Content and licensingview original scan buy a printed copy

Geology of the Country around Stockport and Knutsford (One-inch Geological Sheet 98 New Series)

By B. J. Taylor, B.Sc., R. H. Price, B.Sc. and F. M. Trotter, D.Sc., M.I.M.M. with a contribution by W. Bullerwell, B.Sc., Ph.D.

Bibliographic reference: Taylor, B.J., Price, R.H. and Trotter, F.M. 1963. Geology of the Country around Stockport and Knutsford (One-inch Geological Sheet 98 New Series). London: Her Majesty's Stationery Office.

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

London: Her Majesty's Stationery Office, 1963

© Crown copyright 1963 Published by Her Majesty's Stationery Office.Printed in England under the authority of Her Majesty's Stationery Office by Mendip Press Ltd., Bath.

(Front cover)

(Rear cover)

Preface

The district represented on Sheet 98 (Stockport) of the New Series one-inch map, published in two editions, Solid and Drift, in 1962, includes parts of the two Old Series one-inch quarter-sheets 80 NE and 81 NW. These were first surveyed in 1860 and 1864 by E. Hull. Memoirs descriptive of these two Old Series sheets were published, respectively, in 1861 and 1866. A second edition of the former was prepared by C. E. De Rance in 1893, following six-inch mapping of most of the area. This edition was not published, but the MS. has been used in the preparation of the present memoir.

A six-inch survey of the whole of Sheet 98 was begun in 1938 by Messrs. F. W. Cope, R. C. B. Jones, L. H. Tonks and D. A. Wray under W. B. Wright as District Geologist, and was continued under Dr. T. Robertson. Owing to war-time commitments the field-work was interrupted in 1940 and was not resumed until 1946, when Messrs. J. E. Prentice, R. H. Price, B. J. Taylor and F. M. Trotter took over the fieldwork and completed it in 1952 under the last-mentioned as District Geologist.

Since nine-tenths of the district is drift-covered little or no revision could have been made to the 'solid' edition of the map by the ground survey alone, and it was necessary to drill ten boreholes in areas where there was a paucity of information to explore the sub-drift geology. The results derived from these and other boreholes coupled with the geophysical studies made by Dr. W. Bullerwell have enabled a revision of the structure to be made.

The break in field-work occasioned by the war, and staff changes during the interval, left a legacy of roughly the north-western half of the sheet surveyed but with few notes or description other than those that were to be found on the field-slips. Consequently the account of the drift deposits is somewhat unbalanced in that details are scanty in respect of the north-western half; and no distinction can now be drawn in that area between the Upper and Lower boulder clays nor the Upper and Middle sands, since distinguishing symbols had not been used by the surveyors.

Mr. Taylor has had the difficult task of assembling all available information and welding it into memoir-form. Credit for contributions has been given where possible by the insertion of the author's initials, but in cases where no notes had been left the account, as factual as possible, is derived from a reading of the field-maps. The names of the geologists responsible for the mapping of any particular area can be found by reference to the list of six-inch maps (p. vii).

Fossils collected from the Millstone Grit Series have been identified by Dr. W. H. C. Ramsbottom and those from the Coal Measures by Mr. M. A. Calver. Dr. K. C. Dunham has described thin sections of Keuper Marl which throw light on the petrology of that formation. Dr. Bullerwell has contributed an appendix on the geophysical work and results. The memoir has been edited by Mr. J. V. Stephens.

Assistance rendered during the survey by officials of the National Coal Board, owners and managers of quarries, surveyors and waterworks engineers of local government authorities, landowners, agents and others is gratefully acknowledged.

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

Notes

Figures in square brackets are National Grid map references in the 100-km. square SJ.

List of six-inch maps

Geological six-inch sheets included wholly or in part in the one-inch Sheet 98 (Stockport) are listed below with initials of the surveyors and dates of survey. The surveyors, in alphabetical order, were: F. W. Cope, R. C. B. Jones, J. E. Prentice, R. H. Price, B. J. Taylor, L. H. Tonks, F. M. Trotter, D. A. Wray and W. B. Wright.

The first list is of six-inch sheets on the old County Series of Lancashire and of Cheshire, which, being on different meridians, overlap. Some of the Lancashire sheets include pans of Cheshire, and it was found convenient to map these areas of Cheshire on Lancashire sheets.

Six-inch sheets of the new National Grid Series were not available at the time of survey. They will include those listed below, all in the 100-km square SJ. Those which include a substantial area of Coal Measures will be published, and are marked with an asterisk; the others will not be published, but will be available for examination in MS form at the Geological Survey Offices.

Chapter 1 Introduction

The Stockport district^‡1  forms part of the South Lancashire–Cheshire plain. In the east are the foothills of the Pennines, rising to the main gritstone uplands of Derbyshire. In the plain to the north lies the conurbation of Manchester and Salford, a dominating influence throughout the district. With the increasing ease of modern transport many of the smaller towns and villages have become dormitories for city workers, and even Alderley Edge and Poynton, once mining centres, have changed into residential districts. A large area of land around Wythenshawe and Ringway has been acquired by Manchester Corporation for the housing and employment of its growing population and for the municipal airport.

The rivers Tame and Goyt join at Stockport to form the Mersey, which meanders through the southern suburbs of Manchester in the north of the district,' its flood-plain forming a green belt of golf courses and open fields in a wilderness of houses. The river is confined in parts of its course by high reinforced banks, which restrict meander development.

The high terrace of the Mersey, formed in late-Glacial times when the Mersey waters were diverted to the Dee estuary by ice blocking their present outlet, has, with its flat surface and gravel soil, provided ideal conditions for rapid if somewhat monotonous building development. The southern suburbs of Manchester occupy large areas of this wide terrace.

The geological features of the district are well displayed only in the extreme east, where ridge-and-valley topography reflects the alternation of hard and soft beds at outcrop and the general eastward rise of the ground is directly due to the presence of resistant rocks of the Lower Coal Measures and Millstone Grit Series. The central and western parts are mainly low-lying, comprising part of the Cheshire plain and of the wide alluvial terrace of the Mersey—a landscape redeemed from dullness by the bold escarpment capped by Keuper Conglomerate at Alderley Edge, the low ridge of Keuper rocks east of Lymm, and the rolling Middle-Sands topography of Knutsford and Altrincham.

Thick glacial deposits over the low land mask the underlying rocks, in which boreholes and a geophysical survey have revealed a complex fault-pattern with dislocations almost as numerous and of as great a magnitude as in the Carboniferous rocks to the north and east.

In pre-Norman times the district lay on the border of the Forest of Macclesfield, and was sparsely populated even by contemporary standards. The development of industry began in earnest with the Industrial Revolution, and the local geology had a profound effect upon its development. The abundance of locally produced coal and of soft water in the hill-streams, together with the moist atmosphere resulting from high orographic rainfall—itself a secondary consequence of the geology—all contributed to the rise of the cotton-textile industry in the north-east of the district, and later to the establishment of the silk industry in the south-east. Nowadays, although the Poynton Coalfield and that part of the Manchester Coalfield within the district have ceased production, the textile industries remain around their old centres and still employ large numbers of people. In addition there are, especially around Stockport, many other light and heavy industries of importance, including engineering and the manufacture of paper, chemicals and food-products.

The south-western part of the district lies within the fringe of the main Cheshire saltfield. Some areas, notably at Tabley and Tatton Park, have in the past suffered subsidence of the ground through solution of salt beds, though the points of abstraction have probably lain to the south-west outside the district. The 'controlled-pumping' method of brine abstraction now being operated near Lostock Gralam and southwards therefrom does not cause subsidence at a distance. At Agden and Heatley, near Lymm, salt production from natural brine is still carried on in a small faulted outlier of saliferous beds. A northern extension of the main saltfield at present unworked has been proved by boreholes to the east of Mobberley.

Rich pastures on the extensive spreads of boulder clay of the plain support the dairy herds for which Cheshire has long been famous; and in recent years on both the lowland and hill farms the production of milk has taken precedence over other forms of agriculture. There is, accordingly, little amble land, though market gardening flourishes in the more sandy districts and on the river terraces where the soil is easy to work.

Geological sequence

The formations represented on the map and sections are summarized below.

Superficial formations (Drift)

Solid formations

Geological history

The oldest rocks at surface are the Middle Grits, exposed in the south-east. These are the product of cyclic deposition of mud and sand on a subsiding sea-floor, with pauses at the end of each sedimentary cycle during which vegetation sometimes grew and accumulated in layers, and after being buried gave rise to coal seams. This type of sedimentation continued with small variations throughout much of the remainder of Carboniferous times: some of these variations were favourable to the accumulation of thick sandstone layers as in the Millstone Grit Series, others to the dominance of shale with ironstones and coal seams as in the Coal Measures. In the uppermost beds of the Carboniferous coal seams are rarer, and thin fossiliferous limestones are found.

These rocks were folded during the Hercynian earth-movements, gently in most places but more violently in the country immediately east of the district, where there appear to have been strong compressive and shearing movements. Both the Pennine and Rossendale uplifts were initiated at this time. Erosion removed vast amounts of material from the anticlines, laying bare the Millstone Grit rocks, whilst the Coal Measures were preserved in the syncline. During this period of erosion an arid desert climate appears to have prevailed, and the rocks near the surface were reddened by oxidation to a considerable depth.

Over the eroded edges of the Carboniferous strata the mainly terrestrial Permo-Triassic sediments were then laid, first the Collyhurst and Bunter sandstones, with an intermediate pause for the accumulation of the marine Manchester marl, and then the Keuper, a dominantly argillaceous formation laid down in a subsiding inland basin or sea in which evaporation was high enough to dry up all the water at frequent intervals, with consequent deposition of thick salt beds. The Permo-Triassic deposits probably amount to over 5000 ft in the south-western corner of the district. Farther south in the adjacent district (Sheet 110, Macclesfield) high Keuper beds, including most of the Middle Keuper Marl and Upper Keuper Saliferous Beds, are present. No trace is found of Jurassic, Cretaceous or Tertiary rocks; and if these were deposited, as is likely, they have been removed by denudation together with the higher Keuper beds. The post-Triassic movements which gave rise to the elevation of the Pennines resulted also in a system of tensional faults.

In Pleistocene times the district was invaded at least twice by thick ice from the north and north-west. Boulder clay and outwash deposits of sand, gravel and bedded clay were spread over the low land, filling in pre-existing valleys. Although knowledge of the succession of events is Pleistocene times is improving there is much that is still obscure. These deposits are not only economically important, but a knowledge of them is essential to those responsible for the secure foundations of heavy buildings and bridges.

Chapter 2 Millstone Grit Series

Introduction

The area of outcrop of the Millstone Grit rocks in this district is just over five square miles, or about one fortieth of the total area. Few conclusions can be drawn from so small an area, consequently these rocks are here dealt with briefly. The upper part of the Middle Grit Group (Upper Reticuloceras Age–R₂) and the whole of the Rough Rock Group (Lower Gastrioceras Age–G₁) are present. With the help of additional information from neighbouring areas it is possible to tabulate the succession as follows.

The Millstone Grit Series as a whole tends to thin when followed southwards and westwards on the western flanks of the Pennines. In spite of this, two of the beds, the Holcombe Brook or Rainow Grit and the Rough Rock, become thicker and coarser from north to south within the confines of the district.

Middle Grit Group (Upper Reticuloceras Age–R₂)

The lowest measures are exposed in the extreme south-east, where thick sandstones and gritstones make pronounced features. Exposures in the shales are much obscured by valley-fill, hill-creep and glacial drift, and identification of the beds has necessitated reference to fossiliferous shale exposures near Hooleyhey, a short distance beyond the eastern boundary of the district. Here two exposures of marine shale were found in the stream [SJ 9730 7481], [SJ 9726 7494]. The lower bed yielded the early mutation of Reticuloceras bilingue, and from the higher one—how much higher it was not possible to decide because the measures were much disturbed—Reticuloceras wrighti Hudson was collected. General stratigraphical considerations suggest that these fossil bands occur in the shale sequence above the highest of the Macclesfield Forest Grits, which appear to be the equivalent of the upper part of the Kinderscout Grit. Support for this correlation has been found a short distance beyond the southern margin of the district in the Macclesfield area (Sheet 110), where Reticuloceras gracile Bisat occurs in shales overlying the Macclesfield Forest Grits.

North of the district, at Newton Bank, Hyde, a water bore for the Calico Printers Association was drilled in 1948 to the top of the Kinderscout Grit (p. 10). Although it pierced the plane of a fault which cut out about 200 feet of measures, the section proved has been helpful in the correlation of the Middle Grits of this district, and the hitherto unpublished record is accordingly given on p. 141. Two marine bands were found in the Newton Bank Borehole at 1066 ft and 10874 ft respectively, in the shale above the Kinderscout Grit. The lower yielded a fauna including Reticuloceras gracile Bisat early mutation, the upper yielded R. bilingue (Salter). These species are characteristic of the two lowest zones of R₂ age; and it would seem that the higher of the two marine bands at Newton Bank should be correlated with the lower of the two found in the shales near Hooleyhey. Thus in the measures above the Macclesfield Forest Grits there are three marine bands, containing Reticuloceras gracile, R. bilingue and R. wrighti, in some 100 ft of strata with no intervening gritstone. This shale sequence is not exposed in the district, but it must be present at depth.

The lowest exposed measures are some 300 ft above the base of the R₂ beds, comprising the arenaceous group proved in the Danebent Bore [SJ 9567 7548] (Pocock 1906, p. 119). They include gritstones, sandstones and mudstones, and may be, in part at least, the lateral equivalent of the Gorpley Grit of districts to the north, though there is no confirmation of this from fossils. The fault in the Newton Bank Borehole cuts out the equivalent measures there. Followed southwards into the Macclesfield district the lower sandstones in this group die out, only the uppermost bed persisting as the Windyway Head Rock, a medium-grained sandstone with large ferruginous concretions (Pocock 1906, p. 23).

During the resurvey of the district to the south (Sheet 110) the Windyway Head Rock has been shown, by the discovery of Reticuloceras superbilingue Bisat in the shale above it, to be the correlative of the Hazel Greave Grit of Lancashire (Wright and others 1927, p. 21 and figs. 8, 13) and the Ashover Grit of Derbyshire (Smith and others 1959). In the Newton Bank Bore a thick marine band with fauna including R. superbilingue Bisat rests at a depth of 618 ft on a sandstone, which is thus the equivalent of the Hazel Greave Grit (Figure 3).

About 280 ft above the Windyway Head Rock is the Yearnslow Grit, some 50 ft thick. Little is known of the intervening shales except that they appear to be variable in thickness, becoming much thinner to the north-east of Danebent.

In the south some 50 ft of shale intervene between the Yearnslow Grit and the base of the Rainow Grit. In the north, on the evidence of the Newton Bank Borehole, the Yearnslow Grit is absent, the measures between the top of the Hazel Greave Grit and the base of the Holcombe Brook (Rainow) Grit being represented by some 250 ft of shale.

The Holcombe Brook Grit, the correlative of the Chatsworth Grit and the Huddersfield White Rock of the country to the east and north-east, varies considerably in thickness and lithology. Around Romiley and Hyde it is poorly developed and consists of two leaves of sandstone, the upper one 30 ft and the lower 15 ft thick. The two leaves are separated by a thin shale parting with a ten-inch coal at its base; and a coal twelve to eighteen inches thick immediately overlies the upper leaf. Southwards the lower leaf thickens and becomes coarser—contrary to the general trend of Millstone Grit variation in the region as a whole—and probably reaches its maximum thickness for the district in the country east of Bollington, where the lower leaf is over 200 ft thick and was called the Rainow Grit by T. I. Pocock (1906, p. 22). More than 200 ft were proved in the first of the two water bores sunk at Millbrook, Rainow. Farther south the same bed has been worked at the well-known Tegg's Nose Quarry, just beyond the southern confines of the district. The upper leaf of the Holcombe Brook Grit is fairly uniform in thickness and lithology throughout the district, and is found in the south, with the underlying shale beds, in the Bollington Print Works Borehole (p. 129); and also in the valley at the foot of the bold Rough Rock escarpment of Brink Row, separating the Upper and Lower Holcombe   Brook coals. These seams have been worked by shallow shafts and adits in the valley of Harrop Brook and at intervals along their outcrop almost to Rainow.

Rough Rock Group (Lower Gastrioceras Age–G₁)

The base of the Rough Rock Group is marked by the dominance of the goniatite Gastrioceras (though the genus is noted in the Reticuloceras superbilingue Marine Band at Newton Bank); and since the Gastrioceras cancellatum. Marine Band is found above the Upper Holcombe Brook Coal the top of that coal is here taken as the base of the group and as the boundary between the R, and G, divisions. The shales above the coal carry at least two marine bands, that of Gastrioceras cancellatum some 30 ft above the coal, and the G. cumbriense Marine Band 60 ft above the coal. In the Newton Bank Borehole both marine bands are split into two parts. In the case of the G. cancellatum Marine Band the separation is 17 ft; the lower bed carries Lingula mytilloides and fish remains, the upper bed has a more varied marine lamellibranch and cephalopod fauna including Gastrioceras crencellatum Bisat. The presence of this fossil indicates the upper fauna of three found in the G. cancellatum Marine Band elsewhere, the middle one of which, normally characterized by G. cancellatum, is apparently represented here by the Lingula–fish bed.

In the Romiley and Hyde area the G. cumbriense Marine Band is separated from the G. cancellatum–G. crencellatum marine phase by shales which contain a seatearth but no coal. In Harrop Brook the seatearth was not recorded. In the north the repeated sequence of sandstones, coals or seatearths, and marine bands in the upper part of the R₂ and the lower part of the G₁ beds closely resembles the type of sedimentation common in the overlying Lower Coal Measures; but the thick grit development near the southern boundary of the district makes the same group of strata more typical of the Millstone Grit Series.

There are about 170 ft of mudstone above the Holcombe Brook Grit, and these become more sandy towards the top, passing upwards gradually into the flaggy sandstones which make up the lower layers of the Rough Rock. It is this gradual lithological change which frequently makes the base of the Rough Rock difficult to define exactly in the field; a difficulty found particularly in the ground east of Bollington. The flaggy beds at the base of the Rough Rock may be equated in a general way with the Rough Rock Flags of Yorkshire and the Upper Haslingden Flags of Lancashire, but in this district they cannot be mapped separately, and are all included in the Rough Rock.

The Rough Rock is a massive gritstone with local developments of flaggy sandstone. A short distance from its top and separating it into two leaves is the Sand Rock Mine, a thin coal underlain by a well-developed seatclay. This seam is present in the north around Werneth Low, but only the seatclay is present in the Bollington area.

The development of the Rough Rock in the northern and southern parts of the district is markedly different. In the north near Romiley the upper leaf consists of shaly sandstone 8 ft thick, the lower leaf being a coarse feldspathic pebbly gritstone 120 ft thick: this development of the upper leaf extends northwards to a point about a mile and a half north-east of Bury (Wright and others 1927, p. 24); and the lower leaf shows a marked reduction in thickness when traced northwards to Stalybridge (Tonks and others 1931, p. 64). Towards the south the Rough Rock forms an escarpment at Sponds Hill, a short distance beyond the eastern margin of the district south of Lyme Park; and here, as well as in the Bakestonedale Borehole, the upper leaf is developed as a coarse gritstone and shows an increase in thickness to just over 30 ft, the lower leaf consisting in the main of fine-grained grey micaceous flaggy sandstone. North-east of Bollington the upper leaf, a grey and purple gritstone, maintains the thickness and Ethology of the Bakestonedale Borehole; and gritstone layers are found in the upper part of the lower leaf, the main mass of which consists of fine to medium-grained sandstone, in part flaggy and micaceous. These finer-grained lower layers of the Rough Rock form the outlier of Big Low and the eastern end of Billinge Hill, where they have been extensively quarried.

In the north the Six Inch Mine normally rests upon a seatearth immediately above the upper leaf of the Rough Rock, though in the Romiley Borehole the upper leaf of the grit is missing and the Six Inch Mine is separated from the underlying Sand Rock Mine by 11 ft only of seatearth and mudstone. The Six Inch Mine, like the Sand Rock Mine, fails southwards, and only the seatearth is present at Pott Shrigley. B.J.T., R.H.P.

Details

Hyde, Romiley and Marple

Although it lies to the north just outside the district, the 1948 Newton Bank Bore (p. 141 and (Figure 3)) is included in this account since it helps to interpret the Millstone Grit sequence. It proved beds from the top of the Kinderscout Grit to an horizon about 100 ft above the Gastrioceras cumbriense Marine Band, though several hundred feet of strata including the Windyway Head Rock and associated sandstones were cut out by a fault. Both the Reticuloceras gracile and the R. bilingue early mutation marine bands occur in the shales above the Kinderscout Grit. The former yielded Dunbarella speciosa (Jackson), D. sp., Posidonia sp. and Reticuloceras gracile late mut. Bisat; the latter, some 20 ft higher, yielded Caneyella cf. rugata Jackson, Dunbarella sp., P. sp., Anthracoceras sp. or Dimorphoceras sp.(bilobate growth lines), Reticuloceras bilingue early mut. and R. sp.

Above the Hazel Greave Grit the Reticuloceras superbilingue Marine Band yielded Aviculopecten sp., Lingula mytilloides J. Sowerby, Gastrioceras spp., G.? sigma Wright, Metacoceras sp., Reticuloceras superbilingue Bisat, and fish remains including Megalichthys scales.

The Gastrioceras cancellatum Marine Band is in two leaves. The lower portion, lying 11 ft above the Upper Holcombe Brook Coal, consists of a thin band containing Lingula mytilloides, Palaeoniscid scales and fish teeth. This probably represents the main G. cancellatum horizon of other areas (see p. 9). Some 17 ft higher is a 6-ft band of black marine shale: its basal portion carries an abundant fauna including Gastrioceras crencellatum Bisat, Dunbarella sp., Posidonia sp., Anthracoceras or Dimorphoceras sp., a fish spine and a scale.

The much thinner Gastrioceras cumbriense Marine Band lies 60 ft above the coal. In the borehole it also is split into two, the lower leaf, one foot thick, containing G. cumbriense Bisat, Dunbarella sp. and Palaeoniscid scales, and the upper leaf, 4 in. thick and some 4 ft. higher, G. cumbriense and Dunbarella sp.

There are exposures of the measures between the Holcombe Brook Grit and the Rough Rock, and possibly of the Holcombe Brook Grit itself, on the crest of the Romiley Anticline north-east of Gee Cross, where isolated exposures of micaceous flaggy sandstone may be seen. Blue-grey shale with ironstone nodules in Stanleyhall Brook, 400 yd east of Dove House and due south of Marple Ridge, are believed to represent part of the shale sequence.

The Rough Rock is seen on both flanks of the Romiley Anticline between Gee Cross and Greavefold, but neither the Sand Rock Mine nor the shaly overlying measures of the upper leaf are exposed. In the Romiley Dyeworks Bore (p. 152) the Sand Rock Mine is 18 in. thick with a 3-ft seatclay beneath it. The seatclay was formerly worked for fireclay on the south-western side of Werneth Low, near Lowbank Farm. The lower leaf of the Rough Rock can be seen as a coarse quartzose gritstone containing much fresh pink feldspar with, in abundance locally, quartz pebbles up to half an inch in diameter. East of Gee Cross on Hackingknife there is a thick development of flaggy sandstones immediately below the gritstone.

A down-faulted block of Rough Rock is exposed in the east bank of the River Goyt 750 yd south of Marple Bridge. It consists of a medium to coarse-grained gritstone, occasionally feldspathic, with partings of grey sandy shale and micaceous flaggy sandstone. In the old quarries on the south end of Marple Ridge the rock is a medium to fine-grained pinkish-cream gritstone, containing occasional small quartz pebbles. The rock is very markedly current-bedded in this locality and contains large limonitic concretions.

Bollington and Rainow

The grits in the extreme south-eastern corner of the district belong, as has been shown, to the Middle Grit Group, but their precise equivalents cannot yet be established owing to lack of good exposures. They correspond in a general way to the Readycon Dean Flags and the Pule Hill Grit of the Glossop district, and to the Gorpley–Revidge Grit and perhaps the Helmshore Grit of the Rossendale district. The Danebent Borehole [SJ 9567 7548] 100 yd north of Danebent Farm proved two main arenaceous groups, each much split up by shale partings. These measures crop out to the east of Danebent, the grits forming features on Ely Brow and on the divide between the two brooks east of that hill. Snipe House and Higherland farms stand on the dip-slope of the uppermost bed.

Sections across the area show that the thickness of the shales between the top Danebent grit and the bottom of the Yearnslow Grit is much reduced to the north of Danebent, but whether this is due to actual thinning or to a transgression at the base of the Yearnslow Grit is not known.

The Yearnslow Grit forms the crest of Yearns Low, and the outcrop traced north-eastward crosses Smith Lane just west of Dawsonbarn Farm. Followed to the south-west from Yearns Low, the outcrop descends the escarpment that is capped by Holcombe Brook Grit, and is seen in the River Dean to the west of Danebent Farm. It forms a small outlier on which stands Newbuildings Farm, and is cut off to the west by a fault. The rock is everywhere a fine to medium-grained sandstone or flaggy sandstone, and is 50 ft to 60 ft thick.

The Holcombe Brook Grit, the Rainow Grit of Pocock (1906, p. 22), forms the bold feature of Pike Low just east of the district boundary, and the outcrop ^,crosses Bower Clough between Further Harrop and Harropfold Farm. Ginclough and Rainow lie on its dip slope, and the grit forms the escarpment of The Oaks to the east of Rainow. South of Rainow it forms Gorsey Brow, and is terminated by a north-south fault bringing down Lower Coal Measures to the west. Several bores for water have proved the grit in the Rainow area: the Ginclough Borehole [SJ 9551 7653] went through 190 ft of it (Pocock 1906, p. 22); and of two wells at Millbrook, Rainow, the second, sunk in 1935, penetrated 210 ft of broken and jointed gritstone beneath 50 ft of superficial deposits. On Pike Low the Holcombe Brook Grit is a medium to coarse purplish sandstone with layers of gritstone. South of Ginclough and east of Rainow it is coarser, and more like the massive purple-mottled gritstone of Tegg's Nose Quarry, just beyond the southern border.

Both the Lower and Upper Holcombe Brook coals were found in the Bollington Print Works Borehole (p. 129), at 438.5 ft and 404 ft respectively. The lower coal was here 12 in. thick and the upper 7 in., and the two were separated by a layer of gritstone underlain by shales. An exposure just beyond the eastern boundary of the district at Sester Bridge shows the Upper Holcombe Brook Coal to be 18 in. thick. At the foot of the escarpment of Brink Brow both coals come to outcrop but have been so much worked that no exposure now exists. Two adits [SJ 9658 7879], [SJ 9651 7869] north-west of Further Harrop were to the upper coal, as were also a number of shafts at the foot of Harrop Wood. A level in the upper seam, Jodrell's Level, runs north-eastwards from a point beside Bower Clough Brook about 700 yd west of Further Harrop, and continues under Brink Brow. An adit in Bower Clough some 450 yd west-south-west of Further Harrop [SJ 9623 7842], and a shaft a little to the west, presumably went to the lower seam. The two coals are separated in this area by the upper leaf of the Holcombe Brook Grit, which makes a low feature between the outcrops of the coals. South of Bower Clough the outcrops are lost beneath the glacial drift filling the valley. The lower coal, 12 in. thick. was exposed for a time in the roadside [SJ 9631 7705] 50 yd south-east of Paddock-knoll Farm. A number of old bell-pits and spoil heaps, and an adit on the east side of the road [SJ 9611 7685] 250 yd north-east of Blackrock Farm, were all to this seam, which was again exposed in the roadside [SJ 9541 7687] just north of Lower-house Farm, west of Ginclough. Both seams, but principally the upper one, have been worked from bell-pits on the north, east and south sides of Billinge Hill, and around Big Low. The old pits in Hayles Clough, north-west of Rainow village, are probably sunk to one or other of these seams.

The Gastrioceras cancellatum and Gastrioceras cumbriense marine bands are exposed in Harrop Brook, south of Harrop Wood. The G. cancellatum Marine Band [SJ 9599 7846], of which only a few inches of the upper or G. crencellatum part were visible at the time of survey, lies at the top of an exposure of shale and about 20 ft above the upper coal; it yielded Agastrioceras carinatum (Frech), Anthracoceras sp., Gastrioceras crencellatum and molluscan spat. The G. cumbriense Marine Band lies about 60 ft above the coal, and was found [SJ 9583 7845] 180 yd farther west along the brook. In it were found Aviculopecten aff. losseni von Koenen, Caneyella sp., Posidonia sp., Posidoniella ?, Anthracoceras sp., Gastrioceras crenulatum Bisat, G. cumbriense Bisat and Homoceratoides aff. divaricatus (Hind).

Rough Rock crops out at Brink Brow and Gorsey Brow. Its uppermost layers are of grey and purple gritstone about 30 ft thick, and below this both gritstone and sandstone are present, with coarse sandstone predominating. The thickness here cannot be measured exactly because the base is difficult to define. Lower down the slope is a secondary feature due to a group of flaggy sandstones. Billinge Hill is the summit of a long tongue of Rough Rock which extends eastwards from Bollington and which is probably thrown up by faults to the north and south. Big Low is capped by an outlier of the same rock. Quarries on the summits of both hills are in the sandstones towards the base of the Rough Rock. It is possible that the flaggy sandstones forming the subsidiary feature low on Brink Brow are in part the equivalents of the sandstones in these quarries. The coarser upper layers of the Rough Rock are visible to the west of Billinge Hill in old quarries [SJ 9464 7775] 200 yd south of Laneside Farm, near the Cheshire Hunt Inn [SJ 9467 7816], and close by the south side of the road [SJ 9503 7790] on Blaze Hill 350 yd east of Laneside House. No pebbles are recorded in the Rough Rock at any of these localities. B.J.T., R.H.P.

References

BROMEHEAD, C. E. N., EDWARDS, W., WRAY, D. A., and STEPHENS, J. V. 1933. The Geology of the Country around Holmfirth and Glossop. Mem. Geol. Surv.

POCOCK, T. I. 1906. The Geology of the Country around Macclesfield, Congleton, Crewe and Middlewich. Mem. Geol. Surv.

SMITH, E. G., EDEN, R. A., and lbws, G. H. 1959. Six-inch geological map Sheet SK 26 N.E. Geol. Surv.

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.

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

Chapter 3 Coal Measures

Introduction

Coal Measures are exposed at the surface in a tract extending north and south along the eastern edge of the Stockport district; and the westerly continuation of the Coal Measures beneath the cover of Permo-Triassic rocks forms a concealed coalfield the limits of which have not yet been defined. In the north the southern extremity of the exposed Manchester Coalfield occupies a triangle of ground, north-east of Stockport, the western boundary of which is the unconformable base of the Collyhurst Sandstone. That the junction is not faulted is proved by workings from Lingard Lane Colliery, Bredbury. This coalfield is separated from the Poynton Coalfield farther south by the Romiley Anticline, which plunges south-west. At Poynton the western boundary of the exposed coalfield is the Red Rock Fault, with a westerly downthrow of about 600 feet at that place.

There is much mining information from both coalfields, though no mines are now working; but frequently the shaft records consist merely of the positions and thicknesses of the coals. The Poynton Coalfield had been extensively worked, and all the mines were abandoned many years before the re-survey. Most of the information regarding the stratigraphy of the measures in the exposed coalfield is drawn from shaft sections at Norbury Bye Pit (p. 142) and Lawrance Pit (p. 148) and from a stream section in Norbury Brook. South of Norbury Brook surface exposures are rare. A recent deep bore, the Poynton Bore, No. A 1/20 drilled for the National Coal Board just west of the exposed coalfield, proved the measures beneath the Permo-Triassic rocks west of the Red Rock Fault and added greatly to existing knowledge of the stratigraphy (p. 144).

Non-marine Lamellibranch Zones

The measures have proved to be sufficiently fossiliferous to permit their division into the non-marine lamellibranch zones now well established in other British coalfields. The whole of the zones of Anthraconaia lenisulcata, Carbonicola communis, Anthraconaia modiolaris and Lower Anthracosia similis–Anthraconaia pulchra are known from exposures and bores, as well as nearly 400 ft of the Upper A. similis–A. pulchra Zone. These strata are the equivalent of the plant zones Westphalian A, B and the lower part of C. Nothing is known in this district of the upper part of the Upper similis-pulchra Zone or of the Anthraconauta phillipsii Zone. Measures exposed in the Slade Lane railway cutting at Levenshulme are placed higher than these, being equated with beds in Manchester in which Anthraconauta tenuis has been found, and are therefore referred to the A. tenuis Zone of the Upper Coal Measures.

Marine Bands

Accurate long-distance correlation has in this district, as in many others, been helped by the marine bands, which mark precise horizons within the general pattern of the non-marine zones. These bands are the Six Inch Mine (Pot Clay), one of those above the Bassy Mine, Lower Foot, Upper Foot (Bullion), Big Smut (Cannel Mine), and Tonge's in the Lower Coal Measures, and the Sutton Manor, Poynton (Two-Foot), Bradford and Moston in the Middle Coal Measures. Several of these marine bands are used to define the boundaries of the non-marine zones or subzones, and even when the contained fauna itself is not stratigraphically diagnostic their importance in conjunction with the nearby occurrence of beds yielding non-marine fossils is great.

Lower Coal Measures

Following modern practice (Stubblefield and Trotter 1957, pp. 1–5) this division comprises the strata between the horizon of the Gastrioceras subcrenatum (Six Inch Mine or Pot Clay) Marine Band and the Sutton Manor (Clay Cross) Marine Band lying about the middle of the A. modiolaris Zone. Its total thickness is about 2800 ft. (Plate 3) depicts the correlation of selected sections in this district with those of Hyde Lane Pit in the Manchester Coalfield to the north and of the Ridgeway Bore in the Potteries Coalfield to the south.

The general succession of the Lower Coal Measures compares closely with that of the Rossendale and Manchester districts. The coal seams in the lower part of the series are persistent, though mainly thin and consequently unworkable. The Lower Coal Measures of the Cheshire Coalfield and the Goyt Syncline have been correlated by F. W. Cope (1948). More recently D. Magraw (1957) has described the succession in a number of new bores in Lancashire, Cheshire and Staffordshire, and has given a detailed correlation of the measures in the Chadkirk Print Works Bore with those in the other areas.

Measures from the base of the Coal Measures to the top of the Milnrow Sandstone (Zone of Anthraconaia lenisulcata).

In the north the deepening in 1926 of the Romiley Dyeworks Borehole (p. 152) proved the succession from just below the Bullion Mine to the Rough Rock, and the characteristic marine marker bands were recorded above the Lower Foot and Six Inch mines. The additional presence of a Lingula band in the fossiliferous shales overlying the Bassy Mine was proved in the River Etherow a short distance to the east in the adjoining district (Sheet 99). The full succession at Romiley compares closely with that to the north. Neither the Cannel, Upper Mountain nor Bullion coals were recorded in the log of the upper portion of Romiley Dyeworks Borehole, but this record is an old one and is possibly not completely reliable.

The Six Inch Mine and its overlying marine band are rarely exposed, the seam being very thin and of no economic importance. The marine phase is succeeded by unfossiliferous shales and mudstones which are overlain by a prominent sandstone, the Woodhead Hill Rock—a bed which is present throughout the area and maintains an overall thickness of about 100 ft though its lithological characters vary. In the Pott Shrigley area it is a coarse-grained gritty sandstone, whereas in the country around Compstall it comprises two leaves of highly siliceous sandstone separated by 30 ft of dark grey shale and mudstone.

The Bassy Mine immediately overlies the Woodhead Hill Rock, though sometimes a thin sandy seatearth intervenes: in Bakestonedale it is known as the Yard. The coal contains many shale partings and is of extremely variable quality. Its gross thickness varies from 3 to 4 ft. The overlying shales contain a characteristic mussel-bed which is developed throughout the area, and is notable for being split into two leaves by a thin Lingula band which is seen in Bakestonedale and in the Romily Dyeworks Borehole (Plate 3). A fauna including the Carbonicola fallax Wright and C. protea Wright groups occurs below the Lingula band, whereas the beds above contain the same forms with the addition of C. discus Eagar. The incoming of C. discus at this horizon has been noted by R. M. C. Eagar (1952, p. 28) as occurring over a wide area in Lancashire and Yorkshire. Material from old tips in the Romiley area includes C. aff. limaxWright and C. aff. rectilinearis Trueman and Weir, probably from measures above the Bassy Mine.

A hard white ganister which can be recognized over much of the area is the seatearth of the Lower Foot Mine. This seam, known in Bakestonedale as the Ribbon (or Stinkard), is poorly developed and is rarely exposed. Fish remains are common in the overlying shales: and the Lower Foot Marine Band which is present in this position in the Bolton area and in the North Staffordshire Coalfield (Plate 3) has been recorded in the Romiley Borehole. In a surface exposure in Bakestonedale the marine band containing a fauna including Lingula sp., 'Posidoniella' sp. and fish remains was found at the time of survey to be separated from the presumed position of the coal below (not exposed because of crop workings) by a few inches of shale with poorly preserved non-marine shells. Dr. Eagar identified shells from this locality as Carbonicola fallax and C. artifex Eagar (Eagar and Pressley 1954, p. 2). The development is similar to that at the Ridgeway Bore in North Staffordshire (Taylor in Magraw 1957, p. 30), where the marine fauna is somewhat richer and contains, besides Lingula sp. and shells of the Posidonia–Caneyella [Posidoniella] group, orthocone nautiloids and goniatites—an assemblage comparing closely with that from the Lower Foot Marine Band of, for instance, the Brackley (A 1/15) Underground Bore in the Manchester area (Magraw 1957, p. 26), where again there is a non-marine development below the marine band. Thus in the Lower Foot Marine Band in the three districts there is a further link between the coalfield of Cheshire and those to the north and south.

The thin sandstone which overlies these shales represents the Ganister Rock of Lancashire. It is capped by a commercially valuable fireclay which contains in places lumps of ganister. The Lower Mountain Mine (also known as the Sweet Mine) which rests on this fireclay is thin, only exceptionally reaching a thickness of two feet; and has only been worked locally.

The Bullion Rock underlies the Upper Foot or Bullion Mine, also known in Cheshire as the Little Sweet or Red Ash Mine. When traced southwards from the northern margin of the district it shows progressive thinning, from a maximum of 58 ft in Romiley Dyeworks Borehole to 15 ft in Bakestonedale. The Bullion Mine is thin and of little economic importance, but the marine shale which forms its roof is well developed and very fossiliferous in Bakestonedale. This, the Bullion Mine Marine Band, has been described at Pott Shrigley by Cope (1949, pp. 466–83). Gastrioceras listeri (J.Sowerby) is the main goniatite, and the bed containing it is underlain by a thin band rich in Dunbarella papyracea (J. Sowerby).

In the overlying shales marine conditions appear to have recurred more than once, for at least two layers with marine fossils are found within 20 feet of the main marine band—a condition similar to that at Ridgeway in North Staffordshire, where there are at least four distinct marine horizons in some 60 ft of strata above the Crabtree Coal (Bullion Mine), with some non-marine intercalations containing Curvirtmula [Anthraconauta] sp. and Geisina arcuata Bean sp. (Taylor in Magraw 1957, p. 30). Barren mudstone extends upwards to over 120 ft above the highest marine horizon and is overlain by a sandstone and thin coal—the Big Smut Coal of Bollington.

Two seams equivalent to the Cannel and Upper Mountain mines of Lancashire were proved in a bore for water at Chadkirk Print Works in 1952 (Magraw 1957, pp. 22, 23). The Cannel Mine, 2 in thick, carries in its roof the Cannel Mine Marine Band, a foot thick, with Lingula sp., foraminifera including Rectocornuspira? and fish remains. The Upper Mountain Mine, 14f ft below the Cannel Mine, is 30 in thick. The 18-in Big Smut Coal of Lyme Park and Bakestonedale is thought to be the Upper Mountain Mine, the Cannel Mine being missing there; and the fact that a marine band with 'Posidoniella' sp. lies not in the roof of the Big Smut but some 6 ft. above it near Disley (p. 40) supports this view. Tonge's Marine Band, containing conodonts and foraminifera, was found in the Chadkirk Print Works Bore (p. 131) by Mr. Magraw in 1952—the only record of the marine band for this district.

The measures above the Big Smut Coal are not well exposed. The succession consists of an alternation of sandstones and shales and includes at least one coal horizon. A thick sandstone lies about 60 ft above the Big Smut Coal, and is believed to be the equivalent of the Milnrow Sandstone of the Manchester area and the Crutchman Sandstone of South Lancashire. Locally in Lyme Park this sandstone is up to 100 ft thick, and its highly siliceous character enables it to be recognized over a wide area. No coal seam is developed above it, for the Pasture Mine of Lancashire is missing.

Measures from the top of the Milnrow Sandstone to the Oldham Great Mine (Zone of Carbonicola communis)

The measures from the Milnrow Sandstone up to the base of the Old Lawrence Rock are little known in the Bredbury area. The thick development of flaggy sandstone in the middle of the sequence at Lyme Park is represented at Chadkirk by a thinner arenaceous phase in a predominantly shaly sequence. The broad band of sandstone mapped as crossing the River Goyt north of Chadkirk Print Works is, in the light of evidence provided by the recent borehole at the works, more properly to be regarded as a shale and sandstone sequence. Above this, and immediately beneath the Old Lawrence Rock, are shales with a non-marine fauna; and collections from this horizon yielded, at Lyme Park (p. 41), Carbonicola cf. bipennis (Brown), C. cf. subconstricta Wright and Geisina arcuata. Some 300 yd N.W. of Chadkirk Print Works the bed yielded C. cf. bipennis and G. arcuata but it was not recorded from the Chadkirk Bore, possibly because the highest cores in that bore were fragmentary and badly weathered when examined. Overlying this shale is the representative of the Old Lawrence Rock of Lancashire, a grey flaggy sandstone with shaly partings. A thin coal seam lies in places immediately above the sandstone; it was proved in the Nixon's Farm Bore ((Plate 3), No. 12), though it is nowhere exposed, for the ground is thickly drift-covered. At Nixon's Farm the beds between the coal above the Old. Lawrence Rock and the Arley Mine, some 150 ft higher in the sequence, consist mainly of sandstone with some thin bands of shale. Farther north in the Bredbury area there appears to be an increase in the amount of shale present. These shales, from 30 to 100 ft below the Arley Mine, have yielded an abundant non-marine fauna, but as exposures are few it is uncertain whether more than one well-marked mussel band exists. Shale exposed in the west bank of the River Goyt south-east of Marpledale yielded a fauna representative of the base of the C. communis Zone, including Carbonicola subconstricta, C. bipennis?, Curvirimula sp., Naiadites aff.flexuasus Dix and Trueman and G. arcuata.

The Arley Mine was for long regarded as the base of the Middle Coal Measures in the district, being, generally speaking, the lowest workable seam of the main productive measures. Its recent abandonment as the dividing line between the Lower and Middle Coal Measures (Stubblefield and Trotter 1957, pp. 1–5) is welcome, for the coal was frequently difficult to identify, not being endowed with any conspicuously characteristic roof fauna. Hull (in Hull and Green 1866, p. 28) said of this coal "The base of the series [the then Middle Coal Measures] is the Lower Woodley Mine, which is considered to represent the Royley Mine of Oldham and Rochdale on the north, and the Redacre Mine on the south. But while, from the general range of the coal-seams, this supposition appears in the highest degree probable, it must be admitted that it has never been actually proved by experiment. This arises from the fact that there is a gap of unproved ground between the Royley Mine at Oldham and the Lower Woodley Mine at Hyde; and there is another similar space between the Lower Woodley Mine, where it has been worked on the north bank of the Mersey at Otterspool, and the Redacre Mine at Windle Hurst;… ". During the resurvey the fossils were found to support this correlation, shales containing a fauna which included Carbonicola aff. pseudorobusta Trueman being found in the bed of the stream below Poyntongate, Lyme Park. This fossiliferous horizon lies some 140 ft above the Redacre Coal, and supports the correlation of the Arley Mine of Lancashire with the Redacre Mine of East Cheshire.

The Redacre Mine is nowhere exposed in the Poynton area, but the few records of the seam from shafts and bores show a thickness of less than two feet, as in the Bredbury area to the north. The succeeding measures up to the New or Accommodation Coal are dominantly argillaceous, and contain at least two thin coal seams. A mussel band with Carbonicola aff. pseudorobusta lies from 140 to 165 ft above the Redacre Mine, as in the Lancashire Coalfield: it was noted in the sinking of a shaft to the coal at Middle Cale Colliery, where an 'oyster bed' is recorded 165 ft above the Redacre Coal.

North-east of Stockport the Arley Mine is believed to be represented by the seam about 2 ft thick exposed in the railway cutting a short distance east of Bredbury station; to the north just beyond the district boundary, at Hyde, the seam has not been proved; and south of Bredbury an old working west of 'Otterspool Bridge is believed to have proved the seam. No other information is known. The horizon characterized by Carbonicola pseudorobusta which is believed to lie about 150 ft above the Arley Mine is exposed in the south bank of the River Goyt near Offerton; in the neighbourhood of Marple it has yielded fossils characteristic of the C. pseudorobusta Subzone, including C. aff. pseudorobusta and variants, Curvirimula sp., Naiadites flexuosus, Carbonita humilis (Jones and Kirkby), G. arcuata and fish remains. The succeeding measures up to the New Mine are partially exposed in the bed of the River Goyt, where they comprise sandstones, thin shale partings and a few thin coals.

The New and Old mines, proved in a tunnel at Hyde Lane Colliery north of the district boundary, come closer together when traced south-westwards into the Bredbury area; here their joint correlative, the Woodley New Mine,. was proved in the Bents Lane Shaft to consist of an upper 30-inch leaf and a lower 15-inch leaf, separated by an 18-inch parting. There is also evidence of a thinning of the lower coal when traced in the direction of coalescence, the coals being 26 in and 42 in thick respectively at Hyde Lane. The Accommodation Mine is well developed throughout the Poynton Coalfield, and like the Woodley New Mine is a split seam, the upper and lower leaves being the equivalents of the Old and New mines of Hyde Lane. Around Poynton the parting between the leaves varies between 3 ft at Lawrance Pit and 24 ft at Canal Pit. Each leaf maintains an average thickness of 3 ft of coal and locally one or the other is thicker. In the Poynton Bore the upper leaf at 3920 ft 3 in was 3 ft 8 in, the lower leaf at 3928 ft 4 in being 3 ft 5 in thick.

The three succeeding seams, the Water, Silver, and Nayley seams, are present in the Bents Lane Shaft section where they are called the Rosemary, Stone and Little Stone respectively. They all show thinning when traced southwards. from Hyde.

The Waterloo or Reform Mine, the equivalent of the Rosemary or Water, is present in the north and east of the exposed Poynton Coalfield; but when followed west of Anson Pit in the area subjacent to Petre Bank and Newtown it thins rapidly southwards and becomes unworkable. The split seam called the Silver (or Little) Mine at Norbury, which correlates with the Gees Mine at Poynton, is similar to the Reform Coal in being poorly developed in the Petre Bank–Newtown area.

Both the Reform and Gees coals were proved in the Poynton Bore at 3824 ft 4 in and 3795 ft 2 in respectively. Some indeterminate mussels were found in shale about 6 ft above the former; and the roof of the latter is here a sandstone some 70 ft thick. At the top of the sandstone is a seatearth, evidently near the horizon of the Peacock of Bents Lane Pit, Bredbury and Hyde Lane Pit. The Two Foot Mine of these collieries is represented in the Poynton Bore by a multiple seam at 3658 ft 2 in, the roof of which yielded plant remains, Spirorbis sp., Anthraconaia wardi (Hind pars, non Salter) and Curvirimula subovata (Dewar). The collection shows a close resemblance to a fauna from the roof of the Blindstone Rider (or Upper Coal) of the Burnley Coalfield, and the two horizons appear in fact to be identical. The Peacock Mine of Bents Lane is constant throughout the Hyde and Bredbury district but shows evidence of a southward thinning.

The Stone Mine which lies above the Peacock is correlated with the Cannel of Bents Lane and the Five Foot of Norbury and Poynton. The seams and the sequence from the Bredbury Stone or Silver Mine up to the Peacock are partially exposed in the River Goyt and in Poise Brook near the Red Rock Fault, but here the naming of the seams is tentative. The Five Foot seam maintains an average thickness of 4 to 5 ft throughout the Poynton Coalfield. The shaft section of Norbury Bye-Pit shows this seam to be underlain by a sandstone over 125 ft thick, though this sandstone is nowhere exposed at the surface. In the area of Petre Bank and Newtown a thin seam lies 36 to 55 ft below the Five Foot, and has been known as the Poynton Two Foot Coal.

The shales succeeding the Five Foot seam have yielded an abundant non-marine lamellibranch fauna including Carbonicola aff. acuta (J. Sowerby), C. cf. rhomboidalis Hind, Curvirimula cf. candela (Dewar), Geisina arcuata and Rhizodopsis scales. In the Poynton Bore the Five Foot seam, which is equated there with the Stone Mine of Manchester, was 52 in thick, but had numerous shale partings. The roof shales yielded plant fragments, Carbonicola cf. acuta (J. Sowerby), C. cf. martini Trueman and Weir, fragments of shells of Curvirimula sp. and fish debris. The seam is thought to equate with the Plodder of the West Manchester Coalfield.

The strata between the Five Foot and Four Foot seams of Poynton contain up to four thin coal seams. In the Poynton Bore three of these seams carried non-marine shells in the roof, and fish remains and ostracods were also recorded. A shell band about 10 ft below the Four Foot seam, above a coal-less seatearth, yielded Carbonicola cf. oslancis Wright, C. cf. rhomboidalis, C. cf. robusta (J. de C. Sowerby), Curvirimula sp.[not common], Naiadites sp., G. arcuata and fish debris. The fauna indicates an horizon near the C. communis/A. modiolaris zonal boundary, with the presence of rare Curvirimula favouring a position just below the junction.

In the Manchester Coalfield the Black Mine has been extensively worked as far south as Bredbury, maintaining the average thickness of 4 ft which is constant over a wide area to the north. Lying 40 ft or so above the Black Mine is a thin seam, the Little Black, of Bents Lane: it is probably to be correlated with one 20 in thick which lies 46 ft above the Black Mine at Hyde—where the overlying shales contain 'Carbonicola subconstricta'(Tonks and others 1931, p. 36)—and with the 'Two Feet' of Norbury Bye-Pit. At Poynton the Black is known as the Four Foot; it maintains a constant thickness of 44 to 48 in across the area, and is succeeeded by shaly rocks with an inconstant thin coal, the Norbury Two Foot, lying about 30 ft higher.

Material collected from the tips of mines penetrating these measures has yielded Carbonicola sp., Curvirimula candela, and Geisina arcuata. An isolated Euproops? has also in the past been collected from the tip of Lady Pit, Poynton, and is believed to have come from rocks of this zone.

Measures between the Great Coal and the Sutton Manor Marine Band (the Lower Anthraconaia modiolaris Zone)

The Trencherbone or Wigan Six-Foot seam is taken as the base of the A. modiolaris Zone in Lancashire; and its probable equivalent, the Oldham Great, is united with the next higher seam, the Blenfire Mine, to form the Great Coal of Norbury Bye Pit and Poynton. Shales exposed in Potters Cleugh, a short distance above the Great Coal, have yielded a low A. modiolaris assemblage including Carbonicola aff. oslancis. Shells in the Poynton Bore from the roof of a coal equated with the Smith Mine of Manchester some 40 ft below the Oldham Great are not diagnostic, the highest shell-bed giving zonal evidence below the coal in that bore being the one below the Black Mine (detailed above) yielding high C. communis Zone forms. It is therefore convenient, in the Stockport district, to take the Great Coal—or where its two components are widely separated, the lower leaf—as the boundary between the zones of C. communis and A. modiolaris.

Overlying the upper leaf of the seam—the Blenfire Mine of the Manchester Coalfield—is a sandstone, the Blenfire Rock. This is well exposed in the Tame Valley west of Arden Bridge near Haughton Green as a reddened massive sandstone, and was met with as some 60 ft of flaggy sandstone in the Poynton Bore. It appears from field evidence to thin rapidly when traced north from Norbury Brook.

Some 150 to 180 ft above the Great Coal lie two seams, the Cannel and Higher Chamber or Sheepwash, both of which consist of alternating bands of coal and shale, and have been worked sporadically. It is believed that they come together when traced to the deep and form the Poynton Ten Foot Coal,. a dirt-banded seam with a gross overall thickness of 9 ft.

In the Poynton Bore Naiadites, ostracods and fish debris above a coal at 3165 ft, equated with the Foggs Mine of Manchester, gave no precise evidence of faunal horizon, but a short distance higher at 3126 ft, a mussel and ostracod band includes Anthraconaia sp. nov.? Naiadites sp., Carbonita humilis and Geisina arcuata—the Anthraconaia being similar to those known in the East Pennine Coalfield from just below the Clay Cross Marine Band.

The Sutton Manor Marine Band at the top of the Lower Coal Measures (see p. 147) lies, at Poynton, four cyclothems (90 ft) above the Higher Chamber seam. Only two of these cyclothems carry coal—the second one up from the Higher Chamber, and that immediately beneath the marine band, which is equated with the Bottom Shuttles seam of Manchester. At the base of each cyclothem is a shell-bed with ostracods and with, in some cases, fish remains. From these beds was collected a fauna typical of the upper part of the Lower A. modiolaris Zone, with Anthracosia regularis (Truman) and other, less diagnostic, fossils.

The measures above the Sheepwash Coal are exposed in Norbury Brook, but no definite sequence can be determined. A composite section recorded in E. Hull's manuscript book shows 630 ft of measures succeeding the Sheepwash Coal, the sequence being curtailed by the Red Rock Fault. Hull's sequence contains several coals, three being named 'Mill Mine', 'Smithy Coal' and 'Chapel Mine'; and the rocks exposed in Norbury Brook also amount to about 630 ft of measures succeeding the Sheepwash Coal—which suggests that this may be the section recorded by Hull. The section in the brook is discontinuous, and there are indications that a number of coal seams are present, but it is difficult to correlate them with any confidence. A coal seam exposed in the stream 100 yd north-east of Carr Wood is thought to represent the 'Mill Mine' of Hull's MS. Shales lying 12 and 50 ft above this coal contain a poor non-marine lamellibranch fauna which includes Anthracosia aff.phrygiana (Wright), a fauna possibly of Upper A. modiolaris age. No diagnostic horizons were found in the succeeding measures, the exposures being discontinuous. The exact horizon of the measures exposed in Ochrely Brook, south-east and east of the disused Hazel Grove station of the old Midland Railway, is not known. The crop of a coal seam is shown by shallow workings a short distance east of Fir Tree cottage, but its exact horizon is unknown. Some plants collected a short distance farther east suggest a Westphalian B horizon. B.J.T., R.H.P.

Middle Coal Measures

Measures from the Sutton Manor Marine Band to the Lower Furnace Mine (the Upper Anthraconaia modiolaris Zone)

The Middle Coal Measures crop out in the southerly extension in the present district of the East Manchester Coalfield, and also in the Poynton area. These two regions are separated by the Mossley Anticline, the axis of which, trending north-eastwards, crosses the River Goyt between Stockport and Chadkirk. The rocks are little exposed, and much of our knowledge is based on the records of shaft sinkings, many of which contain no details of strata. In the lack of detailed palaeontological information, the attempts made to correlate the rocks of the Poynton Coalfield with those farther north were tentative until the drilling of the Poynton Bore (see below). At the northern edge of the district about 2000 ft of Middle Coal Measures are present, though when traced southwards towards the axis of the Mossley Anticline the beds are rapidly cut out by the unconformable base of the Permo-Triassic rocks and the Red Rock Fault. In the north no details are known of the highest measures—those lying above the New Jet Amber Coal.

The Sutton Manor Marine Band was found in the Poynton Bore (1955) at 2980.5ft. It has since been established that the coal on which it rests is the Bottom Shuttles seam of the East Manchester Coalfield, which is also the coal underlying the fossil horizon MC2 of Moston Colliery (Tonks and others 1931, pp. 74, 140). The marine band is 6.5 ft thick at Poynton. Abundant foraminifera, including Ammodiscus sp., Ammonema sp. and Glomospira?, are in association with Lingula mytilloides, the conodont Ozarkodina sp. and fish remains, in the lower 4.5 ft. In the top 12 in are the marine ostracods Hollinella and Paraparchites, and there are obscure traces and fragments in this part of the bed of non-marine lamellibranchs as well as ?Geisina arcuata (Bean).

The rich non-marine fauna in the shales above the marine band includes Anthraconaia modiolaris? (J. de C. Sowerby), Anthracosia cf. aquilina (J. de C. Sowerby), A. cf. beaniana King, A. ovum Trueman and Weir, A. cf. phrygiana, A. cf. regularis, A. spp.intermediate between aquilina and phrygiana and between aquilina and ovum, Anthracosphaerium aff. turgidum (Brown), and Naiadites spp.

The Top Shuttles seam is about 97 ft above the Sutton Manor Marine Band. At a slightly higher horizon the Town Lane Mine has been worked in the Denton and Bredbury area, being 40 in thick north of the Tame, but thinning to 24 in at Bredbury. The succeeding Foxholes or Mary Coal is 20 in thick at Denton and only 7 in at Poynton. The overlying Foxholes or Huncliffe Rock is exposed in the River Tame, where it consists of a reddish sandstone with shaly partings. The succeeding measures show the features characteristic of this group in East Lancashire, the successive coal seams being the Cook's Folly or Park at the base, the Hard, and the Stubbs. Of these seams the Hard Mine is the best developed and has been extensively worked; it maintains a thickness of 3 to 4 ft, but contains several partings which increase in thickness locally, are lenticular in shape, and replace the coal. According to Hull, in one locality the Hard Mine passed laterally into black shale for a distance of over 200 yards. At Poynton the Park seam, and possibly also the Hard, is lost in an arenaceous development some 150 ft thick, the lower part of which is probably the equivalent of the Huncliffe Rock.

The Bardsley Rock lies roughly 40 ft above the Stubbs Mine. It is about 100 ft thick in the Bredbury area, where it is a purple or red-stained sandstone, massive at the base and with thin shale partings towards the top. It is represented only by a thin sandstone at Poynton.

In the 430 ft of measures between the Top Shuttles seam and the Lower Furnace there are at least six distinct non-marine fossiliferous horizons, mainly above coals or coal-less seatearths, and these collectively yield a fauna characteristic of the Upper A. modiolaris Zone. Thus the lithological and faunal evidence is that the Lower Furnace seam is at the zonal boundary in this district.

Measures between the Lower Furnace Mine and the Dukinfield Marine Band (the Lower similis-pulchra Zone). The measures in the basal part of the Lower similis-pulchra Zone in the South Lancashire area are extraordinarily variable and difficult to correlate. In the Manchester Coalfield the top of the A. modiolaris Zone is taken at the Rams Mine (Tonks and others 1931, pl. v), and the Top Furnace was correlated by these authors on palaeontological grounds with the Rams, for both seams underlay roof measures which yielded Anthraconaia pulchella Broadhurst (=A. pulchra Wright non Hind sp.).

Nevertheless, this correlation was not made with complete confidence, for it was considered that on stratigraphical grounds the equivalent might equally well be the Lower Furnace (op. cit., p. 56). More recently Magraw and Calver (1960, pl. 17) have put forward a correlation which shows the Lower Foxholes (=Lower Furnace) as the equivalent of the Rams of the Prestwich area.

In this district the Poynton Bore proved three seams in the 120 ft of measures below the Roger—a coal correlated without much difficulty with that of the same name at Manchester. The lowest of these, a 32-inch coal at 2452 ft 9 in, was overlain by 30 ft of mudstone, the lower part of which yielded Naiadites sp., Carbonita and plant remains, and the upper part abundant shells including Anthraconaia pulchella, A. cf. polita (Trueman), Anthracosia cf. aquilinoides (Chemyshev), A. cf. caledonica Trueman and Weir and A. cf. phrygiana. Both the occurrence of A. pulchella and its restriction to the upper part of the bed, support the correlation of this seam with the Upper Furnace of Manchester. The horizon of the Lower Furnace is probably at the top of a seatearth 31 ft lower, which is overlain by mudstone with poorly-preserved shells and annelid tracks.

Between the Upper Furnace and the Roger at Poynton are two coal seams each overlain by fossiliferous mudstone. The roof of the lower, a split coal at 2398 ft 7 in, has yielded Anthracosia cf. caledonica, and some 10 ft above this is mudstone with Anthracosia cf. beaniana, Anthracosphaerium cf. propinquum (Melville) and Naiadites cf. productus (Brown). The upper of the two coals, 1 in thick and only 13 ft below the Roger, carries in its roof-measures poorly preserved non-marine shells. One or other of these two seams, more probably the lower, may be the equivalent of the Brassey in the West Manchester area. The Roger Mine has been extensively worked throughout the Denton–Bredbury area, where the seam is banded and comprises two leaves of coal, an upper 36 to 54 in thick and a lower 12 to 18 in separated by a thin 11 to 3-inch parting. The seam has a variable roof, and is succeeded by shales with thin coals and fireclays followed by a hard, purplish sandstone which underlies the succeeding Ashton Great Mine. The Ashton Great varies in both quality and thickness: at Denton Colliery it is recorded as 42 in thick, whereas in workings subjacent to Castle Hill, immediately south of the River Tame, a thickness of 6 ft was recorded over a small area. Farther south in the vicinity of Bredbury the seam is only 7.5 in, and is overlain by a thin sandstone locally red and purple-stained. The roof measures of this seam in the Poynton Bore, where the seam is 14 in thick, are similar to those in the Manchester area, containing abundant well-preserved plant remains.

The Old Jet Amber Mine of Denton lies 170 ft above the Ashton Great, and is a split seam comprising two or more leaves 18 to 24 in thick. The succeeding measures up to the Permian overlap on the northern margin of the district are not known in detail. Two succeeding seams are recorded in the shaft sections of Denton Colliery, the Sod, 6 ft thick, and the New Jet Amber, 21 ft thick. Higher measures, possibly up to the horizon of the Dukinfield Marine Band, must be present under the drift-cover along the northern margin of the district. A short distance west of Beight Bank Bridge on the north bank of the River Tame, the crops of two coals are recorded, the upper 3 ft thick, but their exact horizon is not known. An exposure of red-stained rocks 420 yards east of the disused Hazel Grove railway station yielded fragments of Naiadites and Spirorbis sp., considered to be possibly of similis-pulchra age. These rocks occur in a fault-plexus, and their exact relationships with those in the Poynton area to the south are not known.

It is doubtful if any seam higher than the Bottom Furnace Mine crops out in the exposed Poynton Coalfield, and the stratigraphy of the higher measures must therefore be based on the three boreholes that have penetrated them beneath Permo-Triassic rocks west of the Red Rock Fault. These are the Poynton Station, Hazel Grove and Poynton bores. Only the last mentioned gives any significant information about the Lower A. similis–A. pulchra Zone.

At Poynton the Roger Mine was just under 5 ft 4 in thick, and the Old Jet Amber (Stonedelph or Bradford Top) was a multiple seam with 55 in of coal. Between these two were the correlatives of the Ashton Great (Bradford Deep) and Bradford Middle mines, neither of them of workable thickness. Several shell-beds were found in this group of strata, one over a seatearth a short distance above the Roger yielding Anthraconaia cf. confusa (Trueman),. Anthracosia cf. aquilinoides, A. sp. cf. fulva (Davies and Trueman), Anthracosphaerium cf. propinquum, as well as Naiadites sp., Carbonita and fish remains. Another bed above the Middle Mine included Anthraconaia cf. oblonga (Wright), Anthracosia cf. lateralis (Brown) and A. cf. planitumida (Trueman).

About 60 ft above the Old Jet Amber seam a thin coal underlies shales containing the Poynton Marine Band. This is overlain by a rich non-marine fauna, characteristic of the roof of the Ashclough Mine of Manchester (Tonks and others 1931, p. 146). It included, in the Poynton Bore, Anthraconaia cymbula (Wright), A. librata (Wright), Anthracosia acutella (Wright), A. cf. atra (Trueman), A. aff. concinna (Wright), A. lateralis, A. sp.(cf. ovum True-man and Weir), Anthracosphaerium radiatum (Wright), as well as Naiadites sp., Carbonita spp.and fish remains. The marine band is the correlative of the Two-Foot Marine Band of the East Pennine Coalfield (see Edwards and Stubblefield 1948, p. 219). It is 11 ft 4 in thick, and contains Lingula sp. throughout; a thin layer of 'Estheria', at the base, is succeeded by some 5 ft of shale with well-preserved foraminifera; and these give place upwards to marine ostracods including Hollinella cf. bassleri (Knight) and Paraparchites sp., followed by indeterminate ostracods which persist to the top of the band. Between the 'Estheria' band and the coal is non-marine shale with Naiadites sp. and fish remains. The marine band has been called the Ashclough Marine Band by Magraw and Calver (1960, p. 483) because of its occurrence above that seam at Bradford Colliery; but it is considered that the adoption of a coal-seam name for a marine band can lead to confusion—as indeed has happened in the past—should any doubt arise about the original correlation of the seam: the more normal practice of recent years is, therefore, adopted of using the non-committal place-name of the locality where the marine band was first noted in the area concerned, and it is accordingly named the Poynton Marine Band.

About 60 ft above the Ashclough coal lies the Sod or Pottery Mine, a dirty seam, as in the Manchester Coalfield, consisting of alternations of coal and seatearth; above this is a succession of sandstones, fossiliferous shales, coals and seatearths just under 300 ft thick, up to the Bradford Marine Band. In the Poynton Bore the shales at several horizons yielded Anthracosia atra or A. cf. atra. About 60 ft above the New Jet Amber seam the cannelly mud-stone roof of a thin coal contained, besides plant fragments and fish remains, Anthracosia atra, A. cf. aquilina and A. sp. between atra and barkeri Leitch. This is a possible horizon for the Clown Marine Band of the East Pennine. Coalfield (see Edwards and Stubblefield 1948, p. 222), though no trace of marine fossils was observed.

Both the Bradford and Moston marine bands are present in the Poynton Borehole, where they lie above thin nameless coals at 1761 ft and 1653 ft respectively. The Bradford Marine Band exhibits two distinct phases separated by a non-marine intercalation about 15 ft thick, with some mixing of the marine and non-marine faunas at the junction of the phases—the whole occupying nearly 28 ft of strata. Small, possibly stunted, shells of Anthracosia are in close association with Lingula and foraminifera, at the base of the upper part of the marine incursion at about 1737 ft in the bore. Similarly, Curvirimula occurs just below the highest Lingula of the lower part of the marine band, an occurrence which supports the view that Curvirimula sp. was more tolerant of near-marine conditions than the other non-marine lamellibranch genera. The marine fauna is closely comparable with that found in the Haughton Marine Band of the East Pennine Coalfield (see Edwards and Stubblefield 1948, p. 223), and gives another record of Sphenothallus [Serpulites], which is characteristic of this horizon in many of the Midland and Pennine coalfields. Several of the marine fossils, notably Nuculana sp.,cf. Tomaculum sp., and some gastropods, have also been recorded from the Bradford Marine Band of Bradford Colliery (Magraw and Calver 1960, p. 482). The overall thickness of the marine band is 27 ft 9 in, including the non-marine intercalation overlying the bottom 9 ft of the band; the thickness of the upper part of the band is about 3 ft 8 in. Between the base of the marine band and the underlying coal are some 9 ft of mudstones with fragmentary Naiadites, Carbonita and fish remains. Above the marine band are a few feet of shale with a fauna including Anthracosia sp. nov. cf. acutella (Wright), 'Estheria' sp., cf. Planolites ophthalmoides lessen, fish scales and Naiadites sp.

The next coal is about 60 ft above the one that carries the Bradford Marine Band. It is overlain by 20 ft of non-marine fossiliferous shale, in which the shells occur at intervals throughout and do not form conspicuous shell-bands. Certain layers show only the flattened tubular structures of presumed worm-tracks identified as Gyrochorte carbonaria Schleicher and Planolites montanus Richter. An interesting record from these beds is the occurrence of Curvirimula, rarely found above the C. communis Zone, but recalling the similar record in the Drinkwater Park (A1/2) Borehole in the Manchester area, between the Bradford and Moston marine bands (Poole and Whiteman 1955, p. 308). An elongate Anthraconaia from 1695 ft 5 in is provisionally compared with A. pruvosti, but probably represents an undescribed species. Similar elongate shells are found occasionally in the East Pennine Coalfield near the horizon of the Sutton (Moston) Marine Band.

A thin coal two cyclothems above the Bradford Marine Band carries the Moston Marine Band in its roof, the fossils being most abundant in six inches of slightly silty and pyritous mudstone lying about a foot above the coal. The fauna obtained at the Poynton Bore included foraminifera such as Glomospira sp., also Planolites ophthalmoides Jessen and Lingula sp.

A fault at about 1587 ft in the Poynton Bore cuts out about 100 ft of strata including the Dukinfield Marine Band. Several shell-beds occur between the Moston Marine Band and the fault, the combined fauna including Planolites montanus, Anthracosia sp., Curvirimula sp., and Naiadites cf. obliquus Dix and Trueman.

Measures from the Dukinfield Marine Band to the Top Marine Band (the Upper similis-pulchra Zone).

A tentative correlation is given in (Figure 6) between the three bores in the concealed coalfield of Cheshire, those at Hazel Grove, Poynton Station, and Poynton (N.C.B. No. A1/20). Failing palaeontological evidence in the first-mentioned two holes, the correlation must be used with caution, but it fits with the facts as they are known. For instance, the seam named Worsley Four Foot in the Poynton Bore (on good faunal evidence) is about four feet thick, and is the only one of that thickness for a considerable distance below the base of the Permo-Triassic rocks. The same is true of the seams with which it is tentatively correlated, and which are in fact the only seams in their respective boreholes to attain a thickness of four feet. Again, as shown in (Figure 6), if the correlation is correct, measures about 700 ft higher are preserved beneath the Permo-Triassic rocks in the most westerly of the three bores, the Poynton Station Bore, than in the Poynton Bore; and this implies an angular discordance between the Carboniferous and the base of the Permo-Triassic of about 14°—a not unreasonable figure in that area. In the Hazel Grove Bore, if the coal at 1627 ft 3 in is correctly correlated with the Worsley Four Foot, there are some 500 ft more of the higher measures than in the Poynton Bore, which is consistent with the Coal Measures in the Hazel Grove Bore being farther down dip, so far as is known, than the Poynton Bore, but not so far as the Poynton Station Bore. This provisional correlation would put the horizon of the Top Marine Band, that is the top of the Middle Coal Measures, somewhere near the position of the coal at 1738.5 ft in the Poynton Station Bore, or possibly above a sandstone at about 1790 ft.

A superficial examination of the section of the Hazel Grove Bore in (Figure 6) might suggest that the variegated red measures between the base of the Collyhurst Sandstone and a depth of 1316 ft are the equivalents of the 'Barren Group' at the base of the Ardwick Limestone Group of the Manchester area—a group in which the cyclic sedimentation of Coal Measures type is not apparent—and that the coal-bearing measures from this depth upwards are equivalent to the Bradford Coal Group. But the log of the boring left by De Rance (see also De Rance 1893, p. 454) states that a free-falling rock bit (which would obtain only chippings) was used to 1316 ft, and a diamond core bit from this depth downwards. Thus the apparent absence of cyclic sedimentation in the Carboniferous above 1316 ft is probably due more to the method of drilling than to any stratigraphical reason; and these measures are likely to be the reddened equivalent of the upper part of the Middle Coal Measures succession in the Poynton Station Bore.

The lowest rocks of Upper similis-pulchra age in the Poynton Bore occur just above the fault at 1580 ft which cuts out the Dukinfield Marine Band. Between this fault and the Worsley Four Foot seam, some 250 ft higher, are several fossil bands above thin coals or coal-less seatearths; and these yielded for the most part a non-diagnostic fauna including Naiadites cf. hindi Trueman and Weir, N. sp., Carbonita sp.[with furrow] and fish remains. At one horizon, about 120 ft below the Worsley Four Foot, an Anthraconaia sp. of the warei/hindi group was collected; apart from the A. hindi band above the Worsley Four Foot Coal, this group is not well represented in the Upper similis-pulchra Zone. It is noted, however, that a similar shell was recorded in the Prestwich Station (A1/17) Borehole at 839 ft in a position between the Worsley Four Foot and Parker seams (Magraw 1961, p. 440). On this evidence the horizon of the Parker Mine of the Manchester coalfields—which is not now regarded as the equivalent of the Warsley Four Foot (Poole and Whiteman 1955, p. 301) is placed in this bore at 1500 ft, at the top of a ganister seat-earth which overlies a sandstone 30 ft thick. The Parker Mine of Manchester also usually overlies a sandstone. The Warsley Four Foot seam, just under four feet thick, is overlain by ten feet of grey mudstone with Anthraconaia cf. hindi (Wright), Naiadites cf. hindi, N. sp. cf. quadratus (J. de C. Sowerby), Euestheria sp., Geisina? subarcuata (Jones), and fish remains; a fauna which supports the identification of the coal.

Little can be said with certainty about the Middle Coal Measures above the Worsley Four Foot seam. In the Poynton Bore the measures are reddened to within 60 ft of the top of the coal, and although a calcareous band was found in about the correct position for the Manchester Marine Band (Poole and Whiteman 1955, p. 299) the rock was too highly altered for any organic remains to be identified. If the top of the division is taken, as proposed above, at 1736 ft 9 in, the roof of the coal in the Poynton Station Bore, the succession is not unlike that of the same measures in the Manchester area, with a series of coals, one of which attains a thickness of 2 ft 8 in, and two thick sandstones, the lower one of which may be the Prestwich Rock. B.J.T., R.H.P.

Upper Coal Measures

The base of the Upper Coal Measures is now taken at the Top or Anthracoceras cambriense Marine Band which marks the base of the Anthraconauta phillipsii Zone (Stubblefield and Trotter 1957, p. 3), instead of at the top of the Bradford Group of coals as was done in the Manchester Memoir (Tanks and others 1931, p. 59). In the Manchester area the measures have been divided into the Bradford Coal Group and the Ardwick Group by Poole and Whiteman (1955, p. 396). F. M. Trotter adopts a system for the Lancashire area as a whole which divides the Upper Coal Measures into three groups, a Lower Group equated in general with the Bradford Coal Group, a Limestone Group—the equivalent of the variegated marls with limestones at Ardwick—and an Upper Group which is not exposed at Manchester (Trotter 1953, pp. 263–267; Edwards and Trotter 1954, p. 56). A more recent classification is that adopted by Magraw (1961, fig. 3) which includes the Bradford Coal Group, the Barren Group consisting mainly of structureless variegated mudstones, and the Ardwick Limestone Group.

As (Figure 6) shows, measures referable to the Upper Coal Measures are known at only two localities in the district—the Poynton Station Bore and the Slade Lane railway cutting at Levenshulme. The classification of the uppermost Carboniferous measures in the Poynton Station Bore as Upper Coal Measures depends on the identification of the coal at 2335 ft 1 in (on lithological and structural grounds only) as the Worsley Four Foot. Some 250 ft of measures are here considered to be almost certainly in the Upper Coal Measures. They are shales and sandstones with thin coals, and the uppermost 50 ft are reddened beneath the Permo-Triassic unconformity; they are not unlike the lowest part of the Bradford Coal Group of Poole and Whiteman (1955, p. 296), with which they are provisionally equated. No equivalents are known in the Stockport district of the rest of the Bradford Coal Group.

The measures in the Slade Lane railway cutting have long been grassed over and inaccessible, except for a few of the limestone bands. Fortunately they were carefully described when the cutting was made (Brockbank 1883, p. 125; Brockbank 1890, p. 47; Roeder 1892A, p. 114; 1892B, p. 199; Brockbank and De Rance 1891, p. 282), and Jones and Kirkby reported on ostracods from the shales which were submitted to them by Roeder (Jones and Kirkby 1890, p. 137). The beds were formerly visible from about 30 yards west of the Slade Lane Bridge over the railway, where they dipped westwards under the edge of the Permo-Triassic rocks, to a point about 350 yards east of the bridge where they became obscured by drift. The section given by Brockbank and De Rance (1891, p. 282) is the one used in (Figure 6), for it takes in a greater length of cutting than that of Roeder, and includes nearly 450 ft of strata. The section is almost unfaulted, the dip being for the most part 20° towards the west-south-west, lessening to 10° on the west side of the Slade Lane bridge.

The measures are green and purple calcareous shales with freshwater limestone bands mainly less than a foot thick, but with occasional thicker bands. The fossils include ostracods, Spirorbis sp., and non-marine lamellibranchs, fish, amphibian and plant remains. Full lists are given in the papers quoted. Spirorbis is most abundant in the limestones, and the non-marine lamellibranchs in the shales. Ostracods and fish occur in both. The type of Anthraconauta phillipsii (Williamson) came from this locality (Weir 1960, p. 281). Nevertheless there can be little doubt that the beds, in general, equate with the measures in the Seedley and Ardwick districts of Manchester in which A. tenuis has been recorded (Tonks and others 1931, pp. 59, 111, 123), and that the whole of the Carboniferous measures exposed in the Slade Lane cutting belong to the A. tenuis Zone. B.J.T.

Details

Lower Coal Measures

For convenience of description the outcrops of the Lower Coal Measures may be divided into two areas, north and south of Marple.

Area north of Marple

The Six Inch Mine and its overlying marine band are exposed only in one locality, in the small stream 400 yd S.W. of Arnold Hill reservoir, Gee Cross, where the section is black shale with marine fossils, including poorly preserved specimens of Gastrioceras subcrenatum C. Schmidt and Dunbarella papyracea (J. Sowerby), 2 ft, over coal, the Six Inch Mine, 8 in, grey-blue seatclay 12 in, and coarse micaceous gritstone, the Rough Rock.

On the south-eastern flank of Werneth Low at Low Bank Farm fossiliferous shale lies on the tips from disused day-holes which previously worked the fireclay of the Sand Rock Mine in the Millstone Grit. Both coals and the marine band were proved in the Romiley Dyeworks Borehole, though a detailed section was not recorded, and no fossils were named. West of the Romiley Anticline the succeeding measures up to the Milnrow Sandstone are not exposed, and nothing is known of the details of the sequence. Hull (in Hull and Green 1866, p. 22) states that "At Hyde this series [Lower Coal Measures] forms a narrow band, between the outcrop of the Lower Woodley Mine and the Millstone Grit of Gee Cross. One or more of the coals have been worked here, probably the Gannister seam, but no information could be obtained regarding them."

The Woodhead Hill Rock lies about 100 ft above the Six Inch Mine and follows a sequence which is dominantly argillaceous. This succession is nowhere well exposed, and knowledge of it is derived mainly from the Romiley Borehole. There a sequence of largely unfossiliferous shale and sandy shale succeeds the Six Inch Mine Marine Band, some plant debris being recorded at the top. The Woodhead Hill Rock is developed in two leaves separated by a thick layer of shale. The following section was recorded in the Romiley Dyeworks Borehole:

The shale parting is nowhere exposed within the district. Exposures of the sandstone north of the River Etherow near. Beacon Houses show it to be a creamy grey micaceous sandstone with thin shaly partings, and where it crops out in the River Etherow east of the district boundary it is brown and highly siliceous. Locally it is flaggy with layers of gritstone.

The Bassy Mine, Which immediately overlies the Woodhead Hill Rock, was previously wrought in the area extending from Marple Bridge northwards to Compstall church, where the following section of the seam, locally called the 'Mountain Mine', is recorded: engine coal 14 in, over good coal 12 in and bottoms 10 in. The seam is nowhere exposed at the surface, though in the past an outcrop of coal, was recorded along the minor road 230 yd south-west of Needhams Farm, Compstall. Spoil heaps from the shafts south and east of Werneth Hall, on the eastern flank of Wemeth Low, yielded mussels similar to those from above the Bassy Mine. Carbonicola aff. limax and C. aff. rectilinearis were collected from a spoil heap near Higher Mossacre, Romiley. These fossils are thought to belong to the Bassy Mine fauna and provide evidence that the seam was worked, though on a local scale, in the area north of Romiley. Nothing is known of the thickness of the seam, but it was apparently worth working in this general locality.

The measures overlying the Bassy Mine are exposed in the River Etherow immediately downstream from Compstall weir, a short distance east of the district boundary. This section is: blue shale and ironstone nodules with Carbonicola cf. discus, C. aff. fallax, C. aff. protea and fish scales 5 ft, over black shale with Lingula mytilloides and Palaeoniscid scales 3 in, blue shales with occasional Carbonicola sp. 10 ft, followed by a gap—the position of the Bassy Mine—and grey flaggy sandstone, the Woodhead Hill Rock. The Romiley Borehole section does not show the Lingula band; and the measures succeeding the Bassy Mine are described as containing abundant plant remains, the main horizon with Carbonicola sp. being developed 53 ft above the coal.

The Lower Foot Mine lies 81 ft above the Bassy Mine in the Romiley Borehole section; but in the area immediately north of Marple it must be, if present, more than 100 ft above that seam. The intervening measures are predominantly shale and are not exposed at the surface. At Ernocroft Wood, Ludworth (a short distance east of the district boundary), a partial exposure of the Lower Foot Mine shows coal 6 in, on white fine-grained ganister 2 ft 6 in, and ganister-like sandstone 3 ft. No other details are known concerning this seam; it is probably thin throughout the area, and in consequence has not been wrought.

The shales immediately overlying the Lower Foot Mine in the Romiley Borehole contain Carbonicola sp., Lingula sp. and plants, but the log does not separate the marine from the non-marine phases. This fossiliferous horizon is not exposed in the locality. The succeeding shales are capped by a thin sandstone, the representative of the Ganister Rock of Lancashire, overlying which is the Lower Mountain Mine. This seam is exposed in the River Etherow, 70 yd east of Compstall Bridge, where the following section was visible: grey shaly sandstone 2 ft, over grey-blue sandy shale with ironstone nodules 1 ft, coal 2 ft, ganister passing down into ganister-like sandstone 2 ft, and blue shale. At Ludworth, a short distance outside the district, the Lower Mountain Mine is largely washed out by the overlying Bullion Rock. A section recently proved near Rock Tavern showed coal 9 in, over seatearth 2 ft 6 in, and brown mudstone 1 ft. There are no records of the seam having been worked within the area west and north-west of Compstall, though one of the shafts to the Bassy Mine, 400 yd south of Compstall Bridge, must have passed through the seam. The rocks hereabouts are much faulted and obscured by thick drift.

The succeeding measures up to the Upper Foot or Bullion Mine are exposed in part in the River Goyt between Marple Bridge and the bridge over the river in Brabyn's Park. The succession consists of blue shales with an intercalated band of sandstone and pebbly gritstone. A section in the western bank of the River Goyt, 170 yd N.N.E. of Brabyn's Hall, shows blue shale 2 ft, over hard creamy grey medium-grained conglomeratic gritstone containing angular quartz pebbles up to 0.5-inch diameter in the upper part, 2 ft, and grey flaggy sandstone 3 ft. The Upper Foot Mine lies 75 ft or so above the Lower Mountain Mine. Measures thought to be those immediately underlying the Upper Foot Mine are exposed in the River Goyt 130 yd east of its confluence with the Etherow, where a siliceous seatearth passes down into grey ganister-like sandstone which in turn overlies mudstone. Neither the coal nor the marine band are exposed at this locality, and confirmation of the horizon here is lacking. The Bullion Rock, the sandstone which immediately underlies the seam, is recorded as 58 ft thick in the Romiley Borehole, but no coal was proved. Neither the coal nor the Bullion Mine Marine Band is exposed in this area, and no information concerning them is available; but east of the district boundary the seam and its overlying marine shale is exposed at Ludworth, where the coal is 14 to 16 in thick. There is no evidence that the seam has been worked anywhere within this area, and it is probably too thin.

The succeeding measures up to the Upper Mountain Mine are known only from the two boreholes at Romiley and Chadkirk (pp. 152 and 131). The log of the upper part of the Romiley Borehole is difficult to interpret and cannot be correlated with the Chadkirk section. In it, 86 ft of shale succeeds the position of the Upper Foot Mine, and this is overlain by 97 ft of 'hard grey rock' which suggests the presence of the Helpet Edge Rock. The Upper Mountain Mine should lie immediately above this sandstone, but is not recorded in the log. The Chadkirk Print Works Borehole, situated about one mile south of the Romiley Dyeworks Borehole, went down to a level 109 ft below the position of the Upper Mountain Mine, but in the largely argillaceous succession with occasional thin-shelled lamellibranchs and fish scales there is no suggestion of a thick development of the Helpet Edge Rock as stated in the log of the Romiley Borehole.

Both the Cannel and Upper Mountain mines were present in the Chadkirk Borehole (Magraw 1957, pp. 22–23), their thicknesses being 2 in and 30 in respectively. The Upper Mountain Mine is not known to have been wrought within the area, although an old shaft [SJ 9565 8953] beside the railway north of Ley Hey Park, Marple, may be connected with workings in it. A 12-in shaly coal is reported to have been exposed in a trench at Guywood Cottages, Romiley; it lies at the approximate horizon of the Upper Mountain Mine but may represent the overlying Cannel Mine. The Cannel Mine in the Chadkirk Borehole was 12 ft above the Upper Mountain Mine. The overlying marine band contained Lingula sp. and fish remains only, and was separated from the coal below by 3 in of carbonaceous mudstone with fish remains.

Tonge's Marine Band rests on a smut lying on a thin sandstone band 93 ft above the Cannel Mine in the Chadkirk Borehole, the fauna of the band being confined to marine microfossils. The sandstone exposed at the top of the cutting along the Macclesfield railway immediately south of Marple Wharf Junction may represent the sandstone underlying this smut.

The Milnrow Sandstone is well developed. North of Romiley it forms a prominent feature on the western limb of the Romiley Anticline, extending from the railway cutting north-west of Romiley station northwards to Heald just west of Greavefold. It is well exposed as a grey-brown to creamy brown current-bedded rock, frequently containing well marked micaceous partings, and has been extensively quarried along the hill-side. Grain-size ranges from coarse in the north to medium-grade in the south. The sandstone is not exposed in the central part of the area. In the Chadkirk Borehole it is 75 ft thick, ranging from coarse-grained at the base to fine or medium-grained at the top. A sandy seatearth immediately overlying the sandstone is thought to represent the Pasture-Mine horizon of Lancashire. The mudstone overlying this seatearth contains fish scales.

Details of the succeeding sequence up to the base of the Old Lawrence Rock are known chiefly from the Chadkirk Borehole, for although there are many exposures they are not readily fitted into the sequence. In the borehole, 200 ft of mudstone and sandy mudstone overlie the Milnrow Sandstone, and these are succeeded by 35 ft of sandy shale and mudstone with thin sandstone partings. Both north and south of the River Goyt there are at this horizon many outcrops of pale grey brown-weathering flaggy sandstone. Such rock is well exposed in the cliff face overlooking the river terraces just behind Marple Hall, where it is reddened. Much sandstone also occurs at this horizon in the area north of the River Goyt, where it caps Bunkers Hill and is exposed in the small stream flowing south from Hatherlow to a point 450 yd north of Otterspool Bridge, Chadkirk. There it is a finely current-bedded flaggy sandstone with thin partings of mudstone. The succeeding shales and mudstones extending up to the Old Lawrence Rock are as much as 170 ft thick, but are poorly exposed. Shales are seen on the side of the old road on Harrison Brow, 270 yd of Otterspool Bridge, and have yielded a few undetermined mussels. Another exposure of this mussel band occurs in faulted ground in a small gully [SJ 9529 8958] 20 ft from the River Goyt and 220 yd N.51°E. of Nabtop, Marple, and has yielded Carbonicola cf. pontifex Eagar.

The Old Lawrence Rock comprises about 120 ft of fine-grained grey flaggy sandstone with interbedded bands of mudstone. At the western portal of the George Lane tunnel, Bredbury, a grey-brown ganister-like sandstone may be this rock. At Chadkirk the sandstone is exposed in the river, and consists of red-stained thinly bedded brown rock with thin purplish flaggy bands. The succession through the Old Lawrence Rock is well exposed in a fault-block in the River Goyt, commencing at a point 250 yd east of Marpledale. It comprises alternating bands of grey medium-grained sandstone and blue sandy shale passing up into a creamy grey, medium to coarse-grained current-bedded sandstone. No coal is visible on top of the sandstone here.

The measures lying a short distance above the Old Lawrence Rock are exposed in the River Goyt for a short distance south-east of Marpledale. They are blue shales with ironstone nodules and grey mudstones. A mussel band [SJ 9513 8989] in the western bank of the Goyt 330 yd S.E. of Marpledale yielded an abundant fauna including Spirorbis sp., Curvirimula sp., Carbonicola subconstricta, C. bipennis?, C. sp. cf. centralis (J. de C. Sowerby), Naiadites aff. flexuosus, Geisina arcuata and Rhizodopsis sp.[scales].

The rocks immediately below the Arley Mine are visible in the railway cutting north-west of George Lane tunnel, Bredbury:

The exposure of the mussel-band is poor, and only fragmentary Carbonicola spp. were obtained; these were associated with Geisina arcuata, Rhabdoderma?, and plant fragments. The mussel-band south-east of Marpledale contains a fauna typical of the lower part of the Zone of Carbonicola communis; but its identity with the band in the Bredbury cutting cannot be proved.

The measures, mainly sandstone, exposed along the eastern leg of the incised meander of the River Goyt south of Marple aqueduct are believed to be those underlying the Arley Mine. Two thin coals which lie about 120 ft and 200 ft below the Arley Mine respectively are exposed in a small gully draining into the eastern side of the Goyt 430 yd south of the aqueduct. The incompletely exposed upper seam shows 8 in of coal beneath 3 ft of blue mudstone. The section of the lower seam, with its roof and floor, is grey mudstone with ironstone nodules 3 ft, on blue mudstone 4 ft, coal about 12 in and seatclay and grey mudstone. The intervening measures between the seams are exposed in the River Goyt, and consist of fine-grained thinly bedded sandstones with thin shaly partings. The measures 'below the lower coal are grey to purple fine-grained sandstones. If the estimate of the horizon for the coals is correct, either the upper and possibly both coals lie above the Old Lawrence Rock, or else the upper coal lies on the rock—an horizon which is not known elsewhere to be coal-bearing.

A section [SJ 9544 8957] in a small faulted block on the south bank of the River Goyt, 930 yd W.13°N. of Marple station, shows blue shale 2 ft, on coal 10 in, seatearth with thin ribs of ganister 2 ft, fine-grained grey sandstone with haematite nodules 2 ft, and fine-grained massive grey sandstone with thin purplish shaly layers 6 ft. The exact horizon of this coal is not known; it may be the upper one mentioned above, and is undoubtedly high in the measures below the Arley Mine.

Few details are known of the measures lying between the Arley Mine and the New Mine in the Bredbury area. The Arley is believed to be represented by a coal about 2 ft thick exposed in the railway cutting 650 yd S.E. of Bredbury station, where the following discontinuous section is visible:

No other exposures of the Arley Mine were seen during the present survey south of the Bardsley area. Hull, however, records (in Hull and Green 1866, p. 20) that the Lower Woodley Coal, which he correlates with the Arley or Royley Coal of Oldham, was proved at Hyde. There is no present confirmation of this, and it may be that the seam proved was not the Arley. Hull (ibid. p. 28) also refers to "the Lower Woodley Mine, where it has been worked on the north bank of the Mersey at Otterspool"; and an old adit 570 yd W.N.W. of Otterspool Bridge shows, with little doubt, that the Arley Mine was worked on a small scale at this point. Evidence from the Poynton area to the south suggests that the seam may be expected to maintain an average thickness of just under 2 ft throughout the area. There are discontinuous exposures in the bed of the Goyt between the conjectured crop of the Arley Mine a short distance south of Otterspool Bridge and the presumed position of the crop of the New Mine near Lower Waterside. The measures visible are reddish-stained flaggy sandstone and red and purple-stained shales; and tipped material just north of Lower Waterside suggests the presence of thin coal seams in this sequence. The horizon characterized by Carbonicola pseudorobusta is exposed in the south bank of the River Goyt 140 yd south-east of Lower Waterside:

The fauna recorded from here comprises Carbonicola aff. communis, C. aff. pseudorobusta, a Palaeoniscid scale and a cochliodont fish tooth. The succeeding measures are poorly exposed, the sandstone bands forming reefs across the river.

The New Mine is recorded as a split seam in the Bents Lane Shaft (Plate 3, No. 1), measuring coal 30 in, parting 18 in, coal 15 in; a small area of coal was worked in the vicinity of the shafts. Old outcrop workings in this seam can be traced in the area east and south-east of Goyt Hall. Some 75 ft above the New Mine the Bredbury Rosemary or Water Mine is 2 ft thick, and there are no records of workings on any scale. The Bredbury Stone or Silver Mine, 2 ft 8 in thick and reputedly of poor quality, lies 43 ft above the Water Mine and has been worked fairly extensively around Bredbury. The crop of the seam can be traced for a short distance on either side of the River Goyt, crossing the river at a point immediately opposite its confluence with Poise Brook. The shales succeeding the coal contain a few poorly-preserved Carbonicola sp. They are overlain by a prominent sandstone, which is well exposed in the beds of the River Goyt and of Poise Brook near their confluence; it is medium-grained, purplish in colour, and in part stained red. At this point the measures dip steeply south-west on the nose of the Mossley Anticline towards the Red Rock Fault, which crosses the River Goyt a short distance to the west.

The succeeding measures up to a short distance above the Peacock Mine of Bredbury are exposed along Poise Brook, the positions of the coals being indicated by old bell-pits and gaps in the exposed section. These measures are dominantly argillaceous, and contain much carbonaceous shale and thick seatclays; thin bands of rooty sandstone are also present. The Peacock Mine is 2 ft 4 in thick, and has been worked along a strip extending northwards from Bents Lane through Haugh-ton Green. At Haughton Colliery the section was: rock bind 22 in over the Peacock Coal 21 ft, and black shaly metal 8 in. The Two Foot Mine, lying 48 ft above the Peacock Mine, was also worked from this pit, the section being' rock bind 2 ft, on coal 2 ft, and dark blue metal 1 ft. The Bredbury Cannel is a split seam, the section being coal 2 ft, dirt 3 ft, coal 18 in. It has been worked to a limited extent in the vicinity of the Bents Lane Shaft. A borehole at Bredbury penetrated these measures, commencing below the Bredbury Cannel and finishing a short distance below the New Mine. All the coal seams penetrated had probably been worked and therefore were not recorded, consequently the interpretation of the section is tentative and can only be used as a rough guide to the strata. It shows a dominantly argillaceous succession with thin sandstone bands below the presumed positions of the Rosemary (Water) and Little Stone (Nayley) seams.

The Black Mine, 128 ft above the Bredbury Cannel, varies in thickness from 38 to 48 in. It has been extensively worked, the old workings extending southwards to the proximity of Dark Lane, Bredbury, near where the seam abuts against the Red Rock Fault. The Little Black Mine, a thin but fairly constant seam, lies about 25 ft above the Black Mine. No coals above the Little Black Mine are recorded in the Bents Lane Shaft section, though, depending on the thickness of drift, higher measures possibly up to the Foggs Coal may be present—these measures are not shown on the section on Plate 3.

Measures from the Black Mine up to the Blenfire Rock are poorly exposed in the River Tame at Arden Bridge, only a sandstone, below the presumed position of the Oldham Great seam, being visible. To the west of Arden Bridge measures from the Blenfire Rock up to the Roger Mine are exposed in the River Tame, though in most cases actual details of the coals are not available.

The Blenfire Rock is seen in quarries at Lower Haughton and also farther north at Haughton Green. It is over 200 ft thick, and comprises a massive reddish sandstone at the base, passing upwards into fine-grained flaggy sandstone at the top. The Fogg. Mine, the thickness of which is not known, rests directly on this sandstone. The succeeding measures up to the Oxicrow or Higher Chamber seam consist of alternations of reddish sandstone, argillaceous sandstone and sandy mudstone. The following section was formerly visible in the Tame: Oxicrow Coal, thickness not known, over coaly shale and seatearth 15 ft, argillaceous sandstone 15 ft, massive red sandstone 20 ft, and red sandy shale.

The measures from the Oxicrow (Higher Chamber) Mine up to the Rocher Rock are poorly exposed, only a few patches of purple sandstone and shale being visible. The Rocher or Chamber Rock is variable in character; the sandstone is massive at the base and passes upwards into brown laminated sandstone with partings of sandy mudstone. A section in the bank of the Tame, recorded by the earlier surveyors and not now visible, showed a seatearth, presumably that of the Bottom Shuttles Coal, resting on the sandstone and overlain by dark shale. This is probably at the horizon of the Sutton Manor Marine Band, the boundary between Lower and Middle Coal Measures.

The upper part of the Lower Coal Measures is present in two small faulted basins in the Marple area, the Aqueduct and the Rosehill outliers. In the Aqueduct outlier a coal, apparently 18 in thick and previously worked below the aqueduct over the River Goyt at Marple, was exposed near Aqueduct Mill a few years ago. North of the railway viaduct at a point on the river due south of Higher Watermeetings another coal, 12 in thick, is visible. Shale exposed in the bed of a small stream 90 yd north-west of Watermeetings contains a mussel band with Spirorbis sp., Carbonicola aff. pseudorobusta, C. aff. robusta, Curvirimula sp., Naiadites flexuosus?, Geisina arcuata, and fish remains including Palaeoniscid scales—a fauna characteristic of the Carbonicola pseudorobusta Subzone, and associated with beds lying 150 ft or so above the Arley Mine. The Arley Mine is, therefore, considered to be the seam cropping out immediately south of the aqueduct. The line of its outcrop shown north of the canal is, however, conjectural.

In the Rosehill outlier the following section is visible on the south bank of the River Goyt, 930 yd N.77°W. of Marple station: blue shale 2 ft, over shale with abundant Carbonicola sp. 10 in, blue-black shale with abundant plant remains 6 in, poor fireclay 1 ft, coal and carbonaceous shale 1 ft, seatearth with ganister-like bands 4 ft, and fine-grained grey flaggy sandstone 3 ft. The fauna from these beds is a Carbonicola aff. pseudorobusta assemblage associated with Spirorbis sp.,. Naiadites sp., Carbonita humilis (Jones and Kirkby), Geisina arcuata and Rhabdoderma sp., and is characteristic of an horizon about 150 ft above the Arley Mine —on which basis the conjectural outcrop of that seam has been drawn. Shales exposed in the small stream which drains into the south side of the incised meander of the Goyt have also yielded some poorly-preserved Carbonicola, believed to represent a lower Carbonicola communis Zone fauna. A thin coal apparently at a higher horizon is seen in the railway cutting 800 yd N.E. of Rosehill station, Marple, the section being seatearth 1 ft, over coal 1 ft, and seatearth 1 ft.

The southerly extent of the Rosehill outlier is conjectural; the area south and south-east of the Macclesfield railway is drift-covered, and the outlier is bounded on the west and east by faults.

Area south of Marple

The Six Inch Mine is not exposed within this area, though the overlying fossiliferous marine shale is seen in the bed of the River Goyt at a point 720 yd south of the bridge at Marple Bridge. The Bakestonedale Bore proved the• Six Inch Mine Marine Band, which yielded Gastrioceras subcrenatum, but the coal was absent. The succeeding measures up to the Woodhead Hill Rock are poorly exposed; the borehole in Bakestonedale showed a sequence comprising 42 ft of dark grey fissile mudstone passing upwards into 38 ft of sandy shale with sandstone bands, beds forming a transition to the massive sandstone of the Woodhead Hill Rock.

The Woodhead Hill Rock is developed throughout the area, its thickness varying from 100 to 150 ft. It is almost continuously exposed in the railway cutting from a point 300 yd south of Marple station for a distance of 1300 yd south-eastwards towards the viaduct. To the south the sandstone is again seen in Barlow Wood and in the River Goyt for a short distance downstream from Roman Bridge, where it is a creamy-pink massive fine-grained gritstone, much current-bedded and with a band of flaggy sandstone near its base. Farther south the Woodhead Hill Rock forms a marked feature on Park Moor lying for the most part east of the district boundary, but curving westwards on to Sponds Hill and into Bakestonedale. Here it is a purplish cream gritstone, the grain-size showing a progressive coarsening towards Bakestonedale. On the south side of Bakestonedale the rock forms a capping on Andrews Knob, where it consists of a medium to coarse-grained sandstone with thick gritstone partings occasionally containing small quartz pebbles. Plant remains are visible in the small quarry 420 yd S.18°W. of Bakestonedale Farm. In the vicinity of Bollington it is well exposed in the large, chiefly disused, quarries below Green Lane. No bands of gritstone are present, the rock being a grey medium-grained current-bedded sandstone, much used as a freestone in the past. Many large concretions containing an iron-carbonate cement are present in the sandstone here.

The Bassy Mine, locally called the 'Mountain Mine', overlies the Woodhead Hill Rock. This seam used to be worked at Bottoms Hall Pit, Marple Bridge, and at Marple Lime Works, the coal being 3 ft thick. Farther south in Barlow Wood a small area of coal was subsequently worked, and was 3.5 ft thick with a shale roof and a rock floor, being locally known as the Peacock Coal. In Bakestonedale the seam is partially exposed in the stream opposite Bakestonedale Farm. Hereabouts it has been called the Big Mine or Lime Kiln Coal: it is approximately 4 ft thick and of very poor quality, consisting of alternations of coal and carbonaceous shale; it rests directly on the Woodhead Hill Rock. Opencast trials on Sponds Hill in 1948 showed that the quality of the coal deteriorated from north to south in that area.

The shales above the Bassy Mine are partially exposed in and near the stream opposite Bakestonedale Farm. The coal is overlain by blue shales followed by mudstone with ironstone nodules which have yielded Carbonicola fallax and C. aff. habergharnensis Wright. The marine band about 20 ft above the Bassy Mine-is a thin band of hard black shale containing Lingula sp., and is poorly exposed in the south bank of the stream. In the Bakestonedale Borehole (p. 130) mudstone with ironstone nodules succeeds the Bassy Mine, and the Carbonicola band, there associated with a fish horizon, lies about 24 ft above the coal.

The Lower Foot Coal lies some 110 ft above the Bassy Mine at Marple, but 87 ft above it in Bakestonedale to the south. The seam is present throughout the area, though less than a foot thick. The underlying sandstone, with a marked ganisterlike top, is present in the north and as far south as Bakestonedale; but sections in the Bollington area show that a seatclay underlies the coal and that the sandstone is there more argillaceous. In the north the sandstone is exposed at the weir on the River Goyt at Marple Bridge. Farther south, on the western slopes of Sponds Hill, the sandstone makes a marked feature, and it is well exposed in the stream 300 yd west of Bakestonedale Farm. Few sections of the Lower Foot Mine are available; that recorded in the shaft of Clarence Fireclay Mine, Bollington, is Stone Mine (Ribbon or Stinkard Mine) 11 in, on fireclay (the Drab Clay) 6 ft. In the west bank of Clough Pool, Bollington, the following section was measured: soft brown flaggy sandstone 2 ft, over blue-grey shales with obscure plant remains at their base 10 ft, coal 10 in, and sandy micaceous seatearth, shaly at base, 6 ft.

The measures from the Lower Foot Mine up to the Lower Mountain Mine are partially exposed. In Bakestoneclale, about 500 yd north of Bakestonedale Farm, the Lower Foot coal has been dug at outcrop, and only the ganister-like seatearth and the marine roof-measures are exposed. The marine band with Lingula sp., 'Posidoniella' sp. and fish remains is separated from the presumed position of the coal by about a foot of mudstone containing poorly-preserved mussels including Carbonicola fallax and C. artifex Eagar (see p. 17). Farther north a sequence of alternating sandstones and sandy shales is exposed along the east bank of the River Goyt, commencing at a point 270 yd south of Marple Bridge and continuing southwards to the fault.

The Lower Mountain Mine is not exposed in the northern part of the area, and there is no evidence of any exploitation, so that no details of thickness and quality are known. To the south in the Bakestonedale and Bollington area the coal, locally called the Sweet Coal, has been, and is at present being worked at Bakestonedale Moorside Mine, together with its associated fireclay. The seam section recorded from the shaft of this mine is shales, over coal (Sweet Coal) 20 to 22 in, on seat-earth 4 ft. To the south-west, at Clarence Fireclay Mine, Bollington, the section was coal 22 in on fireclay 6 ft, the fireclay being used for refractory bricks. North of Bakestonedale the seam has been worked up to the wall surrounding Park Moor, but is, according to the mine-plans, untouched throughout the park area. Large lumps of fusain, often pyritized, are frequently found on the tips from old shafts sunk to this coal in the Bollington area (the presence of thick bands and lenses of fusain is characteristic of the Lower Mountain Mine in parts of Lancashire).

The shales which overlie the Lower Mountain Mine have been, in the past, worked together with the fireclay and used in brick manufacture. Above these shales lies the Bullion Rock, which is exposed in the bluff overlooking the River Goyt a short distance south-east of Marple station. There it is split into two leaves, the section being fine-grained sandstone 12 ft, over shales 6 to 8 ft, and creamy grey sandstone with flaggy bands 12 ft. Farther south on Sponds Hill and on the south margin of Park Moor the Bullion Rock makes a marked feature, an isolated exposure showing it to be a rusty-weathering pinkish grey fine-grained gritstone.

No details of the Upper Foot or Bullion Mine are known from the Marple area. At Disley, a short distance beyond the eastern boundary of the district, the seam has been worked under the local name of Red Ash Mine, and was 17 in thick on grey flaggy sandstone. To the south, in Bakestonedale, the coal locally called the Little Smut is a mere 8 in thick and has not been worked for this reason. The Bullion Mine Marine Band is well exposed in Bakestonedale in the stream a few yards east of the road bridge, where grey shale with nodules and bands of ironstone 12 ft, rests on shale with Gastrioceras listeri and Dunbarella papyracea 15 in, hard micaceous dark grey shale and mudstone with a few non-marine lamellibranchs 14 in, followed by a gap, which includes the Little Smut Coal and seatearth horizons, about 4 ft, and hard flaggy micaceous sandstone. Cope (1948, p. 473) divides the marine band into layers based on lithology and fossil content, finding a bed 11 in thick near the base which is composed almost entirely of Dunbarella papyracea. This thin bed occurs immediately above the coal in Higgins Cleugh, Disley, a short distance outside the eastern boundary of the district, and material derived from it is present on all the old tips around the shafts sunk to the coal in this vicinity.

A thin band of black shale containing a marine or quasi-marine fauna occurs a short distance above the Bullion Marine Band proper, and is seen in the following two sections, both of which lie just beyond the eastern boundary of the district. The one, an exposure in Higgins Cleugh, Disley, commencing roughly 12 It above the Bullion Mine, shows blue shale 4 ft, over contorted shale (crozzle) 6 in, blue shale 6 ft, black shale with fish scales and Caneyella sp. 1 in, and blue pyritous shale. The other is in Bollinhurst Brook, 36 yd south (upstream) from Bollinhurst reservoir, Disley, where blue shale 4 in overlies black shale containing Lingula mytilloides, an orthocone nautiloid, Geisina arcuata, fish remains including Rhabdoderma and Palaeoniscid scales and an Acanthodian spine 1.5 in, blue shale 3 ft, blue shale with Caneyella sp. 2 in, and blue shale. It is possible that these two exposures represent two different bands.

The succeeding measures up to the Big Smut Coal are poorly exposed. The Bakestonedale Shaft section shows 140 ft of shale capped by a sandstone 18 ft thick, which underlies the Big Smut Coal. The sandstone is exposed at the roadside in Bakestonedale, 250 yd west of the road bridge above the brickworks, as 10 ft of current-bedded grey-brown flaggy rock with shaly partings.

The correlation of the Big Smut Coal of Bollington with the Upper Mountain Mine of Lancashire has already been discussed (p. 18). In Bakestonedale the coal is 18 in thick and has been much wrought. It has also been worked in Coalpit Cleugh, Lyme Park, just outside the district, where the overlying blue shales and the underlying ganister-like sandstone are visible in the stream. The marine band not far above the coal is well exposed in the banks of Horsepasture Reservoir, Disley, where blue shale 1 ft is seen overlying black shale containing Caneyella sp. [juv.] 1 in, and blue shale with ironstone nodules 4 ft. This band is about 6 ft above the presumed position of the coal, and probably represents the Lingula band found in the roof of the Cannel Mine about 12 ft above the Upper Mountain Mine in the Chadkirk Print Works Borehole.

The Milnrow Sandstone, lying some 90 ft above the Big Smut or Upper Mountain Mine, forms a prominent feature traceable from Jacksonedge at Disley to Bakestonedale. On Jacksonedge a quarry face shows 40 ft of creamy-brown fine to medium-grained current-bedded sandstone. South of the Stockport–Buxton main road the sandstone caps Cage Hill in Lyme Park, and small quarries along the outcrop show a varying lithology from purplish-cream medium-grained current-bedded sandstone north of Lyme Cage, to grey-brown highly siliceous fine-grained gritstone alongside the drive close to Lyme Hall. South of the Hall the sandstone forms the prominent dip-slope of Potts Moor, where exposures show a creamy brown or pinkish grey current-bedded highly siliceous sandstone. At Dale Top on Potts Moor the sandstone is in the main highly siliceous, but locally near its base contains small quartz pebbles and rhombs of fresh pink feldspar. South of Bollington the basal part of the Milnrow Sandstone caps the eastern side of Kerridge, and consists of a coarse feldspathic gritstone with occasional pebbles, overlying medium-grained flaggy sandstone with partings of shale. This is the so-called 'Bollington Grit' of Hull and Green (1866, p. 22) and the 'Kerridge Rock' of Pocock (1906, p. 48).

Shales some 120 ft thick overlie the Milnrow Sandstone; they are exposed along the stream past Cluse Hay, Lyme Handley, where they are blue, with ironstone nodules and thin bands of black shale and of contorted shale. The black shale contains Calamites sp. and plant debris, but no other fossils have been found. At the top is a grey mudstone overlain by shaly sandstone. A thick sandstone, up to 150 ft thick, is developed above the last group. It is well exposed in Poynton Brook east of West Parkgate, as a grey flaggy rock, occasionally showing curled bedding, some shaly partings, and irony concretions; thin slumped bands also occur. In Lyme Park it has in places been quarried for building-stone. The rock forms a marked feature from Knott in Lyme Park southwards to Pott Shrigley. Exposures in the stream in Gibhill Wood, Shrigley Park, show a nodular concretionary grey sandstone with thin shaly partings, and others west of Pott Shrigley show closely current-bedded grey flaggy sandstone with thin shaly mudstone partings and large irony concretions. North and west of Lyme Hall the ridge formed by this sandstone runs west of Elmerhurst Wood and north of Bollinhurst Brook through Carr Brow towards Windlehurst House. Exposures of grey flaggy sandstone occur along the old coaching road at Carr Brow and also in Marple Brook near Old Clough. Along this ridge, however, it has not been possible to separate this sandstone from the succeeding one which possesses a similar lithology.

The succeeding measures consist of a group of grey-blue shales, thin bands of ganister-like sandstone and, at the top, blue shales with ironstone, altogether about 70 ft thick. The blue shales at the top have yielded abundant non-marine lamellibranchs including Carbonicola cf. bipennis, and C. cf. subconstrieta, with Geisina arcuata. This mussel band is exposed on the south side of the valley at Poyntongate, Lyme Park, 70 yd east of the park wall; in Poynton Brook 80 yd upstream from the bridge at West Parkgate, Lyme Park; and in the small stream 520 yd west of Birchencliff, Pott Shrigley.

The succeeding sandstone, the Old Lawrence Rock, is exposed in Poynton Brook immediately downstream from, and underneath, the bridge at West Parkgate, where it is a grey flaggy sandstone with occasional shaly partings. Underneath the bridge is grey massive flaggy sandstone 2 ft, over hard grey sandstone with irregular base 1 to 2 in, slumped and contorted grey sandstone, thickening eastwards and transgressing on to lower bedding-planes in that direction 9 to 18 in, on grey flaggy sandstone 2 ft. To the south, exposures in the vicinity of Caphurst Knot show a cream current-bedded fine-grained sandstone with irony concretions. At Styperson Park the sandstone has been extensively quarried, a face 50 ft high shows well-bedded grey sandstone with shaly partings, closely current-bedded in the lower part, flaggy and with poorly-preserved plant remains at the top. Some of the flaggy bands are purplish in colour. The upper part of the Old Lawrence Rock is nowhere well exposed; a coal which lies on top of it was once worked from a shaft near Green Farm, Lyme Handley, and is reputed to have been 3 ft thick. Hull records the log of an old borehole at Nixon's Farm, Adlington, the site of which is thought to have been near Roddick Knoll; a seam recorded at the bottom of this borehole as 65 in of coal and dirt mixed is believed to represent the above-mentioned coal seam. The measures succeeding this seam and extending up to the Redacre Mine crop out in Poynton Brook, where only a grey flaggy sandstone with shaly partings lying immediately below the Redacre Mine is exposed. The section recorded in Nixon's Farm borehole shows that 24 ft of shale succeeds the coal, and this is overlain by 36 ft of alternating bands of sandstone and shale, followed by 74 ft of flaggy sandstone and the seatearth of the Redacre Coal.

The Redacre or Arley Mine is not now exposed, but was formerly visible in the bed of Poynton Brook 140 yd upstream from the aqueduct portal in Redacre Wood. In this locality the following section of a pillar left underneath the railway tunnel east of Middlewood station is typical: strong rock 24 ft, over shale 6 ft, coal 172 in, pricking (dirt) I in, soft coal 3 in and seatclay. As it is so thin the seam has only been worked sporadically on the south and west of the coalfield, and no details of the quality of the coal are available. North of Windlehurst the outcrop is conjectural, being based on old boreholes sited along Torkington Road. From this point northwards to where the seam was formerly worked near Otters-pool Bridge it has not been proved. The area south-west of Redacre Hall is drift-covered, and the position of the crop as shown is hypothetical—and it may lie much farther north.

The measures close above the Redacre Mine are exposed in Poynton Brook on either side of the aqueduct portal, and are chiefly grey flaggy sandstone with partings of shale, sandy mudstone with thin seatearths and rooty sandstone bands. The succeeding measures up to the Accommodation Mine are not well exposed. A few sections can be seen in the brook just south-west of Poyntongate, Lyme Park, but they are confused by the valley being along the line of the Marl or Accommodation Fault. The shaft section of Dingle Pit, Middlecale Colliery, shows two thin coals lying 50 ft and 96 ft respectively above the Redacre Mine. An 'oyster bed' is recorded 165 ft above the Redacre Mine and is thought to represent the lowest mussel band characterized by the presence of Carbonicola pseudorobusta in Lancashire. An exposure of this mussel band in the stream below Poyntongate, 135 yd downstream from the park wall, shows blue shale with large ironstone nodules, with casts of Carbonicola aff. pseudorobusta and Spirorbis sp. No details exist of the remaining measures up to the Accommodation Mine, which is 261 ft above the Redacre Mine at Anson Pit, Poynton.

The Accommodation Mine is well developed throughout the area, and consists essentially of two leaves, both averaging 3 ft in thickness, separated by a variable parting. When traced from west to east this parting tends to increase in thickness; thus at Lawrance Pit, Poynton, it is 3 ft thick, and at Canal Pit, Poynton, 24 ft. Although only the upper leaf of this seam is really the equivalent of the New Mine of the Manchester Coalfield, the whole seam has been called New Mine at Woodley and Norbury. Hull (in Hull and Green 1866, p. 30) states "The New Mine, near its outcrop, consists of two seams, the upper one of which may be seen in the railway cutting by the canal aqueduct. It is here separated from the lower by 16 yards of strata, nearly the whole of which thins out in the distance of a quarter of a mile westward." This observation could not be verified during the resurvey; for the crop of the coal is no longer visible in the railway cutting. The seam was more recently worked from a drift on the south side of the railway line, and the following section is recorded on the abandonment plan: blue metal, over top coal 39 in, warrant 16 in, middle coal 18 in, warrant 9 in, and bottom coal 3 ft.

South of the Marl or Accommodation Fault a small area of Accommodation Mine was worked as far as Poynton Brook, but no information exists regarding the seam south of this line. Bearing in mind its thickness, it must be presumed to have been worked out in this area long ago. In the northern part of the area the 'Queen Mine', a seam believed to be the New Coal, was worked from Queen Pit, High Lane; and in the Torkington area a coal worked from a pit at Clough House is believed to be the same seam. Hull also states (in Hull and Green 1866, p. 31) "Under Marsden House the New Mine is cut through at a depth of 70 yards from the surface by a 'sand-fault', or ancient channel hollowed down through the strata, and filled in with sand." This occurrence cannot be verified from the abandonment plans.

The measures from the Accommodation up to the Reform or Waterloo Mine are unexposed, except for a pink-stained sandstone seen in Norbury Brook. In the north the seam has the section top coal 21 in, earth 9 in, bottom coal 11 in. In the area between Norbury Brook and the Worth Hall Fault the seam is 30 to 34 in thick, but followed south of the Worth Hall Fault it thins west of a north-south line through Petre Bank. The southerly extent of this impoverishment is not known, nor if it has ever been worked south of the Marl Fault.

The measures lying between the Reform and Gees coals are partially exposed in Norbury Brook, where a pink and grey flaggy sandstone is visible from 140 to 190 yd west of the aqueduct portal. The Gees or Silver Mine lies 30 to 40 ft above the Reform Mine and is developed throughout the area north of the Marl Fault. A narrow tongue of impoverishment in this coal extends east-northeastwards from Lady Pit, Poynton, for a distance of 600 yd; and at Quarry Pit, which lies within this area, the coal is only 8 in thick. Elsewhere the seam maintained a workable thickness. At Norbury Bye Pit it comprised three leaves, the upper two being locally called the Silver Coal and the bottom leaf the Little Coal, the section being: rock, over Silver Mine, consisting of inferior coal 18 in, floor 18 in and coal 12 in; on floor 15 in on Little Mine, coal 18 in, and floor 2 ft. Within the Poynton royalty the seam is noted as being 42 in thick in the shaft sections, but a detailed section taken from the mine plans is coal 2 ft, dirt 1 ft, on coal 16 in.

In the Norbury shaft the Gees or Silver Mine is succeeded by 96 ft of 'blue metal' with bands of sandstone, and these measures are in turn overlain by a sandstone about 150 ft thick which passes up into the seatearth of the Five Foot Coal. The measures in Norbury Brook, however, do not resemble this section, for at a point 300 yd west of the canal portal a series of alternating grey mudstones and flaggy sandstones lying about 100 ft above the Gees Mine can be seen, and these are succeeded by a sequence of thin coals, carbonaceous shales and seatearths. The following section was exposed in a gully [SJ 9485 8459] 350 yd W.S.W. of the aqueduct near the Middlewood curve: grey mudstone with ironstone nodules 2 ft, over carbonaceous shale 6 in, carbonaceous shale and fireclay 15 in, seatearth 2.5 ft, coal 3 in, seatearth 2.5 ft, carbonaceous shale 2 in, coal 2 in, carbonaceous shale 8 in, carbonaceous shale with fireclay 18 in, and coal (base not seen) 6 in. At a point 246 yd west of the aqueduct-portal strata with a coal seam, truncated by a northerly-throwing fault, are exposed with the following section: carbonaceous shale and fireclay 1 ft, over ironstone nodule band 2 in, fireclay 4 in, carbonaceous shale 3 in, coal 4 in, carbonaceous shale 2 in, shale 4 in, coal 10 in, fireclay 4 ft, on grey sandy rooty mudstone containing large ironstone nodules. Probably both of these sections are of the same seam—one not shown in the Norbury Shaft section—which lies 70 to 80 ft above the Silver Mine. A composite section of 'Coal Series at Norbury' listed in Hull's MS book shows two banded seams in the sequence between the Gees and Five Foot coals. The lower 'Dirt Mine' is described as dirt and coal 14 ft 4 in thick lying some 66 ft above the Gees Mine; the upper 'Dirt Mine' as dirt and coal 19 ft thick, lying 60 ft below the Five Foot Coal.

The measures between the Gees or Silver Mine and the Five Foot are poorly exposed, and they show a decrease in thickness when traced eastwards and south-eastwards from Norbury Colliery, possibly because the thick sandstone at the top of the group thins in those directions. A 2-ft coal seam occurs 35 to 50 ft below the Five Foot in both Quarry and Lady pits, where it is known as the Two Foot.

This seam is not present in the Norbury Shaft, but was proved in the Poynton Bore. It is interesting to note the development of this seam in this locality where both the lower seams, the Gees and Reform, are impoverished.

The Five Foot Mine was a profitable seam throughout the area and was exhausted in the last century. A section recorded near the Vernon Shaft reads: black metal over coarse coal 8 in, top coal, soft, 10 in, hard coal 27 in, soft coal 5 in, a parting, soft coal 17 in, and soft thill (seatearth).

Strata close above the Five Foot are exposed in the Middlewood Brick Pit, where the following section was measured 270 yd east of Middlewood station: grey-blue mudstone with ironstone nodules 6 ft, over contorted blue shale (crozzle) 3 in, and blue shale with large ironstone nodules containing mussels 1 ft. The bottom bed yielded Carbonicola aff. acuta (J. Sowerby), C. cf. rhomboidalis, Curvirimula cf. candela, Geisina arcuata, and Rhizodopsis sp. [scale]. Exposures round the edge of this brick pit are discontinuous, but show an alternating sequence of mudstone, sandstone and a few thin coals and seatearths. The main cut, as abandoned, showed the following beds: dark grey mudstone with plant debris 10 ft, grey sandstone with much carbonaceous matter 9 in, coal 4 in, grey rooty mudstone, replaced laterally by rooty sandstone 10 ft, grey banded nodular sandy mudstone with much plant debris on bedding-planes 7 ft, black banded mudstone 7 ft, dark grey nodular mudstone with ironstone nodules and few plants 8 ft, alternating bands of grey nodular sandy mudstone and shaly sandstone 10 ft, grey-brown massive sandstone showing slump structures 3 ft, alternating bands of grey nodular sandy mudstone and shaly sandstone 4 ft. The following plants were collected from this section: Alethopteris lonchitica, Calamites sp., Lepidodendron ophiurus and Lepidostrobus lanceolatum. Exposures in this group also occur in Norbury Brook within the triangle formed by the railway lines at Middlewood. The succeeding measures up to the Four Foot seam are not exposed.

The Four Foot Mine maintains a thickness between 3 ft 8 in and 4 ft throughout the area, and has been largely worked out. A section measured in the area north of the Park Fault reads strong grey metal over ironstone 3 in, black metal 19 in, good coal 3 ft 81 in, and strong grey thill (seatearth). Both the Five Foot and the Four Foot coals were worked in a northerly direction from Norbury Colliery, the limit of extraction lying roughly along the line of the New Mills and Heaton Mersey railway. An old plan, now deposited at the Mining Records Office, National Coal Board (North Western Division), shows deep levels in both seams and adds " ... two levels, one in the Four Foot Mine and the other in the Five Foot Mine, which have been driven to a supposed 'Torkington Fault' and which is further north than any drivings we have taken in working these two mines." There is no other information about these seams in the Torkington area, though both must crop out.

A seam known locally as the Norbury Two Foot lies some 30 ft above the Four Foot, and has a thickness of approximately 2 ft in the vicinity of Lady and Quarry pits, where it has been worked. A section shows metal roof, over coal 22 in, on seatearth.

Some 90 ft or so above the Norbury Two Foot lies the Great Mine. Information about this seam is very scanty, the section in the Norbury Bye Pit shaft being coal 3 ft, on dirt 1 ft, and inferior coal 2 ft 5 in. Old shallow crop workings in it extend from west of Correction to Oxhey, north of the Stockport–Buxton railway line. There is no evidence that it was worked to the deep at either Poynton Colliery or Norbury Colliery. The seam is not recorded at either Quarry or Lady pits; the top seam recorded in either case, lying 70 ft above the Norbury Two Foot, is 18 in thick. It is possible, however, that this seam may be the local representative of the Great Mine. In the shafts of Lawrance and Park pits the Great Mine is cut out by the Park Fault, which intersects both shafts and has a downthrow of 100 ft in a northerly direction. More recently a trial pit for opencast mining showed the following section: dark grey shale 6 in over coal 14 in, seatearth 12 in, coal 29 in, and shale. A search on the spoil-heap of Quarry Pit yielded many solid pyritized mussels, the exact horizon of which is not known but is thought to be a short distance below, or immediately above, the correlative of the Great Mine. The fauna comprises Carbonicola cf. martini, C. aff. oslancis, C. cf. rhomboidalis and C. sp. intermediate between oslancis and bipennis—characteristic of the lowest part of the A. modiolaris Zone.

A sandstone overlies the Great Mine, and in the Norbury Bye Pit shaft is 63 ft thick. It is well exposed above the Middlewood road in Norbury Hollow and in the railway cutting 413 yd north-west of Middlewood station. It is pale grey or pink in colour and is medium-grained. In the shaft of Norbury Bye Pit the succeeding 78 ft of measures up to the Cannel Mine are shales with two thin seat-earths and occasional beds of sandstone—a succession which cannot be reconciled with the exposures in Norbury Brook or in the railway cutting from Norbury Hollow bridge south-eastwards to the crop of the Great Mine, where much sandstone is exposed. The outcrops show a hard massive pale grey, commonly pink, medium-grained sandstone with flaggy bands and subsidiary bands of purple-stained mudstone, and the sandstone is often found to contain haematitized pellets of clay-ironstone. Hull's composite section (Hull and Green 1866, p. 30) shows a sandstone some 120 ft thick overlying the Great Mine and extending up to within 19 ft of the Norbury Cannel Mine. While the surface evidence does not suggest such an absolute sandstone sequence there is no doubt that in the Norbury Brook section sandstone is certainly the dominant member of the succession up to within a few feet of the Cannel Mine. Farther south an exposure of shale in the bank of the brook in Potter's Cleugh, 200 yd S. of W. from the road junction at Greenlane and lying some 100 ft above the Great Mine, yielded Carbonicola aff. oslancis and Naiadites sp., suggesting a level in the basal part of the A. modiolaris Zone.

The Cannel and Sheepwash coals are both split seams. The lower, the Cannel, was recently exposed in a pit [SJ 9383 8489] made by the Opencast Executive near Cawley Lodge: grey shale 2 ft over coal 15.5 in, dirt 6 in, cannel coal 7 in, shale 1 in on seatearth. The shaft section of Norbury Bye Pit shows the seam to be 39 in thick and to contain two shale partings and a band of cannel. The seam was worked on a small scale north of the Robin Hood Inn on the Buxton road. The Sheepwash Mine consists in the Norbury shaft of three thin leaves of coal separated by shale partings of 22 and 33 in. It was also exposed in a pit made by the Opencast Executive near Cawley Lodge; sandstone over smut 16 in, shale 15 in, coal 17 in, and seatearth. The area west of Cawley Lodge is pitted with the remains of many shallow crop workings in this seam, which suggests that the coal was thicker than that found by the Opencast Executive. A seam named the Poynton Ten Foot was worked on a small scale from Lawrance Pit, a section showing sandstone over clod 10 in, coal 27 in, dirt 12 in, coal 14 in, dirt 27 in, coal 29 in, and shale. It is likely that the Sheepwash and Cannel coals are united at depth to form the Poynton Ten Foot. R.H.P.,

Middle Coal Measures

East Manchester Coalfield

The measures between the Top and Bottom Shuttles coats ((Figure 5)) are not exposed, the crop of the Top Shuttles being marked by old coal diggings. The succeeding measures up to the Town Lane Mine are poorly exposed in the River Tame near Haughton Green, only grey mudstone with sandy bands and sandstones being visible in a few places.

The Town Lane Mine was previously worked from both Denton and Bredbury collieries. At Denton, where the workings were more extensive, the seam was 40 in thick. At Bredbury, Lingard Lane Pit, the workings all lie north-northeast of the shaft; the seam comprises bone coal above separated by a parting from coal below, the whole being 24 to 33 in thick; the roof is of hard metal and the floor of soft grey holing dirt. There is thus evidence of south-westerly deterioration in this seam.

The Foxholes or Huncliffe Rock, about 60 ft thick, is exposed in the River Tame; the underlying Mary Mine is not exposed. Details of the strata from the Cooks Folly or Park Mine up to the Old Jet Amber are given in the shaft section of the Lingard Lane Pit, Bredbury Colliery (Figure 5), the Hard, Furnace and Roger coals being substantial seams formerly worked extensively. The thickness of the Cooks Folly Mine varies greatly, for example in the Lingard Lane shaft section from 3 to 51 in; and farther north at Denton 20 in is recorded. The. Hard Mine is characterized by many variable partings: a section at Lingard Lane Pit, Bredbury

Colliery, shows rock roof over dark metal 1 ft, parting 1 in, top coal 16 in, parting I in, middle coal 15 in, parting 1 in, bottom coal 31 in, on warrant. At Denton Colliery the recorded thickness is 28 in, but whether this is the overall thickness of the seam or merely that of the bottom coal in the above section is not known. The succeeding Stubbs Mine at Lingard Lane Pit, locally known as the Colonel Mine, comprises a sequence of thick seatearths with coal streaks. The Bardsley Rock is well developed and exposed in the Tame section, where it is a massive purple sandstone with partings of red sandy mudstone containing haematite nodules at the base.

The Lower and Upper Furnace seams lie 204 and 249 ft respectively above the Stubbs Mine at Lingard Lane Pit. The Lower Furnace Mine is only 15 in thick; the Upper Furnace or Albert Mine is 49 in thick, and was worked to a limited extent north of the Lingard Lane shaft. Here, as in the Manchester area, it was often referred to as the Furnace Mine. The Upper Furnace is recorded at Denton as 'bad coal' 2.5 ft thick. The shales above it contain a mussel band which is exposed in the Tame section, on the south bank 400 yd E.N.E. of Beight Bridge, where grey mudstone rests on dark grey shaly mudstone with Anthracosia sp.

The Roger Mine has been extensively worked throughout the area. Records of the seam show the presence of a thin parting, as in the following sections: Lingard Lane Pit, Bredbury Colliery, rock 8 in, over blue metal 4.5 in, coal 35 in, dirt 1.5 in, coal 19.5 in, on warrant; farther north at Denton Colliery, variable shale and rock over hard black shale 2 in, top coal 4.5 ft, parting 3 in, bottom coal 1 ft, on hard shale floor.

The Ashton Great Mine is well developed in the north, but is impoverished south of an east-west line about 500 yd north of the Lingard Lane shafts. It was extensively worked at Denton Colliery, where the section was hard rock over hard black shale 1 in, top coal 2 ft, parting, middle coal 2.5 ft, parting, bottom coal 2 ft, on soft shale floor. In the shaft the seam is recorded as being 3.5 ft thick, but this may only represent the thickest individual leaf of coal. A small area of the seam in the vicinity of Castle Hill was worked from the Lingard Lane shafts, where its section was red rock, over coal 6 ft, on a floor of earthy warrant. A section of the seam in the impoverished area is afforded by Lingard Lane shaft, in which 30 ft of sandstone overlie the coal, 7.5 in thick. It is possible that a washout in the coal is associated with this sandstone.

The succeeding Old Jet Amber Mine is typically a split seam in the area; at Bredbury the upper leaf is 26 in thick and the lower 18 in. The coals above the Old Jet Amber are cut out at Bredbury by the unconformity at the base of the Permian. At Burton Nook Pit, Denton, two higher coals are recorded, the Sod Mine 6 ft thick and the New Jet Amber Mine 21 ft thick; but otherwise no details of the 250 ft of strata between the New Jet Amber and the base of the drift are available. Two coals are said to have been worked on the north bank of the River Tame 650 yd north-west of Beight Bridge, the upper seam being 3 ft thick. The precise horizon of these seams is unknown, but may be just below the Dukinfield Marine Band. R.H.P.

Poynton Coalfield

The most important record of the Middle Coal Measures is the log of the Poynton Bore (Appendix 1, p. 144); and this, with the fossil lists, has been so freely drawn upon for the general account that it is unnecessary to repeat the details here.

The measures between the presumed position of the Sutton Manor Marine Band and the Red Rock Fault are not well known at outcrop; and although exposures do occur in Norbury Brook and to a lesser extent in Ochreley Brook, it is not possible to observe the detailed sequence. A composite section recorded by Hull (in Hull and Green 1866, p. 30) shows that 630 ft of measures succeeding the Sheepwash Coal are present up to the Red Rock Fault, and this agrees closely with the thickness calculated from the map. The sequence quoted by Hull contains several coal seams, the thicker seams being named Mill Mine, Smithy Coal and Chapel Mine. There is evidence of several coal seams in the Norbury Brook section, but these cannot be identified. A coal partially exposed 100 yd N.E. of Can Wood is thought to represent the Mill Mine; Hull gave the thickness as 4.5 ft. The overlying measures are exposed beneath the footbridge at Norbury Mill, and 40 yd farther west afford the following section: blue shale with ironstone nodules, fish scales and poorly preserved Anthracosia 2 ft, grey nodular mudstone 3 in, hard blue shale with Anthracosia 3 in, grey sandy shale 3 in, blue shale with large nodular band 1 ft, grey mudstone 4 in, coal and carbonaceous shale 6 in, on seat-earth. The shales yielded the following fossils, which are considered to indicate the upper part of the A. modiolaris Zone; Anthracosia aff. phrygiana, Naiadites?, Rhizodopsis [scale] and Neuropteris gigantea. Another coal is partially exposed 200 yd W.S.W. of Carr Wood in the banks of the stream, with a barren blue shale roof. Remains of old shallow workings are present along the banks of the stream west of this point, and this seam may be the 'Chapel Mine' of Hull's section (1866, p. 30).

Of the measures thought to lie above the Sheepwash Mine there are a few exposures in Ochreley Brook, east and south-east of the disused station at Hazel Grove. Shallow workings show the position of an outcrop a short distance east of Fir Tree cottage, but no exposure of the coal was seen. To the south-east at Oxhey, shallow workings exist in a seam reputed to be 2 ft thick. The exact horizon of these measures is not known, the only fossils found being Lepidodendron ophiurus, Neuropteris heterophylla, Spirorbis sp. and fragments of Naiadites. The plants are more likely to be of Westphalian B age than Westphalian C. R.H.P., B.J.T.

References

BROCKBANK, W. 1883. On the Levenshulme Limestone; a section from Slade Lane towards the east. Mem. Proc. Manch. Lit. Phil. Soc. (3), 8, p. 125

BROCKBANK, W. 1890. Entomostraca and Annelida in the Levenshulme Mottled Limestones. Mem. Proc. Manch. Lit. Phil. Soc. (4), 4, p. 47

BROCKBANK, W. and DE RANCE, C. E. 1891. Notes on a Geological Section in the railway cutting from Levenshulme to Fallowfield. Mem. Proc. Manch. Lit. Phil. Soc. (4), 4, p. 282

COPE, F. W. 1948. Correlation of the Coal Measures of Macclesfield and the Goyt Trough. Trans. Inst. Min. Eng., 108, pp. 466–83

DE RANCE, C. E. 1893. On the boring for coal on the Freeholders' Estate at Hazel Grove. Trans. Manch. Geol. Soc., 22, pp. 452–8

EAGAR, R. M. C. 1952. The succession above the Soft Bed and Bassy Mine in the Pennine region. Liv. and Manch. Geol. J., 1, pp. 23–6

EAGAR, R. M. C. and PRESSLEY, E. R. 1954. A Section in the Lower Coal Measures near Pott Shrigley, Cheshire. Mem. Proc. Manch. Lit. Phil. Soc., 95, pp. 66–8

EDWARDS, W. and STUBBLEFIELD, C. J. 1948. Marine bands and other faunal marker-horizoru in relation to the sedimentary cycles of the Middle Coal Measures of Nottinghamshire and Derbyshire. Quart. J. Geol. Soc., 103, pp. 209–60

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

HULL, E. and GREEN, A. H. 1866. The Geology of the country around Stockport, Macclesfield, Congleton and Leek. Mem. Geol. Surv.

JONES, T. R. and KIRKBY, J. W. 1890. On the ostracoda found in the shales of the Upper Coal Measures at Slade Lane near Manchester. Trans. Manch. Geol. Soc., 21, pp. 137–42

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

MAGRAW, D. 1961. Exploratory Boreholes in the Central Part of the South Lancashire Coalfield. Trans. Inst. Min. Eng., 120, pp. 432–45

MAGRAW, D. and CALVER, M. A. 1960. Coal Measures proved underground in cross-measures tunnels at Bradford Colliery, Manchester. Trans. Inst. Min. Eng., 108, pp. 475–92

POOLE, E. G. and WHITEMAN, A. J. 1955. Exploratory Boreholes in the Prestwich Area of the South-East Lancashire Coalfield. Trans. Inst. Min. Eng., 114, pp. 291–318

POCOCK, T. I. 1906. The Geology of the Country around Macclesfield, Congleton, Crewe and Middlewich. Mem. Geol. Surv.

ROEDER, C. 1892A. Notes on the Upper Coal Measures at Slade Lane, Burnage (with section). Trans. Manch. Geol. Soc., 21, pp. 114–35

ROEDER, C. 1892a. Further notes on the Upper Coal Measures at Slade Lane, Burnage. Trans. Manch. Geol. Soc., 21, pp. 199–203

STUBBLEFIELD, C. J. and TROTTER, F. M. 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., SHERLOCK, R. L. and WRIGHT, W. B. 1931. The Geology of Manchester and the South-East Lancashire Coalfield. Mem. Geol. Surv.

TROTTER, F. M. 1953. Exploratory Borings in South-west Lancashire. Trans. Inst. Min. Eng., 112, pp. 261–284

WEIR, J. 1960. A Monograph of British Carboniferous Non-marine Lamellibranchia. Part X. Palaeont. Soc.

Chapter 4 Permo-Triassic rocks

Introduction

The Permo-Triassic rocks underlying the district form part of the northwestern margin of the great Permo-Triassic basin of Cheshire and South Lancashire. In the northern part of this basin they are depicted on six one-inch sheets, which fall into two groups. The northern group comprises Formby (83), Wigan (84) and Manchester (85); the southern, Liverpool (96), Runcorn (97) and Stockport (98). Since the survey of the Stockport Sheet completes this block of maps, it is convenient to review the stratigraphy of the Permo-Triassic rocks there displayed, which show considerable lateral variation.

The divisions mapped within the three northern sheets are as follows:

• Triassic
• Keuper Marl (undivided)
• Keuper Sandstone
• Bunter Sandstone
• Permian
• Manchester Marl
• Collyhurst Sandstone
• Those within the southern three sheets are:
• Triassic (Keuper)
• Middle Keuper Marl
• Lower Keuper Saliferous Beds
• Lower Keuper Marl
• Keuper Waterstones
• Keuper Sandstone
• Triassic (Bunter)
• Upper Mottled Sandstone
• Pebble Beds
• Lower Mottled Sandstone (thin or absent from
• Stockport district)
• Permian
• Manchester Marl
• Collyhurst Sandstone (with marl)

In both the northern and southern districts the Permo-Triassic rocks appear to represent a conformable sequence. Deposition commenced after the Hercynian earth-movements had ceased and after denudation had removed vast thicknesses of Carboniferous rocks from the uplifted areas; and continued without orogenic interruption into the succeeding Rhaetic times. The Permo-Triassic sediments are essentially of continental type. The hypothesis which has been advanced of movement along faults during Collyhurst Sandstone times must be discarded, since the evidence on which it was based, namely abrupt variations in the thickness of the Collyhurst Sandstone, has been shown by Poole and Whiteman (1955, pp. 33–41) to be due to irregularities of the old land surface on which this rock formation rests.

Sandstone bands containing pebbles occur at three horizons: at the top of the Collyhurst Sandstone or in the Manchester Marl a short distance above, as 'Pebble Beds' in the sub-division of the Bunter, and at the base of the Keuper Sandstone. The pebbles at all three horizons are scattered throughout a sandstone which contains many rounded grains of quartz, although locally there may be a concentration of pebbles in lenticular layers of shingle. The pebbles are predominantly of quartz and quartzite, but also include rare basic igneous rocks. The bed at the base of the Manchester Marl at Stockport contains a substantial proportion of indurated greywackes and other metamorphic rocks. Viewed regionally the pebbles disappear towards the north and north-west at all three horizons; increasing abundance towards the south indicates a southerly source.

The Bunter Pebble Beds are, in the southern group of one-inch sheets (96, 97, 98), easily distinguished from the pebble-free sandstones above and below. Although it is known that scattered pebbles occur in the Bunter Sandstone which crops out within the boundaries of the three northern sheets (83, 84, 85), it was not possible to map the Pebble Beds as a distinctive formation. Furthermore, no Pebble Beds have been recognized farther north in the Bunter of the Fylde district and the Furness district of North Lancashire, nor still farther north in the Bunter of Cumberland.

Another lateral change in a northerly direction is to be noted in the Keuper Sandstone. In the southern group of sheets the junction between the Keuper and the Bunter is sharp—indeed not infrequently it is represented by a hard conglomerate lying on soft sandstone: in the Formby and Wigan country, however, the Keuper Sandstone is almost indistinguishable in character from the Bunter Sandstone. Again, the Waterstones, an easily recognized formation in the Midlands and in the area covered by the southern group of sheets, loses its distinguishing characters in the Formby district, where it cannot be mapped separately from the Keuper Marl.

There are also lateral changes in an east-west direction. Thus in the Runcorn district to the west numerous recent boreholes have shown that the beds of the Manchester Marl become progressively more sandy when traced in a westerly direction, until north and north-west of Widnes they are wholly sandstones; and from thereabouts westwards to Liverpool the sequence below the Pebble Beds is represented by sandstones of approximately 1,200 ft thickness which have long been known as Lower Mottled Sandstone. At Liverpool these are the combined lateral equivalents of the Collyhurst Sandstone, the Manchester Marl and the Lower Mottled Sandstone of the Warrington–Manchester area. The Lower Mottled Sandstone of the last mentioned area is not only thin—nowhere more than 200 ft—but south-east of Manchester it is so attenuated that in the neighbourhood of Stockport it cannot be recognized as a mappable division. In the Stockport area, in consequence, the Pebble Beds are shown directly overlying the Manchester Marl. F.M.T.

Permian

Collyhurst Sandstone

Over the Lancashire and Cheshire Plain the Collyhurst Sandstone, the typical development of which is at Collyhurst, Manchester, varies from a maximum thickness of 2345 feet in Formby No. 1 Well (Wray and Cope 1948, p. 5) to nothing at Prestwich (Poole and Whiteman 1955, pp. 33–41). In the Stockport area the variation is from an estimated 480 ft at Levenshulme and 500 ft in bores in the centre of Stockport to more than 900 ft at Poynton, where the formation was penetrated in two bores (see Plate 4, nos. 20, 21). Binney (1846, pp. 12–26) and Hickling (1918, p. 189) related the variations to postulated post-Collyhurst, pre-Manchester Marl faulting, and this explanation was elaborated by Tonks and others (1931, p. 174) to include faulting during deposition of the Collyhurst Sandstone. Poole and Whiteman (1955, p. 41) refute this theory—except in the case of the Bradford Fault—and claim that variations in the thickness of the formation are unrelated to faulting (see pp. 87).

The Collyhurst Sandstone is soft, uncemented, free from pebbles, and strongly false-bedded. The foreset beds in the false-bedded units commonly consist of thin layers with fine angular grains, abruptly alternating with layers of coarse rounded grains with frosted surfaces suggesting wind-etching. The red colour of the rock is due to a pellicle of red iron oxide on the grains.

In the bores at Portwood Gas Works [SJ 9005 9066] and at Hazel Grove (Plate 4. no. 19) the sandstone is more compact and fine-grained towards the base. Beds of mud stone (frequently termed 'marl' in borehole logs) may occur at any horizon. A fairly persistent bed of red mudstone is found in the Stockport area and has been referred to as the Lower Stockport Marl (P. F. Kendall in MS record), but it is doubtful if this term can have a precise application (see Plate 4). The open texture and lack of cement between the grains of the Collyhurst Sandstone make it an ideal aquifer; and its massive character, coupled with extreme ease of excavation, enables large unsupported cavities and tunnels to be made in it.

Some previous publications (e.g. Wray 1948, p. 61) refer to a breccia at or near the base of the Collyhurst Sandstone; and H. C. Versey (in Evans and Stubblefield 1929, p. 306) mentions an 'Upper Breccia' which intervenes between the Manchester Marl and the Collyhurst Sandstone. The basal breccia described at Levenshulme by Roeder (1890B, p. 615) and at Torkington by Hull (in Hull and Green 1866, p. 35) is of local derivation, with pebbles of clay-ironstone in part oxidized to haematite, and angular fragments of rocks from the Coal Measures. The 'Upper Breccia' is a single persistent bed of conglomerate, containing far-travelled pebbles of southern origin. This bed is more correctly classified with the Manchester Marl, and is discussed under that heading below.

Details

Exposures along the River Tame

North-east of Stockport the River Tame meanders over the outcrop of the Collyhurst Sandstone for two and a half miles, but good exposures are rare. In the west bank, north of the railway bridge at Tiviot Dale station, are 12 ft of strongly false-bedded bright red sandstone. The larger grains, almost exclusively of quartz, are well-rounded; they tend to occur in thin bands a quarter to half-an-inch apart alternating with fine-grained material, and in each layer there is upward grading from coarse to fine: large grains also occur in lenses: pebbles are absent. Upstream towards Reddish the only exposure deserving mention is at the foot of a gully leading into the Tame from the east, almost opposite Willow Grove Cemetery, South Reddish; here the dip is at a low angle, a little south of west. In the river above Reddish Vale lying just below Beight Bridge is a section first described by Binney (1855, p. 209) in which the Collyhurst Sandstone rests unconformably upon Coal Measures. Workings from Lingard Lane and Burton Nook collieries pass beneath the featheredge of the Collyhurst Sandstone, proving that the eastern boundary of the Permian rocks hereabouts is not a faulted junction as it is to the south. A bore near Reddish Junction proved about 300 ft of the sandstone, and Lingard Lane No. 1 Pit of Bredbury Colliery (p. 130) went through 118 ft of "red rock with yellow balls" beneath about 150 ft of glacial drift before reaching Coal Measures at 268 ft, on which the Collyhurst Sandstone was seen to lie with an uneven base.

Exposures along the River Goyt

The Goyt flows on Collyhurst Sandstone from where it crosses the Red Rock Fault about 500 yd S.S.E. of Goyt Hall Farm to a point near Tiviot Dale railway station, where a fault downthrowing west brings. in the Bunter Sandstone. At this point the Goyt and Tame, which have so far meandered in wide sweeps across the soft Collyhurst Sandstone, join together to pass through the centre of the town in a narrower valley and on a straighter course. Upstream from Tiviot Dale there are numerous exposures. Between Portwood Gas Works and Vernon Park 20 ft of sandstone is visible in the south bank, and a similar thickness is seen below Bredbury Hall. The great width of outcrop—a mile and a half hereabouts—is due to two large faults throwing, down east, one passing east of Portwood Gas Works and the other through the-grounds of Bredbury Hall. It was the lack of evidence, now available from bore-holes, that led the earliest surveyors to assign a thickness of 1500 ft to the sandstone (Hull and Green 1866; Horizontal Sections of Geological Survey, Sheet 65); whereas it is probably not much more than 600 ft thick to the east of Stockport.

Torkington area

The basal beds of the Collyhurst Sandstone are exposed in Ochreley Brook half a mile above Torkington, where a red breccia overlain by more than 5 ft of sandstone with marl bands rests upon reddened shales and sandstones of the Coal Measures. The actual junction is not seen. The breccia consists of locally-derived material, including fragments of reddened Coal Measures. and haematite pebbles probably derived by oxidation from sideritic mudstonee nodules in the Coal Measures. The dip of the Permian strata is 10° northwards; that of the Coal Measures in the vicinity is 20° to the south-west. In Torkington Brook at a stream confluence 640 yd above Danbank Bridge the section is as follows: boulder clay on sand and gravel 20 ft, over red marly sandstone with bands of pebbles 4 ft, and red ill-graded sandstone passing down into breccia 1 ft.

Norbury Brook

The drift-covered outcrop extends from just west of Norbury Bridge to the foot of Long Plantation south-west of Norbury Mill. Binney (1846, pp. 12–26) saw the Manchester Marl here, but now the only exposures are of Collyhurst Sandstone, somewhat more marly than at Stockport. These exposures. are between Towers Farm and Long Plantation, where also are found the most westerly exposures of Coal Measures shale. The Coal Measures, which are broken, dip eastwards for a few yards, and farther east take on the regional westerly dip.. Binney (ibid.), judging by his sketch of this section illustrating the description, apparently regarded it as an unconformable junction between Carboniferous and Permian, though the actual junction was not seen; but the shattering of the mud-stones and their reversal of dip point to a fault, a view strengthened by the fact that less than 100 yards upstream from the plantation the mudstones of the Coal' Measures are of normal grey colour, and a coal seam crops out. If the junction were unconformable these measures might be expected to lie well within the zone of reddening beneath the base of the Permian.

North-west of Stockport

The only recorded exposure of Collyhurst Sandstone• is in the Levenshulme railway cutting, in which the outcrop extends from a point 170 yd west of where the Fallowfield–Levenshulme railway crosses the Crewe line north of Mauldeth Road Station to about 330 yd east of this crossing. Roeder (1891) calculated the thickness of the Collyhurst Sandstone to be 480 ft. At the base is a conglomerate, varying in thickness up to 12 inches, which is calcareous,. with cavities filled with calcite, and contains marl, well rounded quartz grains, and brownish clay-ironstone pebbles—material presumably derived locally from Upper Coal Measures containing limestones. Brockbank and De Rance (1891, p. 282) recorded the bottom few feet of the Collyhurst Sandstone in this section resting upon brecciated purple shales of the Carboniferous.

West, centre and south of Stockport

Hull (in Hull and Green 1866, p. 34) wrote of a deep pit at Hope Hill in which 'Permian Sandstone' was worked for moulding sand. Apart from this, details in this area are based almost entirely on records of boreholes. The thickest development of sandstone, 930 ft, was found in the Poynton Station Bore ((Plate 4), no. 20). Here there was no record of a basal breccia; nor was one proved in the Poynton Borehole (p. 144), where the total thickness, 908 ft, was penetrated by rock-bit without coring. Less than a mile to the north the Hazel Grove Bore ((Plate 4), no. 19) proved the thickness to be about 630 ft, the basal 180 ft being described by the driller as hard and close-grained. A total thickness of 502 ft was proved in a well at the Unicorn Brewery, Lower Hill-gate, sunk in 1930 ((Plate 4), no. 10). The bore at Portwood Gas Works (1932) proved the lower 240 ft of the Collyhurst Sandstone with a thin basal conglomerate resting on Coal Measures: the bottom 70 ft was described by the driller as 'stronger red sandstone' (compare Hazel Grove Bore above). Several bores, mainly for water, have proved the upper part of the sandstone, and in a number of these a bed of red marl or mudstone, varying in thickness from a few feet to more than 50 ft, appears about 50 to 100 ft below the Manchester Marl. Some sections of these bores are shown in (Plate 4).

Manchester Marl

The lower part of the Manchester Marl is a series of red calcareous mud-stones with limestone bands. These are equated with a narrow group of marine Permian strata widespread throughout north-west England, which constitutes an important marker horizon in the Permo-Triassic rocks of the region. Its most northerly outcrop in Lancashire is in Skellow Clough (Jones and others 1938, pp. 97–98) where 6 ft of dolomitic limestone rests upon red marl with marine fossils. The fauna includes a similar assemblage to that collected from the Manchester Marl of Manchester. Still farther north, dolomitic limestone with Permian marine fossils is found in the Vale of Eden, near Whitehaven, in the Barrow-in-Furness area and in Northern Ireland.

The proved occurrences of Manchester Marl are confined to the northeastern sector of the district. Although the base of the formation is generally well defined, the top is not, for the fossiliferous marls pass up into the overlying Bunter by becoming sandier and developing sandstone layers. Indeed, the uppermost transition beds between the Manchester Marl and the overlying Bunter Pebble Beds may be the lateral equivalent of part of the Lower Mottled Sandstone as defined in areas to the north and west (but not to the south); but failing absolute proof of this it is convenient to group these with the Manchester Marl, and to take the top of this where unmistakable pebby sandstone of the Bunter Pebble Beds appears. Plate IV shows a variation in thickness of the Manchester Marl from 123 ft at the Poynton Bore to upwards of 330 ft at the Albion Flour Mill Bore. At Broadstone Spinning Mills (P1. IV, no. 1) the top of the Manchester Marl is taken at the base of the pebble-free sandstone 20 ft thick which intervenes below the Pebble Beds. The maximum thickness given above is more than the maximum given for the Manchester area (Tonics and others 1931, p. 166); but as the method of determining the top is entirely arbitrary, little can be deduced from this except perhaps a hint of southerly thinning towards the Poynton area. There is no proof that, within the Stockport district, the Manchester Marl dies out completely towards the south as it does to the west of St. Helens (One-inch Sheet 97: Runcorn). It is not present, however, among the rocks which crop out around the southern part of the Cheshire Basin and in the Midlands. At or near the base of the Manchester Marl is a bed of conglomerate, noted also in the Manchester district (conks and others 1931, p. 165), containing pebbles of rock derived from far outside the Region. The earliest mention of this bed appears to have been made by J. Dickinson (in Roeder 1890s, p. 615). The composition of the pebbles points to their derivation from one or more of the pre-Carboniferous ridges possibly in the Midlands. The conglomerate was proved immediately beneath the drift in No. 2 Borehole at the Co-operative Wholesale Society's Confectionery Works at South Reddish (p. 132). Here it contained pebbles of quartzite, vein quartz and metamorphic sandstone in a matrix of mudstones with much dolomitic material cementing and coating the pebbles. No record exists at Stockport of more than one bed of conglomerate containing far-travelled rocks, and it is therefore treated, in the absence of any more easily identified horizon in the numerous old and abbreviated records of wells in the town, as a local marker-bed. No regional significance is claimed for the bed as a marker.

Both the limestones and the associated calcareous mudstones in the lower part of the Manchester Marl are fossiliferous, with marine shells and fragments of drifted vegetation. The earliest systematic collections were made by J. W. Gray, P. F. Kendall and C. Roeder (Roeder 1890A, p. 536), and were submitted to H. B. Geinitz of Dresden, who considered that they were of Upper Zechstein age. Sherlock (1947, p. 114), in a review of the world's Permo-Triassic rocks, considered the Manchester Marl to have been laid down in a westerly arm or embayment of the Zechstein Sea, at a time when the formation of the Pennine Range was just beginning, and that the marine incursion ended the deposition of the Collyhurst Sandstone which, though probably partly laid down in water, is a terrestrial deposit. The earth movement responsible for the change of conditions may also have uncovered, by elevation and denudation, the source of the pebbles in the Stockport Conglomerate, and provided the energy for their transport to the Stockport area. The general features of the Manchester Marl are shown in Plate 4, which illustrates borehole sections in the Permian rocks.

Details

In the Levenshulme railway cutting described by Roeder (1890B, p. 619; 1892B, p. 109) the conglomerate at the base of the Manchester Marl overlies Collyhurst Sandstone. No detailed section of the conglomerate is given, but it may be deduced that it forms more than one layer in strata some 10 or 15 ft thick; a condition similar to that noted in the record of the Adswood Dairy Bore (Plate 4, no. 17). Where it crops out in the cutting about 150 yd west of the crossing with the main Crewe line, Roeder described it as "of green white and red colour, of very hard consistence and composed of subangular and pitted quartz and quartzite pebbles up to 2 inches long and 1 inch wide, the whole cemented together by carbonate of lime". A gap of 78 feet horizontally above the conglomerate represents about 20 feet of unexposed strata, and above this lie 40 ft of red calcareous marl with subordinate thin layers of limestone, calcareous sandstone and sandstone. The fossils collected are listed in the papers of Roeder (1890, 1892) and Geinitz (1890). Briefly, shells of Schizodus, Bakevellia [Gervillia], Turbo, Pleurophorus and Rissoa are common, such species as Rissoa gibsoni Brown and Bakevellia [Gervillia] ceratophaga (Schlotheim) being chiefly confined to the ferruginous (ochreous) beds, and absent from the marls and sandstones. Impressions of plants, including Voltzia, are confined to the red marls. Lenticular beds containing limestone nodules of all sizes up to 19 inches long were recorded at one horizon. The nodules are thickly coated on the outside with shells of marine organisms, and their interiors are in some cases filled with red clay also containing fossils. One sandstone bed contained well-preserved impressions of Schizodus. Another harder and more compact sandstone displayed such shallow-water phenomena as sun-cracks and ripple-marks.

An excavation at Robinson's Brewery in Lower Hillgate, Stockport, was examined by J. W. Gray in 1888, and the details were read to the Stockport Natural History Society in that year. He gave the section as follows:

A bore for water was subsequently drilled at the bottom of the excavation and this further section obtained:

If any examination of this hole was made by a competent geologist no record has been left; which is to be regretted since the marls both above and below the conglomerate are likely to have been fossiliferous. Specimens from the excavation were submitted to H. B. Geinitz, who named the following marine lamellibranchs: Bakevellia (Gervillia) antiqua Munster, Clidophorus pallasi De Vemeuil (synonymous with Cardiomorpha modioliforrnis King), Pleurophorus costatus Brown sp., Schizodus rotundatus Brown, S. schlotheimi Geinitz, cf. Edmondia elongata Howse, Astarte sp. Also present were the gastropods Rissoa obtusa Brown and Natica minima Geinitz; and the plants Annularia? carinata Gutbier (trace of), Asterophyllites spicatus Gutbier, Voltzia liebeana Geinitz, cf. Chondrus binneyi or male ^,catkin (?) of Voltzia liebeana, twig of Ullmannia selaginoides Brongniart (or Voltzia liebeana Geinitz). Guilielmites permianus Geinitz was also recorded, but this is now considered to be an inorganic structure and not a plant (Wood 1935). The 7-inch bed of limestone with Bakevellia was mainly composed of moulds of the fossil; and in the thin seams of fossils associated with a sandy limestone a little lower down, the shell was found in a particularly good state of preservation.

A development of marl below the conglomerate bed 'Clipper Breccia') is recorded in a number of bores in the northern and western purlieus of Stockport, notably the following (numbers refer to sites on Plate 4); Cheshire Sterilized Milk Co. (No. 8), Reddish Brewery (No. 5), Broadstone Mills (No. 1), Heaton Mersey Bleach Works (No. 7), and Tiviot Colour Works (No. 4). In the last-mentioned bore fossiliferous strata were found both above and below the conglomerate.

Rebuilding of a retaining wall 60 yards north-west of the steps leading from Stockport Parish Church to Millgate [SJ 8978 9054] temporarily exposed the following section in 1947:

The lowest bed contained Bakevellia antiqua (Munster) and Schizodus sp., Bakevellia antiqua (Munster), Edmondia?, Schizodus obscurus (J. Sowerby) and S. sp. were found in the lowest beds of the Manchester Marl in a gully [SJ 9174 8997] draining into the River Goyt 653 yd W. 16° S. of Goyt Hall Farm.

Limestone bands, or layers of limestone nodules, in the Manchester Marl are recorded from numerous bores throughout the Stockport area, and bands of sandstone or argillaceous sandstone are frequent. These increase towards the top of the formation as it passes upwards into the Bunter Sandstone.J.T., R.H.P.

Triassic

Bunter

The base of the Bunter, throughout the area of its occurrence west of the Pennines, is frequently found to be difficult to define. Even where the Manchester Marl is present, as in the Stockport area, no hard and fast line can be drawn between the rocks that are manifestly Permian on the evidence of their fossils, and those included by tradition and for convenience in the Trias. Red sandstone with pebbles is found almost immediately above the highest marl bed of the Manchester Marl, and although at one or two localities a few feet of sandstone without pebbles may intervene, there is no deposit which can be equated with the thin Lower Mottled Sandstone as defined in the Runcorn area (One-inch Sheet 97). E. Hull, in the original survey (Hull and Green 1866, p. 35), concluded that the Bunter (which he called the New Red Sandstone) was unconformable on the Permian below; but Gray and Kendall (1893) showed this to be a mistake, and modem evidence supports their view that the two formations are conformable.

The Stockport district is the farthest north in which subdivision of the Bunter has been attempted on the Geological Survey maps of north-west England. Pebble Beds are recognizable in the Manchester and Wigan districts, but there is nothing comparable with the coarse gravelly deposit typical of the Bunter Pebble Beds of the Midlands, and no outcrop is known that would be worth working for gravel. In the Stockport district the Bunter can be divided into a lower section with pebbles, albeit sometimes sporadic, and an upper section, the Upper Mottled Sandstone, free from pebbles.

The sandstones of the Bunter are current-bedded throughout. The sand grains are coated in varying degree with oxide of iron which gives colouration to the rock ranging from bright red through brown and yellow to grey. Red mudstone bands occur but are rare; on the other hand red mudstone pellets are a characteristic feature of the Pebble Beds. The Bunter as a whole is considered to be a terrestrial deposit, laid down in temporary sheets of water under predominantly arid conditions, the pebbles being brought from the south in times of flood. The total known thickness of the Bunter formation is about 1800 feet in the Stockport area; and it covers about one quarter of the district. Plate 4 illustrates the relationship of these rocks to the Manchester Marl below and the Keuper Sandstone above.

Bunter Pebble Beds

Generally speaking, pebbles are more abundant in the lower part, where they occur as lenticular bands of conglomerate and shingle, than in the upper part where they are sporadic. The pebbles are mainly of quartzite, mostly grey though there are red and purple varieties: vein-quartz pebbles are present but less frequently than those of quartzite; some basic igneous rocks and hard Lower Palaeozoic grits have been noted, and pellets of red mud-stone are common in bands or scattered singly throughout the formation. On the whole the Pebble Beds are rather more strongly cemented than the Upper Mottled Sandstone. The increasing abundance of the pebbles towards the south indicates a southerly source, and it is reasonable to suppose that they may have originated in the same general area, probably in the Midlands, as the pebbles in the conglomerate at the base of the Manchester Marl, which also contains, besides some igneous and metamorphosed sedimentary types, an overwhelming preponderance of quartz and quartzite.

Since bores for water usually obtain an adequate supply in Bunter rocks, within about 500 ft of drilling, and since no bore has, as yet, penetrated the whole thickness of Bunter Pebble Beds in search of minerals lower down, we have no precise measure of that thickness in the area: but to the west of Stockport, calculated on dip and breadth of outcrop, it must be at least 800 ft, and perhaps more. Outcrops of Pebble Beds are confined to the eastern half of the district, and most records come from the vicinity of Stockport. B.J.T., F.M.T.

Details

West of Stockport

In 1943 a bore [SJ 8621 9142], examined by Dr. D. A. Wray, at the works of the Renold and Coventry Chain Company to the east of Didsbury [SJ 8621 9142] proved 315 ft of red sandstone with pebbles mainly of quartzite, both in layers and scattered sporadically through the rock; marl pellets were noted in the upper part of the bore. Some distance south, on the north bank of the Mersey north of Cheadle, the bore at Heaton Mersey Bleach Works [SJ 8671 8999] penetrated 97 ft of Pebble Beds before entering Manchester Marl. The regional dip in the Stockport area is to the west-southwest, and these two bores are considered to be in the same outcrop of Pebble Beds, the eastern limit of this outcrop being indicated by the Stockport Sewage Works bore [SJ 8705 8975], which entered Manchester Marl beneath the drift. Not far to the east of the last-mentioned bore there must be a large fault throwing down east, for a second belt of Bunter rocks is proved, in bores and surface exposures, to run from the region of Hope Hill to Edgeley. This fault is probably the southern extension of the Pendleton Fault of Manchester, crossing the Mersey close to the intersection of the railway lines from Manchester to New Mills and from Stockport to Timperley. East of the fault, the bore at Squirrel Confectionery Works [SJ 8806 9026] penetrated 388 ft of Pebble Beds beneath 15 ft of drift. A bore at the Cheshire Sterilized Milk Factory [SJ 8839 9042] and another at Heaton Mersey sidings [SJ 8840 9032] proved 160 ft and 122 ft respectively of pebbly Bunter Sandstone overlying Manchester Marl. A short distance to the east a bore at Chetham's Brewery [SJ 8848 9035] proved Manchester Marl near the surface—brought up, it is thought, by a small fault throwing up towards the east-southeast.

The Pebble Beds crop out along the Mersey west of Stockport between Gorseybank and a point about 100 yd upstream from the Grenville Street bridge, and dip at 15° to 20° towards the west-southwest. West of Gorseybank the Upper Mottled Sandstone is exposed. Tunnels excavated in the sandstone below the hillside between Brinksway and Lark Hill road, and used as air-raid shelters during the late war, proved unfaulted Pebble Beds. From certain layers water-seepages deposit calcareous tufa on the tunnel sides, bearing witness to the hardness of Bunter water. Southward along the strike from Brinksway a group of bores at Edgeley Bleach Works [SJ 8848 8900] proved 481 ft of pebbly red sandstone, and another bore at Edgeley sidings [SJ 8805 8883] penetrated 424 ft of Pebble Beds in 1890, being later deepened by 200 ft, probably in the same rock. Thick drift to the south masks all outcrops of Pebble Beds in that direction. B.J.T.

North and centre of Stockport

The East and West Manchester faults (Tonks and others 1931, p. 162) probably become one north-west of Heaton Chapel, and the combined fault continues towards the centre of Stockport to cross the Mersey just west of the railway viaduct. Its effect is to throw Bunter down to the east against Permian rocks to the west. Thus, a third belt of Pebble Beds extends from west of Reddish southwards through the centre of Stockport.

The exact position of the outcrop to the north of Stockport can only be conjectured. A bore at Levenshulme Print Works [SJ 8829 9456], in the area of Sheet 85 just to the north, proved Pebble Beds beneath more than 300 ft of Upper Mottled Sandstone; therefore the western boundary must be to the east of this bore. Records of old wells at the Mercerising Company's factory [SJ 8844 9372] and Heaton Chapel railway station [SJ 8820 9209] both list upwards of 200 ft of Bunter Sandstone with no mention of pebbles. These records must, however, be treated with reserve, for pebbles were present in an old (1886) bore at Lowes' Chemical Works [SJ 8939 9379] which penetrated 439 ft of Pebble Beds on Manchester Marl beneath 127 ft of drift, and also in another drilled in 1910 at Broadstone Spinning Mills, Reddish [SJ 8913 9293], where 108 ft of Pebble Beds rested on Manchester Marl. The eastern boundary of the outcrop must pass close to the more easterly of the two last-mentioned bores. Indeed, a short distance south-east of Broadstone Mills, one borehole at the C.W.S. Confectionery Works, Reddish [SJ 8951 9241] proved 73 ft of Pebble Beds on Manchester Marl, and another (p. 132) only 160 yd to the south entered basal Manchester Marl beneath drift. A fault, of which the trend is unknown, is thought to intervene between these two bores, throwing down towards the northern one.

Numerous outcrops of Pebble Beds are noted in the vicinity of the town centre. At Tiviot Dale station a typical section of an extensive exposure behind the water tank is red-brown current-bedded massive sandstone with bands of pebbles 5 ft, on coarser and more friable red-brown sandstone 2 ft, over friable coarse sandstone with abundant red marl pellets 2 to 3 ft and more massive red-brown sandstone with occasional pebbles 3 ft. At the south end of Lancashire Hill, opposite the station, is seen 16 ft of pebbly sandstone, and a similar rock is continuously exposed in the railway tunnel and cutting from the station to a point underneath Wellington Road North. Between Hatton Street and Old Road and to the north of the railway tunnel, a system of tunnels used in the late war as an air-raid shelter has been excavated entirely in Pebble Beds. The rock here is generally dry. A small fault intersects the tunnels near the Hatton Street end, throwing down north-east. A fault, possibly the same as that in the Hatton Street tunnels, throwing down north-east, is noted in an elongated exposure running north-east of Hatton Street, south of the Roman Catholic church. There is pebbly sandstone on both sides of the fault, but on the upthrow side it is tougher and coarser. There are numerous exposures in both banks of the Mersey between Mersey Square and Bridge Street Bridge, of typical false-bedded pebbly red sandstone, the foreset beds facing south-west, with mica on some bedding-planes.

South of the river there are exposures in Chestergate and High Bank Side, and a system of tunnels, again used as air-raid shelters, has been made entirely in Pebble Beds. From a network of tunnels just west of St. Peter's Square two main galleries, joined at intervals by short tunnels, run parallel with Chestergate and High Bank Side to High Street. Single tunnels extend from this system along the centres of St. Peter's Square, Fletcher Street, Etchells Street and High Street. The ends of these are joined by the St. Petersgate tunnels, in which, half-way between Fletcher Street and Tatton Street, a channel filled with gravel was encountered. Apart from this the excavations were in Pebble Beds throughout, largely unfaulted —though on the evidence of bores a fault downthrowing east must pass close to the junction of High Street and St. Petersgate. All the above-described surface and underground exposures, together with others too numerous to include, show dips generally between west and west-southwest, ranging from 10° to 18°.

Southwards along the outcrop numerous wells south of the town-centre prove Pebble Beds on Manchester Marl; some draw their water from both the Bunter and the Collyhurst Sandstone. Outside the town the evidence is scarce, but the Hazel Grove Bore [SJ 9181 8655], completed in 1894, proved 31 ft of Pebble Beds resting on Manchester Marl (Plate 4, no. 19).

Pebble Beds crop out at intervals along Norbury Brook between Jacksonlane Farm and its junction with Poynton Brook. The Poynton Bore [SJ 9173 8428], though uncored through the Permo-Triassic, brought up fragments of quartzite pebbles in red sand between 45 ft, the base of the drift, and 135 ft where the top of the Manchester Marl is placed. The Poynton Station Bore, sunk in 1909, pierced 341 ft of Pebble Beds before entering Permian rocks and Coal Measures. The two Poynton bores, the Norbury Brook exposures, and the Hazel Grove Bore are considered to lie east of a fault throwing down east and passing to the east of Great Moor, Stockport—where it brings in a wedge of Pebble Beds in the Stepping Hill area—and to the west of Hope Green, Poynton.

South of here the Pebble Beds abut against the Red Rock Fault; a well immediately west of the fault at Bollington Gas Works [SJ 9277 7728] giving a record of 300 ft of Pebble Beds beneath 100 ft of drift, and overlying what may be thin Manchester Marl (see p. 53). One other well, drilled in 1939 for Macclesfield Corporation at Tytherington [SJ 9148 7576], proved 226 ft of Pebble Beds. Pebbles here included predominantly quartzites, and some sandstone, felsite, ash and vein-quartz. R.J.T., R.H.P.

Upper Mottled Sandstone

Within the district the Upper Mottled Sandstone is very little seen. Exposures around Alderley Edge display the formation as a medium to coarse-grained highly false-bedded sandstone with abrupt colour-changes from bright red to grey-white; occasionally it presents a mottled red and white appearance. It is composed largely of rounded grains of quartz, but sub-angular grains also occur. Normally the rock lacks coherence and weathers into a sand down to depths of 20 ft; and the unweathered rock can be crushed into a sand. Exceptionally, in near proximity to faults which have carried mineralizing solutions, the rock is harder because of the presence of innumerable 'ghost' crystals of barytes which cement the sand grains. An outcrop, largely drift-covered in the neighbourhood of Carrington, trends to the east-south-east, and is terminated to the west of Sale by the Ashton-on-Mersey Fault. The main outcrop stretches southward from the northern margin of the sheet in the vicinity of Chorlton-cum-Hardy and Didsbury (suburbs of Manchester), past Handforth and Wilmslow, to Alderley Edge. Between Wilmslow and Adlington the outcrop is repeated by at least two northerly-trending faults throwing down east against the dip, and the formation occupies the ground beneath Woodford, Prestbury and Upton.

One of the best continuous sections of Upper Mottled Sandstone is given by the Stockport Corporation's water bores at Wilmslow, the log of one of which is summarized in Appendix 1, p. 155. A series of specimens from No. 1 Bore were examined by S. W. Alty (1926, p. 278), who described the heavy mineral content and related it to that at other localities in Britain. This author considered that a Keuper age was indicated for the rocks in the upper part of the borehole by the presence of a footprint-bed at 660 ft. A specimen of this bed is preserved at Stockport Museum, where the impressions are considered to resemble those in the footprint-bed at the Storeton quarries, Wirral (see Swinton 1960). It is felt, however, that the occurrence of footprints should not be regarded as a precise indicator of horizon, for the weight of stratigraphical evidence around Wilmslow would appear to put the horizon of the footprint-bed in the borehole well down in the Upper Mottled Sandstone, some hundreds of feet below the better-known footprint horizon near the base of the Keuper at Storeton, Daresbury, Lymm and Tarporley. F.M.T.,

Details

The escarpment of Alderley Edge, rising to a maximum height of 250 ft above the plain to the north, is, although capped by the basal conglomerate of the Keuper, mainly of Upper Mottled Sandstone; and displays many small exposures of soft red sandstone. Two sections at the foot of the escarpment are worthy of note. The first [SJ 8538 7828], alongside the road about mile E. 10° N. of the main (five-pronged) crossroads in the town of Alderley Edge, displays some 6 ft of mottled sandstone underlain by about 15 ft of grey sandstone. 'Ghost' crystals of barytes appear throughout the sandstone as laths or needles up to inch in length, and barytes also lines the joint-planes. The exposure lies very near the continuation of the line of the Edge Fault, along which adits for copper ore have been driven farther east (see p. 120). The second section is in a roadside quarry [SJ 8613 7834] opposite Dickens Farm and 2000 yd E. 6° N. of the above-mentioned crossroads.

In this quarry a small north-westerly fault is exposed, to the west of which the Upper Mottled Sandstone has weathered to a depth of about 15 ft into a loose sand; to the east of the fault some 30 ft of very soft red sandstone is exposed. At the time of the survey, 1946, the quarry was being worked for sand by the Alderley Edge Moulding Sand Company.

The Edge Fault is visible on the north-easterly facing part of the escarpment 500 yd N. 24° W. of Edge House, where it separates basal Keuper conglomerate on the north from soft red and mottled Upper Mottled Sandstone on the south. Both formations are patchily stained blue-green by copper ore; the staining is also seen in an adit which has been driven from here in the soft Upper Mottled Sandstone (see p. 121). About 100 yd. farther east at the mouth of another adit, situated at the foot of the escarpment and also driven on or near to the Edge Fault, some 10 ft of Upper Mottled Sandstone are exposed.

Keuper

After the deposition of the Upper Mottled Sandstone a marked change in conditions of sedimentation took place which resulted in a decided difference in lithology. The rounded and subangular-grained soft sandstones of the Upper Mottled Sandstone gave place to angular-grained and relatively hard sandstones, which in the Alderley Edge area and elsewhere in Cheshire have conglomeratic basal beds. At Alderley Edge the line of junction is quite sharp, and where the overlying beds are conglomeratic it could be interpreted as an unconformity; nevertheless, as if to testify by interdigitation against the unconformity hypothesis, mappable beds of sandstone displaying all the characteristics of the Upper Mottled Sandstone occur between the two basal conglomerate beds in the Alderley Edge area. Taking a broad view of Keuper sedimentation, there is a gradual upward change from arenaceous beds at the base through a series of alternating argillaceous and arenaceous beds into a dominantly argillaceous series; and in the latter there are measures containing thick beds of rock-salt. It is into this gradually upward-changing lithological sequence that divisional lines are drawn to give the three-fold subdivision into Keuper Sandstone, essentially sandstones with conglomerates at and near base, Keuper Waterstones, an alternating series of marl and fine sandstones or silt-stones, and Keuper Marl dominantly a marl with saliferous beds.

The estimated total thickness of the Keuper that crops out within the district is of the order of 4000 ft. Above this sequence, a few miles beyond the southern margin of the district, a borehole has proved another 1000 ft of Keuper Marl.

Still higher measures have been proved on the main synclinal axis at Wilkesley, near Audlem (One-inch Sheet 122, Nantwich), where a recent Geological Survey borehole pierced the full thickness (4437 ft) of Keuper Marl from the base of the Rhaetic downwards. It proved the presence of a second saliferous series much higher, and thicker, than that found in this district. F.M.T.

Keuper Sandstone

Typically the Keuper Sandstone is a medium-grained to fine-grained brown to buff sandstone consisting of angular to sub-angular grains of quartz with scattered flakes of mica; it makes a good building stone. Conglomerates occur in the basal part of the sequence, and shale bands that are markedly micaceous occur in the higher beds. Viewed regionally the conglomerates appear to be markedly impersistent. Thus they are present in force at Alderley Edge, but three miles to the north-northwest, in the River Bonin east of Wilmslow, they are represented only by a six-inch basal band in which the pebbles are small, rarely exceeding half an inch in length. At Partington, in the north-west of the district, the conglomerates are represented only by sporadic pebbles of pink quartzite in a sandstone matrix. Nevertheless, the dying out of the pebbles northward falls into the regional picture, and is indeed a repetition of the pattern displayed by the Pebble Beds, although in the case of the basal Keuper beds the pebbles were not carried so far to the north. Near the southern margin of the district, where the ground is not obscured by drift, three conglomerates can be mapped. The bottom and most important bed consists dominantly of pebbles (quartz and quartzites with occasional grits and rarely basic igneous rocks) set in a medium-grained to coarse-grained sandstone. Some of the pebbles are as much as 4 in long. The upper two conglomeratic beds are less coarse but contain similar pebbles. At Alderley Edge a reversion to the soft bright-coloured false-bedded rounded-grained sandstone that is typical of the Upper Mottled Sandstone occurs between the middle and uppermost conglomerate; and this Bunter-type of sandstone also occurs in the Keuper Sandstone exposed in the River Bollin. A similar and more extensive development has been noted (Strahan 1882, p. 9) near Chester in the upper part of the sequence below the Waterstones, where these Bunter-type sandstones have been given the name of Frodsham Beds; and this is matched at Lymm in the north-west of the district, where the uppermost part of the Keuper Sandstone displays lithology similar to that of the Frodsham Beds.

The upper part of the Keuper Sandstone is characterized in the Alderley Edge area by massive posts of medium-grained to fine-grained sandstone up to 20 ft thick, separated by chocolate-coloured shales which are markedly micaceous. These posts are well-bedded, and are often quarried for building stones; only occasionally do they display subordinate false-bedding. In the western part of the district where the beds are poorly exposed they are thought to be about 400 ft thick. In the central part north of Mobberley a thickness of over 700 ft was proved in the Lady Lane Borehole ((Figure 7), no. 6), and in the south-eastern part of the district between Nether Alderley and Over Alderley the Keuper Sandstone cannot be less than 1000 ft thick.

Specimens of Euestheria were found by C. E. De Rance in an old stone quarry on the summit of the Alderley Edge Escarpment [SJ 8607 7764]. The fossils were in a bed of soft micaceous shale, and their discovery was noted by W. Brockbank (1891, pp. 12–13 and 31) and T. R. Jones (1891, pp. 52–3 and pl. II). The latter work erroneously assigned the horizon to the Keuper Marl, instead of the Keuper Sandstone. F.M.T.,

Details

Along Alderley Edge the outcrop of the basal conglomerate of the Keuper Sandstone, although cut into segments by several faults, can be traced in a general east-southeasterly direction from the centre of the town of Alderley Edge for about two miles to Hilltop. It is about 60 ft thick, and is broken into frequent crags along the uppermost slope of the Edge. It dips in a south-westerly to west-southwesterly direction at angles varying between 8° to 14°. There are several places where the junction between the Upper Mottled Sandstone and the Keuper Sandstone may be seen, the best and most easily accessible being a crag (Castle Rock [SJ 8561 7799] on six-inch maps) 1400 yd E. 7° S. of the crossroads in the town of Alderley Edge (Plate 5B).

Other good exposures of the Bunter–Keuper junction are to be seen along the easternmost segment of the escarpment, which faces north-east, and upon which Hilltop is situated. This escarpment is terminated by a north-south fault which displaces the Keuper about 1.5 miles to the north on its eastern or downthrow side. From this side of the fault the outcrop of the basal conglomerate trends past Kirkleyditch to the south-southeast, to be lost beneath glacial drift east of Harehill: a good section is displayed at the old quarry [SJ 8745 7840] at Kirkleyditch, where two posts of conglomeratic sandstone each 10 ft thick are separated by some 4 ft of softer somewhat obscurely-exposed sandstone; half a mile further north good exposures of these beds are to be seen in a stream (Putt Brook of the six-inch map) that obliquely crosses their strike. In these exposures the dip is to the west-southwest at 8° to 12°.

The beds immediately overlying the basal conglomerate are not well exposed; the best section is in an old quarry 400 yd N.W. of Edge House where, dipping westward at 12°, some 24 ft of buff to brown micaceous sandstones are divided midway by a 12-inch bed of red shale.

In the overgrown old quarry (Church Quarry [SJ 859 774] of the six-inch map) 500 yd W. 3° S. of Edge House, about 15 ft of the middle conglomerate rests sharply upon some eight feet of massive sandstone. The total thickness of sandstone between the basal and the middle conglomerate hereabouts is estimated at about 40 ft; the middle conglomerate also approximates to this thickness.

In a narrow outcrop that can be traced from Alderley Road in Alderley Edge south-eastwards for a distance of about 1.5 miles, a type of sandstone identical with the Upper Mottled Sandstone occurs between the middle and the uppermost conglomerates. The best exposure of these soft sandstones is an old quarry [SJ 8515 7760] 450 yd N. 5° W. of Brynlow, where the dip is 12° to the south-west. The following section was measured:

At the north-western end of the quarry the middle bed shows blue-green malachite impregnations associated with a small north-westerly fault of about 1 ft downthrow.

A sharp junction of the uppermost conglomeratic sandstone of the Alderley Edge area and the underlying sandstone is seen in a cutting [SJ 8543 7720] on the south side of the road that runs south-westwards from the Wizard Inn past Brynlow and 250 yd east of that farm. The conglomeratic sandstone is brown-red and flaggy, and the pebbles are rarely as much as an inch long. From this cutting the conglomeratic sandstone, which cannot be more than 20 ft thick, can be traced in a general south-easterly direction to the road that runs past Broadheath, but south of this road it disappears beneath thick glacial drift.

The sandstones that overlie the three conglomeratic beds of the Alderley Edge area are present to the south-east of the town, and to the east of the Alderley Fault; and, although they are covered by thin drift, exposures are fairly frequent in old quarries from which the stone has been excavated for building. The most southerly exposure to the immediate east of the Wilmslow Fault is at Alderley Mill, 250 yd north-east of the church at Nether Alderley. In the old quarry [SJ 8505 7703] on the eastern side of the road 200 yd S.W. of Brynlow 10 ft of red-brown micaceous sandstones dipping at 12° to the south-west are capped by 5 ft of boulder clay. The largest quarry [SJ 857 765] of this area lies about 300 yd west-southwest of Finlowhill, where a massive post of fine-grained sandstone, some 15 ft thick, has been worked under 15 ft of alternating beds of sandstone and shale. The quarry extends for about 150 yd along the strike, and the dip of the beds is 12° to the south-west. F.M.T.

Lymm to Agden

The most westerly exposures in the district of the Keuper Sandstone are in the town of Lymm, where a succession is visible, with some gaps, from the base of the Keuper to the base of the Waterstones. The basal Keuper beds form the banks of the Sow Brook west of Danebent House, and consist of red and yellow sandstones with pellets of red mudstone. The best available description of the beds is an unpublished one by Goodchild (in MS) which, freely quoted, is as follows:

"A short distance above Lymm Station the section commences with soft rather fine-grained and thinly bedded flaggy sandstones, ranging in colour from bright tile-red to saffron, pale brown, and cream colour. The colour is distributed in an irregular manner, and may be said to occur in blotches and patches… these beds are regarded as the equivalents of the Upper Mottled Sandstone."

"Resting with an even junction on these and clearly graduating downwards into them are about 60 ft of blocky sandstone with a prevailing pale saffron or whitey-brown line in the lower part but graduating upwards into beds of a more decidedly dull and brick-red tint. Much false bedding occurs along some of the planes. Fragments of shale, arranged along bedding lines, occur mostly near the base, but there is no clear evidence of anything that could well be called a breccia. These beds give rise to a picturesque waterfall just below where the Bridgewater Canal crosses. In the village of Lymm (they) are capped by a few feet of soft sandstone and shaly marl… and these are succeeded by the dull brick-red evenly bedded freestone so largely quarried for building purposes. Bands and irregular patches of cream colour and pale greenish grey diversify the prevailing tint of this rock. (The beds) are well exhibited between the Cross at Lymm and the foot of Lymm Mere, and probably extend to a thickness of about 100 ft or a little more."

"At the foot of the Mere the Building Stones are surmounted by the brighter red sandstones of the Frodsham type. Like the rock below these too are diversified by light cream-coloured patches and bands which contrast strikingly with the bright tile-red of the body of the rock. This rock may be well seen on the banks of the Mere… "

Samples collected along the shore of Lymm Lake and near Damhead Bridge show this rock to be a friable bright red sandstone, with an appreciable proportion of large rounded grains with etched surfaces. The rock is very similar to that exposed at Frodsham Station. The dip at Lymm is southerly between 5° and 6°, which gives a thickness for the Keuper Sandstone of 320 to 360 ft.

On the east side of the lake 300 yards south-west of St. Mary's Church Keuper Sandstone of Frodsham type is overlain by reddish-brown flaggy and argillaceous sandstones, which are placed in the Waterstones. Near the head of the Dingle just below the Dam, two bores were sunk for Lymm Waterworks in 1887 and 1888 to 950 ft and 235 ft respectively. The deeper of these, if not both, must penetrate through the base of the Keuper into the Bunter rocks; but available records are not sufficiently good to enable the base of the Keuper here to be fixed.

Exposures in the Keuper Sandstone east of Lymm are along the line of a subdued scarp trending towards Agden Brow, the steeper northern face of which marks the base of the Keuper. Glacial drift is thin immediately to the east of the town, and the sandstone is exposed in Longbutts Lane. Near the old gas-works half a mile east of Danebent House (now Danebank House), De Rance recorded an exposure of white grit resting on a sandstone which he assigned to the Bunter. In a quarry [SJ 6907 8698] west of Oughtrington Hall, now long disused and overgrown, he noted the following section:

Beds 8–12 he regarded as part of the 'Frodsham Beds', which were considered at that time to be a regular division of the Keuper Sandstone. Beds 1–7 he assigned to the 'Keuper Building Stones'.

The disused quarry [SJ 7008 8695] at Helsdale east of Oughtrington Hall yielded this section: boulder clay 4.5 ft, on soft mottled sandstone 5.5 ft, soft yellow sandstone 3.5 ft, hard yellow sandstone 5 ft, and hard white sandstone 15 ft. The two beds of soft sandstone at the top are of 'Frodsham' type. Strata below those exposed in the quarry crop out in the gorge to the north, where some 15 ft of pale red sandstone with small quartz pebbles rests upon what is considered to be Upper Mottled Sandstone. De Rance also noted the junction of the basal Keuper and Upper Mottled Sandstone in Burford Lane, north of Burford Lane Farm, recording, in a quarry east of the farm, 15 ft of massive white grit affected by a north-northeasterly system of jointing and containing vein-quartz pebbles, beneath boulder clay. Neither of these exposures is now open.

A filled-in quarry at Agden Lane Farm once showed the lowest Keuper beds; and a disused quarry [SJ 7131 8618] higher up the hill at the junction of Agden Brow and Agden Lane is in Keuper Sandstone of 'Building Stones' lithology—yellow and red fairly well-cemented medium-grained sandstone with subangular grains. Soft red and yellow current-bedded sandstone of the Frodsham type is exposed beside a footpath [SJ 7156 8569] some 250 yards north of Agden Hall, the weathered surfaces being covered with small raised knobs which are spherical calcareous concretions, slightly harder than the remainder of the rock. The Waterstones are visible only a few feet above these beds. It was apparently in the three quarries east of Lymm that Rawlinson (1853) noted footprints, presumably reptilian; but there are no remaining traces of these. Williamson (1867) later described footprints of Chirotherium from a similar horizon near Daresbury.

North-West of Altrincham

Several exposures of rock alongside the Manchester Ship Canal are assigned to the Keuper Sandstone. One immediately south-west of Milbank Paper Mill shows 15 ft of soft salmon-pink and yellow sandstone with abundant rounded grains. Similar red and yellow sandstone is exposed beneath the lower edge of the high terrace of the river Mersey immediately north-west of Milbank Mill. A third exposure 300 to 400 yards south-west of the railway bridge over the canal at Partington, showing a gentle dip towards the south-west, is of false-bedded coarse yellow sandstone with red patches. Occasional small pebbles of pink quartzite suggest that the beds are not far from the base of the Keuper.

The Hogswood Bore (Geological Survey No. 2) [SJ 7437 9004], bottomed the drift at 86 ft and was drilled to 158 ft in sandstone of 'Frodsham Beds' type and continued in Keuper Sandstone to 360 ft (p. 136). The character of the Keuper Sandstone alternated between red medium-grained well-sorted sandstone and soft red and yellow medium to coarse false-bedded sandstone in which thin layers rich in large rounded grains alternated with those containing finer-grained material; contemporaneous breccias of mudstone in sandstone matrix were found between 281 ft and 309 ft; and a few small pebbles, similar to those in the exposure south-west of Partington railway-bridge, were found in soft round-grained sandstone around 340 ft. This bore, down to 340 ft at least, is considered to be in Keuper Sandstone. It appears that sandstone with the 'Frodsham' type of lithology is thicker in this area at the expense of the 'Building Stones' type. There is probably a lateral passage, accompanied by interdigitation, of one type into the other; and this lateral change may account for the absence hereabouts of the Keuper escarpment, so marked in other parts of Cheshire. The Hogswood Farm Bore may have penetrated into the Upper Mottled Sandstone in the lowest few feet, but since the Frodsham lithology is indistinguishable from that of the Upper Mottled Sandstone it is impossible to draw a definite line between the two formations.

Sale and Timperley

The sources of information in this area are two quarries and a borehole. In the quarry [SJ 7877 8881], 270 yd N.W. of Timperley Vicarage, still open though now disused, 7 ft of boulder clay rest upon massive red and yellow fine to medium-grained sandstone: 25 ft of this rock was once exposed, when it was quarried for building stone and for making water filters. Goodchild in a MS account of this and other exposures in the Timperley area speaks of the sandstone as "showing a little oblique lamination and streaked and mottled with greenish-grey. Here and there a few pebbles and conglomerate bands occur, but they seem to be absent from the greater part of the rock. The rock is remarkable for the regularity and well defined character of the joints, which have been turned to good account in quarrying the stone". About 200 yd east of this quarry the Timperley Fault cuts off the easterly extension of these beds and throws Keuper Marl down against them. The fault was once exposed in a trench dug along Bloomsbury Lane just north of the quarry; and in this trench, west of the fault, the Keuper Sandstone was visible with two thin layers of shale, beneath boulder clay, the whole capped by the sands of the highest terrace of the Mersey. The other quarry [SJ 7876 8848], 300 yd S.W. of Timperley Vicarage, is now filled in, but De Rance (in MS) left a note referring to the rock here as 'Keuper Building Stones' and giving the dip as south-west at a low angle.

Maple Road Bore (Geological Survey No. 1) [SJ 7948 9002] (p. 139) entered what was interpreted at the time of drilling as Keuper Sandstone at 288 ft 10 in, and was still in it at 360 ft, the bottom of the hole. This is a fine-grained red-brown sandstone with layers of red and greenish-grey shale, and mottled with reddish-grey in places: bands of grey sandstone are common: the shales exhibit such evidence of shallow-water deposition as suncracks, ripple marks, and 'rain-pitting'.

Altrincham

In the Altrincham–Bowdon area there are no exposures, and knowledge is based on the unsatisfactory records of four old bores for water.

Styal

The following details of sections exposed in the vicinity of Quarrybank Mill will serve to illustrate the character of the Keuper Sandstone hereabouts.

They are roughly in ascending stratigraphical order. By the track [SJ 8355 8313] some 100 yards north-east of the mill are 12 ft of dark red current-bedded sandstone with a 4-ft pebble bed containing quartz pebbles and marl pellets in friable sandstone: behind the mill there is red current-bedded sandstone with well rounded grains 5 ft, on grey and red pebbly sandstone with subangular quartz pebbles 5 ft: in a small gully about 160 yards south of the mill pebbly sandstone overlying sandy chocolate-coloured marl and sandstone is exposed: immediately south of the mill current-bedded friable red sandstone is seen: north of the mill there is strongly current-bedded soft red sandstone with cream-coloured bands 30 ft: opposite the mill in the valley side is 20 ft of current-bedded red and cream coarse friable sandstone with some micaceous and marly partings, weathering out in honeycomb structure: on the north side of the path [SJ 8336 8306] 75 yd W.N.W. of the bridge over the river Bollin are 20 ft of current-bedded massive red and cream banded sandstone: and 150 yd N.W. of the mill 10 ft of current-bedded red sandstone is exposed. The beds with marl pellets and pebbles are considered to be near the base of the Keuper. The Prodsham' type of lithology is displayed in several of the exposures, the best being in the valley side [SJ 8335 8295] directly opposite the mill where the dip is 24° N.W. These beds do not continue southwards along their strike, but give place in a short distance to chocolate-coloured and grey sandy mudstones which are exposed at the next bend of the river—a fact which points to a fault of some magnitude between the two exposures. The fault is exposed again in the river [SJ 8316 8314] 350 yd N.W. of the mill, and its trend is thus north-northwesterly. The dip in these exposures is between 15° and 26° away from the fault, the average direction being a little north of west.

Keuper Waterstones

Although there is no unconformity at this horizon, the change in sedimentation which took place after the deposition of the Keuper Sandstone led to the most abrupt change in lithology in the whole of the Trias of Cheshire; and the base of the Waterstones is therefore one of the most easily recognized horizons in the formation. This has been found to be true also in the Chester area (Taylor and others, in preparation). The change is even more marked where the underlying Keuper Sandstone is of Frodsham type, as at Lymm (p. 65). At the base of the Waterstones, sandstones of lower Keuper type, open-textured, often current-bedded, and containing thick and massive posts, give place to platy thin-bedded sandstones and siltstones with much mica on the bedding-planes and with much argillaceous material both in thin bands of mudstone and in the sandstone layers themselves. Salt-crystal pseudomorphs, ripple-marks, suncracks, and desiccation-breccias, caused by redistribution of sun-cracked material, tell of deposition in shallow water which frequently dried up, as do the footprints which have been recorded in the quarries east of Lymm (Rawlinson 1853, pp. 37–40). The only current-bedding found is on a minute scale, commonly involving very fine-grained arenaceous material in the individual sandstone laminations.

The Keuper Waterstones are frequently referred to as passage beds between the dominantly arenaceous groups below and the dominantly argillaceous Keuper Marl above. This is not strictly accurate, for the Ethological characteristics of the Waterstones are much more closely allied to the Keuper Marl than to the Keuper Sandstone; and many of the features noted in the Waterstones continue through the whole of the Keuper Marl above, the main change being a decrease both in grain size and in amount of arenaceous material, and an increase in the amount of evaporite minerals, including dolomite and gypsum and, in the Saliferous Series, halite.

The origin of the name Waterstones is controversial. There have been those who thought the name was due to a resemblance between the play of light on the highly micaceous bedding-planes and on 'watered' silk, for the rock is not noted—in Cheshire at any rate—for its ability to yield copious supplies of water in wells, what water there is being excessively hard. Indeed, the Waterstones as a whole are in the vertical sense an almost impervious formation owing to the abundance of mudstone bands. Nevertheless, when these rocks are found outcropping on the sides of stream gullies, it is almost invariably found that water, held up by the numerous shale partings, oozes out at numerous points over the rock face, which is frequently covered by ferns and other moisture-loving plants. This would seem to be the more plausible origin of the name.

Although the base of the Waterstones is well marked the top is less easy to define, for there is a gradual passage upwards into the Keuper Marl. Moreover, there seems to be considerable lateral variation in the arenaceous content of the lower part of the Lower Keuper Marl. In the Booth Mill Bore [SJ 7682 7936] ((Figure 7), no. 4), some 250 ft of strata were referred to the Waterstones by De Rance when his opinion was asked in 1902, the top being put at 1219 ft. Above this are 289 ft of red and grey marls followed by a further arenaceous phase 167 ft thick. These sandy strata, indistinguishable from the Waterstones proper, had been previously noted by De Rance (1894, p. 278) in the Marston Borehole near Northwich, where he named them the Upper Keuper Sandstone; and similar beds were noted in the Plumley No. 3 Borehole (Sherlock 1921, p. 46). In the Ashley Borehole (Geological Survey No. 9) [SJ 7738 8355], 886 ft of dominantly arenaceous strata of a lithological type identical with that of the Waterstones were found overlying the Keuper Sandstone; and it is thought that these strata represent the Keuper Waterstones and the 'Upper Keuper Sandstone' of Booth Mill, as well as the intervening red and grey marls which pass laterally into the arenaceous sequence of Ashley (see (Figure 7)).

The lithology of the Waterstones proved in the Ashley Bore is typical of these measures wherever they occur in Cheshire. The dominant characteristic is the frequency of alternation between fine-grained sandstone and siltstone and the finest of mudstone, together with all types intermediate between the two extremes. Only rarely does a bed of comparatively uniform lithology occur more than a few inches thick, and this is then either an argillaceous red sandstone or a red unstratified mudstone or sandy mudstone which is frequently seen on close examination to be an autobreccia.

In the finely banded strata, alternations are found between fine-grained sandstones frequently showing small-scale current-bedding, dolomitic silt-stones, sandy mudstone, and thin layers of extremely fine-grained mudstone of a soapy texture. Ripple-marks upon a sandstone or siltstone are frequently preserved by a succeeding mudstone layer, and the pseudomorphs of hopper-shaped halite crystals, moulded in the top surface of a mudstone layer, are frequently found preserved as casts on the underside of a succeeding arenaceous layer. Dolomite occurs as minute specks and rhombs throughout the rock, and it forms the cementing material in some of the harder platy sandstone and siltstone layers. Gypsum occurs interstitially, as well as in small pellets and grains and in veins which may cut the rock at any angle. The emplacement of gypsum veins is discussed in the succeeding section on the Keuper Marl (p. 75).

The dominant colour of the Waterstones is dark brownish-red, but in the banded strata red layers are frequently found alternating with grey or grey-green bands, the coarser-grained layers tending to be grey and the finer-grained layers red. Pale grey sandstone or siltstone is also found alternating with extremely fine-grained green mudstone. The sedimentation appears to have been cyclic, as in the Keuper Marl above. The reddish-brown colour is due to an iron oxide, probably hydrous, this mineral being absent from the grey or green layers.

The presence of gypsum often renders the rock efflorescent, and hand specimens obtained from boreholes are often spoiled as they dry by the spalling off of the surface-layer, and the obliteration of the finer features by the crystallizing gypsum.

Details

Lymm, Broomedge and Millington

As already described, the base of the Waterstones is clearly visible at Lymm; but their top is less easily defined, for the gradual passage upward into Keuper Marl provides no horizon where differential hardness can give rise to a distinctive topographic feature. A line for the top has been drawn where the succession, when followed upwards, becomes predominantly shaly, and this line crosses Bradley Brook, south of Lymm, about 250 yards downstream from its junction with Mag Brook. This makes the width of the outcrop 700 yards and the thickness of the Waterstones about 200 ft.

Along the low ridge of Broomedge between Higher Lane and Agden Park thin boulder clay partly covers the outcrop. From quarries originally opened for the working of flags and fine-grained building stones, and now disused, footprints of a Labyrinthodont (Chirotherium) have been obtained (Rawlinson 1853, pp. 37–40). Hull (1861, p. 3) wrote "Beside reptilian footprints which occur not infrequently and especially where the slab is covered over and protected by a stratum of fine marl, there are sometimes present littoral phenomena, as sun-cracks and raindrops and tracks of annelids. The ripplemarks are beautifully distinct, and the whole together recall vividly to mind the fact that we are standing on the sands of an old sea shore". While it is not disputed that these beds, containing abundant evidence of shallow-water deposition, may well represent a marginal facies of an inland sea, it should be made clear that they extend for many miles in all directions from Broomedge, and are not the deposits of a narrow coastal belt.

In the grounds of Agden Hall the crest of the ridge is free from drift. With the faulting down of the Keuper Sandstone north of the hall by a fault oblique to the strike of the rocks, the Waterstones become the dominant hard bed, and form a more pronounced escarpment for a distance of about half a mile eastward, before they, too, are faulted out. The Waterstones have been extensively worked in a quarry [SJ 7235 8460] south-east of Stonedelph Farm, where the following section was obtained: sandy soil 7 ft, over red flaggy sandstone 5 ft, grey sandy marl 5 ft, flaggy sandstone 1 ft, and fine-grained red-grey sandstone with ripple marks and rain-pitting 15 ft.

The Geological Survey No. 3 Borehole was drilled at Grey's Gorse [SJ 7298 8568], in an attempt to prove an easterly extension of the Heatley–Agden salt-field north of the Warburton Fault. Instead, the bore proved gypsiferous Lower Keuper Marl, with siltstone layers to 232 ft, and below this a more arenaceous sequence comparable with the Waterstones. At that time it was considered that these measures were equivalent to the Waterstones proper, and the structure given on the published map showing Keuper Sandstone and Upper Mottled Sandstone thrown up between two converging faults in the Dunham Woodhouses area was based on the strata and angle of dip proved in the bore. In the light of later work it is equally possible that the arenaceous measures below 232 ft in the Grey's Gorse Bore are part of an upper arenaceous phase, higher in the Lower Keuper Marl (see p. 69). This would simplify the map; for neither the fault between the Grey's Gorse Bore and the Agden salt-field nor the Dunham Fault would have such large throws as are shown, and the Keuper Sandstone and Upper Mottled Sandstone at Dunham, though still present at depth, might not then come to outcrop.

Altrincham, Sale, Timperley and Hale

The Waterstones in this area are almost completely obscured by drift except in Sinderland Brook, a mile south of Parting-ton, where red flaggy micaceous sandstone dips southwards at a low angle, and in Timperley Brook [SJ 789 877], north-east of Delahays Farm, where fine-grained red and grey flaggy and marly sandstones are exposed, dipping eastward for about 700 yd along the brook. The dip at the second locality increases towards the Timperley–Mobberley Fault, which throws down the Keuper Marl to the east just west of Wellfield Lane. In Altrincham and Hale several bores (with somewhat unsatisfactory records) prove measures referable to the Waterstones. They include bores at the disused Richardson and Goodall Brewery, Altrincham Gas Works, where 243 ft of Keuper Waterstones are thought to rest upon Keuper Sandstones of Frodsham type, and one at the Linotype works which shows 157 ft of Waterstones resting on soft sandstone thought to be Frodsham Beds (see p. 63). North-east of the Ashton-on-Mersey Fault at Sale the Maple Road Bore (Geological Survey No. 1) [SJ 9748 9002] proved at least 147 ft of typical Waterstones, and there is the possibility that a further 71 ft below should properly be referred to this group (see p. 139): the top of the Waterstones was faulted against the Keuper Marl above.

South of Hale the River Bollin between Bankhall and Halebarns reveals numerous exposures of red and grey marls with arenaceous layers resembling Waterstones. At the time the map was made these were included, in the absence of other evidence, in the Keuper Marl. It is possible that these beds are, at least in part, equivalent to the upper part of the Waterstones sequence proved in the Ashley Borehole, and to the 'Upper Keuper Sandstone' of the Marston and Plumley bores, already mentioned (p. 69).

Ashley and Mobberley

Little is seen of the Waterstones at the surface except for a few exposures south-west of the Dunham–Ashley Fault in Sugar Brook and Mobberley Brook, in the vicinity of Tithebarn Farm, where the measures dip steadily south-westward at 3° to 5°. The Waterstones were proved in the Ashley Borehole, briefly described above, of which a full account is given in Appendix 1, p. 125.

Four bores, drilled in 1948 for the then Ministry of Town and Country Planning, proved Waterstones west of the Mobberley Fault near Mobberley and east of the unstable ground of Tatton Park and Knutsford where salt in the Keuper Marl presumably lies near the surface. The most complete record is that given by the Kellhouse Bore (Ministry of Town and Country Planning No. 5) [SJ 7697 8234], one of the four referred to. 346 ft of strata were included in the Waterstones, which was found to rest at 455 ft upon the red and mottled Keuper Sandstone. The lithology was typical, with banded flagstones, red and greenish-grey in colour. numerous layers of mudstone and occasional gypsum veins. The Breach House Lane Bore (Ministry of Town and Country Planning No. 3) [SJ 7844 8192] proved 289 ft of Waterstones, the base of which was not reached at the bottom of the hole at 551 ft. The arbitrary top was here placed at 262 ft, where the strata, in upward passage to the Keuper Marl, became predominantly argillaceous (p. 69). The Lady Lane (Ministry of Town and Country Planning No. 1) [SJ 7907 8070] and Mobberley New Hall (Ministry of Town and Country Planning No. 4) [797179551 bores both proved short sequences of Waterstones, and their records are given in Appendix 1, pp. 125–155. The Booth Mill Bore, drilled for water by the Knutsford Light and Water Company in 1902, has been discussed above (p. 69), and the record has been published by R. L. Sherlock, 1938, p. 52). It proved, as well as the Waterstones, the upper arenaceous phase named Upper Keuper Sandstone by De Rance, who examined the cores at the time of drilling.

Styal and Alderley

There are several exposures of Waterstones in the vicinity of Quarrybank Mill, Styal; for example, along the Bollin in the woods owned by the National Trust west of the mill, and in a small tributary brook which joins the river south of the mill. An old quarry on the south side of the Bollin opposite Norcliffe Hall shows 7 ft of flaggy red and grey sandstone with marl partings over 13 ft of massive red and yellow mottled sandstone; this is probably the junction of Keuper Sandstone and Waterstones.

A bore at Stamford Lodge [SJ 8303 8229] proved 43 ft of Waterstones beneath Keuper Marl. The Lindow Moss Bore (Geological Survey No. 6) [SJ 8254 8109] penetrated 132 ft of very sandy strata which were interpreted as belonging to the main Waterstones sequence rather than to the higher 'Upper Keuper Sandstone'. The top of these beds was faulted against a thick autobreccia, resembling the collapse-breccia produced by the solution of the salt. Just west of Alderley Edge a bore sunk for water for Isaac Massey and Sons [SJ 8423 7819] went through 15 ft of strata assigned to the Waterstones beneath 60 ft of drift, and then entered Keuper Sandstone. This bore lies to the west of the south-trending fault which terminates on the west of the high ground of Alderley Edge. It is thought that the throw of this fault increases south of Alderley Edge so that the outcrop of the Waterstones swings eastwards and is cut off against it, and that in the region of Nether Alderley the Keuper Marl is thrown against Keuper Sandstone.

Three miles south-east of Alderley Edge the Whirley Grove Bore (Geological Survey No. 8) [SJ 8842 7483] proved 254 ft of Keuper Waterstones. Between 150 ft and 360 ft the Waterstones were, in the main, of normal lithology; but between 106 ft (the base of the drift) and 150 ft there occurred thick beds of yellow and buff false-bedded massive sandstone, quite unlike the platy micaceous sandstones below. Similar sandstones to these have been noted recently, probably at a comparable horizon, in the district to the south (one-inch sheet 110, Macclesfield). It is largely on the strength of this bore that a fault is shown on the one-inch map, trending approximately north and south and separating the Waterstones of Whirley Grove from the Keuper Sandstone south of Alderley Edge.

Keuper Marl

Generally speaking, the same sedimentary types are present in the Keuper Marl as in the Waterstones below, but with less arenaceous and more argillaceous material; and what arenaceous material there is tends to be finer in grain. An irregular rhythm is discernible in the stratification: each sedimentary cycle, where well developed, has banded strata or striped beds at the base, frequently including such rocks as fine-grained dolomitic siltstones and even fine-grained sandstones, in thin layers alternating with mudstone which may be of exceedingly fine and even grain. Sometimes the banded strata are found to consist of alternations of light and dark mudstone, the paler layers being somewhat coarser in grain than the darker; and it is in the banded strata that such features as suncracks and the pseudomorphs of halite crystals (see p. 152) are chiefly seen. These are evidence of deposition in shallow water which frequently dried up. Ripple-marks are less common in the Keuper Marl than in the Waterstones, and no footprints have been recorded from these beds in Cheshire. Pittings in the top surface of some mudstone layers have been likened to pitting by rain; but the cause may equally well be that by which pitting is formed in modem estuarine muds when they dry out and releas‘ minute bubbles of air or other gas.

The banded strata, which may be either red or grey, pass upwards into 'blocky' unstratified mudstone, usually red but occasionally grey; and this frequently appears to owe its lack of structure to the fact that it has been broken up, mixed, and allowed to settle again before final consolidation took place. Mottling in the red blocky mudstone is of two main types. Firstly, there are irregular masses coloured light red or greyish green, the lithology of which is often found to he slightly different from that of the ground-mass in which they lie. The boundaries of these masses are not clear-cut as in the case of an autobreccia, but are somewhat indefinite, and it is suggested that they are caused by the actual incorporation of grey or light red material in the red mud while the whole was still semi-liquid. The incorporated grey sediment owes its colour to the same causes (which are as yet unsatisfactorily explained) as do the grey beds in the banded strata, the colour of which is clearly primary, that is to say that the beds were laid down grey. The second type of mottling is secondary, and includes such phenomena as the 'fish-eyes' which occur throughout the Keuper Marl in the red mudstones. 'Fish-eyes' are small spherical regions in which the red iron-oxide colouration has been discharged about a centre. A minute dark speck is frequently found at the centre and to this the name is due. The colour has been attributed to decay of specks of organic matter (see a number of works referred to in Maw 1868, pp. 354–6); but evidence has been obtained recently which suggests that in some cases at least the discharge of colour takes place around a centre which is radioactive (Ponsford 1954, p. 59). Other examples of secondary change of colour from red to greenish-grey are seen along joint-planes, where the altered zone may be only a fraction of a millimetre thick, and sometimes on the cheeks of gypsum veins.

The ferruginous colouring-pigment is apparently finely disseminated over the surface of individual grains of sediment and accounts for a very small proportion of the rock. It is thought that where the rock is grey or grey-green either from primary or secondary causes the oxide pellicle has been chemically removed, in the one case during deposition and in the other case subsequently, unmasking the true colour of thee minerals in the sediment. This view was long ago expressed by Maw (1868, pp. 369, 371), whose paper on variegation of strata is a classic. The active principle in the chemical change is, however, unknown.

Five descriptions by Dr. K. C. Dunham of thin sections of rocks from various levels in a bore drilled for Lord Egerton in 1947 [SJ 7725 8102] in Broadoak Lane, Mobberley, will help to illustrate the petrology of the Keuper Marl. This bore proved Keuper Marl to a depth of 383 ft beneath 64 ft of drift. The serial number of the rock-slice in the Geological Survey collection and the depth are given in each case:

• (E22128), depth 75 ft. Dull red dolomitic silty marl, containing, in order of abundance, dolomite in rhombs and irregular specks averaging about 0.02 mm; angular quartz grains averaging about 0.03 mm; tiny flakes of muscovite or illite and streaks of reddish-brown iron oxide, probably hydrous.
• (E22129), depth 318 ft. Grey powdery gypsiferous marl carrying bands of fibrous gypsum; composed of dolomite in crystals averaging about 0005 mm, and trains of gypsum crystals up to 0.1 mm in length, some of which lie parallel to the bedding. A little detrital quartz, muscovite and tourmaline are present.
• (E 22130), depth 332 ft. Dull red marl in which layers composed of very fine-grained dolomite, clay minerals including illite, and streaks of reddish iron oxide alternate with bands rich in angular quartz grains of about 0.05 mm average diameter. The mudstone layers appear to have been injected by offshoots from the siltstone layers. Bands of fibrous gypsum (with all refractive indices less than F54) are present.
• (E22131), depth 343 ft. Red marl similar to (E22130); the silty layers show false bedding.
• (E22132),depth 354 ft. Grey slightly efflorescent marl in which layers up to 4 or 5 mm thick of dolomitic siltstone (composed of angular quartz grains of 0.05 mm, and very fine-grained dolomite) alternate with thin, partly broken-up layers of heavily pigmented dolomitic mudstone. Highly irregular layers of fibrous gypsum appear to have been injected into the mudstone under pressure.

Certain clues to the origin of the Keuper Marl may be found in the above descriptions. There are virtually no large or rounded grains of detrital sediment. Both the grain size and the grain shape are consistent with the sediment being the "smallest tailings of wind-carried material", as it was described by Lomas (1907B, p. 195). The sedimentation of the wind-blown material, transported mainly during dust-storms, took place, it seems, in a region where a lake or lakes were intermittently forming and drying up. It is here suggested that the banded material represents dust blown into standing water, the drying up of which formed the pseudomorphs and suncracks. The blocky unstratified material may be the result of dust deposition on dry or nearly dry ground, a theory consistent with the presence of suncracks and pseudomorphs in the banded layers and their virtual absence from the 'blocky' layers.

The 2600 ft of Keuper Marl cropping out in this district do not represent the full sequence of Cheshire, for much higher beds come on towards the centre of the syncline. The Lower Keuper Marl, 1400 ft thick, is lithologically indistinguishable from the 400 ft or so of Middle Keuper Marl present in the district, where this is undisturbed by collapse due to solution of the underlying rock salt. These two units are separated by the Lower Keuper Saliferous Beds, which are 755 ft thick near the south-western margin of the district, and which represent a temporary change in conditions of deposition in the Keuper leading to a great increase in the precipitation of salt (see below).

The evaporite minerals present in the Keuper Marl include dolomite, anhydrite, gypsum, and especially halite, which far exceeds the other three in amount. No minerals higher in the 'evaporite sequence' than halite have been recorded from Cheshire, though carefully looked for in many boreholes. The dolomite occurs almost exclusively in fine-grained form disseminated through the mudstone and acting as a cementing material in some of the siltstones and fine-grained sandstone layers. Gypsum is found to some extent in crystals and grains scattered through the mudstone; in bores anhydrite has been encountered at depth in the same form (anhydrite is not usually stable within several hundred feet of the ground-surface in Keuper Marl, tending to be hydrated towards gypsum). Gypsum occurs most abundantly in veins which cut through the rock in all directions, and these may branch and join again, forming a lace-work of great complexity. The observer is struck with the analogy between these and igneous veins (see description of (E22132) above), for the mineral has the appearance of having been injected under pressure: but this cannot be the whole explanation of its emplacement, for it is clear that crystallization has taken place, presumably from aqueous solution or solution in brine, from the cheeks of the vein towards a median plane. The crystalline form is that of satin spar, the fibrous variety of gypsum, in contrast to the granular crystal form of the gypsum incorporated in the mudstone. Mixed veins of gypsum and halite may occur within, or close above or below, the Saliferous Series. In these cases the halite occupies the middle of the vein and the median plane bisects the halite, which like the gypsum is forced to adopt the fibrous habit when only the inner face of each crystal is able to grow.

A possible explanation of the mechanism by which these veins were emplaced is as follows: much of the calcium sulphate was originally deposited in the form of anhydrite, perhaps in granules finely disseminated throughout the rock; subsequently the anhydrite became hydrated, taking water from the mud around it, and perhaps even abstracting some of the loosely-combined water from the clay minerals. The hydration involved an increase in volume of the order of 30 per cent which, taking place throughout the rock, would shatter the surrounding rock and produce fissures. The newly-produced gypsum would then tend to occupy the fissures in the form in which it is found. The amount of gypsum in vein-form may in places be as much as 5 to 10 per cent of the rock, but is usually less. Taken over the whole of the Keuper Marl the amount must be very large, although no locality in the present district is known where individual veins are thick enough to repay working. Both dolomite and gypsum occur throughout the Keuper Marl in greater or less amounts.

The only evaporite mineral of commercial importance in the Keuper Marl of the district is halite, which in the main is confined to the Keuper Saliferous Beds. This occurs chiefly in the form of bedded rock salt, a mixture of halite and mudstone, but substantial amounts occur in veins, in which the crystalline habit is fibrous. The rock salt is coloured yellow, orange, brown and pink by the included mud, whereas the vein salt is usually either red or pure white, and normally has no included mudstone. The red fibrous vein salt has long been known as 'beef' by the rock-salt miners.

A fuller account of the lithology and mode of occurrence of the rock salt is to be given in the Memoir 'Geology of the Country around Chester' (in preparation),descriptive of an area which contains the only working rock-salt mine in the country. Briefly, it may be said here that the mineral is a bedded deposit, probably laid down very rapidly when the region was temporarily occupied by an embayment of a sea surrounded by hot desert, and when evaporation was high. Connexion with the open sea was probably through a narrow strait or over a bar, and the replacement for the evaporated water brought in a continuous supply of salt. It is to be inferred that sedimentation of mud derived from wind-blown dust went on continuously; and that small changes in the equilibrium between evaporation and provenance in the subsiding Keuper basin sufficed to increase or decrease greatly the deposition of salt by changing the salinity to a value above or below saturation-point, thus determining whether halite with mud, that is rock salt, or mud alone was deposited. B.J.T.

In the three bores for the Ministry of Town and Country Planning which proved rock salt in the Mobberley area, the bottom of the Saliferous Beds was found to be marked by up to 60 ft of highly brecciated and disturbed strata displaying bedding lying at all angles. Identical phenomena at the base of the Saliferous Beds has been observed in boreholes of the Holford area which have passed through the rock salt into the Lower Keuper Marl, and similar occurrences have been noted in boreholes in the Preesall saltfield of Lancashire at the same horizon. The presence of brecciated beds above rock salt is readily explained as arising from the solution of the salt by ground waters at relatively shallow depth causing collapse of the overlying strata. The presence of brecciated and disturbed beds beneath the rock salt is probably also due to solution and consequent collapse of strata; but in this case the solution of the rock salt occurred immediately after its deposition and arose from a temporary reversal of the climatic conditions. A climatic change towards aridity undoubtedly initiated the onset of rock-salt precipitation. It is suggested that a reversion to the previous, less arid, climate brought about renewed deposition of marl, and that the change to a relatively wet climate gave rise to an influx of water into the basin which redissolved the recently-formed rock salt, thereby giving rise to the penecontemporaneous breccia that marks the base of the Lower Saliferous Beds not only in Cheshire but also in Lancashire. Arid conditions, however, quickly returned, and persisted during the deposition of the rock salt of the Lower Saliferous Beds. F.M.T.

Details

Lower Keuper Marl

South of Broomedge the Waterstones pass upwards gradually into Keuper Marl by thickening of the mudstone bands and thinning of the arenaceous layers. Skerries (thin layers) of sandy material, however, are found high above the arbitrary base of the formation. Outcrops were seen in a ditch between the north-east corner of High Legh Park and Hulse Heath, and in Bradley Brook west of Primrose Hill. In the Bucklow Hill Bore [SJ 7319 8387] beds of sandstone were met with in the Keuper Marl.

The Lower Keuper Marl occupies most of the ground west of the Bucklow Fault as far south as Arley Brook and possibly farther. In the extreme south the Saliferous Beds crop out under the drift, and it is probable that Pickmere lies on or near them. The top of the Lower Keuper Marl is provisionally placed, in the absence of better evidence, just to the north of Pickmere. The ground is unrelieved by any marked feature, and is blanketed in the south by a cover of boulder clay which thins and becomes patchy north of Arley Brook. From Bradley Gorse on the edge of the district to Burnthouses near Bucklow Hill the ground is free from drift, thence the drift-cover is thin and intermittent for a distance of some two miles to the south of the Warrington–Mere Road. Over all this area are sporadic exposures of Keuper Marl, and there are numerous old pits where it has been worked for spreading on the land or for brickmaking. De Rance records that boulder clay and Keuper Marl were worked together for bricks in a brickworks, now long disused, between the north-east corner of High Legh Park and Hulseheath: the same practice is followed today at Oversleyford [SJ 811 831] near Ringway. The dip is everywhere low, 3° to 5° towards the S.S.W. being a common value. Towards the conjectural line of the Bucklow Fault the strike swings round towards the S.S.E. in the Bucklow Hill area, and exposures in Arley Brook between Stockley Farm and Waterless Bridge also show low dips towards the S.S.E. With such low dips, even small flexures cause large changes in strike.

North of Warburton there are sporadic outcrops of Lower Keuper Marl beneath the alluvium of the river Mersey east of the Ship Canal. Superficial deposits mask most of the ground, and here also, in consequence, the line marking the top of the formation cannot be placed accurately.

The arenaceous marls and 'flagstones' exposed in the river Bollin south of Hale, and their possible equivalence with the upper part of the Waterstones' of Ashley, has been discussed above. In relegating these beds to the Lower Keuper Marl, the extremely arbitrary character of the line between the two formations is stressed.

Around Ringway and over most of the area now occupied by Manchester's Wythenshawe suburb the ground is underlain by Lower Keuper Marl. Drift is present almost everywhere but is frequently thin, and there are numerous exposures in streams such as Fairywell and Mill Brooks, Baguley, and in Timperley Brook east of the Timperley Fault. The formation is exposed almost continuously in the river Rollin between the Timperley Fault at Pigsleystair and the Styal Faults near Quarrybank, and in the gullies tributary to the Bollin in Sunbank Wood and Cotteril Clough. The problem of drawing a line marking the top of the Lower Keuper Marl is again met with at the edge of the Mobberley saltfield. As is explained in the discussion on Keuper Saliferous Beds (p. 79 and (Figure 8)), experience has shown that the only practical line to map for the top of the Lower Keuper Marl and the base of the Lower Keuper Saliferous Beds is the 'outcrop' of the junction of these formations against the collapsed material caused by salt solution. This line (through B of (Figure 8)) is also the limit of salt underground. It is drawn to pass to the south-west of the Lindow Moss Bore [SJ 8254 8109], which proved a thick collapse-breccia and no salt, and to the east of the three Mobberley bores (see p. 80) which proved salt.

Evidence for the outcrop of the Lower Keuper Marl in the Mobberley and Ollerton district west of the Mobberley–Timperley Fault is based entirely on bore-holes, for superficial deposits are too thick for streams to have cut through them. The Breach House Lane, Mobberley New Hall and Kellhouse bores sunk for the Ministry of Town and Country Planning at Mobberley in 1947–8 respectively proved 247 ft, 435 ft, and 55 ft of Lower Keuper Marl resting upon Waterstones and covered by thick drift. Farther south the Radbroke Hall Bore (Geological Survey No. 10) passed through 481 ft of Lower Keuper Marl before reaching the top of the Waterstones at 562 ft. The rhythmic quality of the sedimentation in this bore is described above (p. 72) as an example of the Keuper Marl as a whole.

Logs of all these bores, with National Grid references of their sites, are given in Appendix 1, pp. 125–155.

Lower Keuper Saliferous Beds

In North Cheshire the Lower Keuper Saliferous Beds have a total thickness of upwards of 800 ft of which more than eight-tenths is salt. By kindness of the directors of Imperial Chemical Industries Limited, the section of bore H.130 in the Holford brinefield near the southern edge of the district [SJ 7134 7475] is given in Appendix 1, p. 136. Here 755 ft of Saliferous Beds were proved, with the top at 292 ft. The top of the salt (rock-head) was 'wee; that is, solution had occurred and the uppermost beds of the salt, known in the main Cheshire saltfield to the south, were missing. Above the salt, red and grey marl with gypsum was partially disintegrated by the collapse resulting from solution. According to normal practice, the base of the Saliferous Beds was taken at the base of the lowest bed in which halite was the predominant mineral, though some beds below contained a small portion of salt. A thickness of some 50 ft at the base is an alternating series of bedded rock salt and marl. There follows the 'Hundred-foot Salt', almost free from mudstone inclusions. Between 853 ft and 883 ft is the 'Thirty-foot Marl', a bed which can be recognized over a considerable area of the main saltfield. The 561 ft of Saliferous Beds above the Thirty-foot Marl consists mainly of rock salt, with a few beds of marl up to 16 ft in thickness. These can be used for water circulation before the ice-invasion. In other areas, notably, though not exclusively, those in which there has been extensive extraction of rock salt either by mining or by artificial solution in the production of 'wild brine' (see p. 117), there may be subsidence of the ground of all degrees of severity. Subsidence of ground can only normally take place where salt is so near the surface as to be in the zone of ground-water circulation, and where its upper surface, referred to in such areas as 'wet rock-head', is undergoing solution. The production of 'wild' or natural brine in the areas where the top of the salt is 'wet' is described in Chapter 7, p. 117. Followed to the deep with increasing cover the upper surface of the salt is eventually found to be 'dry', and is then referred to as 'dry rock-head'. Here the beds are not subject to solution and are disposed like the normal insoluble strata above and below them. A large area of the Cheshire saltfield is underlain by salt with a dry rock-head, and for this reason is safe from the standpoint of foundation stability—but it is doubtful if any part of the saltfield lying within the present district (Sheet 98) can be included in this 'safe' category.

Within the 'outcrop' the salt beds are overlain by beds stratigraphically higher, which during salt-solution are progressively let down towards the up-dip edge of the 'outcrop' until they are separated from the beds below the salt only by the residual beds of marl which once formed a proportion of the Saliferous Beds before solution. These, as well as much of the overlying strata, are usually highly brecciated owing to piecemeal collapse during the pro-. gressive removal of the salt. The brecciated beds crop out against the surface or against the base of the drift, and represent, in part at least, the true outcrop of the insoluble residue of the Saliferous Beds.

In making the map a decision has had to be made on where to draw the line representing the stratigraphical top and bottom of the Saliferous Beds. Normally, in insoluble strata, the line which marks the outcrop of the top of one bed also defines the lower limit of the bed above; but this is not so with the junction of the Lower Keuper Marl and the base of the Saliferous Series. (Figure 8) shows the top of the Lower Keuper Marl at A and the limit of the salt, the base of the next bed above, at B. Where the dip is shallow the distance between A and B may be large; for instance where the depth of solution was 250 ft and the dip of the undisturbed strata 3° the distance would be more than half a mile.

The line marking the junction of the undissolved top of the salt and the zone of solution (passing through C on (Figure 8)) is almost impossible to place accurately without recourse to a series of boreholes: but an approximate position can be given because it is the down-dip limit of active subsidences. It seems probable that this line, marking the lower limit of the undisturbed Middle Keuper Marl, occurs only in the extreme south-western corner of the district.

A uniform method of showing the outcrop of both the Lower and Upper Keuper Saliferous Beds has now been adopted for maps in the Cheshire salt-field. The 'outcrop' is mapped by using lines through B and C ((Figure 8)) which represent the crop underground of the bottom and top of the saliferous series against the collapsed and brecciated strata; these collapsed strata are regarded as being more in the nature of landslip, or of 'gob' in coal workings, than of solid rock.

Details

Heatley–Agden area

On the down-throw side of the Warburton Fault lies the full succession of the Lower Keuper Marl and part of the Saliferous Beds. Rock salt has been proved in a number of bores in and around Heatley village, and alongside the canal north-west of Agden Bridge. In Heatley the upper surface of the rock salt was proved between 320 and 370 ft below O.D., and the rock head is probably 'wet' throughout the area. Nearer to Agden Bridge the rock head is 100 ft deeper and is 'wet' here also, for salt works at both Agden and Heatley have produced salt by pumping natural or 'wild' brine. Since it is not necessary in the exploitation of natural brine to sink further than the 'brine-run' the full thickness of the Saliferous Beds has not been proved here. There is little doubt, however, that the salt beds in this small detached field are the same as those in the main Cheshire saltfield, though probably only the lower part of the succession has escaped solution. The northern boundary of the saltfield is the line along which the salt, traced up-dip towards the surface, is completely removed in the zone of solution.

The Heatley–Agden saltfield has been described both by Calvert (1915) and Sherlock (1921, p. 49); and little more has become known since that time, except that on the evidence of the Grey's Gorse Bore [SJ 7298 8568] the field is probably limited on the east by a fault between Agden Bridge and Bollington, which brings up lower measures to the east. Only the works at Agden Bridge are still in production.

Knoll's Green (Mobberley) and Chelford area

It has long been known that rock salt was present at Chelford (Sherlock 1921, p. 65), where it was proved in the Mere Leigh Bore [SJ 8092 7520], but it was not known that this salt extends northwards into the area east of Mobberley until, in 1947, seven trial bores were sunk by the Ministry of Town and Country Planning, at the suggestion of the Geological Survey, to prove the site for a proposed new town. The bores proved the Saliferous Beds to a total thickness of 258.5 ft in Beeches Farm Borehole [SJ 8012 8116], and 279 ft and 198 ft respectively in Mount Pleasant Farm [SJ 8095 7987] and Stubbs Farm [SJ 8001 8002] boreholes. In all cases it is thought that only the lower part of the salt is present, the upper having been removed by solution. The other four bores in this series of seven have already been referred to in discussing the Lower Keuper Marl (p. 77). It is inferred that a fault and a throw of not less than 2000 feet ranges north and south between Mobberley and Knolls Green (p. 90), and that this fault bounds the saltfield on the west. The eastern limit of the salt underground has not been defined exactly; and it must be assumed provisionally that rock salt exists south and west of a line approximately through Stockinghey, Blakeley and Coppock farms, then through Lindow End and Warford Hall. Like the Lindow Moss Borehole, the Sossmoss Borehole (Geological Survey No. 7) [SJ 8286 7663] found no salt, but proved a thick collapse-breccia with its top at 201 ft and its base at 430 ft; and this bore, too, is thought to lie in the zone of collapsed ground between the edge of the salt underground and the top of the Lower Keuper Marl. That the salt deposit east of Mobberley was hardly suspected before the sinking of the trial bores is due mainly to the slight amount of subsidence there, in spite of 'wet rock-head' conditions. Many instances of alleged subsidences were given during a public enquiry held on the Mobberley New Town proposals, but at least half of these are now known to refer to ground not underlain by salt; and it was impossible on the evidence given to distinguish active solution-subsidence from that due to other causes such as clay or peat shrinkage. The relative absence of active subsidence east of Mobberley appears to be due, as in some other areas, to the protection which thick boulder clay now affords to ground beneath which solution may have been active in pre-glacial times, by preventing water from getting into the saliferous beds except at a very slow rate.

Rostherne to Lostock Gralam

This is the largest of the three areas of saliferous ground in the district (Sheet 98), forming together with the Mobberley–Chelford deposit part of the main Cheshire saitfield to the south. The observed phenomena in this area include active subsidence at Tabley, Tatton Park and Knutsford, as well as actual rock-salt proved in the Holford Brinefield, and could be explained by the bed of rock salt rising from the south almost to outcrop near Tabley, and thence flattening out northwards to extend under Knutsford and Tatton Park. In view of the widespread block-faulting in immediately adjacent areas, and because of geophysical evidence in Tabley parish (see Appendix 2, p. 156), it has been deemed expedient to refer the northward extension of the saliferous measures to a fault trending south-eastwards through Over Tabley Hall and Heesomgreen Farm, throwing down north-east and repeating the measures.

The active subsidences beneath which salt is being dissolved include those in Tatton Park, the most spectacular of which lie between the north end of the Mere and the Hall. Here the new subsidences are bounded by lines of fracture at ground-surface which are, in effect, faults; and a new mere has been recently formed. Southwards from Tatton a zone of subsidence passes through Knutsford, where the Moor is affected and where houses on the west side of the Mobberley Road at Cross Town have developed cracks. South of Knutsford a line of ancient subsidence appears to pass to the east of Toft Hall through the dry valley now partly occupied by the lake (which, however, is itself artificial, being dammed at the southern end), and thence south-westward from near Clump o' Trees Farm. Serious subsidence has been recorded in recent times in Tabley Park, where both the church and the Old Hall were damaged. The line bounding the Saliferous Beds at Tabley may possibly be drawn too far to the south, and it should be regarded as provisional only. The evidence here is not good.

Rostherne Mere is a feature which does not at the present time appear to be affected by solution-subsidence. Nevertheless it seems probable that this, a typical subsidence-mere, is the product of natural salt solution in the recent geological past, and since the retreat of the last ice sheet. A possible explanation of the cessation of subsidence here may be that a natural brine-run, active during the immediately post-glacial low sea-level, is now inhibited by the present reduced fall to the sea. Or again, it may be that all the salt has by now been removed.

It has long been known that subsidence caused by the abstraction of 'wild brine' (p. 117) may initially affect the ground near the site of pumping and then develop radially along well-marked lines of disturbance, the distal ends of which are the seats of the most active collapse. The lines of subsidence mark the 'brine-runs', of which the older parts, nearer to the point of abstraction, tend to reach stability because water entering the salt beds rapidly reaches saturation, and therefore causes most solution near the point of entry. The linear subsidences through Toft, Knutsford and Tatton Park may be of this type. As most of the brine produced in the Northwich area is now got by the controlled method, in which no connexion with surface ground-water is made, subsidence may now abate. Nevertheless it is possible that a brine run once started will still operate by natural processes, though perhaps at a reduced rate; so delaying the cessation of active subsidence.

Middle Keuper Marl

The line laid down on the map for the base of this bed is, as explained above (p. 79), that separating the region of undisturbed Middle Keuper Marl, overlying salt too deep for solution to have taken place, from the region where the Middle Keuper Marl has collapsed above shallow salt with a 'wet rock-head'. The line is at position C of (Figure 8). Thus, Middle Keuper Marl is depicted, on Sheet 98, only in the extreme south-western correlation over short distances, but the upper part of the sequence is generally more variable than the lower. Whilst there is little doubt that the salt at Heatley and Agden, and at Mobberley, is of the same series as at Holford, only the lower part of the succession is present in those localities, the upper salt layers proved in bore H.130 having been removed by solution.

In mapping the Saliferous Beds a difficulty is at once met with; for salt being soluble does not crop out at the surface in England, and in this context 'surface' means the base of the drift where drift is present. A number of bores have been sunk in places near the up-dip edge of the saltfields in the Agden, Heatley, Mobberley and Holford areas of the present district, as well as in the Middlewich and Winsford areas of the district to the south (Sheet 110). Some are in areas of active subsidence, and some are near the known 'featheredge' of the salt as nearly as it can be determined by bores. In no case is the top of the salt less than 200 ft from the surface of the ground except at Meadow Bank, Winsford, which lies in the valley of the Weaver considerably below the general level of the country thereabouts. Even in the northernmost bores of the Holford area the salt is everywhere more than 250 ft from the surface, and usually more than 200 ft below the base of the drift. In some cases where salt is recorded within 200 ft of the base of the drift, it is suspected that the disintegrated collapsed marl which is almost invariably found above salt which has undergone solution, has been mistaken for drift.

It is clear that in the districts mentioned the salt does not 'crop out' against the base of the drift, but against an undulating surface which varies between about 200 ft and 400 to 500 ft below the present land surface. This surface represents the lower limit of the zone of ground-water circulation, within which salt has been removed by solution. There is strong evidence that in some places thick sheets of impervious boulder clay have, since their deposition in Pleistocene times, protected the ground beneath, so that what is seen in those areas when stripped of drift is the position that obtained immediately before invasion by the ice. In such areas there may be little or no subsidence at the present time, in spite of the presence of salt at relatively shallow depth; and this salt may be overlain by many feet of highly brecciated and collapsed marl, the lower surface of which indicates the base of the zone of ground corner, for it is only there that it is considered to be undisturbed. Elsewhere in the district no record is known of Saliferous Beds that have undergone no solution. The material which lies between the 'wet rock-head' and the surface must consist mainly of Middle Keuper Marl, but it is not, strictly speaking, in place, having been progressively let down, in some cases through hundreds of feet above the dissolving rock salt, and in many cases having suffered extreme brecciation in the process (see p. 79). To mark such measures on the map as Middle Keuper Marl, even though they do overlie the Lower Saliferous Beds, would be to obscure the stratigraphical picture, and indeed would prevent the outcrop of the Lower Saliferous Beds being shown at all, for the collapsed material extends beyond the up-dip limit of the salt underground.

Lithologically, the Middle Keuper Marl is indistinguishable from the Lower Keuper Marl. It is recorded in the logs of Plumley No. 3, Holford No. 130 and Stubbs Farm bores (see (Figure 7) and Appendix 1, pp. 125–155). The collapse suffered by these beds ranges from slight, with minor disturbance of strata and the production of joints and minor planes of shear, to severe, with total brecciation of many feet of strata due to piecemeal collapse into solution cavities. Once the marl is thoroughly broken up there is probably less resistance to the entry of surface water, and solution of the salt below is thereby accelerated.

The exposures in Wincham Brook, north of Lostock Gralam, showing red mudstones with a variable though generally southward dip of between 3° and 5°, are considered to be partially collapsed Middle Keuper Marl. B.J.T.

References

ALTY, S. W. 1926. The petrographic features of Keuper Rocks from a boring at Wilmslow, near Stockport, Cheshire. Proc. Liverpool Geol. Soc., 14, pp. 278–83

BINNEY, E. W. 1846. On the relations of the New Red Sandstone to Carboniferous strata in Lancashire and Cheshire. Quart. 7. Geol. Soc., 2, pp. 12–26

BINNEY, E. W. 1855. On the Permian beds of the north-west of England. Mem. Manch. Lit. Phil. Soc. (2), 12, pp. 209–69

BROCKBANK, W. 1891. Notes on the discovery of Estheria minuta var. Brodieana, by Mr. C. E. De Rance, F.G.S., at Alderley Edge. Mem. Proc. Manch. Lit. Phil. Soc. (4), 4, pp. 12–13 and 31

BROCKBANK, W. and DE RANCE, C. E. 1891. Notes on a geological section in the railway cutting from Levenshulme to Fallowfield. Mem. Proc. Manch. Lit. Phil. Soc. (4), 4, p. 282

CALVERT, A. F. 1915. Salt in Cheshire. London.

DE RANCE, C. E. 1894. The Salt Union borehole at Marston. Trans. Manch. Geol. Soc., 22, pp. 269–92

EVANS, J. W. and STUBBLEFIELD, C. J. 1929. Handbook of the Geology of Great Britain. London.

GETNITZ, H. B. 1889. Ueber die rothen and bunten Mergel der oberen Dyas bei Manchester. Ges. Isis in Dresden, 3, pp. 48–57

GETNITZ, H. B. 1890. Red and variegated marls of the Upper Dyas, near Manchester. Trans. Manch. Geol. Soc., 20, pp. 537–54

GRAY, J. W. and KENDALL, P. F. 1893. The Relations of the Triassic and Permian rocks at Stockport. Rep. Brit. Assoc. (Nottingham).

HICKLING, G. 1918. The geology of Manchester as revealed by borings. Trans. Manch. Geol. Soc., 35, pp. 189–237

HULL., E. 1861. The geology of the country around Altrincham, Cheshire. Mem. Geol. Surv.

HULL., E. and GREEN, A. H. 1866. The geology of the country around Stockport, Macclesfield, Congleton and Leek. Mem. Geol. Surv.

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

JONES, T. R. 1891. On some more fossil Estheriae. Geol. Mag. (3), 8, pp. 49–57 and Pl. II

KENDALL, P. F. 1917. in Handbuch der Regionalen Geologic', British Isles, pp. 171–92

LOMAS, J. 1907A. Desert conditions and the origin of the British Trias. Geol. Mag. (5), 4, pp. 511–4, 554–63

LOMAS, J. 1907B. Desert conditions and the origin of the British Trias. Proc. Liverpool Geol. Soc., 10, pp. 172–97

MAW, G. 1868. On the disposition of iron in variegated strata. Quart. J. Geol. Soc., 24, pp. 351–400

PONSFORD, D. R. A. 1954. Note on the occurrence of Uranium at certain horizons in the Enville Beds. Bull. Geol. Surv. Gt. Brit., No. 5, pp. 59–60

POOLE, E. G. and WHITEMAN, A. J. 1955. Variations in thickness of the Collyhurst Sandstone in the Manchester Area. Bull. Geol. Surv. Gt. Brit., No. 9, pp. 33–41

RAWLINSON, R. 1853. On foot-tracks found in the New Red Sandstone at Lymm, Cheshire. Quart. J. Geol. Soc., 9, pp. 37–40

ROEDER, C. 1890A. Some newly discovered species in the Upper Permian deposits of Manchester. Trans. Manch. Geol. Soc., 20, pp. 535–7

ROEDER, C. 1890B. Notes on the Upper Permians, etc. at Fallowfield, lately laid open. Trans. Manch. Geol. Soc., 20, pp. 615–27

ROEDER, C. 1892A. Description of fossils found in the Permian Upper Series at Fallowfield. Trans. Manch. Geol. Soc., 21, pp. 13–6

ROEDER, C. 1892B. Notes on the Permians and superficial beds at Fallowfield. Trans. Manch. Geol. Soc., 21, pp. 104–13

SHERLOCK, R. L. 1921. Rock Salt and Brine. Mem. Geol. Surv., Min. Resources, 18

SHERLOCK, R. L. 1938. Boring at Booth's Mill, Knutsford. Summ. Prog. Geol. Surv. for 1936, pp. 52–3

SHERLOCK, R. L. 1947. The Permo-Triassic Formations. London.

STRAHAN, A. 1882. The Geology of the Neighbourhood of Chester. Mem. Geol. Surv.

SWINTON, W. E. 1960. The History of Chirotherium. Liv. and Manch. Geol. J., 2, pp. 443–73

TAYLOR, B. J., EARP, J. R., POOLE, E. G. and MAGRAW, D. In preparation. Geology of the Country around Chester. Mem. Geol. Surv.

TONKS, L. H., JONES, R. C. B., LLOYD, W., SHERLOCK, R. L. and WRIGHT, W. B. 1931. The Geology of Manchester and the south-east Lancashire Coalfield. Mem. Geol. Sum

TRECHMANN, C. T. 1930. The Relation of the Permian and Trias in north-east England. Proc. Geol. Assoc., 41, pp. 323–35

WILLIAMSON, W. C. 1867. On the Cheirotherian footprint from the base of the Keuper Sandstone at Daresbury, Cheshire. Quart. J. Geol. Soc., 23, pp. 56–7 Wool), A. 1935. The Origin of the Structure known as Guilielmites. Geol. Mag., 72, pp. 241–5

WRAY, D. A. 1948. The Pennines and adjacent areas. Edit. 2. British Regional Geology. Geol. Surv.

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

Chapter 5 Structure

The structure of this district is most readily understood when appraised in its regional setting. Immediately to the east of Stockport lie Coal Measures, which form the south-eastern extension into Cheshire of the Lancashire Coalfield. Stockport itself lies on Permo-Triassic rocks, which form the northeastern rim of the Cheshire Basin. Viewed broadly, the Lancashire Coalfield lies on the western limb of the major Pennine Anticline; and this field is the western counterpart of the Yorkshire Coalfield which lies on the opposite side of the anticline. The Pennine Anticline, however, is not a simple structure but includes a number of north-south subsidiary folds. A southerly-pitching syncline increasing in magnitude towards the south trends from Rochdale through Chadderton to Levenshulme, where it is obscured by Permo-Triassic rocks and lies to the north of the district. The Mossley Anticline—the 'Marginal Anticline' of G. Hickling (1915, p. 279 and fig. 2)—passes just to the east of the district, and the Goyt Syncline lies still farther east. To these folds may be added, farther south, the syncline of the North Staffordshire Coalfield and its complementary anticlines to the east and to the west, as well as the syncline containing the Cheadle Coalfield. All these north-to-south folds are of Hercynian age. There is, however, another definite fold trend of Hercynian age which, in general, has an easterly direction, although there are variations both to the north and to the south of east. Thus a series of east-north-easterly anticlines are seen to lie in the Clitheroe region and are flanked to the south by the Burnley Syncline of similar trend which, in turn, is flanked by the Rossendale Anticline farther south. It is possible that other east-west folds lie buried beneath Permo-Triassic rocks in the Cheshire Basin. For example, a borehole at Heswall on the Wirral proved, beneath Permo-Triassic rocks, thin Lower Coal Measures on Millstone Grit, thereby indicating a pronounced pre-Permo-Triassic arching in that area. Again, at Ardwick, Manchester, Permo-Triassic rocks rest on Upper Coal Measures, but south of Macclesfield Millstone Grit immediately underlies the Trias, thus indicating an upturn of Carboniferous rocks towards the south which may extend westwards beneath the Cheshire Plain.

The Permo-Triassic rocks of the Cheshire Basin are heavily faulted. The longer axis of the basin trends towards the north-northeast, being flanked on the west by the Carboniferous rocks of North Wales and on the east by the foothills of the Pennine Uplands. Within the district of Sheet 98 the structure is dominated by the main synclinal feature, which gives rise to a progressive swing of dip from south-southwest in the north-west of the district to due west in the east. Where they are seen together in the east of the district, the Carboniferous and Permo-Triassic rocks have the same general direction of dip, though the amount differs; and it appears, from a study of the relationship of the two formations in the Manchester and Wigan areas, that this also holds, generally speaking, for the Carboniferous rocks concealed beneath the Permo-Triassic rocks along the northern margin of the district.

Superimposed on the main synclinal fold are minor flexures. The Romiley Anticline, a branch of the Mossley Anticline, trends south-west through Romiley from the north-east corner of the district, and disappears beneath the Permo-Triassic rocks at a faulted junction east of Stockport. It is responsible for a change of strike in the Lower Coal Measures through almost a right-angle around Romiley and even more at Werneth, yet its presence has not been detected in the Permo-Triassic rocks south-east of Stockport. The Bollington Anticline, a much-faulted fold trending a little north of west through Bollington, has no discernible effect on the Triassic strata west of the Red Rock Fault; albeit exposures in the red rocks are not good, and bores are not sufficiently numerous to permit detailed structures to be worked out. The Poynton Syncline intervenes between the Romiley and Bollington anticlines, and accounts for the existence of the Poynton Coalfield.

The dips in the Permo-Triassic rocks reflect the steady swing of the beds round the north-eastern rim of the Cheshire basin, except to the north of Alderley Edge, where a gentle anticlinal fold centred on Wilmslow plunges westward, and is intersected by a number of north-south tension-faults. Most of the district lies within the belt of major faults that has been described in the Manchester area to the north (Tonks and others 1931, p. 170).

Earlier geological maps of parts of Cheshire have displayed a deceptive simplicity in the structure affecting the Permo-Triassic rocks. Faults known in the coalfields have been shown as dying out towards the centre of the basin, because the evidence failed where the rocks were concealed beneath thick drift, and because the few isolated exposures were difficult to interpret in the absence of recognizable horizons in the Permo-Triassic rocks. The resurvey, supported by the programme of boring (see Preface and p. 156) and by the geophysical investigation (pp. 156–167), has shown that the Permo-Triassic rocks are almost as intensely faulted as the Carboniferous on which they rest. Out of ten bores drilled to depths down to 1000 feet by the Geological Survey to prove structure, four penetrated the planes of faults of greater or less magnitude and a fifth was probably very close to a fault. (Figure 9) shows all faults with throws of more than 1000 feet; except one to the south of Marple, all these affect the Permo-Triassic rocks. The precise pattern of faulting beneath the heavily drift-covered areas of the district is to some extent conjectural, though the extrapolation of faults from the known to the unknown has been, in some cases, assisted by geophysical evidence. In every case where doubt exists, the simplest explanation to fit the known facts has been adopted: new evidence, should it be obtained in the future, is bound to lead to some modification. Nevertheless, the main structural features, in particular the main faults, can be accepted with confidence. The most conspicuous feature of the major faults is the way in which the trend of the fault belt as a whole changes from south-east to south as it is followed towards the eastern rim of the Cheshire Syncline. Thus the southerly continuation of Manchester's Pendleton Fault is thought to enter the present area, possibly with a somewhat reduced throw, trending south-eastwards towards Cheadle Heath; for here a large fault is known with a downthrow east of more than 1000 feet. East to west gravity-traverses through Cheadle Heath, Bramhall Park and Kitt's Moss indicate that this fault probably continues due south.

The East Manchester and West Manchester Faults and the Bradford Fault all have a south-easterly trend and throw down north-east. Southwards they join and become known as the Heaton Chapel Fault of the Stockport area; and this fault and its branches adopt a nearly north-south trend towards the south of Stockport town. The Red Rock Fault—really a group of faults, the name being given locally to the one which happens to throw Carboniferous and Permo-Triassic rocks together—runs almost north and south, a trend followed also by the Cheadle Heath, Kirkleyditch and Alderley faults. The Warburton Fault enters the district with a south-easterly trend and probably does not extend as a major dislocation far beyond Arthill. The Timperley–Mobberley Fault ranges north and south and continues beyond the southern margin of the district with the same trend.

The blocks between the major faults are intersected by numerous minor faults of widely different magnitudes; and there are probably many, of relatively small throw, whose presence is as yet unsuspected.

Tectonic history of the area

Since Upper Carboniferous rocks are the oldest visible at the surface or proved in bores, no evidence of earlier folding exists within the district. Movements which have left their imprint on the exposed rocks belong to two periods, post-Carboniferous (Hercynian) and post-Triassic, probably Tertiary; the former being responsible for the strong sub-Permian unconformity, and the latter for the folding accompanied by extensive major faulting affecting rocks of all ages in the district.

Pre-Permian folding

The effect of the pre-Permian movements in this district was to throw the Carboniferous rocks into two sets of folds with easterly and northerly trends respectively, the crests of which were denuded. The initiation of the Rossendale Anticline to the north of Manchester, and of the Pennine uplift, dates from this time, and this also was the period during which the main coalfields, as they are known today, were determined. The folding was accompanied by elevation of the land; and this, together with the desiccating climate, led to deep oxidation of the Carboniferous sediments (Trotter 1953, p. 1), and perhaps also to the actual ignition of coal seams, the edges of which were at crop in the desert. The period of uplift and erosion was long enough for several thousand feet of Carboniferous sediments to be removed, leaving a surface of considerable relief, before the earliest of the Permo-Triassic rocks, the Collyhurst Sandstone, was deposited—at first in the hollows and then over the whole area across the eroded and reddened edges of the Carboniferous strata.

A precursor of the main Hercynian movements, late in the Upper Carboniferous times, was postulated in the Wigan memoir (Jones and others 1938, p. 63) to explain an apparent transgression of 'red and purple marls' of Carboniferous age across the eroded edges of the Middle Coal Measures. Since these 'marls' are now seen, in the light of work in the St. Helens area (Trotter 1954), to include Middle and Upper Coal Measures reddened beneath a desert land-surface, evidence for an unconformity at their base disappears—as it does also in Cumberland in respect of the base of the Whitehaven Sandstone Series' (Taylor 1961, p. 18). Instead, an unconformity at the top of the 'Red Beds' is indicated.

Howbeit, this argument does not prove that the land surface, over which the Permo-Triassic rocks were later laid down, was the only one affected by reddening. Some reddening may be related to a land surface elevated by the earliest precursors of the Hercynian movements, perhaps pre-dating the Ardwick Limestone Group. The presence of similar early reddening on the east of the Pennines is hinted at by Edwards (1951, p. 77).

Besides folding, there was considerable compression, involving shearing and perhaps thrusting, along a belt of country passing to the east and south of the district, possibly at the junction of deep-seated tectonic blocks; but the main effect in this district was to tilt the Carboniferous strata down towards the west. South of Macclesfield the juxtaposition of the highly sheared Carboniferous and the relatively undisturbed Triassic rocks dates the movements as pre-Permo-Triassic. Once started, the Cheshire syncline continued to develop well into Triassic times, for upwards of 8000 feet of Triassic sediments were laid down round a centre of deposition which is thought to lie somewhere within the present tectonic syncline.

Pre-Permian faulting

In memoirs on adjoining areas (Tonks and others 1931; Jones and others 1938) it has been considered that the folding and faulting are inseparable, and that roughly half the movement on the major faults took place in Hercynian times. The evidence used was the variation in thickness of the Collyhurst Sandstone, which was believed to show that the faults were moving while the sandstone was being deposited. Poole and Whiteman (1955, pp. 33–41) have, in the light of recent bores through the Collyhurst Sandstone, re-interpreted this evidence in the vicinity of Manchester, and have shown that the variations in thickness of this formation are due to the uneven land surface on which it was deposited. Any apparent relationships that they bear to faulting are considered by these authors to be fortuitous, except in the case of the Bradford Fault: even here the evidence is inconclusive, for Perrno-Triassic rocks are present only on the downthrow side of the fault in the Bradford area; and no assessment, except by extrapolation, can be made of the amount of throw which affects the Permo-Trias. The Bradford Fault is thought to join the East Manchester and the West Manchester faults to form the Heaton Chapel Fault in this district. There is no evidence of its throw in the Carboniferous, hence no conclusion is possible about its movement in Hercynian times.

In the coalfield east of the Pennines many faults proved in colliery workings do not affect the overlying Permian rocks, but some are entirely post-Triassic. In the Stoke-on-Trent memoir the Florence Fault is described as having a larger throw in the Carboniferous than in the Triassic rocks; but the other major faults in this coalfield may, though listed under the heading 'Pre-Triassic Faults', equally well, on the evidence, be post-Triassic. The Apedale Fault, in particular, has a very large post-Triassic throw. The strong tendency amongst early geologists working on the western side of the Pennines to treat the major faults as of Hercynian age is now seen to be mistaken: it gave a spurious simplicity to their maps of the Permo-Triassic rocks.

The evidence of pre-Permian faulting in the district is summed up as follows: The Hercynian faulting of other areas may well have affected the Carboniferous rocks of this area to some extent; but no instance is known in this district of a fault which can be definitely dated as Hercynian, or which can be said to have an Hercynian component in its throw. All the big faults are normal tension-faults and are post-Triassic.

Post-Triassic folding

The movements which initiated the Rossendale Anticline and the Pennine uplift in late or post-Carboniferous times were repeated later, probably during the Alpine earth-storm of Tertiary age; but the major fold of this date resulted in the Cheshire basin as it is today, in which Permian, Triassic and Jurassic rocks are folded and preserved.

To the north of the district there is a gentle, but strongly faulted, anticlinal flexure in the Permo-Triassic rocks trending north-east and south-west through Wigan and plunging towards Liverpool. Its axis is parallel to that of the Cheshire Syncline, to which it is complementary. This gentle fold is responsible for the removal of Permo-Triassic material from the exposed Wigan and West Manchester coalfield: it is, therefore, of profound economic importance, and is also responsible for the southerly component in the dips along the northern part of the district. It is almost certainly of Tertiary age.

Post-Triassic faulting

The major faults affecting the Trias, some of which are very large, are individually described below. They are almost certainly Tertiary in age, their formation accompanying or closely following the folding. Further, the larger faults affecting the Carboniferous rocks on the Pennine flanks are probably of this age too, especially if their trend is north to south. In this category are included the Rainow and Kerridge faults, which run almost parallel to the component of the 'Red Rock Fault' which passes through Bollington station.

All these post-Triassic faults are, as far as can be ascertained, normal; though the possibility exists of some lateral movement on the north-south faults along the western flanks of the Pennines, including the 'Red Rock Fault'.

Summary

The tectonic history of the district is summed up as follows: Gentle folding, accompanied by uplift and erosion of the anticlinal crests, possibly began late in Upper Carboniferous times and developed into the main Hercynian folding movements, the chief effects of which in this district were the initiation of the Rossendale and Pennine uplifts to the north and east. At the same time strong compression was affecting a narrow belt of country to the east and south of the district. In post-Triassic (probably Tertiary) times further compressive movements deepened the Cheshire Basin and further elevated the Rossendale and Pennine uplands; but this time the folding was accompanied by intense faulting which displaced the rocks in many places by more than 2000 feet. B.J.T., F.M.T.

Details of faults

Warburton Fault

This fault was noted by G. W. Ormerod (1848, p. 268) and indicated on the map accompanying his paper. He estimated the throw at more than 1500 feet, and showed it trending south of Rostherne Mere and extending almost as far as the 'Red Rock Fault' south of Macclesfield. Actually the throw must be greater than 2000 feet, for Lower Keuper Saliferous Beds are thrown against Upper Mottled Sandstone. The pronounced geophysical anomaly detected by the torsion-balance at Oughtrington (Bullerwell 1954, p. 10) and by gravimeter-traverses during the resurvey (Appendix 2) appears to die out south-east of Arthill; but the Grey's Gorse Borehole [SJ 7298 8568] proved Keuper Waterstones near Arthill, that is north of the projected line of the Warburton Fault and in line with the Agden–Heatley outcrop of the Lower Saliferous Beds. A major fault, throwing down west, is thus inferred to lie between this bore and the saltfield, and to take on most of the throw of the Warburton Fault, which it probably meets near Arthill. As this fault appears to have little effect on the outcrop of Keuper Sandstone exposed in the Ship Canal at Partington and proved in the Hogswood Farm Borehole [SJ 7437 9004], it is concluded that most of its throw is lost against a fault trending south-east, described below as the Dunham–Ashley Fault.

Bucklow Fault

A large fault with an easterly downthrow, known to the south as the King Street Fault, enters the district near the south-western corner with a north-northwesterly trend, then changes direction to north-northeast. The line separates ground underlain by the Lower Keuper Marl between Pickmere and High Legh, from country partly occupied by the Lower Keuper Saliferous Beds between Knutsford and Lostock Gralam. Farther north there is clearly a fault, also down east, between the Keuper Waterstones of Millington and Bucklow Hill and the outcrop of saliferous measures, indicated by present or past subsidence, around Mere, Tatton Park and Rostherne.

Breaks in the gravity gradients north-west of Wincham [SJ 6826 7568] and near Feldy Green [SJ 6978 7904] indicate the fault, and tend to show that the King Street–Pickmere Fault and the Bucklow Fault are the same, forming a master-structure at least twenty miles in length.

Dunham–Ashley Fault

The presence of this fault is inferred between the Ashley Borehole (which penetrated some 900 feet of Keuper Waterstones) and the country to the north-east where Keuper Marl is exposed, dipping south-west, along the Bollin. South-eastward the fault is believed to meet the Timperley–Mobberley Fault, and north-westward to pass between the Keuper Waterstones of the Grey's Gorse [SJ 7298 8568] and Bollington Vicarage [SJ 7271 8665] boreholes and the supposed Keuper Marl underlying Bowdon. No confirmation of the presence of this fault was obtained from the geophysical survey, due perhaps partly to the extreme uncertainty of its position, and partly to the juxtaposition of materials of comparable specific gravity along much of its length.

Ashton-on-Mersey Fault

Since the time of the original survey by Hull in 1860 it has been known that a fault, throwing down east, must run between the Bunter

Sandstone of Carrington and the Lower Keuper measures in the north-eastern environs of Sale. The old map shows a fault passing through Ashton-on-Mersey and to the east of Timperley, where the Keuper escarpment is abruptly terminated.

The geophysical evidence now shows that the Timperley Fault has a north to south trend and is part of a major structure passing near to Mobberley, but the Ashton-on-Mersey line is retained in the present survey, though it is slightly altered in trend to a position indicated by breaks in the gravity-gradient along two of the traverses at points [SJ 7810 9160] and [SJ 7732 9248].

The belief in a separate fault with a north-westerly trend through Ashton-on-Mersey is strengthened by the fact that the Maple Road Borehole, sited in line with the two gravity anomalies mentioned above, actually penetrated the plane of a fault throwing Keuper Marl against Keuper Waterstones. This fault is thought to pass to the west of Fairywell Brook, where Keuper Marl is exposed, and is taken on the map through a line of minor anomalies detected on three traverses [SJ 8086 8563], [SJ 8129 8483] and [SJ 8188 8373].

Timperley–Mobberley Fault

The northern portion of this fault was first noted near Timperley by Hull (1861, p. 7), whose mapping showed a subdued escarpment of Keuper Sandstone ending at Timperley, and Keuper Marl outcropping in a brook to the east, along the extrapolated line of strike. He estimated the throw at about 200 yd, and conjectured that it crossed the Bollin at Quarry Bank. The fault was later seen in a sewer-trench along the main road through the village: just west of the main cross-roads 'white rock' and red shale were seen in contact at a fault, the plane of which was filled with white clay; but the precise trend was not then ascertained.

The Mobberley portion of the fault was unsuspected until bores were drilled by the Ministry of Town and Country Planning in 1947 (see p. 80). These showed that a major fault with an easterly downthrow of some 2000 feet must pass near the village, bringing Keuper Saliferous Beds on the east against Keuper Waterstones. At first this fault was regarded, in the absence of other evidence, as a continuation of the Warburton Fault; but the gravity-survey indicated a pronounced and almost continuous anomaly trending north and south through Timperley and Mobberley, the most reasonable explanation for which is that the fault at Timperley and that at Mobberley are one and the same.

Cheadle Heath Fault

This is the southerly continuation of the Pendleton Fault of Manchester. Boreholes for water around Cheadle Heath have long since proved its position, and a pronounced break in the gravity-gradient near where the old Cheshire Lines Railway crosses the Stockport to Altrincham Road [SJ 8756 8958] supports this. South of Cheadle Heath the fault, in the Manchester area one of the main 'north-westers', swings to a southerly trend, and its course is thought to be marked by gravity-breaks at Bramhall Park [SJ 8816 8624] and Kitt's Moss [SJ 8835 8466]. The southerly continuation of this fault is inferred to pass west of Mottram Old Hall and east of Harebarrow. This is possibly an over-simplification of the real structure, but no evidence is available for any other. The Whirley Grove Borehole [SJ 8842 7483] proved some 250 feet of Keuper Waterstones on Keuper Sandstone, giving strong evidence of a considerable fault between that point and the Keuper Sandstone areas to the west; moreover, a gravity-break near New Lane Farm [SJ 8802 7628] is near the line where such a fault might be expected.

Heaton Chapel Fault

The East Manchester and West Manchester faults, the Ardwick Fault and the Bradford Fault, the last mentioned having a throw of some thousands of feet in the Carboniferous, all throw down east and unite to the southeast of Manchester, entering the district almost along the line of the Levenshulme to Stockport railway, and following that line as far as Heaton Chapel, passing to the east of the exposures of Upper Coal Measures in the Slade Lane cutting at Levenshulme. South of Heaton Chapel, evidence from boreholes and surface exposures show the course that it must follow through Stockport. A break in the gravity-gradient near Bramhall Green [SJ 8960 8634] is thought to indicate its trend south of the town, and it is shown on the map as dying out south of Adlington Park, where there is no further evidence for it.

Red Rock Fault

There is evidence that the Red Rock Fault is not everywhere the same dislocation, but is merely that particular fault in a plexus of westerlydownthrowing structures which brings the red (Permo-Triassic) rocks against the Carboniferous, thus bounding the coalfields of Poynton and Macclesfield. It is not present to the north of the Stockport to Woodley road, for colliery workings between there and the River Tame show a normal junction between the Collyhurst Sandstone and the Coal Measures. There is evidence of a fairly large fault throwing down east, separating the country to the south of Stockport (where Manchester Marl and Collyhurst Sandstone are near the surface) from the country containing the Hazel Grove Bore and the exposures of Pebble Beds in Norbury Brook near Millbank; and this evidence is supported by sharp breaks in the gravity-gradients along traverses near Grundy Fold [SJ 9086 8600] and Poynton station [SJ 9104 8370] and east of Adlington station [SJ 9162 8040]. It is this fault which is thought to 'neutralize' the westerly-throwing Red Rock Fault north-east of Stockport.

The Red Rock Fault has a throw of at least 600 feet at Poynton, probably increasing southwards. An east-west gravity traverse through Hazel Grove-cum-Bramhall parish shows two breaks in the gradient near the Hazel Grove to Macclesfield road [SJ9230 8568], [SJ 9288 8560]; but in the absence of other supporting evidence a generalized line is shown through this district on the map. Farther south a major anomaly detected on three east-west traverses [SJ 9305 8342], [SJ 9290 8200], [SJ 9270 8026] indicates a position for the fault which agrees with the geological evidence.

South of here the fault continues towards the centre of Macclesfield, where a sharp break in the gravity curve was detected; and the geological evidence points to the presence of Triassic sandstones on both sides of it for some three miles near the southern edge of the district, having been brought on to the east by a second fault also throwing down west and trending through Bollington station and Hurdsfield, which probably joins the main fault north-east of Whiteley Green,

Kirkleyditch Fault

The Keuper Sandstone Conglomerates dipping west-southwest at and to the south of Kirkleyditch, are clearly detached by a fault from the country to the west underlain by Upper Mottled Sandstone, and from the main mass of Keuper Conglomerate capping Alderley Edge. A break in the gravity gradient near Kirkleyditch [SJ 8730 7848] supports the inferred position of this fault. To the north and south its line must be to a certain extent conjectural, and it is shown as having a roughly north-south trend.

Alderley Fault

The original map by Hull and Green showed a normal junction between the Lower Keuper Sandstone of Alderley and the Keuper Marl to the south-west. Subsequently a bore in 1894 at Alderley Edge [SJ 8423 7819] proving Keuper Waterstones indicated the intervention of a fault between this position and the Keuper Sandstone to the east.

Other faults

The faults shown on the one-inch map are almost certainly a small fraction of the total which exist, for structural evidence is very limited in the drift-covered Triassic areas; and to this extent the structures shown are generalized.

The fault shown as trending south-eastward near Dairyhouse Farm, Tabley, and Ullardhall Farm, Toft, throws down north-east, repeating the crop of the Lower Saliferous Series. It is responsible for the existence of salt beneath Tatton Park and Knutsford and near Lower Peover, and its mapped position is supported by gravity-breaks at three points [SJ 7300 7844], [SJ 7226 7948] and [SJ 7494 7492]. The structure shown as trending south-east from Knutsford and dislocating the outcrop of the Lower Saliferous Series, is a preferred position, for there is some geophysical support for a more southerly trend which would take the line near to Ashtree Farm, Ollerton. In either case the fault probably ends against the large Mobberley Fault. Several faults in Stockport are plotted from borehole evidence and are not named. In the Carboniferous area, where exposures are generally better, numerous minor faults are shown. In the Poynton Coalfield small dislocations having trends with a large east and west component were known to the miners as the Marl, Worth Hall, Park and Sheepwash Faults. It is not known if these affect the Triassic rocks, and they are shown as ending against the Red Rock Fault. J.T.

References

BULLERWELL, W. 1954. A Gravitational Survey over a concealed portion of the Warburton Fault near Lymm, Cheshire. Bull. Geol. Sum Gt. Brit., No. 6, pp. 1–12

EDWARDS, W. 1951. The Concealed Coalfield of Yorkshire and Nottinghamshire. Edit. 3. Mem. Geol. Surv.

HICKLING, G. 1915. The geological structure of the South Lancashire Coalfield. Trans. Manch. Geol. and Min. Soc., 24, pp. 274–96

HULL, E. 1861. The Geology of the Country around Altrincham, Cheshire. Mem. Geol. Surv.

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

ORMEROD, G. W. 1848. Outline of the principal Geological features of the Salt-Field of Cheshire and the adjoining districts. Quart. J. Geol. Soc., 4, pp. 262–88

POOLE, E. G. and WHITEMAN, A. J. 1955. Variations in the thickness of the Conyhurst Sandstone in the Manchester area. Bull. Geol. Surv. Gt. Brit., No. 9, pp. 33–41

TAYLOR, B. J. 1961. The Stratigraphy of Exploratory Boreholes in the West Cumberland Coalfield. Bull. Geol. Sun^,. Gt. Brit., No. 17, pp. 1–74

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.

TROTTER, F. M. 1953. Reddened Beds of Carboniferous age in North-West England and their origin. Proc. York. Geol. Soc., 29, pp. 1–20

TROTTER, F. M. 1954. Reddened Beds in the Coal Measures of South Lancashire. Bull. Geol. Surv. Gt. Brit., No. 5, pp. 61–80

Chapter 6 Pleistocene and Recent deposits

Introduction

It was in 1864 that Edward Hull wrote in 'The Geology of the Country around Oldham' (1864, p. 48): "The aspect of the Boulder Clay is so familiar to all of us that it scarcely requires description; at the same time there are few formations which require closer scrutiny in order to arrive at a true notion of the phenomena attending their deposition": and although Hull himself is now known to have been in error regarding the origin of the drifts, his statement is as true today as when it was written. There is an extensive literature dealing with the drift deposits on the western side of the Pennines; the works quoted below are a selection, some of them ranging outside the immediate district for their subject matter, for the glacial history of Stockport must be studied with that of northern England as a whole.

History of research

Research into the nature and origin of the drift of North-western England began early in the nineteenth century. Sir Philip Grey-Egerton (1835) was the first to find marine shells in the Cheshire drift, and he was followed by many others including Andrew Knowles (1865), R. D. Darbishire (1865), Mellard Reade (1874) and W. Shone (1874). Shone found foraminifera in both boulder clay and Middle Sand, the most nearly perfect specimens being preserved in the whorls of Turritella. The published lists of marine shells, some from nearly 1200 ft above sea-level on the Pennine slopes, lent colour to the view that there had been a great submergence of the land in Pleistocene times, a view held among others by E. Hull and by C. E. De Rance until 1892.

The stratigraphy of the drifts of the Manchester area was first pursued by Binney (1862, p. 351), who stated that there are two or more beds of till parted by sands and gravels. Hull (1864, p. 49; 1866, p. 75) gave the names Upper Boulder Clay, Middle Sand and Gravel, and Lower Boulder Clay to the tripartite sequence which he found to be maintained in the Stockport area, describing in 1866 a section at Reddish Mills which displayed it. De Rance (1870) recognized Hull's sequence over wide areas of Lancashire and Cheshire; and it is found to hold good today.

The north-west of England was—possibly because of the abundance of marine shells—one of the last strongholds of the diluvial theory of drift, a theory upheld by E. Hull and Mellard Reade (1874) among many others in the face of strong adverse evidence elsewhere; and Tiddeman (1872) was the first to postulate and provide convincing evidence for the 'land ice' explanation of the glacial drift of Northern England. The twentieth century produced many workers including Harmer (1907, pp. 447–81), and Jowett and Charlesworth (1929, pp. 307–34), who accepted the 'land ice' theory in this district and whose writings explained the glacial history of Lancashire and Cheshire in terms of one major advance and retreat of an ice-sheet; the marine shells, once regarded as important in the diluvial hypothesis, were seen as derived forms, scooped from the sea-bed by the ice and to be found either embedded in the boulder clay or as derived 'pebbles' or fragments in the Middle Sands. L. J. Wills (1937) considered that the Irish Sea ice—for which he invented the term Main Irish Sea Glaciation—having retreated northwards from Cheshire, re-invaded part of its former domain: the authors of the Wigan Memoir (Jones and others 1938, p. 114) recognized that the Upper Boulder Clay, in its position on top of the Middle Sands, required a readvance of the ice to explain it; and they postulated a forward movement of at least 20 miles—within the confines, that is, of the area they were describing. The same authors, in 'The Geology of Preston and Chorley' (unpublished MS by W. B. Wright and others)¹ stated that the drift below about 550 ft O.D., though simpler at higher altitudes, is tripartite. They show that the well-known Brinscall–Croal glacial-drainage channel is partly occupied by boulder clay, and that ice has advanced over it since it was first cut (see also Wright 1934, pp. 52–53; and 1935, pp. 55–56). In this work of Wright and his colleagues is seen the reason why Jowett and Charlesworth (Jowett 1914: Jowett and Charlesworth 1929), having traced in detail the retreat-stages of the Main Irish Sea ice-sheet from its maximum position on the Pennine flanks towards the low land, found it difficult to continue the story across the plain to the sea. The lower ground was over-ridden again by ice from the north-west which obscured, with a deposit of Upper Boulder Clay, much of the evidence of the earlier glaciation and its retreat. Recent work by the Geological Survey shows that the re-advance of the Irish Sea ice which deposited this boulder clay continued right across Cheshire and at least into Shropshire.

Present knowledge of the stratigraphy of the glacial deposits of Lancashire and Cheshire is summed up by Trotter (in Edwards and Trotter 1954, p. 70). The general succession is as follows:

• Upper Sands and Gravels
• Upper Boulder Clay Middle Sands
• Lower Boulder Clay

Simpson and West (1958) have described tree-bearing organic muds at Chelford, just south of the Stockport district. They lie in nearly white silica-sand regarded by these authors as Middle Sands, and are given a carbon-14 age of 57 000 years. The authors regard the muds as contemporary with the Gottweiger Interstadial (Wurm I–II) of North Germany and Denmark, quoting especially their resemblance to deposits of this age described by S. A. Andersen (1957) from Brorup in Denmark.

The Chelford deposits are under investigation by the Geological Survey, and will be described in the forthcoming memoir^‡2  on the country around Macclesfield (Sheet 110); and no firm conclusions can yet be stated as to their stratigraphical position in the Pleistocene sequence of the Cheshire Plain. Meanwhile, although it is very desirable that further tests should confirm the carbon-14 dating of the Chelford mud, the views of Shotton (1958, p. 16) and Godwin (1961, p. 290) favour correlation with the Würm interstadial. Edwards and Trotter (1954, p. 70) suggest the probability that all the visible drifts of the Lancashire–Cheshire basin are of Newer Drift Age, implying that no Older Drift is known in this area. And there the matter rests for the present. B.J.T.

Glacial deposits

To the east of the Red Rock Fault the ground rises towards the Pennines, and several of the foothills, particularly around Pott Shrigley and Bollington, are free from drift, as is the Keuper escarpment of Alderley Edge: also, the rivers in places have cut down through superficial deposits to expose solid rock. Apart from these small areas—which do not account for more than 10 square miles—the whole district (Sheet 98) is covered by glacial and superficial deposits.

The glacial deposits fall into two types: unstratified boulder clay and stratified silts, sands and gravels. The boulder clay varies in composition from a stiff heavy clay, obviously derived from argillaceous rocks and with a few stones, to a very sandy clay containing many stones. The stones lie at all angles within the clay, and there is no sign of sorting. The harder stones are subangular and display scratches and grooves which not infrequently cross one another. The stones consist of far-travelled as well as local rocks: the far-travelled erratics include Ennerdale granophyre, Eskdale granite, lavas (including Eycott type) and tuffs from the Borrowdale Volcanic Series of the Lake District, Criffel and Dalbeattie granites from the Scottish side of the Solway Firth, and Lower Palaeozoic grits and greywackes which probably came from the southern side of the Lake District and also from Galloway; the local rocks represented as boulders are Carboniferous sandstones and grits, and pebbles and fragments of coal (which may also be of northern origin), as well as fragments of Permo-Triassic sandstone. A few fragments of shells have, as stated above, also been found in the boulder clay.

The stratified sands and gravels show unmistakable signs of grading. Although interbedded with sands the gravels are sorted, usually being less coarse in upward succession. A similar tendency is shown by the sands, and not uncommonly these are current bedded. Where the sands are fine and devoid of gravel-layers they may contain interbedded silts and, less frequently, bands of silty clay. The rocks most abundant as pebbles in the gravels are from the same sources as those found in the boulder clay. Shells also occur in the sands and gravels, and some of the gritty layers are not infrequently found to contain numerous particles of coal. These stratified beds are water deposited and clearly represent resorted glacial material.

The threefold division of the drifts of Binney and Hull (see p. 93) is recognized in the district under description; and in addition there are deposits of sand and gravel which lie on top of the Upper Boulder Clay. Thus the normal sequence is as follows: Upper Sands and Gravels, on Upper Boulder Clay, on Middle Sands and Gravels, on Lower Boulder Clay. The sequence, however is not comparable with a normal sedimentary succession. For example, both Upper and Lower Boulder Clay are not uncommonly missing, and the Upper does not occur on ground above 700 ft O.D. Again, the Middle Sands and Gravels, although of widespread occurrence, are far from being continuous; and where they are absent it is impossible to distinguish between Upper and Lower boulder clays, since both carry the same suite of erratics and both have the same kind of matrix. Enough occurrences are known of Upper Sands and Middle Sands to lend validity to this account, but since it has not been possible, as explained in the Preface, to distinguish between them in every case, they are not differentiated on the map.

Lower Boulder Clay

This can be mapped only beyond the limits of the Upper Boulder Clay or where it occupies narrow outcrops on the lower slopes of river valleys. The matrix varies noticeably in composition with the underlying solid rock, being a stiff heavy clay on marls and mudstones and sandy where it overlies sandstone or grit; albeit there is a carry-forward in the direction of ice-movement of clayey boulder clay on to sandstones and of sandy boulder clay on to mudstone or marl. Where the Lower Boulder Clay lies on Keuper Marl it has been found difficult to distinguish in boreholes between the solid rock and the overlying clay, since the bottom layers of the clay are almost wholly composed of broken marl with only occasional erratics.

Middle Sands and Gravels

These well-stratified deposits lie abruptly on the Lower Boulder Clay where this is present. In places, however, they lie directly on the 'solid' rock. They vary considerably in thickness and may indeed exceed 100 ft where they fill hollows or buried valleys. Their upper surface may present the hummocky appearance of 'kettle gravels' that are thinly plastered with Upper Boulder Clay; contrariwise this upper surface may form roughly horizontal, flat and featureless ground. The sands are normally buff to red in colour, being derived mostly from Permo-Triassic rocks, except towards the east where they tend to have a greyish colouration, due to the presence of grains derived from Carboniferous sandstones and grits. Pebbles and particles of coal also occur.

Within the Middle Sands are some fine silts and clays which, like the sands and gravels, are covered by boulder clay, and are very poorly exposed; they were proved in excavations on a post-war housing estate at the town of Alderley Edge to the north of the escarpment.

From Alderley Park and Birtle Hall stretching eastward and northeastward to Harehill the ground presents the hummocky appearance of outwash sand and gravel moraine, irrespective of whether sands and gravels or boulder clay are at the surface. Detailed mapping indicates that, in general, the hummocky ground is mantled by a thin deposit of sandy Upper Boulder Clay but that there are many small areas free from this overlying deposit. The tributary valleys of Bog Brook, almost 100 ft deep to the east of Over Alderley in the vicinity of Highlees, are cut through the Upper Boulder Clay, through the Middle Sands and Gravels into the Lower Boulder Clay. At Acton, to the east of Higher House, the Middle Sands and Gravels rise free from Upper Boulder Clay to a height of 585 ft O.D. to form a flat-topped ice-front delta with ice-contact slope facing to the west. An old gravel pit in the delta shows 15 ft of gravel with sand, the pebbles of which include Carboniferous sandstone, Borrowdale Volcanic rocks and Eskdale granite.

The nearly white sands of Chelford which are exposed farther south just within the confines of the adjoining Macclesfield district and which, with their organic mud, have been alluded to on p. 94 probably extend into the present district, for the Mere Leigh Borehole [SJ 809 752] records 40 ft of grey sand. At Chelford these sands are composed, to the extent of 96–99 per cent, of rounded grains of quartz, and are being worked to a depth of 20 ft or more.

Boreholes show them to rest on 'clay' which has been seen in places to be Keuper Marl.

Upper Boulder Clay

Only where it caps Middle Sands and Gravels can the Upper Boulder Clay be identified and mapped. It nowhere lies much above 700 ft O.D., and below that level it is of patchy occurrence and varies in thickness from a few inches to a maximum of 15 ft. In composition it reflects the nature of the deposits on which it lies: exceptionally, as on the north-eastern borders of the town of Alderley Edge where it overlies silts and silty clays, it is a firm heavy clay; but as it is usually found overlying red sands and gravels it more commonly has a light sandy texture and contains numerous stones, many of which are well rounded.

Upper Sands and Gravels

There are a few outcrops of Upper Sands and Gravels, notably in the area of Alderley Edge where they form a series of small patches to the west of the Manchester–Congleton road. They consist essentially of flat-topped deposits of sand and gravel which have been considered to represent beach deposits of a glacier-lake (see p. 106).

Interpretation of the drifts

The Glacial Period was marked by recurrent extensions of ice-sheets which in Northern Europe—apart from local diversions—spread southwards, covering the land and invading the surrounding seas; and these ice-sheets have left an unmistakable stamp on the countryside in the form of unconsolidated clays, sands and gravels. On the continent of Europe and in southern and eastern England these deposits have been interpreted as representing up to four major glaciations alternating with warmer interglacial periods (see e.g. Zeuner 1958, pp. 113–21). In Britain the evidence is less readily interpreted than on the continent; but it is generally agreed that in the southern and eastern parts of Britain there is Older Drift, corresponding with glaciations earlier than the last interglacial period, and Newer Drift, corresponding with the last glaciation (Würm); and that these appear to have been separated by a time interval sufficiently long to allow the land surface of the Older Drift to be eroded and valleys to form in which gravels were deposited (see e.g. Edwards and Trotter 1954, p. 67). These gravels have yielded mammalian remains including those of Hippopotamus and Rhinoceros. In the north-western parts of Britain, including the area under description, the deposits of the Older Drift have not been firmly identified, nor have any traces of the succeeding interglacial period been detected.

It has been considered that the Upper Boulder Clay and the Lower Boulder Clay of the Cheshire Plain each represents the ground-moraine formed during the forward movement of the ice-sheet; and that sands and gravels were deposited in front of the ice-sheet during its recession. Thus two episodes are recognized in the Newer Drift; first, the Lower Boulder Clay and the Middle Sands and Gravels, or some part of them, representing the first waxing and waning of the ice-sheet—the Main Irish Sea glaciation; and second, the Upper Boulder Clay and the Upper Sands and Gravels representing a readvance and retreat of the ice-sheet—the Irish Sea Readvance. But this may well be a simplification of a more complex sequence of events, and it is yet possible that some deposits now described as Middle Sands may eventually prove to be associated with the final retreat.

The boulders in the drifts show that the ice-sheet which twice invaded the district had its source in the mountains of the Lake District and south-west of Scotland, and that in its southward march it crossed the basin now occupied by the northern part of the Irish Sea, bringing with it shells from the sea-bottom.

The sands and gravels are regarded as having been washed out of the ice-sheet; and shell fragments as well as rock pebbles were carried by the melt waters and deposited in front of the melting ice-sheet. The Middle Sands may, however, represent a varied sequence of episodes including, if Simpson and West are correct, deposition of clean sands with organic muds during the Gottweiger Interstadial.

It is a matter of serious consideration whether the presence, at many places, of a deposit of Middle Sand and Gravel overlain by an Upper Boulder Clay should be interpreted as one continuous recession of the ice-sheet followed by one readvance, or as a recession interrupted by a series of readvances of the ice-sheet. Within the district under description no clear-cut proof has been found which would support one hypothesis and invalidate the other. It may be suggested that since a series of deposits overlapping in the manner of slates on a roof has nowhere been found, this negative evidence implies one continuous recession followed by one readvance. If this be accepted, it would appear that the ice-sheet receded at least as far as the Irish Sea, since Middle Sands overlain by Upper Boulder Clay are recorded from Liverpool and from the coast to the north (Morton 1897; Wray and Cope 1948). However, little is known of the mechanics of the emplacement of the varied deposits of the Middle Sands and the Upper Boulder Clay; and even less is known of the interval between the two glaciations of this region. As previously stated (p. 000), Messrs. Simpson and West describe the Chelford muds as a deposit of this interval. There is evidence of weathering of the top of the Middle Sands in an old pit adjoining Alderley Cemetery.

The age of the upland drifts

The history of the lowland drift is multiglacial, for it has to deal with the deposits of both the. Main Irish Sea glaciation and the Irish Sea Readvance; that of the upland drift, above about 700 ft O.D., is for all practical purposes monoglacial—though the possibility of much earlier periods of glaciation than either of those under discussion is not here ruled out. It is therefore necessary to decide which of the two episodes was the major one. In other words, is the upland drift Upper or Lower Boulder Clay?

In clay composition and boulder content the Upper and Lower Boulder Clays are so similar that their appearance is no guide. Exposures are not good enough to allow any one bed to be traced from the low ground to the high; and even where clay can be traced by mapping all the way from the plain to the high ground this is no proof that it is everywhere of the same age. In fact, such an assumption is particularly to be guarded against, for it is to be expected that there will be places where the Upper Boulder Clay will directly overlie the Lower Boulder Clay with no intervening sands.

Such evidence as there is in the district tends to show that of the two episodes the earlier—the Main Irish Sea Glaciation—was the major one. It can be argued that if the reverse had been true, and if the Irish Sea Readvance had so filled up the Cheshire Basin with ice that its eastern margin abutted against the hills at 1400 ft, then this fact would have been clear in the evidence left during its retreat stages: thus the numerous overflow and meltwater channels cut in rock would be floored by nothing more than recent alluvium in places, and the deltas deposited where these channels debouched into glacier-lakes would be unaffected by any subsequent glacial episode. This, however, is demonstrably not the case. The valley to the east and south of Swanscoe Hall is clearly a meltwater channel, one of a series in the peripheral drainage pattern associated with the retreat of the ice away from the uplands: and the sand deposit of Doncaster Hill at Hurdsfield is a deltaic deposit at the mouth of this channel. Boulder clay overlies the deltaic sands and extends up the floor of the channel. In the adjacent district to the south (Macclesfield, Sheet 110) there are several instances of overflow channels associated with the retreat of the ice from the high land, but partially blocked by boulder clay. In short, the evidence points to a Lower Boulder Clay age of the upland drift.

There remains the possibility that the upland drift might belong to the second phase—the readvance—if the boulder clay in some of the channels is the result of a minor push forward during a period of general retreat; but this would involve the coincidence that this readvance took place approximately at the boundary between the multiple drift of the lowland and the single upland drift. In this account, therefore, the history of the drifts is written on the assumption—an assumption which may yet prove to be wrong—that, of the two hypotheses, the former is correct. Study of the district to the south may help to decide the question one way or the other.

In both the Stockport and Macclesfield districts the retreat phenomena on the high ground, uncomplicated by any subsequent episode, are fresh and clear. On the low ground the history of the earlier retreat is confined to the numerous deposits of Middle Sands which protrude in places through the later drifts, all other geomorphological evidence having been obliterated.

The main Irish Sea glaciation

Professor L. J. Wills (1937) gave the name Main Irish Sea Glaciation to the glacier which, in Newer Drift times, brought erratics from Scotland and the Lake District to the West Midlands by way of the Irish Sea. It is presumed that this name was used to distinguish the episode from the later readvance of the same glacier, after withdrawal, into "the northern part of its old domain" (1937, p. 94). The name is here used in the same sense. Evidence is accumulating that the two episodes may represent the first two cold periods of the last glaciation of Western Europe.^‡3  On the other hand, the topography of the ice-front deposits regarded as Middle Sands (p. 96) is, as Mr. W. Edwards pointed out orally, matched by that of the Danish Würm 2 (see below, footnote).

The main Irish Sea ice, in its initial advance from the north-west, left no evidence by which the details of its progress can be elucidated. Rivers and streams must have been blocked at a fairly early stage, and it is likely that a great lake was formed in the Cheshire–Shropshire plain. Any deposits associated with the advance were covered and obliterated by, or incorporated in, the ground moraine.

¹

The detailed history of this glacial episode, as based on tangible evidence, begins with its maximum development (see (Figure 10)). The distribution of ice-work phenomena, boulders, and drift in the country to the north and south of this district, shows that the ice reached at least 1400 ft on the flanks of the Pennine foothills; and at this time all the present district was under ice. When recession began the extreme south-eastern corner of the district was uncovered first, and this took place at about the same time as the deposition of small mounds of high-level gravels containing marine shells at Blue Boar Farm, Brook Low and the Setter Dog Inn (these deposits are a short distance to the east and south of the present district. Laminated clay at 1150 ft O.D., 300 yd S.E. of Waggonshaw Farm approx [SJ 973 762], shows that the gravels were deposited in a temporary lake which drained southwards over the col at Walker Barn into the Langley valley. This condition could have been produced by an ice-front at position 1 on (Figure 10).

A notch cut in shale at 950 ft O.D. on the western flank of Big Low gives a local position 2 for the ice at a later stage. Position 3 is determined by the Cage Hill channel near Lyme Hall at 850 ft O.D., and the Moorside channel near Pott Mill at 830 ft O.D. These were the products of the overflow of waters impounded in the Goyt valley east of Disley (Jowett and Charlesworth 1929, p. 324). The gravels in the Bollington–Pott Shrigley valley, well exposed at Spuley Bridge, were probably deposited at this stage in a lake which overflowed at the col south of Kerridge at about 800 ft O.D.

Stage 4 is marked at four points. West-south-west of Lyme Hall near the hill called Knott there is a pair of confluent channels [SJ 956 821] at about 780 ft O.D. entirely cut in thick sandstones underlying the Old Lawrence Rock. One channel, that from the north, was probably cut by mixed meltwater and impounded drainage water following the periphery of the ice; the other, from the east, carrying mainly land-drainage water from the uplands. The combined waters thence flowed south-west by way of the Birchencliff channel—a gully [SJ 949 811] between the ridges of the Old Lawrence Rock and the flaggy sandstone series below it—and entered the upper end of the Shrigley Park East channel at about 730 ft above sea level [SJ 945 802] just west of Gib Hill; thence to add their quota of sediment to that already deposited in the Bollington Lake, now grown a little larger. There is no means of telling whether the lake overflowed at this stage to the east or west of Kerridge. The water left the area being described by way of a channel at 750 ft O.D. [SJ 935 744] cut along the line of a minor fault in a gritstone outcrop west of Cliff Farm.

The recession was now well under way. Large areas of land previously under ice to the north and east were uncovered, and the combined drainage and meltwaters were forced to flow southwards along the ice-margin. As might be expected, the lower overflow channels are, generally speaking, larger and more spectacular than those at higher altitudes. But from here on the picture is complicated by the deposition of the drift of the Irish Sea Readvance in the channels and over the deltaic sand and gravel deposits associated with them.

Stage 5 saw the over-steepening by water flowing between ice and hill of the western face of Kerridge. Lake Bollington, its surface now at 680 ft O.D., overflowed through the channel [SJ 937 772] at Redway Lane, Kerridge; and the deep in-and-out channel [SJ 939 753] to the east and south of Swanscoe Hall was formed at this stage. Already it would seem that a small lake was forming to the north-east of Hurdsfield, a lake later to become enlarged into Lake Tytherington, for there are deltaic deposits of sand and gravel at 600 ft O.D. near Doncaster Hill and Higher Fold Farms, at the mouth of the Swanscoe channel. These deposits are partly masked, and the channel itself partly blocked, by late boulder clay. The name Lake Tytherington is used deliberately to distinguish it from the 'Lake Macclesfield' of Jowett and Charlesworth (1929, pl. xix), which could not, as shown by these authors, have been the depository of the Middle Sands of the Macclesfield areas and at the same time have overflowed through the Cow Brook valley, cut in late-Glacial times after the Irish Sea Readvance.

Evidence from the district to the south shows that the combined drainage and meltwaters up to this time were flowing by way of the Chumet valley into the Trent system of drainage, whence it reached the Humber basin. The cutting of the Ironbridge Gorge (Wills 1924) is thought to have taken place at about this time, and from then on, during the succeeding retreat stages and until the northern river mouths were once again open, the water flowed into the Severn drainage system by way of that gorge.

The detailed story of the further recession across the district is much obscured by Upper Boulder Clay, but the salient features can be distinguished. After a brief period (Stage 6) during which the second Kerridge overflow-channel, Chancery Lane [SJ 935 772], operated at about 610 ft above sea-level east of Hollin Hall, the ice-front receded all along the flanks of the hills between Bollington and Disley. Lake Goyt, into which had been flowing the combined headwaters of, among others, the rivers Goyt, Etherow and Tame, was then able at Disley to overflow at about 600 ft O.D. down a channel now occupied by part of the railway line to Stockport. The edge of the ice must at this time have been approximately at position 7 on (Figure 10). Farther south the water gave rise to the spectacular in-and-out channel at Styperson Park at about 575 ft O.D., thence to deposit sediment in Lake Tytherington, dammed between the ice-front and the rising ground of Alderley to the west and the Carboniferous hills to the east. For a short time between stages 6 and 7 the Shrigley Park West channel took water that had previously drained to Lake Bollington via the Pott Shrigley channel.

The sands and gravel of Lake Tytherington north-west of Macclesfield and around Prestbury reach an elevation of a little over 500 ft in places. They have been rather severely dissected by rivers: also by the effects of the Irish-Sea Readvance and its subsequent retreat; and Upper Boulder Clay is seen in some places capping mounds and in others filling hollows. The bedding of the sand is sheared and disturbed by ice pressure, and there are numerous examples of frost structures, the most common being the penetration of clayey gravel into the sands below. The deposit is best exposed at Whirley Sand Pits, which display all the characteristic features of the Middle Sands. The pit [SJ 885 746] east of Sandy Lane, Whirley Grove, has a working face more than 30 ft high, of sand, which is capped by three to twelve feet of Upper Boulder Clay. The depth of the pit is limited by the level of ground-water, which at the time of the re-survey was some 40 ft below the original land surface at the southern end of the pit; and it is possible that sand may extend to almost 80 ft below the surface, for the section of drift proved in the Whirley Grove Borehole [SJ 884 748] was:

As this hole was drilled through the drift by percussion the precise nature of the stony clay in the upper part of the hole is uncertain. Some of it may be part of the lake deposit, but some is almost certainly Upper Boulder Clay.

In the sand-pits the current-bedding generally slopes down towards the south-west. Many of the bedding-planes carry washes of rotted coal, pieces of which are up to 2 inches across; fragments of calcareous marine shells, probably scooped up by the ice from the sea-bed and washed out of the Lower Boulder Clay, are common, and workmen have frequently found nearly perfect specimens of Turritella sp. The current-bedding is disturbed and in places the sands are sheared; and differential compaction has led to iron impregnation along shear-planes (Taylor 1958).

As the ice receded westward the level of the glacier-lake fell progressively, but there appear to have been several stand-still levels. It is almost certain, for example, that the strand-line at about 300 ft O.D. in the Alderley Edge area was not wholly formed in the recession stages of the second episode (see p. 106). Also, with the departure of the ice, fine sediments were carried into the expanding glacier-lake, and floor-deposits in the form of fine silt and sandy clays accumulated.

North and west of Stage 7 there is a zone, several miles broad, bounded by a line passing north of Altrincham and west of Heaton Norris (the extremely conjectural Stage 8 on (Figure 10)), in which are numerous patches of Middle Sands, more or less covered by a later till. These were probably deposited during a progressive recession north-westwards across the plain, for there is a gentle fall in level from about 400 ft in the Adlington–Poynton area to about 300 ft around Woodford and Hazel Grove.

Lying to the north of the escarpment of Alderley Edge and stretching towards the river Bollin is a plain which appears to be bevelled at about 300 ft O.D., on which numerous sections of red boulder clay are seen at ponds and in old claypits; specific mention may be made of the old brick-pit northwest of Belmont that covers about 20 acres, and in which the boulder clay appears to have been dug to a depth of about 6 ft. Boulders found on the fields of this 300-foot flat include Borrowdale volcanic rocks (numerous) and several large ones of Eskdale granite. The presence of underlying sands and gravels in this area is suggested by sections seen in sewer foundations excavated in 1946 for a housing estate west of Belmont, in which 18 ft of red boulder clay rested on fine silt and silty clay in one hole, and in another 10 ft of red boulder clay rested on 6 ft of fine silt; and also by an exposure in a small digging 150 yd west of The Hole, where an estimated thickness of about 20 ft of boulder clay rests on sand of unknown thickness. An old well at The Hole 36 ft deep is reported as being sunk in sand.

In the western outskirts of Mobberley several pits have been dug for building-sand in an outcrop of Middle Sands and Gravels. These are best displayed in a sandpit 500 yd east of Grimsditch Farm, where 30 ft of dominantly sharp well-bedded pinkish-red sand is overlain by 1 to 3 ft of red sandy boulder clay. In the sand are occasional lenticular beds of gravel up to a foot thick, also two thin beds, each less than 1 foot thick, of argillaceous loam. Apart from minor current-bedding of the sands the deposits are horizontal. The following rocks were recognized as pebbles in the gravel lenses: Silurian grits, lavas of the Borrowdale Volcanic Series, Eskdale granite and Criffel granite. The transgressive nature of the junction between Middle Sands and Gravels and Upper Boulder Clay is best displayed in another sandpit in Mobberley, 750 yd north-east of Grimsditch Farm, where 3 ft of red boulder clay rests with a sharp and irregular junction on bedded sands. East of Mobberley and to the north-east of Mobberley Brook a stiff red boulder clay with few stones is at surface, and has been dug in clay pits 600 yd south of Mobberley to supply local pottery needs. In this neighbourhood the Mobberley New Hall and Stubbs Farm bores [SJ 7971 7955]; [SJ 8001 8002] proved stiff boulder clay from the surface to the solid rock, thereby demonstrating the absence hereabouts of Middle Sands and Gravels. By contrast the Middle Sands and Gravels underlie a thin boulder clay north-eastward from Mobberley for about a mile, as is shown by the presence of narrow outcrops of Middle Sands and Gravels along the southern valley-side of Mobberley Brook and on both sides of Pedley Brook; there is also an inlier of these deposits at Glevehouse Farm. From Bostock Barns, however, eastwards almost as far as Norbury House, there are no signs of Middle Sands and Gravels along the sides of the two brooks mentioned above, and the ground between these brooks is composed of heavy boulder clay which has been worked to a shallow depth for brick-making in several old clay pits; and it appears possible that there is here an area similar to that around Mobberley Hall from which Middle Sands and Gravels are absent. South-west of Pedley Brook the ground is of boulder clay as far as Marthall Brook; and alongside this brook, by the roadside 450 yd S.S.W. of Firtree Farm, Brook Farm Borehole, a percussion borehole made for the Ministry of Town and Country Planning, proved 149 ft of glacial drift. The top 32 ft of this was undoubtedly Upper Boulder Clay, and was separated by a thin layer of sand with traces of coal from a lower clay sequence 113 ft thick; the sand layer may be the thin local representative of the Middle Sands.

Middle Sands and Gravels occupy an inlier east of Norbury House. On both sides of the north-trending tributary of Mobberley Brook and on the eastern margin of this outcrop a sandpit displays 10 ft of sand with gravel beneath 2 ft of Upper Boulder Clay. Farther east another inlier of Middle Sands and Gravels trends from Heathgate to Littlemoss, and a sandpit in it 500 yd W.S.W. of Littlemoss displays coarse sand that contains current-bedded black layers composed essentially of small fragments of coal. Interbedded bands of gravel also occur, and pebbles of the following rocks were found: Carboniferous sandstone, Permo-Triassic sandstone, fine-grained Silurian grits, lavas of the Borrowdale Volcanic Series, Eskdale granite and Criffel granite. At one place in the pit the sands and gravels are unconformably overlain by 2 ft of red boulder clay. North of these two inliers Middle Sands and Gravels also form narrow outcrops on both valley-sides of Mobberley Brook, their lower limits being marked by pronounced wet lines.

Farther east yet another inlier of Middle Sands and Gravels lies around Tanyard Farm. The old sandpit on the north side of the road 350 yd northeast of that farm show 3 ft of red sandy clay with gravelly patches, resting on 4 ft of bedded sand; much of the section is now obscure and covered by infill, but it is reported that the sands were proved to a depth of 37 ft. In this inlier the Middle Sands and Gravels give rise to a typical hummocky outwash-moraine topography which, although masked somewhat by boulder clay, can be recognized eastward as far as the main road to Wilmslow immediately north of the town of Alderley Edge. Two examples of morainic forms may be mentioned: a north-south kame-like ridge on which Tanyard Farm is situated, and which is capped to the south of the road by boulder clay; and the esker-like east-west ridge some 300 yd in length lying immediately north of Commoncar, a ridge which appeared to be composed wholly of boulder clay until tests in 1947 proved the clay to be underlain by sands. The sandpit which was opened in 1948 proved the ridge to be composed of highly false-bedded sand with occasional gravel lenses 10 to 20 ft thick, overlain by Upper Boulder Clay which thickened from 5 ft on the crest of the ridge to 10 ft down its slopes.

Over the western and central-northern parts of the district the summits of the Middle Sands do not rise above about 250 ft, and only at one or two points do they do so in the adjoining district (1-in Sheet 97, Runcorn) to the west. In the Delamere Forest and Marton areas (1-in. Sheet 109, Chester) there is a similar concordance over a broad zone of summits at about 260 ft above sea-level, and in places a few feet of banded silts intervene between the Middle Sands and the overlying boulder clay. These facts, considered in conjunction with the nature of the deposit itself, suggest that the Middle Sands at this stage were laid down in a large lake with an outflow somewhere to the south. The Ironbridge Gorge, perhaps not quite cut down to its present base-level, would satisfy this requirement.

Further recession cleared the ice from the present district, and the evidence for its subsequent history lies in districts to the north and west. B.J.T., F.M.T.

Irish Sea Readvance

As in the case of the Main Irish Sea Advance, nothing is known about detailed events during the building up of the ice-sheet. The evidence for the episode is confined to the existence of Upper Boulder Clay—which can only be identified with any certainty when it overlies Middle Sands—and to the shearing from both lateral and vertical loading stresses in the deposits over which the ice passed. In composition the Upper Boulder Clay reflects the nature of the deposits on which it lies. Exceptionally, as on the north-eastern borders of the town of Alderley Edge where it overlies silts and silty clays, it is a firm heavy clay; where it can be most easily identified, that is overlying sands and gravels, it usually has a lighter sandy texture and contains numerous erratic stones, many of which are well rounded. The deposit tends to be thinner over the crests of sand-lenses and thicker on the flanks. At Whirley Sand Pits, north-west of Macclesfield, it varies abruptly from three to twelve feet, as if it filled hollows in the surface of the sands.

The ice of the Irish Sea Readvance is inferred to have been thinner and less extensive than that of the preceding episode. As in the case of the Main Irish Sea Advance, there are no recognizable lateral moraines to mark its maximum height along the high ground on the eastern side of the district; but that it did not extend much above 700 ft O.D. is inferred from the fact that whereas below that level overflow channels associated with the earlier episode contain a partial infilling of till, those on the higher ground do not, nor do the deltaic deposits at greater altitude than about 700 ft carry a covering of Upper Boulder Clay. Thus the channels near Swanscoe Hall and at Styperson Park, at 650 ft and 580 ft O.D. respectively, contain boulder clay; whereas the Pott Shrigley Channel at about 730 ft O.D. does not. The confluent channels cut in rock near Hase Bank are exceptions, since they are mapped as having a boulder-clay floor at about 780 ft O.D. It is possible that the upper surface of the ice of the Irish Sea Readvance may have sloped upwards towards the north, in this region. The line A–A in (Figure 11) marks the possible limit of the Irish Sea Readvance in this region, showing the ice abutting against the steep western flank of Kerridge, the westerly-facing slopes of Shrigley Hall grounds, and Lyme Park. The rest of Cage Hill may well have stood clear of this ice-sheet.

This glacier is not clearly associated with a series of outwash deposits and successive marginal features comparable in magnitude and economic importance with those of the previous episode when the Middle Sands were laid down. The Main Irish Sea ice, almost 1500 feet thick over parts of the Cheshire Plain, is thought to have been a lobe of a 'living' ice-sheet even during its retreat. The ice of the readvance, possibly not more than 700 feet thick over Cheshire and South Lancashire, may well have left during its decay random patches of ice which persisted long after the main ice-front had receded.

Nonetheless it is possible to deduce something of the development of the present-day drainage during its decay stages. The fall of the ground is towards the north-west over most of the region; but in spite of this there are patches of ancient alluvium distributed along lines at right-angles to this trend, and having a general fall to the south-west. These were probably laid down in shallow lakes or meres, possibly connected by meandering streams, around the periphery of the decaying ice. Some of these patches actually cross divides between present-day streams, and have been left high and dry as the drainage was able to take its modern course (see (Figure 11)).

The first of these to be formed appears to have been a strip of alluvium some two miles long at grade with the highest terraces of the rivers Dean and Bollin, connecting the two rivers across the divide by way of a shallow valley between Bonis Hall and Plant House, Butley. This was clearly a diversion westward of the north-westerly flowing River Dean, which could only have been brought about by a barrier to the north-west; a condition that would be met by an ice margin standing at or near the position B–B ((Figure 11)). The joint waters of the Dean and Bollin were then further diverted along the foot of the Alderley Edge escarpment, and there is evidence that a temporary lake was formed to the north of Mottram where there is an alluvial spread at grade with the ancient Bollin–Dean terrace. Here also, a flat-topped sand and gravel delta between Parkside and Brook Cottage lies at the mouth of a deep valley, the waters from which presumably ceased to cut down on depositing their load into the glacier-lake at 300 ft O.D.

The feature at about 300 ft O.D. to the north of the escarpment of Alderley Edge, which separates the flat ground from the rising ground, turns from an easterly to a southerly course in the town of Alderley Edge and runs thence past Nether Alderley to the southern margin of the district. This feature is regarded as the strand-line of a glacier-lake which for a time received the combined waters of the Bollin and Dean, and later, for a short time, possibly also that of Poynton and Norbury brooks.

Farther west another feature of southerly trend is visible at about 270 to 275 ft O.D. The lower level is not marked by beach deposits, although alluvium in an abandoned course of Bag Brook just beyond the southern edge of the district is at grade with it. The upper level, however, has thin beach-like deposits where valleys opened on to the 300-ft flat. One such deposit stretches south-eastwards from Heawood Hall for a quarter of a mile to the main road, and the sand-pit in it shows 4 ft of sand and gravel resting on stiff red boulder clay. Another deposit on the 305-ft strand-line stretches westwards from Bollington House; this also lies at the mouth of a dry valley. The deposit most clearly related to the line of the 305-ft beach lies just within the region of Sheet 110 to the south; situated to the north of Bag Brook it can be traced eastward into the valley of that brook, where it is at grade and is continuous upstream with the gravel river-terrace of the brook. The flat at 250 to 260 ft O.D. mentioned in connexion with the Middle Sands represents a lower lake-level in the recession of the Irish Sea Readvance.

The fact that a number of the features just described lie a little above or below 300 ft O.D. has led to the theory that they mark the eastern shore of a great lake which stretched in late-Glacial times from the Ironbridge Gorge in the south to the vicinity of Bolton in the north (Tonks and others 1931; Poole and Whiteman 1959). This theory receives little support from the resurvey: for the southerly diversion of Poynton and Norbury brooks, and of the River Dean valley and the associated terrace which grades down from around 300 ft to about 260 ft O.D., shows where ice must have stood, even at a later stage than that of the 300-ft lake. Moreover, the profiles of the terrace-systems of rivers flowing westwards off the hills in this area do not show that they were graded for any considerable period to the 300-ft level. Whether the lake between the ice and the hills of Alderley at this stage formed the north-eastern tip of a larger lake controlled by the Ironbridge Gorge (which had been cut in Middle-Sands times), or was merely one of a series of peripheral lakes and marshy areas falling in level gradually to the south, may be decided during the study of the Macclesfield district now proceeding. In any case, the 300-ft episode in this district did not last long enough to cause any considerable deposition, even at a time when rivers and streams were laden with sand and silt.

The next stage in the development of the drainage pattern saw the abandonment of the channel joining the Dean and Bollin at Butley, the two rivers flowing independently as far as the vicinity of Lumb Farm and Newton Hall respectively, between which points they are once again joined by a high terrace across the divide, now abandoned. At this time the waters of Poynton and Norbury brooks flowed first into a shallow mere lying to the west of Poynton between Park House and Shirdfold, and then southwards by way of a broad shallow valley—now floored by alluvium and not occupied by any major stream—between Shirdfold and Woodford aerodrome to join the combined Dean and Bollin just south of New Hall. The line C–C (Figure 11) marks the possible position of the margin of a decayed ice-mass which still occupied the plain, thus diverting the water towards the west and south where it deposited the alluvial spreads or 'Upper Sands' near Dane Villa [SJ 830 770], on Sossmoss [SJ 825 765], and around Chelford. The position D–D (Figure 11) marks a possible later position. A line of abandoned patches of alluvium at 230 to 250 ft O.D. to the south and south-east of Wilmslow, and Upper Sands at Littlemoss, Marthall and Ollerton, appears to mark the route taken by these waters along the margin of the ice towards the south-west, possibly through a chain of meres connected by sluggish streams. E–E (Figure 11) marks a further stage in the decay of the ice: the Bollin and Dean remained separate streams to beyond Wilmslow, using channels that they occupy to the present day; a mere in the vicinity of Lindow Moss drained south-west towards Ollerton and Toft, where a tract of 'Upper Sand' south-east of Toft church marks the site of a shallow lake, the overflow from which appears to have reached the valley of Red Brook by way of a channel now occupied only by a small brook southwest of Clump o' Trees Farm.

Few further details of the decay of the final ice-sheet and its disappearance from the district can be deduced, and the impression is left that it melted quickly, possibly because of a sudden amelioration of climate. As described below, it continued to affect the development of drainage in the district until its final clearance from the mouth of the Mersey estuary, and the abandonment of the Deva Spillway (see p. 110). B.A.T., F.M.T.

Lake Lapworth

The suggestion has been put forward that North Cheshire, including part of this district, was submerged in late-Glacial times by a great lake which stretched from Ironbridge in the south to Lancashire. I. M. Simpson (1959, p. 118) and E. G. Poole (in discussion of Simpson's paper) regard this as the Lake Lapworth of L. J. Wills (1924). The essence of Wills's Lake Lapworth concept is that its overflow cut the Ironbridge Gorge, thus connecting the drainage of Shropshire and Cheshire with that of the Severn valley; and it is becoming increasingly clear that the gorge was cut in Middle Sands times if not before. The Middle Sands were laid down in a lake which at its greatest extent filled most of the Cheshire–Shropshire basin, and which was held for a long time at somewhere near 300 ft O.D. by an outflow to the south, evidently the Ironbridge Gorge. Wills himself regarded the lake as a product of the retreat stages of the Main Irish Sea Glaciation (Wills 1937, p. 91), and not of the subsequent readvance and retreat.

The southward diversion in late-Glacial times of the waters of the rivers Bollin and Dean and of Poynton Brook and Norbury Brook, all in the Stockport district and described above, demonstrates enough of the retreat stages of the last ice-sheet to show that a post-Glacial lake at the 300-ft level could not have reached as far north as these rivers. The conclusion is therefore that there were two lake systems. The first, in Middle Sands times, involved the ponding up of the waters of Cheshire and Shropshire and the western Pennines and the cutting of the Ironbridge Gorge; this was the lake in which most of the Middle Sands of the region were deposited—the true Lake Lapworth. A later lake-system followed the final retreat after the Irish Sea Readvance and made certain shore-line features, cut in places into Upper Boulder Clay. In the southern part of the basin the later lake must inevitably have occupied at some stage more or less the same ground as Lake Lapworth, but in the northern part its extent was limited by the ice which still occupied the valley. Therefore, the term late-Glacial Lake Lapworth (Simpson 1959, p. 118) is not used in the sense apparently intended by Wills.

The high terraces

After the ice had left the immediate vicinity, extensive sheets of sand and gravel were laid down in the valleys of the Mersey west of Stockport, the Bollin below Styal, and Mobberley Brook. This is true also of rivers in adjacent districts, the Irwell to the north and the Dane and Weaver to the south and south-west, all of which drain to the Mersey estuary. These deposits are shown on the maps as Fluvio-Glacial Gravel. In the lower reaches of all these rivers is the same pattern of a top terrace, in places more than 30 feet above present river level, and very wide compared with the later terraces, which form a group including the present-day alluvium confined to the immediate vicinity of the river. It appears that after the formation of the high terrace there took place an event which suddenly lowered the base-level to which the rivers were being graded; and that this happened to all the rivers mentioned above simultaneously, for their high terraces are at grade with one another—the Bollin with the Mersey, the Mersey with the Weaver, and so on. No such marked change in terrace level is noted in the lower reaches of rivers flowing to the Dee estuary.

The origin of the high terrace has hitherto presented a problem. It is more nearly parallel with the present alluvium than it would be if its formation were merely a result of increased stream load; a circumstance attributed by O. T. Jones (1924, pp. 89–123), for the Manchester Plain (the Mersey high terrace), to a greatly-increased rate of flow during the pluvial period. Nevertheless the ancient thalweg suggests that the river was graded to a level higher than present sea-level. The clue is thought to lie in the great glacial-drainage channel recently mapped by Dr. J. R. Earp near Chester and named by him (in MS) the Deva Spillway. This crosses the neck of the Wirral peninsula between the village of Stoke, 4.5 miles N. by E. of Chester, and the city of Chester itself, and has cut down through Upper Boulder Clay and Middle Sands into solid rocks; and he therefore dates it confidently as late-Glacial in age. The channel will be more fully dealt with in the forthcoming memoir on the Chester district, but it can be stated here that the highest terraces of the rivers feeding the Mersey estuary were most probably formed when the mouth of the estuary was still blocked by ice in the Irish Sea; thus water was ponded up in the lower Mersey valley and escaped over the neck of the Wirral peninsula by the Deva Spillway. It is to this spillway, which for a time controlled all water flowing to the Mersey, that the high terraces are graded: and the high terrace is of late-Glacial and not post-Glacial age. Many long-standing problems can now be explained: the sudden fall in the base-level of the rivers took place when the Deva Spillway was abandoned and the present Mersey channel became open; the reason for the marked differences in terrace-pattern between the Mersey and the Dee systems becomes clear; the pli771ing laminated clays found beneath the terrace gravels of the area west of Manchester (Tonks and others 1931, p. 185), and in the present district near Ashton on Mersey and Carrington, were laid down in the Mersey lake, the overflow from which cut the spillway. These deposits are shown as Glacial Lake Deposits and Brickearth on the one-inch map.

Blown sand

After the ice receded and before vegetation was firmly established, winds re-distributed the loose sand of the high terrace in the Mersey and Bonin valleys, forming low dunes and thin sheets of stoneless grey sand; deposits which are probably contemporaneous with the Shirdley Hill Sand (Jones and others 1938, p. 122). These deposits are shown on the map as Shirdley Hill Sand. The sand-grains are almost wholly of silica; and the iron content is low, either because the ferruginous pellicle normally carried by glacial sands in the district was removed by abrasion, or because deposition of the sand went on at the same time that peat was forming on the terrace so that much of the sand was at some stage subjected to the leaching action associated therewith.

Blown sand has been mapped on the high terrace south of the Mersey between Warburton and Broadheath, along the south side of the Boffin valley from Lymm to Spode Green, and in small patches near Mobberley and Birkin brooks between Ashley and Mobberley stations. Faceted pebbles (dreikanter) and wind-etched stones are commonly found at the surface over the whole of the low land. The faceting of some stones may date from the Blown Sand period, but it is possible that many, especially those now in sandy areas, are more recently formed.

Peat

Peat probably started to form on low ground soon after the recession of the ice. Patches of lowland peat such as Lindow Moss, Sink Moss and Sossmoss probably started first, and those on the terrace such as Holcroft, Chat and Carrington mosses could not have begun much later, for Erdtmann (1928, pp. 129–130) distinguished zones of the Boreal period at Chat Moss. Paradoxically the upland peat, patches of which were mapped on Park Moor, Lyme Park, in an area which was almost certainly free from ice first, appears to have started forming later, for Erdtmann (1928, p. 131) refers its basal layers to early Atlantic times.

Wherever it occurs in this district peat appears to be wasting rather than forming. This is partly due to improved drainage. Carrington Moss has for many years been used for the disposal of rubbish, which is dug into the peat surface and then sown with crops. It is possible that peat deposits may have once covered most of the ground now occupied by the High Terrace, and perhaps some of the ground to the north and south also, for Chat Moss overlaps on to the Upper Boulder Clay. This would present a formidable obstacle to north-and-south transport across the Mersey valley, and it is not therefore surprising that Manchester was the site of a Roman station.

River terraces

Apart from the High Terrace, the origin of which has been explained above, there are a number of lower terraces marking successive stages in the development of the rivers. A recent paper by Simpson (1959) touches on those in the Mersey valley. They are of little importance in the geology of the district, though the use of the present-day alluvium as golf courses and open spaces south of Manchester adds something to the amenities of the district. J.T.

References

ANDERSEN, S. A. 1957. Lolland i den sidste Istid. Meddelelser fra Dansk Geol. Forening, 13, H. 1

BINNEY, E. W. 1862. The Geology of Manchester and its neighbourhood. Trans. Manch. Geol. Soc., 3, pp. 359–65

DARBISHIRE, R. D. 1865. On the genuineness of certain fossils from the Macclesfield Drift beds. Geol. Mag., 2, pp. 293–9

DE RANCE, C. E. 1870. On the glacial phenomena of western Lancashire and Cheshire. Quart. J. Geol. Soc., 26, pp. 641–5

EDWARDS, W. and TROTTER, F. M. 1954. The Pennines and adjacent areas. Edit. 3. Brit. Reg. Geol., Geol. Sun'.

ERDTMANN, G. 1928. Studies in the Postarctic History of the Forests of North Western Europe, I. Investigations in the British Isles. Geol. Foren. Stockholm Fürhandl., 50, pp. 123–92

GODWIN, H. 1961. Radiocarbon dating and Quaternary history in Britain (Croonian Lecture). Proc. Roy. Soc., B, 153, pp. 287–320

GREY-EGERTON, P. 1835. On a bed of gravel containing marine shells of recent species at 'The Willington', Cheshire. Proc. Geol. Soc., 2, pp. 189 and 145

HARMER, F. W. 1907. On the origin of certain canon-like valleys associated with lake-like areas of depression. Quart. J. Geol. Soc., 63, pp. 470–512

HULL, E. 1864. The geology of the country around Oldham. Mem. Geol. Surv. HULL, E. and GREEN, A. H. 1866. The geology of the country round Stockport, Macclesfield, Congleton and Leek. Mem. Geol. Surv.

JONES, O. T. 1924. The origin of the Manchester Plain. J. Manch. Geogr. Soc., 39–40, pp. 89–123

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

JOWETT, A. and CHARLESWORTH, J. K. 1929. The glacial geology of the Derbyshire Dome and the western slopes of the Southern Pennines. Quart. J. Geol. Soc., 85, pp. 307–34

KNOWLES, A. 1865. Report of Manchester Geological Society meeting on the Macclesfield drift-beds, the fossils therein, and a fulgurite. Geol. Mag., 2, pp. 365–8

MORTON, G. H. 1897. The geology of the country around Liverpool. London.

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

READE, T. M. 1874. The drift beds of the north-west of England; Part I. Shells of the Lancashire and Cheshire low-level boulder clay and sands. Quart. J. Geol. Soc., 30, p. 27

SHONE, W. 1874. Discovery of foraminifera, etc. in the boulder clays of Cheshire. Quart. J. Geol. Soc., 30, p. 181

SHOTTON, F. W. 1958. A Note on Mr. E. G. Poole's Correlation of the Midland Drifts. Proc. Geol. Soc., Session 1958–59, pp. 15–16

SIMPSON, I. M. 1959. The Pleistocene succession in the Stockport and South Manchester area. Quart. J. Geol. Soc., 115, pp. 107–19

SIMPSON, I. M. and WEST, R. G. 1958. Stratigraphy and Palaeontology of a late-Pleistocene Organic Deposit at Chelford, Cheshire. New Phytologist, 57, pp. 239–50 STRAHAN, A. 1886. On the glaciation of South Lancashire, Cheshire and the Welsh Border. Quart. J. Geol. Soc., 42, pp. 369–91

TAYLOR, B. J. 1958. Cemented shear-planes in the Middle Sands of Cheshire and Lancashire. 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

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.

WILLS,L. J. 1924. The development of the Severn Valley in the neighbourhood of Iron-Bridge and Bridgnorth. Quart. J. Geol. Soc., 80, pp. 274–314

WILLS,L. J. 1937. The Pleistocene History of the West Midlands. (Presidential Address to Section C), Rep. Brit. Assoc. (Nottingham)

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

WRIGHT, W. B. 1934. in Sum. Prog. Geol. Surv. for 1933, pt. 1, pp. 51–3

WRIGHT, W. B. 1935. in Sum. Frog. Geol. Surv. for 1934, pt. 1, pp. 55–7

ZEGNER, F. E. 1958. Dating the Past. 4th Edition. London.

Chapter 8 Mineral products and water supply

Coal

Coal mining had virtually ceased in this district before the resurvey took place, consequently no first-hand information is available on workable reserves either for that part of the Manchester Coalfield north-east of Stockport, or for the Poynton Coalfield. There is reason to believe that the closure of pits in both areas was as much due to the economic circumstances prevailing at the time as to the progressive exhaustion of the seams; and in the Poynton Coalfield the need to pump out large quantities of water from the mines was yet another adverse factor in a generally discouraging economic climate. After World War IL redevelopment plans were confined mainly to that part of the coalfield between St. Helens and Manchester, though one deep bore was put down near Poynton into the concealed coalfield.

Apart from such reserves as may exist in the exposed coalfields of the district, the main future prospect for deep-mined coal lies west of the Red Rock Fault in the area between Offerton and Booth Green. Here there is a strip of country in which most of the seams in the main productive measures from the Arley Mine to the Worsley Four Foot may be expected to lie within 4000 ft of the surface. The precise width and shape of this strip can only be determined by drilling. It seems likely that the Romiley Anticline extends in the Carboniferous rocks beneath the Permo-Triassic in the town of Stockport, terminating the strip of productive measures in that direction; and the same thing probably happens towards the south, where a faulted anticlinal structure trending north-west from Bollington is likely to impose a southern limit.

Rapidly increasing cover of New Red rocks renders the measures progressively more inaccessible westward from the Red Rock Fault. In addition, the Coal Measures probably dip westward more steeply than the Permo-Triassic rocks in this region, so that west of the longitude of Poynton Station the relatively barren Upper Coal Measures may intervene, thickening westward, between the main coal-bearing strata and the Permo-Triassic. Farther west than this, though all the seams are probably present at depth, and in spite of large faults which throw against the dip and bring the measures nearer to the surface on their western side, mining is not likely to be economic with present techniques. There is a similar strip of concealed measures, partly worked from the east in the Lingard Lane pit, Bredbury, north-east of Stockport and north of the Romiley Anticline.

Fireclay

The fireclays that have been worked in this district, as in other parts of eastern Cheshire and South Lancashire, are seatearths in the Coal Measures. The leaching action of plant rootlets from the Carboniferous forests tended to remove from the underlying seatearth all constituents except the most refractory, and it has sometimes happened that the constitution of a sediment, thoroughly altered in this way, has been suitable for the production of a commercially valuable fireclay. The seatearth of the Lower Mountain Mine is such an example, both in this district and over wide areas of South Lancashire and Staffordshire, and it is widely used as fireclay. In this district it is a pale brownish-grey somewhat sandy seatearth which apparently contains enough free granular silica to prevent excessive shrinkage, but not enough to lower the melting point too far. The cone value^‡4  of a sample from the Clarence Mine, Bollington, was between 29 and 30. The clay has long been worked at the mine of William Hammond Ltd. at Pott Shrigley, and at the Clarence Fireclay Mine, now disused. At Hammond's mine, the 20 to 22-in coal, known locally as the Sweet or Shore seam, rests on 3.5 to 4 ft of seatearth, consisting of one foot of ganister and 18 in of 'best' fireclay on 18 in of 'seconds' fire-lay. At Clarence Mine the coal, 22 in thick, rests on 4 to 6 in of ganister, 'fireclay' 20 in, and 'silica rock' (presumably sandy fireclay) 4 ft 4 in. In both places the coal has been worked with the clay and also the ganister, which can be added to the fireclay for special high-temperature materials. Details of both mines are given, together with analyses and a discussion of refractory qualities, in the Geological Survey's Special Reports on Mineral Resources, vols. 14 (1920) and 28 (1924). At the Clarence Mine, Bollington, the seatearth of the Lower Foot Mine, locally known as the Stone or Ribbon Mine, and lying 43 ft below the Sweet Seam, was also worked with its coal, the clay being inferior to the Sweet Seam fireclay. The Stone Mine is about 11 in thick and its fireclay about 6 ft.

Apart from such reserves as may exist in the two mines it is possible that there may be reserves of Lower Mountain Mine fireclay wherever the seam occurs in the district, for it has been shown to be consistent in quality over wide areas. North of Macclesfield the seam comes to outcrop east of Kerridge, and is probably present at depth west of Kerridge and north of Hurdsfield: precise information can only be obtained by drilling. The same is true of the seam in the Romiley–Compstall area, where it is almost certainly present, though thick drift deposits have prevented the mapping of its precise position. The seatearth of the Lower Foot Mine, though worked at Clarence Mine, is more variable, and its occurrence as a commercial fireclay cannot be predicted with the same degree of confidence. Where the seam crops out in Bakestonedale, for instance, its seatearth is probably too arenaceous.

Numerous other coals in the Lower and Middle Coal Measures rest upon seatearths leached to an advanced degree in the direction of fireclay, but only individual physical tests can determine their suitability as commercial materials. Many of these clays are known in deep bores or shafts where their working would not repay the heavy cost of exploitation. One seatearth that may be mentioned as a possible source of fireclay is that beneath the Reform. Mine, also known as the Water or Waterloo Mine: both in the concealed coalfield west of the Red Rock Fault and in the exposed Poynton field, where the seam crops out, it has been proved at several places to be a somewhat arenaceous light-coloured seatclay, between 6 and 8 ft thick. Possible reserves in the Bakenstonedale Mine include the Upper Mountain Mine seatearth, 4 ft thick, some 216 ft higher than the Lower Mountain Mine in the shaft.

Stone

Quarrying of sandstone for masonry, flagstones, kerbstones and road metal was once the basis of a flourishing trade, and in the upland area much local stone was dug for dry walls or 'fences'. The industry has declined, due to competition from substitutes such as bricks and concrete, whose manufacture lends itself more to automatic methods than does stone working, and dry walling is a dying art. Few if any of the sandstone beds in this district have sufficient crushing strength or homogeneity to recommend them as concrete aggregates, and even for the loose road-metal for farm tracks there is now a tendency to use crushed limestone from large quarries in the Buxton area.

The important sandstones occur in the Millstone Grit, the Lower Coal Measures, and the Keuper. In the Millstone Grit only the Rough Rock has been used to any great extent in the district, workings in the lower grits being confined to small diggings for walling-stone. Large quarries in the Rough Rock at the southern end of Marple Ridge have yielded a medium-grained pink and cream massive gritstone, and at Billinge Hill and Big Low, between Bollington and Rainow, the lower finer-grained layers have been worked for building stone. All these quarries are now abandoned.

The Lower Coal Measures contain the Woodhead Hill Rock and the Milnrow or Crutchman Sandstone. A flaggy group of sandstones, the Old Lawrence Rock, have also been worked. The Woodhead Hill Rock caps Andrews Knob, Pott Shrigley, and until recently sawn freestone blocks were produced in a small quarry near the eastern side of the hill. Large abandoned quarries below Green Lane, Bollington show the rock as a medium-grained current-bedded sandstone. It was much used as a freestone in the past. The Milnrow or Crutchman Sandstone, fine to medium-grained and current-bedded, has been worked at Jackson Edge Quarries near Disley and in small quarries on Cage Hill in Lyme Park. It caps Kerridge, where a layer of gritstone overlies medium-grained and somewhat flaggy sandstone from which flagstones and building stones have in the past been quarried. The rock here breaks easily into small parallel-sided building blocks of particularly even size and shape. It has been extensively quarried along its outcrop between Romiley station and Heald, where it is grey-brown and cream in colour, varying in grain-size between a fine gritstone and a medium-grained sandstone. The flaggy arenaceous group overlying the Milnrow Sandstone, possibly the part-equivalent of the Elland Flags of Yorkshire, has been worked for building stone in Lyme Park. The Old Lawrence Rock was quarried in Styperson Park, where abandoned quarries show a 50-ft face of grey sandstone with shale partings; there are some purple-stained layers in the upper flaggy portion.

The red freestone of the 'Keuper Building Stone' is familiar in buildings and bridges throughout north and west Cheshire. It is easily quarried and yields large free-working blocks, and though soft at the time of quarrying it has the quality of hardening on exposure to the weather. The 'Building Stone' represents a particular lithology of medium-grained massive sandstone within the Keuper Sandstone, and may not always lie at precisely the same horizon. It seems likely that the rock quarried in the northern part of the district is the lateral equivalent, in part at any rate, of the conglomerates of Alderley Edge which die out northwards. There is now no working quarry of any importance in Keuper Sandstone in the district, but there are old quarries, mostly long abandoned, along the escarpment east of Lymm, at Timperley, at Quarry-bank, Styal, and near Alderley Edge.

Rock salt and brine

Salt, besides its use as a condiment and preservative, is the basis of a large chemical industry. In the form of brine it is one of the basic raw materials of the alkali trade, particularly in the manufacture of soda-ash and caustic soda; hydrochloric acid, chlorine and bleaching powder are made from it. All these are in turn used by many other industries.

Salt production in Cheshire dates from pre-Roman times, natural brine-springs being the main source until the late seventeenth century. Rock salt was accidentally discovered at Marbury in 1670 during a search for coal, and there followed a period when the main production was by rock-salt mining. At the same time brine was obtained by sinking shafts to the brine-runs at the top of the rock salt, and later the brine was pumped from the flooded mines. Gradually the importance of brine production rose at the expense of salt mining, until today there is only one working salt mine in the country, that at Winsford. Over 4 million tons of salt are now extracted annually in Britain, mostly as brine, and over 80 per cent of this is from Cheshire.

The industrial exploitation of rock salt in this district has been dealt with by R. L. Sherlock (1921). His data on the physical and chemical properties of the rock, so far as they affect the district, are still valid and will not be repeated here. Since then there has been a great increase in production, the 'controlled' method of brine production has outstripped all other methods in importance, and the occurrence of rock salt at Mobberley has been proved (p. 80).

Rock salt is nowhere mined in the district. Brine production is carried on by two different methods. In the Heatley–Agden saltfield 'wild' brine is tapped by sinking a shaft or borehole to the top of the rock salt, where, if the bed is near enough to the surface to be within the zone of solution, brine is encountered. The brine is pumped and is replaced by water entering the ground by way of fissures caused by previous solution-collapse. The most active subsidences are at the point of entry of fresh water to the saliferous measures; this may be near the point of abstraction or at a distance from it, for the well may eventually be fed by a ramifying system of brine-runs on the surface of the rock-salt, some of which, in the main Cheshire saltfield, are several miles in length. In the case of long brine-runs it is the distant ends which are likely to give rise to the most active subsidences, for the water becomes saturated with salt soon after its first contact with the mineral and thereafter can dissolve no more. The limited extent of the Heatley–Agden saltfields restricts the area within which subsidence due to pumping can take place.

The northern tip of the great Holford brinefield enters the south-western corner of the district. Here brine is produced on a large scale by the 'controlled' method, the use of which started in the Preesall saltfield in 1892.

Large cavities are developed within the rock-salt strata, their shape being controlled so as to preserve the stability of the ground above. Water introduced under pressure dissolves salt from the chamber walls until the required maximum size and shape are attained, when no more solution is allowed and the chamber is sealed off. The advantage claimed for 'controlled' pumping—and this is borne out by experience—is that since no connexion is made with the brine streams at the top of the rock salt it cannot result in the haphazard subsidences characteristic of 'wild' brine production. Moreover, if the chamber should fail and collapse, resulting damage would be confined to the immediate vicinity of the well and to the operating company's own ground. The difference between the subsidence-risks due to the two methods was recognized in 1952 in the legislation on compensation for damage from subsidence.

The existence of the Heatley–Agden saltfield, near Lymm, is due to the Warburton Fault, which throws the Lower Keuper Saliferous Beds down against Bunter rocks to the south-west. Rock salt was discovered there early this century, and two companies have exploited the deposit at Heatley and near Agdenbridge by pumping 'wild' brine. No. 3 Geological Survey bore at Grey's Gorse, Millington [SJ 7298 8568] showed that the saltfield does not extend far south-east of Agden; and it seems that although there are enough reserves for the two existing companies no further development here would be possible. Sherlock (op. cit., pp. 49–50) gives an account of strata proved in bores in this saltfield.

The proving of rock salt near Mobberley in 1947, in several bores for the Ministry of Town and Country Planning (pp. 128–153), was the first firm indication of a major extension of the main Cheshire saltfield to this area. The Mobberley salt is probably continuous with that at Chelford, proved in the Mereleigh Borehole (p. 80). Although this area, like the other northward extension of the main saltfield in the neighbourhood of Tabley, Knutsford and Rostherne undoubtedly contains substantial reserves of rock salt at workable depth, the mineral is unlikely to be exploited in the forseeable future. The thickness of rock salt is probably not sufficient to support an industry based on 'controlled' pumping in competition with that in the main field to the south; and any new proposal for 'wild' brine abstraction would certainly be strongly opposed on planning grounds.

Since most of the Holford brinefield is within the district to the south—the subject of a forthcoming map and memoir—and since the main reserves lie in that direction, it is not thought likely that there will be any important extension of the working area within the present district.

Water supply

Public supplies

Almost since its inception, the textile industry on the western flanks of the Pennines has depended on an abundant and cheap supply of soft water for cloth processing. This, added to the demand for soft water for domestic use, has led to the development in most of the suitable valleys of catchment and impounding schemes of greater or less size. Stockport has impounding reservoirs at Lyme Park and Kinder, and buys additional water from Manchester Corporation.

The towns in the areas underlain by the Keuper Marl and Keuper Waterstones are in a particularly difficult position with regard to water supply. They are too far from the hills to have impounding schemes, and such small supplies as they may be able to pump from the underlying rocks are frequently found to be so hard as to be undrinkable. In addition the water may be saline. The towns of Sale, Altrincham and Knutsford therefore all buy in bulk, from Manchester Corporation, water piped from the Lake District through the Thirlmere and Haweswater aqueducts.

The town supply at Lymm is obtained from wells in Keuper and Upper Mottled Sandstones, and is extremely hard. Boreholes into the Upper Mottled Sandstone at Wilmslow augment Stockport Corporation's supply to Wilmslow and Alderley Edge. Macclesfield Corporation, in addition to its supplies from reservoirs, has a well sunk in Bunter Pebble Beds at Tytherington, near the southern edge of the district. Bollington obtains its supplies from wells in the Middle Grits of the Millstone Grit Series near Rainow (Millbrook, Danebent and Ginclough) and in the Woodhead Hill Rock and Rough Rock in Bakestonedale. Most other towns and villages obtain their supplies from one or other of the major concerns.

As regards quality the impounded water is much the softest; and that from the Bunter and Keuper wells the hardest, usually requiring treatment before it is distributed. The Millstone Grit water at Bollington lies somewhere between the two, with a temporary hardness, largely due to carbonate, of 6° and a permanent hardness of 2°.

Industrial and private supplies

Numerous wells, some capable of yielding many thousands of gallons an hour, have been sunk at textile factories, breweries and other industrial premises in and around Stockport, where the Bunter and Collyhurst sandstones provide a vast reservoir. Some wells penetrate a portion of both aquifers which lie above and below the Manchester Marl. The district is traversed by numerous faults, most of them with a large northerly component in their trends, and these assist the ready passage of water within the area, and from one aquifer to another. Some textile firms, notably at Romiley, Chadkirk and Bollington, have wells in the Lower Coal Measures and Millstone Grit, the water being derived chiefly from the sandstone layers. Some private houses and farms also obtain water from this source. Many farms and private houses obtain enough for their requirements from shallow wells in the drift deposits: in those areas of the Cheshire–Shropshire plain underlain by Keuper Marl the coincidence of villages with lenses of water-bearing Middle Sands illustrates the importance of this source of supply in days gone by; though many outlying farms on the clay plain have, even until recent times, had to rely on roof catchment and ponds. In this district, the original siting of Knutsford was probably influenced strongly by the occurrence of water-bearing sands. In the neighbourhood of Mere and Tabley supplies from the Middle Sands have sufficed for several hamlets, through a private estate scheme.

Reserves

The upland catchment areas and their impounding reservoirs are now probably yielding nearly their full amount; and it is unlikely that any large additions can be expected from this source, though total storage capacity may be slightly increased by raising dams or bringing some of the smaller valleys into use as reservoirs.

It seems that for the future (leaving out of consideration possible long-distance aqueduct schemes) the almost inevitable increase in demand for water will have to be met from underground sources. Moreover, the problem of hardness is somewhat less acute now that synthetic detergents are supplanting soap for washing.

In the country underlain by Carboniferous rocks east of the Red Rock Fault a number of thick sandstone and gritstone beds in the Lower Coal Measures and Millstone Grit come to crop. In general the yield of wells penetrating these rocks depends largely upon the degree of jointing and shattering to which the rocks have been subjected, for such sandstones are usually well-cemented, or 'tight'. Predictions of yield are thus difficult for a well of say, 750 feet depth may give less than 2000 gallons per hour in unfissured ground or as much as 10 000 or 12 000 gallons per hour if the rock is well broken. With the amount of jointing that exists in the area generally it would not be unreasonable to expect 5000 to 6000 gallons per hour from a well sited to penetrate an adequate thickness of arenaceous rock, perhaps a little more in the coarser gritstones and a little less in Coal Measures sandstones.

Probably the existing abstractors already take a high proportion of water that is easily available in the Carboniferous rocks. For certain purposes the flooded coal mines in the Poynton Coalfield could yield large quantities of water, but this is unlikely to be of a quality suitable for domestic use.

A far better prospect lies in the Permo-Triassic sandstones west of the Red Rock Fault, in the quadrilateral Wilmslow–Cheadle–Hazel Grove–Whiteley Green. Here the Collyhurst Sandstone, Pebble Beds and Upper Mottled Sandstone crop out; and a bore almost anywhere in the quadrilateral, except the extreme east, might be expected to encounter well over 1000 feet of open-textured sandstone forming an almost ideal aquifer. The Pebble Beds tend to contain somewhat more interstitial cement than the other two units, and to yield slightly harder water.

The yield from the Permo-Triassic sandstones is not so dependent on fissuring as that from Carboniferous strata, for the water moves interstitially: and the rock as a whole, especially the Collyhurst Sandstone, may have a porosity as high as 20 per cent. A well or group of wells of suitable dimensions in this type of ground may yield as much as one million gallons per day. There is, moreover, good evidence from similar districts in Lancashire that percolation may be as much as seventeen per cent of rainfall, even through a cover of glacial drift; and it may be stated with confidence that there are here large reserves of underground water, with adequate conditions for replenishment. In Stockport town itself, whilst there is as yet no indication of serious overpumping, the number of wells already in use makes the prospect less attractive, and the same is true immediately west of the town.

Upper Mottled Sandstone crops out north of Lymm, and between Sale and Irlam. In both these areas there are strong indications that a layer of fresh interstitial water several hundred feet thick rests upon highly saline water below. The origin of the saline substratum—probably more saline even than sea-water—may be connected with the proximity of the saltfield to the south. These two areas are thus ruled out as possible important future sources of fresh-water supply. B.J.T.

Non-ferrous metals

The only substantial occurrences of metalliferous ores in the district are at Alderley Edge and Mottram St. Andrew, where the principal ore is of copper, associated with lead, cobalt, manganese, antimony and other metals. Small amounts of silver and a trace of gold have been detected in selected samples. The mines and minerals of Alderley and Mottram have been fully described by Dewey and Eastwood (1925), who give numerous references to previous literature.'^‡5 

The ore occurs in the Upper Mottled Sandstone and in the basement beds of the Keuper Sandstone. The minerals are disseminated throughout these rocks but are more concentrated in veins that occur along lines of faulting. The ore-bearing sandstones lie above the water table in the zone of oxidation, consequently most of the minerals are secondary and occur as carbonates, silicates, oxides and sulphates. The exception is the sulphide of lead (galena) which occurs sporadically in massive forms in the veins. Chalcopyrite also occurs, although it was not found during the recent survey. The mines were worked essentially for copper, and the ore occurs as malachite, azurite and chrysocolla. Minerals containing arsenic in association with copper probably include olivinite. Copper sulphate and carbonate form incrustations on the mine walls and on old timbers. Cobalt in association with manganese and arsenic is found as wad and cobalt bloom. As already mentioned galena occurs in the fault veins, albeit sporadically and with wide intervals between occurrences. Secondary minerals of lead are found in the double salts of copper and lead, linarite and caldonite. The lead carries small quantities of silver, gold, vanadium, antimony, cobalt and nickel. The gangue mineral is barytes; it occurs in the veins in massive form, and is also widely disseminated throughout the sandstone, occurring quite abundantly as needle-shaped ghost crystals in the Upper Mottled Sandstone and in the Keuper Sandstone. The barytes ghost crystals extend locally beyond the impregnations of the metalliferous minerals. More faults were recognised during the survey than have been previously suspected; and it is now possible to state that the highest concentrations of the metalliferous minerals and of barytes occur along the faults, and that away from the faults the mineralization fades.

Selected samples of ore that are locally enriched have been found to contain as much as 7.5 per cent of copper; but in the field as a whole, the value in the workable parts of the stone varies between 1.5 and 2.5 per cent. Over 20 years of mining the amount of copper obtained by smelting averaged 2.1 per cent of the ore mined. The stone at Mottram was said by E. Hull (1864, pp. 65–9) to contain up to 22 per cent of copper ore with an average of 5 per cent, but the higher figure probably refers to selected samples.

In the West Mine at Alderley Edge three cupriferous sandstone beds were said to occur, of which the lowest was the richest. The main bed was said to be a massive white coarse sandstone up to twenty feet thick, impregnated with ore; but it is doubtful whether this is an accurate description. The workings do not maintain constant horizons, and there appears to have been a tendency to extract a soft sandstone, mainly composed of loosely-bound rounded grains, which occurs not only in the Upper Mottled Sandstone but also between the Keuper conglomerate beds, rather than to work the relatively hard subangular-grained sandstones containing quartzite pebbles, although these Keuper conglomerate beds are also cupriferous.

In the Wood Mine and at the Mottram Mine the workings were mainly in Keuper conglomerates. Copper was obtained from the ore both at Alderley and Mottram by crushing and digesting in hydrochloric acid, scrap-iron thrown into the resulting green liquor precipitating metallic copper. A later process employed sulphuric acid to obtain a solution of copper sulphate.

Whatever opinions may have been expressed in the past as to the origin of the ores, the recent survey has shown that the mineralization is strictly related to the faulting. The date of the faulting is post-Keuper, probably Tertiary, and the mineralization obviously post-dates the faulting. The dissemination of the minerals into the sandstones, and their oxidation, occurred at a still later date, probably late in the Tertiary period.

There is no positive evidence to show whether the mineralization ascended or descended; but on general grounds it is difficult to imagine a mineralization from descending solutions at this horizon, since immediately above the ore-bearing sandstones there are sandstones interbedded with shales, and as we ascend the sequence it becomes progressively more argillaceous until there are thousands of feet of argillaceous measures in the Keuper Marl. On the other hand these argillaceous measures would act as an excellent cap to ascending solutions. The probabilities therefore would appear to indicate a magmatic origin for the mineralization.

The Alderley Edge and Mottram Mines have been closed for many years. There is no suggestion that the area was approaching exhaustion, though some lodes were worked to adit levels at the time. Future operations would undoubtedly depend on the ruling price of copper. M.T.

Sand and gravel

The widespread deposits of Middle Sands are extensively worked for building purposes. They vary in quality from clean sharp sand to somewhat loamy deposits with layers of clay. Coal fragments are common, and though concentrated in beds they are difficult to exclude during working. Irregular lenses of gravel locally make up as much as one quarter of the deposit, but are usually much less; their grade varies from cobble size down to small pebbles, mainly rounded hard igneous or metamorphic rocks of northern origin. Where the Middle Sands are overlain by Upper Boulder Clay the increasing overburden often makes a pit uneconomic long before the deposit is worked out. There are large reserves of sand and gravel wherever the Middle Sands are well developed. The main concentration of potential quarry sites is around Tytherington, Bollington Cross, Butley and Prestbury; but parts of these reserves have already been sterilized by building.

The high river terraces of the Bollin and Dean may be worth investigating for gravel, of which there is a shortage in the district. Near Brook House a few feet of silt rest upon 7 feet of gravel.

A number of thin spreads of older blown sand on the terraces of the rivers Mersey and Bollin are mentioned on p. 111 as resembling the Shirdley Hill Sand (which is used in glass-making), but it is doubtful if these isolated patches can be regarded as of much importance as reserves for that industry. A more promising prospect for sand of low iron-content seems to lie in the area immediately north of Chelford village, at the extreme southern edge of the district; for there is some evidence that the well-known white sand of Chelford (see p. 96) may extend northwards into the district here, perhaps beneath a cover of sandy boulder clay or reddish glacial sand.

The Upper Mottled Sandstone is incoherent enough to be quarried for sand at the foot of the Alderley Edge escarpment near Hough, and there are large reserves.

Brick clays

Brick-making clays include the mudstones of the Upper Carboniferous and Keuper, and the boulder clays and late-glacial clays of the Pleistocene. In the Coal Measures the grey mudstone above the Poynton Five Foot seam has been worked at Middlewood and processed for brick-making, and this quarry was abandoned mainly because there was no room for expansion. There are undoubtedly large reserves of this type of material in the Millstone Grit and Coal Measures at many localities east of the Red Rock Fault.

Keuper Marl is dug at Oversleyford, south of Ringway, together with the overlying boulder clay, and gives a tough, light coloured, somewhat mottled brick with some of the characteristics of boulder-clay bricks. Used in this way the Keuper Marl does not appear to exhibit its most common fault as a brick-making material—that of subsequent spalling and splitting due to hydration of included calcium sulphate.

Boulder clay alone has been dug for bricks at a number of localities, including large pits at Adswood and near Middlewood Junction. It makes a tough brick, extremely resistant to weathering. There are vast reserves, in many parts of the district, of boulder clay which could be worked either alone or with the underlying Keuper or Carboniferous mudstone. A small amount of the laminated clay underlying the Mersey terrace deposits, north of Carrington and near Ashton-on-Mersey, has been dug for bricks.

Peat

Peat has been cut to a limited extent on Lindow Moss and Holcroft Moss. Carrington Moss has been used mainly for the disposal of ashes and other rubbish which has been ploughed into the surface to make arable land. Chat Moss (see Tonks and others 1931, p. 207) extends into the present district. In all these areas there are limited reserves of peat, which, however, shrink year by year.

It is doubtful if any of the isolated patches of upland peat such as those on Park Moor, Lyme Park, have any commercial value.

References

DEWEY, H. and EASTWOOD, T. 1925. Copper Ores of the Midlands, Wales, the Lake District and the Isle of Man. Mem. Geol. Surv., Min. Resources, 30

ENNOS, F. R. and SCOTT, A. 1924. Refractory Materials: Fireclays. Analyses and Physical Tests. Mem. Geol. Surv., Min. Resources, 28

HOWE, J. A. (Edited by). 1920. Refractory Materials: Fireclays. Resources and Geology. Mem. Geol. Surv., Min. Resources, 14

HULL, E. 1864. On the Copper-Bearing Rocks of Alderley Edge, Cheshire. Geol Mag., 1, pp. 65–9

SHERLOCK, R. L. 1921. Rock-Salt and Brine. Mem. Geol. Surv., Mk. Resources, 18

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.

Appendix 1 Sections of boreholes, wells and shafts

Sections of important boreholes and colliery shafts are listed below. All are either published for the first time or give revised interpretations. Most of the accounts are abridged. Some of those dealing with highly repetitive strata. such as the Keuper rocks, are restricted to brief summaries; at the same time the Ashley, Holford H.130 and Radbroke Hall bores (pp. 125, 136 and 150) have been given more fully in order to illustrate typical sequences in the Keuper Waterstones, Lower Keuper Saliferous Beds and Lower Keuper Marl, respectively.

The following mining terms require explanation: bass, carbonaceous shale; floor, stratum immediately underlying a coal seam; leys, clay, usually overlying a coal seam; metal, shale, mudstone and silty mudstone; mussels, non-marine lamellibranchs; rock, thickly bedded sandstone; sod, seatclay; warrant, seatearth. The term 'mine' is of common usage in the coalfield for 'seam'. It has been omitted from the name of each coal in this appendix for the sake of brevity. Grid-references of sites are all within 100-km square SJ.

Alderley Edge (Isaac Massey's) BH

Height above O.D. about 280 ft. 6-in SJ 87 N.W. (Ches. 28 S.W.). Site 10 yd E. of railway and 60 yd S.W. of junction of Chapel Street and South Street, Alderley Edge. Grid. ref. [SJ 8423 7819]. Drilled 1894. Not examined by Geological Survey.

Ashley BH (Geol. Surv. No. 9)

Height above O.D. 105 ft. 6-in SJ 78 S.E. (Ches. 18 S.W.). Site 220 yd S. 29° W. of road and rail crossing south of Ashley and 13 yd S.E. of road. Grid ref. [SJ 7738 8355]. Drilled 1954. Cores examined by B. J. Taylor. Cutting samples to 21 ft—cores below.

General note: 'Striped beds' denotes an alternation of siltstone and mudstone, in bands usually less than half an inch and frequently less than one eighth of an inch thick. Upper surfaces of siltstone are commonly ripple-marked, and salt-crystal pseudomorphs are common on upper surfaces of mudstone. Desiccation-cracks in places cut vertically through the strata. Most of the thicker layers of 'blocky' unstratified red mudstone are highly autobrecciated mixtures of fine-grained and silty mudstone. Gypsum is common throughout, mostly as veins, in the fibrous habit, but also as small pellets and as interstitial infilling.

The measures here referred provisionally to the Keuper Waterstones may include strata equivalent to part of the Lower Keuper Marl and 'Upper Keuper Sandstone' of other areas (see p. 69).

Bakestonedale BH

Height above O.D. about 940 ft. 6-in SJ 97 N.E. (Ches. 29 S.W.). Site immediately south of confluence of streams, 335 yd W. 5°S. of Bakestonedale Farm, Pott Shrigley. Grid ref. [SJ 9594 7951]. Drilled for water 1949. Cores examined by F. W. Cope, The dip varies between 5 and 10 degrees.

Beeches Farm BH

Height above O.D. 189 ft. 6-in SJ 88 S.W. (Ches. 27 N.E.).  Site 200 yd due N. of Beeches Farm, Davenport Lane, Mobberley. Grid ref. [SJ 8012 8116]. Drilled 1948, for Ministry of Town & Country Planning. Cores examined by F. M. Trotter and D. A. Wray. Also called 'Ministry of Town and Country Planning No. 2'. No cores above 48 ft.

Bollington Print Works BH

Height above O.D. 504 ft. 6-in SJ 97 N.W. (Ches. 29 S.W.). Site 65 yd N.E. of corner of Church Street and Ingersley Road, Bollington. Grid ref. [SJ 9398 7797]. Drilled for water 1934. Cores examined by R. C. B. Jones. Cores were weathered and mixed when examined; and the exact level of G. cancellatum could not be established.

Breach House Lane BH

Height above O.D. 148 ft. 6-in SJ 78 S.E. (Ches. 27 N.E.). Site 160 yd S. of junction of Breach House Lane and Wood Lane, 150 yd S.W. of Ivy Cottage, Wood Lane, Mobberley. Grid ref. [SJ 7844 8192]. Drilled 1948, for Ministry of Town & Country Planning. Cores examined by F. M. Trotter and D. A. Wray. Also called 'Ministry of Town and Country Planning No. 3'.

Bredbury Colliery, Lingard Lane Pit No. 1

Height above O.D. about 295 ft. 6-in SJ 99 S.W. (Lancs. 112 N.W.).Site 90 yd N. of Lingard Lane and 180 yd N.E. of railway bridge over Lingard Lane, Bredbury. Grid ref. [SJ 9189 9254]. Date of sinking not known. Strata not examined by Geological Survey.

The Park Mine varied in thickness from 3 in to 4 ft 3 in in this shaft section. This record is preferred to several which differ slightly in detail.

Brook Farm BH

Height above O.D. about 182 ft. 6-in SJ 77 N.E. (Ches. 27 S.E.). Site on south side of road, 500 yd W.S.W. of Brook Farm, Mobberley. Grid ref. [SJ 7867 7727]. Drilled by percussion 1947, for Ministry of Town & Country Planning. Samples examined by F. M. Trotter. Also called 'Ministry of Town and Country Planning No. 4 Percussion',

Chadkirk Print Works BH

Height above O.D. 198 ft. 6-in SJ 98 N.W. (Lancs. 112 S.W.). Site immediately E. of tanks on E. side of works. Grid ref. [SJ 9394 8951]. Drilled for water 1951–2. Cores examined by B. J. Taylor. Certain details of this bore, and a vertical section, have been published,^‡6  and a correlation made with adjacent areas.

CWS Confectionery Works No. 2 BH

Height above O.D. 252 ft. 6-in SJ 89 S.E. (Lancs. 112 N.W.). Site 90 yd S.W. of junction of Eastcote Road and Newark Road, South Reddish. Grid. ref. [SJ 8954 9227]. Drilled for water 1954. Cores examined by B. J. Taylor.

Deanwater BH (Geol Surv. No. 5)

Height above O.D. 240 ft. 6-in Si 88 S.E. (Ches. 28 N.W.). Site 50 yd S.W. of centre of Deanwater Bridge, Wilmslow. Grid ref. [SJ 8769 8181]. Drilled 1953. Cores examined by B. J. Taylor. Cutting-samples to 27 ft, cores below.

Glevehonse Farm BH

Height above O.D. about 190 ft. 6-in SJ 77 N.E. (Ches. 27 S.E.).

Site on N. bank of Pedley Brook, Mobberley, 400 yd S.S.E. of Glevehouse Farm. Grid ref. [SJ 7854 7845]. Drilled by percussion 1947, for Ministry of Town & Country Planning. Samples examined by F. M. Trotter and D. A. Wray. Also called 'Ministry of Town and Country Planning No. 2 Percussion'.

Greenwell's (Norbury) BH

Height above O.D. about 350 ft. 6-in SJ 98 N.W. (Ches. 20 S.W.). Site approximately 300 yd S.S.E. of Carrwood, Norbury. Grid ref. 933852. Drilled about 1915. Not examined by Geological Survey.

Grey's Gorse BH (Geol. Suff. No. 3)

Height above O.D. 110 ft. 6-in SJ 78 N.W. (Ches. 17 S.E.). Site 20 yd S.S.E. of N.W. corner of Grey's Gorse Wood, Millington. Grid ref. [SJ 7298 8568]. Drilled 1953. Cores examined by B. J. Taylor. Cutting-samples to 73 ft, cores below.

General Note: Cores to 114 ft were shattered and heavily jointed, and recovery was poor. Below this, dips varied between 8° and 11° except near a (small?) fault crossing the hole at 339 ft. Strata throughout were impregnated with secondary vein-gypsum. Penecontemporaneous deformation, including thin mudstone breccias and suncracks, was common.

The strata provisionally assigned to Keuper Waterstones may equally well belong to a higher arenaceous phase within the Lower Keuper Marl (see p. 71).

Hazel Grove BH

Height above O.D. 295 ft. 6-in SJ 48 N.W. (Ches. 19 S.E.). Site on S. side of railway 400 yd N.N.E. of Norbury Fold, Hazel Grove. Grid ref. [SJ 9181 8655]. Drilled for coal 1894. Cores (only below 1316 ft) examined by C. E. De Rance. Most of the log has been published.^‡7  The main features, with an intepretation of the Permo-Triassic rocks and a revised correlation of the Coal Measures, are given below.

Healdmill BH

Height above O.D. about 130 ft. 6-in SJ 78 S.E. (Ches. 27 N.W.). Site on E. bank of Mobberley Brook, 520 yd S.S.E. of Mobberley Station and 150 yd W. of Healdmill, Mobberley. Grid ref. [SJ 7797 8094]. Drilled by percussion 1947, for Ministry of Town & Country Planning. Samples examined by F. M. Trotter and D. A. Wray. Also called 'Ministry of Town and Country Planning No. 1 Percussion'.

Hogswood BH (Geol. Surv. No. 2)

Height above O.D. 65 ft. 6-in SJ 79 S.W. (Ches. 9 S.W.). Site 750 yd E. of Green Lane Farmhouse, and 620 yd S. of Brookheys Farmhouse, Dunham Massey. Grid ref. [SJ 7437 9004]. Drilled 1953. Cores examined by B. J. Taylor. Cutting-samples to 86 ft, cores below.

Holford No. 130 BH

Height above O.D. about 110 ft. 6-in SJ 77 S.W. (Ches. 34 N.E.). Site 720 yd W. 16° S. of Yewtree Cottage, Trouthall Lane, Plumley. Grid ref. [SJ 7134 7475]. Drilled 1950. Details from, and published by permission of, Imperial Chemical Industries Ltd.

Kellhouse BH

Height above O.D. 122 ft. 6-in SJ 78 S.E. (Ches. 27 N.W.). Site 300 yd W. of northern end of Kellhouse Farm and 1420 yd N.N.W. of Mobberley railway station. Grid ref. [SJ 7697 8234]. Drilled 1948, for Ministry of Town & Country Planning. Cores examined by F. M. Trotter and D. A. Wray. Also called 'Ministry of Town and Country Planning No. 5'.

Lady Lane BH

Height above O.D. 206 ft. 6-in SJ 78 S.E. (Ches. 27 N.E.). Site at junction of Hobcroft Lane and Lady Lane, Mobberley; 600 yd due N. of Mobberley Church. Grid ref. [SJ 7907 8070]. Drilled 1948, for Ministry of Town & Country Planning. Cores examined by F. M. Trotter and D. A. Wray. Also called 'Ministry of Town and Country Planning No. 1'.

Lindow Moss BH (Geol. Surv. No. 6)

Height above O.D. 241 ft. 6-in SJ 88 S.W. (Ches. 27 N.E.). Site 115 yd N.E. of Newgate House and 270 yd S.E. of Boundary Lodge, Wilmslow. Grid ref. [SJ 8254 8109]. Drilled 1954. Cores examined by B. J. Taylor. Cutting-samples to 113 ft, cores below.

General note: The collapse-breccia is after salt solution, and probably includes. fragments from both the Lower Keuper Saliferous Beds and the Middle Keuper Marl.

Maple Road BH (Geol. Surv,. No. 1)

Height above O.D. 92 ft. 6-in SJ 79 S.E. (Ches. 9 S.E.). Site 21 yd of central point of Maple Road, 340 yd E. of its junction with Brooklands Road, Baguley. Grid ref. [SJ 7948 9002]. Drilled 1953. Cores examined by B. J. Taylor. Cutting-samples to 47 ft, cores below.

General note: Gypsum is present as veins of satin spar above 200 ft in the hole—The Keuper Marl and Keuper Waterstones exhibit such features as suncracks, ripple-marks, and desiccation breccias, which are evidence of shallow-water deposition.

Millbrook No. 1 BH

Height above O.D. about 666 ft. 6-in SJ 97, N.W. (Ches. 27 N.W.). Site 50 yd S. of Rainow Bridge, Rainow. Grid ref. [SJ 9497 7578]. Drilled for water 1922. Cores not examined by Geological Survey.

Mobberley New Hall BH

Height above O.D. 202 ft. 6-in SJ 77 N.E. (Ches. 27 S.E.). Site on N. side of Hall Lane, 60 yd W.N.W. of Lodge and 240 yd S. of Mobberley New Hall, Mobberley. Grid ref. [SJ 7971 7955]. Drilled 1948, for Ministry of Town & Country Planning. Cores examined by F. M. Trotter and D. A. Wray. Also called 'Ministry of Town and Country Planning No. 4'. Recovery of core was poor.

Moss Nook BH (Geol. Surv. No. 4)

Height above O.D. 250 ft. 6-in SJ 88 N.W. (Ches. 19 S.W.). Site 106 yd S.S.W. of 'The Laurels', and 10 yd W. of Styal Road, Heald Green. Grid. ref. [SJ 8385 8512]. Drilled 1954. Cores examined by B. J. Taylor. Cutting-samples to 52 ft, cores below.

General note: The strata above 260 ft were shattered by numerous minor faults, and dips varied from 26° to 64°. Below 260 ft dips varied from 12° to 15°. Gypsum was present only as small irregular pellets and lining small cavities, in the upper part of the bore. Suncracks, desiccation-breccias and ripple-marks were common throughout, the latter chiefly below 287 ft.

Mount Pleasant Farm BH

Height above O.D. about 210 ft. 6-in SJ 88 N.W. (Ches. 27 S.E.). Site immediately S.W. of Mount Pleasant Farm, Moss Lane, Paddock Hill, Mobberley. Grid ref. [SJ 8095 7987]. Drilled 1948, for Ministry of Town & Country Planning. Cores examined by F. M. Trotter and D. A. Wray. Also called 'Ministry of Town and Country Planning No. 6. No cores above 108 ft.

General note: The section of the superficial deposits is based on the borer's record, no samples were taken. The brecciated strata at the bottom of the hole are regarded as part of the Saliferous Beds.

Newton Bank BH

Height above O.D. about 375 ft. 6-in SJ 99 N.E. (Lanes. 105 S.E.). Site 620 yd E.S.E. of Heaviley Bridge, 640 yd S.W. of Mount Pleasant, Godley. Grid ref. [SJ 9582 9506]. Drilled 1948. Cores examined by R. H. Price.

Norbury Bye Pit

Height above O.D. about 405 ft. 6-in SJ 98 N.W. (Ches. 20 S.W.). Site 210 yd N. 15° W. of Norbury Hollow Bridge, Norbury. Grid ref. [SJ 9383 8554]. Date of sinking not known. Strata not examined by Geological Survey.