Geology of the country around Chapel en le Frith. Explanation of one-inch geological sheet 99, New Series

By I. P. Stevenson, MonograptusSc. and G. D. Gaunt, B.Sc. Palaeontology by Monograptus Mitchell, MonograptusA., W. H. C. Ramsbottom, Ph.D. and Monograptus A. Calver, MonograptusA. Petrography by R. K. Harrison, MonograptusSc.

Bibliographic reference: Stevenson, I.P. and Gaunt, G.D. 1971. Geology of the country around Chapel en le Frith (Explanation of one-inch geological sheet 99, New Series).  Memoirs of the Geological Survey of Great Britain England and Wales. London : HMSO.

Natural Environment Research Council. Geological Survey of Great Britain. Institute of Geological Sciences

Memoirs of the Geological Survey of Great Britain England and Wales

London Her Majesty's Stationery Office 1971 © Crown copyright 1971 SBN 11 880115 5 * Printed in England for Her Majesty's Stationery Office by Hull Printers Ltd., Willerby, Hull HU10 6DH

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

(Front cover)

(Rear cover)

Preface

The district represented on the New Series One-inch Geological Sheet 99 (Chapel en le Frith) was first geologically surveyed by E. Hull, John Phillips and W. W. Smyth. Old Series maps were published in 1852 (81 NE and 81 SE) and 1864 (81 NW and 81 SW). Subsequent additions by A. H. Green, C. le Neve Foster, J. R. Dakyns and E. Hull were published in 1866, 1867 and 1874. The western part of the district was described in a memoir by Hull and Green published in 1866 and the remainder in 1887 in a memoir by A. H. Green, C. le Neve Foster and J. R. Dakyns.

Small marginal areas of the Chapel en le Frith sheet were surveyed during work on adjoining sheets between 1927 and 1950. Systematic fieldwork was started in 1951 by Mr. I. P. Stevenson, later joined by Mr. R. A. Eden for a few seasons, and then by Mr. G. D. Gaunt, with whose help the sheet was completed in 1961. The six-inch maps covered by the various surveyors are listed on p. xii. Solid and drift editions of the one-inch map were published in 1967. Part of the Chapel en le Frith district is covered by a special 1: 25,000 sheet (Edale and Castleton) published in 1969.

Mr. Stevenson has written most of the present memoir and was responsible for its compilation. Mr. Gaunt wrote parts of the Introduction and chapters on Millstone Grit Series, Pleistocene and Recent Deposits, Mineral Products and Water Supply. The memoir was edited by Mr. D. R. A. Ponsford and Dr. A. W. Woodland. Mr. Monograptus Mitchell identified fossils from the Carboniferous Limestone and contributed a chapter on the Stratigraphical Palaeontology of the series. Dr. W. H. C. Ramsbottom and Mr. Monograptus A. Calver identified fossils from the Millstone Grit and Coal Measures respectively and contributed to the relevant stratigraphical chapters. Petrography of the sedimentary and igneous rocks is by Mr. R. K. Harrison.

Thanks are given to Dr. D. E. Owen (Director) and Mr. D. Rushton, of the Manchester Museum, and to Mr. I. E. Burton, Curator and Librarian, Buxton Library and Museum, for allowing us to borrow bones of Pleistocene mammals from Doveholes; also to Dr. A. Sutcliffe, British Museum (Natural History) and Mr. H. E. P. Spencer, late of the Ipswich Museum, for examining them on our behalf.

Acknowledgement is here made to the Derwent Valley Water Board who have kindly placed a series of borehole records at our disposal and in appropriate parts of the text to many other concerns who have kindly furnished or released information.

K. C. Dunham, Director, Institute of Geological Sciences, Exhibition Road, London, S.W.7. 30th April, 1971.

List of six-inch maps

Geological six-inch maps inchided wholly or in part in the one-inch map Sheet 99 (Chapel en le Frith) are listed below together with the initials of the surveyors and the dates of survey. The surveyors were: R. A. Eden, W. N. Edwards, G. D. Gaunt, R. H. Price, J. V. Stephens, I. P. Stevenson and B. J. Taylor. Small parts of one-inch Sheet 99 are included on the following six-inch maps which are not yet complete: SJ97SE, SK07SW, SK07SE, SK17SW, SK17SE, SK27SW. Printed maps marked with an asterisk are uncoloured, or, to suit individual requirements, hand-coloured. The remaining maps are available for public reference in manuscript form.

Chapter 1 Introduction

Geographical setting

This memoir describes the geology of the district covered by the Chapel en le Frith (99) Sheet of the One-inch Geological Map of England and Wales.Throughout this memoir the word 'district' refers to this area. This area lies mainly in the Peak District of Derbyshire but also extends into Yorkshire in the north-east and into Cheshire in the west. The relations of the district to adjacent areas are shown in (Figure 1). Large tracts lie within the Peak District National Park. The region described lies across the axis of the Pennine uplift. The morphology, drainage and pattern of land usage clearly reflect variations in the lithology and structure of the underlying rocks. The principal physical features are illustrated in (Figure 2).

In the south, the Carboniferous Limestone outcrop forms a plateau, ranging in height from 1100 ft to just over 1500 ft on Bradwell Moor. This tract is gently dissected with some more deeply-cut valleys. Much of the drainage of this area is underground and surface streams are limited to valleys near the margin of the outcrop and to areas with perched water tables over impervious igneous rocks. Karst features such as potholes, sink-holes, caves and limestone scars are well-developed, though limestone pavements, typical of certain areas of Yorkshire, are little developed. Numerous spoil heaps and open workings along the lines of veins are the result of centuries of lead mining. In many places the lines of the more important veins stand out by virtue of the trees which have been planted along them. At the present time the working of limestone itself is producing striking modifications to the landscape.

To the north and east of the limestone area lie broad expanses of high, often peat-covered moorland, covering much of the Millstone Grit outcrop and rising to 2088 ft O.D. on the plateau of Kinder Scout, the highest point in the southern Pennines. The alternation of hard sandstones and soft shales produces ridges and hollows along the deeply incised valleys and, where the beds are inclined, a well-developed scarp and dip-slope topography is developed. Tors and craggy escarpments or 'edges' are conspicuous along the outcrops of the more massive and resistant sandstones, and collapse of the latter over shale on some steeper slopes has produced spectacular, and in certain localities still active, landslips. The moors furnish rough grazing for sheep, and grouse shooting. Afforestation is practised to stabilize valley slopes in the extensive reservoir areas in the upper Derwent valley and also furnishes a source of timber. Two small outcrops of Lower Coal Measures are present along the eastern margin of the district.

In the west, sandstones and shales of the Millstone Grit Series and Lower Coal Measures, sharply folded into the Goyt Trough and Todd Brook Anticline give rise to less elevated but more diverse scenery, with marked dip-slopes and scarps and some areas of moorland separated by stretches of largely pastoral farmland along the valleys. The availability of an abundant water supply has led to the establishment in the valleys of a number of settlements associated with the textile industry; these include Hayfield, Chinley, Birch Vale, New Mills and Whaley Bridge. Works in these places are now mainly concerned with bleaching and printing of fabrics. The town of Chapel en le Frith is the home of the large Ferodo works.

Except for a small area in the extreme north-east, where streams flow eastwards to the River Don, the eastern half of the district is drained by the Derwent and its tributaries, the Ashop, Alport and Noe, which lie in deeply incised valleys between the Millstone Grit moorlands. Water from the greater part of the limestone area also flows into the Derwent either direct or via the Wye just south of the district. Much of the Derwent catchment area within the district has been tapped to supply Sheffield and other cities in the East Midlands. Reservoirs in the extreme north-east also supply Sheffield.

With minor exceptions the western half of the district is drained by the River Goyt and its tributaries, including the Etherow which traverses the north-west corner to join the Goyt just beyond the western boundary of the district. Stockport is supplied by a number of reservoirs in the Goyt catchment area. G.D.G., I.P.S.

Historical

The earliest signs of human occupation in the district are the worked flints, including microliths, of Mesolithic age found beneath the peat on the moorlands (Armstrong 1956, pp. 99–101). Neolithic remains are scarce but include the Bull Ring, a stone circle at Dove Holes and a smaller circle at Green Low, Chapel en le Frith (Armstrong ibid, p. 105; Edwards and others 1962, p. 122). In contrast, the Bronze Age appears to have marked a sharp increase in the settlement of the district. Many hills in or near the limestone area bear tumuli dating from this period and this accounts for the prevalence of the synonym 'low' in place-names in this tract, examples being Bee Low, Hurd Low and Cow Low. Evidence of Iron Age occupation is less widespread but includes the hill forts of Mam Tor and Castle Naze.

The Romans established the town of Aquae Arnemetiae (now Buxton) on account of its thermal waters and linked it with their fort at Anavio (Brough) by a road, Batham Gate. Another Roman road, Long Causeway, ran from Stanage Pole over the Snake Pass to Glossop linking the forts of Templeborough and Melandra Castle (Bartlett and Preston 1956, p. 115). In pre-Saxon times much of the limestone area and the lower Millstone Grit ground was forest, though tree cover was probably sparse in the more exposed areas. Saxon times saw a partial clearance of the forest for agricultural purposes (Edwards and others 1962, pp. 61–2), but after the Norman Conquest the establishment of a royal hunting forest, centred about Peak Forest, stopped further clearance for a time.

The working of minerals in the district is of considerable antiquity. The first mineral to be produced was lead and the Odin Mine at Castleton has been considered by some to have been first worked by the Romans though this is more usually attributed to the Saxons. A Roman pig of lead has been found at Brough (Smythe 1940, pp. 139–45) but may have been produced elsewhere in Derbyshire. Lead working continued in many parts of Derbyshire in the Middle Ages and after the Norman Conquest was sufficiently widespread for the establishment of a special code of laws. These stem from the Inquisition of Ashbourne in 1288 (Fuller 1965, p. 378) which also established special courts, the Barmote Courts, to enforce them; these courts are still in existence today. Smelting of the lead ore was carried out in scattered hearths or 'boles' using local timber and the word 'bole' survives in place names at several localities. More recent working in the seventeenth and eighteenth centuries has been associated with the driving of drainage levels or 'soughs' to de-water the workings, the most important in the present district being Stoke Sough and Moor-wood Sough. Raistrick and Jennings (1965, pp. 276–7) state that the maximum production of lead was reached in the mid-eighteenth century.

Coal has been worked for over three hundred years in the area of the Goyt Trough. Bunting (1940, p. 156) states that workings at Fernilee were in operation in 1627. The most extensive coal working in the district was carried out in the nineteenth century at Whaley Bridge and the coal was used partly for lime burning. More recent working has been in conjunction with that of fireclays. The industry is now nearly extinct though considerable reserves remain.

Lime-burning is yet another local industry which has been long established. Bunting (ibid., pp. 297–9) states that fourteen kilns were in operation at Dove Holes in 1650. The older workings took the form of a series of closely spaced shallow excavations situated close to one or more kilns. Many of these areas have been planted with trees. I.P.S.

Geological sequence

The formations represented on the one-inch geological map and sections of the district are summarized below:

Geological history

The Woo Dale Borehole (Cope 1949) supplies the only information regarding the pre-Carboniferous rocks of the Peak District. The borehole, in the Wye valley just beyond the southern boundary of the Chapel district, proved pyroelastics of probable Pre-Cambrian age overlain unconformably by 892 ft of Lower Carboniferous strata. This unconformity represents a large gap in the geological history for which details are lacking. Following the Dinantian marine transgression, it is possible to follow the development of a stable shelf area of deposition, largely coincident with the present limestone outcrops and a surrounding basinal area in which terrigenous deposits, largely muds, accumulated. Extensive vulcanicity, occurred mainly on the shelf.

Penecontemporaneous movement along the margins of the stable shelf area was associated with the development of the apron-reef at Castleton and subsequently with shallowing and the formation of knoll-reefs and flat reefs in the marginal part of the shelf area. Erosion in the marginal area gave rise to non-sequences and unconformities. In late Viséan times basinal conditions extended to the shelf area though in some areas shoals persisted on which reef-limestones were deposited. At the end of the Viséan carbonate deposition gave way everywhere to that of shales. During the Viséan, vulcanicity resulted in the extensive extrusion of lavas and, more locally, of pyroclastics.

Namurian sedimentation commenced with the deposition of marine muds though, in the case of the lowest strata, non-deposition or strongly condensed deposition occurred in the shelf area. Later the pattern of sedimentation was changed by the advance into the area of a large delta from the north giving the Mam Tor Beds, Shale Grit and Kinderscout Grit. A lesser and shorter-lived delta, from the south, produced the Roaches, Corbar and Ashover grits. Near emergence is shown by the formation of seatearths and coals, though these were better developed in later Namurian times; and less saline conditions are indicated by the presence of mussels in the Heyden Rock (R₂) and higher beds. Sedimentation continued with very little change into the Lower Coal Measures, though coal deposition was more regular and frequent.

Igneous activity, probably of late Carboniferous age, resulted in the intrusion of dolerite sills into the Viséan limestones and heralded the Hercynian (Variscan) orogeny which produced the main structural features of the Chapel en le Frith district. There followed a period of mineralization when the veins, flats and pipe-veins were formed. The Hercynian mountain chain suffered peneplanation before the Permian transgression, known from adjacent areas.

Post-Carboniferous solid deposits are absent from the area though the effects of Permo-Triassic conditions are considered to have resulted in deep reddening of certain Upper Carboniferous sandstones in the western part of the area. There is otherwise no vestige of the later Mesozoic or Tertiary history of the district. Tertiary orogenic movements resulted in the uplift and doming of the area and initiated the modern topography.

During the Pleistocene the ice sheets of at least one of the earlier glaciations apparently covered the greater part of the district, but few traces of glacial activity now remain. A later and more clear-cut glaciation affected the lower, western ground, but in most places failed to extend much beyond a height of about 1000 ft on the hill slopes. At this time the remainder of the area suffered periglacial conditions with the formation of valley bulges and the deposition of sheets of solifluxion drift or head. Post-glacial deposits include peat, river-terraces, alluvium and landslip.

Previous literature

In this memoir previous research is summarized under the relevant chapter headings. Nevertheless, certain general works on the geology of the area are worthy of mention here for historical reasons.

Whitehurst (1778) first noted the general succession in the area, with limestone and interbedded toadstones overlain by shale, and the latter by 'millstone grit'.

Mawe (1802) described many features of the geology of the Castleton area and also noted the presence of toadstones. He described the working of Blue John fluorspar and listed the other mineral occurrences in the area. A more detailed description was given by Farey (1811) and this has been widely quoted in the description of the Carboniferous Limestone and Millstone Grit.

The Old Series Geological maps covering much of the area of Sheet 99 were 81 N.E. and S.E. published in 1852 and 81 N.W. and S.W. published in 1864. The first two sheets fell in the area described by Green and others (1887). The two western sheets were described by Hull and Green (1866). I.P.S.

References

ARMSTRONG, A. L. 1956. Palaeolithic, Neolithic and Bronze ages. In Sheffield and its region. Brit. Ass. Sheffield, 90–110.

BARTLETT, J. E. and PRESTON, F. L. 1956. Iron age and Roman period. In Sheffield and its region. Brit. Ass. Sheffield, 111–20.

BUNTING, W. B. 1940. Chapel-en-le-Frith. Manchester.

COPE, F. W. 1949. Woo Dale Borehole near Buxton, Derbyshire. Q. Jl geol. Soc. Lond., 105, iv.

EDWARDS, K. C., SWINNERTON, H. H. and HALL, R. H. 1962. The Peak District. London.

FAREY, J. 1811. General view of the agriculture and minerals of Derbyshire, Vol. 1. London.

FULLER, G. J. 1965. Lead-mining in Derbyshire in the mid-nineteenth century. E. Midld Geogr., 3, 373–93.

GREEN, A. H., FOSTER, C. LE NEVE and DAKYNS, J. R. 1887. The geology of the Carboniferous Limestone, Yoredale Rocks, and Millstone Grit of North Derbyshire. 2nd edit. with additions by A. H. Green and A. Strahan. Mem. geol. Surv. Gt Br.

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

MAWE, J. 1802. The mineralogy of Derbyshire. London.

RAISTRICK, A. and JENNINGS, B. 1965. A history of lead mining in the Pennines. London.

SMYTHE, J. A. 1940. Roman pigs of lead at Brough. Trans. Newcomen Soc., 20, 139–45.

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

Chapter 2 Carboniferous Limestone Series (Dinantian)

Introduction

The Carboniferous Limestone Series crops out between Water Swallows, Castleton and Stoney Middleton. This area is the northern extremity of the Derbyshire Dome (see p. 320). Much of the outcrop is a plateau with relief much less marked than that of the Millstone Grit; dissection of this area has, however, caused the formation of valleys (dales) which provide many of the best sections of the Carboniferous Limestone Series. The presence of marginal apron-reef in the Castleton area (see p. 13) is also associated with strong topographical features.

The term 'Carboniferous Limestone Series' is here used as synonymous with Dinantian or Lower Carboniferous. All the exposed rocks of this age in the present district fall within the upper Dinantian or Viséan. The chief subdivisions of the Carboniferous Limestone used in this account are given in (Table 1), together with the major faunal subdivisions on which they are based.

The stratigraphical palaeontology is described separately in Chapter 3. The more important elements of the fauna only are given in the details while full fossil lists are quoted in Appendix 3.

In the present district the rocks of the Carboniferous Limestone Series consist predominantly of limestones with some interbedded basaltic lavas and tuffs referred to in the older literature as 'toadstones'; the total thickness exposed is about 1500 ft. Just beyond the southern margin the Woo Dale Borehole (Cope 1949, p. iv), starting at about the horizon of the lowest strata exposed in the Chapel en le Frith district, proved a further 892 ft of limestone (much intensely dolomitized) overlying pyroclastics of probable Pre-Cambrian age. In addition to the outcrop, Lower Carboniferous rocks are known at depth from the Edale and Alport boreholes.

Previous research

Whitehurst (1778, pl. i, fig. 6) first published a generalized section from Grange Mill to Darley Moor showing limestone with three beds of toadstone underlying shale and grit. Though the section lay to the south of the present district it is evident that Whitehurst intended it to apply to the whole of Derbyshire as he refers (ibid., pp. 149–50) to local names for the toadstones; at Castleton ('cat-dirt') and Tideswell ('channel'); the toadstones were considered to be lavas. Whitehurst further (ibid., p. 199) noted the presence of chert and crinoids ('entrochi' or 'screwstones') in the limestone.

Mawe (1802), in a work devoted largely to the mines of north Derbyshire, followed Whitehurst in stating that the limestone was overlain by shale. He further noted the presence of chert in the limestone at Bradwell and Middleton Dale (pp. 30–31) and of the toadstone outcrops at Wormhill and Castleton (p. 39). A description of a highly fossiliferous stone found at Foolow (pp. 29–30) and used for ornamental purposes probably refers to one of the knoll-reef limestones.

White Watson (1811) added to the knowledge of the Derbyshire Dome, though again his chief published section lay largely to the south of the present district. He also produced a series of inlaid sections across the area (Ford 1960, 4) showing, among other features, the igneous rock underlying the limestones of Middleton Dale and the presence of two lavas between Peak Forest and Wardlow. The work of Farey, which also appeared in 1811, added little to the knowledge of the limestone though it also (pp. 237–9) refers to the presence within it of thick "Basaltic Beds here called Toadstones".

The first Geological Survey map of the district, Old Series 81 N.E., covered most of the limestone outcrop and was published in 1852 (revised 1866), based mainly on the work of J. Phillips. The remainder formed the northern margin of Sheet 81 S.E. by J. Phillips and W. W. Smyth, published in 1852 (revised 1866 and 1867). The explanatory memoir by Green and others (1887) gave the first clear description of the succession and named two of the subdivisions, the "Chee Tor rock" and "Miller's Dale rock" (see p. 22). The presence of a thin 'toadstone' at Dove Holes was noted and the important sections with a thin coal and seatearth in Coombsdale Quarry described (ibid., pp. 21–2). Further (p. 33) the steep marginal dips in the Castleton area were noted.

Barnes and Holroyd (1897) described the occurrence of rolled-shell beds at Castleton and elsewhere. These were attributed to a shoreline extending from Castleton to Barmoor Clough. In two papers, published in 1894 and 1907, Arnold-Bemrose described first the petrography and later the field relations of the igneous rocks. The two main lavas (the Lower and Upper lavas of Miller's Dale, see p. 23) were considered by Arnold-Bemrose to be widespread over the Derbyshire Dome. Although an over-simplification in other areas (see for example Traill 1939, pp. 859–61, for the Millclose area) Arnold-Bemrose's correlations are, for the most part, valid so far as the present district is concerned. In addition the true pyroclastic nature of the Dove Holes and Litton tuffs was recognized and the lava underlying the latter first described. The vents at Monk's Dale and Castleton (Speedwell Vent) were recorded. Arnold-Bemrose further noted, the intrusive nature of the Waterswallows, Peak Forest, Potluck and Tideswell Dale sills.

Hind and Howe (1901, p. 361) first drew attention to the faunal resemblances of the limestones of the Castleton area to those of the Cracoe knolls. They also recorded some details of the section in the railway-cutting (now disused) north of Dove Holes.

Following the publication of Vaughan's classic zonal work in the Avon Gorge (1905), Sibly (1908) was the first to apply the coral-brachiopod zones to the Carboniferous Limestone of the Derbyshire Dome. Sibly recognized three subzones in the Wye valley: the lowest, the Dibunophyllum θ (D₁) Subzone, included the "Upper Toadstone" and underlying strata and was succeeded by the Lonsdaleia (D₂) and Cyathaxonia (D₃) subzones.

Jackson (1908, p. 309) noted the presence of a bed with fish remains in Barmoor Clough Quarry. Later (1925), in a paper concerned with the limestone-shale unconformity, he described sections between Dove Holes and Bradwell and noted the presence of Goniatites crenistria at Nun Low. In 1941 (pp. 241–2) he recorded the presence of Girvanella at the base of the D₂ limestones and of the underlying D₁ coral band in Pin Dale; the reef-limestones at the northern end of this section were regarded as the lateral equivalent of the bedded D₂ succession.

Morris (1929) gave a detailed description of the succession in Middleton Dale and Coombs Dale. Beneath the exposed beds he recognized the presence of basalt, though he confused this with the Upper Lava of Miller's Dale. Morris further noticed the presence of the Linen Dale knoll and the knoll-affinities of the highest beds in Middleton Dale. The latter were referred to a probable "D₃" age and the underlying beds were placed in D₂. Morris published extensive faunal lists.

Fearnsides and Templeman (1932) described the succession in a borehole at Hope, including a thick development of pillow lavas beneath basal Namurian.

In a series of papers, published between 1933 and 1939, Cope discussed the succession in the Wye valley just south of the present district. This succession is the type sequence for all but the highest beds of the shelf facies. A particularly important feature of this work was the recognition of the S₂ age of the lowest beds.

Shirley and Horsfield (1940) mapped the Castleton–Bradwell area and interpreted the reef-limestones with a B₂ goniatite fauna as lying with marked unconformity against a cliff of standard limestones. The outward dips of the reef-limestones were interpreted as largely depositional. The succession in the standard limestones was also described, the presence of two bands with Davidsonina septosa recorded, and the Cave Dale Lava recognized as the Lower Miller's Dale Lava. In the higher beds the presence of a band with Girvanella at the base of D₂ was noted and near the top of the zone two coral bands, a lower with Lonsdaleia duplicata and, some 30 ft higher, an upper band with Orionastraea were discovered. The same authors (1945) described the structure and ore deposition of the Eyam area and gave details of the succession in Middleton Dale where the uppermost beds, the Eyam Limestones, of P₂ age, were stated to rest unconformably on D₂. The sequences in Coombs Dale and Cressbrook Dale were also determined and the presence above the Litton Tuff of an algal band with Girvanella nodules, the Upper Girvanella Band, noted in the latter.

