Content and licensingview original scan buy a printed copy

Geology of the country around Barnard Castle Explanation of one-inch geological sheet 32, (New Series)

By D. A. C. Mills, B.Sc. and J. H. Hull, M.Sc. with contributions by C. R. Burch, B.Sc., E. A. Francis, B.Sc., W. H. C. Ramsbottom, M.A., Ph.D., M. A. Calver, M.A., Ph.D., J. Pattison, M.Sc., G. A. L. Johnson, D.Sc., B. Owens, B.Sc., Ph.D., R. K. Harrison, M.Sc. and T. S. Tomlinson, B.Sc.

Natural Environment Research Council Institute of Geological Sciences. Memoirs of the Geological Survey of Great Britain England And Wales

London Her Majesty's Stationery Office 1976. © Crown copyright 1976. ISBN 0 11 880742 0

The Institute of Geological Sciences was formed by the incorporation of the Geological Survey of Great Britain and the Museum of Practical Geology with Overseas Geological Surveys and is a constituent body of the Natural Environment Research Council.

(Front cover) The castle at Barnard Castle (L392). The ruined castle stands besides the River Tees on a steep bluff made of Top and Bottom Crag Limestone and interbedded shales.

(Rear cover) View looking north from Brusselton Hill (L404). Coal measures country; the Gaunless Valley between West Auckland and Bishop Auckland.

Preface

The Barnard Castle district was originally surveyed on the six inch to one mile scale between the years 1870 and 1881 by W. Gunn, and by H. H. Howell who also supervised the work. The map was published, hand coloured, on the one-inch scale on Old Series Sheet 103 SW, the Solid edition in 1881 and the Drift edition in 1883. Some revisions were inserted in 1889. Some, but not all, of the six inch to one mile maps were published between 1875 and 1879 and Vertical Sections Sheet 65, published in 1878, included some sequences in the Coal Measures of the district. No explanatory memoir was published.

The district was resurveyed between 1958 and 1963, the bulk of the work being done by Mr. D. A. C. Mills in north-central, central, eastern and south-eastern areas and by Mr. J. H. Hull in north-western and south central parts. Mr. C. R. Burch resurveyed parts of the west and south, and Mr E. A. Francis the extreme north-east corner of the district. The resurvey was supervised by Mr. W. Anderson, Dr. E. H. Francis and myself. A list of six-inch maps with the names of the surveyors is given on page xi. Solid and Drift editions of the new one-inch map were published in 1968.

The task of compiling this memoir has fallen to Mr. Mills, who also wrote most of the text, though a substantial part was written by Mr. Hull. Contributions from Messrs Burch and Francis are incorporated in the structural account, and in some of the stratigraphical chapters. Viséan and Namurian macrofaunas have been identified by Dr. W. H. C. Ramsbottom and the microflora by Dr. B. Owens; Westphalian fossils were determined by Dr. M. A. Calver and those from the Permian by Mr. J. Pattison. Mr. R. K. Harrison wrote the sections on petrography. The Economic Geology chapter contains a contribution on coal rank and quality by Mr. T. S. Tomlinson of the National Coal Board. Appendix 3, an account of the Mount Pleasant Bore, was contributed by Dr. G. A. L. Johnson of Durham University. The memoir has been edited by Mr. B. J. Taylor.

Willing assistance, during the resurvey and the writing of the memoir, from officials in the National Coal Board, the various water authorities, local authorities and quarry companies, and from landowners, is gratefully acknowledged.

A. W. Woodland Director, Institute of Geological Sciences, Exhibition Road, South Kensington, London. SW7 2DE. 15th June 1976.

List of six-inch maps

Six-inch geological maps covering the one-inch geological sheet 32 are listed below with the date of issue (in brackets), the initials of the surveyors and date of survey for each map. The surveyors were C. R. Burch, E. A. Francis, J. H. Hull, D. H. Land, D. A. C. Mills and R. H. Price.

Printed maps are marked P with the date of publication. Dyeline copies of the other six-inch geological maps are available, and copies of all the maps are held for public reference in the libraries of the London and Leeds offices of the Institute of Geological Sciences.

A narrow strip of ground along the southern margin of the sheet is covered by six-inch geological maps which are available in manuscript form only.

Explanatory notes

• In this book, the word 'District' means the area included in the one-inch geological sheet 32 (Barnard Castle).
• Numbers in square brackets are National Grid References. The prefaces NY and NZ are not used since the numerical references are unique in the district. The 100-km square NY includes a narrow strip along the western margin of the district; the rest of the sheet falls within the 100-km square NZ.
• Numbers preceded by the letter E refer to the Sliced Rock Collection of the Institute of Geological Sciences.
• Numbers preceded by the letter L are serial numbers in the Institute's collection of Geological Survey Photographs.
• Natural sections or Boreholes marked with an asterisk (*) are detailed in the relevant appendices.
• Other explanatory notes, relevant to particular parts of the book, are given in the appropriate chapters.
• Authors of fossil names are given in the Index.

Chapter 1 Introduction

Geographical setting and industries

This memoir describes the geology of the district covered by the Barnard Castle (32) Sheet of the One-Inch Geological New Series Map^‡1  of England and Wales. Part of the district, north of the River Tees, lies within County Durham, the remainder forms part of the North Riding of Yorkshire. The location of the district with reference to northern England is shown in (Figure 1), while (Figure 2) shows the outlines of the solid geology.

The district comprises two contrasted areas. The smaller area, in the north, is underlain by Coal Measures and is partly industrialized: the rest of the district is occupied by Carboniferous Limestone, Millstone Grit and Permian strata and is chiefly rural.

The northern area, which forms the south-western part of the Northumberland and Durham Coalfield, became industrialized in the latter half of the 19th century with the advent of large-scale coal mining. The history of coal mining, however, extends back to the year 1375 when Henry Vavasour's mine was working on Cockfield Fell—one of the first inland collieries on record. Centres around which the early coal industry grew include Hindon, Woodland, Copley, Butterknowle, Cockfield, Evenwood, Toft Hill, West Auckland, St Helen Auckland, Bishop Auckland and Shildon. The coal reserves of this area are now largely exhausted, though small areas of coal are still being mined at one locality by a private operator under licence from the National Coal Board, and small private opencast sites in areas formerly worked by underground methods are being operated between Woodland and Toft Hill. Quarrying was never a major industry in this northern part of the district, and it has, like mining, steadily declined. The Cleveland Dyke, once extensively worked for roadstone on Cockfield Fell, is now quarried only to the north-west of Bolam and even here operations have virtually ceased. Magnesian Limestone is now being removed from only two quarries near Middridge. Despite the long history of mining this part of the district retains a semi-rural aspect. Mixed agriculture is extensively carried out, though to the west on the higher ground stock rearing and sheep farming are more important. Other employment in the area is provided by light engineering, chemical and coke works at Evenwood, a coal washing plant at West Auckland, and light industrial estates at West Auckland, St Helen Auckland, Tindale Crescent and at Shildon, where there is also a railway wagon works. There are brickworks and a coal washing plant at Eldon.

In the north-western, central southern and eastern parts of the district farming is particularly important being mainly of mixed type, sheep and stock cattle becoming more important on the higher ground in the west. Minor industries in this area include the quarrying of Carboniferous limestone and sandstone, and sand and gravel. A chemical plant at Barnard Castle is the largest single source of employment in the western part of the area, while in the east many people are employed in a light industrial estate at Newton Aycliffe and in Darlington, whose western suburbs extend into the area. The main administrative centre of the Durham part of this area is Barnard Castle—a market town of about 6000 population—while those parts that are in the North Riding are administered from Barnard Castle and Startforth, and from Richmond, which lies in the (Sheet 41) district to the south.

Roads are the main means of communication within the district, the most notable being the A66 route from Scotch Corner to Penrith which traverses the southern part of the district. Railway services have been discontinued except for the line from Darlington to Bishop Auckland.

Water for parts of the district is obtained from storage reservoirs to the west in the adjacent Brough-under-Stainmore (Sheet 31) district. Some supplies, however, are obtained locally from springs and boreholes, while a large part of Darlington's water is obtained by pumping from the River Tees near Low Coniscliffe.

Physical geography

A large part of the district falls within the Mid-Tees valley which may be taken to extend eastward from the Pennine slopes of Stainmore to the broad dale around Darlington. In the south-western part of the district the River Tees is joined by three major south-bank tributaries, namely the River Balder, Deepdale Beck and the River Greta. Elsewhere, however, the streams draining into the River Tees are, except for Eggleston Burn and Langley Beck, small. An area up to four miles wide, which extends along most of the northern margin of the district, falls within the catchment of the River Wear, the chief tributary here being the River Gaunless. On the southern margin of the district a small area east of Newsham is drained by the River Gilling, a tributary of the River Swale.

Most of the high ground lies in the west and north where it forms part of a dissected plateau tilted to the east. In the north-west it includes the wide moorland expanse of Eggleston Common (up to 1590 ft OD), Woodland Fell (1448 ft OD) and Langleydale Common (1408 ft OD) all forming part of the Tees–Wear watershed. The south side of the divide between the Wear and Tees is marked by a strong south-facing scarp composed mainly of massive sandstones of late Namurian and early Westphalian age. It extends from Eggleston in the west to Houghton le Side in the east, though it is ill-defined between Wackerfield and Hilton because of faulting. To the east and north-east of Houghton le Side the scarp dies out as Magnesian Limestone caps the sandstone sequence. In the south-west, beyond Scargill and Barningham, is Scargill Low Moor rising to over 1450 ft and leading to the divide between Teesdale and Arkengarthdale. The major south-bank Tees tributaries have cut deep gorges for some distance above their respective confluences; these gorges are well-wooded and contrast with the bleak open moorlands farther upstream. Below Barnard Castle the Tees Valley broadens out progressively, though locally the river flows through a series of gorges, the broad ridges and valleys of the Carboniferous country giving way farther east to the gently rolling area formed by the Magnesian Limestone.

Geological sequence

The formations represented on the One-Inch New Series Geological Map and sections of this district are summarized below.

Classification

The Carboniferous rocks of England and Wales have traditionally been divided on a lithological basis into Carboniferous Limestone at the base overlain successively by Millstone Grit and Coal Measures. It has been known for many years that the divisions so called in northern England are not equivalent to their counterparts farther south. Faunal correlations have become sufficiently precise to allow for the reclassification of the northern England sequence. The standard classification now applied to the rocks of the Barnard Castle district is shown in Table 1 together with its relationship to older classifications now abandoned.

The classification of the Permian rocks, in terms of formational names, is a modified form of that adopted in the Durham and West Hartlepool district (Smith and Francis 1967, pp. 91, 95). It is essentially based on the Durham sequence, while taking into account adjoining parts of Yorkshire. Recent work has enabled further refinements, which are not applied here, to be made in terms of beds and evaporitic cycles, and this work has been summarized by Smith (1970, p. 67).

Geological history

Nothing is known of the pre-Carboniferous rocks of the district, for the oldest known strata are of high Viséan (P₂) age. It is probable that earlier Viséan sediments are present at depth resting on Skiddaw Slates or granite as they do in neighbouring districts (Woolacott 1923, p. 60; Dunham and others 1965, p. 383). These sediments were probably deposited in a gradually subsiding shallow sea in which conditions particularly favoured the formation of limestone and shale, though locally 'channel' and 'sheet' sandstones were introduced.

Interpretation of the depositional history owes much to the concept of rigid and buoyant crustal blocks with intervening subsiding troughs (for criteria see Kent 1966, p. 325). The south-eastern part of the Alston Block occupies the north-west of the district with the Cotherstone (Stainmore) Syncline to the south. The greater part of the district would appear, therefore, to be marginal between block and trough.

There was little change in conditions of deposition in early Namurian times; the sediments are similar to those of the Viséan except that 'channel' sandstones are more common and limestones are generally thinner. Towards the end of Namurian times, however, there was a marked change: where, hitherto, sandstones, other than 'channel' sandstones, had been only component members of cyclic units they now became dominant. Limestones are absent from these cyclothems and marine shales are subordinate. These conditions continued into the early Westphalian. They were followed by a phase of sedimentation in a near-shore, estuarine and deltaic environment where local intermittent subsidences were followed by relatively stable periods conducive to coal formation.

During late Carboniferous and early Permian times the district was affected by the main Hercynian orogeny, which resulted in the folding and faulting of the Carboniferous rocks and the intrusion of quartz-dolerite dykes and the Great and Little Whin sills. These earth movements led to uplift and erosion, so that by the end of Lower Permian times a low-lying desert fringed by low hills had been produced. The axis of this shallow depression probably extended east-south-east from the Piercebridge area. The first deposits laid on this surface were sporadic breccias probably representing the result of ephemeral sheet floods, gully deposits and residual talus accumulations. During Upper Permian times the Zechstein Sea transgressed into much of the district, locally depositing the Marl Slate, followed upwards by carbonate rocks, limestones and dolomites, laid down for the most part under shallow water with restricted access to the open sea. The carbonates were followed by a series of interbedded siltstones, mudstones and evaporites forming the Middle Permian Marl succeeded by further limestones of the Upper Magnesian Limestone and in turn by the Upper Permian Marls. It is not known what thickness of higher Permian and younger measures may have been laid down and subsequently removed by erosion.

Both Carboniferous and Permian formations were faulted by Tertiary earth movements. During this time Hercynian faults affecting Carboniferous rocks were reactivated and their lines can be traced in the overlying Permian beds in the eastern part of the district. Associated with the orogeny was the intrusion of the Cleveland Dyke, which is thought to be of late Eocene to early Oligocene age. The uplifting and eastward tilting of the region, which commenced at this time, formed a surface on which the present pattern of erosion was initiated. The drainage system first established on this surface was substantially modified by the later Pleistocene glaciation. After the retreat of the ice the present regime was established, and while over much of the eastern part of the district streams are fairly well graded, in the west erosion is still a significant factor in the higher reaches of the Tees and Gaunless drainage systems.

Summary of previous research

The earliest geological work relevant to this district was that of Forster (1809) who named lithological units in the Carboniferous. In 1836 Phillips described the Carboniferous Limestone Series strata of the district in his classic Geology of Yorkshire. The district was first surveyed between 1870 and 1881 by H. H. Howell and W. Gunn for the Geological Survey; most of their six inches to one mile geological maps were published, though a few sheets in County Durham for the area east of Piercebridge and Bolam were made available only as library reference copies. The one-inch map (Old Series 103 SW) was published in solid edition in June 1881 and in drift edition in July 1883. Further editions, with minor amendments, were published in December 1889. The maps were not accompanied by an explanatory memoir though an account by Gunn relating to the west of the district survives in manuscript. The Carboniferous strata of the north-western part of the district are marginal to the Northern Pennine Orefield and were discussed in general terms by Dunham (1948); this memoir was the only stratigraphical account of the Pennines north of the Tees–Swale watershed until work on the Carboniferous Limestone Series and Millstone Grit Series was carried out in the south-western and southern parts of the district respectively by Reading (1957) and Wells (1955, 1957) and more recently by Johnson and others (1962), Mills and Hull (1968), and Hull (1968).

The only work relating to the coalfield is by Kirkby and Duff (1872, pp. 150–98) who gave a short account of part of the area between Bishop Auckland, Woolly Hill and Arnghyll. This account incorporated some shaft and borehole sections and brief notes on adjacent areas to south and east, including the geology of the area between Staindrop and Heighington (Millstone Grit Series and Coal Measures) the Cleveland (or Cockfield) Dyke, the Magnesian Limestone and Drift.

The Permian rocks of the district have been mentioned by Winch (1817), Sedgwick (1829) and Browell and Kirkby (1866). They have also been referred to in the wider context of the descriptions of the Permo-Triassic rocks of northeastern England by Trechmann (1913, 1914, 1921 and 1925). The same author (1921) refers specifically to the Permian exposures around Thickley.

The igneous rocks have been dealt with by Teall (1884), who gave an account of the Cleveland Dyke, and by Holmes and Smith (1921), who undertook research on the Wackerfield Dyke.

Detailed work on the Pleistocene deposits of the western part of the district was carried out by Dwerryhouse (1902), who described the glaciation of Teesdale following earlier mention by Goodchild (1875) and Dakyns (in Dakyns and others 1891). The only published work on the eastern part of the district is by Fawcett (1916), who researched on the pre- and post-glacial drainage system of the Mid-Tees valley. Allusion to this work and that of Dwerryhouse (1902) was made by Trotter (1929a, b) in his description of the glaciation and drainage of the country to the west of this district. More recently the Quaternary of Durham county and the north of England has been summarized, respectively, by Francis (1970) and Smith (in Taylor and others 1971). D.A.C.M., J.H.H.

References

BORINGS and SINKINGS. 1878–1910. An account of the Strata of Northumberland and Durham as proved by Boring and Sinkings. The Council of the North of England Institute of Mining and Mechanical Engineers (usually bound in 4 books, but originally issued as 7 volumes. Generally referred to as "Borings and Sinkings").

BROWELL, E. J. and KIRKBY, J. W. 1866. On the chemical composition of various beds of the Magnesian Limestone and associated Permian rocks of Durham. Nat. Hist. Trans. Northumb., 1, 204 30.

DAKYNS, J. R., TIDDEMAN, R. H., RUSSELL, R., CLOUGH, C. T. and STRAHAN, A. 1891. The Geology of the country around Mallerstang. Mem. geol. Surv. Gt Br.

DUNHAM, K. C. 1948. The Geology of the Northern Pennine Orefield; Vol. 1, Tyne to Stainmore. Mem. geol. Surv. Gt Br.

DUNHAM, K. C. DUNHAM, A. C., HODGE, B. L. and JOHNSON, G. A. L. 1965. Granite beneath Viséan sediments with mineralization at Rookhope, northern Pennines. Q. Jnl geol. Soc. Lond., 121, 383–417.

DWERRYHOUSE, A. R. 1902. The Glaciation of Teesdale, Weardale and the Tyne Valley, and their Tributary Valleys. Q. Jnl geol. Soc. Lond., 58, 572–608.

FAWCETT, C. B. 1916. The Middle Tees and its tributaries: a study in river development. Geogrl. Jnl, 48, 310–25.

FORSTER, W. 1809. A treatise on a Section of the Strata from Newcastle-upon-Tyne to the Mountain of Cross Fell, in Cumberland, with remarks on Mineral Veins in general. 1st Edit. Alston.

FORSTER, W. 1821. A treatise on a Section of the Strata from Newcastle-upon-Tyne to the Mountain of Cross Fell, in Cumberland, with remarks on Mineral Veins in general. 2nd Edit. Alston.

FORSTER, W. 1883. A treatise on a Section of the Strata from Newcastle-upon-Tyne to the Mountain of Cross Fell, in Cumberland, with remarks on Mineral Veins in general. 3rd Edit., revised by W. Nall. Newcastle.

FRANCIS, E. A. 1970. Quaternary (in Geology of Durham County). Trans. nat. Hist. Soc. Northumb., 41, 134–52.

GOODCHILD, J. G. 1875. The Glacial Phenomena of the Eden Valley and the Yorkshire-Dale District. Q. Jnl geol. Soc. Lond., 31, 55–99.

HOLMES, A. and SMITH, S. 1921. The Wackerfield Dyke, Co. Durham. Geol. Mag., 58, 440–54.

HULL, J. H. 1968. The Namurian stages of north-eastern England. Proc. Yorks. geol. Soc., 36, 297–308.

JOHNSON, G. A. L., HODGE, B. L. and FAIRBAIRN, R. A. 1962. The base of the Namurian and of the Millstone Grit in north-eastern England. Proc. Yorks. geol. Soc., 33, 341–62.

KIRKBY, J. W. and DUFF, J. 1872. Notes on the geology of part of South Durham. Nat. Hist. Trans. Northumb., 4, 150–98.

KENT, P. E. 1966. The structure of the concealed Carboniferous rocks of northeastern England. Proc. Yorks. geol. Soc., 35, 323–52.

MILLS, D. A. C. and HULL, J. H. 1968. The Geological Survey borehole at Woodland, Co. Durham (1962). Bull geol. Surv. Gt Br., 28, 1–37.

PHILLIPS, J. 1836. Illustrations of the Geology of Yorkshire. Part II: The Mountain Limestone District. London.

READING, H. G. 1957. The stratigraphy and structure of the Cotherstone Syncline. Q. Jnl geol. Soc. Lond., 113, 27–56.

SEDGWICK, A. 1829. On the geological relations and internal structure of the Magnesian Limestone, and the lower portion of the New Red Sandstone Series in their range through Nottinghamshire, Derbyshire, Yorkshire and Durham to the southern extremity of Northumberland. Trans. geol. Soc. Lond., Ser. 2, 3, 37–124.

SMITH, D. B. 1970. Permian and Trias (in Geology of Durham County). Trans. nat. Hist. Soc. Northumb., 41, 66–91.

SMITH, D. B. and FRANCIS, E. A. 1967. Geology of the country between Durham and West Hartlepool. Mem. geol. Surv. Gt Br.

TAYLOR, B. J., BURGESS, I. C., LAND, D. H., MILLS, D. A. C., SMITH, D. B., and WARREN, P. T. 1971. Northern England. Br. reg. Geol.

TEALL, J. J. H. 1884. Petrological Notes on some north of England Dykes. Q. Jnl geol. Soc. Lond., 40, 209–27.

TRECHMANN, C. T. 1913. On a mass of anhydrite in the Magnesian Limestone at Hartlepool, and on the Permian of south-eastern Durham. Q. Jnl geol. Soc. Lond., 69, 184–218.

TRECHMANN, C. T. 1914. On the lithology and composition of Durham Magnesian Limestones. Q. Jnl geol. Soc. Lond., 70, 232–65.

TRECHMANN, C. T. 1921. Some remarkably preserved brachiopods from the Lower Magnesian Limestone of Durham. Geol. Mag., 58, 538–43.

TRECHMANN, C. T. 1925. The Permian Formation in Durham. Proc. Geol. Ass., 36,135–45.

TROTTER, F. M. 1929a. The Tertiary uplift and Resultant Drainage of the Alston Block and Adjacent Areas. Proc. Yorks. geol. Soc., 20, 161–80.

TROTTER, F. M. 1929b. On the Glaciation of Eastern Edenside, the Alston Block and the Carlisle Plain. Q. Jnl geol. Soc. Lond., 85, 549–612.

WELLS, A. J. 1955. The development of chert between the Main and Crow Limestones in North Yorkshire. Proc. Yorks. geol. Soc., 30, 177–96.

WELLS, A. J. 1957. The Stratigraphy and Structure of the Middleton Tyas–Sleightholme Anticline, North Yorkshire. Proc. Geol. Ass., 68, 231–54.

WINCH, N. J. 1817. Observations on the geology of Northumberland and Durham. Trans. geol. Soc. Lond., 4, 3–7.

WOOLACOTT, D. 1923. A Boring at Roddymoor Colliery, near Crook, Co. Durham. Geol. Mag., 60, 50–62.

Chapter 2 Lower Carboniferous Viséan (Carboniferous Limestone Series)

Introduction

THE Lower Carboniferous'^‡2  crops out in a small area north of the Lunedale–Staindrop Fault near Eggleston, but the main outcrop extends across the southwestern part of the district from Bowes to East Layton. Elsewhere these measures are buried beneath younger rocks and have been proved only in a few boreholes.

Only the late Viséan strata are known within the district, the sequence extending from close above the inferred position of the Scar Limestone to the base of the Namurian, which is taken in this account, following Johnson and others (1962), at the base of the Great Limestone. This succession is about 500 ft thick, and includes representatives of the Five-Yard, Three-Yard and Four-Fathom limestones (Figure 3). The Rookhope and Roddymoor bores provide well-documented sections through upper Viséan measures in districts to the north and north-west and are included for comparison in (Figure 4).

Classification

Within the Lower Carboniferous of the district a fauna diagnostic of precise horizon has been obtained only from above the Four-Fathom Limestone, where Girtyoceras? costatum indicates a P_2c age (Johnson and others 1962, p. 349). Correlation with the measures in other districts suggests that the whole sequence here lies within the P₂ goniatite stage and the D₂ coral-brachiopod zone (Rayner 1953, pp. 285–95) and thus forms part of the upper Viséan.

These measures also fall within the Middle Limestone Group, as defined in Northumberland by Fowler (1926, p. 18), a classification later extended into Cumberland by Trotter and Hollingworth (1932, p. 16) and into Durham by Dunham (1948, p. 14). However, there has been some confusion about the lower limit of the group (Johnson 1959, p. 95; Frost 1969, p. 279) and this, together with the proposed abandonment of the term 'Upper Limestone Group' (Mills and Hull 1968, p. 1) for the overlying strata, has led to the discontinuance of this classification.

By still older terminology these measures form part of the 'Yoredale Series'— a term originally proposed by Phillips (1836, p. 37) and used by him as a strati-graphical unit. The usage is now obsolete, though the term 'Yoredale' has survived, after Hickling (1931, p. 222), to describe a type of sedimentary facies.

Lithology and conditions of deposition

The sediments are arranged in repeated sequences which have been variously called, by different authors, cyclothems, rhythms or cycles. Variations in the meanings of these terms have been discussed by Duff and Walton (1962, pp. 235–55), though as Wells (1960, p. 390) has indicated they have become almost synonymous. The 'rhythmic unit' (Brough 1929, p. 117) or 'cyclothem' (Dunham 1948, p. 14) typical of the northern Pennines is, in upward succession: limestone, shale with marine fossils, unfossiliferous dark shale with ironstone nodules, sandy shale or shaly sandstone, sandstone, ganister or fireclay, coal. The sequences in the Barnard Castle district generally conform to this arrangement, but additional minor cycles, represented by seatearth or coal and/or marine strata, are recorded in the sandstone phase. The local pattern of sedimentation is thus more comparable with that of the Northumberland Trough (Johnson 1959, p. 89; 1962, p. 328) than that of the rest of the northern Pennines. Other observed differences are that many of the sandstones grade up into limestone with no intervening seatearth or coal. Alternatively where coal is present it is commonly separated from the base of the limestone by a few inches of shale with abundant shell debris.

It is generally accepted that the deposition of the Lower Carboniferous in northern England was influenced by the presence of a relatively stable block flanked by more rapidly subsiding sedimentary troughs or gulfs. The concept of a stable block in the northern Pennines during Lower Carboniferous times was first postulated by Marr (1921, pp. 63–72). Subsequently the northern half of the structure became known as the Alston Block (Trotter and Hollingworth 1928, p. 433) and the southern half the Askrigg Block (Hudson 1938, p. 309), the two being separated by the Cotherstone (Stainmore) Syncline (Reading 1957, p. 27). The south-eastern margin of the Alston Block was later more closely delineated by Bott (1961, fig. 4), who showed it to comprise a 'hinge' approximating to the line of the Butterknowle Fault; this interpretation was subsequently followed by Kent (1966, fig. 1). In terms of these structural elements, as defined by previous authors, the Barnard Castle district includes the south-eastern part of the Alston Block, the north-eastern portion of the Askrigg Block and an eastward continuation of the Cotherstone Syncline, in the form of a gentle monocline (see (Figure 17)). The criteria, based on the nature and thickness of the sediments, for distinguishing between blocks and troughs (gulfs) have been listed by Kent (1966, p. 325). With these in mind it would appear that in Carboniferous times the depositional environment over most of the district was intermediate between block and trough. Furthermore, the evidence from the Woodland Bore (Mills and Hull 1968, p. 11) seems to indicate that margins may have migrated with time and also that they are not necessarily coincident with faults.

As with the overlying Namurian sediments, the upper Viséan beds generally show evidence of deposition in relatively shallow water, irrespective of whether or not the environment was one of block or trough. Mechanisms by which shallow-water environments can be maintained in spite of differential subsidence, and in which cyclic sedimentation can occur are adequately reviewed by Dunham (1950, pp. 46–63), Wells (1960, pp. 389–403), Bott (1964, p. 1082), and Bott and Johnson (1967, pp. 421–41).

Nomenclature and correlation

Beds in the Lower Carboniferous in this district have in the past been named in terms of local usage on either the Askrigg or the Alston block. In Swaledale it was formerly the practice of miners to name limestones by counting down from the Main or Great Limestone (Namurian, see p. 28) and calling them respectively Underset, Third Set, Fourth Set, etc. This classification was seen by the primary surveyors (Dakyns and others 1891, p. 107) to break down when the Third Set was locally absent; thus the Fourth Set of one area became the Third of another. They resolved this problem by using the current Alston Block terms Three-Yard and Five-Yard limestones for the upper and lower beds respectively, a practice subsequently followed by other workers and summarized by Dunham (1959, fig. 3). In this account it is proposed to discontinue the use of the term 'set' completely and to use Alston Block names (Dunham 1948, fig. 3); accordingly in addition to the names mentioned the Underset Limestone is called Four-Fathom Limestone.

Though the marker beds in the Lower Carboniferous do not contain any unique palaeontological characteristics their exposure is sufficiently continuous, and their lithologies and thicknesses distinctive enough, for correlation to be relatively easy.

General stratigraphy

Strata below the Five-Yard Limestone

Strata below the Five-Yard Limestone (Figure 4) crop out in the River Greta and also farther south on Barningham Moor south-west of Barningham. The lowest exposed measures comprise 18 ft of dark grey silty mudstone with thin sandstone laminae and are inferred to occur close above the Scar Limestone and therefore, by comparison with other areas (Johnson and others 1962, p. 347), to be of early P_2b age. They are overlain by 100 to 125 ft of sandstones, including a mudstone band, 7 to 10 ft thick, in the lower 50 ft and a thin coal about 20 ft from the top; the mudstone has yielded a marine fauna in the River Greta, near Rutherford Bridge, but is apparently unfossiliferous elsewhere. The uppermost 1 to 1.5 ft of sandstone, immediately beneath the Five-Yard Limestone, contains shell casts and the sandstone-limestone junction is sharp at some localities and gradational at others.

The Five-Yard Limestone

The Five-Yard Limestone (Figure 4) is a grey, fine-grained, thin- to thick-bedded^‡3 , bioclastic limestone with a fauna including corals and brachiopods (p. 18).

Locally, as on the north side of Barningham Moor, the limestone includes bands of shale containing an abundant fauna. The thickness of the limestone ranges from 25 to 30 ft, compared with the 20 to 30 ft recorded farther south in Swaledale (Dakyns and others 1891, p. 107) and with the 28 ft proved in the Roddymoor Bore, near Crook, County Durham (Woolacott 1923, p. 51). On the Alston Block the comparable range is from 7 to 23 ft (Dunham 1948, p. 21) with a thickness of almost 16 ft recorded in the Rookhope Bore some 4 miles NW of Stanhope, County Durham (Dunham and others 1965, pl. 34).

Strata between the Five-Yard and Three-Yard limestones

Strata between the Five-Yard and Three-Yard limestones (Figure 4) are discontinuously exposed at two localities in the River Greta. Near Thackholme Farm they are about 79 ft thick, and 3.5 miles farther east, 98 ft. At both localities the lowest beds are similar, consisting, in upward sequence, of 10 to 14 ft of mudstone, fossiliferous in the lower part, 30 ft of sandstone and 3 ft of silty shale. The higher beds, however, are different at the two localities. In the west the silty shale is overlain successively by 12.5 ft of sandstone with a shale parting, 14 in of coal with dirt bands, 7 ft of shale with Lingula at the base, and 11.5 ft of sandstone; east of Brignall in the bed of the River Greta near Scotchman's Stone, the equivalent beds comprise 51 ft of sandstones with a 1-ft limestone, which is correlated with the Lingula band of the western sequence.

These measures were also proved in the Mount Pleasant Bore* (see Appendix 3) where the sequence, though lithologically similar to that near Scotchman's Stone, was only 31 ft thick. As this thickness is even less than the minimum recorded on the Alston Block (Dunham 1948, p. 2l) it is thought that 40 to 60 ft of strata may have been cut out by faulting. In the northern part of the district the Woodland Bore* penetrated below the Three-Yard limestone but then entered and ended in the Great Whin Sill.

Three-Yard Limestone

The only completely exposed section of the Three-Yard Limestone (Figure 4) is in the River Greta, near Scotchman's Stone, where it is 12 ft thick and includes shale partings and a 1.5-in coal. A similar section 14.25 ft thick, was proved in the Mount Pleasant Bore*. Other partial sections are exposed in the River Greta and on Barningham Moor, where the limestone is estimated to have an overall thickness of at least 16 ft, including a 1-ft seatearth-sandstone which locally cuts out some of the shales in the lower part of the limestone. In the Woodland Bore* 6 ft 3.5 in of limestone occurs close above the Great Whin Sill; it is uncertain whether this bed represents the total thickness of the Three-Yard Limestone or whether more limestone may be present beneath the sill. With this exception thicknesses in the Barnard Castle district are rather greater on average than those recorded to the north and south on the Alston and Askrigg blocks respectively (Dunham 1948, p. 22; Dakyns and others 1891, p. 108).

Strata between the Three-Yard and Four-Fathom limestones

Strata between the Three-Yard and Four-Fathom limestones (Figure 4) have their best outcrops in the River Greta. They are variable in thickness and fall broadly into a lower argillaceous and an upper arenaceous subdivision. These subdivisions are respectively 36 and 40 ft thick in the area south-east of Bowes increasing to 79 and 62 ft respectively 5.5 miles to the east, south of Greta Bridge. Erosion is locally apparent at the base of the upper sandstone division in the eastern area, near Eastwood Hall, while west-south-west of Brignall, near Moor House Farm, the base of the sandstones extends down to the horizon of the Three-Yard Limestone.

Elsewhere in the district good sections through these measures are recorded only in boreholes. In the Woodland Bore,* where they are almost 112 ft thick, the lower argillaceous division is relatively thin and the upper is split by the intrusion of the Little Whin Sill. In the Mount Pleasant Bore* these beds are 150 ft thick.

The upper, mainly arenaceous, division is correlated with the Nattrass Gill Hazle of the Alston Block (Forster 1809, p. 58; Dunham 1948, p. 21) and at the Mount Pleasant Bore*, as in the Wycliffe Hall Bore*, it consists of four discrete sandstones separated by shale bands, the middle one of which contains marine fossils.

Throughout the district the contact between the Four-Fathom Limestone and the underlying strata is relatively sharp, limestone or a thin marine shale overlying either a coal or seatearth resting on a sandstone of the upper arenaceous division of the measures. The ranges of thickness and lithology exhibited by the measures in the district are broadly comparable with those in adjacent areas to the north and south (Dunham 1948, p. 22; Dakyns and others 1891, p. 110). A P_2c age may be inferred (Johnson and others 1962, p. 348) for the shales above the Three-Yard Limestone.

Four-Fathom Limestone

The Four-Fathom Limestone (Figure 4) generally consists of a grey, fine-grained, bioclastic limestone; massive at the base, it becomes more thinly bedded upwards. Like the underlying strata, it crops out not only in the southern part of the district but also farther north in the River Tees, near Eggleston Hall, on the upthrow side of the Lunedale–Staindrop Fault. Its thickness is broadly in accord with the range of 20 to 40 ft recorded in Swaledale (Dakyns and others 1891, p. 108).

