Geology of the country around Preston (One-inch geological sheet 75 New Series)

By D. Price, W. B. Wright, R. C. B. Jones, L. H. Tonks  and T. H. Whitehead

Bibliographic reference:  Price, D. et al. 1963. Geology of the Country around Preston (One-inch geological sheet 75 New Series). London: Her Majesty's Stationery Office [for Geological Survey of Great Britain.

Authors: D. Price, B.Sc., The Late W. B. Wright, Sc.D., MonograptusI.Min.E., R. C. B. Jones, MonograptusC., D.Sc., MonograptusI.MonograptusMonograptus, MonograptusI.Min.E., L. H. Tonks, MonograptusSc., and T. H. Whitehead, MonograptusSc., A.R.C.S., F.R.S.E. with contributions by A. E. Mourant, D.Monograptus, MonograptusA., D.Phil., F.R.C.P., F.R.A.I., Calver, MonograptusA., and W. H. C. Ramsbottom, MonograptusA., Ph.D.

Department of Scientific and Industrial Research. Memoirs of the Geological Survey of Great Britain. England and Wales

London: Her Majesty's Stationery Office1963 © Crown copyright 1963 Printed and published by Her Majesty's Stationery Office

(Front cover)

(Rear cover)

Preface

The area covered by the one-inch New Series map Sheet 75 (Preston) was originally surveyed by E. Hull, R. H. Tiddeman and C. E. De Rance. The geology of the major part of the district was shown on the one-inch Old Series Maps 89 N.E., first published in 1868, and 89 N.W., first published in 1871; revised editions were subsequently published, the latest being that of 1883 which showed De Rance's re-interpretation of the drift deposits of the western areas. Six-inch maps of much of the district were published by 1875. No memoir descriptive of the area restricted to Sheet 75 was printed, but the geology was described in 'The Geology of the Burnley Coalfield' and 'The Superficial geology of the country adjoining the coasts of south-west Lancashire', published in 1875 and 1877 respectively.

Resurvey on the six-inch scale was carried out between 1922 and 1935, con­currently with that of districts to the east and south, under the late W. B. Wright as District Geologist. The officers concerned, and the areas surveyed by them, are detailed in the list of six-inch maps on pp. vii-viii. Subsequently, Messrs. D. Magraw, E. G. Poole, D. Thomas and A. J. Whiteman examined the cores from a number of recent boreholes. A 'Solid' edition of the New Series map was published in 1938, and a 'Drift' edition two years later; an emended version of the 'Solid' map, with the National Grid added and with revisions by Mr. J. V. Stephens and Dr. F. Monograptus Trotter, was published in 1958. It is not proposed at present to issue an emended version of the 'Drift' map.

With the exception of the palaeontology chapter, Mr. D. Price has written the memoir from manuscript descriptions left by the offiers concerned, and he has incorporated information obtained since the resurvey. The contributions of each author are in general indicated by appended initials. Mr. Monograptus A. Calver and Dr. W. H. C. Ramsbottom have named the fossils collected since the time of resurvey and have re-examined the collections studied originally by Drs. W. B. Wright and C. J. Stubblefield respectively; they have contributed the chapter on palaeontology. The photographs, a list of which is given in Appendix 2, were taken by Mr. J. Rhodes. The memoir has been edited by Mr. W. N. Edwards and Mr. B. J. Taylor.

We are grateful to the local water-engineers, surveyors and colliery managers for their co-operation and for the assistance which they so freely gave at the time of the survey. To various firms and to the National Coal Board we are especially indebted for a number of borehole records and for opportunities of examining cores.

C. J. Stubblefield, Director. Geological Survey Office, Exhibition Road, South Kensington, London, S.W.7. 22nd April, 1963

List of six-inch mapsOn the obsolescent 'County' system. Topographic maps on the National Grid system are now available for the district and include the following sheets (all in the 100-kilometre square SD): 31 NE, SE; 32 NE, SE; 33 SE; 41 NW, NE, SW, SE; 42 NW, NE, SW, SE; 43 SW, SE; 51 NW, NE, SW, SE; 52 NW, NE, SW, SE; 53 SW, SE; 61 NW, NE, SW, SE; 62 NW, NE, SW, SE; 63 SW, SE. Geological six-inch maps on the National Grid system will be published for those parts of the district in which there is a substantial area of Coal Measures.

Geological six-inch maps included wholly or in part in the one-inch map Sheet 75 (Preston) are listed below together with the initials of the surveyors and the dates of survey. The surveyors were R. C. B. Jones, F. Marsden, A. E. Mourant, R. L. Sherlock, L. H. Tonks, T. H. Whitehead and W. B. Wright. Those maps which include a substantial area of Coal Measures—marked with an asterisk in the list below—are published. They are issued uncoloured but are obtainable hand-coloured to order. The remainder will not be published but are available for public reference, in MS form, at the Geological Survey Offices, Leeds and London. Certain revisions of the Solid geology shown on the 1958 version of the one-inch map are not yet shown on the six-inch maps.

Chapter 1 Introduction

Geographical range, physiography and industries

The districtThroughout this memoir the word 'district' refers to the area represented on one-inch Sheet 75 (Preston). described in this memoir, covered by Sheet 75 (Preston) of the New Series One-inch Geological Survey Map, lies entirely in Lancashire and includes the towns of Preston, Chorley and part of Blackburn. Its situation is shown in (Figure 1). Within it rocks of Carboniferous and Permo-Triassic ages crop out (Figure 2), but for the most part under drift. The Carboniferous rocks comprise the Millstone Grit Series and the Lower Coal Measures which form part of the Lancashire Coalfield. The Permo-Triassic rocks are principally the Bunter Sandstone, Keuper Sandstone and Keuper Marl; and there are small outcrops of Collyhurst Sandstone and Manchester Marl. The Carboni­ferous strata exhibit a pattern of broad folding and associated faulting; the Permo-Triassic rocks show little evidence of folding, although several major faults affect them.

An area of elevated moorland in the east, an extension of the Pennine uplands, and a low-lying area in the west, forming part of the West Lancashire Plain, are the principal physiographic features of the district. The higher ground, south of Blackburn and east of Chorley, rises from about 300 ft to nearly 1500 ft above sea-level, the more elevated points in this tract being Winter Hill (south)There are in the district two hills known as Winter Hill: one about 2 miles south of Blackburn, the other about a mile south-west of Belmont. 1498 ft, Cartridge Hill 1317 ft, Great Hill 1182 ft and Winter Hill (north)There are in the district two hills known as Winter Hill: one about 2 miles south of Blackburn, the other about a mile south-west of Belmont. 906 ft. Blackburn lies in a broad valley separating this area from high ground to the north which rises to 733 ft at Mellor Beacon. West of Samlesbury and Chorley the low ground of the West Lancashire Plain falls gently from about 300 ft to sea-level. The solid rocks of the higher ground are entirely of Carboniferous age, mainly Millstone Grit Series; those of the plain are predominantly of Permo-Triassic age.

The Ribble is the most important river in the district; it meanders through a wide valley from Elston to Preston docks, whence it flows to the sea in an artificially maintained channel. The River Darwen flows through Blackburn and Hoghton to join the Ribble at Preston; for the most part its valley is broad and open, but at Feniscowles and Hoghton Bottoms it passes through impressive gorges. The River Douglas flows north into the Ribble estuary in a shallow valley; its principal tributary, the Yarrow, rises on the moors in the south-east of the district, and flows in a sinuous course to join it east of Croston. The Lostock has a curious course; it rises near Feniscowles and flows south-west to Whittle le Woods, thence flowing north to within two miles of the River Darwen before turning southward to join the Yarrow near Croston. Almost all the drainage of the district belongs to the Ribble catchment; but a number of small streams north of Belmont drain into Belmont Brook, which is in the Irwell–Mersey catchment. The principal watershed separates Roddlesworth Brook from Belmont Brook, and runs southwards along the crest of the high ground in the south-east.

The pattern of industry in the district has changed markedly in recent years. Coal mining and the cotton trade were formerly of great importance, but now only one working colliery remains and the cotton industry has contracted. Light engineering and industry with a chemical bias are of increasing importance; around Chorley much labour is employed by the motor industry and the Royal Ordnance Factory; leather and rubber are processed and man-made fibres produced in the Preston area. An Atomic Energy establishment is situated west of Preston. In the rural areas agriculture is important. The plain, except where boulder clay lies at the surface, is arable and produces cereals and roots, and market gardening is pursued in places. In the Ribble estuary large areas of saltings have been enclosed by flood banks, and these rich soils form a valuable extension to the arable lands of the plain. In the hilly ground and boulder-clay covered areas nearly all the land is under permanent pasture. Small-scale dairy farming with subsidiary sheep and cattle rearing and poultry farming are the main agricultural activities on these pasture lands. Crops are cultivated on the small patches of glacial sand. The moorland area of the south-east has been taken over as catchment-ground for water supply, and farming has been discontinued.

Geological sequence

The formations represented on the maps are summarized below. Thick­nesses of the Carboniferous strata are generalized from data collected in various parts of the district: the Permo-Triassic strata are not fully proved, and the thicknesses given are estimates arrived at from consideration of adjacent districts.

Solid geology

Despite their Carboniferous Limestone age given on the 1958 emended version of the one-inch geological map, strata of the Bowland Shale Group cropping out in the Preston district are here included in the Millstone Grit Series, since, as far as is known, they are all of Upper Carboniferous age (see pp. 8, 10).

Geological history

Geological history evident in the Preston district commences with the formation of the upper part of the Bowland Shale Group. Towards the end of the Lower Carboniferous period and the beginning of the Upper, large quantities of mainly argillaceous sediment with minor amounts of sandy detritus were introduced, and a sequence of shales and mudstones with thin sandstones and limestones was deposited. At the end of this time there commenced periodic influxes of arenaceous material; and sedimentation of the Millstone Grit and Coal Measures was almost continuous in what may be regarded as a shallow sea, or a broad deltaic area occasionally invaded by the sea. Sedimentation was accompanied by somewhat variable subsidence, and a thick sequence of shales, mudstones and sandstones was formed. In later Millstone Grit times, and throughout the period of the Coal Measures, silting up of the depositional basin sometimes occurred, leading to the formation of seatearths and coals.

Carboniferous sedimentation was terminated by the oncoming of the later and more intense phases of the Armorican orogeny. The area was subjected to uplift, folding and faulting, which produced the major tectonic features now recognizable in the Carboniferous rocks. Extensive denudation occurred, removing a great thickness of strata. Following the Armorican movements, and possibly during their later stages, the first Permo-Triassic rocks were deposited; the Collyhurst Sandstone was laid down, probably sub-aerially, in hollows in the land surface. The district was then invaded by the sea in which the Manchester Marl was deposited. This sea eventually silted up, and there ensued a further period of mainly sub-aerial or shallow-water sedimentation during which the Bunter Sandstone and Keuper Sandstone were formed. In early Keuper times a gradual change of physiography took place, leading to the formation of a land-locked basin in which the Keuper Marl was deposited. There is little evidence of the geological history of the district from Keuper times to the beginning of Pleistocene times, since there are no deposits of Jurassic, Cretaceous or Tertiary age. Further faulting occurred and some gentle folds were developed in this interval.

During Pleistocene times the district was glaciated. No traces are found of Older Drift, but there are extensive younger glacial deposits. In Newer Drift times ice moved chiefly from the north-west, though in the early stages ice from Ribblesdale invaded an area in the north-east. The widespread occurrence of glacial sands and gravels underlain and overlain by boulder clay points to a major recession and readvance before the ice finally retreated. The post-Glacial history of the district is evidenced by aeolian sands, river terraces, alluvium, and peat at both high and low levels.

Previous research

There is little literature bearing directly on the geology of the Preston district, and that for the most part of slight importance. The occurrence of shells in the glacial deposits appears first to have attracted attention, and papers on this subject were published by Gilbertson and Taylor (1830), Murchison (1833), Gilbertson (1835), Maw (1869), Wood and Harmer (1871), Reade (1872) and Darbyshire (1874). In 1870 De Rance published an account of the glacial drifts of West Lancashire. He described Lower Boulder Clay without Lake District erratics between Chorley and Blackburn and in the Ribble valley, and ascribed it to land-ice; he gave a comprehensive description of the Lower and Upper Boulder Clays of the Preston area and of the Middle Sands—which he regarded as marine; and in the same year he described the post-glacial deposits of West Lancashire. Much of this work was later incorporated in Survey memoirs.

A survey of the district was carried out by officers of the Geological Survey in the years around 1870. Old Series one-inch maps 89 N.W. and 89 N.E., first published in 1871 and 1868 respectively, depict the geology of the district; six-inch maps of some areas were also printed. In 1875 the survey memoir 'Geology of the Burnley Coalfield' by Hull, Dakyns, Tiddeman, Ward, Gunn and De Rance (now out of print) was published, Hull and De Rance dealing with the major part of the Preston district. Hull's mapping was in the main confirmed by the resurvey. His most serious defect was his failure to correlate the strata across the Blackburn syncline: here he mistook the Revidge Grit for the Rough Rock, and as a result large areas of the Rough Rock Group were mapped as Coal Measures. He also mistook the grits of Anglezarke Moor for Kinderscout Grit. Furthermore, the boundary between the Permo-Triassic and Carboniferous rocks was thought to be a fault, though it is now shown to be for the most part an unconformity. Part of the Preston district was dealt with by De Rance in the survey memoir 'Superficial geology of the country adjoining the coasts of south-west Lancashire' published in 1877.

In 1914 Jowett described the glacial drainage round the western end of the uplands, and much later this work was extended by Dean (1953; 1958). The Brinscall overflow channel was discussed in the survey memoir 'Geology of the Rossendale Anticline' (Wright and others 1927, pp. 139–140).

R. C. B. Jones (in Wright 1925) announced the first correct determination of the horizon of the grits of Anglezarke Moor. The zonal sequence in the Sabden Shales exposed at Samlesbury Bottoms was described in 1927 by E. W. J. Moore (published 1930) and later by Bisat and Hudson (1943, pp. 397­398) and Hodson (1957, pp. 13–14). In 1934 Wright described a number of species and varieties of Carbonicola from above the Bassy Mine in the Feniscowles section of the Darwen, a section since described by Eagar (1952). Earp and Magraw (1955, pp. 29 and 30) described Tonge's Marine Band in the Heskin Bore and at a locality recorded by A. E. Mourant during the resurvey, and in 1957 Magraw described the succession of Coal Measures below the Arley Mine, proved in borings in the district.

Amongst other papers relevant to the geology of the district may be mentioned those of Reade on the post-glacial deposits near the mouth of the Douglas (1889); of De Rance on brine in the Coal Measures (1886); and of Dickson on the Preston dock excavations (1889a and 1889b) and the Ribble estuary (1897). D.P.

References

BISAT, W. S., and HUDSON, R. G. S. 1943. The Lower Reticuloceras (R₁) succession in the Namurian of the north of England. Proc. Yorks. Geol. Soc., 24, pp. 383–440.

DARBYSHIRE, R. D. 1874. On a deposit of Middle Pleistocene gravel in the Worden Hall Pits, Leyland, Lancashire. Quart. J. Geol. Soc., 30, pp. 38–42.

DEAN, V. 1953. Some unrecorded overflow channels in north-east Lancashire. Liv. and Manch. Geol. J., 1, pp. 153–60.

DEAN, V. 1958. An initial outlet of pre-Glacial Lake Accrington. Published privately.

DE RANCE, C. E. 1870. On the glacial phenomena of west Lancashire and Cheshire. Quart. J. Geol. Soc., 26, pp. 641–54.

DE RANCE, C. E. 1870. On the post-glacial deposits of west Lancashire and Cheshire. Quart. J. Geol. Soc., 26, pp. 655–68.

DE RANCE, C. E. 1877. Superficial geology of the country adjoining the coasts of south-west Lancashire. Mem. Geol. Surv.

DE RANCE, C. E. 1886. On the occurrence of brine in the Coal Measures. Trans. Manchester Geol. Soc., 18, pp. 61–81 and 140–8.

DICKSON, E. 1889a. Notes on the excavations for the Preston Docks. Proc. Liv. Geol. Soc., 5, pp. 249–56.

DICKSON, E. 1889b. Geological notes on the Preston dock works and Ribble development scheme. Proc. Liv. Geol. Soc., 5, pp. 369–76.

DICKSON, E. 1897. The Ribble estuary with notes on the formation of sand and the disposal of dissolved matter in river water. Proc. Liv. Geol. Soc., 7, pp. 135–54.

EAGAR, R. Monograptus C. 1952. The succession above the Soft Bed and Bassy Mine in the Pennine region. Liv. and Manch. Geol. J., 1, pp. 23–56.

EARP, J. R., and MAGRAW, D. 1955. Tonge's Marine Band in Lancashire. Bull. Geol. Surv. Gt. Brit., No. 9, pp. 22–32.

GILBERTSON, W. 1835. On marine shells of recent species, at considerable elevations near Preston. Rep. Brit. Assoc. for 1834, p. 654.

GILBERTSON, W. , and TAYLOR, R. C. 1830. A collection of shells from Preston. Mag. Nat. Hist., 3, pp. 170–1.

HODSON, F. 1957. Marker horizons in the Namurian of Britain, Ireland, Belgium and western Germany. Publ. Assoc. Etud. Paläont., 24, pp. 1–26.

HULL, E., DAKYNS, J. R., TIDDEMAN, R. H., WARD, J. C., GUNN, W., and DE RANCE, C. E. 1875. The Geology of the Burnley Coalfield and of the country around Clitheroe, Blackburn, Preston, Chorley, Haslingden and Todmorden. Mem. Geol. Surv.

JOWETT, A. 1914. The glacial geology of east Lancashire. Quart. J. Geol. Soc., 70, pp. 199–231.

MAGRAW, D. 1957. New boreholes into the Lower Coal Measures below the Arley Mine of Lancashire and adjacent areas. Bull. Geol. Surv. Gt. Brit., No. 13, pp. 14–38.

MAW, G. 1869. On some raised shell-beds on the coast of Lancashire. Geol. Mag., 6, pp. 72–3.

MOORE, E. W. J. 1930. A section in the Sabden Shales on the river Darwen, near Blackburn. J. Manch. Geol. Assoc., 1, pp. 103–8.

MURCHISON, R. I. 1833. Observations on certain accumulations of clay, gravel, marl and sand around Preston, in Lancashire, which contain marine shells of existing species. Rep. Brit. Assoc. for 1832, pp. 82–3.

READE, T. Monograptus 1872. The geology and physics of the post-Glacial period as shewn in the deposits and organic remains in Lancashire and Cheshire. Proc. Liverpool Geol. Soc., Session 13, pp. 36–88.

READE, T. Monograptus 1889. On a section across the river Douglas at Hesketh Bank—A post-Glacial deposit in which were human bones. Proc. Liverpool Geol. Soc., 5, pp. 100–3.

WOOD, S. V., and HARMER, F. W. 1871. On the palaeontological aspects of the middle Glacial formations of the east of England and their bearing upon the age of the Middle Sands of Lancashire. Rep. Brit. Assoc. for 1870, pp. 90–1.

WRIGHT, W. B. 1925. In Sum. Prog. Geol. Surv. for 1924, pp. 66–9.

WRIGHT, W. B. 1934. The freshwater fauna of the Lower Coal Measures of Lancashire. Sum. Prog. Geol. Surv. for 1933, pt. 2, pp. 8–22.

WRIGHT, W. B. , SHERLOCK, R. L., WRAY, D. A., LLOYD, W., and TONKS, L. H. 1927. The geology of the Rossendale Anticline. Mem. Geol. Surv.

Chapter 2 Millstone Grit Series

Some 5000 ft of Millstone Grit Series crop out in the east of the Preston district, over an area of about sixty square miles. The rocks give rise to the moorland in the south-east, the high ground north-west of Blackburn, and the diverse topography of the country between Chorley and Pleasington. A narrow belt of Millstone Grit lies between Whittle le Woods and Heskin, but is for the most part concealed by thick superficial deposits.

The base of the Series is normally fixed at the horizon of Cravenoceras leion, i.e., at the base of the Upper Carboniferous. During the resurvey of the neighbouring Clitheroe and Nelson district this horizon could not be satis­factorily mapped, and the base of the Series was there taken at the base of the Pendle Grit some 400 ft higher (Earp and others 1961, p. 5); thus the whole of the Bowland Shale Group was included in the Carboniferous Limestone Series, as is shown on the one-inch map Sheet 68. The 1958 emended version of the one-inch map of the Preston district also shows the Bowland Shale Group as belonging to the Carboniferous Limestone Series. In fact, Cravenoceras leion has not been found in the Preston district, and there is no evidence that beds of earlier age appear at the surface within the sheet area. For the purpose of this account therefore, normal practice is followed and all the Bowland Shales that appear on the map are included in the Millstone Grit Series.

During the resurvey the top of the Millstone Grit Series was taken at the base of the Six Inch Mine, or in its absence at the base of the Gastrioceras subcrenatum Marine Band in the immediate roof of that seam. In this account the marine band is used in order to conform with current practice.

Classification

A generalized vertical succession of the Millstone Grit Series of the district is shown in (Figure 4))." data-name="images/P988345.jpg">(Figure 3) and (Figure 4), the classification used being in part lithological and in part palaeontological. The major divisions, and their relationship to the goniatite stages established by Bisat (1924, p. 40), are as follows:

Lithology

The Millstone Grit Series, at least half of which consists of shale, is characterized by the occurrence of thick and conspicuous beds of hard sandstone which are generally coarse and angular grained, and are com­monly referred to as 'grits' or gritstones. From time immemorial millstones have been made from these rocks; hence the name of the Series (Whitehurst 1778, p. 147). The sandstones are essentially aggregates of quartz, feldspar and mica, and may be classed as arkoses. They vary from fine to very coarse-grained and are commonly pebbly; the finer particles are generally angular, the pebbles rounded. False-bedding is a characteristic feature of the sandstones. More even-textured rocks, which are not usually termed 'grits', also occur.

Of the shales and mudstones, many are devoid of fossils save for plant impressions. Marine fossils have a more restricted development than the non-marine, and are found in well-defined layers, generally not more than a few feet thick—the upper part of the Sabden Shales is an exception in that it contains a thick fossiliferous development of shales and mudstones. Thin coals and seatearths are present in the upper part of the Series, where the sequence shows the imprint of cyclic sedimentation, the generalized cyclic unit being as follows: seatearth, thin coal, marine shale, non-marine shales and mudstones, sandstone, ganister and seatearth.

Bowland Shale Group

Bowland Shales crop out only in the extreme north-east of the district in the core of the Pendle Anticline; they are 200 to 300 it thick and occupy an area of about one square mile, in which exposures are few. They appear to comprise dark grey fissile shales and calcareous mudstones with sporadic thin earthy limestones and sandstones; Cravenoceras malhamense (Bisat) has been found near the top of the Group at one locality. In the district to the north-east (Clitheroe Sheet 68) the base of the Upper Carboniferous, marked by the occurrence of Cravenoceras leion, lies about 375 ft below the horizon of Cravenoceras malhamense (Earp and others 1961, p. 5), and it is therefore unlikely that Lower Carboniferous strata crop out in the Preston district.

Details

The Cravenoceras malhamense Band occupies about 10 ft of dark calcareous mudstones and shales with earthy limestone bands, which crop out [SD 6774 3201] in a small stream 570 yd N. 5° W. of Ramsgreave Hall. The fauna is given on p. 60. These measures appear to pass upwards into sandy mudstone which is capped by 2 ft of fine-grained sandstone with shale partings. The strata immediately above this sandstone are not exposed, but have been mapped as Bowland Shales on the basis of topography; it now seems likely that they are part of the Lower Wilpshire Grit, since in the railway cutting at Wilpshire just beyond the margin of the district the base of its equivalent, the Pendle Grit, is only a few feet above the Cravenoceras malhamense Band. In the stream about 400 yd. S.S.E. of the inn at Mellor Brook, sandy shales with thin sand­stone bands are exposed [SD 642 309] close below the Lower Wilpshire Grit; the thin sandstones show graded bedding from coarse to fine upwards within the thickness (1 to 2 in) of each band. L.H.T., D.P.

Wilpshire Grit Group

The Wilpshire Grit Group crops out in the Pendle Anticline north-west of Blackburn. It is 1300 to 1600 ft thick and comprises Lower Wilpshire Grit, main Wilpshire Grit and intervening shales (Figure 4))." data-name="images/P988345.jpg">(Figure 3). The Lower Wilpshire Grit, about 250 ft thick, is a well-bedded fine to medium-grained sandstone with numerous shale partings. From the topography is it inferred that a belt of shales some 200 ft thick separates this grit from the main Wilpshire Grit; but these shales are not exposed. The main Wilpshire Grit is a coarse-grained massive gritstone 800 to 1000 ft thick. It is not exposed on the northern limb of the anticline and is not seen in clear and continuous sections elsewhere; but numerous small quarries along its outcrop from Ramsgreave to Hoolster Hill show its general character.

Details

The Lower Wilpshire Grit is exposed in quarries west and north of Mellor Beacon [SD 657531291, as a massive grey and yellow, fine to medium-grained sandstone with shale partings. In Abbot Quarry [SD 649 315], 1000 yd E. 20° N. of the inn at Mellor Brook, it is worked for building stone and is a well-bedded and massive grey-white gritstone, coarse-grained below and rather finer-grained above: some beds are noticeably feldspathic. Shale partings and included pellets and flecks of shale are common. Small exposures at Mellor Brook, apparently near the base of the rock, show coarse unsorted gritstone with pebbly bands. The most westerly exposure of the Lower Wilpshire Grit is in a quarry [SD 630 303] 600 yd E. 24° S. of Samlesbury Hall (Higher), where the rock is a well-bedded medium-grained white, grey and brown sandstone with partings of dark micaceous shale.

The shales which lie above the Lower Wilpshire Grit are not exposed in this district. The next higher bed, the Wilpshire Grit, makes a marked ridge along the south side of the anticline from Ramsgreave to Hoolster Hill: numerous small quarries along this ridge show coarse to medium-grained grey and yellow gritstone with pebbly bands at some horizons. In the nose of the anticline the top of the Grit is exposed [SD 6054 2954] in Hole Brook, 1.25 miles W. 28° S. of Samlesbury Hall (Higher); these uppermost beds are fine-grained, thin-bedded grey gritty sandstones with thin shale partings.

On the north side of the anticline the Carboniferous rocks lie hidden beneath a featureless boulder-clay terrain which extends northward to the Ribble. The outcrop of Wilpshire Grit shown on the map between Myerscough and Osbaldeston is conjectural, and is based on evidence of the presence of the grit immediately beyond the north-eastern margin of the map. L.H.T., D.P.

Sabden Shales

The Sabden Shales comprise shales and mudstones with subsidiary sand­stones and thin bands of mainly argillaceous limestone; they are about 1000 ft thick and are characterized by an abundance of marine horizons. The lowest part of the sequence, comprising some 300 ft of shales with thin limestones and sandstones, is poorly exposed; a number of marine bands have been recorded from it by Moore (1930, p. 107), but the Eumorphoceras bisulcatum Band, which lies near the base in adjacent districts, has not been identified. These lowest measures are succeeded by about 270 ft of poorly fossiliferous sandy mudstones and sandstones. In contrast to the paucity of exposures of the lower part of the Sabden Shales the upper part is seen in the clearest section in Lancashire: this, the classic Samlesbury Bottoms section (see below), gives almost continuous exposure of the upper E₂, H and R₁ measures; to date more than 16 distinct fossiliferous horizons have been recognized in this sequence, and the detection of further subdivisions should be possible.

Details

In Hole Brook [SD 605 294] which enters the River Darwen about half a mile N.E. of Roach Bridge, 8 ft of sandy shales and thin sandstones are exposed immediately above the Wilpshire Grit; about 8 ft higher in the sequence are 19 ft of dark shale with thin limestones and bunions in the lower part. No fossils were found in these measures (under more favourable conditions the shales might be examined in more detail; when seen the high water-level in the brook made an exhaustive examination impossible). The succeeding measures in the Hole Brook section were not exposed at the time of the survey, but from them Moore (1930, p. 107) has recorded three marine horizons. The lowest of these was about 40 ft above the Wilpshire Grit, and comprised 6 in of hard shale with poorly preserved indeterminate marine fossils including goniatites (at Sales Wheel about six miles to the north-east the Eumorphoceras bisulcatum Band lies about 30 ft above the Wilpshire Grit, but no attempt at correlation with this band was possible from the material found in Hole Brook). The second marine band lies in 12 in of hard shale about 250 ft above the Wilpshire Grit, and the third about 20 ft higher in a thin silty limestone; the lower of these two bands contains Posidoniella sp., Anthracoceras sp., and Cravenoceras holmesi Bisat, and the fauna of the upper includes Posidoniella aff. vetusta (J. de C. Sowerby), Anthracoceras sp., Cravenoceratoides stellarum (Bisat) and Dimorphoceras (Metadimorphoceras) aff. moorei Hodson (Hudson 1944, p. 237; Hodson 1954, p. 366).

The Samlesbury Bottoms section is situated on the east bank of the River Darwen immediately north of Samlesbury Bottoms (i.e. between the points [SD 6172 2936] and [SD 6181 2909]). It has been closely studied by Mr. E. W. J. Moore, who has supplied much of the material upon which other authors have based their accounts (Bisat and Hudson 1943, pp. 397–8; Hodson 1957, pp. 13–14). Some details are as follows, and further details of this and associated sections are given on pp. 60–62. At the bend of the river north of the village, Moore (1930) recorded Anthracoceras glabrum Bisat at a horizon probably higher in the sequence than the third marine band of Hole Brook (see above). There follow in upward succession about 270 ft of poorly fossiliferous sandy mudstones and sandstones, closely overlain by two marine bands from which Moore has recorded Nuculoceras nuculum Bisat and Eumorphoceras bisulcatum Girty. These bands crop out almost due west of the chapel at Nabs Head; and between this point and the base of the Parsonage Sandstone at Samlesbury Bottoms there is almost continuous exposure of the remainder of the Sabden Shales sequence. The following composite section (see also (Figure 5)) is based on Geological Survey investigation and on the work of Moore (1930), Bisat and Hudson (1943) and Hodson (1957):

Three bullion bands yielding Homoceras subglobosum are exposed [SD 6089 2927] downstream from the above section, about 1500 yd W. of the chapel at Nab's Head and about 250 yd N.W. of Gate Cote Farm. Farther downstream the Hudsonoceras proteus Band is again exposed [SD 6040 2915] in the river bank north-east of Knights Bottom Farm, about one and a quarter miles W. of Nab's Head.

A marine band near the top of the Sabden Shales crops out in two places in the stream in Woodfold Park—[SD 6372 2886] 475 yd S. 10° E. of the Hall, and [SD 6370 2869] 630 yd S. 7° E. of the Hall. The first locality has yielded the following: Neuropteris schlehani Stur; Caneyella squamula (Brown), Dunbarella rhythmica (Jackson); Anthracoceras or Dimorphoceras sp., Homoceras striolatum (Phillips) and Reticuloceras cf. reticulatum (Phillips).

The higher beds of the Sabden Shales are also exposed [SD 6800 3081] at Ramsgreave in the north-east corner of the district in a stream 620 yd N. of Pleckgate; they yield Homoceras striolatum and Reticuloceras aff. moorei (Bisat and Hudson 1943, p. 399). L.H.T., D.P.

Kinderscout Grit Group

The base of the Kinderscout Grit Group is drawn by the Geological Survey (Earp and others 1961, p. 4) at the Homoceras magistrorum Marine Band; but since this horizon is not widely recognizable in the Preston district it has been deemed expedient for the purpose of this memoir to employ the base of the Parsonage Sandstone instead (see (Figure 4)). This leaves the important Sabden Shale sequence for consideration as a whole.

With its base thus defined, the Kinderscout Grit Group in this area has a thickness of about 1100 ft. In the Preston district the Parsonage Sandstone, the equivalent of the Todmorden Grit, is the only conspicuous arenaceous development in the Group; it is about 500 ft thick and crops out north-west of Blackburn from south of Ramsgreave to just beyond Samlesbury Bottoms. The lithology is rather variable; the rock is generally a fine- to coarse-grained sandstone with numerous shale partings, but in places it includes lenses of massive, unsorted, coarse-grained gritstone. Marine shales have been found apparently close above the Parsonage Sandstone, but the actual relationship is obscured by faulting. A marine band has also been recorded about 350 ft above the sandstone north-west of Blackburn.

The absence of thick arenaceous beds from that part of the group which lies above the Parsonage Sandstone is due to the thinning out of the Kinderscout Grit in the area north-east of Blackburn, as has been described in the Rossendale Memoir (Wright and others 1927, p. 17).

Details

The Parsonage Sandstone is fairly well exposed over the greater part of its outcrop. In the brook 100 yd S.E. of Yew Tree Inn, Billinge, 20 ft of grey and dark grey gritty sandstone with shale partings are exposed [SD 659 294], the basal beds being coarse and angular grained. A similar development is seen [SD 657 290] in the stream 230 yd W. 15° S. of Billinge Scar. Farther west shale partings appear to be less important. In the stream south of Woodfold Hall some 30 ft of fairly coarse pale coloured gritstone crop out [SD 6362 2841]. On the north-east side of the mill at Samlesbury Bottoms over 20 ft of coarse gritstone is visible in an old quarry [SD 620 290].

Marine shales which appear to lie just above the Parsonage Sandstone are seen at two localities; but in each case faulting partially obscures the relationship between them and the Parsonage Sandstone. The shales are exposed [SD 6241 2864] on the right bank of a small tributary of the River Darwen at a point 700 yd S. 18° E. of the chapel at Nab's Head; here black sandy shales with few fossils are overlain by 9 in of compact shale, 1 to 2 in of ironstone and 15 in of dark soft shales, succeeded by dark shales. The following fossils were collected: from the compact shale, plant fragments; Caneyella squamula, Posidonia sp.; Anthracoceras or Dimorphoceras sp., Homoceras striolatum, Reticuloceras reticulatum, R. davisi (Foord and Crick), and an orthocone nautiloid: from the ironstone rib, Caneyella squamula; Anthracoceras or Dimorphoceras sp., Homoceras striolatum, and Reticuloceras reticulatum: and from the dark shales at the top of the section, Caneyella cf. squamula, Dunbarella aff. rhythmica; Anthracoceras or Dimorphoceras sp., and Reticuloceras reticulatum. At the second locality [SD 6182 2888], on the north bank of the River Darwen 540 yd S.W. of the chapel at Nab's Head, the marine band is also divisible into three parts. The following fossils have been identified: from the lower part, plant fragments; Caneyella cf. squamula, Dunbarella sp.; Homoceras striolatum, Reticuloceras reticulatum: from the middle (a bullion), Dimorphoceras (Paradimorphoceras) looneyi (Phillips), Homoceras striolatum, Reticuloceras reticulatum, an orthocone nautiloid, Thoracoceras?: and from the upper part, Caneyella cf. squamula, Dunbarella rhythmica, Dunbarella sp.; Anthracoceras or Dimorphoceras sp., Homoceras striolatum, Reticycloceras sp.

Shales and thin sandstones above the Parsonage Sandstone are exposed in Alum House Brook south of Woodfold Park. They are also seen in the stream about 300 yd W. of Beardwood Hall; here, almost due west of Beardwood Hall, two ribs of soft silty sandstone 2 in thick crop out [SD 6596 2884] below a marine band which has yielded the following: Caneyella sp., Dunbarella rhythmica; Homoceras striolatum, Anthracoceras or Dimorphoceras sp., Reticuloceras cf. reticulatum, and an orthocone nautiloid. Bisat and Hudson (1943, p. 416) also record Reticuloceras cf. regularum Bisat and Hudson from this locality. L.H.T., D.P.

Middle Grit Group

The Middle Grit Group extends from the base of the Reticuloceras gracile Marine Band to the base of the Gastrioceras cancellatum Marine Band (Figure 4). In the Preston district it is about 1600 ft thick and includes a number of well-developed arenaceous horizons and several marine bands.

In the area west of Blackburn the Alum Crag Grit, 300 to 400 ft thick, lies close above the basal marine band. It is well developed about Alum Crag, a mile north of Hoghton Bottoms, but appears to thin rapidly when followed eastwards towards Blackburn, and the base of the grit is markedly transgressive, cutting across underlying bedding at sharp angles—features which suggest that it may represent a large washout. Such a grit is not known at this horizon elsewhere in the Preston district; its occurrence contrasts sharply with the failing of the Kinderscout Grit referred to above, but is on a parallel with the general south-westerly thickening of the Middle Grits, a fact established early in the resurvey of the Millstone Grit Series of Lancashire (Tonks and Wright 1924).

The lowest measures of the Middle Grit Group normally consist of mudstone and shale with thin sandstone bands. These are succeeded by the Revidge Grit or its equivalents—the Fletcher Bank and Helmshore grits. The Revidge Grit is developed between Blackburn and Whittle le Woods, and probably to the south-west. North of Blackburn it is 400 to 600 ft thick, but at Whittle le Woods it is only about 375 ft. It is a massive current-bedded coarse-grained gritstone, commonly pebbly. South of Blackburn a shale parting is developed near the top; the beds below and above this parting are known respectively as the Fletcher Bank and Helmshore grits.

The Fletcher Bank Grit is similar in lithology to the Revidge Grit, but contains impersistent shale partings in some areas. It is about 400 ft thick.

A thin coal or fireclay is usually found on top of the highest bed, and is succeeded by some 25 ft of sandy shale with a thin Lingula band: above these shales lies the Helmshore Grit, which is much finer grained than the Fletcher Bank Grit and is not known to contain pebbles; in many places it is a flaggy fine-grained sandstone. It is about 60 ft thick. Its top is also commonly marked by a thin fireclay or rootlet bed.

The shales which overlie the Revidge and Helmshore grits are characterized by four marine horizons—in upward succession, two with Reticuloceras metabilingue W. B. Wright, one with R. superbilingue Bisat and one with Pygmaeoceras sigma (W. B. Wright). In the Preston district the two lowest horizons have been found in superposition in one borehole and in a stream section west of Blackburn, where they are closely overlain by the Hazel Greave Grit, here from 40 to 60 ft thick. This bed is represented at Ryal Fold by 10 ft of arenaceous measures, but is entirely wanting elsewhere in the south-east of the district.

In the area around Blackburn little is known of the upper part of the Middle Grit Group. The several beds have been mapped by surface features, supported by the evidence of exposures north-east of Blackburn and south of Brindle.

The Brooksbottoms Grit lies about 80 ft above the Pygmaeoceras sigma Marine Band. It is generally in two leaves separated by up to 50 ft of shales and mudstones. The lower leaf is a well-jointed flaggy sandstone up to 40 ft thick; the upper leaf is commonly similar to the lower, but in places is fairly coarse, and in the south-east of the district it is from 50 to 70 ft thick. The Brooksbottoms Grit is well developed around Belmont and west of Chorley; followed north from Belmont the lower sandstone appears to thicken towards Great Hill, but beyond this it fails, and is absent about Brinscall. Neither sandstone is developed in the Blackburn area. The Brooksbottoms Coal, 12 in thick, lies close above the upper sandstone; it is not developed around Brinscall. The Holcombe Brook Grit does not show the same abrupt changes in lithology as in Rossendale. In the south-east it comprises two flaggy sandstones each capped by a thin coal. The lower sandstone, some 20 to 30 ft thick, is only developed in the Belmont, Rivington and Anglezarke area; the upper, although usually only 6 to 10 ft thick, is more persistent. The coal above it, the Holcombe Brook Coal, has been extensively worked; it is usually from 12 to 24 in thick, but in workings near Withnell Mill it is said to have been 4 ft thick. The highest measures of the Middle Grit Group consist of from 12 to 15 ft of unfossiliferous shales and mudstones between the Holcombe Brook Coal and the Gastrioceras cancellatum Marine Band. D.P.

Details

The Reticuloceras gracile Marine Band is exposed [SD 6368 2805] on the east side of Alum Crag, 90 yd N.N.E. of Alum Scar and about 2000 yd S.E. of the chapel at Nab's Head. It has yielded the following: Caneyella sp., Dunbarella cf. speciosa (Jackson); Anthracoceras or Dimorphoceras sp., Reticuloceras gracile Bisat late mut.; and fish debris. The marine band is succeeded by some 25 ft of shale, and resting on the shale is about 20 ft of massive gritstone, the Alum Crag Grit. This bed makes a fine show in the Darwen Gorge north of Hoghton Bottoms where it is a massive to flaggy, coarse to fine gritstone with subordinate bands of sandy shale. The feature made by the Alum Crag Grit can be traced eastwards with diminishing prominence from Samlesbury Bottoms to south of Billinge. The base of the Grit is markedly trans­gressive; in Alum Crag and in sections along the river farther west the base in places cuts down into the underlying shales to more than 30 ft below its general level. In a sewer trench [SD 6322 2771] 550 yd S.W. of Alum Crag, shale with obscure marine fossils was proved resting on gritstone, but nowhere else is the top of the Alum Crag Grit known.

The next higher beds to be seen at the surface are flaggy gritstones west of Billinge Hill and sandy shales and gritty sandstones exposed [SD 604 262] in a stream half a mile S. of Straits. These apparently lie immediately under the main bed of the grit above. This, the Revidge Grit, attains a thickness of approximately 600 ft north-west of Blackburn, and is generally a coarse-grained massive current-bedded rock, often seen to be pebbly. It is well exposed in large quarries south-west of Billinge Hill, north of Hoghton Towers, and west of Hoghton. It makes a well-defined ridge from the north-west side of Blackburn to and beyond Hoghton, through which the River Darwen cuts in the magnificant gorge of The Horr [SD 628 263], south of Hoghton Bottoms; here, on the west side of the river, 100-ft faces of grit are visible, and spectacular potholed surfaces may be seen in the river bed when the water-level is low. There are good sections of the grit in Duxon Hill Quarry [SD 611 258] 400 yd W. 20° S. of Hoghton church, the west face showing approximately the following (from base to top): 15 ft massive gritstone (base not seen), 9 ft flaggy gritstone, 5 ft sandy shale with sandstone bands, 8 ft flaggy gritstone and sandstone, 40 ft massive gritstone (top not seen). The flaggy gritstones and sandy shales form part of a big lens in the massive gritstone; they are not seen in the east and south faces of the quarry. North of Hoghton the Revidge Grit crops out in the middle of a small syncline. Quarries near Stanley Grange and north of Straits show coarse massive pebbly gritstone, which is stained red and purple in some beds. The Revidge Grit has been worked at Hough Hill [SD 592 230] and Denham Hill [SD 591 228] about a mile N.N.E. of Whittle le Woods, where it is a coarse current-bedded and occasionally pebbly gritstone. It has also been quarried extensively at Whittle le Woods. L.H.T., R.C.B.J.

In the south-east the Fletcher Bank Grit, the Helmshore Grit and the shale between them are equivalent to the Revidge Grit. The Fletcher Bank Grit is generally a current-bedded coarse pebbly gritstone, the dominant pebbles being of white vein-quartz, but in some localities the higher beds contain few or no pebbles; the top is often found to be a ganister and to be overlain by a thin coal. Beds of shale up to 3 ft thick occur in the grit, but are impersistant and variable in thickness. The grit is well exposed in quarries and streams east of Brinscall, and thence southwards along the fault escarpment to beyond White Coppice. Near that place the shale bands are well exposed in quarries. On the grit escarpment overlooking White Coppice several millstones cut from the gritstone are visible [SD 622 188]. East of Anglezarke Reservoir the grit is well seen in Leicester Mill Quarry [SD 619 163] (Plate 2A), where the floor of the quarry is formed by one of the shale bands. The top of the grit is also exposed here, and the overlying coal and thin shales are seen resting on its irregular surface. East of the quarry the grit is well seen in the River Yarrow and in its northern tributary, Limestone Brook.

On the east of the moorland area the Fletcher Bank Grit is rarely exposed; the only good section [SD 6743 1613] is at Belmont in the gorge 350 yd N. 15° E. of the church, where current-bedded coarse grit is overlain by 42 in of seatearth, 2 to 4 in of shaly coal, 6 in of seatearth, 3 in of coal and 6 in of mudstone with rootlets. The grit in this area was penetrated by two boreholes, one [SD 6661 1669] 1200 yd N. 40° W. of Belmont church, the other [SD 6785 1512] at Lower Heights 950 yd S. 36° E. of Belmont church: these show it to be about 300 ft thick, the beds below comprising a series of sandstones and mudstones so that it is difficult to determine the exact base.

The measures between the Fletcher Bank and Helmshore grits are exposed [SD 6590 2114] in the Roddlesworth valley 150 yd N. of Halliwell Bridge and about two miles E. 9° S. of Brinscall Station (Plate2B). Here the Fletcher Bank Grit is overlain by 3 ft of coal and fireclay, 20 ft of shales and thin sandstones, and above them the Helmshore Grit. A 0.5-inch micaceous mudstone about 10 ft above the Fletcher Bank Grit yielded Lingula mytilloides J. Sowerby, Orbiculoidea cf. nitida (Phillips) and a rhizodont fish scale. Shales and thin sandstones between the two grits are also seen in a stream [SD 628 188] 1650 yd E. 30° N. of the head of Anglezarke Reservoir, and in the River Yarrow [SD 6423 1626] one and a half miles east of Anglezarke Reservoir. They were found to be about 30 ft thick in the Lower Heights Bore and yielded Lingula mytilloides and cf. Nuculana sp.near their base. Lingula mytilloides and Sanguinolites ovalis Hind were found at this horizon in the Star Paper Mills 'B' Borehole (p. 124).

The Helmshore Grit is about 60 ft thick and is a yellow flaggy sandstone or fine-grained gritstone. It is best exposed in the River Roddlesworth immediately south of Higher Roddlesworth Reservoir, and around Hempshaws on the River Yarrow. Exposures on the moors are masked by peat, but the grit forms a readily-recognized feature, particularly north of Great Hill. In the Lower Heights Bore it comprised about 40 ft of grey sandstone, shaly in parts, with a number of mudstone partings. R.C.B.J.

At Heskin, W.S.W. of Chorley, the Revidge Grit—the lowest horizon known west of the Great Haigh Fault—is exposed in an old quarry [SD 5194 1553] about 700 yd E. of the Old Hall; it is a white coarse pebbly gritstone. In the stream just to the south are seen flags which overlie the coarse gritstone and are probably the equivalent of the Helmshore Grit. Identification of the rock as the Revidge Grit is based on its lithology and its relationship to the Holcombe Brook measures. A.E.Monograptus

Shales above the Helmshore Grit are well exposed in the small stream [SD 650 165] at the head of the River Yarrow about 300 yd N.E. of Hempshaws, where the following section was measured:

The R. metabilingue Band yielded the following: Crurithyris sp.;Dunbarella sp. nov.; an indeterminate gastropod; Reticuloceras cf. bilingue (Salter), and R. meta­bilingue Wright. The fauna of the superbilingue Band was as follows: Dunbarella sp., Posidonia sp. juv.; Anthracoceras?, Homoceratoides aff. divaricatus (Hind), Pygmaeoceras [Gastrioceras?] sigma (Wright), and Reticuloceras superbilingue Bisat. The fossils occurring in the sigma Band comprised Pygmaeoceras sigma almost exclusively, only Lingula mytilloides and fish fragments accompanying it.

A metabilingue band is well exposed [SD 6283 1636] in a stream near the old lead mines half a mile east of Leicester Mill Quarry, where it is faulted down against the Fletcher Bank Grit. Here the fauna extends through 19 ft of shale and includes the following: Dunbarella sp., Posidonia cf. insignis (Jackson); Anthracoceras sp., Pygmaeoceras cf. sigma, Reticuloceras metabilingue, orthocone nautiloids and Huanghoceras sp.The superbilingue Band is also present, but its relationship to the beds above and below is obscure.

The sigma Band crops out [SD 622 159] at the foot of the shale bluff beside the road, 350 yd N. of the S.E. corner of Anglezarke Reservoir; 9 in of dark platy mudstone yield Lingula mytilloides (at the base), with Posidonia aff. insignis, Posidonia sp.juv. and the goniatites Homoceratoides sp.and Pygmaeoceras sigma. It is also exposed [SD 6578 1792] in a stream three-quarters of a mile N.N.W. of Bromiley; it yielded the following: Caneyella multirugata (Jackson), Posidonia insignis; Pygmaeoceras sigma, Thoracoceras?, an orthocone nautiloid; and Palaeoniscid scales.

Farther north three marine bands crop out in the several small streams which flow from Ryal Fold, west of Darwen Hill, into the River Roddlesworth. A metabilingue band is exposed [SD 6620 2152] 280 yd S.S.E. of the S.E. end of Higher Roddlesworth Reservoir in a stream south-west of Ryal Fold, where 1 ft of hard grey mudstone yields the following: Aviculopecten sp., Caneyella sp., Dunbarella sp.; Anthracoceras sp., Reticuloceras metabilingue, and an orthocone nautiloid. Higher in this section, about 100 yd upstream and 360 yd S. 36° E. of the S.E. end of the reservoir, the sigma Band is exposed [SD 6630 2149]; in addition to Pygmaeoceras sigma it yields only Lingula mytilloides and Posidonia insignis. In the next stream to the north the superbilingue Band was found in a section [SD 6626 2170] 160 yd E. 20° S. of the S.E. end of the reservoir; from it the following have been obtained: Caneyella cf. rugata (Jackson), Dunbarella sp.;Anthracoceras sp., cf. Gastrioceras lineatum Wright, Homoceratoides sp., and Reticuloceras superbilingue.

Two of the marine bands are visible in the stream entering below the dam of Higher Roddlesworth Reservoir. A metabilingue band, with its characteristic fauna, occurs [SD 6573 2225] 100 yd W. 18° N. of the northern end of the dam and 12 yd above the waterfall: upstream the superbilingue Band is exposed [SD 6576 2230] 80 yd N.W. of the northern end of the reservoir. R.C.B.J.

In the area west of Ryal Fold 10 ft of sandstone, ganister and siliceous ironstone, associated with coal smuts, is present between a band with R. metabilingue and the superbilingue Band; this is an attenuated representative of the Hazel Greave Grit of the area of Sheet 76 north and east of Blackburn (Wright and others 1927, pp. 20–1). South-west of Blackburn 20 ft of hard grey gritstone cropping out [SD 5855 2563] in the north-east bank of the stream 1420 yd W. of Jack Green and one and a half miles E. of Bamber Bridge is presumed to represent this grit. Shales between this same bed and the Revidge Grit are exposed in Mill Brook, one and three quarter miles E. of the Smithy at Bamber Bridge: two R. metabilingue bands are seen in this section, the upper [SD 5945 2556] 130 yd E. of Mill House, and the lower [SD 5951 2549] 60 yd S.S.W. of Turf House. R.C.B.J., L.H.T.

A marine band with Reticuloceras metabilingue was found about 130 ft above the Revidge Grit in the Wiggins Teape No. 2 Borehole (p. 128) at Withnell Fold. The superbilingue Band was 42 ft higher in the borehole, and contained the following: Lingula mytilloides; Caneyella cf. multirugata; Anthracoceras or Dimorphoceras sp., Reticuloceras superbilingue; and Palaeoniscid scales. A marine horizon 10 ft above yielded Gastrioceras sp.with a cancellate ornament, and Hindeodella sp.;this might represent the sigma Band, but the characteristic Pygmaeoceras sigma was not found. Unidentified goniatites occurred immediately above the Helmshore Grit in the Star Paper Mills 'B' Borehole (p. 124). Reticuloceras metabilingue was found from 7 to 11 ft above the Grit and was here accompanied by the following: Caneyella sp., Posidonia sp.;and Anthracoceras sp. Reticuloceras metabilingue was also found 42 to 54 ft above the Helmshore Grit. The superbilingue and sigma bands were not proved, but poorly preserved Reticuloceras sp.and Lingula mytilloides were collected 44 ft and 54 ft respectively above the higher metabilingue horizon. D.P.

Shaly beds above the sigma Band are exposed in the sections near Ryal Fold described above. Farther south they are well exposed in the deep gorge [SD 629 154] at the western end of Dean Brook, half a mile north of Rivington church, where some­what platy blue shales are capped by the lower leaf of the Brooksbottoms Grit. The shales can also be seen in the steep slopes above Hempshaws and Bromiley, north­west of Belmont, and on the north face of Great Hill. In the stream section [SD 651 165] 500 yd N.E. of Hempshaws over 30 ft of blue-grey shaly mudstone, with ironstone in the lower part, is visible above the sigma Band; the section is terminated by a fault.

The Brooksbottoms Grit generally comprises two leaves separated by argillaceous strata up to about 50 ft thick. The lower leaf—a jointed flaggy sandstone—and the overlying shales are exposed in the sides of Dean Brook gorge [SD 629 154] below the waterfall. The Grit has been worked just east of the southern embankment of Yarrow Reservoir, 10 ft of flags with shaly partings being exposed in a small quarry [SD 6271 1534]. On the slopes above Hempshaws and Bromiley, and at the top of Great Hill, the Grit is much thicker than to the south-west, and gives rise to a marked feature. Both leaves of the Brooksbottom Grit and the intervening shales and mudstones are exposed near Belmont in Hill Top Wood [SD 673 156] about 200 yd S. of St. Peter's Church, and also [SD 669 157] 600 yd W. 15° S. of that church, in the stream draining into Wards Reservoir; the lower leaf is a well-bedded yellow sandstone and the upper a coarse false-bedded gritty sandstone. The upper sandstone is well exposed [SD 6314 1544] in Dean Brook above the waterfall, 1060 yd E. 8° S. of the south end of Anglezarke Reservoir; also in the disused Rivington Moor Quarry [SD 646 155] on the south side of the Belmont–Rivington road, 1800 yd E. 35° N. of Rivington Hall, where it is a flaggy sandstone. It is well seen half a mile east of Anglezarke Reservoir, where the River Yarrow enters Yarrow Reservoir, 40 ft of measures varying from flaggy sandstone to coarse current-bedded gritstone being exposed in the floor and sides of the valley. R.C.B.J.

A borehole [SD 6136 1996] just west of White Coppice was drilled to the Brooksbottoms Grit: the hole terminated in the lower leaf, having penetrated it to a depth of 14 ft; the upper leaf, some 20 ft above the lower, comprised 40 ft of mainly white sandstone with sandy mudstone bands. In the Wiggins Teape No. 2 Borehole (see p. 128) three sandstones were proved at about the horizon of the Brooksbottoms Grit: 13.5 ft of sandstone were overlain by 7 ft of sandy mudstone and 17.5 ft of sandstone and shale; above were found some 50 ft of mudstone containing a number of mussel-bands and a further 7.5 ft of sandstone and shale. Carbonicola sp.cf. pseudorobusta Trueman and C. sp. nov. [tumid] were collected 16 ft above the base of the above mudstone; fragmentary Carbonicola sp.were found 13 ft higher, and C. ornata Trueman and C. cf. pseudacuta Trueman [juv.] occurred near the top of the mudstone.

Mudstone exposed [SD 6171 1914] between two faults in the right bank of the stream leaving the reservoir 950 yd E. 33° S. of Heapey Station yielded a similar fauna to that of the lowest band from the Wiggins Teape Bore (see above); Carbonicola sp.cf. pseudorobusta, C. cf. pseudacuta [juv.] and C. sp. nov. [tumid] have been collected here. This evidence suggests that this mudstone and the overlying sandstone belong to the Brooksbottoms measures, and not to the Haslingden Flags as shown on the one-inch map. The occurrence of Gastrioceras cumbriense Bisat recorded by R. C. B. Jones during the survey was not confirmed by subsequent collecting. D.P.

Farther north, in the area south and west of Ryal Fold, the Brooksbottoms Grit is again in two leaves. The lower leaf is not exposed; the upper is visible [SD 6640 2172] 260 yd W. 20° N. of Ryal Fold, where at least 25 ft of sandstone with shale partings near the top lies close to a fault. In small quarries alongside the Belmont road west and south of Ryal Fold, the upper leaf is a fine-grained massive current-bedded gritstone. R.C.B.J.

South-west of Chorley the Brooksbottoms Grit has been quarried in Hurst House Delf [SD 519 150], 800 yd S.E. of the Old Hall, where about 45 ft of yellowish-white compact false-bedded gritstone are visible. In the Euxton House Bore (see p. 114) it was shown to comprise 101 ft of red and purple sandstone, flaggy at the base. North of Chorley it is a fine-grained highly siliceous sandstone, much finer than the rock at Hurst House Delf. It is exposed in the quarries [SD 5902 2065] 100 yd W. and [SD 5961 2056] 570 yd E. 10° S. of the canal junction at Johnson's Hillock. A.E.Monograptus

The Brooksbottoms Coal lies on top of or close above the Brooksbottoms Grit. It is exposed [SD 6693 1564] in Great Gutter, 500 yd W. 27° S. of St. Peter's Church, Belmont, the Brooksbottoms Grit being overlain by 1 to 2 in of seatearth and 12 in of coal, succeeded by mudstones and sandy mudstones. The coal is also exposed [SD 6634 1592] in a quarry 1100 yd W. 5° N. of St. Peter's Church. Farther north the coal, again 12 in thick, is visible [SD 6659 2128] in a stream section 400 yd S. of Ryal Fold; it is overlain by 8 ft of blue slightly sandy mudstone with ironstone. South of Wheelton and around Brinscall occasional boreholes confirm the conclusion drawn from the somewhat obscure exposures that the Brooksbottoms Coal is absent here­abouts, but to the west in Wiggins Teape No. 2 Borehole it was recorded as 5 in thick. The seam was about 6 in thick in the bore near White Coppice. R.C.B.J., D.P.

At Heskin the Brooksbottoms Coal, about 12 in thick, is exposed [SD 5203 1493] in the stream south of Hurst House Delf, 920 yd S. 33° E. of the Old Hall; it rests on the ganister-like top of the Brooksbottoms Grit, and is overlain by shales with fish scales near their base. Above the shales with fish scales lie contemporaneously contorted beds resembling those described by Cope (1946). A 4-in cannel proved in the Euxton House Bore, about 8 ft above the Brooksbottoms Grit, probably represents the Brooksbottoms Coal. A.E.Monograptus

The Holcombe Brook Grit is well exposed in Dean Brook, where it comprises two flaggy sandstones, both overlain by coals, the higher of which is the Holcombe Brook Coal: the lower sandstone, 20 to 30 ft thick, crops out below Sparks Bridge [SD 6335 1532], 1000 yd N. of Rivington Hall; and the upper, 6 to 10 ft thick, in the sides of the valley upstream. Fine-grained flaggy sandstone in the small quarry [SD 6311 1583] just east of Morris House 900 yd E. 20° N. of the south end of Anglezarke Reservoir is probably the lower of the two sandstones. About a quarter-mile N.N.E. of Manor House the two sandstones crop out in the lane [SD 619 175] where it descends to the head of Anglezarke Reservoir. In the borehole near White Coppice the Grit was represented by 28 ft of arenaceous measures, but to the north in Wiggins Teape No. 2 Borehole only 13.5 ft of sandstone was recorded. In some areas around Withnell Fold, Wheelton and Brinscall the Grit appears to be either absent or replaced by a sequence of thin jointed sandstones and shales. West of Chorley the Holcombe Brook Grit is not exposed, but in Euxton House Bore (p. 114) it was represented by 15.67 ft of mainly flaggy sandstone. R.C.B.J., D.P.

The Holcombe Brook Coal is exposed [SD 6429 1540] in Dean Brook, 1300 yd N. 33° E. of Rivington Hall, where 24 in of coal underlain by 3 in of fireclay rest on the ganister-like top of the upper leaf of the Holcombe Brook Grit. It is again visible [SD 6195 1746] in the lane a quarter-mile N.N.E. of Manor House. Beside the brook [SD 613 184] a quarter-mile north of Anglezarke Reservoir the coal was formerly worked under the name Margery Mine—not to be confused with the Margery Mine of the Lower Coal Measures of the Horwich area—and varied in thickness from 13 to 17 in. It was also worked farther north at Withnell Mill where it was said to be 48 in thick, but in Wiggins Teape No. 2 Borehole, about two miles to the west, a thickness of only 4 in was recorded. A 5-in coal about 14 ft below the Gastrioceras cancellatum Marine Band, probably the Holcombe Brook Coal, is exposed [SD 5999 2151] on the south side of the canal, 400 yd N. 10° W. of the crossroads at Wheelton. At Heskin a line of old workings south-east of Hurst House Delf marks the outcrop of the Holcombe Brook Coal, not there visible. In the Euxton House Bore it was 13 in thick and rested on some 3 ft of seatearth. Shales and mudstones from 12 to 15 ft thick, lying between the Holcombe Brook Coal and the Gastrioceras cancellatum Marine Band, are seen above the 'exposures of the coal. R.C.B.J., A.E.Monograptus, D.P.

Rough Rock Group

The Gastrioceras cancellatum Marine Band at the base of the group is well developed; and is well exposed, partly due to the working of the under­lying Holcombe Brook Coal. Within the marine band a tripartite faunal sequence can be recognized, comprising a lower division characterized by the Gastrioceras branneroides fauna, a middle division with G. cancellatum, and an upper with G. crencellatum. The three divisions are not commonly found together, and the complete sequence has only been recorded at one locality in the Preston district.

Over much of the district the mudstones above the basal marine band pass upwards into a series of mainly flaggy sandstones, frequently found to be interbedded with mudstones. These, the Lower Haslingden Flags, show their maximum development west of Chorley, where a thickness of 246 ft has been proved. Around Blackburn they are 140 to 180 ft thick, but they fail towards the south-east of the district; around Wheelton they are very shaly; and on Winter Hill at Belmont, in the extreme south-east, they are not developed, 100 ft of mudstone lying between the G. cancellatum Marine Band and the G. cumbriense Marine Band which marks the top of the Lower Haslingden Flags (see (Figure 6)).

The G. cumbriense Marine Band has been recognized in the south and east of the district, but it has not been found in the Blackburn area though known in the district to the north-east (Earp and others 1961, p. 112). The Upper Haslingden Flags which overlie the marine band are generally shaly in character. They appear to be wanting at Blackburn, but are present close below the Rough Rock to the south-east. They reach a maximum thickness of 250 ft on Counting Hill south of Belmont, and there 50 to 80 ft of mudstone lie between them and the marine band below. In the west they are thin, less than 100 ft of them having been proved west of Chorley. Over much of their outcrop the Upper Haslingden Flags are directly overlain by the Rough Rock. In the south-west and parts of the south-east, however, the two may be separated by as much as 50 ft of mudstone with sporadic Anthraconaia bellula (Bolton).

The lower leaf of the Rough Rock shows little variation in thickness or lithology. Around Blackburn and north of the moorland area it is 60 ft thick; on Rivington and Smithills moors it has a uniform thickness of 30 ft; west and south-west of Chorley it is from 20 to 40 ft thick, being thinnest at Wright­ington. It is a coarse feldspathic gritstone, commonly containing small quartz pebbles, and is usually white or yellow (except in the south-west where in many places it is red).

The Sandrock MineIn Lancashire coal seams are, by tradition, called 'Mines'., which overlies the lower leaf of the Rough Rock, shows considerable variation but is almost everywhere present, though it has not yet been found in a small area north of Withnell. Around and south of Blackburn it is only a few inches thick; on Rivington and Smithills moors it comprises two workable seams separated by argillaceous measures up to 21 ft thick; farther west in the Chorley and Euxton areas the seam is from 8 to 50 in thick, but to the south it appears to be split, and the two leaves may be as much as 20 ft apart (see p. 29). The upper leaf of the Rough Rock is much more variable than the lower; around Blackburn its thickness is less than 10 ft; on Smithills Moor in the south-east it appears to be about 35 ft thick, but on the adjacent Rivington Moor it is absent; in the Chorley and Euxton areas it is from 18 to 60 ft thick, but it is absent around Wrightington where the Sandrock Mine is overlain by mudstones which yield a characteristic fauna of non-marine lamellibranchs.

The Six Inch Mine, whilst generally recognizable from its position below the Six Inch Mine Marine Band, is usually only a few inches thick; it may indeed be absent from some areas. It has the exceptional thickness of 14 in at Wrightington and in this general area a non-marine fauna has been found in the overlying mudstones. D.P.

The Gastrioceras cancellatum Marine Band is exposed [SD 6435 1538] in Dean Brook, 150 yd S. of Higher House, and 2 miles W. of Belmont; here 15 in of grey-black shaly mudstone yield the middle or cancellatum fauna, which includes the following: Caneyella multirugata, Dunbarella sp.; Gastrioceras cancellatum Bisat, G. cf. crencellatum Bisat [rare], Reticuloceras superbilingue; and fish debris. The upper or crencellatum fauna is exposed [SD 6623 1992] 60 yd W.N.W. of Hollinshead Hall, about three miles north of Belmont. The following were collected: Caneyella sp.; Agastrioceras carinatum (Frech), Anthracoceras sp. and Gastrioceras crencellatum. A quarter-mile N. of the head of Anglezarke Reservoir only Lingula mytilloides has been found above the Holcombe Brook Coal; farther north in the disused brick-pit [SD 631 221] at Withnell Mill no marine fossils were obtained at this horizon although dark platy shale of typically marine appearance is exposed. The most important section [SD 5999 2151] of the band is 400 yd N. 10° W. of Wheelton crossroads south of the canals, where the three faunas are present within the small thickness of 3 ft 8 in; the marine band comprises 12 in of hard greyish mudstone (Bed A), overlain by 8 in of black shaly mudstone (Bed B), 6 in of black mudstone (Bed C), and 18 in of mudstone and shale (Bed D). Bed A appears to contain a poorly-preserved branneroides fauna; it yields Gastrioceras branneroides? Bisat and Stroboceras? accompanied by Posidonia sp.Beds B and C yield the cancellatum s.s. fauna comprising the following: Caneyella multirugata, C. cf. multirugata, Dunbarella elegans (Jackson), D. sp.; Gastrioceras cancellatum and Reticuloceras superbilingue. Bed D contains the following crencellatum fauna: Caneyella sp., Dunbarella sp.; Agastrioceras carinatum, Gastrio­ceras crencellatum; and Palaeoniscid scales. Homoceratoides aff. divaricatus (Hind) was found loose in the section. A little to the north the cancellatum s.s. fauna was obtained from an exposure [SD 5998 2187] 750 yd N. 18° W. of St. Paul's Church, Wheelton, near the top of the right-hand bank of the River Lostock. R.C.B.J.

South-west of Chorley the G. cancellatum Marine Band is exposed [SD 5203 1486] about 12 ft above old workings in the Holcombe Brook Coal in Howe Brook, 1560 yd N.N.W. of Wrightington church. There it yields the crencellatum fauna including the following: Caneyella multirugata, Dunbarella elegans; Agastrioceras carinatum, Anthracoceras sp., and Gastrioceras crencellatum. Above the marine band are beds of contorted shale, similar to those described by Cope (1946) above marine bands in the South Pennines. The log of Euxton House Bore (p. 114) shows bullions and a 54-in shell bed at this horizon. A.E.Monograptus

Mudstones above the marine bands are visible in a gulley [SD 661 151] on the north of Winter Hill, 1600 yd W. 30° S. of St. Peter's Church, Belmont. Some 87 ft of mainly pale grey soft mudstone are exposed, and are succeeded by the Gastrioceras cumbriense Marine Band, the Lower Haslingden Flags being absent. In the disused brick-pit [SD 631 221] at Withnell Mill dark platy shales of marine type are overlain by more than 36 ft of slightly sandy shales and mudstones. R.C.B.J.

In the area west and south-west of Chorley the mudstones above the G. cancellatum Marine Band are not well exposed, but sporadic sections are to be seen in the stream [SD 521 148] south-east of Hurst House Delf and in the Yarrow valley [SD 537 179] about a mile west of Bolton Green. The Euxton House Bore (p. 114) proved about 86 ft of mudstone between the marine band and the base of the Lower Haslingden Flags.

The Lower Haslingden Flags are in two leaves over much of the eastern part of the district, and are well developed around Sunnyhurst. Just east of the margin of the district the upper leaf is well exposed in a quarry [SD 683 225] 300 yd E. of Sunnyhurst, where over 25 ft of massive fine purple sandstone with a few 'thin shale partings lie below the Gastrioceras cumbriense Marine Band. Hard greenish flaggy sandstone visible in a small quarry [SD 6670 2268] 1100 yd S.W. of St. Stephen's Church, Chapels, and in the stream [SD 659 234] immediately west of that church, have been shown on the map as Lower Haslingden Flags, as has 20 to 30 ft of ripple-marked flaggy sandstone exposed [SD 646 229] in the River Roddlesworth 200 yd N.W. of Red Lee. Since the Gastrioceras cumbriense Marine Band has not been found in association with these sandstones, and since the horizon of marine shales cropping out close-by is in doubt (see below), there is uncertainty as to the horizon of these arenaceous measures. About 2 miles to the south-east, on the western slopes of Cartridge Hill, there is little if any Lower Haslingden Flags; stream sections here show shales, sandstones and sandy shales, but again the Gastrioceras cumbriense Marine Band has not been found hereabouts, so there is doubt as to how much of the succession represents the horizon of the Lower Haslingden Flags.

Flaggy sandstones are exposed around Withnell Fold, but here also the marine band has not been found. About half a mile south-east of Withnell Fold 20 ft of shaly flags and sandy mudstone with some ripple-marked beds are visible in a stream section [SD 619 223] about half a mile long. Small exposures of flaggy sandstone lie in the valley of the River Lostock. From Wheelton to south of Heapey the Lower Haslingden Flags form a considerable spread, and are well seen in old quarries [SD 607 214] about 600 yd E.N.E. of St. Peter's Church, Wheelton, where up to 12 ft of flaggy sandstone is visible. The rock is also exposed in old quarries [SD 604 205] about 300 yd E. of Heapey church.

The map purports to show Lower Haslingden Flags forming the valley floor from Knowley Top southward to Cowling, but the rocks are rarely seen in the northern part of this outcrop. Exposures [SD 597 172] on the east side of the canal, about 400 yd north of Cowling, show some 10 ft of very fine-grained white sandstone overlain by 6 ft of sandy shale and a further 10 ft of fine white sandstone with a ganister top.

Just west of the canal at Cowling 20 ft of ripple-marked sandstone, shaly towards the base, is exposed in an old quarry [SD 594 167]. These exposures in general show whiter and more sandy beds than is usual, and there is reason to doubt the correlation, particularly in the absence of the G. cumbriense Marine Band; indeed, the finding of Anthraconaia bellula in the tip from a nearby well (see p. 28) suggests that the rocks seen may be Upper Haslingden Flags, not Lower Haslingden Flags as shown on the maps.

No Lower Haslingden Flags have been seen in the Rivington and Winter Hill areas, except for an 8-ft band of massive white sandstone, the typical 'lonkey' of Rossendale, which is exposed in the higher part of the Dean Brook section two miles west of Belmont. R.C.B.J., D.P.

Euxton House Bore (p. 114) recorded the greatest known thickness of Lower Haslingden Flags-193 ft of alternations of flaggy sandstone and sandy mudstone, overlain by about 54 ft of sandstone, flaggy in part. The Booth's Farm Bore (p. 107) proved 1311 ft of flaggy sandstone with numerous sandy mudstone partings, overlain by 831 ft of mainly massive fine to medium-grained sandstone. A comparable development is found in the Yarrow valley [SD 545 179] about a mile south-west of Euxton, where the Flags comprise fine-grained mainly smooth-bedded flaggy sandstones with occasional shale partings and, near the top, thick beds of massive sandstone. The massive sandstone of the boreholes and the Yarrow section is well seen to about 30 ft in an old quarry [SD 5433 1782] just south of the river, 1350 yd W. 30° S. of Euxton Hall. This material has been much used locally as a building stone. A.E.Monograptus, D.P.

In the north-east of the district the Lower Haslingden Flags were formerly exposed in small quarries on the north-west side of Blackburn. South-west of Blackburn at Riley Green the rock makes a good feature; and two bands of flaggy sandstone with intervening brown shales crop out in a small stream 300 yd south of the village. L.H.T.

The Gastrioceras cumbriense Marine Band lies on top of or close above the Lower Haslingden Flags where these are developed. An exposure of the band [SD 5952 1925] in the cutting north of Knowley Top about one and a quarter miles N.N.E. of Chorley Station has yielded the following: Orbiculoidea cf. nitida, Glabrocingulum?, an indeter­minate turreted gastropod; Aviculopecten aff. losseni (von Koenen), Caneyella cf.. multirugata, Dunbarella cf. elegans, Sanguinolites sp.;Anthracoceras sp., Gastrioceras^. crenulatum Bisat, G. cumbriense Bisat, Homoceratoides aff. divaricatus, an orthocone nautiloid, Solenocheilus sp.;and fish debris. In the south-east the G. cumbriense Marine Band is exposed [SD 6452 1530] in Shore Brook, 320 yd S.E. of Higher House, and two miles west of Belmont, a 9-in black paper-shale yielding the following fauna: Posidoniella sp.;Anthracoceras sp., Homoceratoides aff. divaricatus, Gastrioceras crenulatum and G. cumbriense. Wright and others (1927, p. 119, fig. 34) record only G. listeri from this locality, but re-examination of the material shows this determination to be incorrect. A similar fauna was obtained from an exposure [SD 6386 1458] of the marine band, 600 yd E. 10° N. of Rivington Hall. R.C.B.J.

West of Chorley the G. cumbriense Marine Band is visible [SD 5473 1795] in the Yarrpw valley on the south side of the weir, 900 yd W. 40° S. of Euxton Hall, where massive sandstone of the Lower Haslingden Flags is capped by about 9 ft of red mudstone with rare Schizodus, followed by about 17 in of soft black marine shale and 4 ft of blue shaly mudstone. The marine shales yield the following: Lingula mytilloides, Orbiculoidea cf. nitida; Glabrocingulum?, an indeterminate Bellerophontid gastropod; Aviculopecten aff. losseni, Parallelodon sp., Dunbarella cf. elegans, Posidoniella sp.; Gastrioceras crenulatum, G. cumbriense, an orthocone nautiloid and fish debris. A few small shells were recorded at this horizon in the Euxton House Bore (p. 114). The marine band was proved about 15 ft above the Lower Haslingden Flags in the Booth's Farm Bore (p. 107). The fossils were poorly preserved, but the following were obtained: Lingula mytilloides; Caneyella sp.; Anthracoceras sp., Gastrioceras cumbriense; and fish fragments. A.E.Monograptus, D.P.

Marine shales exposed at a number of points near Chapels—shown as fossil localities on the geological map—were thought, at the time of the survey, to represent the Gastrioceras cumbriense Marine Band. Material was collected from only one of these localities, that 560 yd N.N.W. of St. Stephen's Church, and it has now been shown (see p. 41) that the marine band exposed there is in fact the Gastrioceras subcrenatum or Six Inch Mine Marine Band—marking the base of the Coal Measures.  There is thus some doubt as to the horizon of the marine shales cropping out at the other localities. D.P.

The Upper Haslingden Flags have a maximum thickness of about 250 ft around Rivington, Winter Hill and Counting Hill in the south-east of the district, but the outcrop is largely covered by peat or boulder clay and exposures are few. Farther north the Flags are less well developed. They are visible in an old quarry [SD 6705 2030] 900 yd E. 28° N. of Hollinshead Hall, where 10 ft of shaly sandstone is bared, and there is a similar development of shaly flaggy sandstone in small exposures between Chapels and Winter Hill. A thin band of shaly flags, representing the Upper Haslingden Flags, is seen close below the Rough Rock in the brick-pit [SD 639 238] at Stanworth Edge about 1000 yd N. of Withnell Station. Upper Haslingden Flags crop out at Brimmicroft [SD 626 248] a mile S.E. of Hoghton in a cutting on the Preston–Belmont road, fine-grained grey and brown flaggy sandstones being laid bare. The Flags have been worked for building stone in nearby quarries. Between Pleasington and Feniscowles, 400 yd S.W. of the Old Hall, there is a clear section [SD 6343 2557] of the top of the Upper Haslingden Flags. West and south-west of Stanworth Edge they are thicker, and have a considerable outcrop between Withnell and Ollerton and about Windy Harbour. An old quarry [SD 629 223] 250 yd W. 35° S. of St. Paul's Church,. Withnell, shows 18 ft of flaggy sandstone, but elsewhere exposures are poor. Farther south, thin bands of shaly flags are to be seen around White Coppice and on the slopes of Healey Nab.

Flaggy sandstones exposed in Limbrick Quarry [SD 604 163] at Limbrick, a mile and a half south-east of Chorley, and again in Duxbury Quarry [SD 601 157] about a third of a mile south of Limbrick, have been shown on the maps as Upper Haslingden Flags. The rock seen is not of typical lithology, but was mapped as such partly in the belief that fossiliferous mudstones exposed nearby represented the 'Anthraconaia bellula Band'. However, faunal evidence suggests that this occurrence is not the 'Anthra­conaia bellula Band' but is of a higher horizon, possibly above the Bassy Mine of the Coal Measures (see p. 44). It seems likely that the sandstone is not Upper Haslingden Flags, but is of early Coal Measures age. R.C.B.J., L.H.T., D.P.

West of Chorley the Upper Haslingden Flags are exposed [SD 5457 1777] in a small stream about 900 yd W. 6° N. of Bolton Green. In Euxton House Bore they comprise 55 ft of alternations of mudstone and massive or flaggy sandstone. A little to the east in Black Pit Bore (p. 106) 85 ft of shaly sandstone and hard ribs' were recorded at this horizon. In Booth's Farm Bore (p. 107) the Upper Haslingden Flags were represented by 5.5 ft of reddened flaggy sandstone overlain by 23.5 ft of sandy mudstone and 17 ft of grey, fine to medium-grained sandstone with sandy mudstone partings. A.E.Monograptus, D.P.

Commonly, the Upper Haslingden Flags are directly overlain by the Rough Rock, but in some areas mudstone intervenes. In the Booth's Farm Bore (p. 107) 44 ft of mudstone were penetrated at this horizon; Anthraconaia cf. angulosa Pastiels occurred a foot above the Upper Haslingden Flags, and Anthraconaia bellula was found 6 ft and 14 ft higher in the sequence. The Heskin Bore (p. 116) did not enter the Upper Haslingden Flags but proved mudstone with Anthraconaia bellula and Naiadites cf. stockmansi Pastiels below the Rough Rock. Fossiliferous mudstone which was probably derived from this horizon was found on the tip from a 60-ft well [SD 5982 1810] 350 yd N.E. of Lower Healey Bleach Works, about a mile E. 25° N. of Chorley Station. It yielded the following fauna: Anthraconaia angulosa, A. bellula, A. ventricosa Pastiels, Carbonicola cf. circinata Pastiels, and Naiadites cf. stockmansi. This fauna is more varied than that usually obtained from the 'Anthraconaia bellula Band', although in view of the source of the material more than one shell band may be involved. D.P.

The Rough Rock is well developed north and west of Withnell. Quarries at Stanworth Edge north of Withnell show up to 40 ft of coarse current-bedded gritstone. The rock caps several small hills between Ollerton and Withnell, and up to 25 ft of it may be seen in small quarries in this area. East and south of Chapels and in the south of the Preston district the Sandrock Mine is developed, and the Rough Rock is thus in two leaves. The lower leaf is, in the east and south-east of the district, uniformly coarse gritstone with small pebbles of vein quartz, and is thickest in the north of this area. This lower leaf forms a well-marked platform east and south of Chapels and above Hollinshead Hall. The rock is seen at Higher Hill, half a mile south of Chapels, where 25 ft of coarse pebbly gritstone with large ferruginous concretions are exposed in an old quarry [SD 659 226]. Another good section [SD 670 214] is in Stepback Brook, 500 yd E.S.E. of Ryal Fold. The Rough Rock is only poorly exposed on Bunkers Hill and the outcrop shown on the map is conjectural. In the south-east, on Rivington and Smithills moors, the Rough Rock underlies a dip slope, and has a considerable outcrop although the lower leaf is only 30 ft thick. R.C.B.J.

West of Chorley the lower leaf of the Rough Rock is seen as a moderately coarse massive red sandstone in two quarries on opposite sides of the Yarrow, one [SD 5528 1800] 550 yd S. 10° W. of Euxton Hall, the other [SD 5501 1792] 700 yd S. 35° W. of Euxton Hall. Farther south it crops out [SD 5225 1403] in Howe Brook, 600 yd N.W. of St. James's Church, Wrightington, where about 20 ft of gritty sandstone is partially exposed. In the Euxton House Bore (p. 114) the lower leaf of the Rock was recorded as a fine to coarse red sandstone 115 ft thick, but a mile and a half to the south-east the Black Pit Bore (p. 106) found only 40 ft of fairly massive sandstone alternating with shaly sandstone. Booth's Farm Bore (p. 107) proved 56 ft of medium to coarse-grained sandstone, flaggy in the lower half; the Big Wood Bore (p. 105) found about 54 ft of micaceous sandstone with sandy mudstone partings and with 6 ft of open-textured gritstone near the base; but farther south, in the Heskin Bore, this lower leaf was only 26 ft thick. A.E.Monograptus, L.H.T., D.P.

The Sandrock Mine is known at Chapels, where it was formerly exposed [SD 6629 2299] above the lower leaf of the Rough Rock in Weasel Lane, 560 yd S. 36° E. of St. Stephen's Church. It has also been seen in Stepback Brook about 600 yd E. 26° S. of Ryal Fold. It is probably about 6 in thick in this area. To the south it is present on Rivington Moor as two seams separated by as much as 20 ft of measures, the lower and upper coals being about 18 in and 10 in thick respectively. It has been almost completely worked out. In the valley of the River Yarrow from Blindhurst, west of the upper Rivington Reservoir, northwards to Limbrick, the succession is open to considerable doubt. Below Blindhurst two coals 33 ft apart have been worked, and these workings appear to pass beneath the outcrop of the Margery Flags (see p. 43) without faulting: hence it is concluded that the lower coal is the Sandrock Mine and the upper probably the Six Inch Mine. Farther north these coals appear to be repeated by faulting. R.C.B.J.

South of Euxton the Sandrock Mine is traceable south-westwards from the Yarrow by a line of adits, in one of which [SD 5484 1778], 950 yd S. 40° W. of Euxton Hall, the upper part of the coal is visible. The seam is reported to consist of 31 in of coal lying on 20 in of cannel; and this reported reversal of the more common condition in which cannel occurs at the top of a seam is confirmed by the presence of cannel in the tip from an adit, while the upper part of the seam, in place, is a true coal.

In Fox Hole Wood Bore (p. 115) the Sandrock Mine was 25 in thick, but in Black Pit Bore a mile to the south-east only 10 in of coal were proved. In the Euxton House Bore the seam comprised 10 in of coal with a half-inch parting an inch from the base. In Charnock Old Hall and Tan House Farm bores (pp. 107, 125) the Sandrock Mine was 7 in and 10 in thick respectively. Big Wood Bore (p. 105), sited about half a mile from both the above, proved two coals, some 20 ft apart, above the lower leaf of the Rough Rock, and at first sight it would appear that these represent the Sandrock Mine and the Six Inch Mine. However, in the roof of the upper coal were found two faunal bands separated by 2 ft of apparently barren shale. The lower band yielded a fauna comparable with that usually found above the Sandrock Mine, and including the following: Spirorbis sp.; Carbonicola exporrecta Eagar, C. aff. protea Wright, C. spp., Naiadites sp.;and Geisina arcuata (Bean). But the upper band seems undoubtedly to represent that usually found between the Six Inch Mine and the Six Inch Mine Marine Band (see p. 30). Acceptance of the upper coal as the Six Inch Mine would imply that the lower faunal band represents the lower part of the Six Inch Mine fauna, but this is not supported by the faunal evidence. The alternative, and perhaps more likely, explanation is that the Six Inch Mine is absent here, that the Sandrock Mine is a split seam, and that the distance between the faunal bands above the Sandrock and Six Inch mines is very small. Some support for this second interpretation is found from the Wrightington Bore, sited just to the south of the Preston district, which proved only a one-inch coal at the Six Inch Mine horizon, and only 6 ft of strata between the two faunal bands. The Sandrock Mine, comprising two 24-in seams with an 18-in seatearth between them, is exposed [SD 5228 1402] in Howe Brook, 600 yd N.W. of St. James's Church, Wrightington; overlying shale and mudstone is also visible, but no fossils have been found. The faunal band above the Sandrock Mine was recorded in the Charnock Old Hall and Tan House Farm bores, but contained only a small number of fossils; no details of the fauna are known. No shells were recorded in other bores in the district proving this horizon, but of these, only the Heskin Bore received systematic examination. L.H.T., A.E.Monograptus, D.P.

The upper leaf of the Rough Rock in the area west of Darwen Hill appears to be thin, and to consist of sandy shale and shaly sandstone. To the south, on Smithills Moor, it is represented by about 35 ft of shaly sandstone which dies out entirely when followed to the west on Rivington Moor.

Borings west of Chorley reveal variation in the measures between the Sandrock Mine and the Six Inch Mine, the upper leaf of the Rough Rock having a limited development. Euxton House Bore proved 18.5 ft of almost entirely argillaceous strata between the two seams, but in Fox Hole Wood Bore the measures, some 28 ft thick, included 17.5 ft of 'brown rock'. The shaft section of Bolton Green Colliery [SD 5493 1758] shows the seams separated by 67 ft of strata, including 41 ft of 'grey-red rock with beds of dark and light linsey'; a nearby adit shows 5 ft of sandy shale above the Sandrock Mine; and there are two exposures of flags and sandy shale hereabouts, but these are insufficient to confirm the shaft section. To the south-west the Charnock Old Hall and Tan House Farm bores proved some 24 ft of mainly argillaceous measures between the two seams, but in the Heskin Bore they were separated by only 10 ft of mudstone and sandy mudstone with hard sandstones and 2 ft of seatearth. R.C.B.J., A.E.Monograptus, D.P.

The Six Inch Mine is poorly exposed [SD 6806 2215] north of Darwen Hill 380 yd E. 4° N. of the northern corner of the reservoir. In Stepback Brook about two miles S.E. of Chapels coal debris marks the position of the seam, which crops out in three places due to the structure. Farther west the coal, 18 in thick, is exposed [SD 6393 2381] on the south-east side of Withnell Brickpit, 1100 yd N. of Withnell Station.

A number of boreholes in the Chorley area proved the Six Inch Mine and the overlying non-marine and marine faunas, but only in recent boreholes have the two faunas been distinguished, previously 'shell band' only being recorded. The thickness of coal recorded in the bores varies from 3 to 9 in. In Charnock Old Hall Bore (p. 107) it was 6 in thick and was overlain by 13 in of mudstone containing poorly preserved non-marine shells, and above that by the Six Inch Mine Marine Band. Tan House Farm Bore (p. 125) proved only 3 in of coal overlain by 54 in of mudstone, the lower 24 in of which yielded a non-marine fauna. The seam was 6 in thick in the Heskin Bore (p. 116), and was capped by mudstone which yielded the following: Lepidostrobus sp.; Anthraconaia cf. bellula, Carbonicola? [juv.] Geisina arcuata; and fish remains including Elonichthys cf. aitkeni Traquair [scale]. The Six Inch Mine appeared to be absent from the Big Wood Bore (see p. 29), but the non-marine and marine bands were found. The non-marine fauna was as follows: Anthraconaia bellula, A. lenisulcata? (Trueman), Carbonicola?; Geisina arcuata; and Elonichthys sp.[scale]. The seam, 14 in thick, is exposed [SD 5228 1398] in Howe Brook close to Brook House, 550 yd N.W. of St. James's Church, Wrightington. R.C.B.J., D.P., L.H.T.

References

BISAT, W. S. 1924. The Carboniferous goniatites of the North of England and their zones. Proc. Yorks. Geol. Soc., 20, pp. 40–124.

BISAT, W. S. and HUDSON, R. G. S. 1943. The Lower Reticuloceras (R₁) goniatite succession in the Namurian of the North of England. Proc. Yorks. Geol. Soc., 24, pp. 383–440.

COPE, F. W. 1946. Intraformational contorted rocks in the Upper Carboniferous of the southern Pennines. Quart. J. Geol. Soc., 101, pp. 139–76.

EARP, J. R., MAGRAW, D., POOLE, E. G., LAND, D. H., and WHITEMAN, A. J. 1961. Geology of the country around Clitheroe and Nelson. Mem. Geol. Surv.

HODSON, F. 1954. A new species of Dimorphoceras from the Homoceras Zone of the Irish Millstone Grit. Ann. Mag. Nat. Hist. (12), 7, pp. 362–6.

HODSON, F. 1957. Marker horizons in the Namurian of Britain, Ireland, Belgium and Western Germany. Publ. Assoc. Etud. Paleont., 24, pp. 1–26.

HUDSON, R. G. S. 1944. The faunal succession in the Ct. nitidus zone in the mid-Pennines. Proc. Leeds Phil. Lit. Soc., Sci. Sect., 4, pp. 233–42.

MOORE, E. W. J. 1930. A section in the Sabden Shales on the River Darwen, near Blackburn. J. Manch. Geol. Assoc., 1, pp. 103–8.

TONKS, L. H., and WRIGHT, W. B. 1924. The south-westerly thickening of the Millstone Grit in Lancashire. Sum. Prog. Geol. Surv. for 1923, pp. 150–7.

WHITEHURST, J. 1778. An enquiry into the original state and formation of the earth. London.

WRIGHT, W. B., SHERLOCK, R. L., WRAY, D. A., LLOYD, W., and TONKS, L. H. 1927. The geology of the Rossendale Anticline. Mem. Geol. Surv.

Chapter 3 Coal Measures

Coal Measures crop out in three areas within the Preston district—around Blackburn and Feniscowles, forming the westerly extension of the Blackburn and Accrington Basin (Wright and others 1927, p. 2); some three to six miles south of Blackburn on Darwen Hill and Darwen Moor; and south of Chorley, where they form the northern extension of the Coal Measures of the Wigan district. West of Blackburn and in the Chorley area the outcrops are usually much obscured by drift, and such mining as has been done in these measures was chiefly carried out so long ago as to leave few or no records. However, recent boreholes drilled in the district by the National Coal Board have added much to knowledge of the Coal Measures, and, in fact, form the basis of this account.

Immediately west of Blackburn, and on Winter Hill, Darwen Hill and Darwen Moor, the succession compares closely with that in Rossendale to the east; in the south of the district the upper part of the sequence resembles that around Wigan. The lower part of the sequence in this southern area, however, shows some unusual features, for below the horizon of the Lower Mountain Mine there is in places an exceptional development of sandstones similar to that in the neighbourhood of Harrock Hill, just south of the Preston district. This was a prime cause of the difficulties of correlation discussed in the Wigan Memoir (Jones and others 1938, pp. 13–16).

The Coal Measures of the Preston district, about 2600 ft thick, are depicted in vertical sections on (Figure 7). At the time of the survey the base of the Coal Measures was taken at the Six Inch Mine or, where the coal was absent—as on the south side of Rivington Moor—at a short distance below the Gastrioceras subcrenatum Marine Band which normally overlies that seam. The base of the Middle Coal Measures was at that time taken at the Arley Mine. It has since been found possible to establish a standard succession for the chief British coalfields, based on the presence of marine strata at certain horizons throughout those coalfields (Stubblefield and Trotter 1957): accordingly the base of the Coal Measures is now taken at the base of the Gastrioceras subcrenatum Marine Band, and the base of the Middle Coal Measures at the base of the marine horizon which has Anthracoceras vanderbeckei (Ludwig) as its characteristic goniatite—a band known in Lancashire as the Sutton Manor Marine Band. The highest Coal Measures horizon known in the Preston district has been shown—in the country to the south—to lie 50 to 80 ft below this marine band, consequently the whole of the sequence now falls within the Lower Coal Measures. It is here described as such, though shown on the maps as Lower and Middle Coal Measures.

Of the seven non-marine lamellibranch zones which are now recognized in the British Coal Measures (Trueman and Weir 1946, p. xxvii), only the lowest three are represented in this district. The Anthraconaia lenisulcata Zone extends from the base to the horizon of the Pasture Mine (see Eagar 1956, p. 355); the Carbonicola communis Zone embraces the overlying measures up to the horizon of the Trencherbone Mine; and the remaining measures are included in the lower part of the Anthraconaia modiolaris Zone. The whole sequence lies within the Westphalian A division.

General stratigraphy

The account below deals briefly with the main features of the stratigraphy of the Coal Measures. It is followed by a more detailed account (pp. 41–59).

Base to Lower Mountain Mine

The measures between the Gastrioceras subcrenatum Marine Band—or as it is called in this district, the Six Inch Mine Marine Band—and the Lower Mountain Mine, are from 250 to 390 ft thick. They are thinnest in the north­east around Blackburn, and thickest around and south of Chorley (Figure 7), (Figure 8).

The basal marine band is well developed throughout, and yields a charac­teristic fauna including Gastrioceras subcrenatum C. Schmidt. In the east it is succeeded by 50 to 100 ft of mudstone overlain by the Woodhead Hill Rock, a bed which varies in thickness from about 60 ft at Feniscowles to only a few feet on the northern slope of Darwen Hill, and which ranges lithologically from coarse-grained massive sandstone to fine-grained shaly sandstone. In the Chorley area the mudstones above the marine band are followed by the Margery Flags and the Ousel Nest Grit. The Margery Flags resemble, to some extent, the Haslingden Flags, and are usually very shaly; they may be as much as 40 ft thick but are generally poorly developed; the Margery Mine, a thin coal which about Horwich to the south lies above them, has not been found in the Preston district. The Ousel Nest Grit, 40 to 100 ft thick, is a coarse-grained pebbly gritstone around Rivington, but elsewhere is a massive sandstone.

The Bassy Mine, which lies close above the Woodhead Hill Rock or Ousel Nest Grit, consists of about 18 in of coal and coaly shale in the north-east, but around Chorley is either absent or varies from a few coal streaks to 7 in of coal and coaly shale. The seam is generally overlain by mudstone and shale, with a thin sandstone near the base in the Chorley area. The mudstones are very fossiliferous, and the faunal sequence described by Eagar (1952) has been recognized in borehole cores from south-west of Chorley. Eagar's 'Lower Division' of the sequence is not as well developed as elsewhere, probably due to the presence of the sandstone; it is succeeded by the Lower Bassy Marine Band and his 'Middle Division', characterized by Carbonicola haberghamensis Wright; there follows the Upper Bassy Marine Band and the 'Upper Division', the fauna of which is dominated by Carbonicola aff. rectilinearis Trueman and Weir and C. declinata Eagar. The fauna above the Bassy Mine at Feniscowles was described in part by Wright (1934), and later by Eagar (1952, pp. 29–43), who recognized the 'Lower' and 'Middle' divisions of his faunal sequence. In parts of the Chorley area much of the normal sequence from below the Bassy Mine to above the Lower Foot Mine is replaced by the Harrock Hill Grit and equivalent sandstones.

The Lower Foot Mine is developed on Darwen Hill and Winter Hill and over the Chorley area, except toward the southern margin of the district where it has been cut out by the Harrock Hill Grit. Prior to the National Coal Board's recent programme of boring it was thought to be absent from the Chorley area, and it is not shown on the map. The new boreholes proved the presence of the Lower Foot Mine, a seam 12 to 18 in thick, but also showed the Lower Mountain Mine to be thin or absent. Further, it now appears that the seam formerly worked as the Lower Mountain Mine, and mapped as such, is in fact the Lower Foot Mine. In the Chorley area the seam is succeeded by mudstone with a non-marine fauna, overlain by the Lower Foot Mine Marine Band; but this fossiliferous horizon has not been recorded around or south of Blackburn. The Ganister Rock is only a few feet thick in the north-east; around Chorley it varies from 0 to 40 ft in thickness; in the extreme south, where it is probably equivalent to the higher part of the Harrock Hill Grit, it cuts out measures down to below the Lower Foot Mine.

The Lower Mountain Mine, which lies on or close above the Ganister Rock, has been widely exploited in the north-east but, as stated above, is poorly developed in the Chorley area.

Lower Mountain Mine to Pasture Mine

Around and south of Blackburn the Lower Mountain Mine is separated from the Pasture Mine by about 350 ft of strata, but in the Chorley area the sequence is considerably thicker, up to 630 ft having been recorded, as illustrated in (Figure 9).

Mudstones above the Lower Mountain Mine have locally yielded a few non-marine fossils. They are succeeded by the Bullion Mine Rock. The presence of this rock in the Blackburn area is inferred from evidence on the ground to the east where it is 25 ft thick; it is found on Darwen Hill and Winter Hill (north), where it appears to be from 15 to 35 ft thick; and boreholes and shafts in the Chorley area have proved it to be from 30 to 150 ft thick, although the last thickness is well above average. The rock is generally a flaggy sandstone.

The Bullion or Upper Foot Mine has been exploited in the north-east of the district. It is poorly developed or absent around Chorley, and was not recognized as such during the survey of this area; but recent evidence suggests that the 'thin coal' shown on the map as capping a sandstone above the so-called Lower Mountain Mine is in fact the Bullion Mine. The seam is overlain by the Bullion Mine Marine Band, which yields Gastrioceras listeri (J. Sowerby). The Inch Mine Rock, which succeeds the mudstones above the Bullion Mine, is only present on Darwen Moor in the north-east, but a 10 to 15-ft bed of sandstone commonly occupies this horizon in the Chorley area; it is overlain by the Inch Mine seatearth.

The Inch Mine is developed on Darwen Moor, and has been proved by several boreholes in the Chorley area. It varies from a few thin coal streaks to a 10-inch coal. The seam is not found on the north face of Darwen Hill, where the Inch Mine Rock and the Warmden Sandstone are united. It is overlain by as much as 50 ft of mudstone, commonly with fish remains at the base: above this lies the Warmden Sandstone, which varies in thickness from 20 to 60 ft and in lithology from a medium-grained sandstone to a massive coarse-grained gritstone.

The Upper Mountain Mine has been widely exploited. On Winter Hill (north) and Darwen Hill its thickness is said to have been 24 in; in the Chorley area it is generally between 24 and 42 in, but immediately east of the Great Haigh Fault near the southern margin of the district it varies from 30 in to 3.5 in over a short distance. On Darwen Hill and Darwen Moor the seam is im­mediately overlain by the Icconhurst Sandstone, but this sandstone is seldom developed in the Chorley area, where the Upper Mountain Mine and Cannel Mine are generally separated by about 20 ft of mainly argillaceous measures.

Of the higher beds little is known in the Blackburn area; the outcrops shown on the map are continued from the ground to the east where exposures are more numerous and from which there is more mining information. The Cannel Mine, or Little Mine, is present over much of the Chorley area, where it is from 5 to 16 in thick. The Cannel Mine Marine Band has been recorded from two boreholes, and yielded foraminifera and conodonts. Lying some 100 to 130 ft above the Cannel Mine, the Darwen Flags comprise 10 to 50 ft of mainly flaggy sandstone and sandy mudstone. Tonge's Marine Band lies close above them and, as elsewhere in Lancashire, is characterized by large Dunbarella and conodonts (Earp and Magraw 1955, p. 31); but of greater interest is the presence in the band of Gastrioceras, a genus rarely found at this horizon in Britain. A thin coal is sometimes found below the marine band. Some 30 to 70 ft of mainly argillaceous measures succeed the marine band, and are overlain by the Crutchman Sandstone—a coarse-grained, in places pebbly, current-bedded sandstone 80 to 90 ft thick, which forms marked ridges along its outcrop at Charnock Richard. The Pasture Mine has only been recorded in the Preston district at Moor Road Pit, Chorley, where it was 8 in thick; elsewhere its horizon is commonly marked by a seatearth at the top of the Crutchman Sandstone.

Pasture Mine to base of Arley Mine

The total thickness of these measures, some 530 ft, has been proved in only one borehole in the Preston district. The Accrington Mudstones comprise 130 to 150 ft of mudstone which is commonly shaly. The Pasture Mine and Ditton marine bands have not been found in them in the district, though they were proved just to the south in the Wrightington Borehole (Magraw 1957, p. 21). The Accrington Mudstones are not exposed in the Blackburn area, and they are there mapped on the basis of the succession known to the east, as are also the Dyneley Knoll Flags, an arenaceous development found at this horizon in Rossendale. The Accrington Mudstones may be succeeded by the Old Lawrence Rock or separated from it by as much as 160 ft of sandy mudstone and thin sandstones. The Old Lawrence Rock comprises two leaves, a lower mainly flaggy sandstone up to at least 40 ft thick, and, some 40 ft above, a more massive sandstone 45 ft thick. A mudstone parting in this bed has yielded fossils of the Carbonicola communis Zone.

A thin coal above the Old Lawrence Rock has been correlated with the Dib Hole Coal of Blackburn (Magraw 1957, p. 19). Measures above this coal yielded the fauna described from Daubhill Brickworks near Bolton (Tonks and others 1931, pp. 134–135; Eagar 1956, p. 359), and also two fossiliferous horizons new to Lancashire but subsequently proved in other parts of the coalfield (see p. 52).

Arley Mine and succeeding measures

The strata above the base of the Arley Mine—formerly classified as Middle Coal Measures (see p. 32)—are about 1200 ft thick and are found only in the area south of Chorley; comparative sections of the measures are shown in (Figure 10) and (Figure 11). The Arley Mine, now almost entirely worked out, was the most valuable coal in the district, and here appears to reach its maximum thickness for the Lancashire Coalfield-71 inches. In the 180 to 240 ft of measures between it and the Smith Mine lie a number of fossiliferous horizons, notably the band 130 to 160 ft above the Arley Mine characterized by Carbonicola pseudorobusta Trueman in the lower part and C. bipennis (Brown) above.

The Smith Mine is 17 to 30 in thick and has been worked. A shell band was recorded in its roof at Duxbury Park Colliery but is not known elsewhere. The seam is generally closely overlain by the Smith Top Coal and the Cockloft Mine, above which a few small shells have been recorded. About 50 ft of measures separating the Cockloft and Bone Mines are for the most part argillaceous, but a thin sandstone is developed near their top in the east. The Bone Mine, about 25 in thick, derives its name from the 'bone-coal' or hard dull coal which is commonly present in it. It is overlain by some 140 ft of mudstones and sandstones with thin coals, except in the fault trough at Kingsley where there is an abnormal development of sandstone.

The Yard Mine, 17 to 33 in thick, has been worked from numerous collieries. The measures between it and the Ravine Mine comprise some 140 ft of mudstone with thin sandstones and occasional inferior coals; a well-marked shell band containing Carbonicola pseudorobusta lies just above the Yard Mine. The Ravine Mine is generally an unworkable composite seam comprising up to 30 ft of thin mainly inferior coals interbedded with seatearths and mudstones; only the topmost coal, the Ravine Mine Tops, approaches a workable thickness and quality. About 60 ft of mainly argillaceous strata separate this seam from the King and Queen Mines.

The King and Queen mines comprise a closely associated group of coals which, with partings, are from 6 to 9 ft thick. The coals have been worked extensively. The thickness of the measures between them and the Cannel Mine is very variable, being 90 ft in the east but possibly under 10 ft in the west—where, however, the sequence is not clear. The mudstones above the King Mine have yielded Curvirimula cf. candela (Dewar).

The Cannel Mine is generally a bituminous coal, of poor quality in places and 17 to 30 in thick; cannel coal is developed locally at the top of the seam. The overlying Cannel Rock is about 70 ft thick in the west but fails to the east. The Little King Mine is from 12 to 26 in thick; it is worked at Ellerbeck Colliery as the 'Upper King Mine', but elsewhere is of very poor quality. It is not shown on the geological map. It is overlain by about 100 ft of mudstone with a single thin coal; near their base the mudstones yield Carbonicola pseudorobusta, and Carbonicola cf. polmontensis (Brown) has been found near their top.

The Peacock Mine generally has a thickness of 30 to 47 in, but except at Ellerbeck Colliery it is of poor quality. The roof measures carry an important shell band characterized by Carbonicola pseudorobusta, Curvirimula candela and the ostracod Carbonita humilis (Jones and Kirkby), and above the main shell-bed is a thin band of mudstone which yields abundant Geisina arcuata (Bean). This horizon is the highest at which Carbonicola pseudorobusta is found in Lancashire.

The Wigan Six Foot or Trencherbone Mine lies 6 to 15 ft above the Peacock Mine; it is generally 54 to 66 in thick but is subject to washouts. The Trencherbone Rock, which usually fills these washouts, commonly forms the roof of the coal but may be separated from it by as much as 35 ft of sandy mudstone; it is a fine to medium-grained sandstone 50 to 110 ft thick. No fossils have been found in the roof of the Trencherbone Mine in the Preston district. The Trencherbone Rock is succeeded by 20 to 30 ft of mudstone and seatearth.

The Wigan Two Foot Mine has not been mapped: boreholes show it to be 17 to 24 in thick or to be a thicker composite seam comprising thin coals and seatearths. It is overlain by about 60 ft of mainly argillaceous measures, including the seatearth of the Wigan Four Foot Mine which may attain a thickness of nearly 40 ft (Figure 11). The Wigan Four Foot Mine is generally a good coal 51 to 54 in thick. The overlying mudstones contain a number of shell bands characterized by Anthracosia regularis (Trueman). Geisina arcuata is abundant at this horizon, as throughout the Pennine coalfields. The Wigan Five Foot Mine, about 60 ft above the Wigan Four Foot, is a composite and very variable seam, generally unworkable, comprising up to 20 ft of coals, seatearths and mudstones. The Ravenhead Rock, lying about 5 ft above it, is a medium to coarse-grained sandstone; its total thickness may not be present in the Preston district, but 76 ft of it has been proved. D. P .

Details

Base to Lower Mountain Mine

The Six Inch Mine Marine Band crops out [SD 6378 2572] in the north bank of the River Darwen, 120 yd S.E. of the Old Hall, Feniscowles. The following fauna was collected during the survey: Caneyella multirugata (Jackson), Dunbarella papyracea (J. Sowerby), Posidonia gibsoni Salter; Gastrioceras subcrenatum, Homoceratoides divaricatus (Hind); Hindeodella sp.;fish remains. In the north side of Darwen Hill the marine band is visible [SD 6806 2215] 650 yd N. 18° E. of Darwen Tower, but has not yielded a good fauna. In the Stepback Brook section, west of Darwen Hill, the band is exposed [SD 6731 2065] 1300 yd S. 42° E. of the inn at Ryal Fold, where it yielded the following: Caneyella multirugata, Dunbarella papyracea, Posidonia cf. gibsoni; turreted gastropods; orthocone nautiloid, Anthracoceras sp., Gastrioceras sub­crenatum; Hindeodella sp.Marine shales which crop out [SD 6745 2080] about 350 yd to the north-east are considered to represent the Six Inch Mine Marine Band, although neither Dunbarella nor typical Gastrioceras subcrenatum has been found; a markedly crenulate Gastrioceras collected here may be the same species noted elsewhere at this horizon (see below). Farther west the band is exposed [SD 6394 2381] on the south-east side of Withnell brickpit, 1100 yd N. of Withnell Station; here the Rough Rock and a narrow strip of Coal Measures are faulted against mudstones of the Haslingden Flags series. L.H.T., R.C.B.J.

Marine shales exposed [SD 6576 2400] 560 yd N.N.W. of St. Stephen's Church, Chapel, between two north-south faults, were at the time of the survey thought to represent the Gastrioceras cumbriense Marine Band. Re-examination of the fossils collected has shown that the band is in fact the Six Inch Mine Marine Band, with a fauna as follows: Caneyella multirugata, Dunbarella papyracea, Posidonia gibsoni?; orthocone nautiloid, Gastrioceras subcrenatum, G. sp., Homoceratoides divaricatus; Hindeodella sp.The strata between the two faults are probably Lower Coal Measures, not Millstone Grit Series as shown on the map.

In the area around and west of Chorley the Six Inch Mine Marine Band is best known from boreholes. It is, however, exposed [SD 5228 1398] in Howe Brook immediately south of Brook House, about 600 yd N.W. of St. James' Church, Wrightington, where it has yielded the following: Dunbarella papyracea, Posidonia cf. gibsoni; Anthracoceras sp., Gastrioceras subcrenatum, G. sp. nov. [aff. cumbriense], G. sp.[crenulate]. Some of the goniatites are here preserved 'solid' in bullions and contain oil. A similar fauna to the above was found on a tip [SD 5138 1360] on the northern slope of Harrock Hill, about 1400 yd W. of St. James' Church, Wrightington; it included 'solid' specimens of Gastrioceras sp. nov. [aff. cumbriense].In the Heskin Bore (p. 116) the marine band comprised 62 inches of dark mudstone, in part calcareous, with the following fauna: Rectocornuspira?; crinoid columnals; Crurithyris?, Dielasma?, Lingula mytilloides; gastropod spat; Caneyella multirugata, Dunbarella cf. papyracea, D. aff. elegans (Jackson), Edmondia?, Posidonia sp.;coiled nautiloid fragments, Anthracoceras arcuatilobum (Ludwig), Gastrioceras subcrenatum, G. sp. nov. [aff. cumbriense], G. sp., Homoceratoides?; platformed conodont; fish remains including Acanthodian and Palaeoniscid scales and Elonichthys aitkeni Traquair [scale]. The marine band was also proved in the Big Wood (p. 105), Charnock Old Hall (p. 107) and Tan House Farm (p. 125) boreholes; thin argillaceous limestones were a feature of the band in these holes. It is interesting to note that in all the above boreholes a thin contorted shale or 'crozzle' occurred at the top of the marine phase.

The measures above the Six Inch Mine Marine Band up to the Warmden Sandstone are very well exposed—with the exception of the Lower Foot mine—in Stepback Brook on the west of Darwen Hill. The shales above the marine band are seen well in this section, but still better in Bog Height brickworks quarry [SD 674 247], where some 40 ft of spheroidal-weathering grey and blue mudstone, overlain by about 5 ft of black shale, are present below the overlying Woodhead Hill Rock. Blue shales which are probably close above the Six Inch Mine Marine Band are exposed [SD 5543 1797] behind the house 330 yd S. 16° W. of the inn north of Bolton Green; and sandy shale and shaly sandstone which probably overlie these are seen in the Yarrow valley just to the south. Apart from these exposures the mapping of the Coal Measures was based almost entirely on a small number of boreholes, controlled by a few sandstone outcrops.

East-south-east of the Old Hall, Feniscowles, the Woodhead Hill Rock forms a steep cliff on the north bank of the River Darwen. At the Lodge [SD 6431 2569] 100 yd W. 19° S. of Immanuel Church, Feniscowles, 14 ft of fine purplish grey and yellow ripple-bedded sandstone are exposed below 8 ft of sandy shales and mudstones with sandstone bands. The lower beds crop out to the south and west in 30 to 40-ft faces along the river bank; they are here coarser, more massive, and current-bedded. Purple staining in some cases affects whole beds, but in others gives a mottled effect. The Woodhead Hill Rock is well seen in old quarries half a mile south-east of Bunkers Hill, which show up to 24 ft of purplish mainly flaggy sandstone, interbedded with thin bands of shale. L.H.T., D.P., A.E.Monograptus, R.C.B.J.

In Tan House Farm Borehole (p. 125) the Six Inch Mine Marine Band was overlain by some 70 ft of mudstone and sandy mudstone, followed by 33 ft of alternating fine-grained sandstone and sandy mudstone. These are correlated with the Margery Flags, which are exposed [SD 5468 1739] about 800 yd W. 16° S. of Bolton Green, and in the south bank of the River Yarrow at Pinook Bridge [SD 5545 1780]. In the borehole, about 18 ft of sandy mudstone with thin sandstone bands separated the Margery Flags from some 70 ft of reddened mainly massive sandstone overlain by 32 ft of more flaggy sandstones and sandy mudstone. This second arenaceous group probably corresponds with the main part of the Ousel Nest Grit as mapped, but the upper less massive part may represent the Woodhead Hill Rock of other areas. The Charnock Old Hall Bore (p. 107) proved a similar sequence, but the massive sandstone was less well developed. Towards the south of the area the Adlington Bore (p. 102) and the Heskin Bore (p. 116) proved a single sandstone-45 ft thick in the former and 20 ft in the latter—between the Six Inch Mine and Bassy Mine horizons; lithologically it resembles the Ousel Nest Grit rather than the Margery Flags.

Fox Hole Wood Borehole (p. 115) proved about 50 ft of mudstone above the Six Inch Mine. Overlying this were about 80 ft of flaggy measures passing upwards into 80 ft of red sandstone. A thin coal lying 20 ft above the sandstone is now correlated with the Bassy Mine; the underlying sandstones are referred to the Margery Flags and the Ousel Nest Grit, which are here united. In the Black Pit Bore (p. 106) about 180 ft of sandstone lie about 40 ft below the Lower Mountain Mine. Although 'mussel' bands were recorded above the sandstone none were recorded below it, suggesting that the Bassy Mine horizon is above the base of the sandstone, which may in its lower part represent the Ousel Nest Grit. D.P.

The Ousel Nest Grit is exposed as a coarse current-bedded gritstone around Rivington village and in quarries north of Anderton Hall. A thin band of Margery Flags and part of the Ousel Nest Grit, here a sandstone, are seen in a section [SD 612 155] in the River Yarrow just west of Anglezark Reservoir.

The Bassy Mine follows close above the Woodhead Hill Rock near Blackburn and around Darwen Moor. At the Lodge [SD 6431 2569], 100 yd W. 19° S. of Immanuel Church, Feniscowles, 18 in of coal are seen above 8 ft of sandy shales and mudstones, which here overlie the Woodhead Hill Rock. The seam has been mapped on the north and west of Darwen Hill where it is said to be 15 in thick, but is only exposed [SD 6728 2108] in the Stepback Brook section, 975 yd E. 31° S. of the inn at Ryal Fold, where it rests on flaggy sandstone. L.H.T., R.C.B.J.

Charnock Old Hall Bore proved the Bassy Mine 200 ft above the Six Inch Mine Marine Band, as 3.5 inches of poor coal on about 9 ft of seatearth. A mile to the east it was represented in the Tan House Farm Bore by canneloid shale, cannel and coal (1.5 in) totalling 7 in, resting on 9.75 ft of seatearth. A 3.5-in coal, probably the Bassy Mine, was proved in the Fox Hole Wood Bore, but no coal was found at this horizon in the Black Pit Bore where the Ousel Nest Grit appeared to be united with the sandstone which normally overlies the Bassy Mine in this area. Towards the southern margin of the district the Bassy Mine is not developed; it was absent from the Adlirigton and Heskin bores, but in the former there were coal streaks underlain by a hard sandy seatearth at this horizon. D.P.

Shales above the Bassy Mine are exposed [SD 6455 2588] in a bank 220 yd N.E. of Immanuel Church, Feniscowles. They yield a rich flora including the following: cf. Alethopteris valida Boulay, Mariopteris acuta (Brongniart), Mariopteris sp., Neuropteris schlehani Stur, Calamites sp., Bothrodendron punctatum Lindley and Hutton, Lepidodendron sp., Lepidophloios acerosus Lindley and Hutton, L. laricinus. Sternberg and Stigmaria ficoides (Sternberg). A little higher in the sequence fossiliferous shales are exposed [SD 6462 2596] in the south bank of the River Darwen 360 yd N. 40° E. of Immanuel Church. The fauna was studied by Wright (1934), who from it described and figured Carbonicola protea and Carbonicola fallax; Spirorbis sp. and 'Anthracomya minima' were also recorded. Eagar (1952) described the locality; he found his 'Lower' and 'Middle' divisions of the Soft Bed—Bassy Mine succession, but neither of the Bassy Mine marine bands. Fossiliferous shales are also exposed [SD 6731 2104] above the Bassy Mine in the Stepback Brook section, 1020 yd E. 31° S. of the inn at Ryal Fold, where the fauna includes the following: Spirorbis sp.; Carbonicola fallax Wright, C. cf. declinata, C. pilleolum Eagar, C. cf. rectilinearis. The shells are poorly preserved, and precise determination is uncertain; the fauna may be that of Eagar's 'Lower Division' of the Bassy Mine sequence, but is more likely that of the 'Upper Division'. L.H.T., R.C.B.J., D.P.

West of Chorley the Charnock Old Hall and Tan House Farm bores (pp. 107, 125) proved the Bassy Mine faunal sequence. A pale sandstone about 17 ft above the Bassy Mine is overlain by 55 to 60 ft of fossiliferous mudstone. Eagar's 'Lower Division' fauna is poorly represented, and as such is not typical, perhaps due to the presence of the sandstone below. In Charnock Old Hall Bore the shells were in two bands about 8 ft apart, the lower band yielding Carbonicola sp. cf. acuta (J. Sowerby), C. cf. limax Wright and small Naiadites, and the upper the following: Spirorbis sp.; Carbonicola spp., Curvirimula spp. nov., Naiadites sp.[small, oblique]; Geisina arcuata (Bean); and fish remains. In the Tan House Farm Bore only Carbonicola recti­linearis, C. aff. protea Wright, and fragmentary Curvirimula sp.were obtained at this horizon. The Lower Bassy Marine Band 3 to 4 in thick yielded only Lingula mytilloides and fish remains. Eagar's 'Middle Division' in this area, as proved in the boreholes, comprises two bands with Carbonicola, separated by mudstone containing only fish fragments and Curvirimula?. The lower band contains the following: Spirorbis sp.; Carbonicola artifex ? Eagar, C. fallax ?, C. protea, C. aff. protea; Geisina arcuata; fish remains. The higher band yields the following fauna: Spirorbis sp.;Carbonicola haberghamensis, C. protea, Curvirimula sp. nov. [fine and distinct ornament], C. sp. nov. [broad form], Naiadites sp.;and Geisina arcuata. The Carbonicola discus band has not been recorded, but dark pyritic shale just above the lower shell band probably represents the oscillation referred to by Eagar (1952, p. 27) as indicating its position. The 'Middle Division' of the sequence is separated from the 'Upper' by the Upper Bassy Marine Band which, like the Lower, yields only Lingula rnytilloides and fish remains. The 'Upper Division' is well developed, a particularly fine collection of shells being found in Charnock Old Hall Bore. The fauna includes the following: Carbonicola aff. artifex, C. declinata, C. fallax, C. limax?, C. pilleolum, C. aff. rectilinearis, Curvirimula sp. nov., Naiadites sp. [juv.]; Geisina arcuata; Rhabdoderma sp.

Fossiliferous measures recorded between 230 and 260 ft in the Fox Hole Wood Bore (p. 115) and between 8 and 28 ft in the Black Pit Bore (p. 106) probably represent the Bassy Mine faunal sequence, but, especially in the Black Pit Bore, the lower parts may have been replaced by sandstones. South-east of Chorley the Adlington Bore (p. 102) proved only sandstone between the Bassy Mine horizon and the Lower Mountain Mine. Sandstones were also found to be well developed in the Heskin Bore (p. 116), south of the Charnock Old Hall and Tan House Farm bores, but an incomplete faunal sequence was recognised. The measures from 17 to 25 ft above the probable horizon of the Bassy Mine in this hole yielded a fauna including Carbonicola fallax and C. aff. rectilinearis, and are thought to represent the 'Lower Division' of Eagar's sequence (Magraw 1957, p. 28). Non-marine shells collected from 90 to 100 ft above the Bassy Mine horizon included Carbonicola aff. fallax, C. aff. limax, C. pilleolum?, C. artifex, Curvirimula sp. nov. and Naiadites sp. [oblique]. The fauna is too limited and poorly preserved to give definite indication of horizon, but probably represents Eagar's 'Upper Division', sandstones and sandy mudstones having replaced the 'Middle Division' and part of the 'Lower' and 'Upper' (Magraw 1957, p. 28).

Fossiliferous mudstones exposed [SD 6029 1556] in the left bank of the stream about 130 yd S. of Holland Fold yield the following fauna: Carbonicola cf. declinata, C. fallax, C. limax, C. rectilinearis?, Curvirimula sp. nov., C. sp.; Geisina arcuata. This horizon was at the time of the survey thought to be in the Millstone Grit Series, but the above assemblage is much more likely to come from one of the bands above the Bassy Mine.

The Lower Foot Mine is not exposed in the Blackburn basin and has not been recorded in boreholes in this area. It can be traced on the west side of Winter Hill, and when followed from here is found to fail towards the north. It is well seen on the east of Darwen Hill, a little beyond the margin of the map. The seam was proved in the Charnock Old Hall Bore (p. 107) as 10.5- in of coal overlain by a 1.5 in parting and 4 in of dirty coal, resting on seatearth 8.75 ft thick. In the Tan House Farm Bore (p. 125) the seam was 16 in thick, and was underlain by 6.75 ft of seatearth.

Fox Hole Wood Bore (p. 115) proved 12 in of coal at 220.667 ft, overlain by mudstone 'of a fossil nature', and underlain by mudstone in which Lingula 'Anthracosia' and 'Posidonia gibsoni' were recorded at three horizons. The measures proved in this borehole compare closely with those in Tan House Farm Bore, less than a mile to the south-west; the 12-in coal corresponds with the Lower Foot Mine of that hole, and the fossiliferous measures below with the Bassy Mine faunal sequence. In this hole 'Posidonia gibsoni' may be a misidentification, since this fossil is not found elsewhere in the Bassy Mine sequence. The fauna below the coal, which extends through some 40 ft of measures, is not thought to represent the Lower Foot Mine marine and non-marine phases, since these have a much thinner development and generally do not so closely approach the overlying coal. The 18-in coal recorded at the bottom of Black Pit shaft, 5 ft above which Gerrard (1908, p. 12) recorded non-marine shells, is now correlated with the Lower Foot Mine; it was formerly thought to be the Lower Mountain Mine (Magraw 1957, p. 28, (Figure 4))." data-name="images/P988345.jpg">(Figure 3)). Indeed it would appear that throughout the area of Coal Measures west and south-west of Chorley the coal mapped as Lower Mountain Mine is in fact the Lower Foot Mine. Some confirmation of this is given by fossils obtained from a small tip of an old pit [SD 5566 1733] 400 yd S. 40° E. of Bolton! Green. The pit worked the so-called Lower Mountain Mine, above which Carbonicola was recorded in the shaft section. The fauna collected from the tip included the following: Spirorbis sp.; Carbonicola artifex, C. declinata, C. obliqua Wright, Curvirimula sp.;fish remains. This assemblage suggests that the horizon is that of the Lower Foot Mine. The mudstone 'of a fossil nature', above the Lower Foot Mine in the Fox Hole Wood Bore (p. 115), and the shells observed by Gerrard in the Black Pit sinking, probably represent this non-marine phase.

The non-marine fauna above the Lower Foot Mine was found in the Charnock Old Hall and Tan House Farm bores (pp. 107, 125). It included the following Spirorbis sp.; Carbonicola artifex, C. declinata, C. fallax, C. obliqua, C. aff. obliqua, C. sp. nov.? [cf. Eagar 1956, figs. 5a-c], Curvirimula spp. nov., Naiadites sp.cf. subtruncatus (Brown) [small], Naiadites sp. [juv.]; Geisina arcuata; fish fragments.

The Lower Foot Mine Marine Band is only known with certainty in this district from these boreholes. It comprises a main development several inches thick, and a higher Lingula phase. In Charnock Old Hall Bore the main band yielded the following fauna: Lingula mytilloides; Caneyella cf. multirugata, Posidonia sp.,^- Anthracoceras sp., Gastrioceras sp., mollusc spat; fish remains. Tan House Farm Bore proved the marine band, but Gastrioceras and Caneyella were absent. Marine shales on a tip from an old shaft [SD 5718 1708] 400 yd N. 30° W. of Gillibrand Hall contain Caneyella multirugata, Anthracoceras sp. and Gastrioceras?; if this fauna is representative, the shale is likely to have been derived from the Lower Foot Mine Marine Band rather than the Bullion Mine Marine Band (see p. 68). Elsewhere in the Preston district the marine band has not been recorded, and it seems likely that it is absent from many areas (Magraw 1957, p. 33, fig. 2).

Shales and mudstones above the Lower Foot Mine vary in thickness, in general being thinner where the overlying Ganister Rock is thicker: around and north of Darwen Moor they are poorly exposed, but appear to be from 8 to 30 ft thick; west of Chorley, where proved in borings, they are about 20 ft thick; southward they appear to be replaced by the expansion of the overlying Ganister Rock. D.P.

The Ganister Rock is not generally developed in the Blackburn area and has not been mapped there. In the south bank of the River Darwen, 620 yd N. 40° E. of Immanuel Church, Feniscowles, 5 ft of rather coarse flaggy sandstone crop out [SD 6479 2617] at this horizon. Farther south the Ganister Rock is exposed in a small quarry [SD 6724 2102] on the west of the Stepback section, and in small quarries on the northern side of Winter Hill. It is hereabouts a white highly siliceous sandstone, about 35 ft thick.

Around Chorley the Ganister Rock varies from 0 to 40 ft in thickness. In the Charnock Old Hall Bore it was represented by 2.75 ft of ganister, but a mile to the east 25 ft of white fine-grained compact sandstone were proved in the Tan House Farm Bore. It was at least 18 ft thick in the Fox Hole Wood Bore but was not developed in Black Pit shaft. Towards the south the Ganister Rock is thicker, and appears to unite with the Harrock Hill Grit where that bed is developed. This was shown in the Heskin and Adlington bores (pp. 116, 102 and (Figure 8)); in the former the Ganister Rock cuts out the Lower Foot Mine and its marine band, and in the latter sandstone and subsidiary sandy mudstones were proved from below the Lower Mountain Mine to the. Bassy Mine horizon.

The Lower Mountain Mine has been mapped in the Blackburn and Darwerr Hill areas on the evidence of old coal workings, of which small tips of shale are almost the sole remaining traces. Ganister, the seat of this coal, crops out [SD 6488 2588] in a small stream about 500 yd E. 19° N. of Immanuel Church, Feniscowles, but the coal is not exposed. Where the Lower Mountain Mine can be correlated with certainty in the Chorley area it is not well developed. In the Charnock Old Hall Bore it was represented by 4 in of canneloid shale and coal resting on 8 in of sandy fireclay and the thin ganister which represents the Ganister Rock. It was not found in the Tan House Farm and Fox Hole Wood bores, but in the former ganister formed the top of the Ganister Rock. The coal was also absent from the Heskin Bore, but in the south-east of the Chorley area 6 in of coal were proved at this horizon by the Adlington Bore.

As noted above (p. 45) the recent boreholes and the correlation of the coal in the Fox Hole Wood Bore with the Lower Foot Mine demonstrate that the coal mapped as Lower Mountain Mine in the Charnock Richard area is the Lower Foot Mine, and that over the whole Chorley area the coal generally thought to be the Lower Mountain Mine is the Lower Foot Mine. R.C.B.J., D.P.

Lower Mountain Mine to Pasture Mine

The shales above the Lower Mountain Mine are generally badly exposed, and have not been proved in borings in the Blackburn and Darwen Hill districts although from the mapping they appear to be from 15 to 50 ft thick. In the Chorley area boreholes proved from 40 to 70 ft of mudstone and sandy mudstone above the Lower Mountain Mine. In the Charnock Old Hall Bore (p. 107) an 8-in sandstone formed the roof of the seam and was overlain by some 40 ft of mudstone and sandy mudstone. In the Tan House Farm Bore (p. 125) cf. Planolites ophthalmoides (Jessen) was found in the mudstone just above the Lower Mountain Mine horizon; some 50 ft higher there occurred Carbonicola sp. nov., Curvirimula sp. nov. and Naiadites sp.cf. productus (Brown). At a similar horizon in the Heskin Bore (p. 116) Carbonicola cf. fallax, Curvirimula sp., Naiadites sp. and indeterminate ostracods were found. The mudstones above the Lower Mountain Mine in the Adlington Bore (p. 102) yielded only Curvirimula sp. nov. and Naiadites sp.

The Bullion Mine Rock varies considerably in thickness. In the Blackburn and Darwen Moor area it appears to be from 15 to 35 ft thick. It forms much of Winter Hill but is only seen there in isolated exposures of flaggy sandstone. A little to the south it is exposed [SD 6728 2254] in Beech Hill Clough, about 1200 yd N. 37° E. of Ryal Fold, where 20 ft of sandstone is visible. In an old quarry [SD 6765 2150] on the face of Darwen Hill, about 200 yd W.S.W. of the Tower, it is flaggy, and is capped by the Bullion or Upper Foot Mine. It crops out [SD 6740 2093] in Stepback Brook about 900 yd S. 36° W. of Darwen Tower, where about 15 ft of flaggy sandstone with mudstone partings is exposed. A number of isolated exposures occur on the moors south of Darwen Hill. Up to 150 ft of Bullion Mine Rock have been proved in borings in the Chorley area. Tan House Farm Bore proved some 40 ft of white, mainly flaggy sandstone below the Bullion or Upper Foot Mine. A similar thickness of sandstone occurred in this position in Black Pit shaft (p. 106), but was underlain by 15 ft of linstey and mudstone and about 30 ft of flaggy sandstone. Flaggy sandstone exposed in the road-cutting [SD 5537 1718] 400 yd N. of Charnock Green probably corresponds with the flaggy sandstone. In an old quarry [SD 5725 1706] in Copper Works Wood, 300 yd N.N.W. of Gillibrand Hall, 8 ft of fairly coarse gritstone is exposed; this probably corresponds with the upper part of the Bullion Mine Rock in Black Pit shaft. The Heskin Bore (p. 116) proved an abnormally great thickness of Bullion Mine Rock, comprising 150 ft of white to grey mainly flaggy sandstone with some thin mudstone partings—one of which, near the base, yielded a single specimen of Carbonicola cf. fallax and fragmentary Curvirimula sp.In the Adlington Bore (p. 102) in the south-east of the district, 58 ft of mainly flaggy sandstone was recorded. R.C.B.J., A.E.Monograptus, D.P.

The Bullion or Upper Foot Mine has been worked on Bunkers Hill, and although it can no longer be seen its presence is evidenced by the marine fauna found on old spoil-heaps. The coal, 12 in thick, is visible [SD 6741 2092] to the south in Stepback Brook, 900 yd S. 35° W. of Darwen Tower. It is also exposed [SD 6732 1960] 450 yd S. 38° E. of the top of Cartridge Hill, close to the fault which throws Coal Measures against Millstone Grit. The Bullion Mine has not been mapped as such in the Chorley area, since at the time of the survey it had not been identified there. Subsequently boreholes have shown it to be poorly developed in the area. The 1.5-in coal proved in Black Pit shaft about 120 ft below the Upper Mountain Mine, and which has been mapped as 'thin coal' on the six-inch maps, can now be correlated with the Bullion Mine. In Tan House Farm Bore it comprised an inch of coal resting on a thin seat-earth capping the Bullion Mine Rock, but it was not proved in the nearby Charnock Old Hall Bore, nor in the Heskin Bore to the south. It was represented in the Adlington Bore by 2 in of carbonaceous shale with coal streaks.

The Bullion Mine Marine Band is exposed [SD 6741 2092] above the Bullion Mine in Stepback Brook, 900 yd S. 35° W. of Darwen Tower. Farther south it is visible [SD 6732 1960] in the stream a quarter-mile S.E. of Cartridge Hill. The fauna at these localities has not been studied in detail but appears to be typical. R.C.B.J., D.P.

In the Chorley area two boreholes have proved a non-marine phase between the Bullion Mine and the marine band: the roof of the coal in the Tan House Farm Bore comprised 16 in of bastard ganister overlain by 8 in of mudstone which yielded Carbonicola cf. artifex, C. rectilinearis? and Naiadites sp. cf. productus; in the Adlington Bore (p. 102) an inch of mudstone above the seam contained Curvirimula sp., Naiadites sp., and Geisina arcuata. The main marine band was 70 in thick in the Tan House Farm Bore. Lingula? occurred at the base, and above this the following were found: Caneyella multirugata, Dunbarella papyracea, Posidonia gibsoni, P. sp. nov.; gastropods [small]; Anthracoceras sp., Gastrioceras listeri (J. Sowerby); mollusc spat, conodont assemblages; and fish remains. Lingula mytilloides occurred from 5.25 ft to 9.25ft above the main marine band. In the nearby Charnock Old Hall Bore both the non-marine development and the lower part of the marine band, which carries the Dunbarella/Gastrioceras phase, were faulted out; the Lingula phase above the main band was not found in this borehole. Within the marine band in the Heskin Bore (p. 116) there were two horizons with characteristic marine fossils, separated by about 45 in of mudstone which contained only fish remains and a little plant debris. The lower marine horizon, comprising 16 in of shaly mudstone, carried the Dunbarellal Gastrioceras phase, and yielded the following fauna: Caneyella multirugata, Dunbarella papyracea, an indeterminate Pectinid, Posidonia sp., P. sp. nov.; gastropods; indeter­minate orthocone nautiloids, Anthracoceras or Dimorphoceras sp., Gastrioceras listeri; fish remains. The upper horizon, a 3-in ironstone, contained the following: Lingula mytilloides; Posidonia?; Anthracoceras?; Hindeodella sp.; fish scales. Similarly in the Adlington Bore (p. 102) a tripartite sequence was proved, 14 in of mudstone with marine macrofossils being overlain by some 5 ft of mudstone yielding only indeter­minate lamellibranch fragments, conodonts and fish debris, in turn overlain by a 2-in ironstone containing marine shells. The fauna was similar to that found in the Heskin Bore. D.P.

The marine band is overlain by argillaceous measures which are succeeded in many areas by the Inch Mine Rock. The Rock is not well developed in the Blackburn area, and is not found either in Stepback Brook or on Darwen Hill, though present to the south on Darwen Moor. The rock may cap Bunkers Hill, but here the succession is obscure. R.C.B.J., D.P.

In the Chorley area these measures have been proved in borings and in a shaft sinking, and show considerable variation in thickness and lithology. In Charnock Old Hall Bore the marine band was overlain by mudstone, which passed upward by alternation into the Inch Mine Rock comprising 16 ft of reddened sandstone. The nearby Tan House Farm Bore entered the Inch Mine Rock beneath drift and proved 36 ft of purple-grey flaggy sandstone underlain by mudstone with scattered fish debris. In the Heskin Bore the Inch Mine Rock was only 9 ft thick and was a massive fine-grained white sandstone. To the east the Inch Mine Rock appears to be poorly developed; in Black Pit shaft (p. 106) and in the Adlington Bore (p. 102) it comprised some 12 ft of sandstone with numerous mudstone partings.

The Inch Mine has not been proved between Blackburn and Darwen Moor, but has been mapped over part of this area on the basis of the succession to the east. At the time of the survey it had not been identified in the Chorley area and was not mapped as such; subsequently boreholes have revealed that the thin 'coal' shown on some of the six-inch maps about 60 ft below the Upper Mountain Mine is the Inch Mine. The seam was 5 in thick in the Charnock Old Hall Bore and was capped by an inch of sandstone overlain by 2 in of coaly mudstone. It was 10 in thick in Black Pit shaft and in the Adlington Bore, but in the Heskin Bore it was only represented by thin coal streaks in mudstone above a thin sandy seatearth. D.P.

The shales and mudstones above the Inch Mine are from 10 to 50 ft thick. Mudstones at this horizon are exposed [SD 6744 2090] in Stepback Brook about 900 yd S. 33° W. of Darwen Tower, just north of the fault which repeats the Six Inch Mine and its marine band. They are not exposed elsewhere in the north-east of the district. Shales recorded by the late Edward Hull at a point [SD 5609 1699] 500 yd S.S.W. of the ford near Bolton Green probably overlie the Inch Mine. The measures are, however, best known from boreholes. Charnock Old Hall Bore proved 31 ft of mudstones with fish fragments at the base, but the junction with the overlying Warmden Sandstone was faulted. To the south and south-east, in the Heskin and Adlington bores (pp. 116, 102), the mudstones just above the Inch Mine also yielded fish fragments including Rhadinichthys sp., Strepsodus? and indeterminate Palaeoniscid scales, and Curvirimula sp.was found near the top of these mudstones.

The Warmden Sandstone is visible in isolated exposures along the sides of the Stepback valley, and in an old quarry [SD 6715 2080] about 1-mile S.W. of Darwen Tower where flaggy sandstone is seen resting on more massive sandstone. It forms the summit of Darwen Hill, and the tower which stands there is probably built of it. It caps Darwen Moor, but the outcrop is largely concealed by peat. In the Chorley area the Warmden Sandstone is exposed [SD 5600 1695] in a stream 800 yd E. 30° S. of Bolton Green, where it is a medium-grained reddish sandstone. In Charnock Old Hall Bore it was a fine- to medium-grained ripple-bedded sandstone with a faulted base, and a thickness of 37 ft was recorded. In Black Pit shaft the mudstones above the Inch Mine were succeeded by about 26 ft of measures comprising linsteyFor definition see p. 102. and mudstones with thin sandstone bands and a 1-in seatearth; these were overlain by some 14 ft of white sandstone capped by ganister and seatearth. The Warmden Sandstone occurred in two leaves in the Heskin Bore (p. 116); the lower leaf was a well jointed pale sandstone with occasional mudstone partings, and the upper a fine to medium-grained massive sandstone. In the south-east the Adlington Bore (p. 102) proved only 14.667^, ft of Warmden Sandstone, but the Upper Mountain Mine which generally lies close above it was here separated from it by some 40 ft of sandy mudstone and linstey.

The Upper Mountain Mine crops out on Darwen Hill; it is not exposed, but has been worked from numerous shallow shafts. It has been similarly worked on Darwen Moor, and in this area it is frequently referred to as the Yard Mine. The coal has been worked extensively in the Chorley area, where in the past it was also known as the Mountain Mine or Middle Mountain Mine. It varies in thickness from 3.5 to 54 in but is usually between 24 and 42 in. Its outcrop is well marked by crop workings west of the Yarrow. Traces of coal and seatearth were seen [SD 5598 1692] above the Warmden Sandstone in the stream section about a half-mile S.E. of Bolton Green. It was said to be 30 to 54 in thick in the workings of Moor Road Pit, but at the greater thickness was 'very gross' coal. To the west in Heskin No. 4 Shaft (p. 119) it was 36 in thick, but in the Heskin Bore about a mile to the south-east it was only 24.5 in. South-east of Chorley the coal was worked from its outcrop south of Hall o' the Hill to a depth of 360 ft; in Rosbottoms Pit [SD 5985 1472] about 1300 yd E. 15° S. of Duxbury Hall it was 30 in thick, but three-quarters of a mile to the south-east the Adlington Bore proved only 3.5- in of coal at this horizon. This thinning of the seam probably accounts for the limitation of its working in this area.

On Darwen Hill and Darwen Moor the Upper Mountain Mine is separated from the Cannel Mine by the Icconhurst Sandstone. This bed crops out over much of the moorland area but is not exposed at the surface, being for the most part covered by peat; it has been proved by numerous shafts sunk to the Upper Mountain Mine. In the district to the east the measures between the two seams are very variable (Wright and others 1927, p. 29), and such variation may also occur in the Blackburn area but of this there is no evidence.

Around Chorley the Upper Mountain and Cannel mines are from 6 to 18 ft apart, but the Icconhurst Sandstone is not generally present. It is developed about half a mile south-east of Bolton Green, where in a stream [SD 5596 1690] the Upper Mountain Mine is overlain by about 4 ft of sandy mudstone and 16 ft of white sandstone and sandy seatearth. In a nearby old shaft [SD 5583 1685] 7 ft of soft white sandstone were recorded below the Cannel Mine. The Icconhurst Sandstone was also represented, albeit poorly, at Birkacre Colliery, where 12 ft of mudstone overlain by 4 ft of sandstone separated the Upper Mountain and Cannel mines. All other available records show dominantly argillaceous measures, mainly seatearth, between the two seams. The Cannel Mine, also known as Little Mine, is present over most of the coalfield about Chorley, where it varies in thickness from 5 to 16 in. It has been proved in a number of shafts and boreholes in the area, but was not found in the Adlington Bore. R.C.B.J., A.E.Monograptus, D.P.

The Cannel Mine Marine Band, known in the Preston district from two bores, is characterized by large specimens of Ammodiscus. In Charnock Old Hall Bore (p. 107) it lay 20 in above the Cannel Mine and comprised 22 in of black and grey shale yielding the following: foraminifera, including Ammodiscus sp., Agathammina sp. and Hyperammina sp.; Lingula sp. [rare]; and Acanthodian and Palaeoniscid scales. The second record of the marine band in this district is from the Crook Fold Bore (p. 110), in which it comprised 18 in of pitted black shale from which the following were obtained: foraminifera including Ammodiscus sp.;condonts; and fish remains including Palaeoniscid scale and Rhadinichthys sp.

The Cannel Mine is generally overlain by from 65 to 90 ft of mudstone and sandy mudstone with thin beds of sandstone. These measures are increasingly arenaceous towards the top, and generally pass upward into the Darwen Flags. The Darwen Flags were not found in Charnock Old Hall Bore (p. 107), in which about 120 ft of predominantly argillaceous measures separate the Cannel Mine from Tonge's Marine Band. In this bore some of the more argillaceous parts of these measures contained Curvirimula sp. and Naiadites sp. cf. subtruncatus. The measures in the Crook Fold Bore (p. 110) were less fossiliferous, yielding only Curvirimula sp.at an horizon about 35 ft above the Cannel Mine. In the south-east the Adlington Bore (p. 102) proved mudstone with Curvirimula sp. and Naiadites sp.from 55 to 62 ft above the Cannel Mine. Mudstones above the Cannel Mine are exposed in a number of streams west of Chorley, and are best seen in Roscoe Wood [SD 561 168] east of the railway cutting at Charnock Green.

The Darwen Flags are a group of dominantly arenaceous measures which overlie the mudstones described above. They are exposed in the section in Roscoe Wood. They were not found in Charnock Old Hall Bore (p. 107), but were recorded in all other bores and shafts. In the Crook Fold Bore (p. 110) they were represented by 11.5 ft of grey flaggy sandstone with sandy mudstone partings in the lower part. In Heskin No. 4 Shaft (p. 119) 6 ft of sandstone and 15 ft of linstey represent the Darwen Flags. At Moor Road Pit (p. 123) they comprised 18 ft of flaggy sandstone overlain by11 ft of more massive sandstone, 7.5 ft of linstey and 4.5 ft of sandstone. To the south the Heskin Bore (p. 116) proved 50 ft of mainly flaggy, white sandstone with partings of linstey and sandy mudstone. The Adlington Bore (p. 102) proved 30 ft of white and pink sandstone, flaggy and ripple-bedded in the lower parts, overlain by 5 ft of linstey and 25.5 ft of turbulently bedded white fine-grained sandstone with some mudstone partings. D.P.

Mudstones and a thin coal and its seatearth commonly lie between the top of the Darwen Flags and Tonge's Marine Band. In the Crook Fold Bore (p. 110) the mudstones, 18 ft thick, yielded sporadic Curvirimula sp.;they were overlain by some 10.667 ft of seatearth and a 4-in coal. This coal was also proved in Heskin No. 4 Shaft where it was 6 in thick, and in Charnock Old Hall Bore. It was not found in the Heskin or Adlington bores, but in the former the top of the Darwen Flags was uneven and capped by 33 in of ganister-like seatearth. The coal is exposed [SD 5598 1664] at the surface in the railway cutting 720 yd E. 14° S. of Charnock Green, where an inch of dirty coal rests on the ganister-like top of the Darwen Flags.

Tonge's Marine Band is visible above the coal in this section, as 7 in of dark shaly mudstone and 1.5 in of shale with marine fossils including goniatites and Ammodiscus. It also crops out in a small overgrown quarry just east of the cutting, where it yields the following fauna: Caneyella sp. nov. aff. multirugata, Dunbarella cf. papyracea; Anthracoceras sp., Gastrioceras cf. amaliae H. Schmidt; conodonts including Hindeodella; fish remains including Elonichthys sp.In the Crook Fold Bore (p. 110) the main marine band was underlain by a foraminiferal phase comprising about 4 in of black shale with Ammodiscus sp.The main band, a limy mudstone 3 in thick, contained a fauna similar to that found at outcrop, including Gastrioceras cf. amaliae. About 4 in above the marine band Planolites ophthalmoides and Geisina arcuata were found. No foraminiferal phase was recorded below the main band in the Charnock Old Hall Bore (p. 107), but a thin foraminiferal/Planolites phase occurred just above it. The marine band was also proved by the Heskin Bore, and there yielded the following: Lingula sp.; Caneyella sp. nov. aff. multirugata, Dunbarella cf. papyracea, Posidonia cf. gibsoni; gastropod; indeterminate orthocone nautiloid, Anthracoceras?, indeterminate goniatites [ghost-like preservation]; Hindeodella sp., platformed conodonts; and fish remains. At Birkacre Colliery, where it was formerly exposed, the band provided no goniatites and the fauna was as follows: foraminifera including Ammodiscus; Caneyella sp. nov. cf. multirugata, Dunbarella papyracea; Hindeodella sp.;and an indeterminate Palaeoniscid scale. Tonge's Marine Band was not found in the Adlington Bore.

Between the horizon of Tonge's Marine Band and the Crutchman Sandstone there are from 30 to 70 ft of mudstones and sandy mudstones with thin sandstone partings. Fish fragments are common near the base, and in the Heskin Bore were also found towards the top. Curvirimula sp.was recorded in less sandy measures towards the top in Charnock Old Hall Bore (p. 107). Two sandstones, 6 ft and 3 ft thick, were recorded in Heskin No. 4 Shaft (p. 119). The succeeding Crutchman Sandstone forms a series of ridges, separated by faults, along its outcrop at Charnock Richard. Along these ridges are numerous quarries and other exposures. The sandstone is very coarse, even tending to be pebbly. It is exposed [SD 5597 1647] in the railway cutting 800 yd E. 22° S. of Charnock Green, where 15 ft of coarse to very coarse sandstone is overlain by 10 ft of flaggy sandstone followed above a 5-ft gap by thick coarse red sandstone. In the canal and railway cuttings north-east of Ellerbeck Hall, and in a quarry [SD 6008 1437] north-east of these, current-bedded, mainly fine-grained sandstones overlie coarser beds. These are referred to the Crutchman Sandstone.

Charnock Old Hall Bore (p. 107) was sited on the outcrop of the Crutchman Sandstone and entered some 40 ft of open-jointed reddened coarse-grained sandstone, limonitic in patches. In Moor Road Pit (p. 123) 87 ft of brown sandstone were proved, and a similar development-84 ft of coarse red and brown sandstone—was found in Heskin No. 4 Shaft (p. 119). Crook Fold Bore (p. 110) proved 79 ft of reddened medium to coarse-grained sandstone, flaggy in parts, with numerous partings of purple-grey sandy mudstone in the basal 20 ft. In the Heskin Bore (p. 117) the rock was a massive, well-jointed, grey to purple, coarse to very coarse-grained highly siliceous sandstone with micaceous partings, and with 3 in of purplish hematitic sandy mudstone 10 ft from the top. In the Adlington Bore (p. 103) it had a total thickness of 102.5 ft, and comprised pink sandstone, current-bedded at the base and with thin chocolate-coloured mudstone partings in the upper parts, overlain by well-jointed, massive pink sandstone with some highly micaceous partings.

The Pasture Mine was proved in Moor Road Pit where it was 8 in thick; it is not known elsewhere in the Preston district, but has been mapped in the Blackburn area on the basis of the succession proved to the east. The top of the Crutchman Sandstone is poorly exposed [SD 5441 1579] 300 yd N.E. of Park Hall, but there is no coal on it. In boreholes in the Chorley area the horizon of the seam is commonly marked by a seatearth capping the Crutchman Sandstone. R.C.B.J., A.E.Monograptus, D.P.

Pasture Mine to base of Arley Mine

The Pasture Mine and Ditton marine bands have not been proved in the Preston district, although they were present in the Wrightingtoh Bore about a mile to the south (Magraw 1957, p. 21). Nevertheless, vermicular and spherulitic pyrites, a feature of the bands in the Wrightington Bore, were recorded at similar horizons in the Adlington Bore (p. 102).

The mudstones above the Pasture Mine horizon, frequently called the Accrington Mudstones, are not exposed in the Blackburn area and have there been mapped on the basis of the known succession to the east. South-west of Chorley they are exposed in Swift Wood [SD 543 154] and Dam Wood [SD 545 158], east and north-east of Park Hall, where they are blue shaly mudstones. The full thickness has been proved in two boreholes and a shaft sinking—Heskin Bore (p. 116), 180 ft; Moor Road Pit (p. 123), 190 ft; and Adlington Bore (p. 102), 130 ft. They are here grey to dark grey mudstones, occasionally sandy, and frequently shaly. Worm tracks are common near the base and fish fragments occur in the higher parts. A.E.Monograptus, D.P.

The Dyneley Knoll Flags, mapped in the Blackburn area, form a group of arenaceous beds which are developed near the base of the Accrington Mudstones in some areas. They are mapped on the basis of the succession proved in the area to the east.

The base of the Old Lawrence Rock is variable and somewhat indefinite. In the Adlington Bore the Accrington Mudstones were overlain by 16 ft of fine to medium-grained micaceous sandstone under drift. This sandstone has been mapped as a lower leaf of the Old Lawrence Rock; it is exposed about half a mile to the south-west in an old quarry [SD 600 136] 850 yd E. 22° S. of Ellerbeck Hall, where 30 ft of flaggy sandstone are visible. In the Heskin Bore, however, the Accrington Mudstones passed up into about 160 ft of sandy mudstone and linstey with bands of flaggy sandstone. These measures were succeeded by 29 ft of mainly flaggy, fine-grained sandstone, which are taken to represent the lower leaf of the Old Lawrence Rock; the upper leaf, some 40 ft above, comprised 17 ft 10 in of mainly massive sandstone overlain by 7.75 ft of fossiliferous mudstone and 20 ft of flaggy and massive sandstone. The fossiliferous mudstone yielded the following: Lepidostrobus sp.; Spirorbis sp.; Carbonicola martini? Trueman and Weir, C. spp., Curvirimula cf. trapeziforma (Dewar), C. sp., Naiadites aff. flexuosus Dix and Trueman; Geisina arcuata; and fish scales. Moor Road Pit (p. 123) was sunk on the outcrop of the lower leaf of the Old Lawrence Rock, and proved, under drift, 38 ft of soft flaggy sandstone; some 40 ft of linstey and sandy mudstone lay between this and the Accrington Mudstones.

The measures between the Old Lawrence Rock and the Arley Mine are, with the exception of the top few feet, only known with certainty in the Preston district from the Heskin Bore. In this hole the Old Lawrence Rock was overlain by about 8 ft of seatearth with partings of mudstone and half an inch of dirty coal. This coal has been correlated with the Dib Hole Coal of the Blackburn–Accrington area (Magraw 1957, p. 19); and is not known elsewhere in the district though represented to the east and south. The coal was overlain by about 65 ft of mudstone and sandy mudstone. Fragments of Naiadites sp.were found 9 ft above the coal, and Carbonicola sp., Geisina arcuata and fish remains in a thin band 5 ft higher. Some 4 ft of dark mudstone about 40 ft above the coal contained 15 layers of shells and yielded the following fauna: Spirorbis sp.; Anthraconaia?, Carbonicola cf. bipennis, C. subconstricta Wright (non J. Sowerby), C. aff. torus Eagar, C. sp., Curvirimula sp., Naiadites sp.; Geisina arcuata; fish remains including an Acanthodian spine, and scales of Elonichthys sp., Megalichthys sp., Rhabdoderma sp., Rhadinichthys sp. and Rhizodopsis sp.This fauna equates with the Daubhill fauna from Daubhill Brickworks near Bolton, described by Wright (Tonks and others 1931, pp. 134–5) and Eagar (1956, p. 359). The mudstones were overlain by 14 ft of ganister-like sandstone which yielded Carbonicola cf. antiqua (Brown) and C. sp.near the top. Eight feet above the sandstone were 10 in of carbonaceous shale and 4 in of coal, the coal being separated from the overlying seatearth of the Arley Mine by 9.33 ft of grey mudstone which at the base contained the following: Spirorbis sp., large indeterminate lamellibranchs (Carbonicola?), and Geisina arcuata. The fossils found at the top of the sandstone and above the 4-in coal represent new faunal horizons for the Lancashire Coalfield, but are poorly preserved and few in number. The two horizons have since been proved in a number of boreholes in other parts of the coalfield. In the Wrightington Bore, just to the south of the Preston district, the lower horizon contained a varied fauna including the following: Spirorbis sp.; Carbonicola cf. bipennis, C. aff. subconstricta?, C. sp. [large], Curvirimula cf. trapeziforma, Naiadites sp.; Carbonita cf. humilis (Jones and Kirkby) and Geisina arcuata. The upper horizon yielded Curvirimula cf. trapeziforma and Naiadites sp. D.P.

Around Welch Whittle and Birkacre there is a sandstone immediately below the Arley Mine seatearth. A borehole [SD 5507 1387] about 700 yd E. 30° N. of Welch Whittle Colliery, proved 18 ft 10 in of dark argillaceous sandstone at this horizon, with a small fault at the top. In the haulage-tunnel at Birkacre Colliery the Arley Mine was underlain by 28 in of fireclay and ganister and 6 in of fireclay and coal, overlying 18 ft of hard white sandstone with a ganisteroid top. Farther north in the Higher Kingsley Bore [SD 5670 1676], 700 yd W. of Gillibrand Hall, about 19 ft of red sandstone were proved below the Arley Mine seatearth. A.E.Monograptus, D.P.

Arley Mine and higher measures

The Arley Mine, the thickest seam in the Preston district, has been worked extensively. It is nowhere exposed at the surface but is well known from bores, shafts and old workings. The seam, with included dirt partings, is generally 67 to 74 inches thick, but there are a number of records of thinner developments; included dirt partings may be up to 6 in thick. The top 6 to 10 in of the seam commonly comprise inferior coal known locally as buzzard; very friable coal or 'burgy' is also common at the top. The best development of the Arley Mine was recorded in Higher Kingsley Bore [SD 5670 1676] 700 yd W. of Gillibrand Hall, in which it is said to have been 74 in thick and to have contained only half an inch of dirt; the thinnest known development was recorded in Plock Colliery No. 1 Shaft [SD 5800 1573], 600 yd N.N.E. of Burgh Hall,. where the seam was only 39 in. Other sections are detailed in Appendix I.

The Arley Mine is separated from the next higher workable seam, the Smith Mine, by 180 to 240 ft of mudstones with subsidiary sandstones and, in some areas, thin coal seams. These measures are not exposed at the surface but are known from a number of shafts, boreholes and colliery workings. The sandstones are not generally over 15 ft thick and do not generally make up more than about a tenth of the measures.

Be this as it may, in the Barlow's Farm Bore (p. 104), of some 180 ft of measures proved below the Smith Mine over 75 ft were sandstone. A borehole [SD 5507 1387] 1600 yd W. 18° S. of Coppull Station proved about 2 ft of seatearth and 60 ft of current-bedded sandstone above the Arley, but this sandstone has not been found in other nearby boreholes and probably represents a localized washout.

The roof of the Arley Mine is generally of dark shale or mudstone containing fish debris. In the Heskin Bore (p. 116) the fauna included Acanthodian spines, indeterminate Palaeoniscid scales and Rhabdoderma sp.A similar fauna occurred above the Arley Mine in a borehole [SD 5507 1423] 1500 yd W. 4° S. of Coppull Station, and here Planolites was recorded 13 ft above the Arley Mine.

A 2-in ironstone band about 85 ft above the Arley Mine, exposed in tunnels at Ellerbeck Colliery south-west of Ellerbeck Hall, yielded poorly preserved fossils including the following: Spirorbis sp.; Carbonicola cf. pseudorobusta, Curvirimula sp.; Geisina arcuata. At a corresponding horizon in the Barlow's Farm Bore (p. 104) a 3-in ironstone contained shell fragments, and about 18 ft higher 2 in of ironstone yielded Spirorbis sp. and indeterminate fragmentary shells.

A widely-recognized faunal horizon, generally characterized by Carbonicola pseudorobusta, lies 130 to 160 ft above the Arley Mine. It was well developed in Barlow's Farm Bore, where a 14-in coal, split by a 2.5-in dirt band, was overlain by shale and mudstone which contained the following fauna: Spirorbis sp.; Carbonicola pseudorobusta, Curvirimula trapeziforma, Naiadites flexuosus; Geisina arcuata; and fish remains. This band was closely overlain by mudstones, from which were obtained the following: Carbonicola acuta?, C. bipennis, Curvirimula sp.; and Geisina arcuata. The horizon was proved about 135 ft above the Arley Mine in a tunnel at Ellerbeck Colliery, where the section from bottom to top was as follows: coal 6 in, cannel and black shale—main Carbonicola band-14 in, cannelly shale 4 in, dark shale with shells 3 in, grey mudstone with ironstone and scattered shells. The dark cannelly measures yielded Anthraconaia sp. nov., Carbonicola pseudorobusta, Curvirimula trapeziforma, C. subovata (Dewar), Naiadites sp.;and Geisina arcuata. The overlying grey mudstone contained Carbonicola aff. communis Davies and Trueman and Geisina arcuata, along with fish fragments. To the west at Welch Whittle Colliery the section was: coal 24 in, cannel (poor) 4 to 6 in, dark grey mudstone 4 to 6 in, grey mudstone 24 in. The mudstones yielded the following fauna: Carbonicola bipennis, C. pseudorobusta, C. subconstricta, Curvirimula trapeziforma, Naiadites flexuosus; Geisina arcuata. In the upper part of the band C. bipennis and C. subconstricta largely replaced the C. pseudorobusta. Corresponding shell bands were recorded in Coppull Pit (p. 109) and in Duxbury Park Colliery Shaft (p. 111), but no details of the fauna are known. The band was also proved in a tunnel from the Arley to the Smith Mine just south of Kingsley, but the tunnel was inaccessible at the time of the survey and there is no detailed record of the strata penetrated. R.C.B.J., A.E.Monograptus, D.P.

The Smith Mine varies in thickness from 17 to a maximum of 30 inches in Duxbury Park Colliery Shaft. It is underlain by a seatearth from 2 to 7 ft thick. The coal is of good quality but is largely worked out. A shell-bed was recorded in its roof at Duxbury Park Colliery, but at Ellerbeck Colliery, 500 yd to the south, the roof measures contained only a few scattered plant remains. The shell-bed is not known elsewhere in the district. R.C.B.J., A.E.Monograptus, D.P.

The Smith Mine is generally closely overlain by the Smith Top Coal and the Cockloft Mine. In Welch Whittle downcast shaft (p. 126) the section was:

A similar sequence was proved at Pemberton House Colliery [SD 5397 1512], about 450 yd S.S.W. of Park Hall, and in the more recent Barlow's Farm Bore (p. 104). In the Kingsley House Bore (p. 121) the seams were more widely spaced; there were 13 ft 1 in of measures between the Smith Mine and the Smith Top Coal, and 50 in of measures between the latter and the Cockloft Mine. In the Duxbury area only one seam occurs close above the Smith Mine, and this is generally correlated with the Cockloft Mine. In the Coppull Colliery Shaft it was only 18 in above the Smith Mine, but in Duxbury Park Colliery shaft 20 ft of shale and seatearth intervened.

Mudstones just above the Cockloft Mine in Welch Whittle downcast shaft are said to have yielded 'Carbonicola cf. aquilina'and 'C. fallax' . In Coppull Pit (p. 109) fish scales and 'Anthracosia' were recorded at this horizon; and in this pit a 9-ft sandstone lay close below the Bone Mine. An arenaceous development was also found at Duxbury Park Colliery (p. 111), where two thin sandstones separated by 5 ft of mudstone were penetrated below the Bone Mine seatearth. Part of the succession between the Cockloft and Bone mines is poorly exposed [SD 545 146] in the banks of the Yarrow just south of the reservoirs at Birkacre. Mudstone overlain by strong sandy shale and by 10 ft of flaggy sandstone are visible [SD 5920 1587] below the Bone Mine in the Yarrow valley 900 yd N.N.E. of Duxbury Hall.

The Bone Mine varies in thickness from 19 to 36 in, but does not generally much exceed 24 in. It is exposed [SD 5928 1585] in the bank of the Yarrow, 900 yd N.N.E. of Duxbury Hall, where it appears to have a sandstone roof. Thicknesses proved in shafts and boreholes include the following: Kingsley House Bore 19 in; Welch Whittle downcast shaft 20 in; Lower Kingsley Bore 24 in; Coppull Pit 26 in; Duxbury Park Colliery 36 in; Duxbury Colliery 25 in. The seam has been worked extensively.

The Bone Mine is separated from the Yard Mine by 130 to 140 ft of strata, normally comprising three distinct cycles. The complete succession is only known from three shaft sections and a borehole. In the downcast shaft of Welch Whittle Colliery (p. 126) the Bone Mine was overlain by 13 ft 7 in of mudstone and linstey, 12.75 ft of sandstone and 7 ft of seatearth capped by a 4-in coal. The succeeding second cycle comprised 41 ft of mudstone and linstey, 20 ft of sandstone and 22 ft of mudstone and linstey, overlain by a 6-in coal. The third cycle consisted of 25 ft of mudstone with sandstone bands, overlain by the Yard Mine and its seatearth. In Duxbury Park Colliery Shaft (p. 111) the coal at the top of the lowest cycle was 6 in thick; the second thin coal was absent, but 4 ft of seatearth occurred at its horizon. In Coppull Pit (p. 109) only the higher coal was present; it was 3 in thick. In the west the Kingsley House Bore (p. 121) proved only the lowest cycle and a few feet of the succeeding mudstones; the coal was 6.5 in thick. The Lower Kingsley Bore (p. 122) proved about 90 ft of strata above the Bone Mine. The succession differed from the fairly consistent succession proved elsewhere; for above the Bone Mine some 40 ft of mudstone with a thin sandstone and 15 in of 'bass and coal' in the middle were overlain by 55 ft of red sandstone, followed by mudstones and thin sandstones. This thick sandstone is not known elsewhere in the area.

The Yard Mine has been worked from numerous old collieries near Coppull and Ellerbeck. Recorded thicknesses range from 27 to about 38 in, and include the following: Welch Whittle downcast shaft 29 in; Springfield Pit 34 in (including 2 in of hoo-cannel at the top); Coppull Pit 33 in; Duxbury Park Colliery 30 in; Duxbury Colliery 38 in.

Strata above the Yard Mine are exposed in the Yarrow 600 yd N. of Duxbury Hall. A cliff at the point where the river turns sharply to the south shows the following section:

The top part of this section is succeeded in the river bed to the south by more sandstone, making a total of about 20 ft. A thick bed of seatearth succeeded by grey mudstone is seen a little higher in the sequence. The fossiliferous carbonaceous shale in the above section yields the following: Carbonicola cf. centralis (J. de C. Sowerby), Curvirimula trapeziforma; Geisina arcuata; and fish remains. What appears to be this same shell-band was also found in the roof of the Yard Mine at Birkacre Colliery about a mile to the west, but it carried an abundant Carbonicola pseudorobusta fauna. At Birkacre the shell-band comprised 8 in of dark mudstone crowded with fossils including the following: Spirorbis sp.; Carbonicola pseudorobusta [and variants], Curvirimula trapeziforma; Geisina arcuata; and fish remains. This faunal horizon has not been found elsewhere in the Preston district; at Welch Whittle Colliery only poor plant impressions were recorded above the Yard Mine.

In the Birkacre shaft-section 76 ft of red sandstone was recorded about 30 ft above the Yard Mine, and this is evidently a swollen representative of the sandstone seen in the Yarrow section north of Duxbury Hall. The increased thickness is accompanied by an increase in the distance between the Yard Mine and the seams above. Other shaft sections in the area show from 3.5 to 15 ft of sandstone at this horizon. The seatearth seen above the sandstone in the Yarrow section has been recorded in a number of shafts, and appears to be about 3 ft thick; but at Duxbury Park Colliery, about a mile south of the river section, it was found to be 17.5 ft thick. A coal is generally present at the top of, or close above, the seatearth: in Highfield Farm Bore (p. 120) it comprised 5 in of coal overlain by 9 in of seatearth and a further 7 in of coal, the roof of which yields a few indeterminate shells; in Welch Whittle downcast shaft (p. 126) 3 in of coal, 6 in of black bass and 15 in of cannel were recorded. A single 5-in coal was found in Coppull Pit (p. 109), and a 6-in coal with a sandstone roof at Duxbury Park Colliery (p. 111). D.P., L.H.T., A.E.Monograptus, R.C.B.J.

The Ravine Mine in this district is made up of a number of thin and commonly inferior coals, interbedded with seatearths, carbonaceous mudstone and occasionally sandstone; the total thickness may exceed 30 ft. The seam may be considered in two parts—the Ravine Mine and the Ravine Mine Tops— since it generally comprises a group of mainly thin coals and seatearths, separated by 10 to 20 ft of seatearth and mudstone from a higher and thicker coal. In Highfield Farm Bore (p. 120), the part here called the Ravine Mine was 22 ft thick; the coals, for the most part of poor quality, accounted for about 4 ft of this thickness: the Ravine Mine Tops, 18 ft above, was 25 in thick and had a single 1.5-in dirt parting an inch from the base. In Coppull Pit (p. 109) the Ravine Mine was only 16 ft 2 in thick, and the Ravine Mine Tops 20 in thick. A coal a little over a foot thick which probably represents part of the Ravine Mine is exposed [SD 5872 1417] in the loop of the Yarrow, 1600 yd E. 7° S. of Coppull Station, and is overlain by dark shales with coal streaks.

Some 50 to 70 ft of measures separate the Ravine Mine Tops from the King and Queen mines. These are generally mudstone with subsidiary sandstones, but in Welch Whittle downcast shaft (p. 126) 23 ft of sandstone was found about 20 ft below the King and Queen mines. In Springfield Pit (p. 123) an inch of coal on a 9-in seatearth, which overlay 2 ft of sandstone, was recorded some 35 ft above the Ravine Mine Tops; at this horizon in the Coppul Hall Bore [SD 5802 1360], 1700 yd W. 12° S. of Ellerbeck Hall, coal was absent, but a 6-in seatearth overlay 5 ft of silty sandstone.

The King and Queen mines, a closely associated group of coals, succeed these measures. The coals and partings have a total thickness of from 6 to 9 ft and overlie 2 to 7 ft of seatearth. The following sequence was proved in the Coppull Hall Bore:

In Duxbury Park Colliery Shaft (p. 111) about three-quarters of a mile to the north-east, the Queen Mine was a single seam 30 in thick, but the King Mine showed a similar development to that detailed above. In Highfield Farm Bore (p. 120) the Queen Mine contained two partings of seatearth, and was separated from the King Mine by 33 in of mudstone and seatearth. At Springfield Pit (p. 123) the section was similar to that proved in the Coppull Hall Bore, but in Welch Whittle downcast shaft (p. 126), about a mile to the west, the Queen Mine appeared to be represented by only 2 in of coal, about 2 ft below the King Mine.

The measures between the King Mine and the Cannel Mine vary in thickness from about 90 ft at Duxbury Park Colliery (p. 111) in the east to 58 ft at Springfield Pit (p. 123) two miles to the west, and possibly down to less than 10 ft a mile farther west at Welch Whittle Colliery. The following section of these measures was proved in the Coppull Hall Bore:

Fish fragments occurred in the roof of the King Mine, and Curvirimula cf. candela was found 9 ft and 19 ft above. Carbonicola? was collected just above the 1.5-in inferior coal. In Highfield Farm Bore (p. 120) the measures were only 70 ft thick and only one inferior coal was proved: Naiadites sp. and fish fragments were recorded in mudstone above the King Mine; the inferior coal, found about 55 ft above the King Mine, rested on seatearth which capped an 18 ft sandstone. The inferior coals were not recorded at Springfield Pit, where some 45 ft of mudstone and 10 ft of seatearth lay between the King and Cannel mines. In Welch Whittle downcast shaft (p. 126) the King Mine was overlain by (in upward order of succession) a thin mudstone, 5 ft 5 in of sandstone, and 17 in of hoo-cannel and coal, the coal probably representing the Cannel Mine.

The Cannel Mine varies in thickness and composition. It is generally bituminous coal, sometimes found to be inferior; and cannel-type coal has only been recorded in the area at Springfield Pit and at Welch Whittle. Recorded thicknesses include the following: Springfield Pit (p. 123) 20 in; Highfield Farm Bore (p. 120) 46 in (including an 18-in dirt parting); Coppull Hall Bore 18 in (mainly inferior coal and dirt); and Duxbury Park Colliery (p. 111) 36 in (including a 3-in parting).

The Cannel Rock is well developed at Welch Whittle but fails to the east. In Welch Whittle downcast shaft it immediately overlay the Cannel Mine and comprised 68 ft of white sandstone with two mudstone partings; at Springfield Pit it was 27 ft thick, and was separated from the underlying coal by 18 in of 'black bass'; elsewhere the rock is very thin, or absent. In the Coppull Hall Bore (see p. 55) some 30 ft of measures separated the Cannel Mine from the Little King Mine; and here mudstone above the Cannel Mine yielded Curvirimula candela and Carbonicola pseudorobusta in addition to fish debris. Shells were also recorded at this horizon in the Highfield Farm Bore (p. 120). D.P., L.H.T., R.C.B.J.

The Little King Mine was proved by the Highfield Farm and Coppull Hall bores, and a seam at this horizon is also recorded in the shaft-section of Duxbury Park Colliery. It would also appear that the seam now being worked at Ellerbeck Colliery under the name of Upper King Mine is the Little King Mine. In Coppull Hall Bore the seam was 24 in thick and overlay about 9 ft of seatearth and carbonaceous mudstone, in the middle of which was a 4-in inferior coal. It was also 24 in thick in the Highfield Farm Bore, but contained a number of dirt partings. At Duxbury Park Colliery the seam was 36 in thick, with a 6-in dirt parting 6 in from the top. The Upper King Mine of Ellerbeck Colliery comprises 16 in of coal overlain by 3 in of cannel.

The complete succession between the Little King and Peacock mines has only been penetrated by the Duxbury Park Colliery shaft, in which were recorded about 100 ft of measures, mainly mudstone and seatearth: the roof of the Little King Mine was seatearth, and seatearth was also recorded above a thin sandstone some 30 ft higher; a 9-in coal and its seatearth were found about 25 ft below the Peacock Mine. The Coppull Hall Bore (see p. 55) proved about 110 ft of measures, mainly mudstone, above the Little King Mine, but entered the sequence below the Peacock Mine: mudstone just above the Little King Mine yielded Carbonicola pseudorobusta, and two seatearths were recorded, 40 ft and 75 ft above the seam. The Ellerbeck Hall Bore (p. 113) proved 53 ft of strata below the Peacock Mine. A sandy seatearth overlain by thin black carbonaceous shale, found 32 ft below the Peacock in this hole, probably represents the 9-in coal recorded in Duxbury Park Colliery shaft. Carbonicola cf. polmontensis (Brown) was found in mudstone 12 and 17 ft below the Peacock Mine.

The Peacock Mine has been proved in Duxbury Park Colliery shaft and in a number of boreholes between Ellerbeck Hall and Duxbury Hall; it is at present worked at Ellerbeck Colliery. In the Ellerbeck Hall Bore the seam was only 20 in thick, but generally the thickness, including dirt partings, appears to vary from 30 to 47 in. The seam is commonly tripartite, being divided by two seatearth partings 1 to 6 in thick. The coal is generally of poor quality, and except at Ellerbeck Colliery is not worth working.

The Peacock and Trencherbone mines are separated in this district by 6 to 15 ft of strata which have been proved in a number of boreholes including those named Ellerbeck (p. 112), Ellerbeck Hall (p. 113) and Woodland Cottage (p. 128). The mudstones a few feet above the Peacock carry a good, well-documented non-marine fauna which includes the following: Carbonicola cristagalli Wright, C. aff. cristagalli, C. pseudorobusta, C. rhomboidalis Hind, C. aff. rhomboidalis, C. cf. robusta (J. de C. Sowerby), Curvirimula candela, C. sp., Naiadites flexuosus, Naiadites sp.; Carbonita humilis, C. cf. pungens (Jones and Kirkby) and Geisina arcuata. The ostracods occur throughout the fossiliferous mudstones, but are abundant in a band about a foot above the Carbonicola-bearing horizon; Geisina arcuata appears to be restricted locally to this higher band.

Non-marine lamellibranchs were found in loose shale in the small stream that joins the River Yarrow west of Ellerbeck Hall, and these no doubt represent the fauna above the Peacock Mine and mark the original outcrop of that seam (which has been removed).

The Trencherbone Mine is generally from 54 to 66 in thick, and commonly includes a number of dirt partings totalling 1 to 4.5 in; it is underlain by from 4 in to 5 ft of seatearth, which is commonly sandy and is sometimes found to be ganister-like in parts. The seam has been proved in numerous boreholes drilled in connection with its working at Ellerbeck Colliery, where it is subject to washouts, generally by the overlying Trencherbone Rock. A washout was proved by the Ellerbeck and Ellerbeck Hall bores (pp. 112, 113), and was recorded at Duxbury Park Colliery. In Shade Lane Bore [SD 5879 1461], about 900 yd N. 37° W. of Ellerbeck Hall, the seam was only 32 in thick—probably an effect of this washout.

In Duxbury Park Colliery shaft and in nearby boreholes the Trencherbone Rock forms the roof of the Trencherbone Mine. But in the Ellerbeck Hall Bore to the south, and in the Iron Gate Bore [SD 5896 1482], 1050 yd N. 22° W. of Ellerbeck Hall, the Trencherbone horizon and the Rock were separated by sandy mudstone, 16 ft thick in the former bore and 35 ft thick in the latter (Figure 11). No fossils have been found in the roof measures of the Trencherbone Mine in the Preston district. Where it rests directly on the Trencherbone Mine the Trencherbone Rock is from 90 to 105 ft thick, the thickest development being proved in the Londonderry Cottage Bore [SD 5885 1455] 600 yd S. 5° E. of Duxbury Hall. In the Iron Gate Bore, where it was underlain by mudstone, the rock was only 50 ft thick. The rock is typically a fine to medium-grained well jointed sandstone which is sometimes found to be flaggy towards the base and also towards the top; thin mudstone bands in the more massive parts are not uncommon; and it is commonly stained red or reddish-brown in colour, probably due to the proximity of faults. Purplish and brown flaggy sandstone, representing part of the Trencherbone Rock, is exposed [SD 5835 1404] in the stream which joins the River Yarrow about three-quarters of a mile west of Ellerbeck Hall. D.P., R.C.B.J.

The Trencherbone Rock is overlain by 20 to 30 ft of mudstone and seatearth, which are succeeded by the Wigan Two Foot Mine. In the Iron Gate Bore the Trencherbone Rock was followed by 25 ft of mudstone and 12 ft of seatearth and mudstone. In the Ellerbeck Hall Bore about 22 ft of seatearth and ganister overlay the Trencherbone Rock; there followed two coals, 8 in and 5 in thick, separated by 22 in of seatearth; and these coals were succeeded by 7 ft of seatearth and the Wigan Two Foot Mine. These thin coals, and one other, were proved in both the Londonderry Cottage and Woodland Cottage bores, but they were close under the Wigan Two Foot Mine and have been considered to be part of it.

The Wigan Two Foot Mine is generally from 17 to 24 in thick, but in the Londonderry Cottage Bore, as stated above, thin coals were present below the seam, giving the following section:

The Woodland Cottage Bore (p. 128) proved a similar sequence, but the top coal was only 7 in thick.

From 55 to 66 ft of mudstone, seatearths and occasional thin sandstones overlie the Wigan Two Foot Mine; mudstones and sandy mudstones pass upwards into alternations of mudstone and seatearth, the seatearth predominating in the Ellerbeck Hall, Ellerbeck and Iron Gate bores. Thin sandstones were developed about 20 ft above the seam in the Ellerbeck Hall and Woodland Cottage bores.

The Wigan Four Foot Mine is a good coal, generally containing only small amounts of dirt. It is only known in the Preston district from four boreholes in the Ellerbeck area. In the Ellerbeck Hall Bore it was 51 in thick, in the Iron Gate Bore 52 in, and in the Ellerbeck Bore 54 in. Diversion of a borehole alongside the Woodland Cottage Bore proved a sequence not found in the above boreholes; the Wigan Four Foot Mine comprised a workable section of coal 56.5 in thick underlain by some 10 ft of thin and mainly inferior coals, and seatearths (see footnote on p. 129).

The Wigan Four Foot is overlain by mudstones with a number of fossiliferous horizons. In 5 ft of measures above the seam in the Ellerbeck Hall Bore the following were collected: Anthraconaia cf. williamsoni (Brown), Anthracosia aff. regularis (Trueman), A. sp. nov. aff. regularis, Naiadites spp.; Geisina arcuata. In the Ellerbeck Bore fossiliferous mudstones were found from 4 to 10 ft above the seam and yielded the following: Spirorbis sp.; Anthracosia sp. nov.aff. regularis, Carbonicola cf. sp.cristagalli, Naiadites sp.;Carbonita humilis, C. pungens and Geisina arcuata. In both boreholes Naiadites sp.occurred 15 to 20 ft above the coal, and the following fauna. was found 5 to 15 ft higher in the sequence: Spirorbis sp.; Anthracosia regularis, A.. sp. nov.aff. regularis, Naiadites sp.; Geisina arcuata; fish remaiins. Poor specimens of Anthracosia? were found some 35 ft above the Wigan Four Foot Mine in the Ellerbeck Bore, and at a similar horizon in the Ellerbeck Hall Bore the followng were identified. Spirorbis sp.; Anthracosia regularis, and Naiadites sp.

The Wigan Five Foot Mine lies about 60 ft above the Wigan Four Foot Mine.. In the Ellerbeck and Ellerbeck Hall bores (pp. 113,114) the seam had overall thicknesses of 21 ft 10 in and 16 ft 2 in respectively, and in each case comprised thin coals of unworkable quality, and seatearth. The borehole alongside the Woodland Cottage Bore proved an overall thickness of 10 ft 10 in, made up of a workable section 69 in thick (including a 7-in dirt band) overlying thin inferior coals and seatearths (see footnote on p. 129).

The Ravenhead Rock which closely overlies the Wigan Five Foot Mine is the highest horizon known in the Coal Measures of the Preston district. The Ellerbeck Bore entered this sandstone under drift, and proved a thickness of 76 ft; the Ellerbeck Hall Bore passed from the drift through 6 in of mudstone and penetrated 51.5 ft of sandstone. The rock is medium to coarse-grained and micaceous; it is for the most part stained red, and contains well-marked soft hematitic partings; in the Ellerbeck Bore its base was conglomeratic. D.P.

References

EAGAR, R. Monograptus C. 1952. The succession above the Soft Bed and Bassy Mine in the Pennine region. Liv. and Manch. Geol. J., 1, pp. 23–56.

EAGAR, R. Monograptus C. 1956. Additions to the non-marine fauna of the Lower Coal Measures of the
North Midlands Coalfields. Liv. and Manch. Geol. J., 1, pp. 328–69.

EARP, J. R. and MAGRAW, D. 1955. Tonge's Marine Band in Lancashire. Bull. Geol. Surv. Gt. Brit., No. 9, pp. 22–32.

GERRARD, J. 1908. Fossil-shells from Chorley. Trans. Manch. Geol. and Mining Soc., 30, p. 12.

JONES, R. C. B., TONKS, L. H. and WRIGHT, W. B. 1938. Wigan District. Mem. Geol. Surv.

MAGRAW, D. 1957. New boreholes into the Lower Coal Measures below the Arley Mine of Lancashire and adjacent areas. Bull. Geol. Surv. Gt. Brit., No. 13, pp. 14–38.

STUBBLEFIELD, C. J. and TROTTER, F. Monograptus 1957. Divisions of the Coal Measures on Geological Survey maps of England and Wales. Bull. Geol. Surv. Gt. Brit., No. 13, pp. 1–5.

TONKS, L. H., JONES, R. C. B., LLOYD, W. and SHERLOCK, R. L. 1931. The Geology of Manchester and the South-east Lancashire Coalfield. Mem. Geol. Surv. TRUEMAN, A. E. and WEIR, J. 1946. A Monograph of British Carboniferous non-marine lamellibranchs. Palaeont. Soc. London.

WRIGHT, W. B. 1934. The fresh-water fauna of the Lower Coal Measures of Lancashire. Sum. Prog. Geol. Surv. for 1933, pt. 2, pp. 8–22.

WRIGHT, W. B. SHERLOCK, R. L., WRAY, D. A., LLOYD, W. and TONKS, L. H. 1927. The geology of the Rossendale Anticline. Mem. Geol. Surv.

Chapter 4 Upper Carboniferous palaeontology

Millstone Grit Series

Fauna of Lower Eumorphoceras age (E₁, Pendleian)

Below the Pendle Grit the highest goniatite horizon in E₁, the Cravenoceras malhamense Band, has been seen at one place near Ramsgreave (p. 10). The fauna is typical of the band and includes Actinopteria persulcata (McCoy), Posidonia corrugata (R. Etheridge jun.) and elongate forms of that species which have sometimes formerly been confused with Caneyella membranacea (McCoy), also Cravenoceras malhamense (Bisat), indet. Dimorphoceratid, and a fish bone.

Faunas of Upper Eumorphoceras age (E₂, Arnsbergian)

Cravenoceratoides nitidus Zone

Apart from badly preserved goniatites and lamellibranchs reported by Moore (1930, p. 108) from 40 ft above the upper Wilpshire Grit, the lowest determinable goniatite horizon in E₂ is that of Cravenoceras holmesi Bisat which occurs with Anthracoceras and Posidoniella in Hole Brook, one mile west-north-west of Samlesbury Bottoms (Hudson 1944, p. 237). Twenty feet higher in the succession Cravenoceratoides stellarum (Bisat), and its usual associate Posidoniella aff. vetusta (J. de C. Sowerby) occurs (Hudson 1944, p. 237), in characteristic platy shale similar to that in which a similar fauna at the same horizon is found at Westfield Farm, Cowling (Clitheroe Sheet 68), and in the River Wharfe at Netherby (Leeds Sheet 70). Dimorphoceras (Metadimorphoceras) aff. moorei Hodson is associated at the same locality in the River Darwen (Hodson 1954).

Nuculoceras nuculum Zone

This is exposed in the district only in the Samlesbury Bottoms section (p. 14). Only the upper two of the three known horizons containing N. nuculum Bisat have been found at Samlesbury. The upper horizon contains the richer fauna which includes N. nuculum, Cravenoceras darwenense Moore [type locality, Moore 1946], Dimorphoceras sp., Kazakhoceras hawkinsi (Moore), and forms of Eumorphoceras bisulcatum Girty s.l. which have been described by Moore (1946, pp. 430–433). The examples of N. nuculum from here have variable spacing of the transverse striae, and some of those with closely set striae might be termed N. tenuistriatum Demanet. The Eumor­phoceras bisulcatum from this zone have a fine spiral ornament and are variable in several features, especially the venter, which may be highly arched to almost flat, and the occasional rib suppression. In the form E. bisulcatum mut. β H. Schmidt, which occurs in Mr. E. W. J. Moore's collections from Samlesbury Bottoms, every third rib is suppressed. A tooth of the rare fish Edestus (Edestodus) sp. nov. ((Plate 3), fig. 2) and a fragment of squamation of a large Acanthodian fish have also been collected from these beds.

Faunas of Homoceras age (H, Sabdenian)

The zonal sequence used here is that proposed by Hodson (1957).

A full sequence of faunal bands of Homoceras Age is present at the Samles­bury Bottoms section ((Figure 5) and p. 14) and has been detailed by Moore (1930) and Hodson (1957). Several beds with Homoceras subglobosum Bisat occur near the base, which lies about 70 ft above the highest N. nuculum Bed, and comprise the H. subglobosum Zone. Three bands of bullions with the zone fossil also occur in the River Darwen near Gate Cote Farm (Moore 1930, p. 107). Most of the specimens of H. subglobosum are small examples of about 10 mm diameter. About 120 ft higher in the succession is the H. beyrichianum band which contains bullions in which the zone fossil is preserved 'solid'. H. beyrichianum is a generally coarsely ornamented form with strong transverse striae. A band with Aviculopecten occurs between those yielding H. beyrichianum and Hudsonoceras proteus respectively, 30 ft below proteus (Moore 1930, p. 104).

Homoceras smithi Zone

The basal faunal band of this zone is the wide­spread Hudsonoceras proteus Band, which is composite, having Hd. proteus (Brown) as the only goniatite on the basal portion, followed by an association of Homoceras smithi (Brown) with Hudsonoceras proteus, and this in turn is followed by a thin bed in which H. smithi occurs without Hd. proteus. The total thickness is 6 to 9 in. The Hd. proteus Band is also seen in a small exposure in the River Darwen about 60 yd north-east of Knights Bottom Farm, one mile west of Samlesbury Bottoms. Hudsonoceras proteus is characterized by dominant spiral ornament, the spiral striae being more closely spaced in the mid-flank area. Homoceras smithi is a strongly ornamented form in which the transverse striae are sharply defined and angular.

Homoceras undulatum Zone

H. undulatum (Brown), which differs from H. smithi in that the transverse striae are evenly rounded, is recorded from the Samlesbury Bottoms section at two levels, 4 ft and 9 ft above Hd. proteus.

Homoceras eostriolatum Zone

Hodson (1957) does not record H. eostriolatum Bisat from the Samlesbury Bottoms section, though Moore (1930) recorded H. striolatum from approximately this level. It is possible, if H. eostriolatum is really absent, that the record of H. striolatum refers to H. magistrorum Hodson or an ally, of basal R₁ age. The thin band with Homo­ceratoides prereticulatus Bisat, and Homoceras sp., the top of which was formerly taken as the boundary between H and R₁, has been recorded from Samlesbury Bottoms by Hodson (1957). The top of H was moved upwards to the base of the earliest R₁ goniatite horizon by Hodson (1957). In Ht. prereticulatus there is a prominent lingua, and the well-marked transverse striae bifurcate on the flanks.

Faunas of Lower Reticuloceras age (R₁, Kinderscoutian)

The zonal division of R₁ to be used here is as follows (based on Bisat & Hudson 1943, with modifications by Hudson & Cotton 1943, and Hodson 1957):

Representatives of all the subzones are exposed in the district, and the section at Samlesbury Bottoms played a large part in working out the faunal sequence.

Reticuloceras circumplicatile Zone

The basal fauna at Samlesbury Bottoms includes Homoceras magistrorum Hodson, and bullions yielding it crop out where a small tributary stream enters the River Darwen; that species has forwardly directed plications at the umbilical edge, not found in H. henkei H. Schmidt, its associate in the fauna. Reticuloceras compressum Bisat and Hudson (1943) was described from specimens found loose by Mr. E. W. J. Moore at Samlesbury Bottoms. Subsequent work by Hodson (1957) has shown that this species is found only in the faunal band containing H. magistrorum and H. henkei, and this is therefore its likely position in the section at Samlesbury. The holotype was refigured by Hodson (1957).

Some 3 ft higher in the succession than the H. magistrorum Band is the base of a 10-ft belt of shales containing R. circumplicatile (Foord), R. pulchellum (Foord), R. umbilicatum Bisat and Hudson, Ht. varicatus H. Schmidt, Ht. mutabilis Bisat and Hudson, and H. henkei (p. 14). In the section at Roughlee (Sheet 68) there are three faunal horizons at this level characterized by R. pulchellum (in the highest bed), R. umbilicatum, and R. circumplicatile (at the base), and it is probable that more detailed collecting at Samlesbury would yield similar results there. Eighteen feet above the top of the H. magistrorum Band R. paucicrenulatum Bisat and Hudson, an evolute species with strong umbilical plications, is recorded (Hodson 1957), but the higher faunas of this zone including that of R. todmordenense Bisat and Hudson have not yet been recognized at Samlesbury. It is probable that R. samlesburyense Bisat and Hudson, described from 100 yd north-west of the bridge at Samlesbury, belongs to this zone.

Reticuloceras eoreticulatum Zone

R. dubium, characterized by the almost non-crenulate nature of its striae, was recorded from the River Darwen at Samlesbury Bottoms by Bisat and Hudson (1943). Dunbarella sp.was found in the same shales. Twelve feet above the dubium horizon is a further band of Reticuloceras in bullions in which Caneyella squamula (Brown) also occurs. Only poorly preserved goniatites are found at Samlesbury, up to the horizon and type locality of R. moorei Bisat and Hudson. The holotype of R. moorei is figured here for the first time ((Plate 3), fig. 1); it is a fairly involute form with bifurcation of the transverse striae taking place about one third of the way across the flanks. The horizon 20 to 21 ft above that of R. moorei contains goniatites determined as R. cf. eoreticulatum Bisat and Homoceras striolatum (Phillips); this band also occurs in the section at Gate Cote Farm, where Mr. Moore collected R. regularum Bisat and Hudson four feet below it. R. aff. moorei has also been found near Ramsgreave Laundry (p. 15) and to the east of the district at Lower Hen Moss (Bisat and Hudson 1943, p. 433).

Reticuloceras sp.has been collected from 2 ft 6 in below the Hudsonoceras ornatum and R. cf. reticulatum Band which lies 9 to 10 ft above R. moorei.

Reticuloceras reticulatum Zone

The highest faunal band below the Parsonage Sandstone at Samlesbury Bottoms, containing R. cf. reticulatum and the spirally ornamented Hudsonoceras ornatum (Foord and Crick), belongs to the R. reticulatum Subzone. This band is also seen in the section near Gate Cote Farm, about half a mile west of Samlesbury Bottoms (Moore 1930) where it contains Parametacoceras pulchrum (Crick). Hd. ornatum differs from the lower Hd. proteus in lacking the area of closely-set spiral striae on the flanks. Collections of fossils from this zone have been made from points 700 yd S. 18° E. of the chapel at Nab's Head, and at 540 yd S.W. of the same chapel (faunas listed on pp. 15–16) from apparently just above the Parsonage Sandstone, but Hd. ornatum was not found at these places.

The rocks 300 yd west of Beardwood Hall, Billinge, probably belong to the R. coreticulatum Subzone. Bisat and Hudson (1943, pp. 416, 443) record R. cf. regularum Bisat and Hudson from this locality, though the type specimens of that species are from a horizon evidently below the Todmorden (=Parsonage) Grit and in the R. nodosum Subzone. The fauna here includes Caneyella sp., Dunbarella rhythmica, Homoceras striolatum, Reticuloceras cf. regularum and R. cf. reticulatum.

Faunas of Upper Reticuloceras age (R₂, Marsdenian)

Reticuloceras gracile Zone

Good examples of R. gracile late mut. ((Plate 3), fig. 3) were collected from just below the Alum Crag Grit near Alum Scar (p. 17). This mutation was also collected from the stream 20 yd west of Duckworth House. The 'late mutation' of R. gracile is a more evolute form than R. gracile and has strong umbilical plications in the young stages. In the adult the closely set cancellate ornament is similar to that of R. gracile.

Reticuloceras bilingue Zone

No collections are available from the marine band immediately overlying the Alum Crag Grit and proved in the sewer trench 550 yd south-west of Alum Crag (p. 18). This band might be expected to be on the horizon of the R. bilingue Salter sp. (=mut. β Bisat) or early mut. βmarine band.

Plants have been recorded below the Fletcher Bank Grit in the Bromiley Borehole by Wright and others (1927). Between the Helmshore and Fletcher Bank Grits in the River Roddlesworth, 150 yd north cf Halliwell Bridge, Lingula mytilloides, Orbiculoidea cf. nitida and a fish scale were collected. Lingula and small gastropods and lamellibranchs were recorded by Wright and others (1927, p. 19) at a similar horizon in a borehole at Lower Heights, Belmont, in the south-east portion of the district, and the band was also found near Bury, farther to the east. This horizon in the Star Paper Mills 'B' Borehole, Feniscowles, yielded Lingula mytilloides and Sanguinolites ovalis Hind, which latter species was first described from Holt Head, Slaithwaite (Holmfirth and Glossop Sheet 86) in a shale parting within the Pule Hill Grit (a lateral correlative of the Fletcher Bank and Helmshore grits.)

There are two horizons above the Helmshore Grit which contain forms of R. metabilingue Wright. The holotype and two paratypes of this species came from the upper of these two bands at a stream in the Longworth Valley (Rossendale Sheet 76). Two other paratypes (Wright 1926, pl. xii, fig. 2; and here (Plate 3), fig. 4) came from the present district from the stream 300 yd north-east of Higher Hempshaws, two miles west of Belmont, where the marine band rests almost directly on the grit. These two bands have been confirmed in the Star Paper Mill 'B' Borehole at Feniscowles (p. 124) where they are 30 to 40 ft apart. The two bands also occur in Mill Brook (see p. 20). R. metabilingue has also been found in several other localities (pp. 19–20). The species is more evolute than R. superbilingue Bisat and there are a few spiral striae on the lingua which are not seen in R. superbilingue. Other fossils in these bands include Crurithyris sp., Dunbarella sp. nov. [4 to 5 costae in anterior ear], Caneyella sp., Posidonia cf. insignis (Jackson), Anthracoceras sp., and the nautiloid Huanghoceras sp.

Reticuloceras superbilingue Zone

The lower faunal horizon in this zone, the R. superbilingue Marine Band, has been seen at four surface exposures in the district (pp. 19–20). The fauna includes R. superbilingue, Caneyella cf. rugata (Jackson), Dunbarella cf. elegans (Jackson), Posidonia sp., Streblopteria sp., Gastrioceras cf. lineatum Wright, Homoceratoides aff. divaricatvs (Hind), and Pygmaeoceras [Gastrioceras?] sigma (Wright).

The stream section north-east of Higher Hempshaws exposes the R. superbilingue Marine Band 20 ft above the underlying R. metabilingue Marine Band; and 7 ft 6 in higher in the succession in the same stream is the P. sigma Marine Band, this locality being, in fact, the type-locality of P. sigma (Wright).

The genus Pygmaeoceras Gordon (1960) was recently instituted for an American species Gastrioceras pygmaeum Mather from the Morrow Series of Arkansas, and G.? sigma Wright appears to be congeneric. The genus differs from Gastrioceras in lacking umbilical tubercles. The fauna of the P. sigma Band in the present district includes Posidonia insignis (specimens from the stream 200 yd from road south-west of Ryal Fold, were cited by Jackson (1927) when describing the species), Thoracoceras?, and Lingula mytilloides. L. mytilloides and fish occurred in the basal layers of the R. superbilingue Band in Wiggins Teape No. 2 Bore.

The lowest horizon from which non-marine lamellibranchs have been recorded in the present area is at 444 ft in Wiggins Teape No. 2 Bore, or 112 ft below the G. cancellatum Marine Band. The shells are not well preserved but two distinct species of Carbonicola are present. The larger shells ((Plate 3), fig. 7) resemble C. pseudorobusta Trueman and one of these specimens was figured by Trueman and Weir (1948, pl. xiv, fig. 3) as Carbonicola sp. (? aff. pseudacuta; cf. pseudorobusta). The smaller shells ((Plate 3), fig. 5) have marked tumidity and do not compare closely with any described species except possibly C. deansi Eagar. These same two species ((Plate 3), fig. 6) are also present in the collections obtained from the exposure in the stream leaving the reservoir, south-east of Heapey Station (p. 21), and it is likely that this is the same band as that found in the Wiggins Teape Bore.

Another shell-band occurs at a slightly higher horizon in the bore, i.e. 80 to 83 ft below the G. cancellatum Marine Band. This contains Carbonicola ornata Trueman and small elongate shells which are possible young forms of C. pseudacuta Trueman. A shell from this fauna was figured by Trueman and Weir (1948, pl. xiv, fig. 4) as C. aff. ornata. This higher band appears to be the equivalent of that found in Victoria Mills Bore, near Halifax, from which the holotypes of C. ornata and C. pseudacuta were obtained (Trueman 1929, pp. 87–88). MonograptusA.C.

Faunas of Lower Gastrioceras age (G₁, Yeadonian)

Gastrioceras cancellatum Zone

The section seen in a small embankment on the Leeds and Liverpool Canal, 400 yd N. 10° W. of Wheelton crossroads (p. 25) contains all three marine associations of this zone (see Ramsbottom and Calver 1962) within 3 ft 8 in. The uppermost 1 ft 6 in contains Agastrioceras carinatum (Frech) and G. crencellatum Bisat, the middle 1 ft 2 in contains G. cancellatum Bisat and R. superbilingue, and the lower foot contains poorly preserved G. branneroides? Bisat. This occurrence of all three faunas in superposition at one locality in Britain is unique. G. branneroides has hitherto been known only from North Wales (Bisat 1940) and Warwickshire (Ramsbottom 1955):

Other localities in the district contain either the G. crencellatum fauna (stream 60 yd west-north-west of Hollinshead Hall; Howe Brook, 1560 yd north-north-west of Wrightington church) or the G. cancellatum fauna (Dean Brook, 150 yd south of Higher House; stream 750 yd N. 18° W. of church, Wheelton).

Apart from the diagnostic goniatites, fossils collected from this band include Caneyella multirugata (Jackson), Dunbarella elegans (Jackson), Posidonia sp., Homoceratoides aff. divaricatus (Hind), Anthracoceras, and Epistroboceras?.

Gastrioceras cumbriense Zone

The G. cumbriense Marine Band contains the usual goniatite assemblage of G. crenulatum Bisat and G. cumbriense Bisat. The records of G. listed in this band (Wright and others 1927, p. 119) cannot be sustained (see also Ramsbottom and Calver 1962). In addition to Gastrio­ceras, the following were collected from this marine band in the district: Lingula mytilloides, Orbiculoidea cf. nitida; Glabrocingulum?, turreted gastro­pods indet.; Aviculopecten aff. losseni (von Koenen), Caneyella cf. multirugata, Sanguinolites sp., Parallelodon sp., Dunbarella cf. elegans, Posidoniella sp.; Anthracoceras sp., Homoceratoides aff. divaricatus (Hind); Solenocheilus sp., orthocone nautiloid; and fish debris. W.H.C.R.

A well sunk north-east of Lower Healey Bleach Works intersected what is believed to be the horizon of Anthraconaia bellula above the Upper Haslingden Flags. The collections from the tip produced a more varied fauna than is usually found in the A. bellula Band and it is possible that more than one shell band is represented. The assemblage includes Anthraconaia angulosa Pastiels ((Plate 3), fig. 9), A. bellula Bolton sp. ((Plate 3), fig. 12), A. ventricosa Pastiels ((Plate 3), fig. 10), Carbonicola cf. circinata Pastiels ((Plate 3), fig. 8) and Naiadites cf. stockmansi Pastiels. Most of these species occur at the approximately equivalent horizon in Belgium (Pastiels 1960, pp. 84, 163) and are here recorded for the first time from Britain.' A. cf. angulosa and A. bellula also occur in mudstones underlying the Rough Rock of the Booth's Farm Bore, and A. bellula and N. cf. stockmansi were also present in the Heskin Bore some 50 ft below the Sand Rock Mine.

The non-marine band between the Six Inch Mine and the overlying marine band has been described by Eagar (1953, p. 174, pl. xii, figs. 2 & 3) from Howe Brook (p. 30) and StepbackCalled Stanback Clough by Eagar. Brook (p. 30). It was also found in the Heskin Bore, from which A. cf. bellula, Carbonicola?, Geisina arcuata (Bean) and fish remains were collected. In the Big Wood Bore two shell-bands were found 3 ft apart, the higher lying immediately below the Six Inch Mine Marine Band. This higher band contained A. bellula, A. lenisulcata? (Trueman), Carbonicola? and Geisina arcuata, and is the usual fauna from this position. The fauna of the lower band included Carbonicola exporrecta Eagar, C. aff. protea Wright, C. spp.[including the C. sp.of Eagar 1952, fig. 16c], Naiadites sp. and G. arcuata. A comparable assemblage is not known from above the Six Inch Mine in Lancashire (but see Eagar 1956, p. 332) although it has been recorded locally in the Sheffield area (Eagar 1953, p. 170). The interpretation followed here is to take this lower band to represent the Sand Rock Mine fauna, although the distance below the Six Inch Mine is much less than usual (see p. 29). MonograptusA.C.

Coal Measures

In the following account only the more important or distinctive faunal horizons are discussed, but other records appear in the relevant section concerned with the stratigraphy (Chapter 3) or are noted in the abstracts of the borehole logs (Appendix I).

The Six Inch Mine Marine Band

The Six Inch Mine Marine Band (horizon of Gastrioceras subcrenatum) at the base of the Coal Measures is well represented in the district. The character­istic fauna, which has been collected from numerous boreholes and field exposures, may be summarized as follows: turreted gastropods; Aviculopecten sp., Caneyella multirugata (Jackson), Dunbarella papyracea (J. Sowerby), Posidonia cf. gibsoni Salter, P. sp. nov. [right valve with prominent anterior ear] (see (Plate 4), figs. 9, 10), Pleurophorella?; orthocone nautiloid, Anthracoceras sp., Gastrioceras subcrenatum C. Schmidt, G. sp. nov. (aff. cumbriense), G. sp. [crenulate tubercles], Homoceratoides divaricatus (Hind); Hindeodella sp., platformed conodonts; and fish remains.

The band is well exposed in the section in the River Darwen, south-east of Old Hall, Feniscowles (p. 41); also in the dough 560 yd north-north-west of St. Stephen's Church, Chapel (p. 41), whence Caneyella [Posidoniella] multirugata was cited by Jackson (1927, p. 119). The collections from Howe Brook (p. 41) and from the tip on the northern slope of Harrock Hill (pp. 41–2) include 'solid' goniatites obtained from bullions; at these localities two other distinctive species of Gastrioceras are present apart from G. subcrenatum. One species, referred to in the above list as G. sp. nov. (aff. cumbriense), is a small form and has coarser and wider spacing of the transverse lirae than G. subcrenatum; this same species is known from several British coalfields at this horizon (see Woodland and others 1957, p. 55; Earp and others 1961, p. 196). The other species of Gastrioceras differs from subcrenatum by the prominent nodes and the markedly crenulate transverse lirae.

Between the Six Inch Mine Marine Band and the Bassy Mine only few fossils have been recorded, but they include small Anthraconaioid lamellibranchs found in siltstone at 15 ft and 45 ft below the Bassy Mine of the Charnock Old Hall Bore. The shells resemble some of the variants of Anthraconaia bellula figured by Eagar (1953, pl. 12, S.W. quadrant) from the immediate roof of the Six Inch Mine. A similar occurrence was noted in the Adlington Bore at 945 ft 6 in, associated with small Naiadites.

The measures above the Bassy Mine

The measures above the Bassy Mine contain abundant non-marine lamelli­branchs which have been intensively studied by Wright and Eagar; three distinct bands or divisions, called Lower, Middle and Upper by Eagar, are now recognized, separated by two Lingula-bearing horizons referred to here and on pp. 35, 43, 44 as the Lower and Upper Bassy marine bands (Eagar 1947; 1952, pp. 48–53; Magraw 1957, p. 27). The present area offers a fine example of these beds and extensive collections of individual bands have been made, particularly from boreholes.

The 'Lower Division' fauna is represented by the shell bands exposed in the banks of the River Darwen, near Feniscowles (p. 43). This is the locality from which Wright obtained his types of Carbonicola fallax and C. protea, and the collections from here formed the basis of his study of the variation of the Bassy Mine fauna (Wright 1934 a, b). The fauna and succession were later investigated and illustrated by Eagar (1952, pp. 29–43) who described Carbonicola pilleolum Eagar, and subsequently (1954, p. 6) added C. artifex Eagar to the species named from this exposure.

The fauna of the 'Lower Division' is not well represented in boreholes, but beds of sandstone occur in this part of the sequence and these may replace or cut out part of the fossiliferous mudstone. The following list is based mainly on the Charnock Old Hall and Tan House Farm bores, but the band was also thought to be present in the Heskin Bore (Magraw 1957, p. 28): Carbonicola sp.cf. acuta (J. Sowerby), C. fallax, C. cf. limax Wright, C. aff. protea, C. rectilinearis Trueman and Weir, C. aff. rectilinearis, Curvirimula spp. nov., Naiadites sp. [small, oblique]; Geisina arcuata (Bean); fish remains including scales of Elonichthys cf. aitkeni Traquair, Megalichthys sp., Rhabdoderma sp., Rhadinichthys sp. and Rhizodopsis sp.The C. aff. rectilinearis ((Plate 4), fig. 7) are distinctive, showing rectangular outline, strong carination and some tendency for tilting of the growth lines. Two distinct forms of Curvirimula are present. One species (see (Plate 4), figs. 3–5) shows a fine but distinct ornament of concentric growth lines crossed by radiating cracks (cf. Eagar 1947, fig. 27H, and Pastiels 1960, p1. iii, fig. 18). The other (see (Plate 4), figs, 1, 2) is larger with a broader outline, and lacks the distinctive ornament of the former species; it compares with the shell figured by Weir (1960, pl. xxxii, fig. 53) from above the Hard Bed Coal, Belle Clive Borehole, Yorkshire, and resembles the 'subovalaire' examples of Curvirimula figured by Pastiels (1960, pl. i, figs. 1–7) from approximately similar horizons in Belgium. Curvirimula from these beds in the Heskin Borehole were figured by Weir (1960, pl. xxxiii, figs. 7 and 28) as C. aff. belgica (Hind) and C. juv. cf. trapeziforma (Dewar).

The description of the remainder of the faunal sequence above the Bassy Mine is based on the Charnock Old Hall and Tan House Farm boreholes.

The Lower Bassy Marine Band

The Lower Bassy Marine Band is developed as a thin band with Lingula and fish remains at the base of the 'Middle Division'. No foraminifera were observed in either borehole.

The fossiliferous beds containing the 'Middle Division' fauna follow closely upon the marine band and continue for a further 15 feet; towards the base is a thin band of dark shale with pyrite which presumably represents the C. discus horizon of Eagar (1952, p. 27) although the species itself was not found. In the upper part of the band Carbonicola haberghamensis Wright is associated with poorly preserved large shells probably representing the C. sp.cf. pseudorobusta' of Eagar (1952, p. 51). The two species of Curvirimula occurring with the 'Lower Division' faunas are also present ((Plate 4), figs. 1, 2, 4), as well as the small, oblique Naiadites. Below the presumed C. discus horizon shells are less common, but include C. protea, Curvirimula sp. and G. arcuata.

The Upper Bassy Marine Band

The Upper Bassy Marine Band is represented by Lingula and fish remains; as in the Lower Bassy Marine Band no foraminifera have been recorded, and the absence of these fossils seems to be a general feature of the two bands.

Fine collections of the 'Upper Division' fauna were obtained from both boreholes from a band about 13 feet thick. The assemblage is dominated by Carbonicola aff. rectilinearis and C. declinata Eagar; associated species include C. aff. artifex, C. fallax, C. limax?, C. pilleolum, Curvirimula sp. nov. [broad form], Naiadites sp. [small] and G. arcuata. The C. aff. rectilinearis (cf. Trueman and Weir 1948, pl. xiii, fig. 9) is smaller, less rectangular and less carinate, than the similar shells found in the 'Lower Division'.

The shell-band above the Lower Foot Mine

The shell-band above the Lower Foot Mine lies between the coal and the overlying marine band, and was typically developed in the Charnock Old Hall Bore. A thin layer with fish debris and Curvirimula fragments occurred in the roof of the coal. This is immediately overlain by a 5-ft shell-band with Carbonicola artifex, C. declinata, C. fallax, C. obliqua Wright and C. sp. nov.? (cf. Eagar 1956, figs. 5a—e). The two Curvirimula spp. nov. noted in the Bassy Mine faunas are also present (see (Plate 4), figs. 3, 5), associated with small Naiadites sp.cf. subtruncatus (Brown) and G. arcuata. C. artifex is the most common species, but C. limax which is usually present in this fauna (Eagar 1956, p. 335) was not identified with certainty. A similar development occurred in the Tan House Farm Bore.

The Lower Foot Mine Marine Band

The Lower Foot Mine Marine Band lies immediately above the shell-band; a 2 to 3-in basal layer containing a varied marine fauna is overlain by a Lingula/Planolites phase extending for a further 4 feet. In the Charnock Old Hall Bore Gastrioceras is present in the basal layers; although preservation is poor, it is seen that the species differs from G. subcrenatum in the presence of conspicuous tubercles and possibly coronate form, and is distinguished from G. listeri by the fine hair-like transverse lirae. The associated fossils include: L. mytilloides [and ? spat]; Caneyella cf. multirugata, Posidonia gibsoni, P. sp. nov. [right valve with prominent anterior ear] (see (Plate 4), figs. 9, 10); Anthraco­ceras sp. and mollusc spat. Unlike the slightly higher Bullion Mine Marine Band this band did not contain Dunbarella.

The Lower Mountain Mine

The Lower Mountain Mine cyclothem is not prolific in fossils, but a poorly developed shell-band occurred in the Tan House Farm Bore some 50 ft above the coal. The shells include Carbonicola sp. nov. (cf. Eagar 1947, figs. 9d, e; 1956, p. 344), Curvirimula sp. nov. [fine ornament] and Naiadites sp.cf. productus (Brown) ((Plate 4), fig. 6). A similar occurrence was also found in the Adlington and Heskin boreholes (Magraw 1957, p. 25).

The Bullion Mine Marine Band

The Bullion Mine Marine Band (horizon of Gastrioceras listed) is one of the best-known marker bands in the Lower Coal Measures because of its persistence and characteristic fauna. Commonly a non-marine phase occurs between the underlying coal and the marine band, as in the Tan House Farm Bore where the following typical sequence of faunal phases was recognized. At the base is a thin _.non-marine layer with macrospores, Carbonicola cf. artifex, C. rectilinearis? and Naiadites sp.cf. productus, the latter covering certain of the bedding planes. This is overlain by a 2-in band with Lingula? and fish remains, which passes up into a 6-ft band carrying the usual rich fauna of the horizon. The fossils identified were: gastropods [small]; Canevella multirugata, Dunbarella papyracea, Posidonia gibsoni, P. sp. nov. [right valve with prominent anterior ear] ((Plate 4), figs. 9, 10); Anthracoceras sp., Gastrioceras listeri (J. Sowerby); mollusc spat; conodont assemblages; and fish remains. The P. gibsoni, D. papyracea and G. listeri are confined to the basal 2 in. The regression of the marine incursion is represented by 4 ft of measures with Lingula occurring some 5 ft above the main part of the band carrying the richest fauna.

The Cannel Mine Marine Band

The Cannel Mine Marine Band was found in Charnock Old Hall and Crook Fold bores. It is about 1 ft 9 in thick and is largely a foraminiferal development with Ammodiscus, Agathammina and Hyperammina; the Ammodiscus tend to be larger than in the other marine bands of the Lower Coal Measures. Associ­ated fossils include Lingula and conodonts. In the higher part of the Cannel Mine cyclothem are several thin bands containing Curvirimula sp.((Plate 4), fig. 8; see also Weir 1960, pl. xxxiii, figs. 5, 6) and small, oblique Naiadites referred to as N. sp.cf. subtruncatus.

Tonge's Marine Band shows in this district the pattern known elsewhere in Lancashire (Earp and Magraw 1955; Earp and others 1961, p. 198), and is notable for its relative thinness of a few inches as well as for its distinctive fauna. The fauna collected from the band is as follows: gastropods [small]; Caneyella sp. nov.aff. multirugata, Dunbarella cf. papyracea [large]; orthocone nautiloid, ?coiled nautiloid, Anthracoceras sp., Gastrioceras cf. amaliae H. Schmidt; conodont assemblages including Hindeodella. Of particular interest is the exposure east of Charnock Green (p. 50), since this is one of the few surface localities at which Gastrioceras has been found at this horizon. The species was also found in the Charnock Old Hall ((Plate 4), fig. 11) and Crook Fold bores. The examples available are poorly preserved, but are seen to possess markedly crenulate transverse lirae (see (Plate 4), fig. 12) and are compared with Gastrioceras amaliae from the Plashofsbank Marine Band of Westphalia (see Ramsbottom and Calver 1962). Conodonts are abundant, particularly in the layers containing Dunbarella; the latter are large and commonly cover the bedding plane as in the development from Birkacre Colliery (p. 50). The Caneyella sp. nov.aff. multirugata differs from typical C. multirugata in the relatively shorter hinge line, more inclined posterior margin and consequently more acute postero-ventral angulation.

The richest part of the band may be preceded and followed by a thin foraminiferal phase. In the Crook Fold Bore Planolites ophthalmoides occurred a few inches above the main band, associated with G. arcuata. At a slightly higher horizon, just below the Crutchman Sandstone, Curvirimula was recorded in the Charnock Old Hall Bore.

The measures between the Pasture Mine and Arley Mine

The measures between the Pasture Mine and Arley Mine horizons have afforded few faunal records, apart from the shell-bands noted in the Heskin Bore. These are referred to only briefly in this account since they have previously been described by Magraw (1957, pp. 19–21). In the absence of diagnostic faunal evidence the current practice (Earp and others 1961, pp. 195–6) of drawing the junction of the A. lenisulcatal C. communis boundary at the horizon of the Pasture Mine has been followed here.

In the Heskin Bore a poorly developed shell-band with fossils of the C. communis Zone lay some 25 ft below the Dib Hole Coal. The fauna included Carbonicola martini? Trueman and Weir, Curvirimula cf. trapeziforma (Dewar), Naiadites aff. flexuosus Dix and Trueman and Geisina arcuata. This horizon is possibly the equivalent of the shell-band recorded above the Old Lawrence Rock in disused brick-pits at Horwich, just to the south of the present area (Wright in Jones and others 1938, p. 79). The well-known 'Daubhill fauna' (Tonks and others 1931, p. 134; Eagar 1956, pp. 356 — 60) is represented in the Heskin Bore by a 4-ft shell-band 68 ft below the Arley Mine and containing Anthraconaia?, Carbonicola cf. bipennis (Brown), C. subconstricta Wright (non J. Sowerby), C. aff. torus Eagar, Naiadites sp., Geisina arcuata and abundant fish remains.

The beds above the Arley Mine

The beds above the Arley Mine are characterized by the Carbonicola pseudorobusta Trueman group which dominates the main shell-bands up to the horizon of the Trencherbone Mine. The lowest horizon at which typical C. pseudorobusta occurs is the well-developed band some 130 to 160 ft above the Arley, for example in Ellerbeck Colliery (p. 53). Here a cannelly mudstone contains Anthraconaia sp. nov., C. pseudorobusta, Curvirimula trapeziforma, C. subovata (Dewar), Naiadites sp. and Geisina arcuata. The A. sp. nov.is a distinctive shell ((Plate 4), figs. 13, 14), and has not been seen in the higher C. pseudorobusta bands. At some localities, e.g. Welch Whittle Colliery and the Barlow's Farm Bore, the upper part of this band is a pale grey mudstone in which Carbonicola bipennis and the related C. subconstricta Wright (non J. Sowerby) ((Plate 4), fig. 15) largely replace the C. pseudorobusta.

The Yard (Haigh Yard) Mine

The Yard (Haigh Yard) Mine fauna is a typical C. pseudorobusta assemblage with variants approaching C. cristagalli Wright and C. robusta (J. de C. Sowerby). A fine collection was made from the shell-band in the roof of this coal in Birkacre Colliery (p. 55), where the associated fossils included Curvirimula trapeziforma, G. arcuata and fish remains. The examples of Curvirimula were examined by Dewar (1939) during his investigation of the Anthraconauta minima group, and he selected and figured specimens from this collection as holotypes of Curvirimula [Anthraconauta] trapeziforma and C. [A.]trapeziforma var. tenuoides. These were subsequently re-figured by Weir, who also figured associated specimens as Curvirimula belgica Hind sp. (see Weir 1960, pl. xxxiii, figs. 16–23).

In the Coppul Hall Bore, well-preserved C. pseudorobusta were found above the Cannel Mine and also above the Little King Mine. At the lower horizon they were associated with Curvirimula candela (Dewar).

The shell-band above the Peacock Mine

The shell-band above the Peacock Mine is the highest level at which C. pseudorobusta has been found in the district and the part of the sequence between the band 130 ft above the Arley Mine and the present horizon can be conveniently referred to as the C. pseudorobusta 'Subzone' (see Wright in Jones and others 1938, p. 80; Calver 1956, p. 33). The Peacock Mine fauna is well developed in Ellerbeck Colliery and was also present in nearby bores (p. 57); the fossils include Carbonicola cf. cristagalli, C. pseudorobusta, C. rhomboidalis Hind, C. cf. robusta, Naiadites flexuosus, Curvirimula candela [large]; Carbonita humilis (Jones and Kirkby), C. cf. pungens (Jones and Kirkby); and Rhizodopsis sp. Geisina arcuata is rare or absent in the main shell-band but occurs abundantly in a band immediately overlying.

The roof of the Trencherbone Mine

The roof of the Trencherbone Mine has not yielded fossils during the present survey. In certain respects the assemblage from the roof of the Peacock Mine is similar to that found elsewhere above the Trencherbone (Wigan Six Feet), but differs mainly in the presence of Curvirimula and Carbonicola pseudorobusta and the absence of Carbonicola oslancis Wright. The Peacock Mine fauna is here regarded as representing a high position in the C. communis Zone, so that the usual procedure of taking the Trencherbone Mine as the top of the C. communis Zone has been adopted.

The Wigan Four Foot Mine

The Wigan Four Foot Mine shell-bands are dominated by Anthracosia regularis, which is characteristic of the measures in the upper part of the lower A. modiolaris Zone (Calver 1956, p. 33). In the Ellerbeck and Ellerbeck Hall bores shell-bands were found up to 45 ft above the coal, and the following fossils were collected: Anthraconaia cf. williamsoni (Brown), Anthracosia regularis (Trueman), A. sp. nov.aff. regularis (cf. Melville 1947, fig. 3e), Carbonicola sp. cf. cristagalli ((Plate 4), fig. 16), Naiadites sp. intermediate between productus (Brown) and quadratus (J. de C. Sowerby); Carbonita humilis, C. pungens, Geisina arcuata; fish remains including Rhabdoderma sp., Palaeoniscid scales indet. and Platysomid scales indet. The abundance of ostracods at this level is a feature of the Pennine coalfields.

The beds above the Wigan Four Foot Mine are the highest fossiliferous measures in this part of the coalfield, so that the whole of the faunal sequence described above belongs to the Lower Coal Measures as now defined (p. 32). MonograptusA.C.

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MOORE, E. W. J. 1946. The Carboniferous goniatite genera Girtyoceras and Eumorphoceras.
Proc. Yorks. Geol. Soc., 25, pp. 387–445.

PASTIELS, A. 1960. Les lamellibranches non marins de la zone a Lenisulcata de la Belgique (Namurien et Westphalien A). Centr. nat. Geol. houill., No. 2, pp. 1–206.

RAMSBOTTOM, W. H. C. 1955. In Sum. Prog. Geol. Surv. Gt. Brit. for 1954, p. 54.

RAMSBOTTOM, W. H. C. and CALVER, Monograptus A. 1962. Some marine horizons containing Gastrioceras in North West Europe. C. R. Cong. Carb. Strat. Heerlen, 1958, 3, pp. 571–6.

SCHMIDT, H. 1934. Cephalopodenfaunen des alteren Namur aus der Umgegend von Arnsberg in Westfalen. Jahrb. preuss. geol. Landes., 54, pp. 440–61.

TONKS, L. H., JONES, R. C. B., LLOYD, W. and SHERLOCK, R. L. 1931. The geology of Manchester and the South-East Lancashire Coalfield. Mem. Geol. Surv.

TRUEMAN, A. E. 1929. Some new Carboniferous lamellibranchs. Ann. Mag. Nat. Hist. (10), 4, pp. 82–95.

TRUEMAN, A. E. and WEIR, J. 1948. A monograph of British Carboniferous non-marine Lamellibranchia. Part IV. pp. 75–100. Palaeont. Soc.

WEIR, J. 1960. A monograph of British Carboniferous non-marine Lamellibranchia. Part X. pp. 273–320. Palaeont. Soc.

WOODLAND, A. W., ARCHER, A. A. and EVANS, W. B. 1957. Recent boreholes into the Lower Coal Measures below the Gellideg - Lower Pumpquart Coal horizon in South Wales. Bull. Geol. Surv. Gt. Brit., No. 13, pp. 39–60.

WRIGHT, W. B. 1926. New goniatites from the Millstone Grit of Lancashire. Sum. Prog. Geol. Surv. Gt. Brit. for 1925,192–9, pl. xii.

WRIGHT, W. B.. 1934a. The fresh-water fauna of the Lower Coal Measures of Lancashire. Sum. Prog. Geol. Surv. Gt. Brit. for 1933, Pt. II, pp. 8–23.

WRIGHT, W. B. 1934b. Variation of fresh-water shells in the Lower Coal Measures of Lancashire. Ibid., pp. 24–36.

WRIGHT, W. B. SHERLOCK, R. L., WRAY, D. A., LLOYD, W. and TONKS. L. H. 1927. The geology of the Rossendale Anticline. Mem. Geol. Surv.

Chapter 5 Permo-Triassic rocks

West of the Carboniferous hills the district is occupied by Permian and Triassic rocks. Exposures and borings are neither very numerous nor equably spaced, and there are wide areas of the low plain in the west where there is no evidence of the character of the solid rocks beneath the thick cover of drift. In con­sequence the construction of a rational map has presented some difficulty. It has been assumed that the Boundary Fault of the Wigan Coalfield (Jones and others 1938) continues northward, and this line has been used as the eastern boundary of the Keuper Marl of the coastal plain. East of this, borings south of Preston have proved Keuper Marl and Keuper Sandstone in an area previously thought to be Bunter Sandstone. This evidence is difficult to interpret unless east-west faulting separates these younger beds from the Bunter Sandstone of Preston and the Ribble: a fault in this direction has accordingly been drawn from the assumed extension of the Boundary Fault near the mouth of the River Douglas, through Penwortham to Higher Walton, crossing the conjectured extension of the Great Haigh Fault (see (Figure 12)—which shows some variation from the one-inch map). The base of the Keuper Marl and the outcrop of Keuper Sandstone south and south-south-east of Preston are mainly conjectural.

The boundary between the Triassic and Carboniferous rocks was formerly mapped as a fault running north-eastwards across the map, but, although there is apparently some north-east faulting in the area between Eccleston and Chorley, the line separating the Permo-Triassic from the older rocks at outcrop is now considered to be in the main an unconformity, and has been so mapped except in the immediate neighbourhood of Eccleston.

The following is the Permo-Triassic succession:-

• Keuper Marl
• Keuper Sandstone
• Bunter Sandstone
• Manchester Marl
• Collyhurst Sandstone

The thicknesses of the various members of the succession have not been proved in the Preston district and the thicknesses given on p. 3 are based on extrapolation from adjoining areas.

Collyhurst Sandstone

No exposures of the Collyhurst Sandstone occur in the district, and its presence has not been confirmed in boreholes. (A borehole at the Royal Ordnance Factory near Chorley proved some 10 ft of brown argillaceous sand­stone below Manchester Marl, but in view of its absence from other nearby boreholes this is likely to be an altered Carboniferous sandstone rather than Collyhurst Sandstone). The narrow outcrop of Collyhurst Sandstone mapped south of Mawdesley is continued from the areas to the south, where the rock, 35 ft thick, is exposed in Skellow Cough. The Collyhurst Sandstone is absent east of Preston, Where Bunter Sandstone Rests Directly On Millstone Grit Series.

Manchester Marl

Manchester Marl has been proved only in the area north of Chorley, where it rests unconformably on Millstone Grit. It is from 30 to 60 ft thick and comprises buff, chocolate and red marls and mudstones. No fossils have been recorded from it. East of Preston it is absent; and the Bunter Sandstone is regarded as overstepping it in a north-easterly direction.

Details of Manchester Marl

A number of boreholes on and near the site of the Royal Ordnance Factory near Chorley proved the Manchester Marl. The R.O.F. No. 7 Bore [SD 5668 2043], 1200 yd W. 23° S. of Shaw Hill, passed through Bunter Sandstone into 30 ft of very soft red marl resting on mudstones of the Millstone Grit Series. In the R.O.F. No. 3 Water Well [SD 5621 2100], 1600 yd W. 4° N. of Shaw Hill, the Manchester Marl comprised 51 ft 4 in of buff, chocolate and purple mudstones, capped by Bunter Sandstone and resting on Millstone Grit. In the R.O.F. Pilot Hole [SD 5629 2079], 1500 yd W. 4° S. of Shaw Hill, it was represented by 57 ft of reddish brown marl.

Bunter Sandstone

The Bunter Sandstone of this area was formerly divided into Pebble Beds and Upper Mottled Sandstone. This division has now been abandoned, since the rock formerly mapped as Pebble Beds contains few pebbles and is quite different from the typical Pebble Beds of the Midlands, and nowhere can the boundary between the former divisions be accurately placed.

Bunter Sandstone crops out in a belt about four miles wide in the north between the Boundary Fault and the higher ground east of Samlesbury and around Bamber Bridge, and in the southern part of the district is present around Rufford, Eccleston and Mawdesley. Its overall thickness is not known. East of Preston a borehole recorded 878 ft of the rock but did not prove the base or the top, and in numerous wells in and around Preston it was found to exceed 500 ft in thickness. The rock may be well bedded or massive, is fine to medium-grained and varies in colour from white, grey or yellow to brown, red or purple; thin partings of marl or manly sandstone are occasionally present; pebbles are rare.

Details of Bunter Sandstone

The Bunter Sandstone is exposed [SD 599 289] in the south bank of the River Darwen 400 yd E.N.E. of Roach Bridge, where well-bedded soft manly sandstone dips west at 10°. The base is not visible, but immediately to the east Carboniferous mudstones dip at 30° to the south. The Bunter is also visible on the north bank of the river, where there are several exposures of soft red marly sandstone and more massive sandstone. Slightly higher beds seen downstream comprise massive red, white and yellow sandstone. To the south-west of the sections described above, Bunter Sandstone occurs in the bed of the river at Roach Bridge [SD 5956 2884] where it is a red sandstone. In a boring at Roach Bridge Paper Mill [SD 596 288] it was 47 ft thick and comprised yellow, red and grey sandstone. At Waterfall [SD 5888 2811], three-quarters of a mile S.W. of Roach Bridge, it is a red and yellow, fine to medium-grained sandstone with partings of soft red manly sandstone. Further sporadic exposures are seen in the bed of the river downstream towards Higher Walton. During periods of drought the rock is visible in the bed of the Ribble between Samlesbury Hall and The Holme in Preston, and where accessible appears to be all red sandstone without pebbles. Preston Dock was excavated in Bunter Sandstone, and red sandstone was proved along the river diversion south of the dock.

A borehole at Courtaulds works [SD 5768 3191], 1100 yd E. 5° S. of Ribbleton Station, passed through 164 ft of drift and 878 ft of sandstone with occasional thin marl partings, but did not reach the base. As the surface level is here about 150 ft O.D.. the base of the Bunter Sandstone must be more than 890 ft below O.D.

East of Preston, between Red Scar and Gamull Lane End, over 500 ft of red and mottled sandstone has been proved below the drift (here over 100 ft thick) in various borings. In Preston town the Bunter has been penetrated in several boreholes; few details of the borings are available, however, and the rock is usually recorded simply as red sandstone with the occasional mention of a few pebbles. The base of the Bunter was reached in a boring [SD 5479 3017] 1400 yd N.E. of Preston Station, which penetrated, below the drift, red sandstone to a depth of 433.5 ft. Samples preserved from the bottom of the hole were dark blue Carboniferous mudstone; and since the surface level is 125 ft, the Bunter–Carboniferous junction here lies 308 ft below O.D.

A group of boreholes at the Springfield Atomic Energy Establishment, four miles W. 20° N. of Preston Station, proved 390 to 420 ft of red sandstone with grey bands but did not reach the base of the Bunter. Shallow boreholes at the sewage farm a mile S.E. of Freckleton entered red and grey sandstone, showing that the outcrop of the Bunter Sandstone extends at least thus far west of Preston.

Boreholes at the Royal Ordnance Factory, near Chorley, proved Bunter Sandstone, the R.O.F. No. 3 Water Well [SD 5621 2100], 1600 yd W. 4° N. of Shaw Hill, finding, under 150 ft of drift, 218.5 ft of reddish sandstone resting on Manchester Marl. In the south, Bunter Sandstone is exposed in brooks south-west of Eccleston, where it comprises beds of coarse and fine soft red and brownish-red sandstone. The New Mills Bore [SD 523 168] at Eccleston proved over 300 ft of red and brown sandstone with marl bands. Red sandstone crops out in and east of Mawdesley village. A boring [SD 4616 1643] near the canal, 500 yd N. 20° W. of Rufford Old Hall, proved 55 ft of red sandstone under 117 ft of drift.

Keuper Sandstone and Keuper Marl

Keuper Sandstone is almost invariably coarser and more angular in grain than the underlying Bunter Sandstone. It is also harder and firmer. In colour it varies from grey to dull red, rarely being of such a bright colour as that characteristic of the Bunter. Quartz pebbles occur at many horizons. It is assumed to crop out under the drift between Rufford and Croston and north of Eccleston; there is, however, no evidence to demonstrate this. The small outcrop south of Walton le Dale is also conjectural. Indeed, the rock has only been proved at one point in the Preston district, about a mile and a half south of Preston, though it is better known in the districts to the south and south-west.

Keuper Marl crops out under drift over about sixty square miles of the area. It occupies the ground west of the Boundary Fault extension, and an area about five miles wide south of the east-west fault through Hutton. There is also a small isolated outcrop south of Walton le Dale. The full thickness of Keuper Marl is not known, but up to 660 ft have been proved. The Marl comprises red, blue and green mudstones with thin bands of grey to purple sandstone; gypsum veins are common.

Details of the Keuper Sandstone and Keuper Marl

Keuper Sandstone

A borehole at Penwortham Mills [SD 5393 2742], 1570 yd S. 17° E. of Preston Station, proved basal Keuper Sandstone—a coarse-grained grey pebbly gritstone—to a depth of 21 ft, with red and mottled Bunter Sandstone below. Three quarters of a mile beyond the southern boundary of the area at Burscough Bridge Station [SD 4444 1243] a borehole proved 185 ft of Keuper Sandstone under Keuper Marl;, it comprised fine to coarse-grained red and brown sandstone, conglomeratic in the: bottom 32 ft.

Keuper Marl

Grey marl crops out [SD 5620 2755] in Holland Wood on the banks of the River Darwen about a third of a mile S.E. of Walton le Dale, and is presumed to represent Keuper Marl brought in by the supposed east-west fault crossing this area. South of Preston, the Keuper Marl has been proved in a number of boreholes. On the west side of the Bamber Bridge railway line 700 yd N. of Preston Junction Station the Preston Gas Company's boring [SD 5453 2676] proved 274 ft of red and blue marl with some bands and veins of gypsum. Half a mile to the north-west, at the north-western end of the reservoir shown on the one-inch map, a borehole [SD 5394 2728] for Penwortham Mills recorded 57 ft of drift, 200 ft of red and mottled marl, and 82 ft of hard blue Carboniferous shale. The Keuper Marl is not known to rest on Carboniferous else­where in this district, and in all adjacent areas several hundred feet of Bunter Sandstone lie between the Keuper and the Carboniferous. It may well be that the junction with Carboniferous rocks is faulted in this borehole.

Dickson (1889) recorded the results of shallow boreholes drilled along the course of the Ribble below Preston Docks. The more westerly holes, between six and seven miles from the docks, proved 10 to 12 ft of red and blue-grey marl with gypsum at about 15 ft below O.D.; Dickson correlated these with the Keuper Marl. The more easterly holes, from four and a half to six miles below the docks, proved about 15 ft of 'strong red marl' and 'stiff red clay' about 10 to 15 ft below O.D.; these may also represent Keuper Marl but could be superficial deposits. De Rance (in Hull and others 1875, p. 127) recorded Keuper Marl at the mouth of the Ribble between Hesketh Bank and Freckleton Point. Some four miles to the south he records Keuper Marl in the bed of the Douglas at Placks near Tarleton.

Keuper Marl has been recorded in boreholes at Leyland. The Stannings Bleach–Works Bore (exact site not known) proved 218 ft of red marl under 62 ft of drift. The Seven Stars Bore [SD 5283 2161], 2400 yd W. 30° S. of Leyland Station, passed through 33 ft of drift into 147 ft of measures comprising 18-in bands of micaceous sandy marl alternating with 7 to 8-in bands of white and purple fine-grained sandstone. This lithology is reminiscent of the Keuper Waterstones, a division not recognized in the area at the time of the resurvey. South-west of Leyland red marl with bands of grey, very fine-grained sandstone crops out [SD 5226 2096] in the bed of the River Lostock alongside Leyland Sewage Works. About a quarter-mile to the south-west, one mile W. 40° S. of Worden Hall, red and grey marls crop out [SD 524 199] in Hollins Brook.

Red marl was seen in a small isolated exposure [SD 4259 1482] 200 yd N.W. of Holcrofts, which lies two miles S.W. of Rufford. At the pumping station 450 yd N. of Berry House, red marls with gypsum have been dug in the adjacent drain [SD 4241 1617]. L.H.T., D.P.

References

DICKSON, E. 1889. Geological notes on the Preston dock works and Ribble develop­ment scheme. Proc. Liv. Geol. Soc., 5, pp. 369–76.

HULL, E., DAKYNS, J. R., TIDDEMAN, R. H., WARD, J. C., GUNN, W. and DE RANCE, C. E. 1875. The geology of the Burnley Coalfield and of the country around Clitheroe, Blackburn, Preston, Chorley, Haslingden and Todmorden. Mem. Geol. Surv.

JONES, R. C. B., TONKS, L. H. and WRIGHT, W. B. 1938. Wigan District. Mem. Geol. Surv.

Chapter 6 Structure

The Preston district falls into two structurally different units—the Carbon­iferous strata to the east and south-east and the Permo-Triassic of the west and north (see (Figure 12)). The structure of the Carboniferous is fairly well evidenced; but due to the almost complete drift cover and lack of marker horizons that of the Permo-Triassic rocks is less clear.

Structure of the Carboniferous rocks

The structures of the Carboniferous rocks of the eastern part of the district are continuations of those described in the Rossendale country to the east (Wright and others 1927, p. 2–3). The moorland area in the south-east is structurally a continuation of the Rossendale Anticline, which stretches from the Pennines into Lancashire. This is bounded on the north by the south­westerly continuation of the Blackburn–Burnley Syncline, the north-western limb of which forms one limb of the Pendle Anticline, a structure resulting from the convergence of the Pendle Monocline and the Dinckley Anticline of the district to the north-east (Earp and others 1961, fig. 18). The Chorley Coalfield and the adjacent Millstone Grit strata appear to form a continuation of the Pemberton Syncline (Jones and others 1938, p. 62).

As in the rest of South Lancashire a system of faults varying in trend from north to north-west predominates. A marked north-easterly set of faults and a more irregular set of roughly east-west faults are also present. The major faults in the district are continued from the adjacent areas to the south and east.

Details

Folding

The extension of the Rossendale Anticline forms the moors of Darwen, Withnell, Anglezarke and Rivington. It is here a gently domed structure with the crest about a mile south of Great Hill; it is narrower than in Rossendale. The approximate horizontality of the beds within the structure gives rise to the extensive outcrop of the Fletcher Bank and Helmshore grits. Along a line from Brinscall to the Rivington reservoirs the anticline is much broken by faulting; from here to the Great Haigh Fault the ground is poorly exposed, and no confident deductions as to the structure can be made; and west of the Great Haigh Fault no northerly-dipping Carboniferous strata are known, so that the Rossendale Anticline does not appear to extend to the west.

The continuation of the Blackburn–Burnley Syncline is clearly defined to the south-west of Blackburn. The axis of the fold runs south-west from Blackburn through Feniscowles and thence appears to swing south towards Wheelton Lock. However, in this area the ground is much obscured by drift and the fold axis is displaced by faulting, so that the fold is not readily defined. The fold pitches to the north-east. Near Blackburn it is well marked along its northern limb by the steeply dipping—at 30 to 50° —Revidge Grit, which is traceable with dwindling dip almost continuously to Whittle le Woods. In contrast the southern limb is characterized by very gentle north-westerly dips along its length. The syncline is terminated by the Great Haigh Fault.

North-west of Blackburn the steep limb of the syncline forms the southern limb of the Pendle Anticline, the axis of which runs from the north-east corner of the district through Mellor towards Roach Bridge. The northern limb of this fold is largely hidden beneath a featureless terrain of boulder clay. This anticline brings in the oldest measures found in the district—the Upper Bowland Shales.

Traced to the south-west the Blackburn–Burnley Syncline and the Pendle Anti­cline both diminish in intensity; their axes diverge, and north of Hoghton a subsidiary anticline and syncline develop between them. The Revidge Grit lies in the core of the subsidiary syncline.

Faulting

The Pendle Anticline and Blackburn–Burnley Syncline are traversed by a number of north-westerly faults of throw generally up to about 500 ft, and a number of minor faults trending roughly east or north-east also occur. The Darwen Valley Fault continues from the district to the east with a downthrow to the north-east of about 600 ft, but followed northward its throw decreases and, on crossing the axis of the Blackburn–Burnley Syncline, is reversed; north-west of Blackburn its downthrow in the Revidge Grit is about 250 ft to the south-west. The fault cannot be traced through the drift-covered northern limit of the Pendle Anticline.

The north-westerly system of faults continues in the high ground in the east and south-east of the district; the subsidiary fault patterns are also well represented. Faults trending roughly east to west are localized, and occur on Winter Hill, north of Darwen Hill, between Great Hill and White Coppice, and west of Belmont. Faults of the north-easterly set occur on Winter Hill, north of Darwen Hill, on Darwen Moor, and at Hollinshead Hall: the best example of these is the Brinscall Fault from east of Healey Nab to Brinscall, forming the western limit of outcrop of the Fletcher Bank Grit.

In the area of Carboniferous strata around and south of Chorley the major faults continue from the Wigan district to the south (Jones and others 1938). The Great Haigh Fault, with a downthrow to the west of about 1700 ft, runs northward through Duxbury Park to Chorley, whence it runs N.N.W. through Whittle le Woods. A number of faults of similar trend lie between the Great Haigh Fault and the Stranger or German Barn Fault—which runs N.W. through Springfield with a downthrow to the west of about 750 ft. West of this the principal faults have a regular north­westerly trend. The Shevington Fault, with a downthrow of over 2000 ft to the east, runs N.W. through Wrightington, and along much of its length throws fairly high Lower Coal Measures against Millstone Grit. A number of small cross-faults have been proved between the north to north-west faults.

Structure of the Permo-Triassic rocks

A shallow syncline east of Preston is revealed by dips seen in the Bunter Sandstone in the River Ribble, and probably has a north-north-easterly trend, as shown in (Figure 12). There is no other evidence of folding in the Permo-Triassic rocks.

The boundary between Permo-Triassic and Carboniferous was formerly thought to be a fault running north-eastward across the map (Hull and others 1875, p. 170); the junction is now considered to be, in the main, an unconformity, and has been mapped as such except in the neighbourhood of Ecdeston.

The fault pattern of the Carboniferous is also seen in the Permo-Triassic. The major faults vary in trend from north to north-west; but it must be made clear that a number of faults are shown on the map as continuing from the Carboniferous rocks, without evidence of their actual existence in the Permo­-Triassic rocks. In other words, their existence and position in the latter are inferred. The true structure of the Permo-Triassic rocks may, indeed, be much more complicated than that indicated on the map; any or all of the faults proved in the Carboniferous may extend north-westward in the younger rocks, displacing boundaries to an unknown extent, and there may be other faults, and substantial ones at that, not yet known.

Details

From Elston to Walton le Dale the Bunter Sandstone seen in the River Ribble dips generally to the west at from 2° to 10°. Just west of Walton le Dale the strata are horizontal, but farther west the dip is generally to the east at from 5° to 12°. The trough of a shallow syncline thus runs across the river near Walton le Dale, with a probable axis running, as mentioned above and shown in (Figure 12), in a north-north­easterly direction; it is not defined elsewhere.

The Great Haigh Fault has, on the map, been continued into the Permo-Triassic rocks and runs from Whittle le Woods through Preston. South of Preston it is inferred to throw Keuper Marl against Bunter Sandstone. The Shevington Fault has likewise been continued to Longton. The Boundary Fault of the Wigan Coalfield has been extended west of Rufford, through Tarleton and Freckleton to Kirkham (followed south into the Wigan district it ceases to separate Carboniferous from Permo-Triassic rocks five miles south of Rufford). Its position in the present district is fairly narrowly defined, since in the south it must lie between the Rufford Borehole (p. 77), where Bunter Sandstone has been proved, and the exposures of Keuper Marl near Berry House and Holcrofts (p. 78). At the Ribble its position is also well defined, since it must lie between the sewage-farm boreholes, S.E. of Freckleton, which proved Bunter Sandstone (p. 77), and Freckleton Point where De Rance recorded Keuper Marl (p. 78).

The east-west fault inferred to run from the mouth of the Douglas through Hutton to Higher Walton has been drawn to separate the Bunter Sandstone west of Preston from Keuper Marl to the south. Its position south of Preston is fixed within narrow limits, since it must lie between the two Penwortham Mills boreholes, one of which (p. 77) proved Keuper Sandstone and Bunter Sandstone whereas the other proved thick Keuper Marl.

The course of the Euxton Fault running north-east from Eccleston Green to Clayton le Woods, and throwing Permo-Triassic strata against Carboniferous in the south, is hypothetical over much of its length. Be that as it may, its existence has been proved by boreholes at the Royal Ordnance Factory near Chorley. Here the R.O.F. No. 2 Well [SD 5554 2140], 1600 yd E. 5° S. of Leyland church, proved Keuper Marl to a depth of 320 ft; 430 yd S. 34° E. of this hole the R.O.F. No. 1 Bore [SD 5576 2107] proved Bunter Sandstone to a depth of 271 ft. The fault must lie between these holes. All Authors

References

EARP, J. R., MAGRAW, D., POOLE, E. G., LAND, D. H. and WHITEMAN, A. J. 1961. Geology of the country around Clitheroe and Nelson. Mem. Geol. Surv.

HULL, E., DAKYNS, J. R., TIDDEMAN, R. H., WARD, J. C., GUNN, W. and DE RANCE, C. E. 1875. The geology of the Burnley Coalfield and the country around Clitheroe, Blackburn, Preston, Chorley, Haslingden and Todmorden. Mem. Geol. Surv.

JONES, R. C. B., TONKS, L. H. and WRIGHT, W. B. 1938. Wigan District. Mem. Geol. Surv.

WRIGHT, W. B., SHERLOCK, R. L., WRAY, D. A., LLOYD, W. and TONKS, L. H. 1927. The geology of the Rossendale Anticline. Mem. Geol. Surv.

Chapter 7 Pleistocene and Recent

The greater part of the Preston district is covered by glacial and post-glacial deposits which in places are of the order of 200 ft thick. Estuarine alluvium covers a large area at the mouth of the Ribble, and extensive deposits of peat lie on the low ground in the south-west and on the moorland of the south-east; however, glacial deposits are of greater importance.

The whole district has clearly been glaciated, even to the summits of Rivington, Anglezarke and Darwen moors. There is nowhere evidence of Older Drift; and this account refers entirely to the Newer Drift of post-Eemian age. During the Newer Drift period the district was invaded by two ice-sheets, generally named the Irish Sea Ice and the Ribblesdale Ice. The former, which advanced principally from the north-west, gave rise to the north-western drift with its characteristic erratics from the Lake District and the Southern Uplands; the latter, advancing from the north-east, produced the Ribblesdale drift, characterized by erratics of limestone and chert. The Irish Sea ice was the greater, covering the whole area at the maximum of glaciation; the Ribblesdale ice advanced into an area in the north-east in the first phases of glaciation, but was probably held back later by the more powerful Irish Sea ice.

The glacial deposits comprise boulder clay and sand and gravel. In some areas below about 550 ft O.D. they form a tripartite sequence consisting of Lower Boulder Clay, Middle Sands and Upper Boulder Clay. These divisions are not distinguished on the geological maps; but they were recognized on the ground by the surveyors and are accordingly described here. The lateral extent and stratification of the Middle Sands are such as to rule out any theory of their formation subglacially; moreover, the Upper Boulder Clay is locally too thick to permit any such interpretation. Clearly the ice must have receded and later readvanced, before the final retreat.

Glacial deposits

Boulder Clay

In areas where deposits of Middle Sands are found, both Lower and Upper Boulder Clay may be distinguished. But as noted above this is only possible below 550 ft O.D., so that the boulder clay of the high ground cannot be differentiated.

Lower Boulder Clay

This boulder clay is considered to be the ground-moraine of the first ice-advance. It has only been mapped near the margins of the Ribble plain from above Walton le Dale Bridge to the northern margin of the district. Exposures are scattered and poor, and the base has not been seen; further, it is possible that in some instances the deposit mapped is not the Lower Boulder Clay but a bed of clay within the Middle Sands.

Ribblesdale drift of Lower Boulder Clay age lies in the bottom of a small valley half a mile south-east of Samlesbury Hall (Lower), the boulder clay containing pebbles and boulders of limestone but no igneous erratics. It was not observed elsewhere during the resurvey, but De Rance (in Hull and others 1875, p. 140) records about 13 ft of till with blocks of 'Black Carboniferous Limestone' lying beneath Middle Sands and Upper Boulder Clay in the railway cutting at Brinscall. North-western drift of Lower Boulder Clay age was only seen in small and very poor exposures during the resurvey. It is probably for the most part a stiff red clay with numerous Lake District erratics. It was recorded by De Rance (in Hull and others 1875, p. 140) in a cutting near the Preston Wagon Works at Marsh End (now the site of dock-works); here was exposed reddish brown clay with numerous Lake District erratics, including a block of greyish white granite measuring 5 x 4 x 3 ft and blocks of volcanic breccia over a yard long. De Rance also noted similar Lower Boulder Clay in the brooks north of Fulwood Barracks.

Upper Boulder Clay

This, regarded as the ground-moraine of the second advance, is better known than the Lower Boulder Clay. In and about Preston it is generally between 20 and 50 ft thick, and it shows its maximum proved thickness of 90 ft at School Lane near Bamber Bridge. It is entirely north­western drift. It contains numerous characteristic erratics commonly ranging up to a foot in length, but larger boulders are not wanting. A block of Galloway Granite, seen at Holme Slack Brickworks north-east of Preston, measured 4 x 3 x 3 ft. The matrix is generally a red or reddish brown slightly sandy clay.

The junction of this boulder clay with the underlying Middle Sands is always seen to be sharp and clear, and is not noticeably irregular or uneven. There is little disturbance of the smooth bedding of the Middle Sands, nor, in any sections so far examined, are the beds of laminated clay and silt, that in places cap the sand, distorted or caught up into the boulder clay. It seems that the ice of the readvance rode over the unconsolidated sands without deforming them, a possible explanation of this being that the sand's and their interstitial water were frozen during the readvance. It is, of course, improbable that the ice failed to erode these frozen sands at all, but it is likely that such erosion as there was took place by widespread abrasion rather than by deep local scour. Further, the Upper Boulder Clay does not contain the great proportion of sand that might be expected had the readvancing ice eroded large areas or great depths of the underlying sands. Planes of shear, visible as small-scale faults, have been noted in Middle Sands exposed in cuttings along the Preston Motor­way, and have been attributed to stresses from the superincumbent load of ice (Taylor 1958, p. 361).

Undifferentiated boulder clay

The boulder clay of the high ground is typical north-western drift. It is not generally very thick, except in the neigh­bourhood of Belmont where boreholes have proved up to 130 ft of boulder clay in a drift-filled channel.

Glacial Sand and Gravel

On the ground below about 550 ft extensive deposits of glacial sand and gravel lie beneath the Upper Boulder Clay. They appear mainly to be of the nature of outwash, and to be related to a single retreat of the ice; as in neigh­bouring areas, they are termed Middle Sands. On the higher ground smaller patches of sand and gravel occur; these may overlie or underlie boulder clay, and since they cannot be related to particular stages of retreat they have not been differentiated from each other; they may be related either to the Middle Sands retreat, the last retreat, or to minor oscillations of the ice-front. Near Chorley there are deposits of boulder clay, sand and gravel which show morainic form; the sands and gravels may be interbedded with or overlain by the clay; their age is uncertain. At Whittle le Woods and Duxbury Park there are gravels which appear to be related to the last phase of glacial drainage; and these are interpreted as Late Glacial Flood Gravels.

Middle Sands

With thicknesses up to about 140 ft, and variable lithology, the Middle Sands are not so well exposed now as formerly. They are fully described by Hull and others (1875, pp. 141–151) under 'Middle Drift'. At the time of the last survey clear sections were available in several sand pits on the east side of Preston. Here the sands are predominantly fine and even-grained and are horizontally bedded, with minor cross-bedding in places. Beds of gravel and coarser sand occasionally occur, but are subordinate in extent and thickness; locally a bed of gravel some 3 to 4 ft thick caps the main mass of the sand. The fine-grained sand is usually overlain by a silt, in places capped by a few inches of laminated clay. East of Fishwick the Middle Sands are in two beds separated by stiff plastic clay with a few stones; they are well seen in the pit of London Road Brickworks (Plate 5), about three-quarters of a mile west-south-west of Fishwick Hall, where the following section was exposed:

In this section the upper and lower junctions of the middle bed of clay and the sand are sharp and well defined, and there is no semblance of a passage from clay to sand, as might be expected if both had been laid down as sedimentary deposits in the same body of water. Farther east the upper surface of the clay is seen in an old sand-pit one-third of a mile north-east of Fishwick Hall, 20 ft of fine horizontally-bedded sand resting with sharp discordance on a clay surface which is inclined at 70° to 90°. It is possible to trace the clay in the Middle Sands along the steep overgrown banks of the Ribble by the change of slope which is visible at the level of the exposures in the sand-pit; this extends for about a mile east of Fishwick towards Brockholes on the north side, but has not been recognized on the south-eastern side of the valley.

A dissected plain of Middle Sands underlies the greater part of Preston and extends westward; and exposures can be seen along the northern edge of the district to beyond Kirkham. South of the Ribble, in the extreme west of the district, Middle Sands are not exposed; they may be concealed by thick Upper Boulder Clay, or they may be absent. They are said to have been penetrated by well-sinking at Croston, but a borehole at Rufford found only boulder clay with a 2-ft band of gravel above the Bunter Sandstone. In the plain the most westerly exposure of Middle Sand is some three miles from Chorley, and from here towards Chorley the Middle Sands are known to be present, generally below boulder clay. Occasionally the beds of sand form flat spreads at the surface owing to the absence of Upper Boulder Clay; but the surface of the plain shows no relief, thus illustrating the irregular nature of the base of the boulder clay. West and south-west of Chorley the drift has been recorded in the logs of a number of boreholes: these purport to show that the Middle Sands are here very variable; they may be absent or up to 60 ft thick, and frequently contain conspicuous beds of silt and clay. The best development appears to be to the south-west around Birkacre.

Undifferentiated glacial sand and gravel

On the high ground in the east are a number of isolated patches of sand and gravel. Sections are virtually non-existent and little is known of these deposits. Near Belmont 31 ft of sand has been proved in borings, but although this is underlain and overlain by boulder clay there is no evidence as to whether it is Middle Sands or is simply the product of a minor oscillation of the ice-front.

Morainic sands and gravels

A ridge of boulder clay, sand and gravel extends northwards from the Yarrow through Chorley to Whittle le Woods. This, the Chorley Moraine, is one of the most conspicuous glacial features of the district. The crest of the ridge is continuous except for a number of narrow gaps, the most important of these being occupied by the rivers Chor and Lostock; the gaps appear to be original features of the moraine. The beds of sand are irregular and in places very thick; and near the gaps through which the Chor and Yarrow flow they take on a coarse gravelly facies and project as hillocks from beneath the boulder clay. The moraine cannot be traced with certainty north or north-east of Whittle le Woods; it is obscure to the south of the Yarrow but may extend through Duxbury Park, where a borehole has recorded 132 ft of sand under 35 ft of boulder clay. East of the Chorley Moraine there are sands in the rounded hill south of Heapey; at its southern end the core of the hill is of mudstone, but to the north it may comprise morainic sands, for 40 ft of sand are here exposed in a sand pit. A ridge running south from Clayton Hall, on the western flank of the Chorley Moraine, may also be morainic: it shows a good development of sand ridges near Astley Hall, but farther south it appears to fork and lose its identity; westwards it slopes imperceptibly into the plain. The Worden Gravel Pit, a half mile south of Clayton Hall, was excavated in a great mound of gravel which rises through boulder clay on this ridge; the gravel exhibited magnificent current-bedding and contained fragments of marine shells. Just south of this pit a number of boreholes drilled on the site of the Royal Ordnance Factory passed through 83 to 180 ft of drift; the logs of these holes record beds of sand from 65 to 140 ft thick, overlain by up to 60 ft of clay, and containing irregular, and in places thick, beds of clay and clayey sand. North of Clayton Hall on the eastern face of the ridge there are exposures of two thick persistent beds of sand, separated and capped by boulder clay.

Late Glacial Flood-Gravel

The highest terraces of the River Lostock near Whittle le Woods, and of the River Yarrow around Duxbury Hall, have been mapped as Late Glacial Flood-Gravel, and were formed either during the period of marginal glacial drainage or at some later period when the streams were locally out of gradient and eroding rapidly. In the upper reaches of these spreads the gravel and sand is coarse, and is largely derived from local Carboniferous rocks. Downstream the terraces are of fine-grained sand not readily distinguished from Middle Sands.

Inferred sequence of events during Newer Drift times

The following accounts is based largely on notes written by the surveyors on completion of the resurvey. A more searching investigation of the glacial phenomena of the district, in the light of subsequent advances in Pleistocene geology, would possibly lead to a different interpretation; such an investigation has not been found expedient, and the account is presented in the knowledge that further study might show that some parts require modification.

The Lower Boulder Clay Advance

During this episode an ice sheet built out from Scotland and the Lake District, filled the Irish Sea Basin and moved across Lancashire; at the same time ice accumulated in the Pennines and also moved across parts of north-east Lancashire (see e.g. Edwards and Trotter 1954, pp. 70–71). In the Preston district glacial striae are rare; they were not seen at all on the high ground during the resurvey, although Tiddeman (1872, p. 490) recorded north-north-west striae at about 600 ft on Grey Heights, Healey Nab. Two records of striae on the low ground west of Chorley indicate movement of the ice from north-west or north-north-west on to the high ground. Striae north of Whittle le Woods point to ice-flow from west-north-west, but east-north-east striae also occur there, and probably resulted from the early invasion of the area by Ribblesdale ice—an inference supported by the presence of remnants of Ribblesdale Drift near Samlesbury and Brinscall. The flow of Ribblesdale ice may have deflected the Irish Sea ice, causing it to move in a more southerly direction.

Lower Boulder Clay cannot generally be distinguished from Upper Boulder Clay,. and thus the relative extent of the two ice-advances is not known. It is, however, probable that during the first advance ice completely covered the district. The drainage channel at Brinscall (see below) shows that, when this was cut, ice reached an elevation of at least 600 to 700 ft.

Retreat of Lower Boulder Clay ice and deposition of Middle Sands

The Chorley Moraine and deposits of similar nature and topographic expression which are found in more southerly areas have been regarded as a product of the retreat of the ice-sheet which produced the Lower Boulder Clay, and have been described as 'Middle Sands' (Poole and Whiteman, 1961); the Middle Sands proper, more regular deposits, are generally accepted as outwash laid down at this time, under partial, or even dominantly, lacustrine conditions; further, a suite of marginal drainage channels, in certain of which, to some extent, boulder clay has been deposited, has also been linked with the same episode—although certain other channels are regarded as of Upper Boulder Clay age.

As a working hypothesis the above is pursued here, though without full confidence; the sequence of events during the Newer Drift glaciation, partly understood by Wright and his colleagues when they surveyed this district nearly forty years ago, is still not clear. The sandy moraines and other phenomena are patently Newer Drift, but whether formed during the episode of the Lower Boulder Clay or the Upper is not yet certain (see e.g. the several Geological Survey memoirs, now being prepared, on the Chester, Stockport, Nantwich and Macclesfield districts).

It is supposed that as the ice of the Lower Boulder Clay glaciation retreated, glacial lakes formed between it and the high ground, and in them was deposited much of the Middle Sands. These lakes drained through channels cut along the ice-margin or across cols, and as the retreat progressed their level fell and drainage channels were initiated at successively lower levels. The moors east of Brinscall and Rivington show no trace of glacial drainage; so that as the ice retreated from them the marginal drainage must have found outlet elsewhere, outside the Preston district.

The first channel to be cut in this district was at Brinscall. It was first described by Jowett (1914, p. 224), who considered that its initiation led to the abandonment of the Cliviger Gorge overflow, diverting into the Mersey and Irwell basin water that had previously flowed into the Yorkshire Calder basin. According to Jowett, the cutting of the Brinscall channel commenced at about 750 ft O.D. In the Rossendale Memoir (Wright and others 1927, p. 140) the intake was said to be much lower, 'probably between 550 and 600 ft.' This view was probably influenced by misinterpretation of the final level of the Cliviger outlet, as the following observations show: 'gravel' 180 ft thick was reputed to be present at Copy Colliery near the Cliviger watershed (Hull and others 1875, p. 7); this was interpreted as post-glacial filling, and the final level of the glacial outlet was assumed to be about 600 ft O.D. Williamson (1956, p. 400) has pointed out that the record of gravel is unreliable and almost certainly represents fault-breccia; thus the channel could not have operated at such a low level as 600 ft. The present Cliviger watershed stands at 760 ft; the gorge probably ceased to operate as an outlet for glacial drainage at about 700 ft (Earp and others 1961, p. 238), post-glacial filling having since raised the watershed. Dean (1958) considers that the northern part of the Brinscall channel was initiated at 725 ft, and led to the abandonment of the Cliviger outlet at this level.

The geological structure of the area does not permit accurate reconstruction of the land-surface at Brinscall before the retreat. However, a study of various cross-sections of the channel suggests that cutting by marginal drainage com­menced at between 650 and 725 ft above sea-level. It appears that in the initial stages the western wall of the channel was formed by the ice-front; that drainage flowed through the Brinscall channel to just south of White Coppice, where it probably entered a narrow lake between the ice-front and the high ground; and that overflow from this lake passed through a short 'in and out' channel about three miles south of Brinscall, now occupied by the Chorley Reservoir. This channel, like the Yarrow Reservoir channel (see below), was not recognized during the resurvey of the area, but was described by Dean (1958); it has an arc of about 170°, the concave wall being to the east, and was initiated at between 650 and 700 ft O.D.; ice seems to have formed the western wall in the early stages. Drainage flowed through this channel into another narrow lake near Rivington. When the down-cutting of the Brinscall and Chorley Reservoir channels had lowered the water level to about 600 ft, a second 'in and out' channel was initiated about four miles south of Brinscall. This channel is now occupied by the Yarrow Reservoir, and its form has been largely obliterated by the waterworks and by post-glacial stream erosion. The Brinscall channel has been supposed to drain a lake which stretched through Blackburn and Accrington to Burnley (Jowett 1914; Wright and others 1927); but it seems small to have acted as the recipient of the drainage of such a large area, and an ice-front about twenty miles long would have been required to impound this lake. More information is needed about the distribution of the Middle Sands before the relationship of this channel to the Blackburn—Burnley drainage system can be ascertained.

The intake level of the Brinscall—Chorley Reservoir—Yarrow Reservoir spillway was cut down to between 500 and 525 ft, and the channels were abandoned when the ice-front retreated from Brinscall to near Wheelton, a movement which coincided with a more limited retreat of the ice in the Anglezarke area. A small channel north of Wheelton was cut at about 500 ft, and probably conducted drainage into a lake at Wheelton, whence it passed by the channel south-east of Heapey to the southern end of the Brinscall channel near White Coppice. The drainage then flowed south, cutting the channel now occupied by the Anglezarke and Rivington Reservoirs. For about two miles the western side of the channel is now rather flat and low-lying; and it seems that for some time after the initiation of the channel the drainage must have flowed along the ice front. The intake of this Wheelton—Anglezarke spillway was cut down to about 450 ft. A further slight retreat led to the opening of the Lostock channel about a quarter-mile west of the Wheelton channel, at about 400 to 450 ft. This channel—along which the Leeds and Liverpool Canal now runs—was extended to south of Feniscowles, where the inlet was cut down from about 375 ft to about 350. It was in the lakes drained by this channel and the earlier Wheelton channel that the extensive deposits of Middle Sands of Pleasington and Blackburn were deposited. Drainage channels at Mire Ash north-west of Blackburn, near Hoolster Hill and through Woodfold Park, probably carried water into this lake from an extensive lake impounded in the Ribble Valley.

The Lower Boulder Clay Retreat cannot be interpreted in terms of glacial drainage beyond this stage, since no undoubted channels of this age are known at lower levels. Drainage from the Lostock channel probably ran south along the ice-front. The Chorley Moraine and other morainic deposits of this area, if related to this stage, suggest a rather protracted ice-stand with gradual retreat along a north-south line. The presence of Middle Sands three miles west of Chorley and as far as the edge of the district west of Preston indicate the minimum extent of the retreat.

The Readvance

The full extent to which ice re-invaded the district is not known. Upper Boulder Clay is found up to at least 500 ft above sea-level, and it is probable that the readvancing ice covered all the ground below this elevation. Upper Boulder Clay is found in the Brinscall channel, and the intake of this channel was probably blocked at about 550 ft O.D. The absence of Ribblesdale Drift of Upper Boulder Clay age suggests that only the Irish Sea Ice readvanced across the district.

The Final Retreat

This stage differed markedly from the earlier retreat in that it was not accompanied by any great production of glacial sand and gravel. Indeed, such deposits are unknown in the Preston district. The retreat appears to have been either rapid or relatively 'dry'. Perhaps the ice became thinner during the readvance, and disappeared quickly once melting was renewed; perhaps it wasted with little melting. In either case little cutting action is to be ascribed to the subsequent marginal drainage which reopened the Brinscall and other channels. All the final retreat channels may have been open and in operation during the earlier retreat and merely occupied by a relatively feeble flow during the later phase. They have all the appearance of this, being in some instances broad open valleys with here and there an infilling of drift which seems to have been cleared out sufficiently to make way for the second flow—though evidence for this is neither clear nor convincing.

The first marginal drainage passed through the Brinscall channel. This and subsequent drainage seems to have followed the pattern of drainage of the earlier retreat, using the Wheelton, Heapey and Lostock channels. A lake was formed at Whittle le Woods, in which the waters from the Lostock channel deposited fairly extensive late-glacial flood gravels. This lake had two con­secutive outlets, the first at about 340 ft into a lake on the west side of Healey Nab, the second at about 305 ft into 'Lake Gale' about a mile to the south. The lake west of Healey Nab drained by a channel at Limbrick, at about 340 ft, into the Yarrow valley. 'Lake Gale' drained along the route of the canal at Botany Bay and thence south by Cowling also into the Yarrow valley. The drainage along this valley deposited the late glacial flood gravels near Duxbury Hall. A channel north of Pippin Street, with intake at about 285 to 290 ft, carried drainage south by Clayton Green into the Lostock valley. This channel was either of short duration or took little water. Its outlet level is not obvious as it is now occupied by a stream in its lower part.

No traces of glacial drainage are provable at lower levels, and further stages of retreat cannot be interpreted.

Pre-glacialAs mentioned on p. 83, no Older Drift is known in this district, and the term pre-glacial is here used in the sense 'pre-Newer Drift'. and Post-glacial drainage

In contrast to the heavily-mined district to the south and south-east, very little is known about the surface upon which the Pleistocene and Recent deposits were laid down. The general drainage of the high ground east of Brinscall and the Anglezarke reservoirs was probably much as it is today, except perhaps in the neighbourhood of Belmont. A borehole about a mile north-west of Belmont shows that the 'pre-glacial' stream which drained the valley here lay to the west of Belmont and probably ran in a south-westerly direction from about Bromiley.

The drift around Coppull is over 100 ft thick, but borings and shafts have not revealed any buried channels in the area; the general slope of the sub-drift surface appears to be northerly. From this area a drift-filled channel extends north for several miles, dropping northwards until, a third of a mile east of Euxton Station, it is 200 ft deep with a bottom 16 ft below O.D. The River Yarrow coincides with this channel, quite fortuitously, for a distance of a mile north of where the Moor Road from Chorley crosses it near Kingsley.

The general sub-drift surface probably declines everywhere towards the estuary of the Ribble but nowhere reaches any great depth. Keuper Marl has been recorded in the River Douglas near Tarleton and at the mouth of the Ribble (Hull and others 1875, p. 127), and outcrops of Keuper Marl and Bunter Sandstone occur at intervals across the southern margin of the district. The log of a borehole east of Rufford Hall near the canal gives 117 ft of drift on Bunter Sandstone, showing that the sub-drift surface is here about 100 ft below O.D.; this borehole was probably sited on the pre-glacial valley of the Douglas, which trended west or north-west of this point.

The rivers Yarrow and Lostock have curiously anomalous courses, which are closely comparable with that of the Douglas in the district to the south (Jones and others 1938, pp. 120–121). They follow glacial drainage channels in the upper part of their course, in both cases as far as the Chorley Moraine, and thence break out of these and trend away to the north-west across the plain.. Alternative courses were open to the south at no great height above the present stream, and were occupied by the marginal glacial drainage; there seems to be no obvious reason why the post-glacial streams should not have continued to occupy the same channels. A similar diversion occurred in the case of the three streams descending from Rivington, Anglezarke and Withnell moors.

The post-glacial course of the Darwen is partly a result of glacial diversion. For about two miles below the south-western fringes of Blackburn the river follows what was probably its 'pre-glacial' course: it thence swings south, but in 'pre-glacial' times the channel may have run due west by Pleasington to Houghton Bottoms. Shortt (1880, pp. 6–8) considered that glacial deposits had blocked such a channel, causing both diversion of the river and post-glacial cutting of the gorges, at Feniscowles and south and north of Houghton Bottoms, through which the river now flows.

The Ribble has no drift-filled valley corresponding in general position to its present course. This course is entirely post-glacial, having been cut through the drift on to the approximately plane surface of the Triassic rocks. A buried valley no doubt exists, but it must lie to the north of Preston; for south of the present valley the River Darwen, a tributary of the Ribble, has rock exposed all along its course. Borings in the Ribble channel opposite the mouth of the Douglas proved a drift-filled channel which may be the pre-glacial valley of the Douglas (Dickson 1889 b, pp 375–376). If this is the case it suggests that the pre-glacial course of the Ribble was to the north of its present channel; on the other hand this buried channel may be part of the pre-glacial course, not of the Douglas, but of the Ribble.

Post-glacial or Recent deposits

Shirdley Hill Sand

Typically an incoherent yellow or white sand with grains generally more or less rounded, and in which the uppermost parts are sometimes found to be partially or completely cemented by ferric oxide, the Shirdley Hill Sand is found in the south-west corner of the district, around and west of Rufford. Its base is seldom proved except where the sand thins out, but its thickness probably averages between 10 and 20 ft. It rises over low hills of boulder clay and is probably a blown sand, notwithstanding the absence of dune-forms in this area.

Downholland Silt

A marine clay found in west Lancashire, and containing Scrobicularia and other marine shells, was called Lower Scrobicularia and 'Cyclas Clay' by De Rance (1870, p. 6), and was renamed 'Downholland Silt' by Wray and Cope (1948, p. 26). The deposit is generally a pale blue silty clay. It was not seen during the resurvey and is not shown on the map, but according to De Rance (Hull and others 1876, p. 158) it underlies the peat in the extreme south-west of the district. It is possible that 'marl' proved beneath peat along the line of the railway at Bescar Lane at depths of 4 to 23 ft was this clay; but it may have been boulder clay or, more doubtfully, Keuper Marl.

Peat

A thin bed of peat below the Shirdley Hill Sand was proved in auger holes near Mere Sands Wood; but all other known occurrences on the plain appear to be younger than the Shirdley Hill Sand. Peat mosses are no longer actively worked for fuel, but in the past much has been removed. Only remnants now remain of Farrington, Longton and Little Hoole mosses, places where there were formerly thicknesses of 10 to 20 ft of peat; even the area south of Hutton was alluded to by Hull and others (1875, p. 160) as showing traces of a former peat covering.

Peat covers some twelve square miles in the south-west corner of the district, the main development being in the bed of the artificially-drained Martin Mere around Mere Hall. Here it is certainly 15 ft and perhaps 30 ft thick, and contains many old tree trunks. In this south-western area the peat may be interbedded with clays and silts; for example during deepening of Back Drain north-west of Mere Hall, the following section was proved: peat 36 in, clay 9 in, clayey peat 2 in, grey silt 54 in, silt 12 in, heavy brown peat 24 in—the last items by augering. The level-bedded silt in this section is traversed by channels filled with irregularly bedded silt with vegetable debris.

Much of the ground above 900 or 1000 ft O.D. in the south-east is covered by typical moorland peat. The general thickness appears to be from 3 to 5 ft.

River Terraces and Freshwater Alluvium, including Alluvial Downwash, Alluvial Cone, and Older Alluvium

The River Ribble flows in a valley upwards of a mile wide. South of Preston there is a wide alluvial flood plain, but upstream the valley is occupied largely by two river-terraces 3 to 5 ft and 8 to 10 ft above the flood plain. A small third terrace lies about 15 ft above the flood plain south of Fishwick Hall. The terraces are mainly of gravel capped by sand and silt; the alluvium is mainly sand and silt. A similar development of fluviatile alluvium and terraces is found in the valley of the River Darwen, which joins the Ribble above Preston.

The fluviatile alluvium of the Lostock and Yarrow rivers is almost uniformly sandy in the higher parts, due to the abundance, especially in the valleys, of glacial sand. Towards the west it is more clayey. The valley of the Yarrow is lined sporadically by a well developed gravel terrace about 6 ft above the main alluvium. The fluviatile alluvium of the Douglas and some of its tributaries is clay, commonly with a thin bed of sand near the top. Small patches of Alluvial Downwash are marked on the one-inch Drift map, bordering the alluvial flat of the River Ribble in a few places. A patch of Older Alluvium is shown on the map near Kirkham in the north-west. An Alluvial Cone is present in the valley near White Coppice, two and a half miles north-east of Chorley.

Estuarine Alluvium and Tidal Flat

Extensive tracts of estuarine alluvium lie at the mouth of the Ribble below Preston and in the valley of the Douglas as far south as Rufford, and the same deposit extends up the Yarrow valley to Croston, and up the Lostock to about a mile and a half above its junction with the Yarrow. The estuarine alluvium consists mainly of laminated clays, silts and sands, with thin beds of peat and occasional lenses of gravel. Preston Docks were constructed partly in estuarine alluvium; and during the excavation numerous bones of human and animal origin and artifacts including a 'dug-out' canoe were discovered (Dickson 1889a, 1889b). The Tidal Flat at the mouth of the Ribble forms Hesketh Sands, and extends short distances up both rivers beyond the confluence with the Douglas. All Authors

References

DEAN, V. 1958. An initial outlet of pre-glacial Lake Accrington. Published privately. DE RANCE, C. E. 1870. Geology of the country between Liverpool and Southport. Mem. Geol. Surv.

DICKSON, E. 1889a. Notes on the excavations for the Preston Docks. Proc. Liverpool Geol. Soc., 5, pp. 249–56.

DICKSON, E. 1889b. Geological notes on the Preston dock works and Ribble development
schemes. Proc. Liverpool Geol. Soc., 7, pp. 369–76.

EARP, J. R., MAGRAW, D., POOLE, E. G., LAND, D. H. and WHITEMAN, A. J. 1961. Geology of the country around Clitheroe and Nelson. Mem. Geol. Surv.

EDWARDS, W. and TROTTER, F. Monograptus 1954. The Pennines and adjacent areas. Edit. 3. Brit. Reg. Geol., Geol. Surv.

HULL, E., DAKYNS, J. R., TIDDEMAN, R. H., WARD, J. C., GUNN, W. and DE RANCE, C. E. 1875. The geology of the Burnley Coalfield and of the country around Clitheroe, Blackburn, Preston, Chorley, Haslingden and Todmorden. Mem. Geol. Surv.

JONES, R. C. B., TONKS, L. H. and WRIGHT, W. B. 1938. Wigan District. Mem. Geol. Surv.

JOWETT, A. 1914. The glacial geology of East Lancashire. Quart. J. Geol. Soc., 70, pp. 199–231.

POOLE, E. G. and WHITEMAN, A. J. 1961. The glacial drifts of the southern part of the Shropshire-Cheshire Basin. Quart. J. Geol. Soc., 117, pp. 91–130.

SHORTT, J. 1880. A brief sketch of the history of Hoghton, in the county of Lancaster. Blackburn.

TAYLOR, B. J. 1958. Cemented shear-planes in the Middle Sands of Lancashire and Cheshire Proc. Yorks. Geol. Soc., 31, pp. 359–65.

TIDDEMAN, R. H. 1872. On the evidence for the ice-sheet in North Lancashire and adjacent parts of Yorkshire and Westmorland. Quart. J. Geol. Soc., 28, pp. 471–91.

WILLIAMSON, I. A. 1956. A guide to the geology of the Cliviger valley, near Burnley, Lancs. Proc. Yorks. Geol. Soc., 30, pp. 375–406.

WRAY, D. A. and COPE, F. W. 1948. Geology of Southport and Formby. Mem. Geol. Surv.

WRIGHT, W. B., SHERLOCK, R. L., WRAY, D. A., LLOYD, W. and TONKS. L. H. 1927. The geology of the Rossendale Anticline. Mem. Geol. Surv.

Chapter 8 Mineral products and water supply

Little industry in the Preston district is directly dependent upon local mineral resources. Coal mining, once important, has almost ceased. A small number of stone quarries are working and small amounts of sand and clay are dug. The moors in the south-east supply surface water to large reservoirs; and underground water is extracted locally.

Coal

Coal was formerly worked from numerous small pits, but at present there is only one producing colliery in the district. This is Ellerbeck Colliery, two miles south of Chorley, which works the Little or Upper King, the Peacock, the Trencherbone and the Wigan Four Foot mines. Elsewhere seams are exhausted or of inferior quality. The following notes on the individual seams treat them in ascending stratigraphical order.

Seams of the Millstone Grit Series

Although these measures contain a number of small seams, few are thick enough to repay exploitation even at outcrop. The seam commonly present on top of the Fletcher Band Grit in the south-east of the district is usually only a few inches thick and quite valueless. Nonetheless, De Rance (in Hull and others 1875, p. 97) stated that east of Great Hill on Withnell Moor the coal was worked at a thickness of 24 in—the pits are still visible. Farther south the coal was proved north of Bromiley and is there 20 in thick.

The Brooksbottoms Coal has been worked at outcrop south of Belmont village where it is 14 in, and at Heskin where it is about 12 in thick. Elsewhere it has not been exploited.

The Holcombe Brook Coal was formerly worked from levels in the stream beside the Belmont–Rivington road, where it was about 18 in thick. It has been exploited on a somewhat larger scale from levels and pits on the east side of Healey Nab. Here it crops out in the stream and, dipping north, underlies at small depth a considerable area west of White Coppice. It is from 13 to 17 in thick. It was formerly worked at Withnell Mill, where from 5 to 7 ft of fireclay were extracted as well as 16 in of coal. There is no evidence of the 4-ft coal stated by De Rance (in Hull and others 1875, p. 96) to lie some 20 ft below it. The Holcombe Brook Coal has been extracted at outcrop at Heskin, but around Wheelton where there are miles of almost bare outcrop it does not appear to have been worked.

The Sand Rock Mine near the top of the Rough Rock, as regards thickness, is a much better proposition. It has been worked at its outcrop at Charnock Richard and at a small colliery nearby, and here is said to consist of 20 in of cannel overlain by 31 in of coal, though the quality must be rather poor as none of the ventures seems to have met with lasting success. The thickness is given as 25 inches in the Fox Hole Wood Boring (see p. 115), but the Heskin Bore (p. 116) south of Charnock Richard proved only 12.5 in of coal. On Rivington Moor and Smithills Moor the Sand Rock Mine is a double seam, and both coals together with their fireclays have now been exhausted. It is probably these two coals which have been worked at Heath Charnock south-east of Chorley, from north of Anderton Hall towards Limbrick. Records of the thickness are scanty: at the Hospital in Heath Charnock the lower coal is given as varying from 16 to 36 in, and the upper coal as 12 in with a workable fireclay below; and a more recent section at Shawe's Colliery, beside the River Yarrow 250 yards west of Blindhurst, gives the section, under drift, as fireclay 11 ft, on grey rock 22 ft, coal 24 in and fireclay 8 in. To the south this coal is only 10 in thick. Small areas of the coal and fireclay may still exist on the sides of the Yarrow valley. The Sand Rock Mine is known to be present on the north and west of Darwen Hill but has not been worked.

The highest seam of the series, the Six Inch Mine, exhibits at Wrightington the unusual thickness of 14 in, and has been mined at a small outcrop-working, close to the inn half a mile north-west of Wrightington church.

Seams of the Lower Coal Measures

The Lower Foot Mine has in the past been miscorrelated in the Chorley area with the Lower Mountain Mine or Mountain Mine. It has been worked at its outcrop and from shallow shafts at Charnock Richard and just west of Chorley. The Black Pit Shaft of the Chorley Colliery Co. was deepened to this seam, but the coal, 18 in thick, is said not to have been worth extracting. It does not appear to have been worked elsewhere.

The Lower Mountain Mine was formerly one of the principal seams of the Darwen Hill area, where it was known as the Ganister or Half Yard; it is recorded as varying in thickness from 18 to 24 in. It was extracted chiefly by levels in the hill faces and sent down to Darwen by inclines. It was also worked farther north on Winter Hill and probably also on Bunker's Hill, south-west of Blackburn. In the Blackburn Syncline it was worked from a series of small pits near Feniscliffe; there are no records of the extent of these workings but the coal is reported to have been from 26 to 28 in thick.

The Upper Mountain Mine is one of the most important seams in the Lower Coal Measures. It is exhausted on Darwen Hill and also on Winter Hill and is recorded as 24 in thick in these localities. Immediately east of the Great Haigh Fault it has been followed from its outcrop south-west of Hall o' the Hill to a depth of 360 ft immediately west of Ellerbeck Hall. It is here recorded as varying from 18 to 27 in thick. It was not followed farther south, probably due to thinning of the seam; in the Adlington Bore (p. 102) it was only 3.5 in thick. The seam was one of the mainstays of mining in the Chorley area, where it varies from 21 to 40 in or more in thickness but is generally about 27 in. It has been worked out to considerable depth almost throughout the area.

The Cannel Mine or Little Coal has been worked to a small extent at its outcrop at Heskin Green, where it consists of 12 in or less of rather poor coal.

The Arley Mine was on account of its thickness a valuable seam, but is now almost entirely exhausted. It comprised 4 to 5 ft of coal with thin dirt partings, overlain by a thicker dirt-band and 6 to 12 in of 'bulgram' or inferior coal. At Ellerbeck Hall, on the southern margin of Sheet 75, there was a maximum thickness of 5 ft of clean coal. About Coppull it was worked southward of its outcrop at Springfield. The position of this outcrop is very uncertain; and borings between here and Coppull show that over 100 feet of drift rest on measures a little above the Arley Mine, and that the ground is much faulted. The thin cover between the coal and the base of the drift, together with the thickness of the drift and the presence of faults, explain why the coal has not been completely removed.

The Smith Coal, perhaps locally the best-quality seam in the upper part of the Lower Coal Measures, is also largely worked out. The Smith Bottom Coal was that usually worked, but where the dirt above it was sufficiently thin the Bottom and Top Coals were worked simultaneously. The Cockloft Coal does not appear to have been exploited. The Bone Coal, a seam about 2 ft thick, has been very extensively won. The Yard Mine, 27 to 29 in thick, lies beneath only a small part of the present area, where it has been worked to a considerable extent. A thin seam about 45 feet above the Yard Mine was worked at shallow depths at Welch Whittle, where it was said to consist of cannel. The Ravine Mine and the coals just below probably represent a great thickness in the aggregate, but the innumerable fireclay partings render the seam unworkable. The King Mine is mostly worked out; two seams, each about 18 in thick, are separated by a parting of about 12 in. The Peacock Mine, from 20 to 47 in thick, is at present worked at Ellerbeck Colliery. It is generally of poor quality, and except at Ellerbeck is not worth working. The Trencherbone Mine, also worked at Ellerbeck, is of moderate quality and varies in thickness from 54 to 66 in; it is subject to 'washouts'. The Wigan Four Foot Mine is a good-quality coal and has been extensively mined over its limited area in this district. It is generally from 51 to 54 in thick. It is worked at Ellerbeck Colliery. The Wigan Five Foot Mine is in this district variable and generally unworkable. It is a composite seam comprising up to 20 ft of coals, mudstones and seatearths.

Fireclay and ganister

No refractory minerals are at present mined in the Preston district. The fireclay and ganister of the supposed Cannel Mine were once worked at Heath Charnock; and the fireclay of the Cannel Mine may have been worked at Heskin Green. The sandstone 70 ft below the Upper Mountain Mine was used to line an iron-smelting furnace in Copper Works Wood west of Chorley. On the Rivington and Smithills moors the fireclay associated with the Sandrock Mine was exploited for stone-ware, but is now exhausted. Fireclays associated with the Lower and Upper Mountain Mines at Darwen Hill were also worked in the past.

Ironstone

Traces of an ancient iron smelting industry are to be seen in Copper Works Wood on the west of Chorley. Owing to both iron and coal having been mined in the wood the horizon of the ironstone is uncertain, but it probably lies about 100 ft below the Upper Mountain Mine, where ironstone is recorded in the section of Moor Road Pit (p. 123). The sinkings are shown on the first six-inch geological map as being for 'ochre and iron'. One shaft in this neighbourhood, 350 yd west of Gillibrand Hall, is beyond the boundary fault of the Birkacre trough and probably begins just below the Arley Mine. The ground round it is thickly covered with an ochreous deposit.

Lead and barytes

Three occurrences of lead ore are known on Anglezarke Moor—and there may be others. The known lodes are in the Fletcher Bank Grit, and lie a short distance east of the south-easterly continuation of the Brinscall Fault. They are in fault fractures, but the throw of these appears to be insignificant. Only in one locality has any considerable amount of mining been done.

The most northerly occurrence is in the valley of Dean Brook about half a mile east of White Coppice, where a lode trending approximately E. 20° N. can be traced for a little over a quarter-mile by means of old trial pits. Working can only have been on a small scale. It has been recorded that near the surface this vein carried only lead ore, mainly in the form of anglesite (G. V. Wilson and others 1922, p. 63). A short distance to the west an old adit visible in quarries at White Coppice was presumably also a trial for lead. Three–quarters of a mile to the south, just north of Manor House, can be seen workings for lead on a limited scale. Judging from the disposition of trial pits the lode trends more nearly north-east than that at Dean Brook. The original field map of this area notes that this lode contains galena, barytes, copper pyrites and quartz.

The third and most important occurrence is in Lead Mines Clough north of the River Yarrow on the east side of Anglezarke Reservoir. The mines in this area are mentioned by Leigh (1700) and therefore must have been in operation in the 17th century. The only detailed account, however, is one given by James Watt (1790), and from this the following particulars are taken: the mines had been worked about 100 years previously, but were afterwards left standing until 1781; they were then re-opened, but for the first five years did not produce more than 4 tons of lead per annum; from 1786 to 1789 they produced 73 tons in all. The principal lode seems to have been the Old or Sun Vein, which apparently can be traced for about a quarter-mile by a line of pits trending E. 15° N. Near the surface it was found to hade at a small angle to the north, but it flattened considerably in depth. It varied in width from 6 to 36 in, and consisted mainly of galena with some blende, accompanied by witherite, barytes, iron pyrites and a little calcite as gangue minerals. The part of the vein richest in galena was in gritstone, the shale beds containing mainly blende and pyrites. The vein was irregular, the ore occurring in 'nodules' and 'clusters' and, where wide, in a breccia of sandstone and shale. The witherite was present in greater quantities towards the surface, being mixed with barytes in depth and entirely replaced by it in the lower levels. In 1789 a new engine shaft was sunk on the vein to a depth of 42 yd. An underground shaft in another part of the mine carried the workings to a further depth of 11 yd, being sunk in the shale below the Fletcher Bank Grit.

Four other lodes north of the Sun Vein were worked. These were, from south to north, the Engine, Minehouse, String and New Trial veins. They were all about the same width as the Sun Vein and behaved similarly to it in depth as regards hade. All except the String Vein, which was a branch from the Minehouse Vein, trended more nearly east to west than the Sun Vein, and converged on it eastwards. Watt noted that most of the veins appeared to have their origin in the 'Chorley Road Vein', i.e. the south-easterly continuation of the Brinscall Fault. In addition to the above there are some old pits in the Yarrow valley, 200 to 300 yd south of the Sun Vein outcrop.

In considering the possibility of this area as a source of barytes and witherite it was noted that " there is probably less than a ton of barium minerals in the whole of the dump [waste tips]. The barytes is of fair quality, with slight iron-staining, and not hard; it carries occasional streaks of lead. The witherite is exceedingly good white, though it occasionally contains specks of blende " (Wilson and others 1922, p. 63). According to Watt (1790) this is the type-locality for witherite, specimens described by Withering (1784) being from this area and not, as he first thought, from Alston Moor. The mineral analysed by Withering was a fibrous variety—the 'aerated barytes' of Watt (1790). It was named witherite by Werner (Hoffman 1789). Turner (1963) considers that Withering's original locality, Alston Moor, may have been the correct one, and not Anglezarke.

A vein of earthy pink barytes from 1 to 2 ft wide is visible in the tramway cutting leading into Withnell Brickpit, north of Withnell. It occurs along the fault which throws the Rough Rock down to the east.

Alum shales

In the past alum was obtained from the shales below the Alum Crag Grit at Alum Scar, about a mile north of Pleasington. A concise account of the industry is given by Loch (1946). The shales were worked as early as 1611 and were probably exploited intermittently up to the late 18th century. In the early days the shale was allowed to weather, digested with water and treated with potassium chloride, often in the form of kelp-ash; and the alum was extracted by crystallization from the resulting solution. Later, considerable time was saved by calcining the shale instead of allowing it to weather, the carbonaceous matter in the shales aiding this process. Some 100 tons of rock were probably required to produce one ton of alum. The only remaining traces of the industry are thickly overgrown dumps of shale and waste.

Sandstone

Most of the Carboniferous gritstones and sandstones have been quarried for building stones which were used locally in walls and farms, but most of these small quarries were only worked for a limited time. Extensive working was restricted to a few larger quarries, and even in these the output was very variable.

The Lower Wilpshire Grit has been worked for some considerable time in Abbot Quarry, Mellor, where it is a good general-purpose stone which has been utilized for sawn flags, dressed setts and kerbs, and as a building stone. Inferior stone was crushed for use in concrete. The rock was also worked at Park Quarry, Samlesbury.

The Revidge Grit has been worked on a large scale between Blackburn and Whittle le Woods, originally for building stone, but later mostly crushed for sand, concrete aggregate and road metal. Its equivalent, the Fletcher Bank Grit, has been extensively quarried from Anglezark to Withnell for setts, kerbs and ashlar. Much material, particularly from the old quarry-waste dumps, has been used as road metal and concrete aggregate.

The Brooksbottoms Grit in its coarse development has been worked at Heskin; the much finer-grained stone was exploited in several small quarries to the north-east.

The Lower Haslingden Flags were extensively quarried for building stone in the Yarrow valley at Euxton, and at Heapey where they were somewhat massive. They were worked for flags at Cowling, where they were even mined to a small extent. The Upper Haslingden Flags were quarried for flags at Wheelton and Limbrick; but in the extreme south-east of the district they appear to be too shaly to be of much value and their exploitation has been for local use only. The Rough Rock has been quarried at Euxton, on Healey Nab, and north of Withnell.

The sandstones in the Lower Coal Measure have not been much exploited. Small quarries were worked in most of the sandstones exposed on the higher ground, and old quarries at somewhat doubtful horizons exist at Charnock Richard and Heath Charnock. A sandstone 70 ft below the Upper Mountain Mine was used in ancient buildings at Gillibrand Hall. The Crutchman Sand­stone was extensively quarried along its outcrop at Charnock Richard, and was used for building and paving.

Brick clay

In the Preston area the Upper Boulder Clay is dug for the manufacture of bricks. The principal product is the common general-purpose brick, but facing, rustic and 'plastic' bricks have also been made from this clay. Bricks were at one time made from boulder clay at a number of places in the neighbourhood of Chorley.

The most important brickworks in the Carboniferous area of the Preston district lie a mile north of Withnell, where the mudstones and shales for 80 ft below the Rough Rock are utilized (the Upper Haslingden Flags being repre­sented by only 12 ft of shaly flagstone). Terra cotta and Withnell Plastic Brick (pressed) are the chief products, the latter being widely distributed for facing and constructional work. Bricks were also made from the shales overlying the Holcombe Brook Coal at Brinscall.

Sand and gravel

Glacial sands have been extensively worked around Pleasington and Feniscowles for building sand. They here commonly contain thin impersistent lenses of clay and silt; one variety of silt, known as 'bing', is highly esteemed as a moulding sand for use principally in the manufacture of aluminium ware. In the Preston area brick-pits in the Upper Boulder Clay generally extend down into the Middle Sands, and these have been worked for building and general purposes. Glacial sands, extensively developed in the Chorley area, are largely dug. for building sand and moulding and pig-bed sand; coarser deposits in the area yield gravel for concrete making. Gravel has been obtained from the alluvial deposits of the River Ribble threequarters of a mile west of Samlesbury Hall.

Water supply

Surface supplies

The moorlands of the south-east of the Preston district form important catchment areas for reservoirs which supply the surrounding towns and Liverpool. The extreme south-east of the district supplies Bolton: Belmont Reservoir is for compensation water, the supply reservoirs lying outside the district, to the south-east. Darwen is supplied by reservoirs at Sunnyhurst on the north of Darwen Hill. The Liverpool water undertaking utilizes the remainder of the moorland catchment area, some 9700 acres. The water from Roddlesworth Reservoirs in the north is conducted into the Anglezarke and Rivington Reservoirs by an open channel or goyt. The reservoirs of the Liverpool undertaking in this district have a total storage capacity of about 4000 million gallons. Chorley obtains water from these reservoirs and also from the Thirlmere Aqueduct of Manchester Corporation Waterworks, which passes through the district. Leyland, Wheelton, Heapey and other outlying villages are also supplied by this aqueduct.

The two principal towns of the northern area, Preston and Blackburn, obtain most of their water from gravitational supplies with catchments in the hilly ground north and east of the district.

Underground supplies

Due to the availability of other supplies, underground water is not exploited to any extent by local authorities. At a pumping station at Clayton le Woods, Preston extracts about 180 000 gallons per day from two boreholes 302 ft and 500 ft deep, which are sunk to the shales and sandstones below the Revidge Grit. A borehole 748 ft deep, penetrating measures of the Middle Grit Group at Tockholes, is used to augment Darwen Corporation reservoirs; it yields about 6000 gallons of water per hour. A pumping station beside the canal north-west of Thorpe Green near Brindle formerly supplied Walton le Dale Waterworks; by means of a borehole and well it obtained water from the measures below the Revidge Grit, but the yield was small and the water hard. The following analysis (originally in grains per gallon) of water from this station was made in 1881:

Blackburn formerly obtained some 70 000 gallons per hour from a 215-ft borehole into the Revidge Grit at Mile End Pumping Station. Until recently the supply of surface water to Bolton was augmented by pumping from two boreholes in the Preston district; one, a little south of Bromiley, was 645 ft deep and yielded some 28 000 gallons per hour; the other, at Lower Heights, south of Belmont, was 610 ft deep and yielded about 40 000 gallons per hour. Both these holes obtained water from the Helmshore and Fletcher Bank Grits. Fulwood Waterworks (now defunct) pumped about 1500 gallons per hour from the Bunter Sandstone in a borehole 298 ft deep at Fulwood. Bunter Sandstone was also tapped by the West Lancashire R.D.C. at Rufford in a borehole 172 ft deep.

A number of privately owned boreholes and wells are used, varying from dug wells to boreholes over 1000 ft deep. A borehole at Ramsgreave has obtained a limited supply from shales and sandstone above the Wilpshire Grit. Water from the Middle Grit Group is exploited by industrial concerns at Feniscowles and Wheelton, up to about 20 000 gallons per hour being obtainable from an individual well. The Haslingden Flags yield about 5000 gallons per hour in two shallow shafts at Lower Healey. The Rough Rock, a potential source of moderate amounts of good-quality water, has only been penetrated by one shallow well at Feniscowles, where 1000 gallons per week are extracted. The Lower Coal Measures have been little exploited; but several boreholes in Blackburn and Chorley have obtained water from these rocks.

The Bunter Sandstone is an important aquifer, and numerous wells have been sunk to it in and around Preston and north-west of Chorley. These wells yield from 5000 to 60 000 gallons per hour. An analysis of water dated 1935 from Courtaulds No. 1 Borehole at Ribbleton is as follows:

Water is extracted from the Middle Sands of the Pleistocene by a number of shallow wells west of Preston and around Leyland. The yield is generally small, but at Leyland up to 12 000 gallons per hour are obtainable from individual wells 50 to 60 ft deep. All Authors.

References

HOFFMANN, C. A. S. 1789. Mineralsystem des Herrn Inspektor Werners mit dessen erlaubnis herausgegeber von C. A. S. Hoffmann. Bergmannisches J. 2, 1, pp. 311–416.

HULL, E., DAKYNS, J. R., TIDDEMAN, R. H., WARD, J. C., GUNN, W. and DE RANCE, C. E. 1875. The geology of the Burnley Coalfield and of the country around Clitheroe, Blackburn, Preston, Chorley, Haslingden and Todmorden. Mem. Geol. Surv.

LEIGH, C. 1700. The natural history of Lancashire, Cheshire and the Peak in Derbyshire. Oxford.

LOCH, C. W. 1946. Forgotten mines in Lancashire. Mining Mag., 74, pp. 290–97.

TURNER, J. S. 1963. The type-locality of witherite. Mineral. Mag., 33, pp. 431–2.

WATT, J. 1790. Some account of a mine in which the Aerated Barytes is found. Mem. Lit. Phil. Soc. Manch., 3, pp. 598–609.

WILSON, G. V., EASTWOOD, T., POCOCK, R. W., WRAY, D. A. and ROBERTSON, T. 1922. Special reports on the mineral resources of Great Britain: vol. II, Barytes and Witherite. 3rd Edit. Mem. Geol. Surv.

WITHERING, W. 1784. Experiments and observations on the Terra Ponderosa, etc. Phil. Trans. Roy. Soc. Lond., 74, pp. 293–311.

Appendix 1 Boreholes and shafts

Sections of important boreholes and colliery shafts are listed below. They are given in detail but with some abridgement of the original records—abridgement which, however, detracts little from the value of the sections since it has not been applied to details of coal seams and other strata of economic or scientific importance. Fossil names are usually excluded, since faunal lists are given elsewhere in this memoir.

Immediately below the name of each borehole or shaft is given the height above sea level (O.D.) of the point from which measurements were taken, and the number of the six-inch maps—National Grid edition followed by the County edition in brackets. Then follow details of the site and its National Grid reference (all in 100-km. square SD), and, where known, the date of sinking and source of information.

In the abridged sections, ironstones in mudstones and shales are generally cited without details of number and thickness, as are thin sandstone partings in mudstones and mudstone partings in sandstones. 'Shells' denotes the presence of non-marine lamellibranchs or 'mussels', except where stated or implied (e.g. in marine bands); 'fish' denotes fragments of the hard parts of fossil fish; and 'plants' the debris of drifted vegetation but not the rootlets which occur in seatearths so commonly as not to require mention. All measures are grey unless otherwise stated.

Some old sections are given in miners' vernacular. Among the local terms which require explanation are the following: bass, black carbonaceous shale; bind, hard band in shale, also mudstones generally; bulgram, thin bed of black shale in or associated with a coal-seam; burr, rough or hard rock, often a highly siliceous sandstone; buzzard, layer of inferior coal at the top of the Arley Mine; dirt, shale or clay parting in a coal seam; earth, clay or shale, frequently a seatearth; flue, fissile rock, shale; hoo cannel, argillaceous cannel-coal; lins(t)ey, lin(n) and wool, linsey-woolsey, alternation of thin beds of mudstone and sandstone or siltstone; listing, slickensided shale or mudstone; metal, shale, mudstone and silty mudstone; rock, sandstone; stone, any hard rock; warrant, seatearth.

The terms 'mine' and 'coal' are commonly used in Lancashire for 'seam'. For reasons of brevity they have been omitted from the name of each seam in this appendix.

Adlington Borehole (N.C.B. A2/23)

Height above O.D. 399.6 ft 6-in SD 61 S.W. (Lancs. 86 N.W.) Site 1720 yd W. 6° N. of Anderton Hall. Grid ref. [SD 6062 1391]. Date of sinking 1952. Cores examined by D. Magraw. Certain details of this bore, and a vertical section, have been published and its correlation discussed.Magraw, D. 1957. New boreholes into the Lower Coal Measures below the Arley Mine of Lancashire and adjacent areas. Bull. Geol. Surv. Gt. Brit., No. 13, pp. 14–38.

Barlow's Farm Borehole (N.C.B. A2/118)

Height above O.D. 192.91 ft 6-in SD 51 S.W. (Lancs. 85 N.W.) Site 1290 yd N. 36° E. of St. James's Church, Wrightington. Grid ref. [SD 5334 1459]. Date of sinking 1957. Cores examined by D. Magraw.

Big Wood Borehole (N.C.B. A2/103)

Height above O.D. 147.01 ft 6-in SD 51 N.W. (Lancs. 77 S.W.) Site 1250 yd N. 15° W. of Park Hall. Grid ref. [SD 5376 1667]. Date of sinking 1955. Cores examined by D. Magraw.

Black Pit, Chorley Colliery

Height above O.D. c.285 ft 6-in SD 51 N.E. (Lancs. 77 S.E.) Site 540 yd E. 9° N. of Gillibrand Hall. Grid ref. [SD 5789 1684]. Information from Mr. T. Derbyshire, Chorley Moor Colliery Co. There is no record of the upper part of the shaft; the following section commences just below the Upper Mountain Mine, which is 342 ft from surface

Black Pit Borehole

Sunk in 1907 from the Lower Foot Mine at Black Pit.

Booth's Farm Borehole (N.C.B. A2/102)

Height above O.D. 129.53 ft 6-in SD 51 N.W. (Lancs. 77 S.W.) Site about one mile N. of Park Hall. Grid ref. [SD 5422 1731]. Date of sinking 1955. Cores examined by D. Magraw.

Charnock Old Hall Borehole (N.C.B. A2/104)

Height above 0.D. 261.34 ft 6-in SD 51 N.W. (Lancs. 77 S.W.) Site 1250 yd N. 30° E. of Park Hall. Grid ref. [SD 5473 1656]. Drilled 1955. Cores examined by D. Magraw. Details to 19 ft 5 in from drillers' log; thence continuous cores.

Coppull Pit

Height above O.D. c.225 ft 6-in SD 51 S.E. (Lancs. 85 N.E.) Site 1280 yd E. 14° S. of Coppull Station. Grid ref. [SD 5763 1405]. Information from Mr. Ellis, Manager.

Crook Fold Borehole (N.C.B. A2/105)

Height above O.D. 231.5 ft 6-in SD 51 N.W. (Lancs. 77 S.W.) Site 700 yd E. 35° N. of Park Hall. Grid ref. [SD 5470 1587]. Date of drilling 1956. Chippings to 18 ft, thence continuous cores. Examined by D. Magraw.

Duxbury Park Colliery

Height above O.D. c.225 ft 6-in SD 51 S.E. (Lancs. 85 N.E.) Site 820 yd W. 15° N. of Ellerbeck Hall. Grid ref. [SD 5857 1405].

Ellerbeck Borehole (N.C.B. A2/19)

Height above O.D. 281^.64 ft 6^-in SD 51 S.E. (Lancs. 85 N.E.) Site 470 yd N. 38^° W. of Ellerbeck Hall. Grid ref. [SD 5903 1420]. Date of sinking 1950. Cores examined by D. Magraw.

Ellerbeck Hall Borehole (N.C.B. A2/20)

Height above O.D. 279.34 ft 6-in SD 51 S.E. (Lancs. 85 N.E.) Site 300 yd W. 4° S. of Ellerbeck Hall. National Grid ref. [SD 5903 1384]. Date of sinking 1950. Cores examined by D. Magraw.