Shirley and Horsfield's conclusions in the Castleton area were attacked by Parkinson in a series of papers (1943, 1947, 1953). This author argued on faunal grounds and from field relations that the postulated unconformity was absent, or at the most a local non-sequence, and that the B₂ and P₁ reef-limestones were the lateral equivalents of the D₁–D₂ standard succession. Ford (1952) described the geology of certain caves in the Castleton area, which supported lateral passage of reef to standard limestone.

Hudson and Cotton (1945a, 1945b) described the succession in the Alport and Edale boreholes. Their work has provided the only description of the beds of the basinal area within the present district and has been quoted in detail below.

As a result of a study of the palaeoecology of the Castleton reef-belt Wolfenden (1958) discovered the presence of wall-like masses of algal limestone at the junction of the fore-reef limestones (see p. 18) with back-reef limestones forming a transition to those of the shelf area. This arrangement clearly showed the lateral passage from the fore-reef limestones to those of the shelf and represented a great advance in the understanding of the morphology of the reef-belt.

The origin of the 'Beach Beds' of the Castleton area has been discussed by Sadler (1964), who concluded that they represented material deposited contemporaneously with the fore-reef limestones at the foot of a submarine channel.

Eden and others (1964) dealt with the detailed stratigraphy of Pin Dale and the area of Earle's Quarry, Hope, and this work has been extensively referred to below. Some of the more important points in this paper are the proof of the presence of a bed of tuff, the Pindale Tuff, beneath both reef and shelf facies (thus giving final proof of the absence of unconformity between these) and the description of detailed stratigraphical variation in the shelf facies adjacent to the reef-belt, including the presence of large knoll-reefs in the upper part of D₂.

Parkinson has recently (1965) summarized his own work and that of other authors on the reef-belt and has postulated a break within the B₂ apron-reef.

Sedimentation

There is a general structural division in the present district between the Carboniferous Limestone outcrop, forming the northern part of the broad uplift of the Derbyshire Dome, and the neighbouring down-warped or synclinal region of Kinder Scout and the Goyt–Todd Brook area. The structure of these areas is considered in greater detail on pp. 320–8. It is now generally accepted (see p. 320 and Kent 1966, p. 338) that a stable block of Lower Palaeozoic or Pre-Cambrian rocks, similar to the Alston and Askrigg blocks farther north, underlies the Derbyshire Dome. As in the case of the northern blocks, this is inferred to have exercised a considerable influence on sedimentation during Lower Carboniferous times and this effect continued on into the Namurian (seep. 161).

The above structural entities correspond to two main types of Viséan sedimentation (see (Figure 3)) and special local marginal conditions (see below) lead in places to the development of a third.

Shelf Province

This, developed in the area of the stable block, is marked by a sequence of predominantly pale massive limestones with a coral-brachiopod fauna comparable with that of the Great Scar Limestone on the Askrigg Block (see for example Rayner 1953, p. 249). Argillaceous sediments are, for the most part, rare or absent. Where the full differences between basin and shelf facies are developed, as in the Widmerpool Formation of the Duffield area, the thickness of these beds is noticeably less than that of corresponding beds of basin facies (see for example Ann. Rept. Inst. geol. Sci. for 1967, 1968, p. 82). In the Chapel en le Frith district, however, the thickness variations are not marked (see (Figure 3)). The beds of shelf facies (lithofacies and biofacies) are often termed 'standard limestones' and are present over nearly all the outcrop of the Lower Carboniferous of the Chapel en le Frith area.

Basin Province

This is marked by a thick development of thin-bedded dark limestones and shales with a goniatite-bivalve fauna. Sediments of this type were formed in negative areas subject to continuing subsidence. Though it has been suggested by Rayner (1953, pp. 248–9) that subsidence rather than depth of water was the prime factor in the formation of basinal deposits there is reason to believe that in the present area the sea-floor of the basin was at least some hundreds of feet deeper than that of the shelf (see p. 18). George (1958, p. 286) attributes the differences between the two facies to both depth of accumulation and rate of subsidence. Beds of basin fades are known in the present district only at depth in the Edale and Alport boreholes north of the shelf area. To the north-west and west of the shelf area the presence of beds of basin facies may be inferred from indications at the edge of the outcrop at two points and from the proved presence outside the district of beds of this type at outcrop in Staffordshire (Prentice 1951, pp. 175–90) and in the Gun Hill Borehole (Hudson in Hudson and Cotton 1945a, p. 318). The basinal area north of the shelf has been referred to by Kent (1966, p. 337) as the 'Edale Gulf'.

Marginal Province

In the present district a marginal reef facies, separating the shelf and basin facies, is developed between Hope and Sparrow Pit, on the northern margin of the shelf area. The fauna, while manifestly shallow-water, shows affinities with that of the basin in the presence of goniatites. The development of the apron-reef (see pp. 17–8) marks the most extreme effect of the underlying margin of the block on sedimentation. At higher horizons where the apron-reef is not developed, the margin of the block was reflected in post-apron (D₂ and P₂) times by the development of knoll-reefs and flat reefs (see p. 18) in or near the marginal area. A fuller discussion of the deposition of reef-limestones is given on pp. 17–9.

The early relations in time of shelf and basin are uncertain, due to lack of knowledge of the lower beds, especially in the basin. The lowest beds (S₂) known in detail in both shelf and basin areas, however, both show a continuous or nearly continuous limestone sequence with a coral-brachiopod fauna and only slight difference in lithology. During B₂ times the establishment of the apron-reef at Castleton coincided fairly closely with greater variation in sedimentation between shelf and basin, the upper part of these beds in the Alport Borehole bearing shale partings and yielding a goniatite fauna while the lower part shows a lithology and fauna closer to those of the shelf. The greatest facies variation was in D₂ times, with the deposition of 'standard limestones' in the shelf area and of thin-bedded dark limestones succeeded by shales in the basin. Near the close of Viséan times, local uplift (see p. 32) was followed by subsidence, which allowed the spread of beds of basin type (P₂) on to the shelf area.

Effects of contemporaneous earth movements

Earth movements during the deposition of the Viséan rocks of the present district may be inferred from lateral facies variations, from the presence of the reef-belt and from the occurrence of unconformities. The detailed evidence is presented later under strati-graphical headings but the general sequence of events may be summarized as follows:

1. Deep-seated movement involving the uplift of the margin of the block initiated the formation of the apron-reef. The age of this movement would be either late S₂ or early D₁ (Cravenian of Hudson and Mitchell 1937).
2. Local intra-B₂ (D₁) movement is postulated to account for anomalous features in the structure of the apron-reef at Peaks Hill. Parkinson (1965, pp. 172–3) has suggested on faunal grounds that a widespread break in the reef succession is present at this horizon but this cannot be regarded as firmly established. There is, however, some reason to postulate movement of Dirtlow Rake in the region of the reef-belt in late B₂ times (see p. 34).
3. Pre-P₂ movement; this was acute around the edges of the block resulting in angular unconformity and at one locality (p. 96) in emergence with the local formation of a thin coal and seatearth. Shirley and Horsfield (1945, p. 293) considered that widespread unconformity existed below P₂ but the present work suggests that this may have been exaggerated. Movements of this age are responsible for an east-west 'pre-Namurian' fault south of Dove Holes with P₂ resting on D₁ limestones on its southern side (see (Figure 7)).
4. Intra-P₂ movement is represented by the unconformity at the base of the P₂ shale facies or, where P₂ shales are lacking, by the break between the Viséan limestones and the Namurian. There is no evidence of unconformity between the shale facies of the Viséan and Namurian. The stratigraphical evidence shows a sharp break around the edges and over the block and a probable absence of any break in the basinal area.

Where P₂ beds are absent it is difficult to distinguish the effect of pre- and intra-P₂ movements and it is convenient to refer to the corresponding unconformity as the 'pre-Namurian unconformity'.

Lithology and lithofacies

The lithology of the different rock types of the Carboniferous Limestone Series is summarized below though the account is somewhat restricted by the fact that it has not been found possible to undertake systematic petrographical work on the limestones, although selected thin sections have been studied. In the stratigraphical descriptions the use of petrographical terms has, in general, been avoided as this would imply a full petrographical study. An attempt is made here to provide a correlation between field and petrographical terms.

The limestones

Many of the limestones are bioclastic, crinoid debris and brachiopods being the main constituents. Corals and algae are important in some cases. Usually the main concentrations of macrofossils are on restricted horizons (coral bands and shell bands).

Shelf Province

Woo Dale Beds

The Woo Dale Beds present a mixed lithofacies showing points in common with both pale and dark facies described below from the higher divisions. The chief rock types include:

1. Dark grey and dark grey-brown limestones (calcarenites), fine-grained and evenly bedded. In view of the association of rocks of this type with dolomites in the Wye valley (Cope 1933, p. 129), a chemical examination of these rocks in the present district was undertaken: this showed, however, only small MgO percentages (0.22 to 0.46).
2. Grey limestones (calcarenites), well-bedded, some bioclastic and including limestones with algal nodules. A large development of pale crinoidal limestones (biocalcarenites) is present at Peak Forest, some of which are partly oolitic.
3. Calcilutites (micrites), usually pale-coloured and either in regular beds or in large lenticular masses. The origin of the latter is uncertain though they are best considered as bioherms in which some binding organism (possibly algal) was present but has now disappeared. This would account for the maintenance of the lens form during the deposition of the adjacent well-bedded limestones.

Bee Low, Monsal Dale and Eyam groups

A striking feature is the sharp contrast between white, pale grey and grey limestone on the one hand and dark bituminous limestones on the other. Intermediate rock types are relatively rare and the distinction between the two lithofacies has been found most valuable for mapping purposes (see for example (Figure 7)).

Among limestones of the pale lithofacies the following types have been recognized:

1. Pale massive limestones (calcarenites) are developed extensively in both D₁ and D₂. Some are finely oolitic though, as Wolfenden (1958, p. 881) remarked, ooliths are not very abundant. Bands with algal nodules occur at some horizons. Rubbly-weathering beds in D₂ are probably developed by the diagenesis of limestones with some non-calcareous mud content leading to segregation of the latter along cracks.
2. Pale cherty limestones show a lithology of the matrix similar to (i). The occurrence of chert is separately dealt with on p. 16.
3. Calcilutites (micrites) occur rarely as thin and well-defined beds in D₁ and near the top of D₂.
4. Oolites (other than the imperfectly developed examples noted under (i)) are of rare occurrence but have been found in the back-reef facies near Eldon Hill (see also p. 59) and in the Wardlow Mires No. 1 Borehole (see p. 93).
5. Coarse-grained limestones (calcirudites) are especially developed in D₂ and are due to the presence of coarse organic material, either crinoid debris or shell debris or both. Crinoid debris, particularly where fine, is also common in the other rock types in variable proportions.
6. Magnesian limestones are known though uncommon in the pale lithofacies only in one horizon in D₁, which may correspond to that of the Lower Miller's Dale Lava, the dolomitization being probably connected with local variations in the composition of the sea-water.

A shallow-water origin for most of the limestones of the pale facies is indicated by the presence of the rare ooliths, by local non-sequences and by rare current-bedding. The last-named is difficult to observe but has been noted in places in D₁ limestones. The higher limestones of D₂ and the crinoidal facies of S₂ (Peak Forest Limestones) often show sorting of coarser and finer constituents. The fauna, especially the presence of algae (cf. Pettijohn 1957, p. 596) and corals (other than zaphrentoids), is also indicative of shallow-water conditions (Ager 1963, p. 41) and the faunal aspect as a whole suggests water which was well oxygenated, allowing the spread of a vigorous fossil community at certain horizons.

The dark lithofacies occurs as both the more continuous development of basin facies and intercalations in the pale facies. Typically the limestones are fine-grained, dark and bituminous. The bedding planes are closely spaced and commonly somewhat undulating. Chert is abundant. Eden and others (1964, p. 93) have remarked that the apparent fine grain of many of these rocks is deceptive; they are in fact fine calcarenites. Some coarser, crinoidal bands occur. Thin shale partings are often present, particularly in P₂ where they increase in thickness in the uppermost beds giving a transition to the shale facies.

The dark facies apparently was deposited under reducing conditions with the formation of hydrocarbons and some pyrite and a variable supply of terrigenous mud. These conditions, rather than depth of water would appear to have been the controlling factors so far as deposition in the shelf area was concerned. A similar environment must have been present at greater depths in the basinal areas (the differences in depth being inferred from a consideration of the structure of the reef-belt rather than from facies differences). A marked facies-fauna is associated with these beds and includes in particular zaphrentoids with some inarticulate brachiopods and small gastropods. However, bands with a fauna common to the pale facies also occur.

Stylolites are of common occurrence in both pale and dark lithofacies. The size of the stylolite, however, usually varies with the lithology of the country rock, the largest examples (up to 9 in high) being found in pale fine-grained massive limestones while the dark facies shows only small structures. In some cases, especially in the dark limestones, there is a capping of a solution residue of hydrocarbon or argillaceous material on the stylolites. The pressure-solution origin of stylolites, as put forward by Stockdale (1922), is now generally accepted.

Basin Province

No new work has been done on rocks of this province and the essential features of the succession in the Edale and Alport boreholes are described on pp. 113–9. Certain distinctive features of the lithology are summarized below.

The dark limestones are similar to those already described from the dark lithofacies of the shelf province, though bands of relatively coarse bioclastic material are apparently foreign to the basinal environment and are here considered to be of turbidite origin. This is borne out by Hudson and Cotton's description of 'slumping' at some horizons in the Alport Borehole, for example at 1632–1642 ft (1945a, p. 287). Graded bedding has been noted in thin bands of finely crinoidal limestone in dark limestones in the Castleton Borehole.

Marginal Province

The apron-reef limestones of the Castleton area show a typical reef lithofacies and vary from calcilutites to bio-calcirudites. These rocks are discussed, together with other reef-limestones, under a general heading below. The overlying Beach Beds are a local deposit of rolled-shell limestones whose relations are discussed on p. 35.

Chert

Lenticular, tabular, or nodular chert is, in the shelf area, present in the D₂ and P₂ limestones of both pale and dark facies at certain moderately well-defined horizons. It also occurs exceptionally in D₁ adjacent to the reef-belt (see p. 61). In the basinal area chert also occurs in the D₁ and S₂ zones and the distribution in these zones resembles that noted by Newell and others (1953, pp. 161–2) in the basin facies of the Permian of the Guadalupe Mountains area, Texas, where chert occurs in the basin and is absent in reef and shelf areas.

Sargent (1921, pp. 267–76) considered that the cherts were consolidated early as bedding was deflected around the nodules. He argued against an organic origin for the silica and attributed its introduction into the sea-water largely to contemporary vulcanism. The present work supports the conclusions of Pettijohn (1957, pp. 439–40) that the cherts are post-depositional and owe their origin to the early replacement of a partly consolidated rock containing diffuse silica, the latter undergoing segregation into the nodules and tabulate bands. The chert is thus in continuity with the surrounding limestones.

In some cases secondary cherts have been produced, probably by a later re-mobilisation of silica; these are most obvious in the vicinity of mineral veins though not completely restricted to this position. The colour of the chert is in most cases governed by that of the surrounding limestone. The later cherts occur as large bulbous masses often showing concentric colour banding and (rarely) as thin veins. The presence of the later cherts is linked with the frequent silicification of fossils at certain horizons. Arnold-Bemrose (1898, p. 178) also noted the presence of quartz crystals in a limestone at the Bull Ring, Dove Holes. Hydrothermal silicification is discussed on p. 310.

Other rock types

A thin coal and seatearth are present in the Coombs Dale area (see pp. 96, 98), resting on a potholed surface (see below) of Monsal Dale Beds. Their formation is clearly linked with emergence associated with the unconformity at the base of the Eyam Limestones.

Shale or mudstone is present in the highest P₂ strata at outcrop and in addition in the lower P₁ beds in the Edale and Alport boreholes and in thin partings in the limestones. The lithology resembles that of the Namurian shales. Other partings, or wayboards, consist of grey-green poorly bedded unfossiliferous and often pyritous clay. Sargent (1912, pp. 409–12) described similar partings from the Crich area and concluded that they were of pyroclastic origin. This view was also taken by Cope (1939, p. 62) and is accepted here. In the present area, clay from a parting in the Chee Tor Rock at Smalldale (see p. 47) is an illite mudstone with coarse pyrite and fine needles of marcasite.

Both clay and mudstone partings in the limestone usually rest on potholed surfaces (see (Plate 2B)) such as were noted by Sargent (op. cit.) and Cope (1939, pp. 61–2). The maximum depth of the potholes is about 2 ft. Clearly these features represent contemporaneous removal of the uppermost limestone surface either by solution, erosion or both during a halt in sedimentation. Actual emergence at Coombs Dale is proved by the presence of a coal and thin seatearth overlying a potholed surface.

Reef-limestones

Following Bond (1950c) the reef-limestones of the Chapel en le Frith district may be subdivided into apron-reef, knoll-reefs and flat reefs. The stratigraphy of these is considered separately on pp. 34–5.

Apron-reef

Following Eden and others (1964), the term 'apron-reef' has been extended somewhat from the original definition of Bond (1950 c, pp. 270–1). The apron-reef is a marginal facies developed between the shelf area and the basin and had been divided by Wolfenden (1958) into fore reef, reef (called algal reef in this account) and back reef, the whole being known as the 'reef-complex'.

The fore reef consists of poorly bedded limestones, commonly highly fossiliferous (some hundreds of species being recorded) but in places poorly fossiliferous and fine-grained. In referring a particular outcrop to this facies it is necessary to consider the whole of its characters including lithology, fauna and bedding. The fore reef shows outward dips (towards the basin) of 10°-40° which have been considered by Shirley and Horsfield (1940, pp. 288–9) and by most workers since, to be the original depositional dips only slightly modified by the effects of compaction and minor tectonic movement. Recent work by Broadhurst and Simpson (1967, pp. 443–8) on the inclination of sedimentary infillings of shells and limestone cavities has demonstrated that the dips of the apron are indeed of depositional origin. The difference in height between the top and bottom of the frontal slope is considered to have been about 400 ft. The fauna, though characteristic in itself, shows affinities both with basin, in the local presence of goniatites, and with standard limestones. The limestones at the foot of the reef-slope are often crinoidal. In addition to the fine-grained limestones (calcilutites), breccias occur in places particularly in the eastern outcrop, fragments up to a foot in diameter having been noted by Eden and others (1964, p. 95). Small Neptunian dykes' of pale crinoidal limestone have been observed locally at the top (higher) part of the reef. From a study of the palaeoecology of the goniatite bed at Cow Low Nick, Ford (1965, pp. 189–90) has concluded that this deposit, situated about two-thirds of the way up the frontal slope of the fore reef, was subject to gentle current action. This and the depositional slope would be incompatible with the accumulation of unconsolidated deposits. Most of the fossils in the fore reef are unworn and must be nearly in situ. Following Black (1933), Wolfenden has suggested that the fine matrix of the fore-reef limestones may represent recrystallized algal deposits, the algae having acted as sediment-binders, at least in the upper part within the range of daylight penetration.

The algal reef ('reef' of Wolfenden) occurs as a discontinuous wall-like mass of limestone with abundant stromatolitic algae (see (Plate 13A)), sponges and other fossils. Algal reefs have been noted by Wolfenden (1958, pp. 872, 879) at two levels at the point where the strong frontal dip of the reef-complex develops. Wolfenden gives the maximum dimensions as about 30 ft wide and 100 ft high. However, recent exposure of the algal reef on Treak Cliff shows a maximum width of about 250 ft locally. The algal reefs are considered to have originated as barrier-like reefs at two horizons, growth of the lower reef having been inhibited by down-warping, producing a greater depth than the algae could tolerate.

The back reef is intermediate in both lithology and fauna between the fore reef and shelf limestones and usually shows gentle inward dips towards the shelf area. The back-reef limestones are typically well bedded and often show elements of the fore-reef fauna. They are also in general more crinoidal than all but the lowest parts of the fore reef. On the inward side this facies passes gradually into standard limestones and it is the outer facies junction which is the best defined; hence both in Wolfenden's account (ibid., pp. 877, 879–80) and in the present work it has been found necessary to group them with the shelf facies for mapping purposes, though they are separately shown on (Plate 11).

Knoll-reefs

Since the original description by Tiddeman (1889) from the Craven area there has grown up an abundant literature on knoll-reefs. This has been summarized by Bond (1950a) and Black (1954). Morris (1929, pp. 49–50) first noted the presence of knoll-reefs in the district at Linen Dale. The present work has shown them to be widespread, though restricted to the peripheral area of the limestone (i.e. the margin of the block).

The outstanding features of the knoll-reefs are the presence of original quaquaversal dips and the relatively pale, poorly bedded and fossiliferous character of the rock. A detailed description of knolls in the Pin Dale area has been given by Eden and others (1964, pp. 87–9). Here they were found to be mainly developed at two horizons and to pass laterally into calcirudite bands in the bedded succession. At one locality the formation of a knoll above an earlier one has led to the development of a composite knoll over 50 ft in height.

The knolls pass into the adjacent limestones by lensing or interdigitation. Eden and others (ibid., p. 89) noted current-bedding and some breccia associated with the knolls and concluded that they "stood up as small mounds above the general level of the sea-bed". In some cases, such as the Earle's Quarry knolls and the Dove Holes knoll (see p. 65), where breccia is present in the upper part of the knoll, this is interpreted as evidence that the structure was consolidated and a true knoll, not a bank deposit as has been suggested (Earp and others 1961, p. 44) for the Clitheroe knolls. Recent work by Orme (1970a) on the Earle's Quarry knolls suggests that algae and bryozoans were the chief sediment binders. In the case of the large knoll (see p. 88) in Earle's Quarry a true biohermal origin is also suggested by the superposition of its two component knolls; the higher being more likely to be due to the re-activation of growth of a lower bioherm than to the formation of one bank deposit precisely above another. Like the apron-reef, the knolls have a rich fauna in which brachiopods are abundant.

Flat reefs

The term flat reef was suggested by Bond (1950c, pp. 271–2) for large lateral spreads of limestone of reef facies. In many cases they may represent knolls which have grown laterally to a point where they lose their knoll form. Large spreads may be formed by the coalition of several such masses.

In the present district knoll form appears to be lost in reefs over some 50 ft in thickness, upward growth being then largely replaced by lateral growth. This contrasts with the much larger knoll forms in other parts of Derbyshire, for example at High Tor, Matlock (about 100 ft) (Smith and others 1967, p. 23) and the Cracoe area (Bond 1950b, p. 172) where thicknesses of 200 ft or more are common. Probably the knolls of the Castleton–Hucklow area were limited in growth by either gentle uplift or a static sea-floor while the larger Yorkshire knolls were formed during gentle subsidence.

Formation of reef-limestones

The conception of facies variation across the reef-complex, and the establishment of an outward-dipping frontal slope requires the postulation of deep-seated movements along the edge of the block with a sharp uplift of the latter to produce the shallow-water conditions allowing the reef fauna to flourish. An alignment of small eruptive centres along the reef-belt is further evidence of deep-seated instability in this zone. The movements produced the initial shallowing which led to the formation of the apron-reef and accord with its linear character.

It is suggested that broad and less acute uplift around the edge of the block was the initial factor which led to the formation of the knoll-reefs and flat reefs. In places (see Eden and others 1964, pp. 79–81) a more restricted local uplift may have controlled knoll formation.

Volcanic rocks

Contemporaneous volcanic rocks associated with the outcrop of the Carboniferous Limestone include lavas, tuffs and agglomerates, some of the last two types occurring in vents. In addition interbedded tuffs are known in the basinal area.

Lavas

Lavas are known at three horizons within the present district; their stratigraphy (see pp. 23–8) and petrography (pp. 119–23) are discussed separately, The rocks are olivine-basalts typically highly vesicular with calcite and chlorite-filled amygdales. In places the lavas are non-vesicular, harder, darker and more coarsely crystalline. The occurrence of pillow lavas was noted by Fearnsides and Templeman (1932, pp. 102, 107–10) in a borehole at Hope. Pillow structure is, however, not a normal feature and appears in this instance to be connected with the extrusion of lava on the marginal slope between shelf and basin at a greater depth than that at which the other lava flows, on the shelf area, were formed. The conditions under which the lavas of the shelf were extruded are uncertain though the associated sediments suggest a shallow-water origin. The thicker flows may have built up above sea-level though this cannot certainly be established.