At the Browson Bank section east of Newsham (p. 21) and at the exposure in the River Tees (p. 21) clisiophylloid corals, including Aulophyllum fungites pachyendothecum and Dibunophyllum bipartitum bipartitum, have been collected from near the base of the limestone. This coral band, originally noted in Wensleydale by Hudson (1924, p. 131) and more recently described elsewhere by Turner (1956, p. 414) and Reading (1957, p. 33), is thus more laterally persistent than is suggested by Wells (1957, p. 241). The coral band is associated with a 14-in bed containing nodules of pale grey fine-grained siliceous decalcified limestone, with shell casts. The shape of the nodules (Plate 2) and their disposition suggests that they are concretions formed in place even though the limestone in which they occur is current-bedded. This nodular bed is known to thicken from 9 to 16 ft in an east-south-easterly direction (Hull 1964, p. 49). At Browson Bank the limestone also contains an 8-in band rich in Saccamminopsis fusulinaformis, which is common at this horizon elsewhere in northern England (Dunham 1948, p. 22; Wells 1957, p. 241).

The strata between the Four-Fathom and Great limestones

The strata between the Four-Fathom and Great limestones (Figure 4) are considered by some authors to comprise two cyclothems because of the presence of the Iron Post Limestone and the underlying Quarry Hazle sandstone (Dunham 1948, p. 23) midway between the two limestones. In this district the only possible representative of the Iron Post is the 5-ft limestone recorded about 70 ft above the Four-Fathom Limestone in the area south of Ovington (p. 22). This limestone, however, may equally well be correlated with the Underset Chert, because the Quarry Hazle, which elsewhere intervenes, appears to be absent over the greater part of the district.

Though the measures between the Four-Fathom and Great limestones crop out extensively in the southern part of the district, and to a more limited extent south-west of Eggleston, exposures are generally poor because of thick drift deposits. The measures, which in much of the district comprise a lower argillaceous and an upper arenaceous sequence, range in thickness from 60 to 138 ft. In exposures along the River Greta at Bowes the argillaceous sequence includes about 20 ft of interbedded calcareous mudstones, cherty mudstones and chert, which lie some 20 ft above the top of the Four-Fathom Limestone. These cherty beds, which locally contain thin bands of siliceous limestone, are the equivalents of the Underset (= Four-Fathom) Chert of other authors (Wells 1957, p. 242; Johnson and others 1962, fig. 2). In the Mount Pleasant Bore* they are 32 ft thick, the base being separated by 13 ft of shales from the Four-Fathom Limestone, and it is from these intervening shales that Girtyoceras? costatum, which indicates a P_2c age, has been collected (Johnson and others 1962, pp. 349–50). The cherty beds are absent farther east in the Wycliffe Hall Bore* and this accords with the statement by Wells (1957, p. 242) that they are known to be absent north and east of a line drawn roughly from Barnard Castle to Barningham Moor, along the south side of the Gilling Valley and across to Middleton Tyas in the Richmond (41) district.

The upper arenaceous part of these measures consists mainly of sandstone and it is the variation in thickness of these beds which accounts for the overall variation between the Four-Fathom and the Great. The uppermost sandstone post of this sequence, which lies close below the base of the Great Limestone, ranges from 2 to 9 ft in thickness. This bed is the probable equivalent of the Tuft or Water Sill of the Alston Block, where it ranges in thickness from 3 to 29 ft (Dunham 1948, p. 25).

A section of special note immediately beneath the Great Limestone was formerly exposed in the floor of East Layton Quarry (p. 23) where the limestone is separated from the top of the local equivalent of the Tuft Sill by 2 to 4 in of silty sand with numerous nodules of bornite and covellite. J.H.H.

Details

(Comparative sections of these measures are shown in (Figure 3) and (Figure 4)

Measures below the Five-Yard Limestone

Measures below the Five-Yard Limestone crop out in the River Greta from above Rutherford Bridge [NZ 0348 1218] down to Tebb Wood [NZ 0737 1179]. At the base are 18 ft of dark grey silty mudstone with numerous sandstone laminae; these beds are presumed to lie close above the Scar Limestone and are exposed at the foot of Black Scar [NZ 0584 1119], about 750 yd NE of Scargill Castle. Above them are 40 ft of white and pale grey fine-grained limonitic sandstones, with worm tubes, possible shell casts and carbonaceous partings near the base. The upper part of these sandstones forms the lowest part of the sequence exposed on a cliff [NZ 0451 1137], about 0.75 mile SE of Rutherford Bridge, as follows:

About 7 ft of the upper mudstone member of this sequence are further exposed in the east bank of Gill Beck [NZ 0622 1107], and much of the upper sandstone can be seen in Brignall Banks [NZ 0541 1128], as follows:

The top of the upper sandstone of this last section, together with the overlying beds which are within 20 ft of the base of the Five-Yard Limestone, are again exposed [NZ 0671 1161], near Brignall Quarry as follows:

The measures immediately beneath the Five-Yard Limestone are exposed in the River Greta [NZ 0366 1210], 220 yd ESE of Rutherford Bridge, where the sequence is:

At this locality the junction between the limestone and the underlying sandstone is sharp, whereas in an exposure [NZ 0393 1187], about 350 yd to the south-east, it is gradational.

South of the River Greta the measures below the Five-Yard Limestone are seen only on the north side of Barningham Moor, where the sequence exposed [NZ 0643 0949] near Cowclose House Farm, is

Five-Yard Limestone

The Five-Yard Limestone is exposed in Eller Beck [NZ 0298 1160], about 430 yd SW of Rutherford Farm, and also at the confluence of the beck with the River Greta. It is best seen, however, in the Greta valley, especially on the north bank between Rutherford Bridge and Tebb Wood, as exemplified by the following section [NZ 0366 1210], about 220 yd ESE of the bridge:

About 350 yd to the south-east, 22 ft of limestone are exposed, while in a quarry [NZ 0480 1146], about 320 yd NE of Brignall Mill, the bed is 20.5 ft thick with solitary corals, crinoids and brachiopods. The limestone is continuously exposed and about 25 ft thick in the north bank of the River Greta between a locality [NZ 0557 1146] 500 yd E of Moor House Farm and Tebb Wood, where it dips into the river. Here [NZ 0756 1187] the upper 15 ft of limestone contain Dibunophyllum sp., Avonia youngiana, Eomarginifera sp.and a smooth indeterminate spiriferoid. On the south bank small exposures of limestone can be seen near an old lime kiln [NZ 0672 1148] and in a quarry [NZ 0562 1123] in an outlier, about 750 yd NE of Scargill.

The limestone is well exposed between Cowclose Hall Farm and Moorcock Hall Farm. In Nor Beck, some 100 yd SSE of Cowclose Hall Farm [NZ 0643 0949], for example, it comprises at least 25 ft of grey thin-bedded fine-grained Shelly limestone. In another exposure [NZ 0701 1012] lower down Nor Beck the limestone is particularly bioelastic, and together with a shale band contains Amplexizaphrentis sp., Diphyphyllum sp., Fenestella sp., bryozoa [indet.], Alitaria sp., Antiquatonia sulcata, Cleiothyridina sp., Dielasma sp., Eomargimfera cf. setosa, Gigantoproductus sp.[fragment], Pleuropugnoides sp., Rhipidomella michelini, and smooth indeterminate spiriferoids.

The only other record of the limestone in the district is from the Mount Pleasant Bore* [NZ 0328 1508] near Barnard Castle, where the upper 8.5 ft were recorded.

Measures between the Five-Yard and Three-Yard limestones

Measures between the Five-Yard and Three-Yard limestones are patchily exposed in the Greta valley and on Barningham Moor. An exposure [NZ 0361 1221] in the north bank of the river, about 150 yd ENE of Rutherford Bridge, shows the limestone to be succeeded by 10 to 14 ft of mudstone, the basal 3 ft of which contains foraminifera (including Endothyra, Stacheoides and Tetrataxis), Holothuroidea, Fenestella frutex, F. aff. occulata, Penniretepora sp., Polypora verrucosa, Rhabdomeson sp., Streblotrypa sp., Alitaria panderi, Antiquatonia sp., Craniops sp. nov., Cleiothyridina fimbriata, Pleuropugnoides sp., Plicochonetes sp., Pugnoides aff. triplex, Quasiavonia cf. aculeata, Rhipidomella michelini, Rugosochonetes sp., Semiplanus cf. latissirnus, Spiriferellina aff. etheridgei, Hypergonia sp., Aviculopecten sp., Leiopteria sp.,Limipecten dissimilis, Streblochondria sp.

Above the mudstone are about 30 ft of grey and brown, thin- to thick-bedded, false-bedded fine-grained, micaceous sandstone with shaly partings and thin coals. These beds are intermittently exposed between 600 and 800 yd upstream from Rutherford Bridge. This sandstone is succeeded by 3 ft of dark grey silty shale, with thin sandstone ribs, exposed [NZ 0765 1190] in the south bank of the river, about 485 yd NNE of Crook's House.

The measures between this shale and the base of the Three-Yard Limestone are exposed at two localities, about 3.5 miles apart, in the Greta valley. The westernmost section, on the north bank [NZ 0222 1281], about 250 yd W of Thrackholme Farm, is as follows:

The eastern exposure extends from the remains of St Mary's Church [NZ 0772 1220] down river to Scotchman's Stone, and consists of

The 1-ft limestone here is correlated with the Lingula band of the western section.

Small sections in the measures below the Three-Yard Limestone are also exposed to the south on Barningham Moor. In a beck [NZ 0728 0997], about 500 yd W of Barningham Park, 1.5 ft of white, fine-grained, calcareous sandstone with shell casts rest on 3 ft of grey thin-bedded fine-grained carbonaceous, micaceous sandstone. In Gordale Gill [NZ 0673 0936], just beyond the southern margin of the district, 17.5 ft of sandstone are exposed below the limestone.

In the Mount Pleasant Bore* these measures appear to be lithologically similar to those upstream of Scotchman's Stone, but they total only 31.25 ft in thickness, part of the sequence being cut out by faulting.

Three-Yard Limestone

The Three-Yard Limestone is proved in the north of the district only in the Woodland Bore* where 6.25 ft of limestone resting on 2.25 ft of mudstone were recorded. The limestone lies close above the Great Whin Sill and it is probably only the upper part which is represented. A complete section through the limestone was proved farther south in the Mount Pleasant Bore* where it is 14.25 ft thick including shale bands and a 7-in coal near the base, and where it resembles exposed sections farther south.

In an exposure [NZ 0218 1282] on the north side of the Greta valley, about 250 yd W of Thackholme Farm, the lower part of the limestone is seen resting on calcareous sandstone as follows:

The sandy limestone post and the underlying sandstone are also partially exposed in the Greta valley as follows: [NZ 0262 1265], about 230 yd SE of Thackholme Farm, limestone 1 ft; [NZ 0763 1231], about 150 yd NNW of St Mary's Church, limestone 2 ft; [NZ 0772 1191], about 600 yd W of Wilson House, limestone 4.5 ft (? not in situ). The following complete section in the limestone is exposed in the river at Scotchman's Stone [NZ 0807 1245]:

Farther south in a stream [NZ 0775 0986], about 500 yd W of Barningham Park, the following comparable section is exposed:

About 100 yd upstream the 1-ft sandstone of this sequence rests on limestone, the 3 ft of fossiliferous mudstone and shale having being cut out.

Measures between the Three-Yard and Four-Fathom limestones

The measures between the Three-Yard and Four-Fathom limestones are not well exposed in the northern part of the district. In the north bank of the River Tees, however, the upper part of the sequence is exposed [NY 9949 2342], about 250 yd WNW of Eggleston Hall, as follows:

Between this area and the main outcrop to the south, which extends from Bowes to East Layton, these measures were proved in the Woodland* and Mount Pleasant* bores, where thicknesses of 111.5 and 150 ft respectively were recorded. The sequence in the Woodland Bore* is notable for including a representative of the Little Whin Sill (Mills and Hull 1968, p. 9; Harrison 1968, p. 38). The upper part of the sequence was also proved in the Wycliffe Hall Bore*[NZ 1228 1328]

In the area south-south-east of Bowes these measures are partially exposed in the western reaches of the River Greta, where the succession east of Robin Hood's Scar [NZ 0026 1322] is:

Farther east a more complete section is exposed in the River Greta between Scotch-man's Stone and a locality [NZ 0851 1300], about 200 yd upstream from Greta Bridge:

The top of this section is thought to lie about 24 ft below the Four-Fathom Limestone.

The thick sandstone below the Four-Fathom Limestone is sporadically exposed to the south, in Barningham Park. It is also equated with the 30 ft of grey massive jointed medium- to coarse-grained sandstone, with an undulating base, which is exposed in a quarry [NZ 1324 0944], 90 yd E of Dunsa Manor, on the southern margin of the district. In a quarry [NZ 0162 1028], about 150 yd N of Spanham Farm, the upper part of this sandstone is rooty and is separated from the overlying limestone by 2 in of black, sandy micaceous shale, with roots and slickensides.

Four-Fathom Limestone

The Four-Fathom Limestone crops out [NY 9944 2342] in the River Tees west-north-west of Eggleston Hall, where it is 18.5 ft thick and grey, fine-grained and massive, with sporadic solitary corals at the base.

The only other record in the northern part of the district is from the Woodland Bore* where a thickness of 32 ft 1 in was recorded. Farther south the limestone was also proved in the Mount Pleasant* and Wycliffe Hall* bores (Figure 4) with thicknesses of 25 and 18 ft respectively.

In the southern half of the district the Four-Fathom Limestone crops out extensively between Bowes and East Layton. In an exposure [NY 9959 1321], near Gilmonby Bridge, it comprises 12 ft of earthy, fine-grained limestone, with crinoid debris. Other small exposures occur south-west of Plover Hall on Scargill Low Moor, but the best section in the south-western part of the district is seen at a locality [NZ 0162 1028], about 150 yd N of Spanham Farm, where the sequence is:

Farther east 5 ft of limestone are exposed [NZ 1222 1064] on the south side of the A66 trunk road, and it can be followed southeastwards along the outcrop in a number of small quarries. The best section is in a quarry [NZ 12971012] north-east of Browson Bank, where the limestone notably contains some siliceous concretions (Plate 2).

Still farther south-eastwards other small exposures can be seen along the outcrop, the most easterly being in a quarry [NZ 1314 0998], about 550 yd N of Dunsa Manor, where 8.5 ft of limestone are exposed.

Measures between the Four-Fathom and Great limestones

The measures between the Four-Fathom and Great limestones are only poorly exposed in the district. North of the Lunedale–Staindrop Fault they can be seen in the north bank [NY 9954 2342] of the River Tees, near Eggleston Hall, where 10 ft of dark grey, slightly silty mudstone, with ironstone nodules is seen to overlie the Four-Fathom Limestone; in Stobgreen Sike [NZ 0016 2356], where a dark grey mudstone is exposed about 15 ft below the Great Limestone, and in the adjacent stream [NY 9977 2368] to the west, where a similar horizon is exposed.

About 2.5 miles to the north in WT/4 Bore* [NY 9986 2750] on Eggleston Common some 20 ft of strata underlying the Great Limestone consisting of alternating mudstones and sandstones were proved; two thin calcareous bioturbated shelly sandstone ribs were recorded 17 ft 1 in and 11 ft 5 in respectively below the Great Limestone. Nearly 6 ft of thin to thick-bedded grey and dark grey fine-grained siliceous sandstone immediately below the Limestone are regarded as the equivalent of the Tuft Sill.

In this northern area these measures were proved to be 69 ft 2 in thick in the Woodland Bore* where they comprise an upper arenaceous sequence overlying some 30 ft of mudstones and shales with thin bands of limestone and calcite mudstone.

In the south-western part of the district near Bowes 14 ft of hard calcareous mudstone overlying 6 ft of cherty mudstone, with chert bands, are seen in the River Greta [NY 9915 1326], about 470 yd W of Gilmonby Bridge; these beds, which lie about 20 ft above the Four-Fathom Limestone, probably represent in part the Underset (= Four-Fathom) Chert (Wells 1957, p. 242; Johnson and others 1962, fig. 2). Part of the Underset Chert is further partially exposed in a road cutting [NY 9961 1324] due north of Gilmonby Bridge as follows:

The 5 ft of grey and brown thin-bedded ine-grained limonitic and dolomitic limestones exposed in a small quarry [NZ 1299 1075] south of Tefit Hall and occurring about 70 ft ibove the Four-Fathom Limestone may be 'scribed to the chert horizon. A complete sequence, 125 ft thick, was proved in the Mount Pleasant Bore* which includes 32 ft of Underset Chert separated by some 13 ft of hale from the top of the Four-Fathom Lime-tone. Girtyoceras? costatum was found 4 ft above the Four-Fathom Limestone. A broadly comparable sequence was proved in he Wycliffe Hall Bore*, but no Underset Chert was present.

The measures between a horizon about 10 ft above the Underset Chert and the Great Limestone crop out in Chert Gill [NY 9889 1240], bout 170 yd WNW of West Plantation, where the sequence is:

A somewhat different sequence underlies the Great Limestone about 6 miles to the east-north-east, where the section [NZ 0788 1427] in the south bank of the River Tees, about 400 yd W of Rokeby Hall, is as follows:

The sandstone at the top of this section is again exposed in the River Greta upstream of a locality [NZ 0849 1423], about 150 yd W of Mortham Tower. About 4.75 miles SE of Mortham Tower the following mineralized sequence can be seen in East Layton Quarry [NZ 1555 1066];

J.H.H., C.R.B., D.A.C.M.

References

BOTT, M. H. P. 1961. A gravity survey off the coast of north-east England. Proc. Yorks. geol. Soc., 33, 1–20.

BOTT, M. H. P. 1964. Formation of sedimentary basins by ductile flow of isostatic origin in the upper mantle. Nature. Lond., 201, 1082–4.

BOTT, M. H. P. and JOHNSON, G. A. L. 1967. The controlling mechanism of Carboniferous cyclic sedimentation. Quart. Jnl geol. Soc. Lond., 122, 421–41.

BROUGH, J. 1929. On rhythmic deposition in the Yoredale Series. Proc. Univ. Durham phil. Soc., 8, 116–26.

DAKYNS, J. R., TIDDEMAN, R. H., RUSSELL, R., CLOUGH, C. T. and STRAHAN, A. 1891. The geology of the country around Mallerstang. Mem. geol. Surv. Gt Br.

DUFF, P. McL. D. and WALTON, E. K. 1962. Statistical basis for cyclothems: quantitative study of the sedimentary succession in the east Pennine coalfield. Sedimentology, 1, 235–55.

DUNHAM, K. C. 1948. The geology of the Northern Pennine Orefield; Vol. 1, Tyne to Stainmore. Mem. geol. Surv. Gt Br.

DUNHAM, K. C. 1950. Lower Carboniferous sedimentation in the northern Pennines (England). Rept XVIIIth Int. geol. Congr., Pt. 4, 46–63.

DUNHAM, K. C. 1959. Epigenetic mineralization in Yorkshire. Proc. Yorks. geol. Soc., 32, 1–29.

DUNHAM, K. C. DUNHAM, A. C., HODGE, B. L. and JOHNSON, G. A. L. 1965. Granite beneath Viséan sediments with mineralization at Rookhope, northern Pennines. Quart. Jnl geol. Soc. Lond., 121, 383–417.

FORSTER, WESTGARTH. 1809. A treatise on a section of the strata from Newcastle-on-Tyne to the mountain of Cross Fell, in Cumberland; with remarks on mineral veins in general. 1st edit. Alston.

FORSTER, WESTGARTH. 1821. 2nd edit. Alston.

FORSTER, WESTGARTH. 1883. 3rd edit., revised by W. Nall. Newcastle.

FOWLER, A. 1926. The geology of Berwick-on-Tweed, Norham and Screinerston. Mem. geol. Surv. Gt Br.

FROST, D. V. 1969. The Lower Limestone Group (Viséan) of the Otterburn district, Northumberland. Proc. Yorks. geol. Soc., 37, 277–309.

HARRISON, R. K. 1968. The petrology of the Little and Great Whin Sills in the Woodland Borehole, Co. Durham. Bull. geol. Surv. Gt Br., No. 28,38–54.

HICKLING, H. G. A. 1931. Contributions to the geology of Northumberland. Proc. Geol. Ass., 42, 219–28.

HUDSON, R. G. S. 1924. On the rhythmic succession of the Yoredale Series in Wensleydale. Proc. Yorks. geol. Soc., 20, 125–35.

HUDSON, R. G. S. 1938. In The geology of the country around Harrogate. Proc. Geol. Ass., 59, 295–330.

HULL. J. H. 1964. In Summ. Prog. geol. Surv. Gt Br. for 1963, p. 49.

JOHNSON, G. A. L. 1959. The Carboniferous stratigraphy of the Roman Wall district in western Northumberland. Proc. Yorks. geol. Soc., 32, 83–130.

JOHNSON, G. A. L. 1960. Palaeogeography of the northern Pennines and part of north-eastern England during the deposition of Carboniferous cyclothemic deposits. Rept XXIst Int. geol. Cong., Pt. 12,118–28.

JOHNSON, G. A. L. 1962. Lateral variation of marine and deltaic sediments in cyclothemic deposits with particular reference to the Viséan and Namurian of northern England. C. r. Congrès IV Avanc. Etud. Stratigr. Geol. carbonif. Heerlen, 1958,2, 323–30.

JOHNSON, G. A. L., HODGE, B. L. and FAIRBAIRN, R. A. 1962. The base of the Namurian and of the Millstone Grit in north-eastern England. Proc. Yorks. geol. Soc., 33, 341–62.

KENT, P. E. 1966. The structure of the concealed Carboniferous rocks of north-eastern England. Proc. Yorks. geol. Soc., 35, 323–52.

MARR, J. E. 1921. The rigidity of north-west Yorkshire. The Naturalist, No. 769, 63–72.

MILLS, D. A. C. and HULL, J. H. 1968. The Geological Survey borehole at Woodland, Co. Durham (1962). Bull. geol. Surv. Gt Br., No. 28., 1–37.

PHILLIPS, J. 1836. Illustrations of the geology of Yorkshire. Part II. The Mountain Limestone district. London.

RAYNER, D. H. 1953. The Lower Carboniferous rocks in the north of England: a review. Proc. Yorks. geol. Soc., 28, 231–315.

READING, H. G. 1957. The stratigraphy and structure of the Cotherstone Syncline. Quart. Jnl. geol. Soc. Lond., 113, 27–56.

TROTTER, F. M. and HOLLINGWORTH, S. E. 1928. The Alston Block. Geol. Mag., 65, 433–48.

TROTTER, F. M. 1932. The geology of the Brampton district. Mem. geol. Surv. Gt Br.

TURNER, J. S. 1956. Some faunal bands in the Upper Viséan Viséan and early Namurian of the Askrigg Block. Lpool Manchr geol Jnl, 1, 410–19.

WELLS, A. J. 1957. The stratigraphy and structure of the Middleton Tyas–Sleightholme Anticline, North Yorkshire. Proc. Geol. Ass., 68, 231–54.

WELLS, A. J. 1960. Cyclic sedimentation: a review. Geol. Mag., 97, 389–403.

WOOLACOTT, D. 1923. A boring at Roddymoor Colliery, near Crook, Co. Durham. Geol. Mag., 60, 50–62.

Chapter 3 Upper Carboniferous Namurian (Millstone Grit Series)

Introduction

Namurian rocks, shown as Millstone Grit Series (d⁴) on the One-Inch map, crop out in a belt 6 to 8 miles wide, crossing the district in an east-south-easterly direction. Towards the north and north-east these beds pass down dip beneath the Coal Measures; to the east they are overlain unconformably by Permian rocks.

In accordance with current practice in other parts of England and Wales, the Namurian is defined as extending from the base of the band containing Cravenoceras leion Bisat to the base of the band containing Gastrioceras subcrenatum. The lower boundary is close to the base of the Great Limestone (Johnson and others 1962); the upper is correlated with the base of the Quarterburn Marine Band (p. 76) though the diagnostic goniatites have yet to be found in northeastern England.

As thus defined the Namurian ranges in thickness from 1000 to 1750 ft and comprises a lower Yoredale-type facies and an upper arenaceous facies. In terms of the former classification in Durham and Northumberland (Hull 1968, table 1) these facies are respectively equivalent to the 'Upper Limestone Group' and the lower two-thirds of the Durham 'Millstone Grit'. The variation in the succession is shown in (Figure 5), together with the approximate limits of the goniatite stages, established farther south primarily by Bisat (1924, 1928) and Hudson (1945). These have been tentatively fixed in this district partly on evidence of newly discovered goniatites and partly on palynological grounds (Mills and Hull 1968, p. 9; Neves 1968; Hull 1968).

The rocks of Yoredale facies forming the lower part of the Namurian are broadly similar to the cyclic repetitions of limestone, shale, sandstone, seatearth and coal in the underlying Visean. They differ slightly, however, for between any two major limestones there are a number of incomplete cycles in which the sandstone or seatearth is succeeded by either a subordinate thin limestone or marine shale and then by a further sandstone and seatearth. Superimposed on these generalized cycles are a number of 'channel' sandstones, which are generally false-bedded and much more coarse-grained than the usual sandstone members of the cycles. Locally 'channel' sandstones cut out underlying strata and thus complicate any correlation based solely on lithology.

The upper part of the Namurian corresponding with the lower two-thirds of the Durham 'Millstone Grit' consists of a number of coarse-grained, massive, false-bedded sandstones separated by relatively thin argillaceous measures, which locally include marine bands and seatearths, some of the latter being overlain by thin coals. These measures too are cyclic and, typically, consist of repetitions of the following in upward sequence: siltstone, sandstone, seatearth and coal; a few cycles have an additional marine mudstone unit beneath the siltstone. In detail, however, many of the cycles are incomplete and consist only of alternations of sandstone and seatearth.

Conditions of deposition

In early Namurian times the factors controlling sedimentation were probably similar to those operating during the Viséan (p. 12). The Alston and Askrigg blocks, separated by the Cotherstone Syncline, continued to function as structural units, and over them were deposited the sediments of Yoredale type characteristic of these areas. In general those beds north of the Lunedale–Staindrop Fault are similar in thickness and in nature to those of the Alston Block (Figure 5), whereas those south of the fault are similar to the Cotherstone Syncline sequence (Reading 1957, fig. 2). This southern sequence differs only slightly in thickness from that of the Askrigg Block and lithologically the sequences are similar.

Superimposed on this division of the sediments of the Barnard Castle district there is a further regional variation, which is independent of the effect of the Lunedale–Staindrop Fault. These changes occur across a line which trends approximately north-north-east to south-south-west and which appears to have migrated progressively with Namurian time between Barnard Castle and Greta Bridge. To the west of this line, 'channel' sandstones are common throughout the lower part of the Namurian, whereas to the east they are absent and even the usual sandstone members of the cycles are relatively subordinate to the thicker developments of limestones and shales.

The upper, arenaceous, part of the Namurian was probably deposited nearer to the contemporary shore-line than the underlying strata. As evidence of this the sandstones are false-bedded and variable in thickness and grain size, though they are relatively persistent over that part of the district where they crop out when compared to the 'channel' sandstones of the underlying measures. There is evidence to suggest that the sandstones of this facies thin to the south-east. This, together with an increase in thickness of the marine parts of cycles, suggests that sedimentation may have been controlled along a similar migratory north-north-east to south-south-west line to that in the underlying measures.

In the eastern part of the district reddened measures of Namurian age are recorded from a number of localities adjacent to the sub-Permian unconformity and from boreholes which have penetrated Permian strata. Some of these localities are up to half a mile away from the Permian outcrop; they include quarries near High Hulam and Headlam. The basal Permian and the underlying reddened measures are exposed south-west of Cleasby, while reddening has also been recorded in boreholes near Aycliffe, Burtree Gate, Thornton Hall*, Newton Morrell and south of Manfield. Because strata of Coal Measures age are also reddened the phenomenon is described in more detail in Chapter 4, p. 75.

Nomenclature and correlation

Within this district there are extensions of a number of well-known structural elements, each of which has its own well-documented stratigraphical nomenclature. The nomenclature prevalent on the Alston Block (Dunham 1948) has been used throughout this memoir, chiefly because mapping commenced in an area of 'block' facies. The names employed here were subsequently carried into areas which have affinities with the Cotherstone Syncline (Reading 1957), the Askrigg Block (Rowell and Scanlon 1957a) and the Middleton Tyas–Sleightholme Anticline (Wells 1957) and consequently the various nomenclatures can be compared (Figure 5).

Lithological correlations, both within the district and with neighbouring areas, have been made by tracing marker bands from area to area or by a comparison with established sequences. These marker bands, which are generally distinctive marine horizons, form the basis of the subdivision of the following stratigraphical account. Where palaeontological or palynological evidence exists it has been used to confirm or modify the lithological correlations.

The lower part of the Namurian can be correlated with reasonable certainty irrespective of area. Thus the Great, Little and Crag limestones of the north have for some time been correlated with the Main, Upper Little and Crow limestones to the south.

The Knucton Shell-Beds (Carruthers 1938, p. 238) constitute the next marker-band above the Crag Limestone on the Alston Block. These have been recognized in the Cotherstone Syncline by Reading (1957, p. 40 and fig. 4) who considers them to lie below the Lower Stonesdale Limestone; this correlation was initially followed by Hull (1961, p. 41). In its type area, however, the Lower Stonesdale Limestone is the next characteristic marine bed above the Crag Limestone (Turner 1955, p. 350). Furthermore, in the Brough-under-Stainmore (31) district there is evidence that this limestone occurs close above the Crag Limestone and their relationship is similar to that between the Knucton Shell-Beds and the Crag Limestone in the Woodland Bore* (Mills and Hull 1968, p. 8) and in more recent boreholes in the north-west part of the district, including, for example WT/4 Bore*. Accordingly the Knucton Shell-Beds of the Alston Block are here correlated with the Lower Stonesdale Limestone of the Askrigg Block. This correlation further implies that the Upper Stonesdale Limestone of the type area is equivalent, at least in part, to the Rookhope Shell-Beds of the Alston Block (Carruthers 1938, pl. xiii; Dunham 1948, p. 39). On the Askrigg Block the lower part of these shell-beds may well be represented by limestones that are known to be developed between the Lower and Upper Stonesdale limestones in the Brough-under-Stainmore district.

The Mirkfell Ironstones of the Askrigg Block have been shown to be of low E₂ age (Hudson 1941, pp. 279–83; Wilson and Thompson 1959, p. 54). These ironstones are underlain by the Mirkfell Ganister which, it is thought, can be mapped into the top of the sandstones below the Lower Felltop Limestone. Spore evidence from this district (Neves 1968, pl. i) suggests that the E₁–E₂ boundary may lie close above the Lower Felltop Limestone and approximate closely to the horizon of the overlying Coalcleugh Shell-Bed (Carruthers 1938, p. 237). The Coalcleugh Coal (Dunham 1948, p. 40), however, occurs beneath the shell-bed and it is correlated with the Yoredale Coal of this district, which has yielded spores thought to be low E₂ in age (p. 59). This somewhat conflicting evidence suggests that the E₁–E₂ boundary lies between the Lower Felltop Limestone and the overlying Coalcleugh Shell-Bed, but because the mapping suggests a correlation between the Mirkfell Ironstones and the limestone and because the latter is a more persistent marker horizon it is considered that the Pendleian–Arnsbergian boundary is best taken at the base of the limestone.

The correlation of the Upper Felltop Limestone with the Hearne Beck Limestone of Swaledale and the Lad Gill Limestone, proposed by Reading (1957, p. 46), is supported by the work in this district. It should be noted, however, that the limestone is not everywhere present in the southern part of the district and the correlation hinges in part on the recognition and persistence of the overlying marker-bed, the Fossil Sandstone, which is also well developed in neighbouring areas (Reading 1957, p. 47; Rowell and Scanlon 1957a, fig. 12). This sandstone has no obvious correlative in the north on the Alston Block, the next marker above the Upper Felltop Limestone being the Grindstone Limestone, here correlated with the Botany Limestone of the area west-south-west of Romaldkirk (Carruthers 1938, p. 244) which in turn has been correlated by Reading (1957, p. 49) with the Shunner Fell Limestone. The Botany Limestone in the type area is lithologically, and faunally very similar (p. 63) to the Grindstone Limestone in the Woodland Bore* (Mills and Hull 1968, p. 6). The record of Cravenoceras sp.from below the former (Richardson 1961, p. 41) is not thought to conflict with the spore evidence from above the Grindstone Limestone, which suggests a probable E_2b age (Neves 1968, pl. i).

The succeeding measures in this district are comparable with those to the north proved in the Roddymoor Bore (Woolacott 1923; Dunham 1948, figs. 4 and 16). Lithological correlations within these beds are of only local significance and the most effective correlations with other parts of northern England are those based on the recognition of the standard Namurian goniatite stages. Various correlations, incorporating evidence from this district, have been attempted on this basis, including those of Wilson and Thompson (1965, p. 221), Ramsbottom (1966a, pl. 4) and Hull (1968, p. 297).

Between the marker bands described above many beds have been given local names and these are indicated in the following stratigraphical account.

General stratigraphy

Great Limestone

The Great Limestone (Figure 6) (Plate 3A) crops out across the southern half of the district and is generally a grey, fine- to medium-grained massive bioclastic rock except for the top 15 to 20 ft where it is commonly argillaceous and thin-bedded.

The thickness of the limestone ranges from 55 ft in the Mount Pleasant Bore* (Johnson and others 1962, fig. 2) to 72 ft about two miles to the east in the River Tees, though in most other parts of the district the thicknesses approximate closely to 55 ft. This is slightly less than the 60-ft average recorded on the Alston Block (Dunham 1948, p. 26) and the Askrigg Block (Wells 1957, p. 244) though in the Cotherstone Syncline thicknesses of up to 102 ft are known (Reading 1957, p. 36).

The Great Limestone is known to contain three biostromes (Johnson 1958) named in ascending order the Chaetetes Band, Brunton Band and Frosterley Band. In this district the Chaetetes Band has been recognized only in quarries near West and East Layton, where it occurs 1 to 3.5 ft above the base of the limestone and is 1.5 to 2.5 ft thick. In addition to Chaetetes depressus, the band also contains Syringopora sp.and productoids. Generally the band is strongly mineralized, being dolomitic, ferruginous and siliceous, with calcite veinlets and laminae. The Brunton Band has been recognized only in the River Tees, near Egglestone Abbey, where the alga Calcifolium bruntonense has been identified 40 ft from the top of the limestone. At this locality the Chaetetes Band cannot be certainly recognized, though it may be represented by a band containing zaphrentoids and productoids 4 ft above the base of the limestone. The Frosterley Band, typified by Dibunophyllum bipartitum bipartitum, has been more widely recognized throughout the district. It is relatively thin compared to areas farther west (Johnson 1958, p. 152; Hull 1967, p. 75, p1. ii), ranging in thickness from 2 to nearly 7 ft and lying 17 to 33.5 ft below the top of the limestone. The fauna collected from the band in this district includes D. bipartitum bipartitum and Koninckophyllum magnificum, together with a variety of brachiopods (Mills and Hull 1968, pp. 9, 29). It is notable that the solitary corals in both the Frosterley and Chaetetes bands are associated with stylolites and with undulating argillaceous partings containing shell debris, suggesting the action of strong currents or waves during deposition.

Measures between the Great and Little limestones

The measures between the Great and Little limestones (Figure 6) range in thickness from 40 to 140 ft, though on the eastern margin of the adjacent Brough-under-Stainmore (31) district a thickness of 203 ft is recorded.

This range of thickness, which is slightly greater than that recorded on the Alston Block, on the Askrigg Block or in the Cotherstone Syncline, is directly related to the presence or absence of a lower group of sandstones known as the Coal Sills, and an upper sandstone, the 'White Hazle'. The Coal Sills, collectively up to 66 ft thick, are generally present north of the Lunedale–Staindrop Fault and extend as far south as the River Tees between Barnard Castle and Greta Bridge. West of Barnard Castle they are absent within the district, though they reappear on the margin of the Brough-under-Stainmore (31) district where they are 68 ft thick; they are also absent east of Greta Bridge where the measures are correspondingly thin. The 'White Hazle' has a maximum thickness of 41 ft, in the south-west, but is absent in the south-eastern part of the district. It is generally shelly and calcareous at the top locally grading up into the overlying Little Limestone.

A thin limestone or calcareous sandstone locally overlies the Coal Sills. It now seems possible that Wells (1955, p. 178) miscorrelated this limestone with the Little and was consequently led to postulate an unconformity at this level here and farther south in Wensleydale. No support for an unconformity has since been found in Wensleydale (Wilson 1960a, p. 300), nor has the resurvey of the present district produced evidence to suggest that the south-eastward attenuation of the measures between the Great and Little limestones is due to anything other than a slight change in the depositional environment.

The measures between the Great and Little limestones also include banded cherts and siliceous shales up to 25 ft thick. They are generally separated from the underlying Great Limestone by about 10 ft of mudstone and shale and form the northward extension of the Main Chert of Swaledale (Wells 1955, p. 177). Their generally unfossiliferous character, their petrography and their field relationship with the associated measures suggest that they are a syngenetic deposit, as was concluded by previous workers (Sargent 1929; Wells 1955, p. 191). The chert, however, is commonly shattered, especially in the top 12 ft, and the fractures and cavities produced are often infilled with secondary silica in the form either of crystalline quartz or chalcedony. It may be of significance that the cherts occur in the south-west part of the district in areas where the Coal Sills are generally not developed.

No diagnostic faunas have been obtained from the measures in this district to supplement the records in Northumberland of Cravenoceras leion (E_1a)(Johnson and others 1962, p. 352) and Eumorphoceras medusa (E_1a) (Ramsbottom 1966b, p. 56).

Little Limestone

The Little Limestone (Figure 6), sometimes called the Upper Little Limestone to distinguish it from the Lower Little Limestone of the Viséan beds below, crops out parallel to, and to the north of, the Great Limestone across the whole district. North of the Lunedale–Staindrop Fault the limestone is 2.5 to 10 ft thick and is fine-grained, thickly bedded, compact, argillaceous and locally siliceous, with brachiopod fragments and sporadic pipe structures in the base (cf. Wells 1955, p. 180). The range of thickness is generally comparable with that of 3 to 21 ft recorded on the Alston Block (Dunham 1948, p. 33). South of the fault the limestone contains appreciable shale partings and Top and Bottom Little Limestones can generally be recognized, though in the area south of Forcett a single argillaceous, bioclastic limestone up to 20 ft thick is mapped.

The Bottom Little Limestone (Figure 6) ranges in thickness from 7.5 to 27 ft being thickest in the south-east of the district. The limestone is often fine-grained, thinly bedded and siliceous, but near Hutton Magna it is almost completely silicified. It is separated from the overlying Top Little Limestone by 3 to 32.5 ft of siliceous shales and mudstones, these measures being thickest around Barnard Castle and thinnest in the south-eastern part of the district.

The Top Little Limestone (Figure 6) has a thickness ranging from 4 ft in the south-east to almost 16 ft near Barnard Castle. Generally the limestone is fine-grained, thinly bedded, siliceous and shelly, but in the Bowes area it is cherty. Farther south, on the Askrigg Block, the measures equivalent to this limestone and the underlying shales are so siliceous (some of the silica being secondary) that Wells (1955, p. 180) called them the Richmond Chert Series, a practice subsequently followed by Rowell and Scanlon (1957a, p. 9 and fig. 4) who recorded a thickness range from 11 to 24 ft.

Measures between the Little or Top Little and Crag limestones

The measures between the Little or Top Little and Crag limestones (Figure 6) comprise fossiliferous shales, often with thin limestones, overlain by sandy beds. North of the Lunedale–Staindrop Fault the thickness varies from 50 to almost 80 ft, the upper arenaceous part of the sequence, which here consists of the Firestone Sill (Dunham 1948, p. 32) ranging from 4 to 40 ft. Below the Firestone Sill and underlying shale a thin shelly sandstone or limestone, which provides a useful marker throughout the district, is termed the Faraday House Shell-Bed (Plate 3B) to indicate its position at the base of the Faraday House Marine Band (Turner 1955, p. 350).

In the northern part of the district there is generally very little sandstone between the Faraday House Shell-Bed and the Little Limestone. This contrasts with areas still farther to the north, where sandstones termed the White and Pattinson sills give rise to an increase in the overall thickness (Dunham 1948, p. 33).

South of the Lunedale–Staindrop Fault, these measures range in thickness from 24 to 237 ft, being generally thickest in the south-western part of the district. The upper arenaceous measures were called the Ten Fathom Grit by Dakyns and others (1891, p. 10) who recognized that it comprised two sandstones separated by coal, shales and a thin 'crow' limestone, which is taken to be the Faraday House Shell-Bed. The lower sandstone has since been termed the Faraday House Sill (Rowell and Scanlon 1957a, p. 10) and the upper sandstone the Uldale Sill (Turner 1955, p. 350). As the Uldale Sill lies between the Faraday House Shell-Bed and the Crag Limestone it is equivalent to the Firestone Sill of the Alston Block. Only in the River Tees at Barnard Castle, is the Faraday House Shell-Bed not recognized in sections through these measures. Here the Ten Fathom Grit, almost 33 ft thick, is only 20 ft above the Top Little Limestone. Other examples of a unified Ten Fathom Grit occur to the west of the district, in the Cotherstone Syncline, where it is 15 to 65 ft thick and is considered to have cut out the Faraday House Shell-Bed by washout (Reading 1957, p. 39).

The Faraday House Sill which ranges in thickness from 0 to 140 ft on the Askrigg Block (Rowell and Scanlon 1957a, p. 11) and from less than 10 ft up to 60 ft in the Cotherstone Syncline (Reading 1957, p. 39) is up to 18.5 ft thick in this district.

West of Barnard Castle the Firestone Sill (Uldale Sill) is almost 18 ft thick, whereas to the east it is up to 39.5 ft. In both areas the sandstone contains shale and mudstone bands up to 6 ft thick, resembling the sections in the Woodland Bore* (Mills and Hull 1968, p. 8) and the Roddymoor Bore (Woolacott 1923). They contrast with the massive sandstones of the north-western part of the district and the Askrigg Block, where thicknesses of more than 60 ft are recorded (Rowell and Scanlon 1957a, fig. 6).

In the south-eastern part of the district the measures between the Little and Crag limestones are notable for the absence of sandstones, and they are accordingly thinner here than anywhere else in the district or the surrounding country.

The only record of a diagnostic fauna from these measures is that of Tylonautilus sp. nov. [= T. nodiferus 'early mut.' of Stubblefield (see, for example, Fowler and Robbie 1961, p. 83)] from 31 ft above the Little Limestone in the Woodland Bore* (Mills and Hull 1968, p. 8). This indicates a late E₁ age and supports the goniatite evidence from districts to the north-west, where Cravenoceras spp. and a number of specimens of Cravenoceras aff. malhamense (E_1c) have been collected from above the Little Limestone (Dunham and Johnson 1962, p. 243; Johnson and others 1962, p. 354).

Crag Limestone

The Crag Limestone (Figure 7) is known to occur as a single bed only at Stobgreen Sike, near Eggleston, where it is 2.5 ft thick, fine- to medium-grained, argillaceous, and contains crinoids and brachiopods. Its lithology here is similar to that on the Alston Block, where it ranges from 1 to 6 ft (Dunham 1948, p. 34; Dunham and Johnson 1962, p. 246), but over the rest of the district it comprises two leaves known as Top and Bottom Crag limestones. The two leaves and intercalated shales together form a sequence up to 58 ft thick as compared with 30 ft and 34 ft, respectively, in the Cotherstone Syncline and the Askrigg Block (Reading 1957, p. 40; Rowell and Scanlon 1957a, p. 13). The measures are generally siliceous, but locally, as near Little Hutton, they have suffered complete secondary silicification. Hey (1956, p. 297) working to the south of the district, concluded that the silicification was secondary, though virtually penecontemporaneous. Thus the origin of the silica in these beds may be similar to that of the 'Richmond Chert Series' (p. 32) but different from that of the Main Chert (p. 31) which was of primary origin.

The Bottom Crag Limestone ((Figure 7), (Plate 1)) ranges in thickness from 9.5 to 24.5 ft and is generally grey, fine-grained, siliceous, argillaceous and shelly, with siliceous shale partings. It crops out, as does the Top Crag Limestone, in Deepdale Beck, Bessy Sike, Smart Gill and in the River Tees and its tributaries at, and below, Barnard Castle. The Top Crag Limestone (Plate 4A) is also grey, fine-grained, thin-bedded, siliceous and shelly, but it commonly contains caudagalli structures; it ranges in thickness from 7.5 to 25 ft.

No faunas of diagnostic merit have been collected from the Crag Limestone.

Measures between the Top Crag Limestone and the Knucton Shell-Beds

The measures between the Top Crag Limestone and the Knucton Shell-Beds (Figure 7) are not well documented in the north of the district, where they comprise only about 5 ft of strata; atypically, in WT/4 Bore* on Eggleston Moor the Knucton Shell-Beds form the roof of the Top Crag Limestone. In the south of the district these beds are better known; they crop out at a number of localities including the River Tees below Ovington. In these areas they range in thickness from 84 to 120 ft, being thickest in the west. They generally comprise a lower argillaceous sequence up to 52 ft thick overlain by a succession of interbedded sandstones and shales (Figure 7). The argillaceous beds are often marine at the base with a fauna including sponge spicules, brachiopods, gastropods and bivalves.

In the north-western part of the district these measures are thin compared with similar sequences on the adjacent Alston Block (Dunham 1948, p. 35) where, locally, the upper part may be cut out by the Rogerley transgression (op. cit., p. 36). On the Askrigg Block the equivalent strata range in thickness from 8 to 72 ft, while in the Cotherstone Syncline a section measured in Shield's Beck shows them to be 32.5 ft thick. This range shows that the trend of increasing thickness from the south to the north-east of the Askrigg Block (Rowell and Scanlon 1957a, p. 15) is continued into the southern part of this district.

The Knucton Shell-Beds

The Knucton Shell-Beds (Figure 7) as defined by Carruthers (1938, p. 238), comprise thin sandstones with brachiopod casts and crinoids. They have been recognized in this form only on the eastern margin of the adjacent Broughunder-Stainmore (31) district in Snaisgill Sike, north of Middleton-in-Teesdale. Elsewhere they are represented by shelly limestones with interbedded shales, which have been named the Knucton Shell-Beds Limestone in the southern part of the district. In the northern half of the district, the horizon is represented by 10 ft 1 in of beds including a shale parting in the Woodland Bore* and by 12 ft 2 in of muddy limestone and calcareous mudstone in a borehole north of Eggleston. In the south, the limestone is intermittently exposed in Deepdale and the River Tees above Barnard Castle, and again in the River Tees below Winston.

In these areas it increases from 17.5 to 32.5 ft in thickness from west to east and is argillaceous, shelly and locally silicified. The fauna of the limestone includes corals, brachiopods, bivalves, nautiloids and occasional trilobites.

The equivalent limestone in areas to the south-west of the district is the Lower Stonesdale Limestone, which is about 6 ft thick (Rowell and Scanlon 1957a, fig. 8) and thus accords with the general trend of east-to-west thinning in this region.

Measures between the Knucton Shell-Beds and the Rookhope Shell-Beds

In the northern half of the district the measures between the Knucton Shell-Beds and the Rookhope Shell-Beds (Figure 7) are exposed only in the River Tees, downstream from Eggleston Hall, where the uppermost 21 ft, comprising sandstones, are seen. In the Woodland Bore* the measures are 76 ft thick, being argillaceous in the lower part and mainly sandstone with marine shale partingsabove. In most of the northern part of the district this sandstone-on-shale sequence persists, but the measures are reduced in thickness, ranging from 32.5 to 46.5 ft between Deepdale and the River Tees, near Winston. Recent boreholes in the extreme north-west of the district have proved thick sandstones with subordinate mudstones extending up to 220 ft above the Knucton Shell-Beds.

Some sandstones are in part 'channel' sandstones like their approximate correlatives farther north-west, the Grit Sills, whose base is known as the Rogerley Transgression (Dunham 1948, p. 36); the others are essentially similar to those found elsewhere on the Alston Block, for example at Coalcleugh (Carruthers 1938, pl. xiii). Recent mapping in the adjacent Brough-under-Stainmore (31) district suggests that the equivalent measures to the west may be at least 50 ft thick in Lunedale, thinning westwards to about 35 ft in Stainmore (Owens and Burgess 1965, p. 21).

Rookhope Shell-Beds

The Rookhope Shell-Beds (Carruthers 1938, pl. xiii) consist, in the type area, of three minor cyclic units each consisting of shale, shaly sandstone and sandstone (Figure 7). In this district equivalent measures with broadly similar cyclic pattern have been proved in boreholes, and are seen at outcrop only in the River Tees near West Barnley where three limestones, each 3 to 4 ft thick, are separated by 10 to 20 ft of mudstone and sandstone. Mapping in the adjacent district to the west has shown the upper two limestones of this sequence to be equivalent to the Upper Stonesdale Limestone of the Askrigg Block and Cotherstone Syncline (Rowell and Scanlon 1957a, p. 17; Reading 1957, p. 42). Locally, in the north-west of the district, there is evidence that these beds are cut out by the transgression of the overlying sandstones. Elsewhere the shell-beds are represented by thin limestones and interbedded shales and they have been mapped as the Rookhope Shell-Beds Limestone. In the Woodland Bore*, the limestone is almost 13 ft thick including a shale parting. Farther south the lower posts of the limestone are exposed west of Barnard Castle in Deepdale and Percy becks and also in the River Tees. The limestone is thickest in the River Tees, above Winston Bridge, where together with subordinate shale partings it amounts to 32 ft 1 in.

Measures between the Rookhope Shell-Beds and the Lower Felltop Limestone

The measures between the Rookhope Shell-Beds and the Lower Felltop Limestone (Figure 7) vary greatly in thickness and lithology. They are thickest in the River Tees, near West Barnley, where they consist of up to 9 ft of shale succeeded by about 115 ft of sandstone with a median 15-ft band of shale including a thin limestone. In an adjacent section near the confluence of the Tees and Wilden Beck the upper part of the sandstone overlies a 26-in coal, with interbedded shale, and contains a 2-in coal about 31 ft from the top. The latter is correlated with a seam, 10 to 12 in thick, recorded by W. Gunn (in manuscript) at Barnard Castle, where it is estimated to be only 17 ft below the Lower Felltop Limestone. To the west of Barnard Castle, in Percy Beck, the measures are about 50 ft thick, including a 1-in coal near the top. They include only a little sandstone in the Woodland Bore*, where a thickness of about 45.5 ft is recorded.

In the Eggleston area the sandstone sequence is demonstrably locally transgressive. It is in part equivalent to the Mirkfell Ganister and the Lower Howgate Edge Grit, which rests unconformably on the underlying strata in certain areas of the Askrigg Block (Rowell and Scanlon 1957a, p. 18; 1957b, fig. 1). This unconformity is further correlated with that at the base of the Grassington Grit in the Greenhow area (Dunham and Stubblefield 1945, p. 234; Rowell and Scanlon 1957b, p. 89; Wilson 1960a, p. 304). To the north, this unconformity has no strict equivalent. It could be represented, however, by either the Rogerley and Coalcleugh transgressions (Dunham 1948, pp. 36, 40), or by an unrecognized intermediate transgression. Of these transgressions, which are essentially the relatively restricted results of the 'channeling' of sandstones, a correlation with the Rogerley Transgression is thought to be more likely.

Lower Felltop Limestone

The Lower Felltop Limestone (Figure 8) is 6 to 8 in thick north of the Lunedale–Staindrop Fault and 1.5 to 3 ft farther south. It is locally silicified, as east of Barnard Castle, but is otherwise fine-grained and shelly with shale partings. The base of this limestone is thought to be the best position for the boundary between the Pendleian and Arnsbergian stages (p. 28).

Measures between the Lower and Upper Felltop limestones

The measures between the Lower and Upper Felltop limestones (Figure 8) can be divided naturally at the Coalcleugh Shell-Bed (Carruthers 1938, p. 237). In the north-western part of the district the strata below the shell-bed comprise 25 to 30 ft of shale overlain by 36 to 60 ft of sandstone, which is here equated with the Coalcleugh Transgression Beds of the Alston Block (Dunham 1948, p. 40). Farther east and south, however, these measures are very variable; moreover, east of a line from Staindrop to Gain ford, where the measures are thought to be thickest, they are difficult to correlate because of the extensive cover of Permian strata and drift. The shales overlying the Lower Felltop Limestone are fossiliferous at the base and range in thickness from 16 ft in the River Tees near Cotherstone to 50 ft near Barnard Castle. In the same area the overlying equivalent of the Coalcleugh Transgression Beds comprise two sandstones separated by up to 26 ft of silty shales with sandstone laminae. The lower sandstone, which has a transgressive base, thins eastwards from the River Tees, above Barnard Castle, where it is up to 15 ft thick, and is apparently absent east of Barnard Castle. The upper sandstone is almost 53 ft thick in Percy Beck where it includes a 1- to 2-in coal and a 3-in shale band. It thins westwards to less than 25 ft in the River Tees, where it contains a 4-in shaly coal and more siltstone partings, and it also appears to be thin near Whorlton. Still farther east, however, near Winston Station, a borehole proved a 130-ft sequence consisting mainly of sandstone, which may represent either the reappearance of the lower sandstone or the re-establishment and splitting of the upper sandstone. The top of the Coalcleugh Transgression Beds is usually marked by the Coalcleugh Coal (Carruthers 1938, pl. xiii) or its seatearth. In the south-eastern part of this district, around Winston, this coal is sufficiently thick to have been mined under the name of Yoredale or Winston Coal. It was once worked about 1 mile west of Winston in the North Tees Drift, where it ranges in thickness, including bands, from 33 in to 66 in. A spore analysis of the seam by the Scientific Department of the National Coal Board suggested a low E₂ age.

The Coalcleugh Shell-Bed (Figure 8) was recorded in the Woodland Bore* as 1 ft 5 in of dark grey, fine-grained shelly limestone. Elsewhere in the district the position of the bed is inferred from the presence of the underlying Coalcleugh Coal or its seatearth.

The beds succeeding the Coalcleugh Shell-Bed in the north-western part of the district consist of about 30 ft of shale and mudstone overlain by a 30-ft sandstone; elsewhere, however, they are much more variable and comparable to the Askrigg Block sequences (Figure 8). In general they comprise a lower mainly argillaceous sequence and an upper arenaceous one, which includes thin coals and marine bands and which overlies locally a prominent coal, the probable equivalent of the Tan Hill or Kettlepot Coal (Rowell and Scanlon 1957a, p. 22). The lower measures range in thickness from 40 to 80 ft and locally include a sandstone equivalent to the Upper Howgate Edge Grit and the Kettlepot Ganister of the Askrigg Block (op. cit., p. 21). The upper sandy beds range in thickness from 85 to 250 ft and for the most part represent the Tan Hill Grit and overlying Lad Gill Sill of the Askrigg Block (op. cit., p. 23).

Upper Felltop Limestone

The Upper Felltop Limestone (Figure 9) comprises alternations of limestone and shale up to 25.5 ft thick in the area north of the Lunedale–Staindrop Fault. South of the fault, however, the limestone is only 1 ft thick on the western margin of the district and is only locally present to the east, where its position is generally inferred from the overlying strata, especially the Fossil Sandstone. The thick development of the limestone in the northern part of the district is similar to that in the Roddymoor Bore where it was termed the Felltop Limestone (Woolacott 1923, p. 51) but it differs in thickness from that in any other neighbouring area (Dunham 1948, p. 41; Reading 1957, p. 46; Rowell and Scanlon 1957a, p. 23).

Measures between the Upper Felltop and Grindstone (Botany) limestones

The measures between the Upper Felltop and Grindstone (Botany) limestones (Figure 9) are markedly different in thickness and lithology on either side of the Lunedale–Staindrop Fault. North of the fault they are up to 67 ft thick comprising a lower argillaceous and an upper arenaceous succession, of which the Grindstone Sill forms the major part. The Grindstone Sill ranges in thickness from 36 to 43 ft and resembles its equivalent on the Alston Block (Dunham 1948, p. 42), except that in Knotts Plantation, near Eggleston, and Crag Gill to the east, it includes a shale parting. South of the fault the beds are much thicker (Figure 9), with a range from 225 ft in How Beck to the west, to 260 ft north-east of Barnard Castle. They include at least three sandstones of which the lowest is the Fossil Sandstone of Carruthers (1938, p. 250) or the 'Fossil Grit' of Dakyns and others (1891, p. 156). This is 12 to 20 ft thick, and lies 20 to 33 ft above the Upper Felltop Limestone. The next sandstone above is generally 40 to 45 ft thick and has been extensively quarried (p. 62 and (Plate 4B)), though it is absent on the western margin of the district in How Beck. The uppermost sandstone, which is the probable equivalent of the Botany Grit (Reading 1957, p. 47) is up to about 30 ft thick and is separated from the overlying Botany Limestone by 14 to 26 ft of mudstone. On the eastern margin of the adjacent Brough-under-Stainmore (31) district Cravenoceras sp., indicating a low E₂ or earlier age, has been collected (Richardson 1961, p. 41) from the top of these argillaceous measures.

Grindstone Limestone

The Grindstone Limestone (Figure 9) was defined in the Woodland Bore* as being the group of limestones with intercalated shales which lie immediately above the Grindstone Sill (Mills and Hull 1968, p. 20). It reaches a maximum known thickness of just over 14 ft in the borehole, but elsewhere it is thought to be impersistent and locally represented by a shelly quartzitic sandstone. The limestone is the probable equivalent of the Botany Limestone, which crops out near Botany Farm (Carruthers 1938, p. 244) and which was subsequently recognized near Barnard Castle (Reading 1957, p. 49), where it is 13.25 ft thick with a fauna including Dibunophyllum sp., Fenestella sp., Lingula sp.,Schellwienella sp.and other fossils that are also common in the type area.

Measures between the Grindstone and Whitehouse limestones

The measures between the Grindstone and Whitehouse limestones (Figure 9) are the youngest Namurian strata to have been preserved south of the Lunedale–Staindrop Fault, and they are there represented by a few feet only of fossiliferous sandstone. North of the fault these strata crop out extensively north and northeast of Eggleston, where they range in thickness from 73 to 127 ft and comprise a number of minor cyclothems, one of which includes a thin unnamed limestone (Figure 9). In the Woodland Bore* Homoceras cf. henkei (indicative of the R_1a Zone) was recorded (Mills and Hull 1968, p. 6) about 83.5 ft above the Grindstone Limestone.

Whitehouse Limestone

The Whitehouse Limestone (Figure 10) was defined in the Woodland Bore* (op. cit., p. 6); it crops out near, and north-east of Eggleston. It generally ranges in thickness from 1 in to 1.5 ft, but locally it may be up to 5 ft thick (p. 64). The limestone was also recorded in the Roddymoor Bore but it has not been described elsewhere in County Durham.

Measures above the Whitehouse Limestone

The measures above the Whitehouse Limestone to the top of the Namurian (Figure 10) are 199 to 330 ft thick and consist mainly of sandstones, with subordinate thin coals, seatearths and shales which are sporadically fossiliferous. This part of the succession includes the First Grit and the Second Grit of the Primary Survey, which together constituted the lower two-thirds of the 'Millstone Grit' of former classifications.

The 'grits' give rise to well-defined features, and it is clear from the mapping and from a comparison of stream and borehole sections that they each split into two or more sandstone units which are only locally persistent. The 'First and Second grits' are thus of doubtful stratigraphical significance and the names are likely to be misleading if extrapolated over a wide area. For this reason an attempt has been made to correlate the sequence by means of marine marker bands, some of which are named here for the first time, others having been defined in the Woodland Bore* (Mills and Hull 1968, p. 6). Each of these markers contains a restricted brachiopod, bivalve and gastropod fauna and each is liable to be cut out by overlying sandstones. The most notable of such markers in these measures lies close above the Whitehouse Limestone, where Reticuloceras stubblefieldi (R_1b) has been recorded (Hull 1963, p. 45). Goniatites of the R. nodosum group were found at a similar horizon in the Woodland Bore*.

The lowest marker, the Sharnberry Shell-Beds, takes its name from Shamberry Beck in the adjacent Wolsingham (26) district, where it is 4.25 ft thick and where the fauna includes Reticuloceras sp., probably indicating a Lower Reticuloceras(R₁) age. In terms of the former classification it lies midway in the 'First Grit', overlying a sandstone, locally called the 'Basement Grit'.

The Woodland Shell-Beds which were defined in the Woodland Bore*, consist of 11 to 28 ft of mudstones, generally with thin sandstones, and with a fauna commonly including Serpuloides sp., Lingula mytilloides, Orbiculoidea cf. nitida, productoids and Retispira sp.These shell-beds occur in the measures between the 'First' and 'Second' grits. The lower leaf of the 'Second Grit' separates the Woodland Shell-Beds from the next marker band above. This sandstone contains a number of shale partings and mapping suggests that one of these crops out at a locality where Kirkby and Duff (1872, p. 186) described shales and an inferior limestone containing marine shells. An unnamed marine horizon may exist therefore between the Woodland and Spurlswood Shell-Beds.

The Spurlswood Shell-Beds are named after a locality in Spurlswood Beck, where they consist of two thin bands of fossiliferous shale separated by 16 ft of apparently unfossiliferous mudstone and siltstone. At other localities the beds are represented by an argillaceous sequence from 10.25 to 12.75 ft thick. The fauna from these measures generally includes Lingula and productoids. The shell-beds generally occur midway in the 'Second Grit', but the overlying upper leaf commonly cuts them out. The Spurlswood Shell-Beds are separated from the base of the Coal Measures by 72 to 104 ft of strata consisting of the upper sandstone leaf of the 'Second Grit' and by up to 103 ft of overlying variable measures, which locally contain, where they are thickest, an unnamed marine band. J.H.H., D.A.C.M.

Details

Comparative sections of the Namurian sequence are shown in (Figure 6), (Figure 7), (Figure 8), (Figure 9), (Figure 10); (Figure 11) shows most of the localities referred to in the text.

Great Limestone

North of the Lunedale–Staindrop Fault the Great Limestone (Figure 6) is exposed only in Eggleston Burn [NY 9898 2427] and [NY 9883 2393] where the Frosterley Band (Johnson 1958, p. 151), with corals and brachiopods, is present about 18 ft from the top.

Elsewhere it is proved in boreholes, notably WT/4 Bore* [NY 9986 2750] on Eggleston Common, WT/6 Bore [NZ 0030 2423] north of Eggleston and the Woodland Bore* [NZ 0910 2770]. In these boreholes the thickness ranges from 52 ft 11 in up to at least 64 ft 6 in in Bore WT/6. In WT/4 Bore* a pronounced coral band 6 ft 9 in thick and a coral-brachiopod band 1 ft 10 in thick are present 25 ft and 33 ft 6 in respectively from the top of the limestone. In the WT/6 and Woodland bores the Frosterley Band is 3 ft 5 in and 3 ft 10 in thick respectively.

In the southern half of the district good sections in the limestone can be seen around Lamb Hill (Plate 3A) where its average thickness is 55 ft, and in the River Tees below Barnard Castle downstream from Abbey Mill [NZ 0634 1513], where it is 72 ft. Throughout this area the limestone is generally grey or dark grey, massively bedded, fine- to medium-grained, bioclastic and crinoidal; in the top 15 ft and the basal 8 ft it is generally more thinly bedded and argillaceous. Sporadic clisiophylloid corals and brachiopods are found but no distinctive Frosterley Band has been recognized. The Chaetetes Band (Johnson 1958, p. 149) is similarly difficult to discern in this area, though its horizon may be indicated by sporadic zaphrentoids and brachiopods about 4 ft above the base of the limestone. A specimen 40 ft from the top of the limestone (loc. 1c)^‡4  near Abbey Bridge [NZ 0663 1496] contains the alga Calcifolium bruntonense indicative of the Brunton Band (Johnson 1958, p. 150). At an old quarry [NZ 0229 1339] on the south side of the A66 road at Lamb Hill the section in the Great Limestone is as follows (loc. la):

In the Mount Pleasant Bore* the Great Limestone was 55 ft thick. Sections occur in the River Greta below Greta Bridge [NZ 0862 1317] and also 2.5 miles to the east-south-east in Lanehead Old Quarry [NZ 1260 1177] where 37 ft of limestone are exposed. In the Wycliffe Hall Bore* [NZ 1228 1328] a full thickness of 56 ft 10 in was proved.

Of 32 ft of Great Limestone exposed in a quarry [NZ 1433 1047] north of West Layton (loc. lb) the lowest 2.5 ft represent the Chaetetes Band, consisting of thin-bedded limonitic limestone with abundant laminae of Chaetetes demessus together with Lithostrotion pauciradiale. About 1 ft 2 in above occurs a 6-in band of fine-grained dolomitic limestone with coarsely bioclastic patches containing sporadic Koninckophyllum sp.and Semiplanus sp., [latissimoid]. A fauna collected from the overlying 27 ft 6 in of limestone included Aulophyllum fungites, Caninia sp., Dibunophyllum bipartitum bipartitum, Echinoconchus cf. elegans, Etheridgina complectans, Plicochonetes aff. interstriatus, Schizophoria sp.and Semiplanus sp.[latissimoid].

The Chaetetes Band is also exposed in the floor of East Layton Quarry [NZ 1556 1066], where it is 18 in thick and lies 14 to 20 in above the base of the limestone. The Great Limestone has a total thickness of at least 52 ft and a composite section of the northern and eastern faces reads:

The Chaetetes Band is further exposed, with a thickness of 26 to 28 in, in the floor of Forcett Old Quarry [NZ 1674 1100], where the basal 10 ft of limestone are seen to be dolomitic and ferruginous. There are other exposures of the Great Limestone at East Layton [NZ 1606 1000], in a quarry [NZ 1679 1026] SSW of Carkin Field, and in Gill Wells Plantation [NZ 1702 1013]. Still farther east, the top of the Great Limestone was proved in the Grunton* [NZ 2239 1148] and Brettanby Farm* [NZ 2279 1038] boreholes, and in a borehole* [NZ 2160 1001] at Wath Erne. J.H.H.

Measures between the Great and Little Limestones

The measures between the Great and Little Limestones (Figure 6) are partially exposed north of the Lunedale Fault in Eggleston Burn [NY 9893 2471]. The Little Limestone is seen to rest on a 3-ft siliceous sandstone—the White Hazle—overlying 10 ft of shale and 8 ft of thin-bedded sandstone with shale partings, one of which, about 3 ft from the top, yielded orthotetoid fragments. A more complete section is exposed, a mile southeast, in Stobgreen Sike (loc. 2b) [NZ 0019 2378]:

Further detailed sections of these beds are recorded in WT/4 Bore* and the Woodland Bore* where they are 82 and 92 ft thick respectively and include prominent sandstones forming the White Hazle and Coal Sills. In WT/C Bore [NZ 0041 2596] at Blackton Head and WT/6 Bore the White Hazle is respectively 21 and 8.25 ft thick and is separated from the top of the Coal Sills sandstone by strata up to 2.25 ft thick containing a thin muddy sandy limestone and calcareous sandstone. It is possible that this marine horizon may be equated with the 1-ft limestone overlying the Coal Sills in the Sleightholme Beck section, which is also locally recorded elsewhere. J.H.H., D.A.C.M.

In the southern half of the district complete sequences are not seen, but a short distance to the west, in the Brough-under-Stainmore (31) district, the following sequence is exposed in Sleightholme Beck:

Lateral variation is apparent by comparing the above with the following section, exposed about 3.5 miles to the south-east in Spanham Hush [NZ 0087 0989]:

The base of this section is estimated to lie about 30 ft above the top of the Great Limestone. The 9 ft of chert are taken to represent the top of the Main Chert Series in the Richmond (41) district (Wells 1955, p. 177). C.R.B.

These cherts are exposed in the streams which drain Scargill High Moor northwards into Eller Beck and in Chert Gill [NY 9867 1193], where they are 23 ft thick, but they do not persist as far north as the Mount Pleasant Bore*, nor are they significantly represented in the River Tees between Abbey Mill and Demesne Mill*, Barnard Castle. In this Tees section the Coal Sills are in three posts totalling 26.5 ft of sandstone in 34 ft of strata separated by almost 16 ft from the top of the Great Limestone. Here, the Coal Sills are overlain by 27.5 ft of mudstone, the basal 18 ft yielding an exceptionally rich fauna of brachiopods as well as bryozoa, bivalves, ostracods and a fish tooth (loc. 2a). This mudstone is succeeded by the White Hazle, which is 33.5 ft thick. The top 8 in of the White Hazle is calcareous and Shelly and grades up into the overlying limestone. J.H.H., C.R.B.

A similar sequence is exposed in the River Tees between its confluence with the Greta and a locality three-quarters of a mile downstream near Thorpe Scar [NZ 0961 1443]. About 1.75 miles SE of Thorpe Scar, in the Wycliffe Hall Bore* the Coal Sills are absent, the Great Limestone being overlain by at least 94 ft of dark grey fossiliferous shale with sporadic ironstone nodules. East of the borehole, these measures are not now well exposed, but Gunn records (in manuscript) 5 ft of blue shale on siliceous flags immediately beneath the Little Limestone in a quarry [NZ 1779 1068] south-west of Stanwick Hall. J.H.H.

East and south-east of Aldbrough the measures were proved in two water boreholes at Grunton* and Brettanby Farm* to be 75 ft and 89 ft thick respectively, in both cases including a representative of the White Hazle. At another borehole* at Wath Erne the equivalent measures consisted only of 40 ft of shale. D.A.C.M.

Little Limestone

The Little Limestone (Figure 6) crops out at two localities north of the Lunedale Fault. In Eggleston Burn [NY 9893 2471] it is approximately 5 ft thick, the basal beds comprising 3 in of medium-grained sandy ferruginous limestone overlying, and piping down into, 2.25 ft of dark grey, fine-grained bioclastic limestone. In Stobgreen Sike* the limestone is 10 ft thick; it is grey and fine-grained, with brachiopod fragments. The only other records of this limestone in the north of the district are in WT/4 Bore*, WT/C Bore, WT/6 Bore and the Woodland Bore*, where it is almost 4.5 ft thick, the proved thicknesses ranging between 4 and 5 ft. J.H.H., D.A.C.M.

In the southern half of the district shale partings are common in the Little Limestone; and both a Top and a Bottom Little Limestone, separated by a sequence of shale and mudstone, can be recognized in most areas. JHH

The Bottom Little Limestone is seen in Spanham Hush [NZ 0087 0989];

A similar sequence is exposed in West Spanham Gill [NZ 0058 0995]. C.R.B.

Near Demesne Mill* [NZ 0535 1582] in the River Tees, the Bottom Little Limestone consists of almost 7.5 ft of dark grey thin-bedded fine-grained earthy siliceous limestone, with brachiopods and ostracods (loc. 3a). It is continuously exposed east-south-east of Demesne Mill* at the top of the scarp behind the sewage works and also in the scarp in Cross Berry Plantation [NZ 0900 1466]. The limestone passes gradually down into the underlying sandstone and there are vestigial pipe-like structures near the base.

In a beck [NZ 0930 1463], 550 yd SSE of East Shaws, the Bottom Little Limestone is 10.25 ft thick and a similar thickness is seen in the south bank of the River Tees [NZ 0957 1434] near West Thorpe Wood.

South of the Tees, in a quarry [NZ 1273 1290] north of Hutton Magna, the limestone is at least 12 ft thick and is, like the overlying 3.5 ft of shale, completely silicified: only vestigial patches of the original grey siliceous limestone remain. The limestone is also silicified in an outlier 2 miles SE of Hutton Magna, where the uppermost 5.5 ft are exposed [NZ 1602 1187]. About a mile north-east of this the limestone is relatively unaltered, and the following section is exposed in a railway cutting [NZ 1689 1259]:

About 8 ft of grey and fawn siliceous dolomitic limestone exposed in Cat Wood [NZ 1790 1234] represents part of the same sequence.

Between Stanwick Hall [NZ 1843 1145] and Aldbrough, the Top and Bottom Little limestones are thought to come together into one bed, the lower part of which is exposed in Hergill Quarry [NZ 1759 1101]:

Comparable sections are exposed at two other localities, 150 yd SSW and 700 yd SE respectively, of Stanwick Hall. J.H.H.

A partial section is also seen in the quarry [NZ 1989 1103] south-west of Aldbrough. East of this quarry the Little Limestone is again split, but the parting is too thin to warrant the mapping of two limestones. In Harthorn Quarry* [NZ 2060 1100] about 350 yd SW of Aldbrough Church, the upper part of the Bottom Little Limestone consists of 2 ft 8 in of dark grey fine-grained impure limestone with Alitaria cf. panderi and Martinia sp.(loc. 3b). Beds at about the same horizon exposed [NZ 2034 1056] in Melsonby Lane, Aldbrough, consist of about 10.75 ft of argillaceous shelly limestone with a calcareous mudstone parting 5 to 8 in thick; the fauna which is abundant in the top 2 ft includes Alitaria cf. panderi, Avonia davidsoni, Pleuropugnoides sp., Quasiavonia cf. aculeata, Spiriferellina sp.and Limipecten dissimilis (loc. 3c).

Farther east, where the limestone is concealed by thick drift or Permian strata, the Bottom Little Limestone was 17 ft thick in the Grunton Bore*, at least 14 ft thick in the Brettanby Farm Bore* and 27 ft thick in the Wath Erne Bore*. D.A.C.M.

The measures between the Bottom Little and Top Little Limestones (Figure 6) consist of siliceous shales with thin limestone ribs and sporadic silty bands. These beds are continuously exposed at Demesne Mill*, Barnard Castle, where they are 30 ft 4 in thick and contain Avonia sp., Crurithyris sp., Echinoconchus cf. elegans, Rugosochonetes sp.and Spirifer cf. trigonalis (loc. 4a). At Harthorn Quarry* [NZ 2060 1100] the equivalent strata are 16 ft 8 in thick and contain Hyalostelia smithii, Fenestella frutex, Fistulipora sp.and Cleiothyridina sp.(loc. 4b). East of Aldbrough these measures are represented by only 4 ft of black shale with banded chert in the Grunton Bore* and 3 ft of shale in the Wath Erne Bore*. J.H.H., D.A.C.M.

The Top Little Limestone which generally crops out at the same localities as the Bottom Little Limestone is represented around Bowes by 6 ft of dark grey cherty limestone with irregular nodules of purer chert; it can be seen, for example, in a quarry [NY 9821 1429] about 750 yd NW of Clint House. In the River Tees the top 10 ft of the limestone can be seen downstream from the Woollen Mill [NZ 0484 1617] at Barnard Castle. Collections obtained from various exposures in the limestone hereabouts include Avonia youngiana, Buxtonia sp., Cleiothyridina cf. fimbriata, C. aff glabristria, Eomarginifera cf. setosa, Phricodothyris sp, and Spirifer cf. trigonalis (locs. 5c, 5d). C.R.B.

The most complete section of the Top Little Limestone is near Demesne Mill* where 17.5 ft of siliceous shelly limestone, including a 2-in mudstone band, crops out; it has yielded Avonia cf. youngiana, 'Camarotoechia' sp., Crurithyris sp.,Eomarginifera cf. setosa and Spirifer cf. trigonalis (loc. 5a). The limestone is well exposed in a half-mile stretch of the river [NZ 1035 1473] to [NZ 1187 1434] between Whorlton and Wycliffe, with a typical section:

Three miles to the south-east the lowest 8 ft 2 in of the limestone are exposed in a quarry [NZ 2153 1146], 200 yd NE of Brantcas Farm; it is pale grey, massive and fine-grained, with a few bioclastic argillaceous partings. A section exposed in Caldwell Beck [NZ 1684 1281], 0.5 mile SE of Caldwell Church shows:

J.H.H.

At Harthorn Quarry* [NZ 2060 1100], Aldbrough, the lower part of the Top Little Limestone consists of 12.25 ft of brownish grey flaggy argillaceous siliceous crinoidal limestone with calcareous shale partings at the top. Hyalostelia smithii, Alitaria panderi and an indeterminate turreted gastropod were collected from the basal 2.25 ft (loc. 5b). Farther east in the Grunton Bore* the limestone is 10 ft thick, being reddened at the top, while in the Wath Erne Bore* it is only 4 ft thick. D.A.C.M.

Measures between the Top Little and Crag Limestones

The measures between the Top Little and Crag Limestones (Figure 6) are almost continuously exposed in Eggleston Burn as follows:

The Firestone Sill is also exposed [NZ 0037 2390] in Stobgreen Sike* where its thickness of 40 ft contrasts with 7 ft 5 in, including 1 ft of shale and coal, proved in the Woodland Bore* to the north-east. The Faraday House Shell-Bed is faulted out in the Stobgreen Sike section, but is represented in the bore by an 11-in limestone rich in brachiopods. J.H.H.

In recent Bores WT/4*, WT/C and WT/6 in the north-west of the district these measures are between 50 and 70 ft thick. A thick sequence of mudstones and shales also containing calcareous bands overlies the Little Limestone; in Bore WT/C one of these bands expands to form a limestone 3 ft 3 in thick lying 11 ft above the Little Limestone. The Faraday House Shell-Bed can be recognized in all cases either as a limestone or calcareous shelly sandstone. The Firestone Sill is thin and does not exceed 7 ft. In WT/4 Bore* it is separated from the base of the Crag Limestone by 1 ft 7 in of mudstone containing the Crag Coal, one inch thick. D.A.C.M.

South of the Lunedale Fault, and north of Bowes, these measures are incompletely exposed. The best section is in the north bank of Deepdale Beck [NY 9953 1538]:

The base of this section is about 105 ft above the top of the Top Little Limestone.

In Bessy Sike [NZ 0018 1535] the sequence underlying the Crag Limestone is similar to that in Deepdale Beck, but 3 miles to the east-north-east, at Barnard Castle, it is much thinner, includes loc. 6b, and the sandstones in the upper part of the sequence form a single post that has been called the Ten Fathom Grit (see p. 32). The following section can be seen below the castle [NZ 0482 1640]:

C.R.B.

The equivalent measures are continuously exposed in Whorlton Beck* below the bridge [NZ 1066 1499]. They are 137 ft 1 in thick, including the Faraday House Shell-Bed (3 ft 2 in) and the Firestone Sill (37.5 ft). The fauna at several horizons is abundant and consists of bryozoa, brachiopods, nautiloids and bivalves, the most important forms present being Fenestella cf. frutex, Cleiothyridina cf. fimbriata, Dielasma sp., Dictyoclostus sp., Echinoconchus cf. punctatus, Pleuropugnoides cf. pleurodon, Spirifer cf. bisulcatus, Rugosochonetes sp., Limipecten dissimillis, Parallelodon cf. semicostatus and Pernopecten sowerbii (loc. 6a). Good sections are also exposed in the banks of the River Tees between a locality [NZ 1009 1484] west of Whorlton suspension bridge and the weir [NZ 1314 1497] at Ovington. J.H.H.

In the Grunton Bore* the Top Little Limestone is succeeded by 10 ft of shale, reddened beneath the Permian unconformity, while in the Wath Erne Bore* the complete sequence between the Top Little and Crag Limestones is represented by only 24 ft of shales. D.A.C.M.

Crag Limestone

The Crag Limestone (Figure 7) appears to be split into Top and Bottom leaves throughout most of the district, although it is present as a single bed, 2.5 ft thick in Stobgreen Sike*. Farther west in Eggleston Burn the limestone is apparently absent, its position being indicated by the Crag coal. In Bores WT/4*,

WT/C and WT/6 the Bottom Crag Limestone ranges between 9 ft 3 in and 19 ft 1 in. In Bore WT/4* where it is at its thickest it includes 1 ft 7 in of conglomerate consisting of limestone fragments set in a matrix of calcareous mudstone. In this borehole also the limestone is separated by only 5 in of calcareous mudstone from the Top Crag Limestone. To the north-east in the Woodland Bore* it is represented by 10 ft 4 in of limestone. D.A.C.M., J.H.H.

The Bottom Crag Limestone (Figure 7) crops out in Bessy Sike [NZ 0018 1535], on the western margin of the district, where 12 ft of greyish brown thin-bedded sandy limestone with siliceous laminae rest on shelly sandstone; a similar section is seen in Deepdale Beck [NZ 0071 1604] where on the south side of the Raven's Nest fault 10.5 ft of limestone contains Caninia juddi, Chaetetes depressus, Martinia sp.,Rugosochonetes sp.and Aviculopecten cf. plicatus (loc. 7d). The best of several exposures near Thornberry Farm is in a quarry [NZ 0107 1541] 65 yd N of the farmhouse, where the limestone is 10 ft thick and is grey thin-bedded fine-grained and decalcified with siliceous wisps; it contains crinoids, brachiopods and fish scales. In Smart Gill [NZ 0296 1586] 17 ft of siliceous limestone with chert lenses are ascribed to this horizon, though correlation with the Top Crag cannot be ruled out. The Bottom Crag is more certainly recognized beneath the castle in the north bank of the River Tees at Barnard Castle [NZ 0482 1640] (Plate 1) where the section is:

The fauna, ranged throughout the limestone, consists of bryozoa, Caninia sp., Koninckophyllum cf. echinatum, Cleiothyridina sp., Quasiavonia cf. aculeata and bivalves (loc. 7e). C.R.B.

A comparable section is exposed in Sledwick Hall quarry [NZ 0914 1525] near East Shaws where the fauna comprises Chaetetes depressus, Koninckophyllum magnificum, Eomarginifera cf. setosa, Limipecten dissimilis (loc. 7c). In Whorlton Beck* (loc. 7a) [NZ 1068 1501] the Bottom Crag Limestone has thinned to 9 ft; in the north bank of the River Tees below Wycliffe it is at least 10 ft thick. Other exposures are to be seen in the south bank of the Tees at, and to the west of, Ovington Weir* [NZ 1314 1497]; here it is particularly siliceous with well marked 'cauda-galli' structures and has a thickness of 6.25 ft including shale partings. East of Little Hutton the lower part of the Bottom Crag Limestone can be seen [NZ 1455 1269] to consist of at least 5 ft of grey, massive fine-grained siliceous limestone almost completely silicified; the top of the limestone, however, is dark grey thin-bedded fine-grained siliceous and relatively unaltered at outcrop some 300 yd farther east [NZ 1481 1268]. In the quarries [NZ 1541 1293] north-east of Foxberry the limestone is at least 5 ft thick and grey thin-bedded fine-grained bioclastic, crinoidal and dolomitic. J.H.H.

In the Wath Erne Bore* 21 ft of hard yellow limestone immediately underlying the drift is taken to be the equivalent of at least the Bottom Crag Limestone. in this same area small exposures of the limestone can be seen in Crossbury Bank Wood [NZ 2094 1056] (loc. 7b) where a typical section is:

Other exposures can be found in the beck [NZ 2122 1027] immediately north of Micklow Farm and in the two quarries east of Micklow Hill [NZ 2128 1002]. D.A.C.M.

The measures between the Bottom and Top Crag Limestones (Figure 7) consist of dark grey calcareous, locally siliceous, fossiliferous shale or mudstone with thin limestone ribs. Thickness ranges from 5 in at WT/4 Bore* in the north to 16 ft in the River Tees near Ovington*. In Whorlton Beck* [NZ 1068 1510], for example, they are 12 ft thick and contain bryozoa, Antiquatonia cf. insculpta, Linoprotonia sp.,Tornquistia cf. polita, Cypricardella sp.and ostracods (loc. 8a). J.H.H., D.A.C.M.

The Top Crag Limestone (Figure 7) was recognized in several boreholes in the northern part of the district but is exposed at only two localities. One is in the River Tees [NY 9905 2308], about 800 yd SW of Eggleston Hall, where 5.5 ft of dark grey thick-bedded jointed fine-grained crinoidal limestone are seen; the other [NZ 0706 2200] is in a railway cutting approximately 700 yd SW of Dent Gate Farm:

These beds contain an abundant fauna of brachiopods and bivalves including 'Camarotoechia'sp., cf. Schellwienella rotundata, Spirifer cf. trigonalis, Nuculopsis gibbosa and Polidevcia attenuata; gastropods and trilobites are also present (loc. 9e). Immediately beneath this section Gunn (in manuscript) recorded 5.5 ft of shale on 2.5 ft of limestone, the latter being the possible local equivalent of the Bottom Crag Limestone. J.H.H.

In Bores WT/4*, WT/C and WT/6 in the north-west part of the district the Top Crag Limestone ranges between 2 ft 2 in and 9 ft 8 in, being thickest in Bore WT/4 where it is a dark grey muddy limestone with calcareous mudstone bands. In the Woodland Bore* it is represented by 7 ft 5 in of limestone with shale bands. D.A.C.M.

In the south-western part of the district the Top Crag Limestone is exposed in Deepdale Beck [NY 9920 1546], about 80 yd E of Crag Bridge (Plate 4A), where it consists of at least 9.5 ft of bioclastic limestones interbedded with fossiliferous calcareous shales and impure limestones, all of which are decalcified (lots. 9c, 9d) and again [NZ 0070 1602] south of the Raven's Nest Fault, where it comprises 12 ft 10 in of grey thin-bedded sandy shelly limestone with siliceous wisps. Still farther down the beck [NZ 0281 1627] the upper part of the limestone is seen as follows:

In the north bank of the River Tees [NZ 0483 1642] at Barnard Castle (Plate 1) the Top Crag Limestone consists of at least 25 ft of grey thin-bedded fine-grained sandy limestone with 'cauda-galli' structures and siliceous wisps. The fauna consists of bryozoa, crinoids (in top 4.5- ft), Cleiothyridina sp., Quasiavonia sp.[juv.], bivalves and ostracods (loc. 9b). About 1 mile ESE in a quarry [NZ 0631 1600] near Lowfield Garden the basal members of the limestone are exposed:

J.H.H.

In Whorlton Beck* [NZ 1068 1515] a continuous section of the Top Crag Limestone is exposed, comprising limestone 2 ft 8 in on mudstone 2 ft and limestone 5 ft. The fauna consists mainly of brachiopods including Linoprotonia sp.and Martinia sp.(loc 9a). The Top Crag Limestone is further exposed in the south bank of the River Tees near Ovington*, where it has a total thickness of 6 ft 7 in including 1.5 ft of mudstone. D.A.C.M.

About 2 miles SE of Ovington in a small quarry [NZ 1598 1349] in Caldwell the section exposed is:

J.H.H.

Measures between the Top Crag Limestone and the Knucton Shell-Beds

The measures between the Top Crag Limestone and the Knucton Shell-Beds (Figure 7) are poorly exposed in the northern part of the district; they are recorded however in the WT/4*, WT/6 and Woodland* bores. Atypically, in WT/4 Bore the Knucton Shell-Beds are formed by 3 ft 5 in of calcareous mudstone and siltstone resting directly on the Top Crag Limestone. In WT/6 Bore and the Woodland Bore 5 and 3 ft respectively of calcareous mudstones separate the two horizons. D.A.C.M. J.H.H.

In the south-western part of the district, these beds are well exposed in Deepdale Beck between Crag Force and the River Tees at Barnard Castle. Between Crag Force and the Raven's Nest Fault, for instance, the Top Crag Limestone is succeeded by 68 ft of shale (loc. 10b) containing a fauna including Hyalostelia sp., bryozoa, Rugosochonetes sp., Euphemites sp.and Palaeoneilo cf. mansoni; this in turn is overlain by an 8-ft sandstone. Immediately north of the fault [NZ 0075 1610] the following more complete section is exposed.

Lateral variation in the upper part of these measures is demonstrated by comparing the above section with that in a beck near Rigg Farm*, where the Knucton Shell-Beds Limestone is separated from an underlying 28-ft sandstone by 10 ft of sandy shale. About 300 yd due east a similar sequence is seen in a southern tributary stream of Deepdale Beck. Beneath the lowest sandstone, however, a further 52 ft of beds are exposed consisting of 46 ft of silty shales with sandstone ribs split by a 6-ft median sandstone. The base of the lowest shales is 30 to 40 ft above the Top Crag Limestone. Part, if not all, of this interval consists of argillaceous beds, locally containing ironstone nodules and fossils; they are poorly exposed in Deepdale Ravine and nearby in Smart Gill [NZ 0312 1621], where the lowest 12 ft of siltstone and shale rests directly on the Top Crag Limestone. Still farther east, in Deepdale Beck, the Knucton Shell-Beds Limestone is underlain in the north bank [NZ 0444 1667] by 4 ft of grey fine-grained micaceous shelly sandstone with argillaceous wisp., 'caudagalli' structures and brachiopods below which lie 5 ft of grey pyritous siltstone with sandstone ribs. The siltstone is also partially exposed at the mouth of Deepdale Beck, where it contains lenses and nodules of white, fine-grained, siliceous sandstone: the overlying sandstone can be seen in the north bank of the River Tees [NZ 0477 1659] beneath the gasworks at Barnard Castle. C.R.B.

These measures are next seen nearly 6 miles to the east, in the Tees below Ovington*, where they consist of 101.5 ft of mudstone, with sandstone ribs in the upper 40 ft, and ironstone nodules, sporadic bryozoa, brachiopods and bivalves in the basal 30 ft (loc. 10a). A borehole [NZ 1503 1427] near Greystone penetrated these measures and proved the Knucton Shell-Beds Limestone to rest on 15 ft of sandstone, 4 in of coal and 1 ft of sandstone. J.H.H.

In the south-eastern part of the district a borehole [NZ 2404 1064] at Clow Beck Farm recorded the following section in the lower part of these measures:

The base of this section is considered to be close above the top of the Crag Limestone. The measures exposed in Cleasby cutting* [NZ 2458 1231] are thought to he above those proved at Clow Beck Farm. D.A.C.M.

Knucton Shell-Beds

The Knucton Shell-Beds (Figure 7) are not exposed in the northern part of the district but were proved in three boreholes. In WT/4 Bore* they are represented by 3 ft 5 in of calcareous mudstone and siltstone containing ribbed shelly fossils at the top; atypically the bed rests directly on top of the Top Crag Limestone. In WT/6 Bore, these beds are represented by 12 ft 2 in of dark grey muddy thin-bedded shelly limestone interbedded with hard calcareous laminated mudstones. In the Woodland Bore* they were proved to consist of a lower 13-in and an upper 2-in limestone separated by 8 ft 10 in of calcareous mudstone. J.H.H., D.A.C.M.

In the south-western part of the district the beds are represented by the Knucton Shell-Beds Limestone. This crops out in a beck near Rigg Farm* where it is a grey thin-bedded fine-grained siliceous arenaceous shelly limestone 17.5 ft thick. It is exposed intermittently farther east in both banks of Deepdale Beck, being at least 20 ft thick in an exposure [NZ 0170 1624] about 390 yd NNE of Raven's Nest Farm. It is completely silicified with some chert at another locality [NZ 0444 1667], 130 yd W of Deepdale Bridge. Farther east, in the River Tees the limestone is 12 to 14 ft thick; the lower part, exposed in the south bank [NZ 0453 1674] 45 yd N of Deepdale Aqueduct, is as follows:

In the north bank of the river between the mouth of Percy Beck [NZ 0456 1679] and Barnard Castle gasworks [NZ 0477 1659] the limestone is so intensely silicified that only small remnants of the original rock remain. C.R.B.

The Limestone is next exposed in the River Tees, over 5 miles farther east, upstream from Winston Bridge*, where it is 32.5 ft thick and is grey, fine-grained, thin-bedded, rubbly and Shelly. An abundant fauna is present and includes Hyalostelia, Caninia sp, Cleiothyridina cf. fimbriata, Echinoconchus punctatus, Aviculopecten aff. Sulcatopinna costata and Rayonnoceras sp.(loc. 11a).

According to Gunn (in manuscript) a bore [NZ 1503 1427] near Greystone proved the basal 9 ft of the limestone to be siliceous and impure. J.H.H.

Measures between the Knucton Shell-Beds and the Rookhope Shell-Beds

The measures between the Knucton Shell-Beds and the Rookhope Shell-Beds (Figure 7) are exposed in the northern half of the district only in the River Tees [NY 9956 2338] downstream from Eggleston Hall, where a grey, medium- to coarse-grained, thin- and thick-bedded sandstone, at least 20 ft thick, passes up into a 9-in fine-grained rooty sandstone lying immediately beneath the Rookhope Shell-Beds. This sandstone, which forms a pavement in the river bed hereabouts, has been proved in TO 1 Bore [NZ 0016 2277] to be 26 ft thick and is underlain by 6 in of coal on 2 ft 9 in of sandstone-seatearth. The upper part of the sandstone bears root impressions, is bioturbated and very hard. In recent boreholes in the north-western part of the district, notably WT/4* and WT/C bores, the greater part of the sequence is composed of sandstones, the probable correlatives of the Grit Sills of the district to the north and north-west. In WT/C Bore, of 237 ft of strata overlying the Top Crag Limestone, 220 ft were sandstones with subordinate bands of mudstone, the Knucton and Rook-hope Shell-Beds being cut out. A broadly similar sequence is recorded in WT/4 Bore* although not all of it is proved. In the Woodland Bore* these measures are 76 ft thick, consisting of 37 ft 7 in of sandstone with shale layers, overlying 38 ft 5 in of shales with thin sandstone ribs.

In a borehole [NZ 0027 2299] near West Barnley Farm and on the south side of the Lunedale–Staindrop Fault, the Rookhope Shell-Beds are underlain by 76 ft of grey moderately bedded, variably textured locally coarse-grained pebbly sandstone. J.H.H., D.A.C.M.

In the south-western part of the district these measures are completely exposed in the tributary of Deepdale Beck south of Rigg Farm, where they consist of 7.5 ft of sandstone overlying 26 ft of shales. In Percy Beck, west of Barnard Castle, the following exposed section is comparable, despite a small fault:

C.R.B.

These measures are again completely exposed in the River Tees, upstream from Winston Bridge*, where 17.5-ft of sandstone overlie 15.25 ft of shale containing sponge spicules, bryozoa, brachiopods, bivalves including nuculoids and nautiloids (loc. 12a). D.A.C.M.

Rookhope Shell-Beds

The Rookhope Shell-Beds (Figure 7) are continuously exposed in a bluff [NZ 0033 2187] of the River Tees, near West Barnley, about 1 mile SE of Eggleston Hall (loc. 13b). The section, together with the overlying beds, is:

The lowest 3 ft 11 in of strata contain a fauna which includes sponge indet., productoid fragments indet., Martinia sp., Spirifer cf. trigonalis, Aviculopecten sp.and Weberides sp.[pygidium] (loc. 13b). J.H.H.

The sequence proved in the Rookhope Shell-Beds in TO 1 Bore was as follows:

D.A.C.M.

The sandstone above the Rookhope Shell-Beds is transgressive and locally cuts out much of the upper part of the shell-beds. In the River Tees, 10 yd upstream from Eggleston Bridge [NY 9966 2325], for instance, the section seen is:

In TO 1 Bore the sandstone above the Rookhope Shell-Beds is again transgressive and more than 37 ft thick. A limestone one foot thick is present near its base. Another record of the shell-beds in the northern part of the district is in the Woodland Bore*, where they are represented by the Rookhope Shell-Beds Limestone, nearly 13 ft thick, which includes a 2.5-ft median bed of mudstone. This limestone persists throughout the southern part of the district. J.H.H.

The lower leaf of the limestone is seen in Deepdale Beck [NZ 0079 1619] and Percy Beck [NZ 0470 1695], where it is 1 ft 7 in and 2 ft 4 in thick respectively and grey, fine-grained, thin-bedded, sandy and crinoidal, with hematite grains near the top. C.R.B.

Farther east in the River Tees [NZ 1429 1619] above Winston Bridge* the Rookhope Shell-Beds Limestone consists of at least 33 ft of grey fine- to medium-grained shelly limestone, with numerous bands of calcareous mudstone. Brachiopods are locally abundant and include notably Semiplanus aff. latissimus and Tornquistia cf. polita (loc. 13a). D.A.C.M.

Measures between the Rookhope Shell-Beds and the Lower Felltop Limestone

The measures between the Rookhope Shell-Beds and the Lower Felltop Limestone (Figure 7) consist of mudstone below and a variable thickness of sandstone above. On the eastern margin of the Brough-under-Stainmore (31) Sheet the sandstone is 50 ft thick. This thickness is more than doubled farther east near West Barnley, where in the River Tees and its tributaries, between Eggleston Hall [NY 9977 2334] and the mouth of Raygill Beck [NZ 0053 2133] the following composite section is exposed:

Because of faulting the upper 50-ft sandstone is exposed again in the River Tees [NZ 0077 2117] below the confluence with Raygill Beck. At this locality it contains a median bed of mudstone and two coals; the section is as follows:

The coal at the base of this section was recorded during the original geological survey both at this locality and in the stream 200 yd E of Eggleston Hall, where it is not now exposed. It is correlated with a 10- to 12-in coal which lies beneath Cambridge House [NZ 0548 1691], Barnard Castle, and which is calculated to be approximately 17 ft below the Lower Felltop Limestone and also with the 12-in coal proved at 472 ft 9 inches in Westholme Colliery No. 1 Shaft* [NZ 1347 1785]. The only other continuous record of these measures in the northern half of the district was obtained in the Woodland Bore* and is generalized as follows:

J.H.H.

In the south-western part of the district these measures are exposed in Percy Beck where 20 ft of fossiliferous shale (loc. 15a) are overlain by 34 ft of silty shale with ironstone nodules and thin sandstones. C.R.B.

The measures beneath the Lower Felltop Limestone are also seen in a quarry [NZ 1295 1064] near Osmondcroft Farm on the north side of the River Tees near Ovington, where they consist of 4 ft of white, fine- to medium-grained, quartzitic sandstone. The equivalent sandstone is also exposed in the River Tees, downstream from Winston Bridge*. It there contains a 12-in cherty bed rich in sponge spicules. D.A.C.M.

In thin section (E32023) this bed is seen to be composed of large discrete areas of uniformly extinguishing carbonate (ω=1.766 ± 005) identified as ferrodolomite, in a chert matrix strewn with spicules of carbonate. The spicules are 0.02 to 0.14 mm long with generally circular cross-sections. They are accompanied by subangular to subrounded quartz grains of 0.05 mm average diameter and show marginal carbonate replacement. R.K.H.

Lower Felltop Limestone

The Lower Felltop Limestone (Figure 8) is 8 in thick in the Woodland Bore* and is represented by 6 in of grey fine-grained shelly limestone at outcrop [NZ 0698 2244] in Langley Beck, about 530 yd W of Dent Gate Farm. It is not otherwise exposed or proved in the northern half of the district. Farther south, however, it crops out at two localities. In a section [NZ 0790 1636], near Westwick, the sequence is as follows:

At the second locality in the River Tees below Winston Bridge* the limestone is 3 ft thick and is grey, fine- to medium-grained and argillaceous with sporadic crinoid and brachiopod fragments. J.H.H., D.A.C.M.

The measures between the Lower and Upper Felltop limestones (Figure 8) have the following generalized sequence in the area north-west of Eggleston:

The variable lower sandstone (Coalcleugh Transgression Beds), exposed in the bed of Eggleston Burn [NY 9867 2629], north of the confluence with Druvy Burn, is pale grey, medium- to coarse-grained, pebbly, massive and false-bedded, with sporadic micaceous carbonaceous scars. The upper sandstone, exposed to a thickness of 10 ft farther northeast in two quarries [NY 9894 2605] and [NY 9893 2722], is white, fine- to medium-grained, thin-and thick-bedded and jointed. To the east the Woodland Bore* proved these measures to be 112.5 ft thick, including the Coalcleugh Shell-Bed represented by a 17-in limestone. Farther south, in Langley Beck [NZ 0736 2238], the following sequence was proved in the upper part of these measures:

The base of this section is taken to be approximately 75 ft above the Lower Felltop Limestone.

South of the Lunedale–Staindrop Fault and east of the River Tees, near East Barnley, the following generalized sequence is applicable:

Some 8 ft of the 40-ft sandstone is exposed in a quarry [NZ 0083 2225], 120 yd N of East Barnley, where it is fine- to medium-grained, thin-bedded and flaggy. Minor exposures also occur in Raygill Beck, while in the top of the Tees Bank [NZ 0088 2117] about 20 ft of grey fine-grained, massive, jointed micaceous sandstone is exposed at this horizon. In the River Tees [NZ 0114 2074] to [NZ 0161 2003], north of Cotherstone this bed is seen to consist of at least 30 ft of grey, medium- to coarse-grained, thick-bedded to massive false-bedded sandstone, which becomes more fine-grained and thin-bedded towards the top. J.H.H.

In the River Balder, between the western margin of the district and the River Tees, these measures are similar in sequence to those near East Barnley, but the sandstones are thicker as illustrated by the following section:

C.R.R.

In Osmond Gill [NY 9909 1984] 12 in of coal with shale partings immediately overlies the 75-ft sandstone of this section, while in Wilden Beck [NY 9768 2105], just beyond the western margin of the district, the remainder of the 36.5 ft of unexposed measures are seen to consist of 6 to 7 ft of sandstone overlying 30 ft of grey silty mudstone, with at least two Lingula bands about 20 ft above the base. At the confluence of the rivers Balder and Tees the measures below the Upper Felltop Limestone are further intermittently exposed and are generally thinner; the 75-ft sandstone of upper Baldersdale is about 40 ft thick and in an exposure [NZ 0315 2015] in the River Tees it is separated from the underlying coal (?Tanhill Coal) by 6 ft of silty shale. J.H.H.

The sandstone exposed above the north bank of Deepdale Beck, between Crag Hill [NY 9967 1618] and Cat Castle Quarries [NZ 0115 1636] is thought to be part of this sequence. It is 56 ft thick and is white and brown, coarse-grained, pebbly, massive, locally false-bedded and feldspathic.

In the River Tees between Cotherstone and Barnard Castle there are , good sections in these measures. A composite section* shows them to be up to 314 ft thick and to include four good coals in the upper part and three coaly shales below. The lowest good coal, tentatively correlated with the Tanhill Coal, is 12 to 24 in thick and is overlain by a sandstone which ranges in thickness from 37 to 50 ft. Another sandstone of variable thickness occurs about 16 ft above the Lower Felltop Limestone and contains posts which, for example, increase in thickness from 2 in to 2 ft 9 in over a lateral distance of 13 ft. C.R.R.

North-east of Barnard Castle the only exposed measures within this sequence are those close below the Upper Felltop Limestone. Thus at Old Mill Gill* [NZ 0714 1971] 10 ft of silty mudstone overlie 45 to 49 ft of shaly sandstone on 15 ft of silty mudstone beneath the horizon of the limestone and up to 6 ft of the same sandstone can be seen in two streams [NZ 0955 1827] and [NZ 0958 1830] west of High Barford and in Newsham Beck [NZ 1286 1788]. In these three exposures the sandstone is greyish brown, fine-grained, fiaggy and limonitic, with 'cauda-galli' structures in the latter section.

In a stream [NZ 0790 1636], about 0.5 mile NE of Mount Eff, the Lower Felltop Limestone is overlain by 5 ft of dark grey shale with ironstone nodules; 10 ft above this section is the base of a poorly exposed sandstone estimated to be 26 ft thick, and which, in an adjacent borehole [NZ 0747 1679] is succeeded by a 6-in coal seam taken to be the equivalent of the Yoredale Coal. J.H.H.

This 6-in coal was proved at a depth of 139 ft in a borehole about [NZ 0555 1746] at Barnard Castle where it overlies a shale which contains a diverse well-preserved miospore assemblage. The assemblage is dominated by the genus Lycospora and contains a large number of stratigraphically useful accessory spores. Several of the accessory spores, i.e. Punctatisporites aerarius, Acanthotriletes castanea, Convolutispora ampla, Microreticulatisporites concavus, M. microreticulatus, Rotaspora fracta, R. knoxi, Crassispora niaculosa and Rugospora corporata have been previously recorded from both the Upper Viséan and lower Namurian whilst others, i.e. Convolutispora cerebra, Mooreisporites trigallerus, Knoxisporites seniradiatus, Proprisporites laevigatus and Schulzospora ocellata have been previously recorded only from the lower Namurian of Britain. On the basis of this evidence together with the presence of several undescribed forms previously recorded only between the Little Limestone and the Mirk Fell Ironstones in the Stainmore Outlier, Westmorland (Brough under Stainmore (31) district), an upper E₁ or low E₂ age is suggested for this assemblage. B.O.

Farther east these measures are very variable and they are best discussed by separately considering two geographical areas; that between Whorlton and Winston and that around Gainford.

Between Whorlton and Winston the following generalized sequence obtains:

These measures have been proved in the North Tees No. 1 Bore* [NZ 1212 1762] (loc. 15b) at Little Newsham, and those beds between the Lower Felltop Limestone and the Yoredale Coal are best exposed in the west bank of the River Tees, 50 to 150 yd below Winston Bridge (Figure 8). In this section the limestone is overlain by 65 ft 2 in of shale with two thin sandstones, 13.5 ft of sandstone, 10 to 15 ft of unexposed measures and then the Yoredale Coal. Broadly similar sequences were proved in a borehole [NZ 1266 1674] near Walker Hall (Borings and Sinkings No. 3075), in which a 2.5 ft Yoredale Coal lay about 158 ft above the estimated position of the Lower Felltop Limestone, and in Westholme Colliery No. 1 Shaft*.

The Yoredale Coal was mined until recently from the North Tees Colliery [NZ 1220 1626] and was formerly worked by opencast immediately to the south and half a mile east of the mine. The seam section is variable. In the south-western part of the workings the section is: coal 30 in, on band 7 in, and coal 29 in, while in the northeastern workings the seam section is locally reduced to: coal 6 in, on band 0.5 in, coal 5 in, band 0.5 in and coal 21 in. Records from old workings (1897) around Osmondcroft show the coal to have been about 46 to 50 in thick, brassy at the top and inferior at the base, while south of Winston the worked seam was 36 to 48 in thick including an impersistent 1-in band. The seam was wrought in the south bank of the River Tees [NZ 1465 1680] across from Winston, but no records have been preserved apart from a boring [NZ 1463 1679], about 220 yd N of Hedgeholme in the delivery drift of an old pit, which is said to have proved 4 ft of coal (Kirkby and Duff 1872, p. 184).

An analysis by the National Coal Board of the spore assemblage in specimens of the coal from the North Tees Colliery Drift show it to contain Lycospora spp., Rotaspora knoxi and Crassispora kosankei, which are taken to indicate an age not greater than E₂.

In the Whorlton–Winston area the remaining part of these measures, that is beds between the Yoredale Coal and the Upper Felltop Limestone, are incompletely exposed.

A section in the lower part was recorded in the North Tees Colliery Back Drift [NZ 1226 1657], as follows:

Sections have also been proved in these measures in several boreholes between Whorley Hill and Winston. Two of these boreholes are recorded in Borings and Sinkings (Nos. 2884 and 3075) while a third, Westholme Colliery Shaft* is shown in (Figure 8). In North Tees No. 1 Bore* near Little Newsham, 255.5 ft of measures were proved underlying the Upper Felltop Limestone, the Lower Felltop Limestone having not been proved or reached, although a 6-in limestone containing spiriferoids was proved at 270.5 ft. The measures predominantly consist of siltstones and mudstones although two sandstones are present near the top. A fauna (loc. 15b) consisting of crinoid debris, brachiopods, ostracods and a trilobite, is present at various horizons. Among the most interesting forms present are cf. Planolites montanus, Productus carbonarius, Rugosochonetes sp., Tornquistia cf. polita, and the trilobite Weberides cf. mucronatus.

Around Gainford the measures between the Lower and Upper Felltop limestones are not less than 400 ft thick, increasing towards the east, especially those beds above the Yoredale Coal. The main exposures are in the River Tees and its tributaries and the following is a generalized sequence:

The measures below the Yoredale Coal in the Gainford area are exposed only at Crake Bank [NZ 1634 1635], where the seam is underlain by 4 ft of shale with ironstone nodules. The coal was formerly dug at outcrop at the base of Crake Bank, near the mediaeval village of Old Richmond, and cropped out in an adit near the bottom of Barforth Gill [NZ 1632 1637], where it ranged in thickness from 15 to 20 in. It was 2 ft 2 in thick in a borehole [NZ 1563 1754] near Grant Cottage, north of the Tees (Borings and Sinkings No. 3076). Kirkby and Duff (1872, p. 184) refer to a further sinking near Gainford, where the coal was 2 ft 6 in thick, including 1.5 ft of black band, at a depth of 102 ft. In the Barforth Gill adit the coal is overlain by 12 ft of yellow, fine-grained, massive sandstone which includes an 18-in bed of carbonaceous silty shale. The measures overlying the sandstone are indifferently exposed farther up the gill [NZ 1636 1610], and consist of grey, sandy or silty shales with ironstone nodules and ribs and with shaly sandstone bands. Still higher measures are exposed in the north-east bank of the River Tees at Grant Bank [NZ 1618 1736] as follows:

At the base of Selaby Basses Wood [NZ 1582 1772] 1 ft 10 in of impure, arenaceous ochreous limestone, with brachiopods including Rugosochonetes sp.(loc. 15e) overlies 4 ft 2 in of brown, fine- to medium-grained massive sandstone with carbonaceous micaceous blebs. It is inferred that these beds are older than those exposed at Grant Bank and that they lie approximately 100 ft above the Yoredale Coal. The 30-ft sandstone of Grant Bank is also partially exposed in the south bank of the River Tees at Boat Scar [NZ 1678 1637], where it consists of 20 ft of grey and white mainly massive and locally false-bedded sandstone with ripple-marks, resting with an irregular base on unfossiliferous shale. This sandstone further crops out widely to the north and east of Winston, and in Westholme Colliery Shaft* its equivalent is 80 ft thick, comprising two posts separated by only 5 ft of mudstone. The sandstone of Grant Bank is succeeded by 160 ft of variable strata equivalent to only 30 or 40 ft of measures farther west. They are exposed in the River Tees between Black Scar [NZ 1759 1626] and Chapel Gill [NZ 1871 1594], the section at the former being as follows:

The mudstone and shale are exposed in a bluff [NZ 1756 1637] opposite Black Scar where they are at least 17 ft thick and contain sporadic ironstone nodules. At a high level in the same sequence a 5-in band rich in crinoid columnals occurs [NZ 1782 1639] about 290 yd upstream. East of Black Scar the two sandstone members at the top of the sequence are separated by 4 to 8 ft of grey silty micaceous mudstone with siltstone and sandstone laminae. Some 200 yd east the mudstone [NZ 1827 1638] contains two thin calcareous bands which themselves unite and thicken eastward. At an exposure [NZ 1828 1639] the upper calcareous rib is 2 ft thick and contains Lingula cf. squannformis, Naticopsis sp.,Pseudozygopleura sp., Straparollus sp., Myalina cf. verneuilii and Parallelodon cf. squamifer (loc. 15f). The upper member of the sandstone overlying this sequence crops out impersistently in the River Tees between the old railway bridge and Chapel Gill. Above Gainford Mill it shows a great eastwards thickening and possesses the features of a 'washout' or 'channel' sandstone.

At Gainford Mill the 'channel' sandstone cuts out the mudstone parting but it reappears downstream, and at the Chapel Gill–Tees confluence [NZ 1871 1594] the sequence is:

The whole sequence is equivalent to the 30-ft sandstone at the top of Black Scar.

This sandstone and the succeeding measures are exposed in the Durham Bank of the river south of Snow Hall and at the base of the section between West Scar and Ashes Wood* where it is 43 ft 4 in thick, including mudstone bands and a 6-in Shelly sandstone rib, and is succeeded by 40 ft of siltstone and 17 ft of sandstone. The upper sandstone forms the extensive bed assumed to underly the Upper Felltop Limestone. It is 50 to 60 ft thick at outcrop around Selaby Hall [NZ 1530 1830], but it is split by a shale parting up to 40 ft thick east of Gainford Great Wood [NZ 1650 1795]. Outside the valley of the Tees, the sandstone is rarely seen but the upper leaf is exposed at Balmer's Hill Quarry [NZ 1722 1804], where it consists of at least 13 ft of dull yellow or pale grey massive fine-grained iron-speckled sandstone.

In the country east of Gainford, the only records are from an old borehole* [NZ 2480 1634], south-east of Thornton Hall, where over 250 ft of Carboniferous beds were proved between the presumed horizon of the Upper Felltop Limestone and the Yoredale Coal, and in a further borehole* about [NZ 254 188], 1.5 miles to the north-north-east near Cold Sides. in both cases the correlation is tentative. D.A.C.M.

Upper Felltop Limestone

The Upper Felltop Limestone (Figure 9) is exposed in West Rake Hush [NY 9741 2972], about 600 yd NW of the district boundary, in the Alston (25) district, where the section is:

In the Woodland Bore* the limestone comprises 25 ft 5 in of interbanded limestone ind shale with two calcareous sandstone ribs, but it is not otherwise proved north of the Lunedale–Butterknowle fault complex. In Langley Beck [NZ 0736 2238], between the Butterknowle and Wigglesworth fault systems 180 yd S of Dent Gate Farm the section is as follows:

South of the Lunedale–Staindrop Fault the limestone is exposed only in How Beck [NY 9740 1907] on the eastern margin of the adjacent Brough-under-Stainmore (31) Sheet, where the succession is:

C.R.B.

Beds at the same horizon are completely exposed north-east of Barnard Castle in Old Mill Gill [NZ 0714 1971], but the limestone is apparently absent, though it may be represented by 1.5 ft of calcareous sandstone. Farther east, however, in North Tees No. 1 Bores near Little Newsharn, 2 ft of pale grey, fine-grained, crinoidal limestone is thought to represent the Upper Felltop Limestone. J.H.H.

Measures between the Upper Felltop and Grindstone (= Botany) limestones

The measures between the Upper Felltop and Grindstone (= Botany) limestones (Figure 9) range from 67 ft in the Woodland Bore* to about 225 ft in and around How Beck. In the borehole the section is relatively simple, consisting of 55 ft 11 in of sandstone on 11 ft 1 in of shale. Most of the upper part of the sandstone represents the Grindstone Sill, the probable equivalent of the Botany Grit. The section in and around How Beck* (loc. 16b) includes several beds of shale and sandstone. One of the latter is the Fossil Sandstone, 7.5 ft thick and some 73 ft above the Felltop Limestone, which contains crinoid ossicles and shell casts.

The thinner sequence as proved by the borehole is best seen at outcrop in Crag Gill*, below White House [NZ 0268 2362], where the Grindstone Sill is over 36 ft thick and is underlain by an unnamed 2-ft limestone containing Spirifer cf. trigonalis, estimated to be 26.5 ft above the Upper Felltop Limestone.

South-east of Eggleston the measures are comparable to those of How Beck. In Raygill Beck [NZ 0110 2192] the horizon of the Upper Felltop Limestone is succeeded first by 20 ft of sandy shale with numerous sandstone ribs, then by about 12 ft of grey fine-grained, thin-bedded, carbonaceous sandstone. This sandstone is also exposed on the northern edge of Shipley Wood [NZ 0116 2092] where it is calcareous with worm tubes at the base. Contained shell fragments suggest that it is the equivalent of the Fossil Sandstone. The fossiliferous part of the sandstone is represented by 3.5 ft of arenaceous limestone [NZ 0156 2031] about 170 yd downstream from Low Shipley. The Fossil Sandstone is locally succeeded by up to 85 ft of dark grey, silty, apparently unfossiliferous shales which are partially exposed in the three streams west of High House [NZ 0308 2029]. Above the shales are 40 ft of pale grey, fine-grained, thick-bedded sandstone which is being worked in Shipley Bank Quarries [NZ 0182 2075] and also at Stainton [NZ 1699 1884] and Dunn House [NZ 1136 1938] (see p. 63). This sandstone is further exposed in Howegill Quarries [NZ 0284 2244], where at least 20 ft are exposed, and also in Baxtongill Quarry [NZ 0257 2078].

North-east of Barnard Castle there are good exposures in Hedrick Gill*, Forthburn Beck* and Old Mill Gill* which together range upwards from the horizon of the Upper Felltop Limestone to the base of the Botany Grit. In these sections the Fossil Sandstone is up to 20.33 ft thick, lying about 32 to 33.5 ft above the horizon of the Upper Felltop Limestone. It is succeeded in Hedrick Gill by almost 83 ft of shale and siltstone which is particularly fossiliferous in the basal 47.5 ft. Above these shales are 45 ft of sandstone, which are separated by 11 ft of unexposed measures from the lower 20 ft of the Botany Grit. Small exposures in the Fossil Sandstone also occur in Old Mill Gill east of a locality [NZ 0817 1974], about 150 yd W of Streatlam Castle and in Nelly's Gill, north of the castle. J.H.H.

Farther east it is indifferently exposed in Sudburn Beck between Snotterton Hall and Sudburn Bridge, though in a quarry [NZ 1094 1967] about 120 yd SSE of Snotterton Hall, the following section is seen:

The North Tees No. 1 Bore* near Little Newsham proved 79 ft 6 in of measures above the Upper Felltop Limestone, consisting predominantly of mudstone and siltstone containing crinoid debris, brachiopods including Crania sp., bivalves, and ostracods at various horizons (loc. 16a). D.A.C.M.

The upper part of the thick mudstone sequence which succeeds the Fossil Sandstone and the overlying sandstone, are best exposed in working quarries. In the northwest face [NZ 0699 1884] of Stainton Quarries the sandstone, of which 15 ft is exposed, contains a 6-in shaly coal 6 ft from the base of the exposure. In the south-east corner [NZ 0712 1877] of the quarry, abundant 'cauda-galli? structures can be seen. At Dunn House Quarry [NZ 1136 1938] (Plate 4B) the sandstone, at least 40 ft thick, is pale grey, fine-grained, predominantly massive or thick-bedded, with sporadic lenses of highly micaceous carbonaceous shale and siltstone; it is said to contain 95 per cent free silica together with mica, feldspar and carbonaceous fragments.

To the south-east in Cleatlam Old Quarry [NZ 1171 1832] 2 to 3 ft of shaly micaceous sandstone overlie 14 ft of grey and brown fine-grained thick-bedded to massive sandstone ascribed to this horizon. J.H.H., D.A.C.M.

Above the Stainton–Dunn House sandstone are some 10 to 15 ft of shales which are not now exposed, though 12 ft were proved in a well at Pallet Crag House [NZ 0181 2257] and 10 ft of shale with a 6-in coal were recorded during the original geological survey in railway cuttings [NZ 0750 1891] and [NZ 0556 1974] near Mount Pleasant and Bluestone Grange.

The sandstone which succeeds this shale is probably the lateral equivalent of the Botany Grit of the How Beck section*. It is about 30 ft thick and crops out extensively east of the River Tees and south of the Lunedale–Staindrop Fault. About a mile south-east of Eggleston exposures in Roger Moor Quarry [NZ 0194 2247] and Pallet Crag [NZ 0273 2261] show the sandstone to be pale grey, coarse-grained, thin-bedded to massive and feldspathic. North of Barnard Castle small exposures can be seen in a railway cutting [NZ 0554 1968] near Bluestone Grange, while in Lingberry Quarry [NZ 0859 1057] it is at least 15 ft thick lying about 14 ft below the base of the Botany Limestone. Farther east its probable equivalent at Langton Grange Quarry [NZ 1531 1995] comprises 9 ft of yellow and grey medium- to coarse-grained current-bedded sandstone.

The 14 ft of measures separating the sandstone from the Botany Limestone are seen in this part of the district only in a beck [NZ 1044 2021], near Scaife House, where a thin unnamed limestone with associated shale is exposed at the base of the sequence. These measures are taken to be the equivalent of the 26 ft of mudstone which underlie the Botany Limestone in the type area and which are exposed in How Gill [NY 9551 2045] in the Brough-under-Stainmore (Sheet 31) district.

Grindstone Limestone

In the Woodland Bore* the Grindstone Limestone (Figure 9) consists of 14 ft 1 in of interbedded impure shelly limestone, shale and mudstone with a 7-in calcareous sandstone rib. At a small quarry [NZ 0216 2356], about 500 yd W of White House the following sequence is seen at the position of the limestone (loc. 17a):

The 5-ft sandstone has the characteristic appearance of a weathered limestone and is taken to be the siliceous lateral equivalent of the Grindstone Limestone. Similarly in neighbouring Crag Gill* a Banister is taken to indicate the position of the limestone. The equivalent Botany Limestone is exposed in Hedrick's Quarry [NZ 0518 2144] (loc. 17c), about 2.5 miles north of Barnard Castle, where the sequence is:

Almost 2 miles farther east the following contrasting section with the overlying beds, is exposed in Bolton Close Quarry [NZ 0822 2090] (loc. 17b):

Strata between the Grindstone (= Botany) Limestone and the Whitehouse Limestone

Strata between the Grindstone (= Botany) Limestone and the Whitehouse Limestone (Figure 9) are continuously exposed in Crag Gill* (loc. 18a) and were proved in the Woodland Bore* being respectively about 73 and 127 ft thick and comprising several cycles, one of which includes a thin limestone. In the borehole a specimen of Homoceras cf. henkei (R_1a) was collected about 83 ft above the Grindstone Limestone.

South of the Lunedale–Staindrop Fault only the lowest few feet of this sequence are present. At Bolton Close Quarry [NZ 0822 2090] they include 2 ft of thin-bedded fine-grained decalcified sandstone, which in addition to crinoids and brachiopods, carries a 3- to 6-in band rich in bryozoa at the base.

Whitehouse Limestone

The Whitehouse Limestone (Figure 10) in the type area of Crag Gill* consists of 11 in of impure limestone containing crinoid debris and fragments of Productus sp.(loc. 19a), while in the Woodland Bore* it is 1 ft 1 in thick. The Whitehouse Limestone may further be represented by 5 ft of crinoidal limestone occurring in Stobgreen Sike*, though faulting in the vicinity of the section may make correlation with a stratigraphically lower limestone more feasible. J.H.H.

To the south-east a further possible equivalent is 1.5 ft of grey, fine-grained limestone recorded below the First Grit in Hilton No. 114 Bore* [NZ 1654 2082] west-north-west of Ingleton. D.A.C.M.

Strata between the Whitehouse Limestone and the Sharnberry Shell-Beds

Strata between the Whitehouse Limestone and the Sharnberry Shell-Beds (Figure 10) consist of a few feet of shale and shaly sandstone and an overlying sandstone containing coarse, and in places, pebbly layers, which is locally termed the Basement Grit and which comprises the lower leaf of the 'First Grit'. The most complete section in these measures is exposed in Crag Gill* where the Whitehouse Limestone is succeeded by 7 ft of mudstone, 9 ft of thin-bedded silty sandstone and the lower 20 ft of the 'First Grit'. A particularly rich fauna (loc. 20a) was obtained from the mudstone about 10 in above the Whitehouse Limestone and included an indeterminate zaphrentoid coral, Product us carbonarius, Catastroboceras cf. neilsoni and Reticuloceras stubblefieldi, the latter indicative of an R_1b horizon. The horizon is particularly high for the occurrence of a coral. A comparable section, but in which no mudstone is present, is exposed in a quarry [NY 9908 2608] at Knotts Plantation, about 1.5 miles NNW of Eggleston Parish Church, where the sequence is:

Other exposures of Basement Grit occur in Cloudlam Beck [NZ 0092 2871] on the northern margin of the district between Stobgreen Sike* [NZ 0055 2407] and Crag Gill*, in a former railway cutting [NZ 0814 2318] 100 yd N of Ripton House, and in Langley Beck between the Old Lodge [NZ 0902 2218] and Raby Moor House [NZ 0944 2206]. J.H.H.

A further exposure in Basement Grit is seen in a quarry [NZ 1141 2167] at Raby Plantation, where 3 ft of red, thin-bedded, shaly sandstone overlie 4 ft of red, coarse-grained, massive, soft sandstone. D.A.C.M.

In the Eggleston No. 5 Bore* [NZ 0073 2518] on Eggleston Common the grit was proved to be 66 ft thick while north of Ingleton it ranges in thickness from 7 ft at the Lutterington Estate Bore* [NZ 1875 2447] Bildershaw to 381 ft at Hilton No. 3 Bore* [NZ 1679 2203] near Hilton. Hilton No. 114 Bore* (loc. 20b) records that locally the top of the Basement Grit is separated from the Sharnberry Shell-Beds by about 11 ft of siltstone.

Sharnberry Shell-Beds

The Sharnberry Shell-Beds (Figure 10) take their name from a beck [NZ 0158 3087] immediately north of the district where they consist of 3 ft 9 in of bluish grey shale on 6 in of 'bullion'; the fauna from these beds includes Orbiculoidea, Euphemites and Reticuloceras. Within the district the shell-beds have been proved only in Hilton No. 114 Bore*, where they comprise 5 ft of shale with Retispira on a 7-in ironstone with shell debris (loc. 21a). Elsewhere, though the beds are not exposed, they can, together with the shales in which they occur, be identified lithologically in several old boreholes. North of Eggleston 7 ft of 'dark metal' were recorded in Eggleston No. 5 Bore* and 14.25 ft in Eggleston No. 4 Bore* [NZ 0202 2518] on Woodland Fell.

Near Ingleton these measures range from 3 ft 2 in at Hilton No. 1 Bore* [NZ 1730 2342] near Bolton Garths to 25 ft at the Lutterington Estate Bore*.

Measures between the Sharnberry Shell-Beds and the Woodland Shell-Beds

The measures between the Sharnberry Shell-Beds and the Woodland Shell-Beds (Figure 10) consist mainly of sandstone, representing the upper leaf of the 'First Grit'. In Shamberry Beck the shell-beds are succeeded immediately by the sandstone, whereas in Hilton No. 114 Bore* they are separated by 5 ft of dark grey siltstone with plant debris. In the Woodland Bore* the Sharnberry Shell-Beds and associated argillaceous beds have been cut out by the overlying sandstone, which joins with the one beneath to form a united First Grit, 108.33 ft thick, broken only by a few shale bands. J.H.H., D.A.C.M.

In the north-western part of the district the upper leaf of the First Grit is a poorly exposed grey, coarse-grained, pebbly, thin-bedded sandstone, which ranges in thickness from 66 to 72 ft along the outcrop between Stobgreen Plantation and the Wigglesworth Fault [NZ 0350 2361]. In Eggleston No. 5 Bore* it consisted of a lower 8-ft and upper 5-ft post separated by 12 ft of 'grey metal', while to the east in Gordon Gill 'K' Bore* [NZ 1380 2687] at Snape Foot on the upthrow side of the Butterknowle Fault, the lowest 52 ft of mainly sandstone measures are ascribed to this horizon.

South and east of the Wigglesworth Fault the upper leaf of the First Grit lies close above the lower leaf. It is exposed at Jagger Hill [NZ 0402 2343] and Pinstone Crag [NZ 0710 2364], where it is 35 ft thick and is grey, coarse-grained, pebbly, massive and falsebedded. J.H.H.

The Raby Castle Water Bore* [NZ 1288 2218] proved at least 57 ft of grey and red sandstone at this horizon. Near Ingleton the sandstone ranges in thickness from 35.75 ft in Hilton No. 1 Bore* to 11.25 ft in Hilton No. 114 Bore* and is pale grey, fine-grained, flaggy and micaceous, with shaly partings at the base. D.A.C.M.

Woodland Shell-Beds

The Woodland Shell-Beds (Figure 10) comprise 11 to 28 ft of strata lying between the First and Second Grits. They consist of up to three beds of shale or mudstone with marine shells separated by thin beds of sandstone. In the Woodland Bore* they contain three fossiliferous beds, whereas in the Raby Castle* (loc. 22b) Hilton No. 114* (loc. 22a) and Gordon Gill 'K'* bores, only two such beds were proved or can be inferred from the logs. Other boreholes giving sections through these measures, and listed in Appendix 2, are Eggleston Nos. 3 and 5, Hilton No. 3 and Lutterington Estate bores. J.H.H., D.A.C.M.

Strata between the Woodland Shell-Beds and the Spurlswood Shell-Beds

Strata between the Woodland Shell-Beds and the Spurlswood Shell-Beds (Figure 10) consist mainly of the sandstone forming the lower leaf of the 'Second Grit' together with the overlying few feet of silty shale. The sandstone is at least 60 ft thick in a quarry [NZ 0608 2891] on the north bank of Spurlswood Beck and is grey, coarse-grained, flaggy and false-bedded. In the Woodland Bore* these measures are over 64 ft thick consisting mainly of sandstone and in Gordon Gill 'K' Bore* the sandstone assumed to be equivalent is 20 ft 3 in thick.

North of Eggleston the sandstone is exposed at the head of Stobgreen Sike* [NZ 0109 2430], where it is grey, medium- to coarse-grained, thin-bedded and false-bedded. In the Eggleston Nos. 3, 4 and 5 bores* the sandstone ranges in thickness from 431 ft to 461- ft; it includes 4 in of metal and coal 15 ft from the base of the sandstone in No. 5 Bore.

At a small quarry [NZ 0417 2400], about 2.5 miles ENE of Eggleston, the sandstone contains baryte; baryte and calcite are also present on joints and in thin veins in the sandstone in Penny Hill Plantation [NZ 0781 2371]. There are other exposures at a quarry [NZ 1004 2274] near Henderson House and West Broombank Quarry [NZ 1088 2246], in Raby Park. J.H.H.

Around Ingleton the sandstone is exposed only in Holywell House Quarry [NZ 1747 2152], where 15 ft of grey, medium- to coarse-grained, false-bedded, micaceous sandstone are seen. The variable nature of the bed in this area is recorded in the Lutterington Estate* and Hilton No. 1* bores. East of Hilton the lower leaf of the Second Grit is split into two posts. Part of the lower post is represented in a quarry [NZ 2213 2185], about 350 yd W of Houghton-le-Side, by 15 ft of medium- to coarse-grained, massive, pebbly, feldspathic sandstone, The upper post was formerly seen in an old quarry [NZ 2221 2195] about 150 yd to the north-east, and described by Kirkby and Duff (1872, p. 186) as a yellow, fine-grained, thick-bedded sandstone. On the south side of this quarry and passing beneath the sandstone, Kirkby and Duff also saw a dark grey limestone overlying a "limestone shale" which together yielded: "Productus semireticulatus, var. martini, Sow., Spirifera lineata, Martin, Athyris ambigua Sow., Rhynchonella pleurodon (?) Phillips. Remains of crinoids"; and they recorded the same marine band farther east of the road to Houghton-le-Side. A marine band at this locality would be below the Second Grit and thus be part of the Woodland Shell-Beds. D.A.C.M.

The measures between the top of the lower leaf of the 'Second Grit' and the Spurlswood Shell-Beds (Figure 10) are exposed [NZ 0226 2686] in Spurlswood Beck* where they comprise about 28 ft of shale with sandstone ribs. In the Hilton area they are mainly argillaceous and range in thickness from 1.5 to 8.5 ft. J.H.H., D.A.C.M.

Spurlswood Shell-Beds

The Spurlswood Shell-Beds (Figure 10) take their name from Spurlswood Beck* [NZ 0226 2686] where they consist of 17.5 ft of mudstone including a 2.5 ft siltstone rib. The basal 6 in of mudstone contains a fauna of brachiopods, bivalves, plants and fish which includes Orbiculoidea cf. nitida, Productus carbonarius, Rugosochonetes cf. hindi, Actinopteria regularis, Serpuloides sp. and Paraconularia sp., while the upper 6 in of mudstone contain brachiopods, gastropods and plants including Rugosochonetes cf. hindi, Retispira sp.and Serpuloides sp.(loc. 23b). About 2.25 miles ENE in Greenless Beck [NZ 0576 2775] the beds are cut out by the overlying sandstone and only 15 ft of argillaceous strata remain between the top and bottom leaves of the Second Grit; neither are they present in the Woodland Bore*, where the measures between the two leaves of the Second Grit are represented by only 8 in of shale and mudstone. J.H.H.

South-east of Hilton about 6 ft of shale in this position were proved in Hilton Hall* [NZ 1698 2143] and Hilton No. 60* [NZ 1754 2175] bores near Hilton and in both cases the fossils included Lingula sp. Near Ingleton at the Hilton No. 114 Bore* (loc. 23a) the same shale yielded Orbiculoidea nitida and productoids and at Hilton No. 115 Bore* [NZ 1721 2072] Ingleton (loc. 23c), Serpuloides sp.,Lingula sp., Productus sp., Donaldina sp.and crinoids were collected. Farther east in the area north of Houghton-le-Side the shell beds are not present, the upper and lower leaves of the Second Grit uniting to form a single massive sandstone. D.A.C.M.

Strata between the Spurlswood Shell-Beds and the base of the Coal Measures

Strata between the Spurlswood Shell-Beds and the base of the Coal Measures (Quarterburn Marine Band) (Figure 10) are exposed between a bluff [NZ 0226 2686] in the Spurlswood Beck* and the east bank [NZ 0170 2676] of Quarter Burn*, where they consist of almost 104 ft of strata including the upper leaf of the Second Grit 63 ft thick. This sandstone locally cuts out the underlying strata and its thickness increases east-north-eastwards to about 95 ft at Greenless Beck [NZ 0583 2757]. At the northern margin of the district, on the western side of Spurlswood Beck, the sandstone splits into two posts estimated to be 55 and 45 ft thick, separated by 5 ft of mainly argillaceous strata; the thinner lower post is exposed [NZ 0448 2689] on the southern edge of Hamsterley Forest and in the lower reaches of Rowley Gill [NZ 0495 2683]. About 2 miles to the east in the Woodland Bore* a single sandstone 49 ft thick is recorded, and still farther east, in Gordon Gill 'K' Bore'', the thickness is 25 ft.

In Knott Hole Quarry [NY 9969 2629], about 1.5 miles N of Eggleston Parish Church, part of the sequence exposed is:

The seatearths of this section are equated with those below the Quarterburn Marine Band of Quarter Burn*. The sandstone at the top of this section is therefore assumed to be in the Lower Coal Measures and to cut out the marine band in that area. J.H.H.

Near Ingleton continuous sections between the Spurlswood Shell-Beds and the Quarterburn Marine Band were proved in the Hilton No. 114* and Hilton Hall* bores. The Hilton Hall Bore recorded Lingula bands between the 'Second Grit' and the Quarterburn Marine Band, whereas farther east in the Shackleton Beacon Bore* [NZ 2281 2336], 1.5 miles WNW of Heighington productoids were recorded front an analogous horizon. The measures overlying the 'Second Grit' are exposed in Brownside Quarry [NZ 2035 2283], near Bolam, where 4 ft of dark grey shale, containing ironstone nodules and sporadic plant fragments, overlie 6 ft of fine-grained, carbonaceous, micaceous, baked, shattered sandstone.

Although a number of boreholes have penetrated Namurian strata underneath the Permian in the eastern part of the district, there is insufficient information for firm correlation. Four of these boreholes, notably that near Thornton Hall, Bakelite Water Bore at Newton Aycliffe, Cold Sides, and Broken Scar Pumping Station Bore, Darlington, are quoted in Appendix 2.

Namurian palaeontology

The fauna, which comprises many forms similar to those found in the Viséan rocks below, are those of a well aerated shelf sea with abundance especially of brachiopods and molluscs. There is no repeated change of faunal phase, and fossil assemblages found in the limestones, mudstones and more rarely in sandstones, are each distinctive of the lithological type. Notable features in the district are:

1. Corals are abundant only in the Great, Bottom Crag and the Botany/ Grindstone limestones; at other levels they are rare.

2. At many horizons there are nuculoid phases with Nuculopsis, Palaeoneilo, and Paleyoldia, often associated with bellerophontoid gastropods especially Euphemites and Retispira [formerly called Bucanopsis].

3. As Wilson (1967) noted in Scotland there are few forms with restricted stratigraphical range. Amongst the brachiopods the latissimoid gigantoproductids, here referred to Semiplanus, occur above the Great Limestone only in the Rookhope Shell-Beds Limestone; and Antiquatonia cf. costata only in the Bottom Crag Limestone.

In the following lists of the fossils collected during the resurvey, the numbers and letters following the fossil names indicate respectively the horizon (according to the list below), and the locality (as in the list and below (Figure 11)). The horizons are as follows:

• Great Limestone
• Between Great Limestone and Bottom Little Limestone
• Bottom Little Limestone
• Between Bottom Little and Top Little Limestones
• Top Little Limestone
• Between Top Little and Bottom Crag Limestones
• Bottom Crag Limestone
• Between Bottom Crag and Top Crag Limestones
• Top Crag Limestone
• Between Top Crag and Knucton Shell-Beds Limestone
• Knucton Shell-Beds Limestone
• Between Knucton Shell-Beds Limestone and Kookhope Shell-Beds Limestone
• Rookhope Shell-Beds Limestone and beds immediately above
• Lower Felltop Limestone
• Between Lower and Upper Fell-top Limestone
• Between Upper Felltop and Botany/Grindstone Limestone
• Botany/Grindstone Limestone
• Between Botany/Grindstone and Whitehouse Limestone
• Whitehouse Limestone
• Between Whitehouse Limestone and Sharnberry Shell-Beds
• Sharnberry Shell-Beds
• Woodland Shell-Beds
• Spurlswood Shell-Beds

Localities

• 1a. Old quarry [NZ 0229 1339] at Lamb Hill
• 1b. Quarry north of West Layton [NZ 1433 1047]
• 1c. *R. Tees [NZ 0663 1496] near Abbey Bridge
• 2a *R. Tees [NZ 0552 1554] near Lendings Mill
• 2b Stobgreen Sike [NZ 0019 2378]
• 3a *R. Tees near Demesne Mill [NZ 0535 1582]
• 3b Harthorn Quarry, Aldbrough [NZ 2060 1100]
• 3c Both sides of Melsonby Lane, 1 mile S. of Aldbrough [NZ 2034 1056]
• 4a. R. Tees near Desmesne Mill [see 3a, 5a]
• 4b. Harthorn Quarry, Aldbrough [NZ 2060 1100]
• 5a R. Tees [NZ 0512 1598] near Desmesne Mill
• 5b Harthorn Quarry, Aldbrough [NZ 2060 1100]
• 5c R. Tees [NZ 0489 1593] at end of Thorngate, Barnard Castle
• 5d R. Tees [NZ 0479 1605] south of road bridge, Barnard Castle
• 6a Whorlton Beck [NZ 1067 1498] to [NZ 1088 1457]
• 6b R. Tees [NZ 0480 1615] south of road bridge, Barnard Castle
• 7a *Whorlton Beck [NZ 1068 1501]
• 7b Crossbury Bank Wood [NZ 2094 1056]
• 7c Sledwick Hall quarry, near East Shaws [NZ 0914 1525]
• 7d Deepdale Beck [NZ 0071 1604]
• 7e Cliff [NZ 0481 1641] north of road bridge, Barnard Castle
• 8a. Whorlton Beck [NZ 1068 1510]
• 9a Whorlton Beck [NZ 1068 1515]
• 9b Cliff [NZ 0483 1642] north of road bridge, Barnard Castle
• 9c Deepdale Beck [NY 9920 1546]
• 9d Deepdale Beck [NY 9878 1563]
• 9e Railway cutting [NZ 0706 2200] south-west of Dent Gate Farm
• 10a Deep gully entering R. Tees at Ovington [NZ 1328 1500]
• 10b Deepdale Beck [NZ 0073 1607]
• 10c Deepdale Beck [NZ 0075 1610]
• 11a. *R. Tees [NZ 1408 1591] above Winston Bridge
• 12a. *R. Tees [NZ 1425 1617] above Winston Bridge
• 13a *R. Tees [NZ 1429 1619] above Winston Bridge
• 13b R. Tees [NZ 0033 2187] near West Barnley
• 14a. *Percy Beck [NZ 0472 1701], Barnard Castle
• 15a. *Percy Beck [NZ 0474 1706], Barnard Castle
• 15b *North Tees No. 1 Bore [NZ 1212 1762]
• 15c R. Tees [NZ 1838 1628] near Snow Hall
• 15d Grant Bank [NZ 1618 1736]
• 15e Selaby Basses Wood [NZ 1582 1772] near Gainford
• 15f R. Tees [NZ 1828 1639] near Greystone Hall
• 15g N. Tees Colliery Drift [NZ 1226 1657]
• 16a *North Tees No. 1 Bore [NZ 1212 1762]
• 16b *How Beck [NY 9757 1915]
• 17a Quarry [NZ 0216 2356] 500 yd W of White House
• 17b Bolton Close Quarry [NZ 0822 2090]
• 17c Hedrick Grange Quarry [NZ 0518 2144]
• 18a. *Crag Gill [NZ 0268 2362] near White House
• 19a. *Crag Gill [NZ 0268 2362] near White House
• 20a *Crag Gill [NZ 0268 2362] near White House
• 20b *Hilton No. 114 Bore [NZ 1654 2082]
• 21a. *Hilton No. 114 Bore [NZ 1654 2082]
• 22a *Hilton No. 114 Bore [NZ 1654 2082]
• 22b *Raby Castle Water Bore [NZ 1288 2218]
• 23a *Hilton No. 114 Bore [NZ 1654 2082]
• 23b Spurlswood Beck [NZ 0226 2686]
• 23c *Hilton No. 115 Bore [NZ 1721 2072]

Fossils

• Calcifolium bruntonense 1c
• Hyalostelia parallela 4a
• Hyalostelia smithii 4b, 5b, 11a
• Hyalostelia sp. 9c, 12a
• Sponge indet. 13b
• ?Sponge spicules 5a
• Paraconularia sp. 17c, 23b
• Aulophyllum fungites 1b
• Caninia juddi 7d
• Caninia sp. 1b, 7e, 11a, 17c
• Chaetetes depressus 1b, 7 c, 7d
• Dibunophyllum bipartitum bipartitum 1a, 1b, 17c
• Dibunophyllum bipartitum craigianum 17c
• Dibunophyllum bipartitum konincki 17c
• Fasciculophyllum sp. 17c
• Koninckophyllum cf. echinatum 7e
• Koninckophyllum magnificum 7c
• Koninckophyllum sp. 1b, 17c
• Lithostrotion pauciradiale 1b
• L. portlocki 17c
• Rhopalolasma? 17c
• Zaphrentoid indet. la, lb, 20a
• Fenestella frutex 2a, 4b, 6a, 12a
• Fenestella cf. oblongata 2a
• Fenestella sp. 1a, 2b, 4b, 6a, 9b, 9c, 10a, 10b, 11a, 13a, 17b, 17c, 20a
• Fistulipora sp. 2a, 4b
• Penniretepora sp. 2a
• Rhombopora sp. la, 18a, 20a
• Trepostotnatous bryozoa 2b, 6a, 17c
• Bryozoa indet. 8a
• Chondrites? 15b
• Cornulitella sp. 18a
• Cf. Planolites montanus 15b
• Serpuloides sp. 22a, 23b, 23c
• Actinoconchus? 1a
• Alitaria panderi 3b, 3c, 5b, 7b
• Antiquatonia cf. insculpta 8a
• Antiquatonia muricata 1a
• Antiquatonia cf. costata 7c
• Antiquatonia sp. 3b, 3c, 5d, 6a, 7e, 9a, 9e, 11a, 15b, 17c
• Avonia youngiana la, 3c, 5a, 5d
• Buxtonia sp. 2a, 3c, 5d, 6a, 6b, 9e, 13b, 17b, 17c
• 'Camarotoechia' sp. 2a, 2b, 4a, 5a, 5d, 66,7 b, 9e, 13b
• Cleiothyridina fimbriata 1a, 5a, 5d, 6a, 6b, 11a, 17c
• Cleiothyridina aff. glabristria 5d
• Avonia sp. 3a, 4a, 5a
• Brachythyris sp. 1a, 5d, 6a, 9a
• Cleiothyridina sp. 4b, 6a, 6b, 7a, 9b, 10b
• Composita sp. 7e, 9e, 17b, 17c
• Crania sp. 16a
• Crurithyris sp. 3c, 4a, 5a, 9a, 9d, 10b, 16b, 20a, 22b
• Dictyoclostus sp. 2b, 6a, 18b, 20b
• Dielasma sp. 4a, 5a, 6a, 7b
• Echinoconchus cf. elegans 1b, 2a, 4a, 6a, 6b, 10b
• Echinoconchus punctatus 6a, 11a, 17c
• Echinoconchus sp. 3c
• Eomarginifera lobata la, 2a
• Eomarginifera cf. setosa 2a, 5a, 5d, 7c, 13b
• Eomarginifera sp. 1a, 2b, 3a, 4a, 6a, 6b, 7d, 9a, 13a, 15a, 18a, 22b
• Etheridgina conzplectans 1b
• Lingula mytilloides 9e, 17c, 20b, 22a, 23b
• Lingula cf. squatniformis 6a, 15f
• Lingula sp. 2b, 3a, 6a, 13b, 14a, 18a, 22a, 23c
• Linoprotonia sp. 8a, 9a
• Martinia sp. 1a, 1b, 2h, 3b, 3c, 4a, 6b, 7d, 9a, 13a, 13b, 16b
• Martinothyris cf. lineata 1a, 5a, 7b
• Orbiculoidea nitida 3a, 5d, 9a, 9e, 15a, 16a, 17a, 18a, 22a, 22b, 23a, 23b
• Orthotetoids indet. 2b, 4a, 5a, 6a, 7b, 7c, 7e, 13b, 14a, 18a, 20a, 20b, 22a, 23b
• Phricodothyris sp. 1b, 3b, 3c, 4a, 5c, 17b,17c
• Pleuropugnoides cf. pleurodon 6a
• Pleuropugnoides sp. 3c, 6a, 12a
• Plicochonetes aff. interstriatus 1b
• Plicochonetes sp. 1a, 13a, 17d
• Productoid nov.[with diaphragm] 17b, 17c
• Productus carbonarius 15b, 18a, 20a, 22a, 23b, 23c
• Productus sp. 2a, 19a, 22b
• Pugilis sp. 17c
• Pugilis? 4a, 5a
• Pugnoides triplex 1a
• Quasiavonia cf. aculeata 3c, 7e, 17c
• Quasiavonia sp. 7d, 9b
• Rhipidomella michelini 3b
• Rugosochonetes sp. 2b, 4a, 6a, 7c, 7d, 9c, 9d, 10a, 11a, 12a, 15a, 15b, 15e, 17c, 20a, 20b, 22a, 23b
• Rugosochonetessp. nov.[tumid] 13b, 18a cf.
• Schellwienella rotundata 9e
• Schellwienella sp. 15b
• Schizophoria resupinata 6a
• Schizophoria sp. 1a, 1b, 3a, 9e, 18a
• Schuchertella sp. 1a, 3b, 9a
• Semiplanus cf. latissimus 1a, 1b, 13a
• Setniplanus sp.[latissimoid, broad folds on trail] 1b
• cf. Sinuatella sinuata 17c
• Smooth spiriferoids indet. 3a, 12a, 14a, 15b, 16a, 17c, 23b
• Spirifer cf. bisulcatus 6a, 7d, 10b, 11a, 17c
• Spirifer cf. trigonalis 1a, 2b, 3a, 3b, 4a, 5a, 5c, 6a, 7a, 7b, 7c, 9a, 9e, 13b, 15a
• Spirifer sp. 1a, 1b, 2b, 3c, 4a, 5c, 5d, 6a, 6b, 7e, 9b, 13a, 13b, 14a, 15b, 17c, 20a
• Spiriferellina sp. 3c
• Teznnocheilus cf. coronatus 6b
• Tornquistia cf. polita 3a, 7b, 8a, 13a, 15b
• Aclisina cf. elongata 2a
• Bellerophontoid indet. 2b
• Donaldbia sp. 18b, 23c
• Euphemites sp. 2b, 9d, 17a, 20a, 22a
• Glabrocingulumsp. 6h
• Ianthinopsis sp. 2a
• Naticopsis sp. 1b, 15f
• Platyceras neritoides 9e
• Platyceras sp. 18a
• Pseudozygopleura cf. rugifera 2a
• Pseudozygopleura sp. 15f
• Retispira cf. striata 9e
• Retispira sp. 2a, 18a, 21a, 22a, 23b
• Shansiella globosa 22b
• Straparollus cf. carbonarius 9a
• Straparollus sp. 10a, 15a, 15f
• Turreted gastropods indet. la, 5b, 20a
• Coleolus cf. nanzurcensis 18a, 20a
• Coleolus sp. 2b, 18a
• Actinopteria regularis 15d, 23b
• Actinopteria viculopecten cf. clathratus 2a
• Actinopteria aff. interstitialis 11a
• Actinopteria cf. plicatus 2a, 7d, 10b
• Aviculopecten sp. 1a, 6a, 6b, 9e, 12a, 13b, 15a, 20a, 22a
• A viculopinna mutica 9e
• Cypricardella rectangularis 6b
• Cypricardella sp. 8a, 11a
• cf. Edmondia expansa 6b
• Edmondia cf. gigantea 5d
• Edmondia laminata 2a, 4a, 6a
• Edmondia sp. 7e, 9b, 9e, 14a, 23b
• Euchondria sp. nov.20a
• Euchondria ? 16b
• Limipecten dissimilis 3c, 4a, 6a, 7c
• Myalina mitchelli 17a
• Myalina cf. verneuilii 15f
• Myalina sp. 15c, 15g
• Nuculoids indet. 12a
• Nuculopsis gibbosa 9e, 13b, 17a
• Palaeoneilo cf. laevirostrum 2a
• Palaeoneilo cf. mansoni 9d
• Palaeoneilo sp. 2b, 6a, 15a, 17a, 20a, 23b
• Paleyoldia macgregori 2a, 2b, 20a
• Parallelodon cf. obtusus 22a
• Parallelodon cf. semicostatus 6a
• Parallelodon cf. squamifer 6b, 15f
• Parallelodon sp. 11a
• Pectinoid fragments indet. 4b, 16a, 17a, 23b
• Pernopecten sowerbii 6a
• Pernopecten sp. 9e
• Polidevcia attenuata 9e, 15a, 17a
• Posidonia corrugata 13b
• Sanguinolites aff. v–scriptus 18a
• Sanguinolites sp. 10a, 10b, 18a, 23b
• Schizodus sp. 6a, 15c
• Streblochondria cf. anisota 2a
• Streblochondria sp. 15b, 18a
• Sulcatopinna costata 11a
• Catastroboceras cf. neilsoni 20a
• Catastroboceras sp. 6a, 9a, 11a
• 'Cyrtoceras' rugosum 6b
• Metacoceras? 20a
• Orthocone indet. 6a
• Raymmoceras sp. 11a
• Nautiloids indet. 12a, 20a
• Reticuloceras stubblefieldi 20a
• Weberides cf. mucronatus 15b
• Weberides sp.[pygidia] 13b, 15a, 17c
• Trilobite pygidia fragments 1a, 9e, 17c
• Hollinella sp. 16a, 20a
• Paraparchites sp. 3a,11a
• Ostracods indet. 2a, 3a, 3c, 7b, 8a, 9b, 16a, 20a
• Dithyrocaris sp.[includes buccal tooth] 20a
• Archaeocidaris sp. 1a, 20a
• Fish teeth 2a, 11a, 20a
• W.H.C.R.

References

BISAT, W. S. 1924. The Carboniferous goniatites of the north of England and their zones. Proc. Yorks. geol. Soc., 20, 40–12.

BISAT, W. S. 1928. The Carboniferous goniatite zones of England and their continental equivalents. C. r. Congr. Avanc. Etud. Stratigr. Geol. carbonif., 117–33.

CARRUTHERS, R. G. 1938. Alston Moor to Botany and Tan Hill: an adventure in stratigraphy. Proc. Yorks. geol. Soc., 23, 236–53.

DAKYNS, J. R., TIDDEMAN, R. H., RUSSELL, R., CLOUGH, C. T. and STRAHAN, A. 1891. The geology of the country around Mallerstang. Mem. geol. Surv. Gt Br.

DUNHAM, K. C. 1948. The geology of the Northern Pennine Orefield; Vol. 1, Tyne to Stainmore. Mem. geol. Surv. Gt Br.

DUNHAM, K. C. and JOHNSON, G. A. L. 1962. Sub-surface data on the Namurian strata of Allenheads, south Northumberland. Proc. Yorks. geol. Soc., 33, 235–54.

DUNHAM, K. C. and STUBBLEFIELD, C. J. 1945. The stratigraphy, structure and mineralization of the Greenhow mining area, Yorkshire. Q. Jnl geol. Soc. Lond., 100, 209–68.

FOWLER, A. and ROBBIE, J. A. 1961. The geology of the country around Dungannon. Mem. geol. Surv. N. Ireland.

HEY, R. W. 1956. Cherts and limestones from the Crow Series near Richmond, Yorkshire. Proc. Yorks. geol. Soc., 30, 289–99.

HUDSON, R. G. S. 1941. The Mirk Fell Beds (Namurian E2) of Tan Hill, Yorkshire. Proc. Yorks. geol. Soc., 24, 259–89.

HUDSON, R. G. S. 1945. The goniatite zones of the Namurian. Geol. Mag., 82, 1–9.

HULL, J. H. 1961. In Summ. Prog. geol. Surv. Gt Br. for 1960, 41.

HULL, J. H. 1963. In Summ. Prog. geol. Surv. Gt Br. for 1962, 45.

HULL, J. H. 1967. In Summ. Prog. geol. Surv. Gt Br. for 1966, 75, pl. II.

HULL, J. H. 1968. The Namurian stages of north-eastern England. Proc. Yorks. geol. Soc., 36, 297–308.

JOHNSON, G. A. L. 1958. Biostromes in the Namurian Great Limestone of northern England. Palaeont., 1, 147–57.

JOHNSON, G. A. L. (Ed.) 1970. Geology of Durham County. Trans. nat. Hist. Soc. Northumb., 41.

JOHNSON, G. A. L. HODGE, B. L. and FAIRBAIRN, R. A. 1962. The base of the Namurian and of the Millstone Grit in north-eastern England. Proc. Yorks. geol. Soc., 33, 341–61.

KIRKBY, J. W. and DUFF, J. 1872. Notes on the geology of part of south Durham. Nat. Hist. Trans. Northumb., 4, 150–98.

MILLS, D. A. C. and HULL, J. H. 1968. The Geological Survey borehole at Woodland, Co. Durham (1962). Bull. geol. Surv. Gt Br., No. 28, 1–34.

NEVES, R. 1968. The palynology of the Woodland Borehole, Co. Durham. Bull. geol. Surv. Gt Br., No. 28, 55–60.

OWENS, B. and BURGESS, I. C. 1965. The stratigraphy and palynology of the Upper Carboniferous outlier of Stainmore, Westmorland. Bull. geol. Surv. Gt Br., No. 23, 17–44.

RAMSBOTTOM, W. H. C. 1966a. A pictorial diagram of the Namurian rocks of the Pennines. Leeds Geol. Ass., 7, 181–4.

RAMSBOTTOM, W. H. C. 1966b. In Summ. Prog. geol. Surv. for 1965, 56.

READING, H. G. 1957. The stratigraphy and structure of the Cotherstone Syncline. Q. Jnl geol. Soc. Lond., 113, 27–56.

RICHARDSON, G. 1961. In Summ. Prog. geol. Surv. Gt Br. for 1960, 41.

ROWELL, A. J. and SCANLON, J. E. 1957a. The Namurian of the north-west quarter of the Askrigg Block. Proc. Yorks. geol. Soc., 31, 1–38.

ROWELL, A. J. 1957b. The relation between the Yoredale Series and the Millstone Grit on the Askrigg Block. Proc. Yorks. geol. Soc., 31, 79–90.

SARGENT, H. C. 1929. Further studies in chert. Geol. Mag., 66, 399–413.

TURNER, J. S. 1955. Upper Yoredales and Millstone Grit relations in the Stainmore coalfield. Geol. Mag., 92, 350.

WELLS, A. J. 1955. The development of chert between the Main and Crow limestones in north Yorkshire. Proc. Yorks. geol. Soc., 30, 177–96.

WELLS, A. J. 1957. The stratigraphy and structure of the Middleton Tyas-Sleightholme anticline, north Yorkshire. Proc. Geol. Ass., 68, 231–54.

WILSON, A. A. 1960a. The Carboniferous rocks of Coverdale and adjacent valleys in the Yorkshire Pennines. Proc. Yorks. geol. Soc., 32, 285–316.

WILSON, A. A. 1960b. The Millstone Grit Series of Colsterdale and neighbourhood, Yorkshire. Proc. Yorks. geol. Soc., 32, 429–52.

WILSON, A. A. and THOMPSON, A. T. 1959. Marine bands of Arnsbergian age (Namurian) in the south-eastern portion of the Askrigg Block, Yorkshire. Proc. Yorks. geol. Soc., 32, 45–67.

WILSON, A. A. and THOMPSON, A. T. 1965. The Carboniferous succession in the Kirkby Malzeard area, Yorkshire. Proc. Yorks. geol. Soc., 35, 203–27.

WILSON, R. B. 1967. A study of some Namurian faunas of central Scotland. Trans. R. Soc. Edinb., 66, 445–90.

WOOLACOTT, D. 1923. A boring at Roddymoor Colliery, near Crook, Co. Durham. Geol. Mag., 60, 50–62.

Chapter 4 Upper Carboniferous Westphalian (Coal Measures)

Introduction

Coal measures occupy a broad, complex and much faulted structural depression trending east-north-east across the northern part of the district and extending into the Wolsingham (26) district to the north. They are conformable on the Namurian rocks, which form a rim to the syncline on its western and southern sides. To the east of Shildon, Coal Measures are concealed beneath the unconformable Permian which progressively oversteps southwards on to lower horizons.

A full sequence of Lower Coal Measures is present, as well as a great part of the Middle Coal Measures, to a maximum total thickness of 1520 ft.

Little research has been done on the Coal Measures of this district specifically, although various workers (Kirkby and Duff 1872; Calvert 1884; Anderson and Dunham 1953) have referred to the area in general geological accounts of the Coal Measures of Northumberland and Durham or of special aspects of the Carboniferous. The Coal Measures of the Durham and West Hartlepool (27) district to the north-east have been described by Smith and Francis (1967) and their account contains much general information relevant to the Coal Measures in this district.

Classification

The classification adopted in this memoir is shown in (Figure 12), which also indicates the distribution of the main coal seams, the thicker sandstones and more persistent faunal horizons in the Coal Measures.

Traditionally, the base of the Lower Coal Measures in Durham was taken at the Ganister Clay coal which is the lowest workable coal of the sequence and overlies the highest sandstone, sometimes referred to as the Third Grit, of the old 'Durham Millstone Grit' sequence. This lithological classification no longer accords with palaeontological evidence from other coalfields in Britain and north-west Europe, where the base of the Coal Measures (Westphalian) is defined by a marine band containing Gastrioceras subcrenatum (Frech). Although this fossil has yet to be found in north-east England, other palaeontological evidence indicates that the equivalent horizon in this district is the Quarterburn Marine Band (Mills and Hull 1968, pp. 4–5) between the Second and Third Grits of the old 'Durham Millstone Grit' Series.

The division between the Lower and Middle Coal Measures is taken at the base of the Harvey Marine Band, represented in other coalfields by the marine band containing Anthracoceratites vanderbeckei.

Lithology

As in the Durham and West Hartlepool (27) district the Coal Measures sequence here consists of alternations of shales, mudstones, siltstones and sandstones together with coals and associated seatearths. Although the sequence may be regarded as rhythmic, wide variations in local conditions gave rise to modifications of the standard cyclothem.

For convenience, the sediments may be divided into five main groups: argillaceous sediments, 'mixed beds', arenaceous sediments, seatearths and coals. Argillaceous sediments, generally grey or dark grey in colour, range from highly fissile micaceous carbonaceous shales to blocky mudstones with a variable sand and silt content. The shade of grey is usually directly related to the contained proportion of finely disseminated carbonaceous material, which is often abundant. More rarely, disseminated sulphides occur, usually in the form of pyrite. Ironstone bands and nodules are common at various horizons and in these 'mussels' are commonly preserved.

'Mixed beds' is a convenient term for describing a rapid alternation of mudstones, siltstones and fine sandstones in a sequence in which individual beds nowhere predominate. Small-scale false-bedding and turbulence is often present.

Arenaceous sediments range from dark grey, muddy, micaceous and carbonaceous, silty sandstones to paler grey or off-white bedded and massive sandstones. At outcrop they often weather to a dull yellow or rust colour. Most of the sandstones are fine- to medium-grained. Quartz is the dominant mineral and feldspars are subordinate. Near the base of the sequence the sandstones are commonly coarser, with conglomerate or pebbly layers in places. Conglomerate bands often contain subrounded to subangular elongate fragments of argillaceous sediments. The cement in most of the sandstones is kaolinitic, but in the harder sandstones it is predominantly of silica or ankerite.

Seatearths range from dull grey rooty mudstone in which ironstone nodules are common to hard dull grey siliceous ganister. Fireclay of good commercial quality is not common.

Coals are bituminous, generally have low ash and sulphur content and are suitable for coking. They are more fully described in Chapter 10.

Seam nomenclature

The coal seam names adopted in this district, and which appear on the six inches and one inch to the mile maps, are those used by the National Coal Board. Local names which have been applied in the past are however quoted on the first mention of the current coal seam name. In addition, a glossary of terms applicable to rock types is given in Appendix 2.

Reddened beds in the Coal Measures

By the end of Lower Permian times, the Carboniferous rocks had been uplifted, folded and eroded, and the resulting topography was of generally low relief. Anderson and Dunham (1953) concluded from examination of the Coal Measures of Durham and South Northumberland, including those at Eldon Hill Opencast Quarry in this district, that reddening took place before local Permian sedimentation. These authors noted that reddening was generally absent directly beneath the Permian rocks, but that it usually appeared a few feet below the unconformity. Most of the boreholes which have penetrated the unconformity and subjacent Coal Measures rocks in the north-eastern part of the district have proved an upper grey zone, 2 to 8 ft thick, and two have recorded as much as 20 ft. About half the boreholes proved the reddened zone to extend to between 30 and 50 ft below the unconformity. In one case the base of the reddened zone lay at only 14 ft, and a few boreholes proved reddened beds at over 70 ft, the maximum of 76 ft being recorded in the extreme north-east of the district near Eldon Blue House. Where sandstone lies directly under the plane of unconformity it is typically leached to a light grey colour, and commonly contains a high proportion of pyrite. This pyrite, and the grey colour are thought to be the result of reduction of secondarily oxidised iron by downward-percolating water from the Marl Slate sea (Smith and Francis 1967, pp. 18–19). The petrographical evidence adduced by Anderson and Dunham (1953) from Eldon Hill suggests that reddening is due to in situ oxidation of pyrite and siderite, and to the introduction of red iron oxide along joints and in the pore spaces of sandstones.

General stratigraphy

Lower Coal Measures

Lower Coal Measures account for more than two-thirds of the total area of Coal Measures outcrop in the district. The beds are extensively concealed by glacial drift and exposure is generally confined to short sections in valleys in the western part of the area and to isolated sandstones cropping out on steeper or higher ground. Details of the stratigraphy have been derived from shafts, boreholes and mining operations.

The maximum recorded thickness of Lower Coal Measures in this district is 600 ft. The lowest part, that between the Quarterburn Marine Band and the Ganister Clay Coal, is a predominantly arenaceous or 'mixed bed' sequence, and includes the Third Grit of the old 'Durham Millstone Grit'. Only a few thin coals are present, none of which has been worked. Of the five marine bands found in the Lower Coal Measures of Durham, four are in this part of the sequence. A similar close grouping of marine bands is noted in the 'Anthraconaia' lenisulcata Zone of the Cumberland, Lancashire and Yorkshire coalfields.

Between the Ganister Clay and the base of the Brockwell Coal there are up to nine thin coals, three of which have been worked locally. Again, the sequence is predominantly arenaceous, particularly above the Marshall Green. The upper part of the Lower Coal Measures includes the three seams, Brockwell, Busty and Harvey, which have been of leading importance in the economy of the district. The Tilley group of coals, also included in these measures, has only been worked sporadically on account of the variable quality and thickness of the seams.

The Quarterburn Marine Band (Mills and Hull 1968, p. 4) consists generally of between 1 and 10 ft of shale and mudstone containing brachiopods, bivalves, gastropods and fish debris. Locally the marine band is replaced or cut out by sandstone. Correlations based on comparative lithologies and the presence of productoid fragments, shown on (Plate 6), include records of this marine band in the Roddymoor Bore near Crook, at 442 ft 7 in (Woolacott 1923; Mills and Hull 1968, p. 4), and in the Middle Stotfold Bore between West Hartlepool and Fishburn at about 942 ft (Magraw and others 1963, p. 157).

The measures between the Quarterburn and Kays Lea marine bands range in thickness (Plate 6) from 26 ft at Quarterburn to 90 ft in boreholes between Cockfield and Toft Hill. In general, the thickness is directly related to the amount of sandstone in the succession. Two unnamed marine bands occur in the upper part of these measures in a borehole near Keverstone, the upper of which has also been proved in two other boreholes near Hilton. The fauna collected from these bands includes foraminifera, brachiopods, a conodont, and fish scales; plant fragments also occur. In the Durham and West Hartlepool (27) district, these measures are only 17 ft thick if the mudstone with Planolites sp.recorded at and above 920 ft in the Middle Stotfold Bore (Magraw and others 1963, p. 196) is the assumed equivalent of the Kays Lea Marine Band. The absence of foraminifera, however, makes correlation uncertain. The Kays Lea Marine Band has not been recognized in the Roddymoor Bore but it is thought that about 42 ft of strata there separate the horizons of the Quarterburn and Kays Lea marine bands (Mills and Hull 1968, p. 4).

The Kays Lea Marine Band (Plate 6) is of interest in that it is the lowest marine band containing foraminifera in the Coal Measures. It was defined in the Woodland Bore* (Mills and Hull 1968, p. 4) and has been proved in boreholes elsewhere in this district, though it is apparently absent to north and northeast of Woodland. In the Roddymoor Bore it is apparently cut out by the overlying sandstone (Third Grit).

Most of the interval between the Kays Lea and Roddymoor marine bands (Plate 6) generally consists of sandstone—the Third Grit of the primary surveyors. The Third Grit thins generally towards the south-east from a recorded maximum of 56 ft in Spurlswood Beck to about 6 ft in a borehole near Hilton. Its top is in places separated from the Roddymoor Marine Band by a seatearth and a few inches of coal which has been called the Gubeon Coal in the Durham (27) district (Smith and Francis 1967, p. 13). In the Roddymoor Bore the Third Grit is thought to be about 38 ft thick at about 395 ft (Mills and Hull 1968, p. 4), while in the Durham (27) district it has been shown to range between about 30 and 40 ft (Smith and Francis 1967, p. 35) although in that area a single thick sandstone at this position is unusual.

The Roddymoor Marine Band (Plate 6) is defined as the Lingula band which is present at the base of 6 ft of shale at 350 ft 1 in in the Roddymoor Bore (Mills and Hull 1968, p. 4). In the north-western part of this district it is unrecorded, though near-marine conditions are indicated by the occurrence of Planolites sp.and fish at this horizon in Spurlswood Beck and in the Woodland Bore* (Mills and Hull 1968, p. 4). It is however proved in boreholes around Hilton where its thickness ranges from about 2 to 5 ft. It contains a fauna which includes worm trace fossils, horny brachiopods, gastropods, fish scales and foraminifera. Plant debris is also present.

The Roddymoor Marine Band appears to correlate with the Gubeon Marine Band which overlies the Third Grit and Gubeon Coal in the Durham (27) district (Smith and Francis 1967, p. 13), and in the Offshore No. 1 Bore north of Hartlepools (Magraw and others 1963, p. 157). Some confusion has arisen in this nomenclature, since the Gubeon seam in its type locality in Northumberland, as shown on the Morpeth (14) Sheet, has been shown to equate with the Marshall Green of Durham. It is here recommended, therefore, that the term Roddymoor Marine Band should be used for this horizon in Northumberland and Durham in preference to Gubeon Marine Band.

The measures between the Roddymoor Marine Band and the Ganister Clay Coal (Plate 6) show wide lateral variation in lithology and thickness. North and north-west of Woodland the succession consists of 3 to 21 ft of sandstone, overlain by 33 to 52 ft of an argillaceous or 'mixed beds' sequence, with a thin sandstone near the top in places. South-eastwards the measures thicken to between 65 and 105 ft and a thick sandstone is often present, as well as sporadic seatearths and coals.

There are several fossil bands in the mudstones, and in the Woodland Bore* these have yielded a fauna of ostracods and non-marine bivalves, the latter commonly referred to as mussels. The occurrence of Planolites ophthalmoides at different levels suggests that these measures may contain a number of cyclothems. The occurrence in one borehole of Carbonicola aff. proxima is of interest in that it affords a favourable comparison with the C. proxima fauna from the Norton mussel band of the East Midlands, which is in the upper part of the 'Anthraconaia' lenisulcata Zone.

In the Roddymoor Bore equivalent measures are about 60 ft thick, and farther east in the Durham (27) district (Smith and Francis 1962, p. 35; Magraw and others 1963, p. 157) they range between 40 to 70 ft.

The Ganister Clay Coal (Plate 7) which was once taken as the base of the Coal Measures in County Durham, is a thin seam, generally ranging between 8 and 20 in. It is thickest on the southern and western margins of the coalfield area where it is often strongly banded and where it has been sporadically worked at or near the outcrop. In the Wolsingham (26) and Durham and West Hartlepool (27) districts the coal is usually thin or absent (Smith and Francis 1967, p. 36).

The beds between the Ganister Clay and Marshall Green (Plate 7) range in thickness between 30 and 65 ft. There is considerable variation in lithology, and in places the greater part of the sequence consists of sandstone. Mussels, in places associated with Planolites and fish remains, have been recorded in the middle and upper parts of the sequence in several boreholes.

The Marshall Green (Plate 7) is generally split into Top and Bottom coals, and only to the north-east of Woodland is it a single united seam up to 24 in thick. The thickness of the Bottom Marshall Green rarely exceeds 24 in, including bands. Locally it is absent, its assumed horizon being underlain by seatearth or fireclay. Although it has been worked sporadically in the west and south of the coalfield area and at Randolph Colliery, Evenwood, it has in general been considered too thin to warrant exploitation.

The measures between the Bottom and Top Marshall Green coals (Plate 7) generally range between 15 and 50 ft and usually consist of sandstone, the texture and bedding of which recalls the coarser 'grits' lower down in the sequence. This sandstone is particularly thick south of Cockfield and around Woodland. Locally it apparently cuts out the Top Marshall Green seam while in one locality it extends upwards to the base of the Victoria group of coals. Where the interval between the two seams is small the measures tend to be more shaly, though a thin sandstone often overlies the Bottom Marshall Green. The Top Marshall Green Coal rarely exceeds 10 in and in the east and north-east it fails locally, its assumed horizon being underlain by a thin fireclay. In places it is cut out by sandstone.

The Top Marshall Green and Stobswood coals (Plate 7) are generally 12 to 30 ft apart with local maximum and minimum of 40 ft and 2 ft. In many cases, the Stobswood Coal, which is not marked on the one-inch map of the district but is indicated and first named on the vertical section, is either absent or thin, the maximum recorded thickness being 11 in.

Above the Stobswood, up to the Victoria group of coals (Plate 7), lie 28 to 74 ft of variable strata. Generally the lower part of the sequence consists of argillaceous beds, overlain by a 'mixed bed' sequence or one in which sandstone tends to predominate. The roof of the Stobswood Coal locally contains a fauna of mussels, in places associated with Planolites and fish debris. This horizon is thought to be the equivalent of the Stobswood Marine Band, proved in a borehole at Stobswood, Northumberland (first published on 6-inch geological sheet NZ 38 SW, Blyth) but as yet no marine fossils have been recorded from this position in County Durham. In this sequence, also, there is an impersistent coal, sometimes split into two leaves, which has been termed the Bottom Victoria by the National Coal Board. Where the coal is absent the horizon is marked by the top of a seatearth. Although it approaches within 2 ft of the Victoria in one case, generally the separation is greater and there is no indication in this district or adjacent areas that this coal is the result of a split. A similar coal ranging from 4 to 22 ft below the Victoria is present in the Tynemouth (15) district (Land 1974). The roof measures of this coal, or where split its upper leaf, locally contain Carbonicola, Naiadites, Carbonita, and fish scales, while at one locality mussels occur between the two leaves of the seam. Non-marine fossils have been recorded from these horizons in the East Hetton Busty Bore in the Durham and West Hartlepool district (Smith and Francis 1967, p. 37).

Rarely, virtually the whole sequence between the Top Marshall Green and the Victoria group is occupied by sandstone.

The Victoria group of coals (Plate 7) is, typically, the Victoria Coal separated by a well developed seatearth from the Victoria Rider Coal. Three variations may occur: (1) the Victoria and Victoria Rider coals are united. Where a single seam is present it generally ranges in thickness between 3 and 13 in; (2) only a thick seatearth is present at this horizon; (3) the Victoria Rider Coal is absent, a thick seatearth being present underlain by the Victoria Coal. Where the typical sequence exists the separation usually does not exceed 5 ft, the interval being mainly seatearth with only occasional mudstone bands. Fish scales are occasionally present in the roof of the Victoria Coal.

The measures between the Victoria group of coals and the Brockwell (Plate 7) range in thickness between about 40 and 80 ft. A thick sandstone commonly forms the middle or upper part of the sequence. More rarely sandstone also occupies the lower part of the sequence. The Victoria Rider is overlain by the Victoria Fish-Bed, comprising shale with fish scales and spines, and sometimes with Planolites ophthalmoides and mussels. This in turn is overlain by the Victoria Shell-Bed which is correlated with the Upper Victoria Shell-Bed of the Durham and West Hartlepool district (Smith and Francis 1967, p. 39) and consists of shale with non-marine bivalves including Carbonicola declivis, C. pseudorobusta, and Curvirimula sp.and Naiadites sp.This bed either directly overlies the Victoria Fish-Bed or is separated from it by a few feet of barren mudstone. A coal is locally found close below the Brockwell with a maximum recorded thickness of 35.5 in. It is thought to be the equivalent of the Bottom Brockwell seam of the Durham and West Hartlepool district (Smith and Francis 1967, p. 39).

The Brockwell (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10), the lowest major coal in the sequence, has been extensively worked in the district. Its thickness ranges from 5 to 7 ft, and in the thicker sections the coal is frequently canneloid at the top.

The measures between the Brockwell and Busty coals (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10) average about 100 ft, and typically consist of two sandstones and two thin coals, the lower coal being impersistent; exceptionally, up to four sandstones and three coals are present. The uppermost coal, although of no economic importance, may be equated with the Three-Quarter Coal of the Durham and West Hartlepool (27) district. Two or occasionally three fossil bands have been proved between the Brockwell and Three-Quarter coals. The lowest band, near the roof of the Brockwell, contains mussels, fish fragments and in one locality ostracods, and is the probable equivalent of the Brockwell Ostracod Band of Durham and West Hartlepool (Smith and Francis 1967, pp. 15, 24, 43); the highest band, whose top lies up to 60 ft above the Brockwell, contains fish fragments and mussels but no ostracods.

The Fishburn 'Estheria' Band, in the roof of the Three-Quarter Coal in the Durham and West Hartlepool district (Smith and Francis 1967, pp. 15, 25, 45), is not recorded here, although mussels are locally recorded at that horizon. There is also a band containing mussels some 16 ft higher.

Over most of its area the Busty Coal (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10) is split into two distinct sections. Only west of a line from between Evenwood Gate and Spring Gardens to Toft Hill and Woodhouses is it more often a single composite seam. Even here, however, it is often strongly banded and is locally split by up to 3 ft of seatearth or mudstone. Where regarded as a single seam it generally ranges between 3 and 5 ft and has been extensively worked. East of the line of split the Bottom Busty is usually 2.5 to 4 ft in thickness. The Bottom Busty seam is prone to washout or impoverishment.

The measures between the Bottom and Top Busty (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10) are generally between 5 and 20 ft thick, a sandstone often being present in the roof of the Bottom Busty. Near West Auckland where the Bottom Busty is impoverished the separation between the two seams is in places as much as 54 ft. The Top Busty Coal generally ranges between 1.5 and 3 ft, but in some localities it is much thinner and of little economic importance.

The measures between the Top Busty seam and the Tilley group of coals (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10) are of variable lithology and range in thickness between about 15 and 104 ft, though 40 to 50 ft is most common. A thick sandstone usually overlies the Busty in the western part of its area, and in a few places the whole sequence between Bottom Busty and the Tilley group is occupied by sandstone. To the east the sequence is mainly argillaceous, and a prominent mussel band, sometimes associated with fish remains in the immediate coal roof, commonly overlies the Top Busty or its horizon as in the Durham and West Hartlepool district (Smith and Francis 1967, pp. 15, 26 and 50). In places scattered mussels occur higher in the sequence between the Top Busty and Bottom Tilley.

The Tilley group of coals (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10) occur in up to 48 ft of strata. Individual seams rarely exceed 2 ft and are usually less; some are locally absent. Typically, the group forms Top and Bottom sub-groups of which the Bottom is the most consistent, and gives rise at some localities to a single coal up to 3 ft thick. The measures between the two sub-groups vary considerably; a sandstone in places occupies the whole interval, but more usually the measures are mainly argillaceous. Mussels occur sporadically between the leaves of the Bottom Tilley and between the Bottom and Top Tilley sub-groups. Fish fragments are locally recorded from the roof of the top leaf of the Bottom Tilley. The Tilley coals have been little worked and are of small economic value.

The measures between the Tilley group and the Harvey (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10) generally consist of about 60 ft of variable measures in which sandstone or alternations of sandstone and shale commonly predominates. Between St Helen Auckland and Shildon however the interval is greater and includes up to 109 ft of sandstone. A thin coal or seatearth occasionally present up to 16 ft below the Harvey Coal may be the equivalent of the Hodge seam of north-west Durham. In a few localities one or two thin coals occur immediately under the Harvey Coal and may be splits off the base of the seam. The sequence is relatively unfossiliferous.

The Harvey seam (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10) locally prone to washout or impoverishment, ranges generally between 3 and 4 ft. Locally in the eastern part of the district it is split into Top and Bottom coals separated by up to 8 ft of seatearth or mudstone. Like the Brockwell and Bottom Busty it has been extensively worked.

The Harvey–Harvey Marine Band interval (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10) is generally between 40 and 60 ft, and contains a variable sequence comprising roughly equal proportions of thin sandstones and shales. Two thin coals or seatearths are occasionally present midway in the sequence. The Harvey, or where present the Top Harvey, is overlain by the Hopkins Band (Smith and Francis 1967, pp. 15, 26 and 56), the most persistent ostracod-bearing marker band in the Durham Coal Measures. Mussels and fish fragments are also present at this horizon.

Middle Coal Measures

The Middle Coal Measures are preserved mainly in the north-eastern part of the district, where they are partly concealed by Permian rocks. Farther west, Middle Coal Measures occur in narrow belts along the south sides of the Butterknowle and Wigglesworth faults respectively. The base of the Middle Coal Measures is taken at the base of the Harvey Marine Band, near the middle of the A. modiolaris Zone. The marine band is generally thin and represented only by dark shale or mudstone; only at two localities have marine fossils been found, and these were Lingula. Over most of the district the horizon can only be inferred by correlation.

Between the Harvey Marine Band and the Hutton (Bottom Hutton) (Plate 11) are 100 to 130 ft of measures with up to six sandstones. The sandstones are generally thin, though rarely they form the greater part of the sequence. Several thin coals also occur, the highest of which is most persistent in the west, while the others are most persistent in the east. This upper coal, the Ruler or Jubilee, is equated with the Plessey seam of Northumberland. In the western part of the outcrop it attains a maximum recorded thickness of 38 in. Generally however it is significantly thinner than this and is locally split into Top and Bottom seams.

Fossils are recorded from several levels in the sequence. An important mussel band, sometimes with fish debris at the base, occurs close above the Harvey Marine Band, and although not widely recorded from this district it is well known as one of the more persistent marker bands of the Durham coalfield (Smith and Francis 1967, pp. 16, 59). Three impersistent faunal bands are recorded between this shell bed and the Ruler Coal. Mussels have been recorded from the roof of the Ruler Coal but there is no fossil band comparable with the Plessey Shell-Bed of Northumberland.

In this district the Hutton seam (Plate 11) is split into Top and Bottom coals as in the southern half of the Durham and West Hartlepool (27) district (Smith and Francis 1967, p. 16). The Bottom Hutton, termed the Hutton Coal except in the north-eastern part of the district, generally occurs as a single composite seam between 36 and 48 in thick. In the extreme north-east the seam is generally slightly thinner; and in one or two localities it is impoverished. The seam has been widely worked throughout the district.

The Hutton (Bottom Hutton)–Top Hutton interval (Plate 11) varies from 24 to 70 ft, the usual range being of the order of 30 to 40 ft. The measures are mainly shale, although sandstones may be present, one underlying the Top Hutton. Mussels are common in the shales above the Hutton Coal, and at one locality an abundant mussel fauna, associated with a band containing ostracods persists throughout the greater part of the sequence between the two coals.

The Top Hutton Coal is thin and impersistent over most of its area and of no economic value; occasionally it is split into two or even three seams.

The Top Hutton to Brass Thill interval (Plate 11) varies from 20 to 60 ft, the more usual thickness being about 30 to 40 ft. The beds are mainly argillaceous, although one or more sandstones occur, especially in the west. Poorly preserved mussels have been noted at several horizons, and include Anthracosia and Naiadites as the main genera.

The Brass Thill (Plate 11) throughout most of its area is a single composite seam 3 to 4 ft thick, often with a thin band near the base of the coal. Locally the seam is inferior or impoverished. In some localities, especially in the northeastern part of the district, the coal is split into two leaves separated by up to about 11 ft of strata, and here the lower leaf usually ranges between 12 and 18 in, the upper between 29 and 44 in.

The Brass Thill (or Top Brass Thill) to Durham Low Main interval (Plate 11) varies from 20 to 60 ft, being generally between 30 and 40 ft. The beds are mainly argillaceous with thin impersistent sandstones, though locally sandstone occupies most of the sequence. Occasionally the Durham Low Main Coal has a thin underrider, while a thin coal or seatearth is sometimes present lower in the sequence. The Brass Thill Coal is commonly overlain by shales containing an abundant fauna of mussels in which Anthracosia and Naiadites are common. This bed equates with the Brass Thill Shell-Bed of the Durham and West Hartlepool district (Smith and Francis 1967, pp. 16, 27).

The Durham Low Main (locally known as the Chatham) ranges up to 63 in, but the general range of thickness is between 20 and 36 in; it is locally prone to impoverishment or small washouts, especially around and to the east of Auckland Park.

The Durham Low Main to Main Seam interval (Plate 11) has a maximum thickness of 220 ft, the more general range being 110 to 170 ft. These beds are mainly arenaceous and in most cases include a thick sandstone, the Durham Low Main Post either directly overlying, or separated by a few feet of shaly beds from, the roof of the Durham Low Main. The sandstone, either as a single bed or split into two or three leaves, has a maximum recorded thickness of 120 ft. At the few localities where shales occur in the roof of the Durham Low Main, mussels including Anthracosia are recorded. The Maudlin Coal, a composite seam up to a maximum thickness of 77 in and up to 70 ft below the Main, is impersistent. In the extreme north-east of the district it is split into Top and Bottom coals up to 17 ft apart. In the north-east part of the district, where both Top and Bottom Maudlin are present, the Durham Low Main post tends to be thinner, and this feature becomes even more pronounced in the Durham and West Hartlepool (27) district (Smith and Francis 1967, p. 16). Where the Maudlin is present the measures between it and the Main Coal are predominantly argillaceous.

The Main Coal (Plate 11) though of limited extent in this district, is the thickest seam and has been widely worked. Where the seam is united it ranges between 36 and 132 in; where split into two leaves by bands (which never exceed 3 ft thick) its composite thickness ranges between 80 and 171 in.

Measures above the Main Coal (Plate 12) occur only in the north-eastern part of the district. Except for a limited zone on the south side of the Butterknowle Fault north-west of Woodhouses, they are restricted to the east side of the Gaunless valley between South Church and West Thickley, and bounded to the south-east by an irregular line from West Thickley to Windlestone Park. The highest Middle Coal Measures crop out on Shawbrow Hill north-west of Shildon.

The measures between the Main and Five-Quarter coals (Plate 12) are mainly shales and range in thickness from 47 to 120 ft; sandstones sometimes occur in the thicker sequences; three thin sporadic coals are also present. Fossils are not common; fish fragments are recorded from the roof of the Main, while a band with fragmentary mussels including Anthracosia and sometimes underlain by shales with fish debris, has been recorded above the uppermost thin coal.

The Five-Quarter (Plate 12) locally termed the Bottom Five-Quarter, is generally a single seam ranging between 60 and 72 in. Locally, as between Fieldon Bridge and Shildon, and in places in the sub-Permian concealed coalfield, it is much thinner and in a few isolated localities it is absent. Locally it is united with the Metal seam.

The measures between the Five-Quarter and the Metal seams (Plate 12) range up to 49 ft, the widest separation being mainly confined to the synclinal area. The beds are mainly shales and mud stones sometimes with mussels and fish fragments, but they occasionally include a thin sandstone in the middle or lower part of the sequence.

The Metal Coal (Plate 12) locally termed the Jet, Dicky Dant or Top Five-Quarter, is generally a single seam or composite banded seam between 6 and 66 in thick. The name 'Metal Coal' is derived from the Newcastle upon Tyne area thereby avoiding the inference that it is an upper split of the Five-Quarter Coal although very locally it is united with this seam. This accords with practice in the Durham and West Hartlepool (27) district where Smith and Francis (1967, p. 17) refer to the confusion that has arisen over the nomenclature and correlation of this seam.

The measures between the Metal and High Main (or Bottom High Main) (Plate 12) range between 40 and 81 ft and consist mainly of shale with local thin sandstones. An impersistent coal with a maximum recorded thickness of 26 in occurs in the upper part of the sequence. Fragmentary mussels are occasionally recorded in the roof of the Metal, while fish debris and mussels are recorded in the upper part of the sequence.

The High Main (Plate 12) occurs as a single seam ranging between 18 and 24 in at several localities but is generally split and divided into Top and Bottom High Main. Because the seams are generally very close, and the Top High Main is thin or perhaps locally absent, the two seams have been mapped where they occur as 'the High Main'.

The Bottom High Main, locally known as the Willy Winter, generally ranges between 18 and 38 in, but west of Shildon thicknesses of up to 85 in inclusive of band and shale have been proved.

Where the High Main is split, the measures between the two units are shales generally between 10 and 15 ft thick, with a local maximum of 24 ft, and where separation is greatest, up to two thin sandstones sporadically occur. Fish debris and scattered mussel fragments have been reported from the roof of the Bottom High Main.

The Top High Main ranges up to a maximum recorded thickness of 33 in; more commonly between 6 and 21 in. Locally it is absent or cut out by an overlying sandstone—the High Main Post.

A maximum of 160 ft of Carboniferous strata have been proved above the Top High Main in this district (Plate 12). They are confined to the area of Auckland Park, where they are arenaceous, and around Shawbrow Hill where they are mainly shales and mudstones. The measures include four coals of which the three lowest are thin and impersistent. The lowest coal, up to 7 in thick, carries mussels in its roof. It is overlain by, or separated by a few feet of argillaceous measures from, the High Main Post, a sandstone which in the Auckland Park area ranges up to 67 ft thick, cuts out this coal and extends down to, or locally cuts out, the Top High Main. Farther south, the sandstone rarely exceeds 15 ft, and is locally absent. Both mussels and fish fragments are recorded locally from the roof of two succeeding higher thin coals. The higher band containing fish and mussels and which is not necessarily associated with coal, may be at about the same horizon as the High Main Marine Band of the Durham and West Hartlepool (27) district (Smith and Francis 1967, p. 17). Mussels are known to occur in the sequence between the Marine Band and the succeeding coal. The highest of the four coals, thought to be the Ryhope Little, is recorded as being up to 24 in thick on Shawbrow Hill. This coal is overlain by a sandstone over 30 ft thick. It is possible that a few feet of higher measures are preserved along the synclinal axis extending from Coppy Crook towards Coundon Grange.

Details

In the following details positions of outcrops, shafts and boreholes are as far as possible related to localities shown on the One-inch Geological Map but the exact position is indicated by reference to the National Grid. These localities and their grid references are shown on (Plate 5). Representative sections of both Lower and Middle Coal Measures are shown graphically in (Plate 6), (Plate 7), (Plate 10))." data-name="images/P991426.jpg">(Plate 9), (Plate 10), (Plate 11), (Plate 12). The numbers in parentheses following the names of sections refer to sites on (Plate 5) and to the numbered graphic sections on the relevant plates. Detailed records and synopses of some of the more important outcrops, shafts and boreholes are included in Appendices 1 and 2 and references to these in the text are marked with an asterisk (*).

The following account is derived from many more shaft and borehole sections than can be quoted in detail here, and these are kept for reference in the Northern England Office of the Institute of Geological Sciences.

Lower Coal Measures

Quarterburn Marine Band to Ganister Clay seam (shown graphically on (Plate 6))

Quarterburn Marine Band

The Quarterburn Marine Band is exposed in Quarter Burn* [NZ 0170 2676] where it consists of 1 ft 7 in of mudstone with sporadic limestone nodules, containing a fauna of Lingula mytilloides and Productus carbonarius. To the east-north-east in Greenless Beck [NZ 0597 2748], the marine band itself is not present, but its position can be inferred by correlating equivalent sandstones and seatearths with those in Quarterburn. J.H.H.

In the Woodland Bore* (16) the marine band consists of 2 ft 10 in of shale containing Lingula mytilloides, Productus carbonarius, and Rhabdoderma sp.About 3 miles farther east-south-east, however, in boreholes near Snape Foot [NZ 1379 2691] the horizon cannot be recognized with any certainty although in Gordon Gill 'K' Bore* (55) it may be present in 9 ft of shale at 249 ft. South of Cockfield at Burnt Houses the marine band was recognized in Keverstone No. 44 Bore* (34) and consisted of at least 1.5 ft of mudstone containing Lingula sp.

The marine band has been proved in a number of boreholes in the vicinity of Hilton including Hilton Moor No. 2 Bore* (80), Hilton No. 113 Bore* (74), Hilton No. 114 Bore* (87), and in the Hilton Hall Bore* (91). The marine band which consists of shale, mudstone or siltstone is between 6 in and 9 ft 9 in thick and contains brachiopods, bivalves, gastropods and fish scales. The richest fauna was obtained from Hilton Moor No. 2 Bore* (80) and included Aviculopecten cf. delepinei and a turreted gastropod at the top, and Lingula mytilloides, Orbiculoidea ? and Donaldina ? at the base. In the Hilton Hall Bore* (91) productoid fragments and a palaeoniscid scale were present. The most easterly recorded occurrence of the presumed Quarterburn Marine Band is from the Shackleton Beacon Bore* (146), where 'Productus sp.'is recorded from a thin shale at 58.5 ft. D.A.C.M.

The marine band and associated measures are thought to be absent in Knott Holes Quarry [NY 9968 2628] 1.5 miles N of Eggleston. Here the Third Grit is separated by only 2 ft 10 in of seatearth mudstone from the top of the Second Grit.

Measures between the Quarterburn and Kays Lea marine bands

The measures between the Quarterburn and Kays Lea marine bands were proved in the Woodland Bore* (16) to consist of 47 ft 11 in of strata, 44.25 ft of which were sandstone, while in Quarter Burn* (Plate 6) [NZ 0170 2676] 4.75 miles WSW the measures are only 26 ft thick with a 12.5 ft sandstone. In Greenless Beck [NZ 0592 2736] the equivalent strata consist entirely of coarse-grained sandstone overlain by an 8-in coal. J.H.H.

An exceptional thickness of 891 ft of sandstone was proved farther east in Gordon Gill 'F' Bore* (54) at Snape Foot.

Sandstone is locally less abundant in these beds around Cockfield and Hilton, and in Keverstone No. 44 Bore* (34) they include two unnamed marine bands. The upper is equated with a 4 ft mudstone band containing a marine fauna at the bottom of Hilton No. 53 Bore* (97), and a marine band some 16 ft below the Kays Lea Marine Band in Hilton Moor No. 2 Bore* (80).

The unnamed marine band in Hilton Moor No. 2 Bore* (80) is underlain by a 13-in coal, and coals are recorded from several other boreholes at about the same horizon, including the Hilton Hall Bore* (91), and Hilton No. 113 Bore* (74). The upper marine band was not recorded in the Hilton Hall Bore though its position is assumed to be in shale overlying a 36-in coal at 151 ft. In Hilton No. 114 Bore* (87) the lower of the two marine bands recorded in Keverstone No. 44 Bore* (34) may be represented by 2.5 ft of shale containing Lingula mytilloides and Rhadinichthys sp.only 15 ft above the Quarterburn Marine Band although here only part of the sequence between the Quarterburn and Kays Lea marine bands is recorded.

Kays Lea Marine Band

The Kays Lea Marine Band varies in thickness from 3 to 8 ft and in lithology from shale to siltstone. It is not seen anywhere at the surface and has been recorded only in boreholes. In the Woodland Bore* (16) it consists of 6 ft 5 in of shale containing Planolites ophthalmoides at the top, Agathamminoides? and Ammodiscus sp.in a 1 ft 5 in band below, underlain by Lingula mytilloides in a 3-in band at the base. The marine band has not been proved farther north-west. Other boreholes in which the marine band or its assumed horizon has been recorded include Moorhill No. 1* (21), Gordon House No. 1* (46), Keverstone No. 44* (34), Hilton Moor No. 2* (80), Hilton No. 53* (97) and Hilton No. 113* (74).

Lithologies and faunas are detailed in Appendix 2.

Measures between the Kays Lea and Roddymoor marine bands

Measures between the Kays Lea and Roddymoor marine bands are exposed [NZ 0172 2660] in Spurlswood Beck* (Plate 6) where they consist of 1.25 ft of seatearth-mudstone on 56.5 feet of predominantly medium-grained sandstone —the Third Grit—with a coal horizon some 7 ft from the base. The lower part of the sandstone is also exposed [NZ 0595 2723] about 2.75 miles to ENE in Greenless Beck. The Third Grit crops out extensively in the area of Woodland Fell and Eggleston Common but only partial sections near the base of the sandstone are seen, examples of which are as follows:

• Knott Holes Quarry [NY 9969 2629] 1.5 miles N of Eggleston: 10.75 ft of pink to greenish brown hard thin- to well-bedded sandstone overlain by 7 ft of grey well-bedded medium-grained jointed sandstone.
• Quarry [NZ 0494 2359], north of Billy Lane House: pink to grey, massive coarse-grained sandstone, 10 ft.
• Quarry [NZ 0736 2399], about 370 yd NNE of Crag Top: grey, thin-flaggy and false-bedded, fine- to medium-grained sandstone. J.H.H.

A number of boreholes show that the sequence is generally dominated by the Third Grit which is separated from the top of the Kays Lea Marine Band by between 1 and 12 ft of shale and/or siltstone and occasionally a coal, and from the base of the Roddymoor Marine Band by a seatearth and thin coal ranging between 1 and 18 in thick. In general these measures thin from north-west to south-east corresponding to a thinning of the Third Grit in the same direction. Typical sections are provided by the following boreholes, detailed in Appendix 2: Woodland* (16), Moorhill No. 1* (21), Gordon Gill 'F'* (54), Toft Hill Underground 'B'* (77), Gordon House No. 1* (46), Hilton Moor No. 2* (80), Hilton No. 53* (97), and Hilton No. 113* (74). Atypical sections are proved in Keverstone No. 44 Bore* (34) and Hilton Hall Bore* (91). The section in the former is exceptional in that there is a 2 ft 10 in sandstone immediately overlying the Kays Lea Marine Band, a position normally occupied by argillaceous measures. The latter is unusual in containing no apparent Third Grit.

Roddymoor Marine Band

The Roddymoor Marine Band is absent in the northern part of this district although near-marine conditions may be indicated by the presence of Planolites and fish fragments at this horizon in Spurlswood Beck* (Plate 6) in the Woodland Bore* (16) and in Toft Hill Underground Bore 'B'* (77). Similarly, in Keverstone No. 44 Bore* (34) its horizon may be underlying a mudstone containing mussels and fish fragments at 134 ft 11 in. The Roddymoor Marine Band has been recorded in several boreholes in the Hilton area. In Hilton Moor No. 2 Bore* (80) the fauna included Ammodiscus sp., Lingula mytilloides, Donaldina? and Elonichthys sp.[scales]. At Hilton No. 53 Bore* (97) Serpuloides stubblefieldi, Planolites ophthalnioides, Lingula mytilloides and Euphemites sp.were recorded, and at Hilton No. 113 Bore (74) the fauna included Planolites ophthalmoides, Serpuloides stubblefieldi, Paraconularia sp.and Orbiculoidea cf. nitida. All these boreholes are detailed in Appendix 2.

Measures between the Roddymoor Marine Band and the Ganister Clay Coal

The measures between the Roddymoor Marine Band and the Ganister Clay Coal are very variable in lithology and thickness. In Spurlswood Beck* [NZ 0173 2659] (Plate 6) they are 37 ft 4 in thick with only a thin sandstone present under the assumed position of the Ganister Clay coal. J.H.H.

In the Woodland Bore* (16) these measures are 40 ft 3 in thick and contain two thin sandstones near the top, underlain by predominantly argillaceous beds containing two fossil bands. The lower band some 15 ft 1 in above the assumed horizon of the Roddymoor Marine Band contains Planolites ophthalmoides and Curvirimula sp., while the upper band some 4 ft 8 in higher contains Carboni-cola sp., Curvirimula sp., Naiadites sp.and Geisina arcuata. To the east in Moorhill No. 1 Bore* (21) these measures are 73 ft thick and include an 18 ft sandstone at the top of the sequence, the remainder of the measures being predominantly argillaceous and including a 4 in coal 8 ft from the base. In the adjacent Moorhill No. 2 Bore* (22), the upper part of the sequence is broadly similar but in the shale underlying the sandstone and some 20 ft below the Ganister Clay a fauna consisting of Carbonicola sp.,Naiadites sp., Geisina arcuata and fish remains has been recorded. They are partially exposed in the Gaunless Valley* [NZ 1032 2430] west of Peathrow West where they consist of 67 ft of mudstone and shale, but include a 13 ft sandstone about 10 ft below the Ganister Clay. In Gordon Gill 'F' Bore* (54) these beds include three thin sandstones in a predominantly mixed beds sequence, of which the exact thickness is doubtful on account of faulting. In Toft Hill Underground Bore 'B'* (77) the sequence is 52.25 ft thick and includes three sandstones. These measures were penetrated in Keverstone No. 44 Bore* (34) where they are at least 104 ft 11 in thick and include two sandstones separating measures of a dominantly argillaceous or mixed bed character. The lower sandstone is underlain by a coal 1 ft 4 in thick while in the silty measures below fish fragments are present at two horizons, the lowest together with a mussel band immediately overlying the assumed position of the Roddymoor Marine Band. Fossils are also recorded at other horizons in this sequence notably mussels and fish fragments in 8 ft of shale and mudstone overlying the lower sandstone, fish scales at three horizons in silty shaly laminae in the lower part of the upper sandstone, and fish scales about 17 ft below the assumed position of the Ganister Clay. The sequence is somewhat thinner around Hilton although in most boreholes there is a high proportion of sandstone and sandy mudstone. In Hilton Moor No. 2 Bore* (80) the beds measure 75 ft 4 in, and include a sandstone nearly 35 ft thick at the top. In Hilton No. 53 Bore* (97) there are three separate sandstones; two argillaceous beds containing Curvirimula sp.are present 40 ft 5 in and 57 ft 11 in below the Canister Clay. These forms also occur in the Woodland Bore* (16) at about the same position. In Hilton Moor No. 1 Bore* (81) near Hilton Moor Farm a mudstone containing Spirorbis sp.and Carbonicola aff. proxima is present 40.5 ft below the Ganister Clay. Although only one specimen of C. aff. proxima is available it is comparable with C. proxima from the Norton mussel band of the East Midlands Coalfield, in the upper 'A'. lenisulcata Zone. The band is possibly represented by the upper of the two faunal bands already referred to in the Woodland Bore. In the Hilton Hall Bore* (91) at least 66 ft of strata separate the Roddymoor Marine Band from the Canister Clay. A 7-in coal 7 ft above the Roddymoor Marine Band is possibly the equivalent of the 1 ft 4 in coal at 114 ft in Keverstone No. 44 Bore* (34). The measures however are complicated by faulting and correlation is dubious. At the top of the sequence a second thin seam-6 in of inferior coal—lies near the middle of a 17-ft sandstone immediately below the Ganister Clay Coal. Further sections or synopses of sections of boreholes which show all or part of the measures between the base of the Quarterburn Marine Band and the Ganister Clay are quoted in Appendix 2. These include Eggleston No. 3* (1), No. 4* (2), Arnghyll No. 3* (7), Burfoot Leazes* (12), Woodland Colliery No. 29* (6), Hilton No. 1* (103), Hilton No. 2* (86), Hilton No. 3* (90), Hilton No. 5* (98) and Lutterington Estate* (115). All these boreholes are old, and while in most cases they provide sufficient information to establish correlation, they lack detailed lithological data. D.A.C.M.

Ganister Clay Coal to base of Brockwell (shown graphically in (Plate 7))

Ganister Clay Coal

The Ganister Clay Coal is apparently thickest on the southern and western margins of the coalfield. In the Woodland area it ranges between 11 and 28 in, the thicker sections generally being banded. The coal was extensively worked at Gibbsneese Opencast Site [NZ 088 241] north and north-east of High Wood Farm where it ranged between 14 and 19 in thick. Between Gibbsneese and Woodland the section proved in Arnghyll No. 3 Bore* (7) about 300 yd ESE of Hill House, Copley, was coal 12 in, band 2 in on foul coal 6 in. J.H.H.

Farther east round Butterknowle, Windmill and Oaks the seam is usually between 8 and 10 in thick, while around Cockfield the seam, usually banded, has a composite thickness of coal 14 to 19 in, on band 1 to 9 in, on a thin basal coal 2 to 3 in. A typically in Gordon House No. 98 Bore* (31) on Cockfield Fell the seam is only 0.5 in thick. South of Evenwood and around Hilton, Keverstone and Wackerfield and thence north-eastwards towards Bildershaw thicknesses of between 6 and 25 in have been proved. The coal is typically banded especially at the base of the section. The little which is known about the seam in the West Auckland and Shildon areas suggests it is thin and banded. At Norton Fine 'A' Bore (92) at Spring Gardens, West Auckland, the seam section recorded was: coal, inferior 6 in, shale 5 in, coal 2 in, siltstone 1 in, coal 6 in, seatearth 4 in, on coal, pyritic 2 in. The seam is similarly thin and banded at Charles Pit* (159) Middridge. D.A.C.M.

Measures between the Ganister Clay and Marshall Green

The measures between the Ganister Clay and Marshall Green (or Bottom Marshall Green) seams are between 30 and 65 ft thick and are recorded from many boreholes in the west and south of the coalfield area. A typical section for the Woodland area is provided by the Burfoot Leazes Bore* (12) where the beds are 47 ft thick with argillaceous measures at the base and top with a median 24 ft 8 in of sandstone. Broadly similar sections were proved in Arnghyll No. 3 Bore* (7), Woodland Colliery No. 29 Bore* (6); and in a borehole (14) west of Kays Lea. In the Woodland Bore* (16) these measures, some 45 ft thick, include a thick medium- to coarse-grained sandstone. The upper part of the sequence is also seen in the beck behind Bogle House [NZ 0839 2475] as follows:

J.H.H.

These beds are also exposed in the banks of the River Gaunless 30 yd downstream from an adit [NZ 0920 2487] and consist of shale with siltstone and sandstone ribs 19.5 ft, sandstone 20 ft, overlain by seatearth-mudstone, 6 ft.

They are also exposed in the River Gainless* [NZ 1032 2430] near Peathrow West where they consist of 55 ft of interbedded sandstones and shales.

North of the River Gaunless between Butterknowle, Windmill and Oaks the typical sequence consists of a thin sandstone overlying the Ganister Clay followed by predominantly argillaceous beds in turn succeeded by sandstone, up to 20 ft thick, which is usually separated from the floor of the Bottom Marshall Green coal by a seat-earth. The argillaceous beds sometimes contain mussels. Such a sequence was proved in High Wham No. 32 Bore (27) where the measures totalled 43 ft 2 in. Towards the base of the argillaceous beds the section proved was:

The sandstone, 5 ft 1 in thick, which overlies the Ganister Clay in this borehole appears to thicken towards the north-east.

Around Cockfield, Burnt Houses and north of Wackerfield these measures are generally thicker and more variable, and sandstone or sandy measures tend to predominate. A sandstone is generally present below the Bottom Marshall Green seam; west of Cockfield it is exposed [NZ 1082 2446] along with adjacent measures on the south side of the Gaunless valley near Peathrow. Atypical sections have been proved in a number of boreholes. In Gordon House No. 94 Bore (59), east of Esperley Lane Ends, and Keverstone No. 48 Bore* (70), north of Wackerfield, the measures are almost wholly of mixed bed or argillaceous type. In contrast, in Keverstone No. 128 Bore (52), nearly 0.5 mile NW of Keverstone Grange, they are virtually all sandstone. In some boreholes mussels have been noted in the middle or upper part of the sequence, while in Gordon House No. 98 Bore* (31) mussels, fish debris and worm burrows including Planolites are recorded from mudstone and siltstone 14 to 17 ft and 24.5 ft below the Bottom Marshall Green; and Planolites sp. 2.75 ft above the Ganister Clay. In Gordon House No. 96 Bore (41) at Cockfield a 3-in band containing minute fish fragments is recorded 5 ft above the Ganister Clay horizon.

Around Evenwood Gate sandstone predominates, though argillaceous measures up to 20 ft thick overlie the Ganister Clay. In an underground borehole [NZ 1600 2443] west of Evenwood Gate, drilled from the Bottom Marshall Green seam in Randolph Colliery, Evenwood, a 1-in coal is recorded 8 ft 9.5 in above the Ganister Clay. Some other bores in adjacent areas prove a seatearth on thin coal at about this position.

Around Hilton, sandstone may be present at two and even three horizons, as exemplified by Hilton No. 51 Bore* (76). The upper two sandstones appear to reach their maximum farther to the north-east as proved by boreholes in the vicinity of Bolton Garths, notably Hilton No. 53 Bore* (97). In this borehole plants, including Alethopteris and Mariopteris were obtained from mudstone in the roof of the Ganister Clay, while plants together with several small examples of Curvirimula were recorded in the bed immediately above.

The little which is known about these measures in the West Auckland and Shildon areas suggests that they are between about 60 and 80 ft thick and consist mainly of a mixed bed sequence, although a sandstone up to 36 ft thick immediately underlies the Bottom Marshall Green locally. D.A.C.M.

Marshall Green seam

The Marshall Green seam is typically split into top and bottom components and is present as a united seam only around Moor-hill Drift Mine [NZ 0975 2879] 2.5 miles NE of Woodland where the section is: coal 18 in, band 1 in, on coal 4 in.

The Bottom Marshall Green Coal around Woodland and Copley generally ranges between 17 and 21 in, sometimes with a thin band near the top. Locally it is absent. Atypically thick sections of 49 and 67 in respectively were recorded in Woodland Colliery No. 29 Bore* (6) and Cowley Bore* (5). In the latter the coal was originally correlated with the Brockwell because of its thickness. J.H.H.

Around Butterknowle, Windmill and Oaks the seam generally ranges between 10 and 20 in, with a recorded maximum of 25 in. There is commonly a thin band near the base. The seam thins progressively north-east of Windmill towards Witton Park (Wolsingham (26) district) where it rarely exceeds 10 to 15 in. Around Cockfield and Hilton the seam ranges between 9 and 24 in and tends to be rather thicker in the east than the west. A band between 0.5 and 3-in thick is sometimes present in the lower part of the section. Between Evenwood and Shildon records suggest that the scam thickness lies within the same general range. In underground boreholes [NZ 1644 2789] (78) and [NZ 1646 2800]* (77) near Hunter's Hill House, Toft Hill, the section proved was: coal 12 to 14 in, band (sandy) 7 in, on coal 7 to 11 in. In St Helen Auckland Engine Pit (122) south-west of Tindale Crescent it was a single seam of 17 in. In a borehole from the base of Charles Pit* (159) only 135 yd N of Middridge, the seam was apparently absent. D.A.C.M.

The measures between the Bottom and Top Marshall Green seams generally range between 15 and 50 ft, the extremes being 7 and 80 ft; the thicker sequences including much sandstone. In the Woodland and Copley areas a sandstone generally ranging between 8 and 10 ft rests directly on the Bottom Marshall Green seam; in places argillaceous measures underlie the sandstone. Atypical sections were proved in Arnghyll No. 1 Bore* (9) and Arnghyll No. 3 Bore* (7) where little sandstone is present, while in Cowley Bore* (5) near Cowley the measures are 69 ft 2 in thick and consist of alternating beds of mudstone and sandstone, the latter predominating. J.H.H.

Around Butterknowle, Windmill and Oaks these beds range between 8 and 33 ft, and are predominantly argillaceous in the west, especially where the Top Marshall Green is absent or very thin, and arenaceous in the east; here the roof of the Bottom Marshall Green seam is generally a grey siltstone with sandy bands, sandstone or a grey fine-grained sandstone as in High Wham No. 31 Bore* (23) and High Wham No. 33 Bore* (28). In boreholes where the measures are thinner, e.g. High Wham No. 32 Bore (27) nearly 0.5 mile N of High Wham they are more argillaceous although still often sandy at the base.

Around Cockfield and Hilton these measures range from 5 to 55 ft, being greatest between Cockfield and Keverstone Grange. At many localities a thick sandstone forms the roof of the Bottom Marshall Green seam. It crops out in the Gaunless Valley* [NZ 1082 2444] north of Peathrow, while in a quarry [NZ 1351 2280] in North Wood about 0.25 mile WNW of Keverstone Grange it consists of over 20 ft of yellow and purplish massive to thick-, locally false-bedded medium- to coarse-grained sandstone. In Keverstone No. 133 Bore* (63) it is nearly 40 ft thick and apparently cuts out the Top Marshall Green; by contrast, in Keverstone No. 48 Bore (70) west of the Sun Inn, Wackerfield, the separation between the two seams is only 13 ft, mainly of seatearth. Similarly in Hilton No. 51 Bore* (76) these measures, again argillaceous, are only 5.25 ft thick. Little is known about these beds in the West Auckland and Shildon areas; they appear to range between 15 and 21 ft and are predominantly of a mixed bed or sandy character. Flaggy sandstone overlying the Bottom Marshall Green has been worked [NZ 2069 2420] north of Royal Oak. D.A.C.M.

The Top Marshall Green is everywhere thin and occasionally it is absent. The seam is thickest in the Woodland and Copley areas where it ranges up to 16 in and averages about 11 in. At Dent Gate Opencast Site [NZ 079 244] it was worked together with the Bottom Marshall Green, the separation between the two seams being 12 to 15 ft. J.H.H.

South and east of Copley and between Butterknowle, Windmill and Oaks the seam is in general between 4 and 7 in thick. At High Wham No. 32 Bore (27) it is 16 in, including a 5-in band 2 in from the base; by contrast it is absent in High Wham No. 41 Bore (51) nearly 0.5 mile S of Windmill. The seam rarely exceeds 6 in in the Cockfield, Low

Lands, Burnt House and Keverstone Grange areas and is locally absent, its assumed horizon being marked by the top of a seat-earth. In Gordon House No. 131 Bore* (57) there are two 1-in coals at this horizon, separated by 11 in of black silty micaceous shale containing ?fish scales while in Keverstone No. 133 Bore* (63) a single coal 10 in thick is present. Around Hilton and towards Bildershaw the seam falls generally within the range of 6 to 14 in, and at most places it is less than 10 in. The few records available in the West Auckland, Shildon and Middridge areas suggest that the thickness ranges between 4 and 11 in. The seam is absent at Charles Pit* (159), Middridge. D.A.C.M.

Measures between the Top Marshall Green and the Stobswood coal

The measures between the Top Marshall Green and the Stobswood coal or its assumed position, range generally between 12 and 30 ft, extremes being 2 and 40 ft. In the Woodland and Copley areas a typical sequence was proved by Moorhill No. 121 Bore (20), the details being as follows:

J.H.H.

Between Butterknowle, Windmill and Oaks these measures range between 2 and 22 ft, the thickest sequences being broadly similar to that proved in Moorhill No. 121 Bore (20) above, or where thinner being predominantly argillaceous in character. In High Wham No. 33 Bore* (28) the two seams are separated by a mere 3 ft 5 in of seatearth-sandstone. South of the River Gaunless and around Cockfield, Wackerfield and Hilton the interval ranges generally between 5 to 10 ft, and consists mainly of argillaceous or silty beds. Exceptionally, at Gordon House No. 131 Bore* (57) the separation is over 11 ft, with median sandy beds.

Near West Auckland, 18.25 ft of measures, mainly sandstone, were recorded, and some distance farther north in Toft Hill Underground Bore 'W* (77) these measures, 12.25 ft thick, are again mainly of sandstone though an adjacent borehole records only 6.75 ft of fireclay.

Stobswood Coal

The impersistent Stobswood Coal is rarely more than 6 in thick. In the Woodland and Copley areas it reaches up to 5 in, although it is absent in the Woodland Bore* (16). North of the River Gaunless between Butterknowle and West Auckland it is generally absent, its assumed horizon overlying a fire-clay. Similarly, south of the River Gaunless it is thin and impersistent, although in Hilton No. 51 Bore* (76) it attains 9 in. D.A.C.M.

Stobswood to Victoria group of coals

Stobswood to Victoria group of coals. Between the Stobswood Coal, or its assumed position, and the Victoria group of coals are very variable measures containing up to two coals, one of which, locally split, has been termed 'Bottom Victoria'.

In the Woodland and Copley areas these beds are proved in Arnghyll No. 1 Bore* (9), Pioneer Shaft and Bore* (13) and Moorhill No. 118 Bore* (18). The beds thicken northeastwards from 44 to 72 ft, although exceptionally in Pioneer Shaft and Bore they are only about 28 ft thick. Generally the sequence consists of alternating sandstone and shale although in the Woodland Bore* (16) it is predominantly of sandstone. A dark shale containing fish remains overlies the assumed horizon of the Stobswood in this borehole, occupying a similar horizon in Moorhill No. 121 Bore (20). J.H.H.

North of the River Gaunless between Butterknowle, Windmill and Oaks the thickness of the measures is generally in the range 45 to 55 ft. A typical sequence is recorded in High Wham No. 32 Bore (27). There is a persistent seatearth and/or coal, sometimes in two leaves—the 'Bottom Victoria'—between 14 and 21 ft below the Victoria. Despite its name, the Bottom Victoria is not a split off the Victoria in this district, and always appears as an entirely separate seam. Below this horizon the strata are wholly or predominantly arenaceous to within a few feet of the Stobswood. In places they are underlain by a few feet of argillaceous strata containing fish scales, Planolites ophthalmoides and mussels, possibly at the horizon of the Stobswood Marine Band. In Moorhill No. 12 Bore (36) and High Wham No. 40 Bore (39) the 'Bottom Victoria' is present, the section in the latter case being: coal 3 in, band 1 in, coal 3.5 in, band 1 in, on coal 4 in. Two miles farther south-east, in Gordon House Nos. 130 (43) and 135 bores (64) [NZ 1337 2506], [NZ 1469 2546], in the Gaunless valley east-north-east of Low Lands this coal is split into two leaves, an upper leaf 1 to 12 in thick separated by 11 to 5 ft of strata from a lower leaf 9 to 10 in thick. Two thin coals 5 and 8 in thick respectively separated by 4+ ft of seggar are present in West Tees No. 1 Bore* (65) near Ramshaw. Other details which demonstrate the wide range of variation in this group of strata include the following:

In Moorhill No. 2 (22), High Wham No. 34 (35) and No. 42 Bores (53), near High Wham and Morley, thin conglomerate bands consisting of sandstone containing pebbles of clay ironstone, shale and siltstone overlie the Stobswood or its position. In High Wham No. 36 (32) and Moorhill No. 12 (36) additional seatearths are present between 14 and 20 ft above the Stobswood horizon. In High Wham No. 33 Bore* (28) a 4-in coal is present at the horizon of the lower seatearth.

Strata between the seatearth or Bottom Victoria and the base of the Victoria group of coals are of a mixed bed character, sandstone being impersistent. The sequence in the area around Cockfield, Burnt Houses and Keverstone Grange shows similar variability. The thickness ranges between 37 and 74 ft, the widest variation being in the north, the separation tending to fall to the east. Mussels have been recorded above the Stobswood only from Gordon House No. 93* (47) and No. 131* (57) bores. The Bottom Victoria is impersistent but where absent its horizon is usually marked by its seatearth. Around Cockfield it is usually thickest and occasionally occurs as two thin coals separated by a few feet of argillaceous measures. For example, in Gordon House No. 97 Bore (33) about 0.5 mile WNW of Cockfield Church, two coals 1 and 13 in respectively, the latter banded, are separated by 3 ft 4 in of seatearth-sandstone. Around Buck Head and Keverstone Grange this coal occurs as a single seam and attains its maximum thickness of 18 in in Gordon House No. 94 Bore (59) west-south-west of Buck Head. The measures between the Bottom Victoria and the Victoria group of coals are mainly argillaceous with impersistent sandstones. They vary in thickness from 2 to 36 ft, the widest variations being found north of Cockfield. The most typical thickness is around 24 ft. In Gordon House No. 131 Bore* (57) poorly preserved mussels are recorded in the roof of a seatearth some 15 ft below the Victoria, and mussels are also present 17 ft below the Victoria at Gordon House No. 93 Bore* (47). Exceptionally, in Gordon House No. 98 Bore* (31) the separation between the Bottom Victoria and the Victoria is only 2 ft of seatearth-mudstone.

Around Wackerfield, Hilton and Bildershaw the interval between the Stobswood and Victoria averages about 60 ft, a thin coal, the Bottom Victoria, usually being present in the middle or upper part of the sequence. Sandstones are again impersistent but occur more commonly in the upper part of the sequence than elsewhere. In Keverstone No. 48 Bore (70) there is a sandstone over 30 ft thick in the upper part of the sequence underlain by argillaceous measures containing mussel fragments. A bed with fish scales and spines and ?mussel fragments is recorded in this position in a number of boreholes including Hilton No. 55 Bore* (88), and Hilton No. 52 Bore (89) where 2 ft 10 in of shale containing mussel fragments lies above the Stobswood. The Bottom Victoria ranges up to 12 in; in Keverstone No. 48 Bore (70) it is split in two leaves, 8 and 10 in thick, separated by about 4i ft of seatearth-mudstone and shale, the latter containing large mussels. Mussels and fish scales overlying this coal are recorded in a number of boreholes, notably Hilton No. 50 Bore (73) and Hilton Moor No. 2 Bore* (80).

Around West Auckland scattered boreholes suggest that the sequence is broadly similar to that in the Cockfield and Hilton area, the recorded interval between the Stobswood and the Victoria ranging between about 35 and 47 ft. The lower part of the sequence is mainly argillaceous and the upper part mainly arenaceous or of mixed bed type. A thin coal about the middle of the sequence is sometimes in two leaves separated by up to 2 ft 9 in of fireclay. Toft Hill Underground Bore 'B'* (77) and Norton Fine 'A' Bore (92) exemplify the sequence in this area. There is little reliable information on these beds in the Eldon and Middridge areas. D.A.C.M.

Victoria group of coals

The Victoria group of coals, that is the Victoria Coal or, where split, the Victoria and its upper member the Victoria Rider together with intervening measures, are seen at the surface only near Copley Lodge north of Butterknowle. In the Woodland and Copley areas the group is highly variable. The Victoria Coal, only locally absent, varies from 1 to 24 in and is separated by as little as 1 in of seatearth to a recorded maximum of 35 ft of variable measures from the Victoria Rider, which has a proved maximum of 8 in. In the Woodland Bore* (16) the Victoria Rider is thought to be represented by a single 3 in seam at 54 ft, the Victoria being absent. Sections through the group are also provided by the Pioneer Shaft and Bore* (13), Moor-hill No. 118 Bore* (18) and Cowley Shaft (11). J.H.H.

Between Butterknowle and Oaks this group is generally either a single united seam or is split into Victoria and Victoria Rider. Occasionally the positions of one or both seams may be absent marked only by seat-earths. The combined Victoria and Victoria Rider seams are exposed [NZ 1031 2643] in a stream 250 yd SW of Copley Lodge, Butterknowle where they form a thin coal known locally as the Six-Inch. Some 400 yd NW of this locality only the Victoria Rider (7 in) is exposed, though the Victoria is presumed to be present close below. Other records showing the presence of both coals include Moor-hill No. 1 Bore* (21): coal 2 in, seatearth 1 ft 7 in, on coal 12 in; and Gordon House No. 130 Bore (43): coal 0.75 in, seatearth-mudstone 7.25 ft on coal 13 in. In High Wham No. 32 Bore (27) where only the 9 in Victoria Rider is present, the seam is underlain by 2.25 ft of argillaceous beds, the lower 7 in being black micaceous shale containing fish scales and overlying the assumed horizon of the Victoria.

Around Cockfield, Burnt Houses and Keverstone Grange there are typically two coals. The Victoria ranges generally between 7 and 12 in, the maximum recorded thickness of 19 in (banded) being in Gordon House No. 98 Bore* (31). North and north-east of Keverstone Grange and at Keverstone No. 43 Bore (38) the coal is absent. The measures between the two seams range from 3 ft in Gordon House No. 98 Bore* (31) to an exceptional 35 ft in Keverstone No. 148 Bore (49), a 26-in seatearth being present 18 ft 2 in below the Victoria Rider horizon. Normally the separation ranges from about 9 ft in the west to 25 ft in the east of this area. The measures are generally of shale and seatearth the latter tending to predominate where the separation is least. In Keverstone No. 136 Bore (61) north-east of Keverstone Grange, the two seams are 25 ft apart, 7.75 ft of fire-clay overlying the Victoria Coal. The thickness of the Victoria Rider in this area ranges up to 7 in, but in many places it is absent, its assumed horizon overlying a seatearth.

North of Hilton and towards Bildershaw this group occurs both as a single and a split seam. It is a single 6-in seam in Hilton Moor No. 2 Bore* (80) and in Evenwood Gate No. 1 Bore (75) it is 10 in thick. In Hilton No. 55 Bore* (88) it is split. Around West Auckland the sparse records suggest that the coal is typically split, the section in Norton Fine 'A' Bore (92) at Spring Gardens being: coal 3 in (Victoria Rider), seatearth 7.75 ft, coal 3 in (Victoria) and at Toft Hill Pit (67): coal 8 in (Victoria Rider), seatearth 6 ft, on coal with two bands 27 in (Victoria). D.A.C.M.

Little is known about these coals in the Eldon, Shildon and Middridge area. In Jane Pit* (142) 0.75 mile NNW of St John's Church, Shildon, a 12-in coarse cannel 57 ft below the Brockwell may represent both Victoria and Victoria Rider, while at Charles Pit* (159), Middridge the coal is absent, its horizon overlying 4 ft 2 in of seggar clay. J.H.H.

Measures between the Victoria group and the Brockwell Coal

The measures between the Victoria group and the Brockwell Coal are, except for minor exposures near Butterknowle, recorded only in boreholes. In the Woodland and Copley area there are complete sections of these beds from several boreholes and shafts including Pioneer Shaft and Bore* (13), Woodland Bore* (16), Moorhill No. 118 Bore* (18) and Cowley Shaft (11), the thickness ranging between 44 and 70 ft. A typical section is that from Moorhill No. 118 Bore* (18) where these measures are 48 ft 11 in thick, including a median 24 ft sandstone. This is underlain by the Victoria Shell-Bed—5.5 ft of mudstone containing mussels. In this borehole, the roof of the Victoria Rider comprises 2 ft 11 in of shale containing fish scales—the Victoria Fish-Bed. In the Woodland Bore* (16) the Victoria Shell-Bed contained Planolites ophthahnoides, Carbonicola declivis, C. pseudorobusta and Naiadites sp.in 12 ft 5 in of mudstone, separated by 8 in of black shale from the Victoria Rider. J.H.H.

In boreholes between Butterknowle, Windmill and Oaks these measures have an average thickness of about 50 ft. They are of mainly 'mixed beds' lithology, with, in places, a sandstone up to 30 ft thick in the upper part of the sequence. In most places the Victoria Rider, or its horizon, is overlain by the Victoria Fish-Bed, a shale containing fish debris including scales and spines. In High Wham No. 40 Bore (39) 15 in of shale containing Planolites cf. ophthalmoides intervene between the coal and 3 ft 5 in of black shale containing fish scales and spines, regarded as the Victoria Fish-Bed, which is in turn overlain by the Victoria Shell-Bed. The Victoria Shell-Bed is proved in several boreholes to extend up to 15.5 ft above the Victoria Rider Coal. It mainly contains the small mussel Curvirimula, but Carbonicola sp.and Planolites ophthahnoides are also recorded locally. Near the upper part of the sequence, a seatearth, in places carrying an inferior coal up to 4 in thick is present between 8 and 12 ft below the Brockwell coal. This coal may be equated with the ?Bottom Brockwell of the Keverstone area.

South of the River Gaunless around Cockfield, Burnt Houses and north of Wackerfield the group varies between 40 and 82 ft the latter thickness referring to an exceptional section in Gordon House No. 98 Bore (31) where the interval is mostly occupied by sandstone. The Victoria Fish-Bed and the Victoria Shell-Bed are recorded from most boreholes in this area. In Gordon House No. 97 Bore (33) and Gordon House No. 98 Bore* (31) fish remains are recorded above the Victoria Rider Coal. The base of the Victoria Shell-Bed ranges between 9 and 19.5 ft above the Victoria group; in all cases however, its contained fossils are recorded only as "mussels" or "small mussels". In Gordon House No. 97 Bore (33) a 2 ft 8 in band, 8 ft 10 in above the Victoria Rider and at the top of the shell bed, contains Planolites ophthalmoides. In places, as for example Gordon House No. 131 Bore* (57), a thick seatearth is present up to 5 ft 10 in below the Brockwell and separated from it by argillaceous measures. In some boreholes between Keverstone Grange and Burnt Houses a coal overlies the seatearth and although highly banded and local, it attains a composite thickness of up to 35.5 in. The section in Keverstone No. 133 Bore* (63) is an example. This coal is thought to be the equivalent of the Bottom Brockwell Coal of the Durham and West Hartlepool district (Smith and Francis 1967, p. 38).

Little is known of the beds between the Victoria group and Brockwell in the area north-east of Wackerfield towards Bildershaw. Here the only complete sequence is recorded in Evenwood Gate No. 1 Bore (75) south-south-east of Evenwood Gate, where the thickness is 70 ft 1 in including a median 22 ft sandstone. The Victoria Shell-Bed is represented by 4.5 ft of silty mudstone containing indeterminate mussels, and separated by 9.5 ft of apparently barren mudstone from the Victoria Rider. Partial sections in these measures are recorded in Hilton Moor No. 2 Bore* (80) where neither shell nor fish bed is recorded, and Hilton Moor No. 55 Bore* (88) where fragmentary mussels are present (Victoria Shell-Bed) 17 ft 10 in above the Victoria Rider, the latter being overlain by 2 ft of shale containing fish scales (Victoria Fish-Bed). At Randolph Colliery No. 1 Shaft (72a) the section immediately under the Brockwell coal is: ironstone 10 in, seggar 3 ft, on measures, mainly sandstone, 30 ft.

In the Toft Hill, West Auckland, Shildon and Middridge areas these measures have been recorded in nine boreholes and shafts most of which are old. The group expands eastwards from 48 to 65 ft, and is generally of a mixed bed lithology although sandstones occur impersistently as in Toft Hill Underground 'B' Bore* (77) where both Shell-Bed and Fish-Bed were proved. The Bottom Brockwell has not been recorded in this area, the Brockwell coal being variously floored by thick seatearth or sandstone. In Norton Fine 'A' Bore (92) neither the fish bed nor the shell bed were proved.

Further sections through all or part of these measures include those from Burfoot Leazes Bore* (12), Woodland Colliery No. 29 Bore* (6), Hilton Nos. 1 (103), 2* (86) and 3* (90) bores, Lutterington Estate Bore* (115), Engine Pit, St Helen Auckland (122), Jane Pit, Adelaide Colliery* (142) and Charles Pit, Middridge* (159). D.A.C.M

Brockwell to Harvey Marine Band (shown graphically in (Plate 10))." data-name="images/P991426.jpg">(Plate 9) and (Plate 10))

Brockwell Coal

The Brockwell Coal, known in places as the Main Coal, is the lowest major seam to have been worked in the district. It has been wrought since the earliest times and reserves are all but exhausted. Extraction has taken place from all the major collieries, in addition to the innumerable smaller pits and day holes scattered along the outcrop throughout the northern part of the district. Pillars left by mining from 19th and early 20th century shallow drifts and even earlier 'bell pit' and 'day hole' extraction methods have been removed by opencast working particularly along the northern outcrop, between Woodland and Toft Hill. The coal is now seen only in temporary opencast sections although its outcrop is often well defined by 'sink holes' and other marks of old workings. D.A.C.M.

In the Woodland and Copley areas the coal ranges between 38 and 84 in. The westernmost recording was in a drift [NZ 0356 2467] on Langleydale Common, some 2 miles SW of Woodland, where it was 38 in thick. About a mile farther east Woodland Colliery No. 47 Bore (3; B & S 3096) near Dale Terrace proved: coal 57 in, band 2 in, on coal 20 in; a mile to the south-east in Arnghyll (or Am Gill) the general seam section is: coal 67 in, band 4 in, on coal 15 in. Comparable seam sections were measured in Cowley Shaft (11; B & S 3086), Woodland Colliery Shaft (10; B & S 2338), and in colliery workings 0.5 mile S of High Wood Farm [NZ 0874 2396]. In Pioneer Shaft and Bore* (13) a single seam section of 72 in was recorded. East of Copley, as for example at Diamond Pit* (24), Butterknowle, the seam is 70 in thick. J.H.H., D.A.C.M.

North of the river Gaunless between Butterknowle and the area west of Toft Hill, including that around Gordon Beck, the Brockwell is generally between 72 and 75 in thick, the recorded range being 60 and 82 in. The seam was worked at outcrop at a number of sites in the area, the largest being at Cold Hurst [NZ 1066 2788], north and east of Morley Farm [NZ 1257 2829] and a mile W [NZ 133 283] of Windmill. In an opencast site [NZ 1500 2743] over k mile NNE of Bowes Close the seam ranged between 68 and 76 in. At Lands Engine Pit [NZ 1344 2505] (B & S 1271), Low Lands, the seam section was cannel 11 in, on coal 71 in; while in the nearby Gordon House No. 130 Bore (43) it was coal 45 in, band 11 in, on coal 17 in.

Around Cockfield, on Cockfield Fell, and between Shotton Moor [NZ 104 237] in the west and Keverstone Grange [NZ 1382 2265] in the east, the Brockwell is usually between 70 and 90 in thick, frequently banded, and cannelly at the top. On Shotton Moor [NZ 104 237] the section is coal 51 in, band 9 in, on coal 35 in, and at John Pit* (29) cannel 7 in, coal 49.25 in, band 0.25 in, on coal 14.5 in. On the western side of Cockfield Fell the seam averages up to 81 in including up to 12 in of cannel on top, while farther east on the Fell and north of Hall Pit (45) a typical section is cannel 14 in, coal 60 in, band 4 in, on coal 15 in. East of Keverstone Grange and north-west of Wackerfield [NZ 162 227] the seam is thinner, a typical section being cannel 15 in, coal 9 in, band 1 in, coal 30 in, on splint 6 in.

Around Evenwood, and between West Auckland and Wackerfield, the coal ranges generally between 48 and 75 in, a band 2 to 14 in usually being present up to 24 in from the base of the coal. Very thick sections are, however, recorded locally. For instance, at Randolph Colliery No. 2 Shaft* (72b) the seam section is cannel 48 in, coal 66 in, band 3.5 in, on coal 6 in, while at the base of Staindrop Field House Drift* over 0.5 mile ENE of Evenwood Gate the coal section was cannel (including fish fragments) 12 in, coal 48 in, seatearth-mudstone 13 in, coal 12 in, seatearth-mudstone 4 in, on coal 8 in.

Two small areas of Brockwell Coal occur south of the main outcrop. The first is about 0.5 mile ENE of Wackerfield [NZ 162 227] where the coal incrops against the Hilton Fault and Wackerfield Dyke. The coal, up to 60 in thick, is overlain by shale and underlain by fireclay. The strata are highly disturbed by faulting and the coal is baked and cindered along the dyke margins. A second small area of Brockwell occurs north of Todwell House [NZ 1667 2129]; here the coal, 60 in thick, was found to be so highly disturbed due to faulting as to be virtually unworkable. The coal is cut off abruptly to the north by one of the faults of the Hilton Fault complex. Considerations of structure suggest that a small area of Brockwell may also exist a short distance south of Wackerfield [NZ 154 221].

South and east of Toft Hill, around West Auckland, Tindale Crescent, Hummerbeck and Brusselton, the Brockwell coal generally ranges between 56 and 80 in. At Toft Hill Pit (67) it is 72 in, at Windlestone Pit, West Auckland (106; B & S 2174) 68 in, while at St Helen Auckland Engine Pit* (122) the section is coal 11 in, soft grey metal band 1.5 in, coal 16 in, coal splint 2 in, on coal 37 in. D.A.C.M.

Over the whole of the district farther east and including the South Church, Coundon Grange, Eldon, Old Eldon, Windlestone Park, Fieldon Bridge, Shildon and Middridge areas the coal generally ranges between 55 and 72 in thick. Somewhat thicker sections were proved along the southern outcrop of the seam east of Brusselton Hill [NZ 2037 2498], where measurements in shallow workings show a general thickness of the order of 72 in. The seam was worked opencast at New House site south of Hill Top Farm [NZ 2123 2487] where a typical sequence was coal 12 in, shale up to 24 in, coal 31 in, shale up to 15 in, on coal 27 in. J.H.H., D.A.C.M.

Measures between the Brockwell and Busty coals

The measures between the Brockwell and Busty coals (or where split the Bottom Busty) have been proved in many boreholes, more especially in the central and eastern part of the coalfield area. They are rarely seen at outcrop. The sequence, which overall averages 100 ft thick, may contain up to four sandstones and three thin coals. All these coals tend to be impersistent, although the highest, which is equated with the Three-Quarter seam of the Durham and West Hartlepool district, is proved in most boreholes. Up to four faunal bands are jointly recorded from boreholes through this sequence, notably in the roof measures of the Brockwell, up to 65 ft above the Brockwell, in the roof of the Three-Quarter, and some 16 ft above the Three-Quarter. D.A.C.M.

In the Woodland and Copley areas these measures, rather thinner than over much of the remainder of the coalfield area, range between 68 ft in the west and 58 ft in the east. The following sequence was proved in Woodland Colliery No. 47 Bore (3) near Dale Terrace:

The above sequence is similar in other records farther east though the proportion of sandstone varies considerably from 80 per cent in Woodland Colliery Shaft (10) where it is in two main "posts", to as little as 27 per cent in Diamond Pit* (24), Butterknowle where it forms three thin bands. Neither the Three-Quarter nor the other two thin coals of the sequence are recorded in this area. A 24-in coal which lies 4 ft above the Brock-well in Woodland Colliery Shaft may be regarded as a split off the Brockwell and as an equivalent of one of the thin roof coals to the seam known in the Durham and West Hartlepool district (Smith and Francis 1967, p. 42). J.H.H.

North of the Butterknowle Fault, between Butterknowle and Windmill, only the lower and occasionally the middle part of the sequence crop out, generally under thick drift, and records of exposures are few. In some areas a sandstone up to 30 ft thick is thought to occur in the lower part of the sequence. Sections immediately above the Brockwell Coal were formerly exposed at a number of opencast sites, and one such section at the south-west corner of an opencast site near Rowntree Farm [NZ 1170 2819] was as follows:

Broadly similar sections were obtained at opencast sites north and east of Cold Hurst [NZ 1066 2788] and north and east of Morley Farm [NZ 1257 2829]. On the southern edge [NZ 1315 2807] of an opencast site 600 yd WSW of Windmill the following section was recorded:

At a former opencast site [NZ 119 266] southeast of High Wham a 20-in coal about 22 ft above the Brockwell was worked, the intervening beds comprising 1 ft of shale underlain by 21 ft of sandstone.

South of the Butterknowle Fault in the Gordon Beck area the only complete sequence in these measures was recorded in Providence Pit (62; B & S 957) near Bowes Close where they are nearly 67 ft thick, predominantly argillaceous in character and contain four thin ribs of sandstone. A 6-in coal, possibly the Three-Quarter, is present some 28 ft below the Bottom Busty. Farther south-west, at Lands Engine Pit [NZ 1344 2505] (B & S 1271), 2 and 9 in coals are present at 34 and 38 ft respectively above the Brockwell.

Around Cockfield, on Cockfield Fell, in the Gaunless valley between Butterknowle and Oaks, and between Shotton Moor [NZ 104 237] and Keverstone Grange [NZ 1382 2265] these measures range between 38 and 95 ft, the greatest thicknesses being recorded in the west. Typically, a sandstone up to 20 ft thick and sometimes split into two leaves is present between the Brockwell and Three-Quarter, while a further sandstone between the Three-Quarter and Busty locally forms the floor of the latter. The Three-Quarter seam, recorded in most boreholes, is generally between 6 and 15 in thick, but locally round Cockfield thicknesses of up to 30 in have been recorded. An atypical Three-Quarter section is recorded in Gordon House Nos. 95 (42) and 144 (37) bores on Cockfield Fell.

In the former, the coal section is coal 5 in, shale 22 in, on coal 13 in; while in the latter the coal is 26 in thick with a 4-in band 8 in from the base. At Gordon House No. 135 Bore (64) in the Gaunless valley north-east of Low Lands, the following sequence was recorded:

The 11-in coal in the above section is one of the lower impersistent coals in the Brockwell–Busty sequence and is equated with the 20-in coal at the opencast site [NZ 119 266] near High Wham (see p. 96) and the 2- and 9-in coal at Lands Engine Pit [NZ 1344 2505] (see p. 96). In Gordon House No. 94 Bore (59) near Buck Head the sequence is as follows:

The above sequence is notable for a very low sandstone content and for the presence of mussels at three horizons. In Keverstone No. 133 Bore* (63) over half a mile north-east of Keverstone Grange the lower two faunal bands are present and the lowest is 25 ft above the Brockwell seam. This contrasts with Gordon House No. 94 Bore (59) where the lowest mussel band is only about 6 ft above the Brockwell. Except for small exposures of flaggy micaceous mudstone with thin sandstone bands overlying the Brockwell coal on the south side of the Gaunless valley 0.25 mile SSW of the Slack these measures are not seen at the surface.

In the Evenwood area, and between West Auckland and Wackerfield, the Brockwell–Busty interval generally ranges between 95 and 108 ft. Two thin coals are usually present in the sequence. The lower coal, 3 to 8 in, ranges from 37 to 54 ft above the Brock-well; the upper, 8 to 12 in, ranges from 69 to 84 ft above the Brockwell and is thought to be the equivalent of the Three-Quarter. Northeast of the Sun Inn [NZ 1542 2317] a sandstone up to 30 ft thick is present 10 to 20 ft above the Brockwell. Towards the north-east, this sandstone is absent or sporadic in its distribution. At Randolph Colliery No. 2 Shaft* (72b) the sequence, 88 ft 9 in thick, is mainly arenaceous, but includes the Three-Quarter, 12 in thick, and a lower thin coal. At Staindrop Field House Drift* over 0.5 mile ENE of Evenwood Gate, these measures are 104 ft thick, the Three-Quarter, 1 ft, being separated from the Busty by 20 ft of mainly argillaceous strata. A faunal assemblage 52 ft above the Brockwell is reminiscent of the C. declivis fauna from the Brockwell Ostracod Band of the Durham and West Hartlepool district (Smith and Francis 1967, p. 43) but its position above the coal is stratigraphically very high for this district; moreover ostracodshave been proved from near the roof of the Brockwell seam at West Auckland (see below).

Measures overlying the Brockwell occur in three small areas to the south of the main crop. The first is a 0.25 mile S and the second 0.5 mile NE of Wackerfield and the third north of Todwell House, Hilton ([NZ 153 222], [NZ 162 227] and [NZ 166 215] respectively]. Here the Brockwell abuts against faults and whilst the measures are not exposed at surface, at the second and third localities they may extend up to and include the Busty, close to the faults.

South and east of Toft Hill these measures range between 80 and 96 ft and contain two or three sandstones separated by argillaceous measures. The Three-Quarter ranges from 1 to 18 in. Etherley No. 4 Bore* (79) provides a typical sequence.

Around West Auckland and Hummerbeck these measures range between about 80 and 100 ft thick and usually include three sandstones and two thin coals. The lower coal is locally split into two leaves and is occasionally absent; the upper coal, the Three-Quarter, usually ranges between 6 and 9 in. Typical of the several borehole sections of the Brockwell–Busty interval is the following proved in West Auckland No. 150 Bore (99) 0.75 mile NW of St Helen Auckland:

The mudstone band containing ostracods may be regarded as the equivalent of the Brockwell Ostracod Band of the Durham and West Hartlepool district. Other complete sections through this part of the sequence are recorded in West Auckland No. 168 Bore* (104) and Windlestone Pit (106).

Around Tindale Crescent and southwards towards Brusselton these measures are proved in Catherine Pit (116; B & S 1653) and Engine Pit* (122) at St Helen Auckland, Ladysmith Shaft* (118) near Brusselton, Bildershaw 'A' Bore (111) and Bildershaw 'B' Bore (112) near Hummerbeck. The sequence ranges between 88 and 110 ft and most sections show three sandstones, with interbedded argillaceous measures. Two thin coals are also recorded, a lower coal between 3 and 7 in up to 50 ft above the Brockwell and an upper coal, the Three-Quarter, generally ranging between 5 and 6 in. Boreholes in the vicinity of Hummerbeck show that the Three-Quarter is somewhat thicker; in Bildershaw 'A' Bore (111) it comprises: coal 12 in, band 8 in, on coal 5 in. D.A.C.M.

In the Eldon, Shildon and Middridge areas the Brockwell–Busty interval, up to 150 ft thick contains up to three thin coals, the highest of which may be equated with the Three-Quarter, and a high proportion of sandstone overlying both the Brockwell and Three-Quarter coals. The Three-Quarter is recorded in most boreholes and shafts and has a maximum thickness of 24 in though more usually it is in the range of 7 to 15 in.

In South Pit (129; B & S 2323) Woodhouse Close the sequence recorded was: