughout is unsorted and unbedded, and contains an 'east Pennine' pebble assemblage. The clay till at Edenthorpe [SE 620 064] is shown by boreholes to pass locally down into clayey gravel up to 1.5 m thick, which rests on Sherwood Sandstone.

In view of their intimate association with clay till, and the latter's similar pebble composition, the four deposits of sand and gravel summarised above are believed to have formed directly from ice in situ at the same time as the clay till, the deposits near Kellington and at Edenthorpe as ground moraine and those on Brayton Barff and Hambleton Hough possibly as supraglacial ablation accumulations.

Fluvioglacial sand and gravel

The sedimentary features and compositions of some of the extensive sand and gravel capping the Snaith, Doncaster and Rossington ridges and adjacent hills, and also of two small sand and gravel outcrops east of the Trent, suggest a fluvioglacial origin, involving a considerable degree of meltwater transport. The deposits (shown as part of the Glacial Sand and Gravel on sheets 79 and 88) on the three western ridges comprise beds, lenses and layers of both pebble-free sand, and gravel with a sand matrix. They are well-bedded, with cross-bedding and cut-and-fill channel structures in places, and fairly well sorted, although cobbles and a few small boulders are present. Although resting mainly on Sherwood Sandstone, they transgress locally over clay till and glacial channel deposits. Some of the sand and gravel was subsequently reworked into lacustrine sand and gravel; in such places the fluvioglacial deposits can be differentiated only where the lower periglacial surface at its top, consisting of strongly developed cryoturbation structures and ventifacts, can be identified. Despite having the same ridge-top locations, sedimentary features and stratigraphical relationships, the various fluvioglacial deposits differ considerably in composition across the district.

The critical evidence on the origin of these sand and gravel deposits lies in the composition of those on the Rossington Ridge, which contain abundant 'Bunter' quartzite pebbles. The only possible source of these lies to the south, in the conglomeratic facies (formerly Bunter Pebble Beds) of the Sherwood Sandstone in Nottinghamshire and the northern Midlands. Moreover, the large size of some of these pebbles implies derivation from the coarser conglomerates in the middle and upper Trent Valley, and also transport over the northern watershed of this part of the valley. In the absence of accompanying pebbles of durable Jurassic rocks, the flint pebbles on the Rossington Ridge are unlikely to have come directly from the east, and the only other source lies to the south, in the 'chalky' glacial deposits or in the ice which formed these deposits, in the middle Trent Valley. Transport over the same watershed is again implied. The reddish brown 'clean' nature of the sand on the Rossington Ridge presumes a Sherwood Sandstone source, and in the absence of any trace of transport from the north, this also points to southerly derivation, as does the northward-dipping cross-bedding. In view of clay till mapped at lower elevations to the west and east of the Rossington Ridge, it appears that the ridge already existed as a rock-head feature when the sand and gravel were deposited on it. The only depositional environment that satisfactorily explains southerly derivation, transport over watersheds and emplacement on existing ridges is fluvioglacial, with meltwater flowing northwards from the northern Midlands, possibly in response to considerable isostatic depression to the north or north-east, along courses that were at least partly ice confined. Comparable southerly derived deposits occur south of the district, and remains of beetles in one such deposit [SK 652 908] near Scrooby indicate extremely cold continental conditions (Dr Maureen Girling, personal communication).

Although the sand and gravel on the Snaith and Doncaster ridges are superficially similar in pebble-erratic composition to the clay till and associated glacial deposits, they differ in the virtual absence of pebbles of Carboniferous limestone (as noted by Parsons (1878) with respect to the Snaith Ridge), chert, Permian limestone and igneous rocks; their constituents imply derivation from Coal Measures to the west rather than a trans-Pennine origin from the north-west. In view of their similar ridge-top locations and stratigraphical relationships to the sand and gravel on the Rossington Ridge, therefore, they are believed to have been deposited by eastward-flowing meltwater. A convergence of the northerly flow on the Rossington Ridge and the easterly flow on the Doncaster Ridge is suggested by the presence of 'Bunter' quartzite and flint pebbles on the eastern part of the latter ridge. The absence of Permian limestone pebbles in the fluvioglacial deposits on the Snaith and Doncaster ridges, except near Permian outcrops at Balby, may be due to flow via existing, but still ice-mantled, gaps through the Permian scarps at Ferrybridge and west of Balby.

In the sand and gravel on Hardwick Hill and Hornsey Hill, east of the Trent, the presence of 'Bunter' quartzite pebbles and of flint pebbles, and the scarcity of Jurassic pebbles despite proximity of Jurassic outcrops to the east, suggest a southerly derivation. Comparable deposits, forming terrace-like features, continue southwards on the eastern side of the Trent, and a partly fluvioglacial origin is also probable there.

The spreads of fluvioglacial sand and gravel are considerably more denuded than the older river gravel, for which there is fossil evidence of Ipswichian age (summarised below). They clearly predate formation of the lower periglacial surface, which is demonstrably of Devensian age. They can, therefore, be referred to a deglacial phase of a pre-Ipswichian glaciation. It seems likely that this was the same glaciation as that responsible for the clay till and associated glacial deposits, for otherwise a subsequent pre-Ipswichian cover of 'clean' ice which generated no deposits in situ would be required. The flint pebbles on the Rossington Ridge imply penecontemporaneity with the 'chalky' glaciation of the middle Trent Valley, and presumably a slightly earlier meltwater phase than that which cut the Trent 'trench' between Nottingham and Newark, and deposited the 'Hilton' gravels between Newark and Lincoln, which according to Straw (1963) may also have been due to partly ice-walled flowage. The age of this 'chalky' glaciation, however, other than being pre-Ipswichian, is as yet uncertain, although generally attributed to the Anglian Stage.

Details

In deposits on the Snaith Ridge the sand is yellowish brown, locally silty and less commonly clayey, and contains coal particles; the pebbles consist almost entirely of Carboniferous sandstone and associated rocks such as siltstone, ironstone and coal from the Coal Measures. Much of this deposit was subsequently reworked into lacustrine sand and gravel. Old pits [SE 570 247] north-west of Eggborough Power Station expose 2.4 m of severely cryoturbated sand and gravel. Similar strongly cryoturbated deposits are exposed in the Hensall–Great Heck area, for example at the top of old sandstone quarries [SE 5775 2313] where, beneath the cryoturbation, the deposit, up to 4.0 m thick, is partly level and partly cross-bedded. In a pit [SE 5948 2118] farther south-east, 1.2 m of severely cryoturbated sand and gravel with ventifacts at the top are overlain by lacustrine sand and gravel.

The composition of the fluvioglacial sand and gravel on the Doncaster Ridge is similar to that of the deposits on the Snaith Ridge, with two localised exceptions; they are the inclusion of a few Permian limestone pebbles at Balby, near to Permian outcrops, and the presence, from Wheatley Hills eastwards, of appreciable numbers of 'Bunter' quartzite pebbles and a few flint pebbles. Old records indicate up to 6 m of sand and gravel, some of it clayey, between Balby and the middle of Doncaster, and Corbett (1903) noted cross-bedded dips of up to 302 to the south-east. In the railway cutting [SE 5718 0223], Carboniferous sandstone boulders are present in 1.8 m of clayey sand and gravel above Sherwood Sandstone. Degraded old pits at Wheatley Hills suggest up to 4.5 m of sand and gravel, and a cleared section [SE 6024 0467] revealed well-bedded brown sand, rich in coal particles and containing gravel beds with some 'Bunter' quartzite pebbles. Around Armthorpe, Grace (1906) noted cross-bedded dips to the north-east and south, and Dalton (1943) noted ripple-bedding and southerly dipping cross-bedded fans in sand and gravel. Old pits [SE 614 047] and a railway cutting [SE 6145 0480] show the deposit to be severely cryoturbated and to contain 'Bunter' quartzite pebbles and a few flint pebbles. Markham Main Colliery No. 1 Shaft [SE 6168 0453] penetrated 7.1 m of sand and gravel.

In marked contrast to the deposits on the Snaith and Doncaster ridges, fluvioglacial sand and gravel on the Rossington Ridge, and outliers farther west such as that [SK 600 955] on the ridge south of Wellingley, consist of mainly reddish brown sand, which is largely devoid of silt and clay, and which contains no coal particles, and gravel predominantly comprising 'Bunter' quartzite pebbles, many of them quite large (up to 80 mm across), with a few pebbles of flint and Carboniferous sandstone. Some of this deposit was subsequently reworked into lacustrine sand and gravel. Severely cryoturbated sand and gravel rests on Sherwood Sandstone in old quarries [SE 613 008] at Bessacarr; Dalton (1941) noted well-bedded sand and gravel nearby. Old pits [SK 625 971] north of Hunster Grange also reveal strongly cryoturbated sand and gravel, and in a temporary excavation [SK 6258 9695] nearby, 1.8 m of cryoturbated sand and gravel were seen to be overlain by lacustrine sand and gravel. Similarly cryoturbated deposits, locally more than 3.7 m thick and containing flint pebbles, are exposed in old pits on Tickhill High Common, where one or more thin red clayey layers are present. An almost unique Acheulian ovate hand axe made from naturally perforated flint (Lacaille, 1944) was found in the processing plant at the now degraded pits [SK 635 976] east of Gravel Hill Plantation, but whether it came from below, within or on top of the deposit is unknown.

Numerous exposures along the eastern side of the Rossington Ridge from Bawtry Forest southwards to Austerfield (Plate 2) show up to 3.3 m of sand and gravel, generally cryoturbated near the top, which is strewn with ventifacts and widely overlain by lacustrine sand and gravel. Where not cryoturbated, the lower deposit is fairly well sorted, with distinct beds and lenses of pebble-free sand and of gravel; it is partly level-bedded and partly cross-bedded, with dips mainly to the north, and it contains some cut-and-fill channel structures. In some places it is impregnated with black manganese coatings on the sand grains and pebbles.

On the eastern edge of the district the sand and gravel deposits capping Hardwick Hill [SK 837 997] rest on Mercia Mudstone and contain 'Bunter' quartzite pebbles and pebbles of Carboniferous sandstone, skerry from the Mercia Mudstone, flint and chalk. In addition, Ussher (1890, p.137) noted quartz and liassic (? also Oolite) stones', and farther south-east, where the deposit continues along a ridge top, a boulder of 'green metamorphic rock'. Sand and gravel of similar composition, but with the addition of a rolled specimen of Gryphaea, form the nearby low mound of Hornsey Hill [SK 833 933], which protrudes through alluvium.

Ipswichian interglacial deposits

Deposits of Ipswichian age, the only interglacial deposits known in the district, consist of concealed fossiliferous sediments at Langham, fossiliferous deposits within older river gravel near Austerfield and near Armthorpe, and older river gravel generally.

Concealed fossiliferous deposits at Langham

Boreholes for the motorway interchange at Langham [SE 682 213], south of Rawcliffe, proved up to 5.5 m of interbedded clay, sand and well-sorted, fine to medium gravel containing plant debris, pollen and dinoflagellate cysts at depths between 6.3 m and 12.9 m below OD, as described elsewhere (Gaunt et al., 1974). Most of the pebbles in the gravel are of Carboniferous sandstone, and the sand contains abundant coal particles. These deposits rest on Sherwood Sandstone and are overlain by unfossiliferous, poorly sorted, coarse, cobbly gravel of uncertain age and origin, succeeded in turn by 25-Foot Drift.

The plant debris includes wood fragments, some of oak and pine; a fragment of the latter yielded an age greater than 42 200 radiocarbon years (Shotton and Williams, 1971). Other debris, mainly fruits and seeds, is from plants favouring damp woodland, grassland and open ground peripheral to ponds and streams, and also aquatic plants. More than half of the pollen is arboreal, principally oak and pine with variable amounts of hazel, some birch and locally some alder, indicating a temperate climate. Much of the non-tree pollen suggests freshwater and saltmarsh habitats, and the well-preserved nature of numerous colonies of the freshwater alga Pediastrum presumes minimal transport; however, the dinoflagellate cysts and some foraminiferal test linings imply an estuarine tidal reach.

The pollen correlates most closely with the beginning of Ipswichian Zone IIb and compares well with pollen of this age from Ilford (West et al., 1964) and Wretton (Sparks and West, 1970).

Adjacent rockhead configuration shows that the fossiliferous deposits at Langham are in an incised river course which, although destroyed elsewhere by subsequent deeper erosion in the Devensian, was in view of its location probably that of the Don. The depth of the incised course indicates a pre-existing sea level at or more than 13 m below OD and points to considerable glacioeustatic depression. However, the thickness of the fossiliferous deposits indicates a contemporaneous rise of sea level of several metres. Similar deeply buried fossiliferous deposits appear to be present elsewhere in and around the district. A borehole [SE 667 152] north-east of Fishlake proved 0.9 m of clay and peat at about 8 m below OD in sand and gravel, beneath 25-Foot Drift; a borehole [SE 7650 2595] at Skelton proved sandy clay at 9.9 m below OD containing peat and wood fragments which yielded an age of more than 42 200 radiocarbon years; and a borehole [SE 8488 3086] near Newport, just east of the district, proved 'dark brown to black organic silty clay' with 'some fibrous plant re mains' at about 10 m below OD in sand and gravel, beneath 25-Foot Drift.

Fossiliferous deposits near Austerfield

A bed of black organic silt up to 0.7 m thick containing plant debris, pollen and insect remains was formerly exposed at 3.4 m above OD within older river gravel resting on Sherwood Sandstone at a locality [SK 6664 9601] north of Austerfield, as described elsewhere (Gaunt et al., 1972). That part of the older river gravel above the organic silt is severely cryoturbated and is succeeded by 25-Foot Drift.

The plant debris includes wood fragments, one of which also yielded an age of more than 41 200 radiocarbon years (Callow et al., 1966). Other debris, mainly fruits and seeds, includes hornbeam and Viburnum, and plants favouring damp ground and freshwater habitats. Most of the pollen is arboreal, mainly alder with appreciable amounts of pine and hornbeam, indicating a temperate climate. The insect remains include species now restricted to southern Europe; they suggest that the climate may have been slightly warmer than at present.

Except for the alder, the pollen suggests an Ipswichian Zone III age, and compares well with pollen of this age from Histon Road, Cambridge ( Walker, 1953). The abundant alder, at one time thought to preclude an Ipswichian age, has now been found in other Ipswichian deposits (Beaumont et al., 1969; Sparks and West, 1970).

The organic silt evidently formed in a lake on a wide plain of fully permeable older river gravel and Sherwood Sandstone, so its level cannot have been much above regional drainage base level and, consequently, also close to contemporaneous sea level, which agrees well with the sea level of 0.9 m to 1.5 m above OD deduced from the Ipswichian cliff at Sewerby (Catt and Penny, 1966, p.385).

Another exposure [SK 6710 9718] of black organic silt, up to 0.8 m thick, was subsequently seen farther north within older river gravel with a cryoturbated top overlain by 25-Foot Drift; a fragment of wood from the deposit similarly gave an age of more than 47 570 radiocarbon years.

Pollen analysis, conducted by Dr Anne Bonny, shows a similar pattern to that from the more southerly site. Thermophilous trees and shrubs predominate. The high alder content suggests deposition on alder carr, but appreciable amounts of oak, pine, birch, hornbeam and hazel imply better-drained ground nearby. Much of the non-arboreal vegetation indicates damp or aquatic habitats and is compatible with alder carr deposition, but some taxa suggest open or grassland habitats and may be derived from river banks and bars. Several aspects of the pollen spectra, notably the high hornbeam content, indicate an Ipswichian age. Dr Bonny suggests also, on the relative proportions of hazel, oak, hornbeam and birch, that whereas the highest sample from the deposit, with a marked relative increase in hornbeam, implies Ipswichian Zone III, the three lower samples may be referable to Ipswichian Zone II. On this basis the lowest of the three samples from the more southerly site may also relate to Zone II, and the evidence of swamp and aquatic habitats at both sites implies that older river gravel deposition was reaching equilibrium with a stable drainage base level at about the Ipswichian zones II/III junction.

Fossiliferous deposits near Armthorpe

A borehole [SE 6334 0360] near Westfield Farm, south of Armthorpe, proved 1.8 m of silty clay containing unidentifiable plant debris, pollen and dinoflagellate cysts at 2.0 m above OD, within older river gravel, as described elsewhere (Gaunt et al., 1974).

Much of the pollen is arboreal, mainly pine with some oak and hornbeam, but pollen of open ground and salt-marsh plants is present also. The dinoflagellate cyst assemblage is similar to that from Langham, suggesting an estuarine tidal reach.

An age close to the Ipswichian zones III/IV boundary is suggested by the pollen, and the evidence of tidal deposition suggests a sea level at or just above OD.

Older river gravel

In the south-western part of the district fluvial deposits of sand and gravel form extensive flattish spreads, and also some terrace-like features, at up to 12 m above OD. These deposits consist of beds, lenses and layers of both pebble-free sand and well-sorted fine to medium gravel with a sand matrix, and they include level bedding and gentle cross-bedding, and also shallow cut-and-fill channel structures. They rest mainly on Sherwood Sandstone but transgress locally over clay till and glacial channel deposits. Their top, whether at outcrop or concealed beneath younger deposits, is commonly severely cryoturbated and (Plate 3) and (Plate 4) strewn with ventifacts, which together constitute the lower periglacial surface. There is a wide variation in the composition of the sand and gravel, as shown on (Figure 41); some aspects of this variation were noticed by Corbett (1903) and Dalton (1941).

The sedimentary structures in the sand and gravel suggest deposition in flowing water, presumably in rivers in view of the lack of any evidence of fluvioglacial transport; these deposits were therefore mapped as 'Older River Gravel'. Variations in composition show the more northerly deposits to have come from the west, presumably via the Don, and those in the south to have come from farther south, via the Idle and to a lesser extent the Torne. However, in both areas some localised reworking from pre-existing deposits with similar compositions may have occurred. A lack of valley confines, and deposition, some of it apparently in tidal reaches, little above contemporaneous sea level, allowed the rivers to change course considerably and produce extensive flattish flood-plains, locally supporting small lakes. The 'interglacial' age, suggested by the underlying glacial deposits and superimposed periglacial surface, is confirmed by the contained fossils from near Armthorpe and Austerfield, which indicate a contemporaneous temperate climate and an Ipswichian age sensu Mitchell et al. (1973).

Sand and gravel deposits apparently comparable to the older river gravel are present beneath 25-Foot Drift to the west of the district, where the River Aire enters the Vale of York near Knottingley. A trench crossing this area showed the sand and gravel to consist entirely of material from the Coal Measures and to have a ventifact-strewn top.

Details

In the deposits north, and around the eastern end, of the Doncaster Ridge the sand is yellowish brown, locally silty and clayey, and rich in coal particles; the pebbles are almost all of Carboniferous sandstone and associated rocks from the Coal Measures, and cross-bedding dips commonly include an easterly component. An eastward decrease in the amount of gravel and in the size of pebbles is also discernible. The most western patch [SE 055 018], though unexposed, forms a terrace-like spread on the northern side of the Don near Balby. In a trench across the outcrop [SE 604 060] north of Wheatley Hills, slightly silty and clayey sand were seen by G H Mitchell. Old pits between Kirk Sandall and Stainforth suggest thicknesses of at least 3 m in places, and 3.5 m of sand and gravel were proved in a borehole [SE 6306 0597] east of Edenthorpe. Thicknesses of 4.7 m were seen in old pits [SE 648 083] north of Dunsville, and of 8.4 m, consisting mainly of sand with few pebbles, in large pits [SE 654 075] to the south-east. Much of the 4.5 m visible in a pit [SE 668 085] north of West End also consists of pebble-poor sand. The most north-easterly exposure seen was in a pit [SE 693 100] in the lithologically distinct Devensian glacial sand and gravel forming the ridge on which Tudworth Hall stands; an excavation into the floor of this pit revealed sand and gravel consisting entirely of Carboniferous sandstone pebbles with ventifacts on the contact between the two deposits. The sand and gravel was formerly worked to depths of 3.7 m in places in the Holme Wood area [SE 650 050]. The deposit is virtually unexposed south of Armthorpe, where it is noticeably clayey at the surface and where a borehole proved a thin fossiliferous clay containing pollen which implies an Ipswichian age, as summarised above. A pit [SE 641 028] on the northern part of Cantley Common was the most southerly proving of appreciably clayey sand, rich in coal particles and containing pebbles almost entirely derived from the Coal Measures.

The sand and gravel in a belt of country approximately 3 km wide, which extends from the southern side of Doncaster eastwards through Cantley to Auckley Common and then northeastwards on the western side of Hatfield Moors, contains a mixed pebble assemblage; some pebbles are of Carboniferous sandstone and associated rocks, and some of 'Bunter' quartzite. A borehole [SE 5966 0306] on Doncaster Race Course, and temporary excavations nearby, prove more than 6.7 m of clayey and silty sand and gravel, including pebbles of Carboniferous sandstone and coal; 'Bunter' quartzite pebbles occur on the outcrop hereabouts. Old pits around Auckley suggest thicknesses of at least 2.4 m locally, and a southerly increase in the proportion of 'Bunter' quartzite pebbles is apparent in this area. Few clear exposures were seen-north-east of Auckley Common, but surface occurrences suggest an easterly increase in the proportion of 'Bunter' quartzite pebbles in this direction.

In the deposits farther south, stretching from Blaxton Common to Austerfield and including those north of Misson, the sand is mainly reddish brown with little or no silt, clay or coal particles; the gravel consists mainly of 'Bunter' quartzite pebbles with a few of Carboniferous sandstone and of flint, and cross-bedding dips commonly include a northward component. A northward decrease in the amount of gravel and in the size of pebbles is also discernible. Up to 5.8 m of sand with beds of fine gravel have been extensively worked between Blaxton Common and Finningley (Plate 3). Nearer to Austerfield, sand and fine to medium gravel, up to 5.0 m thick, was seen in many pits, and a bed of organic silt within the deposit yielded pollen implying an Ipswichian age, as summarised above. The deposit assumes a terrace-like form south of Austerfield as it approaches the confines of the Idle Valley farther south. Up to 1.8 m of sand and gravel were seen in pits north of Misson, and a borehole [SK 6854 9699] proved 2.4 m of the deposit.

The sand and gravel deposits described above continue eastwards in places beneath 25-Foot Drift, itself concealed beneath peat and alluvium, and they have been proved in numerous boreholes. They may reach almost to Westwoodside, near which a pit [SE 7409 0104] revealed gravel consisting of 'Bunter' quartzite pebbles with some of flint and Carboniferous sandstone, beneath blown sand.

The terrace-like sand and gravel deposits bordering Potteric Carr and the Torne Valley, west of the Rossington Ridge, have a similar composition to those east of the ridge in the Blaxton Common–Finningley area, except that the more westerly patches contain some pebbles of Permian limestone and are locally clayey. The railway cutting [SE 5991 0172] north-west of Bessacarr exposes 1.4 m of brown sand with numerous pebbles. A trench on the outcrop [SK 584 986] east of Loversall revealed up to 2 m of locally clayey sand and gravel, a ditch [SK 6223 9900] through the outcrop north-west of Rossington proved 2.7 m of sand and gravel, and ditches [SK 617 991] through the outcrop north of New Rossington provefi 1.8 m of sand and gravel. The outcrops farther south are unexposed.

Devensian deposits

The Devensian cold Stage started about 120 000 years ago, beyond the range of radiocarbon dating, and lasted by definition until 10 000 radiocarbon years ago (Mitchell et al., 1973, p.3). However, there is reason to believe that few, if any, of the Devensian deposits in the district, listed in (Figure 35), are older than about 18 000 radiocarbon years. During the long earlier part of the stage, the district experienced considerable fluvial incision and denudation, and also severe periglacial conditions.

Incision and denudation

Contours at and below OD on the base of the Devensian deposits, in effect mainly on the base of the 25-Foot Drift, reveal the former landscape (Figure 42). Wide mature valleys were cut down nearly to 20 m below OD, converging north-eastwards towards the Humber Gap; this indicates prolonged denudation coincident with river incision down to a sea level at least 20 m lower than it had been in the later part of the Ipswichian. The magnitude of that fall of sea level presumes a major eustatic response to renewed glaciation; therefore, this long phase of incision and denudation is included within the Devensian.

Periglacial phenomena

Four types of nondepositional evidence reflect the former existence of periglacial conditions in the district. They are cryoturbation structures, suspected alases, yentifacts and desert pavements. These phenomena are useful as stratigraphical as well as environmental indicators.

Cryoturbation structures are subsurface disruptions resulting from freezing and thawing of groundwater in what is called the active layer. To a certain extent they can form in seasonally frozen ground in which the active layer freezes in winter but the substratum remains unfrozen. Many structures, however, especially where developed in permeable strata, are indicative of perennially frozen ground, or permafrost, in which the active layer freezes and thaws with the seasons but the substratum remains permanently frozen. The most common cryoturbation structures in the district are involutions, which range from open folds to isoclinal folds, and clay-enriched lobate and flame-shaped structures, in which any contained pebbles are vertically aligned; some have been fractured in situ. Frost cracks, ice-wedge casts, superficial faults and stone stripes are also present.

Alases are wide, shallow, steep-sided, flat-bottomed depressions, commonly circular or oval in shape. They form where localised circumstances upset the thermal equilibrium of permafrost by reducing the insulating cover and deepening the active layer. They were first recognised in the Yakutian region of Russia (Soloviev, 1962; summarised by Washburn, 1973). For reasons given elsewhere (Gaunt, 1976a, pp.365–367), the almost circular West Moor depression [SE 650 060] cannot be regarded as a glacial, fluvial, tectonic, evaporite-subsidence or impact feature, or as a pingo (another type of permafrost depression); because it appears to be coeval with widespread cryoturbation and has the necessary form and suitable dimensions of an alas, it is tentatively interpreted as such. Other suspected alases in the district include the almost circular depression [SE 790 065] near Belton.

Ventifacts are stones, generally of large pebble size or bigger, that have been shaped at least partly by prolonged impact of wind-blown particles, normally sand grains. This action produces one or more flattish faces with sharp edges. If a ventifact consists of limestone or contains carbonate cement its faces may have a polished appearance. Characteristically three-faced ventifacts, called dreikanter, were first recognised in the district on Hambleton Hough, on the western part of the Snaith Ridge, and near Whitley by Edwards (1936). Ventifacts indicate aeolian conditions with little or no vegetation, and where formation in low-latitude hot deserts can be discounted, as in the British Quaternary, they imply dry periglacial conditions.

Desert pavement is a remnant accumulation of rock debris after lighter particles have been winnowed out by wind. Within the district it has developed mainly on various sand and gravel deposits and consists of an unsorted structureless pebble layer, up to 0.5 m thick, which conforms to the palaeotopographic surface. It is particularly recognisable where that erosional surface cuts down across underlying bedding structures, for the accompanying desert pavement also cuts down across the structures. Desert pavements commonly include ventifacts, and they have been used in Europe as stratigraphical markers (Van der Hammen et al., 1967; Paepe and Vanhoorne, 1967).

Cryoturbation structures, ventifacts and desert pavements indicate a former landscape that experienced periglacial conditions, i.e. a periglacial surface. Within the district, no evidence of such a surface has been found within any of the pre-Devensian deposits. However, a well-marked periglacial surface, which includes cryoturbation structures indicative of permafrost, is widely traceable across the top of these older deposits and also across outcrops of solid rocks. It is partly, even widely, conformable with the present ground surface, especially in elevated areas, and is therefore assumed to be relatively young. As it continues across the top of older river gravel, including those deposits near Austerfield and Armthorpe which yielded fossil evidence of Ipswichian age, it can be ascribed to the Devensian. Where Devensian glacial or lacustrine deposits occur, the periglacial surface in effect splits into two such surfaces, which are also widely traceable. The lower periglacial surface passes beneath such Devensian deposits, whereas the upper periglacial surface passes above the Devensian glacial, and at least some of the lacustrine, deposits.

Lower periglacial surface

The lower periglacial surface includes widespread evidence of permafrost, and in view of its stratigraphical position at the base of the Devensian deposits, this severe periglacial phase must have occurred at some time during the prolonged incision and denudation phase summarised above. The suspected alas at West Moor is also ascribed to this time, because it is cut through older river gravel but filled with Devensian lacustrine deposits. The lower periglacial surface has now been widely traced beyond the district, being represented by ventifacts beneath Devensian glacial deposits at Aldborough near Boroughbridge (Gaunt, 1970), near Allerton Mauleverer east of Knaresborough (Gaunt, 1976b), and at York (Gaunt, 1974); by ventifacts beneath Devensian terrace deposits in the Aire and Calder valleys (Edwards, 1936; Bisat, 1946); and by ice-wedge casts beneath Devensian lacustrine deposits near Darfield (Gaunt, 1976a, p.373). Some indication of the extreme severity of the climate at this approximate time is provided by insect remains from deposits in the Aire Valley (Gaunt et al., 1970).

Sand and gravel beneath 25-Foot Drift

Sand and gravel deposits are present in places beneath the 25-Foot Drift. In the southern part of the district most of these concealed deposits occur at shallow depth and are buried extensions of older river gravel, described above. Farther north, however, much of the concealed sand and gravel is at considerable depth and appears to lie on the former landscape surface shown on (Figure 42), and so is assumed to be of Devensian age. However, the vestigial Ipswichian fossiliferous deposits under Langham are obvious exceptions in this respect, and other localised patches of deeply concealed organic deposits may be also.

Details

In the area north of the Ouse, sand with pebbles, up to 2.4 m thick, is present beneath Newsholme; sand and gravel up to 3.3 m thick, the pebbles being mainly of flint and chalk with some of 'sandstone', occur at depth from Balkholme eastwards. These deposits may be of Devensian fluvial origin, formed by the rivers that incised the landscape shown on (Figure 42). However, the record of organic material within concealed sand and gravel in the borehole [SE 8488 3086] near Newport, just east of the district, and the peat and wood fragments more than 44 200 radiocarbon years old in the borehole [SE 7650 2595] at Skelton, suggest small relict patches of Ipswichian deposits comparable to those beneath Langham.

In the north-west, up to 8 m of clayey sand and gravel with cobbles are concealed under Burn Airfield [SE 600 280]. These deposits are not in one of the incised valleys shown in (Figure 42), but they do lie close to the conjectured maximum limit of Devensian ice and may be a concealed mass of Devensian glacial sand and gravel (summarised below). Elsewhere north of the Snaith Ridge only a few small patches of concealed sand and gravel up to 0.2 m thick have been proved.

The buried eastward extension of the Snaith Ridge runs under Rawcliffe Station towards Goole and carries a largely concealed mantle of sand and gravel up to 5 m thick, most of the pebbles being of Carboniferous sandstone. Some of these deposits may be pre-Devensian fluvioglacial sand and gravel, as on the ridge farther west. However, they include the 4.6 m of poorly sorted, coarse, cobbly gravel above the fossiliferous Ipswichian deposits at Langham, so some of them may be reworked sediments of later Ipswichian or early Devensian age.

Between the Snaith and Doncaster ridges only a few small and thin patches of concealed sand and gravel have been proved north of the River Went. Farther south, however, provings of such deposits over 3 m thick are widespread, the thickest being 9.4 m in a borehole [SE 5860 1615] near Fenwick. Most of the contained pebbles are apparently of Carboniferous sandstone, and coal pebbles and particles are also recorded. These deposits lie in the incised valley of the River Don (Figure 42) and so may be of Devensian fluvial origin, but the record of 0.9 m of clay and peat within concealed sand and gravel in a borehole ? c. [SE 667 152] north-east of Fishlake suggests a small patch of Ipswichian deposits, comparable to those beneath Langham.

A ridge of concealed sand and gravel, up to 10.4 m thick, runs parallel to and just east of the River Don between East Cowick and Thorne. The presence of pebbles of Permian limestone in the gravelly ridge, as recorded by Parsons (1878) and seen in motorway boreholes, its location as a northerly continuation of the deposits at Thorne, and its alignment across the incised valley of the Don, suggest strongly that it consists of Devensian glacial sand and gravel, as summarised below.

Farther east, only a few thin patches of sand and gravel have been proved beneath 25-Foot Drift, which is itself concealed beneath peat and alluvium, except in a belt running eastwards along the northern edge of Thorne Moors, where up to 10.7 m is proved, and passing to the north of Eastoft. This belt is virtually coincidental with the incised valley of the River Don (Figure 42), so the deposits in it are probably of Devensian fluvial origin. Discontinuous sand and gravel, locally up to 6.4 m thick, are present beneath 25-Foot Drift, itself concealed beneath alluvium, under parts of Hatfield Chase. Some of these deposits approximate to the incised valley of the River Idle, running north to the west of the Isle of Axholme, and so may be of Devensian fluvial origin. Some may be concealed extensions of Devensian glacial sand and gravel, and some may even be north-eastern continuations of older river gravel, comparable to those known farther south.

In the Trent Valley sand and gravel occur beneath 25-Foot Drift, the latter being concealed below alluvium and peat. The sand and gravel reaches depths greater than 15 m below OD in places, especially north of Keadby, and thicknesses of several metres have been proved, as reviewed by Gozzard and Price (1978), James (1976), Lovell (1977) and Thomas and Price (1979).

Head

Deposits of head accumulate by solifluction, the downs-lope movement of near-surface debris without the medium of water, ice or wind. This movement occurs most commonly as a result of freezing and thawing in periglacial conditions, although it can occur in warmer conditions where a slope becomes oversteepened or oversaturated. Head is generally a heterogenous deposit and, within the district, it varies from sandy clay to silty sand containing scattered to abundant pebbles and with little or no trace of sorting or bedding. Some of it mantles slopes, some occurs in the bottoms of shallow valleys and some has accumulated in shallow hollows. No thicknesses of more than 2.1 m have been proved.

Trenches on the slopes of Brayton Barff exposed up to 0.9 m of head varying from sandy clay to clayey sand, with pebbles, which passes up slope into slipped masses of pre-Devensian glacial deposits on the summit.

In the Doncaster area a hollow [SE 620 108] north of Barnby Dun and three others near Cantley contain silty sand with patches of sandy clay and a few pebbles; ventifacts occur on the surface, and the deposits near Cant-ley rest partly on older river gravel. The variably clayey and sandy head in shallow valleys between Barnby Dun and Dunsville, west of Hatfield Woodhouse, south of Armthorpe and on Twelve Months Carr to the south-west of Auckley, rests at least partly on older river gravel and has ventifacts on its surface; the patch south of Armthorpe appears to pass under 25-Foot Drift. Most of the patches of head in the Torne Valley and to the northwest of Austerfield are clayey, with localised silty sand and only a few pebbles. The long narrow stretch of head occupying the bottom of a shallow valley running northwards to Rossington, however, is mainly sandy and contains locally abundant pebbles; in several places it has become cemented by a hard ferruginous carbonate into a tough ferrocreted gravel.

The head occupying shallow valleys and hollows in the Isle of Axholme is mainly sandy and silty clay with few pebbles, but clayey sand occurs locally as pockets, lenses and basal layers. The deposit passes locally under blown sand.

In the absence of oversteepened or oversaturated slopes, the head in the district is presumed to be of periglacial origin, and as some of it rests on older river gravel it is attributed to the Devensian.

Glacial sand and gravel

Small outcrops of glacial sand and gravel, most of them occurring along a line running approximately south-eastwards across the district, have two distinguishing characteristics. The deposits contain pebbles consisting mainly of Carboniferous sandstone and Permian limestone, with a few of other Carboniferous rocks including limestone and chert, and rare Lake District rocks, and they lie between the lower and upper periglacial surfaces. They have been described elsewhere (Gaunt, 1976c) as 'Younger Glacial Sand and Gravel', and their distribution is shown on (Figure 43) as 'Glacial sand and gravel of Devensian age'. On the published sheets 79 and 88 they are grouped with other deposits in a broader category of 'Glacial Sand and Gravel'.

The non-local pebble content is broadly similar to the erratic pebble assemblages in the pre-Devensian glacial deposits, and suggests a similar provenance from the north-west. However, their stratigraphical position above older river gravel near Tudworth Hall, and between the lower and upper periglacial surfaces generally, implies a Devensian age. Fluvial or fluvioglacial transport is precluded by their topographical form and areal and altimetric distribution, so the sand and gravel can have been derived only from Devensian ice entering the district from farther north.

The deposits share their stratigraphical position between the two periglacial surfaces with the lacustrine sand and gravel which, as described below, were formed in and around Lake Humber when at its maximum level of about 30 m above OD in the late Devensian. It is, therefore, highly probable that the ice surged transiently into the lake and deposited sand and gravel, mainly along its western and southern edges, as it melted. This hypothesis explains the water-laid nature of the glacial sand and gravel, and the lack of associated till, except possibly the two small patches east of Belton. It also suggests that the ridge of sand and gravel up to 10.4 m thick and containing Permian limestone pebbles, which runs from East Cowick southwards to Thorne, concealed beneath 25-Foot Drift, forms part of the glacial sand and gravel, as may also the thick sand and gravel similarly concealed under Burn Airfield.

Details

Several small patches of sand with some gravel and scattered pebbles of both Carboniferous and Permian rocks, the latter noted by Parsons (1878), De Rance (1894), Sheppard (1915) and Melmore (1934, 1935), rest on Sherwood Sandstone near Brayton, to the south of Brayton Barff as far west as Lund House, and to the north of Burn. A trench [SE 5918 3155] north-west of Brayton revealed 1.2 m of these deposits, with upward-fining layers, beneath 25-Foot Drift. Another trench [SE 5831 3003] south of Brayton Barff, and old pits [SE 577 295] farther west, proved ventifacts at the base of these deposits, here 0.8 m thick. Ventifacts are present also on their outcrops, and in another trench [SE 5768 2884] south-east of Lund House the sand and gravel forming the southward-pointing ridge there, with its ventifact-strewn top, was seen to pass under 25-Foot Drift. Some of the sand and gravel around the southern side of Hensall, on the Snaith Ridge, contains abundant pebbles of Permian limestone as well as of Carboniferous rocks, as noted by Parsons (1878), de Rance (1894) and Kendall and Wroot (1924, pp.481, 689). In an old pit [SE 585 230] these deposits, 2.7 m thick, are partly level-bedded and partly cross-bedded, but they also include some unstratified and poorly sorted gravel. Ventifacts were found at the base of these deposits, which rest on Sherwood Sandstone, and cryoturbation structures intrude down from their top. Ventifacts occur on the outcrops of these deposits too. In another pit, [SE 594 229] south-east of Hensall, the north-western face contains 7.3 m of sand and gravel containing abundant pebbles of Permian limestone; here also there is evidence of level-bedding, of cross-bedding with mainly south-eastward dips up to 30°, of unstratified gravel, and of ventifacts at the base resting on Sherwood Sandstone. The deposit continues north-eastwards as low ridges [SE 600 231]; [SE 607 233] protruding through 25-Foot Drift.

The sand and gravel ridge at Thorne contains pebbles of Carboniferous rocks and Permian limestone, while pebbles of rocks from the Lake District, presumably igneous, are recorded on the primary geological field maps from an old pit [SE 6902 1335]. An excavation [SE 6913 1241] proved 1.8 m of these deposits. Ventifacts occur on their outcrop, and boreholes show that they rest on Sherwood Sandstone, as also does the small patch of similar deposits on Bradholme Hill [SE 691 115] to the south. Farther east, a small mound of sand containing abundant pebbles of Carboniferous rocks (including limestone) and Permian limestone, and a few pebbles of quartz and igneous rocks, with ventifacts on its surface, protrudes through blown sand [SE 7275 1342] on the southern edge of Thorne Moors.

A similar pebble assemblage, mainly of Carbonferous sandstone and Permian limestone, is present in the sand, with thin fine gravel, forming the ridge [SE 693 103] south of Tudworth Hall. A pit [SE 693 100] exposed 5.2 m of these deposits, which are partly level-bedded and partly cross-bedded, and which contain some ripple-bedding; cryoturbation structures intrude down from their top, which is strewn with ventifacts. Excavation into the floor of this pit proved ventifacts also at the base of the deposits, which here rest on older river gravel.

The presence of Permian limestone pebbles in the sand and gravel ridge under Lindholme Hall [SE 7082 0630] was noted by Read (1858) and Harmer (1928); the latter quotes an 1888 British Association report referring to 'specimens of Hall'aflinta, porphyry, basalt' there also. An old pit [SE 7079 0615] exposed 2.7 m of unsorted and poorly stratified gravel interbedded with lenses of fine gravel containing upward-fining layers and beds of sand, without reaching the base of the deposit.

The Permian limestone pebbles included in the sand and gravel at Wroot were recorded by early workers (Peck, 1815; Read, 1858), and Corbett (1903) refers to large boulders in the deposit. In addition to the abundant Carboniferous sandstone and Permian limestone pebbles, a few 'Bunter' quartzite pebbles and pebbles of Carboniferous limestone, chert, Jurassic oolite, ?chalk, flint, igneous rocks and Brockram were found. A trench south of Wroot showed sand with scattered pebbles and interbedded fine to medium gravel, with cryoturbation structures near the top; the base of the deposit was not proved.

Peck (1815) and Read (1858) also noted the Permian limestone pebbles in the somewhat clayey sand and gravel at High Burnham [SE 784 012], which rests on Mercia Mudstone at just over 30 m above OD, the highest part of the Isle of Axholme. Cameron (in Ussher, 1890, p.141) noted fragments of igneous rocks here, and pebbles of skerry from the Mercia Mudstone are present in the deposit, which is locally reputed to be at least 1.8 m thick.

Several minute sand and gravel patches rest on Mercia Mudstone farther north on the Isle of Axholme, notably [SE 781 051] north of Epworth, [SE 796 066]; [SE 793 059] east of Belton and [SE 782 127] east of Crowle, some being noted by Parsons (1878) and Cameron (in Ussher, 1890, p.141). Most of the contained pebbles are of skerry, but Carboniferous sandstone, limestone and coal, Permian limestone, quartz and igneous rocks are present also. Ventifacts occur on the surface of the deposits.

Lacustrine sand and gravel

Certain sand and gravel deposits have compositions closely comparable to those of subjacent pre-existing Quaternary deposits and/or solid rocks. Most of them lie along slopes at up to 27 m above OD and, where exposures permit, they are seen to occur between the lower and upper periglacial surfaces. Some of these deposits near Hambleton Hough, Brayton Barff, Eggborough and Askern were included by Edwards (1937) in his '100-Foot Strandline' around the Vale of York. Their distribution is shown on (Figure 43). On the published sheets 79 and 88 they are included with other deposits in the 'Glacial Sand and Gravel' category.

These deposits indicate an origin by reworking of pre-existing drift deposits and/or solid rock debris virtually in situ, with no input of sediment from outside the immediate locality. The lack of any evidence of transport implies littoral depositional conditions, a conclusion enhanced by the good degree of bedding and sorting in the deposits. A water level of at least 27 m above OD is required for littoral deposition, but comparable deposits to the west and east of the district occur at up to 30 m above OD, and they rise higher to the north. The deposits are attributed to the Devensian, on the basis of their strati-graphical position between the lower and upper periglacial surfaces. This age is further refined by the date of 21 835 ± 1660 radiocarbon years from a bone fragment found either at the base of, or within, comparable deposits near Brantingham, just east of the district (Gaunt, 1974). However, during the Devensian, especially its later part, sea level was well below OD; hence the high water level in which the deposits formed cannot have been marine and must have been lacustrine, which implies a high-level phase of Lake Humber, impounded by glacial damming of the Humber Gap by ice from the North Sea (Gaunt et al., 1992, pp.109, 121). The patchy distribution of the deposits suggests that the high-level phase of Lake Humber was of short duration. As the deposits do not transgress over the 25-Foot Drift, which was laid down mainly in the longer lasting, low-level lacustrine phase (see below), the high-level phase probably occurred shortly after initiation of the lake. The northerly increase in maximum height of the deposits suggests contemporaneous isostatic depression in that direction. Comparable deposits to the west include the '100-Foot Strandline' of Edwards (1937); to the east they form part of the 'Vale of York Glacial Lake Deposits' (Gaunt et al., 1992, pp.120–123) and to the north they are shown as 'Older Littoral Sand and Gravel' on the Selby (71) Geological Sheet.

Details

Patches of reddish brown sand with scattered pebbles, almost all of Carboniferous sandstone, rest on Sherwood Sandstone at up to 24 m above OD on the higher eastern and western slopes of Brayton Barff, around Hambleton Hough, between these hills and, just to the south, from Lund House westwards and southwards to Gateforth. Ventifacts were seen at the base of these deposits in two old pits [SE 5690 2946]; [SE 5556 2995], and they are also strewn on top of them. Similar deposits rest on Sherwood Sandstone [SE 652 252] south of Camblesforth and also east of Carlton. An excavation near Carlton revealed 1.2 m of level-bedded sand containing ripple structures and with ventifacts at the base; ventifacts also occur on top of the deposits.

A considerable amount of the sand and gravel on the Snaith Ridge rests, with ventifacts at the base, on the cryoturbated top of either pre-Ipswichian fluvioglacial sand and gravel or Sherwood Sandstone. Unless evidence of the lower periglacial surface is available, the two sand and gravel deposits, which have identical pebble compositions, cannot be differentiated. The younger (lacustrine) deposit is well sorted and well bedded, with low-angle cross-bedding; upward-fining layers and ripple structures occur in places, and where the deposit rests directly on Sherwood Sandstone it generally comprises reddish brown sand with little or no gravel. It reaches nearly 5 m in thickness, and in places occurs at heights up to 18 m above OD, the highest level of the Snaith Ridge. Its top is strewn with ventifacts and locally intruded by cryoturbation structures. The deposit was widely proved between ventifact layers in the trench south-west of Kellington and in the railway cutting to Eggborough Power Station (Figure 43); also in two pits [SE 5635 2329]; [SE 5666 2279] near Low Eggborough, where it rests on Sherwood Sandstone. It occurs extensively around Hensall, where it also rests on Sherwood Sandstone, and was proved between ventifact layers in several pits e.g. [SE 598 235]. Up to 4.3 m of the deposit, consisting of well-bedded sand and fine to medium gravel, with low-angle cross-bedding and upward-fining gravel layers, ventifacts at the base and top, and cryoturbation structures intruding down from the top, form the south-eastern face of the pit [SE 594 229] south-east of Hensall; the north-western face comprises Devensian glacial sand and gravel rich in Permian limestone pebbles. The contact between the two deposits was not exposed, but digging at the north-eastern corner of the pit suggested that the lacustrine sand and gravel oversteps glacial sand and gravel.

The lacustrine deposit, with its pebble assemblage of mainly Carboniferous sandstone and associated rocks, was proved between the lower and upper periglacial surfaces at a number of other localities. Several pits around High Eggborough show it to be up to 4.0 m thick, resting on Sherwood Sandstone; in a pit north of Great Heck [SE 5948 2118] it rests on severely cryoturbated pre-Ipswichian fluvioglacial sand and gravel, and traces of stone stripes were seen on its surface there. In another pit, at Pollington [SE 612 201] (Plate 5), both the underlying top of the Sherwood Sandstone and the top of the lacustrine sand and gravel are ventifact-strewn, the latter also being cryoturbated, with traces of stone stripes on its surface. However, due to poor exposure and consequent lack of evidence for the lower periglacial surface, it is not known how much of the sand and gravel on the Snaith Ridge farther east is of original pre-Ipswichian fluvioglacial origin and how much has been reworked.

To the west, much of the sand and gravel near Whitley rests, with ventifacts at the base, on locally cryoturbated Sherwood Sandstone, as seen in several pits e.g. [SE 566 220]; c.[SE 556 208] (Plate 6); the deposit, up to 4.4 m thick, has ventifacts on its surface also.

The sand and gravel deposits at Askern consist of angular to subrounded pebbles of Permian limestone in a grey, coarse-grained silt matrix, and they occur at heights up to 27 m above OD. A thickness of 1.5 m rests on Upper Magnesian Limestone in a quarry [SE 5587 1304], and up to 1.8 m was previously recorded nearby [SE 5598 1324].

A narrow strip of sand and gravel rests on Upper Magnesian Limestone at Newton, south of Bentley; an exposure [SE 5556 0265] reveals 3.0 m of interbedded sand, micaceous silt and gravel consisting mainly of pebbles of Permian limestone but with some of Carboniferous rocks, and containing upward-fining layers. Lateral passage into a more clayey matrix was seen a few metres to the south-west. Farther in this direction there are two small patches of sand and gravel resting on Middle Marl; although unexposed, they have similar pebble assemblages on their outcrops. Excavations [SE 5466 0153] just west of this part of the district exposed 7.6 m of roughly graded, cross-bedded gravel consisting of pebbles and subrounded slabs of Permian limestone banked against and partly resting on Lower Magnesian Limestone at up to about 23 m above OD. The gravel rests partly on silt which, with some underlying sand and gravel, was shown by boreholes to extend to about 2 m below OD.

Boreholes north of Loversall proved up to 3.2 m of silty and clayey sand containing gravel consisting of Permian limestone pebbles, resting on Upper Magnesian Limestone at 14.3 to 17.5 m OD on the highest ground there. Farther south, an excavation into a small patch of sand and gravel [SK 589 959] south-west of Wellingley showed the gravel to consist mainly of Permian limestone pebbles.

A temporary excavation [SK 6258 9695] on the western side of the Rossington Ridge, north-east of Hunster Grange, revealed 0.9 m of well-bedded sand and gravel consisting almost entirely of 'Bunter' quartzite pebbles and resting, at about 26 m above OD, on the top of pre-Ipswichian fluvioglacial sand and gravel with an identical pebble composition. Lack of exposure precluded an assessment of the extent of the upper deposit, but it may be widespread in view of the situation on the eastern side of the ridge. Extensive gravel workings there show that a well-bedded deposit of sand, containing well-sorted fine to medium gravel beds, as well as lenses and layers consisting mainly of 'Bunter' quartzite pebbles, rests on the ventifact-strewn and strongly cryoturbated top of pre-Ipswichian fluvioglacial sand and gravel, and shows the same pebble composition from Bawtry Forest southwards to Austerfield. The upper deposit contains low-angle cross-bedding and some upward-fining layers, and its top is slightly cryoturbated in places and strewn with ventifacts. It is up to 3.0 m thick and, prior to extensive gravel working, was seen to form up to three parallel ridges of terrace-like features running along the eastern slope of the ridge at between about 15 and 25 m OD.

In the Isle of Axholme an excavation [SE 7808 0365] near Epworth through 0.5 m of blown sand at about 15 m OD revealed 0.3 m of level-bedded gravel consisting of pebbles of skerry in a sand matrix, with some upward-fining layers.

25-Foot Drift

The name 25-Foot Drift was given in districts to the west (Edwards et al., 1940, 1950; Mitchell et al., 1947) to the vast expanse of bedded clay and sand which forms most of the flat plain of the southern part of the Vale of York and which lies at an average height of about 25 feet (7.6m) OD. These deposits fill and conceal the valleys in the former landscape shown on (Figure 42) and they occur above the lower periglacial surface; thus they cannot be older than Devensian. Their maximum extent is shown on (Figure 43). Most of the 25-Foot Drift consists of laminated clay comprising the silt and clay subdivision shown on the geological maps. The sand subdivision consists of deposits below, flanking and overlying the silt and clay, and for both descriptive and interpretative purposes they are summarised separately as lower, marginal and upper sand respectively.

Lower sand

The lower part of the 25-Foot Drift consists in most places of sand which rests, demonstrably with the lower periglacial surface beneath it in some localities, variously on solid rock, pre-Ipswichian glacial deposits, older river gravel or concealed sand and gravel, and locally on Devensian glacial sand and gravel. Most of this lower sand is fine-grained and it is commonly silty and clayey, with locally abundant coal particles. Laminae and thin beds and lenses of clay are present in places, and there is local evidence of passage by alternation into the overlying silt and clay. On the peripheral slopes of older deposits and/or solid rock the lower sand passes obliquely up into marginal sand. Thicknesses up to almost 10 m are recorded, but generally the lower sand is not more than 5 m thick, although appreciable local variations in thickness are known in several places.

The lower sand, although undoubtedly of Devensian age in view of its position above the former landscape shown on (Figure 42) and above the lower periglacial surface, may have more than one mode of origin. Some of it may be of aeolian origin, because of its location on the ventifact-strewn lower periglacial surface and its marked local thickness variations, which are suggestive of dunes. However, because of its commonly silty and locally clayey nature, inclusion of thin clay layers and evidence of upward passage by alternation into the lacustrine silt and clay summarised below, the lower sand is thought to be largely, if not entirely, of lacustrine origin, and to have accumulated during the initial development of Lake Humber, possibly by reworking of pre-existing sandy deposits. Some of the isolated pebbles and boulders in the lower sand may be 'drop stones' from floating ice.

Details

In the area north of the Ouse up to 5.0 m of lower sand are present, the deposit being generally thicker towards the east and apparently very thin or absent in a few places west of Howden. Thickness variations from 0 to 3.2 m across less than 1 km occur near Barnby on the Marsh. Some boreholes indicate passage by alternation into the overlying silt and clay. The sand is variously described as fine to medium grained, silty and micaceous, and references to black colour may denote coal particles. Farther west, between the Ouse and the Snaith Ridge, the lower sand is generally less than 4 m thick, but increases locally almost to 8 m. There are considerable local thickness variations, for example from 1 to 4 m in less than 0.5 km at Drax Power Station [SE 663 270] and from 1.8 to 7.6 m in two boreholes only 240 m apart at Drax. Most descriptions refer to fine-grained variably silty sand with coal particles in places, and laminae and thin beds of clay are evident in some boreholes. Between Brayton and Rawcliffe sporadic pebbles are recorded in the sand, and a boulder 1 m across was proved at Drax Power Station.

Between the Snaith and Doncaster ridges the lower sand is generally less than 3 m thick, except towards the south-west. A borehole [SE 6194 1379] near Kirkhouse Green proved 6.6 m, and from here to Bentley, where up to 5.2 m are present, the thicknesses are substantial. The deposit includes coal particles, and references to thin clay within the sand are not uncommon in this area. Just beyond the district to the north-west, a trench crossing Gale Common [SE 535 215] proved ventifacts at the base of the lower sand. Farther east, the lower sand varies from 0 to 5 m thick over the concealed sand and gravel ridge of presumed Devensian glacial origin, between East Cowick and Thorne. It is up to 9.8 m thick in a borehole [SE 7356 2112] near Goolefields, north of Thorne Moors, and considerable thickness variations over short distances are particularly noticeable in this area. Under Thorne Moors there is a generalised southward thickening from 3 to 6 m and also an eastward thickening towards the eastern edge, culminating in 8.8 m in a borehole [SE 7617 1585] on the north-eastern corner of Crowle Moors.

Where 25-Foot Drift occurs east of Doncaster, the lower sand is generally present, although thin. Under West Moor it is up to 2 m thick and fine-grained, and contains thin clay beds. From Doncaster Race Course to Cantley Common it ranges from less than 1 m to more than 4 m thick, and is clayey in places, but farther north-east it is generally thin. An excavation [SE 6552 0458] south of Holme Wood revealed only 0.2 m of lower sand, here rich in coal particles and resting on strongly cryoturbated older river gravel. It is seen to be reddish brown in deep ditches in the area [SE 670 015] east of Auckley Common. The peat and alluvium under Potteric Carr rest on clay which may be 25-Foot Drift, and which in places rests in turn on variably silty and clayey sand, locally with a few pebbles, up to 2.2 m thick. The lower sand which almost fills the channel incised into older river gravel north-east of Austerfield is up to 3 m thick and has been seen in several pits to be thinly level bedded and even laminated in places, with some ripple structures and upward-fining layers. It contains laminae and thin beds and lenses of grey, locally laminated clay, and also a few small pebbles on certain layers, and it rests on the ventifactstrewn cryoturbated top of the older river gravel. Similar but thinner lower sand is proved in boreholes and ditches north and east of Misson. Lower sand is thought to be present in the area stretching from Hatfield Chase southwards to Misterton Carr, but the number of boreholes which differentiate the deposit from the concealed sand and gravel beneath is insufficient to provide a quantitative assessment. In the Isle of Axholme up to 0.2 m of sand occurs impersistently at the base of the three patches of 25-Foot Drift near Belton. Lower sand is thought to be present also in the Trent Valley to the east, but it is difficult in boreholes to distinguish from the underlying sand and gravel.

Silt and clay

The silt and clay subdivision of the 25-Foot Drift consists mainly of bluish grey to reddish brown laminated clay. Most of the laminae are closely spaced, some at little more than 1 mm intervals, and they consist largely of silt and fine-grained sand, commonly containing coal particles and locally exhibiting ripple-bedding, and varying from grey to reddish brown in colour. The clay also contains a few thin beds and lenses of silty sand, some with low-angle cross-bedding and, in places, ripple structures, generally near the base and top of the sequence. Although virtually stoneless, sporadic pebbles, cobbles and even small boulders, probably 'drop stones', have been found in it. The clay rests mainly on lower sand, and where it thins towards a containing slope of older deposits and/or solid rocks it passes in most areas into marginal sand, described below. It is up to 20 m thick, being thickest over the most deeply incised parts of the buried landscape shown on (Figure 42). At the surface it forms an almost flat, monotonous plain which does not exceed 8 m above OD within the district, although it rises imperceptibly farther north. Several aspects of the clay in the northern part of the district were noted by Parsons (1878).

To the east of the district the clay interdigitates with those late Devensian glacial deposits in the Humber Gap which, possibly initially with their parent ice, impounded Lake Humber (Gaunt et al., 1992, pp.118–122). It has a similar relationship with the York and Escrick morainic deposits to the north, for although its upper part thins out against these deposits, there is unpublished evidence that the lower part of the clay passes under them.

A minimum age for the clay within the district is provided by a date of 11 100 ± 200 radiocarbon years from a soil developed on the clay at West Moor (Gaunt et al., 1971). The silt and clay subdivision of the 25-Foot Drift can, therefore, be attributed entirely to the late Devensian. With depositional levels up to 8 m above OD, such an age precludes a marine origin, and as the persistently and evenly laminated nature of the deposit and its other sedimentary features imply quiescent deposition in standing water, a lacustrine origin in Lake Humber is indicated. The upper limit of 8 m above OD of the clay suggests a lake level not much above this height, but it is possible that the lowest part of the clay, and the lacustrine part of the underlying lower sand, are coeval with the lacustrine sand and gravel formed around the edges of the lake during its conjectured initial high-level phase. A subsequent, longer, low-level lacustrine phase may, therefore, be envisaged. The occurrence of subaerial brecciation at 4 m below OD in a borehole north-west of Carlton suggests that between these two phases the lake level may have dropped to more than 4 m below OD. Further evidence of this drop is provided by apparent intraformational cryoturbation structures in marginal lacustrine deposits east of the district near South Cave (Gaunt et al., 1992, p.122), and is indirectly suggested by ventifacts on the top of Devensian glacial sand and gravel and below marginal sand, south-east of Lund House. The possibility of temporary leakage through the glacial blockage of the Humber Gap, which could have produced such a drop in lake level, is suggested by certain aspects of fluvioglacial and lacustrine deposits east of the gap (Gaunt et al., 1992, pp.117–123). A drop in lake level at this time is also suggested by evidence from Holderness (footnote, p.130).

Details

In the area north of the River Ouse laminated clay was seen in several pits. At one [SE 6755 3140], east of Cliffe, the 4.1 m exposed becomes more sandy near the top, and is overlain by upper sand. At another [SE 7864 2997], near Eastrington, in which some 8 m of laminated clay were worked, G H Rhys recorded thin beds of silt and of sand containing coal particles, which accentuate small-scale cross bedding, near the top of the sequence, and traces of contortions in a 1.5 m sequence of reddish brown clay between 2.5 and 4 m below the surface; a few scattered pebbles and small boulders, one of the latter of Carboniferous limestone, were noted. Similar isolated pebbles and boulders, contorted layers and thin silt and sand beds near the top were seen in 9.4 m of laminated clay in a pit [SE 8396 3017] near Gilberdyke. Boreholes prove thicknesses of up to 19.8 m near Hemingbrough, only 11 to 14 m between Howden and Balkholme, but up to 16.5 m farther east.

To the west, between the River Ouse and the Snaith Ridge, the only pit into laminated clay is one [SE 614 307] near Brayton, where 7.6 m of the deposit were seen; a grooved boulder of Carboniferous limestone, 0.6 m across, is said to have been found in the pit. However, a trench running south-west to West Haddlesey extensively exposed the laminated clay to depths of 3.4 m, revealing rippled laminae of red sand near the northern end [SE 575 286] and increasingly silty and sandy clay near the surface generally. Boreholes show that thicknesses increase eastwards from up to 11.9 m south of Gateforth to 17.4 m south-east of Burn Airfield, and then north-eastwards to 19.8 m in Barlow No.2 Borehole. A recent carefully cored borehole [SE 6382 2416] north-west of Carlton revealed intraformational brecciation, suggesting desiccation and/or ice-wedge structures, in the laminated clay at 4.0 m below OD.

Between the Snaith and Doncaster ridges the laminated clay was seen only in ditches and a few shallow excavations, and in some of these the near-surface deposit was observed to be slightly sandy and/or to contain thin sand beds. Thicknesses up to 12 m are recorded north of the River Went, but the laminated clay thins appreciably to the south-west where it rests on thick lower sand and thick underlying sand and gravel. Foster-houses Borehole in the south-east recorded 18.6 m of clay, but nearby boreholes prove only 6 to 11 m. The laminated clay continues eastwards beneath alluvium and peat almost to the Trent. It is up to 13 m thick in places, but thicknesses vary considerably, due to basal irregularities on the top of the underlying deposits and the former landscape (Figure 42), and also to the fact that the top of the laminated clay was itself subsequently subject to deep fluvial incision in places.

To the east of Doncaster the laminated clay on West Moor is up to 1.8 m thick, possibly thicker in places, but from Doncaster Race Course north-eastwards towards Hatfield Woodhouse no more than 2.2 m have been proved and the deposit is locally quite sandy. Ditches prove up to 1.5 m of clay east of Auckley Common. On Potteric Carr alluvium and peat rest on locally sandy clay, with interbedded sand in places, which could be deeper alluvium but is thought to be equivalent to the silt and clay subdivision of the 25-Foot Drift. The deposit is up to 4.5 m thick west of New Rossington.

The clay at the surface in the channel running north-eastwards from Austerfield thickens in this direction from 0.6 to 1.8 m, but the comparable clay north of Misson thickens eastwards to 4.4 m of reddish brown to grey laminated clay with some interbedded sand. The deposit is present under much of the alluvium and peat from Hatfield Chase southwards to Misterton Carr. Although in these areas a southerly thinning from 8.5 m is apparent, thicknesses vary considerably, for the same reasons as those north-east of Thorne. The clay cropping out near Belton, in the Isle of Axholme, is up to 1.0 m thick. Laminated clay underlies the alluvium and peat in places in the Trent Valley, although here also thicknesses vary considerably, the thickest proving being nearly 6 m [SE 810 050] south of Beltoft.

Marginal sand

The sand cropping out marginal to the silt and clay described above rests on and thins out against peripheral slopes of pre-existing deposits and/or solid rock which in many places are strewn with ventifacts and cryoturbated, and it passes obliquely down against this containing slope into the lower sand of the 25-Foot Drift. Away from the containing slope the marginal sand passes laterally into the adjacent laminated clay, partly by gradation but largely by interdigitation, and several exposures revealed a simple arrangement in which the clay thins out in a single wedge within the sand. The sand is fine to, rarely, medium grained, commonly silty and locally clayey, with abundant coal particles in some areas and with a few small pebbles near especially pebbly containing slopes. It is well bedded, much of it level bedded, but low-angle cross-bedding and ripple-bedding are not uncommon. In most places the sand is not more than 3 m thick and it generally rises about 1 m above the level of the adjacent laminated clay, not occurring much higher than 9 m above OD in the district but rising, with the clay, to higher elevations farther north.

From its relationship to the silt and clay subdivision of the 25-Foot Drift the marginal sand is clearly a littoral facies of the latter, formed in quiescent lacustrine depositional conditions around the edge of Lake Humber wherever sand was available for reworking and when the level of the lake did not greatly exceed 9 m OD, i.e. during the low-level lacustrine phase. The northerly increasing height of both the marginal sand and the silt and clay beyond the district suggests contemporaneous isostatic depression in that direction.

Details

The sand fringing most of the Sherwood Sandstone hill on which Brayton Baiff and Hambleton Hough are situated, and also that west of Burn, is at least 2 m thick in places, and both north-west of Brayton and south-east of Lund House it rests on Devensian glacial sand and gravel, with ventifacts at the contact at the latter locality. To the south-east of Brayton the marginal sand merges with extensive upper sand.

The marginal sand around the Sherwood Sandstone outcrops on which Camblesforth and Carlton are situated is seen in ditches to be up to 1 m thick. Here also there is some merging with upper sand, especially to the west.

The marginal sand flanking the Snaith Ridge and the Sherwood Sandstone outcrop at Whitley, although discontinuous, is locally quite thick. A trench [SE 5810 2481] north of Eggborough Power Station revealed 0.5 m of red-brown laminated clay thinning towards the ridge, lying within the lower part of 3.6 m of partly cross-bedded sand containing abundant coal particles and resting, with ventifacts at the base, on Sherwood Sandstone. A similar sequence, but thinner, was seen in an excavation [SE 6523 2139] at West Cowick. It may be mentioned here that the two low ridges of sand with scattered pebbles curving south from West Cowick are neither pre-Devensian fluvioglacial nor Devensian lacustrine sand and gravel, for boreholes have shown some of the 25-Foot Drift silt and clay to pass under them. They appear to have formed from material locally swept off the adjacent part of the ridge towards the end of deposition in Lake Humber, but their origin is otherwise obscure. The marginal sand south of Great Heck and at Whitley was seen in excavations to be at least 1.2 m and 1.7 m thick respectively.

No marginal sand crops out at Askern or Owston, a common situation where 25-Foot Drift thins out against sand-free Permian rocks. Its absence at Thorne, where it would be expected, may be due to lack of evidence of differentiation from the Devensian glacial sand and gravel, especially in built-up areas with no exposure.

In the area east of Doncaster up to 3.9 m of silty sand containing thin silty clay beds flank the laminated clay at West Moor. Sand fringes much of the long, narrow 25-Foot Drift outcrop running from Doncaster Race Course north-eastwards past Hatfield Woodhouse, and it extends well over the adjacent laminated clay in several places, but thicknesses appear to be less than 1 m, except from Huggin Carr north-eastwards, where up to 1.5 m are proved locally. Small patches of sand bordering laminated clay farther south, for example in the 25-Foot Drift-filled channel north-east of Austerfield, are not more than 0.6m thick.

Upper sand

The sand resting on the silt and clay of the 25-Foot Drift is generally not more than 2.5 m thick and is discontinuous, forming low ridges and mounds that in many areas have a linear distribution (Figure 44). It is fine-grained, increasingly silty and clayey towards the edges of the ridges and mounds, and contains thin beds and lenses of clay, notably towards the base, where an interbedded passage from the underlying laminated clay has been seen in places, and locally near the top. In some areas the sand contains coal particles. Incipient dunes show that some of the sand has been subject to wind action.

Although evidence of interbedded passage up from the lacustrine clay suggests near-continuity of deposition, the impersistent and localised distribution of the upper sand is not indicative of a lacustrine origin, even as a regressive shoreline deposit, because its distribution is not arranged in any way concentrically relative to the shorelines indicated by the marginal sand. On the contrary, the distribution forms a radial pattern converging eastwards towards the Humber Gap. This fact, and the flanking position of much of the upper sand adjacent to present rivers, suggest that the deposit formed as levees when, immediately after Lake Humber disappeared, rivers initiated courses across the emergent clay plain.

The courses of most of the old rivers can be recognised from their levees of upper sand (Figure 44). That of the River Foulness crossed the north-eastern corner of the district in a south-easterly direction, being joined near Sandholme by a river flowing east between Porting-ton and Eastrington, which was presumably the Derwent. Even the old course of Selby Dam, north of Thorpe Willoughby, is marked by a minor levee. The upper sand stretching east-south-east from Cliffe past Howden to beyond the district, and locally forming two parallel ridges (on which Newsholme and Asselby, for example, are situated), clearly delineates an old course of the Ouse, but the sand between Brayton and Camblesforth, subsequently much wind-redistributed, probably marks an earlier course. A similar situation appertains to the River Aire; the levee from West Haddlesey to Carlton is obvious, and farther east a course is traceable across Langham, Hales, Goolefields and Marshland to Sand House, presumably earlier than the course passing through Rawcliffe and south of Airmyn. However, the upper sand running east through Balne Moor Cross Roads south of the Snaith Ridge is traceable north-westwards beyond the district towards the Ferrybridge gap, through which the Aire has flowed throughout its known history, and presumably marks an early course, or a branch, of that river. It was joined north of Pincheon Green by the old course of the Went. The River Don has presumably eroded most of its old levees away west of Thorne, but its course is traceable farther east by the blown sand ridges running east along the northern side of Hatfield Chase. Some of the blown sand ridges from there southwards to Misterton Carr suggest wind-modified levees of the rivers Torne and Idle.

The levee nature of the upper sand has a bearing on the disappearance of Lake Humber. In the absence of river incision during levee deposition, regional drainage base level cannot have been lower than the emergent lacustrine clay plain. This implies that the lake did not disappear by breaching of the old barrier of glacial deposits in the Humber Gap, but rather by filling up with sediment. This conclusion is reinforced by the depositional height of the silt and clay of the 25-Foot Drift being only 1 m or so below the level of adjacent marginal sand, and probably level with the latter before compaction, and also by the lack of regressive shorelines. Upper sand deposition had presumably started by 11 100 ± 200 radiocarbon years ago when soil was developing on the emergent lacustrine clay plain at West Moor, and a date of 10 469 ± 60 radiocarbon years from peat above levee sand but below blown sand near Cawood, north of the district (Jones and Gaunt, 1976), gives some indication of the duration of deposition.

Details

Low sand ridges, aligned north-west to south-east, cross the extreme north-eastern corner of the district east of Sandholme, flanking the River Fouless farther east. Incipient dunes are recognisable in this area. A ditch [SE 8247 3081] at Sandholme, revealing 1.8 m of sand on clay, crosses the northerly of two sand ridges running to the west. The sand at Wressle forms the southern end of a sand ridge which flanks the River Derwent for several kilometres to the north.

In the pit [SE 6755 3140] east of Cliffe there is an interbedded passage, 0.9 m thick, up from the laminated clay into the upper sand. An excavation [SE 6745 2996] south of Hemingbrough revealed 1.8 m of sand on clay, and boreholes east of Barmby on the Marsh and at Kilpin prove 2.6 m and 2.1 m of sand respectively. This stretch of upper sand, forming two parallel ridges between Hemingbrough and Howden, continues eastwards beyond the district, protruding through alluvium at Staddlethorpe [SE 845 256] and Gowthorpe House [SE 8515 2520].

A sand ridge, on which Thorpe Hall [SE 5775 3165] stands, flanks the northern side of Selby Dam, the eastward-flowing stream north of Thorpe Willoughby.

Although the distribution of upper sand between Selby, Carlton and Drax appears irregular, much of it forms ridges aligned north-west to south-east, with incipient dunes in places. At the clay pit [SE 614 307] near Brayton the sand is 1.5 m thick, and contains cross-bedding in its middle part and thin clay lenses near its base and top. Thicknesses up to 2.4 m have been proved around Barlow and Drax, and southwards from Camblesforth Common.

A trench [SE 5605 2682] across the western end of the sand ridge flanking the River Aire from West Haddlesey to Carlton proved up to 2.9 m of silty and clayey sand containing coal particles, resting with an interbedded passage on laminated clay, and with a few thin clay lenses near its top. Up to 1.2 m of sand have been proved near Rawcliffe, but thicknesses are not available for the sand ridge running east to the south of Airmyn or that running south-east across Langham [SE 680 211]. To the south of the Dutch River a ditch [SE 6948 2015] near Elms Farm proved 1.5 m of sand, and a sand ridge is traceable by outcrops protruding through alluvium across Hales, Goole Fields and Marshland to Sand House [SE 809 195], where ditches prove 2.1 m of sand.

On the southern side of the Snaith Ridge the line of discontinuous outcrops of upper sand running east through Balne Moor Cross Roads [SE 566 199] to a locality [SE 657 182] north of Pincheon Green, consists locally of two parallel ridges separated by a narrow clayey slack, notably near Balne Lodge [SE 623 183]. It is joined near its eastern end by another line of upper sand outcrops flanking the River Went. Farther south, adjacent to the River Don, upper sand, partly protruding through alluvium, crops out in two patches, one of them slightly pebbly, west of Kirk Sandall, at Braithwaite [SE 622 127], in various places around Fishlake and south of the river at Ashfields [SE 665 127].

Some of the deposits originally mapped as blown sand farther south are thought to have been formed in the same circumstances as the upper sand because of their linear outcrops and alignments. They include the sand ridges running east across Nun Moors and on the northern and southern sides of Hatfield Chase, the double ridge [SE 722 977] north of Idle Stop and the ridges of blown sand and first terrace crossing Misterton Carr (Figure 44).

First terrace

The first terrace features in the district are comparable to low terraces in the Don Valley to the west and in the Idle and Trent valleys to the south. Their constituent sediments are intimately associated with the 25-Foot Drift and, therefore, they provide a link between events in the Vale of York and terrace formation in adjacent valleys.

Details

The first terrace deposits west of Bentley consist of sand, some of it coarse grained, containing coal particles, thin beds of fine gravel in which most of the pebbles are of Carboniferous rocks, and thin clay beds, some laminated. Up to 3.6 m of these deposits were seen beneath 1.2 m of silt and clay of the 25-Foot Drift in an exposure [SE 5702 0575] at Bentley Mill. Borehole evidence, and the lack of any feature at the indistinct surface contact with the silt and clay of the 25-Foot Drift to the northeast, suggest that the terrace deposits pass partly laterally into, and partly below, the silt and clay.

Coarse gravel seen at the base of terrace deposits in another exposure [SE 5708 0564] probably passes north-eastwards into the thick sand and gravel concealed beneath 25-Foot Drift at Bentley and farther to the north-east.

The first terrace deposits east and south-east of Austerfield are seen at the surface and in ditches to consist mainly of sand, in places with scattered to locally abundant pebbles, most of them 'Bunter' quartzites. They become increasingly clayey near the top north-east of Austerfield, where they pass imperceptibly into the lower sand and the silt and clay of the 25-Foot Drift. However, the narrow sand ridges to the east are suggestive of upper sand levees.

The first terrace deposits east of the Trent comprise sand with only a few scattered pebbles, although some gravel is present at depth. They rest on silt and clay of the 25-Foot Drift both at outcrop and farther north where, on both sides of the river, they continue under peat and alluvium; their undulating top implies considerable wind-modification. They are considered to be floodplain sediments formed by the Trent after the disappearance of Lake Humber, and so are valley-bound equivalents of the upper sand levees.

Blown sand

Much of the wind-deposited sand in the district occurs on west-facing slopes of the Isle of Axholme and, farther west, largely concealed beneath peat and alluvium. It is characterised by its fine-grained, well-sorted nature, paucity of interstitial silt, clay and coal particles, absence of pebbles, undulating top incorporating both crescentic and linear dunes, and lack of altimetric constraints. Rounded grains are present but not ubiquitous, probably because the wind-transported distances were not great.

Some of the blown sand resting on rockhead may have originated when the ventifacts on the lower periglacial surface were formed. However, in places the deposit rests on 25-Foot Drift, and it certainly underlies peat and alluvium. This implies a very late Devensian age, after Lake Humber disappeared and before the development of sufficient vegetation to curtail aeolian transport. This age is confirmed by various radiocarbon dates from the base of the blown sand: 11 100 ± 200 on West Moor (Gaunt et al., 1971), 10 469 ± 60 near Cawood (Jones and Gaunt, 1976) and 10 280 ± 120 at Messingham, near Scunthorpe (Buckland and Dolby, 1973); and by radiocarbon dates from within blown sand: 10 700 ± 190 and 9950 ± 180 near Sutton on the Forest, north of York (Matthews, 1970), and 10 550 ± 250 at Messingham (Buckland, 1982). This firmly places the aeolian phase within the last millennium of the Devensian, a time of known climatic deterioration. The prevailing wind direction is uncertain. Older sand-bearing deposits and Sherwood Sandstone to the west provide the most obvious source of sand, but the westward-pointing horns of crescentic dunes indicate wind from the east and the climatic reconstructions of Lamb and Woodroffe (1970) suggest anticyclonic easterly winds at this time.

Details

In the northern part of the district the only blown sand identified on the map forms Burn Hill [SE 730 288], west of Howden, and a well-marked dune ridge [SE 638 265] west of Camblesforth, but much of the surface of the upper sand shows evidence of wind-modification, with incipient dunes in places. Under the peat and alluvium of Thorne Moors and adjacent areas there are extensive deposits of sand which rest in turn on silt and clay of the 25-Foot Drift. This concealed sand varies from 0 to 3 m in thickness, with appreciable thickness variations across short distances, apparently due to its undulating top. Although some of it may be upper sand levee sediment, its wide distribution suggests that it is a wind-blown spread. It crops out locally south of Eastoft, notably at Pademoor [SE 802 147], where boreholes prove up to 6.1 m of sand.

In south-western parts of the district small dunes protrude through peat on West Moor, and at one locality [SE 6484 0718] the blown sand rests on soil which gave an age of 11 100 ± 200 radiocarbon years (Gaunt et al., 1971). Small patches of blown sand, partly protruding through peat, flank the River Torne from Rossington Bridge [SE 6290 9964] northeastwards; up to 1.8 m have been proved. North-east of Auckley Common the sand has a sinuous, linear distribution suggesting wind-modified upper sand levees (Figure 44). The larger patch of blown sand [SK 692 995] east of Finningley rests partly on the ventifact-strewn top of older river gravel and partly on silt and clay of the 25-Foot Drift.

From Hatfield Chase southwards to Misterton Carr much of the peat and alluvium rest on blown sand, which in turn rests on silt and clay of the 25-Foot Drift and extends to the surface against slopes of pre-existing deposits such as those at Wroot, and against the Isle of Axholme to the east. The sand also forms minute outcrops protruding through peat in many places, and some of these are recognisable as the tops of dunes by their crescentic shape, mainly with the horns pointing west. Crescentic dunes, again mainly with west-pointing horns, are recognisable on the blown sand [SE 690 080] south-east of Hatfield Woodhouse and around Wroot. Sand thicknesses above silt and clay of the 25-Foot Drift reach 4.6 m under Hatfield Chase and they are 3.6 m in Lindholme Borehole, 3.0 m in Bank End Borehole and 2.9 m in Haxey Borehole. In an old pit [SK 7325 9595] on Misterton Carr nearly 2 m of blown sand are exposed and numerous Maglemosian (Mesolithic) and later flint artifacts have been found on and just below the sand surface (Buckland and Dolby, 1973).

The sand mantling the western side of Crowle Hill was seen in excavations [SE 778 117] to fill ice-wedge casts intruding into Mercia Mudstone. Crowle Oil Borehole proved 2.4 m of sand, and boreholes in the Crowle Gap proved up to 4.6 m. Crescentic dunes with horns pointing west are discernible in various parts of the extensive blown sand mantling the western side of the Isle of Axholme, and several exposures show iron-pan staining within the sand. There is an old well record of 8.5 m of 'quicksand' at Sandtoft, but no comparable thicknesses have been proved. A pit [SE 7409 0104] on Starr Carr revealed 2.4 m of blown sand, G H Rhys recorded 4.6 m at an exposure [SE 7615 0043] on Coney Garth, and an old pit [SK 747 980] in the Haxey Gap revealed 5.5 m of blown sand without reaching the base. The blown sand [SE 811 047] protruding through alluvium east of Epworth, at Cowsitt Hill, is shown by ditches to be at least 2.4 m thick locally, and to pass extensively beneath the adjacent alluvium.

A mantle of blown sand on the slopes of Hardwick Hill [SK 837 997] has been excavated to depths of 3 m in old pits.

Upper periglacial surface

Ventifacts are abundant on the upper periglacial surface. The most commonly associated cryoturbation structures include frost cracks and poorly developed shallow involutions, with some masses of vertically aligned pebbles but virtually no trace of clay enrichment and no superficial faulting; these all suggest seasonally frozen ground. Discontinuous permafrost may have existed in a few places, however, for more strongly developed involutions were found in Devensian glacial sand and gravel at Wroot, well-developed ice-wedge casts occur in lacustrine sand and gravel near Pollington and north of Austerfield, and stone stripes are present on the latter deposit near Pollington and Great Heck.

The upper periglacial surface is widespread on top of the Devensian glacial sand and gravel and the lacustrine sand and gravel, and so it formed after the surge of Vale of York ice into the district and after the high-level phase of Lake Humber. Imprecise and conflicting evidence precludes more exact dating. Three possibilities exist. The first is that the surface may have formed during the postulated drop in Lake Humber between its high- and low-level phases; this is suggested by the ventifact-strewn top of Devensian glacial sand and gravel passing under 25-Foot Drift south-east of Burton Hall, the evidence of subaerial brecciation at 4 m below OD in silt and clay of the 25-Foot Drift in the borehole north-west of Carlton, and the apparent intraformational cryoturbation in marginal lacustrine deposits near South Cave (Gaunt et al., 1992, p.122). The second possibility, supported by the abundance of ventifacts on the upper periglacial surface, is an origin coeval with the terminal Devensian blown sand. If so, the absence of ventifacts on top of the 25-Foot Drift is obviously due to the lack of suitable pebbles and cobbles there for sand blasting. The absence of cryoturbation on that surface may be due to the fact that such structures do not form readily in clay; while in the sand they may not have been formed due to its dryness at the time, or they may have been destroyed by later wind redistribution. The third possibility is that the periglacial surface formed more or less continuously during the existence of Lake Humber and afterwards until the end of the Devensian, wherever suitable ground was exposed and local conditions allowed ventifact formation and/or the development of cryoturbation.

Flandrian deposits

A depositional hiatus caused by deep fluvial incision intervened between formation of the Devensian deposits and those of Flandrian age, which comprise peat and alluvium.

Incision

Contours at and below OD on the base of the Flandrian deposits (Figure 45) reveal a landscape in which rivers crossing the district, including minor ones like the Went and even streams like Selby Dam, have deeply incised their courses, reaching depths of nearly 20 m below OD as they approach the Humber Gap.

This vigorous fluvial incision was accompanied by little or no interfluvial denudation, except possibly north of Crowle, and it was presumably of short duration. It resulted from a rapid drop of regional drainage base level, when the 'nickpoine of the 'River Humber', in effect a west-bank tributary of the River Hull and graded to the prevailing low sea level, finally eroded westwards through the glacial deposits in the Humber Gap to reach the soft uncompacted and waterlogged 25-Foot Drift farther west. Subsequent dewatering of the 25-Foot Drift is thought to be responsible for the contorted layers in the upper part of the laminated clay seen in pits north of the Ouse, and extensively in trenches north of the district, as well as for the deeply incised courses of the minor streams, such as Selby Dam, which have virtually no surface drainage hinterland.

Dating of the incision is as yet imprecise. It obviously postdated upper sand levee deposition, but may well have started before the end of the Devensian, when a marked lowering of groundwater level would have helped to mobilise blown sand, which occurs below OD in places, and precluded cryoturbation in the marginal and upper sand of the 25-Foot Drift. The incision had probably finished by early 'Boreal' times (about 8500 radiocarbon years ago) when shell marl referable to this time was deposited in a minor incised channel at Burton Salmon, west of the district (Norris et al., 1971), and it had certainly terminated well before 7000 radiocarbon years ago when sea level in the Humber Estuary, and consequent alluvial deposition, had risen to about 9m below OD (Gaunt and Tooley, 1974).

Peat

With minor exceptions the peat in the district occurs in some of the lowest-lying areas, cropping out mainly on Thorne Moors and from Hatfield Moors southwards to Misterton Carr, but peat is also present extensively at shallow depth beneath and within alluvium in some places, notably in the Trent Valley.

Most of the peat, both at surface and concealed, occurs in areas flanking the deeply incised river courses shown on (Figure 45), at elevations between 4 m below and 3 m above OD. The available pollen and radiocarbon dating evidence indicates that, although some basal layers may be nearly 7000 radiocarbon years old, much of it is less than half this age. The peat growth may be attributed mainly to two factors. One is the wetter climate which ensued from Atlantic times onwards, and which, particularly from the onset of Sub-Atlantic times, was conducive to raised bog development in suitable areas. The other is the waterlogged ground and poor drainage in low-lying areas produced in late Flandrian times in the Humber region (Gaunt and Tooley, 1974) by the change of sea level, which rose sharply from about 9 m below OD to between 3 m and 5 m below OD between 7000 and 6000 radiocarbon years ago, but which has oscillated within a metre or two of OD within the last 3500 radiocarbon years.

Details

The only elevated peat, up to 0.6 m thick, occurs in three small hollows in Sherwood Sandstone, the largest at [SE 565 298] south-east of Hambleton. It is incorrectly coloured on the Goole (79) Sheet, as also is at least 1.3 m of peat flanking a minor stream [SE 565 316] to the north which joins the eastward-flowing Selby Dam. A trench across the latter [SE 5945 3197] proved, beneath 0.8 m of clayey alluvium, peat and peaty clay to 5.5 m without reaching the base of the deposit.

Concealed peat is locally present within alluvium adjacent to the Ouse. A borehole [SE 6622 2930] east of Barlow proved 6.7 m of peat beneath 1.8 m of clayey alluvium; another borehole [SE 6513 2744], adjacent to the minor stream flowing towards the Ouse south-east of Barlow, proved 1.7 m of peat beneath 0.5 m of clayey alluvium. Using pollen analysis, Smith (1958) correlated peat at shallow depth beneath alluvium at Goole and organic deposits of Sub-Atlantic age (c. 2500 radiocarbon years to present) in northern Lincolnshire. There is little or no evidence of concealed peat for some distance on either side of the Ouse farther east, although an old borehole [SE 7914 2329] at Reedness proved 3.6 m of 'Black moor earth with rotten wood' under 6.1 m of alluvium.

Near Snaith an excavation [SE 6433 3235] revealed 2.5 m of peaty clayey alluvium on 2.4 m of peat, without proving the base of the latter, but elsewhere adjacent to the Aire there is little evidence of concealed peat, although more than 1.2 m is present, but wrongly coloured on the Goole (79) Sheet, in part of the narrow channel [SE 626 216] through the Snaith Ridge west of Snaith.

Peat and peaty clay up to 7.7 m thick fills the incised former course of the River Went east of the present course of the Don, but other than two small outcrops [SE 685 183]; [SE 686 192], the deposit is concealed beneath floodwarp. The old northward course of Hampole Beck, which flowed past Askern to join the Went prior to diversion into the Don, is flanked by peat more than 1.5 m thick locally. Peat generally less than 1.0 m thick occurs in places down to depths of 7 m within the alluvium flanking the Don, being proved at Doncaster [SE 565 035] and Thorpe Marsh [SE 606 097] power stations.

Concealed peat thickens southwards at shallow depth across Goole Fields and Marshland towards the raised bog of Thorne Moors, which, prior to peat cutting along its south-western side and floodwarping around its margins elsewhere, was considerably more extensive, particularly to the north-east. Parsons (1878) recorded thicknesses of 6.1 m of peat on Thorne Moors, but numerous recent boreholes prove a residual thickness of not more than 3.0 m, reflecting the magnitude of former peat workings, some of which are now permanently flooded. Traces of blackish reedswamp peat containing Phragntites have been seen in a few of the deepest excavations, but elsewhere the lowest peat is purplish brown and contains Calluna. It is succeeded by up to 1 m of interbedded Sphagnum and Eriophorum-rich peat, which passes up into 1.3 m of brown Sphagnum peat. Tree stools and prostrate trunks, apparently mainly of birch, with reportedly some of oak, occur near and at the base of the peat. A birch stool from the base of the peat, and split pine from a Bronze Age trackway within it, have been dated to 3260 ± 100 and 2990 ± 100 radiocarbon years respectively (Shotton and Williams, 1973). A charred trunk in a late Bronze Age clearance level in the peat has been dated to 3080 ± 90 radiocarbon years (Buckland and Kenward, 1973), and levels within the peat indicative of localised middle to late Bronze Age clearance, renewed late Bronze Age activity and extensive early Iron Age clearance have been dated to 3170 ± 115 and 2942 ± 115, 2329 ± 110, and 1855 ± 120 radiocarbon years respectively (Godwin and Willis, 1962; Turner, 1965). The trackway, and associated beetle remains, imply increasingly wet ground conditions. Further details of Thorne Moors are given by Buckland (1979).

The peat cropping out between Crowle and Sandtoft has not been proved to depths of more than 0.7 m, despite its extent, and although some of the locally thick alluvium on Hatfield Chase is peaty at depth, there is little or no evidence of concealed peat there.

Near Doncaster, up to 0.9 m of peat occurs in two shallow channels in Sherwood Sandstone near Botany Bay [SE 6328 0950]. The peat on West Moor is generally less than 0.8 m thick but may increase to 1.5 m in the northern part. Adjacent to the River Torne, north-east of Rossington, and at Peat Holes [SE 663 010], south of Auckley Common, peat is up to 1.1 m thick, and on Potteric Carr and more southerly parts of the Torne floodplain it is at least 1.5 m thick in places.

The raised peat bog of Hatfield Moors is, following extensive peat working, now not much more than 2 m thick in most places on the evidence of augering and boreholes, although Smith (1958) records up to 3.5 m in south-eastern localities. It contains Eriophorum-rich layers in its lower part, but at higher levels it consists mainly of Sphagnum. Pollen analysis by Smith (1958) showed that peat formation started early in Atlantic times (c. 7000 to 5000 radiocarbon years), probably as blanket bog with no previous reed-swamp phase. A layer close to the Atlantic/Sub-Boreal boundary yielded charcoal fragments and pollen of weeds and Plantago lanceolata, the earliest evidence of clearance. This layer, and three higher ones, are less humified and contain Scheuchzeria, suggesting wetter conditions. The second lowest of these four layers gave a date of 2215 ± 110 radiocarbon years and the upper two layers yielded several dates of approximately 1390 radiocarbon years (Godwin and Willis, 1962).

The peat extending southwards to Misterton Carr is, despite its extent, generally not more than 1 m thick, although in a few places at least 1.5 m have been proved by augering, and a few boreholes prove thin concealed peat at shallow depth beneath alluvium. Tree stools and prostrate trunks are ploughed up occasionally. Buckland and Dolby (1973) obtained a date of 4330 ± 100 radiocarbon years from peat resting on blown sand at a locality [SK 728 950] on Misterton Carr. The peat on the 25-Foot Drift-filled channel north-east of Austerfield is up to 1.2 m thick.

In the Trent Valley several patches of peat occur on the floodplain. Most of them appear not to be thicker than 1.0 m, but those south of Owston Ferry are locally at least 1.5 m thick. Boreholes in the valley show that the peat continues extensively at shallow depth beneath alluvium, except in the middle of the valley, and is at least 1.7 m thick locally. Old maps show the peat to have been formerly much more extensive at outcrop, and the artificially straight nature of many of the outcrop edges of the peat indicates that much of the overlying alluvium consists of floodwarp. Peat, locally at least 1.5 m thick, occupies channels and hollows on the first terrace east of the Trent.

Alluvium

Most of the alluvium in the district is of freshwater origin, but some of the near-surface deposits (excluding those of floodwarp derivation) on more eastern parts of the Ouse floodplain and more northern parts of the Trent floodplain are probably estuarine. The alluvium is thick, up to almost 20 m locally, where it fills the incised courses shown on (Figure 45), but outside these channel confines, although extensive, it rarely exceeds 4m. In the deeper parts of the channels much of the deposit consists of sand and silt, commonly with a gravelly base; however, it becomes increasingly clayey upwards, and at the surface, although the upper levee slopes of the major rivers consist of silt, the deposit grades away from the rivers into stiff, heavy and commonly peaty clay.

An upward-decreasing coarseness of the alluvium reflects decreasingly energetic fluvial deposition in the incised river courses as sea level rose rapidly in the Humber region during the Flandrian. After the incised courses were filled with alluvium this trend culminated in thin but extensive spreads of appreciably peaty clay and peat on low-lying areas marginal to the incised courses, as sea level oscillated within a metre or two of OD within the region in the last 3500 radiocarbon years (Gaunt and Tooley, 1974).

Details

Boreholes along the old Derwent between Howden and Kilpin Pike prove up to 5 m of clay, peaty at depth, without reaching the base of the deposit. Along the River Ouse above Goole, a borehole [SE 6674 2983] near Hemingbrough proved silty clay on silt, on sand containing wood fragments, resting on 25-Foot Drift at 14.6 m below OD. Another [SE 7319 2565] south of Boothferry Bridge proved silty and peaty clay and sand resting on Sherwood Sandstone at 16.8 m below OD. Pollen analysis of peaty clay at 15.9 m below OD in the latter borehole yielded sparse Gramineae, Filipendula, Polypodium, Selaginella, Isoetes and Sphagnum, with minute amounts of pine and a few eroded grains of lime (Dr J W Franks, personal communication). If the lime is derived, the assemblage suggests sparse open vegetation and a cool climate. Several abandoned meanders are discernible along this stretch of the Ouse floodplain. Farther east, boreholes near Ousefleet prove alluvium to 16.1 m below OD, resting on Mercia Mudstone, but the alluvium north and east of Laxton and on more southerly parts of Goole Fields and Marshland is generally less than 4 m thick, including the superficial floodwarp where present.

On the Aire floodplain, where several abandoned meanders exist, Kellington No. 3 Borehole proved rather sandy alluvium with a gravelly base resting on Sherwood Sandstone at 12.2 m below OD. Carlton Borehole [SE 6279 2340] proved clay on sand, also resting on Sherwood Sandstone at 12.2 m below OD, and a borehole [SE 6993 2474] east of Newland proved clay on sand, both containing wood fragments, resting on Sherwood Sandstone at 14.6 m below OD.

The alluvium flanking the River Went consists of peaty clay, and the beheaded former course east of the River Don and north of Reedholme Common is recognised by a deeply incised channel filled with peaty clay and peat, partly covered by flood-warp. At one locality [SE 685 183], known as Johnny Moor Long but referred to by Head (1836) as Journey Me Long, numerous microlithic flint artifacts were found on the banks of the old channel. Boreholes on the northern part of this channel [SE 670 205] prove peaty clay to 7.6 m below OD. In contrast, the wider stretch of alluvium [SE 667 205] to the west, which includes floodwarp, does not descend below 0.4 m above OD.

The alluvium forming the floodplain of the River Don to the west of Thorne contains several abandoned meanders, some of them obviously truncated artificially. Boreholes at Thorpe Marsh Power Station [SE 606 097] and a nearby bridge [SE 608 100] prove peaty and silty clay on sand with a gravelly base down to nearly 5 m below OD. Along the present course of the River Don north of Thorne, however, numerous boreholes have failed to find any substantial thickness of alluvium or peat, except one [SE 6690 1866] which proved clayey alluvium on peat to 3.3 m below OD and which relates to the incised course of the River Went. The only alluvium at the surface along the Don north of Thorne is contained between artificial embankments or is floodwarp. Farther east, the surface course, including several adjacent meander scars, of the lower part of the original Don, which was beheaded by Vermuyden in 1625–27, can be traced by a well-marked peaty clay-filled channel across Hatfield Chase, and thence north-east past Crowle, and through Eastoft and Luddington. The underlying incised course is also traceable by boreholes. One [SE 7151 0972] at Crow Tree proved clay on silt, on sand and gravel, resting on Sherwood Sandstone at 11.9 m below OD. Another [SE 7461 1143] near Jaques Cott proved peaty clay on peaty silt and sand, on sand and gravel to the bottom of the borehole at 17.5 m below OD. Other boreholes farther north-east, some recorded by James (1976, pp.37, 40, 42), prove comparably deep alluvium.

The pre-Vermuyden surface course of the Idle is traceable by a peaty clay-filled channel, within flanking clayey alluvium, southwards from Hatfield Chase to Idle Stop. The underlying incised course is also traceable by boreholes. Several boreholes c. [SE 7235 0911] south of Elder House, and one [SE 7291 0865] west of Sandtoft, proved peaty clay and silt, sandy at depth, to the bottom of the boreholes at 11.6 m below OD and 10.6 m below OD respectively. Boreholes [SE 7430 0490] near Ninevah Farm, and [SE 7380 0296] near Auckland Farm, prove clayey alluvium resting on Mercia Mudstone at nearly 7 m below OD, and a borehole [SE 7280 0032] near Bull Hassocks Farm proved peaty silty clay and peat resting on Mercia Mudstone at 4.8 m below OD. Only minute stretches of alluvium flank the River Idle across Misterton Carr, but a clayey outcrop [SK 740 939] on the eastern edge contains shell marl which probably owes its origin to lime-rich water from skerry bands in adjacent Mercia Mudstone (cf. Lamplugh et al., 1911, pp.38, 61; Smith et al., 1973, pp.229–230). A ditch [SK 7471 9320] yielded the freshwater gastropods Bithynia tentaculata, Planorbis leucostoma and Limnea spp. including L. palustris, and the terrestrial Succinea putris, identified by R W Melville.

The narrow stretch of clayey alluvium flanking the old course of the River Torne prior to straightening, north and west of Wroot, is up to 1.5 m thick.

Farther west on Potteric Carr and adjacent parts of the Torne Valley to the south, where the low elevation may be due to solution subsidence of evaporites in the Permian rocks at depth, up to 2 m of peaty clay are proved by augering and in ditches. Non-peaty clay, silt and sand at greater depths may be alluvium, but they are at least as likely to be 25-Foot Drift. Thin shell marl is present locally under the peat on Wadworth Carr.

In the Trent Valley much of the surface alluvium away from the levee slopes consists of floodwarp (see below and shown on (Figure 46), but peaty and locally sandy clay occurs in small areas near Crowle Station, in the area east of Beltoft where up to 1.5 m of peaty clay rest on peat, and in the alluvial embayment south of Beltoft, where comparable thicknesses of peaty clay are present. The incised course of the Trent is traceable by boreholes: one [SE 8446 1258] east of Keadby, just beyond the district, proved peaty clay and sand with a basal gravel, resting on Mercia Mudstone at 16.1 m below OD; another [SE 8331 0734] near West Butterwick proved silty clay on sand, on peaty sand with a basal gravel, resting on Mercia Mudstone at 14.1 m below OD; and another [SK 7887 9441] near West Stockwith encountered clay on sand with some gravel, containing bivalves, gastropods and wood fragments, resting on Mercia Mudstone at 9.7 m below OD. Numerous boreholes through the alluvium of this part of the Trent Valley are recorded by Gozzard and Price (1978), James (1976), Lovell (1977) and Thomas and Price (1979).

River diversions

Several man-made river diversions are recognisable in the district (Figure 46); Gaunt, 1976a, pp.386–390), partly by comparing the early Flandrian courses (Figure 45) with the present courses. The River Derwent was diverted south-westwards past Barmby on the Marsh from its former south-easterly course through Howden, on documentary evidence at some time between the late 13th century and 1577. A side branch of the River Don, formerly known as Turnbrigg Dike, was constructed northwards from Thorne to the River Aire near East Cowick, at some time before 1410 (Gaunt, 1975), beheading the lower course of the River Went at a locality [SE 6679 1878], which is now their confluence, south of New Bridge.

The drainage alterations accomplished by Cornelius Vermuyden in 1625–27 (Read, 1858; Tomlinson, 1882; Korthal-Altes, 1924; Harris, 1953) consisted essentially of diverting three rivers. The northward flowing River Idle was diverted at Idle Stop [SK 7200 9660] eastwards via the pre-existing artificial Bykers Dike into the Trent at West Stockwith. The River Torne, having previously joined the Idle near Tunnel Pits Farm [SE 7353 0409], was channelled into an artificial course, the New River Torne, which joins the Trent near Althorpe. The original lower course of the River Don across Hatfield Chase and past Crowle to join the Trent north-east of Luddington was beheaded at Thorne, diverting the entire flow of the river into the artificial channel running north to the River Aire. Widespread flooding ensued along the Don and the Aire, and the mainly Dutch financial supporters of Vermuyden, known as the Participants, were forced by the 1633 Wentworth Judgement to cut a new channel from the Don to the River Ouse. This channel, the Dutch River, was completed in 1635.

Warp

Artificially induced alluvium, or warp, covers large areas in the eastern part of the district, and is shown as alluvium on the geological maps. Most of it results from flood-warping, but cartwarping was carried out in a few places. Floodwarping utilises the vast load of suspended silt and clay in the local rivers, and the reversal of flow during high tides. The area to be warped is embanked and a warping drain cut from it to the nearest river. Sluice gates at the river end of the drain are opened at high tide, allowing the sediment-rich water to flood the embanked area and deposit its load; at low tide the water is allowed to drain gently back into the river. Each flood deposited an average of 2 mm of silt or silty clay, and up to 0.3 m could be accumulated in a warping season, generally between spring and mid-autumn. A warping programme could last for several seasons, and some ground has been subject to more than one programme. The thickest known floodwarp is 1.5 m.

Only a limited stretch of each river is suitable for floodwarping, depending on its sediment-load characteristics and elevation relative to adjacent ground. Land was warped for various reasons: some was too low-lying and ill-drained; some peaty soils were too acidic; some sandy soils were too prone to wind erosion; and some clayey soils were too heavy. Floodwarping produces a light, well-drained silty soil, and it has increased land values considerably. The earliest recorded floodwarping was in the 1730s near Rawcliffe, although the practice may be older, and the most recent was in a small area east of Yokefleet in 1947. Floodwarped ground is recognisable by its light silty soil, traces of laminations below plough level, presence of a pre-existing soil below it, traces of old embankments, differences in field levels and documentary evidence.

Cartwarping consists of excavating suitable silt or clay, transporting it by carts or wagons on rails, and spreading it manually. The only large extent of cartwarp is that on the north-eastern part [SE 725 066] of Hatfield Moors. It is up to 0.6 m thick and was excavated from a pit [SE 734 065] on the channel of the River Idle south of Hatfield Chase.

All the known floodwarp, cartwarp and warping drains in the district are shown on (Figure 46). Extensive local details are given elsewhere (Gaunt, 1976a, pp.391–421).

In a statement published while this memoir was in press, Bowen and Sykes (1991) comment that 'Amino acid data from the Basement Till [of Holderness] is in press (Eyles et al., 1992) and shows that it is late Devensian in age '. The implication of two Late Devensian ice advances across the eastern end of the Humber Gap, separated by an ice-free interlude during which the Dimlington Silts (c.18 000 radiocarbon years in age) were deposited, provides an explanation for the drop in water level to lower than 4 m below OD between the high- and low-level phases of Lake Humber, when the lake may even have temporarily drained away completely. It suggests also that the date of c.22 000 radiocarbon years obtained from the Brantingham bone (p.116), which was associated with a deposit formed during the high-level phase, may be more accurate than was hitherto supposed.

Chapter 6 Economic geology

The earliest records of exploitation of a geological resource, other than water supply, refer to peat cutting, which has continued from Medieval times and is now carried out on a large scale by mechanised means. There are also old records referring to extraction of clay and, on the Isle of Axholme and near Misterton, of gypsum, but neither material is worked much at present. In contrast, the sand and gravel industry has expanded enormously since the Second World War.

However, the most important industry based on a geological resource is coal mining, which began in the first decade of the 20th century with the sinking of several deep shafts, forming part of the extension of the Yorkshire Coalfield eastward into its 'concealed' region. This industry, more than any other, has been responsible for the large increase in population in the district, mainly concentrated in Doncaster and adjacent areas, during the present century, and it has enabled other industries to develop in these areas. More recently there has been some exploration for deep hydrocarbon sources in the district, and although the results are extremely modest by comparison with other regions in and around Britain, the gas find which produced a spectacular 'blow out' on Hatfield Moors late in 1981 has now been tapped for industrial use.

Coal

The coal resources within the Goole and Doncaster district represent a deep, concealed eastern extension of the Yorkshire Coalfield. Along the western district boundary the major seams have been carried by an easterly dip to a depth of over 700 m from their outcrops around Wakefield and Barnsley some 20 km to the west. They maintain at least this depth throughout the area, tending to become deeper to the east. The major seam of economic interest is the composite Barnsley Coal which, in this region, has probably accounted for more production than all other seams combined.

In the Yorkshire Coalfield, as elsewhere, exploitation began close to the outcrop where the seams were easily accessible, but it was not until mining procedures were relatively well-developed that it became practicable to exploit the deep coal resources. Hence mining did not begin in the district until the first decade of the twentieth century, when several deep shafts were sunk. In the List of Mines published by HM Inspector of Mines and Quarries, Bentley Mine first appeared as a new sinking in 1905, followed by Brodsworth (1905), Maltby (1907), Yorkshire Main (1911), Bullcroft (1908), Thorne (1909), Askern (1909), Hatfield Main (1911), Rossington (1912), Harworth (1914) and Markham Main (1916). Shaft sinking ceased after a few years and the mines came into full production in the following order: Brodsworth (1907), Bentley (1908), Bullcroft (1911), Maltby (1911), Yorkshire Main (1911), Askern (1913), Rossington (1915), Harworth (1916), Hatfield Main (1917), Markham Main (1926) and Thorne (1926). Subsequently, no new mines were opened until 1962 when Kellingley Mine was developed just west of the district. Bullcroft Mine closed in 1970. Thorne Mine ceased to produce in 1956, and Yorkshire Main Mine closed permanently in 1987. Otherwise all the original mines were still active in 1988. All the mines have shafts over 600 m deep; Harworth and Thorne are the deepest with depths of 883 m and 881 m respectively, and four others have shafts over 800 m deep. Working in these mines is normally by fully mechanised longwall methods, the coal being mechanically cut and power loaded. Roof support is almost invariably by self-advancing automatic chocks linked to the face-conveying system.

Mining is concentrated on the composite Barnsley Coal, which is the mainstay of the Yorkshire Coalfield. However, to the north of Askern and Thorne collieries, the Barnsley is split by a mudstone parting into an upper seam known as Warren House and a lower seam called Low Barnsley. Although the lower part of the Barnsley is very important as a source of steam-raising coal to the south, much of the separate Low Barnsley seam in the northern part of the district has deteriorated or is washed out. However, on the northern edge of the district the two seams come together again in the Selby Coalfield; workings in this coalfield are not expected to enter the district. Although the Warren House seam is present over extensive areas to the south of Selby, it is not at present economically attractive and there are no plans to work it in the foreseeable future. In the northwestern part of the district, workings from Kellingley Mine in the Silkstone Coal impinge into a small area to the west of Eggborough, but otherwise there is no mining south of Selby until the workings of Askern, Hatfield and Thorne collieries are encountered.

At Hatfield and Thorne there have been substantial workings in the Hatfield High Hazel Coal. Otherwise at Askern, Bullcroft, Bentley, Brodsworth, Markham Main, Yorkshire Main, Rossington, Maltby and Harworth all the workings are, or were, virtually confined to the Barnsley within this area. The only exceptions occur at Bentley Colliery where the Swallow Wood and Parkgate coals have also been worked.

Thorne Colliery is unusual in that the advent of the First World War and severe water problems caused the shaft-sinking to extend over 17 years. Some 10 years after opening the shafts again began to admit water from Permian strata and by the 1950s the ingress of water and other problems were such that the mine had to close. Although the Barnsley had been reached, workings were confined to the stratigraphically higher High Hazel seam, which has been exploited within a radius of 1.5 to 2 km of the shafts and which connected with Hatfield Colliery (Jackson, 1981). After closure the shafts were repaired, an operation which was finally completed in 1966, but by this time the colliery could not be economically reactivated and it has remained on care and maintenance ever since. A large exploration programme was carried out in 1976, as a result of which proposals were made to work the High Hazel and Barnsley coals from Thorne, in an area bounded by the Keadby Canal to the south, the River Don to the west and the Dutch River to the north.

A plan of the Barnsley Coal showing the divisions occurring within the seam is shown in (Figure 14). The seam is best developed on the north side of Doncaster where it contains several mudstone partings which thicken both towards the south and the north, ultimately splitting the coal into leaves that are conventionally described as separate seams when divided by more than 0.3 m of mudstone. Hence a lower leaf of the Barnsley develops into the Dunsil Coal in the western part of the area near Doncaster; elsewhere, as previously described, the Low Barnsley Coal becomes separated from the Warren House Coal.

The main difficulties involved in mining include the presence of minor faults and other irregularities in the strata; such breaks interrupt the operation of the highly mechanised mining techniques now employed. The presence of washouts also causes difficulties, but on a larger scale. Methane emission varies, but in general the faster the workings advance the greater the emission of methane. Current practice is to reduce the risk of excess flammable gas accumulation at a coal face by boring into the rock above and below the seam to tap off any trapped methane. Spontaneous combustion takes place when the coal in particular sections within certain seams is exposed to the air. The phenomenon is particularly well known in the Barnsley in the Doncaster area, although it also occurs in other seams. In such areas working practice involves sealing off the ventilation to worked areas as soon as practicable after extraction. Spontaneous combustion also affects broken coal which remains in the waste areas. However, the reason why some coals are more susceptible than others remains unclear. Any rock containing a significant proportion of coarse (greater than 5 microns) quartz grains is likely to produce hot sparks when cut by mining machinery; such rock is occasionally encountered in roof or floor strata, and the generation of hot sparks under certain conditions can then lead to a hazard known as Incendive sparking'.

Sand and gravel

Sand and gravel for use in the construction industry are worked extensively near Doncaster and to a lesser extent near Hensall.

At Hensall the deposits consist of glacial sands overlying sandstone of the Sherwood Sandstone Group. In the Doncaster area the main resource of economic interest is the 'older river gravel', which consists of large spreads of sand and gravel, up to 6 m thick, located on the west side of the valley of the River Idle and extending from Austerfield in the south to Stainforth in the north. Some fluvioglacial sand and gravel is also economically important, particularly in the area adjacent to the older river gravel near Rossington. Other superficial deposits, including the 25-Foot Drift of the Vale of York, which frequently overlies the older river gravel, and the blown sand on the Isle of Axholme, have been of little value for construction purposes, although some building sand may be produced from a silica sand working in blown sand at Westwoodside. The Sherwood Sandstone underlies the various sands and gravels and is worked for building sand, asphalt sand or fill, in the bottom of some pits originally excavated for sand and gravel. However, as yet, no new pits have been specifically located in Sherwood Sandstone.

The major sand and gravel deposits in the Doncaster area have been described in detail in Mineral Assessment Reports Nos. 37 and 92 of the British Geological Survey. In these reports the fluvioglacial sand and gravel near Rossington was found to have an average grading of 24 per cent gravel, 65 per cent sand and 11 per cent fines, although the formation varies laterally and vertically from a pebble-free sand to a sandy gravel. The pebbles are usually subrounded and comprise about 60 per cent quartzite, 20 per cent quartz and 15 per cent sandstone, with minor amounts of limestone, chert and igneous rock.

The older river gravel near Misson and Finningley has an average grading of about 28 per cent gravel, 59 per cent sand and 13 per cent fines. The pebbles are usually subrounded and comprise about 50 per cent quartzite, 25 per cent quartz and 15 per cent sandstone, with minor amounts of limestone, mudstone, chert and igneous rock. Thin clay seams are present in the deposits but coal fragments are generally absent. However, north-west of Finningley, towards the River Don, the older river gravel changes in composition as quartz and quartzite pebbles are increasingly replaced by pebbles of Carboniferous sandstone and ironstone. In areas rich in Carboniferous-derived materials, coal detritus, usually in the form of coarse sand sized particles, can comprise up to 1 per cent of the deposit.

At present (1988) there are 11 sand and gravel workings, excluding silica sand workings in the blown sand, in the Goole and Doncaster district. The two workings in the north at Hensall and Great Heck are dry pits that produce building sand by a simple dry screening operation. Farther south, in the area between Hatfield and Misson, the operations are on a much larger scale and in most cases incorporate comprehensive washing and screening operations designed to produce coarse aggregate for concrete, sand for concrete, sand for asphalt and sand for mortar. The low yield of coarse aggregate reduces the value of the material in some pits, and the presence of sandstone rather than quartzite pebbles reduces the range of application of the coarse aggregate in concrete. In addition, the occurrence of coal particles in coarse sand can be a cause for concern. All the pits are located essentially above the water table and are worked by rubber-tyred face shovels; explosives are occasionally necessary when the Sherwood Sandstone is worked.

Hydrocarbons

Since the beginning of the Second World War there have been several periods of hydrocarbon exploration in the district. As a result, an extensive seismic reflection network has been acquired and several exploration wells drilled. However, to date, the only important discovery is the Hatfield Moors Gasfield. The Gainsborough–Beckingham Oilfield, about 15 km south of the district, is the nearest important oil discovery.

The Permo-Triassic rocks of the district have very limited source potential and are immature (vitrinite reflectance values <0.50 per cent). The Westphalian and late Namurian rocks contain large quantities of terrestrially derived organic matter; they are thus gas-prone and can yield only very small amounts of oil. However, almost everywhere in the district the level of organic maturity in these rocks is well below the level of peak gas generation. For example, the mined coals are without exception high volatile bituminous coals with vitrinite reflectance generally less than 0.80 per cent. Higher values, up to about 1.00 per cent, have been recorded in late Namurian rocks.

The main oil source-rocks of the East Midlands oilfields are believed to be early Namurian basinal shales. According to Kirby et al. (1987, fig.7), rocks of this age are mature for oil generation throughout the district, except towards the Gainsborough Trough in the southwest, where they are more deeply buried and have been in the zone of gas generation since at least Cretaceous times. It is noteworthy that the Hatfield Moors Gasfield occurs at the edge of this gas-prone area. Potential sandstone reservoirs are numerous in the Upper Carboniferous succession of the district (cf. the Hatfield Moors Gas-field and the other East Midland oilfields). Almost all of the closed structures are in Carboniferous strata and formed in late Carboniferous–early Permian times (Hercynian Orogeny). While some hydrocarbon generation took place at that time, the main period of formation, according to Kirby et al. (1987), was in Jurassic and Cretaceous times when hydrocarbons migrated away from the Gainsborough Trough towards the surrounding shelf areas.

The Hatfield Moors Gasfield [SE 704 066] is currently the only operating onshore gasfield in the United Kingdom. Unlike small oil reserves, gas production has to be sold to a dedicated customer and in this case the output is supplied to Belton brickworks, some 10 km distant, for firing the brick kilns.

The gasfield was discovered in 1981 during the drilling of the Hatfield Moors No. 1 Borehole when a blowout, originating in the Westphalian B Oaks Rock sandstone, occurred at a depth of 432 m. This borehole was originally aimed at reappraising the potential of Westphalian A and Namurian sandstones and, in particular, a reservoir in the Westphalian A Grenoside Sandstone which had intermittently produced oil on test for several years from 1976. These original deep objectives were subsequently applied to the Hatfield Moors No. 3 Borehole which was sunk in 1984 from the same surface location as Hatfield Moors No. 1; however, the well was abandoned and drilling again ceased in the Oaks Rock (Jones, 1988).

The gasfield started production in December 1985 at an initial flow rate of about 0.3 MMscfd (0.3 X 10⁶ft³/ day) but production was subsequently increased to the current rate of 0.5 to 0.6 MMscfd (0.5 to 0.6 X 10⁶ft³/day) in August 1986. Recoverable reserves have been estimated at 5.2 Bscf (5.2 X 10⁹ft³) (Jones, 1988).

Evaporites

Both anhydrite and halite occur at depth within the Upper Permian strata of the area, the former within the Hayton Anhydrite, Billingham Main Anhydrite and Upper Anhydrite, and the latter within the Fordon Evaporites and Boulby Halite. In the past, anhydrite was mined on a larger scale in the United Kingdom than in any other country, principally as a source of sulphur for the manufacture of sulphuric acid and ammonium sulphate fertilizer. However, the availability of cheap sulphur on world markets made anhydrite an unattractive source of the element and production for these uses finally ceased in 1975. There is now only a minor demand for anhydrite and the occurrence of large resources elsewhere in northern England means that it is highly improbable that there will be any future economic interest in the anhydrite resources of this area.

Halite occurrences proved in the district are thin and discontinuous; the existence of large deposits elsewhere in England will similarly mean that these resources are unlikely to be of future economic interest.

Clay

The major clay resource of the area is the Triassic Mercia Mudstone Group, which occurs over extensive areas in the eastern part of the district. These strata were formerly exploited at Belton and Crowle for brickmaking, but production is now confined to a quarry at Melwood [SE 800 020], south-east of Epworth. The clay is transported to Belton for use in the production of facing bricks, output being about 35 million bricks a year. The bricks are fired in a suspended arch Hoffmann kiln at a temperature of 1000°C. The red mudstones of the Mercia Mudstone contain variable amounts of fine-grained dolomite and calcite, the presence of which has a bleaching effect on the fired colour of the clay; as the MgO + CaO/Fe₂O₃ ratio increases, the fired colour becomes lighter, ultimately producing buff-coloured bricks. Selective quarrying of specific horizons facilitates the production of a range of fired colours. A typical run of-quarry analysis of a clay from the Melwood quarry is shown in (Table 1).

Silica sand

Silica sand for the production of coloured glass containers is produced from blown sand deposits at Langholme Farm [SK 745 980], south of Westwoodside. The deposit is worked below the water table by suction dredging, subsequent processing consisting of coarse screening and upward current classification, to produce a sand product with a particle-size distribution almost wholly within the range 500 gm to 125 gm. The sand deposit has a variable iron content, mainly within the range 0.25 to 0.50 per cent Fe₂O₃, present as coatings on the sand particles and as discrete iron-bearing minerals. Selective quarrying and subsequent blending during processing is thus necessary to maintain the iron content within the specification of <0.35 per cent Fe₂O₃. However, the proposed installation of a high-intensity wet magnetic separator within the processing circuit will enable higher-iron sands to be treated, and will significantly increase reserves. A mean chemical analysis of the sand product is given in (Table 2).

The sand is used in the manufacture of coloured glass containers, with colours ranging from pale green tinted (half white), through to a pale greenish amber to a full brown, and also to a full green. Similar deposits of blown sand are worked to the west of Westwoodside, principally as a source of building sand.

Limestone

Lower Magnesian Limestone crops out along the western margin of the district but is only exploited at Stainton, near Maltby, in Holme Hall Quarry and Glen Quarry. At Stain-ton the Lower Magnesian Limestone, which is otherwise somewhat variable, produces good quality dolomitic aggregates suitable for use in concrete and for coating with bitumen.

Peat

The peat deposits on Hatfield Moors and on Thorne Moors, the latter including Crowle, Swinefleet and Goole moors, have been exploited for many years, and the industry based on these resources is currently one of the largest in Great Britain. Major production is currently centred on Hatfield Moors, although the main resources lie on Thorne Moors.

The peat is extracted by both a mechanised block cutting method and a surface milling technique, the latter accounting for an increasing proportion of the output. Between 1 and 2 m are recovered depending on the original thickness of the peat. Prior to extraction the peat has to be dewatered, which involves the digging of a system of drainage ditches.

The surface milling method involves the use of a rotovator to break up the top few tens of centimetres of peat, which is subsequently removed by a small bulldozer. It is essential that the peat is dry before the bulldozer can operate satisfactorily and hence working is confined to dry periods during the summer months. Peat blocks are stacked and air-dried. Both surface milled peat and peat blocks are coarse screened to remove pieces of wood and may be further milled to break up peat fibres.

The peat is used for a variety of horticultural applications. The upper part of the deposit produces a light brown, open-textured peat which is of premium quality. A darker, more compact material from lower levels is of less value.

Appendix 1 Synopses of shafts and boreholes proving identifiable Carboniferous strata

The most detailed recorded shaft from each colliery, all boreholes in the district which prove an identifiable part of the Carboniferous (Figure 47), and those boreholes outside the district that are mentioned in the Carboniferous chapter are briefly summarised below. Each summary provides depths of the highest and lowest identifiable Carboniferous stratigraphical units, generally marine bands or coals, and includes depths of the Barnsley Coal or Warren House Coal and the marine bands that define the bases of stages. Where these beds are not proved, the depth of the nearest identifiable suprajacent and/or subjacent units are given. Where appropriate, the summaries refer to any of the figures in the memoir which include parts of the pre-Quaternary succession from the shaft or borehole, and also to the detailed records listed by Edwards (1951), although some of the correlations in the summaries differ from those given by Edwards. The recorded depths to the base of Quaternary deposits must be regarded as approximations only, and some of the depths to the bases of the Sherwood Sandstone and the Permian rocks may similarly not be accurate. Detailed logs of all the known shafts and boreholes in the district are deposited in the National Geological Records Centre at Keyworth and, except where restricted by confidentiality, may be studied or copied by prior arrangement.

Abbreviations

Airmyn Grange Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE72SW/40) [SE 7013 2393] SL 4.82 m above OD. (Figure 17) shows Westphalian C strata.

Armthorpe Borehole

Drilled before 1913, probably for Earl Fitzwilliam. 6-in (SE60SW/20) [SE 6207 0370] SL c.7.6 m above OD. (For detailed log see Edwards, 1951, pp.122–123.)

Ash Hill Borehole

Drilled 1956 by John Thom Ltd for NCB. 6-in (SE61NW/2) [SE 6213 1615] SL 4.90 m above OD

Askern Colliery No. 1 Shaft

Sunk 1912. 6-in (SE51SE/7) [SE 5577 1377] SL c.24.4 m above OD. (For detailed log see Edwards, 1951, pp.123–126; (Figure 13) shows lower part of Westphalian B strata.)

Askern Oil Borehole

Drilled 1957 for BP Exploration Co. Ltd. 6-in (SE51NE/1) [SE 5652 1502] SL not recorded BL 7.74 m above OD. (Figure 4) shows Carboniferous Limestone and Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts of Westphalian A strata.

Austerfield Borehole

Drilled 1978 by Kenting Drilling Services Ltd for NCB. 6-in (SK69NE/63) [SK 6594 9633] SL 15.52 m above OD BL 18.57 m above OD. (Figure 18) shows upper part of Westphalian C strata and (Figure 21) shows Permian rocks.

Axholme Borehole

Drilled 1927–28 by Foraky Ltd. 6-in (SE70NE/1) [SE 7597 0637] SL not recorded, but c.3 m above OD. (Figure 27) shows Mercia Mudstone.

Axholme No. 1 Oil Borehole

Drilled 1973 for Candecca Resources Ltd. 6-in (SE70SE/5) [SE 7810 0445] SL 11.88 m above OD BL 15.82 m above OD. (Figure 4) and (Figure 5) show Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata; and (Figure 27) shows Mercia Mudstone.

Axholme No. 2. Oil Borehole

Drilled 1973 for Candecca Resources Ltd. 6-in (SE70SE/6) [SE 7934 0298] SL 33.02 m OD BL 37.37m above OD. (Figure 5) shows Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata.

Axholme No. 3 Oil Borehole

Drilled 1976 by Thompson Drilling (UK) Ltd for Candecca Resources Ltd. 6-in (SE70SE/8) [SE 7868 0434] SL 18.64 m OD. BL 22.41 m above OD

Bank End Borehole

Drilled 1965 by Foraky Ltd for NCB. 6-in (SK79NW/2a) [SK 7063 9972] SL 0.81 m above OD. (Figure 18) shows upper part of Westphalian C strata.

Barlow No. 1 Borehole

Drilled 1904. 6-in (SE62NW/8) [SE 6411 2924] SL 4.91 m above OD

Barlow No. 2 Borehole

Drilled 1964 by Foraky Ltd for NCB. 6-in (SE62NW/2) [SE 6233 2891] SL 4.51 m above OD

Barlow Oil Borehole

Drilled 1973. 6-in (SE62NW/15) [SE 6335 2786] SL 4.22 m above OD BL 8.19 m above OD. (Figure 4) and (Figure 5) show Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata.

Belton Oil Borehole

Drilled 1945 for Anglo-American Oil Co. Ltd. 6-in (SE70NE/4) [SE 7771 0846] SL 2.44 above OD BL 4.72 m above OD. (Figure 4) shows Carboniferous Limestone and Millstone Grit; (Figure 9) shows lower part of Westphalian A strata; (Figure 27) shows Mercia Mudstone; for some other details see Edwards, 1951, p.267.

Bentley Colliery No. 2 Shaft

Sunk to Barnsley Coal c.1907; extended to present depth 1937–39. 6-in (SE50NE/10) [SE 5696 0746] SL 6.40 m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 16) shows upper part of Westphalian B strata; for detailed log see Edwards, 1951, pp.127–130.

Bentley No. 1 Borehole

Drilled 1887–90 by Vivians Boring and Exploration Co. Ltd for Bently Exploration Co. Ltd. 6-in (SE50NE/1) [SE 571 059] SL not recorded, probably c.7.5 m above OD

Bentley No. 2 Borehole

Drilled 1895 by Vivians Boring and Exploration Co. Ltd. 6-in (SE50NE/11) [SE 568 073] SL not recorded, probably c.6.1 m above OD

Blyton Carr Borehole

Drilled 1977 by Kenting (UK) Ltd for NCB. 6-in (SK89SW/56) [SK 8225 9401] SL 2.99 m above OD BL 6.04m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 16) shows upper part of Westphalian B strata; (Figure 21) shows Permian rocks.

Booth Ferry Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE72NW/15) [SE 7385 2583] SL 3.87 m above OD. (Figure 13) shows lower part of Westphalian B strata

Brancroft Borehole

Drilled 1977 by Kenting (UK) Ltd for NCB. 6-in (SK69NE/60) [SK 6726 9663] SL 1.78 m above OD. BL 4.83 m above OD

Brier Hills Borehole

Drilled 1977 by Foraky Ltd for NCB. 6-in (SE70NW/11) [SE 7108 0850] SL 1.88 m above OD. (Figure 13) and (Figure 16) show lower and upper parts respectively of Westphalian B strata; (Figure 17) shows lower part of Westphalian C strata.

Brind Common Borehole

Drilled 1977 by Foraky Ltd for NCB. 6-in (SE73SE/2) [SE 7520 3129] SL 4.64 m above OD. (Figure 16) shows upper part of Westphalian B strata; (Figure 21) shows Permian rocks.

Bryan Close Borehole

Drilled 1979 by Kenting Drilling Services Ltd for NCB. 6-in (SK69NE/66) [SK 6773 9551] SL 8.55 m above OD. BL 11.60 m above OD

Burn Airfield No. 1 Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE62NW/27) [SE 6052 2902] SL 6.40 m above OD

Burn Airfield No. 2 Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE62NW/28) [SE 6018 2721] SL 5.42 m above OD

Camblesforth No. 1 Borehole

Drilled 1964–65 by Foraky Ltd for NCB. 6-in (SE62NW/1) [SE 6487 2558] SL 3.83 m above OD. (Figure 16) shows upper part of Westphalian B strata; (Figure 21) shows Permian rocks.

Camblesforth No. 2 Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE62NW/26) [SE 6406 2763] SL 4.00 m above OD

Camblesforth No. 3 Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE62NW/29) [SE 6290 2589] SL 5.38 m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 13) shows lower part of Westphalian B strata.

Cantley No. 1 Borehole

This borehole has been referred to as 'Armthorpe No. 1 Bore hole' on some records but should not be confused with Armthorpe Borehole summarised above in this appendix. Drilled 1914 by International Bohrgesellschaft, Erkeleng for Sir Arthur Markham.. 6-in (SE60SW/22) [SE 6166 0436] SL c.15 m above OD

Cantley No. 2 Borehole

Drilled between 1914 and 1922 for Sir Alfred Markham. 6-in (SE60SW/18) [SE 6330 0308] SL c.7 m above OD

Carlton (West Bank) Borehole

Drilled in or before 1882. 6-in (SE62SW/6) [SE 6279 2340] SL c.6 m above OD. For detailed log see Edwards, 1951, p.152; a slightly different log was recorded in MS by A H Green, dated 1882, and includes 'Black shale, fish scales, spines or teeth, Anthracosia, Ostracods, Spirorbis' at 361.98 m; by comparison with nearby boreholes most of the Coal Measures proved lie between the Sharlston coals and the Shafton Marine Band, but exact correlation is uncertain.

Carr Head Lane Borehole

Drilled 1974 by Drilling and Prospecting International Ltd for NCB. 6-in (SE61NE/13) [SE 6568 1551] SL 3.61 m above OD

Chapel Haddlesey Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE52NE/21) [SE 5806 2647] SL 6.74 m above OD

Cornley Borehole

Drilled 1975 by Kenting (UK) Ltd for NCB. 6-in (SK79SW/20) [SK 7440 9474] SL 2.8 m above OD

Cross Hill Borehole

Drilled 1953 by John Thom Ltd for NCB. 6-in (SE61NW/1) [SE 6013 1895] SL not recorded BL 6.51 m above OD

Crowle Oil Borehole

Drilled 1966 for BP Petroleum Development Ltd. 6-in (SE71SE/7) [SE 7734 1193] SL not recorded BL 5.21 m above OD. (Figure 4) shows Millstone Grit; (Figure 9) shows lower part of Westphalian A strata; (Figure 21) shows Permian rocks; (Figure 26) shows Sherwood Sandstone; (Figure 27) shows Mercia Mudstone.

Crowle Common Borehole

Drilled 1976 by Foraky Ltd for NCB. 6-in (SE71SE/25) [SE 7619 1387] SL 1.37 m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 13) and (Figure 16) show lower and upper parts respectively of Westphalian B strata.

Drax No. 1 Borehole

Drilled 1912–15 by New Calyx Co.. 6-in (SE72SW/33) [SE 701 249] SL c.3 m above OD. (For detailed log see Edwards, 1951, pp. 164–165.)

Drax No. 2 Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE62NE/26) [SE 6870 2540] SL 3.94 m above OD

Drax No. 3 Borehole

Drilled 1977–78 by Foraky Ltd for NCB. 6-in (SE62NE/22) [SE 6828 2744] SL 4.10 m above OD. (Figure 13) shows lower part of Westphalian B strata.

Drax No. 4 Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE62SE/28) [SE 6726 2424] SL 3.70 m above OD

East Stockwith Borehole

Drilled 1977 by Kenting (UK) Ltd for NCB. 6-in (SK79NE/26) [SK 7974 9565] SL 4.11 m above OD. BL 7.16 m above OD. (Figure 13) shows lower part of Westphalian B strata.

Eggborough No. 1 Borehole

Drilled 1976 by Kenting (UK) Ltd for NCB. 6-in (SE52SE/34) [SE 5660 2399] SL not recorded BL 16.85 m above OD. (Figure 16) shows upper part of Westphalian B strata.

Eggborough No. 2 Borehole

Drilled 1977 by Thompson Drilling (UK) Ltd for NCB. 6-in (SE52SE/35) [SE 5648 2386] SL 17.1 m above OD

Eggborough No. 3 Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE52SE/37) [SE 5773 2320] SL 6.50 m above OD

Eskholme Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE61NW/16) [SE 6372 1742] SL 5.61 m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 13) shows lower part of Westphalian B strata.

Fenwick Borehole

Drilled 1950–51 by John Thom Ltd for NCB. 6-in (SE51NE/3) [SE 5869 1623] SL 6.17 m. (Figure 10) shows upper part of Westphalian A strata; (Figure 16) shows upper part of Westphalian B strata.

Fenwick Common Borehole

Drilled 1956 by John Thom Ltd for NCB. 6-in (SE51SE/3) [SE 5891 1480] SL 6.09 m above OD

Fenwick Grange Borehole

Drilled 1978–79 by Foraky Ltd for NCB. 6-in (SE61SW/33) [SE 6147 1444] SL 4.65 m above OD

Fenwick Hall Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE61NW/15) [SE 6053 1616] SL 5.68 m above OD

Finningley No. 2 Borehole

Drilled 1970s or early 1980s by Kenting (UK) Ltd for NCB. 6-in (SK69NE/67) [SK 6813 9855] SL 3.82 m above OD. No details of Quaternary deposits, Triassic rocks or Permian rocks available. Coal Measures with Meltonfield Coal at 801.57m, Barnsley and Dunsil coals at 945.36m and Parkgate Coal at 1113.13m; final depth not available

Fir Tree Borehole

Drilled 1978–79 by Foraky Ltd for NCB. 6-in (SE73SE/3) [SE 7830 3291] SL 4.55 m above OD

Fishlake Borehole

Drilled 1955–56 by John Thom Ltd for NCB. 6-in (SE61SE/3) [SE 6606 1352] SL 4.75 m

Fosterhouses Borehole

Drilled 1954–55 by John Thom Ltd for NCB. 6-in (SE61SE/5) [SE 6514 1478] SL 5.18 m above OD. (Figure 16) shows upper part of Westphalian B strata; (Figure 17) shows lower part of Westphalian C strata.

Gate Farm Borehole

Drilled 1956 by Craelius Co. Ltd for NCB. 6-in (SE60SE/7) [SE 6644 0390] SL 5.11 m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 16) shows upper part of Westphalian B strata; (Figure 17) shows lower part of Westphalian C strata.

Gowdall Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE62SW/23) [SE 6154 2238] SL 4.85 m above OD. (Figure 17) shows lower part of Westphalian C strata.

Great Heck Borehole

Drilled 1957–58 by John Thom Ltd for NCB. 6-in (SE52SE/4) [SE 5867 2155] SL 13.12 m above OD. (Figure 21) shows Permian rocks.

Grove House Borehole

Drilled 1973–74 by Foraky Ltd for NCB. 6-in (SE71SW/10) [SE 7162 1105] SL 2.29 m above OD. (Figure 17) and (Figure 18) show lower and upper parts respectively of Westphalian C strata.

Hatfield Main Colliery Shaft

Sunk 1916. 6-in (SE61SE/8) [SE 6531 1129] SL 5.36 m above OD. (Figure 26) shows Sherwood Sandstone.

Hatfield No. 1 Oil Borehole

Drilled 1965–66 for BP Petroleum Development Ltd. 6-in (SE60NE/21) [SE 6931 0696] SL not recorded BL 5.09 m above OD. (Figure 4) and (Figure 5) show Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata; (Figure 21) shows Permian rocks.

Hatfield No 2. Oil Borehole

Drilled 1966 for BP Petroleum Development Ltd. 6-in (SE60NE/22) [SE 6724 0674] SL not recorded BL 7.56 m above OD. (Figure 5) shows upper part of Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata.

Hatfield Moors No. 1 Oil Borehole

Drilled 1981–82 by Kenting Drilling Services Ltd for Taylor Woodrow Energy Ltd. 6-in (SE70NW/15) [SE 7035 0668] SL 1.22 m above OD. BL 5.49 m above OD

Hatfield Moors No. 2 Oil Borehole

Drilled 1983 by Kenting Drilling Services Ltd for Taylor Woodrow Energy Ltd. 6-in (SE70NW/16) [SE 7174 0675] SL 2.07 m above OD. BL 5.79 m above OD

Hatfield West Oil Borehole

Drilled 1983 by Kenting Drilling Services Ltd for Taylor Woodrow Energy Ltd. 6-in (SE60NE/68) [SE 6766 0604] SL 2.68 m above OD. BL 7.01 m above OD

Haxey Borehole

Drilled 1893 by Vivian Boring and Exploration Ltd for ?the Duke of Portland. 6-in (SK79NW/1) [SK 7242 9677] SL c.5.5 m above OD. (Figure 26) shows Sherwood Sandstone; (Figure 27) shows Mercia Mudstone; for detailed log see Edwards, 1951, pp.183–184.

Hemingbrough Borehole

Drilled 1967 by Foraky Ltd for NCB. 6-in (SE63SE/3) [SE 6970 3073] SL 5.91 m above OD. (Figure 10) shows upper part of Westphalian A strata.

Heyworth Lane Borehole

Drilled 1956 by Craelius Co. Ltd for NCB. 6-in (SE51SE/2) [SE 5826 1360] SL 6.44 m above OD

Holme Wood Lane Borehole

Drilled 1955 by John Thom Ltd for NCB. 6-in (SE60SW/16) [SE 6433 0459] SL 5.08 m above OD

Idle Borehole

Drilled 197475 by Foraky Ltd for NCB. 6-in (SK69SE/25) [SK 6880 9382] SL 3.52 m above OD

Kellington No. 2 Borehole

Drilled 1957 by Cementation Co. Ltd for NCB. 6-in (SE52SE/3) [SE 5551 2431] SL 11.24 m above OD

Kellington No. 3 Borehole

Drilled 1957 by Cementation Co. Ltd for NCB. 6-in (SE52NE/1) [SE 5503 2562] SL 6.03 m above OD

Kellington No. 7 Borehole

Drilled 1973 by Drilling and Prospecting International Ltd for NCB. 6-in (SE52SE/27) [SE 5518 2316] SL 7.77 m above OD

Kellington No. 8 Borehole

Drilled 1977 by Drilling and Prospecting International Ltd for NCB. 6-in (SE52NE/16) [SE 5519 2557] SL 4.99 m above OD

Kellington Common Borehole

Drilled 1954–55 by Craelius Co. Ltd for NCB. 6-in (SE52SE/1) [SE 5502 2200] SL 8.38 m above OD

Lady Galway Borehole

Drilled 1978 by Kenting Drilling Services Ltd for NCB. 6-in (SK69NE/64) [SK 6605 9657] SL 10.60 m above OD. BL 13.65 m above OD

Langholme Borehole

Drilled 1977 by Kenting (UK) Ltd for NCB. 6-in (SK79NE/27) [SK 7582 9700] SL 3.20 m above OD. BL 6.25 m above OD. (Figure 17) and (Figure18) show lower and upper parts respectively of Westphalian C strata.

Laughton Borehole

Drilled 1975 by Kenting (UK) Ltd for NCB. 6-in (SK89NW/36) [SK 8135 9674] SL 1.80 m above OD. (Figure 27) shows Mercia Mudstone.

Lee Lane Borehole

Drilled 1975 by Thompson Drilling (UK) Ltd for NCB. 6-in (SE52SE/30) [SE 5665 2046] SL 6.39 m above OD. BL 9.96 m above OD

Lindholme Borehole

Drilled 1923 by Simon Carves Ltd. 6-in (SE70NW/5) [SE 7108 0789] SL c.3.5 m above OD

Markham Main Colliery No. 1 Shaft

Sunk 1922 to just below Barnsley Coal; extended to present depth in 1959–60 by Cementation Co. Ltd for NCB. 6-in (SE60SW/15) [SE 6168 0453] SL 19.45 m above OD (Depths down to and including Barnsley Coal appear to have been measured from a level 21.34 m above OD). (Figure 13) shows lower part of Westphalian B strata; (Figure 26) shows Sherwood Sandstone; for detailed log see Edwards, 1951, pp.210–212.

Martin Common Borehole

Drilled 1977 by Kenting (UK) Ltd for NCB. 6-in (SK69NW/82) [SK 6332 9522] SL 32.41 m above OD. BL 35.46 m above OD

Mill Field Road Borehole

Drilled 1974 by Drilling and Prospecting International Ltd for NCB. 6-in (SE61SW/16) [SE 6444 1388] SL 4.74 m above OD

Misson Borehole

Drilled 1955–56 by Foraky Ltd for NCB. 6-in (SK69NE/8) [SK 6950 9578] SL 6.45 m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 13) and (Figure 16) show lower and upper parts respectively of Westphalian B strata; (Figure 17) and (Figure 18) show lower and upper parts respectively of Westphalian C strata.

Misterton Borehole

Drilled 1977 by Kenting (UK) Ltd for NCB. 6-in (SK79SE/33) [SK 7642 9397] SL 20.55 m above OD. BL 23.60 m above OD

Moss Oil Borehole

Drilled 1979 by Foraky Ltd for NCB; deepened below 723 m for BP Petroleum Development (UK) Ltd.. 6-in (SE51SE/19) [SE 5998 1390] SL 7.72 m above OD No information available down to basal part of Coal Measures; Listeri MB at c.891.17 m, base of Coal Measures at ? c.925–930 m; Millstone Grit with C. cancellatum MB at c.956.60 m, B. superbilinguis MB at c. 981.54 m and B. gracilis MB at c.1055.27 m; total depth 1100 m (Figure 6) shows upper part of Millstone Grit and basal part of Coal Measures.

New Bridge Borehole

Drilled 1975 by Thompson Drilling (UK) Ltd for NCB. 6-in (SE62SE/20) [SE 6744 2023] SL 5.92 m above OD

Newington Borehole

Drilled 1975 by Foraky Ltd for NCB. 6-in (SK69SE/26) [SK 6719 9389] SL 5.60 m above OD

North Carr Borehole

Drilled 1975 by Kenting (UK) Ltd for NCB. 6-in (SK79NE/25) [SK 7815 9619] SL 2.50 m above OD

North Ewster Borehole

Drilled 1977 for NCB. 6-in (SE80SW/30) [SE 8363 0389] SL 4.22 m above OD

Ox Carr Wood Borehole

Drilled 1954 by John Thom Ltd for NCB. 6-in (SE60SW/14) [SE 6249 0353] SL 7.46 m above OD. (Figure 17) and (Figure 18) show lower and upper parts respectively of Westphalian C strata.

Pale Lane Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE52NE/23) [SE 5593 2826] SL 7.72 m above OD

Partridge Hill Borehole

Drilled 1978 by Kenting Drilling Services Ltd for NCB. 6-in (SK69NE/61) [SK 6604 9600] SL 10.89 m above OD. BL 13.94 m above OD

Percy Lodge Borehole

Drilled 1975 by Thompson Drilling (UK) Ltd for NCB. 6-in (SE72SW/35) [SE 7187 2203] SL 8.09 m above OD

Pincheon Green Borehole

Drilled 1955–56 by John Thom Ltd for NCB. 6-in (SE61NE/1) [SE 6535 1736] SL 4.13 m above OD. (Figure 17) and (Figure 18) show lower and upper parts respectively of Westphalian C strata.

Pipers Wood Borehole

Drilled 1974 by Foraky Ltd. 6-in (SK69SW/10) [SK 6355 9403] SL 29.58 m above OD

Pollington No. 1 Borehole

Drilled 1911–13. 6-in (SE62SW/7) [c.SE 605 215] SL c.7 m above OD. (For detailed log see Edwards, 1951, pp.223–225. The close correlation of the above-listed coals, and other coals in the log, with those in nearby boreholes demonstrates that the 'shale, black with marine shells' recorded from 641.15 m lies close above the inferred Haigh Moor Coal. No correlations of coals are possible if this supposed marine occurrence is equated with either the Vanderbeckei MB (as previously inferred) or the Maltby MB)

Pollington No. 2 Borehole

Drilled 1958 by Foraky Ltd for NCB. 6-in (SE62SW/1) [SE 6244 2010] SL 5.41 m above OD

Pollington No. 3 Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE52SE/38) [SE 5990 2070] SL 9.86 m above OD. (Figure 26) shows Sherwood Sandstone.

Quay Lane Borehole

Drilled 1976 by Foraky Ltd for NCB. 6-in (SE71NE/8) [SE 7690 1933] SL 2.80 m above OD

Rawcliffe No. 1 Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE62SE/27) [SE 6736 2202] SL 4.54 m above OD

Rawcliffe No. 2 Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE62SE/29) [SE 6908 2231] SL 2.89 m above OD. (Figure 10) shows upper part of Westphalian A strata.

Rawcliffe Bridge Borehole

Drilled 1975 by Thompson Drilling (UK) Ltd for NCB. 6-in (SE62SE/21) [SE 6987 2085] SL 6.78 m(Figure 26) shows Sherwood Sandstone.

Roall Ings Borehole

Drilled 1979 by Foraky Ltd for NCB. 6-in (SE52NE/22) [SE 5550 2560] SL 5.44 m above OD

Rossington Colliery No. 1 Shaft

Sunk 1912–15 to 816.25m, extended 1964 to present depth by NCB. 6-in (SK69NW/23) [SK 6013 9839] SL 5.59 m above OD. (Figure 18) shows upper part of Westphalian C strata.

Scaftworth No 2 Oil Borehole

Drilled 1982 by BP Petroleum Development (UK) Ltd. 6-in (SK69SE/56) [SK 6718 9228] SL 8.3 m above OD. BL 13.9 m above OD. (Figure 4) shows Carboniferous Limestone and Millstone Grit; (Figure 5) shows upper part of Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata.

Selby No. 1 Borehole

Drilled 1909–10 by New Calyx Co.. 6-in (SE63SW/1) [SE 6276 3025] SL c.4.9 m above OD. (For detailed log see Edwards, 1951, pp. 231–232.)

Selby No. 2 Borehole

Drilled 1974 by Foraky Ltd for NCB. 6-in (SE63SW/49) [SE 6011 3233] SL 6.94 m above OD. (Figure 21) shows Permian rocks.

Shaftholme Grange Borehole

Drilled 1975 by Drill Sure Ltd for NCB. 6-in (SE50NE/33) [SE 5764 0877] SL 5.15 m above OD. (Figure 17) and (Figure 18) show lower and upper parts respectively of Westphalian C strata; (Figure 21) shows Permian rocks.

Snaith Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE62SW/45) [SE 6438 2277] SL 3.92 m above OD

Spital Croft Borehole

Drilled 1977 by Foraky Ltd for NCB. 6-in (SK59SE/26) [SK 5757 9493] SL 42.79 m above OD

Stainforth Borehole

Drilled 1955 by John Thom Ltd for NCB. 6-in (SE61SE/4) [SE 6515 1222] SL 4.19 m above OD

Sun Inn Borehole

Drilled 1954 by John Thom Ltd for NCB. 6-in (SE50SE/21) [SE 5536 0492] SL 10.63 m above OD. (Figure 18) shows upper part of Westphalian C strata.

Thorne Colliery No. 1 Shaft

Sunk 1909–24 by Cementation Co. Ltd. 6-in (SE71NW/1) [SE 7066 1588] SL 3.30 m above OD. (Figure 18) shows upper part of Westphalian C strata; (Figure 26) shows Sherwood Sandstone; for detailed log see Edwards, 1951, pp. 249–251.

Thorne Colliery Centre Borehole

Drilled 1978 by Foraky Ltd for NCB. 6-in (SE71NW/29) [SE 7083 1573] SL 5.17 m above OD. (Figure 21) shows Permian rocks.

Thorpe Hall Borehole

Drilled 1973 by Foraky Ltd for NCB. 6-in (SE53SE/12) [SE 5776 3203] SL 6.21 m above OD

Top House Borehole

Drilled 1975 by Thompson Drilling (UK) Ltd for NCB. 6-in (SE71NW/20) [SE 7112 1910] SL 5.50m above OD

Trumfleet Borehole

Drilled 1953–54 by John Thom Ltd for NCB. 6-in (SE51SE/1) [SE 5994 1177] SL 6.23 m above OD

Trumfleet No. 1 Oil Borehole

Drilled 1956–57 for BP Exploration Ltd. 6-in (SE61SW/4) [SE 6052 1264] SL not recorded BL 8.18 m above OD. (Figure 4) shows Carboniferous Limestone and Millstone Grit; (Figure 5) shows upper part of Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata.

Trumfleet No. G1 Oil Borehole

Drilled 1956 for BP Exploration Co. Ltd on the same site as Trumfleet No 1 Oil Borehole; proved Quaternary deposits to c.18 m, Sherwood Sandstone to c.104 m, Permian rocks to 250.55 m and Coal Measures with Manton 'Estheria' Band at c.255 m to bottom of borehole at 280.72 m

Trumfleet No. 2 Oil Borehole

Drilled 1958 for BP Exploration Co. Ltd. 6-in (SE61SW/5) [SE 6033 1246] SL not recorded BL 8.66 m above OD

Trumfleet No. G2 Oil Borehole

Drilled 1956 for BP Exploration Co. Ltd. 6-in (SE61SW/22) [SE 6183 1326] SL 5.00 m above OD

Trumfleet No. 3 Oil Borehole

Drilled 1962 for BP Exploration Co. Ltd. 6-in (SE61SW/20) [SE 6056 1195] SL not recorded BL 6.97 m above OD

Trumfleet No. 5 Oil Borehole

Drilled 1965–66 for BP Petroleum Development Ltd. 6-in (SE61SW/8) [SE 6056 1141] SL not recorded BL 7.74 m above OD. (Figure 5) shows upper part of Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata.

Warmsworth Oil Borehole

Drilled 1982 by Kenting Drilling Services Ltd for RTZ Oil and Gas Ltd. 6-in (SE50SW/64) [SE 5394 0124] SL 44.15 m above OD. BL 48.02 m above OD. (Figure 4) and (Figure 5) show Millstone Grit; (Figure 8) and (Figure 9) show basal and lower parts respectively of Westphalian A strata.

Weeland Road Borehole

Drilled 1982 by Kenting Drilling Services Ltd for NCB. 6-in (SE52SE/40) [SE 5540 2388] SL 14.79 m above OD. BL 18.63 m above OD

West Haddlesey No. 1 Borehole

Drilled 1977 by Foraky Ltd for NCB. 6-in (SE52NE/17) [SE 5626 2720] SL 7.04 m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 13) shows lower part of Westphalian B strata.

West Haddlesey No. 2 Borehole

Drilled 1978 by Kenting (UK) Ltd for NCB. 6-in (SE52NE/20) [SE 5511 2695] SL 6.71 m above OD. BL 9.14 m above OD

Westwoodside Borehole

Drilled 1965–66 by Foraky Ltd for NCB. 6-in (SE70SW/3) [SE 7430 0027] SL 4.30 m above OD. (Figure 26) shows Sherwood Sandstone; (Figure 27) shows Mercia Mudstone.

Whitley Bridge Borehole

Drilled 1957 by Cementation Co. Ltd for NCB. 6-in (SE52SE/2) [SE 5570 2281] SL 7.29 m above OD

Wilsic Hall Borehole

Drilled 1981 by Kenting Drilling Services Ltd for NCB. 6-in (SK59NE/32) [SK 5676 9601] SL 61.83 m above OD. BL 64.53 m above OD. (Figure 10) shows upper part of Westphalian A strata; (Figure 13) shows lower part of Westphalian B strata; (Figure 17) and (Figure 18) show lower and upper parts respectively of Westphalian C strata.

Wilsic Lodge Borehole

Drilled 1977 by Kenting Drilling Services Ltd for NCB. 6-in (SK59NE/24) [SK 5592 9515] SL 78.09 m above OD. (Figure 16) shows upper part of Westphalian B strata.

Wood Close Borehole

Drilled 1978 by Kenting Drilling Services Ltd for NCB. 6-in (SK69NE/62) [SK 6559 9583] SL 19.49 m above OD. BL 22.54 m above OD

Wood End Borehole

Drilled 1973 by Foraky Ltd for NCB. 6-in (SE61SW/15) [SE 6287 1317] SL 5.60 m above OD

Woodhouse Borehole

Drilled 1974 by Drilling and Prospecting International Ltd for NCB. 6-in (SE61SW/19) [SE 6369 1318] SL 4.36 m above OD

Wressle Borehole

Drilled in or before 1912 by New Calyx Co.. 6-in (SE73SW/2) [SE 7205 3034] SL c.6 m above OD. The marine band at 658.06 m is probably the Aegiranum or Haughton MB and the trace of coal at 761.34 m is probably the Hatfield High Hazel or Kents Thick Coal. If valid, the Goniatites?' at 888.49m imply the Vanderbeckei MB. (Figure 26) shows Sherwood Sandstone; for detailed log see Edwards, 1951, pp. 263–264.)

Appendix 2 Geological Survey photographs

Copies of photographs illustrating the geology and landscape of the district are kept for reference in the library of the British Geological Survey at Keyworth. Copies can be supplied at a fixed tariff. Photographs whose number is prefixed with A are available only in black and white; the others can be supplied as colour prints and transparencies.

Goole (79) - Permian and Trias

Doncaster (88) - Permian and Trias

Quaternary

References

Most of the references listed below are held in the Library of the British Geological Survey at Keyworth, Nottingham. Copies of the references can be purchased subject to the current copyright legislation.

ARVESCHOUG, N C. 1986. The Market Weighton Carboniferous trough. Circular of the Yorkshire Geological Society, No. 393, 3.

AVELINE, W T. 1880. The geology of parts of Nottinghamshire, Yorkshire and Derbyshire (2nd edition). Memoir of the Geological Survey of Great Britain, Old Series Quarter Sheet 82NE.

BALCHIN, D A, and RIDD, M F. 1970. Correlation of the younger Triassic rocks across eastern England. Quarterly Journal of the Geological Society of London, Vol. 126, 91–101.

BEAUMONT, P, TURNER, J, and WARD, P F. 1969. An Ipswichian peat raft in glacial till at Hutton Henry, Co. Durham. New Phytologist, Vol. 68, 797–805.

BISAT, W S, and HUDSON, R G S. 1943. The Lower Reticuloceras (R) goniatite succession in the Namurian of the north of England. Proceedings of the Yorkshire Geological Society, Vol.24, 383 440.

BISAT, W S. 1946. Fluvio-glacial gravels at Stanley Ferry, near Wakefield. Transactions of the Leeds Geological Association, Vol. 6, 31–36.

BOTT, M H P. 1988. The Market Weighton anomaly-granite or graben?. Proceedings of the Yorkshire Geological Society, Vol. 47, 47–53.

BOTT, M H P. ROBINSON, J, and KOHNSTAMM, M A. 1978. Granite beneath Market Weighton, east Yorkshire. Journal of the Geological Society of London, Vol. 135, 535–543.

BOWEN, D W. 1978. Quaternary geology. A stratigraphic framework for multidisciplinary work. (Oxford: Pergamon Press.)

BOWEN, D Q and SYKES, G A. 1991. Discussion of 'The correlation of the Speeton Shell Bed, Filey Bay, Yorkshire, to an oxygen isotope stage'. Proceedings of the Yorkshire Geological Society, Vol.48, 463–465.

BROMEHEAD, C E N., EDWARDS, W, WRAY, D A, and STEPHENS, J V. 1933. The geology of the country around Holmfirth and Glossop. Memoir of the Geological Survey of Great Britain, Sheet 86.

BUCKLAND, P C. 1979. Thorne Moors: a palaeoecological study of a Bronze Age site. Occasional Publication of the University of Birmingham Department of Geology, No. 8.

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Index of fossils

• Acanthocladia sp.
• Acanthocladia anceps (Schlotheim)
• Acanthocladia anceps laxa (Korn)
• Agastrioceras carinatum (French)
• Agathammina
• Agathammina milioloides (Paalzow non Jones Parker and Kirkby)
• Agathammina. pusilla (Geinitz)
• Agathamminoides sp.
• Ammodiscus sp.
• Amplexizaphrentis cf. enniskilleni (Milne-Edwards and Haine)
• Anthrococeras sp.
• Anthracoceratites sp.
• Anthraconaia sp.
• Anthraconaia adamsii (Salter)
• Anthraconaia. sp. cf. adamsii (Salter)
• Anthraconaia curtata (Brown)
• Anthraconaia. aff. cymbula (Wright)
• Anthraconaia. librata (Wright)
• Anthraconaia. modiolaris (J de C Sowerby)
• Anthraconaia persulcata (Trueman & Weir)
• Anthraconaia. potoriba Pastiels
• Anthraconaia pulchella Broadhurst
• Anthraconaia. cf. pulchella Broadhurst
• Anthraconaia. cf. pumila (Salter)
• Anthraconaia. rubida (Davies & Trueman)
• Anthraconaia. aff. salteri (Leitch)
• Anthraconaia. cf. spathulata (Trueman & Weir)
• Anthraconaia. williamsoni (Brown)
• Anthraconauta phillipsii (Williamson)
• Anthraconeilo sp.
• cf. Anthraconeilo sp.
• Anthracosia/Anthracosia sp.
• Anthracosia
• Anthracosia acutella (Wright)
• Anthracosia atra (Trueman)
• Anthracosia cf. atra (Trueman)
• Anthracosia aquilina (J de C Sowerby)
• Anthracosia cf. aquilina (J de C Sowerby)
• Anthracosia aquilinoides (Tchernyshev)
• Anthracosia cf. aquilinoides (Tchernyshev)
• Anthracosia beaniana King
• Anthracosia cf. beaniana King
• Anthracosia caledonica? (Trueman & Weir)
• Anthracosia 'carissima'(Wright)
• Anthracosia concinna (Wright)
• Anthracosia disjuncta (Wright)
• Anthracosia disjuncta (Wright)/phrygiana (Wright)
• Anthracosia aff. faba (Wright)
• Anthracosia sp. cf. fulva (Davies & Trueman)
• Anthracosia lateralis (Brown)
• Anthracosia nitida (Davies & Trueman)
• Anthracosia ovum Trueman & Weir
• Anthracosia sp. ovum Trueman & Weir/phrygiana (Wright)
• Anthracosia planitumida (Trueman)
• Anthracosia cf. planitumida (Trueman)
• Anthracosia sp. nov. cf. phrygiana (Wright)
• Anthracosia aff. phrygiana (Wright)
• Anthracosia regularis (Trueman)
• Anthracosia simulans (Trueman & Weir)
• Anthracosia subrecta (Trueman & Weir)
• Anthracosphaerium/Anthracosphaerium? sp.
• Anthracosphaerium affine (Davies & Trueman)
• Anthracosphaerium cf. cycloquadratum (Wright)
• Anthracosphaerium sp. nov. cf. dawsoni (Brown)
• Anthracosphaerium propiniquum (Melville)
• Anthracosphaerium aff. propiniquum (Melville)
• Anthracosphaerium radiatum (Wright)
• Anthracosphaerium turgidum (Brown)
• Anthracosphaerium cf. turgidum (Brown)
• Antiquatonia
• Antiquatonia hindi (Muir-Wood)
• Antiquatonia cf. insculpta (Muir-Wood)
• Astartella?
• Athyris?
• Aviculopinna?
• Bakevellia/Bakevellia?
• Bakevellia binneyi (Brown)
• Baltisphaeridium
• Batostomella
• Batostomella columnaris (Schlotheim)
• Batostomella crassa (Lonsdale)
• Bilinguites
• Bilinguites bilinguis (Salter)
• Bilinguites gracilis (Bisat)
• Bilinguites superbilinguis (Bisat)
• Bithynia tentaculata (Linnaeus)
• Brachythyris integricostata (Phillips)
• Buxtonia sp. nov.
• Calcinema permiana (King), Podemski
• Calcitema?
• Calcitornella? minutissima (Howse)
• Calluna
• Cancelloceras sp.
• Cancelloceras cancellatum (Bisat)
• Cancelloceras crencellatum (Bisat)
• Cancelloceras crenulatum (Bisat)
• Cancelloceras cumbriense (Bisat)
• Caneyella multirugata (Jackson)
• Carbonicola sp.
• Carbonicola aff. communis Davies & Trueman
• Carbonicola crista-galli Wright
• Carbonicola deansi Eagar
• Carbonicola lenicurvata Trueman
• Carbonicola aff. martini Trueman & Weir
• Carbonicola oslancis Wright
• Carbonicola cf. polmontensis (Brown)
• Carbonicola pseudacutaTrueman
• Carbonicola rectilinearis? Trueman & Weir
• Carbonicola rhomboidalis (Hind)
• Carbonicola cf. rhomboidalis (Hind)
• Carbonicola robusta (J de C Sowerby)
• Carbonicola cf. venusta Davies & Trueman
• Carbonita humilis (Jones & Kirkby)
• Cleiothyridina pectinifera (J de C Sowerby)
• Crassispora kosankei (Potonie & Kremp) Bharadwaj
• Crurithyris sp.
• Crurithyris clannyana (King)
• Curvirimula?/Curvirimula sp.
• Curvirimula candela (Dewar)
• Curvirimula subovata (Dewar)
• Curvirimula aff. trapeziforma (Dewar)
• Cyclogyra sp.
• Cyclogyra kinkelini (Spandel)
• Cynthaxonia cornu Michelin
• Cypridina?
• Dasyalosia goldfussi? (Munster)
• Dielasma sp.
• Dielasma elongatum (Schlotheim)
• Dimotphoceras sp.
• Discina sp.
• Discina konincki (Geinitz)
• Dithyrocaris sp.
• Dunbarella sp.
• Dunbarella cf. elegans (Jackson)
• Dunbarella papyracea (J Sowerby)
• Edmondia sp.
• Elonichthys sp.
• Eriophorum
• ?Estheria/Estheria sp. nov.
• Falcisporites zapfei (Potonié & Klaus) Leschik
• Fasciculophyllum cf. densum (Carruthers)
• Fenestella
• Fenestella geinitzi (d'Orbigny)
• Fenestella cf. geinitzi
• Filipendula
• Gastrioceras
• Gastrioceras listeri (J Sowerby)
• Gastrioceras subcrertatum C Schmidt
• Geinitzina sp.
• Geisina?/Geisina sp.
• Geisina arcuata (Bean)
• Geisina subarcuata (Jones)
• Gigantoproductus sp.
• Glomospira sp.
• Glamospirella sp.
• Guilielmites
• Hemkycloceaia minima (Pruvost)
• Hemigordius?
• Hindeodella sp.
• Holinella sp.
• Homoceratoides sp.
• cf. Homocerataides
• Horrindonia horrida (J Sowerby)
• Idiognathodus sp.
• Idiognathoides sulcatus sulcatus (Higgins & Bouckaert)
• Illinites spp.
• Isoetes
• Klausipollenites schaubergeri (Potonie & Klaus) Jansonius
• Leiofusa
• Liebea squamosa (J de C Sowerby)
• Lingula
• Lingula credneri Geinitz
• Lingula elongata Demanet
• Lingula mytilloides J Sowerby
• Limnea spp.
• Limnea palustris (Muller)
• Lioestheria sp.
• Lioestheria vinti (Kirkby)
• Leuckisporites virkkiae Potonie & Klaus emend. Clarke
• Lunatisporites spp.
• Megalichthys sp.
• Micrhystridium
• Mourlonia?
• Myalina?
• Naiadites?/Naiadites sp. nov.
• Naiadites alatus Trueman & Weir
• Naiadites angustus Trueman & Weir
• Naiadites cf. angustus Trueman & Weir
• Naiadites daviesi Dix & Trueman
• Naiadites aff. daviesi Dix & Trueman
• Naiadites cf. daviesi Dix & Trueman
• Naiadites flexuosus Dix & Trueman
• Naiadites hindi Trueman & Weir
• Naiadites melvillei Trueman & Weir
• Naiadites obliquus Dix & Trueman
• Naiadites cf. obliquus Dix & Trueman
• Naiadites productus (Brown)
• Naiadites productus? (Brown)
• Naiadites. sp. cf. productus (Brown)
• Naiadites quadratus (J de C Sowerby)
• Naiadites sp. quadratus/productus (Brown)
• Naiadites cf. subtruncatus (Brown)
• Naiadites cf. triangularis (J de C Sowerby)
• Nuskoisporites spp.
• Orbiculoidea sp.
• Orbiculoidea nitida (Phillips)
• Orbiculoidea. cf. nitida (Phillips)
• Orthothrix
• Orthothrix excavata (Geinitz)
• Orthothrix cf. lewisiana (de Koninck)
• Orthovertella sp.
• Ozarkodina cf. delicatula Stauffer & Plummer
• Paladin sp. ex gr. barkeri (Woodward) maillieuxi (Demanet)
• Paladin barkeri
• Paladin maillieuxi
• Palaeoneilo sp.
• Parallelodon striatus (Schlotheim)
• Pediastrum
• Penniretepora waltheri (Korn)
• Perisaccus granulosus (Leschik) Clarke
• Permophorus costatus (Brown)
• Phragmites
• Planolites sp.
• Planolites ophthalrnoides (lessen)
• Planorbis leucostoma (Millet)
• Plantago lanceolata Linnaeus
• Platysomus cf. striatus Agassiz
• Polypodium
• Posidonia sp.
• Posidonia gibsoni Brown in Salter
• Posidonia sp. /nov
• Posidoniella laevis (Brown)
• Productus sp.
• Productus carbanarius de Koninck
• Protohaploxypinus spp.
• Protoretepora sp.
• Protoretepora ehrenbergi (Geinitz)
• Pseudocatastroboceras cf. rawsoni (Inglis)
• Pseudovoltzia liebeana (Geinitz) Florin
• Pterospirifer alatus (Schlotheim)
• Pygopterus?
• Raistrickia fulva Artuz
• Reticuloceras sp.
• Reticuloceras coreticulatum Bisat & Hudson
• Rhabdoderma sp.
• Rhadinichthys sp.
• Rhizodopsis sp.
• Rhizodopsis sauroides (Williamson)
• Rotiphyllum sp.
• Sanguinolites sp.
• Sanguinolites v-scriptus
• Scaldia minuta (Hind)
• Scheuchzeria
• Schizodus sp.
• Schizodus obscurus (J Sowerby)
• Selaginella
• Serpulites?
• Serpuloides stubblefieldi (Schmidt & Teichmuller)
• cf. Shansiella
• Sphagnum
• Spirifer bisulcatus (J Sowerby)
• Spirorbis sp.
• Stenoscisma sp.
• Stenoscisma cf. humbletonensis (Howse)
• Stenoscisma schlotheimi (von Such)
• Streblochondria? pusilla (Schlotheim)
• Strepsodus sp.
• Streptorhynchus pelargonatus (Schlotheim)
• Strophalosia morrisiana King
• Succinea putris (Linnaeus)
• Tetralasma sp. nov.
• Thamniscus?
• Thamniscus dubius (Schlotheim)
• Tolypammina sp.
• Tomaculum sp.
• Ullmannia sp.
• Veryhachium
• Viburnum
• Vittatina hiltonensis Chaloner & Clarke
• Yunnania
• Yunnania? cf. helicina (Schlotheim)
• Yunnania tunstallensis (Howse)
• Yunnania cf. tunstallensis

Figures, plates and tables

Figures

(Figure 1) The location and geological setting of the district.

(Figure 2) The principal geographical features of the district.

(Figure 3) Chronostratigraphical classification of the Carboniferous System.

(Figure 4) Borehole sections in the Millstone Grit and Carboniferous Limestone.

(Figure 5) Gamma-ray logs, lithologies and fossil bands in boreholes in the upper part of the Millstone Grit.

(Figure 6) Correlation of marine bands in the Moss Borehole and marine bands deduced from the gamma-ray log of the Trumfleet No. 1 Borehole.

(Figure 7) Generalised section of the Coal Measures showing the principal coals, sandstones and fossil bands.

(Figure 8) Gamma-ray logs, lithologies and fossil bands from boreholes through the basal part of the Westphalian A strata.

(Figure 9) Borehole sections through Westphalian A strata from the Top Silkstone or Blocking Coal to the Subcrenatum Marine Band.

(Figure 10) Borehole and shaft sections through Westphalian A strata from the Vanderbeckei Marine Band to the Top Beeston Coal.

(Figure 11) Plan of the Thorncliff and Wheatley Lime coals.

(Figure 12) Plan of the Parkgate Coal complex.

(Figure 13) Borehole and shaft sections through Westphalian B strata from the Kent's Thick Coal to the Vanderbeckei Marine Band.

(Figure 14) Borehole and shaft sections through the Barnsley Coal and its correlatives.

(Figure 15) Distribution of coal types in the Barnsley Coal and its correlatives.

(Figure 16) Borehole and shaft sections through Westphalian B strata from the Aegiranum Marine Band to the Kent's Thick Coal.

(Figure 17) Borehole sections through Westphalian C strata from the Cambriense Marine Band to the Aegiranum Marine Band.

(Figure 18) Borehole and shaft sections through Westphalian C and ?D strata above the Cambriense Marine Band.

(Figure 19) Lithostratigraphical classification of the Permian and Triassic rocks.

(Figure 20a) Thickness and distribution of the formations in the lower part of the Permian succession. Basal (Permian) Sands.

(Figure 20b) Thickness and distribution of the formations in the lower part of the Permian succession. Marl slate and/ or Lower Marl.

(Figure 20c) Thickness and distribution of the formations in the lower part of the Permian succession. Lower Magnesian Limestone (excluding Lower Marl).

(Figure 20d) Thickness and distribution of the formations in the lower part of the Permian succession. ?Hayton anhydrite.

(Figure 21) Borehole sections from the Saliferous Marl to the Basal (Permian) Sands.

(Figure 22) Borehole and shaft sections of strata between the Upper and Lower Magnesian Limestone.

(Figure 23a) Thickness and distribution of the formations in the upper part of the Permian succession. Kirkham Abbey Formation, ?Forndon Evaporites and Middle Marl.

(Figure 23b) Thickness and distribution of the formations in the upper part of the Permian succession. Upper Magnesian Limestone.

(Figure 23c) Thickness and distribution of the formations in the upper part of the Permian succession. Billingham Main Anhydrite, ?Boulby Halite and Carnallitic Marl.

(Figure 23d) Thickness and distribution of the formations in the upper part of the Permian succession. Upgang Formation, Upper Anhydrite and Saliferous Marl including the Sleights Siltstone where present.

(Figure 24) Borehole sections of strata between the Sherwood Sandstone and the Upper Magnesian Limestone.

(Figure 25) Distribution and thickness of the Sherwood Sandstone, with cross-bedding dip directions.

(Figure 26) Borehole and shaft sections through the Sherwood Sandstone.

(Figure 27) Borehole sections through the Mercia Mudstone.

(Figure 28a) Geophysical maps and interpretation for the Doncaster–Goole district. Bouguer gravity anomaly map with contours at 1mGal intervals.

(Figure 28b) Geophysical maps and interpretation for the Doncaster–Goole district. Bouguer anomaly map after compensation for gravity effect of low-density sedimentary rocks down to the base of the Namurian. The gravity effect has been calculated using density contrasts relative to a basement density of 2.66 Mg/m³ and differs in this respect from the models shown in (Figure 29).

(Figure 28c) Geophysical maps and interpretation for the Doncaster–Goole district. Aeromagnetic map with contours at 10nT intervals.

(Figure 28d) Geophysical maps and interpretation for the Doncaster–Goole district. Compilation map showing main structural features; faults shown as pecked lines; contours based on geophysical evidence of depths (in km below OD) to the upper surface of the postulated Market Weighton granite. Heavy dashed lines axes of gravity highs.

(Figure 29e). Datum level -12 mGal." data-name="images/P947285.jpg">(Figure 29a) Profiles and interpretations of Bouguer anomalies and aeromagnetic data along the line AA′ in (Figure 28d). Observed Bouguer gravity anomaly for (Figure 29e). Datum level −12 mGal.

(Figure 29e)." data-name="images/P947286.jpg">(Figure 29b) Profiles and interpretations of Bouguer anomalies and aeromagnetic data along the line AA′ in (Figure 28d). Aeromagnetic profile and calculated profiles for (Figure 29e).

(Figure 29c) Profiles and interpretations of Bouguer anomalies and aeromagnetic data along the line AA′ in (Figure 28d). Model in which the gravity profile is explained partly by low-density sedimentary basins of lower or pre-Carboniferous age. Densities in Mg/m³.

(Figure 29d) Profiles and interpretations of Bouguer anomalies and aeromagnetic data along the line AA′ in (Figure 28d). Alternative model to explain the aeromagnetic profile. The magnetic rocks are confined to pre-Carboniferous basement. Susceptibilities in SI. The model shown was selected from several possible interpretations.

(Figure 29e) Profiles and interpretations of Bouguer anomalies and aeromagnetic data along the line AA' in (Figure 28d). Alternative model to explain the aeromagnetic profile. An additional body of igneous rocks has been introduced in the lower- or pre-Carboniferous sequence. Susceptibilities in SI. The model shown was selected from several possible interpretations.

(Figure 30) Generalised structure contours on the base of the Millstone Grit

(Figure 31) Generalised structure contours on the Barnsley/Warren House seam. Stippled areas are anticlinal structures referred to in the text.

(Figure 32) Generalised structure countours on the Barnsley/Warren House seam with the easterly dip of the Permo-Triassic rocks removed. Stippled areas are anticlinal structures referred to in the text.

(Figure 33) Generalised structure contours on the base of the Permian rocks.

(Figure 34) Generalised structure contours of the bases of the Sherwood Sandstone and Mercia Mudstone.

(Figure 35) Summary of the Quaternary history.

(Figure 36) Schematic horizontal section showing the relationships between the Quaternary deposits.

(Figure 37) Horizontal section through the glacial deposits on Brayton Barff, with stone orientations in the tills.

(Figure 38) Horizontal sections along a trench (A B C) and a railway cutting (D E F) through the Quaternary deposits on the western part of the Snaith Ridge.

(Figure 39) Stone orientations in clay till at Balby.

(Figure 40) Subglacial channels in the Doncaster area.

(Figure 41) Variation in composition of the pebbles in the older river gravel.

(Figure 42) Contours on the base of the Devensian deposits at and below OD.

(Figure 43) Distribution of the late Devensian glacial and lacustrine deposits.

(Figure 44) Distribution of the late Devensian post-lacustrine levee deposits.

(Figure 45) Contours on the base of the Flandrian deposits at and below OD.

(Figure 46) Man-made alterations to river courses, and warped ground.

(Figure 47) Location of shafts and boreholes in Appendix 1.

Plates

(Plate 1) Clay till overlying laminated clay, at Brayton Barff.

(Plate 2) Lacustrine sand and gravel overlying cryoturbated fluvioglacial sand and gravel, at Austerfield.

(Plate 3) Laminated deposits of the 25-Foot Drift resting on severely cryoturbated older river gravel, near Finningley.

(Plate 4) Cryoturbated older river gravel, at Low Common, Austerfield. (L02147).

(Plate 5) Lacustrine sand and gravel resting on Sherwood Sandstone, at Pollington.

(Plate 6) Lacustrine sand and gravel resting on Sherwood Sandstone, at Whitley. (A07041).

(Front cover) Cover photograph Hatfield Main Colliery, South Yorkshire. Photo: A A Jackson.

(Back cover)

Tables

(Geological sequence) Summary of geological sequence. Drift deposits not necessarily in chronostratigraphical order within stage. 1 Included in Glacial Sand and Gravel on published maps. 2 Shown as Boulder Clay on published maps.

(Table 1) Typical chemical analysis of Mercia Mudstone from Melwood quarry. Source: Belton Brick Co. Ltd.

(Table 2) Mean chemical analysis of coloured glass sand, Langholme Farm quarry. Source: Rockware Group plc.

Tables

(Geological sequence) Summary of geological sequence

Drift deposits not necessarily in chronostratigraphical order within stage. 1 Included in Glacial Sand and Gravel on published maps. 2 Shown as Boulder Clay on published maps.

Solid rocks

(Table 1) Typical chemical analysis of Mercia Mudstone from Melwood quarry. Source: Belton Brick Co. Ltd.

(Table 2) Mean chemical analysis of coloured glass sand, Langholme Farm quarry. Source: Rockware Group plc.