A small thickness of clay ('toadstone clay') is in many cases present above or below the lavas. It is invariably highly altered and it is uncertain whether it is derived directly from the overlying flow or whether it is a fine tuff. As noted by Smith and others (1967, p. 12) in the Matlock area, cambering has in places occurred on the clay and is responsible for an apparent decrease in the thickness of the lava at outcrop.

Although vents are present in the area (see below) they nowhere show any evident association with the lavas, the extrusion of which is here considered to have been by eruption along fissures. This is consistent with the uniformity in thickness of the large spreads of lava.

It is usually impossible to determine the number of flows making up a lava-sheet owing to lack of exposures; most are, however, probably composite. The Upper Lava clearly shows this at Hargatewall as it contains a limestone parting in the middle. Similar features are shown by the Lower Lava in Tideswell Dale and in the Litton Dale Borehole.

Tuffs

Tuffs, though less widespread than lavas, are known at outcrop at horizons in D₁ (Pindale Tuff and Dove Holes Tuff) and D₂ (Litton Tuff) and possibly at two lower horizons at depth. Tuffs have also been proved in association with tuffaceous limestones in the Edale and Alport boreholes (see pp. 114, 117).

Most of the tuffs are regularly bedded though depositional form is preserved in the tuff-mound formerly exposed in Earle's Quarry, Hope, which represents a degraded cone (Eden and others 1964, pp. 76–8). Accidental blocks of limestone up to 3 ft in diameter were associated with the tuff-mound. A second mound has also been proved by boreholes at a similar horizon nearby. The Litton Tuff shows features similar to those of the Pindale Tuff, though over a larger area. At Litton it shows its greatest thickness and is locally agglomeratic, indicating proximity to a vent.

The tuffs are in general very altered, the unweathered rocks being much calcitized. They range from coarse lapilli tuffs to fine-grained water-borne rocks of mud grade. Lapilli, where present, are better preserved than the matrix; they are usually cognate but accidental lapilli of limestone are present in the Dove Holes Tuff.

The degree of sorting of the tuffs also varies. For example, drilling on the flanks of the tuff-mound in Earle's Quarry has shown that the unbedded tuff of the mound passes laterally into a well-banded tuff.

Vents are known at three localities. Though structurally intrusive these are clearly associated with explosive episodes when the tuffs were formed. The vents are filled with either fine agglomerate or lapilli tuff. The two vents in Monk's Dale (see (Figure 14)) lie on the axis of a sharp monocline and this relation is unlikely to be accidental. It is probable that deep-seated faulting is responsible for both the monoclinal fold and for the location of the two vents on it.

General stratigraphy

Shelf Province

Woo Dale Group

(Seminula (S₂) Zone and basal Lower Dibunophyllum (D₁) Zone)

Woo Dale Beds

The term Woo Dale Beds is introduced here for the S₂ beds of the Wye valley (Cope 1933, pp. 127–30). It is synonymous with the term Daviesiella Beds' though lateral changes of facies and variations in the vertical distribution of Daviesiella render this term inappropriate. The type area thus lies to the south of the present district.

In the present district outcrops are confined to the Peak Forest Anticline (Figure 4) and to exposures farther south along Dam Dale and Hay Dale (Plate 2A). Two distinct lithofacies (see (Figure 4) and (Figure 5)) are present:

1. The normal facies consists of thinly bedded dark grey and dark brown limestones with some bands of grey limestone and rare oolitic bands. The maximum exposed thickness of these beds is about 165 ft, at the junction of Dam Dale and Hay Dale. The lowest beds contain calcilutites at two horizons, the lower being irregularly bedded and lenticular while the upper is evenly bedded and has served locally as a lithological marker-band. The lowest beds bear Daviesiella sp. though the horizon of this brachiopod here does not correspond closely with its vertical range in the Wye valley (Cope 1939, pp. 60–2). The typical S₂ brachiopods Davidsonina carbonaria and Linoproductus corrugatohemisphericus are also present. The S₂–D₁ zonal boundary does not correspond exactly to the lithological change at the junction of Woo Dale Beds and Chee Tor Rock. In the Dam Dale–Hay Dale section the uppermost 11.5 ft of the Woo Dale Beds bear a D₁ coral fauna including Dibunophyllum bourtonense and Palaeosmilia murchisoni, while at Hernstone Lane Head this fauna occurs in the uppermost 14.5 ft.
2. 7In the northern part of the Dam Dale–Hay Dale section Woo Dale Beds of normal facies pass laterally into a uniform group of pale crinoidal and in places shelly limestones (see (Figure 4)) which occupy the greater part of the Peak Forest inlier. These are here called the Peak Forest Limestones though they are not separately shown on the one-inch map. Though good continuous sections of these beds are lacking the total exposed thickness is of the order of 150 ft. They are of shallow-water facies and show marked sorting into bands with coarser and finer bioclastic material, mainly crinoidal; some oolitic bands have also been found. North of the outcrop, a borehole at Eldon Hill (see p. 42) is interpreted as showing 225 ft of Peak Forest Limestones with a 14-ft dolomitic band 45 ft from the base, and underlain by a probable tuff, proved to a thickness of 100 ft. At Castleton, the presence of pale crinoidal limestones of probable S₂ age underground beneath D₁ limestones has been noted by Ford (1952, pp. 351–2).

The development of beds of shallow-water facies in S₂ near the reef-belt suggests that the Peak Forest Limestones developed as the result of a broad uplift along the edge of the Derbyshire Block which heralded the more acute and localized uplift in D₁/B₂ times which led to the formation of the apron-reef. S₂ beds of comparable facies and in a similar position in relation to the margin of the block have been described by Sadler and Wyatt (1966, pp. 55–64) from the Hartington area. I.P.S.

The normal facies of the Woo Dale Beds ranges in the Hay Dale–Dam Dale section (see p. 40) from grey foraminiferal biocalcarenites showing a poor to moderate degree of sorting to fine micritic rocks (calcilutites) showing variations in colour and in the extent of recrystallization. The Peak Forest Limestones are coarser grained, mainly unsorted biocalcarenites and biocalcirudites, largely crinoidal but in places containing lithoclastic debris. R.K.H.

Bee Low Group

(Lower Dibunophyllum (D₁) Zone)

The presence of the Lower Miller's Dale Lava to the south of a line between Dove Holes and Ox Low allows the subdivision of this group into Chee Tor Rock below the lava and Miller's Dale Beds above it. Where the lava is absent the limestones are not subdivided and are known as the Bee Low Limestones. All these limestones show a uniform lithology, when compared with both the underlying and overlying beds, being fine-grained, massive and pale. In addition, the absence of chert, with one exception, is striking in view of its abundance in the strata above. Fossils are absent or rare though they are in places abundant at restricted horizons.

Chee Tor Rock

The Chee Tor Rock consists of pale fine-grained limestones, for the most part very massive. The thickness varies from about 380 ft in the southernmost outcrops in Great Rocks Dale to about 300 ft in the north. Typically the middle and upper parts of the subdivision show the characteristic closely-spaced vertical joints noted by Cope (1933, p. 131) giving a castellated appearance to weathered sections. The lowest beds frequently stand out as strong features. The Chee Tor Rock is separately distinguished along Great Rocks Dale and Doveholes Dale, around the Peak Forest Anticline and south-east of the latter around Peter Dale.

Much of the Chee Tor Rock is relatively unfossiliferous, fossils where present being mostly restricted to well-defined bands with D₁ Zone coral-brachiopod faunas or, rarely, with algal nodules. The corals present include D. bourtonense, Koninckophyllum θ, Lithostrotion junceum, L. pauciradiale and P. murchisoni. The most important faunal bands, here called the Upper Davidsonina septosa Band and the Lower D. septosa Band, lie near the top of the subdivision. The upper band, lying some 25 ft below the Lower Lava, was originally described as the "Cyrtina septosa Band" by Cope (1936, pp. 48–51) in the Wye valley section and in the present district at Buxton Bridge. Cope subsequently (1939, p. 63) noted the presence of a band with a similar fauna, some 10 to 15 ft lower in the sequence; it is uncertain whether this represents a well-developed band with D. septosa which occurs in the present district some 35 ft below the upper band and which is here referred to as the Lower D. septosa Band. The chief fossil bands in the Chee Tor Rock are indicated in (Figure 6). Despite its monotonous nature certain facts emerge from the detailed study of the stratigraphy:

1. The lowest beds, some 40 ft thick, are usually relatively thin bedded (in 2- to 6-ft posts). A persistent coral band is present at the base on the eastern side of the Peak Forest inlier but has not been located elsewhere. It bears a typical D₁ coral fauna in this area but to the north of Peak Forest appears to be represented by a band of limestone with algal nodules. As noted by Cope (1939, p. 62) bryozoa are relatively abundant both in the basal coral band and in the overlying 30 ft or so of beds.
2. The succeeding beds, about 160 ft thick, are frequently very massive near the base. They contain a 6-ft coral band in Peter Dale and a thinner band in the Hay Dale–Dam Dale section (these bands are shown in (Figure 6) in their positions relative to the base of the Chee Tor Rock; if thinning occurs they may represent the same band). A less important coral band occurs at Wheston.
3. The coral band of Laughman Tor, although sporadically developed, is an important horizon, being 10 ft thick at the type locality with a finely bioclastic and somewhat oolitic matrix. A band in this position has also been noted on Middle Hill (south) and near Wheston.
4. Some 80 ft of beds, again usually very massive, separate the last horizon from that of the Lower Davidsonina septosa Band. In Duchy Quarry, Smalldale, these beds contain a well-marked algal nodule band about 1 ft thick and 40 ft from the base; this appears to be represented on Middle Hill and at Wheston by a coral band. The uppermost beds locally show crinoid debris including some stems. Some 22 ft higher in Duchy Quarry and Buxton Bridge, a thin band yields D. septosa, corals and gastropods. Locally, north of Smalldale these beds are less massive and contain fairly numerous clay wayboards, some with underlying potholed surfaces.
5. The Lower D. septosa Band varies from 10 in to 4 ft and although sporadically developed, has been recognized over a wide area.
6. About 35 to 40 ft of limestones with some finely crinoidal bands, separate the Lower from the Upper D. septosa Band. At Buxton Bridge these beds contain several thin clay wayboards on potholed surfaces. A thin calcilutite band is present near the top of this group of strata in Bold Venture Quarry.
7. The Upper D. septosa Band varies from 1.5 to 5 ft. Although widespread it is locally, at Upper End, largely represented by a thick algal band with only rare D. septosa.
8. The beds above the Upper D. septosa Band are 20 to 25 ft thick and in places very massive. Some finely crinoidal bands are present.

Lower Miller's Dale Lava

The term Lower Miller's Dale Lava is here introduced for the Lower Lava of Arnold-Bemrose (1907, pp. 246–7) to distinguish it from the Lower Matlock Lava of Smith and others (1967, pp. 8–12) which is at a higher horizon. The Lower Miller's Dale LavaThe name is here in places abbreviated to 'Lower Lava' where no ambiguity exists. occurs within the present district south-east of a line from Dove Holes to Ox Low and as an isolated patch to the north at Cave Dale. The thickness of the lava is 100 ft at Wormhill and 90 ft at Wheston but a marked northerly thinning occurs from these localities until the lava disappears.

The lava is an olivine-basalt (see also p. 120), usually very amygdaloidal and with calcite- and chlorite-filled vesicles. In places non-vesicular basalts are developed and appear to represent the central parts of flows. The lava weathers deeply and natural exposures are infrequent except in swallow-holes which commonly mark its outcrop. The Lower Lava has been penetrated in boreholes at two localities: in Great Rocks Dale a thin uppermost flow and two thicker flows below showed intervening beds of clay and tuff, the whole being 98 ft 2 in thick; the Litton Dale Borehole passed through a thick upper flow, separated from a thinner lower flow by 12 ft of limestone, the whole totalling 90 ft 6 in.

The isolated occurrence of Lower Lava at Cave Dale, Castleton, was left uncorrelated by Arnold-Bemrose (1907, p. 248) and Shirley and Horsfield (1940, p. 275) were the first to show its horizon. It is up to 25 ft thick and its outcrop extends from Hurdlow Barn to Cave Dale. To the east of the latter, drilling has shown that the lava dies out and its place is taken by the Pindale Tuff (Eden and others 1964, pp. 76–8), which stretches from the reef-belt, where it is mainly developed (see p. 61), inwards beneath the back-reef facies before dying out.

Miller's Dale Beds

The Miller's Dale Beds (see (Figure 6)) resemble the Chee Tor Rock in lithology, being pale, fine-grained and massive, and contain similar D₁ faunas. Minor differences are the presence locally of limestones almost pure white in colour (a shade not usually found in the Chee Tor Rock) and the generally somewhat less massive character. Fine crinoid debris is more uniformly distributed than in the Chee Tor Rock. A few slightly oolitic bands have been noted. The thickness of the subdivision varies from 142 ft near Dove Holes to 63 ft at Wall Cliff.

The lowest beds are best seen at the north end of Wormhill Moor where they include a few inches of tuffaceous limestone resting on the Lower Lava. The succeeding 30 to 40 ft of strata are richly fossiliferous with an abundant coral fauna and brachiopods including Davidsonina septosa. In this vicinity some of these beds show a distinctly reef-like appearance with an irregular banding of possible algal origin. At Wall Cliff the reef-brachiopods Dielasma hastatum and Pugnax pugnus occur in an 8-ft bed, 32 ft above the Lower Lava. The presence of these two forms may be linked with a shallowing of the sea-floor due to irregularities in the surface of the underlying lava. These more fossiliferous strata include the equivalent of the beds with Lithostrotion aff. maccoyanum noted by Cope (1933, p. 132) immediately above the Lower Miller's Dale Lava in the Wye valley.

The higher parts of the Miller's Dale Beds call for little comment though they include the Dove Holes Tuff in the western outcrop. The tuff, about 7 ft 6 inches in thickness, lies about 50 ft above the Lower Lava and is a greenish grey clay with common limestone lapilli. Borehole sections show it to be pyritous. It rests on a strongly potholed surface.

Bee Low Limestones

In lithology and other features, such as bedding and the local presence of clay wayboards and potholed surfaces, the Bee Low Limestones, which are about 600 ft around Eldon Hill, are indistinguishable from their equivalents, the Chee Tor Rock and Miller's Dale Beds, and faunas typical of the D₁ Zone are present throughout. Detailed correlation is difficult as the discovery of at least four horizons with D. septosa means that correlation of a given band is dependent on its position in relation to the top or base of the group.

Bee Low Quarry shows a 300-ft face of massive limestones, lying some 80 ft below the top of the group. Farther east, a coral band 260 ft from the base of D₁ probably represents that of Laughman Tor (p. 47). At about the same horizon a 3.25-ft porcellanous band is present near Lodesbarn. Near Haddocklow the Upper and Lower D. septosa bands have been identified and a higher band with D. septosa is tentatively correlated with the Lithostrotion aff. maccoyanum horizon.

Within some 200 yd of the reef-belt the Bee Low Limestones show an increase in the content of crinoid debris and contain lenses of limestone with reef faunas which are comparable with those from the B₂ apron-reef and can be correlated with limestones at about the horizon of the Upper D. septosa Band. One of these reef-faunas yielded the goniatite Bollandoceras sp. on Gautries Hill. In Eldon Hill Quarry the Upper D. septosa Band is reef-like up to 500 yd from the boundary of the apron-reef and the lower beds also contain a lens of reef-limestone. Near the reef margin the back reef (Plate 11) is locally coarsely crinoidal, with debris up to 1 in, and some bands with limestone pebbles and breccia. A 9.5-ft oolitic band is also developed north-east of Eldon Hill about 88 ft above the Upper D. septosa Band.

At Windy Knoll, back-reef limestones are well developed; they are fossiliferous with reef-brachiopods and also contain some breccia (in addition to the 'Neptunian dykes' noted on p. 110). The back-reef facies is little developed west of Treak Cliff and in The Winnats, but in Cave Dale it is better developed, the lower beds showing interdigitations of reef-limestone. Here the Lower Lava (see p. 60) is succeeded by pale limestones with a coral band, the L. aff. maccoyamum band of Shirley and Horsfield (1940, p. 275) bearing a sparse fauna of L. cf. aranea at 39 ft above the lava. A thin tuff band is present just above; this has also been proved in a borehole (Plate 4) in the adjacent Michill Bank area. Shirley and Horsfield considered that the Lower Lava was cut out in the vicinity by an unconformity but its disappearance is here (p. 60) thought to be due to the normal dying out of a flow. Local thinning of the beds between the lava and the base of D₂, to about 100 ft, may be due to minor non-sequences or condensed deposition in the back-reef area and shallow-water conditions are indicated by the presence of oolite bands and local cross-bedding in the Cave Dale area.

In Pin Dale some beds of back-reef facies can be recognized but farther east their absence, at least at the present level of erosion, coincides with the general absence of apron-reef of B₂–D₁ age. The section here shows 82 ft of beds beneath D₂ and the Pindale Tuff is calculated from boreholes (see (Plate 5)) to crop just below the exposed beds. An abnormal feature of the section is the presence of nodular chert in some abundance in the lowest 23 ft. The exceptional presence of chert in these limestones is perhaps due to a local silica concentration near the reef; Wolfenden (1959, pp. 566–8) noted the abundance of sponges in the algal reef and the silica may be attributed to this source. The higher beds show wedge-bedding and bands of breccia near the apron-reef (Eden and others 1964, p. 79). The coral band with Dibunophyllum bourtonense φ and Palaeosmilia murchisoni, noted by Jackson (1941, p. 240) and by Eden and others (1964, p. 78) as lying about 65 ft below the top of D₁ is here located at 33 ft from the top, part of the difference being due to the lowering of the base of D₂ in the present work (see pp. 72–3).

Pale brown to light grey limestones referred here to D₁, have been proved in an underground borehole at Glebe Mine, Eyam (see p. 96). I.P.S.

The greater part of the D₁ limestones consists of uniformly textured biocalcarenite. The organic content, especially that of crinoid debris, shows some variation. Foraminifera, productoid spines and rare bryozoa occur in addition to coarser bioclasts. The calcite cement shows sporadic recrystallization. The finer limestones (calcilutites) are micritic, but are seldom free from bioclastic material. Authigenic quartz occurs in small quantity in many of the limestones. A clay parting in the Chee Tor Rock (see p. 47) has been found to be a pyritic illite-mudstone with marcasite needles. R.K.H.

Monsal Dale Group

(Upper Dibunophyllum (D₂) Zone)

In contrast to the rocks of the D₁ Zone these beds are of very variable lithology and include dark beds. They are in addition more uniformly fossiliferous and the faunas are indicative of the D₂ Zone. Both pale and dark limestones are cherty at some horizons. The presence of the Litton Tuff or the overlying Upper Girvanella Band allows these strata to be subdivided into the Lower and Upper Monsal Dale Beds. Where the Upper Miller's Dale Lava is present this is included in the group following Cope (1937, pp. 192–3). Where the lava is absent there is a sharp break at the base of the Monsal Dale Beds suggestive of a non-sequence, though the extent of this is difficult to assess.

Monsal Dale Beds beneath Upper Miller's Dale Lava

A small area of these beds, the northern continuation of the Station Quarry Beds of the Wye valley (Cope 1937, p. 180), extends into the Chapel en le Frith district. They are ill exposed at outcrop though 6.5 ft of alternating pale and dark limestones were proved below the Upper Lava in the Litton Dale Borehole. Elsewhere these beds are absent, the lava resting directly on beds of D₁ age.

In Station Quarry, Miller's Dale, some 800 yd south of the sheet boundary, these beds are 25 ft in thickness and consist of thin-bedded dark grey and grey cherty limestones (Cope ibid., p. 186). The base is strongly erosive and shows a washout at one point.

Upper Miller's Dale Lava

The Upper Miller's Dale LavaThe name is here in places abbreviated to 'Upper Lava' where no ambiguity exists. is of lesser extent than the Lower in the present district, being developed only between Wormhill Moor and Old Moor (north-east of Peak Forest) and Tideswell Dale. It is similar in most respects to the Lower Lava (see p. 23) being an olivine-basalt, usually highly amygdaloidal. The maximum thickness is 100 ft at the south end of the Wormhill Moor outlier and from here the lava thins northwards, eastwards and westwards. In Tideswell Dale a very rapid north-easterly thinning takes place from the junction with Litton Dale, where the thickness is some 60 ft, to the Litton Dale Borehole only 400 yd distant where it has thinned to 8 ft. The rapid easterly disappearance of the lava in the Litton railway-cutting, on the Buxton (111) Sheet has been recorded by Cope (1937, pp. 183–4) whose description suggests a steep snout to the flow; similar conditions probably obtain at Litton Dale.

At Brook Bottom, north of Tideswell, the Upper Lava is replaced by a tuff, the Brook-Bottom Tuff of Arnold-Bemrose (1907, p. 253). At one place (see p. 62), the lava can be seen to overlie the tuff. The tuff locally contains lapilli and is interpreted as a small ash-cone at least partly surrounded and buried by lava.

Lower Monsal Dale Beds

The original term 'Monsal Dale Beds' of Hudson and Cotton (1945b, pp. 30–1) has been here extended to include the whole of the D₂ succession of the Shelf Province. These beds are subdivided for descriptive purposes into a lower group of predominantly dark limestones and an upper group of predominantly pale limestones. Lithological variation of these strata is illustrated in (Plate 6). The total thickness varies from about 100 ft on Tideswell Moor to 230 ft in Cressbrook Dale, where it includes the Cressbrook Dale Lava.

The lower dark beds, usually from about 25 to 80 ft in thickness, are developed over most of the outcrop of the Lower Monsal Dale Beds. They are dark grey, usually thin-bedded and in places cherty. Some localities show paler, bioclastic bands, crinoidal or shelly; others show a bed of pale cherty limestone within the dark beds. The Lower Girvanella Band, 1 ft 9 in to 9 ft in thickness, is present at many localities near or at the base; 6 ft of dark limestone underlying the Lower Girvanella Band in Pindale Quarry is interpreted as occupying a hollow in the underlying D₁ limestones. Near the reef margin 10 to 20 ft of pale-coloured coarsely bioclastic limestone ("first calcirudite" of Eden and others 1964, pp. 81–2) occur within the dark beds and extend over the whole area of Earle's Quarry; a similar section is present at Dove Holes. There is, however, in marked contrast to the B₂–D₁ beds, no uniform development of back-reef facies in the Monsal Dale Beds.

In the absence of the Lower Girvanella Band, Saccamminopsis sometimes occurs in the lowest few feet of the Lower Monsal Dale Beds, the two fossils appearing to be mutually exclusive. A higher horizon with Saccamminopsis is present at Dove Holes and in Earle's Quarry, some 25 ft above the base of D₂; this is probably represented in the expanded sequence in Cressbrook Dale by two bands at 39 ft and 50 ft from the base respectively. At Brook Bottom what is probably the same band is well developed near the top of the dark limestones.

In the western outcrops the uppermost part of the dark beds and the lowest part of the succeeding limestones contain knoll-reefs at Dove Holes, Barmoor Clough and Sparrow Pit. The Barmoor Clough knoll has yielded fish teeth in some abundance (see p. 66). The presence of the corals Zaphrentites enniskilleni and Cyathaxonia rushiana in the dark beds at Barmoor Clough is taken as indicative of the proximity of the basin facies. The latter is further indicated by a small outcrop of P₁ shale in the vicinity (see below).

In the outlier of Wormbill Moor and on the main outcrop between Whiterake and Old Moor the dark beds are ill developed, consisting only of thin dark bands in predominantly pale massive limestones with some oolitic bands. The thickness of the whole of the Monsal Dale Beds is here only some 100 ft. Near Whiterake, a clay band near the base may represent a thin tuff.

The upper pale beds vary normally from about 90 to 120 ft, an exception being the thin development noted above. These beds are mainly pale massive limestones, often crinoidal and with some shell bands. Chert is usually absent but occurs in places in the lowest beds. The most extensive development of these strata is in Cressbrook Dale where a shell bed with Gigantoproductus sp. cf. striatosulcatus semiglobosus is present 22 ft from the base and the Cressbrook Dale Lava (see below) occurs near the top. Striatifera striata occurs close to this horizon both here and elsewhere. In the Pin Dale area, Eden and others (1964, p. 85) have noted the presence of two coarse crinoidal bands (the "second calcirudite" and "third calcirudite") near the middle and at the top of the subdivision. The second calcirudite has been noted to pass laterally into flat reef in the easternmost part of Earle's Quarry. In this vicinity the presence of a local unconformity at the base of the Upper Monsal. Dale Beds results in the cutting out of some 30 ft of the uppermost Lower Monsal Dale Beds. The presence of a small knoll-reef near the top of the subdivision on Bradwell Moor is ascribed to shallowing preceding the unconformity.

The presence of knoll-reefs at the junction of this subdivision with the underlying dark beds in the western outcrops has already been noted. At Barmoor Clough a small thickness of shale at the junction of the main Edale Shales outcrop with limestones of lower D₂ age has been found to contain a P₁ fauna including the goniatite Girtyoceras sp. and is thus the basinal equivalent of part of the upper beds of the subdivision (see also p. 8).

The pale beds are well seen in Victory Quarry, Dove Holes, where they contain a persistent shell band, some 40 ft from their base, with Gigantoproductus dentifer and G. edelburgensis [juv].

The Cressbrook Dale Lava is an amygdaloidal basalt, up to about 20 ft thick and some 30 ft below the Litton Tuff in the northern part of the dale but dying out rapidly to the south. The lava is much more extensively developed at depth and is known over a wide area from Wardlow Mires to Great Hucklow and Middleton Dale. The greatest thickness proved is in an underground borehole in Glebe Mine (see also p. 95) near Ladywash Shaft: 208 ft of basalt, with the top some 140 ft below the horizon of the base of the Eyam Limestones. The occurrence of igneous rocks at depth north of Cressbrook Dale is illustrated in (Figure 8). It will be noted that the thickest occurrences of lava are overlain by the thinnest developments of high D₂ limestone, a fact which may be due in part to the lava building up somewhat near the source, thought in the present state of knowledge, to be near the Ladywash Shaft. As interpreted, the boreholes also show a progressive upward approach of the lava towards the horizon of the Litton Tuff.

The Wardlow Mires No. 1 Borehole proved an unusual shallow-water development of oolitic and crinoidal limestones, 79 ft 5.5 in thick, between the Upper Girvanella Band and the Litton Tuff. These are interpreted as having been deposited on the flanks of a cone built up of Litton Tuff.

Litton Tuff

The Litton Tuff reaches its maximum thickness of 100 ft at Litton where it is agglomeratic with bombs up to 5 in across. Arnold-Bemrose (1907, p. 254) noted this character together with the presence of accidental bombs of fossiliferous limestone. The tuff thins away from Litton, being up to 42 ft in Cressbrook Dale, where it is poorly exposed, 10.5 ft in the Littonfields Borehole and only 2.5 ft in the Wardlow Mires No. 1 Borehole, to the north of which it is absent. At outcrop the tuff is more extensively developed, extending for over 2 miles north-west of Litton.

In the Wardlow Mires No. 1 Borehole the Litton Tuff was blue-grey and very fine-grained with gritty bands in contrast to the thick and agglomeratic nature of the tuff at Litton, which suggests a source near the latter locality. It is reasonable to picture the tuff as having formed a cone which suffered progressive burial. The effects of shallow-water sedimentation on the flanks of this cone have already been noted (see p. 28).

Upper Monsal Dale Beds

The Upper Monsal Dale Beds show a fairly uniform thickness of about 250 ft. The base is marked by the Upper Girvanella Band or in its absence by the top of the Litton Tuff. The succession in these beds (see (Plate 7)) is best shown in Middleton Dale, Cressbrook Dale, Wardlow Mires No. 1 Borehole and in Bradwell Dale. Minor erosion surfaces and clay partings occur locally and are noted in the detailed sections. The more important features are summarized below.

The beds below the Hob's House Coral Band, some 50 to 60 ft thick, are dark limestones with the Upper Girvanella Band at or near the base; the band varies from a few inches in thickness to 8.5 ft in parts of Earle's Quarry (Eden and others 1964, p. 113). The band has also been found, though thin, in pale limestones in the Hucklow Edge No. 2 Borehole. The overlying beds are of variable lithology. In the main outcrop to the north of Litton and in the Littonfields Borehole they consist of dark cherty limestones while in Cressbrook Dale there is evidence of lateral passage southwards from preponderant dark cherty limestones in the northern outcrops into pale partly bioclastic limestones with a little chert.

The Hob's House Coral Band was originally described by Cope (1933, p. 140), though apparently placed by him too low in the sequence. Shirley and Horsfield (1945, pp. 295, 298) determined the horizon of the band in terms of the Cressbrook Dale section and this work is followed here. The band, up to 5 ft thick, bears an abundant fauna with Dibunophyllum bipartitum bipartitum, Diphyphyllum sp., Lithostrotion pauciradiale and L. portlocki. In the Cressbrook Dale section clisiophylloids are less abundant than at Crossdale Head (Cope, op. cit.). In the northern part of the Cressbrook Dale section the band passes laterally northwards into a shell bed and the latter has been recognized in the Wardlow Mires No. 1 Borehole. The band has also been recognized in the Coombs Dale section (see (Plate 7)), but the Middleton Dale section fails to show it (see below).

The beds between the Hob's House Coral Band and the Black Bed, some 50 to 60 ft thick, consist of pale massive limestones showing local variation in detail. The Middleton Dale section shows a lower group of well-sorted crinoidal limestones, of evident shallow-water facies, overlain by pale massive limestones with the Lower Shell Bed ("Lower Giganteus Bed" of Morris 1929, p. 45). These beds have been described by Orme (1967, p. 27) as crinoid calcirudites and crinoid calcarenites. The Lower Shell Bed is some 6 to 7 ft in thickness and crowded with Gigantoproductus edelburgensis, the shells being often silicified. The Wardlow Mires No. 1 Borehole does not show the same development of crinoidal limestones at the base of the group and a bed of pale calcilutite is present in the lower part. The Cressbrook Dale section shows evidence of shallow-water sedimentation in the presence of bands of rolled shells and some oolitic bands at the base of the group.

The Black Bed, which consists of dark bituminous limestone, forms a useful lithological marker band in the middle of the Upper Monsal Dale Beds. It is here named in contrast to the higher White Bed of Morris (1929, pp. 47–8) and includes his Lonsdaleia Bed. The present name is preferred as the dark limestone is of wider extent than the faunal band. In Middleton Dale the bed is up to 5 ft thick and it has also been recognized in the Littonfields (see p. 69) and Wardlow Mires No. 1 boreholes. In Cressbrook Dale the Black Bed thickens to 16 ft and this increase is probably related to the basin-ward passage into dark limestones noted by Eden (1954, p. 37) in the eastern end of the Wye valley. Lonsdaleia floriformis floriformis is commonly present either just above the Black Bed (Lonsdaleia Bed of Morris), at its base or within it (Cressbrook Dale).

The beds between the Black Bed and White Bed are about 55 to 70 ft thick; they consist of pale massive limestones, mostly fine-grained and free from crinoid debris, with abundant chert in the upper one-third and sporadically developed in places below. The Middleton Dale section shows the Upper Shell Bed (Hemisphericus Bed of Morris 1929, p. 42) about 1 to 4 ft thick and with abundant Gigantoproductus crassiventer and G. dentifer ? Some 5 ft higher, Orme (1967, p. 28) has noted a thin algal band and a concentration of foraminifera in the limestones (calcarenites) overlying this. In Stoney Middleton, Orionastraea placenta, Diphyphyllum fasciculatum and other corals occur a little below the White Bed.

The White Bed is not present in Bradwell Dale but its position can be inferred; here the underlying beds are pale massive cherty limestones, crinoidal in the lower part.

The White Bed consists of buff cherty calcilutite up to 7 ft thick. Owing to its pale weathering it forms a conspicuous feature in the Middleton Dale sections where it was first named by Morris (op. cit., p. 42). Work by Orme (1967, pp. 28–9; 1970b) has shown that the White Bed is of somewhat variable texture, part being described as a calcisiltite or fine calcarenite. Insoluble residues contain small silicified gastropods, small Lingula, sponge spicules, conodonts and fish debris. The bed is attributed by Orme to very shallow-water conditions.

The beds above the White Bed, some 50 to 75 ft thick, include massive pale cherty limestones and in places some very fine-grained non-cherty beds at the top (including impersistent calcilutites). In Morris's (ibid., p. 48) Shining Tor section a massive fine-grained bed, the "Hackly Bed" is so-called on account of its fine irregular jointing. Immediately above this lies the Dibunophyllum aff. muirheadi Bed, in which D. bipartitum bipartitum and D. bipartitum konincki occur. The band is of only small lateral extent but appears to lie at the horizon of the Lonsdaleia duplicata Band, present in Furness Quarry 27 ft below the Orionastraea Band. The Orionastraea Band, some 30 to 50 ft from the top of D₂, is about 2 or 3 ft thick and bears O. placenta, Lithostrotion portlocki and other corals. A higher band, with a fauna including Lonsdaleia duplicata duplicata, is present in some localities a few feet above the Orionastraea Band.

The section in Coombs Dale (see (Plate 7)) shows a general resemblance to that in Middleton Dale. However, much of the middle beds is unexposed. The Hob's House Coral Band has been recognized at the base. In the higher beds it appears likely that the White Bed has passed laterally into dark limestones.

The succession in the Hope–Bradwell Moor area (Plate 8) shows a broad correspondence to that outlined above. There is a strong development of dark cherty beds in the lower part of the sequence with the Upper Girvanella Band recognized at the base. The higher beds are pale and frequently cherty. Knoll-reefs are well developed some 30 ft above the base and these have built up in one place to join a higher reef horizon to give a complex knoll-reef some 50 ft in thickness. The L. duplicata Band is well developed in places and can be related to the Orionastraea Band, some 28 ft higher, in Intake Dale, and the band has also been noted in the Wardlow Mires No. 1 Borehole and in Cressbrook Dale. Flat-reef limestones are developed on Bradwell Moor between the horizons of these two coral bands.

In Bradwell Dale (Figure 11) all the exposed high D₂ limestones, including beds down to an horizon some 75 ft below the Orionastraea Band, can be seen to pass northwards into dark cherty limestones of basin facies. Some evidence of a similar lateral passage has been noted south-east of Little Hucklow. I.P.S.

A detailed description of the petrography of the Monsal Dale Beds adjacent to the reef-belt has been given by Eden and others (1964, pp. 93–5) and a systematic description of the large range of rock types has not been attempted for the present work. The pale lithofacies consists of biocalcarenites with some lithocalcarenites and biocalcirudites. The White Bed, near the top of the subdivision, has been described (Orme 1967, pp. 28–9) as varying from a calcilutite and calcisiltite to a fine calcarenite (see p. 30). The occurrence of chert in the limestones is noted in the details; scattered authigenic quartz occurs, becoming abundant in the cherty limestones. Foraminifera vary in abundance and a concentration has been noted by Orme (ibid., p. 28) in a bed near the top of the Upper Monsal Dale Beds in Middleton Dale. The dark lithofacies consists mainly of biocalcarenites and some lithocalcarenites, some of which, as noted by Eden and others (ibid., p. 93), appear deceptively fine-grained, though some finer micritic types do occur. The dark limestones are, in general, finer grained than the pale, though some coarser bands, mainly crinoid calcirudites, are present. R.K.H.

Eyam Group

(Upper Posidonia (P₂) Zone)

Eyam Limestones

The Eyam Limestones, up to about 150 ft in thickness, consist in their simplest development of dark thin-bedded cherty limestones (Plate 10). Locally knoll-reefs and flat reefs are present and the latter may constitute the whole of the subdivision. They contain a rich brachiopod fauna and, at one locality, the P₂ goniatite Sudeticeras sp. Near Great Hucklow, only grey limestones are present.

The Eyam Limestones rest with a marked break on the Monsal Dale Beds. This unconformity was described by Shirley and Horsfield (1945, p. 293) though its effects have been found to be less than suggested by these authors at some localities. It seems reasonable to regard the junction as an angular unconformity in the marginal areas, where its effects can be observed, and as a non-sequence elsewhere. The junction shows in many places evidence of erosion in the presence of a potholed surface, overlain by a clay band. In Coombsdale Quarry a thin coal and seatearth are present at this horizon, providing clear evidence of emergence. At some localities, for example, near Intake Dale, knoll-reefs developed on the base of the Eyam Limestones and were apparently initiated by shallow-water conditions immediately after the pre-P₂ unconformity. Some of these knoll-reefs remain as outliers. In Bradwell Dale some 40 ft of uppermost D₂ strata can be seen to be cut out beneath the Eyam Limestones.

In Coombsdale Quarry the thin coal noted above is overlain by a thin shale, the "Bituminous Shale" of Morris (1929, p. 49) which has yielded the coral Cladochonus sp. Between Calver and Eyam, the Eyam Limestones show a general arrangement of dark cherty limestones with some knoll-reefs and flat reefs below and a widely developed flat reef above. At Calver Peak, a flat reef at the base of the subdivision is overlain by a smaller well-defined knoll and both show a widely developed patchy silicification probably of epigenetic origin (see p. 310). In Middleton Dale, some 35 ft of dark limestones are present at the base and a 1.5-ft coral band, the "Aulophyllum Band" of Morris (op. cit., p. 54) occurs at the junction with the overlying flat reef. Morris considered that this bed overlay the flat reef. The latter, up to 100 ft thick and widespread between Stoney Middleton and Eyam, shows the usual faunal and lithological characters of reef-limestones with, in addition, a slight development of chert in places.

In Eyam Dale, some 75 to 80 ft of predominantly dark cherty beds are present below the flat reef, corresponding to a westerly diminution of the latter, with diachronous base. The dark limestones show a bed with Gigantoproductus giganteus at 21 ft from the base and a 3-ft band 39 ft higher with Dibunophyllum bipartitum subspp. The latter has proved widespread in the Eyam–Foolow area and it is here named the Eyam Dale Coral Band. The overlying flat reef is only some 40 ft in thickness.

To the west of Eyam Dale the flat reef dies out and lateral passage of all but the lowest part of the dark cherty limestones into grey bioclastic limestones takes place. These beds present a more normal shelf facies than the basinal dark beds in the Eyam Limestones and the area in which they are developed is that lying farthest into the shelf area. These beds contain a series of eleven knoll-reefs in their upper part, those in the Grindlow–Foolow area showing a marked elongation parallel to the limestone-shale junction. Lower in the succession a knoll at the junction with beds of the dark lithofacies is well seen in Linen Dale where it was first noted by Morris (1929, p. 52). A bed with Gigantoproductus edelburgensis and G. sp. cf. gigantoides passes laterally into the knoll. The nearby section in the sink-hole near Waterfall Farm shows the Eyam Dale Coral Band.

The Wardlow Mires boreholes proved some 30 ft of dark thin-bedded cherty limestones overlain unconformably by P₂ shale (see below). Mudstone partings were a frequent feature of these limestones, especially in their upper part. Abundant Lingula and sporadic Orbiculoidea and trilobites occurred, especially in the mudstone partings. Inarticulate brachiopods have not been recorded from surface exposures. As elsewhere an erosive base with a mudstone parting is present.

To the south of Great Hucklow the grey lithofacies noted above extends to the base of the Eyam Limestones. To the north-west of the village, however, lateral passage into dark beds again occurs and the grey beds appear to wedge out in the middle of the subdivision. The presence of these dark beds was noted by Shirley and Horsfield (1940), pp. 286, 288) in Jenning's Dale and the fauna compared to that of the dark beds of Cawdor Quarry, subsequently described (Shirley 1959, pp. 414–5) under the name Cawdor Limestones, which contain the P₂ fossil Goniatites granosus. Shirley and Horsfield also noted the presence of a large knoll-reef in these beds north of Nether Water Farm; this is here considered to have been formed by the junction of two knolls.

In Bradwell Dale a large flat reef forms the whole of the Eyam Limestones. Sections at the south end of the dale show two phases of lateral growth on the margin, an initial stage of restricted spread and a later stage of more vigorous spread. Lateral passage into dark cherty limestones is here well marked. The flat reef reaches a maximum thickness of about 130 ft and the uppermost beds are very coarsely crinoidal in places with debris up to an inch in diameter.

Isolated occurrences of beds referred to the Eyam Limestones in the shelf area are also present in the northern and western outcrops. In Windy Knoll Quarry, they occur as dark fillings to Neptunian dykes in pale massive D, limestones of back-reef facies. Near Perryfoot, a small outlier of dark limestone is present, resting on D₁ back reef. Both these are referred to P₂ in view of the presence of the goniatite Sudeticeras sp. in similar limestones near Peakshill (see p. 111).

In the westernmost part of the limestone area, the Eyam Limestones are present in a narrow outcrop around Brook House. (Figure 7) shows the relation of this to the Miller's Dale Beds on which they rest with large unconformity, and to the D₂ limestones which occupy a similar geographical position farther north. The P₂ and D₂ outcrops are separated by a fault of general easterly trend and the diagram demonstrates the pre-P₂ age of this structure.

The greater part of the Brook House outcrop consists of dark cherty limestones some 30 ft thick. The uppermost beds contain an abundant coral fauna in several bands within 14 ft of strata, some or all of which may represent the Eyam Dale Coral Band. Near Brook House, a flat reef some 30 ft thick occurs at the base and it is on the presence in this of Sudeticeras sp., together with the brachiopod fauna, that the dating of these beds depends. Some 16 ft of grey and dark grey limestones overlie the flat reef. T.P.S.

Little petrographical work has been done on the Eyam Limestones, which typically resemble the dark limestones in the Monsal Dale Beds. In Eyam Dale they are dark biocalcarenites, biomicrites and biocalcirudite-biocalcarenites, and intergranular hydrocarbon occurs sporadically. R.K.H.

Shales of P₂ age

On the shelf, shales of P₂ age are known only from the Wardlow Mires outlier. Here some 11 ft of shales have been proved in the Wardlow Mires Nos. 1 and 2 boreholes. No. 1 Borehole yielded Sudeticeras cf. stolbergi at 80 ft 1 in. The base of the shales is unconformable and in the southern part of the outlier they rest on D₂ limestones. At Wardlow Mires itself the shales rest on the lower dark beds of the Eyam Limestones, while west of Castlegate they overlie the higher grey lithofacies. There is no evidence of an unconformable junction with the Namurian.

Marginal Province

The beds present in this province at surface in the northernmost Viséan outcrop in the district include the reef-complex of the Castleton area and a thin development of overlying strata. The lateral development of the reef-complex is to some extent masked by the unconformable base of the Namurian.

Apron-reef

The apron-reef is present nearly continuously from near Sparrow Pit to the vicinity of Bradwell (Plate 11). The lithology and sedimentation have been described on pp. 16–9.

The apron-reef as described here includes the Castleton Limestones (B₂) and part of the Nunlow Limestones (P₁) of Shirley and Horsfield (1940). The poorly bedded character of the apron-reef limestones makes detailed stratigraphy and correlation difficult to establish, but the general faunal succession is as follows:

• Goniatites falcatus Zone (P_1b)
• Goniatites crenistria Zone (P_1a)
• Upper Beyrichoceras Zone (B₂)

The faunas, which are rich in brachiopods, gastropods and bivalves and contain occasional goniatites, are further discussed on p. 140. Beds of high B₂ age are of widespread occurrence while low B₂ and P₁ beds are discontinuous and restricted in general to the inner and outer margins respectively of the apron.

The lateral passage of the apron-reef into beds of shelf facies has already been described (p. 18). At the ends of the reef-belt the apron appears to thin and in these areas it can be seen to overlie beds of shelf facies; this is readily interpreted if the lateral passage is considered as taking place partly by interdigitation.

The B₂ apron-reef is in general massive and poorly bedded while the P₁ reef is more regularly and evenly bedded. Parkinson (1965, p. 164) considers on faunal grounds that a non-sequence of some importance is present between upper and lower B₂. This cannot be considered firmly established though a break in about the right position is present near the Blue John Mine. Intra-B₂ movements have been invoked during the present work to account for the off-setting of the reef-belt and production of a knoll-like mass of reef-limestone at Middle Hill.

To the east of Pin Dale, apron-reef of B₂ age is in general absent at outcrop and it has been suggested (see p. 13) that this is most probably due to penecontemporaneous movement along the line of Dirtlow Rake. Small inliers at the base of Nunlow Quarry and at the extreme eastern end of the reef-belt are, however, of B₂ age.

At Jack Bank, reef-limestones of P_1b age rest unconformably on D₁ shelf limestones with the Pindale Tuff (see p. 108). Strata of P_1a age are present locally, probably as a channel-fill (Eden and others 1964, p. 90) in the upper surface of D₁. Steep inward dips at the top of the frontal slope of the apron-reef have led the above authors to infer the presence of a P_1b knoll, now largely eroded away, at Upper Jack Bank.

Beach Beds

The Beach Beds form a restricted outcrop in a curve in the frontal slope of the apron-reef and at its foot on the west side of Castleton (see (Plate 11)). They consist for the most part of rounded shell debris with some finer-grained grey beds, grey crinoidal bands and dark bituminous bands of basinal type. A detailed description has been given by Sadler (1964) who concluded that they represented a fan-like deposit at the foot of a channel coinciding approximately with the present-day Winnats gorge. The Beach Beds were considered to be contemporaneous with the adjacent apron-reef and of B₂ age.

The above interpretation is not favoured in the present account for the following reasons. The Castleton Borehole (see below) proved the presence of a coral band with a fauna of high D₂ age (see p. 111) associated with beds of Beach Beds type. These beds are considered to fall within the P₂ of the fully developed basin succession. A widespread unconformity is known to be present in many places, for example at Bradwell, near the margin of the limestone outcrop at the base of the Eyam Limestones and close to the base of P₂ (see (Figure 3)). If the source of supply lay, as postulated by Sadler, in the back-reef area, it is difficult to account for the abundance of shell debris, as the back-reef is not very fossiliferous behind Treak Cliff. The interdigitation of reef-like limestones within the Beach Beds can be disregarded as proof of their association with the B₂ apron in view of the widespread occurrence of flat reef in P₂.

The Beach Beds, therefore, are regarded as of probable P₂ age though it is possible that they were formed somewhat earlier than the main transgression of the Eyam Limestones.

Dark limestones overlying the apron-reef

A small thickness of dark limestones is present above the apron-reef in Castleton village. This has failed to yield diagnostic fossils. However, between Pin Dale and Castleton, Parkinson (1947, p. 112) obtained the P_1b fossil Goniatites cf. spirifer Roemer from a dark limestone at the foot of the frontal slope of the apron and perhaps the basinal equivalent of the highest beds of the apron-reef. Near Peakshill (see p. 111) a few inches of dark limestone, resting on B₂ apron-reef, have yielded the P₂ goniatite Sudeticeras sp.

P₂ Shale

Shales of P₂ age apparently crop out in a small area east and south-east of Treak Cliff, Castleton. The outcrop, obscured by head, has been calculated from the record of the Castleton Borehole (see below). In the Hope Cement Works Borehole a small thickness of Viséan shales underlies the lowest Namurian; these beds, however, occur at a greater depth than in the Castleton Borehole and have been interpreted as being cut out by unconformable overlap at outcrop.

Vulcanicity

Vulcanicity in the marginal province resulted in the formation of the Speedwell Vent (see pp. 300–1) from which, however, the surface deposits appear to have been eroded, leaving only the neck. A small thickness of tuff is present in dark post-reef limestones at Castleton, though its source is uncertain. The Pindale Tuff, associated with the tuff-cones in the back-reef area (see pp. 61–2) extends outwards beneath the apron north of Pin Dale and is overlain unconformably by Namurian shales. The Hope Cement Works Borehole proved 149 ft 6 in of pillow lavas with some tuff and a tuffaceous limestone beneath 53 ft of grey to dark grey thin-bedded limestones with Lonsdaleia duplicata at the top. The lavas (see also p. 113) are attributed to a local eruptive centre on the line of the reef-belt, perhaps governed by the same deep-seated fracture.

Basin Province

Beds of the basin province are concealed by the Namurian and are known mainly from the Edale (Hudson and Cotton 1945b, pp. 1–35) and Alport (Hudson and Cotton 1945a, pp. 256–95) boreholes (Figure 3). The succession in these is summarized on pp. 113–9.

Seminula (S₂) Zone.

Beds of this zone are known only from the Alport Borehole where 528 ft were proved. They varied from grey to dark grey limestones with beds of calcilutite and breccia in places. The presence of chert at several levels contrasts with its absence in the shelf area and finds a parallel in the Permian of the Guadalupe Mountains area, Texas (see Newell and others 1953, pp. 161–2). The faunal affinities are with the shelf area with a coral-brachiopod fauna including Davidsonina carbonaria.

Lower Dibunophyllum (D₁) Zone.

Beds of this zone, 326 ft thick in the Alport Borehole, consist of grey and grey-brown limestones with some shale partings in their upper part and some chert throughout. These beds bear a D₁ coral-brachiopod fauna in the lower part while Goniatites sp. ?maximus group was present within the uppermost 59 ft of beds. The uppermost part of the zone is represented by B₂ strata (see below). In the Edale Borehole there is no B₂ and the D₁ Zone is represented by the lowest 77 ft of beds proved: dark grey-brown limestones with a calcilutite band. The fauna of these beds was not diagnostic and their correlation depends on the presence of the Lower Girvanella Band at the base of the succeeding strata.

Upper Beyrichoceras (B₂) Zone.

Beds of this zone are present in the Alport Borehole only and consist of 52 ft of mudstone above and 159 ft of limestone, partly thin-bedded or tuffaceous with shale partings, below. Both bear goniatites including Beyrichoceras cf. delicatum, Goniatites aff. hudsoni and G. struppus.

Upper Dibunophyllum (D₂) Zone.

Beds of this zone are present only in the Edale Borehole as 63 ft of limestones, pale grey with some tuff debris above and dark below, with Girvanella in the lowest 10 ft. In the Alport Borehole these strata are represented by beds assigned to P₁ (see below).

Lower Posidonia (P₁).

In the Alport Borehole these beds, 294 ft thick, are represented by:

(a) Grey and grey-brown limestones, tuffaceous and with tuff bands in their lower part and with a 50-ft mudstone at 56 ft from the base, 153 ft. The fauna includes G. crenistria (P_1a Zone). The thinner development in the Edale Borehole, 198 ft, also shows mudstones, including some limestones, above and a tuffaceous limestone at the base.

(b) Mudstones with some thin limestones representing the Goniatites falcatus (P_1b), G. spaericostriatus (P_1c) and G. koboldi (P_1a) zones, 141 ft.

Upper Posidonia (P₂).

In the Alport Borehole this consists of 97 ft of beds, mainly mudstone but with 10 ft of pebbly limestone and breccia at the base. Three zones are present: Mesoglyphioceras granosum (P_2a), Neoglyphioceras subcirculare (P_2b) and Lyrogoniatites georgiensis (P_2c). In addition to goniatites, Caneyella mernbranacea is abundant in the mudstones. The Edale Borehole shows 94 ft of P₂ strata with 47 ft of grey and dark grey limestones at the base.

Variations in the basin province

A comparison of the sections of the two bore-holes allows certain conclusions to be drawn regarding variation in the basin area. The lowest beds represent an imperfectly developed basin facies and the faunas recall those of the shelf area, resulting in the use of the coral-brachiopod scheme for zonation. Basin faunas appear first (B₂) in the Alport Borehole, farthest away from the shelf area and this also shows a thicker succession than in the Edale Borehole, which is relatively close to the shelf. Another basinal characteristic, the development of thick mudstone, instead of limestones, also occurred earlier (B₂) in the Alport than in the Edale Borehole, and where limestones are present at higher levels they tend to be thinner at Alport than at Edale. These facts point to a gradual spread of true basinal conditions outwards towards the shelf from the Alport area, the conclusion of the process being their encroachment on to the shelf area during the formation of the Eyam Limestones.

Details

Shelf Province

Woo Dale Group (S₂ and basal D₁)

Woo Dale Beds

The main outcrop of the Woo Dale Beds lies in the axial area of the Peak Forest Anticline (Figure 4), (Figure 5). Associated small faulted inliers are present in the valley of Dam Dale and Hay DaleDam Dale, Hay Dale, Peter Dale and Monks Dale are parts of the same valley., south of Peak Forest.

Dale Head to Hernstone Lane Head

The valley (Cope 1933, p. 127). The sectionSections from which faunas have been obtained bear a locality number (see also Appendix 2) and each individual item is distinguished by a small letter. These letters do not imply any correlation between sections. Where necessary, sections are divided between different strati-graphical headings. Woo Dale Beds in this area show lithological (loc. 1) in the main dale at Dale Head characters closely comparable with those of [SK 1234 7662] shows: the S₂ beds of the type section in the Wye

The fauna of bed (a) is indicative of the S₂ Zone. However, the section in the tributary dale at Dale Head (see below), unfortunately separated from this section by faulting, shows a definite D₁ fauna in a nearly similar position with regard to the base of the Chee Tor Rock. All the beds (b) to (e) in this section are accordingly referred to D₁.

The section (loc. 2) in the eastern tributary dale at Dale Head [SK 1248 7653] is more complete than that given above:

The incoming of P. murchisoni in the lowest faunal band is taken to mark the base of the D₁ Zone.

The inlier of Dale Head is faulted off on the northern side, but a further small faulted inlier is present 0.25 mile N.N.W. of Dale Head near the main S₂ outcrop. Exposures here are scanty though a few feet of dark limestone are exposed by a small working for calcite [SK 1200 7694] on the west side of the valley.

At the southern end of the main outcrop the section (loc. 3) at the junction of Dam Dale and Hay Dale [SK 1187 7781] (Plate 2A) provides the best sequence of the Woo Dale Reds in the area:

Traced laterally, the calcilutites of the lower part of the section (though not the 'marker horizon') are found to be very irregular and lenticular in character, swelling out and thinning rapidly. It should also be noted that the horizon of the beds with Daviesiella in this section differs substantially from that found by Cope (1939, pp. 61–2) in the Wye valley. The present section yielded Daviesiella only between a level 130 ft below the base of the Chee Tor Rock and the lowest beds exposed some 23 ft below.

The most northerly section (loc. 4) attributable to the normal facies of the Woo Dale Beds is at Hernstone Lane Head [SK 1220 7876]:

Peak Forest

The Peak Forest Limestones present a facies distinct from that already described, being pale, more massive and crinoidal. They show less contrast in lithology to the overlying Chee Tor Rock than the normal Woo Dale Beds but are still quite distinct. The lateral passage between the two facies takes place quite sharply along a north-north-easterly line running from near Hernstone Lane Head through a point a little north of the large section in Dam Dale described above. The relationships of the two facies are made clear when the calcilutite marker band noted in the Dam Dale section is traced northwards into the outcrop of the Peak Forest Limestones. (Figure 4) shows the positions of the outcrops of the two facies and of the calcilutite marker. The lateral passage appears to occur at a higher horizon at Hemstone Lane Head than in Dam Dale.

The Peak Forest Limestones are well exposed on the west side of Dam Dale [SK 1173 7845]: rather dark grey fine-grained limestone 5.5 ft, on 24 ft of grey-brown fine-grained limestone in posts up to 3 ft thick, with some very crinoidal bands and some productoids. On the opposite side of the valley the most northerly exposure showing the calcilutite marker band is seen [SK 1194 7846] 210 yd E. of the last exposure: pale grey limestone 4 in, calcilutite 1 ft 6 in, on fine-grained pale grey limestone 1 ft 2 in. An exposure (loc. 5) [SK 1170 7809] east of Loosehill Farm showed 2 ft 6 in of pale brown finely granular slightly crinoidal limestone with brachiopods including Monograptus sp. papilionaceus group, smooth spiriferoids and orthotetoids.

Around Peak Forest village the Peak Forest Limestones occur as an outlier forming part of the roof of a large dolerite sill (see p. 295). An exposure (loc. 6) [SK 1198 7928] showed 6 ft of buff crinoidal and oolitic limestone with Koninckopora inflata, Linoproductus cf. corrugatohemisphericus, L. cf. corrugatus and Monograptus sp. papilionaceus group. A small exposure (loc. 7) [SK 1202 7946] yielded Lithostrotion martini [close to the S₂ form of the species]. Partly altered beds overlying the dolerite are seen in another section [SK 1163 7877] near Damside Farm:

In view of the general absence of dolomites in the Peak Forest Limestones, the dolomite in the above section is considered to be secondary. This and the other features of this section due to alteration by the dolerite are discussed on p. 295.

To the north-west of Peak Forest a quarry [SK 1090 7952] near Chamber Farm shows a 21-ft section of the Peak Forest Limestones, finely granular pale grey-brown, rather massive and with very crinoidal bands. Some 0.5 mile to the north-west these beds have been dug in the past in a series of small workings for lime-burning in and around Hartle Plantation. A typical exposure [SK 1053 7992] shows 4 ft of off-white shelly bioclastic and oolitic limestone, and another [SK 1055 7999] nearby shows 12 ft of off-white granular crinoidal shelly limestone. A quarry (loc. 8) to the north of Hartle Plantation [SK 1040 8020] shows beds near the top of the Peak Forest Limestones:

The fauna is indicative of the S₂ Zone, the top of the Peak Forest Limestones corresponding to the S₂/D₁ boundary.

Exposures in Perry Dale show beds near the top of the Peak Forest Limestones, closely overlain by the Bee Low Limestones, though the actual junction is not exposed. A section (loc. 9) [SK 1071 8069] of the uppermost exposed Peak Forest Limestones is as follows: off-white thin-bedded limestone with L. sp. hemisphaericus group and Monograptus sp. papilionaceus group 1 ft, on pale grey to brown well-bedded finely crinoidal limestone with more coarsely crinoidal bands 12 ft. The fauna, though not diagnostic, is probably S₂.

A section [SK 1078 8025] in an old quarry south of Nether Barn shows beds lower in the Peak Forest Limestones than those described in preceding sections: pale brown well-bedded crinoidal limestone 21 ft.

On the north-eastern side of the outcrop a section in Conies Dale (loc. 10) [SK 1201 8019] lies at or near the junction of the Peak Forest Limestones and the Bee Low Limestones: finely crinoidal limestone a few inches, on pale brown fine-grained limestone with Lithostrotion martini, bryozoa and Linoproductus sp. ?hemisphaericus group 1 ft 9 in. Between this locality and Conies Farm the underlying limestones, pale brown and crinoidal, are exposed.

Eldon Hill and Castleton

A borehole at Eldon Hill QuarryInformation from driller's log and from examination of cutting-samples by Dr. D. C. Knill. The samples were loaned by Messrs. Eldon Hill Quarries Limited. [SK 1128 8156], after passing through about 280 ft of beds referred to the Bee Low Limestones (see p. 58), entered a series of predominantly grey and pale grey crinoidal limestones. The only major lithological variations in these beds were the presence of grey non-crinoidal limestones between about 405 ft and 427 ft and of grey fine-grained limestones with a little dolomite between about 446 ft and 460 ft. From 505 ft to the bottom of the borehole at 605 ft feldspar, clay minerals and abundant iron oxides occurred in the samples indicating the presence of igneous rock; this is tentatively interpreted as a tuff. Tuffs in a similar geographical relation to the reef-belt (see p. 61), though at a higher horizon, have been described by Eden and others (1964, pp. 76–8).

At Castleton, the presence underground of limestone "indistinguishable from S₂ limestones of Peak Forest" was recognized by Ford (1952, pp. 351–2) in the Speedwell Mine. These limestones were met in the Speedwell Level (the main crosscut) between its intersection with Faucet Rake at the 'Bottomless Pit' [SK 1400 8235] and its furthermost point [SK 1395 8215]. Ford records a 2-in bed of clay "at the end of the artificial level". The height of the level is given as 742 ft O.D. and the horizon of the surface here, at about 1260 ft O.D., is a few feet above that of the Lower Lava. Assuming an average thickness of about 300 ft for the Chee Tor Rock, the clay parting must lie some 200 ft below the top of S₂ and therefore at or close to the horizon of the igneous rock met with in the Eldon Hill Quarry Borehole.

In Peak Cavern, Castleton, Ford noted "rather dark crystalline limestone" in the entrance, overlain by pale calcite-mudstone of D₁ age. The lowest beds here were also referred by Ford to the S₂ Zone and they become pale and crinoidal when traced into the inner part of the cave beneath the upper end of Cave Dale, only 0.25 mile S.E. of the end of the Speedwell Level.

Bee Low Group (D₁): southern area

Chee Tor Rock

Great Rocks Dale

Extensive quarrying of the Chee Tor Rock has provided excellent sections, particularly in the upper third of the subdivision; the more important of these are quoted below.

On the southern margin of the district all but the uppermost few feet of the Chee Tor Rock is exposed in the inaccessible face of Tunstead Quarry [SK 096 743]. The total thickness is about 380 ft. A generalized sectionSupplied by Mr. P. F. Dagger with permission of Imperial Chemical Industries Limited. of the uppermost beds, those falling within the present district, is as follows:

The lowest beds are about 180 ft above the base of the Chee Tor Rock and the highest near the horizon of the Upper D. septosa Band. The very massive character of the lowest beds in the section is a particularly striking feature.

At the "north end of Tunstead Quarry", about 35 ft and 50 ft respectively below the top of the Chee Tor Rock, Cope (1939, pp. 61–2) recorded potholed surfaces beneath clay partings. The potholes were from 3 to 4 ft in diameter and 2 to 3 ft in depth. The possible origin of these features, which have been found during the present work to be more extensive both laterally and in horizon, is discussed on p. 17.

To the north of Tunstead Quarry most of the sections in the Chee Tor Rock have now been obscured by tipping. Faulting has resulted in the preservation of several patches of Lower Lava in this area (see p. 52). A section [SK 1004 7493], near the railway and starting below the lava, is as follows:

The exceptional extent of the marmorization at this locality is difficult to explain, particularly as the overlying rock is a lava. About 0.25 mile to the north of this locality the Upper D. septosa Band, 2 ft thick, is exposed [SK 0990 7532] in a railway-cutting. The same band is better developed (loc. 11) [SK 1011 7512] near Great Rocks Lees as a 4-ft band with Koninckopora sp. and gastropods.

The old quarry [SK 0980 7576] at Buxton Bridge shows a good section of the Chee Tor Rock, commencing about 12 ft below the top:

At Peak Dale, Duchy Quarry (loc. 12) [SK 0938 7681] (Plate 3A) 280 yd E. of Peak Forest Station the following section is shown immediately underlying the Lower Lava:

On the west side of Great Rocks Dale the section in Bold Venture Quarry [SK 0890 7655] is closely similar to that in Duchy Quarry but does not extend down so far, showing the uppermost 58 ft of the Chee Tor Rock, the top of the section being close to the horizon of the base of the Lower Lava. The section differs from that in Duchy Quarry mainly in the local development of a band of pale calcilutite 1 to 1.25 ft thick and 6.5 ft below the Upper D. septosa Band.

Over half a mile west of the last section, Upperend Quarry (loc. 13) [SK 0833 7707] also shows the uppermost part of the Chee Tor Rock, the highest beds lying 2 to 3 ft below the Lower Lava:

The long section in Newlin Quarry starts in the lowest level of the quarry [SK 0917 7732] north of Peak Forest Station, and finishes mile to the north-west [SK 0888 7778]; the uppermost beds lie a little below the Upper D. septosa Band:

Smalldale, Peter Dale and Monk's Dale

Between Laughman Tor and Peter Dale an expanse of flat-lying or gently undulating Chee Tor Rock forms a broad outcrop. On the plateau surface exposures are numerous, but large sections are lacking. The tendency for fossils in the Chee Tor Rock to be restricted to more or less well-defined horizons enables small exposures of these in many cases to be correlated by calculating their position in relation to the top or base of the Chee Tor Rock.

At Laughman Tor the section (loc. 14) [SK 1015 7799] is as follows:

The coral bed forms the craggy top of the tor. It lies about 140 ft below the top of the Chee Tor Rock (Figure 6).

To the south-east of Laughman Tor the Chee Tor Rock forms a gentle dip-slope, and at the Marvel Stones [SK 1045 7780] weathering of this has given rise to a limestone pavement, an infrequent feature in the area. A quarry [SK 1065 7810] in Smalidale Plantation shows a typical section: brown-white fine-grained limestone, rather crinoidal 10 ft, on pale grey or grey-white massive fine-grained limestone 13 ft.

Near Gorsey Nook a band bearing a diffuse brachiopod-coral fauna is exposed [SK 1042 7685] and has been traced laterally for a distance of about a quarter of a mile. The band lies about 100 ft below the top of the Chee Tor Rock at or near the horizon of the algal band near the base of the Duchy Quarry section. An outlier of the same bed is present at the western end of Middle Hill, an exposure (loc. 15) [SK 1079 7698] showing pale fine-grained limestone, sparsely fossiliferous near base 2 ft 2 in, on pale fine-grained limestone with Caninia sp. [?C. cf. densa Lewis of Hudson and Cotton 1945a, p. 306], Clisiophyllum sp. [juv Lithostrotion martini, Davidsonina septosa, Delepinea aff. comoides, Linoproductus aff. corrugates and Monograptus sp. papilionaceus group. On the east side of the hill lower beds are exposed, the section (loc. 16) [SK 1129 7706], with the uppermost beds [SK 1124 7696] lying about 10 ft below the band with D. septosa of the previous locality, being:

The thickness, rich coral fauna and estimated stratigraphical position of the lower band suggest equivalence to the coral band of Laughman Tor.

The upper coral band of the last section is more strongly developed (loc. 17) [SK 1059 7721] on the north-west side of Middle Hill where it is 6 ft thick and has yielded Lithostrotion cf. aranea, L. aff. maccoyanum, L. aff. martini and P. murchisoni.

Nearly 1.5 miles S.E. of the last locality two fossil-bands are present locally at closely similar horizons to those of Middle Hill. The upper band is the better developed and is exposed [SK 1231 7561] north-east of Hargate Hall in the following section (loc. 18):

A band some 40 ft lower in the succession and 4.75 ft thick is exposed nearby [SK 1241 7553] and yields brachiopods and corals; this appears to be about 150 ft below the top of the Chee Tor Rock. The two bands crop out on the south-western limb of a small sharp anticline traceable for a distance of half a mile and trending N.W.–S.E. The Monk's Dale Vent, first noted by Arnold-Bemrose (1907, p. 251), more fully described on p. 300, lies at the south-eastern end of the anticline near the axis and a further vent has been found mile to the north-west and lying close to the anticline. The association of these two vents with a sharp anticline, foreign to the tectonic pattern of the limestone massif, suggests strongly that the structure was of penecontemporaneous origin.

The relationship of the vents to the anticline is illustrated in (Figure 14).

In Peter Dale the lower part of the Chee Tor Rock is exposed nearly continuously. Beds low in the subdivision stand out as a marked cliff of massive limestones showing the characteristic vertical jointing at Dale Head. The massive beds forming the cliff are underlain by some 40 ft of thinner-bedded limestones. A coral band up to 4 ft thick is present at the base of the Chee Tor Rock in the eastern tributary dale at Dale Head above the section (loc. 2) [SK 1248 7653] of Woo Dale Beds described on pp. 39–40:

At Dale Head the coral band (f) disappears laterally but it reappears farther north in the long section at the junction of Hay Dale and Dam Dale (p. 50). The section (loc. 1) in the main dale at Dale Head [top of section: [SK 1232 7630] shows higher beds in the Chee Tor Rock:

Some 55 ft above the base of the Chee Tor Rock is a well-developed coral band, bed (g) of the preceding section. This is best seen (loc. 19) in a small cliff on the west side of Peter Dale [SK 1222 7626], where it is 6 ft thick and yielded C. vaughani, D. bourtonense φ, Lithostrotion martini, L. pauciradiale, L. cf. sociale, P. murchisoni, A. expansa, Gigantoproductus? sp. nov. [wrinkled concentric ornament], Linoproductus sp. hemisphaericus group and Monograptus sp. papilionaceus group. The overlying limestones, exposed in Peter Dale between the coral band and the vents previously noted, show their usual lithological characters but no fossil bands were found. Near the Monk's Dale vents, however, a 2-ft band overlying 80 ft of unfossiliferous beds on the eastern side of the dale (loc. 20) [SK 1304 7539] yielded Lithostrotion martini, Linoproductus sp. hemisphaericus group and Monograptus sp. papilionaceus group. The band appears to lie about 140 ft below the top of the Chee Tor Rock and to be the equivalent of the lower of the two fossil bands exposed north-east of Hargate Hall. The higher horizon is probably present in an exposure (loc. 21) [SK 1347 7521] near Monks-dale House as 3 ft of grey limestone with Caninia benburbensis and D. bourtonense φ.

Between Monk's Dale and Tideswell Dale the Chee Tor Rock crops out over a broad plateau which, however, shows only minor exposures.

To the east of the outcrop the only information regarding the underground extension of the Chee Tor Rock, is provided by the Derwent Valley Water Board's trial borehole at Litton Dale [SK 1599 7498]. The borehole was not cored and the record is from the borers, supplemented by examination of cutting-samples by Professor F. W. Shotton. The base of the Lower Lava was found at 243 ft and from thence to 340 ft the hole passed through pale fine-grained limestones with some pyrite in the uppermost 5 ft. These beds represent the topmost part of the Chee Tor Rock. Below 340 ft the succession is abnormal, the beds to the bottom of the borehole at 385 ft being either lava with calcitization in places or interbedded lava and tuff. Extrusive igneous rock at this horizon is unknown elsewhere in the district, though this is not the earliest evidence of vulcanicity in the area.

Wheston to Ox Low

Between Wheston and Dale Head faulting brings up beds low in the Chee Tor Rock to crop out on the plateau surface. An exposure (loc. 22) [SK 1270 7637] west of Wheston Hall (see (Figure 6)) showed a coral band 2 ft thick and about 100 ft above the base with Lithostrotion portlocki, Syringopora cf. distans, Gigantoproductus dentifer, Linoproductus sp. hemisphaericus group and Monograptus sp. papilionaceus group. A nearby exposure (loc. 23) [SK 1273 7630] yielded Lithostrotion martini and P. murchisoni from the same band.

Higher up the slope, towards Wheston, an exposure (loc. 24) [SK 1286 7623] shows a 21-in band with Lithostrotion martini, L. pauciradiale, P. murchisoni?, Davidsonina septosa and Linoproductus sp. hemisphaericus group. This exposure lies some 150 ft below the top of the Chee Tor Rock and is at or near the horizon of the coral band of Loughman Tor (see p. 47).

A higher coral band is present over a distance of 300 yd farther up the slope and lies some 100 ft below the top of the Chee Tor Rock. An exposure (loc. 25) [SK 1295 7618] shows the band some 8 ft thick with Dibunophyllum sp., Lithostrotion decipiens?, L. martini, P. murchisoni and Linoproductus sp. hemisphaericus group. These beds rest on a potholed surface with yellow clay which, if equivalent to that developed north-east of Hargate Hall, suggests that the lower part of the band has failed.

At the junction of Hay Dale and Dam Dale the following section (loc. 3) in the lowest part of the Chee Tor Rock, continues that of the Woo Dale Beds given on p. 40 [top of section 1190 7727]:

The coral band at the base is the same as that developed in this position at Dale Head (loc. 2, p. 49). Higher beds in the Chee Tor Rock, uniformly pale, massive and fine-grained, are exposed on the east side of Hay Dale for a distance of a quarter of a mile above this section; beyond here, however, they are faulted off.

About 100 ft from the base of the Chee Tor Rock, on the slopes east of Hay Dale (loc. 26) [SK 1225 7721] a band (traceable for some quarter of a mile) 5 ft thick yields Lithostrotion martini, P. murchisoni, bryozoa, Delepinea aff. comoides and Linoproductus sp. hemisphaericus group. The band appears to be that developed as a coral band west of Wheston (loc. 22, see above).

Between Hay Dale and Hemstone Lane Head the coral band at the base of the Chee Tor Rock is developed in places. At Hem-stone Lane Head the section (loc. 4) of the lowest part of the subdivision is continuous with that of the Woo Dale Beds given on p. 41 [top of section 1226 7876]:

Farther east the Chee Tor Rock forms a broad outcrop with sporadic exposures only. The Lower D. septosa Band, some 60 ft below the top, is exposed in a small limestone scar and can be traced for some hundreds of yards at the crest of a small hill west of Potluck House. An exposure (loc. 27) [SK 1294 7805] shows the band, 2 ft thick, with corals including Caninia sp. subibicina group, P. murchisoni, Davidsonina septosa, Delepinea aff. comoides, Linoproductus sp. hemisphaericus group.

At Wall Cliff the uppermost beds of the Chee Tor Rock are exposed in the following section (loc. 28) [SK 1424 7738]:

The presence of calcilutite bands high in the Chee Tor Rock is a striking feature of the section and recalls that at Bold Venture Quarry (see p. 46).

At the northern end of the outcrop the Chee Tor Rock is well seen on Ox Low. A shell band is present locally on the southwest side of the hill and is seen on the north side of old open workings on Oxlow Rake (loc. 29) [SK 1260 8002] in the top 6 ft of a 40-ft section. This bed yielded P. murchisoni, Gigantoproductus sp. and Linoproductus sp. Some 90 ft higher in the succession, the Upper D. septosa Band is exposed [SK 1265 8014] as a 2-ft band with brachiopods (including D. septosa) and gastropods. This band lies about 30 ft below the base of the Lower Lava and the total thickness of the Chee Tor Rock hereabouts is about 300 ft.

To the north of Ox Low, with the disappearance of the Lower Lava the Chee Tor Rock and Miller's Dale Beds are considered together as the Bee Low Limestones.

Lower Miller's Dale Lava

Water Swallows, Great Rocks Dale and Dove Holes

The outcrop of the Lower Lava enters the district half a mile south of Water-swallows but is almost immediately cut out by the transgressive Waterswallows Sill. The latter has, however, been cut through in Waterswallows Quarry [SK 0860 7504] to show up to 6 ft of pale calcitized amygdaloidal lava resting on limestone and with an irregular junction with the overlying dolerite. Near this junction the lava usually contains pyrite veins and pyrite amygdales. The altered lava has been recently compared by Dr. F. Moseley (in discussion Dunham and Kaye 1965, p. 275) to the White Whin of the Durham area.

To the east of Water Swallows, faulted outliers of the lava are present north of Tunstead Quarry though they are much obscured by tipping. A section [SK 0979 7538] near the railway shows 13 ft of amygdaloidal lava in a down-faulted wedge.

On the eastern side of Great Rocks Dale the Lower Lava has been passed through in a number of boreholesPublished by permission of Imperial Chemical Industries Limited.. The greatest thickness was proved in the southernmost hole T/13/21 [SK 1034 7547], which gave the following abridged succession:

The lava shows a clear division into three flows separated by the clay partings at 75 ft 2 in and 107 ft 2 in. A similar but thinner section was proved farther north in borehole T/B/23A [SK 0985 7614] which started just below the top of the lava and showed 74 ft 8 in of it.

To the west and south-west of Upper End the Lower Lava forms a broad outcrop over the crest of a shallow anticline; in places it is capped by small outliers of Miller's Dale Beds. In this area the outcrop bears frequent swallow-holes, many of which provide sections of the lava. For example, north-east of Water Swallows [SK 0836 7557] where 14 ft of amygdaloidal lava are exposed. Near Batham Gate the lava is 50 to 60 ft in thickness. An exposure [SK 0840 7644], again in a sink-hole, shows 12 ft of amygdaloidal lava. The most northerly exposure on this outcrop of lava in a more or less unaltered state is [SK 0801 7753] 0.5 mile S.E. of Dove Holes station. Between Dove Holes and Lodes Marsh the lava thins steadily, the outcrop showing as a depression with bright yellow clay visible in places. The lava finally disappears [SK 0865 7836] at Lodes Marsh.

Wormhill Moor, Tunstead and Hargatewall

To the east of Great Rocks Dale the Lower Lava crops out around the high ground forming Wormhill Moor. Near Rock Houses the thickness of the lava is about 75 ft but it thins northwards to 30 ft at the northern end of the outcrop near Smalldale. Sections are infrequent though the lowest beds, reddish weathering and amygdaloidal, are well seen close above the abandoned Great Rocks Quarries [SK 0956 7633].

Around the hamlet of Tunstead and at Hargatewall the Lower Lava reaches its maximum thickness of about 100 ft. It is well exposed, for instance, in the sides of the lane [SK 1106 7471] 350 yd S. of Tunstead. Locally, hard dark compact non-amygdaloidal basalt of rather coarse grain is present in small masses within the Lower Lava, as at [SK 1132 7467] south-east of Tunstead and is considered to be the middle part of a flow.

Tideswell Dale to Bradwell Moor

The outcrop of the Lower Lava enters the district at Tideswell Dale but is here complicated by the presence of the Tideswell Dale Sill at the base. On the east side of the dale [SK 154 744] features suggest the splitting of the Lower

Lava with the development of a thin limestone parting, too small to be shown on the one-inch map. The most northerly outcrops in Tideswell Dale are faulted and may not represent the whole of the Lower Lava; the sequence is best illustrated by the Litton Dale Borehole [SK 1599 7498] (see also p. 55). This is as follows:

From Tideswell Dale the outcrop of the Lower Lava is faulted westwards to Heathydale Ward. Around Wheston the thickness of the lava is about 90 ft, but to the north it thins, only some 40 ft being present around Potluck. Near here an exposure 11303 77121 shows non-vesicular lava 6 ft on amygdaloidal lava 7 ft.

At Wall Cliff the section (loc. 28, see also p. 51) shows the Lower Lava [SK 1433 7731] to be 35 ft thick. It is poorly exposed but where seen shows its normal amygdaloidal character. Farther north, at the intersection of the outcrop with White Rake, strike-faulting brings the Upper Lava and the Lower Lava into juxtaposition. An exposure of the latter, deeply weathered, is visible to a depth of 7 ft in an openwork on the vein [SK 1452 7815].

The most northerly exposures worthy of note are at The Cop; these show amygdaloidal lava [SK 1287 7968] and, 60 yd farther north, non-vesicular lava. The total thickness here is some 30 ft. To the north of The Cop the Lower Lava thins rapidly and disappears [SK 1355 8108] near Hazard Mine.

The isolated occurrences of Lower Lava at Cave Dale and of tuff at a comparable horizon at Pin Dale are, for geographical reasons, best considered with the Bee Low Limestones.

Miller's Dale Beds

Water Swallows and Dove Holes

On the southern margin of the district the Miller's Dale Beds form a broad outcrop west of Water Swallows. A section in an old quarry [SK 0707 7457] on Fairfield Common, shows 18 ft of pale massive limestone, Shelly in the lowest 1 ft and with sporadic productoids and corals in a 3.5-ft band at 5.5 ft from the base. To the east of the main outcrop, faulted outliers of Miller's Dale Beds overlie the Lower Lava in places on a shallow ridge between Hardy-barn and Batham Gate. Between Batham Gate and Dove Holes the Dove Holes Tuff is present within the lower half of the subdivision.

Between Batham Gate and Bibbington the Miller's Dale Beds have been proved in a number of boreholes for quarry development. Borehole No. 11 of this series [SK 0749 7674] proved the full thickness of the Miller's Dale Beds':

The outcrop of the Dove Holes Tuff is traceable for a stretch of 300 yd to the east of Peak House. To the south of a line between Peak House and the site of borehole No. 11 this tuff cannot be located at outcrop and it has also been proved absent by several bore-holes. No. 13 Borehole [SK 0780 7628] near Field Farm, however, showed 7 ft 6 in of 'greenish ash with pyritesInformation from examination of cores by Professor F. W. Cope. with base at 89 ft on 11 ft of 'blue limestone' overlying the Lower Lava. This is the only record of a tuff at this horizon in the area.

The upper part of the Miller's Dale Beds is well exposed in Victory Quarry (loc. 30) [SK 0774 7693] 0.25 mile N.W. of Peak House, the lowest beds lying within a foot or two of the Dove Holes Tuff:

A section complementary to the above is that in Dove Holes Dale Quarry (loc. 31) [SK 0782 7748]. This shows the Dove Holes Tuff and some of the underlying beds:

The Dove Holes Tuff was originally described by Arnold-Bemrose (1907, p. 253) from a quarry near the Bull Ring, but this is now covered by tip. Farther east it is well seen in the section in Holderness Quarry (loc. 32) (Plate 3B) [SK 0842 7817];

The lowest beds of this section lie within a foot or two of the top of the Lower Lava.

The uppermost part of the Miller's Dale Beds is visible in the section (loc. 33, bed a) [SK 0799 7828] near the Bull Ring where 9.5 ft of pale grey fine-grained thick-bedded limestone with Gigantoproductus crassiventer and other brachiopods are overlain by Monsal Dale Beds (see p. 65). To the north of Near Ridge-close the Miller's Dale Beds and Chee Tor Rock are grouped together as the Bee Low Limestones.

Wormhill Moor and Hargatewall

To the south of Hargatewall the Miller's Dale Beds form a broad outcrop, approximating to a dip-slope. The best section [SK 1207 7482] near Hargate Hall, shows 11 ft of off-white fine-grained and finely crinoidal limestone with gastropods near the top. Another section [SK 1267 7475] near Wormhill Hall shows 5 ft of pale crinoidal and slightly oolitic limestone with shell debris.

To the north-west of Hargatewall a tongue-like area of Miller's Dale Beds is present beneath and around the outlier of Wormhill Moor. On the south-east side of this area the subdivision is thinly developed, only some 75 ft being present, while at the northern end, near Smalldale, the thickness is about 100 ft. The lowest beds, a few feet above the Lower Lava, are exposed in a roadside quarry north-west of Hargatewall (loc. 34) [SK 1120 7598]: 12 ft of off-white massive fine-grained limestone, slightly crinoidal with, in the top 6 ft, a fauna including Caninia benburbensis, Lithostrotion martini, P. murchisoni, Linoproductus sp., Monograptus sp. papilionaceus group and gastropods. On the western side of Wormhill Moor the Miller's Dale Beds are little seen, except for poor exposures of the lowest beds. At the northern end of the outcrop, however, near Smalidale, they are both well exposed and very fossiliferous. A section in a small quarry (loc. 35) [SK 0977 7700] is as follows:

Tideswell to Old Moor

To the south of Tideswell the Miller's Dale Beds form a broad spread between Heathydale Ward and Tideswell Dale. They are well exposed in the latter south of its junction with Litton Dale. The Litton Dale Borehole [SK 1599 7498] (see also pp. 50–53) proved the Miller's Dale Beds as pale limestones between the base of the Station Quarry Beds at 55 ft and the top of the Lower Lava at 152 ft 6 in.

To the west of Tideswell, exposures of pale massive fine-grained limestone of the Miller's Dale Beds are fairly frequent. An exposure (loc. 36) [SK 1402 7574] near Crossgate, starting some 30 ft above the Lower Lava, showed 18 ft of pale massive fine-grained limestone with Saccamminopsis? 3 ft from the top.

Between Wheston and Wall Cliff, the Miller's Dale Beds form a broad outcrop showing small exposures only of uniformly pale massive fine-grained limestone. These beds give rise to a marked feature at Wall Cliff where the section (loc. 28) (overlying the Lower Lava at about 1440 7726) continues that given on pp. 51–53:

The total thickness, 63 ft, of the Miller's Dale Beds is the minimum found in the area. The coral band at the base of the section is correlated with the Lithostrotion aff.maccoyanum band found above the Lower Lava at Castleton (Shirley and Horsfield 1940, p. 276) and in the Wye valley (Cope 1933, p. 132).

Between Wall Cliff and White Rake the Miller's Dale Beds are cut out by a strike-fault. They are, however, present between White Rake and The Cop, though displaced somewhat by Shuttle Rake and Moss Rake. A section [SK 1380 7875] near the base of the subdivision on Tideswell Moor shows 9 ft of pale fine-grained limestone.

To the north of Batham Gate the lowest part of the Miller's Dale Beds shows its typically fossiliferous character. A section [SK 1351 7939], over 0.25 mile W.N.W. of The Holmes, shows 2 ft of near-white fine-grained limestone with corals, Davidsonina septosa and productoids. Farther to the north-west, "at Cop Round" Shirley and Horsfield (1940, p. 276) record a coral band with Lithostrotion cf. arachnoideum and L. aff. maccoyanum about 20 ft above the base of the Miller's Dale Beds. The feature of Cop Round [SK 1302 8002] is formed by the lowest part of the Monsal Dale Beds and it would appear that Shirley and Horsfield were' referring to a locality a little west of this. The thickness of the Miller's Dale Beds hereabouts is about 80 ft.

To the north and north-west of Old Moor the Miller's Dale Beds are not separately recognized.

Bee Low Group (D₁): Northern area

Bee Low Limestones

Bee Low and Gantries Hill

The Bee Low Limestones are well displayed on Bee Low and, three-quarters of a mile to the east, on Lower Bee Low. To the east again of Lower Bee Low, the lowest beds are ill exposed. On Lower Bee Low a section [SK 1019 7920], starting about 200 ft above the base of the subdivision, showed 83 ft of pale massive fine-grained limestone. Farther west and probably slightly higher in the succession the following section (loc. 37) [SK 0970 7909] is exposed:

The lower of the two coral bands in this section is thus about 260 ft above the base of the Bee Low Limestones and the band is correlated with at least the lower part of the coral-bearing beds of Laughman Tor (see p. 47).

Separated from the above section by a fault and perhaps 50 ft higher stratigraphically, is a band [SK 0938 7903], 1 ft 3 in thick, with Davidsonina septosa and productoids. This band appears to be in that part of the succession where the Upper and Lower D. septosa bands occur, though it cannot be precisely correlated owing to faulting. The same band has also been located at the eastern end of the Bee Low Quarry section though again in the fault-zone. The section in the quarry (loc. 38) [SK 0922 7915] is as follows:

The field evidence suggests that the uppermost beds lie some 80 ft below the base of D₂. The medium grey limestone (i) is considered to lie at the horizon of the Lower Lava. The underlying occurrence of D. septosa would then be at the horizon of the Upper D. septosa Band.

To the south-east of Bee Low, an exposure [SK 0953 7868] near Lodesbarn shows fine-grained finely crinoidal and slightly oolitic limestone 2.25 ft on brown calcilutite 3.25 ft. The stratigraphical position of this exposure is difficult to estimate though it must be near the middle of the Bee Low Limestones. A similar calcilutite band has already been noted (see p. 46) near the top of the Chee Tor Rock at Upper End.

Exposures on both sides of the main road between Sparrow Pit and Peak Forest provide a good cross-section of the Bee Low Limestones. The lowest beds, perhaps 370 ft thick, are well exposed south-east of Harratt Grange and show in general a lithology typical of this part of the D₁ succession, though the lowest beds are somewhat oolitic e.g. [SK 1026 7966]. Higher beds are exposed in Haddocklow Plantation, the section [SK 0984 8024] being:

The upper band yielded D. septosa in the south-eastern corner of Haddocklow Plantation [SK 0992 8001]. The correlation of the two bands is on the basis of their position within the Di sequence.

Some 250 ft of limestones, intermittently exposed, overlie the Upper D. septosa Band. These contain, in Gautries Plantation [SK 0937 8058], a 16-in crinoidal band with sporadic D. septosa. This is tentatively correlated with the higher of the two D. septosa bands on Eldon Hill (see below).

The lowest part of the Bee Low Limestones is well exposed in Perry Dale where some 300 ft of these beds are present between the base of the subdivision and the point where lateral passage into apron-reef takes place. The lowest beds are finely crinoidal, though less so than the underlying Peak Forest Limestones. Within 200 yd of the reef margin the Bee Low Limestones develop thick lenses of shelly, poorly bedded limestone of reef type; such beds are referred to the transitional back-reef facies (see (Plate 11)) and an exposure of these is seen (loc. 39) [SK 1005 8087] on Gautries Hill:

Both in their geographical relation to the reef-belt and their well-bedded character, the limestones of this exposure should clearly be referred to the shelf succession. However, the rich brachiopod fauna and particularly the presence of a goniatite shows faunal affinities with the reef-belt.

On the south side of the summit of Gautries Hill the inward dips towards the shelf area, frequent at the margin of the reef-belt, are present. Such dips are, however, not developed in Perry Dale.

Eldon Hill to Windy Knoll

On Eldon Hill much of the Bee Low Limestones is present. The lower beds, 280 ft thick, were proved in the water borehole at Eldon Hill Quarry [SK 1128 8156] as pale fine-grained limestones. Higher beds are exposed in the quarry (loc. 40) [SK 1128 8134]:

The D. septosa band of this section lies some 300 ft above the base of D₁. The fossiliferous lenses are indicative of the nearness of the reef-belt.

Some 150 ft above the D. septosa band of the quarry, another band is present on the eastern side of Eldon Hill. This is well seen in an old quarry [SK 1218 8102]:

Over much of Eldon Hill, however, the higher band is ill defined. It was considered by Shirley and Horsfield (1940, p. 275) to be at or about the horizon of the Upper D. septosa Band of the Miller's Dale succession. The band or its horizon cannot, owing to probable displacement by Watt's Grove Vein, be traced into the proved succession at Ox Low, but the general geometry of the outcrop suggests rather that the D. septosa band of the quarry is the Upper D. septosa Band of the standard succession, and that the higher band, on Eldon Hill, represents the Lithostrotion aff. maccoyanum horizon.

On the south-west side of Eldon Hill the following section (loc. 41) [SK 1124 8077] shows beds at and below the Upper D. septosa horizon:

The concentration of algae below the Upper D. septosa Band recalls the same association as that in other localities, for example Upperend Quarry (see p. 46).

Beds above and including the Upper D. septosa Band are exposed on the flank of a hill east of Snels Low [SK 1157 8164]:

The coral band near the top of this section was correlated by Shirley and Horsfield (1940, p. 276) with the Lithostrotion aff. maccoyanum band but is here considered to lie at a somewhat higher horizon. Wolfenden (1958, p. 873) noted the presence of oolitic limestones "near the Cyrtina band" in this vicinity.

To the south and south-east of Middle Hill the Bee Low Limestones, mostly above the horizon of the Lower Lava, form a broad plateau. Some 100 ft above the horizon of the Lower Lava a quarry (loc. 42) [SK 1299 8194] 265 yd S.W. of Rowter Farm shows 18 ft of pale finely crinoidal limestone with a 1-ft band 12 ft above the base, with L. junceum colonies in position of growth and Plicochonetes sp. buchianus group. The band lies at or near the horizon of the higher D. septosa band of Eldon Hill.

Between Perryfoot and Eldon Hill the back-reef facies, often showing inward dips, is usually well developed. The Bull Pit [SK 1065 8142], east of Perryfoot, shows 55 ft of off-white to grey massive fine-grained limestone with coarsely crinoidal lenses and some corals and brachiopods. The same facies, here showing variable gentle dips towards the reef, is exposed in a quarry (loc. 43) [SK 1125 8163] opposite Eldon Hill:

Farther to the north-east a quarry (loc. 44) [SK 1208 8236] on the south side of Middle Hill also shows the back-reef facies:

From the vicinity of Oxlow House the back-reef facies extends northwards along the limestone margin to Windy Knoll. Here a quarry [SK 1261 8300] shows 32 ft of limestone, much of it crinoidal and with some breccia; the lowest 9 ft are very fossiliferous, with reef brachiopods and Davidsonina septosa. The top 6 ft of the limestone are impregnated by elaterite (see p. 308). The presence of Neptunian dykes at this locality has been noted on pp. 110–1. The beds with D. septosa were considered by Shirley and Horsfield (1940, p. 275) to be the lower of the two D. septosa bands of Eldon Hill, which is here correlated with the Upper D. septosa Band.

Castleton

To the west of Treak Cliff and in the Winnats gorge the back-reef facies is little developed or absent. The Bee Low Limestones in this area show their normal lithology, being pale, massive and fine-grained. In the Winnats a 1-ft band with sporadic D. septosa is developed [SK 1344 8264] at a horizon some 170 ft below that of the Lower Lava. The same fossil occurs sporadically in the succeeding 60 ft of strata. The band has been correlated by Wolfenden (1958, pp. 873–4) with the 'Cyrtina band' (i.e. the Upper D. septosa Band), but all the occurrences noted here appear to lie below this horizon.

To the south of Castleton the section in Cave Dale shows the most complete development of the Bee Low Limestones. The lowest beds are in the back-reef fades [SK 149 825] just south-east of Peveril Castle; these show relatively strong inward dips near the reef margin but are usually less crinoidal than the back-reef facies near Eldon Hill. A fauna of reef brachiopods is sparsely developed in these beds in places. The extent of the back-reef facies is shown on (Plate 11).

Some 100 ft of Bee Low Limestones of normal facies are present beneath the Lower Lava in Cave Dale.

The Lower Lava, absent over much of the northern outcrops, reappears locally in Cave Dale and continues westwards from thence to near Hurdlow Barn. In Cave Dale it is up to 25 ft thick and shows its normal amygdaloidal character. The Lower Lava thins rapidly northwards and disappears on the east side of Cave Dale but has been proved by boreholes to extend eastwards for a short distance (see (Plate 4)). As the lava disappears its place is taken by the Pindale Tuff described by Eden and others (1964, pp. 76–8; see p. 61 of this account). The disappearance of the Lower Lava was attributed by Shirley and Horsfield (1940, pp. 275–6 and 287) to its being cut out by an unconformity at the base of the "Miller's Dale Beds". This explanation is not accepted here as, although minor non-sequences are frequent near the reef margin, there seems no need to postulate anything other than the normal dying out of a flow, frequently observed in the district. The L. aff. maccoyanum band at the base of the "Miller's Dale Beds", on which the above authors' conclusion was based, appears to be patchily developed and is difficult to trace laterally.

In Cave Dale two sections show the beds above the Lower Lava. The first (loc. 45) [SK 1475 8215] 0.5 mile S.S.W. of Castleton church is as follows:

The coral band does not appear to persist laterally.

The second section [SK 1489 8219] shows a full development of the beds between the lava and the Monsal Dale Beds:

In the higher part of Cave Dale much of the beds above the Lower Lava are exposed. Near the top and some 60 ft below the base of the Monsal Dale Beds the following section (loc. 46) [SK 1416 8178] is exposed:

These beds lie some 60 ft below the base of D₂ and the fossil band would thus appear to be at or near the horizon of the coral band of Pin Dale (see below).

On Michill Bank the upper part of the Bee Low Limestones has been proved extensively. Borehole AF 4See also (Plate 4). Cores examined by Dr. D. V. Frost; record published by permission of Messrs. Earle Limited. [SK 1476 8188], showed the following succession:

A fuller development of the Pindale Tuff has been proved by other boreholes in the area (see (Plate 4)). The thin tuff at a slightly higher horizon is at about the position of that occurring above the Lower Lava in Cave Dale.

Pin Dale and Earle's Quarry

In this area the most important section is that in Pindale Quarry (loc. 47) [SK 1594 8231]:

Certain marginal features of the succession and the lateral passage to apron-reef are discussed on p. 108. The presence of chert in the D₁ limestones in this section is remarkable in view of its total absence in beds of this age elsewhere in north Derbyshire. The coral band is nearer to the top of D₁ than stated by Eden and others (1964, p. 78) but this is due in part to the placing of dark beds below the Lower Girvanella Band in D₂ in this account.

In Earle's Quarry the uppermost D₁ limestones have been extensively worked on the Lower Bench. Near the crusher house [SK 1612 8196] some 20 ft of massive grey limestones are exposed. Eden and others (ibid., p. 79) described these beds as having a maximum thickness of 53 ft in the quarry area. These beds overlie a group of darker grey limestones and overstep these in the vicinity of the tuff mound (see below) only some 10 ft of D₁ beds crossing the axis of the mound.

The Pindale Tuff was formerly seen in Earle's Quarry where it occurred as a cone with dips up to 30° on the flanks and reached to a height of 70 ft (Shirley and Horsfield 1940, p. 282). This cone is now obscured by tip but extensive drilling has shown the widespread nature of the tuff beneath the quarry area and also the presence of a second cone, lying to the north-west of the first. The borehole records are summarized in (Plate 5), which also shows generalized isopachs on the tuff. To the east of the quarry area the Pindale Tuff is represented in attenuated form in a cutting (see p. 109) within the reef-belt.

Monsal Dale Group (D₂)

Monsal Dale Beds below Upper Miller's Dale Lava

Near the southern margin of the district a thin development of dark limestone appears to be present locally beneath the Upper Lava, though exposures are lacking. These beds are in the position of the Station Quarry Beds of Miller's Dale (Cope 1937, p. 180); their presence is inferred from the topography, from debris on the outcrop, and from the relationships of the Station Quarry Beds to the Upper Lava on Hammerton Hill (One-inch Sheet 111) south of the present district. The Station Quarry Beds are of very limited extent within the Chapel en le Frith district, being faulted off near the junction of Tideswell Dale and Litton Dale and not developed again to the north of this point. They are included with the Monsal Dale Beds on the one-inch map. The examination of cutting samples from the Litton Dale Borehole [SK 1599 7498] (see also p. 55) is interpreted as showing the presence of pale grey and black limestones beneath the Upper Lava, between the depths of 8 and 14.5 ft. In view of this thin development the Station Quarry Beds may be expected to disappear at depth only a short distance north of the borehole.

Upper Miller's Dale Lava

Wormhill Moor

In this area the Upper Lava crops out around the base of an outlier of Monsal Dale Beds forming high ground between Bole Hill and Withered Low [SK 100 765]. The lava shows its maximum thickness of 100 ft at the southern edge of the outlier, but thins northwards to 10 to 15 ft on Withered Low. The southern outcrops are unusual in that two beds of limestone are present within the lava; the lower some 30 ft from the base near Hargatewall and the higher, near the top, at Bole Hill. The limestone bands are interesting in view of the difficulty in distinguishing different flows within the outcrops of both Upper Lava and Lower Lava.

Exposures showing the normal amygdaloidal character of the lava are lacking in this area though yellow clay or fragments of weathered lava have been observed in places. At Bole Hill [SK 1059 7543] a roadside exposure shows dark crystalline non-vesicular basalt interpreted, as in the case of similar features in the Lower Lava (see p. 52), as the central part of a flow.

Tideswell Dale to Old Moor

The Upper Lava crops out on the high ground east of Tideswell Dale though a short distance beyond the southern margin of the district it fails. The rapid dying out of the lava in Litton railway-cutting (One-inch Sheet 111) has been described by Cope (1937, p. 179). Near the junction of Tideswell Dale and Litton Dale [SK 1563 7484] the lava shows its normal amygdaloidal character. In this vicinity it appears to be at least 60 ft thick but it must thin rapidly eastwards for the Litton Dale Borehole [SK 1599 7498], starting near the top, showed only 8 ft of weathered lava (purple to grey clay).

The Upper Lava is faulted off at the junction of Tideswell Dale and Litton Dale but it reappears west of Tideswell though it is there rather thin and not exposed. Between Crossgate and Wall Cliff the only exposure [SK 1367 7676], near Wheston, shows dark crystalline non-vesicular lava. On the southwest side of Wall Cliff the lava thins and disappears, though it reappears farther to the east, where a small thickness of Upper Lava is present locally passing southwards into tuff. This was described by Arnold-Bemrose (1907, p. 253), as the Brook-Bottom Tuff. A section [SK 1438 7709] north-west of Highfield House shows amygdaloidal lava 1.5 ft on banded dark calcareous tuff. The tuff thickens southwards and another section [SK 1444 7702] shows 10 ft of dark banded calcareous tuff with dark cognate lapilli up to 0.75 in diameter. The tuff disappears rapidly eastwards across the valley and the lava is interpreted as having been cut out by strike-faulting between Wall Cliff and White Rake. On the south side of White Rake the lava is again present and 11 ft of it, deeply weathered, were exposed in an open working [SK 1480 7810] on the vein.

To the north of White Rake exposures of the Upper Lava are rare, though an excavation made in a sink-hole near the base of the bed [SK 1388 7909] near The Holmes showed yellow clay with blocks of tuffaceous limestone up to 1 ft across at from 7 to 15 ft below ground level. The weathered state of the exposure makes it uncertain whether these beds represent a bedded tuff at the base of the flow or whether the tuff and limestone were dragged up by the flow and incorporated in it. To the north of this locality the Upper Lava is little seen. At Cop Round the outcrop is conspicuous as a 'slack' beneath the scarp of the lowest part of the Monsal Dale Beds. The thickness here is about 20 ft. The lava is last seen on the north wall of an open working on the vein-plexus of Oxlow Rake [SK 1350 8087]. This shows the lowest part of the Upper Lava, much weathered, as 4.5 ft of yellow clay, resting on limestone. Traced northwards from here, the lava thins rapidly and disappears.

Lower Monsal Dale Beds

Dove Holes

At Dove Holes (Figure 7) the Lower Monsal Dale Beds are present between Peak House and Near Ridgeclose. The best section, in Victory Quarry (loc. 30) top at [SK 0748 7702], continues that described on p. 54:

The shell bed at the top of the section is traceable for some 400 yd northwards from this locality, cropping out again [SK 0748 7734] 110 yd N. of Lower Bibbington. The dark limestones at the base of the Monsal Dale Beds are a feature of the whole of the outcrop at Dove Holes.

The section [SK 0799 7828] (loc. 33) along the old Peak Forest railway at Dove Holes shows the lowest part of the Monsal Dale Beds:

When traced northwards the uppermost dark limestones of this section and the lowest 8 ft or so of the overlying beds are replaced laterally by a knoll-reef (loc. 48) [SK 0797 7866] west of Near Ridgeclose; this shows up to 24 ft of pale grey often coarsely crinoidal limestone with a rather poor fauna, including L. martini, A. hindi wettonensis, G. crassiventer and G. dentifer. To the north of the knoll a coral band (loc. 49), probably in the position of that at the top of bed (d) of locality 33, yields Diphyphyllum lateseptatum and L. martini. The overlying limestones yield Gigantoproductus giganteus cf. crassus and G. crassiventer.

Barmoor Clough and Sparrow Pit

This outcrop (Figure 7) is nearly continuous with that of Dove Holes and shows a similar development of dark limestones, up to about 20 ft in thickness, at the base. The higher beds are pale, well-bedded limestones with two knoll-reefs. The dark beds are well seen in small exposures near the road junction at Barmoor Clough. A short distance to the east a section (loc. 50) [SK 0789 7949] at the limestone-shale boundary, is as follows:

The occurrence of the P₁ goniatite Girtyoceras shows the presence of a small area of beds of basin facies at this locality.

The old Barmoor Clough Quarry, east of Bennetston Hall, shows the top of the dark limestones and the succeeding beds; a knoll-reef, developed in the latter on the eastern side of the quarry, complicates the section. At the northern end of the quarryNow filled in.(loc. 51) [SK 0881 7988] the sequence is as follows:

The highest beds form part of the western margin of the knoll-reef. In the middle part of the quarry a non-sequence develops within bed (h) and results in the cutting out of 7 ft of the underlying beds. Another section of the knoll nearby [SK 0878 7977] shows 10 ft of pale grey strongly banded reef-limestones, the top 4 ft conglomeratic, resting on grey normal-bedded cherty limestones, 3.25 ft. A small quarry (loc. 52) [SK 0890 7981] at the eastern end of the knoll, shows the following section:

The presence of the fish Cladodus suggests that this is the locality from which Jackson (1908, p. 309) recorded "Psammodus rugosus" and "Psephodus magnus".

The greatest thickness of Lower Monsal Dale Beds in the vicinity is some 0.5 mile south of Sparrow Pit where it is about 200 ft. The highest beds are exposed in a small quarry [SK 0900 8025] some 0.33 mile S. of Sparrow Pit: grey-brown thin-bedded cherty limestone, somewhat crinoidal and shelly, algae investing shell debris in top 3.5 ft, on pale grey-brown well-bedded granular oolitic limestone, slightly crinoidal, 3.5 ft. The position of the algal horizon compares with the average position of the Upper Girvanella Band (125 ft above base of Monsal Dale Beds at Pin Dale and 300 ft up in Cressbrook Dale) with which it is tentatively correlated.

To the north of the last locality the thickness of the exposed Lower Monsal Dale Beds decreases steadily. The lower, dark beds persist but the higher strata pass laterally into crinoidal knoll-reef limestones forming the crest of a small hill at Sparrow Pit. An exposure [SK 0915 8082] 175 yd N.E. of the crossroads at Sparrow Pit shows grey-brown poorly bedded shelly reef limestone 5 ft, on dark bituminous crinoidal limestone. A little to the north [SK 0918 8098] the Monsal Dale Beds are cut out by the unconformity at the base of the Namurian.

Wormhill Moor

In this area the lowest 50 ft of the Monsal Dale Beds forms an outlier. Here pale limestones usually overlie the Upper Lava though in one place [SK 1040 7624] a foot of dark grey limestone is exposed in this position.

A quarry (loc. 53) [SK 1059 7552] on Bole Hill provides the only good section:

Cressbrook Dale

This dale provides the best, though not continuous, section of the beds below the Litton Tuff in the southern part of the area. The lowest beds consist of dark, thin-bedded cherty limestones. These strata are generally rather poorly exposed. Shirley and Horsfield (1945, p. 297) give the thickness as 80 ft, which is accepted here. The main outcrop lies south of where White Rake crosses Cressbrook Dale and the dark beds also occur as a faulted inlier in the lower part of Tansley Dale and for some 300 yd from its confluence with the larger dale. Shirley and Horsfield also noted the presence of Saccamminopsis sp. at two horizons in the dark limestones, the lower at the base being the better exposed, while the upper band "about 50 feet higher" was known only at the northern end of Litton Frith. The lower band was noted in an exposure by a footpath [SK 1734 7435] on the eastern side of the dale. The section (loc. 54) [SK 1716 7437] at Litton Frith shows the lowest Dart of the Monsal Dale Beds:

This section shows both the lower and higher Saccamminopsis horizons noted by Shirley and Horsfield, the latter 45 ft from the base of the Monsal Dale Beds. There is also a similar band 39 ft from the base. The succeeding beds, some 120 ft thick, consist of pale chert-free limestones. Some 22 ft above the base of the pale beds the shell bed (loc. 55c), noted by Shirley and Horsfield (1945, p. 297) as containing Striatifera striata, can be traced from near the southern margin of the district along both sides of the dale. This fossil has not been confirmed in the shell bed though it has been found just above (loc. 55d).

Near Peter's Stone a thin lava, whose presence was noted by Arnold-Bemrose (1907, p. 255), is present for a distance of some 400 yd along the dale sides close beneath the Litton Tuff. The most complete section (loc. 55) of the Lower Monsal Dale Beds hereabouts [SK 1725 7490] about 0.5 mile S.S.W. of Littonfields, is as follows:

The following section [SK 1729 7506] supplements that given above so far as the relationship of the lava to the Litton Tuff is concerned:

Shirley and Horsfield (1945, p. 295) show the lava as reaching a thickness of 20 ft. In that part of Cressbrook Dale south of Tansley Dale the lava is absent. A section here [SK 1754 7465], starting some 75 ft above the horizon of the shell bed, is as follows:

Litton, Tideswell and Brook Bottom

In this area the beds below the Litton Tuff are in general poorly exposed. The dark beds at the base are present on the southern edge of the district south-west of Litton, but die out rapidly northwards. Debris of dark limestone with corals was seen [SK 1582 7443] in this area. In Litton Dale the dark limestones are apparently absent but they reappear in the northern part of Tideswell village (see below). As in Cressbrook Dale the overlying beds consist of pale and apparently everywhere non-cherty limestones though these are seen only in scattered small exposures. Some 50 ft above the Upper Lava a coral band is exposed (loc. 56) [SK 1584 7468] in Litton Dale; this consists of a 9-in coral-bearing bed below and, 3 ft higher, a similar 12-in bed. Both beds yield L. junceum. The strata above are seen in small exposures of predominantly pale crinoidal limestones south-east of Litton Dale e.g. [SK 1658 7497]. Between Litton and Tideswell some darker beds make their appearance in the middle of the Lower Monsal Dale Beds; these also are only seen in small exposures e.g. [SK 1585 7522].

The upper part of the Lower Monsal Dale Beds was passed through in the Littonfields BoreholeRecord from examination of cutting samples by Professor F. W. Shotton. [SK 1751 7595]:

To the west of the Tideswell–Brook Bottom valley beds low in the D₂ Zone crop out in an elongated tract. The nature of the lowest beds is uncertain south-west of Tideswell though 3 ft of pale limestone were seen 30 ft above the base [SK 1461 7556] near Summer Cross. On the western edge of the outcrop, dark beds make their appearance near Crossgate [SK 1435 7597] where 1.5 ft of dark limestone are present 5 ft above the Upper Lava. A section (loc. 57) [SK 1425 7610] near Crossgate shows the junction of the dark limestones and overlying beds:

To the north of the last locality the dark limestones may be traced as far as Water Lane [SK 1384 7680], north of which they disappear, probably by lateral passage. The beds overlying the dark limestones are exposed in a small quarry (loc. 58) [SK 1383 7669]:

Higher beds, grey to pale grey limestones e.g. [SK 1473 7598] and pale crinoidal limestones e.g. [SK 1448 7631], both chert-free, form a marked dip-slope between the last described exposures and the lip of the Brook Bottom valley.

In Brook Bottom the dark limestones at the base of the Monsal Dale Beds are traceable from the outskirts of Tideswell [SK 1501 7604] to a point [SK 1449 7717] a little north of Highfield House where they pass laterally into pale limestones. The best section (loc. 59) [SK 1473 7638] is as follows:

The position of the lowest 3.5 ft of beds in this section is in some doubt, but these have been referred on lithological grounds to the pale facies of the Lower Monsal Dale Beds; they are, perhaps, the first indication of the southward failure of the dark beds at Tideswell which has already been noted (p. 69). Farther north, the dark beds thin; a shaft [SK 1454 7663] to the sough at the eastern end of Edge Rake, which started near the top of these, proved only 20 ft of limestones overlying 'toadstone'. To the south-west of Highfield House the dark beds bear a Saccamminopsis band at their top [between 1448 7673 and 1445 7683]. This band has also been found [SK 1450 7703] north of Highfield House in the following section (loc. 60):

To the south of Wall Cliff, a section [SK 1377 7723] shows pale beds close above the Upper Lava:

Wall Cliff to The Holmes

Between Wall Cliff and White Rake the lowest part of the Lower Monsal Dale Beds is apparently cut out by a strike fault. Some exposures of higher beds close beneath the Litton Tuff are present south of Tides Low. These show grey limestones e.g. [SK 1503 7758] and grey to pale grey crinoidal limestones e.g. [SK 1488 7754] both non-cherty. Open workings in White Rake show the following section (loc. 61) [SK 1474 7814] in the north wall:

The base of the section lies some 10 ft above the Upper Lava. Immediately to the northwest of this locality a parting of grey clay, possibly weathered tuff, perhaps some 3 to 5 ft in thickness, has been proved in auger holes. The base lies some 15 ft above the Upper Lava and the clay bed extends laterally for some 250 yd.

Between Maiden Rake and Shuttle Rake the lowest Monsal Dale Beds form a strong scarp above the Upper Lava. A section of these beds (loc. 62) [SK 1436 7860] west-northwest of Bushyheath House is as follows:

Near Shuttle Rake a small exposure [SK 1416 7903] shows 1 ft of dark limestone some 20 ft above the Upper Lava but there is sufficient exposure in the vicinity to show that this is exceptional. Higher beds, seen in a number of exposures north of Bushyheath House, consist of pale grey limestones, non-cherty and often massive.

Near The Holmes the Lower Monsal Dale Beds appear to be only some 100 ft in thickness. A section (loc. 63) near the base [SK 1403 7918] is as follows:

A section (loc. 64) starting some 50 ft above the Upper Lava exposed nearby [SK 1411 7920] shows 6 ft of pale grey massive limestone with a 1.5 ft band 3 ft from base, bearing Dielasma hastatum, L. sp. hemisphaerieus group and Productus productus.

Bradwell Moor

At Cop Round the basal Monsal Dale Beds form a conspicuous scarp and are well exposed. Here [SK 1302 8002] 11 ft of near-white fine-grained limestones crop out close above the Upper Lava. Another section of the lowest beds (loc. 65) [SK 1336 8060] is: grey-brown finely bioclastic and oolitic limestone with a colony of L. maccoyanum 1.25ft, grey-brown fine-grained limestone 1.5 ft, on grey-brown finely No-elastic and oolitic limestone 2 ft.

To the north of Dirtlow Rake the recognition of the Upper Girvanella Band in boreholes and surface exposures has made the stratigraphical relations of the Lower Monsal Dale Beds clearer than in the part of Bradwell Moor to the south. The Lower Girvanella Band is probably represented in a small exposure [SK 1417 8149] showing grey-brown finely bioclastic limestone 5 ft thick with algae at 2 ft from base. The section on the south-east side of Cave Dale top of section [SK 1493 8218], continuing that given on p. 60, shows the lowest beds:

Farther east, beds near the base of the Monsal Dale Beds are also seen just north of Dirtlow Rake [SK 1526 8211]: pale crinoidal limestone, coarse in lower half, 3 ft 10 in, on pale massive limestone with a little crinoid debris, finely banded and sorted towards top, 10 ft 6 in. The only other exposures worthy of note in this area lie a little below the Upper Girvanella Band. These include a small knoll-reef (loc. 66) [SK 1440 8149] showing 10 ft of pale massive fine-grained limestone with some calcite veining; the fauna includes Lithostrotion decipiens, a large colony of L. junceum and brachiopods including Eomarginifera tissingtonensis cambriensis. The knoll is apparently on the horizon of the "third pale coloured calcirudite" noted by Eden and others (1964, p. 85) close below the Upper Girvanella Band in Earle's Quarry. A nearby exposure [SK 1436 8147] of beds just underlying the knoll, shows dark bituminous limestone 2 ft, on pale to medium greylimestone with shells and corals, some silicified, 1.25 ft. Dark beds in this position are not frequent in the Lower Monsal Dale Beds but have been noted (ibid., p. 80) in Earle's Quarry No. 4 Borehole.

The most complete section of the Lower Monsal Dale Beds in the area north of Dirtlow Rake is provided by Messrs. Earle's Borehole AF 4See also (Plate 4). Cores examined by Dr. D. V. Frost.(loc. 67):

Pin Dale and Earle's Quarry, Hope

The Lower Monsal Dale Beds have been proved in a large number of boreholes by Messrs. Earle and are also well seen in Pindale Quarry and Earle's Quarry (see (Plate 5)). These beds show non-sequences at several horizons, more acute as the margin of the reef-belt is approached, and there is also much lateral variation within individual beds. The main features of the stratigraphy have been described by Eden and others (1964).

The section in Pindale Quarry (loc. 47) (Shirley and Horsfield 1940, pp. 284–6) shows much of the Lower Monsal Dale Beds (see also p. 61). The section refers, for the greater part, to the southern end of the quarry top at [SK 1581 8216] where the sequence is most complete. Most of the section, except for the lowest and some of the middle beds, is inaccessible and this part has been compiled from observation of the quarry face, from borehole recordsEarle's Quarry No. 7, see Eden and others (1964, pp. 114–6); Earle's Quarry No. 8. close behind the face and from the account by Eden and others (1964):

The lowest item (g) appears to be a local development, probably filling a slight hollow in the underlying Bee Low Limestones, as it is not elsewhere developed. Beds (j-m) constitute the "first calcirudite" of Eden and others. The unconformity within the latter (noted by Shirley and Horsfield 1940, p. 284, fig. 1) cuts out all the lower D₂ beds at the north end of the quarry. The overlying beds of the "first calcirudite" (k-m) pass northwards into pale shelly flat-reef limestones as the reef-belt is approached. Compared with the unconformity the two non-sequences noted are slight, the lower cutting out up to 3 ft of the underlying bed and the upper up to 1 ft.

To the east of the entrance to Pin Dale the lateral passage of beds low in the D₂ sequence into apron-reef limestones (see p. 108) takes place at the crest of the slope above Upper Jack Bank Quarry. A little to the south the large excavation of Earle's Quarry again shows the base of the Monsal Dale Beds. A section (loc. 68) at the south-east end of Upper Jack Bank Quarry [SK 1620 8208] (Eden and others 1964, pp. 99, 105) shows the lowest beds:

The irregular nature of the Lower Girvanella Band is shown by its absence in a section (loc. 69) [SK 1620 8202] only 60 yd to the south:

In the main quarry (loc. 70) the succession in the Lower Monsal Dale Beds has been described in detail by Eden and others (1964, pp. 81, 85) and may be summarized as follows:

The above general succession is supplemented by the selected borehole records shown graphically in (Plate 5). In addition two sections in the lowest beds are worthy of note. The first (loc. 71) was measured by R. A. Eden in a small pillar [SK 1622 8191] (ibid., pp. 99, 105), left by quarrying adjacent to the tuff mound and now tipped over:

Beds (j-l) represent the "first calcirudite". The underlying beds are somewhat thicker than normal; it may be that, as has been suggested for the Pindale Quarry section, the two lowest beds fill a slight hollow in the underlying strata.

To the south-east of Wilson's Monument and the site of the tuff mound (see pp. 61–2) important unconformity is present at the horizon of the Upper Girvanella Band. This cuts out up to 30 ft of the underlying beds and is most acute in the vicinity of the tuff mound. The unconformity is attributed by Eden and others (ibid., p. 78) to later folding on the axis of the mound. This interpretation agrees with the relations in Monk's Dale where two vents are present on the line of a local sharp fold (see p. 323).

The easternmost section (loc. 72) in Earle's Quarry [SK 1643 8189] shows the lowest part of the Monsal Dale Beds adjacent to the reef-belt:

The highest bed (j), representing the "second calcirudite" appears to join the overlying "third calcirudite" to form a composite mass of flat-reef limestones which can be followed for some 200 yd eastwards from this section. Northwards the flat reef passes laterally into apron-reef. The "first calcirudite" is represented in the section by bed (c).

To the south of the quarry area an outcrop of Lower Monsal Dale Beds is present though the limits of this are uncertain. With the exception of Nether Cotes boreholes NC6 to NC8 (see (Plate 5)) there is little information on the detailed stratigraphy of this tract and the relationships are complicated by the lateral passage of the standard limestones into basin facies (see also p. 91) with the development of dark cherty limestones.

Litton Tuff

Cressbrook Dale

The outcrop of the Litton Tuff is well marked though exposures are poor and infrequent. Due east of Litton the tuff (loc. 55q) overlies the beds listed on p. 67, and is some 42 ft thick; the northernmost part of the outcrop [SK 1732 7536] shows only some 25 ft of tuff. The landslip feature of Peter's Stone is due to the slipping of the overlying beds on the Litton Tuff.

Litton

The tuff reaches its maximum development of 100 ft on the slopes north and north-east of the village, the overlying limestones giving rise to a strong feature. Exposures are present in the roadside between Peep o'Day and Litton village, one [SK 1682 7518] close below the top showing 12 ft of weathered brown tuff. A trench [SK 1676 7517] in the roadside 0.25 mile E.S.E. of Stemdale House showed greenish brown calcareous tuff with vesicular cognate lapilli and bombs up to 5 in diameter. The thickness of the tuff at Litton and the presence of the coarse ejectamenta strongly suggest proximity to the source of the deposit.

To the north-east of Litton, the Littonfields Borehole [SK 1752 7596] proved the tuff between 269.5 and 280 ft. The uppermost 8.5 ft were not recovered, but the lowest 2 ft were a pale grey fine-grained tuff. Wardlow Mires No. 1 Borehole [SK 1850 7553] (see pp. 91, 93) proved grey-blue fine-grained tuff 2 ft 6.5 in thick at 452 ft; records of boreholes and shafts north of here show the tuff to be absent.

Tideswell to Tideswell Moor

From the type locality the outcrop of the Litton. Tuff extends north-westwards and then northwards as a conspicuous slack which is traceable as far as Bushy Heath where the tuff dies out. In general exposures are lacking, though there are shows of yellow clay in places. In this area the Litton Tuff has been seen in trenches. In the main A 623 road [SK 1525 7663] to [SK 1529 7661] weathered brown igneous rock was encountered. Another section on a side-road [SK 1529 7641] to [SK 1521 7639] showed weathered tuff, very fine-grained and limonitic in places.

Upper Monsal Dale Beds

Middleton Dale

Here much of the upper part of the Upper Monsal Dale Beds is continuously exposed (see (Figure 9)). Detailed sections at three places are given below to illustrate the succession, and these and supplementary sections are shown on (Figure 10). The sequence was first described by Morris (1929, pp. 37–67), some of whose strati-graphical terms are retained. Two shell bands, here termed the Lower and Upper Shell beds, are traceable over much of the dale and form convenient datum-horizons. The bed of white calcilutite termed the "White Bed" by Morris (ibid., p. 47–8) is also a useful datum, and near the top of these beds the Orionastraea

Band has been followed over part of the section (see (Figure 10)). Towards the western end of the date the section (loc. 73) in Furness Quarry [SK 2085 7596] is as follows:

The two erosion surfaces in items (a) and (b) lie near the horizon of the Lower Shell Bed and one or other may be responsible for its absence (see also p. 81). The Black Bed (d) is thin compared with the sections quoted below.

Farther down the dale, the section (loc. 74) at Shining Cliff [SK 2184 7582] (Plate 1) is as follows:

This appears to be the type section for Middleton Dale described in detail by Morris (1929, pp. 45–8); Shirley and Horsfield (1945, p. 294) suggest that the succession is a condensed one. (Figure 10) shows that the local thinning of the upper part of the succession is restricted to the beds just above the White Bed and is best explained by the presence of a local non-sequence at this horizon, though this is difficult to observe in any one section (see also p. 81).

The third detailed section in Middleton Dale is that at Castle Rock (loc. 75) [SK 2247 7569]:

Shirley and Horsfield (ibid., p. 294) record Orionastraea cf. indivisa from "90 feet above the roadway"; this is about 45 ft above the Upper Shell Bed.

The cliff section (loc. 76) in Stoney Middleton [SK 2279 7560] 0.5 mile E.N.E. of Highfields Farm shows the highest beds in a more accessible position than at Castle Rock:

The section starts about 2 ft above the Upper Shell Bed.

The most important features of the succession in Middleton Dale are summarized below and should be read in conjunction with the detailed sections already given (see also (Figure 10)):

(1) Beds below the Lower Shell Bed. These are present in the floor of the dale from the vicinity of Hanging Flat to Castle Rock. The greatest thicknesses are seen at Shining Cliff (see p. 78) and in Eyam Quarry [SK 211 756]. The latter shows some 46 ft of limestone, mainly pale massive and crinoidal, below the Lower Shell Bed. The relations of these beds to the underlying but unexposed basalt of the Middleton Dale Borehole are discussed on p. 96.

(2) The Lower Shell Bed "Lower Giganteus Bed" of Morris (1929, p. 45) is recognizable throughout the dale east of the longitude of Farnsley Farm. To the west it cannot be recognized with certainty, but it is probably thinly developed in a section west of Hanging Flat.

(3) The beds between Lower and Upper Shell beds are about 35 to 40 ft thick, and consist of pale massive limestones with a bed of dark bituminous limestone up to 5 ft at, or just below, the middle; this may be conveniently termed the 'Black Bed'. The "Lonsdaleia Bed" of Morris (ibid., pp. 42, 46) lies some 3 ft above the dark limestone but appears to be only locally developed.

(4) The Upper Shell Bed ("Hemisphaericus Bed" of Morris ibid., p. 46) is traceable around most of the dale but may be seen to fail in Eyam Quarry. In Furness Quarry also the bed was absent, but farther west it probably reappears.

(5) The beds between the Upper Shell Bed and the White Bed, 20 to 25 ft thick, are pale massive limestones showing the incoming of chert in the upper half, most of the beds above this horizon being cherty. The appearance of chert occurs at about the same horizon throughout the considerable distance covered by the dale.

(6) The White Bed, where fully developed, is up to 7 ft thick, and is so called from its white weathering, a feature which causes it to be very evident on the cliff sections. In many places this bed weathers more rapidly than those above and below and it forms a horizontal gash in the natural sections. The White Bed is absent at Castle Rock where Shirley and Horsfield (1945, p. 294) considered that it had been cut out by the overlying "Hackly Bed". The uppermost part of the bed may be seen to fail before the lower on the west side of Castle Rock, which indeed suggests the cutting out of the bed. The section at Castle Rock shows no evidence of the "conglomerate" noted by Shirley and Horsfield (ibid., p. 294) and the record may be due to the deceptive appearance of fragments of the overlying bed resting on a slightly eroded surface or on a stylolitic bedding plane. Farther east, the White Bed reappears in the cliff at Stoney Middleton.

(7) The beds above the White Bed are 75 ft thick where fully developed, though only 53 ft 7 in at Shining Cliff. They are massive cherty limestones with an irregularly weathering bed (the irregularities being due to a large number of random small joints), the "Hackly Bed" of Morris (op. cit., p. 48), at the base. The Orionastraea Band, normally some 50 ft above the base, has been traced from Furness Quarry to Eyam Dale. It has not been found at Shining Cliff though Shirley and Horsfield (1945, p. 294) record O. placenta from this horizon "at a point intermediate between this (Castle Rock) and Shining Cliff and about 20 ft above the 'White Bed' of Morris". The Lonsdaleia duplicata Band is present in Furness Quarry 27 ft below the Orionastraea Band and may be represented at Shining Cliff by the Dibunophyllum off. muirheadi Bed of Morris, though this does not appear to continue far along the section. Near the top a higher band with Lonsdaleia duplicata duplicata is present locally a few feet above the Orionastraea Band and would appear to be the lateral equivalent of the higher of the two Orionastraea bands of the Coombs Dale section (see p. 82). The thickness variation noted above appears to affect the lowest part of these beds only and is attributed to the presence of a non-sequence rather than to the condensation of the sequence suggested by Shirley and Horsfield. The non-sequence cannot, however, be directly observed in the sections. At the eastern end of Middleton Dale the bedding of this group of strata becomes rather irregular, individual beds thinning and thickening, though this does not affect the overall pattern of the group as a whole.

Cutting out of beds beneath the Eyam Limestones cannot be observed in Middleton Dale though a strongly potholed surface is present at the junction in Stoney Middleton.

Coombs Dale and Middleton Moor

In the part of Coombs Dale falling within the present district, exposure of the Upper Monsal Dale Beds is much less complete than in Middleton Dale. The best sections are at the junction of a southern tributary dale with the main dale. The highest beds are seen at a cliff (loc. 77) on the eastern side of the tributary dale [SK 2239 7429]:

The lower coral band (c) appears to represent the main Orionastraea horizon of Middleton Dale and Bradwell Dale. Some 75 ft of little-exposed beds separate the dark limestone (a) from the lowest beds exposed in the floor of the dale (loc. 78) [SK 2222 7436]:

The dark limestone beneath the main Orionastraea Band is developed on both sides of Coombs Dale for 0.25 mile north and to the west of the junction with the tributary dale.

Between Coombs Dale and Middleton Dale high Monsal Dale Beds (apparently all in the pale cherty limestones of the Middleton Dale sequence) occupy an undulating plateau.

This shows few sections of importance, though recent excavations at Messrs. Glebe Mines' Cavendish Mill showed the following section (loc. 79) [SK 2054 7534]; Eyam Limestones (see p. 101) on 16 ft of pale limestones, part cherty with a l.5-ft band at 8 ft from base with Diphyphyllum lateseptatum, L. junceum and L. pauciradiale. The same band, or one close to this horizon, is exposed (loc. 80) near the head of Middleton Dale [SK 1980 7616]; pale cherty limestone 5 ft, with abundant corals, including Dibunophyllum bipartitum bipartitum and D. bipartitum craigianum, in top 1.75 ft. The horizon is about 25 ft below the Eyam Limestones and the band is referred to the main Orionastraea horizon.

Cressbrook Dale

In this dale the Upper Monsal Dale Beds can be divided naturally into two groups at the horizon of the Hob's House Coral Band. The lower group consists of some 60 ft (see Littonfields Borehole, p. 84) of limestones, dark at the base and in general poorly exposed. These beds correspond to a more extensive development of dark limestones north of Litton (see p. 85). The Upper Girvanella Band at the base was recorded by Shirley and Horsfield (1945, p. 297) "on the west side of the wall at the foot of the slope" (loc. 81) [SK 1731 7537]. The thickness of the exposed part of the band is here about 1 ft, the lower beds immediately above the Litton Tuff being unexposed. During the present study the Upper Girvanella Band, 5.5 ft thick and consisting of dark limestones with Girvanella, was seen (loc. 82) close above the Litton Tuff [SK 1715 7426] 0.33 mile S.W. of Littonfields.

On the east side of Cressbrook Dale the following section (loc. 55) continues that given on p. 67 top of section at [SK 1736 7512]:

The thickness of dark limestones in this group of strata is less than in the Litton-fields Borehole and they decrease farther southwards and are difficult to recognize on the southern limit of the district west of Wardlow Hay.

The beds above the horizon of the Hob's House Coral Band are exposed in the north-eastern part of the dale (loc. 83) [SK 1736 7538]:

The Hob's House Coral Band is underlain by 11 ft of pale massive limestone and then by 40 ft of dark limestones, cherty in part and containing the Upper Girvanella Band of locality 81 at their base.

Shirley and Horsfield (1945, p. 297) considered that a "bed 4 feet thick, with weathering along irregular small joints" at "about 14 feet" below the Eyam Limestones represented the 'Hackly Bed' and D. aff. muirheadi Bed of Middleton Dale; this correlation is rejected here (see (Plate 7)).

On the eastern side of Cressbrook Dale a crag (loc. 84) [SK 1737 7494] yielded a fish-tooth, Psephodus?, from about 5 ft below the Hob's House Coral Band.

Litton and Hucklow Moor

In this area the Upper Monsal Dale Beds occupy a broad tract with few large exposures. The subdivision into a lower group of dark limestones and a higher group of pale limestones made in Cressbrook Dale (see p. 83) still holds, and the outcrops of these subdivisions are considered separately below. Nearly all of the Upper Monsal Dale Beds was passed though in the Littonfields Borehole and all of the group in two percussive boreholesInformation from examination of cutting samples by Professor F. W. Shotton. also made by the Derwent Valley Water Board, near Great Hucklow. The record of Littonfields Borehole (loc. 85) [SK 1751 7595] may be summarized:

The section compares closely with that of the Wardlow Mires No. 1 Borehole. The lowest item is the lower, dark subdivision. As the dark bed at 113 ft 7 in is correlated with the Black Bed of Middleton Dale, the contention of Shirley and Horsfield (1945, p. 297) that the uppermost 40 ft of the Shining Cliff succession are missing in Cressbrook Dale cannot be accepted.

At outcrop the lower group of dark limestones, about 60 ft thick, is traceable over the whole of the tract. Exposures are mainly of the lowest beds in the feature of Litton Edge above the Litton Tuff. The lithology varies from grey well-bedded limestones [SK 1659 7538] to dark crinoidal and shelly limestones [SK 1605 7583] and dark cherty limestones [SK 1590 7644]. Exposures of these beds can be seen in open workings along Tideslow Rake [SK 1520 7798] to [SK 1564 7792] showing dark thin-bedded cherty limestones with some crinoidal and shelly bands. Farther north a section (loc. 86) [SK 1512 7940] on the north side of Shuttle Rake shows beds near the top of the dark limestone group:

The upper pale beds are cherty at the top and mainly non-cherty below. For the most part, good sections are rare in this area, the best being near the top of the Monsal Dale Beds in the small dale extending north-westwards from the site of the Littonfields Borehole. A section here [SK 1717 7639] is as follows:

The lower part of the pale beds is less well exposed. The lithology varies from grey limestone with rolled shell debris [SK 1625 7750] to grey well-bedded limestone [SK 1677 7632]. Farther north, old open workings on High Rake show a number of sections, mainly on the northern (downthrow) side exposing grey cherty limestones in the upper part of the pale beds [SK 1673 7785]; [SK 1632 7778]. To the north of Tideslow Rake [SK 1573 7825] a section shows some of the lower part of the pale beds: grey granular limestone with bands of shells, some rolled, 11 ft.

Beds close below the Eyam Limestones are seen in a section (loc. 87) in a dry valley south-east of Little Hucklow [SK 16507813]:

The presence of dark limestones, high in the Monsal Dale Beds, should be noted here; their incoming recalls a similar development at the north end of Bradwell Dale (see p. 91). The coral band is the Orionastraea Band (Shirley and Horsfield 1945, plate xviii).

To the north of Shuttle Rake the upper pale limestones bear some chert in their lower part, for example near Berrystall Lodge [SK 1508 7989]. Higher beds are well seen in the upper part of Intake Dale [SK 1614 7949] as pale cherty limestones. A section (loc. 88) in a small dale joining Intake Dale [SK 1626 7986] shows the Orionastraea Band:

The section is important as being the locality where the relationships of the Orionastraea and L. duplicata bands can be best established (see also Shirley and Horsfield 1940, p. 277). The occurrence here of L. foriformis floriformis in the L. duplicata Band is exceptional (see p. 138).

On the southern side of Intake Dale the relation of the Orionastraea Band to the Eyam Limestones is shown in the following section [SK 1635 7966]:

The Orionastraea Band has evidently been subjected to considerable winnowing by current action here.

To the north of Intake Dale the Orionastraea Band has been traced to Earl Rake where an exposure (loc. 89) [SK 1619 8007] yielded Lithostrotion portlocki (a common associate of Orionastraea). Farther north a series of exposures of high Monsal Dale Beds is provided by Hartle Drake and Jenning's Dale; these show pale limestones, cherty in places and with some crinoidal bands. An exposure (loc. 90) [SK 1616 8046] at the western end of Hartle Dale is as follows:

The coral band was considered by Shirley and Horsfield (1940 plate xviii), to be the Orionastraea Band but it is certainly at a lower horizon and may represent the Lonsdaleia duplicata Band.

Bradwell Moor

Over much of this area exposure is poor. On the western side the presence of some dark limestones at the base of the subdivision is indicated by scattered exposures. These beds, with the Upper Girvanella Band, are well seen on the northern side of Dirtlow Rake (loc. 91) where a section [SK 1449 8155] in old open workings south-east of Hurdlow Barn shows the following:

The Upper Girvanella Band, 2 ft thick, is also exposed (loc. 92) [SK 1484 8186] at a point a little north of Dirtlow Rake. In the area north of Dirtlow Rake, the band is succeeded by some 20 ft of dark limestones and these by a small knoll-reef [SK 145 817].

The beds between the lowest dark limestones and the L. duplicata Band are little exposed, and knowledge of them is largely from boreholes. A detailed log of a typical hole (No. BM 27) and a partial log of another (No. BM 28) have already been published (Eden and others 1964, pp. 107–10) and these and other typical records are shown graphically in (Plate 8). An exposure (loc. 93) [SK 1424 8045] about 100 ft above the base in the central part of Bradwell Moor showed 19 ft of pale limestone with Shelly and crinoidal bands and large chert masses in the lowest 4 ft; the fauna included G. crassiventer, G. dentifer and G. giganteus cf. crassus.

Beds from the L. duplicata Band upwards form an oval outcrop in the central area of Bradwell Moor. The L. duplicata Band has been proved in Borehole BM 32B [SK 1475 8121] (see Appendix 1, p. 362) and lies some 190 ft above the Upper Girvanella Band. It is exposed (loc. 94) [SK 1471 8114] in an old quarry:

On the eastern side of the outcrop the L. duplicata Band is again exposed (loc. 95) [SK 1525 8123] and Eden and others (1964, pp. 99, 106) list L. duplicata duplicata and brachiopods from this locality. Near this exposure a knoll-reef is developed just above the L. duplicata Band.

Farther east Shirley and Horsfield (1940, p. 281) noted the presence of the L. duplicata Band near Bird Mine. The following section (loc. 96) [SK 1565 8118] was measured during the present work:

To the north of Bradwellmoor Barn an area nearly 0.25 mile wide and extending for 0.5 mile parallel to Dirtlow Rake on its south side is strewn with large blocks of silicified limestone. The largest of these [SK 1543 8199] reaches a thickness of 15 ft and shows traces of purple fluorite. The disposition of the blocks makes it clear that they result from the erosion of a horizon which has suffered preferential silicification adjacent to Dirtlow Rake. The horizon was probably not far from that of the L. duplicata Band (see also p. 313).

Earle's Quarry

In the quarry the lowermost 100 ft or so of the Upper Monsal Dale Beds with the Upper Girvanella Band are present. These beds are predominantly dark limestones (Eden and others 1964, pp. 85–6) with six well-defined but impersistent paler calcirudite bands up to 15 ft in thickness. The calcirudite bands in places pass laterally into knoll-reefs in the vicinity of which they are at their coarsest; towards the reef-belt these beds show an increase in the rounding of their constituents and in extreme cases constitute rolled-shell limestones. The dark limestones also show some lateral variation, becoming more crinoidal towards the reef-belt.

The section [SK 1592 8206] on the Upper Bench (1962) of the quarry (loc. 97) on the northern side of the large knoll-reef is described below (see also Eden and others 1964, pp. 99–103, 106):

The large knoll-reef [SK 1576 8180] referred to (Eden and others 1964, pp. 87–9) as the "main knoll" is the equivalent of beds (f) to (l) inclusive, reaches a thickness of 55 ft and appears to result from the combination of two horizons of minor knolls, the lower some 30 ft above the Upper Girvanella Band, the higher some 50 ft above it. It is composed of unbedded vughy calcilutite with intercalations of dark calcarenite at the edges. Some breccia and a little crinoid debris are present. The fauna of the knoll (loc. 98) includes the goniatite Bollandites sp. in addition to a rich brachiopod fauna; Palaeosmilia murchisoni with P. regia is abundant in a 6-in band near the top. Another knoll [SK 1582 8171] of large dimensions is present 100 yd S.E. of the "main knoll" and lies at the same horizon.

At the south-eastern end of the quarry [SK 163 818] a marked unconformity develops at the base of the Upper Girvanella Band as the tuff mound (see p. 74) is approached.

Smalldale and Bradwell

To the south-east of Earle's Quarry the relations of the lower part of the Upper Monsal Dale Beds are complicated by the lateral passage of pale limestones into dark thin-bedded limestones near the margin of the basinal area (see also p. 91). This phenomenon has already been noted in the Lower Monsal Dale Beds. The two subdivisions are indistinct as a result.

The greater part of the beds described in the quarry passes rapidly southwards into coarsely crinoidal limestones. A borehole, NC1 [SK 1627 8152] proved these limestones to a depth of 87 ft, underlain by dark crinoidal limestones to 99 ft and grey and dark grey bioclastic limestones with 'Girvanella' (the Upper Girvanella Band) to 106 ft. The pale crinoidal limestones, although not completely reef-like, show some affinities with a large flat reef in their development. A typical exposure [SK 1648 8132] at Smalldale Head shows 12 ft of pale coarsely crinoidal limestone on 5 ft of pale cherty limestone. The crinoidal limestones extend southwards to, and a little beyond, Moss Rake, though displaced by the latter. At Outlands Head a quarry [SK 1661 8080] shows 30 ft of pale shelly and often crinoidal limestone. South of Outlands Head the top of the crinoidal beds must lie not far below the Orionastraea Band.

Towards the margin of the limestone outcrop, pale cherty limestones down to about 100 ft below the Orionastraea Band persist locally on the south side of Bradwell. To the south-east, these limestones can be observed to pass into dark limestones and the junction with dark limestones in Bradwell village may also be diachronous.

Bradwell Dale

The main features of the stratigraphy of this dale are summarized in (Figure 11). Two detailed sections are quoted below and other sections are shown graphically in the figure. Variations in the succession are discussed below.

The most complete section measured (loc. 99) is near the southern end of the dale"Morton's quarry" of Shirley and Horsfield.. [SK 1714 8039]:

At the northern end of Bradwell Dale the following section (loc. 100) [SK 1741 8077] was measured:The lettering of beds on this implies no correlation with the preceding section.

The general features of the succession in Bradwell Dale may be summarized as follows:

1. Beds below the Orionastraea Band. These show two non-sequences. The lower is present locally in the northern half of the dale in the position of bed (f) of loc. 100 as a pebbly horizon some 20 ft below the Orionastraea Band; it can be seen as an angular break some 100 yd S. of loc. 100. A higher non-sequence, about 7 ft below the Orionastraea Band, is well seen (see (Plate 9A)) at the southern end of the dale [SK 1722 8046]; beneath lie some 10 ft of massive crinoidal and shelly limestone, bed (a) of loc. 99. The lower beds are folded into an east–west anticline, the upper 8 ft or so being cut out by the non-sequence.The direction of folding and lithological similarity with the lowest beds of loc. 100 are taken to indicate that the structure is anticlinal rather than of knoll form. At this locality the uppermost 3 ft of beds below the Orionastraea Band also bear corals.

To the north of loc. 100 the uppermost part of these beds, down to a horizon a few feet below the Orionastraea Band, is cut out progressively by the unconformity at the base of the Eyam Limestones. The underlying beds pass northwards into thin-bedded dark cherty limestones, which persist at some horizons, e.g. beds (a) and (d) of loc. 100, southwards for some distance into beds of normal shelf facies (see (Figure 11)).

By comparison with the section in Intake Dale a sufficient thickness of strata is exposed for the Lonsdaleia duplicata Band to be present in Bradwell Dale. However, no corals have been seen at this horizon.

2. Orionastraea Band and overlying strata. At the southern end of Bradwell Dale exposures do not allow the joining of the outcrops of the marker-band on the two sides of the dale; otherwise it can be traced around the sides of the dale until it is cut out by the unconformity at the base of the Eyam Limestones. The beds above the Orionastraea Band consist of pale limestones, some cherty, with rather 'reef-like' shelly and crinoidal beds in places.

Concealed Monsal Dale Beds

Wardlow Mires, Great Hucklow and Eyam

The Wardlow Mires No. 1 Borehole (loc. 101) [SK 1850 7553] proved Monsal Dale Beds, overlain by Eyam Limestones, between 113.5 ft and the base of the borehole at 632 ft 2 in. The correlation is illustrated in (Figure 12); the sequence is summarized below:

The presence of oolites in abundance between the Upper Girvanella Band and the Litton Tuff is abnormal and has been discussed on p. 28. The absence of the greater part of the dark beds above the Upper Girvanella Band is remarkable in view of their persistence at outcrop. The recognition of the Black Bed (see p. 81) of the Middleton Dale section provides checks on the correlation of the higher coral bands. The correlation of coral occurrences indicates a section closely comparable to that in Furness Quarry (see p. 75) and disproves the contention of Shirley and Horsfield (1945, p. 297) that some 40 ft of the top beds of D₂ have been cut out in the nearby Cressbrook Dale section by the unconformity at the base of the Eyam Limestones (see (Plate 7)). Wardlow Mires No. 2 Borehole (loc. 102) [SK 1825 7586] (see Appendix 1, pp. 378–82) proved the base of the Eyam Limestones at 107 ft 9 in and pale D₂ limestones from thence to the bottom of the hole at 133 ft 6 in.

The colony of L. portlocki at 129 ft 3 in represents the coral band lying just above the Orionastraea Band in the Wardlow Mires No. 1 Borehole.

Hucklow Edge No. 2 Borehole (loc. 103) [SK 2025 7760] north-east of Shepherd's Flat proved the following abridged section of the Monsal Dale Beds beneath the Eyam Limestones: