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The Pennines and adjacent areas. British regional geology

Fourth edition by N Aitkenhead W J Barclay A Brandon R A Chadwick J I Chisholm A H Cooper E W Johnson

Bibliographical reference: Aitkenhead, N, Barclay, W J, Brandon, A, Chadwick, R A, Chisholm, J I, Cooper, A H, And Johnson, E W. 2002. British regional geology: the Pennines and adjacent areas (Fourth edition). (London: HMSO for the British Geological Survey.)

Contributors: G R Chapman C S Cheney, T B Colman D E Highley G K Lott, T C Pharaoh N J Riley, C N Waters G Warrington

Cover picture: Gordale Beck emerging from Gordale Scar, one of the major scenic attractions in the Yorkshire Dales National Park. (Photographer Colin Raw)

First published 1936. Second edition 1948. Third edition 1954. Fourth edition 2002. NERC copyright 2002

The grid, where it is used on the figures, is the National Grid taken from Ordnance Survey mapping. Maps and diagrams in this book use topography based on Ordnance Survey maps.

© Crown Copyright reserved Ordnance Survey licence number GD272191/2002.

Acknowledgements

This edition of the The Pennines and adjacent areas has been compiled by W J Barclay and edited by him, R D Lake and A A Jackson. Chapters have been written by the following authors:

Foreward to the Fourth Edition

The first and second editions of this guide were written by D A Wray and published in 1936 and 1948 respectively.The rapid progress in research on the rocks of the region after 1948 necessitated a third edition, written by W Edwards and F M Trotter, published in 1954.The popularity of this edition resulted in eight reprints, the latest being in 1993. However, the vast amount of work carried out in the last 40 years makes the publication of this fourth edition long overdue. Detailed mapping of much of the region by the British Geological Survey, mineral exploration and academic research have provided a wealth of new data.Also, our present understanding of tectonic processes, basin dynamics and sedimentation is derived in part from concepts such as plate tectonics and sequence stratigraphy, which were unknown when the last edition of this book was written.

The Pennines, the so-called backbone of England, constitute an upland area of natural beauty much frequented today by walkers and tourists. Industrial conurbations on the flanks of the Pennines owe their origins to coalfields that fuelled the industrial development of the region and contributed much to the prosperity of the United Kingdom. Although now much diminished, coal mining remains an important industry.The region’s fluorspar, baryte and limestone are also major contributors to the UK economy.

This book gives a comprehensive account of the geology of the region. It is written for the student and amateur geologist, but will also provide others, such as the professional geologist, planner and civil engineer, with an overview of the geology.The Quaternary deposits (Chapter 8) are described in more detail, in comparison with the solid rocks, reflecting their importance to many users of earth science information and the increased awareness of the importance of the Quaternary Period to present-day global environmental and climatic modelling.

In compiling this guide, we have drawn heavily on the expertise and experience of staff of the British Geological Survey, some of whom have spent a large part of their survey careers working in the region.We are particularly grateful to N Aitkenhead and J I Chisholm, who wrote the Carboniferous chapters subsequent to their retirement from BGS. A W A Rushton (formerly of BGS) compiled (Plate 2a), (Plate 2b).

David Falvey, PhD Director, British Geological Survey, Kingsley Dunham Centre Keyworth, Nottingham

Chapter 1 Introduction

The region described in this account encompasses parts of Yorkshire, Lancashire, Cheshire, Staffordshire, Derbyshire and Nottinghamshire. The Pennines form the dominant physiographic feature of the region, which extends from the Stainmore Gap in the north to the Midlands in the south (Figure 1). Namurian strata, including the Millstone Grit, underlie much of the high ground of the Pennines, with the younger Coal Measures occupying the flanks (Figure 2). Older Carboniferous strata (the Carboniferous Limestone) outcrop in the Askrigg Block, the Craven lowlands and the Peak District of Derbyshire. The Carboniferous rocks have made an important contribution to the character of the region, particularly in its scenery and economic development. Their contribution to the economy continues today. Pre-Carboniferous rocks outcrop in small inliers near Ingleton and Settle. Post-Carboniferous rocks of Permo–Triassic age occupy the low ground on both sides of the Pennines. A range of Quaternary unconsolidated deposits veneers the solid rocks, attaining maximum thickness in the Lancashire–Cheshire lowlands.

The Pennines constitute a dissected plateau with summits rising up to about 600 m above OD. Broadly, the geological structure of the region comprises an assymetrical anticline, with the Carboniferous rocks dipping gently towards the east, but more steeply towards the west, where they are affected by downfolding and faulting. Many of the highest points are located along the crestline of this fold, perhaps as a result of relatively recent uplift.

The geological succession is shown in (Table1). The known geological history of the region begins in the Ordovician, when it was part of the microcontinent of Eastern Avalonia that had rifted from the southern hemisphere continent of Gondwana and was drifting northwards across the Iapetus Ocean (Figure 3). The Craven inliers provide a small window through the Carboniferous cover into this environment, the oldest beds being the sandstones and mudstones of the Ingleton Group, deposited as deep-sea sands and muds off the coast of Eastern Avalonia. Subduction of Iapetus Ocean crust beneath the microcontinent resulted in uplift and erosion, represented by the unconformity that truncates the Ingleton Group. The overlying Windermere Supergroup, of Ordovician to Silurian age, was deposited in a foreland basin after subduction had ceased and a transgressive event flooded the slowly subsiding landmass. Final closure of the Iapetus Ocean took place in the late Silurian, when the southward-drifting Laurentian continent collided with Eastern Avalonia, resulting in the Acadian deformation of the Lower Palaeozoic succession and uplift of the Caledonian mountain chain.

Towards the end of the Devonian Period, much of the region was probably land. North–south extension produced tilted highs and half graben (‘blocks’ and ‘basins’), the Southern Uplands to the north of the region and the Wales-Brabant High (or St George’s Land) to the south remaining above the transgressing tropical sea. The Carboniferous Period lasted some 60 million years, from about 360 million years before present (Ma) to 300 Ma. The region was then part of a continent known as Laurasia that palaeomagnetic evidence suggests drifted north across the Equator from 5° to 10° south to about 5° north (Figure 3). Such movement would have taken the region from the southern hemisphere tropical arid zone, where it was situated during the Devonian Period, through the much wetter Carboniferous equatorial zone into the northern hemisphere tropical arid zone in latest Carboniferous and Permian times. In the Dinantian, the dominantly fault-controlled ‘block-and­basin’ topography of the region resulted in the deposition of thick marine shale successions in the rift basins and shallow-water carbonate sedimentation on the blocks. The contrasting bathymetry of the Dinantian was progressively buried by clastic sediments during a prolonged period of crustal sag in Namurian and Westphalian times.

In the Namurian, great river delta systems advanced southwards, depositing the feldspathic sands of the Millstone Grit in the Pennine Basin. Deep-water mud deposition persisted in the Edale and Widmerpool half grabens before the sands arrived towards the end of the epoch. The Westphalian Coal Measures represent deposition in extensive fluvio­lacustrine environments subjected to occasional marine flooding caused by glacio-eustatic sea-level rises. During the late Carboniferous to early Permian Variscan orogeny, closure of the Rheic Ocean and continental collision in the Hercynides region not far to the south of the UK resulted in structural inversion of the Carboniferous basins and reactivation of their bounding faults. After the ensuing uplift, erosion and deposition of desert red beds in the early Permian, marine deposition commenced in the late Permian, when seaways opened to the east and west of the Pennines. The resultant limestones (Cadeby Formation and Brotherton Formation) represent deposition in tropical seas of normal salinity; the interbedded red mudstone formations were deposited in evaporitic, playa lake and sabkha environments. Continued east-west rifting in the Triassic was accompanied by deposition of fluvial and aeolian sandstones, the former deposited as sands and gravels in a river system flowing north from the Variscan (or Hercynian) mountain belt. The succeeding Mercia Mudstone Group was deposited in an environment similar to the red beds of the Permian, with in addition, the formation of thick halite sequences in the Cheshire and East Irish Sea basins.

Apart from minor clays and sands of Neogene age preserved in solution subsidence hollows in the Peak District, there is no stratigraphical record in the region of the period from the late Triassic to the Quaternary. It is likely, however, that Jurassic and Cretaceous sediments were deposited over most of the region, only to be removed before Neogene times. Climatic deterioration about two million years ago at the start of the Pleistocene initiated a period of climatic oscillation that continues to the present, with colder times when glaciers covered the region and warmer, interstadial times, such as the present day Flandrian interglacial. A wide range of unconsolidated deposits, including till, glaciofluvial and fluvial sands and gravels, lacustrine clays and solifluction deposits, mantles parts of the region. Much of the glacigenic material originated during the last (Late Devensian) glaciation, but older (? Anglian) deposits survive in many areas beyond the Late Devensian ice limit.

Geology has played, and continues to play, a major role in the economic development of the region. The coals and iron ores of the Coal Measures were formerly the main contributors. Coal production has declined markedly in recent years, from about 100 million tonnes in the early 1950s to about 31 million tonnes in the mid 1990s. The region provides 43 million tonnes of limestone annually, about 35 per cent of the UK output. It is also the country’s major producer of cement, with 4. 5 million tonnes annually. The north and south Pennine orefields were formerly major sources of lead and zinc, but these are now by-products of the extraction of baryte and fluorspar. The Southern Pennine Orefield in the Peak District currently supplies over 80 per cent of UK requirements for fluorspar, and is the second largest source of baryte. The Cheshire Basin, the northern part of which lies in the region, accounts for over 90 per cent of the UK’s salt production. Building stone, clays (brick clays and fireclays), silica sand, bottled waters, oil, gas and peat are minor, but important economic products.

Natural geological hazards include landslipping, and, in the Ripon, Bedale and Brotherton areas, ground collapse due to gypsum dissolution. The region has experienced a number of geologically related disasters and accidents in recent years, including methane explosions at Abbeystead and Loscoe, and the failure of Carsington Dam.

Chapter 2 Pre-Carboniferous rocks

Ordovician and Silurian strata probably form the pre-Carboniferous basement throughout much of the region, but are only seen at outcrop in the Craven inliers on the southern margin of the Askrigg Block, between Ingleton and Malham, Yorkshire (Figure 4). Rocks of possible Precambrian–Cambrian age have been proved in the Wessenden No. 1 Borehole. Devonian strata are generally absent in the region, although red beds proved in the Eakring No. 146 Borehole may be Devonian or early Dinantian, and other recent boreholes reached red beds of possible pre-Carboniferous (? Devonian) age.

Most of the Ordovician and Silurian formations in the Craven inliers can be correlated with ones in the larger Lake District inlier, which adjoins the north-west of the region. Their presence elsewhere in the region is inferred from geophysical evidence and has been proved in a few boreholes that penetrate the Carboniferous cover sequence. The deposition and deformation of the succession reflect the contemporary early Palaeozoic palaeogeography and plate tectonic movements (Figure 3), (Figure 5). The strata in the Craven inliers are disposed in east­south-east-plunging folds that bring Ordovician rocks to outcrop in the west and the youngest Silurian rocks in the east. Two sequences are recognised. The Ordovician Ingleton Group is exposed in Chapel le Dale and around Horton-in-Ribblesdale. The Ordovician–Silurian Windermere Supergroup extends eastwards from near Ingleton for 25 km, by Crummack Dale, Ribblesdale, Silverdale and Malham Tarn, to Goredale Beck (Figure 4). An unconformity separates the two groups of marine strata (Table2). The older Ingleton Group is Arenig in age and was deposited in a deep marine environment. The late Ordovician and Silurian Windermere Supergroup comprises mixed clastic-carbonate and foreland basin successions.

The close of the Silurian brought a change from marine to fluvial continental deposition in the Windermere Supergroup basin as the Old Red Sandstone continent began to form. Illite crystallinity studies suggest that at least 3 km of continental strata were deposited on top of the marine succession, the strata being analogous to the youngest continental strata of the Powys Supergroup in the Welsh Basin.

Ingleton Group

These turbiditic sandstones with interbedded siltstones and conglomerates are believed to have been derived from Eastern Avalonia and deposited in a deep marine environment on its northern margin; contemporaneous slump folds indicate deposition on a north-westerly inclined palaeoslope. No macrofaunas have been found in the group, which, in the past, was considered as evidence of a Precambrian age. However, isotopic dating of samples from Ribblesdale and microfaunal evidence from similar lithologies in the Beckermonds Scar Borehole in Wharfedale (Figure 5);see also below) favour an Arenig age. The absence of distinctive lithostratigraphical units prevents subdivision of the group. This, along with the isoclinal folding and cleavage, makes estimates of the thickness of the group uncertain, although at least 1000 m of strata is seen at outcrop in Chapel le Dale. Smaller outcrops occur in Kingsdale and around Horton-in-Ribblesdale. The Ingleton Group forms part of the Furness–Ingleborough–Norfolk ridge. This positive geophysical feature of the early Palaeozoic basement has a distinctive magnetic signature probably due to the presence of magnetite-bearing sandstones, such as those proved in the Beckermonds Scar Borehole (see below).

Mid-Ordovician Unconformity

The absence of Llanvirn and Caradoc strata represents a period of more than 30 million years, during which the Ingleton Group was uplifted and eroded. The uplift was a regional event that accompanied the south-eastward subduction of Iapetus Ocean crust beneath Eastern Avalonia (Chapter 1). Evidence for subduction is found in the Lake District inlier, where the 8 km-thick, mainly subaerial Borrowdale Volcanic Group was preserved by contemporary rift subsidence.

The only evidence of volcanism in the Craven inliers is provided by a few basic dykes of probable Ordovician age that intrude the Ingleton Group in Chapel le Dale.

Windermere Supergroup

The oldest part of the Windermere Supergroup is the Dent Group (Table 2), a mixed carbonate–clastic shelf succession deposited in shore-face, storm-dominated and deeper marine-shelf environments. The most complete succession occurs in the Cautley and Dent inliers, adjacent to the north-western boundary of the region, where a refined biostratigraphy based on the trilobite and brachiopod faunas (Plate 1) has been established in the continuous, 600 m-thick calcareous siltstone and impure limestone succession. The age of the Dent Group at outcrop in the Craven inliers is Ashgill; older (Caradoc) beds are perhaps present at depth elsewhere in the region. The absence of the older stages in the thinner successions of the Craven inliers and Lake District indicates transgression on to a gradually subsiding low-relief land mass. A hiatus within the Hirnantian succession is related to a fall in sea level associated with the end-Ordovician glaciation.

The Dent Group is divided into two formations in the Craven inliers. The Norber Formation consists mainly of calcareous siltstone and impure limestone; the Sowerthwaite Formation is a varied succession of siltstone and mudstone, with tuff, sandstone and conglomerate interbeds. The strata are best exposed in Crummack Dale.

The unconformity at the base of the Norber Formation is exposed in Douk Ghyll near Horton-in-Ribblesdale, where several metres of siliceous conglomerate fill irregularities in the eroded surface of the Ingleton Group. The conglomerate passes gradationally upwards into calcareous siltstone that contains a Rawtheyan fauna. A Neptunian dyke in the Ingleton Group in the Horton-in-Ribblesdale inlier is filled with fossiliferous limestone presumed to belong to the Norber Formation. Cautleyan strata, 160 m thick, are present in the lower part of the Norber Formation where it is exposed in the Austwick Anticline. The formation is more calcareous in the Crummack and Crag Hill anticlines and consists of at least 30 m of nodular-bedded limestone (Crag Hill Limestone).

The Sowerthwaite Formation is up to 300 m thick in the Austwick Anticline, where its base is defined by the appearance of volcanic rocks. On the northern limb of the anticline, the Dam House Bridge Tuffs comprise 40 m of interbedded rhyolitic, air-fall tuff and silty mudstone. Individual beds of tuff are up to 4 m thick, the number and thickness of the beds decreasing upwards. On the southern limb of the anticline, 40 to 250 m of volcanogenic sandstone (Jop Ridding Sandstone) overlie an erosion surface at the top of the Norber Formation. The unbedded, lithologically uniform, coarse-grained lithofacies indicates that the sandstone is a mass-flow deposit. Rhyolitic tuffs occur at the same stratigraphical level in the Cautley and Dent inliers and in the Lake District; their widespread distribution suggests deposition from a Plinian type of eruption.

The upper part of the Sowerthwaite Formation consists mainly of siltstones and mudstones that are extensively bioturbated in part. Towards the top of the succession, the Wharfe Conglomerate marks the base of the Hirnantian Stage. Most of the pebbles in the conglomerate appear to have been derived from the Ingleton Group, with some from older parts of the Dent Group; the provenance of some vesicular andesite and vein-quartz pebbles is unknown.

In the Silurian, deeper basins formed around the margins of Eastern Avalonia in the remnant Iapetus Ocean. The initial gradual, and later rapidly increasing, rates of subsidence and sedimentation have been interpreted as the development and filling of a foreland basin. Graptolite biozones within the succession indicate continuous marine deposition. The Silurian rocks in the Craven inliers were deposited in the same basin as those in the Lake District inlier, which was linked to the Welsh Basin on the western flank of the Midlands Microcraton

In Llandovery times, the Midlands Microcraton was inundated and the shallow marine-shelf environments around its margin deepened during the transgression. Sedimentation rates of graptolite-bearing muds were low in the initially anoxic, and later oxic, deep shelf and basin environments. The Stockdale Group comprises black, graptolitic mudstones (Skelgill Formation) and thickly bedded, green siltstones (Browgill Formation). The succession in the Craven inliers is 35 m thick and unusual in several respects compared with that found elsewhere; it is considerably thinner, locally incomplete or absent, and the typically anoxic graptolitic Skelgill Formation locally contains thin beds of limestone and calcareous mudstones at the base. These limestones, most abundant in the Crummack Anticline, were deposited in oxygenated water, perhaps over areas of positive relief on the basin floor. The succession is either attenuated or absent in the Austwick Anticline. It is represented on the northern limb of the anticline, by only 0. 15 m of argillaceous limestone overlying Ordovician strata with a Hirnantian fauna, and is overlain by laminated silty mudstones containing Wenlock graptolites. The Stockdale Group is present in Ribblesdale, but its outcrop is mostly drift-covered.

During the Wenlock, the basin was initially starved of coarse sediment, so that only muds and fine silts accumulated from low-density turbidity currents, along with carbonaceous pelagic debris. These formed the distinctive laminated hemipelagites of the Brathay Formation. Later, fans of turbidite sands prograded into the basin and interdigitate with the Brathay Formation. The first and most persistent of these fans comprises the Austwick Formation in the Craven inliers (Plate 2a), (Plate 2b). The northward thinning and geometry of the sandstones in the inliers suggest that the fan system was fed from the south. The distribution and sedimentary structures in the sandstones indicate deposition in an east–west trough. Its northern margin was the Furness–Ingleborough–Norfolk Ridge, suggesting that this continued to form a positive feature throughout the Wenlock.

The thickness of the Wenlock succession in the Craven inliers ranges from 300 m to more than 600 m, depending on the abundance of sandstones in the Austwick Formation. In Ribblesdale, the maximum thickness occurs on the southern limb of the Studrigg–Studfold Syncline adjacent to the North Craven Fault, where 600 m of sandstones are present and older parts of the succession do not crop out. On the northern limb of the syncline, the hemipelagites of the Brathay Formation make up much of the 300 m-thick succession. Here, the base of the formation may locally overstep the Stockdale and Dent groups to rest directly on the Ingleton Group. The Wenlock succession is exposed best in Crummack Dale, on the southern limb of the Studrigg–Studfold Syncline, where it is 400 m thick. The lowermost 80 m belong entirely to the Brathay Formation and contain a basal Sheinwoodian graptolite fauna. The overlying succession comprises sandstones of the Austwick Formation, with intercalated hemipelagites that contain some younger Sheinwoodian and Homerian graptolite faunas.

A eustatic fall in sea level towards the close of the Wenlock resulted in oxic conditions in the basin and the deposition of calcareous silts that now form the Coldwell Formation (formerly named the Arcow Formation) which is 10 to 35 m thick. These siltstones have a mottled appearance due to pervasive bioturbation, which destroyed the bedding. Two types of burrow have been recognised. The more abundant Chondrites-like burrow is vermicular, 1 to 2 mm in diameter, and commonly pyritised; the other superficially resembles Phycodes, but is smaller and branches downwards. A sparse benthonic fauna comprises orthocones, trilobites and brachiopods. Basal Ludlow graptolites have been found in a hemipelagic member in the Lake District inlier, and show that the formation spans the Wenlock–Ludlow boundary.

A sea-level rise in the early Ludlow was marked by the return of an anoxic depositional environment throughout the Windermere Supergroup basin. Increasing subsidence rates preserved up to 7000 m of sand, silt and mud turbidites in the basin during the Ludlow. The thickness of the basal silty mudstone formation varies across the basin, from barely 10 m in the Howgill Fells, adjacent to this region, to 710 m in the Craven inliers, revealing that the succeeding influx of turbidite sands into the basin was markedly diachronous. Provenance studies and palaeocurrent indicators show that the sandstones were derived from Laurentia to the north. The sedimentological evidence suggests that the Windermere Supergroup basin was all that remained of the Iapetus Ocean in the Ludlow. The late introduction of sandstones into the Craven inliers was possibly caused by basin morphology, with the Furness–Ingleborough–Norfolk Ridge acting as a barrier to the southward-prograding turbidite fans.

Only the basal 1 km of the Ludlow succession is seen at outcrop in the Craven inliers. Two formations are distinguished; the Horton Formation (laminated hemipelagic silty mudstone) and the overlying Neals Ing Formation (turbidite sandstone). The nilssoni/scanicus biozone graptolite assemblages within this succession indicate a Gorstian age. The succession is preserved in the Studrigg–Studfold Syncline. Lower parts of the Horton Formation are well exposed in Ribblesdale, particularly in the quarries on the west side of the valley. Bentonites in Combs Quarry (Plate 3) provide evidence of distant, subaerial, volcanic eruptions that were possibly located south of the Midlands Microcraton. Fine-grained, turbidite sandstones (Studfold Sandstone Member) are present 420 m above the base of the formation and crop out on the east side of Ribblesdale. These sandstones persist south-eastwards beneath the Carboniferous cover sequence into Silverdale, where there is a complete section through the Horton Formation. The Studfold Member represents the first incursion of sandstones with a northern provenance into the Craven inliers. It is 80 m thick in Ribblesdale, thinning to 40 m in Silverdale, where it is overlain by 250 m of laminated silty mudstones. The Horton Formation forms the impermeable floor of Malham Tarn and the easternmost outcrop of early Palaeozoic rocks in the small Goredale Beck inlier.

The Neals Ing Formation comprises at least 250 m of turbidite sandstone. It crops out in the Studrigg–Studfold Syncline before plunging beneath the Carboniferous cover sequence on the west side of Fountains Fell. The thickly bedded, mainly coarse-grained sandstones are typical of those in the Coniston Group found elsewhere in the basin. Younger parts of the Ludlow succession may be preserved eastwards, beneath the Carboniferous cover.

Concealed pre­-Carboniferous rocks

Rocks of pre-Carboniferous age have been encountered in thirteen boreholes in the region (Figure 5). In the north, boreholes have proved Ordovician–Silurian strata and intrusive rocks comparable to those in the Craven inliers and the Lake District. In the central part of the region, boreholes have reached red beds of possible Devonian age underlying the thick Dinantian fill of the Craven Basin. In the Peak District and on its fringes, deep boreholes have encountered a rather heterogeneous early Palaeozoic basement. This comprises strongly folded metasedimentary rocks metamorphosed to greenschist facies grade, and Ordovician volcanic rocks. These represent the continuation of the Caledonide fold-belt of northern England and the Lake District volcanic arc into the concealed Caledonides of eastern England.

?Precambrian–Cambrian

The Wessenden No. 1 Borehole recovered 24 m of deformed, chlorite-rich, pale green siltstones and fine-grained sandstones dipping at 40. to 80. . Sedimentary structures, including lamination, grading and ripples, and synsedimentary slump-bedding indicate a distal turbiditic environment of deposition. Some intervals are strongly folded, cleaved and listricated, and yield epizonal (greenschist facies) mica crystallinity values. In the Grove No. 3 Borehole, 37 m of green chloritic phyllites with a foliation dipping at 70. to 80. to the south-south-west are similar to those proved by Welton No. 1 Borehole, just outside the region (Figure 5). Geochemical data suggest that all three provings belong to one suite fed by a calc-alkaline volcanic arc source. Lithologically similar rocks are known from the Precambrian Mona Complex of Anglesey, the Longmyndian Supergroup of the Welsh Borders and the Precambrian–Cambrian Tubize Group of the Belgian Caledonides. There are also lithological similarities to the Ingleton Group. They do not resemble the slaty rocks of the Charnian Supergroup, however, which are the nearest exposed Precambrian rocks, at the northern edge of the Midlands Microcraton, 70km farther south. A younger (Cambrian or Ordovician) age cannot be ruled out, however, in the absence of reliable radiometric and biostratigraphical data.

Ordovician

The Beckermonds Scar Borehole was drilled to investigate the origin of a high aeromagnetic anomaly associated with the flank of the concealed Wensleydale granite. The borehole proved, beneath Dinantian strata, 260 m of steeply dipping and tightly folded siltstones and turbidite sandstones of Arenig age (unbottomed) that are correlated with the Ingleton Group. They are cleaved and contain porphyroblastic chlorite, mica and feldspar attributed to the thermal effects of the nearby Wensleydale granite. Their magnetic susceptibility indicates the presence of up to 3 per cent magnetite by volume, sufficient to account for the anomaly observed. Both primary and secondary, hydrothermal origins have been proposed for the magnetite. A 15 m-thick quartz-microdiorite intrusion comparable in composition to andesites of the Borrowdale Volcanic Group is interpreted as a product of mid-Ordovician calc-alkaline arc magmatism, predating emplacement of the Wensleydale granite.

Ordovician strata are more commonly encountered in boreholes in the Peak District and surrounding areas. The Eyam Borehole proved 48 m of grey and purple mudstones of probable early Llanvirn age dipping at 45. to 60. beneath Dinantian strata. The Woo Dale Borehole found 39 m of lavas and tuffs underlying Dinantian strata. Flow-banded, pink and green rhyodacites are overlain by highly weathered purple and brown tuffs of similar composition. Originally thought to be of Uriconian affinity (see third edition of this book), the volcanic rocks have yielded a Rb–Sr isochron age of 399 ± 9 Ma. However, they are compositionally similar to the calc-alkaline tuffs proved by North Creake Borehole in East Anglia, reliably dated at 449 ± 13 Ma using the U–Pb zircon fraction method, and the Rb–Sr isochron age may therefore indicate later resetting. The Eakring No. 146 Borehole proved 84 m of grey phyllitic mudstones with thin, fine-grained quartzites, chloritic phyllites and thin layers of intermediate tuff and lava, dipping at 40. to 70. . The volcanic rocks are also calc-alkaline in composition, and similar to those proved by the Woo Dale and North Creake boreholes, and an Ordovician, possibly Caradoc age, is likely. The Ironville No. 5 Borehole encountered 95m of grey, laminated sandstone and silty mudstone dipping at 55. to 65. and intruded by numerous sheets of highly altered lamprophyre, up to 5 m thick. The sedimentary strata are strongly bioturbated, contain water-escape structures, and are cleaved and affected by kink folding. Rare acritarchs suggest an early Ordovician (Tremadoc or Arenig) age. The lamprophyre sheets are similar to those found throughout the Midlands where similar minor intrusions at Nuneaton, 60 km to south of the region, have been dated as early Ashgill (442 ± 3 Ma).

Wensleydale granite

The Raydale Borehole, drilled to identify the cause of a prominent negative gravity anomaly within the Askrigg Block, proved the concealed Wensleydale granite. The granite is pink, medium grained and equigranular, with a mineralogy comprising potassium feldspar (salmon pink microperthite), greenish cream albitic plagioclase, quartz and chlorite (pseudomorphing magmatic biotite). Petrographically and geochemically, the granite is most similar to the Ordovician (Caradoc) synvolcanic Lake District plutons, such as Ennerdale and Eskdale, and the concealed Moorby microgranite of Lincolnshire, rather than the high heat production granites (such as Skiddaw, Shap and Weardale) emplaced in the early Devonian. The Rb–Sr whole-rock isochron age of 400 ± 10 Ma, while comparable to that obtained for Caledonian granites elsewhere in northern England, may therefore be anomalous, reflecting later Acadian disturbance of the Sr isotopic system.

Silurian

Laminated siltstones in the Silverdale and Chapel House boreholes on the Askrigg Block have been correlated with the Horton Formation (Ludlow) of the Windermere Supergroup. They are of comparable low (anchizonal) metamorphic grades.

Devonian

The Eakring No. 146 Borehole penetrated 506 m of red, polymict conglomerate underlying probable Chadian strata. These have not yielded a biostratigraphical age, so a Devonian or early Dinantian age is possible. The Caldon Low Borehole also penetrated red beds of possible Devonian age. More recent hydrocarbon exploration boreholes (Boulsworth No. 1 and Roddlesworth No. 1) reached up to 40 m of red, dolomitic mudstones of possible Devonian age beneath a thick Dinantian succession.

Chapter 3 Carboniferous: introduction

Rocks of the Carboniferous System underlie much of the region, mostly at outcrop in the Pennines, but also concealed by younger strata in the flanking lower ground. These rocks have made an important contribution to the character of the region, particularly its scenery and its economic development.

As long ago as the late 18th century, three main divisions of the Carboniferous rocks were recognised: Carboniferous Limestone, Millstone Grit and Coal Measures. Later, these lithostratigraphical (rock) divisions were broadly equated with chronostratigraphical (time) divisions — Dinantian, Namurian and Westphalian. Because these are internationally recognised, and because rock successions vary considerably from place to place (the Carboniferous Limestone, for example, passes laterally into mudstone), the rocks are described under these broad chronostratigraphical headings. In order to make detailed comparisons of the rocks from area to area, it is necessary to correlate the local successions within a more detailed framework by subdivision into chronostratigraphical stages (Table 3). In practice, this subdivision is largely based on biostratigraphy, which relies on the identification of key fossils (Plate 4) and fossil assemblages, and the recognition of how these change through successions of strata. Fortunately, there were rapidly evolving and widely distributed marine animals, and their fossilised remains enable a firm chronostratigraphical framework to be erected. Particularly useful are the foraminifera and conodonts in the Dinantian and the ammonoids (goniatites) in the Namurian to early Westphalian (Plate 4). The nature of the rocks, including their contained fossils, provides the main evidence for the reconstruction of past (palaeo-) environments. Lateral and vertical facies changes show how the palaeoenvironments evolved through the Carboniferous (Figure 6).

A period of crustal extension began in the late Devonian and continued through Dinantian times, gradually producing a rifted topography of fault-bounded blocks (highs) and intervening grabens and half-grabens (basins). These structures were actively growing beneath the area of Dinantian deposition, causing the sea to be persistently deeper in some places and so influencing the type of sediment that was laid down in different areas. For example, shallow-water, repetitive sequences of marine limestones and terrigenous clastic rocks (Yoredale facies) formed on the Askrigg Block while a deeper water mudstone–limestone succession accumulated in the Craven Basin. Extension ceased in the mid-Carboniferous and the block-and-basin topography of Dinantian times was progressively buried by sediments during a long period of thermal relaxation and crustal sag that affected the entire region in late Namurian and Westphalian times.

During the Dinantian a tropical sea transgressed the region leaving the Southern Uplands to the north and the Wales–Brabant High to the south emergent. Sedimentation almost certainly started earliest in the downfaulted basinal areas, but the resulting beds of Courceyan age occur at depths of several kilometres, barely detectable by seismic techniques and largely unproved by deep drilling. By contrast, the oldest rocks on the Askrigg Block (Kilnsey Limestone), which lie unconformably on the Lower Palaeozoic basement, are of possible Holkerian age. This shows that Dinantian sedimentation had been proceeding in some parts of the region for perhaps 15 million years before it was finally and completely inundated by the sea. Commonly, rifting produced fault-bounded, tilted blocks, so that sedimentation began earlier on their lower parts. Moreover, tilting movements continued during sedimentation, so sequences thicken markedly in the direction of tilt. For example, in the case of the generally northerly tilting Askrigg Block, sequences thicken markedly towards the north into what eventually became the Stainmore Basin (Figure 7). This basin separates the Askrigg Block from the Alston Block in the adjacent region to the north.

Carbonate deposition was predominant during the Dinantian. It is represented by the Carboniferous Limestone, in environments ranging from shallow shelf seas through ramp and slope areas to the deep basins. During the Namurian, crustal subsidence continued in a more regular fashion, and deposition was predominantly of sand, silt and mud, carried into the region by a huge southerly prograding river delta, to form the rocks of the Millstone Grit Group. By the Westphalian, the region had evolved into a flat landscape of rivers and lakes in which the Coal Measures had their origins. This was at times covered in equatorial forests and peat mires, but lay close to sea level, and was periodically inundated by marine incursions. The youngest Westphalian beds, the Warwickshire Group, are red beds, indicating oxidising environments in drier climatic conditions.

In much of the Carboniferous succession, various rock types succeed each other in a regular, rhythmic manner, although at a wide range of scales and with varying degrees of complexity. Such cyclicity is most readily seen in sequences deposited in shallow marine carbonate and delta-top environments on the structural highs such as the Askrigg Block and the carbonate platform surmounting the Derbyshire High. Here, sedimentation reflects most clearly and sensitively palaeoenvironmental changes. Examples from the Yoredale sequence on the Askrigg Block and the Brigantian shallow marine carbonate sequence on the Derbyshire High are shown in (Figure 13). The cycle boundaries in the Dinantian are generally placed at the tops of beds with lithological character that indicate emergence and penecontemporaneous subaerial exposure. Typical of such beds are those immediately underlying the so-called ‘clay wayboards’ in the late Dinantian limestone succession of the Derbyshire carbonate platform. Emergent features include mammillated dissolution surfaces, relict rootlet structures and crusts developed by soil-forming processes. These have their analogues in the root-bearing fossil soils (seatearths) and coals of the delta-top facies of the Yoredales, the Millstone Grit Group and the Coal Measures. The junctions between these and the overlying marine or fresh water mudstones are taken as cycle boundaries.

It is generally thought that the marine carbonate cycles were primarily caused by worldwide (eustatic) sea-level oscillations related to the repeated growth and melting of southern hemisphere ice sheets. This is probably also the main cause of the cyclothems containing fluviatile or deltaic sandstones and siltstones. However, advancing delta lobes can produce cyclic deposits of mudstone and sandstone by delta switching. In this process, distributaries shift to find shorter outlets to the sea. This mechanism is independent of sea-level change. Cyclic deposition can also be affected by local tectonism, such as that associated with syndepositional fault movements. Such effects would be expected to be on a quite different time scale from eustatic cyclicity and therefore distinguishable by careful analysis of well exposed sections.In recent years, seismic reflection profiling has become the primary technique for analysing basin evolution; from it has developed the discipline of sequence stratigraphy, which is concerned with the large-scale architecture of sedimentary rock successions. Sequences are defined as stratigraphical units bounded by regional unconformities or disconformities related to cyclical changes of sea level. Sequence-stratigraphical models distinguish between sedimentary units (systems tracts) produced during different parts of the cycle of base-level variation: examples are transgressive systems tracts, formed when base level is rising, highstand systems tracts formed when base level is high, and lowstand systems tracts formed when base level is low. Rises and falls of global sea level, combined with local subsidence effects and climatic variations, cause the base level changes. Sequences are on different scales, and are arranged in a hierarchy from 1st order (of longest duration) to 5th order. Sequence stratigraphy is normally applied in the search for hydrocarbons in deeply buried successions, and is not always easy to use in surface and near-surface areas like those described here, because large-scale spatial relationships between stratigraphical units can rarely be established at outcrop scale. Nevertheless, both Namurian and Westphalian rocks of the region have recently been interpreted from a sequence-stratigraphical point of view, largely at the ‘high­frequency’ (4th or 5th order) level, with attempts made to interpret erosion surfaces overlain by fluvial sandstones as being regionally significant sequence boundaries. However, the recognition and correlation of these surfaces is difficult, and the well-tested use of marine bands (maximum flooding surfaces of sequence stratigraphical terminology) remains the most suitable method of correlation for the Carboniferous rocks of the region.

Chapter 4 Dinantian

Dinantian rocks crop out in two widely separated areas in the north and south of the region (Figure 7). In the north, the outcrop may be subdivided into the Askrigg Block and the Craven Basin, lying to the north and south-west of the Craven Fault System respectively. In the south, the Dinantian outcrop forms an extensive inlier that is commonly referred to as the Derbyshire Dome because it is surrounded by younger strata dipping away from it. Other names are the Derbyshire Block, Derbyshire High and Woo Dale High. Elsewhere, Dinantian rocks are also present extensively at depth, as proved mainly by oil exploration.

The Askrigg Block, Craven Basin and Derbyshire Dome each have their own successions of strata, shown in generalised form in (Figure 8). The rocks were formed mainly from a variety of carbonate sediments ranging in grain size from mud to limestone pebble and boulder beds. These were deposited in a number of different marine environments, including shoreline, shelf, ramp, slope and basin (Figure 9) ;(Table 4). Land-derived, clastic rocks are also present at several levels on the Askrigg Block and in the Craven Basin.

Platform development began when warm, clear, tropical waters flooded low-lying areas and the sea bed was colonised by an abundance of benthonic organisms. These typically included calcareous algae, corals, sponges, bryozoans, brachiopods, gastropods, bivalves, trilobites, ostracods and echinoderms (especially crinoids). The calcareous skeletal remains of these creatures were bored, partially digested by other organisms and finely comminuted by wave and current action. The resultant carbonate sand, silt and mud is often referred to as the product of the ‘carbonate factory’. Once started, the process is self-perpetuating, forming thick accumulations of carbonate that keeps pace with rising sea level and/or tectonic subsidence so that the optimum shallow marine conditions for carbonate production persist. The factors which prevent or stop platform carbonate sedimentation are those which kill off the benthic community. These include emergence, an increase in the rate of subsidence to the extent that the sea floor lies below the reach of sunlight (the photic zone), an influx of terrigenous sediment and changes in water temperature and chemistry.

In their early development, platforms generally pass laterally into very gently sloping ramps. These encompass a range of environments dependent on water depth and the effects of wave and current action. One spectacular set of limestone build-ups that developed on certain ramps in the region are those shown on some BGS maps as knoll reefs. These include build­ups described in the literature as reef knolls, Waulsortian banks, bioherms and, most recently, mud mounds. They consist largely of lime mud probably produced mainly by microbial activity in both the deeper and shallower parts of the ramps. The mud is thought to have lithified almost immediately after it was generated, to produce a firm substrate and suitable habitat for an abundance and wide variety of other organisms. Later in the Dinantian, lime mud also built upwards and outwards to produce apron (or Cracoean) reefs on the marginal slopes of the platforms when they reached their acme of self-generating growth during Asbian times. When the Cracoean reefs were at their shallowest depth, they supported a framework community constructed by an encrusting biota of microbes (probably cyanobacteria), lithistid sponges, bryozoans and tabulate corals (Figure 10).

The action of waves and currents moved some of the sediment generated on the platforms to the surrounding areas. Apron reefs tended to prevent this movement, rimming the platform and increasing its relative height, causing the slope environments to have an increasingly steep inclination away from the platform. These slopes were relatively starved of sediment except where gullies cut through the platform margin and directed coarse debris fans and sediment-laden turbidity currents towards the basin. Rocks formed in the slope environment commonly show evidence of slump structures, indicating downslope movement of the sediments before they were fully lithified. Bioclastic grainstone shoals may also have inhibited the movement of sediment off the platforms. These developed at times near the margins of the platforms and on the higher parts of ramps. The slopes and ramps pass down into basin environments dominated by dark grey to black, calcareous mudstones and siltstones with only a minor proportion of coarse-grained carbonate sediment derived from the shallower environments.

Askrigg Block

There is good evidence from the Beckermonds Scar and Raydale boreholes, and from gravity and seismic studies, to indicate that the Askrigg Block (Figure 11) tilted intermittently to the north, probably from late Devonian to early Namurian times. Its southern margin is placed at the Settle to Cracoe reef belt, just south of the Middle Craven Fault (Figure12). The northern margin merges into the Stainmore Basin, with some more marked northward thickening of the early Dinantian succession across the Stockdale Fault (Figure 7), (Figure 8). The Stainmore Basin is abruptly flanked on its northern side by the Lunedale-Butterknowle fault system that forms its boundary with the Alston Block. All these faults had a pronounced component of vertical displacement during sedimentation, thus greatly influencing thicknesses and facies. The western margin of the block is marked by the complex Dent Fault System, which is thought to have had dextral oblique-slip movement in the late Devonian and early Carboniferous.

Dinantian sedimentation took place in three main phases (Figure 8). The first spanned the Courceyan to Arundian stages, when much of the block was often an emergent land surface supplying sandy sediment to the surrounding submerged shelf. When submergence occurred, it was localised and favoured the development of a minor evaporitic basin at the southern margin of the block. These environments were not generally favourable to organic growth, unlike those in the second phase, from the Arundian to early Brigantian. This was marked by open, shallow marine conditions in which the carbonate platform represented by the Great Scar Limestone Group developed. The third phase, represented by the Wensleydale Group, extended into earliest Namurian times. During this phase, the platform was repeatedly smothered with mud, silt and sand as deltas prograded from the north-east. Marine organisms and carbonate deposition were re-established after each clastic influx, because either the deltas moved laterally and directed their load of sediment elsewhere or sea level rose to drown the delta and shut off the clastic supply.

Rocks of Courceyan age just outside the region at Ravenstonedale comprise a sequence of intercalated dolomites and sandstones. These are thought to represent intertidal and fluviatile environments, respectively, at the shallow, western end of the Stainmore Basin. Alluvial fan conglomerates of the same age or older, and probably associated with the Dent Fault scarp, are exposed in Garsdale near Sedburgh, where they rest unconformably on Silurian basement rocks. Other famous localities where the basal unconformity is well displayed include Combs Quarry (Plate 3) near Horton in Ribblesdale and Thornton Force near Ingleton.

The Chadian and early Arundian rocks proved in the Raydale Borehole are shallow marine dolomites and terrigenous, clastic rocks (Figure 8) which contain palaeosols at many levels. A long period of platform carbonate sedimentation on the Askrigg Block, from the Arundian to the earliest Brigantian, is represented by the thick Great Scar Limestone Group. This group of rocks is of considerable economic importance. It not only gives rise to much of the attractive scenery which brings millions of visitors each year to the Yorkshire Dales National Park, but also provides the major mineral resource of the area in the form of limestones of chemical grade and aggregate quality.

The limestones of the Great Scar Limestone Group are typically bioclastic, formed mainly from the comminuted calcareous skeletal remains of the organisms that lived in the platform and ramp environments. The limestones tend to be dark grey in the lower part of the succession, becoming pale grey upwards. The group comprises several formations, their nearly horizontal beds forming the steep, terraced slopes of most of the valleys in the southern part of the Askrigg Block. The Kilnsey Formation is the oldest of the formations that is well exposed, as in Wharfedale where it forms the spectacular Kilnsey Crag (Plate 5). In the Settle district, the overlying formations, the Cove Limestone and Gordale Limestone, take their names from two of the most awesome cliffs in the Pennines, at Malham Cove and Gordale Scar (Plate 6).

From the late Holkerian to early Brigantian, an apron reef and associated Cracoean knoll reefs developed along the southern margin of the platform. Its present discontinuous outcrop, the ‘Craven Reef Belt’, lies just south of the Middle Craven Fault between Settle and Burnsall, partly concealed by unconformably onlapping Namurian strata (Figure 12). The area is classic for the study of knoll reefs.

The rocks of the Wensleydale Group, commonly known as the ‘Yoredale beds’ (or facies), are subdivided into cyclothemic repetitions of similar lithologies. There are ten such cycles in the Brigantian strata and seven in the overlying Pendleian. The cyclothems generally comprise, in upward succession, limestone–mudstone–siltstone–sandstone–seatearth–coal. The name of each cyclothem, one of which is shown in (Figure 13), is derived from the name of a limestone at its base. Other components may be duplicated in some cyclothems and absent in others. The limestones, which are of marine origin, are most prominent in the south. The other lithologies, representing the prograding deltaic component, become collectively thicker towards the north.

Craven Basin

The Craven Basin is an asymmetrical graben tilted to the south. In the Dinantian, it was bounded to the north-west by the Southern Lake District High, to the north-east by the Craven Fault System and to the south by the Central Lancashire High (Figure 7). Subordinate half-grabens within the basin are detected largely by seismic reflection and by their local effects on sedimentation. One half-graben, the Bowland Sub-basin, contains over 3000 m of possibly late Devonian to Courceyan strata, most of which are unproved; only the top 658 m in the upper part of the Courceyan Chatburn Limestone Group were penetrated by the Swinden Borehole. The total thickness of Dinantian strata known from boreholes and outcrop estimates is about 2500m (Figure14). A summary of the depositional events in the basin is shown in (Table 5).

The Swinden Borehole demonstrated that late Courceyan ramp deposition of interbedded marine carbonates and silty muds, containing land-derived quartz and mica, more or less kept pace with subsidence. The Chatburn Limestone was deposited in ramp environments that were established by the late Courceyan to early Chadian, probably over the whole of the Craven Basin. Renewed southward tilting led to the development of a new ramp environment in which the basal part of the Chadian to early Asbian Worston Shale Group (the Clitheroe Limestone Formation) was deposited. This formation includes a number of knoll reefs or mud mounds that form isolated groups of steep-sided hills (knolls) in the Clitheroe and Hodder valley areas. A range of shallow and deeper water limestones characterise the higher part of group, and represent steeper slope and basin floor environments. The slope environment developed in response to a combination of basin subsidence, sediment starvation and the growth of the carbonate platforms surrounding the basin. The Bowland Shale Group represents the final phase of Dinantian (late Asbian to Brigantian) basinal sedimentation, which continued into Namurian times. The group consists of dark, organic-rich mudstones, with varying proportions of fine, calcareous sediments carried into the basin mainly by turbidity currents. These currents also reworked sand and silt from deltas which prograded across the platform areas to the north during sea level lowstands, forming, for example, the Pendleside Sandstones Member.

Derbyshire Dome

The Derbyshire Dome outcrop consists largely of two shallow-water carbonate platform sequences (the Derbyshire Platform and the Staffordshire Platform) separated by deeper ramp and basinal limestones and mudstones of the Widmerpool Gulf (Figure 7); (Table 6).

The relationship of the Derbyshire Dome sequences to the underlying tilt blocks is a matter of continuing speculation and controversy. The best evidence for the existence of these blocks is provided by the Woo Dale and Eyam boreholes (Figure 7), which although only 11.7 km apart, reached Lower Palaeozoic basement rocks underlying the limestone sequence at markedly different depths, 45 m below OD and 1573 m below OD respectively. The ages of the lowest Carboniferous beds are also very different — probably early Arundian at Woo Dale and Courceyan at Eyam. The Caldon Low Borehole, in the south of the region, proved 170. 3 m of red sandstones and conglomerates (Redhouse Sandstones) to its terminal depth of 535. 37 m. These probably straddle the Devonian–Carboniferous boundary. Initial sedimentation in restricted basins during the Courceyan produced alluvial fan gravels (Redhouse Sandstones) and dolomites (Rue Hill Dolomites) in the Caldon Low Borehole, and marine evaporites (Middleton Dale Anhydrite Member) in the Eyam Borehole (Figure 8); (Table 6). in the Eyam Borehole (Figure 8);(Table 6). With continuing sea level rise and syn-rift subsidence, open marine conditions were established and by the Chadian, the building of carbonate ramps was well underway. These evolved into platforms by Asbian times. The thick, shallow-water carbonate succession of Courceyan to early Brigantian age in the Eyam Borehole, for example, appears to be complete, although it is extensively dolomitised and has not yet been studied in detail. Elsewhere, in the Staffordshire Platform succession around Caldon Low, and in the shallow to deep ramp sequences of the Widmerpool Gulf in the Dovedale–Manifold valley area, there are considerable gaps in the fossil record at some localities. These gaps represent uplift due mainly to basement fault movements that were common, particularly during the Chadian and Brigantian. In other areas, for example in the Wye valley between Litton Mill and Ashford, these movements had the opposite effect of producing an intrashelf basin on the Derbyshire carbonate platform in early Brigantian times. This is represented by locally thick sequences of dark, thinly bedded and laminated limestones with some slumped beds and turbidites, part of the ‘dark facies’ of the Monsal Dale Limestones.

In the late Brigantian, environmental changes led to conditions that were inimical to most benthonic life on the platform. Carbonate production largely ceased and only slow deposition of dark, land-derived mud continued to the end of the Dinantian and into the Namurian, represented by the Longstone Mudstones and Edale Shale Group respectively.

The deep valleys incised into the broad plateau formed by the Derbyshire Platform limestones provide a wealth of exposure of the late Dinantian formations from the upper part of the Woo Dale Limestones upwards. The only exposed Staffordshire Platform limestones of pre-Holkerian age occur around quarries at Caldon Low.

The limestones of the two platform successions typically occur in thick to very thick, uniform and extensive beds of grey to pale grey-brown, bioclastic and peloidal grainstones and packstones. Finer grained, thinner bedded wackestones and packstones are also present, especially in parts of the Holkerian succession. Bedding planes pitted by subaerial palaeokarstic dissolution and affected by soil-forming processes which altered the top few centimetres of the underlying limestone occur cyclically through much of the Asbian and Brigantian succession (Figure 13), column b). The palaeokarstic surfaces are commonly overlain and made highly conspicuous by beds of varicoloured clay derived from fine volcanic ash, known locally as ‘clay wayboards’.

During Asbian times and possibly earlier, when carbonate production and platform growth reached its acme, a Cracoean apron-reef facies developed around much of the northern, western and southern rims of the Derbyshire Platform. This facies forms some of the most spectacular scenery in the southern Peak District around Castleton and Earl Sterndale, where numerous exposures have yielded the most abundant and diverse fossil assemblages of the Carboniferous Limestone. The limestones in which they are found are micritic, formed from sediment containing a high proportion of lime mud. Geopetal mud infilling the fossils (see example in (Figure 10) indicates deposition on slopes dipping towards the basin at about 25°. The mud may have been held in place by a mucilaginous, surficial, microbial layer before being rapidly lithified. Isolated knoll reefs (mud mounds) grew in the eastern part of the platform during the Brigantian (Plate 7). It has been suggested that the considerable variation in the height of these structures is due to marked local variations in the rate of subsidence.

Apart from the ‘clay wayboards’ and rare thin coals, basaltic lavas and tuffs, together with a few dolerite sills and vent agglomerates, form the only non-carbonate element in the Derbyshire Platform succession (Figure 8), column 3, (Figure 15). The lavas formed extensive subaerial and shallow submarine flows, probably erupted from a few scattered shield volcanoes. Away from the platform, the volcanic rocks show a more pyroclastic character; rare pillow lavas are also present.

The few boreholes that penetrate the Woo Dale Limestones suggest that partially or wholly dolomitised limestones are present extensively at depth, as well as in the surface outcrop in the type area of the Wye valley near Buxton. The dolomitisation appears to be stratigraphically controlled and may therefore have been initiated by the action of hypersaline brines during occasional periods of restricted circulation and intense evaporation in the shelf sea. It may also have occurred during deep burial in late Carboniferous times through the action of magnesium- and iron-rich fluids. These may have emanated either from the underlying volcanic rocks or from surrounding basinal sequences, and migrated into the more permeable limestone beds at various levels.

A second type of dolomitisation affects limestones mainly within about 200 m of the surface in the southern part of the outcrop of the Derbyshire Platform and adjacent ramp facies. This type seems most likely to be due to magnesium-rich, downward percolating groundwater during Permian and Triassic times.

Widmerpool Gulf

The narrow part of the Widmerpool Gulf that lies between the Derbyshire and Staffordshire platforms within the Derbyshire Dome outcrop has been variously described as off-shelf and basin, but ‘carbonate ramp’ is now the preferred term. The ‘Gulf’ (actually a half-graben) broadens and deepens to the south-east (Figure 7), where an argillaceous, turbiditic basin facies may be present. Where an apron reef rimmed the platforms, there was an abrupt basinward change to deep water. Elsewhere, there was a gentle slope to deeper water. A wide variety of limestone lithologies were formed in this ramp environment, including dark, micritic, cherty beds in the deeper quieter parts and paler, alternating coarse and finer grained, laminated beds in the shallower parts that were more affected by current action. Sporadic conglomeratic limestones represent storm layers. However, by far the most conspicuous and remarkable features are the huge masses of grey, micritic limestone knoll reefs, which dominate the scenery in parts of the Manifold valley and in Dovedale (Plate 8).

The ramp facies of the Widmerpool Gulf, represented by the Milldale Limestones and the Hopedale Limestones formations (Table 6), is well exposed in the deeply incised valleys of the rivers Dove, Manifold and Hamps in the south-west of the Peak District. The Hopedale Limestones were deposited mainly in shallower water over the large composite knoll reefs of Chadian age in the Milldale Limestones. A few knoll reefs are also present in the Hopedale Limestones, representing renewed development of this facies in Asbian times.

As in the Craven Basin from Arundian to Brigantian times, platform growth and differential subsidence, probably caused by tilting of the underlying basement blocks, led to steepening of the platform margins from ramps to slopes (Figure 9). The now relatively deeper Widmerpool Gulf and North Staffordshire Basin became the sites of predominantly turbidite deposition. At first, these turbidites (the Ecton Limestones) were sediments derived mainly from adjacent platform areas. Later, however, muds and sands probably derived from the Wales–Brabant High (Figure 7) were deposited with the carbonates to form the Widmerpool Formation and the Mixon Limestone–Shales Formation.

Chapter 5 Namurian

Rocks of Namurian age include the Edale Shale Group, the Millstone Grit Group, and the upper parts of the Wensleydale Group and Bowland Shale Group. They characterise the central part of the Pennine Range and form a continuous outcrop extending from the northern to the southern boundaries of the region (Figure 1), (Figure 2). There are also numerous outliers forming isolated hills in the Askrigg Block and Craven Basin areas (Pen-y-ghent for example), and the more extensive outcrop of the Bowland Fells between Lancaster and Settle. Anticlinal inliers occur within the Lancashire Coalfield between Chorley and Bacup. To the south of Skipton, a single broad outcrop forms the core of the Pennines, culminating at Kinderscout. This outcrop divides south of Edale on either side of the Peak District Carboniferous Limestone outcrop, defining the flanks of the Derbyshire Dome.

Coarse-grained to granular, feldspathic sandstones are the dominant and characteristic component of the Millstone Grit Group (Figure 16), (Figure 17). In the north-west of the region, the oldest feldspathic sandstones, notably those of the Pendle Grit Formation, are of Pendleian (E1c) age. In the south, the oldest feldspathic sandstones are of Marsdenian (R2) age — the Ashover Grit of R2b age near Derby in the east and the Chatsworth Grit of R2c age near Leek in the west. The underlying Namurian mudstones here are assigned to the Edale Shale Group (Figure 18), and although sandstones are present in this group, their protoquartzitic composition (less than 1 per cent feldspar and over 75 per cent quartz) easily distinguishes them from those that characterise the Millstone Grit. The term ‘Millstone Grit Series’ used on older BGS maps was a synonym for the Namurian Series and included both the Edale Shale Group and the Millstone Grit Group of the present classification (Figure 16).

Further classification of the Namurian succession is based on its remarkable cyclical nature, marked by the regular occurrence of marine bands that define the base of each cycle. These bands, typically 0.5 to 3 m thick and consisting of dark grey to black calcareous shaly mudstone, contain crushed, fossilised shells, mostly of free-swimming marine organisms. Of these, the ammonoids (or goniatites) are by far the most useful stratigraphically (see (Table 9) for an example). As a consequence of the rapid evolution of these, each successive marine band, with few exceptions, contains a different species and is therefore a unique marker band. Moreover, these bands allow extensive correlation, for many can be traced throughout the region, and indeed for thousands of kilometres beyond. They are thought to represent interglacial sea level highstands associated with the fluctuations of the southern polar ice cap; 46 such marine bands are recognised, each named after the key ammonoid present (Table 7). A further three have recently been found (Blacko, Saleswheel and Butterly), but ammonoids have so far not been discovered in the first two. Marine bands are assigned an index symbol (for example, R2a1 for the Bilinguites gracilis Marine Band) and grouped into zones (R2a). The  zones are further grouped into stages (as in the Marsdenian, with the index R2) which are based on the dominant ammonoid genera (Table 7).

Before W S Bisat first used the ammonoids to produce a biostratigraphical zonation in the 1920s, the main Namurian sandstones were correlated by numbering them from the top downwards. This led to serious miscorrelations on many of the ‘Old Series’ geological maps, on which the lowest coarse ‘grit’ in the succession was usually named ‘Kinderscout Grit’. This grit is now assigned a late Kinderscoutian (R1c) age. Former so-called ‘Kinderscout Grits’, such as the Warley Wise Grit of the Clitheroe and Bradford districts and the Ashover Grit of the Derby district, are now known to range in age from late Pendleian (E1c) to late Marsdenian (R2b) (Figure 16). The marine bands provide an essential stratigraphical framework, enabling repetitive and closely similar rock units, especially the coarse-grained sandstones of the Millstone Grit, to be correlated across the Pennine Basin. Even if only the six marine bands that define the stage boundaries are plotted out in a cross-section (Figure 16), the overall picture demonstrates their importance in basin analysis. It should eventually be possible to elucidate the facies variations, sedimentology and palaeogeography of each cycle throughout the basin. Attempts to do this have already met with some success, especially for the Rough Rock. However, comprehensive studies have more often been confined to the outcrop of major sandstones such as the Ashover and Roaches grits, to groups of cycles, or to particular stages in the sub-basins. In some parts of the succession where marine bands are poorly developed or locally absent, particularly in the late Kinderscoutian (R1c), disconformities enable the application of sequence stratigraphy.

Traditionally, only the mappable sandstones were named in the Namurian succession. In recent decades, many of the more important marine bands have also been mapped, and these, although mostly recognised by their fossil content, are now regarded as lithostratigraphical units. However, only in the recently published maps and memoir of the Lancaster district has subdivision of the entire Namurian rock succession been attempted. Elsewhere, the lithostratigraphy remains largely informal (Figure 16), (Figure 17), (Figure 18); (Table 8).

The Namurian rocks are mostly formed from mud, silt and sand carried into the Central Pennine Basin by a large river system draining tectonically active mountains that were being rapidly eroded, probably located in an area that now includes Scandinavia and Greenland. The abundance of fresh feldspar in the typical Millstone Grit sandstones (Plate 9) testifies to erosion of and rapid transport from a granitic source area. A great delta system intermittently prograded south-eastwards, so that at first, in the late Pendleian (E1c), fluvial sands extended only as far as the former Askrigg Block. They eventually reached the north Staffordshire area in the late Marsdenian (R2c), four to five million years later. The intermittent character of delta progradation was primarily due to the same fluctuations of sea level that caused the cyclicity referred to above. Each time sea level rose, the deltas and the river valleys of the hinterland were flooded to varying degrees by marine waters and black mud slowly accumulated, together with the shells of marine organisms and finely comminuted plant debris. As the rise in sea level slowed and stopped, and sea level started to fall, fluviodeltaic sediments again prograded into the basin — fine muds and silts at first, then increasing amounts of sand, often carried by density or turbidity currents down the prodeltaic slopes far beyond the river mouth. If the progradation extended far enough before being halted by the next marine flooding event, the distal prodeltaic deposits were overstepped progressively by proximal sands, river mouth bar sands and delta-top, fluvial sands. A phase of weathering and soil formation may be preserved locally. Also, a coal, representing peat formation in rising water table and swamp conditions, may be preserved, preceding the next marine transgressive phase.

Other factors besides sea level and basin bathymetry (largely inherited from Dinantian times) undoubtedly influenced sedimentation, but their individual effects can be distinguished only with difficulty. These included ‘thermal subsidence’ following regional stretching, thinning and heating of the Earth’s crust, climatic influences on sediment supply and river discharge, currents within the basin and the compaction of the underlying sediments.

Detailed mapping and sedimentological studies have shown that the form of the deltas varied considerably. The two main types are turbidite-fronted deltas and sheet deltas. A third, uncommon type, recognised only in the Yeadonian (G1) Lower Haslingden Flags and Upper Haslingden Flags of east Lancashire, is the elongate delta. The turbidite-fronted deltas required a deep and extensive basin to develop fully. Their distribution was controlled largely by sea floor topography comprising the ‘block and basin’ features and carbonate platforms inherited from the early Carboniferous. They prograded progressively, but intermittently, south-westwards, filling the depositional space available. Their deposits, which largely comprise the Pendle Grit, the Lower Kinderscout Grit and its correlatives, and the Ashover and Roaches grits, provided the bulk of the Central Pennine Basin fill (Figure 16), (Figure 17), with maximum thicknesses of 600 m, 570 m and 360 m, respectively. Deposition in these turbidite-fronted delta systems started with distal silty muds and silts and ended with river channel and floodplain sands, prior to the succeeding marine flooding event. However, some delta systems span two or more marine transgressive–regressive cycles, the effects of which seem to have been diminished by continuing input of fresh water and transported sediment. Thus the marine bands, if present, are mostly mudstones containing brachiopods such as Lingula and bivalves such as Sanguinolites that tolerated waters of lower salinity. They may also be recognised by subtle changes in palynomorph and mineral content. Several thick sandstone bodies, the Lower Kinderscout Grit for example, overlie erosion surfaces which cut deeply into the underlying strata. They probably represent the fill of valleys incised during sea level lowstands.

Sheet deltas became generally more extensive with time. The early Arnsbergian (E2a) Ward’s Stone Sandstone/Red Scar Grit delta, for example, only extended southwards as far as north Lancashire and the Askrigg Block, whereas the late Marsdenian Holcombe Brook Grit/Huddersfield White Rock/Chatsworth Grit delta extended across the Pennine Basin to the Derby and Stoke-on-Trent districts. The water depths of the basins across which the sheet deltas prograded were relatively shallow, as shown by the reduced thicknesses of the deposits of each system. Even at their thickest, they are a quarter of the thickness, or less, of the turbidite-fronted delta systems (Figure 16), (Figure17). Each cycle coarsens upwards, representing the progradation of the delta into the marine environment and the establishment of a fan-like system of distributary river channels. The sandstones of the elongate delta systems in the lower parts of the Lower and Upper Haslingden Flags similarly coarsen upwards, but do not attain the coarse grain size of the sheet delta sandstones. The upper sandstones form long, narrow bodies, which are analogous to the sand bodies in the modern Mississippi ‘birdsfoot’ delta.

In the following regional descriptions, the Namurian rocks are described largely as they occur at outcrop. However, much of the general information summarised above is derived from many deep and shallow boreholes. The rocks of Pendleian age mainly crop out around the Dinantian outcrops and are thus restricted to the Askrigg Block and Craven Basin in the north, and around the Carboniferous Limestone outcrop of the Peak District in the south. Younger strata, particularly those of Kinderscoutian, Marsdenian and Yeadonian age, have more extensive outcrops.

Wensleydale Group of the Askrigg Block

On the Askrigg Block, the late Dinantian cyclothemic (‘Yoredale’) succession, in which limestones are a major component, continues into the Namurian and is included in the Wensleydale Group (p. 27). The Namurian (early Pendleian) part of this group has a maximum thickness of about 180 m at the northern boundary of the region. The succession present in the Swaledale area is progressively cut out southwards by an unconformity, so that it is absent in approximately the southern third of the block. This unconformity was caused largely by northward tilting of the block, associated with movements on the Craven Fault System and downwarping of the Stainmore Trough (see also Chapter 9). The unconformity is of intra- E1c age and occurs at the base of the Grassington Grit Formation and its equivalents. The largest stratigraphical gap is in the Greenhow area, where the Grassington Grit overlies the Asbian Greenhow Limestone.

Bowland Shale Group

Over most of the region, except for parts of the former carbonate platforms, fissile mudstones of latest Brigantian age pass up conformably into similar beds of Pendleian age. These are represented by the Upper Bowland Shale Formation in the Craven Basin (Plate 10), and by the lowest parts of the Edale Shale Group in the Peak District. The Upper Bowland Shale extends a short distance on to the southern margin of the Askrigg Block at Grassington, and also at Malham, where it onlaps a pre-existing fault scarp of the Brigantian Middle Limestone.

Flanking much of Ribblesdale from near Preston to Settle, Skipton and beyond to Wharfedale, the Upper Bowland Shale is exposed in numerous streams and gullies draining the prominent escarpments formed by the overlying Pendle Grit Formation. Its base is arbitrarily taken at the base of the Cravenoceras leion Marine Band (E1a1). The top is placed at the base of the lowest feldspathic sandstone corresponding to the base of the Pendle Grit Formation (and the base of the Millstone Grit Group). The formation has an average thickness of about 150 m and consists of thinly interbedded dark, pelagic, fissile mudstone and blocky or platy, weakly calcareous, silty mudstone or siltstone. Thin muddy limestones and dolostones occur locally, especially in association with the Cravenoceras leion, Cravenoceras brandoni (E1b1), Tumulites pseudobilinguis (E1b2), and Cravenoceras malhamense (E1c1) marine bands. The blocky beds probably originated as mud transported into a deep basin by weak turbidity currents and deposited out of suspension. A thin, turbiditic, feldspathic sandstone member (Hind Sandstone) on the Bowland Fells escarpment immediately underlying the Cravenoceras malhamense Marine Band is a precursor of the Millstone Grit delta systems.

Edale Shale Group

The Edale Shale Group, like the Upper Bowland Shale, has its base at the base of the Cravenoceras leion Marine Band, but differs in having a highly diachronous upper boundary with the Millstone Grit Group (Figure 18). Only on the exposed northern, western and southern margins of the Dinantian carbonate platform in the Peak District around Castleton, Earl Sterndale and Wirksworth, respectively, is there evidence of a basal unconformity, with shales of Arnsbergian (?E2a) age overlying an exhumed, deeply embayed limestone topography. Scattered exposures in the eastern outcrop and borehole sections in the concealed part of the platform to the east show a highly condensed, thin, black shale succession. For example, the whole of the Pendleian Stage is represented by only about 1. 7 m of mudstone in a borehole penetrating through to the platform succession at Birchover in the Peak District. In contrast, the equivalent succession is 170 m thick and contains thick sequences of turbidites in the Duffield Borehole in the Widmerpool Gulf, north of Derby. A similar thickness is present in the North Staffordshire Basin around Werrington (Figure18). Thus, in early Namurian times, the Dinantian platform remained an isolated positive feature within the basin, starved of the mud, silt and sand that accumulated in the adjacent sub-basins — the Alport/Edale Basin, the North Staffordshire Basin and the Widmerpool Gulf, to the north, west and south, respectively (Figure 7).

In these basins, the turbiditic, calcareous mudstones and siltstones that dominated the lower parts of the underlying late Dinantian succession, persisted in the lower parts of the cycles until the end of E2b times. These include the marine bands, which are typically several metres thick. Their faunas are fragmented and dispersed in the unlaminated, calcareous, turbidite beds, and concentrated in a more or less complete but flattened state in the dark, fissile mudstones that represent slow pelagic sedimentation. Rare distal falls of fine volcanic ash are represented by laminae of pale grey, K-bentonitic clay. The upper parts of several cycles are characterised by tough, pale grey, protoquartzitic siltstones and sandstones (quartz arenites), interbedded with varying proportions of dark, fissile mudstone. Groups of these beds of Pendleian (E1b) to Arnsbergian (E2c) age form named units in the North Staffordshire Basin (Figure 18), such as the Minn Sandstones and Hurdlow Sandstones, the former being the more extensive. These sandstones tend to crop out in the axes of large north-south-orientated anticlines that form long, whale-back hills, for example Bosley Minn, Lask Edge and Gun Hill. Protoquartzitic sandstones higher in the succession include the Ipstones Edge Sandstones, of Chokierian (H1) to late Kinderscoutian (R1c) age, which reach a maximum thickness of about 270 m in the south of the North Staffordshire Basin. It subdivides northwards into the Cheddleton Sandstones (H1 to H2) and the Kniveden Sandstones (R1c), and then farther north still into the Lum Edge Sandstones (H1b) and Blackstone Edge Sandstones (R1b). The facies of these sandstones changes from shallow-water fluviodeltaic in the south to mainly turbiditic in the north. Palaeocurrent evidence indicates sediment transport from the south or south-west, presumably from the Wales–Brabant High that defined the southern margin of the Basin during much of the Namurian. In the Stoke-on-Trent district, just beyond the south­western margin of the region, the highest protoquartzites in the succession are the Brockholes Sandstones of mid-Marsdenian (R2b) age, which interdigitate with the local basal feldspathic sandstones of the Millstone Grit Group. These belong to the Roaches Grit, very close to its western limit.

Millstone Grit Group

Pendleian

Beds of Pendleian age assigned to the Millstone Grit Group crop out only in the north of the region, mainly on the Askrigg Block and in the Craven Basin. A representative of the lower part of the Grassington Grit Formation (‘Bearing Grit’) occurs locally on the block, reaching a maximum thickness of 31 m on Grassington Moor. It is noteworthy in being a delta-top sandstone that appears to pass laterally into thick, basin-facies, proximal turbidites of the Pendle Grit Formation (see below). This lateral passage is inferred from the fact that both units are immediately overlain by the Blacko Marine Band (E1c2). The main, upper part of the Grassington Grit, which overlies the Blacko Marine Band and includes the Lower Howgate Edge Grit and the Underset Grit, caps some of the prominent hills on the block, such as Ingleborough and Fountains Fell. On the latter, it comprises 50 m of mainly coarse-grained sandstone with quartz pebbles, with minor siltstones, seatearths and thin coals. This lithological variability characterises the formation as a whole on the Askrigg Block and is matched by thickness variation ranging from a maximum of 66 m to a minimum of 1. 2 m in Upper Swaledale, where it comprises a fine-grained, siliceous sandstone palaeosol, the Mirk Fell Ganister.

The Pendle Grit Formation is the oldest and thickest sandstone-dominated unit in the Millstone Grit Group. It reaches a maximum estimated thickness of about 550 m in the fell country south-west of Settle, and is generally well over 360 m thick in its extensive outcrops from Lancaster south to the type area at Pendle Hill and east to Skipton Moor. It includes the Wilpshire Grit of the Preston and Rossendale districts. A good impression of its outstanding topographical expression can be obtained by the distant view from the isolated ridge of Longridge Fell (itself formed of Pendle Grit). All the northern, eastern and southern aspects are largely occupied by escarpments of Pendle Grit, overlooking lowlands underlain mostly by the Worston Shale and Bowland Shale groups.

The formation consists of sandstones (Plate 11), siltstones and silty mudstones of turbidite facies interbedded in varying proportions. The predominantly finer grained beds in the upper part of the formation have been separately distinguished as the Surgill Shale Member. This includes the Blacko Marine Band (E1c2), which contains a dispersed, marginal marine fauna characterised by the bivalve Sanguinolites. In general, the finer, thinly interbedded lithologies constitute a background facies into which fans and channelised bodies of coarser grained sand were deposited, although thick sequences of coarse-grained sandstone also occur. Topographical features on the outcrop of the formation reflect the geometry of the sand bodies. The clearest expression of this is on Skipton Moor, where there is a series of short, whale-back ridges, many with small crags of coarse-grained pebbly sandstone at their crests. Each ridge represents the fill of a channel cut into the ‘background facies’ which draped the submarine prodelta slope. The ‘background’ rocks underlie the ground between the ridges. Apart from the association with the Bearing Grit noted above, little is known of the great river and its delta distributaries that transported the enormous amount of sediment represented by the Pendle Grit. However, palaeocurrent measurements indicate that it probably lay between the Askrigg and Lake District blocks.

The Pendle Grit Formation is succeeded by correlatives of the main upper part of the Grassington Grit — the Brennand Grit Formation in the Bowland and Lancaster Fells: the equivalent Warley Wise Grit Formation in the outcrop between the Pendle Hill area and Skipton: the Almscliff Grit near Harrogate. Thicknesses at outcrop range from about 250 m in the Brennand area, 220 m near Colne, and 140 m at Follifoot near Harrogate, thinning westwards to a feather-edge in the Lancaster and Bowland fells. These grits are all thick units of mainly coarse-grained, cross-bedded sandstone interpreted as braid delta deposits. In some areas, for example Brennand and Skipton Moor, a cross-bedded, fluvial facies is underlain by massive conglomerates thought to represent channelised, subaqueous, delta-front, mass flow deposits. The fluvial deposits are overlain in the Skipton area by the thin Bradley Coal and the Bradley Flags. These probably represent delta swamp and river mouth bar environments, respectively, established as sea level started to rise again, culminating in deposition of the widespread Cravenoceras cowlingense (or Cockhill) Marine Band (E2a1). This marks the Pendleian (E1)/Arnsbergian (E2) boundary.

Arnsbergian

During the Arnsbergian (E2), the thickest sediment accumulation and, by inference, the maximum subsidence, continued to be centred on the north Bowland Fells area of the Craven Basin. Indeed, the combined upper Pendleian and Arnsbergian successions there, totalling about 1600 m, are amongst the thickest in Western Europe. Here, thick turbidite successions, such as the Dure Clough and Cocklett Scar sandstones of the Roeburndale Formation, are up to 100 m and 65 m thick, respectively. However, there was also a marked degree of general regional (thermal) subsidence as well as differential subsidence, for deep­water turbiditic beds were also deposited over the eastern part of the former Askrigg Block. This is exemplified by the Nidderdale Shale between the Cravenoceras cowlingense (or Cockhill) Marine Band and the Red Scar Grit, which is up to 93 m thick, and the late Arnsbergian Scar House Formation, which is 47 m thick. The only time the sedimentation rate matched the subsidence rate over a wide area was during deposition of the fluviodeltaic Red Scar Grit and Ward’s Stone Sandstone (and their associated palaeosols and thin coals), and of the slightly older Sapling Clough Sandstone Member, and of the Marchup Grit of the Bradford district. The general subsidence affected, and would continue to affect, the rest of the Pennine Basin, but the other former ‘highs’ are overlain only by condensed mudstone successions, having been starved of clastic sediments.

The search for exposures of key marine bands has been particularly rewarding in the Lancaster district, where they have proved essential for correlating the sandstone sequences. For example, the Eumorphoceras ferrimontanum Marine Band (E2a2) has been found at 31 localities. Contorted and slumped beds are characteristic of the Arnsbergian deposits in this part of the Pennine Basin, the result of rapid deposition on unstable prodelta slopes and occasional seismic activity caused by local fault movements. Fault movements around the margins of the Askrigg Block had probably largely ceased by the late Arnsbergian and depositional slopes were thereafter gentle.

The Arnsbergian succession in the area of the Craven Basin from Lancaster to Rochdale (Figure 7), (Figure 16) includes the thickest sandstone-poor, shaly mudstone sequences in the Millstone Grit Group of the Pennine Basin. Some of these, particularly those containing numerous marine bands, have been given local names. They include the Caton Shale Formation (70 m thick, of E2b age, and equivalent to the Marchup Marine Beds of the Bradford district) and the Sabden Shales Formation (600 m thick and of E2a–R1c age). The latter form a ‘slack’ between the dip slope of the Warley Wise Grit and the escarpment of the Kinderscout Grit, and underlie the Sabden valley near Blackburn on the steeply dipping southern limb of the Pendle Monocline. The Sabden Shale is well exposed at Salmesbury Bottoms (the stratotype for the Kinderscoutian Stage) in the Preston district, and contains marine fossils throughout, as well as conspicuous carbonate concretions. There are some good sections along the outcrop to the north-east, including a ‘type section’ at Stonehead Beck, Cowling [SD 9475 4330] (the stratotype for the Chokierian Stage and the European mid-Carboniferous boundary reference section). This exposes a shale succession spanning the Arnsbergian–Chokierian boundary and containing seven marine bands, including the Nuculoceras nuculum Marine Band (E2c3) at the base and the Homoceras beyrichianum Marine Band (H1b1) at the top. Latest Arnsbergian sandstones are confined to the northern parts of the basin, including the fluviodeltaic Silver Hills Sandstone Formation, the Lower Follifoot Grit and the Middleton Grit of the Lancaster-Settle, Masham-Harrogate and Bradford districts, respectively.

Chokierian and Alportian

There is no evidence for the presence of Alportian (H2) rocks over the Askrigg Block. They are inferred to be present in the Harrogate and Bradford districts, but the succession is poorly exposed and borehole control is lacking. The Chokierian succession in the Lancaster district consists mainly of hemipelagic mudstones. Some marine bands are missing towards the north-east of this district, indicating a non-sequence that is widespread elsewhere in the northern hemisphere. The fluviodeltaic Accerhill Sandstone Formation lies approximately at the level of the Chokierian/Alportian boundary. It is 23 to 70 m thick, and has the formerly worked Clintsfield Coal at or near its top around High Bentham. The sandstone is overlain locally by the Homoceras undulatum Marine Band (H2b1), proving that some Alportian strata are present. The fluvial Upper Follifoot Grit of the Harrogate district lies at the same level as the Accerhill Sandstone. In the Bradford district, the Chokierian succession comprises 30 to 45 m of argillaceous beds ranging from H1a1 to H1b1 in age, overlain by the Brocka Bank Grit, a lenticular, coarse-grained sandstone up to 55 m thick. The thickest unbroken Chokierian sequence proved at outcrop is at Salmesbury Bottoms [SD 6172 2936], where the full thickness of about 58 m of shales is almost completely exposed. This section continues upwards to expose mainly marine mudstones, including about 6 m of Alportian shales with the Hudsonoceras proteum Marine Band at its base. These are overlain by Kinderscoutian strata up to the R1c Zone (Figure 19).

Kinderscoutian

Late Namurian marine bands in and around the area of the former Askrigg Block tend to have a different lithology and faunal content from those farther south in the Pennine Basin. They commonly consist of calcareous sandstones with a benthonic, shelly fauna, including brachiopods, crinoids and bryozoans, together with rare solitary corals, trilobites and foraminifera. This indicates near-shore conditions with an abundant sediment supply. There are few ammonoids, making precise correlation with the coeval, hemipelagic marine bands to the south difficult. The late Kinderscoutian (R1c) succession of the central Pennines is characterised by great thicknesses of coarse sandstones, brought into the basin by large rivers. Marine faunas are mainly restricted to benthonic forms dominated by Lingula mytilloides, with thick-shelled ammonoids rare or absent.

The Cayton Gill Shell Bed, thought to lie in the middle of the R1a Zone, is perhaps the best known of the shelly marine bands. Its type locality is at Cayton Gill [SE 277 632] in the Harrogate district, and it is also widely exposed in the Pateley Bridge and Masham districts. Other shell beds are much less widespread. They include the Otley Shell Bed, which was formerly exposed at Otley Chevin [SE 200 443]. There, marine shells dispersed through 5. 8 m of strata are of late R1b or early R1c  age. In the Reticuloceras todmordenense Marine Band (R1a4), diagnostic ammonoids are commonest in the basin margin districts, making it the most widely recognised marine band. Logged sections and faunas from basin margin and basinal environments (Table 9; (Figure 19) demonstrate the thicker marine bands and richer faunas of the former. The section at Salmesbury Bottoms (Figure 19) continues up to the base of the Parsonage Sandstone in the R1c Zone. This marks the upper boundary of the Sabden Shales and the base of the Kinderscout Grit delta succession. The section is a type locality for the Alportian (H2a) to Kinderscoutian (R1b) basinal succession.

Rocks of the R1c Zone consist largely of the Kinderscout Grit delta succession, the lower of the two great turbidite-fronted delta complexes of the late Namurian. The other is the Ashover/Roaches grit complex of R2b age. The R1c succession, widespread from Wharfedale southwards, starts with thin-bedded distal turbidites typified by the Mam Tor Beds (Plate 12). These are overlain in north Derbyshire by the very thick-bedded turbidite sandstones of the Shale Grit. This is, in turn, overlain by the Grindslow Shales, interpreted as prodelta slope deposits in the lower part, and shallow mouth bar deposits in the upper part. The latter also contains thick lenses of coarse-grained sandstone interpreted as feeder channel-fills. Similar successions elsewhere include the Todmorden Grit in Yorkshire and the Parsonage Sandstone in Lancashire, but precise correlation is uncertain. Shallower water deposits predominate in the Settle district, and north of Wharfedale, as proved in the Farnham Borehole (Figure 19), (Figure 20).

The BGS Bradup and Hag Farm boreholes near Ilkley in the Bradford district showed that the R1c deltaic succession spans at least five marine–fluvial–marine, coarsening-upwards cycles (Figure 20), section 2). The lowest cycle grades up from turbiditic delta slope deposits of inferred R1c1 age. It is tempting to correlate this succession with the coarse sandstone–mudstone and siltstone sequences that characterise the Kinderscout Grit and its correlatives elsewhere in the Central Pennine Basin, but of the few marine bands found here most are lacking in diagnostic ammonoids. The typical coarse-grained, cross-bedded fluvial sandstones form spectacular landmarks such as Brimham Rocks (Plate 13), the Cow and Calf Rocks, the Doubler Stones, Laddow Rocks and Kinder Downfall.

Research on the main Lower Kinderscout Grit outcrop of the Glossop and Chapel en le Frith districts has identified nine coarse-grained, lenticular sandstone units, each up to about 90 m thick. They thin out at successively higher levels in a down-depositional dip direction in the lower part of the succession. Each unit overlies an erosion surface and is interpreted as the fill of a valley, probably incised during glacio-eustatic sea-level fall. Four of the sandstones are capped by palaeosols and thin coal seams, indicating a sea-level rise that waterlogged the delta. However, evidence for marine transgression has only been found above the topmost unit (in this case the Butterly Marine Band–R1c5).

Cross-bedding and channel sand body orientations indicate flow from the north or north-east. The progradation of the delta towards the south and south-west is indicated by wedging out of the fluvial sandstones in that direction at progressively higher levels, notably in the Rochdale, Chapel en le Frith and Buxton districts. Thus the highest sandstone between the Butterly and the Bilinguites gracilis marine bands extends farthest, lensing out near Blackburn in the west, at Buxton in the south-west and near Hathersage in the south. Turbiditic slope sandstones assigned to the Kinderscout Grit in the south and the Longnor Sandstones in the south-west extend farther south, nearly to Bakewell and Leek.

Marsdenian

The Marsdenian (R2) succession begins with the widespread Bilinguites gracilis Marine Band (R2a1). This has been recorded at numerous exposures and boreholes throughout the region, except in the north. It is documented at Bentham in the Lancaster district, in the Farnham Borehole near Harrogate, and in the Derby and Ashbourne districts, where it occurs in successions now assigned to the Edale Shale Group. The Marsdenian succession is greatly attenuated in North Yorkshire; only about 13 m of fissile mudstones with a Lingula band are present near Kirkby Malzeard in the Masham district. In contrast, the greatest thickness of about 600 m of beds occurs between Preston and Macclesfield to the west and south of the great thickness of Kinderscoutian delta deposits, where they fill the accommodation space left after the Kinderscoutian. Augmented by protoquartzitic sediments locally derived from the Wales–Brabant High, the depositional rates of this thick Marsdenian succession almost matched subsidence rates throughout the basin. Only three (R2b3, R2b5, and R2c2) of the eight Marsdenian cycles contain major, widespread sandstones. These are the Midgley (or Pule Hill) Grit and its correlatives, the Ashover/Roaches Grit and the Chatsworth Grit/Huddersfield White Rock, respectively (Table 8). Sandstones in the lowest two cycles, such as those in the Readycon Dean Grit, are mostly interbedded with siltstones, only the Scotland Flags and the East Carlton Grit of the Bradford district being substantial fluvial sandstones. In the Preston district, near Blackburn, about 200 m of turbidites were probably deposited at this time. They include the Alum Crag Grit Member below and an unnamed unit above the Bilinguites bilinguis Marine Band (?R2b1) respectively. Thus, there seems to have been a substantial turbidite-fronted delta here in early Marsdenian times, with no delta-top fluvial deposition.

During the R2b5 cycle, fluviodeltaic sandstones, such as the Hazel Greave Grit in the Blackburn district and the Guiseley Grit in West Yorkshire, continued to be deposited extensively. However, the main depocentre became the large sub-basin flanking the north side of the Wales–Brabant High in the south known as the Widmerpool Gulf, which was linked to the partially filled Macclesfield to Preston sub-basin. It became the site of the last of the great turbidite-fronted Namurian deltas which, unlike the earlier Pendleian and Kinderscoutian examples, prograded from the south-east, although the coarse-grained feldspathic sands were probably derived from the same northerly source. The succession starts with the Bilinguites metabilinguis Marine Band (R2b5). The overlying localised, thick turbidite deposits, such as the Five Clouds Sandstones, are mostly found in the Macclesfield district and the western part of the Buxton district, where the main delta slope siltstones, mouth bar sandstones and turbidite feeder channel sandstones also occur. The main delta-top sandstones, the Ashover Grit in the east and the Roaches Grit in the west, were once linked as a continuous sand body over the southern part of the former Derbyshire limestone platform. Here, they comprise the lowest formation of the Millstone Grit Group, overlying the Edale Shale Group. This succession is well known from boreholes, for example those at Birchover and Tansley (Figure 18). The Roaches [SK 00 63], at the upturned southern end of the Goyt Syncline, provide some of the most spectacular crag scenery in the Pennines, as well as displaying fine examples of various forms of cross-bedding and channel fill. Indeed, the main sand body here is thought to be the fill of a palaeovalley incised at least 80 m into the underlying beds during the regressive part of the R2b5 cycle. The sea-level rise that followed is represented locally by a coal (formerly worked in the Belper area), and the widespread Bilinguites superbilinguis Marine Band (R2c1).

The R2c2 cycle largely comprises a coarsening-upwards, prograding succession. It culminates in the extensive Chatsworth Grit and its local correlatives, notably the Huddersfield White Rock and Holcombe Brook Grit with the underlying Brooksbottoms Grit. This is a good example of sheet delta deposition, although the lower prodeltaic beds locally include a few thin sharp-based turbiditic sandstones. The thickest (45–60 m) and coarsest deltaic pebbly sandstones crop out in two belts on either side of the Pennine Anticline; the one between Moscar and Chatsworth in the east is about 18 km long, the westerly one between Kettleshulme and Stoke-on-Trent is about 28 km long. There are some spectacular crag exposures in both. The distribution of the sandstones, and the west to south-west-directed palaeocurrents indicate that the main delta progradation was towards the west-south-west from around Sheffield, across the central and northern parts of the former Derbyshire limestone platform, to the area north of Stoke-on-Trent. However, the finer grained deposits on the flanks of this sheet delta extended at least as far as the Bradford district in the north and the Derby district in the south. The sandstones are overlain by locally worked coals and the Cancelloceras cancellatum Marine Band (G1a1), which marks the base of the Yeadonian (G1).

Yeadonian

Two units of interbedded fine-grained sandstone and siltstone (the Lower and Upper Haslingden Flags) in the Rochdale district are separated by the Cancelloceras cumbriense Marine Band (G1b1). The succession is unusual in several respects. A ‘green facies’ indicates a westerly source, as opposed to the more normal northerly one. Also, the deltaic sandstones have elongate, west-to-east bar-finger form and commensurate palaeocurrent directions. The Upper Haslingden Flags are succeeded by mudstones, but these appear to be locally cut out by the erosion surface at the base of the Rough Rock. In the eastern outcrop, in the Bradford, Huddersfield and Glossop districts, the northerly sourced Rough Rock Flags are perhaps slightly younger and directly underlie the Rough Rock.The Rough Rock is the most extensive sandstone in the Millstone Grit Group, giving rise to craggy, much quarried escarpments on both flanks of the Pennines (Plate 14) and some long dip slopes. The sandstone is typically very coarse grained and sparsely pebbly. It is mainly about 15 m thick, but up to about 45 m in the Rochdale district, where it is split by the formerly worked Sand Rock Mine Coal. In the Chesterfield district, it becomes fine grained and impersistent. The sandstone displays a range of cross-stratification and bedforms that indicate deposition in braided river channels, generally flowing south-west, but with some marked deviation, especially in the southern districts.

Chapter 6 Westphalian

Estimates of the duration of the Westphalian Epoch range from 6. 5 to 13. 0 million years, with a mid-point around 310 Ma. It is divided into four stages, originally lettered A to D, the three lowest having since been formalised as Langsettian, Duckmantian and Bolsovian (Table 10). Deposition in the Pennine region persisted unbroken from the Namurian and was essentially continuous through the four Westphalian stages, but the highest strata have been eroded off and the transition to beds of Stephanian age is probably not preserved here.

The Westphalian succession is divided into Coal Measures (below) and Warwickshire Group (above). These are lithostratigraphical units and the passage between them is diachronous. The Coal Measures are predominantly grey in colour, and contain significant amounts of coal; the Warwickshire Group includes red and brown beds as well as grey, and coal is generally rare. In the previous classification, the term Coal Measures was used for all strata of Westphalian age, irrespective of facies, and included both groups of the present classification. The distinction between the two sets of strata was made by the use of such terms as ‘Productive Coal Measures’ or ‘grey measures’ for the coal-bearing beds, and ‘Barren Measures’ or ‘red measures’ for the overlying strata. The combined thickness of the two groups is about 2200 m in the area of maximum development, near Manchester.

Westphalian strata were laid down over most of the region, but the Variscan earth movements of the late Carboniferous and early Permian deformed them into gentle folds and produced extensive faulting. Uplifted areas were soon eroded, and Westphalian beds were preserved only in the downwarped areas that make up the present coalfields. The separation of the coalfields is not an original feature, therefore, but results from deformation and erosion of a once-continuous series of strata. Despite this erosion, rocks of Westphalian age are present beneath about half the region (Figure 21). The largest areas are the coalfields in Yorkshire, Derbyshire and Nottinghamshire, east of the Pennines, and in Lancashire and Cheshire west of the Pennines. Small outliers exist at Ingleton and near Ripon.

Subsequent sedimentation in the region, starting in late Permian times, produced an unconformable cover of Permo-Triassic rocks over much (perhaps all) of the original Westphalian outcrop. Erosion has since removed parts of the cover. The ‘exposed coalfields’ are those where the Westphalian strata crop out at surface; the ‘concealed coalfields’ are hidden beneath Permo-Triassic strata.

Coal Measures

The Coal Measures of the Pennine region were laid down in a single depositional basin, the Pennine Basin, which occupied the area between the Southern Uplands High, in Scotland, and the Wales–Brabant High to the south (Figure 6). Differential subsidence within the basin gave rise to areas of greater and lesser thicknesses of strata; the maximum thickness, about 1900 m, was deposited near Manchester. (Figure 22) shows generalised thicknesses for successions within the region. Deposition of the Coal Measures began at the start of the Langsettian (Westphalian A) Stage and ended by diachronous passage to red beds during the Bolsovian (Westphalian C) Stage (Table 10); (Figure 22).

The Coal Measures are made up of interbedded grey mudstones, siltstones and sandstones with subordinate amounts of coal and ironstone (Plate 15), (Plate 27). Volcanic rocks are also present in the south. Most mudstones are well bedded and grey, the darkest of them being the most carbonaceous and the most fissile. They may contain fossils, notably nonmarine bivalves and plants; marine faunas are less common, and occur in thin beds termed marine bands. Siltstones are also grey, and many show a range of laminations and burrow structures. These ‘striped beds’ grade both into mudstones and sandstones. Ironstone, generally in thin layers or flattened nodules, is common in the mudstones. It is composed of iron carbonate (siderite) with varying amounts of clay and silt. It is sometimes called ‘clayband ironstone’ to distinguish it from ‘blackband ironstone’, a less common variety containing abundant carbonaceous laminae.

Mudstones and siltstones with roots are called seatearths (or palaeosols), and vary in colour from dark grey to pale grey and brown. Bedding is generally less clear than in the mudstones and siltstones without roots, and ironstone occurs as irregularly shaped nodules. Polished (‘listric’) surfaces run through the rock at all angles in the more clayey beds. Fireclays are seatearths with a high kaolinite content, and are suitable for the manufacture of refractory products such as firebricks for furnace linings.

Tonsteins are mudstones rich in kaolinite. They make up a very small proportion of the sequence, but have received much attention because of their potential for correlation. Typically, they occur as thin beds (rarely over 10 cm) in coal seams or, less commonly, in associated seatearths and mudstones. In hand specimen they have a subconchoidal fracture and are tougher than the adjacent mudstones. They may be pale or dark grey, brown, cream or greenish brown, and tend to be translucent on thin edges. It is thought that they originated as layers of fine airborne volcanic dust, because some tonsteins show textural and compositional similarities with undoubted kaolinitised tuffs. Their distribution in the Pennine Basin can be related to the location of known volcanic centres. They are most common in Nottinghamshire and Derbyshire, close to the area of lava eruption described below.

Fragmental clayrocks are kaolinitic mudstones showing a pelleted or autobrecciated texture, with fragments of one colour set in a matrix of another colour. They are a minor constituent of mudstones and seatearths in or near coal seams. In composition and occurrence they resemble tonsteins, but they appear to have no connection with volcanic rocks and have proved useful for correlation over short distances only.

Sandstones are pale grey, weathering to pale brown at the surface (Plate 16). Most are fine- to very fine-grained, but medium-grained and locally coarse-grained beds also occur. Ripple lamination, cross-bedding and low-angle planar lamination are the common sedimentary structures. Massive beds are also found. Petrographically, the sandstones are dominated by quartz grains, with up to about 10 per cent each of feldspars and lithic grains. Texturally they vary from subgreywackes, which have a clay matrix and low primary porosity, to grainstones in which the original porosity has been reduced by compaction or filled with cements of carbonate or quartz. Some sandstones with plant roots have been leached of feldspar and enriched in quartz to give the distinctive hard beds called ganisters.

Coal is composed mainly of carbon and generally occurs as thin seams resting on seatearth. Bright coal is finely laminated, with a high proportion of cellular plant structures such as bark and leaves. Dull coal is less well layered and is composed mainly of spores and degraded plant material. Layers of fusain, the loose dusty component, are found mainly in bright coal. Cannel is not laminated and breaks with a subconchoidal fracture. Cleat is the name given to the closely spaced vertical fractures in coal, which commonly form two sets almost at right angles to each other. They may contain thin films of minerals such as pyrite and ankerite (ferroan dolomite).

Only at the very edge of the region, south and east of Nottingham, are significant amounts of volcanic rocks present (Figure 21). These are lavas and tuffs of alkali basalt type that were erupted from sources near the edge of the basin and intertongue westwards with the contemporaneous sediments. They are restricted to the Lower Coal Measures, so all are of Langsettian age. Dolerite sills up to 40 m thick were intruded into the Lower and Middle Coal Measures of the same general area and are not easily distinguished from the lavas except in cored boreholes. The sills are of similar composition to the lavas but are younger, as shown by radiometric ages of 296 ± 15 and 302 ± 20 Ma.

A thin bed of volcanic origin, associated with the Black Rake Ironstone, lies about 10 m below the Vanderbeckei Marine Band and extends over a large area between Nottingham and Mansfield. It is a dolomitised tuffaceous siltstone up to about 0. 4 m thick, with graded layers containing basaltic glass shards and pumice. Accretionary lapilli occur closer to the source, which is thought to have been made up of several vents located in the area north-east of Nottingham. Elsewhere in the Pennine Basin, rocks of volcanic origin are rare, but probably include the tonsteins described above.

The order in which the main lithologies follow one another tends to show a cyclical pattern, a typical cyclic unit (cyclothem) being:

The nature and origin of cyclothems have been much discussed, and it appears that no single explanation will suffice. Many cycles are local upward-coarsening lake-fill deposits, and the only external mechanism needed to produce them is continuous subsidence. Others, notably those containing marine faunas, can be correlated over large areas and were probably caused by changes of sea level, which in turn were related to fluctuations in the polar ice sheets and ultimately to cyclical variations in the amount of heat received from the sun.

Flora and fauna

Remains of the coal-swamp vegetation are common fossils in the Coal Measures (Plate 4). Masses of compressed plant material make up the coal seams, roots are found in situ in seatearths, drifted leaf fronds and plant stems occur in mudstones and siltstones, and chaotic ‘log-jams’of broken tree trunks and branches are a feature of the thicker sandstones. The Carboniferous vegetation was very different from that of the present day, comprising non­flowering plants related to such groups as the tree ferns, horsetails and clubmosses. The forests are thought to have been dominated by lycopods (also known as lycophytes), a group which at the present day consists of low-growing plants such as Selaginella and Lycopodium (clubmoss). The Westphalian types were tree-sized, the most familiar being Lepidodendron, with its distinctive bark pattern of rhomboidal scales and its root system, Stigmaria. Calamites, a giant relative of the present-day horsetail Equisetum, was also common, and its stems are frequently found. Palynomorphs (plant spores of various kinds) are ubiquitous in coal and fine-grained sediments and provide a basis for stratigraphical correlation.

Nonmarine faunas were dominated by bivalves, fish and ostracods. The bivalves (Plate 4), commonly known as ‘mussels’ because of their resemblance to modern forms, are found generally in mudstones and ironstones, and are used for stratigraphical correlation. They belong to the genera Curvirimula, Naiadites, Carbonicola, Anthraconaia, Anthracosphaerium, Anthracosia and Anthraconauta. Ostracods and fragmented fish remains are also common in the mudstones. Many of the ‘nonmarine’ species could tolerate some salinity, because they are found with near-marine faunas. Fish, in particular, were present in a wide range of environments, and small crustaceans referred to as estheriids (or ‘Estheria’) apparently occupied a brackish habitat transitional to that of foraminifera and the brachiopod Lingula.

Marine faunas are found only in thin marine bands, which were formed during periods of high world sea level. A typical marine band shows a succession of different faunas related probably to the increase and decrease in salinity that accompanied a marine transgression and regression. The idealised sequence of faunal facies related to increasing salinity is:

  1. Planolites ophthalmoides facies
  2. Foraminifera facies
  3. Lingula facies
  4. Cephalopod-brachiopod-bivalve facies

The last of these is fully marine and can include rich and diverse faunas, including the ammonoids Gastrioceras (Plate 4) and Anthracoceras, productoid brachiopods, and bivalves such as Dunbarella, Caneyella and Posidonia. Minor rises of sea level did not produce fully marine conditions, so faunas peaked at lower levels in the succession of facies, giving rise to bands containing foraminifera or Lingula. Some ‘Estheria’ bands are as widespread as the marine bands and may also represent near-marine conditions. They are included with the marine bands in (Table 10) and (Figure 22).

The major marine bands are present over very wide areas and contain characteristic fossil assemblages, so they have become the primary means of stratigraphical correlation. However, they vary laterally and it is notable that many of them attain only Lingula facies at the basin margins.

Trace fossils are common at some levels in the succession. The commonest are Planolites ophthalmoides, a sinuous burrow in near-marine deposits (see above); Pelecypodichnus (or Lockeia), a vertical disturbance produced where a nonmarine bivalve escaped after being buried in sand: Cochlichnus kochi, a horizontal burrow with a characteristic sinusoidal wave shape; and Arenicolites carbonarius, a vertical U-shaped burrow probably made by a worm.

Depositional environment

The Coal Measures were deposited in extensive waterlogged plains that drained ultimately to the sea. The Pennine region lay in equatorial latitudes at that time, so a hot, ever-wet climate is assumed. Large shallow lakes and peat mires separated rivers traversing the plains. The position of the coastline at any particular time was dependent mainly on world sea level, which varied greatly during the Westphalian, just as it had in the Namurian. The open sea lay to the south, but direct connection to it was generally hindered by the presence of the Wales–Brabant High, and the rivers probably drained out of the Pennine Basin by circuitous routes to the east or west of the high.

At times when the sea was distant, the alluvial plains were dominated by freshwater river and lake environments in which most of the Coal Measures lithologies were deposited. At times when the sea level was high, however, the region was flooded by the sea and the thin, but extensive, marine bands were laid down.

The prevalent grey mudstones, with their common bivalve faunas and ironstone beds, were deposited in the lakes, which were also filled laterally from the river channels by overbank deposition of crevasse splays and minor deltas during periodic floods. Lake-fill units that coarsen upwards from mudstone to siltstone and fine-grained sandstone were produced in this way. Emergent and near-emergent surfaces were then colonised by vegetation, and soil profiles developed.

Thin beds of dark grey mudstone with marine or brackish water faunas were deposited in bays and lagoons. These mudstones are generally more extensive than their lacustrine counterparts and many can be traced throughout the region (Figure 22), (Figure 26). Some of the marine mudstones are condensed deposits enriched in uranium and can be recognised by their gamma-ray signature.

Sandstones deposited in the river channels tend to show a linear ‘shoestring’ geometry, with their bases on erosion surfaces that may cut down far enough to form washouts in underlying coal seams (Figure 23), (Figure 24). Major channels such as that shown in (Figure 24) contain fine- to medium-grained, cross-bedded sandstones and may be over 20 m deep and more than 10 km wide. Smaller channels up to 8 m deep and 1 km wide contain finer grained, ripple-laminated and cross-bedded sandstones, as well as siltstones, mudstones, mixed lithologies, seatearths and coal. Swilleys in coal seams are a particular kind of minor channel-fill.

A washout is an area where the thickness of a coal seam has been reduced by erosion at the base of an overlying sandstone. Washouts tend to be linear features and are generally supposed to mark the courses of the rivers that carried the sediment into and across the region. The washouts encountered in coal seams mark the most deeply eroded parts of the river channel systems, so are a guide to the trend of the rivers and may provide some indication of the possible source areas from which they flowed. In the East Pennine Coalfield, many washouts in the Top Hard seam, for example, trend between north-north-east, north­east and south-east (Figure 23); in Lancashire, the Trencherbone Coal washout trends between north and north-north-east.

A major channel sandstone that is known in detail is the Silkstone Rock of the east Pennines (Figure 24), which follows a west-to-east course for over 30 km and ranges between 3 and 15km in width. The sandstone locally exceeds 50m in thickness, but it is notable that the underlying coal is only rarely eroded to form a washout. Lateral strata include two coal seams that split and increase rapidly in ash content towards the sandstone, showing that coal and sandstone were being deposited contemporaneously. The implication is that the sandstones were laid down in a series of river channels that occupied the same general course for a long period. The location of this sandy belt was not influenced by basement structures, for it does not deviate from its eastward course at the boundaries of the Edale Basin and Gainsborough Trough. Sandy belts of this type, in which increased thickness is not accompanied by notable incision, have been recorded throughout the Coal Measures above the level of the Kilburn Coal.

A different type of sandstone occurs in the lowest Coal Measures, below the 80 Yard Coal, where marine bands are closely spaced. Sandstones here commonly thicken into channels eroded in the underlying strata (Figure 26). The difference between the two types of sandstone may be related to distance from the coast, as discussed under sequence stratigraphy (see below).

Vegetation colonised areas where the sediment built up to water level, and soil profiles (palaeosols) developed. These are generally argillaceous deposits, but sandstones also occur.

They are classified according to the drainage regime that affected the soil profile. Immature palaeosols are grey seatearths, with sedimentary layering evident. Rooted and unrooted layers alternate, showing that plant development was not always able to keep pace with deposition of sediment. Poorly drained palaeosols are also grey seatearths, but are fully rooted. They tend to fine upwards, with little sign of sedimentary layering. Irregularly shaped ironstone nodules are common. This type of palaeosol formed where the water table was at or above ground level for long periods, and where deposition of sediment was slow. Partly drained palaeosols are brown, or mottled brown and grey. Red mottling may also occur, providing a transition to the type of palaeosol found in the Warwickshire Group. They are normally well rooted, with little sedimentary layering, and ironstone may be present either as irregular nodules or scattered grains of sphaerosiderite. They were formed when the water table periodically fell below ground level, allowing oxidation of the sediment (to produce the characteristic brown colour), and thus are commoner over channel deposits than over lake-fills. They are also more abundant towards the basin margins, where the succession is thinner. Well-drained palaeosols are generally pale at the top, due to leaching. They include fireclays (seatearths enriched in kaolinite), and ganisters (quartzitic sandstones) in which unstable minerals such as feldspar have rotted away. They are only common in the lowest Coal Measures and may owe their origin to prolonged weathering during periods of lowered sea level.

Accumulation of plant material in vegetated areas, whether over lake-fills or abandoned channels, gave rise to peat mires which were eventually submerged beneath the lakes when water levels rose faster than peat growth. Compaction of the peat produced the coal seams, as described below. Coal is the compressed remains of vegetation that flourished in the equatorial climate of the time, and is likely to have accumulated in environments similar to those found in present-day peat mires such as those in the East Indies. These can be divided into raised ombrotrophic bogs fed with water only by rainfall, and flat rheotrophic swamps fed by groundwater. Rheotrophic mires are normally waterlogged, but ombrotrophic ones are subject to fluctuating water levels, and hence to periodic degradation by oxidation. Initial drowning of an area leads to rheotrophic conditions, but as the peat accumulates its surface becomes raised and ombrotrophic conditions take over. Submergence of the mire by rising water level reverses the process.

Systematic variations in coal character and spore content observed through some coal seams have been explained by analogy with the modern examples. Thus the contrast between high-ash and low-ash coals is seen as a result of their formation respectively in rheotrophic and ombrotrophic conditions. Low-ash coals may also show variations that can be explained in terms of the upward-drying trend that accompanies the growth of an ombrotrophic mire. Bright coal types in the lower part of a seam may give way upwards to dull types, and there is commonly a parallel change in the miospore content from lycospores to densospores. The part played by forest fires in the development of the coal swamps has also been identified. Layers of fusinite, the soft dusty element in coal, were probably formed as charcoal in fires started by lightning strikes. Cannel was deposited as humic mud composed of finely divided plant material in lakes on the peat mires.

All sedimentary rocks compact during deposition and burial, but coal represents an extreme case; a 1 m seam may represent between 7 and 13 m of peat. Mudstone, by comparison, is about half as thick as the mud originally laid down, and sandstone is only about ten per cent thinner than the original sand.

Seam splits (Figure 25) are a common feature of the Coal Measures and are well documented in mine workings. A well-known example of a simple split affects the coal beneath the Listeri Marine Band. A single seam is found in the east Pennine area, but in Lancashire this splits into two, and the intervening mudstone and sandstone thicken up to 30 m or more in the Wigan–Chorley area (Figure 26). The line of split trends north-west and runs near and parallel to the Deerplay Fault (Figure 25)b. The coincidence has been taken to show that synsedimentary movement on faults can be a factor in the production of seam splits. The mechanism envisaged is that greater subsidence on the downthrow side of a fault causes a lake to form, drowning the peat, whereas vegetation continues to grow on the upthrow side. The cumulative effect of fault movement may be better recorded in coal because of its slow rate of deposition, and because the vegetational difference between lake and peat mire, once created, may persist for a long period. However, structural control of seam splits can rarely be proved, and it is likely that in the Pennine region other factors, such as differential compaction and/or thickness variations of the underlying sediments, were normally responsible for the localised flooding of a peat surface in the area of a split. A good example is the Middleton Main split in Yorkshire (Figure25)a, where thickness variation of the sediments immediately beneath the seam appears to be responsible for the location of the split.

Stratigraphy

Within small areas, coal seams have been correlated directly by mining and drilling, but the lateral continuity and workability of most seams is limited, so that correlation over wider areas depends on recognition of distinctive marker beds, or on palaeontological zonation (Table 10);  (Figure 22), (Figure 26). The major marine bands with distinctive faunas, such as the Subcrenatum, Listeri, Vanderbeckei and Aegiranum bands, are the most reliable marker beds. Marine bands with less diagnostic faunas are useful within the framework provided by the major bands. Nonmarine bivalve assemblages have limited stratigraphical ranges, allowing the strata to be assigned to a sequence of zones (Table 10). In addition, some ‘mussel’ bands are distinctive enough to be used as marker beds. The macrofloras (leaves and stems) were used in the original definition of the Westphalian stages A, B, C and D, but have proved too long-ranging to be used for further subdivision of the sequence. However, the microfloras give a finer zonation based on miospore assemblages.

Lithostratigraphical subdivision of the Coal Measures is also based on the marine bands (Table 10). The three units, Lower, Middle and Upper, are regarded as formations. Members are not generally recognised, except in the Upper Coal Measures in Yorkshire, where there are four members bounded by marker bands. However, despite the lack of formal subdivisions, some parts of the sequence are distinct enough to be recognised on a local or regional scale, as described below. On a more detailed level, most of the named units (coal seams, sandstones, marine bands, ‘mussel’ bands) can be regarded as ‘beds’ in the hierarchy of lithostratigraphical nomenclature.

Correlation of individual coal seams depends upon their lateral persistence and the extent to which they split or join with other seams. (Figure 22) shows generalised sequences for six areas, with tie lines where the available information allows firm correlations. Very few seams can be identified throughout the region, notable examples being the Kilburn Coal (Better Bed, Arley) and the Halifax Hard Bed (Ganister, Alton, Union) (Figure 26). The Barnsley Coal of Yorkshire correlates with the Top Hard of Derbyshire, but its correlation with the Rams Coal of Lancashire is less certain.

The principles of sequence stratigraphy can be applied most easily to those parts of the Coal Measures that were open to some marine influence, and hence to the effects of sea-level variations. These effects are most apparent in the lowest beds (‘Ganister Coal Series’), where variations of sea level produced the set of basin-wide cycles shown in (Figure 26). The marine bands represent maximum flooding surfaces of sequence-stratigraphical terminology. Localised coarse-grained, erosive-based sandstones such as the Harrock Hill Grit may be incised valley-fills deposited after lowstand incision of river channels. Widespread well-drained palaeosols, such as that below the 36 Yard Coal and its equivalents, may also have formed during lowstands.

Attempts to identify elements of the sequence-stratigraphical model at higher levels in the Coal Measures have not been so successful, probably because most of these beds accumulated in regions more distant from the sea. During a high stand, water would back up to produce a marine embayment or large lake by regional flooding; during a lowstand, the incision of a river channel may not have had time to work its way upstream from the coast before being overtaken by the next flooding event. This may explain why the major sandstones typified by the Silkstone Rock (Figure 24) do not incise markedly at the base, but persist through several cycles of lake-fill and peat mire development. The lack of regionally developed well-drained palaeosols also suggests that periods of enhanced drainage were too short to have had any effect.

The base of the Lower Coal Measures is drawn at the base of the Subcrenatum Marine Band, and the top at the base of the Vanderbeckei Marine Band. Three divisions can be recognised throughout the basin. The lowest division, between the Subcrenatum Marine Band and the 80 Yard (Pasture) coal horizon, was formerly called the ‘Ganister Coal Series’ (or ‘Group’). This sequence is made up of well-marked cyclothems, most of them with a marine band at the base and a palaeosol (with or without coal) at the top (Plate 17). Ganisters and fireclays were formed by leaching in the palaeosols during periods of lowered sea level. The sandstones have many features in common with those of the underlying Millstone Grit, including some coarse-grained beds and some strongly micaceous lithologies. Some, like the Crawshaw Sandstone of Derbyshire, entered the basin at its eastern side, but all were derived ultimately from the northern source that supplied the Millstone Grit. Some of the coals have been worked, notably the Halifax Soft Bed (Coking, Belperlawn, Bassy), the Halifax Hard Bed (Ganister, Alton, Union), and the Lower Mountain (a split from the Union Coal). (Figure 26) shows how the ‘Ganister Coal Series’ varies in thickness and lithology across the main coalfields, and summarises the names that have been given to individual beds in different areas.

The middle division, between the 80 Yard Coal and the Kilburn (Better Bed, Arley) Coal, contains three basin-wide cyclothems, but only the highest contains a palaeosol that is notably leached. Coals are thin and rare, except for the Kilburn Coal at the top. The marine bands have very restricted faunas. Flaggy sandstones are widespread and, because they had different source areas, they have different lithologies. Strongly micaceous sandstones (Elland Flags (Plate 18), Dyneley Knoll Flags, Grenoside Sandstone) were derived from the same source area as the Millstone Grit and entered the basin from the north and east; weakly micaceous sandstones with a distinctive greenish colour (Greenmoor Rock, Wingfield Flags, Old Lawrence Rock) came in from the west.

The highest division, which is much the thickest, extends from the Kilburn Coal to the base of the Vanderbeckei Marine Band. True marine bands are absent, and cyclical units do not extend over large areas. Thick coal seams (Plate 27) are numerous, and many have been worked. Sandstones are dominantly of western provenance, but the greenish colour that is characteristic of sandstones sourced from this direction at lower levels in the sequence is only rarely apparent in these higher beds.

The Middle Coal Measures extend from the base of the Vanderbeckei Marine Band to the top of the Cambriense Marine Band and can be divided into two parts. The lower division, from the base of the formation to the base of the Maltby Marine Band, closely resembles the highest division of the Lower Coal Measures; cyclical units do not extend far, sandstones are mainly of western provenance, and coals are thick, numerous, and widely worked. The only marine band is the Vanderbeckei at the base.

The upper division contains eight marine bands, including the Aegiranum band marking the Duckmantian–Bolsovian boundary, and several ‘Estheria’ bands. Workable coals are less common than in the beds below. In Yorkshire there is a change just above the base of the division, with a general increase in grain size and thickness of sandstones. The provenance also changes, with derivation apparently from the north, east and south-east instead of the west. Many of the sandstones here are medium grained, and the lowest of them, the Woolley Edge Rock, is coarse grained and contains quartz pebbles up to 1 cm in diameter. Farther south, however, in Derbyshire and Nottinghamshire, sandstones are generally thin, no general increase in grain size has been noted, and the change in provenance occurs at a higher horizon. Thick sandstones are less noticeable in Lancashire than in Yorkshire, but include the Nob End Rock and Newton Heath Sandstone.

The Upper Coal Measures extend from the top of the Cambriense Marine Band to the diachronous base of the Warwickshire Group. There are no marine bands, although beds containing estheriids are quite common. There are few workable coals. In Yorkshire, four members are recognised on the basis of a coal (Brierley, Blyth) and marker bands containing nonmarine bivalves, estheriids and ostracods. In upward succession they are the Ackworth, Brierley, Hemsworth and Badsworth members. Sandstones are common here, and, like those in the top part of the Middle Coal Measures, are medium grained, with derivation mainly from the south-east. This sandy development is localised, for to the south, in Derbyshire and Nottinghamshire, the sandstones are generally thin.

In Lancashire, these measures were called the Bradford Coal Formation and coals were worked locally. A thick sandstone, the Worsley Delf Rock, is present near the base. West of the Pennines, the upward passage to red beds of the Warwickshire Group is well documented in Manchester, where the red beds come to crop, and the transition is also recorded, beneath the Permo-Triassic cover, in boreholes near St Helens. East of the Pennines, the Warwickshire Group is everywhere concealed beneath the Permo-Triassic cover, but borehole and shaft sections show the transition in two areas between Doncaster and Nottingham (Figure 21), (Figure 22).

Warwickshire Group

Deposition of the Warwickshire Group conformably followed that of the Coal Measures, the best development being at the southern end of the Pennine Basin, in Warwickshire and south Staffordshire. Deposition there continued into Stephanian and early Permian times, but the youngest beds preserved in the Pennine region are thought to be of late Westphalian age. Generally similar successions are found on both sides of the Pennines (Figure 22), suggesting that the group may have been deposited throughout the region. The greatest thicknesses preserved are about 300 m near St Helens and about 200 m near Newark. At Ingleton, a sequence of reddened late Westphalian strata resting unconformably on the Coal Measures is assigned tentatively to the Warwickshire Group.

The base of the Warwickshire Group is markedly diachronous. Red bed conditions started first in the south of the basin, as early as the Langsettian in south Staffordshire, but in most parts of the basin did not begin until the Bolsovian. West of the Pennines, the base lies less than 50 m above the Cambriense Marine Band near St. Helens and rises eastwards to over 350 m above it in the Manchester–Stockport area. East of the Pennines, the boundary rises northwards, being 65 m above the Cambriense Marine Band near Newark and at least 250 m above it near Doncaster.

Unconformities are developed within the succession southwards towards the basin margin in the East Midlands. Both the onset of red bed deposition and the occurrence of unconformities have been linked to intra-Carboniferous earth movements affecting the Wales–Brabant High. An unconformity farther north at Ingleton (see above) may be linked to movements on the Craven Fault System.

The Warwickshire Group consists of interbedded mudstones, siltstones and sandstones similar to those of the Coal Measures, but the colour range includes brown, red, purple, yellow and green, as well as shades of grey, and varicoloured mottling is common. Nonmarine limestones are a feature of some parts of the sequence, and ironstones also occur. Palaeosols include many well-drained types, but coals are rare. Lenses of conglomeratic, poorly sorted sandstone, common in the Midlands and known there as ‘espleys’, have been recorded only rarely in the Pennine region.

Oxidative reddening affected the Carboniferous strata during erosion in the Permian, locally to great depths, and the distinction between this secondary effect and the reddening of primary origin is not always clear. Rival interpretations have caused confusion in the past, and continue to do so.

Plants, nonmarine bivalves, small crustaceans including the ostracod Carbonita and the conchostracans ‘Estheria’ and Leaia, the worm tube Spirorbis, and fish fragments are the main fossils found in the Warwickshire Group, especially in the grey mudstones. The nonmarine bivalves are mainly Anthraconauta and elongate forms of Anthraconaia. Spirorbis dominates the fauna in some of the limestones, the so-called ‘Spirorbis limestones’. No marine faunas are known.

The sediments of the Warwickshire Group were deposited in alluvial and lacustrine environments beyond the influence of marine transgressions. Periods of lowered water table allowed atmospheric oxidation of the surface layers, so that primary red beds alternate with grey deposits formed in waterlogged conditions similar to those of the Coal Measures. Mudstones (and locally limestones) were formed in lakes and on overbank floodplains; siltstones and sandstones were deposited mainly in river channels and small lacustrine deltas. Palaeosols range from waterlogged types like those found in the Coal Measures, to well-drained ferruginous and ferallitic types more characteristic of the group.

Marker bands are rare in these red bed successions and the stratigraphy of the Warwickshire Group is therefore based on formations recognised by their lithology. The group contains up to six formations in Warwickshire, but in the Pennines only the two lowest of these have been identified with certainty (Table 11). The presence of a third, the Salop Formation, is still in doubt.

To the west of the Pennines, Warwickshire Group red beds, formerly referred to as the Ardwick Group, crop out at intervals between the Coal Measures and the Permo-Triassic outcrops along the north side of the Cheshire Plain, from the east side of Liverpool through Manchester to Stockport (Figure 21). Their southward and westward subcrop beneath the Permo-Triassic cover is extensive. Exposures in and around Manchester and Stockport are no longer visible, and the group is best known from borehole records. The two lowest formations of the standard sequence are recognised.

The Etruria Formation (formerly known as the Ardwick Marls) consists mainly of mottled brown, red, purple, green and grey, poorly bedded mudstones and siltstones. It varies in thickness from about 65 to 145 m. The base is transitional to the grey Coal Measures, and the top is drawn at a rapid reversion to grey beds. Fossils are rare.

The Halesowen Formation comprises up to 200 m of mixed grey and varicoloured strata lying conformably on the Etruria Formation. Mudstones and siltstones predominate, with some sandstones. The distinguishing feature of these beds is the presence of micritic limestones with Spirorbis, in beds up to 4. 9 m thick. Also common are thin coals, rootlet beds, ironstones and dark grey shales with mussel/ostracod/fish faunas, very like the highest Coal Measures. The base is drawn where grey beds overlie the variegated Etruria Formation, but the top is apparently defined by the erosion surface beneath the Permo-Triassic cover. There is no evidence of a transition to the Salop Formation.

East of the Pennines, two areas of red-bed subcrop are known beneath the Permo-Triassic cover (Figure 21). In the patch south of Doncaster, ‘coloured measures’ of supposed primary origin have been distinguished from ‘stained measures’ of secondary origin. The coloured beds are at least 140 m thick and the First and Second Cherry Tree Markers can be traced into them from the Upper Coal Measures. No firm equivalents of the Etruria and Halesowen formations have been identified.

In the patch north-east of Nottingham, boreholes and shaft sections show that both the Etruria and Halesowen formations can be recognised in the west, but to the east the amount of sandstone in the sequence increases, unconformities are present, and the distinction between the formations becomes difficult to draw.

In boreholes between Mansfield and Newark, the Etruria Formation consists mainly of poorly bedded varicoloured mudstones and siltstones with minor sandstones including some thin conglomeratic beds of ‘espley’ type. The thickness ranges from 120 to 145m. A sharp upward change to grey beds in these boreholes is taken as the base of the Halesowen Formation. The grey beds are about 28 m thick, and are mainly mudstones and siltstones with ironstones, nonmarine faunal bands, seatearths and thin coals. Up to 35 m of varicoloured strata lie between the top of the grey beds and the base of the Permo-Triassic rocks in the boreholes. They consist of about 20m of purple, brown and grey sandstone above about 15m of similarly coloured mudstone. They were originally thought of as ‘Keele Beds’, so in the present-day classification could belong either to a red part of the Halesowen Formation or to the Salop Formation. An unconformity has been inferred at the base of the sandstone.

Chapter 7 Permian and Triassic

In early Permian times, Britain lay within the large continental mass of Pangea, situated in tropical latitudes about 10° north of the equator. By Triassic times the region had moved to about 30° north. The Permian Period lasted approximately 47 million years (from about 298 to 251 Ma); the Triassic was about 51 million years (from about 251 to 210 Ma). Depositional environments in the region during these periods ranged from continental deserts, to tropical seas, enclosed evaporitic seas, fluvial outwash plains and playa lakes.

Denudation of Carboniferous strata, folded and uplifted during the Variscan orogeny, commenced during the Permian, when desert conditions prevailed (Figure 27). In the late Permian, continental extension opened a seaway, probably from the north connecting to the Boreal Sea. Low-lying areas were inundated, and enclosed hypersaline seas developed on the flanks of the Pennine High (Figure 28). Eastwards, the widespread Zechstein Sea extended to Poland. To the west, the Bakevellia Sea spread approximately across the area of the present-day Irish Sea and its marginal areas. Sequences that accumulated in the Zechstein and Bakevellia seas comprise repetitive evaporitic cycles; these seas may have been connected by a restricted passage, or may have evolved separately.

Desert environments, in which fluvial and aeolian red bed sedimentation took place, were re-established in early Triassic times. Subsequently, there followed periodic flooding of basin areas and the development of ephemeral, evaporitic playa lakes, succeeded by enclosed, highly hypersaline seas in which halite deposits formed. The Triassic culminated with a transgression related to flooding from the Tethys Ocean of southern Europe. This was a precursor of the open marine conditions that followed in Jurassic times.

Permian

The Variscan earth movements caused partial inversion of the Carboniferous depositional basins. Regional uplift and tilting of Carboniferous basin and stable block areas occurred, with localised folding concentrated along basin margins adjacent to the blocks.

At the start of the Permian Period, the uplifted landscape was subject to considerable erosion in a harsh desert environment. The magnitude of the Variscan uplift, and the extent of the associated erosion, is illustrated by the Carboniferous–Permian unconformity to the east of the Pennines. Near Doncaster, the Permian rests on the highest part of the Westphalian succession, but only 55 km to the north, near Harrogate, it rests on the middle part of the Namurian Millstone Grit. Farther north, near Richmond, it rests on strata near the top of the Dinantian. Both at Knaresborough (Plate 19) and east of Richmond, anticlinal areas of Carboniferous rocks remained as upstanding areas that influenced Permian deposition.

The early Permian was largely a time of erosion and reddening of the underlying Carboniferous rocks. Aeolian and flash-flood fluvial deposition was extensive (Figure 27), though exposures of the rocks formed are scarce. East of the Pennines, pockets of breccia, some with desert-varnished clasts and windblown sand are locally present, especially on the flanks of contemporary ridges near Richmond, Knaresborough and Wetherby. These breccias are generally lenticular, and less than 2 m thick, with angular clasts of local Carboniferous lithologies. Breccias also occur from Richmond south to Garforth near Leeds, and are proved in boreholes at depth to the east.

At outcrop, from Garforth southwards to near Doncaster, the sporadic basal breccias are replaced or overlain by lenticular deposits of yellow aeolian sandstone, the Basal Permian (or Yellow) Sands. These occur along the base of the Permian escarpment, and range up to a maximum thickness of about 6m. At depth beneath the Vale of York, 10 km east of Knaresborough, they reach a maximum of 46 m. Borehole information suggests that these sands form north-east-trending ridges up to about 3 km wide and 10 km long, typical of large-scale sand dunes (or draa). They have large-scale cross-bedding and contain rounded and frosted sand grains that indicate aeolian deposition. The yellow colour comes from oxidised ferruginous coatings on the grains, but in boreholes where the sandstones are not oxidised they are typically bluish grey. Southwards from Doncaster to the Nottingham area, the sands are largely absent and thin lenticular conglomerates and spreads of piedmont gravels occur instead.

West of the Pennines, the Permian outcrop is restricted to the Manchester area and drift-covered parts of Lancashire (the West Lancashire Basin). The earliest Permian rocks comprise the lenticular, fluvial and aeolian sandstones of the Collyhurst Sandstone. Up to 220 m are present in the Manchester area, some thickness variation being related to contemporaneous faulting. This formation has a maximum thickness of 715m in a borehole at Formby, situated in an east-north-east-trending trough near the fault-controlled eastern margin of the East Irish Sea Basin (Figure 40).

The late Permian sequences east of the Pennines formed near the western edge of the Zechstein Sea. The inferred shoreline was only slightly to the west of the present Permian outcrop (Figure28), but this swung eastwards in the south, near Nottingham. The Zechstein succession comprises five cycles (EZ1–EZ5) traditionally interpreted as the result of flooding and evaporation, possibly related to glacio-eustatic sea-level changes. Where complete, these cycles range from carbonate rocks at the base, through sulphates to chloride-bearing rocks at the top. An alternative sequence-stratigraphic interpretation suggests the presence of seven flooding–deposition–evaporation cycles. The complete cycles are interpreted as beginning with the chloride rocks and passing upwards into the sulphate and carbonate phases as the basin flooded; these cycles are inverted compared with those of the traditional concept. In both schemes, the limestone formations represent deposition in tropical seas of fairly normal salinity; the intervening mudstone, marl and gypsum sequences are the lateral equivalents of evaporitic successions developed farther into the basin. The Permian succession in north Nottinghamshire and most of Yorkshire comprises, from the base upwards: the Cadeby, Edlington, Brotherton and Roxby formations (Figure 28); outside the region, northwards into the Durham province, a different Permian nomenclature is used.

The initial flooding of the Zechstein Basin was rapid, with the deposition of the thin (0 to 2 m) ‘Marl Slate’. This is an organic-rich mudstone at the base of the marine strata, proved by boreholes mainly in the east of the region. The Cadeby Formation (formerly the Lower Magnesian Limestone) forms the first Zechstein carbonate deposit, and has the most extensive outcrop. As its former name implies, it is composed largely of dolomite. It has two members, the Wetherby Member (formerly Lower Subdivision) and the Sprotbrough Member (formerly Upper Subdivision). The junction between them is placed at the top of the lower dolomite of the Hampole Beds, or in their absence, by the Hampole Discontinuity. The two members are recognisable between Ripon and Mansfield, but not in the south and north (nor at depth in the east) of the region. At outcrop, the Cadeby Formation is up to 60m thick, but is more generally about 40 m. It wedges out locally over the Carboniferous highs at Knaresborough and Catterick, and towards the southern margin of the depositional basin from Mansfield to Nottingham.

The Wetherby Member comprises up to 40 m of moderately fossiliferous, ooidal dolomite with bryozoan-algal patch reefs. Locally, the basal few metres are sandy dolomites incorporating sand grains reworked from the Basal Permian Sands. The member has an extensive biota, including diverse reef communities. The dominant fossils are the bivalves Bakevellia binneyi, Liebea squamosa, Permophorus costatus and Schizodus obscurus. These occur mostly in coquinas near the base of the member. They also occur in patch reefs with ramose bryozoa, especially Acanthocladia anceps and Thamniscus dubius. Locally, as at the type locality of the Cadeby Formation at Cadeby Quarry [SE 52 00], patch reefs are flanked by bedded dolomites containing material derived from the reefs. Elsewhere, for example at South Elmsall, laterally extensive well-preserved, domed, algal stromatolites overlie bedded, dolomitic, peloidal grainstones. The member wedges out completely over Carboniferous highs around Knaresborough and near Catterick, but at Newsome Bridge Quarry near Wetherby, one bedrock high formed the focus for patch reef development. At its southern limit in Nottinghamshire, and locally north of Knaresborough, the lower part of the Wetherby Member has a lenticular basal facies of mudstone and calcareous dolomite, the ‘Lower Marl’. Similar beds in Nottinghamshire contain remains of land plants, including conifers and pteridosperms derived from the nearby land.

The Hampole Discontinuity represents a subaerial erosion surface underlying the Hampole Beds. These beds form a thin distinctive unit that straddles the Wetherby and Sprotborough members. The beds have been traced along outcrop for about 150 km and represent a peritidal shoreline sequence of extraordinary uniformity. That part of the Hampole Beds at the top of the Wetherby Member rest on the Hampole Discontinuity and comprise between 0.2 and 0.8 m of algal-laminated ooidal bindstone. This has an open cellular (or fenestral) fabric, typical of subaerial exposure in the intertidal zone. The upper part of the Hampole Beds forms the basal beds of the Sprotborough Member and comprises a thin sequence of interbedded mudstone and dolomite.

Throughout much of the outcrop of the Cadeby Formation, the Sprotbrough Member comprises dolomitised oolite ranging from 8 to 40 m in thickness. Large-scale cross-bedding is common from near Bedale southwards; at Knaresborough, the sets are up to 18 m high and well exposed in the gorge of the River Nidd. These deposits formed as ooidal sandwaves in a shallow marine environment similar to the present-day Bahamas Banks. They pass to the south, west and north into evenly bedded ooidal dolomites indicative of an inner shelf environment. The top of the member is marked by algal laminated dolomites interbedded with evaporites (mainly gypsum). Preserved at depth in the subsurface, the evaporites are represented at outcrop by silty and sandy clay partings, the residues left by their dissolution, as for example at Quarry Moor near Ripon.

The Cadeby Formation is overlain by the Edlington Formation (formerly named the Middle Permian Marl). This consists largely of gypsiferous red-brown mudstones deposited at the margin of the Zechstein basin (Figure 28). It ranges from 8 to 20 m in thickness, wedging out over the Carboniferous bedrock highs west of Knaresborough and near Catterick. In the south of the region, the formation comprises a sandy siltstone facies, which thins southwards and is overlain, then replaced farther south, by fluvial and aeolian sandstones (Lenton Sandstone Formation) around Nottingham. From the Doncaster area northwards to Catterick, the formation includes appreciable amounts of gypsum (CaSO4. 2H2O), mainly in its lower part. The gypsum at and near outcrop is rehydrated secondary anhydrite (CaSO4). The latter was derived from gypsum which formed in two of the main evaporitic cycles of the Zechstein basin and is preserved down-dip below about 100 m. Gypsum is rarely seen at outcrop, but in the Ripon area, where it is up to 40 m thick, it is exposed adjacent to the River Ure at Ripon Parks. Tight, overturned and disharmonic folds in this gypsiferous sequence were possibly caused by the volume increase as groundwater hydrated anhydrite to gypsum during exhumation. Gypsum is soluble and dissolves rapidly at and near surface, forming a buried karst with caves. Cavern collapse at Ripon (Plate 29) and elsewhere along the outcrop of the Edlington Formation results in active subsidence and the formation of enclosed subsidence hollows that present a problem for building and civil engineering.

The succeeding Brotherton Formation (formerly named the Upper Magnesian Limestone) comprises a lithologically uniform succession of mainly thinly bedded dolomitic limestone and dolomite. It reflects a return to marine conditions in the Zechstein basin (Figure 28). At outcrop, its thickness ranges from 8 to 16 m, increasing to 30m at depth to the east of the region. It is replaced laterally by the Lenton Sandstone Formation near Ollerton, which extends south to Nottingham. The beds commonly have ripple-marked surfaces and contain a restricted fauna of small bivalves, including Leibea squamosa and Schizodus obscurus. Abundant small, rod-like remains of the filamentous alga Calcinema permiana are characteristic of the formation.

The highest part of the Permian sequence in Yorkshire is the Roxby Formation (formerly named the Upper Permian Marl). This formation is very similar to the Edlington Formation and comprises mainly red-brown calcareous mudstones (or marls), generally between 10 and 20 m thick, with up to 10 m of anhydrite at the base. Near rockhead, the anhydrite passes into gypsum. As in the Edlington Formation, the gypsum is largely dissolved at outcrop and locally causes subsidence problems. The gypsum thins southwards in the vicinity of Mansfield. Down­dip from the outcrop the formation passes into a succession of evaporites that includes anhydrite and halite. Throughout much of Yorkshire, the Roxby Formation passes gradually upwards into fluvial and aeolian sandstones of the Sherwood Sandstone Group. Fossils are absent from this part of the succession and the junction between the Permian and the Triassic cannot be recognised. However, in Yorkshire it is thought to lie somewhere near the boundary between the Roxby Formation and the overlying sandstones. In the south of Yorkshire, the Roxby Formation thins and passes laterally southwards into the Lenton Sandstone Formation, which forms the lower part of the Sherwood Sandstone Group.

West of the Pennines, four evaporitic cycles (BS1 to BS4) accumulated in the Bakevellia Sea, but are known mostly from offshore boreholes outside the region. Onshore, the equivalent Manchester Marls Formation comprises red mudstones that are marine in the lower part and include subordinate carbonate and siltstone beds. The marine beds have yielded a limited fauna, including Schizodus schlotheimi, Bakevellia binneyi and Liebea squamosa, indicating a connection with the Zechstein Sea. The Manchester Marls are 15 to 45 m thick near outcrop, but thicken to around 120 m at Formby. They pass southwards into the mainly aeolian Kinnerton Sandstone Formation, which is largely indistinguishable from the underlying Collyhurst Sandstone Formation. The Kinnerton Sandstone thickens westwards to around 260 m in the Dee estuary, the upper part probably being Triassic in age.

Triassic

During the Triassic period, extension and rifting continued on the sites of the former Permian basins. Grabens and half-grabens developed, especially west of the Pennines. The basins were the sites of continental desert aeolian and fluvial red-bed sedimentation, with the deposition of the dominantly arenaceous Sherwood Sandstone Group (Figure 29). Playa lake, evaporitic and marine environments followed, resulting in the fine-grained rocks and evaporites of the Mercia Mudstone Group. Subsidence was greatest to the west of the Pennines, where the thickest accumulations of Triassic rocks and their associated salt deposits occur in the Cheshire and Irish Sea basins. Seismic investigations show that the eastern margin of the Cheshire Basin was controlled by a syndepositionally active fault. Consequently the succession thickens dramatically towards this margin. A similar situation probably existed at the margin of the Irish Sea Basin. At the end of the Triassic, transgression from the Tethys Ocean, situated to the south, caused a change to fully marine conditions. This change resulted in the deposition of the Penarth Group which crops out just outside the region in Yorkshire, Lincolnshire, Nottinghamshire and Staffordshire, and in the southern part of the Cheshire Basin.

The pebbly, fluvial rocks of the early to mid-Triassic Sherwood Sandstone Group were deposited in the Cheshire Basin and in the south of the region (Figure 29). They were laid down by a major river system that drained northwards from the Variscan foldbelt situated to the south. In the Irish Sea area, the distal deposits of this fluvial system include fine-grained sandstones and thick siltstone sequences with evaporites that indicate a marine influence. In the Cheshire Basin, the Sherwood Sandstone Group is subdivided into three formations and numerous members. The Chester Pebble Beds Formation at the base is up to 490m thick and comprises conglomerates and mainly medium- and coarse-grained, well-cemented sandstones with scattered quartzitic pebbles. The succeeding Wilmslow Sandstone Formation is 595 m thick near Knutsford. It comprises porous, aeolian sandstones (130 m) overlain by slightly more argillaceous, fluvial sandstones. The top of this formation is marked by a stratigraphical break equated with the Hardegsen Disconformity of Germany. In Cheshire, however, the aeolian and fluvial, pebbly sandstones of the Helsby Sandstone Formation (200 m), which overlie this break, are also included in the Sherwood Sandstone Group.

In west Lancashire, Triassic rocks form a 10 to 20 km wide, mainly fault-bounded crop at the margin of the Irish Sea Basin. The Sherwood Sandstone Group here is up to 1100 m thick, and, from Formby northwards, it can be subdivided locally into a lower unit (St Bees Sandstone Formation) and an upper unit (Ormskirk Sandstone Formation). The lower unit correlates broadly with the Chester Pebble Beds and Wilmslow Sandstone formations, and the upper unit with the Helsby Sandstone Formation. The St Bees Sandstone Formation is known in boreholes from Formby northwards and in the offshore area. It comprises mainly fine- to medium-grained, dominantly red-brown (but commonly grey), fluvial sandstone, with mudstone present as thin beds and clasts. Pebble layers are present, especially towards the south in the lower part of the formation. The upper part includes more aeolian sandstone, suggesting mixed aeolian and fluvial deposition. The overlying Ormskirk Sandstone Formation of the Formby area has a facies transitional between that of the locally pebbly Helsby Sandstone Formation of the Cheshire Basin and the finer grained Ormskirk Sandstone Formation of the Morecambe Bay gasfields, where it is the main reservoir rock. The formation is generally fine grained and includes mixed fluvial and aeolian sandstones, the proportion of the latter increasing towards the top of the formation.

To the east of the Pennines, the Triassic groups are difficult to subdivide into formations, except at the southern edge of the region. In Yorkshire, the Sherwood Sandstone Group ranges up to 400 m thick, but is undivided. It comprises mainly fine- to coarse-grained, reddish brown, fluvial sandstones. These are commonly cross-stratified and contain channel structures and sporadic layers of mudstone clasts. Southwards from Yorkshire, the lower part of the succession includes numerous sandstone beds with pebbles; southwards from Worksop and Retford these pass into sandy conglomerates of the Nottingham Castle Formation (formerly the Bunter Pebble Beds).

The Sherwood Sandstone Group is succeeded by the mudstone-dominated, evaporite-rich Mercia Mudstone Group; halite is the main evaporite (Figure 30). The base of this group is diachronous and becomes younger when traced southwards; proximal and marginal marine facies occur in the Midlands and more distal marine facies are present in the Irish Sea and North Sea basins. West of the Pennines, the Irish Sea and Cheshire basins saw the development of thick halite deposits; east and south of the Pennines, the margin of the North Sea Basin was marked by the development of gypsiferous sequences.

The Mercia Mudstone Group (Figure 30) is up to about 400 m thick onshore in Lancashire near Blackpool and 600 m at Formby. Exposures of the group are scarce, but four formations are recognised in boreholes. These are all of mudstone, but include three salt members. At the base, 30 m of medium grey interlaminated mudstones and siltstones form the Hambleton Mudstone Formation. This is overlain by the Singleton Mudstone Formation (up to 280 m of red-brown mudstones) which includes the Rossall Halite Member (0 to 15 m) near its base and the Mythop Halite Member (14 to 35 m) near its top. Above these lies the Kirkham Mudstone Formation; it is divided into the Thornton Mudstone Member (110 m) at its base, the Preesall Halite Member (up to 180 m) in the middle, and the Coat Walls Mudstone Member (40 to 123 m) at the top. The Thornton Mudstone Member comprises interlaminated mudstones and siltstones with alternating greenish grey and reddish brown colour cycles. The Preesall Halite Member is the thickest salt unit in the area. The overlying Coat Walls Mudstone Member is dominated by laminated and structureless reddish brown mudstones. The top of the group is formed by the Breckells Mudstone Formation, composed of up to 209 m of reddish brown mudstones with gypsum nodules;a collapse breccia is present at the top. Where the salt of the halite members approaches its subcrop beneath the drift, it is dissolved away by groundwater (at wet rockhead) to a depth of 100 to 120 m. Consequently, the overlying mudstone formations (and the top of the Breckells Mudstone Formation) have suffered collapse, brecciation and disruption down to this level.

The Mercia Mudstone Group of the Cheshire Basin is subdivided into eight formations, proved mainly in boreholes. The succession is about 1200 m thick and broadly cyclic. It has the following succession of formations, from the base upwards (with thicknesses and former names): the Tarporley Siltstone Formation (100 to 280 m; Keuper Waterstones), the Bollin Mudstone Formation (over 500 m; Lower Keuper Marl), the Northwich Halite Formation (up to 283 m; Lower Keuper Saliferous Beds), the Byley Mudstone Formation (150 to 182 m; lower Middle Keuper Marl), the Wych Mudstone Formation (150 to 186 m; upper Middle Keuper Marl), the Wilkesley Halite Formation (up to 404 m; Upper Keuper Saliferous Beds), the Brooks Mill Mudstone Formation (up to 161 m; Upper Keuper Marl) and the Blue Anchor Formation (15 to 17 m; Tea Green Marl). Red-brown mudstones and siltstones with green mottling, spots and beds dominate the sequence. Sandstones are common in the lower part of the sequence; halite and anhydrite are widespread in the upper part. All the sediments, except for the greenish grey, marine­influenced Blue Anchor Formation, are typical of deposition in a restricted, evaporitic, enclosed basin. The Northwich and Wilkesley halite formations vary considerably in thickness and are dissolved away at crop, and at subcrop beneath the drift, to a depth of 75 to 200 m (wet rockhead), resulting in the collapse and brecciation of the overlying mudstone succession. The salt and brine at wet rockhead were formerly exploited by wild brine pumping resulting in catastrophic local subsidence in towns such as Northwich. Where it is deep (below dry rockhead), the Northwich Halite is commercially exploited by mining or by controlled dissolution and brine pumping (p. 146).

In Yorkshire and the northern parts of Nottinghamshire, the Mercia Mudstone Group overlaps the Sherwood Sandstone Group with a sharp erosional basal contact and local non-sequence correlated with the Hardegsen Disconformity. Within Yorkshire, the Mercia Mudstone Group is up to 190 m thick. It is dominated by red-brown mudstone, but also includes gypsum beds at three levels near the base, middle and top of the sequence.

At the southern edge of the region, the Mercia Mudstone Group is 180 to 250 m thick around Nottingham, where it is subdivided into six formations. The lowest, the Sneinton Formation, comprises up to 50 m of fine- and medium-grained sandstones (formerly the Keuper Waterstones). The succeeding Radcliffe Formation (10 to 13 m), Gunthorpe Formation (about 70 m) and Edwalton Formation (45 m) comprise mainly red-brown and grey-green siltstones and mudstones with subordinate sandstones. Calcareous siltstones and sandstones are locally called skerries. Pseudomorphs after halite are common in the greenish grey siltstone beds. Above these formations, the Cropwell Bishop Formation (37 to 54m) is of similar lithology, but contains thick units of commercially exploited gypsum, including the Newark and Tutbury gypsum beds. The top of the Mercia Mudstone Group in Nottinghamshire, as in the Cheshire Basin, is marked by a change towards marine conditions. These are reflected in the green dolomitic mudstones of the Blue Anchor Formation (7 to 10 m) and the succeeding black shales with calcareous beds of the Penarth Group (formerly the Rhaetic); these sequences crop out just beyond the southern and south-eastern margins of the region.

Chapter 8 Neogene and Quaternary

The region is devoid of deposits laid down during the Jurassic, Cretaceous and Palaeogene, and little can be gleaned of events over this period of 170 million years. Apatite fission track analyses of rocks in northern and central England suggest burial by over 1.5 km of deposits. Subsequent regional Palaeogene and early Neogene (Alpine) uplift and accompanying erosion removed this overburden and the present general outline of Britain emerged. The earliest post-Triassic rocks are Neogene fluvial sands deposited during a period of subtropical oceanic climate and preserved in karstic collapse structures in the Carboniferous limestones of the southern Pennines.

The start of the Quaternary Period, about 2 million years ago, was marked by climatic deterioration. The period is characterised by dramatic climatic oscillations, thought to be related to Milankovitch earth orbital changes. They form the basis of chronological subdivision into stages and have been most clearly demonstrated by oxygen isotope studies of foraminiferal shells in deep ocean bed cores in which more or less complete Quaternary sequences are found.

However, a complete and satisfactory stratigraphical framework for terrestrial sequences has not yet emerged, the current pollen-based British stage classification (see below) being insufficiently refined to distinguish between different warm or cold periods. This has led increasingly to the use of marine oxygen isotope stages in correlation (Figure 31); (Table 12). In Britain, periods of stadial or colder climates were interspersed with shorter periods of milder interglacial climates. Britain is currently experiencing the latest interglacial climate (oxygen isotope stage 1); some parts of previous interglacials were warmer. In at least two stadials sheet glaciers advanced across much of lowland Britain. Global glacio-eustatic and local isostatic sea-level changes were profound during the Quaternary: the major glaciations of the northern hemisphere caused sea-level falls of more than 100 m.

Because of the uncertainties of the existing terrestrial stratigraphical and chronological framework, there is no consensus about the ages of many of the Pleistocene deposits in this region. Local lithostratigraphical successions are difficult to correlate regionally, and the deposits predating the last (Late Devensian) glaciation are particularly discontinuous, poorly exposed and inadequately researched.

One early concept that has stood the test of time is the division of the glacigenic sediments into ‘Older Drift’ and ‘Newer Drift’. In this respect, the region is clearly divisible into two contrasting geomorphological domains, the boundaries of which are defined by the maximum extent of the last extensive glaciation to affect Britain (Figure 32), (Figure 33). North and west of this limit, landforms are relatively fresh. The deposits (apart from rare remnants in caves) date back to the glaciation (oxygen isotope stage 2) which had its acme about 18 000 years BP. The drainage pattern in this domain is largely a legacy of meltwater routes established during deglaciation about 13 000 years BP. The drainage system is immature, and rapid downcutting (commonly through unconsolidated superficial deposits) causes hill slopes to become unstable. By contrast, to the south and east of the Devensian ice limit, the landscape is mature and the present drainage system dates back to a much older, more widespread glaciation, of which only residual deposits survive. This is currently thought to belong to the Middle Pleistocene Anglian Stage (oxygen isotope stage ?12), about 0. 5 million years ago. The rivers are flanked by suites of terrace deposits that relate to oscillating climatic regimes and both vertical and lateral valley incision. A rare cave deposit in a Derbyshire limestone revealed mammalian remains such as those of sabre-toothed cats and mastodons which roamed the area during the early Pleistocene, contemporaneous with sedimentation of one of the marine Crags deposits of East Anglia.

Neogene

Neogene pocket deposits (the Brassington Formation) are preserved in solution cavities (or dolines) in the limestone of the southern Pennines (Figure 32). They are the remnants of a former widespread cover of near-sea-level terrestrial sediments that comprise a conformable fining-upward sequence of the Kirkham Member, Bees Nest Member and Kenslow Member. The white, pink and yellow, fine- to medium-grained, siliceous, pebbly sands of the basal member are up to several tens of metres thick and were worked for refractory sand. Their lithology and cross-bedding indicate derivation by rivers from Triassic sandstone outcrops to the south. The Bees Nest Member consists of up to 40 m of poorly bedded, variegated silts and clays. The Kenslow Member comprises up to 6 m of lacustrine to semi-paludal grey clay with some lignite. Plant remains in the upper part indicate surrounding heathland and mixed woodland environments of late Miocene to early Pliocene age. Wood of spruce, fir, possible redwood and several types of pine has been identified. The pollen of hemlock, birch, alder, hornbeam, and hazel has also been recognised. Some 30 per cent of the plant genera are today confined to tropical and sub-tropical localities, and a warm, oceanic climate can be inferred. The Neogene deposits are overlain by head or undisturbed till of possibly Anglian age.

Quaternary

Pleistocene

Deposits predating the ‘Older Drift’ Glaciation: pre-Anglian

Any later Neogene and Early Pleistocene deposits were removed before and during the ‘Older Drift’ glaciation. The main legacy of this period may be a series of upland peneplanation surfaces, perhaps formed during phases of uplift and marine or subaerial erosion; however this remains the subject of speculation and dispute. Moreover, the modification to the landscape by one or more possible pre-Anglian glaciations must have been considerable. A unique cave deposit at Victory Quarry, Dove Holes, near Buxton contained extinct mammal remains indicating a warm climate. They include hyaena, great scimitar cat (a ‘sabre-toothed tiger’), Auvergne mastodon, horse, southern elephant and deer. The fauna may have been deposited over a long period of time and mixed, but is no older than the Antian (oxygen isotope stage ?63) and no younger than the Cromerian (oxygen isotope stage ?15). It is approximately equivalent to a fauna of the Early Pleistocene Norwich Crag of East Anglia, dating back over 1 million years.

Small patches of calcite-cemented Ashbourne Gravel in and around Ashbourne, Derbyshire on a bench 15 m above the River Dove and its tributaries are probably the cold-climate, high-energy deposits of a small river flowing from the north and north-west. Cemented blocks of the gravel within the overlying till indicate that cementation predated the ‘Older Drift’ glaciation. The precise age of these gravels is unknown, but they may correlate with the pre-Anglian Bytham River deposits of the East Midlands.

Erosion has probably long since removed from the region any vestiges of the deposits of older cold stage Early Pleistocene (for example Baventian) or Middle Pleistocene (for example Beestonian) glaciations. Evidence for these comes from Pennine erratics in pre-Cromerian cold stage gravels in East Anglia.

Deposits of the ‘Older Drift’ Glaciation: Anglian

Patches of tills and glaciofluvial sands and gravels in the southern Pennines, outside the Devensian ice sheet-limit, are relicts of formerly more extensive glacigenic deposits. These glacial deposits were formerly considered to belong mostly to the Wolstonian Stage (oxygen isotope stages 8–6), about 300 000 to 130 000 years BP. However, recent work in the middle Trent basin has shown that only periglacial conditions existed there in the late Wolstonian (oxygen isotope stage 6); early Wolstonian (oxygen isotope stage 8) glaciers may have been present elsewhere in Britain. The current consensus is that most of the older glacial deposits in eastern England and the Midlands belong to the complex Middle Pleistocene Anglian sheet glaciation (thought to belong to oxygen isotope stage 12), of about 0.5 million years ago. Evidence from marine cores suggests that more ice accumulated during this stage than in any of the later glacial episodes. More widespread deposits presumed to have been derived from this glaciation are preserved in the Midlands, Lincolnshire and East Anglia. The ice reached as far south as the Thames valley and is therefore likely to have covered the entire Pennine region. Any younger Wolstonian ice sheets are thought to have been restricted to eastern parts of the country and to upland regions later reglaciated.

The Anglian cold period is known to have been climatically complex and may have incorporated more than one glacial episode (shown as Anglian I and II on (Figure 31), (Table 12). There was probably at least one temperate episode, during which man reached the British Isles. In the late Anglian, there is evidence of a cold, possibly nonglacial period (? oxygen isotope stage 10). The ‘Older Drift’ glacial deposits are preserved at higher levels relative to the present-day drainage, and display more dissection, weathering and superficial disturbance than the Late Devensian deposits, with no constructional landforms.

The detailed distribution of the various glacigenic deposits in the region is not clearly known; the generalised pattern is shown in (Figure 32). Till (formerly termed Boulder Clay) is an unsorted heterogeneous mixture (diamicton) of erratic stones, clay and sand deposited from melting or ablating ice without the action of running water. Till typically forms ground moraine or lodgement till. The best known ‘Older Drift’ tills are in the Peak District and the extreme south of the region north of Derby, but also occur as small remnants in other areas. Two main facies of ‘Older Drift’ tills, distinguished on lithology and erratic content, can be related to two major ice advances with separate provenances. Over most of the Pennines ice flow was from the north-west. This Pennine (including Trans-Pennine) Ice Sheet brought striated erratics from the Lake District and Scottish igneous centres, together with various Pennine Carboniferous and Permo–Triassic lithologies (particularly reddened ‘Bunter’ pebbles of rounded vein quartz and quartzite from the conglomerates of the Sherwood Sandstone Group) from intermediate and local areas. The clay matrices of the ‘Pennine Drift’ tills were primarily derived from Carboniferous mudstones and are generally grey where unweathered; those with a significant Permo–Trias component are reddish brown. In the south of the region, from the Trent valley near Nottingham to Henmore Brook at Ashbourne, the Pennine Ice Sheet probably abutted against the Eastern Ice Sheet advancing from the North Sea area to the east and east-south-east. There is good evidence farther south in the East Midlands, where the northern Thrussington Till facies is overlain by the eastern Oadby Till facies, to indicate that the northern ice initially reached farther south but later receded when the Eastern Ice Sheet entered the region. The latter overrode areas previously occupied by the Pennine Ice as far north as Breadsall and Heanor to the north of Derby. The Oadby Till (formerly Chalky Boulder Clay) is characterised by a high content of grey flint and chalk from the Cretaceous outcrops of Lincolnshire; common tabular flints come from the Upper Chalk of north Lincolnshire. Other erratics include Jurassic rocks, as well as more local Permo–Triassic and Carboniferous lithologies. Near Derby, the Oadby and Thrussington tills and related glaciolacustrine clays infill a tunnel valley cut by powerful subglacial meltwater under extreme hydrostatic pressure. Ground moraine in Lincolnshire, such as the Wragby Till, indicates that the last ice movement in the south-east of the region was to the south-south-east. However, this ice may have belonged to an early Wolstonian glaciation (oxygen isotope stage 8).

In the Peak District, the ‘Pennine Drift’ tills are mainly confined to the Manifold valley around Butterton, and the Wye–Derwent catchment around Bakewell. The tills are brownish grey where fresh, but are typically deeply weathered, and with variable stone content. Locally, flows from both north-west and north-east directions are recognised. A striated limestone pavement at Shining Bank Quarry [SK 229 652] indicates ice movement towards the south­east. Another pavement showing a general west to east ice movement is preserved around Eyam and Stoney Middleton Dale. Although there are larger patches of till in the lower ground (below 245 m above OD) in the southern part of the Peak District, this northern ice is thought to have completely overridden the entire region, as its erratic suite is found scattered over the higher ground. It has, however, been argued that this higher, generally more weathered, remanié drift may be all that remains of an earlier, more extensive glacial advance.

Neogene pocket deposits at up to 360 m above OD are overlain in places by undisturbed till of this facies and there are some till patches on interfluves, such as those near Bakewell. Rare, highly weathered flints in these tills are presumed to be of Irish Sea origin.

At Kneesall and Ompton in the Ollerton district, there are patches of till and sand and gravel on interfluves rising to 90m above OD. They contain, in addition to local ‘Bunter’ pebbles and far-travelled, north-westerly derived erratics, Lower Jurassic limestone and chalk erratics that were apparently transported by an ice sheet moving generally south-westwards. Farther north, remnants of ‘Pennine Drift’ occur on the eastern Pennine foot slopes. Dissected, weathered, grey till and gravel patches reach about 130 m above OD north-east and east of Leeds, about 100 m above OD north of Barnsley, about 200 m above OD bordering the Aire valley in the Wakefield district and east of the Rother near Sheffield, and about 300 m above OD between Chesterfield and Matlock. A scatter of erratics at greater heights on the drift-free areas testifies to a formerly extensive cover. The erratics in the till are mostly of local origin, such as Carboniferous sandstones, ganisters and coal, but sporadic chert and Lake District volcanic rocks and granites (including Shap Granite) indicate a predominant ice flow from the north-west. ‘Bunter’ quartzite and vein quartz pebbles are numerous on the Triassic outcrop but their presence to the west, such as in the Sheffield and Matlock areas, is difficult to account for. Either an easterly source needs to be invoked (see below) or they were derived from the Irish Sea Basin. Any calcareous clasts were generally leached away as a result of protracted decalcification, although ice-scratched clasts of Carboniferous Limestone have been found in a deep cutting at Staincross, Barnsley. The presence of ‘Magnesian Limestone’, for instance at Rothwell near Wakefield and accompanying Liassic limestone with Gryphaea incurva at Royston near Barnsley, indicates a south-easterly or easterly component in the drift. Lying just outside the margin of the ‘Newer Drift’, 25 m of till has been preserved in a col at Pikenaze, Longdendale at 350 m above OD.

Eastwards, there are larger patches of less dissected and decalcified bluish grey to reddish brown clay till. They occur in the central and southern parts of the Vale of York from Balby to Bawtry in the Doncaster area. These were derived from a northerly and westerly direction, from an ice sheet that traversed the eastern Pennine slopes, possibly by way of Stainmore. The decalcified and dissected Harrogate Till farther north, largely containing clasts of local sandstones, is of uncertain origin and could be either ‘Older Drift’ or date from the Main Dales Late Devensian glaciation (see below). On entering the Vale of York, the Pennine Ice Sheet moved south. Outliers of mostly red-brown till up to 60 m above OD also extend southward to between Worksop and East Retford and the Creswell Crags area, becoming noticeably sandy on Triassic sandstone outcrops. They occur on slightly higher ground than the Devensian till in the Vale of York, along with glaciolacustrine and glaciofluvial deposits (see below). In the same Doncaster area, several, deep, narrow, north-west-trending tunnel valleys are filled with over-consolidated, almost stoneless, laminated clay and silt.

At all stages of glaciation, but most notably during deglaciation when copious amounts of water were available for sediment sorting and transport, sand and gravel were deposited in bodies similar to those of the much more intact ‘Newer Drift’. Both glaciofluvial ice-contact deposits and glaciofluvial sandar (outwash) occur. Most occurrences of remanié till include lenses of sand and gravel, as for instance below till at 60 m above OD in the Rothwell area near Wakefield. Outwash sheets of gravel forming the highest terrace in the middle to lower reaches of major river valleys are more easily recognised and several have been named, for example, the Eagle Moor Sand and Gravel of the Trent basin. This was the outwash valley sandur from the Oadby Till glaciation and marks the initiation of Trent basin drainage (see below). There are extensive hill cappings of sand and gravel in the Doncaster district, such as at Snaith, Doncaster and Rossington (Plate 20). They are strongly cryoturbated in their upper parts, and relate to a deglaciation phase of a pre-Ipswichian period. These gravels were mostly westerly derived. However, at Rossington, ‘Bunter’ pebbles, flints, and cross-bedding in gravels and Triassic-derived red sands imply northward flowing meltwater from the north Midlands around Sherwood Forest and possibly from the middle Trent valley in south Nottinghamshire and Staffordshire. This meltwater probably initiated the valley of the Idle and its south-westward continuation into the Meden, because similar high-level quartzite-rich gravel patches containing ‘Bunter’ pebbles that are too large to be of local provenance are found along their courses from East Retford to Mansfield. There are few known occurrences of glaciolacustrine clays in the ‘Older Drift’ of the region, apart from those filling the tunnel valleys mentioned above. Thin deposits at Rothwell near Wakefield contain possible drop-stones.

It has been suggested by several authors, most notably Linton, that the drainage pattern in the southern Pennines was initiated in the Neogene or earlier on a series of denudation or peneplanation surfaces. The Proto-Trent was interpreted as a major west to east consequent river, and rivers such as the south-flowing Dove and Derwent developed subsequent to it. However, this model ignores the effects of major continental glaciations in the region. It seems likely that each sheet glaciation led to modification of the drainage pattern and to major landscape evolution. Till filled many preglacial river valleys. Deep tunnel valleys incised bedrock subglacially, and, during deglaciation, subglacial and supraglacial meltwater systems carved new courses that were adopted subsequently by ‘normal’ runoff. Thus, outside the Late Devensian ice limit, much of the drainage was probably initiated on a former widespread cover of glacigenic sediments of possible Anglian age, just as many of the rivers within the limits of the Late Devensian ice sheet originated at the end of that stage. Other particularly large, open valleys that were not obliterated in the Late Devensian, or those which were re-exhumed by later meltwater flow, may predate the Anglian glaciation, particularly where till remnants appear to drape valley slopes. Till in the Derwent valley and in the Wye valley above its confluence with the Derwent may be remnants of infillings of preglacial valleys. The amount of erosion and incision in the last half million years was considerable. Downcutting from the ‘Older Drift’ cover led to superimposed river courses in the Peak District that disregard local structure and bedrock type. The Dove around Hartington, Derbyshire is a good example of this, where the ‘Older Drift’ cover has long since been removed. The river, still following in its original course, flows through gorges in the Carboniferous limestones where the cover of glacigenic sediments and underlying Edale Shale were later removed, and in open courses where Edale Shale remains. Many other examples exist in the area not glaciated during the Devensian, such as the Wye from Buxton to Monsal Head and the Derwent at Matlock. The east–west course of the River Trent at Nottingham was probably initiated later as a major meltwater route, possibly at the contact of the northern and eastern ice sheets. This river is now incised through Triassic bedrock at a much lower level than remnant patches of ‘Older Drift’ high up on the valley shoulders. The Trent Trench, situated downstream of Nottingham, probably formed as the river incised vertically into a pre-Anglian interfluve area and subsequent lowering of base level resulted in the deep ravines (‘dumbles’) on the north side of the valley. Some southern Yorkshire river basins probably came into existence at the same time.

Pleistocene deposits and associated features between the ‘Older Drift’ and ‘Newer Drift’ glaciations: Hoxnian to Middle Devensian

The number of warm and cold (periglacial) climatic cycles between the Anglian and Devensian is not yet clearly established. The deep-sea oxygen isotope record implies that there are more interglacial stages than the two (Hoxnian and Ipswichian) recognised in the over-simplified British onshore model (Figure 31). It is now known that some deposits formerly ascribed to one or other of these two interglacial stages belong to different warm periods and that at least two interglacials, separated by stadial episodes, are encompassed in the two named interglacial stages. Thus, the interglacials formerly termed Hoxnian are probably referable to oxygen isotope stages 11 and 9 and the Ipswichian probably represents stages 7 and 5e. Deposition of the Late Devensian ‘Newer Drift’ was preceded by a long period of generally cold climate during the Early and Middle Devensian, with several interstadials, such as those represented by the Chelford and Upton Warren deposits. The climate during these interstadials is considered to have been continental in character with warm summers but very cold winters. Their precise ages are still uncertain but they probably both occurred during the Early Devensian; the Chelford Interstadial dates to at least 60 ka BP, and the Upton Warren is radiocarbon-dated at about 45 000 years BP, this being a minimum age.

Although global interglacial sea levels were probably close to that of the present-day, uplift has elevated their relict traces to higher levels in this region. Possible water-eroded notches, stacks and caves between 15 and 30 m above OD in Carboniferous Limestone around the northern part of Morecambe Bay have been ascribed to a Hoxnian sea level. They correspond to a raised Hoxnian shoreline at between 20 and 30 m above OD in eastern and southern England. Wave-cut notches in cliffs of Carboniferous Limestone around Morecambe Bay at 4. 9 to 6. 4 m above OD may relate to an Ipswichian sea level.

Glacioeustatic sea level changes had a profound effect on incision and deposition in the lower reaches of rivers. Sea levels are known to have dropped considerably when the polar ice caps increased in size during stadial episodes. Eustatic adjustment to the reduction of northern hemisphere ice caps led to sea levels tens of metres below that of the present day for the early parts of interglacials, so that these remained times of incision in the downstream parts of rivers. Later, as the sea levels recovered, estuarine deposits formed in the incised drainage courses, as for example during the Ipswichian at Langham to the west of Goole. Evidence for wide, deeply incised, pre-’Newer Drift’ courses in the lower reaches of the main Yorkshire rivers, graded to a low sea level, lie buried beneath Vale of York glacigenic deposits. There, the valleys of the former courses of the Idle, Don, Ouse and Aire rivers are concealed and partly filled by Lake Humber lacustrine deposits. Similarly, farther north, the courses of the proto-Ure, proto-Swale and proto-Nidd are identifiable as buried valleys beneath sands and gravels and glaciolacustrine clays below Late Devensian till (Figure 33). The present-day Ure and Swale follow similar courses to the preglacial rivers, but the Nidd now takes a considerably different course along a glacial diversion.

For middle and upstream stretches of rivers, deposition and vertical and lateral incision leading to terrace formation were primarily controlled by changes of climate, augmented by sustained eustatic uplift. Rivers aggraded coarse sediment more rapidly during the periglacial periods when the run-off and bedload increased significantly and when the lower reaches were rapidly adjusting to lowering sea level. These sediments were then incised and terraced during the early part of the next interglacial cycle, with regional uplift facilitating these processes. Thus, most river terraces of this type (in contrast to Late-glacial and Flandrian terraces formed after withdrawal of Late Devensian ice) are underlain by discrete sheets of sands and coarse sandy gravels (separated by bedrock steps) that were formed on braidplains mainly from the large-scale reworking of soliflucted deposits. Interglacial deposits, as in the case of the Trent basin, are typically preserved as infills of meandering or anastomosing channels cut into bedrock below these cold-stage gravels.

The larger mammal faunas are one of the most stratigraphically useful groups of fossils in the Middle and Late Pleistocene. Although the larger carnivores, such as wolf (Canis lupus), spotted hyaena (Crocuta crocuta), brown bear (Ursus arctos) and extinct cave lion (Panthera leo) appear to have flourished in a broad range of climates covering both interglacials and stadials, the herbivores were more restricted (Table 12). The temperate interglacials are characterised by forest or parkland species such as the extinct straight-tusked elephant (Palaeoloxodon antiquus), extinct narrow-nosed rhinoceras (Stephanorhinus hemitoechus), extinct aurochs or wild ox (Bos primigenius), red deer (Cervus elaphus) and fallow deer (Dama dama). The extinct woolly mammoth (Mammuthus primigenius) and the extinct giant deer (Megaloceros giganteus) also appeared in more open interglacial and interstadial environments, and elk (Alces alces) favoured swampy forest. Common components of treeless cold stage faunas, arranged in order of adaptability from steppe to arctic tundra environments, are:

The faunas are environmental rather than temporal indicators, although migratory reindeer and bison herds appear to have flourished more in the open environments of the Devensian than in earlier stadials. However, the temperate forest-type ‘hippopotamus fauna’, the oldest fauna unequivocally recognised in the region between the ‘Older’ and ‘Newer’ glaciations, has special significance. Hippopotamus (Hippopotamus amphibius) is regarded as diagnostic of the middle part of the Ipswichian Stage (oxygen isotope substage 5e) when the climate was warmer than that of today. Elements of this large-mammal faunal assemblage are found in numerous cave and riverine deposits in the region, making it a useful stratigraphical indicator. The assemblage typically comprises:

Remains of horse and man (Homo sapiens) are notably absent. There are no known occurrences of Hoxnian fossiliferous deposits in northern England. Temperate ‘Ilfordian’ (oxygen isotope stage 7) and stadial Late Wolstonian (oxygen isotope stage 6) faunas have been found just outside the region in the Trent valley south of Lincoln (see (Table 12) and the former may be represented in at least one cave site in Derbyshire.

Riverine gravels comprise a mixture of reworked older Pleistocene deposits and clasts of the bedrock in the river’s catchment area. Apart from the Trent basin, little modern research has been carried out on the terrace deposits of the major river valleys in the region not directly affected by the Late Devensian glaciation. The main river systems form a radial drainage pattern around the east and south sides of the Pennines (Figure 32). The rivers include, in order, the Aire and its main right bank tributary the Calder; the Don, its left bank tributary the Dearne and right bank tributary the Rother; the Idle and its left bank tributary the Ryton; and numerous left bank tributaries of the Trent, such as the Lean, Erewash, Derwent and Dove.

Good sections in the riverine deposits are mostly confined to sand and gravel quarries, but few of them are in pre-Late Devensian gravels. Most of the main valleys have deposits underlying two to four recognisable river terraces between the present-day Flandrian floodplain and the high-level outwash of the ‘Older Drift’ glaciation. The Trent basin, including the valleys of the lower Derwent and lower Dove (just outside the region), has a much better preserved ‘staircase’ of four parallel terraces. In other valleys which received copious amounts of glacial meltwater from the Late Devensian ice margin to the west or north, much of the evidence, especially for the lower terrace deposits, has been destroyed. Individual terraces and their deposits have been named or numbered (up sequence) for all the middle and lower reaches of most of the major valleys and their tributaries. However, correlation within and between valleys is not always straightforward because of the discontinuous preservation of the deposits and lack of fossils and other age indicators. Correlation in the upper reaches of valleys, where the deposits are commonly patchily preserved, is especially difficult. Their heights, both above Ordnance Datum and in relation to the level of the present-day floodplain, vary according to the position on the longitudinal profile of the river.

By reference to the Trent basin, the surface of the first (lowest) terrace underlain by cold stage deposits typically lies 5 to 8 m above the present floodplain. These deposits generally date from the Early to Middle Devensian (oxygen isotope substage 5d to stage 3) and overlie rare channel fills of Ipswichian (oxygen isotope substage 5e) fossiliferous silts and sands. The second highest widespread cold stage deposits, underlying a terrace surface typically 10 to 13 m above the floodplain, are late Wolstonian age (oxygen isotope stage 6) and may contain fossiliferous channel deposits of the ‘Ilfordian’ interglacial (oxygen isotope stage 7) at the base. Higher cold stage terrace deposits are generally more patchily preserved and leached.

Pre-Devensian fossiliferous deposits within terrace sequences are uncommon in the region outside the Trent Basin, and there are few accounts of them. Organic silty clays within the fluvial ‘older river gravel’ sequences of the Don and Idle and lying beneath the Devensian deposits of the ‘25-Foot Drift’ have been studied at Langham, Armthorpe and Austerfield in the south-west of the Vale of York. They indicate temperate, partly arboreal environments that have been variously ascribed, on the basis of pollen studies, to zones II– IV of the Ipswichian. However, pollen assemblages of the Ipswichian and ‘Ilfordian’ interglacials cannot be distinguished at present. The first two deposits also contain dinoflagellate cysts, foraminifera tests and pollen of saltmarsh species that indicate deposition within the estuarine tidal reach at sea levels a little above that of the present day. The gravels above may therefore be preglacial Devensian or late Wolstonian in age. An organic interglacial deposit between tills in a hollow in the Carboniferous Limestone outcrop at Scandal Beck near Ravenstonedale, Cumbria is ascribed to the Ipswichian because the upper till is Devensian.

The ‘Leeds (or Armley) Hippopotamus’ (which is in fact a large quantity of bones of several animals found in 1852 at Wortley, Leeds) comes from an interglacial deposit, unequivocally of Ipswichian age. The bones were discovered when a terrace deposit of the River Aire, 6 m above the present floodplain, was being worked for brick clay. Other members of the ‘hippopotamus fauna’ were also recovered (straight-tusked elephant?, red deer and ox), as well as trunks of oak and hazel nuts. Beetles, pollen and macroflora indicating a cold tundra environment were found in fluvial deposits below the floodplain of the River Aire at Oxbow opencast site, south-east of Leeds. A mammoth tusk is radiocarbon-dated at 38 600 years BP (Middle Devensian). The site is just outside the Late Devensian glacial limit and the overlying sand and gravel, attributed to the Dimlington Stadial of the Late Devensian, contains periglacial features, including cryoturbation and formerly frozen blocks of sand.

Datable pre-Late Devensian riverine deposits are rare within the area covered by the ice sheets of the last glaciation, having been removed by erosion or covered by deposits during the glaciation. Marine shells ascribed to the Ipswichian Interglacial have been found in Late Devensian glacigenic deposits in the south Pennine foothills south of Macclesfield. Extensive fluvio-aeolian sands of the Chelford Sands Formation and residual earlier deposits predate a complex suite of Late Devensian glacigenic sediments (Stockport Formation). They occur in east Cheshire, and were exposed in sand pits near Chelford, south of Alderley Edge, where they lie on a ventifact-strewn surface (indicating a major phase of wind abrasion). The surface is cut in Mercia Mudstone and residual older deposits, the latter preserved in a palaeovalley and comprising the Oakwood Till complex above nonglacigenic gravels and organic silts. Plant, molluscan, insect and ostracod assemblages from the silts indicate deposition in a cool, open, treeless environment. The age of the till and lower stadial deposits is unknown, but the balance of evidence favours a pre-Devensian age. The reddish yellow to white, well-sorted, medium-grained sands of the Chelford Sands are up to 70 m thick, but are absent locally due to Late Devensian erosion. Scattered clasts are mainly of medium- to coarse-grained sandstone, orthoquartzite and vein quartz, but there are some flints. Cross-stratification indicates overall east to west palaeocurrents. Above cross-bedded sands in the lower part of the formation, an erosion surface with ice wedge casts is overlain by a palaeosol with rootlets. Fluvial incision into this surface produced a series of north-west-trending channels, infilled with sediments of the Chelford Interstadial (Table 12). These form a complex sequence, but include organic muds and peats and clear evidence of in situ tree growth, as well as syndepositional ice-wedge casting. Palaeobotanical and beetle studies of the muds indicate a continental boreal forest environment with birch, pine and spruce (the last natural appearance of spruce in Britain) and dwarf shrubs. July temperatures around 12°C or higher, and January temperatures as low as –10° to –15°C are indicated. The Chelford Interstadial deposits probably belong to the Early Devensian (oxygen isotope substage 5a or 5c). The overlying Chelford Sands are planar bedded and may be fluvio-aeolian in origin, perhaps deposited in a periglacial, polar desert environment.

The main valleys of the Carboniferous Limestone areas of the Pennines were deeply incised after ‘Older Drift’ times. The resultant lowering of the water table led to the formation of dry limestone tributary valleys in the southern Pennines, such as Hope Dale, Hall Dale and Nabs Dale (tributaries of the Dove above Ashbourne) and the Via Gellia (a tributary of the Derwent south of Matlock). It also inaugurated extensive karst formation and cave development, the latter particularly associated with interglacial climates; the larger cave systems are presumed to have formed during several climatic stages. Passages in cave systems around Morecambe Bay are commonly choked with glacial debris of the ‘Newer Drift’ and thus date back at least to the Ipswichian.

Uranium series dating of speleothems (cave deposits of travertine) in the Peak and Craven districts shows that growth took place in warm periods in the Hoxnian (oxygen isotope stage 9), ‘Ilfordian’ (oxygen isotope stage 7) and Ipswichian (oxygen isotope substage 5e) interglacials, the Middle Devensian interstadial (oxygen isotope stage 3), the Late-glacial Devensian and the Flandrian (Table 12). By contrast, speleothem growth was minimal during severely cold periods when deep permafrost prevented the migration of groundwater. However, growth continued, albeit diminished, through the cold oxygen isotope stage 8 in north-west Yorkshire.

The deposits of several Derbyshire and Yorkshire caves contain infiltrated glacigenic sediment and mammalian and other faunas dated to several warm and cold periods between the two main glaciations. As with the river terrace deposits, no fossiliferous deposits of undisputed Hoxnian age have yet been discovered. In situ flowstone in sands and silts in Robin Hood’s Cave, Creswell, north of Bolsover has been dated at about 165 000 years BP by U-series analysis, probably indicating the ‘Ilfordian’ interglacial. Palynology indicates a change from grassland to open deciduous woodland of the interglacial optimum, subsequently reverting to steppe then tundra, presumably in the succeeding late Wolstonian.

Elder Bush Cave in the Manifold valley south of Buxton contains a complex sequence of deposits, with faunal remains at several levels, interbedded with travertine. An Ipswichian (oxygen isotope substage 5e) ‘hippopotamus fauna’ is overlain by Early Devensian faunas, including hyaena, lion, steppe bison, horse, woolly rhinoceros, cave bear (Ursus spelaeus), reindeer and lemming. As with other cave assemblages, the herbivore bones were introduced by carnivores. A rich interglacial cave fauna, including roe deer (Capreolus capreolus), was revealed by quarrying at Hoe Grange, near Longcliffe. Although hippopotamus is absent, the assemblage is thought to be Ipswichian rather than ‘Ilfordian’ on the presence of fallow deer. Details of several other possible Ipswichian cave sites such as that at Etches Cave, Earl Sterndale remain unpublished. Ipswichian deposits with ‘hippopotamus fauna’ have also been reported in the lowest deposits of Robin Hood’s Cave and Mother Grundy’s Parlour in the Cadeby Formation at Creswell Crags in the Bolsover area. In the Calder valley, a similar fauna was found in a limestone fissure during quarrying at Raygill Delf, Lothersdale. Farther north, Victoria Cave near Settle is an old hyaena den probably first occupied during the Ipswichian. Bones of members of the ‘hippopotamus fauna’ found in the Lower Cave Earth are some of the many bones brought in during the Ipswichian climatic optimum. This level is overlain by stony clay and laminated clay of the Dimlington Stadial.

Flowstone in Stump Cross Cave in northern Yorkshire, dated by U-series to about 83 000 years BP (oxygen isotope substage 5b), has yielded the remains of reindeeer and wolverine (Gulo gulo), indicating a cold Early Devensian environment. Several caves and fissures in the Carboniferous Limestone of the Peak District have yielded vertebrate faunas attributable to cold, stadial parts of the Devensian stage, as well as more temperate Flandrian species. The former include brown bear, lion, spotted hyaena, wolf, steppe bison, reindeer, woolly rhinoceras, both Norway (Lemmus lemmus) and arctic (Dicrostonyx torquatus) lemmings, and other rodents, as well as birds. Other sites, many of which were discovered during quarrying operations, include a fissure at Hazlebadge in the Bradwell area, Boden’s Quarry at Matlock Bath, Langwith Bassett Cave in the Poulter valley, Yew Tree Cave in Pleasley Vale and Fox Hole Cave in Upper Dovedale. Steppe bison, reindeer and several other species were especially abundant in a fissure at Windy Knoll near Castleton.

To date, there is no direct evidence that man, with his Lower Palaeolithic hand axe industries, inhabited the region during the Middle Pleistocene, although implements in terrace deposits of the Trent basin to the south suggest that he did. Evidence that northern England was inhabited from the Early Devensian onwards is found in the various cave deposits of the region. Middle Palaeolithic Mousterian artefacts and Early Devensian pollen spectra have been recovered from Robin Hood’s Cave, Creswell Crags. Other Middle Palaeolithic implements and many vertebrate remains, including mammals (notably spotted hyaena), amphibians, birds and fish of probable Early Devensian age were recovered from Pin Hole Cave nearby. Earlier Upper Palaeolithic artefacts from Pin Hole Cave and Robin Hood’s Cave, the latter also yielding a bone of brown bear radiocarbon-dated at 28 500 years BP, testify to the presence of people during the Middle Devensian period.

Rubified soils developed during the warm interglacial periods, although few are preserved within the region. The cryogenically disturbed red Ipswichian Hykeham Soil is developed on terraced deposits at several places in the Trent valley. A reddened, weathered soil beneath solifluction deposits formed during the last cold stage at Sherburn-in-Elmet near Leeds has also been referred to the Ipswichian. There was also formation of extensive residual deposits, particularly over limestones. Many of the limestone fissures are filled with red clays that may have formed in one or more of the Pleistocene interglacial periods. A basal reddish brown and orange-brown clay and sand in a cave at Leapers Wood Quarry at Nether Kellet near Lancaster is overlain by finely laminated grey and pale brown clay. The lowest deposit is thought to have been derived from an interglacial palaeosol, with the sequence ascribed to the last interglacial/glacial cycle. There was also extensive tufa formation and cementation of screes in limestone areas.

There are few periglacial features that can be ascribed to the period between the ‘Older’ and ‘Newer drifts’. An unusual example is a possible camber gull in Triassic conglomerates south of Turnditch, near Belper in Derbyshire. The gull is filled with red and buff sands and clays containing scattered erratics, including flints, derived from the ‘Older Drift’. In the Edale valley and near the Alport–Ashop confluence, valley bulge structures are overlain by undisturbed head, indicating that they formed prior to a period of periglaciation of probable Late Devensian age.

Deposits of the ‘Newer Drift’ Glaciation: Late Devensian

There is a consensus that the maximum expansion of Devensian ice took place towards the end of the Devensian cold stage. The Late Devensian between 24 000 years BP and 10 000 years BP began with a climatic deterioration, the Dimlington Stadial or Older Dryas (oxygen isotope stage 2). The climate rapidly became arctic, and polar desert conditions prevailed before piedmont ice sheets engulfed much of the region and surrounding offshore areas. Ice streams from the Lake District and the Pennine valleys flowed southwards to coalesce with flows from north Cumbria and western Scotland (Figure 33). These ice streams incorporated eroded bedrock, earlier drift deposits and marine deposits dredged from the floor of the Irish Sea. The growth, expansion and in situ decay of the ice sheets are now considered to be due to a single glacial event, in contrast to an earlier model invoking two glacial events. The succession of ‘Lower Boulder Clay’, ‘Middle Sands’ and ‘Upper Boulder Clay’ of Lancashire and Cheshire was formerly given stratigraphical significance, the tills being attributed to separate glacial advances, with an intervening glacial retreat when the ‘Middle Sands’ were deposited in the ice-dammed ‘Lake Lapworth’. This model resulted from the misinterpretation of widely occurring supraglacial deposits where intercalated flow tills, laminated silts and glaciofluvial sands and gravels overlie lodgement till. The model was abandoned in the early 1970s following studies of modern Spitzbergen glacial systems, in which a single glacial advance produces a multi-layered till and sand succession.

As Late Devensian organic deposits in the region are confined to the Late-glacial period, the chronology of the glaciation is deduced from evidence outside the region. Marine shells in Cheshire till derived from the Irish Sea are radiocarbon-dated at about 28 000 years BP. Ice cover reached a maximum about 18 000 to 17 000 years BP. Its limits are well marked in some areas, but less precisely known in others. At the glacial maximum, the ice may have been over 1 km thick in the north and west of the region. However, a number of the higher northern Pennine summits, such as Ingleborough and Pen-y-ghent may have been nunataks subjected to intense periglacial weathering during at least part of the glaciation. The ice surface appears to have fallen markedly to the south, where lobes penetrated into the southern Pennine upland east of Manchester. Southwards and eastwards beyond the ice margin the region suffered intense periglacial conditions.

An extensive Late Devensian ‘till plain’ occupies the low-lying areas of south and west Lancashire and Cheshire. Glacigenic deposits, up to 90 m thick, comprise complex intercalations of lodgement, meltout and flow tills, glaciofluvial sands and gravels and glaciolacustrine, laminated, stoneless clays. The glaciation lowered sea levels, perhaps by 100m or more, exposing the floor of much of the present Irish Sea. The ice sheet probably stabilised because of lack of supply, but melting was slow because of sustained low temperatures. Subsequent rapid in situ ice wasting took place during an abrupt climatic amelioration about 13 500 to 13 000 years BP, when sea levels began to rise at the start of the Late-glacial period. However, pollen and beetle studies have shown that most of lowland north-west England became ice-free as early as 14 600 years BP. In the upland area south of Kirkby Stephen centred on Wild Boar Fell, which had generated its own glaciers, there was rapid backwasting to the ice divides, with no sign of any stillstand or valley glacier activity.

The Late Devensian glaciation had a dramatic affect on the geomorphology of the region lying within the ice margin, in terms of erosion and deposition. Characteristically, the deposits have fresh, constructional form, except for modifications by Late-glacial solifluction. Much of the Lancashire and Cheshire Plain and the Vale of York would be beneath the sea today but for the presence of these glacial deposits. The Devensian ice appears to have been a very effective transporter of debris, but its erosional effects varied, with only minor modification of many features formed in earlier glacial periods. Much erosion of the Pennine areas appears to have been the result of meltwater or periglacial action. However, glacial erosion was important in the north. Across the Howgill Fells, just outside the region, and the Yorkshire Dales, erosion was mainly by valley glaciers, perhaps overdeepening the valley floors. Also, many examples of ice-breached watersheds occur at low cols on the divides. Extensive corrie (or cirque) formation occurred in the Howgill Fells. As ice advanced across outcrops of Carboniferous Limestone, it swept away soil and regolith and differentially plucked and abraded the weaker limestone beds. This resulted in a staircase-like landscape of scoured karst pavements with clints and grikes, separated by cliffs (Plate 21). Such features are not present in the Peak District, which was outside the ‘Newer Drift’ glacial limit. However, in the cave systems of north-west Yorkshire, the preservation of speleothems dating back to three interglacial stages shows that the ice did not have a profound erosional effect and there was minimal stripping of the overlying strata.

Several distinct ice streams can be recognised (Figure 33). The convergent Irish Sea and Lake District ice streams are collectively termed the Main Irish Sea Glaciation and their deposits have been termed the North-western Drift. Ice advanced southwards and south-eastwards across the Lancashire plain, and was largely constrained to the east by the Pennine escarpment. At maximum advance, the glacier reached up to 365m above OD in the Chapel en le Frith district and 380 m above OD in the Glossop district, as shown by the upper limit of erratics. In south-east Lancashire in the early stages of the glaciation, the Irish Sea–Lake District ice flowed south-south-eastwards and converged with the more southerly ice flow of Ribblesdale ice stream. Later, the Ribblesdale ice was forced eastwards (see below) by the more dominant Irish Sea–Lake District ice, which, in the Forest of Rossendale, eventually covered all but the highest summits. Tills around Preston on the Lancashire plain and in the lower Ribble valley are thought to have been deposited during a single south­westerly glacial advance. They show vertical differentiation of erratics, with the lowest tills almost all of Carboniferous provenance and a progressive upward change to tills of further travelled Irish Sea–Lake District provenance. However, at Whalley, Burnley and northern Rossendale, interdigitations of Ribblesdale and north-western tills with no zones of mixing probably result from interplay between the two ice streams. The deposits associated with Irish Sea ice farther south on the Cheshire Plain, the Stockport Formation, comprise a mixture of till, outwash and lacustrine deposits.

Local ice that accumulated around the ice divides in the Mallerstang area, Howgill Fells and the head of Wensleydale flowed in valley streams and coalesced into sheet glaciers collectively termed Pennine ice. Ice streams that flowed southwards amalgamated to form the Lonsdale ice stream north and west of the Bowland Fells and the Ribblesdale ice to the east. The Pennine ice streams that flowed south-eastwards down the Yorkshire Dales are, together with the Ribblesdale ice, referred to as the Main Dales Glaciation. At its farthest limit, this ice was possibly responsible for the Harrogate Till near Harrogate.

In the Bowland Fells, ice from Lonsdale and upper Ribblesdale covered the hill summits and left a thick residue of tills and other sediments on the lower slopes. Watershed cols, such as Salter Fell, were substantially enlarged, and here ice striae show flow south-south-eastwards along the col. The main Ribblesdale ice stream formed from a large number of feeder ice streams. As it flowed southwards, it breached the Ribble–Hodder watershed west of Rathmell and penetrated into the Hodder valley at Slaidburn. To the south-west, the Irish Sea–Lake District ice prevented further progress at Whalley and it was deflected through the low col at Chipping. At the time of its maximum extent, the Ribblesdale ice covered all the low ground east of the Whalley gorge and the hills of Pendle and Longridge. Its flow south-westwards down the Ribble valley was checked by the Irish Sea–Lake District ice and it was diverted eastwards to breach the main Pennine divide between the Aire and the Ribble at Hellifield. East of Pendle Hill, ice flowed south-eastwards through the low gap between Barnoldswick and Foulridge. Its southern limit was on the Trawden and north Rossendale uplands where there are many limestone blocks in the till up to 385 m above OD. This ice was later deflected eastwards by the dominant Irish Sea–Lake District ice (see above) to breach the Pennine watershed through low cols around Cliviger and feed Ribblesdale erratics into the Calder valley.

Northward-flowing ice streams from the Mallerstang area and the Howgill Fells converged and amalgamated with Lake District ice flowing eastward, transporting erratics including Shap granite boulders. This easterly flowing Pennine ice crossed the Stainmore Gap at the northern margin of the region and proceeded southwards as the Vale of York ice. It was augmented by Main Dales ice moving eastwards down Swaledale, Wensleydale, Nidderdale and Wharfedale;in Airedale the glacier halted west of Leeds. The Vale of York ice may have reached the Isle of Axholme in north-west Lincolnshire, before quickly wasting back to positions of more prolonged stillstand. Subparallel, lobate terminal moraines were formed at York and Escrick. South of the ice front, the level of the ice-dammed Lake Humber (p. 110) rose up to 33 m above OD, with sand and gravel shoreline deposits marking its former margin.

Lodgement till (or ground moraine) is generally a very compact, ill-sorted diamicton, formed extensively in the wet, subglacial environments of the Late Devensian glaciation. It drapes the rockhead surface and gives rise to relatively low- relief till plains with little distinctive topography except where rapid ice movement moulded the deposit into impressive drumlin swarms (Plate 22);see below). The changing composition of the matrix and stones of the lodgement tills across the region closely reflects the provenance of the many ice streams. As an example, the Irish Sea–Lake District ice moved into the lowlands of Lancashire and Cheshire across relatively soft Carboniferous and Triassic bedrock overlain by sandy marine deposits. The resultant lodgement till is typically a brown to reddish brown, weathering yellow brown, sandy diamicton. Even up to heights of 365 m above OD on the Pennine slopes it contains unbroken shells and comminuted marine shell debris. Although the till contains a range of far-travelled erratics, including Lake District granites, Borrowdale volcanic rocks, green Lower Palaeozoic sandstones, Southern Uplands rocks and debris from the Irish Sea floor, much of it is of more local Permo–Triassic and Carboniferous derivation. Cold-tolerant species of foraminifera are incorporated into tills at Bare and Quernmore near Lancaster. In places, there was considerable intermingling with the corresponding deposit of the Ribblesdale ice which is typically a stiff, blue-grey clay diamicton full of Lower Carboniferous limestone and chert erratics ranging up to boulder size. Most other tills in the region are grey where fresh because of their high Carboniferous rock content.

Drumlin fields are particularly well developed in the region covered by the Late Devensian glaciation, for example in Ribblesdale and Lunesdale (Plate 22). The drumlins are ovate mounds typically composed of lodgement till, but other subglacial sediments may be incorporated: sand and gravel drumlins are known. Other examples are rock-cored and some are composite. For example, most of the drumlins in an extensive field in Ribblesdale between Hellifield and Barnoldswick are 100 m in length, many are rock-cored and some consist of sand and gravel capped by till. Along with glacial striae, roches moutonnées and erratic trails, such features are useful in reconstructing ice flow directions; in some locations superposed drumlins record two stages of ice flow. Drumlins are thought to have been moulded under fast-flowing, thick ice streams moving over their own till plains during the final active phase of the Late Devensian glaciation. However, their formation is the subject of debate; ice surge conditions related to glaciomarine ice sheet collapse might explain the drumlin fields along ice streams directed towards the Irish Sea Basin.

The tills of the Irish Sea–Lake District ice on the Lancashire Plain around Lancaster are moulded into a remarkable drumlin field. The drumlins are aligned approximately north to south, range from about 75 to 1600 m in length, and rise up to 150 m above the surrounding terrain. South of the River Conder, into The Fylde, they are less common and their form less distinct, but they persist on the Wyre estuary from Thornton to Preesall. Near the coast and southwards, they are buried by supraglacial and marine deposits. However, the rock-cored drumlin form of the ‘Lower Boulder Clay’ lodgement till is evident from boreholes in the Blackpool area.

Drumlins in valleys and interfluve areas up to 667 m above OD in the Yorkshire Dales are particularly useful in reconstructing local ice divides and directions of ice flow. Three drumlin swarms — Wensleydale, Dentdale/Ribblesdale, and Rawthey valley — radiate outwards from the drumlin-free ice divide extending southwards from Wild Boar Fell. The Wensleydale swarm indicates that eastward-directed ice from the interfluve areas of the River Ure’s catchment converged in the main valley. Southward ice flow produced the Dentdale–Ribblesdale drumlin group. This comprises a continuous belt of drumlins from Dent Head across to the upper part of Ribblesdale, and a separate swarm east from Deepdale and then south into Kingsdale. The third group indicates south-westerly ice flow off Wild Boar Fell and Baugh Fell, which coalesced with ice flowing down the lower parts of Garsdale and Dentdale to become part of the ice occupying the Lune valley. Evidence from superposed drumlins, such as those at Grisedale, indicates two local ice flow events. Initial ice flow from an area between Baugh Fell and Great Coum was succeeded by a flow from a source area that had extended northwards to include Wild Boar Fell. A further ice divide devoid of drumlins across the Howgill Fells to Wild Boar Fell separates a northerly directed Vale of Eden drumlin group from the Rawthey drumlin group, the former converging with the Lake District drumlin group towards Stainmore.

On the Lower Carboniferous limestone surfaces of north Yorkshire, for example on Norber Brow at the mouth of Crummackdale and Winskill above Langcliffe in Ribblesdale, large erratic boulders of Silurian sandstone (‘perched blocks’) are all that remain of glacigenic deposits removed by erosion since the Late Devensian. Each erratic rests on a pedestal of limestone up to 0. 5 m high which has been protected from dissolution.

Ice striae are commonly preserved on smoothed, glazed rock surfaces such as Millstone Grit sandstone and record ice movement. As the ice passed over sandstone outcrops, it smoothed, striated and glazed upflow sides of upstanding rock masses and plucked the leeside, leaving characteristic asymmetrical features referred to as roche moutonnée and crag and tail. Such features commonly occur in groups on upland Pennine surfaces and give rise to contrasting terrain when viewed up and down the former ice flow direction.

Tunnel valleys formed when subglacial or englacial meltwaters flowing under great hydrostatic pressure, loaded with ice and rock debris, incised channels into the underlying bedrock. Their formation in this region has been related to the Irish Sea ‘drumlin event’, when there was rapid ice movement and increased subglacial water flow. The channels, which commonly have overdeepened sections, were partly filled by till, sands and gravels and subglacial lacustrine silts and clays. The Lune–Quernmore tunnel valley in the Lancaster area contains an enclosed hollow at Claughton filled with laminated clays and silts on gravels and tills down to 54 m below OD. Some hollows with up to 36 m of sand, gravel and till underlie the valleys of the lower Wye and Pilling Water in The Fylde area of Lancashire. The subdued bedrock relief below the Lancashire and Cheshire plain extending from south Manchester to the Dee estuary is dissected by a numerous subparallel, deep, narrow troughs, some of which have overdeepened sections down to between 30 and 60 m below sea level. The Dee and Mersey estuaries are situated above some of the larger tunnel valleys, and the courses of the Weaver and Douglas rivers are controlled by buried valleys. The troughs are variously aligned approximately north­west to south-east, parallel to the main direction of ice flow, along the strike of less resistant strata, or along fault zones. In Yorkshire, deep, buried U-shaped channels filled with up to 60 m of laminated clays and sand and gravel occur beneath alluvial sediments of Wharfedale and Airedale.

Areas of hummocky drift in the Aire and Wharfe valleys may be terminal moraines. Examples are the Apperley Bridge, Bingley and Cononley moraines in Airedale and the Arthington moraine in Wharfedale. The Lanshaw Delves moraine, flanking the south-west side of the Guiseley gap between Airedale and Wharfedale, is one of several possible lateral moraines in this area.

The stretches of the Yorkshire rivers (such as the Aire and Wharfe) lying beyond the margin of the Late Devensian ice sheet received large amounts of proglacial outwash sediment from meltwaters issuing from the ice margin during glacial advance and retreat. These coarse sand and gravel braidplain deposits were laid down as valley sandar or ‘valley-trains’, but because of Late-glacial and Flandrian dissection, they now underlie the lowest terraces of the river valleys, at levels ranging up to about 10 m above the modern floodplains. Similarly, in the south of the region around Nottingham, braidplain deposits, the Holme Pierrepont Sand and Gravel, were aggraded along the Trent valley. The sediment was derived from an ice margin situated upstream beyond Uttoxeter and Burton upon Trent, along the Dove and the Trent respectively.

The incursion by Late Devensian ice sheets resulted in a number of drainage diversions. For example, in the Mersey headwaters, the Bollin at Macclesfield and the Goyt at Turf Lee were completely blocked by ice and diverted from their former courses. Parts of the preglacial Ribble valley have been re-exhumed by the modern river between Paythorne and Clitheroe. East of Sawley, the former channel remains filled with glacial sediments and the modern river follows a more southerly route through a deep gorge cut in bedrock by glacial meltwaters. Several important drainage diversions also occurred along the western margin of the Vale of York as a result of ice advancing southwards. They include diversions of the Nidd, Swale and Ure towards the west and south of their preglacial courses. A number of glacially impounded lakes were formed during periods of glacial advance and isostatic depression, the best-known being Lake Humber.

Well-formed end moraines occur in the Vale of York. The York and Escrick moraines mark successive retreat positions of the ice across the Vale. About 10km north of the York Moraine, the lobate Flaxby and Tollerton moraines mark later stillstands. Valley moraines marking up to seven glacial retreat stages have been recognised in some of the lower reaches of the Yorkshire Dales. Other retreat moraines occur at Grassington in Wharfedale, Aysgarth in Wensleydale and Grinton in Swaledale. Many of these moraines ponded drainage, resulting in ephemeral lakes which are now the sites of extensive alluvial flats.

Hummocky morainic topography underlain by contorted heterogeneous deposits is the product of supraglacial deposition. An important factor contributing to the amount of supraglacial and englacial debris was the presence of bedrock rises which caused forward shearing of debris-laden basal ice. Commonly flanked by local hill barriers, these melting ice masses disgorged their load into relatively confined spaces in which meltwaters were concentrated. They became draped by supraglacial deposits and surrounded by hollows filled with glaciofluvial sands and gravels, lacustrine clays and silts, flow tills and other diamictons. As the buried ice melted to produce kettleholes and release its englacial debris, the supraglacial topographical relief inverted, distorting the sediments to varying degrees. Slumps, sags and faults are associated with steeply inclined and even overturned and rolled strata. The resultant topography is characterised by kettle-kame landforms where kettleholes are surrounded by smooth, rounded kame ridges.

The hummocky drift is present in many of the Pennine valleys, such as Ribblesdale and Lunesdale. It is also common in ice-marginal valleys along the west Pennine foothill zone, such as Cessbank Common and Cleulow Cross to the south of Macclesfield, on the north and south flanks of Alderley Edge, and in the lowland area between Middleton, Oldham and Rochdale. Much of the Lancashire and Cheshire plain is underlain by these hummocky deposits. They also cover much of The Fylde and the area from Preston to Scorton, where sections of complex distorted strata, including the sands and gravels of the Middle Sands, have been proved in boreholes at Blackpool and on the M6 and M55 motorways. The Kirkham moraine is probably part of a supraglacial system. It forms much of The Fylde and comprises a discontinuous, broad and undulating ridge with a crest at about 30 m above OD, which emerges from the Lancashire plain and runs west and then north-west to the cliffs at Bispham.

Lines of supraglacial moulins (or sink holes) parallel to the ice margin are now represented by trains of isolated, conical or subconical mounds known as moulin kames (Plate 23). Sand and gravel filled the holes and collapsed as the ice melted. Swaintley Hill is a good example of a cone and is part of a belt of sand and gravel mounds that crosses Roeburndale, above Wray in the north Bowland Fells. The north-west-trending Linton–Stutton kames north-east of Leeds are a belt of gravelly moulin kames, probably developed close to the Vale of York ice margin.

Englacial and supraglacial drainage was commonly concentrated in linear tracts. During deglaciation, inversion of the topography caused the deposits to form eskers. These are linear or beaded, commonly sinuous and anastamosing ridges of sand and gravel (Plate 24). Such features are not generally common in the region, but a degraded esker occurs on the south side of Pendle Hill. In the Lancaster district, small eskers occur near Dam Head in the Conder valley south-east of Lancaster and at Thursland Hill to the west of Galgate. Others have been mapped east and south of Carnforth. Sinuous eskers up to a kilometre long are present between Wigglesworth and Halton West in the Settle area.

In the Vale of York and adjoining area, linear englacial and supraglacial drainage was important at certain stages of glaciation. Two main south-south-east-trending belts of sand and gravel form irregular anastamosing ridges 10 to 20 m above the surrounding areas. Between the York and Escrick moraines, a well-developed esker-like ridge runs south-south-east from York. Farther north, this is aligned with the Helperby–Aldwark esker, which can be traced northwards into the Newby Wiske–Cundall esker of the Thirsk district, the length of which is at least 50 km. The Hunsingore esker runs on a parallel line 8 km to the west of the Helperby–Aldwark Esker through Flaxby. The short Roecliffe esker between Boroughbridge and Staveley probably represents an offshoot from the main drainage channel. In the north of the Vale of York, an esker extends southwards for about 15 km through Leeming and Carthorpe to Sutton Howgrave.

Meltwater channels were carved, mostly subglacially, through glacial drift and bedrock either during an active phase of glaciation, or at the ice margin during the waning phase. Extreme seasonal discharges resulted in rapid erosion and high sedimentation rates. The channels may extend over several kilometres and are typically 50 to 100 m wide and up to 40 m deep. The channel bases generally show a consistent direction of fall, but some profiles are undulating, implying that meltwater flowed uphill under hydrostatic pressure. Whereas the original channel forms of many were later greatly modified by fluvial activity, others are now dry and completely independent of modern drainage, or carry misfit streams.

A scattered group of col meltwater channels breaching the Pennine watersheds were probably mostly eroded subglacially when the ice surface was 100 m or more above the watersheds. Some channels were deeply incised; for example, that at North Britain is 25 m deep. A series of channels flowed from an ice front banked up against the rising ground in the west across the Pennine axis. For example, the Walsden and Cliviger gorges south of Walsden fed torrential meltwater into the Calder system; Lake District erratics, including glacially striated granite boulders, have been found in gravels along the River Calder between Mytholmroyd and Dewsbury. Several cols in the north Bowland Fells probably formed in this way, one example being the Trough of Bowland.

During the waning of the ice sheets, a complex system of subglacial marginal drainage was inaugurated, but groups of meltwater channels are sporadic and only present where relief favoured their development. Their distribution was formerly cited as evidence for an elaborate system of glacial retreat stages, involving ice-dammed lakes in most of the Pennine valleys. They commonly fed into spreads of hummocky sand and gravel on the lower ground and are carved deeply through glacial drift and bedrock. Numerous examples of subglacial channel complexes occur within the ‘Newer Drift’ domain and only a few are cited here. A good example is the Cheesden series on the south Rossendale hill slopes between Bury and Whitworth. This fed meltwaters eastwards towards the hummocky moraine south of Rochdale, the waters eventually crossing the Pennine watershed by way of Walsden Gorge. Cheesden Brook valley, north-east of Bury, is a fine example of a deep bedrock-incised channel. A similar complex of channels occurs on the south side of the Lune valley, where ice-marginal meltwater flowed in deep channels such as Artle Beck westwards along the northern slopes of the Bowland Fells into the hummocky drift area of the Conder–Quernmore valley. Other channel complexes were cut on the northern flanks of the Trawden hills north of Cliviger: in the west Pennine foothills north of Macclesfield and between Macclesfield and Congleton: at Stainburn on the north side of Wharfedale: and at The Riggs, south of Bingley Moor on the north side of Airedale. In the Settle district, a complex of channels between Rathmell and Bowland Knotts fed meltwaters towards the hummocky drift of the Ribble valley. Gordale Scar near Malham (Plate 6) is a fine example of part of a channel complex incised in Carboniferous Limestone.

Although drainage diversions can occur during glacial advance (see above), most are initiated during ice downwasting when new drainage systems result from the network of meltwater channels. Many meltwater flow paths were important in creating substantial drainage derangements within the Pennine and Rossendale valleys that were partially blocked by glacial deposits.

Large spreads of sand and gravel accumulated in the low-lying regions along the Lancashire coastal areas as proglacial outwash fans (or sandar). Outwash sediments also occur in the Horwich area near the eastern margin of the Lancashire lowlands. Sandar are extensive in the eastern parts of the Cheshire Plain between Alderley Edge and Audlem and to the east of the Ellesmere ridge. Boreholes drilled across Morecambe Bay indicate a large underlying sandur. Fans of coarse fluvioglacial sand and gravel were deposited in the Vale of York glacial lake (see below). Much of the coarse, proglacial outwash produced during glacial meltback was confined to the valleys. Sands and coarse gravels form valley sandur terraces up to 10 m above the floodplains along the main valleys to the west of the Pennines, such as the Bollin, Mersey, Weaver, Ribble and Lune. The deposits may also underlie lower terraces where later river incision and reworking took place. Valley sandur deposits underlie the wide Flandrian floodplains in the lower reaches of many rivers, such as the Lune at Lancaster.

The formation of watershed or col meltwater channels was formerly ascribed to erosion by water overflowing from glacial lakes impounded by advancing ice. Chains of lakes related to marginal drainage channels were also supposedly formed during progressive stages of glacial retreat. The reconstruction of hypothetical shorelines suggested considerable bodies of water. Examples, forming part of a series thought to have been related to retreat stages of the ice, are ‘Lake Accrington’, ‘Lake Rossendale’, ‘Lake Irwell’, ‘Lake Littleborough’ and ‘Lake Rochdale’ in and south of the Rossendale uplands. Many more examples are cited in the literature, particularly in memoirs of the Geological Survey. However, apart from supposed small marginal gravel deltas, which can probably be reinterpreted as other forms of glaciofluvial deposits, there are only rare occurrences of extensive glaciolacustrine deposits, analogous to those of Lake Humber (see below), to substantiate the lake hypotheses. Nevertheless, numerous small and medium-sized ephemeral glacial lakes are known to have formed during either glacial advance or retreat. The most typical deposit is laminated clay and silt with scattered drop-stones. Kettleholes were commonly sites of smaller lakes, such as in the Vale of Chipping, the Waddington–Edisford area of the Ribble valley and the Hodder and Langden Brook valleys near Garstang. Laminated clay at Chapel en le Frith was deposited in a lake caused by a Late Devensian ice lobe ponding the Chinley and Chapel en le Frith valleys. Borehole and seismic data offshore of Heysham in Morecambe Bay indicate about 16 m of varved clays overlain by up to 47 m of proglacial lake clays, silts and sands below sandur deposits.

At about 18 000 years BP, one or more glacial advances of North Sea Ice across Holderness and into the Humber gap blocked drainage from the Vale of York and impounded Lake Humber south of the York and Escrick moraines. The lake rose initially to up to 33 m above OD and littoral or beach sand and gravel was deposited around the lake margins, preserved discontinuously along a strand line in the Pontefract and Doncaster areas; rivers such as the Don were graded to this level. Subsequently, a tongue of transient ice may have surged southwards down the Vale of York. There is evidence that the lake completely drained when the ice melted before a further ice advance caused renewed impounding at about 4 to 10 m above OD. Up to 20 m or more of lacustrine ‘25-Foot Drift’ were deposited over a large area. Laminated bluish grey to reddish brown clays and silts with sporadic drop- stones are underlain and flanked by fine sands. They underlie most of the flat plain of the southern part of the Vale of York up to a height of about 8 m above OD. The deposits fill and conceal the wide, deeply incised valleys of the former courses of the Idle, Don and Aire. The northerly increasing height of the fill suggests former contemporaneous isostatic depression, followed by rebound, in that direction. The Escrick moraine was the northern limit of Lake Humber until ice began to melt and the lake spread round its northern side, depositing laminated clay on the morainic surface. During glacial downwasting, extensive laminated clays were deposited in the more northerly Vale of York glacial lake, which was impounded behind the York moraine as far north as the Tollerton moraine. This lake was fed by meltwaters issuing from the Ure, Swale and Nidd valleys. Fans of coarse fluvioglacial sand and gravel were deposited around the lake, with sand, silt and clay deposited in the more distal parts.

During the colder periods of the Devensian, and particularly in the Late Devensian glacial episode, ice-free areas, including the southern and eastern Pennines, were subject to widespread permafrost development in the periglacial climate. Lowered sea level and the action of wind- and frost- enhanced erosion. Incision took place in the lower reaches of river valleys that now lie offshore. Degradation of the landscape by mass slope-wasting was extreme, accompanied by the formation of head deposits (see below).

Subsurface cryoturbation (frost-heave disruption) is characteristic of the periglacial environment, produced by seasonal freezing and thawing of groundwater. The most typical cryogenic forms seen in exposures are festoons of involutions and clay-enriched, lobate and flame-shaped structures in which pebbles are vertically aligned. Other common structures that are widespread in pre-Late Devensian deposits and in the weathered zone of bedrock are ice wedge casts and frost cracks induced by thermal contraction. The former form polygonal patterned ground that is commonly discernible on aerial photographs. Several sites are known in the Trent valley.

Head accumulates by solifluctional downslope movement of water-saturated, near-surface material that involves freezing and thawing. This deposit is extensive outside the limits of the Late Devensian ice sheet. Much of it accumulated in the Late Devensian periglacial climate, but some is dissected, cryoturbated and terraced, and may belong to earlier Devensian or pre-Devensian ‘arctic’ episodes. It is generally an unsorted, heterogeneous, massive diamicton and varies in composition, depending on the parent materials upslope. It consists of stones in a matrix of sandy clay to silty sand and typically formed solifluction terraces and lobes.

Numerous examples of sharply folded and contorted Permo–Triassic and Carboniferous argillaceous strata in valley bottoms and slopes are ascribed a nontectonic origin under the influence of Late Devensian periglaciation (Plate 25). These valley-bulges may extend downwards for several tens of metres and result from local pressure of overlying competent beds on the valley sides and lateral shear causing squeezing of incompetent argillaceous strata in the load-free valley bottom, particularly during periods of ground-ice thawing. Cambering is the lowering or tilting of sandstones, limestones and other competent rocks on interfluves and valley sides due to the failure of underlying mudstones. It is commonly associated with valley-bulging. Valleyward movement of the upper unit results in a draping effect, with consequent fracturing to form dip-and-fault structure. Joints approximately at right-angles to the direction of slope, and especially at the back of a cambered block, are widened to form fissures or gulls. These may be filled with drift, or remain as open voids. There are many examples of cambering on Pennine slopes, especially where thick beds of Millstone Grit sandstones form escarpments overlying mudstone. Gulls are also recorded in the Cadeby Formation overlying Coal Measure mudstones at Maltby. Enlarged voids form caves in the Went gorge.

Various aeolian erosional and depositional features are recognised. Loess and coversands were transported mainly from unvegetated, glacial outwash plains and poorly lithified sandstone outcrops by the winnowing action of the strong dry winds that were prevalent across northern Britain in the more continental climates of the stadial periods. They are widespread over much of the periglaciated area, but as they were commonly incorporated into Flandrian soils their presence is not always apparent. Coversands are characterised by their fine-grained, well-sorted nature and paucity of fines and pebbles. Rounded sand grains are not generally conspicuous, mainly due to the short transport distances involved. Deposition was before the vegetation cover developed sufficiently to prevent wind transport during the Late-glacial period. The outcrops of the Triassic sandstones and Pleistocene sands and gravels provided ample source material. In the Peak District, much of the limestone area is mantled with thin loess generally less than 0. 3 m thick. It comprises orange-brown, silty loam mostly derived from the surrounding Millstone Grit outcrop. Local intense cryoturbation indicates a pre-Late Devensian age for some of the loess. Similar loess patches occur on the karstic limestone pavements of north-west Yorkshire, such as Hutton Roof and Farleton Fell. The loess is again generally thin, although up to about 1 m are present in former snow patch hollows.

Ventifacts are characteristic of periglacial desert surfaces; they are stones glazed, etched and facetted by sand and silt borne by winds in dry periglacial conditions. Their formation implies barren, sandy landscapes and powerful, persistent winds. They commonly display flat surfaces with sharp edges and in the classic three-sided form are known as dreikanter. Ventifact-strewn sites are particularly well seen in ploughed land on older gravelly deposits containing hard quartzite (‘Bunter’) pebbles derived from the Sherwood Sandstone Group. Likewise, many of the relict pebble strews of ‘Older Drift’ on the Pennines have abundant ventifacts, including dreikanter, as, for example, on interfluves between Pontefract and Wakefield. A widespread Devensian periglacial desert surface with ventifacts and cryoturbation structures has been recognised in many areas. In the Vale of York, ventifacts are preserved beneath the Late Devensian till at Aldborough, near Boroughbridge, and near Allerton Mauleverer.

Tors are resistant, residual, isolated pinnacles of rock that have been exposed to severe weathering after the removal of the surrounding rock. Initial differential weathering may have developed as a result of a range of factors, such as deep chemical weathering (saprolite formation) in a sustained warm subtropical climate, leaching in a nontropical climate, or frost-shattering in periglacial conditions. The tors in this region are thought to have become isolated from retreating scarp edges during a severely cold climate when gelifluctional mass movement removed the surrounding shattered debris. Such processes may have occurred during the main Late Devensian glaciation or during the following Loch Lomond Interstadial. Tors are common on the Millstone Grit escarpments. There are examples on Hathersage Moor: at Gog, Magog and Harston Rock near Ipstones: on the Chatsworth Grit escarpment in the Peak District: at Ravenstones in the Kinderscout Grit of the Greenfield valley east of Oldham: at Brimham Rocks in Nidderdale (Plate 13): the Brennand and Whitendale hanging stones on the Brennand Grit escarpment in the northern Bowland Fells: and Plompton Rocks near Knaresborough. Fine examples of tors of dolomite or dolomitised Carboniferous Limestone are Black Rocks and Rainster Rocks near Brassington in the southern Peak District.

Late-glacial deposits: Late Devensian

The last 3500 years of the Devensian, after the final wastage of the glaciers, was a time of climatic instability. The period began with abrupt climatic amelioration at 13 500 years BP. During this warm Windermere Interstadial, until about 11 000 years BP, the Polar Front migrated well to the north of the British Isles, the climate was warm and birch forests flourished. After this, in response to an abrupt climatic deterioration, a tundra or polar-desert climate prevailed over much of Britain. This period, the Loch Lomond Stadial (or Younger Dryas; oxygen isotope stage 2), lasted until the start of the Flandrian Interglacial at 10 000 years BP. Local glaciers were mainly confined to Scotland, the Lake District and Wales. However, five small cirque glaciers were established south of Kirkby Stephen, at Cautley Crags, Combe Scar, Great Coum, Swarth Fell and Whernside. The glaciers covered areas between 0. 2 and 0. 4 km2 and terminal moraine ridges mark their lower limits.

The most important process at that time was the paraglacial modification of the glacial landforms by remobilisation of glacigenic deposits, especially tills, by solifluction and slope failure. The complexity of the Late-glacial climate is indicated by the sedimentary sequences filling kettleholes and underlying other low-lying sites such as Chat Moss, Manchester and Red Moss, Horwich (p. 115).

The Late-glacial witnessed the demise of the large herbivores such as the woolly mammoth and woolly rhinoceras. Whether this was due to a failure to adjust to the forest ecosystem that succeeded the tundra, or to hunting by Upper Palaeolithic man, or to a combination of both, is still debated. Giant deer flourished in Britain during the Windermere Interstadial and then became extinct. A fine pair of antlers of this species, and a skull and partial horns of the aurochs, were recovered from excavations in silts at Heysham Dock. The remains of these two species found close to flint artefacts in Kirkhead Cave, Morecambe Bay, show the importance of large mammals to man at this time. Aurochs was probably exterminated later by hunting in the Later Bronze Age. Elk also dates from the Late-glacial period and became extinct in the early Flandrian. At High Furlong, Poulton-le-Fylde, an elk skeleton bearing weapon marks and barbed points was found in lake mud (p. 115).

Uranium series ages of speleothems indicate renewed growth in caves in north-west England during the Windermere Interstadial. This continued during the Loch Lomond Stadial, when temperatures were not low enough to inhibit groundwater movement.

In the Vale of York, radiocarbon dating of soil and peat on the emergent lacustrine clays of the former Lake Humber provided Late-glacial dates of 11 100 years BP. The subsequent development of courses of rivers such as the Ouse and Aire towards the Humber led to the formation of sand levées on the emergent plain. At Cawood, near Selby, radiocarbon dating of overlying peat showed that levée deposition ceased by 10 500 years BP. An organic deposit in a hollow on the Escrick moraine yielded Late-glacial pollen. Other sites at Malham and in The Lunds in upper Wensleydale have yielded pollen of similar age.

During the Loch Lomond Stadial, there was renewed development of many of the periglacial features that characterised unglaciated areas during the Dimlington Stadial and many examples have been attributed to this cold period. For example, ice wedge casts formed on till surfaces at Congleton in Cheshire, in overburden above sandstones and shales at Scout Moor and in quarries at Whitworth in the Rossendale Forest. Cryoturbation structures, including involutions, occur in Triassic sandstones east of Ashbourne. Gelifluction and other forms of mass movement were the dominant agents of debris transport. Gently sloping solifluction terraces formed on the sides of the main valleys of the Pennines and Bowland Fells, much of the upland till being remobilised. An example of remobilised till also occurs on lower ground in The Fylde at Grange Farm, Elswick, where it overlies organic deposits. Tabular stones arranged vertically by freezing processes are recorded in superficial deposits at Peel near Blackpool and Longton near Preston. Good examples of valley bulge structures are common in the Edale Shale and Mam Tor Sandstone of the Edale, Alport, Ashop and Derwent valleys in Derbyshire. The coeval ‘Upper periglacial land surface’ of the Vale of York overlies Dimlington Stadial glacigenic sediments and is characterised by ice wedge casts, ventifacts and a desert pavement.

Periglacial processes were especially intense in upland areas during this stadial, with much landsliding, rock falls and creep of frost-shattered angular rock. Blockfields and screes, commonly cemented and stratified, formed in some of the deeper Pennine valleys and below the higher scars and cliffs of the Carboniferous Limestone and Millstone Grit. Aprons of partly cemented scree are present below some of the large limestone scars and cliffs of Carboniferous Limestone in the Settle area, for example below Giggleswick Scar. Cemented screes also occur in the Manifold valley, in the south Pennines (where they reach 24 m in thickness at Ecton) and they overlie glacially striated limestone surfaces around Morecambe Bay. Many of the Pennine tors developed at this time (see above).

Landslips (or landslides) are common along the steep escarpment slopes of the Pennines. Many were initiated during and after withdrawal of the Late Devensian ice when, along with other forms of slope failure ranging down to small debris flows, many of the glacially modified and over-steepened slopes became metastable. Most failures appear to be Late-glacial in age and renewed slope activity was probably facilitated by the return of periglacial conditions during the Loch Lomond Stadial. Others formed subsequently during periods of water oversaturation and high pore pressure that reduced rock shear strength. Mass movements have continued intermittently to present times. The landslips range from deep-seated rotational slides to relatively shallow translational slides. Many slips are composite rotational slumps, with mass flow of less coherent material around their toes. Many examples involve the juxtaposition of rocks of high mass strength above weak layers. In the Pennines, this is mainly competent, fissured Millstone Grit sandstones overlying incompetent, impervious mudstones. Landslips are common on the steep slopes of the northern Peak District, involving the Mam Tor Beds, Grindslow Shales and Kinderscout Grit. A famous example is Mam Tor in Derbyshire (Plate 12). Similar spectacular slips are present along the nearby Ashop and Alport valleys. Others occur, particularly along the deeply incised valleys of the western Pennines, for example along Longdendale, east of Manchester, although some are Flandrian in age. There are good examples in the Langden valley and north and south of Ward’s Stone in the Bowland Fells. Farther north, rotational deep-seated failure and numerous boulder flow lobes occur at Swarth Fell, the site of a Loch Lomond Stadial cirque glacier. Extensive and progressive multiple slope failures involving mudslides, complex rotational deep-seated landslides and large boulder stream lobes, are present in the north of the region on the glacially eroded slopes of Mallerstang, and along the flanks of Wild Boar Fell and Little Fell. All these features formed subsequent to the melting of small cirque glaciers.

Aeolian deposits (coversand) mobilised during the Loch Lomond Stadial have been identified over a wide area of the Vale of York. Radiocarbon assays on organic material obtained from the lower and upper parts of the sand near York gave dates of 10 700 and 9 950 years BP, respectively. Inland from the present-day coastal dune belt of the south-west Lancashire coast, coversands of the Shirdley Hill Sand were deposited by strong drying winds which ablated much of the fine-grained material from exposed till and outwash surfaces. These yellow, brown or white glass sands are commonly more than 3 m thick and contain ventifacts, including dreikanter, as well as frost cracks and other cryoturbation features. A peat below the sands at Clieves Hills, north of Ormskirk, contains a Zone III pollen flora dominated by grasses, sedges and dwarf shrubs and radiocarbon-dated at 10 455 years BP.

Late-glacial lacustrine deposits are present in numerous kettleholes left by the retreating Late Devensian ice. Molluscs and ostracods from sediments in a kettlehole at Bingley Bog, Airedale indicate a rapid climatic amelioration at the start of the Windermere Interstadial and a general cooling towards the Loch Lomond Stadial. During the latter, the fauna died out and the flora changed from birch woodland to tundra. Late-glacial deposits have also been identified at The Lunds in upper Wensleydale and at Malham. At Red Moss, near Horwich in the Lancashire lowlands, Late-glacial lake deposits contain assemblages of beetles which demonstrate the replacement of temperate taxa with more cold-tolerant ones; the climatic change is radiocarbon-dated at 12 160 years BP. The pollen assemblage from Late-glacial lake mud at the High Furlong elk site indicates birch woodland in the vicinity. Elk bone and lake mud have provided radiocarbon dates of around 12 000 years BP.

Ossum’s Cave in the Manifold valley of the Peak District has yielded a Late-glacial fauna including horse, reindeer, red deer and steppe bison. Flint artefacts indicating the presence of Later Upper Palaeolithic, Mesolithic and Neolithic man are found in some of the caves of the Peak District. They occur with the remains of the mammals and birds, which the humans hunted, showing that the caves were occupied from Late-glacial times, following the amelioration in climate after the withdrawal of the Devensian ice sheet. The complex of caves at Creswell Crags, north of Bolsover, such as Pin Hole, Mother Grundy’s Parlour and Robin Hood’s caves, have yielded, in addition to flint artefacts belonging to distinct Middle and Upper Palaeolithic industries, several Late Devensian (?Late-glacial) vertebrate levels and Late-glacial to early Flandrian pollen sequences. At Pin Hole Cave and Robin Hood’s Cave, Later Upper Palaeolithic implements occur with human remains. The vertebrate faunas are dominated by spotted hyaena, but include bison, woolly rhinoceros, horse and reindeer. Fish, amphibians, birds, insectivores, bats and rodents are also found. Two horse bones from Robin Hood’s Cave yielded radiocarbon dates of about 10 500 years BP, and a human skull fragment of comparable age. Dead Man’s Cave at North Anston in the Creswell area also contains deposits dating back to the Late-glacial. Deposits of this age contain Upper Palaeolithic artefacts, apparently in association with reindeer antlers radiocarbon dated at about 10 000 years BP. An interstadial environment of birch woodland has been deduced from the pollen record. Uranium series dating of travertine from Robin Hood’s Cave gave dates ranging from the ‘Ilfordian’ through the Ipswichian to the early to middle Flandrian. In Yorkshire, Victoria Cave, Settle, was the site of Later Upper Palaeolithic occupation from about 12 000 to 11 000 years BP.

Small patches of typically soft, porous, calcareous tufa deposited from springs are present in the Carboniferous Limestone of the Peak District and Craven area. The Malham district contains extensive deposits of tufa; Janet’s Foss in Gordale Beck is a good example of a tufa-producing spring. In the southern Pennines, concentrations of tufa occur around Matlock, Youlgreave and Bakewell. A notable example of tufa is the deposit on the west bank of the River Derwent at Matlock Bath, which is up to 4. 6 m thick, and was precipitated from warm spring water. In the north-east of the region, extensive deposits of tufa west of Thirsk form mounds up to 100 m wide, deposited from highly carbonated, artesian spring water from the Permian dolomites and gypsiferous marls. Similarly derived tufa deposits occur farther south in the Holbeck valley to the north of Copgrove, in the Burton Salmon area, at Ripon racecourse and at Dropping Well, Knaresborough. Elsewhere, tufa deposits formed from lime-rich waters issuing from sandstones in the Mercia Mudstone Group occur in the East Retford and Ollerton districts.

Holocene

The Holocene Epoch is represented by the present Flandrian Interglacial, which is defined as beginning at 10 000 radiocarbon years BP. At many of the Late-glacial sites deposition continued uninterrupted and the base of the Flandrian is not recognisable in the sedimentary succession. The boundary is primarily climatic, when rapid warming and forest expansion produced a marked increase in tree pollen. Pollen assemblage zones of the first three of the four interglacial chronozones have been recognised. Red Moss, near Horwich in Lancashire, possesses the standard stratigraphical sequence of chronozones, and has been designated the Flandrian type site. The Flandrian is also subdivided by the Blytt–Sernander scheme of climatic periods, which is based on plant macrofossil sequences. In upward sequence these are: Pre-Boreal, Boreal, Atlantic, Sub-Boreal and Sub-Atlantic. These subdivisions of the Flandrian and their chronology are shown in (Table 12).

During the early Flandrian, sea levels were as low as 20 m below OD. Peat and woodland were established well below present-day sea level and river valleys were incised in their lower reaches. As sea level rose near to its present level about 6000 years ago, these valleys were drowned and partially infilled with silt, producing the modern estuaries. There have been few physiographical changes in this last period. The Early Flandrian was marked by the stabilisation of slopes, the re-establishment of a submeandering stream pattern, the formation of peat, the development of soil and vegetation cover and the deposition of modern floodplains. Latterly, land clearance and increase in modern arable farming practice has led to widespread colluviation, while urbanisation produces increasing amounts of made ground.

The Later Upper Palaeolithic and Earlier Mesolithic human cultures probably coexisted and continued into the earliest part of the Flandrian, when a land bridge connecting Britain to Europe allowed movement of hunter-gatherer people. This was the time when Mesolithic cultures spread; their flint implements are found in caves (see above) and beneath peat in hilly areas, for example at March Hill on Buckstones Moor, at other sites west of Huddersfield and at Holmfirth. The use of microlith flint tools became prevalent in the Mesolithic, and the extended lowland plains provided wintering grounds for hunting groups. Sea level rose during the Later Mesolithic (after about 8000 years BP) and probably flooded earlier coastal settlements. It also reduced the land area of Britain and breached the land bridge connection at that time, when there were occupation sites in the Pennines. Afforestation took place under the influence of an ameliorating climate, and around 7000 years BP forest or scrub probably grew up to about 500 m above OD over most of the southern Pennines. Peat formation became widespread at the start of the Atlantic Period in this area. A well-developed mixed-oak forest flourished at lower elevations by about 6000 years BP while a mosaic of hazel scrub and herbaceous communities probably existed on the high plateau surfaces. Neolithic farmers arrived by sea from about this date onwards and started limited deforestation and land clearance. Their characteristic flint artefacts are widely scattered over the Pennine hills. Later Bronze Age (1400–500 BC) people built hill-top settlements such as that on Mam Tor in Derbyshire. The onset of cultivation led to soil deterioration, heather moorland development and peat growth, and deforestation increased apace into the Iron Age.

All the main river systems of the region developed during and after the retreat of the Late Devensian ice sheet. Although in upland areas they may partially follow exhumed pre-Late Devensian drainage systems, many parts of their courses were established along newly incised meltwater routes, former ‘tunnel valleys’ and other channels formed during the Late Devensian glaciation. An entirely new system developed in the lowlands of Lancashire and Cheshire, using meltwater routes incised through the thick drift cover. The lowland river drainage probably evolved from a braided system, through a multichannel anastomosing network, into the single-thread submeandering channel system of today.

In the Early Flandrian, the immature landscape inherited from the Late Devensian evolved through the action of these rivers. Incision produced youthful ‘V’-shaped valleys with small landslips. Glacial and periglacial deposits were reworked and coarse gravels were deposited and preserved as minor river terrace remnants in the upland valleys. The terraces were aggraded mainly during flood events, although some of the higher ones may be Late-glacial in age. In the lower reaches of the major valleys, up to three terraces lie within 8 m of the modern floodplain. Some are post-glacial erosional terraces cut in thick valley sandar, with minimal deposition. Others appear to be aggradations which postdated solifluction processes.

In later Flandrian times, under increasing influence of man, the trend has been towards partial destabilisation of the landscape. In historical times, there has been widespread deposition of silty alluvium or ‘warp’ on all the river floodplains. Removal of vegetation and agricultural practices, particularly since Roman times, have increased colluvial downwash to the valley floors.

Many alluvial sites are characterised by abundant drifted tree remains, perhaps the result of peat bog expansion and land clearance by Neolithic man. In Yorkshire, examples occur at Oxbow opencast site near Leeds, at Armley, Bingley, Keighley and Skipton in Airedale, at Elland, in Calderdale and one below the Aire confluence at Burton Salmon. Pollen studies show the deposits at these sites to span the Boreal, Atlantic and Sub-Boreal periods. Similar sites are known from the Trent valley at Shardlow and Long Eaton.

The headwaters of the rivers of the Pennines and Bowland Fells are characterised by systems of linear to dendritic tributaries. Hill-slope gullies were cut during phases of downslope destabilisation in Flandrian times. Many of the larger gullies have stabilised, but smaller gullies are still being incised. Sediment load is dropped in alluvial fans and debris cones where larger gullies and small steep gullies respectively join the main valleys.

At present, slope movements are generally limited to minor slippage around the toes of the major slips and mudflows; movements on a large scale affecting the main back scars occur only intermittently. Small to moderate rotational slips are, however, common in valleys in the immature landscape of the western Pennines. Here, streams are actively incising downwards and laterally into relatively soft tills and Namurian mudstones and are constantly eroding the toes of the slips, which thereby become unstable. Movements induced by human excavation also occur.

The mosslands or raised bogs of the waterlogged lowlands of west Lancashire, Greater Manchester, Cheshire and the Morecambe Bay estuary, together with Thorne Moors near Goole and Hatfield Moors near Doncaster, are the most extensive lowland peat deposits in Britain outside the Fenland. Most mosslands originated as the deposits of nutrient-rich lakes, derived from the partly humified remains of reed (Phragmites), sedge (Carex) and alder-willow fen carr. Later stages were characterised by a predominance of species of the bog-moss (Sphagnum), growing in acidic, nutrient-poor conditions and decaying to form raised peat bogs. The stability of the environment around a particular lake basin determined the duration of the transition from open water to raised bog conditions, which may have taken 500 to several thousand years. Although most lowland mires were initiated during the Flandrian, some, like Chat and Red mosses, date from the Windermere Interstadial. Peat extraction and drainage have caused several mossland areas to be greatly reduced and few active areas of extensive raised bog remain. Many of the sites are now agricultural or used for dumping waste materials.

There are three types of lowland mossland in the region. Coastal and estuarine peatlands above marine clay and silt at between 3 and 15 m above OD are extensive in the Wyre and The Fylde areas. They include Heysham Moss in the western Lune estuary, Winmarleigh Moss at Over Wyre, Lytham and Great Marton mosses and Marton Mere in The Fylde lowlands;Rawcliffe and Inskip mosses lie in the lower Wyre catchment. A string of raised bogs of this type, including Tarleton, Burscough, Halsall, Downholland, Croston, Mawdsley and Hoscar mosses, also occurs in the Douglas–Alt hinterland of south-west Lancashire and at Halton Moss in the lower Mersey estuary. Peatlands of large inland basins on till, glacial sand and gravels and blown sand deposits at 20 to 120 m above OD include the mosslands of south-central Lancashire. Examples are Red Moss at Horwich, and Farrington and Hoole mosses between the Douglas and Lostock rivers, south of the Ribble: Bickerstaffe, Simonswood, Holiday, Rainford and Parr mosses in the River Alt and Sankey Brook catchments: and Moss Lake at Liverpool. Other mosslands of this type in the upper Mersey catchment include Ashton and Linnyshaw mosses in the Irwell–Irk–Medlock hinterland: Chat, Holcroft, Risley, Trafford and Carrington mosses in the central Mersey valley:Lindow and Danes mosses in the upper Bollin catchment: and Sink and Gale mosses in north-central Cheshire. A number of medium-sized raised mosses of this type, for example White Moss, occur between 150 and 200 m above OD in the upper Ribble valley. The third category of lowland mosses includes the numerous small mires in the kettleholes of the hummocky drift areas and small basins of the drumlin fields. It also includes the meres and mires of the Delamere Forest and Dane catchment in the kettled-drift of north Cheshire.

The Millstone Grit outcrop in the upland Pennine areas gives rise to acid soils on which extensive upland blanket peat bogs, such as Holme Moss, contain peat up to several metres thick. Blanket mire began to form in the Bowland Fells and the Pennines between 7500 and 2000 years BP, mainly in response to increased rainfall and lower temperatures; human deforestation and the introduction of grazing animals probably also played their part. The bogs were initiated on the high plateaux and basinal areas, later subsuming the lower slopes. The remains of trees, chiefly birch and oak, but also pine, are widespread at the base of the peat. Today, erosion outstrips peat formation, due to a combination of factors operating over at least 1000 years, including lowering of the water table by cutting drainage ditches. Over large parts of the gritstone moors, the peat is dissected and gullied and commonly reduced to isolated hags, the faces of which dry and are rapidly eroded. Peats in the northern Peak District were initiated about the Boreal–Atlantic transition, at about 7000 years BP, as a result of increased wetness of climate. Between then and 4000 years BP, waterlogging at the start of wet episodes killed trees which had grown during the previous drier episodes. Pollen analysis of younger peat shows that its growth was hindered by agricultural land clearances, particularly in the early Iron Age. Expansion of heath and blanket bog vegetation and shallow peat cover over large areas in the immediate post-Roman period was probably a result of agricultural practice.

Many shallow lowland meres and wide courses of sluggish streams continued to be infilled with lacustrine shell marls, commonly interbedded with peats. They contain numerous freshwater species of gastropods and bivalves. Examples occur at Plemstall along the River Gowy north-east of Chester, in Hollins Syke near Chatburn and in the Trent basin near Nottingham.

There are three distinctive landscape associations around the coast of north-west England:

In south-west Lancashire, the coastal barrier comprises up to 12 m of sands and sandy silts with sporadic clay laminae and shelly sands beneath the coastal dunes. Shingle barriers north of the Ribble estuary were supplied with coarse material from the marine erosion of till. The barriers served later as a locus for the accumulation of blown sand, which appears to have begun about 4000 years BP and was interrupted by two distinct periods of dune stability at about 2300 years BP and 800 years BP, when peat accumulated between dunes. The coastal dune sediments overlap tidal flat and lagoonal deposits. Sand dunes are well developed at Starr Hills in The Fylde and in the Ainsdale and Formby areas of south-west Lancashire. Extensive sand beaches and dune belts occur around Morecambe Bay, The Fylde and Liverpool Bay. Until about 7000 years BP, coastal sand dunes and salt marshes were being formed despite frequent marine inundation. Tidal flat and lagoonal deposits comprise low and high tidal-flat silts and sands, marine, brackish water and freshwater clays, and intercalated saltmarsh and terrestrial peats and lake muds. They occur at Downholland Moss in south-west Lancashire, Nancy’s Bay and Lytham Common in the south-west Fylde and elsewhere. Their lithostratigraphy provides unequivocal evidence of marine transgressive and regressive events. Perimarine deposits consist mainly of fluvial sand and limnic clay and peat. The clastic layers were deposited during marine transgressions when the water table rose, the organic deposits forming during regressive phases. Several sites have been studied in the perimarine zone of south-west Lancashire. For example, palynological studies of organic deposits in Martin Mere, an extensive freshwater lake inland from Southport drained in the 17th century, provide evidence of the sedimentation in the zone during Flandrian Chronozone II and its relationship to sea-level movement. Other sites studied are at Rushland Lake and Helton Tarn around Morecambe Bay.

Marine and estuarine deposits are best known from boreholes and the many excavations for docks. Extensive deposits of early Flandrian (Older Marine) deposits along the Lancashire coast occur up to about 5 m above OD. They lie mostly within the range of high tides and would be flooded but for the protection afforded by sea walls. They comprise bluish grey, foraminiferal marine clays, shelly silts and fine sands up to 10 m thick. Boreholes, such as those in Morecambe Bay, indicate the presence of organic soils at several levels within the marine sequence. From these, twelve phases of marine transgression and regression have been established from about 9000 years BP in the Mersey Estuary–Morecambe Bay area. The transgressions indicate a rapid rise in sea level to about 6000 years BP, since when minor oscillations have taken place. Peaty ‘forest beds’ and silts containing the remains of oak, pine and birch and the bones of large mammals (such as red deer and aurochs) formed during regressive phases. They occur at or below sea level at many places along the Lancashire coast.

The estuarine–marine Downholland Silt of the Preston to Formby areas of south-west Lancashire is up to 12 m thick. It contains Scrobicularia and other marine molluscs and foraminifera, as well as freshwater molluscs, thin beds of peat and vertebrate remains. Similar estuarine–marine laminated clays, silts and sands with thin beds of peat cover large areas at the mouths of the Mersey, Ribble, Wyre and Lune rivers.

Artificial made ground is ubiquitous in developed areas and is being dumped at an increasing rate today. It occurs in a wide range of situations, including landfill sites, infilled quarries, flood, railway and road embankments and areas raised for development in valleys and coastal areas. It consists of a range of materials, from industrial and domestic waste products to excavated bedrock and superficial deposits.

Chapter 9 Structure

The surface and subsurface structure of the region can be described in terms of three major rock units, separated by unconformities, whose degree of structural deformation increases with depth and age. The oldest and deepest unit comprises the Caledonian basement, which crops out in the Craven inliers, the rocks of which are strongly faulted, folded and cleaved. The upper two units form the sedimentary cover sequence which rests with strong unconformity upon the basement. A Carboniferous succession, present virtually everywhere within the region, comprises variably thick, tilted, faulted and locally folded extensional-basin strata. It constitutes more than 60 per cent of the surface outcrop in the region, and, by volume, more than 90 per cent of the preserved sedimentary cover. In parts of the region, Carboniferous rocks are overlain unconformably by Permo-Triassic strata, which are tilted and locally faulted, but generally unfolded. This uppermost unit comprises about 40 per cent of the surface outcrop in the region, but less than 10 per cent by volume of the preserved sedimentary cover.

Because of its structural complexity and minimal surface outcrop, the nature of the Caledonian basement is poorly understood (Chapter 2). In contrast, regional seismic reflection coverage, acquired in the last twenty years in the search for hydrocarbons (Chapter 10), has given fascinating and detailed insights into the structure of the sedimentary cover succession.

Evolution of the Caledonian basement

The origin of the crust beneath the Pennine region is largely a matter of conjecture, but it is currently believed to have formed in late Precambrian times by the accretion of volcanic arcs and marginal basin complexes on to an ocean margin of the southern hemisphere supercontinent of Gondwana. Subsequent to this, in early Ordovician times, a small continental fragment, East Avalonia, is believed to have separated from Gondwana, to commence a protracted northward drift (Figure 3). The Pennine region lay close to the leading edge of this drifting microcontinent, and became subjected to subduction-related tectonic processes, including extrusion of the Borrowdale Volcanic Group of the Lake District, and the contemporaneous emplacement of granitic intrusions. Continued northward drift led to the gradual convergence of Avalonia with other continental masses, such that in late Ordovician or early Silurian times it suffered oblique juxtaposition with Baltica to the north-east. To the north-west, the Iapetus Ocean continued to close through Silurian times, leading to the eventual collision of Avalonia with Laurentia. This culminated in the Acadian orogenic events of the early Devonian. By reactivating or overprinting earlier structures, Acadian deformation was responsible for much of the structure of the Caledonian basement now observed. A pronounced arcuate basement structural trend is evident. North-east trends in the west of the region veer east to west in the central part and turn to the north-west in the east. They are believed to have resulted from the northward ‘indentation’ of the apex of a relatively rigid crustal block to the south (the Midlands Microcraton) into the more mobile rocks of the Caledonian Fold Belt. Further emplacement of granitic intrusions occurred during, or very soon after Acadian tectonism.

Subsequent to the main Acadian collisional events, in middle to late Devonian times, the elevated terrain of the Caledonian fold belt was gradually eroded and peneplaned, prior to renewal of deposition in the early Carboniferous. The present structural form of the top of the Caledonian basement (Figure 34) is essentially the product of Carboniferous, Permo-Triassic and younger tectonic processes, all of which were associated principally with sedimentary basin development.

Carboniferous evolution

The plate-tectonic process that most strongly influenced Carboniferous structural development of the region took place several hundred kilometres to the south, where subduction of the Rheic Ocean led to formation of a collision-type orogenic belt in the Iberian–Armorican–Massif Central area. In earliest Carboniferous times, extension of the Pennine region initiated a major sedimentary basin system that developed through the Carboniferous. Towards the end of the epoch, final closure of the Rheic Ocean culminated in the Variscan orogeny, with large-scale thrust and nappe deformation in Belgium, northern France and southern Britain. The Pennine region lay on the foreland to the north of the Variscan fold belt, where deformation was much less pervasive, being largely restricted to partial reversal of the earlier basin-controlling normal faults, and associated basin inversions.

Carboniferous basin development

In early Carboniferous (Dinantian) times, regional extension, directed roughly north-south, initiated the ‘syn-rift’ phase of basin evolution. Major normal faults developed which divided the region into a system of rapidly subsiding, fault-controlled, extensional basins and intervening structurally elevated blocks (Figure 35). Principal depocentres at that time included the Stainmore and Gainsborough troughs and the structurally complex Craven Basin. The overall form of this Dinantian block and basin system, although modified somewhat by subsequent tectonic processes, still persists at depth to the present day (Figure 34). In Namurian and Westphalian times, syn-rift subsidence gave way to the ‘post-rift’ phase of basin development characterised by a lack of major normal faulting and the development of a regional ‘sag’ basin, the Pennine Basin. Submergence and depositional onlap of the earlier structural highs led to Namurian and Westphalian strata effectively blanketing and concealing the ‘syn-rift’ basin architecture. The depocentre of the ‘sag’ basin gradually migrated southwards from the Pendle area of the Craven Basin in Namurian times to around Manchester in the Westphalian. More localised thickness changes in the post-rift succession can largely be ascribed to infilling of residual topography at the end of the syn-rift phase and differential compaction of the underlying strata.

A consequence of this style of basin evolution is that the nature of the main Dinantian syn­rift basins is not revealed at outcrop in the region. The thick syn-rift basin-fills are poorly exposed. In addition, the large basin-controlling normal faults, which may have subsurface throws of several kilometres, generally have only quite small displacements at the surface, or may be concealed beneath the post-rift succession (Figure 35). The surface expressions of the main Dinantian rift structures therefore appear either as minor normal faults, or quite commonly, linear zones of folding in the post-rift succession. It is only relatively recently, with the advent of seismic reflection data, that the true subsurface nature of the Dinantian ‘block and basin’ system has been revealed.

Principal structures

The principal structural features of the Carboniferous basin system (Figure 35), (Figure 36) are described briefly below, from north to south. The south-western flank of the very deep Stainmore Trough lies within the region. Only the upper part of the very thick Dinantian basin-fill is exposed at the surface, but borehole and seismic reflection data indicate that basement depths increase from perhaps less than 2000 m below OD near the Dent Fault to more than 5000 m in the far north-east (Figure 34). The strata are mostly undisturbed, except for localised Variscan folding at the faulted basin margins. Westphalian rocks are not preserved, having been removed by erosion, but Namurian strata crop out in the west of the basin, giving rise to the high moorlands of Stainmore.

The Askrigg Block, underpinned by the rigid Wensleydale granite, is the principal structural high in the region (Figure 36), forming a northerly dipping tilt-block bounded to the south by the Craven faults, to the west by the Dent Fault and to the north by the concealed Stockdale Fault. Caledonian basement lies at depths generally less than about 1500 m below OD and locally comes to crop (Figure 34). The Carboniferous rocks on the Askrigg Block are virtually undeformed, dipping only gently northwards. The succession is thin and incomplete, indicating that the block remained emergent through much of the Dinantian. It thickens steadily north-eastwards into the Stainmore Trough, both stratigraphically and by the preservation of progressively older Dinantian rocks. It comprises the clastic/carbonate succession of the Wensleydale Group and the platform carbonates of the Great Scar Limestone Group. The Dinantian succession is thinnest close to the southern margin of the block, as for example at Horton in Ribblesdale, where basal platform carbonates rest unconformably on exposed folded Caledonian basement rocks (Plate 3). Scattered outliers of Namurian strata generally cap the higher elevations.

The stepped southern margin of the Askrigg Block is formed by the North and Middle Craven faults (Figure  7), (Figure 35), which, together, extend for some 70 km. The effects of the North Craven Fault are best appreciated in the Settle district where Lower Palaeozoic rocks of the Askrigg Block locally form its footwall at outcrop. The fault forms a complex of subparallel fractures, which dip to the south and throw the Malham Formation (of late Holkerian to Asbian age) down to the south by as much as 160 m. Displacement of the fault at depth hereabouts is uncertain, but is likely to be much greater. The Middle Craven Fault in the Settle district is rather better understood. It has a steep to moderate (locally as little as 45. ) southerly dip. It throws the Malham Formation down to the south some 300 m and the top of the Chapel House Limestone about 400 m, indicating pre-Brigantian, syndepositional, normal displacements. More specifically, Arundian to Holkerian normal displacement can be inferred from the abrupt southward thickening of the Kilnsey Limestone. Minor reversal in the early Brigantian (an early precursor of Variscan basin inversion) is indicated by northward thickening of the Lower Hawes Limestone. Renewed normal displacement took place in late Brigantian times, with the Upper Bowland Shale Formation onlapping against a contemporaneous south-facing fault scarp. There is also evidence for intra-Pendleian and post-Pendleian movements on the fault, the latter characterised by northward tilting of the footwall-block. To the east of the Settle district, the North and Middle Craven faults coalesce to form a single structure. Seismic data show this to be a subplanar normal fault dipping to the south at about 50. , and with a southerly downthrow at basement level of about 1800 m (Figure 34). The throw is largely accomplished by a threefold thickening of the Dinantian succession across the fault, from about 800 m on the Askrigg Block to more than 2200 m in the Craven Basin.

Bounded by the Lake District Block to the north-west, the Askrigg Block to the north-east and the Central Lancashire High to the south, the Craven Basin constitutes a major, structurally complex basinal feature straddling the region from west to east (Figure 35). In the west, north-east structural trends are dominant, the main structural feature being a deep Dinantian half-graben (also known as the Bowland Sub-basin), bounded to the south by the Pendle Fault and to the north by the poorly understood subsurface faults of the Bowland Line (Figure 35); and see below). The fact that the subsurface nature of these major, syn-rift basin margin structures cannot be deduced directly from their surface expressions is exemplified by the Pendle Fault. This fault is one of the largest structures in the region, but, unlike the Craven Faults, it is entirely concealed. It is a normal fault over 60 km long and has a present-day northerly downthrow at basement depths of up to 1200 m (Figure 34), (Figure 36). It does not, however, reach the surface, being overlain by post-rift (Namurian) strata which are folded into the major south-facing Pendle Monocline (Figure 36), (Figure 37). Allowing for the amount of fault reversal which accompanied development of the monocline, the original northerly downthrow on the Pendle Fault may have locally approached 3000 m. Present-day basement depths are only about 2000 m below OD in the central part of the Craven Basin, around Gisburn. However, this is principally an effect of strong Variscan basin inversion, which folded and uplifted the axial part of the basin here by several thousand metres, to form the Ribblesdale Fold Belt (see below). Basement depths increase south-westwards to more than 5000 m below OD west of Preston, where the Carboniferous basin-fill is concealed beneath Permo-Triassic strata. In the eastern part of the region, the Craven Basin is characterised by basement depths generally between 3000 and 4000 m below OD (Figure 34), deepening gradually eastwards as the Carboniferous succession becomes buried beneath Permo-Triassic rocks. Localised zones of Variscan folding form the easterly continuation of the Ribblesdale Fold Belt here. Namurian strata form the outcrop over much of the Craven Basin but, along the inverted central axis of the basin, basinal Dinantian mudstones and limestones crop out in the low-lying farmland of the Ribble valley.

South of the Craven Basin, the syn-rift basin architecture comprises a mosaic of fault-bounded tilt-blocks largely concealed by Namurian and Westphalian strata. Basement depths are less than 2000 m below OD on localised fault-controlled structural culminations, such as the Central Lancashire and Holme highs (Figure 35), where the Dinantian sequence comprises relatively thin platform carbonates. Elsewhere, thicker, more basinal Dinantian sequences are found in small, asymmetrical grabens such as the Rossendale and Huddersfield basins, where basement depths may locally exceed 3000 m below OD. Hereabouts, surface structures do not directly relate to the underlying syn-rift fault system. It is likely that many of the complex network of faults cutting the post-rift succession in this area (which have been mapped in great detail in the coalfields) developed much later, probably during Permian–Mesozoic extension (see below). North-west trends, typified by the Darwen Valley Fault (Figure 35), are dominant in Lancashire, with north-east trends evident in West Yorkshire. The surface displacements of these faults are small compared to the underlying basin-controlling syn-rift structures, and it is not certain whether they formed in Dinantian times to be reactivated as Variscan features, or are much younger. Another prominent surface feature is the north-south- trending linear zone of faults and folds known as the Pennine Line (Figure 35). Its nature in the subsurface is poorly understood, so its role as a syn-rift structure is uncertain; most of the surface structures appear to have a Variscan origin (see below). Basement depths increase gradually south-westwards to over 4000 m below OD (Figure 34) as the Carboniferous succession becomes buried beneath the Permo-Triassic cover of the Cheshire Basin (Figure 36).

In the south-east of the region, a strong north-west structural trend reflects the dominant grain of the underlying Caledonian basement (Figure 34). Basin and block structures are more clearly demarcated than in the area immediately to the north. Again, however, the syn-rift basin architecture is revealed only by seismic reflection data, being mostly concealed by post-rift Namurian and Westphalian rocks, and, in the far east of the region, by younger Permo-Triassic cover.

The Alport Basin forms a south-east-trending half-graben, basement depths being greatest in the south, and locally in excess of 4000 m below OD (Figure 34) close to the Alport Fault at the southern margin of the basin. The syn-rift sequence is concealed and not fully penetrated by drilling, but borehole information suggests some derivation from the contemporary carbonate platform on the Holme High to the north.

The Edale Basin, unlike many of the syn-rift structures in the region, is partially visible at outcrop, but its subsurface structure is poorly understood due to the lack of seismic data. It is believed to have a similar geometry to the Alport Basin, forming an asymmetrical graben bounded to the south by the putative subsurface Bakewell Fault, the assumed root of the outcropping Taddington–Bakewell Anticline (Figure 35). Apart from local provings such as the Eyam Borehole, basement depths are generally poorly constrained, but are likely to exceed 2000 m close to the southern margin of the basin (Figure 34). Much of the syn-rift sequence is concealed by post-rift strata, but limited borehole data suggest a more basinal Dinantian facies than that on the Woo Dale High to the south. However, Dinantian outcrops higher in the succession in the central and southern parts of the basin comprise a thick succession of platform carbonates.

The Woo Dale High forms the culmination of the tilted footwall-block of the Bakewell Fault, Caledonian basement lying at depths of less than 500 m below OD (Figure 34). The high is bounded rather abruptly to the west by the Variscan folds of the Pennine Line, but it dips more gently to the east. The Dinantian succession on the high comprises thin platform carbonates, a lack of pre-Arundian strata indicating that the structure was emergent through much of the syn-rift phase of basin development.

The Edale Basin and Woo Dale High gradually lose their structural identity as they pass south-eastwards into the East Midlands Platform, where basement depths lie generally between 1500 and 2000 m. Here, the Carboniferous succession is largely concealed by Permo-Triassic strata which form the subdued topography of north Nottinghamshire.

The Widmerpool Gulf lies to the south of the East Midlands Platform, separated from it by the Cinderhill Fault. The Widmerpool Gulf merges westwards into the deeper parts of the south-west-tilted footwall block of the Bakewell Fault (Figure 35), down-dip of the Woo Dale High, but the main part of this deep half-graben lies to the south, outside the region.

The Gainsborough Trough lies in the easternmost part of the region (Figure 35). As with the other basins, surface exposures give little hint of subsurface structure. This major syn-rift basin has the overall form of a north-west-trending, asymmetrical graben. It is deepest in the north-east, where it is bounded by the Morley–Campsall Fault, which locally has a south­westerly downthrow in excess of 3000m at basement depths. Around Doncaster, Caledonian basement beneath the trough lies at depths well in excess of 5000 m below OD, with a syn­rift basin-fill more than 4000 m thick and a thick post-rift succession also preserved. The basin-fill strata are mostly tectonically undisturbed, except for localised Variscan folding at the faulted basin margins.

Variscan basin inversion

In latest Carboniferous times, basin subsidence in the region gave way to regional uplift as Variscan crustal compression initiated the process of basin inversion (Figure 37), during which most of the major basin-bounding normal faults were partially reversed (or, more commonly, obliquely reversed). The principal effects of fault reversal were to reduce net normal displacements on the deep syn-rift faults and to produce local reverse faulting, anticlines and monoclines at higher structural levels (Figure 37).

The main Variscan movements postdated the preserved Westphalian rocks and predated deposition of Permian strata that rest unconformably on the Carboniferous beds. There is some evidence, however, that earlier, minor episodes of compression locally influenced patterns of latest Dinantian, Namurian and Westphalian deposition.

Principal inversion structures

In contrast to the major syn-rift normal faults, Variscan inversion structures in the region, which lie at much shallower structural levels, can be readily discerned at outcrop. This is particularly the case with the Ribblesdale Fold Belt which suffered quite severe Variscan folding as it lay sandwiched between the rigid Lake District Block to the north, the Askrigg Block to the north-east and the Central Lancashire High to the south. The fold belt extends east-north-east for at least 80 km and is up to 25 km wide (Figure 35), marking the inversion axis of the Craven Basin. Variscan uplift here was greater than anywhere else in the region, and may locally have exceeded 4000 m.

The southern margin of the Ribblesdale Fold Belt is marked by the Pendle Monocline, which is the largest individual inversion structure in the region, and is traceable at the surface for about 40km (Figure35). This structure, which formed by reversal of the underlying northerly downthrowing Pendle Fault (Figure 37), (Figure 38), faces south, and affects mostly Namurian and Westphalian strata. The fold amplitude is more than 1000m along much of its length and locally up to 2000 m. In the Clitheroe district, nearly 3000 m of Dinantian to Westphalian strata, dipping at 50. to 70. , crop out in a distance of less than 5 km. Locally, the fold has a well-defined axial crest with significant development of a northern limb, forming subsidiary structures such as the Dinkley and Lothersdale anticlines, the latter passing eastwards into the major Skipton Anticline.

At outcrop, the northern margin of the Ribblesdale Fold Belt corresponds roughly to a series of Variscan folds and reverse faults associated with reversal of the subsurface faults of the Bowland Line and the North Craven Fault (Figure 35). Typical inversion structures of this type include the Plantation Farm Anticline (Figure 39) and the Sykes Anticline, the latter being well exposed in the Trough of Bowland.

Within the Ribblesdale Fold Belt, there is a set of en échelon anticlines with intervening synclines. Because the fold belt marks the main inversion axis of the Craven Basin, its structures have been exhumed from considerable depth. Deep structural levels within the Dinantian succession are best exposed in the River Hodder, where some beds display an axial plane cleavage. The anticlines are mostly between 5 and 10 km long and asymmetrical;seismic reflection evidence indicates that they formed by reversal of earlier normal faults. Good examples include the Clitheroe Anticline (Figure 36), (Figure 39), well exposed in local quarries, the Grindleton Anticline (Figure 39) and the complex Harrogate Anticline; all of these are associated with reverse faulting.

Another area of significant Variscan folding is in the south-east of the region, where several anticlines and monoclines (for example, the Don Monocline) affect the Edale Basin, the Widmerpool Gulf, the Gainsborough Trough and the East Midlands Platform. The more westerly of these structures can be seen at outcrop; the Longstone Edge Anticline is particularly well displayed, with mineralisation along its east-trending axial crest. Other prominent folds include the Calow-Brimington, Ashover and Crich anticlines, the last two culminating as Dinantian inliers surrounded by Namurian strata. Farther east, important inversion structures, exemplified by the Eakring Anticline are concealed beneath the Permo-Triassic cover. These structures are somewhat enigmatic because they are not, in general, associated with the reversal of major basin-bounding syn-rift faults, but formed by reverse reactivation of smaller, intra-basin faults. Their dominant north-west trends are perpendicular to the structures of the Ribblesdale Fold Belt, and closer in orientation to the folds of the Pennine Line and associated structures (see below).

Other Variscan inversion structures in the region are also commonly associated with reversal of parts of the syn-rift fault network. The Dent Fault and the Pennine Line are examples. The Dent Fault marks the western margin of the Askrigg Block, and is unusual in showing a net reverse (down-east) displacement of the Caledonian basement, any Dinantian normal movements on the fault being outweighed by subsequent reversal. The structure at the surface comprises an east-facing and slightly overturned monocline cut by a series of vertical to steeply west-dipping fault strands, and throws Caledonian rocks of the Howgills Anticline against and over Dinantian rocks of the Askrigg Block. The amount of reverse displacement on the fault is uncertain, but may well exceed 1000 m. The en échelon Hutton Monocline/Quernmore Thrust has a similar origin, involving Variscan reversal of a Dinantian westerly downthrowing normal fault.

The north-trending Pennine Line is a prominent linear feature, stretching nearly 100 km southwards from the southern margin of the Craven Basin and affecting mostly Namurian strata at crop. It is generally asymmetrical, with steep dips on its western flank and gentle dips on its eastern one. In the north, a monocline faces west, and as with the Dent Fault, shows net reverse displacements of the Caledonian basement. Southwards, the structure takes on a more anticlinal form, swinging into a north-westerly orientation near Todmorden, where it is associated with a complex series of faults known as the Todmorden Smash Belt. South of this, the structure is less well defined for several kilometres, before appearing again as the Mossley Anticline, a generally asymmetrical, west-verging structure. Towards the southern edge of the region, it branches into a series of en échelon north-trending folds (Figure 35), some of which are well seen at outcrop. The synclines, by reason of their axial coalfields (for example the Goyt Syncline), are better known than the anticlines. The axial parts of two of these folds, the Ecton Anticline and the Dovedale Anticline are spectacularly exposed in the gorges of the Manifold valley (Plate 26) and Dovedale.

The wide range of orientation displayed by the inversion structures of the region is noteworthy. The dominantly east-north-east trends of the Ribblesdale Fold Belt contrast with the more northerly trends of the Pennine Line and Dent Fault, and with the north-westerly trends in the south-east of the region. Components of both east- and north-directed shortening are evident and it seems that Variscan inversion involved complex block interactions with a range of localised stress fields.

Permo­-Triassic basin development

By earliest Permian times, Variscan continental collision had led to final consolidation of the Pangaean supercontinent, with associated regional uplift. The region lay deep within this continental mass; it suffered erosion and progressive peneplanation during the early Permian, with significant deposition not recommencing until late Permian times. At the present day, Permo-Triassic rocks crop out in the east and west of the region, forming flat, low-lying areas flanking the higher ground of the Pennines. Despite incomplete preservation of the sedimentary succession, sufficient evidence remains to draw firm conclusions about many aspects of Permo-Triassic structure.

Strongly contrasting structural styles characterise the eastern and western parts of the region (Figure 40). To the east of the Pennine High, Permo-Triassic strata were deposited on the Eastern England Shelf, where subsidence was of a regional nature, on the periphery of the basins of the southern North Sea. To the west, the West Lancashire and Cheshire basins formed part of a major rift system that extended southwards to the English Channel and northwards into Scottish waters. Development of these rift basins involved partial reactivation of the Dinantian fault network, for example along segments of the Pendle Fault, and the southerly continuation of the Darwen Valley Fault in the north-eastern Cheshire Basin. Mostly, however, the impression is of a new fault system with dominantly north–south trends superimposed on the older fault network. This is consistent with east–west-directed extension reactivating basement faults in a different manner to that of the north–south early Carboniferous extension.

Principal structures

The West Lancashire Basin constitutes the landward portion of a much deeper basin beneath the East Irish Sea. Its eastern margin is formed by two large normal faults (Figure 40), the Western Boundary Fault (of the Lancashire Coalfield) and the Pendle Fault; in the latter case, partially reactivating the earlier Carboniferous structure. Preserved Permo-Triassic thicknesses are typically around 1000 m and locally in excess of 2000 m. However, a full sequence is nowhere preserved, so initial thicknesses were undoubtedly much greater.

Only the northern part of the deep Cheshire Basin impinges upon the region. Permo-Triassic sedimentary thicknesses exceed 2500 m at the southern edge of the region (Figure 36), but thicken markedly to nearly 4000 m farther south in the centre of the basin. Major faults in the northern part of the basin include the Brook House and Irwell Valley faults (Figure 40), which cut the basin into a system of tilted fault-blocks. Thickness changes across these easterly downthrowing normal faults indicate that they were active throughout deposition of much of the Permo-Triassic succession. As discussed above, these faults may have developed by the reactivation of Carboniferous structures similar to the Darwen Valley Fault.

The bounding faults of the Askrigg Block (the Dent Fault in the west and the North Craven Fault System in the south) probably suffered oblique-normal displacements during the Permo-Triassic, as in early Carboniferous times. Sedimentary thicknesses are very poorly constrained, but analogy with the Lake District Block suggests that the Askrigg Block, underpinned by rigid granite, continued to act as a structural high, with a relatively thin Permo-Triassic sequence, thickening gradually eastwards towards the Eastern England Shelf.

The Permo-Triassic evolution of the large and rather ill-defined Pennine High is poorly understood, as, for the most part, post-Carboniferous strata are not preserved. It is likely that Permo-Triassic deposits were markedly thinner than in the surrounding basins, but with significant local variations; sites of the earlier Carboniferous basins probably received thicker Permo-Triassic sequences than the Carboniferous structural highs.

To the east of the Pennine High, subsidence was mainly of a flexural nature with only minor faulting. Here, on the Eastern England Shelf, Permo-Triassic rocks thicken and dip gently eastwards towards the offshore basins beneath the southern North Sea.

Post-Triassic subsidence and uplift

The evolution of the region from the Triassic to the Quaternary is somewhat conjectural, because almost no strata deposited in that period are preserved. Analogy with more fully preserved successions in southern England and offshore indicates that extensional basin subsidence probably continued through the Jurassic and into early Cretaceous times. Basin development was largely controlled by the Permo-Triassic structural template, with the thickest post-Triassic successions likely to have been deposited in the West Lancashire and Cheshire basins and on the Eastern England Shelf, and much thinner sequences on the Askrigg Block and the Pennine High. A period of post-rift, regional subsidence followed in the late Cretaceous; apatite fission-track analysis indicates that maximum sediment thicknesses were attained in earliest Cainozoic times.

Subsequent to this, the region has lain within a dominantly erosional regime until the present day. It is believed that Cainozoic uplift comprised two distinct components. Regional flexural uplift was possibly associated with development of the Scottish Tertiary igneous province; superimposed on this were more localised uplifts corresponding to basin inversions associated with Alpine crustal compression. Recent estimates based on stratigraphical extrapolation and modelling of 0 palaeotemperatures, suggest that Cainozoic erosion removed between 1000 and 2500 m of strata from much of the region. However, the precise patterns of uplift remain poorly understood. It is likely, however, that features such as the ‘Pennine Anticline’ owe their origin more to Carboniferous and Mesozoic patterns of differential subsidence than the relatively recent effects of Cainozoic uplift.

Chapter 10 Geology and man

Th  rich mineral resources of the Pennines and adjacent areas are listed. They  have been extracted by man for centuries. Although the extraction of coal has declined markedly, oil and gas production remains economically viable. The industrial mineral resources of the region continue to be a major contributor to the UK economy, with limestone, sand and gravel, and fluorspar being the main commodities. Also important are the region’s groundwater and surface water resources. The expansion of the urban areas around the towns and cities and the redevelopment of former industrial brownfield sites involve resource and hazard assessments, for which detailed geological advice is necessary. Geological factors affecting the growth and development of the principal conurbations, including some case histories of constraints and problems, are briefly discussed.

Fuel and energy

Coal

Mining of the Coal Measures, mainly for coal, but also for ironstone and fireclay, has played a decisive role in the economic development of the region. The East Pennine Coalfield is the UK’s principal area of coal production. In 1998–1999, it produced 18. 1 million tonnes of coal from 14 deep mines and 3. 0 million tonnes from opencast workings, representing 55 per cent of total UK production. The Lancashire Coalfield, although formerly an important deep-mining area, now has only opencast workings, the output of which in 1998–1999 was 0. 2 million tonnes. In the more distant past, coal was also produced from the small Ingleton Coalfield, and from other minor occurrences in rocks of Westphalian and Namurian age. Most recently, the coalfields have attracted interest as a source of methane gas (p. 139).

The earliest coal workings were close to the seam outcrops, using adits (small tunnels) and bell pits (small shafts up to about 10 m deep). Exhaustion of the shallow reserves and advances in mining techniques resulted in working at progressively greater depths, mainly from shafts but also from inclined tunnels called drift mines. At first these deeper workings were of the ‘pillar and stall’ type, where about half the coal was left in place to support the roof. This was gradually superseded by longwall mining, where all the coal is removed from a panel up to about 300 m wide and of variable length up to 3 km or more. As the working face is advanced along the panel, the roof behind the face is allowed to collapse, leaving only the access tunnels open. This is the method currently used. Coal seams as thin as 0. 3 m were worked in former times but nowadays the minimum workable thickness is about 1. 8 m. Seams over 2 m thick are rare in the region. Mining followed the coal seams to greater depths on both sides of the Pennines, until, in 1996, only one deep mine, to the east of Wakefield, had surface works situated on the Coal Measures crop. The others are sited on the Permo-Triassic crop, up to 20 km to the east, and are working coal to depths of 880 m from the surface. Ironstone and fireclay were also mined locally in the past, mainly by bell pits and ‘pillar and stall’ workings close to the outcrops.

Underground working produces various subsidence effects at the surface. The older, shallow ‘pillar and stall’ workings are the most troublesome in this respect, because the roof above open voids left after extraction of a seam may eventually collapse, and crown holes may form at the surface. Old shafts that were not properly backfilled may also collapse to give crown holes.

Opencast operations began during the Second World War and are able to recover the thin seams that remain unworked in the Coal Measures crop (Plate 27). Opencast pits are large quarries where the coal seams are extracted and the intervening mudstones, siltstones and sandstones are returned as backfill. This method is now more economical than deep mining, and normally 20 per cent more profitable. The proportion of coal opencasted has increased markedly since 1985 as deep mines have closed; however, current environmental pressures are inhibiting exploration and development.

A number of coal seams were formerly deep-mined, most notably the Barnsley, Parkgate and Beeston in Yorkshire and the Top Hard and Deep Hard in Nottinghamshire. Recently, underground production in Yorkshire has been concentrated in the Barnsley seam complex, especially in the Selby group of mines, the most modern in the region, which was developed in the 1970s. The seams are up to 4m thick, and the coals of high-volatile bituminous types with over 32 per cent volatile matter. Calorific values range between 7800 and 8700 kcal/kg and equilibrium moisture contents are between 2 and 16 per cent. Most of the coal raised is used as steam coal for power generation.

Oil and gas

Amounts of oil and gas discovered in the region have generally been small, but relatively low costs have made exploration and development an attractive commercial proposition. The principal exploration target is the Carboniferous succession, which provides both suitable source and reservoir rocks. Of the numerous exploration wells drilled, over half encountered hydrocarbon shows, but economically viable accumulations are few and concentrated almost exclusively in the East Midlands (Figure 41). Outside the region, to the east and south-east, are some other important East Midlands discoveries, as well as the Eskdale and Lockton gasfields of the Cleveland Basin. Offshore to the west, major oil and gas discoveries have been made in the basins beneath the east Irish Sea, including the Morecambe Bay, Hamilton and Douglas fields.

Source and reservoir rocks

The relatively deep-water deposits of the late Dinantian and Namurian Bowland, Edale and Sabden shales are believed to comprise the main organic-rich units with source potential in the region (Figure 41). In the East Midlands, the Edale Shale forms the main source for oil, with other marine shales forming a minor component. Optimal development of the shale facies occurred within Dinantian basins such as the Gainsborough Trough and Widmerpool Gulf (Chapter 9), with local lesser developments on the East Midlands Platform. Average total organic content (TOC) is about 4 per cent, with considerable areas of source rock having levels of maturity suitable for oil or gas generation. In Lancashire and offshore beneath the Irish Sea, the Bowland, Sabden and Holywell shales are all potential oil-source rocks. The Bowland Shale has TOC values up to nearly 10 per cent; it contains both oil- and gas-prone kerogens and lies within either the oil or gas generation window. The Sabden Shale contains dominantly oil-prone kerogen, with rather lower TOCs of around 4 per cent. There are few available analyses from this formation, but they indicate that it is generally submature with respect to oil generation. This may not be the case, however, where it is more deeply buried in the west of the region, where it and the comparable Holywell Shale have been suggested as a source for the Formby and East Irish Sea oil.

Coal, being rich in humic material, is dominantly gas-prone, though cannel coals, composed of sapropelic kerogen, can be good oil-source rocks. Maturity values of the Coal Measures in the Pennine region are generally below peak maturity for gas generation, but many oil and gas seepages have been recorded in coal mines and coal exploration boreholes.

There is a wide variety of potential reservoir rocks in the region, ranging from early Carboniferous to Triassic in age. Carboniferous deltaic clastic rocks form the principal proven reservoir facies in the region, delta-top mouth bar and channel sandstones being particularly important. Rocks of this type occur principally in the Namurian and Westphalian successions, although Dinantian clastic reservoirs may be present in the north and west of the region. Burial history strongly controls clastic reservoir quality, both porosity and permeability decreasing steadily with maximum burial depth. Permo-Triassic sandstones have much more favourable reservoir characteristics, particularly where well developed in the south-west of the region. Offshore, they form important reservoirs in the East Irish Sea Basin, but have not provided significant production in the Pennine region to date. Carbonate reservoirs are likely to be less important, being mostly restricted to Dinantian reef complexes, present only in the central and southern part of the region. As well as being difficult to identify in the subsurface, such carbonate rocks generally have low porosity, although permeability may be locally enhanced by the fracturing, dolomitisation and dissolution that occurs within the cores of Variscan anticlines.

The principal (Carboniferous) reservoir-sealing horizons generally correspond to the regionally extensive marine shales, although the possibility of more local trapping by lacustrine mudstones cannot be ruled out.

Prospectivity and hydrocarbon occurrences

It is likely that there were two main periods when hydrocarbons were generated from the Carboniferous source rocks in the region — late Carboniferous and late Mesozoic to earliest Cainozoic times — both periods corresponding to regional burial following extensional basin development (Chapter 9). Because any late Carboniferous hydrocarbon accumulations are likely to have escaped during Variscan and subsequent tectonism, it is believed that Mesozoic burial and maturation constitute the main control on present-day prospectivity. Even so, since hydrocarbon generation was probably more or less frozen by early Cainozoic regional uplift, prospective traps will have had to retain their integrity for periods up to, and perhaps in excess of, 60 million years. Much of the central part of the region (the Pennine High, Chapter 9) is unlikely to be prospective, burial having been insufficient to trigger significant oil generation. The western part of the region (west Lancashire) is likely to have variable prospectivity. Here, Mesozoic rift subsidence, with large-scale faulting, produced marked local variations in burial history and complex patterns of maturity and reservoir quality. In addition, Mesozoic faulting may well have breached many potentially prospective Variscan inversion structures. The south­eastern part of the region (the East Midlands) appears to offer the best prospectivity, having suffered adequate, but not extreme Mesozoic burial, accompanied by gentle easterly tilting which caused only minor disruption of the (predominantly Variscan) structural traps.

The East Midlands oil province contains by far the largest proven hydrocarbon reserves in northern England, extending beyond this region to the south and east. The first discovery was made at Hardstoft in Derbyshire in 1919, in fractured Dinantian shelf carbonates on a tightly folded Variscan anticline, but serious development of the area waited until 1939 when the Eakring structure was discovered. By 1996, 90 million barrels of oil equivalent and 30 billion cubic feet of gas had been extracted. Oil quality is generally good, except for rare sour crudes and high wax contents (10 to 20 per cent) due to the contribution of plant matter.

The hydrocarbon accumulations are generally found within Variscan inversion structures, typified by the Eakring oilfield (Figure 42), where a series of en échelon anticlines adjacent to the north-north-west-trending Eakring–Foston Fault (Figure 35) trapped oil in Namurian to early Westphalian sandstones. Other significant finds include the Beckingham–Gainsborough oilfield (in 1959) and the Hatfield Moors gasfields where the reservoir is in Coal Measures. The latter suffered a blowout in its discovery hole in 1981. The Calow gasfield is worthy of mention because it lies in a shallow Variscan structure, the Calow–Brimington (Figure 35). The largest East Midlands oilfield was discovered in 1981, at Welton near Lincoln (outside the Pennine region), with estimated total recoverable reserves of nearly 17 million barrels.

Outside of the East Midlands, the main oil discovery was at Formby in west Lancashire (Figure 41), in an area where oil shows had been recognised for centuries. Between 1939 and 1965, the oilfield (now abandoned) produced between 10 and 100 barrels of oil per day, with a cumulative total of about 76 000 barrels. Production was from unusually shallow depths of around 30 to 40 m, in peat and the underlying fractured Mercia Mudstone Group. In the 1950s, an unsuccessful search was made for a deeper pool from which the shallow accumulation was assumed to have leaked. Elsewhere, oil seeps were common in the mines of the Lancashire, Yorkshire and North Derbyshire coalfields. There has been limited commercial production of gas from coal mines, notably from Parkside Colliery near Warrington. More recently, in 1990, gas was discovered near the village of Elswick on the Fylde. Original reserves were estimated at 6 million cubic metres, with production being used for power generation at the site.

Coalbed methane

Methane is a by-product of natural coalification — the low-grade metamorphism of peat through lignite to coal and anthracite. Some of this methane migrated from the source rock as it formed, but some remains, either adsorbed on to maceral surfaces or held as a free gas within the cleat. It was formerly regarded entirely as a hazard in coal mining, but may become a potential source of energy in the future. Coal can hold large quantities of coalbed methane — the maximum UK in situ measurement is 18 m3 tonne-1. Coalbed methane is produced from boreholes by pressure reduction, brought about by pumping water from the coals, resulting in desorption of the gas and diffusion into the borehole.

The search for onshore coalbed methane resources was instigated by the Department of Trade and Industry in 1991 under existing oil and gas licensing procedures. The southern part of the Lancashire Coalfield, beneath Permo-Triassic cover, appears to be potentially the most prospective area, having a total coal thickness of 20 to 25 m and high gas contents (typically 8m3 tonne-1). However, recent coalbed methane exploration boreholes drilled in the Merseyside–Wirral area failed to prove economic amounts of gas. Much of the East Pennine Coalfield is poorly prospective, being largely exposed and heavily mined, although unworked pockets of coal may have potential for coalbed methane. The eastward, concealed extension of the coalfield may have some coalbed methane potential where the coals are unworked, beyond the limits of this region. Recently, methane vented from abandoned collieries at Markham in Derbyshire and Steetley in Nottinghamshire has been exploited, the latter for power generation and input to the National Grid. Other coalfields in the region have coal reserves that are either too thin or too shallow to have significant coalbed methane potential.

Geothermal energy

Two methods of extracting geothermal heat have been examined in the UK. ‘Hot dry rock’ systems pump cold water from the surface into hot, fractured rocks at depth, where it is heated, and then returned to the surface via an adjacent borehole. ‘Low enthalpy’ systems extract hot groundwater directly from deep aquifers. The hot water can be used for space heating, or, if its temperature is sufficiently high, to assist electricity generation.

Heatflows in the region are similar to the nationwide average, being generally in the range 40 to 70 milliwatts per square metre (mWm-2), with somewhat higher values in the far south-east. The lack of very high heatflow values (>100mWm2), of the type associated with high heat production granites, probably rules out any hot dry rock geothermal potential. For the low enthalpy method, the best aquifers in the region lie within the Permo-Triassic succession, but at insufficient depths to have significant geothermal potential. Deep aquifers of the necessary depth (below 2000 m) and temperature may be found in the succession, but are likely to have low porosity and permeability. The geothermal potential of the region is, therefore, rather unpromising, although the possibility of meeting small-scale local demands cannot be ruled out.

Industrial minerals

Limestone and dolomite

(Figure 43) shows the industrial resources of the region. It is the principal source of limestone in Britain, producing about 43 million tonnes annually, equivalent to about 35 per cent of the country’s output. Production is concentrated on the Carboniferous limestones of the Peak District and the Yorkshire Dales, which supply the major proportion, and the Permian limestones and dolomites of North Yorkshire and Nottinghamshire.

Carboniferous limestones account for some 66 per cent of total UK limestone output. They typically produce strong, durable and low porosity aggregates and are consistent in quality over large areas. They are generally thickly bedded and shallow-dipping and thus easy and cheap to work. Moreover, outcrops are relatively close to major centres of demand. Consequently, they are the principal source of crushed rock aggregate in Britain. However, demand for industrial limestone is relatively small (see below). Other non-aggregate uses include cement making (see below) and agriculture.

The Peak District and, to a lesser extent, the Yorkshire Dales, are major sources of limestones (Figure  8),(Table  6) of very high chemical purity (over 98.5 per cent CaCO3). The Peak District supplies a major proportion of the high purity limestone produced in Britain. Industrial applications include lime production, glassmaking, flux in ironmaking, flue gas desulphurisation and as a filler in paint, rubber and plastics. The Bee Low Limestones are of consistently very high purity, uniform chemistry and adequate aggregate properties, and provide a major proportion of the limestone quarried in Derbyshire. The underlying Woo Dale Limestones are only marginally less pure and, although not widely exposed, are worked in several quarries. The Bee Low Limestones are extensively quarried in the Buxton and Wirksworth areas and are also mined at the Middleton Mine near Wirksworth. The limestone is dolomitised in much of the Matlock–Wirksworth–Brassington area and was formerly valued for its magnesia content. Between 1963 and 1966, the dolomite was used for the extraction of magnesium metal, but the process was uneconomic. It is locally worked as a minor source of aggregate, although producing a weaker and more porous aggregate than the undolomitised limestone. The limestone succession above the Bee Low Limestones, comprising the Monsal Dale and Eyam limestones, is chemically more variable and less pure. It also contains several volcanic units. However, both limestones are quarried at several sites for crushed rock aggregate. In Staffordshire, the Kevin and Milldale limestones, which are equivalent to the Bee Low and Woo Dale limestones of Derbyshire, are worked for aggregate and cement making.

The high and very high purity limestones in the Yorkshire Dales are suitable for industrial use, although most production is for aggregate. The Cove Limestone and equivalent reef limestones are chemically very pure and of consistent quality, and are worked at several quarries near Settle and Grassington. The Great Scar Limestone near Leyburn is worked for aggregate. In the Craven lowlands, the dark grey, shaly Chatburn Limestone is worked on a large scale near Clitheroe for cement manufacture and aggregate.

The Permian ‘Magnesian Limestones’ are the main source of dolomite {CaMg(CO3)2} in Britain. They consist of dolomites, dolomitic limestones and limestones, and vary markedly in chemical, physical and mechanical properties, and thus in suitability for particular applications. This material is generally inferior to Carboniferous limestone as a source of aggregate, because of its variable character, generally lower strength and higher porosity. However, it is extensively quarried for a range of construction uses, mostly for fill and sub-base roadstone, and less commonly for concreting aggregate and coated roadstone. Some is sold for block-making, and some as a building stone; fines are commonly sold for agricultural use to reduce soil acidity, and to contribute calcium and magnesium. Most quarries are located on the Cadeby Formation (Lower Magnesian Limestone), but the Brotherton Formation (Upper Magnesian Limestone) is also worked in North Yorkshire. Permian dolomites are not generally of high chemical purity, but impurities such as silica, iron and alumina are locally sufficiently low for them to be of industrial use. At Whitwell quarry in Derbyshire, dolomite with low silica and iron contents is used, after calcination, as a refractory raw material and as a flux in steelmaking. Dolomite is also quarried near Doncaster as a source of magnesia in the manufacture of flat glass.

Portland cement clinker is manufactured by heating to partial fusion (1400 to 1500. C) an intimately homogenised and controlled mixture of calcareous and clayey raw material. The clinker is then finely ground with 5 per cent of gypsum/anhydrite to form cement. Cement production was originally based on chalk, but other limestone is increasingly used because of its lower energy consumption during manufacture, as a result of its lower porosity and thus lower moisture content. In this region there are large plants at Hope, near Castleton in Derbyshire (the largest in Britain), Cauldon near Waterhouses in Staffordshire and Clitheroe in Lancashire, and a small plant within Tunstead quarry near Buxton in Derbyshire. The total combined cement capacity is 4. 5 million tonnes a year.

Cement raw materials

Cement production normally takes place at sites where the two main raw materials are available and all the plants in the Pennines are based on Carboniferous limestones as the primary raw material. A high-purity limestone is not essential for cement manufacture, as common impurities such as silica, alumina and iron oxides are essential components of the cement mix and normally supplied by the clay admix. However, other contaminants, such as magnesia, are deleterious and dolomitised limestones are avoided. At Hope, the Monsal Dale Limestones (Table 6) are quarried on a large scale and the adjacent Edale Shale is used as the source of clay. Similarly at Cauldon in Staffordshire, the Milldale Limestones and mudstones from the Edale Shale and Mixon Limestone–Shales Formation are utilised. However, at Clitheroe in Lancashire, the Chatburn Limestone is of generally low purity and contains sufficient interbedded shale to be worked as a natural cement mix. At the large Tunstead quarry (see above), clay impurities washed from the limestone are used with limestone for cement production as an ancillary operation to the production of limestone for other purposes.

Sand and gravel

Although conveniently grouped together, sand and gravel are separate commodities. The term ‘gravel’ is currently used in industry for material which is coarser than 5 mm and the term ‘sand’ for material finer than 5 mm and coarser than 75 . m. The principal uses of sand are as fine aggregate in concrete, mortar and asphalt. The main use of gravel is as coarse aggregate in concrete;substantial quantities of sand and gravel are used for constructional fill. The sand and gravel resources of the region may be divided into two broad categories: superficial Quaternary deposits, which are the most important economically, and weakly cemented sandstones of the Triassic Sherwood Sandstone Group. Locally, some Carboniferous sandstones are crushed to produce concreting and building sand.

The principal resources of sand and gravel are river terrace gravels, and glaciofluvial outwash deposits resulting from the melting of the late Devensian ice sheet. River gravels occur beneath alluvium along the floors of the major river valleys and in river terraces on the valley sides. They tend to be of good quality, with a uniform thickness, although their composition varies regionally, reflecting the lithologies of the rocks from which they were derived. As the water table is close to the surface in river valleys, the gravels are usually extracted by wet working and the worked-out sites left as lakes unless suitable fill is available. Workings are mainly confined to the east of the Pennines, in the valleys of the Swale, Ure, Wharfe, Calder and Trent. The sands and gravels that are extensively worked in the Doncaster area (the ‘Older River Gravels’) are not confined to river valleys, but occur as large spreads, up to 6 m thick. In Lancashire, deposits in the Wyre and Keer valleys have been worked, but are now almost exhausted. Gravels in the Ribble valley are worked near Preston.

Glaciofluvial deposits are generally more variable in composition and particle size than the river gravels and less predictable in geographical extent. Sand and gravel beneath or within till (boulder clay) is difficult to locate. These deposits are important locally to the east of the Pennines, but in Lancashire and Cheshire they are mostly fine-grained sands derived from local Carboniferous sandstone outcrops. They are generally suitable for mortar and asphalt, and, after washing, as fine aggregate in concrete, but are at the fine end of the specified range. Important deposits of construction sand occur in the Vale Royal in Cheshire, but elsewhere only scattered deposits are worked. In addition, Holocene beach sands are worked from the foreshore at St Annes and Southport for aggregate use, mainly as constructional fill.

The Sherwood Sandstone Group is an important resource of sand and gravel in the Midlands, but in the Pennine region it is largely devoid of pebbles. It is, however, worked as a source of building sand and asphalting sand at several localities in Nottinghamshire. Farther north, it is extracted from the base of pits originally excavated for sand and gravel in superficial deposits. To the west of the Pennines, it is worked locally, mainly for constructional fill. It is weathered locally to sand immediately below drift cover, providing a potential source material.

Igneous rocks

There are few igneous rock resources in the region. Recent working was confined to Water Swallows Quarry near Buxton (Plate 28), where the 24 m-thick dolerite sill, intruded into Carboniferous Limestone, was quarried until 1993 mainly for roadstone, and, on a smaller scale, for the manufacture of rock wool insulation. The Dinantian lavas and tuffs of the Peak District (known locally as ‘toadstones’) are invariably altered and not suitable for use as aggregates.

Clay and shale

Clay and shale are used mainly in the manufacture of bricks (which use the largest tonnage of raw material), pavers, clay tiles and vitrified clay pipes. They are also used in cement manufacture (see above), as a source of constructional fill and for lining and sealing landfill sites. The suitability of a clay for the manufacture of bricks depends principally on its behaviour during shaping, drying and, most importantly, firing. This dictates the properties of the fired brick, including its aesthetic qualities for architectural use. Small brickworks, mainly producing ‘common’ bricks from clay dug in adjacent pits, were formerly widespread in many industrial areas of Britain. However, major rationalisation of the brick industry in the last twenty to thirty years has resulted in less plants operated by a few large companies. These plants tend to use clays from a variety of sources, and some clays, particularly fireclays, are transported long distances for brick manufacture. With the demise of the ‘common’ brick, the main products are now high-quality facing bricks, engineering bricks and related products such as clay pavers. Modern brickmaking technology is highly dependent on raw materials with predictable and consistent firing characteristics. Blending of different clays to achieve improved durability and a range of fired colours and aesthetic qualities is increasingly common.

The mudstones of the Namurian and Westphalian provide the most important resources. They are worked at a number of locations on both sides of the Pennines, their suitability depending partly on carbon and sulphur contents, high amounts of which may cause problems during firing, and in the case of sulphur, unacceptable emissions. In general, carbon and sulphur levels should be less than 1. 5 and 0. 2 per cent respectively, although absolute levels depend on the firing characteristics of the clay and on the kiln. Mudstones are worked in conjunction with sandstones (for aggregate) at several quarries, particularly in Lancashire. A large concentration of workings in the Penistone area of South Yorkshire extracts mudstones to produce the blended feed for the manufacture of vitrified clay pipes.

The red silty mudstones of the Mercia Mudstone Group are worked for brick manufacture in Nottinghamshire and on the Wirral peninsula. Glacial till is worked near Warrington and Stockport.

Fireclay

The extraction of fireclay was an important industry in Britain in the 19th and first half of the 20th centuries, with production from most coalfields, including those in the east Pennines and Lancashire. Historically, fireclays were valued as a refractory raw material because of their relatively high alumina contents, and were widely used in the production of firebricks and other refractory goods. Subsequently they were also used in the manufacture of salt-glazed pipes and sanitaryware. Demand for fireclay for these applications has, however, declined markedly since the late 1950s, mostly due to changing technology in the iron and steel industry, for which higher quality refractories are now required. Salt-glazed pipes have been replaced by vitrified clay pipes (see above). Some fireclays have relatively low iron contents and are now valued for the production of buff-coloured bricks.

Fireclays typically occur as the palaeosols (seatearths) beneath coal seams (p. 68) and resources are thus mainly confined to coal-bearing strata. They consist principally of disordered kaolinite, hydrous mica and quartz; the relative proportions of each have a marked effect on the ceramic properties of the clay. Carbon and iron are impurities. Until the advent of opencast coal mining during the Second World War, fireclay was produced at many underground mines in Yorkshire and Lancashire. Since that time, fireclay has been increasingly obtained as a by-product of opencast coal mining. However, production from opencast coal sites is not common because of the highly variable quality of the fireclays and because of operational and planning reasons. The only fireclay mine currently operating in Britain is in the Shibden valley, near Halifax, where the siliceous Halifax Hard Bed fireclay is extracted. This unusual fireclay has been used for nearly 200 years in the manufacture of glasshouse pots — a refractory pot used for melting speciality glasses such as lead crystal glass. Fireclay from the mine is blended with similar clay quarried from the same bed near Oxenhope, Keighley.

Sandstone

The Lower Palaeozoic greywacke sandstones and siltstones in the small inliers in the upper Ribble valley near Settle and at Ingleton were affected by low-grade metamorphism and, as a result, have a high resistance to polishing and abrasion. They are used as hard-wearing and skid-resistant aggregates which are particularly valued for road surfacing. Ordovician greywackes are worked at a quarry at Ingleton, and Silurian greywackes at the Dryrigg and Arcow quarries near Settle. Total production averages about 1 million tonnes a year.

The sandstones of the Millstone Grit and Coal Measures are extensively quarried, particularly in West Yorkshire and Lancashire, for crushed rock aggregate, in addition to building stone (pp. 152–155). In general, crushed Carboniferous sandstones are too weak and porous (and thus susceptible to frost damage) to be used for concrete aggregate or roadstone. They are, however, much worked in some areas for crushed rock for less demanding aggregate applications, principally for constructional fill and locally for use as a drainage medium. They are also crushed for building and concreting sand, the latter being used mainly in the production of concrete products, including reconstituted stone and flags.

The Sherwood Sandstone Group has been used locally as a source of constructional fill and may find use as a building sand (see above).

Silica sand

Silica sand (or industrial sand) is marketed for purposes other than direct application in the construction industry. It is an essential raw material for glassmaking and foundry casting, as well as for a wide range of other products such as ceramics, chemicals and water filtration. The physical and/or chemical properties of silica sands effectively govern their usefulness and value, different applications demanding different combinations of properties. These include a high silica content, an absence of deleterious impurities, specific grain-size distribution and grain shape. For most applications, silica sands have to conform to very closely defined specifications.

These sands are produced from unconsolidated material and crushed sandstones, with subsequent processing of varying complexity depending on their end use. Production is concentrated on a few, high-quality deposits. The Quaternary sands of the northern part of the Cheshire Basin are of particular importance and are extensively quarried near Chelford and Congleton, the latter lying just outside the region. The sands are well sorted and well rounded, contain little silt or clay impurities, and have relatively high silica contents. They are the most important source of foundry sand in Britain and are used as mould and core-making materials in the production of iron, steel and nonferrous castings. At Chelford, some of the sand has a low iron content (about 0. 1 per cent Fe2O3) and is the sole source of silica sand for the manufacture of flat glass by the float glass process at St Helens.

The Rough Rock at Oakamoor in Staffordshire is an important resource. Heavy iron-staining on the surface of the sand grains is removed by leaching with hot sulphuric acid to yield a silica sand containing 0. 035 per cent Fe2O3 which is suitable for the manufacture of colourless glass containers and whiteware ceramics. A similar operation also using sandstones from the Millstone Grit at Blubberhouses near Harrogate produced glass sand for colourless container glass until 1991.

The Shirdley Hill Sand of Lancashire (p. 114) was important in the past as a source of glass sand, particularly after the development of St Helens as a major glassmaking centre. The sand was extensively worked in the Ormskirk–Rainford area for the production of container glass and, more importantly, flat glass. However, the thinness of the deposit and consequent high working costs led to its gradual replacement by the Chelford Sands. Extraction for flat glass manufacture ceased in the mid-1970s, although Shirdley Hill Sand is worked near Rufford for horticultural use.

Silica sands in the Neogene Brassington Formation (p. 92) of the Peak District contain kaolinitic clay and, because of their refractory properties, were formerly worked for use in a range of refractory products.

Salt

The Cheshire Basin, the northern part of which falls within the region, contains very large resources of rock salt and currently accounts for over 90 per cent of salt (NaCl) production in Britain. The Mercia Mudstone Group contains two rock salt-bearing units, the Northwich Halite Formation with a maximum thickness of 283 m, and the younger Wilkesley Halite Formation with a maximum thickness of 404 m (pp. 84–85). These consist of beds of almost pure halite and others with variable amounts of mudstone and siltstone.

Salt has been produced in Cheshire since Roman times, and Northwich became the pre­eminent centre because of the proximity of the navigable River Weaver. Underground mining began in the late 17th century. Some mines became flooded and where the brine was pumped, dissolution of the supporting pillars caused spectacular subsidence. Initial production was by natural or ‘wild’ brine pumping from shafts or boreholes sunk to the wet rockhead where salt dissolution occurs at the groundwater–salt interface. As brine is pumped to the surface, fresh groundwater flows in to dissolve more salt, eventually leading to subsidence over wide areas. This process has now been almost entirely replaced by controlled brine pumping, the largest operation being at the Holford brinefield near Northwich, which lies on the southern margin of the region. This process involves the injection of water through boreholes into the halite formation, followed by the extraction of the resultant brine, leaving cavities of predetermined size and shape consistent with ground stability. The cavities are about 100m in diameter and up to 170m in height. The ‘salt-in-brine’ is used as a feedstock for the chemical industry in the manufacture of soda ash (sodium carbonate) by the ammonia-soda (Solvay) process and of chlorine and caustic soda (sodium hydroxide) by electrolysis of the brine. The total output of salt-in-brine in the Cheshire Basin is about 3 million tonnes per annum (Mt/a). The brine is also used as the feedstock for the production of white salt by the vacuum process. Total production of white or brine salt is 1. 3 to 1. 4 Mt/a.

The only rock salt mine in the Cheshire Basin is the Meadowbank mine near Winsford. This was opened in 1844, then closed from 1892 to 1928. Since 1928, the mine has expanded to become the major source of rock salt in Britain. The bulk of its output is used for de-icing roads, but a small amount is used as a fertiliser for sugar beet. Annual output depends on the severity of the winter, but averages about 1. 1 to 1. 2 Mt/a. Mining is currently in the Bottom Bed of the Northwich Halite Formation, in galleries 7.5m high. The rock salt has a purity of about 95 per cent NaCl.

The Preesall saltfield in the Blackpool district was discovered in 1872 in boreholes drilled for hematite. A shaft sunk in 1889 penetrated over 100 m of salt-bearing strata and brine pumping began in 1889 and continued until 1993. In addition, rock salt was mined between 1894 and the early 1930s. The brine was initially used in the manufacture of soda ash by the ammonia-soda process until the plant became obsolete. This was replaced by a Castner-Keller plant at Hillhouse for the production of chlorine and caustic soda by the electrolysis of brine, and production continued until 1993. Production of brine was always modest compared with output from the Cheshire Basin. However, the Preesall saltfield is important in the role that it played in the development of the controlled brine pumping method which eventually led to brine extraction without associated subsidence.

Gypsum

Gypsum (CaSO4. 2H2O) and anhydrite (CaSO4) are the naturally occurring forms of calcium sulphate, which occur in beds usually up to a few metres thick. Anhydrite occurs at depth, becoming hydrated near the surface and passing into gypsum. Anhydrite is thus much more extensive than gypsum, but, in its pure form, is not of economic importance because of its limited commercial application. Gypsum is used in the manufacture of plaster and plasterboard, and as a retarder in Portland cement. A mixture of gypsum and anhydrite is also used as a cement retarder.

Gypsum and anhydrite occur in strata of late Permian age, which crop out in narrow, roughly north-south belts on the east of the Pennines (pp. 81–82). Several gypsum–anhydrite beds occur, but the most persistent is the Upper (or Sherburn) Anhydrite in the Roxby Formation. This bed occurs east of Leeds and was formerly mined at Sherburn-in-Elmet for the manufacture of plasterboard. The mine was sunk in 1966, but flooded in 1988 and was abandoned. There is no current production in the region.

Fluorspar, baryte and calcite

Fluorspar (CaF2) is the only significant source of the element fluorine and is used mainly in the production of hydrofluoric acid, the feedstock for the manufacture of a wide range of fluorine-bearing chemicals. Small amounts of fluorspar are also used as a flux in steel manufacture and for other industrial applications. Production in Britain is confined to the former lead mining areas of the southern and northern Pennine orefields. Production from the latter, which falls mainly outside the district, ceased in 1999. The Southern Pennine Orefield in the Peak District has, however, traditionally been the principal source of fluorspar in Britain and currently (1999) supplies over 40 000 tonnes. About 5 million tonnes of fluorspar have been produced.

Baryte (BaSO4) has a high specific gravity (4. 5 when pure) and one major use is to increase the density of drilling fluids in oil and gas exploration wells to prevent gas blowouts. It is also used as a filler in paint and rubber and as a heavy aggregate for radiation shielding. It occurs with fluorspar, with which it is recovered as an important by-product. Small amounts of calcite are produced from the Long Rake vein in the Peak District, mainly for use as a decorative aggregate.

The fluorspar–baryte–calcite–lead mineralisation in the Southern Pennine Orefield occurs in steeply dipping east–west and east-north-east-trending fissure veins (locally known as ‘rakes’) in limestones. These are up to several kilometres long and 10 m wide. The main mineralisation is confined to the eastern part of the orefield and to the highest (Monsal Dale) limestones beneath the overlying cover of Longstone Mudstone and Edale Shale, which acted as an impermeable caprock to the mineralising fluids. However, following years of working, many of the major veins are depleted as sources of surface-mined fluorspar. Recent exploration has been largely directed towards finding deposits concealed in cavities and replacement deposits in receptive beds of the Monsal Dale Limestones.

Production is from open pits and underground mines, the former contributing about two-thirds of the total output (p. 148). Typical ore grades fall in the range 20 to 50 per cent CaF2, 10 to 20 per cent BaSO4 and up to 2 per cent galena (PbS), the higher grades being derived from underground operations because of the higher costs of production. Almost all the ore is treated at Cavendish Mill, near Stoney Middleton for the production of acid-grade fluorspar (>97 per cent CaF2) by froth flotation. Baryte and lead (galena) flotation concentrates are also recovered as by-products, as well as limestone for construction use. Cavendish Mill is the second largest source of baryte in Britain, and the small amount of lead produced in Britain is wholly a by-product of fluorspar mining in the Southern and Northern Pennine orefields. There is also a small production of metallurgical grade fluorspar near Ashover. Outside the Southern Pennine Orefield very small amounts of fluorspar and baryte have been produced from the former lead mining area of Greenhow Hill, near Pateley Bridge.

Peat

Peat is dug in England almost entirely for horticultural purposes, either as a growing medium (by far its most important application), or as a soil improver. It is mainly extracted from the raised lowland bogs (p. 117). These are important conservation sites and future peat extraction will be limited to areas already damaged by recent human activity. There are economically important deposits of lowland peat on both sides of the Pennines. Large extraction operations are centred on Thorne Moors and Hatfield Moors in South Yorkshire, with smaller pits in Merseyside, the Wigan and Salford area and in Cheshire. Typically, between 1 and 2 m are extracted, depending on the thickness of the peat.

Metalliferous minerals

Metalliferous minerals have been worked in the region for centuries. Pigs (ingots) of lead metal with Roman inscriptions have been found in several areas, some of them dated to the 1st century AD. Little is known about the period up to the 17th century when authentic records begin, although lead mining is mentioned in the Domesday Survey of 1086. The mining laws of the Southern Pennine Orefield were defined in 1288 with the establishment of the Barmote Court, which still meets to solve disputes. The most important mining area has been the Southern Pennine Orefield in the Peak District, where lead and latterly fluorspar and baryte (see Industrial minerals) have been worked. Total estimated production to date is about 2 million tonnes of lead, 4. 3 million tonnes of fluorspar, 0. 88 million tonnes of baryte, 0. 75 million tonnes of calcite and 60000 tonnes of zinc. The Askrigg area of the Northern Pennine Orefield was also a major producer of lead with an estimated total production of 0. 8 million tonnes. There was also minor lead, fluorspar and calcite production from the Clitheroe district of Lancashire. Copper was produced from Ecton mine, on the western side of the Peak District, from the Alderley Edge area of Cheshire and from Middleton Tyas, near Scotch Corner in North Yorkshire. Iron ore was formerly produced from ‘claystone’ ironstone seams in the Coal Measures and formed the basis of the iron and steel industries in the region. There is potential for the discovery of further mineral deposits in both the known orefields of the region, and also in the Craven Basin. In the latter, the geology is similar to that of the Midland Plain of Ireland where several major lead–zinc ore deposits have been discovered and exploited since 1961. The mineralisation is of low temperature, hydrothermal origin and is thought to be a fluoritic sub-type of the Mississippi Valley Type deposit. Mississippi Valley Type mineralisation typically consists of lead–zinc ore deposits in limestones and dolomites. The mineralising fluids were generated during the compaction of the late Dinantian and early Namurian shale succession and migrated to the limestone host rocks during Variscan compression.

Lead and zinc

Southern Pennine Orefield

Lead sulphide mineralisation (galena, PbS) has been worked in the area from large numbers of veins. There are several hundred named veins and many small, unnamed ones. They are up to several kilometres long, less than 10 m wide, of limited vertical extent and steeply dipping, and consist of galena, fluorite, calcite and baryte. The major veins are commonly known as ‘rakes’, the minor ones as ‘scrins’. Fluorspar and baryte have also been worked in more recent years and are now the main economic minerals recovered (p. 147); no veins are now worked solely for lead. Semi-concordant ‘flats’ have also been worked as at Masson Hill near Bonsall. A few short, tubular, subhorizontal pipe oreshoots also occur, as at Hubberdale pipe. The mineralisation is largely confined to the eastern half of the exposed Dinantian limestone outcrop and is mainly hosted within the Monsal Dale Limestones, where the overlying Namurian shales formed an impermeable caprock to the mineralising solutions. The extent of the orefield and the major ore deposits are shown on (Figure 44). The most important deposit was at the Millclose Mine near Darley Dale, where over 400 000 tonnes of lead concentrates and 90 000 tonnes of zinc concentrates were recovered from a remarkable orebody where natural concentration of galena in a cave system produced very high grades of mineralisation. Elsewhere in the orefield, the grades were about 5 per cent Pb, the exact figure dependent on the width of vein worked. Modern exploration has continued to develop the orefield, with the emphasis on fluorspar. In the early 1950s, there was an attempt to further develop the Riber Mine on the Great Rake for lead and zinc. Initial boreholes showed promising widths and grades of lead mineralisation. However, subsequent underground development showed that earlier miners had removed much of the mineral and that the boreholes had fortuitously passed through unworked pillars, giving a false impression of the possible resources left in the vein. The mine was closed in 1958. Calcite production continues from the Long Rake vein in the centre of the orefield.

Northern Pennine Orefield

Only the southern part of the Northern Pennine Orefield, centred on the Askrigg Block, lies within the region. There has been little activity in this area for many years. The most intensively worked areas were around Grassington and Greenhow (where worked veins extend from the Dinantian limestones up into the overlying Namurian Grassington Grit) and in the area around Muker and Keld, north of Swaledale. In the latter, mines such as Lownathwaite, Old Gang and Arkengarthdale worked deposits in a linked system of east–west faults for over 30km. There were attempts to explore along the Craven Faults for ‘Irish-style’ stratabound lead–zinc mineralisation in the 1970s, and also to reopen some of the old lead veins in the Grassington area for fluorspar. This orefield differs from the Southern Pennine one, being underlain by Lower Palaeozoic sedimentary rocks that are intruded by the Caledonian Wensleydale granite (p. 15). This is similar to the setting of the Alston area farther north, but mineralisation is less well developed. Some zonation of the mineralisation has been noted, with centres of dominant fluorite around Greenhow and Grassington and in Wensleydale and Swaledale.

Craven Basin

Several small lead veins have been worked in the area. The largest deposit was in the Cononley mine south of Skipton. Baryte was produced from the Raygill mine, west of Cononley. The BGS Mineral Reconnaissance Programme carried out exploration in the Craven Basin in the mid to late 1970s, following the discovery of a major stratabound lead–zinc deposit at Navan in Ireland in rocks of similar (Dinantian) age to those of the Craven Basin. The varied structural setting, with early Dinantian (Tournaisian and Chadian) carbonates (including Waulsortian-type knoll reefs) and shales in a shelf to basinal sequence, is similar to the environment of the Navan and other Irish deposits. A number of short boreholes were drilled in the Cow Ark area, near Clitheroe, and minor stratabound lead–zinc mineralisation found. BP Minerals carried out additional exploration throughout the basin and two main target areas were identified. One was at Marl Hill Moor close to the BGS drilling area, the other was around the old Brennand lead mine west of Slaidburn. Additional stratabound mineralisation was found, with values of 2 to 3 per cent Pb and Zn over a few metres, but the results did not justify further work.

The mineralisation is mainly confined to the thicker late Dinantian limestones, notably the Clitheroe and Pendleside limestone formations, which have impermeable shale caprocks.

Copper

Alderley Edge and Mottram St Andrews

The Triassic Sherwood Sandstone Group in the Cheshire Basin hosts a weak, but widespread, baryte mineralisation and a locally concentrated, stratabound, polymetallic assemblage dominated by copper, but including smaller amounts of lead, cobalt, nickel, manganese, arsenic, vanadium and other elements. The largest known occurrence of the base metals was at Alderley Edge, where remnants of the orebodies remain accessible in more than 12 km of disused mine workings.

Alderley Edge is a 3 km-wide, north-south-trending horst with a core of Sherwood Sandstone Group rocks. This structure formed a trap for intrastratal fluids migrating within the sandstone succession below a former cover of the impermeable Mercia Mudstone Group. Baryte occurs in both the Wilmslow Sandstone Formation and the overlying Helsby Sandstone Formation; the base metal ores are mainly in the latter. Lead ores occur mainly in and adjacent to faults within the horst. Copper and other minerals were in more extensive orebodies, mainly in fluvial and aeolian sandstone members of the Helsby Sandstone Formation, but also in the topmost Wilmslow Sandstone Formation. Some of the orebodies occur in footwall situations, down-dip from faults which ponded mineralising fluids. The largest and most extensive orebodies occur in aeolian sandstones; those in fluvial sandstones, with mudstone interbeds, are smaller and less regular in form. The ores are mostly secondary species, principally carbonates and arsenates, and form disseminations in the sandstones; galena is the principal sulphide ore.

Mines were noted at Alderley Edge in 1598, and documented mining occurred intermittently between then and 1919; the date of the earlier working is uncertain. Copper ore was the main product; a small amount of lead ore was also worked, and cobalt ore was mined between its discovery in the district, in 1805 or 1806, and the end of the Napoleonic wars. Documented output of copper ore is about 250 000 tonnes, containing about 1. 5 per cent copper. Most of this output was produced between 1857 and 1877, when an acid leaching process was used to dissolve disseminated carbonates and other minerals from crushed sandstone. Scrap iron was used to precipitate copper from the resulting solution. Cobalt and nickel-rich concentrates were produced from the same process for a short time. Earlier, undocumented production was probably less than that documented; thus, the total copper ore production may have been no more than 500 000 tonnes. The output of other ores was relatively insignificant.

A copper ore deposit worked nearby at Mottram St Andrew is similar to, but much smaller and less well known than those at Alderley Edge. Roscoe recognised the presence of vanadium in solutions from an acid leaching plant at this mine in 1865 and used residues from the site in studies which resulted in the determination of the valency of that element. He named the mineral mottramite, a vanadate of lead, zinc and copper, after this locality.

Ecton

Several important copper deposits occur around Ecton Hill, on the south-western side of the Derbyshire Dome, about 10 km north-west of Ashbourne. Veins and semi-vertical pipes in Dinantian limestone contain chalcopyrite and calcite, with minor galena, baryte and sphalerite. At least 60 000 tonnes of copper ore were produced, at a reported grade of around 15 per cent, between 1760 and 1816. Sporadic working continued until the end of the 19th century. The origin of the deposits is unknown, but fluids from the Permo-Triassic rocks of the Cheshire basin have been suggested as a source.

Middleton Tyas

A number of small copper-bearing veins and disseminations in Dinantian limestones were worked near Middleton Tyas in North Yorkshire over an area of about 0. 5km2. Total production was around 1500 tonnes of copper from 3 500 tonnes of ore. The original copper mineralisation (chalcopyrite) was low grade. However, supergene enrichment produced much higher grade ores containing bornite, covelline and digenite, with malachite and azurite. The BGS Mineral Reconnaissance Programme carried out some mineral exploration in the area, but did not locate additional copper resources.

Iron

Considerable amounts of iron were produced in the 18th and 19th centuries from sideritic ironstone nodules and thin beds in the Westphalian Coal Measures, and, to a lesser extent, in Namurian shales. The iron and steel centres of Sheffield, Staveley, Clay Cross and Stanton all developed from the exploitation of local iron ores (pp. 58–59). The iron content varied from 20 to 35per cent Fe. The seams were sometimes worked alone near the surface, but mainly in conjunction with coal mining. Production records are very incomplete, but Yorkshire, Derbyshire and Nottinghamshire produced between 100 000 and 200 000 tonnes per year in the 1880s, with a maximum of 617 000 tonnes in 1868. The main producing seam was the Low Moor or Black Bed Ironstone in the Leeds–Bradford area, where the 1 to 2 m-thick ironstone lies directly on the Black Bed Coal, enabling them to be mined together. Small amounts were also produced from the south Lancashire coalfield. The industry could not compete with increasing competition from richer, more easily worked ores and declined rapidly in the early part of the 20th century. There is no current production.

Future prospects

The potential for development of the metalliferous minerals in the region is highest in the Craven and Cheshire basins. In the former, recent exploration has found uneconomic, but significant, lead–zinc mineralisation in a style which is mined in large orebodies in rocks of similar age in Ireland at Navan, Lisheen and Galmoy. The exact geological and structural setting is not identical to the Irish deposits and it may be that a vital component of the mineralisation process was missing. A recent study of the Cheshire Basin by BGS concluded that there is potential for the discovery of other small-tonnage, high-grade copper deposits in sandstones beneath the Mercia Mudstone Group. Other areas with potential for mineralisation include the margins of the Gainsborough and Stainmore troughs for stratabound lead–zinc deposits, although in both cases, the likely favourable horizons are at considerable depths.

Building stones, millstones and grindstones

The varied rocks of the region have been exploited for centuries to provide a wide range of stones for building. A cursory examination of the vernacular buildings in the villages and towns shows how important stone quarrying has been in the local economy. The exploitation of stone for building extends back at least to Roman times in parts of the Pennines. The Romans introduced quarrying to Britain and most of their important buildings used local stone, as for example, the dolomitic limestone of the Cadeby Formation for the Roman villas at Well and Mansfield Woodhouse. Tadcaster (Calcaria) was renowned in Roman times for its quarries which supplied stone to York and elsewhere. At Handbridge, on the Dee, Roman quarries worked the red Triassic Sherwood Sandstone for building the legionary fortress in Chester. There is extensive evidence of quarrying in parts of the region during the medieval period. By the 17th century, the expansion of the woollen trade in the high moorland areas brought with it a boom in the local quarrying industry. Many of the characteristic and picturesque weavers’ cottages of the Pennines which date from this period are built of Carboniferous sandstone.

In some counties, detailed agricultural and mineral surveys were undertaken early in the 19th century. For example, in 1815, Farey, in his mineral survey of Derbyshire (the boundary of which was slightly enlarged compared to the present day), documented 175 quarries producing various types of building stone, primarily for local use, 53 quarries producing paving flags, and 48 producing stone roofing slates. The first national survey of building stone production was carried out in 1856 by Hunt. In his detailed list, published in 1858, there were 76 building stone quarries operating in Lancashire, 34 in Cheshire, 113 in Yorkshire, 36 in Derbyshire and 5 in Nottinghamshire. Although the region is still nationally important for its building stone production, sending a wide variety of stone to almost all parts of the country, only about 80 building stone quarries (8 in Lancashire, 5 in Cheshire, 40 in Yorkshire, 24 in Derbyshire and 3 in Nottinghamshire) are currently operating.

The small inliers of Ordovician slates, coarse grits and conglomerates at Ingleton and Horton in Ribblesdale were once extensively exploited for local building stone, flagstone and roofing slates. The Silurian rocks were worked for flagstones at Ingleton and Horton-in-Ribblesdale, the best known being those of the Horton Formation, which were quarried around Helwith Bridge from the 17th to the 19th centuries. They are seen in older buildings throughout the Ribblesdale, Littondale and Craven areas. The quarries were worked for flagstones until the early 1900s, and mainly for aggregate thereafter. The massive sandstones of the Austwick Formation were also used locally for building.

The rocks of the Carboniferous are the most important in the region for the production of building stone. Almost every limestone or sandstone in the succession has been exploited at some time, at least locally, for building material, as is evident from the vernacular houses of the area. Examples are the limestone villages of Arncliffe and Malham in Yorkshire and Carsington and Bonsall in Derbyshire and the sandstone villages of Ribchester and Chipping in Lancashire, Ripley and Haworth in Yorkshire and Hathersage and Cromford in Derbyshire.

The Carboniferous Limestone is generally too hard to have been of use as a freestone outside the region. However, it is widely used in the Yorkshire Dales and White Peak area of Derbyshire. It was used to particular effect in some of the impressive railway viaducts in the area, the one at Dent Head being built with the nearby dark grey Simonstone Limestone. Probably the best known use of the limestones, however, was for the construction of the extensive network of drystone rubble walls that criss-cross the countryside.

Several quarries in Deepdale, North Yorkshire produced the hard, black, fossiliferous limestones known as Dent Marble from the Hardraw Scar, Simonstone and Underset limestones in the Yoredale facies of the Wensleydale Group. Dent Marble was used both for decorative purposes and for building the Arten Gill viaduct. Fossiliferous limestones from the upper Dinantian–basal Namurian succession were also worked as ‘marbles’ at Barton near Richmond. Less well known perhaps than the Dent Marble was the Nidderdale Marble, worked in Blayshaw Quarry near Lofthouse and the Egglestone Marble. Crinoidal limestones are known to have been quarried and polished for decorative stone as far back as the 13th century from their use in Fountains Abbey. They were widely exploited in the 19th century because of the popularity of decorative polished stones with Victorian architects.

The Carboniferous limestones of Derbyshire were also famous as decorative stones, commonly termed ‘marbles’ by the trade because of their ability to take a high polish, their varied colours and attractive structure. They included the Ashford Black Marble, Bird’s Eye Marble, Rosewood Marble, Duke’s Red and Muscle Marble. None of these stones are produced today, but they can be seen as decorative inlays in many of the great houses of Derbyshire such as Chatsworth, Hardwick and Bolsover Castle. Today, polished limestones are produced from the Bee Low Limestones at Hopton Wood and Griffeton Wood quarries. Hopton Wood Stone has been used in many major buildings, including the Bank of England and the city halls of Manchester and Sheffield. On a sombre note, the creamy grey, crinoidal, Hopton Wood Stone provided the headstones for the graves of tens of thousands of British and Commonwealth troops who fell in the 1st and 2nd World Wars.

Flagstones were quarried in Deepdale High Pike Quarries, the Scotcher Gill Quarries near Dent, and in the Thwaite to Low Row area of Swaledale, all from flaggy sandstones in the Yoredale facies. Richmond Castle, bridges over the Swale at Richmond and Catterick and many buildings in Darlington, including the town hall, were constructed of Yoredale facies sandstones worked at Gatherley Moor just to the north of the town. Flaggy limestones from Fremington were used for paving and roofing in local villages such as Reeth. Sandstones of the Yoredale facies were formerly extensively quarried for flagstones around Hawes, West Witton, Carlton and Leyburn in Wensleydale, supplying roofing and paving for cottages throughout the Dales.

The Millstone Grit Group provides some of the best and most durable building stones in the country, and is still quarried on a large scale. Quarrying of the sandstones began many centuries ago for local building. During the 19th century, and particularly with the coming of the railways, quarrying activity reached a peak as new towns and cities expanded throughout Victorian England. There are few cities or towns in the Midlands and north of England without at least some of their major civic buildings built of these sandstones.

In Lancashire most of the major Namurian sandstones were quarried for local housing (the Kinderscout Grit in Hadfield and Mossley, for example), factories, mills and engineering projects such as railway bridges, viaducts and reservoirs. The Pendle Grit, for example, was used for Ogden Reservoir, the Warley Wise Grit for the Sabden Reservoir, and the Kinderscout Grit for the Walshaw Dean and Longdendale reservoirs. The Fletcher Bank Grit was used for the construction and restoration of Manchester Cathedral. Extensive quarrying industries developed in several areas, notably along the Tame valley and in Longdendale. The sandstones of the Pendle Grit Formation were extensively quarried for building stone near Longridge in the middle to late 19th century, the town hall at Preston being built of Longridge Stone. The Haslingden Flags were worked in several areas, as around Chorley and, most extensively, along the Rossendale valley from Whitworth through Haslingden to Pickup Bank.

In Yorkshire also, most Namurian sandstones have been worked for centuries, under a plethora of local names. The 12th century abbeys of Kirkstall (Rough Rock from Bramley Fall Quarry) and Bolton are two early examples of their use. The main sandstone beds, the Guiseley, Kinderscout and Pule Hill (Midgley) grits and Rough Rock, were all extensively quarried. For example, the Kinderscout Grit and its correlatives were worked around Todmorden and Hebden Bridge (Heptonstall Church is an example), at Haworth, Addingham Edge, Caley Crags and Pool, near Otley. Stone from the last locality was widely used in the Leeds area (for example in the building of St Ann’s Roman Catholic Cathedral) and was also exported to other parts of the country. The Midgley Grit is still worked today at Clock Face Quarry near Huddersfield.

Quarries in the Chatsworth Grit (known locally as the Rivelin Grit) supplied stone for many of Sheffield’s buildings. The Bradley Flags, Rough Rock Flags (at Ferniehurst and Baildon) and Scotland Flags (at Midgley, near Halifax) have provided building stones and flagstones for paving and roofing since at least the early 18th century. They are still quarried today and used throughout the country.

The Scotgate Ash Quarries near Pateley Bridge worked the Libishaw Sandstone (one of the Kinderscout grits). They were active from at least medieval times, but expanded enormously with the advent of the railways from 1862 until the 1920s, supplying stone for many important city buildings and for export abroad. The most widely exploited of the many Namurian sandstones are probably those of the Rough Rock; it provided much of the building stone (‘Crosland Hill Stone’) for Halifax, Huddersfield and many villages. The original ‘Bramley Fall Stone’ quarried at Horsforth in Leeds from the Rough Rock acquired an enviable reputation for strength and durability and was widely used in bridge and dockyard construction in London and elsewhere.

The exploitation of the Namurian sandstones in the Peak District also has a long history, and all the major sandstones have been quarried for building stone. In the High Peak area, sandstones of the Shale Grit (at Kinder Bank), Kinderscout Grit (at Chinley Moor, Ladybower and Hayfield), the Heyden Rock (at Thornseat), Roaches Grit (at Combs, Ridge Hall and Longhill), Chatsworth Grit (at Birch Vale and Buxworth) and the Rough Rock (at Cracken Edge) have all been extensively worked.

The most important area of sandstone quarrying in Derbyshire lies farther south and east, along the Derwent and Amber valleys and the intervening hillsides, where the Namurian sandstones crop along the valley sides from Hathersage to Belper. Quarries have long worked the Kinderscout Grit (at Stokehall quarries), the Ashover Grit (at Darley Dale, Birchover, Pilough, Duke’s, Whatstandwell and Stanton quarries), and the Chatsworth Grit (at Yarncliff, Beeley Moor, Bole Hill, Lumshill and Millstone Edge quarries). The Rough Rock from the Coxbench quarries was used extensively for buildings in Derby. The Stancliffe Darley Dale Stone is particularly famous for its durability and quality and has been widely used in towns and cities (for example Derby Cathedral, the Guildhall in Nottingham, St George’s Hall in Liverpool and the Royal Exchange in Manchester). The Ashover Grit used in the buildings in the village of Kirk Ireton is stained pink by percolation of groundwaters through the former Triassic red-bed cover. The Shale Grit was used for the Kinder Reservoir, and ‘Stokehall Stone’ from Grindleford for the Howden and Derwent reservoirs and Sheffield town hall.

The sandstones of the Coal Measures of Lancashire have been extensively exploited, those of eastern Cheshire to a lesser extent. Those in the Lower Coal Measures include the Ousel Nest Grit, Woodhead Hill Rock, Milnrow (Crutchman) Sandstone, Dyneley Knoll Flags and Old Lawrence Rock. Fissile sandstones such as those from Appley Bridge, Billinge and Stalybridge quarries provided paving slabs and roofing tiles for many towns such as St Helen’s, Wigan, Bolton, Darwen, Accrington and Burnley. The more massive sandstones were worked for building stone. Sandstones at higher levels in the Coal Measures, such as the Cannel, Trencherbone and Peel Hall rocks, were quarried for building stone at Haigh near Wigan and Farnworth near Bolton.

In Yorkshire, the sandstones of the Coal Measures are still extensively quarried. West Yorkshire has perhaps the largest concentration of sandstone quarries in Britain. The sandstones are sold as ‘York Stone’, this term including both Coal Measures and Millstone Grit sandstones. Perhaps the most famous of the sandstone quarrying industries in Yorkshire were those around Elland near Halifax. The Elland Flags were quarried from the 12th century, but their heyday was during the late 19th century. By 1900, there were at least 40 flagstone quarries and mines operating around Northowram, Southowram, Hipperholme and Brighouse. These produced roofing tiles and paving slabs for Leeds and Bradford, as well as for many other towns and villages throughout the country. After the 1st World War the industry went into rapid decline and is now continued by only a few operators, but these natural riven paving flags are today quarried for internal and external flooring and landscaping. The ‘Bolton Woods Stone’ or Gaisby Rock (a local development of the Elland Flags) has also long been worked for dimension stone. The town halls of Leeds, Bradford and Manchester (‘Spinkwell Stone’) are among many major Victorian buildings to be built of this sandstone. The Thornhill Rock was extensively quarried in the Wakefield–Morley area and is still worked today. The 13th century Pontefract Castle is built of a reddened Coal Measures sandstone, the Newstead (Pontefract) Rock.

In Derbyshire, the sandstones of the Coal Measures have been used locally for building since Roman times, the Roman site at Ockbrooke being an example. There are numerous disused small quarries, but no large-scale working, except of the Crawshaw Sandstone (Woodhead Hill Rock) and Wingfield Flags. In the High Peak area, the Woodhead Hill Rock and Milnrow Sandstone have been worked around Whaley Bridge. Farther south and east, the Crawshaw Sandstone was extensively worked in the Holymoorside, Alton and Woolley areas near Chesterfield. Large quarries formerly exploited the Wingfield Flags for building stone, paving and roofing slates at Freebirch to the west of Chesterfield. The flags were also worked at Wingerworth. The 15th century manor house at South Wingfield was constructed of sandstone from the Wingfield Flags quarried from the Crich Moor area. Some quarries, like the one operating within the estate of Hardwick Hall for example, were opened to supply stone for building the original halls and have since been operated intermittently for conservation work.

The production of millstones took place at many sites throughout the Pennine region, with stone quarried from numerous Namurian sandstones and giving the Millstone Grit its name. In Lancashire, for example, there were quarries at Grinding Stones Rocks (in the Brennand Grit), and Baines Crag in Littledale (Ward’s Stone Sandstone). In Yorkshire, millstones were produced at Leyburn in Wensleydale, at Millstones Quarry, Summerbridge in Nidderdale and on Rombalds Moor above Addingham Moorside. Millstones from Hathersage, Curbar, Froggat, Cluther Rocks, Millstone Edge, Robin Quarry, Crich Chase and Shiningcliff Wood in Derbyshire were shipped from Hull to London and Holland.

Grindstones were also produced from Carboniferous sandstones. Thirty quarries were cutting Millstone Grit for this purpose in Derbyshire in 1815, and by the mid 19th century at least 30 quarries were working sandstones in the Upper Coal Measures at Wickersley near Rotherham, which, although providing stone for building, largely provided grindstones for the booming Sheffield cutlery industry and for export to America. Other grindstone quarries developed at Ackworth near Pontefract and Silverwood near Rotherham, and farther north at Thorner near Leeds and near Dacre in Nidderdale. Grindstones were produced until relatively recently from the Chatsworth Grit at the Oakes Quarry near Tansley, Derbyshire and from the Rough Rock at Morley Moor, near Derby.

Stokehall Quarry, Grindleford gained a considerable reputation for its pulp stones, exported for the paper mills of Norway and Sweden. Pulp stones were also produced at quarries near Pateley Bridge in Nidderdale.

The Cadeby Formation (Lower Magnesian Limestone) has long been exploited for building stone. It was favoured by the Romans when building some of the military and civilian structures in York, Aldborough and elsewhere. It was the main building stone for the great cathedrals of York (from Jackdaw Crag Quarry, Tadcaster and Huddleston Quarry, Sherburn-in-Elmet), Beverley (Smawse Quarry, Bramham Moor) and Southwell (Mansfield Woodhouse Quarry, Mansfield), the abbeys at Selby (Park Nook Quarry), Roche (Roche Abbey Quarry) and Welbeck, and the great Norman castle of Conisborough. Quarries at Steetley and Shireoaks supplied stone for many buildings in the Doncaster area (St George’s Church, for example), and for Thoresby Hall in Nottinghamshire.

There were other important quarries at Bolsover Moor (for Bolsover Castle and local housing) and Anston in South Yorkshire. ‘Magnesian Limestone’ from the latter was used to build the present Houses of Parliament. Numerous quarries in the Mansfield area exploited the siliceous, sandy, dolomitic limestones known as the White and Red Mansfield stones. The red variety was used extensively as a decorative stone in local buildings and farther afield, as in St Pancras Station in London, for example. The white variety was more widely used as a  dimension stone and is common in many older buildings such as Southwell Minster. The White Mansfield quarries remain in operation today. Other former quarries include Linby (used for Newstead Abbey) and Bulwell. ‘Bulwell Golden Stone’ was used extensively in churches and older buildings in the Nottingham area.

Sandstones of the Triassic Sherwood Sandstone Group, although generally less durable than the Carboniferous sandstones, have been exploited for building stone. In Lancashire, the pebbly red Sherwood Sandstone was quarried for building stone at Knowsley. On a much bigger scale, large quarries at Storeton, Rainhill, Woolton and Bootle (now inaccessible) exploited the dominantly red sandstones during the 19th century. These sandstones can be seen in many of the civic buildings in Liverpool, Birkenhead and Runcorn, and in other towns of the north-west. ‘Storeton Stone’, for example, was used for the town hall in Birkenhead and the Custom House, Lime Street Station, St George’s Church and the Philharmonic Hall in Liverpool. ‘Woolton Stone’ was used for Liverpool Anglican Cathedral. Triassic sandstones were also formerly extensively exploited as a local building stone, notably near Lymm, Timperley and Alderley Edge in Cheshire. In the Chester area, quarries, including those in Christleton, Tarvin, Manley and Helsby, supplied stone for the villages and all the principal buildings. In contrast, the Sherwood Sandstone in Yorkshire generally makes a poor quality building sandstone, but was used locally in Ripon and Boroughbridge.

The red mudstone-dominated Mercia Mudstone Group contains thin, hard, pale greenish grey sandstones and siltstones, known locally as skerries. These are generally too hard to be cut and dressed easily, but were extensively used in the past as a building stone. Irregularly coursed, rubble walls and footings of skerry are a common feature in the churches and older buildings of many villages along the Vale of Trent.

Hydrogeology

The lowlands flanking the Pennines are partly underlain by the Sherwood Sandstone Group, a major aquifer from which substantial quantities of water are abstracted for public supply. The Carboniferous strata of the Pennines constitute a complex, multi-layered series of minor aquifers.

Carboniferous Limestone aquifers

The nature of the Carboniferous Limestone aquifer varies considerably across the region. The limestones are water-bearing whereas the interbedded mudstones and volcanic rocks act as aquicludes or aquitards. The limestones generally have very low porosity and permeability, thus making a negligible contribution to groundwater flow. Porosity may be increased locally where extensive dolomitisation has occurred, as, for example, in the southern Peak District, but this has little effect on permeability. The limestones constitute an aquifer only due to the presence of a secondary network of solution-enlarged fractures and joints (conduits) which commonly form complex branching systems, ranging in scale from extensive cave systems to microfractures. Groundwater flow is largely concentrated in the larger conduits and directed towards discrete discharge points at a single spring or group of springs. Groundwater flow directions are often difficult to predict and may change markedly with variations in water table levels.

Borehole yields are variable, being highly productive if large conduits are intersected, but low-yielding or even completely dry if no fissures are encountered. The frequency and size of fissures commonly decrease markedly with depth, giving an effective aquifer thickness of only 50 to 80 m, although the actual thickness of the limestone unit may be considerably greater. The unpredictability of the aquifer, as compared to the Carboniferous sandstones, has resulted in few wells being drilled.

During mining in the southern and eastern parts of the Peak District, drainage tunnels (soughs) were constructed to lower the water table. Sough discharges can be substantial: for example, a group of four soughs (Magpie, Meerbrook, Yatestoop and Hillcarr soughs) discharge in excess of 460 litres per second (l/s). The discharges from both springs and soughs vary significantly in response to variations in rainfall.

Groundwaters are generally potable, though hard, commonly being of calcium bicarbonate type, but the aquifer is highly vulnerable to pollution where not overlain by low permeability strata. Where deeply buried by younger strata, the groundwater is commonly saline, in some cases excessively so.

Warm mineral springs occur at Buxton and Matlock, which developed as spa towns. The Buxton springs appear to have been known to the Romans, but the town’s popularity as a spa dates from the Elizabethan period. The mineral waters were considered to have medicinal properties capable of curing a range of ailments. A warm spring at Bakewell was used for bathing to a lesser extent and another at Stoney Middleton was used for the treatment of rheumatic disorders.

Millstone Grit aquifers

The Millstone Grit constitutes a multilayered aquifer in which the thick, well-cemented grits and sandstones effectively act as separate aquifers; the intervening mudstones act as aquicludes or aquitards. The more important aquifers include the Pendle, Warley Wise, Todmorden, Kinderscout and Chatsworth grits, the Rough Rock and their lateral equivalents. Groundwater storage and movement is predominantly through joints and fractures, with only minor intergranular flow. Borehole yields are dependent on the number and size of fractures encountered in a productive horizon, and many boreholes penetrate more than one aquifer. The groundwater potential of the main water-bearing strata is variable and some are only of local importance. The Pendle Grit provides considerable yields in the Earley area, as does the Guiseley Grit in the vicinity of Guiseley. The Huddersfield White Rock is a very good aquifer beneath and to the south of Huddersfield, but yields decline markedly to the east as the sandstone thins. The Rough Rock is arguably the most consistent aquifer horizon, and is tapped by numerous boreholes across the region. Particularly good yields are obtained in the Bradford area, in contrast to the north of Glossop, where it is unusually dense and lacking in fractures, and yields are commonly very low.

Thus, yields from the Millstone Grit are highly variable, even over short distances, but tend to be greatest in the northern and central parts of the region, reducing southwards due to thinning of a number of the water-bearing sandstones. Borehole yields are often between 5 to 10 l/sec, but under favourable conditions may range up to 50 l/sec. Initial yields are not, however, always sustainable, sometimes declining with time as storage is depleted by pumping.

Groundwater quality is generally potable. Soft water is common in confined horizons, and was formerly important to the textile industry. At considerable depth beneath the Coal Measures, groundwater is commonly saline. Elevated concentrations of iron (over 1 mg/l) and, more rarely, manganese are locally present, rendering the groundwater unfit for many uses. There are several mineral springs issuing from the Millstone Grit, such as White Wells at Ilkley. The largest group (of 94) centred on the spa town of Harrogate is highly mineralised, with up to 15 500 mg/l of total dissolved solids. The springs are mainly positioned along the axis of the Harrogate Anticline, and are most abundant in the vicinity of its intersection with the Harrogate Fault. Although the water chemistry of the springs bears a marked relationship to structure, with those near the axis of the anticline having the greatest degree of mineralisation, the waters do not appear to be in hydraulic continuity. The principal ions are sodium and chloride, but bicarbonate and dissolved sulphide (HS-) may also be high. Some waters also contain barium (up to 68 mg/l).

Coal Measures aquifers

The Coal Measures  form a compex, multilayered minor aquifer. Argillaceous strata act as aquitards or aquicludes, isolating the few thicker sandstones, which effectively act as separate aquifers. The more important water-bearing sandstones include the Worsley Delf, Pemberton, Ravenhead, Trencherbone, Old Lawrence and Woodhead Hill rocks and Crutchman Sandstone to the west of the Pennines and the Ackworth, Mexborough, Oaks and Woolley Edge rocks, Wingfield Flags and Crawshaw Sandstone to the east. Folding and faulting result in isolated blocks of aquifer which inhibit lateral continuity. These conditions have been greatly modified by mining activities — directly by the construction of shafts, drainage adits (soughs) and galleries, and indirectly by the opening of fractures by mining subsidence, thereby connecting previously separate aquifers.

The sandstones are generally fine grained, well cemented and laterally impersistent, and groundwater movement and storage are largely dependent on fractures. Borehole yields depend on the number, size and lateral extent of fractures in the sandstones penetrated. They are therefore highly variable, but commonly range up to 10 l/sec and occasionally exceed 20 l/sec, with over 40 l/sec from some colliery shafts. Increased fracturing close to faults may enhance yields. They may also be enhanced where water-filled mine workings are penetrated, although often with a decline in water quality. Yields from sandstones that receive little or no direct recharge may decline as storage is depleted.

Groundwater quality is generally good at outcrop, being typically hard and of calcium bicarbonate type, with low concentrations of chloride and sulphate (of the order of 30 mg/l and less than 100 mg/l respectively). Down-dip, groundwaters generally become more mineralised with increasing confinement, and excessively hard with increasing sulphate concentrations, eventually grading into brackish or saline groundwater. Here, chloride concentrations are commonly in excess of 1000 mg/l and iron concentrations over 5 mg/l.

Permo-Triassic aquifers

The principal Permo-Triassic aquifers are the ‘Magnesian Limestones’ and the Sherwood Sandstone. The Basal Permian Sands are highly permeable, but thin and impersistent, and normally incapable of providing a sustainable supply. However, borehole yields of up to 1 l/sec have been reported. In the east of the region, the sands are separated from the overlying water-bearing limestones by the ‘Marl Slate’, which acts as an aquiclude.

Magnesian Limestone aquifers

The ‘Magnesian Limestones’ comprise two aquifers (the Cadeby and Brotherton formations. The intervening Edlington Formation acts as a leaky aquitard and maintains a slight head difference between the two limestones. There is, however, some hydraulic continuity between the two limestones and many boreholes penetrate them both. The two formations (where both are present) are therefore generally regarded as a single aquifer. The Brotherton Formation thickens and increases in importance as an aquifer to the north of and down-dip to the east from Worksop, but wedges out to the south. The importance of the Cadeby Formation as an aquifer also decreases southwards, due to lateral facies variations. To the north of Doncaster, the aquifer is confined by the Roxby Formation. However, this becomes progressively more arenaceous to the south, and around Worksop it passes into the sandstones at the base of the Sherwood Sandstone Group.

The permeability of the limestones and dolomites depends on fracturing, although there may be some intergranular storage, particularly in reef limestones and where dolomites predominate. Yields are extremely variable, but highest where the fracture density is greatest, as is common in the vicinity of faults. Yields may also be enhanced by collapse in the Brotherton Formation caused by dissolution of gypsum in the underlying Edlington Formation. Borehole yields are commonly in the range of 1 to 3 l/s from individual fissures but, under particularly favourable conditions, may range to over 20 l/s and 7 l/s in larger diameter boreholes in the Brotherton and Cadeby formations respectively. Failure to penetrate fissures occasionally results in dry or very low-yielding boreholes.

Groundwater quality at outcrop is generally good but very hard, with total hardness commonly in the range of 400 to 600 mg/l (as CaCO3) and total dissolved solids of up to 1200 mg/l. Chloride ion concentrations are normally less than 50 mg/l. The aquifer is highly vulnerable to surface pollution, and nitrate concentrations commonly exceed 10 mg/l. Sulphate and chloride ion concentrations increase markedly down-dip due to the presence of gypsum and halite in the confining marls.

Sherwood Sandstone aquifers

The Sherwood Sandstone Group forms the second most important aquifer in the UK and the major aquifer in the areas adjacent to the Pennines. A number of towns and cities, including Manchester, Liverpool, Leeds, Nottingham and Doncaster, obtain at least part of their water supplies from it.

To the east of the Pennines, the base of the aquifer is generally the impermeable Roxby Formation. To the west, the Manchester Marls Formation, where present, forms an aquitard separating the underlying Collyhurst Sandstone from the overlying Sherwood Sandstone aquifer. The Collyhurst Sandstone is only exploited to a minor extent in its outcrop area to the south of Manchester and Stockport. The Manchester Marls become more arenaceous to the west and south, being represented by the water-bearing sandstones of the Bold Formation in the western Cheshire Basin. The Mercia Mudstone Group is an aquitard, overlying and confining the Sherwood Sandstone aquifer on both sides of the Pennines.

Sedimentary character and post-depositional diagenesis greatly affect the aquifer properties of the sandstones. The sandstones are predominantly poorly cemented, with high porosity and permeability. However, grain size, and consequently primary (intergranular) permeability, generally decrease northwards. Fine-grained sandstones have lower permeabilities and may act as confining layers, although the lateral persistence of individual sandstone beds can be highly variable, even over short distances. Finer grained sandstones occur throughout, but commonly increase towards the top of the group. Variations in cementation also affect intergranular porosity and permeability; for example, the pebbly horizons of the Chester Pebble Beds and the Helsby/Ormskirk Sandstone formations are generally better cemented than the rest of the sandstones and have lower porosities and permeabilities. Iron-rich cements occur locally.

Although intergranular permeability and groundwater storage are commonly substantial, fracture flow through the sandstones is often greater. Discontinuities can provide preferential flow paths and have a significant effect on the physical properties of the aquifer, particularly in the better-cemented and finer grained strata. In regional terms, fractures are unlikely to be interconnected, possibly being sand-filled, but can be significantly developed close to pumping boreholes. In Yorkshire, it is considered that most fracture flow is limited to the upper 100 m of the aquifer, fractures probably being closed at greater depths. The hydraulic effects of faults vary widely, ranging from impermeable features (such as the Roaring Meg Fault in Merseyside) which dissect the aquifer into distinct blocks, to highly transmissive features that act as recharge channels.

Yields from boreholes with diameters of over 450 mm are commonly of the order of 40 to 50 l/s, but even greater yields are possible from large diameter wells with headings and where fractures are numerous. The presence of fracture systems enhances borehole yields, particularly in areas which have been undermined (for example by coal mining in the Nottinghamshire and Doncaster areas) or where fracturing is due to subsidence related to evaporite dissolution at depth (for example between Doncaster and Catterick). In Yorkshire, large-abstraction boreholes that are heavily pumped have a 25 per cent chance of pumping sand, requiring the installation of a suitable screen and gravel pack to control its ingress. Similar problems are occasionally encountered elsewhere in the region.

Groundwater quality, although generally potable, varies with depth. In the unconfined outcrop section of the aquifer, groundwaters are generally potable. They are commonly of calcium bicarbonate type, with subsidiary magnesium and sulphate ion concentrations and very minor sodium and chloride ion concentrations. Near the base of the group at outcrop, for example in Yorkshire, elevated concentrations of sulphate resulting from the dissolution of anhydrite and gypsum in the underlying mudstones may be encountered. Nitrate concentrations due to agricultural contamination may also be significant. In the East Midlands, beneath the confining Mercia Mudstone Group, groundwater chloride and nitrate concentrations are considerably lower than at outcrop. There, the groundwater was recharged under periglacial conditions between 10 000 and 35 000 years ago. Sulphate concentrations are at a minimum along the western fringe of the confined zone, with higher concentrations in the unconfined aquifer to the west, largely due to the activities of man. These increase progressively down-dip to the east due to the dissolution of gypsum and anhydrite. Groundwater remains usable up to 20 km down-dip from the outcrop, beyond which its quality declines, eventually becoming saline. In Yorkshire, elevated iron and manganese ion concentrations (occasionally leading to precipitation and clogging of borehole screens) are encountered locally where the aquifer is confined by either the Mercia Mudstone Group or drift deposits. Natural brines occur in the Cheshire Basin due either to dissolution of halites in the Mercia Mudstone Group or the presence of deep connate waters.

Mercia Mudstone aquifers

The Mercia Mudstone Group is composed predominantly of virtually impermeable mudstones. The coarser basal formations of Nottingham and Cheshire (Sneinton and Tarporley Siltstone formations) may form local minor aquifers, but few boreholes penetrate only them, most continuing into the underlying Sherwood Sandstone. To the east of the Pennines, limited quantities of water are obtainable from the thin sandstones and siltstones (skerries) interbedded with the mudstones. Yields only rarely exceed 1 l/s and often decline with pumping due to limited aquifer recharge and depletion of storage. Dry and very low-yielding boreholes are common. Groundwaters, although often potable, are commonly very hard due to the dissolution of anhydrite and gypsum present in the mudstones. To the west of the Pennines, the Mercia Mudstone Group is only rarely utilised, because the water is commonly brackish or saline due to the dissolution of halite.

Quaternary alluvial and glaciofluvial sands and gravels

Local groundwater supplies are widely available from shallow wells and boreholes penetrating Quaternary alluvial and glaciofluvial sands and gravels spread over the lower ground to the west and east of the Pennines. Such minor aquifers are most extensive in the north of the region and are of particular importance in providing agricultural supplies. Yields are generally small (up to 2 l/s); larger yields are commonly only sustained where the deposits are in hydraulic continuity with local surface waters. Groundwaters are generally potable, but highly susceptible to surface contamination.

Groundwater resources and abstraction

The availability of abundant, generally good quality groundwater resources has played an important role in the development of the region, and although fully exploited in some areas, will undoubtedly continue to be vital to future developments.

Groundwater abstractions account for approximately 39, 14 and 12 per cent of total public water supplies in the Midlands, the north-west and Yorkshire regions respectively, as well as representing an important resource for the industrial and agricultural sectors. Abstraction licences total almost 603 million cubic metres per annum (Mm3/a) for all aquifer sources in the region, with over 480 Mm3/a being licensed from the Sherwood Sandstone aquifer alone.

Total licensed abstraction for each aquifer is given in (Table 13), together with details of water use (expressed as percentages of total abstraction volumes). Subtotals are also included for the two separate areas of Carboniferous Limestone within the region and for the Sherwood Sandstone to the east and west of the Pennines. Abstraction data for small areas of Sherwood Sandstone aquifer along the southern flank of the region have been included with the eastern division.

The considerable importance of the Carboniferous Limestone, Millstone Grit and, particularly, the Sherwood Sandstone aquifers for the provision of public water supplies is readily apparent from (Table 13). Industrial supplies are derived mostly from the Coal Measures, ‘Magnesian Limestones’, Millstone Grit and Sherwood Sandstone. Although the percentage for the Sherwood Sandstone is somewhat lower than for the other aquifers, the volume of water is higher than for any other source. The only substantial volumes licensed for bottling as mineral waters (total 0. 338 Mm3/a) are from the Carboniferous Limestone at Buxton, but this constitutes only about 1 per cent of the total licensed for abstraction from these strata in the Peak District. However, the bottling of groundwater by the Buxton Mineral Water Company is important to the local economy. This company also bottles water from the Triassic at Ashbourne, close to the southern boundary of the region. Bottled water sales of Buxton Natural Mineral Water and Ashbourne Spring Water increased by 225 and 130 per cent respectively between 1994 and 1998.

The proportion of licensed abstraction utilised for agriculture is substantially higher for the ‘Magnesian Limestones’ than for the other aquifers, due to a preponderance of larger licences for spray irrigation. Although the proportion of groundwater abstracted for agriculture is relatively small, the quantities represent many hundreds of small licences spread widely across the region. The importance of groundwater abstraction to the agricultural sector is thereby distinctly underemphasised.

Estimates of groundwater resources for the minor Carboniferous aquifers are not generally available across the whole region. With a few localised exceptions, there appear to be potentially substantial Carboniferous resources remaining to be exploited, but limitations are frequently imposed due to the nature of the aquifers. Dewatering of coal mines has declined sharply since reaching a peak in the late 1950s and few mines remain open. Large-scale industrial abstraction has also declined sharply since the early 1960s as the heavy industries have declined.

Available resources in the ‘Magnesian Limestones’ aquifer are estimated to be of the order of 400 Mm3/a. Total licensed abstraction is substantially less than this, suggesting that much of the resource is available for development. This is, however, likely to be limited, because yields tend to be poor and further limitations are imposed by the need to maintain baseflow discharges from the aquifer to assist in ameliorating problems associated with low flows and quality of water courses on the Sherwood Sandstone to the east.

The Sherwood Sandstone aquifer resource to the west of the Pennines is estimated to be of the order of 218Mm3/a, which matches the total licensed abstraction fairly closely. To the east of the Pennines, the resource is estimated at about 400 Mm3/a, suggesting that further development is possible. However, the distribution of abstraction licences is uneven across the aquifer, and in some areas (for example in the aquifer between Nottingham and Doncaster), licensed abstraction totals exceed or approximately equate to the estimated resource, leading to long-term declines in water levels. In some urban areas (Liverpool and Nottingham, for example), abstraction has declined as user industries have closed, leading to rising water levels. The presence of potential contaminants in such urban areas is likely to preclude the use of this water for any purpose other than industry.

Geology of the main cities

This article examines the geology of the major conurbations of the Pennines and adjacent areas. Most owe their origins to geographical factors, but their development and major expansion were due to the underlying geology. With increasing modern stress on the environment from man-made causes, such as pollution (of ground, water and air), subsidence, interruption of natural drainage lines, disposal of industrial and domestic wastes and extraction of minerals, as well as the rapid post­war expansion of the urban areas, geology continues to play a major role in the life, planning and development of any town or city. The six major cities of the region — Manchester, Liverpool, Leeds, Bradford, Sheffield and Nottingham (Figure 1), (Figure 2) — are selected for a closer look at their geology and its interaction with human activity. All were dynamos of the Industrial Revolution that gave 20th century Britain its prosperity. The mining and manufacturing industries that fuelled this prosperity have been in decline since the Second World War.

There are common themes to all the cities. Increasing population places increasing pressure on the limited land resources. All the cities have suffered industrial decline and rapid urban expansion, and are now in the process of renewal. For regeneration, the planning of development requires consideration of a range of interconnecting factors, many of which relate directly or indirectly to the underlying geology. It is true that geological matters have not always been at the forefront of planning considerations, and, in addition to the neglect of natural and man-made hazards, geological resources such as coal and sand and gravel have been sterilised by new building development.

Whilst the following account deals mostly with the geology within the confines of the cities, it is impossible to divorce the cities from their surroundings. With modern communications, many of the people who work within the cities and contribute to their economies live considerable distances away. Similarly, amenities and resources on which cities rely, such as waste disposal sites, construction materials and water, may be remote. It is worth remembering that until the advent of canal and rail communications in the Victorian era, the towns and cities were self sufficient in the commodities required for building, development and economic success. Water supplies were largely obtained from rivers and wells within the cities until the expansion in Victorian times necessitated the construction of reservoirs in the Pennines. Much of the new development of the cities is taking place on former industrial and waste disposal sites. The made ground deposits which underlie these sites require careful attention prior to development because of the potential settlement problems arising from the heterogeneous nature of the materials, the presence of contaminated deposits, and, in the case of former domestic refuse sites, the generation of methane gas.

There has been considerable expansion of the urban areas in recent years, together with redevelopment of the inner cities and derelict industrial land. Prior to 1872 there was no statutary obligation to record plans of mines, there are few records, and the extent of old workings is largely unknown. The long history of quarrying and shallow mining has thus left a legacy of shafts, adits, shallow workings and backfilled quarries, many of which are poorly documented. This therefore presents an important constraint to development, necessitating detailed site investigations and remedial ground stabilisation measures in undermined areas.

Manchester

The city of Manchester (population about 405 000) lies in the shadow of the Pennines, on the edge of the Cheshire Basin and on the north-east margin of the Lancashire Coalfield. To the south is the Cheshire plain underlain by Permo-Triassic rocks; to the north and east are the Carboniferous Coal Measures and Millstone Grit. Overlying the solid rocks is a thick and extensive cover of glacial and glaciofluvial deposits. Coal Measures, comprising interbedded argillaceous measures and sandstones, form much of the bedrock of the city area. They are cut by a suite of north-west-trending faults, which lets down the Permo-Triassic succession of the Collyhurst Sandstone, Manchester Marls and Sherwood Sandstone in fault blocks. The Carboniferous and Permo-Triassic strata dip at moderate angles to the west and south-west.

Coal-bearing Lower and Middle Coal Measures underlie the city at depth, coming to crop to the north and east.

Manchester’s expansion during the Industrial Revolution was fuelled by power generated by the nearby, fast-flowing, steep streams. These same streams have caused flooding problems throughout the city’s history. Descending rapidly from the hills, they follow meandering courses across the lowland plain and are particularly prone to flooding during summer thunderstorms. South of Manchester, the River Mersey is formed by the confluence of the rivers Tame and Goyt at Stockport. The wide floodplain downstream of Stockport has a long history of flooding. Flooding was also widespread throughout the Greater Manchester section of the Mersey and in the Irwell which flows through the centre of Manchester. The most recent flooding of the Mersey was in 1973, when 75 mm of rain in 24 hours caused damage to the Merseyway shopping precinct and farther downstream at Brinksway. The river’s floodplain was modified during construction of the M63 motorway, which crosses the river four times between Stockport and Urmston. The modifications included building embankments to contain the river, cutting off meanders and the construction of culverts. Former gravel pits at Chorlton and Sale, now converted into recreational lakes, have storage capacity for floodwater, which is released by removing off-take weir gates upstream of the lakes. However, dramatic alterations to unprotected stretches of the rivers can and have taken place during flooding, when meanders may be cut off, channels alter and chutes form. Peak discharges increased as a result of agricultural drainage and urban development may also cause changes, as in the case of the River Bollin during flooding in the 1930s.

The industrial and urban development of Manchester had a dramatic effect on the rivers flowing through the city centre, particularly the Irwell, which floods on average every 15 years. The practice of discharging refuse and cinders from mills and factories into the river resulted in drastic reduction of channel capacity and increased flooding. The rapid urban expansion also contributed to flooding by increasing runoff rates, as did the increased amount of drainage schemes in the farming land of the catchment area. The Irwell, Mersey and Bollin flow into the Manchester Ship Canal, bringing sediment which requires dredging. The dredged sands and silts are dumped over a large area between the canal and the old channel of the River Mersey upstream of Warrington.

The drift deposits on which Manchester is built provide an economic resource as well as a potential hazard and are an important factor for consideration in planning development. The deposits comprise a multi-layer sequence of tills, clays, sands and gravels, much of the Manchester area being mantled with supraglacial tills and glaciofluvial deposits underlain by glacial lodgement till. A ridge of glaciofluvial outwash sands extends from Swinton through Pendlebury, across the Irwell valley to Prestwich and Cheetham Hill. Where the Irwell meanders against the ridge between Lower Kersal and Higher Broughton, it has undercut a steep slope in sands and clays known as The Cliff. The undercutting has caused a series of mass movements and extensive damage to houses and roads. Damage to pipelines, buildings and roads in other parts of Salford and Bury is related to ground movement caused by the instability of glaciofluvial sands.

Subsidence from coal mining has also been a problem in Manchester. For example, extensive subsidence took place as a result of mining the Roger Seam at Bradford Colliery to the north-east of the city centre. Problems, including damage to houses, factories, a gas holder and the beds of the Rochdale Canal and River Medlock, were alleviated when the mine closed in 1968.

Liverpool

Liverpool, the second largest port in the British Isles, grew as a major seaport in the heyday of trans-Atlantic cargo trading in the 18th century. It is sited on the east bank of the River Mersey, linked to its smaller neighbour of Birkenhead on the Wirral peninsula by the Mersey tunnels. Both conurbations have spread to incorporate neighbouring settlements, producing a vast built-up area with over 1. 25 million people. Situated on a dry site 30 m above the marshes of the Mersey, and underlain at depth by Triassic bedrock, the city was largely built of local sandstones and conglomerates from the Sherwood Sandstone Group. The presence of the underlying Triassic sandstone aquifer across almost all the Liverpool and Wirral districts provided the city with its water supply until the late 19th century, when the increasing demand for water for industry necessitated the construction of reservoirs in the surrounding countryside. Over much of the urban area, the solid rocks are mantled by tills and glaciofluvial sand and gravel. Recent blown sands form a narrow coastal strip, and older aeolian sands (the Shirdley Hill Sand) occur in thin spreads inland. The port is sited where the Mersey narrows and fast tidal currents scour the river bed and maintain a silt-free, deep channel. There is a tidal range of 10 m, but the soft estuarine deposits were easily excavated to depths sufficient to allow ships to remain afloat in the docks.

The drift deposits of the area cause problems and constraints to building and construction works sited on them. Their complex nature and the presence of sands liable to become thixotropic present problems similar to those in Manchester. The reclamation and redevelopment of former industrial sites and derelict waste ground has been extensive in Liverpool, including the site of the Liverpool International Garden Festival.

The decline in industrial groundwater abstraction in Liverpool, as in many other cities throughout the world, has resulted in rising groundwater levels. The main potential problems are flooding of tunnels, basements and other deep structures, and the reduction in load-bearing capacities of the rocks and superficial deposits.

Bradford

Bradford (population 457 000) is situated on a south bank tributary of the River Aire, in the north-west corner of the Yorkshire Coalfield. Its bedrock comprises sandstones and argillaceous beds of the Lower Coal Measures. The beds undulate gently and are cut by faults with mostly east and north-east trends. The Millstone Grit crops out to the north and west of the city and forms typical moors and pastureland, with bold sandstone escarpments and long dip slopes alternating with intervening shale ‘slacks’. Part of the city area is mantled by a thick cover of till. This attains thicknesses of at least 18m and is a variable deposit, ranging from sandy clay rich in sandstone debris to a stiff grey till with numerous erratic pebbles, cobbles and boulders. Millstone Grit clasts predominate, with lesser amounts of limestone, chert, ironstone, ganister and shale. Silurian sandstone boulders have also been recorded. The till is generally weathered at the surface to a brown or yellow, more or less decalcified clay.

Coals, ironstones, shales and sandstones of the Lower Coal Measures have all been exploited in the past. The Romans are known to have worked the ironstones. The Black Bed or Low Moor Ironstone was the most important in the 19th and 20th century and working continued at Low Moor until 1926, with some extraction from brick clay pits in the early 1930s. The ore, in the form of concretions in shale up to 75 mm in diameter, was extracted after the underlying Black Bed Coal had been mined. The mined nodules averaged 29 per cent metallic iron, with a maximum yield in Bowling Colliery of 30. 79 per cent. This was less than in other Yorkshire ores, but the product, known as Low Moor iron, enjoyed a worldwide reputation, probably because of the low sulphur content of the Better Bed Coal that was used in its smelting. Maximum production was in 1868, when 607 746 tonnes of ore were recovered from the Low Moor Ironstone, representing 76 per cent of the Westphalian ore mined in Yorkshire that year.

Coal mining at Bradford had ceased by the 1950s, but formerly contributed substantially to the industrial growth of the city. The worked coals were the Soft Bed, Hard Bed, Better Bed and Crow coals. Some of the thin coals of the Millstone Grit were also worked for local use. The Elland Flags sandstones were extensively quarried and mined for building, paving, roofing and tiling. Among the former mines in Bradford were the undocumented workings at Peel Park [SE167348], rediscovered in 1974. Mining appears to have ceased in 1900. The presence of old, shallow workings in the sandstones, many of them uncharted, presents a potential subsidence hazard in Bradford, in addition to the former coal and ironstone workings.

Water is another natural resource on which Bradford’s growth and prosperity is based. The plentiful supply of soft water in the Millstone Grit was one of the factors in the development of the local wool industry. Later, the streams provided power for the textile factories. Today, Bradford is the chief wool and cloth market of the region, and has an important engineering industry. After a phase of industrial dereliction and decline in some traditional industries, the city is undergoing extensive urban renewal, including reclamation of derelict land. Also, the tourist potential of the city, including the attractive surrounding countryside, is being developed.

Leeds

Leeds (population 680 000) lies 15 km east of Bradford, the two cities linked by continuous urban development. They share much of the same mineral inheritance and legacy of environmental problems. Leeds is the principal commercial and administrative centre for Yorkshire. Coal mining dates back to the 12th century, but it was the construction of the Leeds–Goole canal in 1704 that provided the stimulus for the major development of collieries in the area. Other industries that developed during the Industrial Revolution include those related to wool, leather, metals and engineering, the last being particularly associated with railway equipment.

The bedrock of the city comprises mainly sandstones and mudstones with coal seams of the Lower and Middle Coal Measures. The underlying sandstones and shales of the Millstone Grit crop out in the north and north-west of the city area. A suite of east-north-east and north-east-trending faults affects the rocks. Although solid rocks crop out over much of the city area, alluvium and river terrace sands and gravels are extensive in the Aire valley and there are spreads of till in the west and north-west. Most of the sand and gravel resources are now sterilised by development. As a result of mineral extraction and construction work, there are extensive areas of fill and disturbed ground. Coal and stone were the main worked commodities.

Various geological horizons were exploited for brick clay, fireclay, coal, ironstone, limestone, sand and gravel and sandstone. Early mining for coal and ironstone was from bell pits. For example, the Black Bed Ironstone was worked in this fashion in the city centre near what is now the Corn Exchange [SE 304 334]. Later, deeper mines extracted coal on a larger scale and, in some cases, ironstone and fireclay from above and below the coals respectively. In the early years of intensive mining near the city centre, the more productive shallow seams, such as the Beeston, were worked. This seam, and then other coals, were worked in a general east or south-east (down-dip) direction. Much of the workable upper leaf of the Beeston Coal was exhausted by the 19th century; its lateral equivalents (the Churwell Thick and Thin coals) were worked out by 1912.

It is thought that coal mining in the floor of the Aire valley was restricted because of water problems associated with the overlying water-bearing alluvial deposits. However, there is some evidence for working of the Beeston in the Hunslet area beneath terrace deposits, and Gibraltar Colliery was sited on alluvium. Underground mining in the Leeds area ceased in 1981 with the closure of Ledston Luck Colliery. Prior to this, much of the activity ended in the post-war years, although Primrose Hill Colliery was worked until 1970. Much of the district to the south and east of the city centre has been mined at some stage. Opencast mining has been extensive since its inception in the 1940s, but the most recent working at Skelton Grange [SE 34 31] is now closed.

Quarrying was formerly extensive in the district, mainly for clay and sandstone. The sandstones were dug extensively in the past for building, roofing, flagstones and general aggregate. Much of the outcrop of the Elland Flags was exploited for flagstone. Workings in the Elland Flags in the Gamble Hill area [SE 247 337] were probably from adits from a quarry.

The extent of the excavations was in many cases determined by the local requirements and geology. Thus, for example, the flagstone workings concentrated on the beds of better quality stone that split evenly. Clay pits may have developed in a manner to optimise secondary extraction of coal to reduce fuel costs. Some ganister and freestone workings may have exploited beds beneath a thin capping of clay in order to obtain unweathered stone.

With the depletion of resources coupled with expansion of the urban area and changing needs, mineral extraction is now limited to two sites. The Rough Rock and Rough Rock Flags are quarried near Horsforth Woodside [SE 255 376] for aggregate and flagstone and brick clay is dug at Swillington [SE 385 315].

Sheffield

Sheffield’s industries and the skills and crafts of its people, which have evolved since medieval times, result from its geology and geography. Some of the skills have survived, although local resources have declined and been replaced by others from farther afield.

The city, with a population of 501 000, lies on the eastern limb of the Pennine Anticline and the north-east flank of the Derbyshire Dome. It is sited at the confluence of the rivers Don and Sheaf, where the former breaks through the composite Middle Coal Measures escarpment. These measures, the Lower Coal Measures and the Millstone Grit underlie the city, the sandstones forming north-east-dipping slopes. On the north side of the city, the strata swing to strike north-eastwards along the Don valley, which follows the axis of the Don Monocline. The Lower Coal Measures contain thick sandstones, such as the Crawshaw Sandstone, Loxley Edge Rock, Greenmoor Rock and Grenoside Sandstone, which contribute to the fine scenery on the northern and western outskirts of the city. The top half of the Lower Coal Measures and all the Middle Coal Measures contain most of the worked coals of the area. The stratigraphically lowest rocks exposed within the city boundary are the upper parts of the Heyden Rock of Marsdenian age.

The sideritic iron ores of the Coal Measures were the first mineral to be worked on a large scale in the area. Although the Romans are known to have mined iron ore, it was the iron working established in medieval times that laid the foundations of the modern steel industry. However, even from an early date, iron ore was imported, and local iron mining has long ceased. Cutlery manufacture, for which Sheffield is world famous, dates back to the 13th century. The wooded valleys of the district provided the charcoal for iron smelting, and the sandstones at outcrop around the city were utilised for grinding. Although coal mining took place as early as 1167, it was not until the approaching exhaustion of the woodlands in the early 17th century and the improvements in transport in the 17th and 18th centuries that coal began to be mined to a large extent. The major expansion in coal mining took place with the Industrial Revolution, to meet the demand for local coking coal for iron smelting and for raising steam with the advent of the steam engine. Since then until relatively recently, increasing coal production came firstly from pits in and around the city, then eastwards and down-dip as shallow reserves became exhausted. The deep mining to the east was concurrent with opencast mining of the coals at outcrop to the west. East of Conisborough, the Coal Measures are concealed below the Permo-Triassic rocks and continue to the east at increasing depth. In the most productive part of the coalfield, north of Sheffield, there is, or was, estimated to be about 18 m of coal in seams over 0. 6 m thick, as well as many thinner seams.

Nottingham

The city of Nottingham (population 284 000) has been a settlement since Roman times or earlier. It owes its origin to a strategic postion on high sandstone ground close to fording and bridging positions on the River Trent. The rapid growth of the city took place in the late 1800s, in tandem with the expansion of coal mining to the north and west of the city and the establishment of the three manufacturing industries which continue to provide the economic backbone of the city today — pharmaceuticals, cigarettes and bicycles.

The geological resources of the city and its surroundings include coal, brick clay, gypsum, building stone, sand and gravel and water. The Permo-Triassic Sherwood Sandstone Group, on which much of the city of Nottingham lies, is a major aquifer. It comprises two formations; the Lenton Sandstone and the Nottingham Castle Sandstone formations. The latter has a conspicuous crop running north from the city centre through Sherwood Forest and forms the crag on which Nottingham Castle stands. To the south, it is truncated by the east-south-east­trending Clifton–Gamston fault system. The underlying Cadeby (Lower Magnesian Limestone) Formation crops out to the north-west of the city centre; Lower and Middle Coal Measures come to crop to the west and underlie the city at increasing depths towards the east and south-east. The Mercia Mudstone Group overlies the Sherwood Sandstone and crops out to the east of the city.

Of special interest are the man-made caves below the city, of which over 400 have been discovered. Their distribution is mainly confined to the outcrop of the Nottingham Castle Sandstone. The friable nature of the rock made it easy to excavate by hand tools, but the resultant excavations can stand unsupported. The first caves were almost certainly cut into the bluffs and cliffs facing the River Trent as human shelters and byres and date back to the 13th century. Used later for industrial purposes, for example a tannery existed in the Broadmarsh or Drury Hill cave system, they were later excavated below houses for storage, waste disposal and as wine and beer cellars. Some caves were excavated for building sand. The Victorians dug many caves as follies, with fine carvings of biblical and mythical characters. Many were modified or extended during the Second World War and used as air raid shelters.

The caves provide a good example of a feature that is both a geological hazard and a resource. They are a potential hazard to building development, although the sandstones below central Nottingham would provide sound, reliable foundations almost everywhere if it were not for the caves. Road collapses have taken place, but there are no records of building subsidence. Modern building has generally allowed for the presence of caves, by filling them with concrete, by leaving them as a feature, or by excavating to the lowest cave floor level and incorporating deep basements in the building design. However, given the known extent of cave networks and the lack of complete documentation, the possibility of localised subsidence remains. Rising ground water levels below the city may introduce a new hazard as caves become flooded, thereby weakening roof pillars. The former utilisation of the caves as a resource spans a wide range of activity from industrial, dwelling and storage to shelter. Today, some continue to be used as bar and house cellars. The better-known caves are a tourist attraction and are a resource capable of further development.

Coal mining has taken place from mines sited around the outer city limits, stretching clockwise from West Bridgford in the south, through Wollaton, Aspley, Bulwell, Bestwood, Gedling and Carlton. Most of the city is undermined. Shallow workings lie to the west where the Coal Measures crop out, with deep mining to the east and north. Substantial coal reserves remain under the city, but current coal economics have resulted in the closure of all the collieries in the area.

The well-bedded dolomites of the Cadeby Formation have long been quarried for building stone, roadstone and agricultural lime. They are today quarried only at Bulwell, mainly for rough blocks for garden walls and rockeries. The Sherwood Sandstone has been quarried and mined in the past for building sand on account of its weakly cemented, friable nature. The Mercia Mudstone Group provides a good local source of brick clay and is worked at Dorket Head. It was also quarried until recently for gypsum south-east of the city at Cropwell Bishop. The alluvium and terrace deposits of the Trent valley provide a local supply of sand and gravel for the construction industry, although much has been sterilised by urban development. There are current workings at Attenborough, Holme Pierrepont, Hoveringham and Bramcote.

Geological hazards

Ignorance of geological hazards may result in major unanticipated expense, injury and occasional loss of life. The region is no exception, with major incidents such as the Abbeystead Tunnel explosion and the Carsington Dam failure occurring in recent decades. Weak strata and drift deposits in the foundations of roads, buildings and dams, as well as in tunnels and other construction works, present potential geological hazards. Landslips and dangerous gases also present problems. Natural voids due to the dissolution of salt or gypsum, and man-made ones left by extraction of minerals, particularly coal, are major hazards in the region. Collapse of old sand mines in the Basal Permian Sand presents a hazard in the Castleford–Pontefract area.

Landslides and mining subsidence perhaps produce most problems in the region. Weak strata such as weathered mudstones, glacial till and head underlie many Pennine hill slopes and ancient degraded landslides are common. Slope stability is commonly disturbed where old roads crossing these landslides are upgraded to take modern heavy traffic, necessitating frequent repair. In the case of the A625 that crossed the large Mam Tor landslip (Plate 12), the expense of repair became so great that the road had to be permanently closed. Poor design and the presence beneath the embankment of a layer of clay head probably caused the expensive failure of the Carsington Dam near Ashbourne in 1984. Head is a very widespread but generally thin deposit immediately beneath the soil layer. It commonly contains clays and relict shear planes, making it a potentially very weak foundation material.

Although subsidence from modern coal mining is largely predictable and manageable, the precise location of earlier pillar and stall workings at shallow depth near coal seam outcrops may be less well known and undetected voids left by bell pits are particularly prone to collapse. Even when, as is commonly the case, collapse occurred soon after abandonment, the fill material may have a low bearing capacity. Extensive subsidence has been caused by the natural dissolution of Triassic salt beds under the Cheshire Plain. Extraction of brine and rock salt exaggerated and speeded the natural processes, but is now subject to strict controls so that the subsidence effects are largely predictable and can be managed. In contrast, there is an increasingly recognised subsidence problem affecting buildings in and around Ripon in Yorkshire (Plate 29), caused by the natural underground dissolution of thick Permian gypsum beds. Gypsum-related subsidence is also present to a lesser extent north from Ripon to Bedale and south to Brotherton. Predicting this subsidence is very difficult, making thorough ground investigation an essential prerequisite to development.

Two recent major disasters in the region were caused by methane which was trapped in confined spaces. The methane that exploded in the Abbeystead Aqueduct Tunnel pump house in 1984 killing 16 people probably originated in the Bowland Shale, and migrated in solution in groundwater into the sandstone walls of the tunnel. The methane that exploded and destroyed a bungalow at Loscoe in Derbyshire in 1986, severely injuring the three occupants, was a component of landfill gas that migrated through the subsurface strata from an old refuse-filled quarry about 100 m away.

Selected bibliography

Only key references and those from which diagrams have been derived are listed. British Geological Survey memoirs and maps have been used as reference sources throughout this book. Memoirs and maps covering this region are listed (pp. 188–190).

Most of the references listed below are held in the Library of the British Geological Survey at Keyworth, Nottingham. Copies of the references can be purchased subject to current copyright legislation.

Chapter 1 Introduction

TORSVIK, T H. 1998. Palaeozoic palaeogeography: a North Atlantic viewpoint. Geologiska Foreningen I Stockholm Forhandlinger, Vol. 120, 109–11.

Chapter 2 Pre-Carboniferous rocks

BASSETT, M G, BLUCK, B J, CAVE, R, HOLLAND, C H, and LAWSON, J D. 1992. Silurian. 37–56 in

Atlas of paleogeography and lithofacies. COPE, J W C, INGHAM, J K, and RAWSON, P F (editors). Geological Society of London, Memoir, No. 13.

BERRIDGE, N G. 1982. Petrography of the Pre-Carboniferous rocks of the Beckermonds Scar borehole in the context of the magnetic anomaly at the site. Proceedings of the Yorkshire Geological Society, Vol. 44, 89–98.

BEVINS, R E, BLUCK, B J, BRENCHLEY, P J, FORTEY, R A, HUGHES, C P, INGHAM, J K, and

RUSHTON, AW A. 1992. Ordovician.19–36 in Atlas of paleogeography and lithofacies.COPE, J

W C, INGHAM, J K, and RAWSON, P F (editors). Geological Society of London, Memoir, No. 13.

BOTT, M H P. 1961. Geological interpretation of magnetic anomalies over the Askrigg Block. Quarterly Journal of the Geological Society of London, Vol. 117, 491–493.

BOTT, M H P. 1967. Geophysical investigations of the Northern Pennine basement rocks. Proceedings of the Yorkshire Geological Society, Vol. 36, 139–168.

CANN, J R. 1982. In discussion of Berridge, N. 1982. Proceedings of the Yorkshire Geological Society, Vol. 44, 89–98.

COOPER, A H, MILLWARD, D, JOHNSON, E W, and SOPER, N J. 1993. The early Palaeozoic evolution of northwest England. Geological Magazine, Vol. 130, 711–724.

COPE, F W. 1973. Woo Dale borehole near Buxton, Derbyshire. Nature, Physical Science, Vol. 243, 29–30.

COPE, F W. 1979. The age of the volcanic rocks in the Woo Dale borehole, Derbyshire. Geological Magazine, Vol. 116, 319–320.

CORNWELL, J D, and WALKER, A S D. 1989. Regional geophysics.25–52 in Metallogenic models and exploration criteria for buried carbonate hosted ore deposits — a multi-disciplinary study in eastern England. PLANT, J A, and JONES, D G (editors).(London:The Institution of Mining and Metallurgy and Keyworth: British Geological Survey.)

DUNHAM, K C. 1973. A recent deep borehole near Eyam, Derbyshire. Nature, Physical Science, Vol. 241, 84–85.

DUNHAM, K C. 1974. Granite beneath the Pennines in north Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 40, 191–194.

DUNHAM, K C, DUNHAM, A C, HODGE, B L, and JOHNSON, GA L. 1965.Granite beneath Viséan sediments with mineralization at Rookhope, Northern Pennines. Quarterly Journal of the Geological Society of London, Vol. 121, 383–417.

EDWARDS, W, and TROTTER, F M. 1954. British regional geology: the Pennines and adjacent areas. (Third edition). (London: HMSO for Institute of Geological Sciences.)

FORTEY, R A, HARPER, D AT, INGHAM, J K, OWEN, A W, and RUSHTON, A W A. 1995. A revision of Ordovician series and stages from the historical type area. Geological Magazine, Vol. 132, 15–30.

HUGHES, R A, EVANS, J A, NOBLE, S R, and RUNDLE, C C. 1996. U-Pb chronology of the Ennerdale and Eskdale intrusions supports sub-volcanic relationships with the Borrowdale Volcanic Group (Ordovician, English Lake District). Journal of the Geological Society of London, Vol. 153, 33–38.

KNELLER, B C, SCOTT, R W, SOPER, N J, JOHNSON, E W, and ALLEN, P M. 1994. Lithostratigraphy of the Windermere Supergroup. Geological Journal, Vol. 29, 219–240.

MCKERROW, W S, and SCOTESE, C R. 1990. Revised world maps and instruction.1–21 in Palaeozoic palaeogeography and biogeography. MCKERROW, W S, and SCOTESE, C R (editors). Geological Society of London, Memoir, No. 12.

MERRIMAN, R J, PHARAOH, T C, WOODCOCK, N H, and DALY, P. 1993. The metamorphic history of the concealed Caledonides of eastern England and their foreland. Geological Magazine, Vol. 130, 613–620.

MOLYNEUX, S G. 1991. The contribution of palaeontological data to an understanding of the Early Palaeozoic framework of eastern England. 93–106 in Proceedings of the International Meeting on the Caledonides of the Midlands and the Brabant Massif.ANDRE, L, HERBOSCH, A, VANGUESTAINE, M, and VERNIERS, J (editors). Annales de la Société Géologiquie de Belgique, Vol. 114.

NOBLE, S R, TUCKER, R D, and PHARAOH, T C. 1993. Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes. Geological Magazine, Vol. 130, 738–747.

PHARAOH, T C, ALLSOP, J M, HOLLIDAY, D W, MERRIMAN, R J, KIMBELL, G S, RUNDLE, C C, BREWER, T S, NOBLE, S R, and EVANS, C J. 1997. The Moorby Microgranite: a deformed high level intrusion of Ordovician age in the concealed Caledonian basement of Lincolnshire. Proceedings of the Yorkshire Geological Society, Vol. 51, 329–342.

PHARAOH, T C, BREWER, T S, and WEBB, P C. 1993. Subduction-related magmatism of late Ordovician age in eastern England. Geological Magazine, Vol. 130, 647–656.

PHARAOH, T C, MERRIMAN, R J, EVANS, J A, BREWER, T S, WEBB, P C, and SMITH, N J P. 1991. Early Palaeozoic arc-related volcanism in the concealed Caledonides of southern Britain. 63–91 in Proceedings of the International Meeting on the Caledonides of the Midlands and the Brabant Massif.ANDRE, L, HERBOSCH, A, VANGUESTAINE, M, and VERNIERS, J (editors). Annales de la Société Géologique de Belgique, Vol. 114.

PHARAOH, T C, MERRIMAN, R J, WEBB, P C, and BECKINSALE, R D. 1987. The concealed Caledonides of eastern England: preliminary results of a multidisciplinary study. Proceedings of the Yorkshire Geological Society, Vol. 46, 355–369.

SOPER, N J, WEBB, B C, and WOODCOCK, N J. 1987. Late Caledonian (Acadian) transpression in north-west England: timings, geometry and geotectonic significance. Proceedings of the Yorkshire Geological Society, Vol. 46, 175–192.

THORPE, R S, GASKARTH, J W, and HENNEY, P. 1993. Tectonic setting of Caledonian minor intrusions of the English Midlands. Geological Magazine, Vol. 130, 657–663.

TUCKER, R D, and MCKERROW, W S. 1995. Early Paleozoic chronology:a review in light of new U-Pb zircon ages from Newfoundland and Britain. Canadian Journal of Earth Sciences, Vol. 32, 368–379.

TURNER, J S. 1949. The deeper structure of central and northern England. Proceedings of the Yorkshire Geological Society, Vol. 27, 280–297.

WADGE, A J, GALE, N H, BECKINSALE, R D, and RUNDLE, C C. 1978. A Rb-Sr isochron for the Shap Granite. Proceedings of the Yorkshire Geological Society, Vol. 42, 297–305.

WEBB, P C, and BROWN, G C. 1984. Lake District granites: heat production and related geochemistry. Investigation of the geothermal potential of the UK. (Keyworth, Nottingham: British Geological Survey.)

WEBB, P C, and BROWN, G C. 1989. Geochemistry of igneous rocks. 95–112 in Metallogenic models and exploration criteria for buried carbonate-hosted ore deposits — a multidisciplinary study in eastern England.PLANT, J A, and JONES, D G. (London: Institution of Mining and Metallurgy and Keyworth: British Geological Survey.)

WILSON, A A, and CORNWELL, J D. 1982. The Institute of Geological Sciences borehole at Beckermonds Scar, North Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 44, 59–88.

Chapter 3 Carboniferous — general

COPE, J C W, INGHAM, J K, and RAWSON, P F. (editors). 1992. Atlas of palaeogeography and lithofacies. Geological Society of London, Memoir, No. 13.

LEEDER, M R. 1988. Recent developments in Carboniferous geology: a critical review with implications for the British Isles and NW Europe. Proceedings of the Geologists’Association, Vol. 99, 73–100.

Chapter 4 Dinantian

AITKENHEAD, N. 1977. The Institute of Geological Sciences borehole at Duffield, Derbyshire. Bulletin of the Geological Survey of Great Britain, No. 59, 1–38.

BOWDEN, A, WEBSTER, M, and MITCHAM, T. 1997. Salthill Quarry Geology Trail. Geologists’ Association Guide, No. 58.

BRIDGES, P H. 1982. The origins of cyclothems in the late Dinantian platform carbonates at Crich, Derbyshire. Proceedings of the Yorkshire Geological Society, Vol. 44, 159–180.

BRIDGES, P H, and CHAPMAN, A J. 1988. The anatomy of a deep-water mud-mound complex on the SW margin of the Dinantian platform in Derbyshire, UK. Sedimentology, Vol. 35, 139–162.

BRIDGES, P H, GUTTERIDGE, P, and PICKARD, N A H. 1995. The environmental setting of Early Carboniferous mud-mounds. 171–190 in Carbonate mud-mounds: their origin and evolution. MONTY, C V L, BOSENCE, D W J, BRIDGES, P H, and PRATT, B R (editors). Special Publication of the International Association of Sedimentologists, No. 23.

CHARSLEY, T J. 1984. Early Carboniferous rocks of the Swinden No.1 Borehole, west of Skipton, Yorkshire. Report of the British Geological Survey, No. 84/1, 5–12.

COPE, F W. 1997. Geology explained in the Peak District (2nd edition). (Cromford: Scarthin Books.)

DUNHAM, K C, and WILSON, AA. 1985. Geology of the Northern Pennine Orefield:Vol.2, Stainmore to Craven. Economic Memoir of the British Geological Survey.

ELLIOTT, T. 1975. The sedimentary history of a delta lobe from a Yoredale (Carboniferous) cyclothem. Proceedings of the Yorkshire Geological Society, Vol. 40, 505–536.

FORD, T D (editor). 1977. Limestones and caves of the Peak District. (Norwich: Geo Abstracts Ltd.)

FORD, T D. 1996. Geology of Castleton. Geologists’Association Guide, No. 56.

GAWTHORPE, R L. 1986. Sedimentation during carbonate ramp-to-slope evolution in a tectonically active area: Bowland Basin (Dinantian), northern England. Sedimentology, Vol. 33, 185–206.

GAWTHORPE, R L. 1987. Tectono-sedimentary evolution of the Bowland Basin, northern England, during the Dinantian. Journal of the Geological Society of London, Vol. 144, 58–71.

HUDSON, R G S, and COTTON, G. 1945. The Lower Carboniferous in a boring at Alport, Derbyshire. Proceedings of the Yorkshire Geological Society, Vol. 25, 254–330.

LEES, A, and MILLER, J. 1985. Facies variation in Waulsortian buildups, Part 2; Mid-Dinantian buildups from Europe and North America. Geological Journal, Vol. 20, 159–180.

LUDFORD, A. 1951. Stratigraphy of the Carboniferous rocks of the Weaver Hills district, North Staffordshire. Quarterly Journal of the Geological Society of London, Vol. 106, 211–230.

MILLER, J. 1986. Facies relationships and diagenesis in Waulsortian mudmounds from the Lower Carboniferous of Ireland and N England. 311–355 in Reef diagenesis.SCHRODER, J H, and PURSER, B H (editors). (Berlin: Springer-Verlag.)

MILLER, J, and GRAYSON, R F. 1972. Origin and structure of the Lower Viséan ‘reef’ limestones near Clitheroe, Lancashire. Proceedings of the Yorkshire Geological Society, Vol. 38, 607–638.

MUNDY, D J C. 1978. Reef communities. 157–167 in The ecology of fossils.MCKERROW, W S (editor). (London: Duckworth.)

MUNDY, D J C. 1994. Microbialite-sponge-bryozoan-coral framestones in Lower Carboniferous (Late Viséan) buildups of northern England (UK). 713–729 in Pangea: global environments and resources.EMBRY, A F, BEAUCHAMP, B, and GLASS, D J(editors). Canadian Society of Petroleum Geologists, Memoir, No. 17.

PARKINSON, D, and LUDFORD, A. 1964. The Carboniferous Limestone of the Blore-with-Swinscoe district, north-east Staffordshire, with revisions to the stratigraphy of neighbouring areas. Geological Journal, Vol. 4, 167–176.

PRENTICE, J E. 1951. The Carboniferous limestone of the Manifold valley region, North Staffordshire. Quarterly Journal of the Geological Society of London, Vol. 106, 171–210.

RAMSBOTTOM, W H C. 1974. Dinantian. 47–73 in The geology and mineral resources of Yorkshire. RAYNER, D H and HEMINGWAY, J E (editors). (Leeds:Yorkshire Geological Society.)

RILEY, N J. 1990. Stratigraphy of the Worston Shale Group (Dinantian), Craven Basin, north­west England. Proceedings of the Yorkshire Geological Society, Vol. 48. 163–187.

SCHOFIELD, K, and ADAMS, A E. 1985. Stratigraphy and depositional environments of the Woo Dale Limestones Formation (Dinantian), Derbyshire. Proceedings of the Yorkshire Geological Society, Vol. 45, 225–233.

SCHOFIELD, K, and ADAMS, A E. 1986. Burial dolomitization of the Woo Dale Limestones Formation (Lower Carboniferous), Derbyshire, England. Sedimentology, Vol. 33, 207–219.

WALKDEN, G M. 1972. The mineralogy and origin of interbedded clay wayboards in the Carboniferous Limestone of the Derbyshire Dome. Geological Journal, Vol. 8, 143–159.

WOLFENDEN, E B. 1958. Paleoecology of the Carboniferous reef complex and shelf limestones in north-west Derbyshire. Bulletin of the Geological Society of America, Vol. 69, 871–898.

WILSON, A A. 1992. Geology of the Yorkshire Dales National Park. (Grassington:Yorkshire Dales National Park Committee.)

Chapter 5 Namurian

AITKENHEAD, N, and RILEY, N J. 1996. Kinderscoutian and Marsdenian successions in the Bradup and Hag Farm boreholes, near Ilkley, West Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 51, 115–125.

ALLEN, J R L. 1960. The Mam Tor Sandstones: a ‘turbidite’ facies of the Namurian deltas of Derbyshire, England. Journal of Sedimentary Petrology, Vol. 30, 193–208.

BISAT, W S. 1924. The Carboniferous goniatites of the north of England and their zones. Proceedings of the Yorkshire Geological Society, Vol. 20, 40–124.

BRANDON, A, RILEY, N J, WILSON, A A, and ELLISON, RA. 1995. Three new early Namurian (E1c–E2a) marine bands in central and northern England, UK, and their bearing on correlations with the Askrigg Block. Proceedings of the Yorkshire Geological Society, Vol. 50, 333–355.

BRISTOW, C S. 1993. Sedimentology of the Rough Rock: a Carboniferous braided river sheet sandstone in northern England. 291–304 in Braided rivers. BEST, J L, and BRISTOW, C S (editors). Geological Society of London Special Publication, No. 75.

CHISHOLM, J I. 1977. Growth faulting and sandstone deposition in the Namurian of the Stanton Syncline, Derbyshire. Proceedings of the Yorkshire Geological Society, Vol. 41, 305–323.

COLLINSON, J D. 1988. Controls on Namurian sedimentation in the Central Province basins of northern England. 85–101 in Sedimentation in a synorogenic basin complex.The upper Carboniferous of northwest Europe.BESLY, B M, and KELLING, G (editors). (Glasgow and London: Blackie.)

COLLINSON, J D, and BANKS, N L. 1975. The Haslingden Flags (Namurian, G1) of south-east Lancashire: bar finger sands in the Pennine Basin. Proceedings of the Yorkshire Geological Society, Vol. 40, 431–458.

COLLINSON, J D, JONES, M A, and WILSON, AA. 1977. The Marsdenian (Namurian R2) succession west of Blackburn: implications for the evolution of the Pennine delta systems. Geological Journal, Vol. 12, 59–76.

COPE, J C W. 1983. High resolution biostratigraphy. 257–265 in High resolution stratigraphy. HAILWOOD, E A, and KIDD, R B (editors). Geological Society of London Special Publication, No. 70.

EAGAR, R M C, BAINES, J G, COLLINSON, J D, HARDY, P G, OKOLO, S A, and POLLARD, J E. 1985. Trace fossil assemblages and their occurrence in Silesian (Mid-Carboniferous) deltaic sediments of the central Pennine basin, England. 99–149 in Biogenic structures; their use in interpreting depositional environments. CURRAN, H A (editor). Special Publication of the Society of Economic Palaeontologists and Mineralogists, No. 35.

HAMPSON, G J. 1997. A stratigraphic model for the Lower Kinderscout Delta, an Upper Carboniferous turbidite-fronted delta. Proceedings of the Yorkshire Geological Society, Vol. 51, 273–296.

HOLDSWORTH, B K. 1963. Prefluvial, autogeosynclinal sedimentation in the Namurian of the southern Central Province. Nature, Physical Science, Vol. 199, 133–135.

HOLDSWORTH, B K, and COLLINSON, J D. 1988. Millstone Grit cyclicity revisited. 132–152 in Sedimentation in a synorogenic basin complex; the Upper Carboniferous of northwest Europe. BESLY, B M, and KELLING, G (editors). (Glasgow and London: Blackie.)

JONES, C M, and CHISHOLM, J I. 1997. The Roaches and Ashover grits: sequence stratigraphic interpretation of a ‘turbidite-fronted’ delta system. Geological Journal, Vol. 32, 45–68.

LEEDER, M R. 1988. Recent developments in Carboniferous geology: a critical review with implications for the British Isles and NW Europe. Proceedings of the Geologists’Association, Vol. 99, 73–100.

MCCABE, P J. 1978. The Kinderscoutian Delta (Carboniferous) of Northern England: a slope influenced by density currents. 116–126 in Sedimentation in submarine canyons, fans and trenches.STANLEY, D J, and KELLING, G (editors). (Stroudsburg: Dowden, Hutchinson and Ross.)

RAMSBOTTOM, W H C. 1966. A pictorial diagram of the Namurian rocks of the Pennines. Transactions of the Leeds Geological Association, Vol. 7, 181–184.

RAMSBOTTOM, W H C. 1974. Namurian. 73–87 in The geology and mineral resources of Yorkshire. RAYNER, D H, and HEMINGWAY, J E (editors). (Leeds:Yorkshire Geological Society.)

RAMSBOTTOM, W H C, CALVER, M A, EAGAR, R M C, HODSON, F, HOLLIDAY, D W, STUBBLEFIELD, C J, and WILSON, R B. 1978. A correlation of Silesian rocks in the British Isles. Special Report of the Geological Society of London, No. 10.

READING, H G. 1964. A review of the factors affecting the sedimentation of the Millstone Grit (Namurian) in the central Pennines. Developments in Sedimentology, Vol. 1, 340–346.

RILEY, N J, CLAOUÉ-LONG, J, HIGGINS, A C, OWENS, B, SPEARS, A, TAYLOR, L, and VARKER, W J. 1995. Geochronometry and geochemistry of the European Mid-Carboniferous boundary global stratotype proposal, Stonehead Beck, North Yorkshire, UK. Annales de la Société géologique de Belgique, Vol. 116, 275–289.

TREWIN, N H. 1968. Potassium bentonites in the Namurian of Staffordshire and Derbyshire. Proceedings of the Yorkshire Geological Society, Vol. 37, 73–91.

TREWIN, N H, and HOLDSWORTH, B K. 1973. Sedimentation in the Lower Namurian rocks of the North Staffordshire Basin. Proceedings of the Yorkshire Geological Society, Vol. 39, 371–408.

Chapter 6 Westphalian

BESLY, B M, and FIELDING, C R. 1989. Palaeosols in Westphalian coal-bearing and red-bed sequences, central and northern England. Palaeogeography, Palaeoclimatology Palaeoecology, Vol. 70, 303–330.

BROADHURST, F M, and SIMPSON, I M. 1983. Syntectonic sedimentation, rigs, and fault reactivation in the Coal Measures of Britain. Journal of Geology, Vol. 91, 330–337.

BURGESS, I C. 1982. The stratigraphical distribution of Westphalian volcanic rocks to the east and south of Nottingham. Proceedings of the Yorkshire Geological Society, Vol. 44, 29–44.

CALVER, M A. 1968a. Distribution of Westphalian marine faunas in northern England and adjoining areas. Proceedings of the Yorkshire Geological Society, Vol. 37, 1–72.

CALVER, M A. 1968b. Coal Measures invertebrate faunas. 147–177 in Coal and coal-bearing strata.MURCHISON, D, and WESTOLL, T S (editors).(Edinburgh and London:Oliver and Boyd.)

CHISHOLM, J I. 1990. The Upper Band-Better Bed sequence (Lower Coal Measures, Westphalian A) in the central and south Pennine area of England. Geological Magazine, Vol. 127, 55–74l.

CHISHOLM, J I, WATERS, C N, HALLSWORTH, C R, TURNER, N, STRONG, G, and JONES, N S. 1996. Provenance of Lower Coal Measures around Bradford, West Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 51, 153–166.

EAGAR, R M C. 1956. Addition to the non-marine fauna of the Lower Coal Measures of the north-Midlands coalfields. Liverpool and Manchester Geological Journal, Vol. 1, 328–369.

ELLIOT, R E. 1968. Facies, sedimentation successions and cyclothems in productive Coal Measures in the East Midlands, Great Britain. Mercian Geologists, Vol. 2, 351–372.

ELLIOTT, R E. 1969. Deltaic processes and episodes: the interpretation of productive Coal Measures occurring in the East Midlands, Great Britain. Mercian Geologist, Vol. 3, 111–135.

GLOVER, B W, LENG, M J, and CHISHOLM, J I. 1996. A second major fluvial source land for the Silesian Pennine Basin of northern England. Journal of the Geological Society of London, Vol. 153, 901–906.

GOOSSENS, R F, and SMITH, E G. 1973. The stratigraphy and structure of the Upper Coal Measures in the exposed Yorkshire Coalfield between Pontefract and South Kirkby. Proceedings of the Yorkshire Geological Society, Vol. 39, 487–514.

GOOSSENS, R F, SMITH, E G, and CALVER, M A. 1974. Westphalian. 87–108 in The geology and mineral resources of Yorkshire.RAYNER, D H, and HEMINGWAY, J E (editors). (Leeds:Yorkshire Geological Society.)

GUION, P D. 1992. Westphalian. 79–85 in Atlas of palaeogeogarphy and lithofacies. COPE, J C W, INGHAM, J K, and RAWSON, P F (editors). Geological Society of London, Memoir, No. 13.

GUION, P D, BANKS, N L, and RIPPON, J H. 1995. The Silkstone Rock (Westphalian A) from the east Pennines, England: implications for sand body geometry. Journal of the Geological Society of London, Vol. 152, 819–832.

GUION, P D, and FIELDING, C R. 1988. Westphalian A and B sedimentation in the Pennine Basin, UK. 153–177 in Sedimentation in a synorogenic basin complex. BESLY, B M, and KELLING, G (editors). (Glasgow and London: Blackie.)

GUION, P D, FULTON, I M, and JONES, N S. 1995. Sedimentary facies of coal-bearing Westphalian A and B north of the Wales–Brabant High. 45–78 in European Coal Geology. WHATELEY, M K G, and SPEARS, D A (editors). Geological Society of London Special Publication, No. 82.

HALLSWORTH, C R, and CHISHOLM, J I. 2000. Stratigraphic evolution of provenance characteristics in Westphalian sandstones of the Yorkshire Coalfield. Proceedings of the Yorkshire Geological Society, Vol. 53, 43–72.

LENG, M J, GLOVER, B W, and CHISHOLM, J I. 1999. Nd and Sr isotopes as clastic provenance indicators in the Upper Carboniferous of Britain. Petroleum Geoscience, Vol. 5, 293–301.

RIPPON, J H. 1996. Sand body orientation, palaeoslope analysis and basin fill implications in the Westphalian A–C of Great Britain. Journal of the Geological Society of London, Vol. 153, 881–900.

SMITH, A H V. 1962. The palaeoecology of Carboniferous peat as based on the microspores and petrography of bituminous coals. Proceedings of the Yorkshire Geological Society, Vol. 33, 423–474.

TROTTER, F M. 1952. Exploratory borings in south-west Lancashire. Transactions of the Institution of Mining Engineers, Vol. 112, 261–283.

Chapter 7 Permo-Triassic

CHARSLEY, T J, RATHBONE, P A, and LOWE, D J. 1990. Nottingham: a geological background for planning and development. British Geological Survey Technical Report, WA/90/1.

EVANS, D J, REES, J G, and HOLLOWAY, S. 1993. The Permian to Jurassic stratigraphy and structural evolution of the central Cheshire Basin. Journal of the Geological Society of London, Vol. 150, 857–870.

JACKSON, D I, MULLHOLLAND, P, JONES, S M, and WARRINGTON, G. 1987. The geologcal framework of the East Irish Sea Basin. 191–203 in Petroleum geology of north west Europe. BROOKS, J, and GLENNIE, K W (editors). (London: Graham and Trotman.)

PATTISON, J. 1970. A review of the marine fossils from the upper Permian rocks of Northern Ireland and north-west England. Bulletin of the Geological Survey, No. 32, 123–165.

SMITH, D B. 1989. The late Permian palaeogeography of north-east England. Proceedings of the Yorkshire Geological Society, Vol. 47, 285–312.

SMITH, D B. 1992. Permian. 275–305 in Geology of England and Wales.DUFF, P MCL D, and SMITH, A J (editors).(London:Geological Society of London.)

SMITH, D B. 1995. Marine Permian of England. Joint Nature Conservation Committee. (London: Chapman and Hall.)

SMITH, D B, HARWOOD, G M, PATTISON, J, and PETTIGREW, T. 1986. A revised nomenclature for Upper Permian strata in eastern England. 9–17 in The English Zechstein and related topics. HARWOOD, G M, and SMITH, D B (editors). Geological Society of London Special Publication, No. 22.

SMITH, D B, and TAYLOR, J C M. 1992. Permian. 87–96 in Atlas of palaeogeography and lithofacies. COPE, J C W, INGHAM, J K, and RAWSON, P F (editors). Geological Society of London, Memoir, No. 13.

TUCKER, M E. 1991. Sequence stratigraphy of carbonate-evaporite basins: models and application to the Upper Permian (Zechstein) of northeast England and adjoining North Sea. Journal of the Geological Society of London, Vol. 148, 1019–1036.

WARRINGTON, G, and IVIMEY-COOK, H C. 1992. Triassic. 97–106 in Atlas of palaeogeography and lithofacies. COPE, J C W, and INGHAM, J K, and RAWSON, P F (editors). Geological Society of London, Memoir, No. 13.

WILSON, AA. 1990. The Mercia Mudstone Group (Trias) of the East Irish Sea Basin. Proceedings of the Yorkshire Geological Society, Vol. 48, 1–22.

WILSON, AA. 1993. The Mercia Mudstone Group (Trias) of the Cheshire Basin. Proceedings of the Yorkshire Geological Society, Vol. 49, 171–188.

Chapter 8 Neogene and Quaternary

BRIGGS, D J, GILBERTSON, D D, and JENKINSON, R D S. 1985. Peak District and northern Dukeries. Field Guide. (Cambridge: Quaternary Research Association.)

BOWEN, D Q (editor). 1999. A revised correlation of Quaternary deposits in the British Isles. Special Report of the Geological Society of London, No. 23.

DALTON, R, FOX, H, and JONES, P. 1990. Classic landforms of the Dark Peak. Geographical Association Classic Landform Guides. No. 11.

DAWKINS, W B. 1903. On the discovery of an ossiferous cavern of Pliocene age at Dove Holes, Buxton, Derbyshire. Quarterly Journal of the Geological Society of London, Vol. 59, 105–32.

EHLERS, J, GIBBARD, P L, and ROSE, J (editors). 1991. Glacial deposits in Great Britain and Ireland. (Rotterdam: Balkema.)

FORD, T D (editor). 1977. Limestones and caves of the Peak District. (Norwich: Geo Abstracts Ltd.)

FORD, T D, GASCOYNE, M, and BECK, J S. 1983. Speleothem dates and Pleistocene chronology in the Peak Distrcit of Derbyshire. Transactions of the British Cave Research Association, Vol. 10, 103–115.

GALE, S J. 1985. The Late and Post-glacial environmental history of the southern Cumbrian massif and its surrounding lowlands. 282–298 in The geomorphology of north-west England. JOHNSON, R H (editor). (Manchester: Manchester University Press.)

GASCOYNE, M, SCHWARCZ, H P, and FORD, D C. 1983. Uranium-series ages of speleothem from north-west England: correlation with Quaternary climate. Philosophical Transactions of the Royal Society of London, Vol. B301, 143–164.

HARVEY, A M. 1985. The river systems of north-west England. 122–142 in The geomorphology of north-west England.JOHNSON, R H (editor). (Manchester: Manchester University Press.)

IMBRIE, J, SHACKLETON, N J, PISIAS, N G, MORLEY, J J, PRELL, W L, MARTINSON, D G, HAYES, J D, MACINTYRE, A, and MIX, A C. 1984. The orbital theory of Pleistocene climate:support from a revised chronology of the marine record. 269–305 in Milankovitch and climate, Part I. BERGER, A and four others (editors). (Dordrecht: Reidel.)

JENKINSON, R D S. 1984. Creswell Crags: Late Pleistocene sites in the East Midlands. British Archeological Reports, British Series, 122. (Oxford.)

JOHNSON, R H. 1985a. The geomorphology of the regions around Manchester: an introductory review. 1–23 in The geomorphology of north-west England.JOHNSON, R H (editor). (Manchester: Manchester University Press.)

JOHNSON, R H. 1985b. The imprint of glaciation on the west Pennine uplands. 237–262 in The geomorphology of north-west England. JOHNSON, R H (editor). (Manchester: Manchester University Press.)

JONES, R L, and KEEN, D H. 1993. Pleistocene environments in the British Isles. (London: Chapman and Hall.)

JOWETT, A, and CHARLESWORTH, J K. 1929. The glacial geology of the Derbyshire Dome and the western slopes of the southern Pennines. Quarterly Journal of the Geological Society of London, Vol. 85, 307–334.

LONGWORTH, D. 1985. The Quaternary history of the Lancashire Plain. 178–200 in The geomorphology of north-west England.JOHNSON, R H (editor). (Manchester: Manchester University Press.)

MITCHELL, G F, PENNY, L F, SHOTTON, F W, and WEST, R G. 1973. A correlation of Quaternary deposits in the British Isles. Geological Society of London, Special Report, No. 4.

MITCHELL, W A (editor). 1991. Western Pennines. Field Guide. Quaternary Research Association. (London: J Winn.)

PENNY, L F. 1974. Quaternary. 245–264 in The geology and mineral resources of Yorkshire. RAYNER, D H, and HEMINGWAY, J E (editors). (Leeds: Yorkshire Geological Society.)

SHIMWELL, D W. 1985. The distribution and origins of lowland mosslands. 299–312 in The geomorphology of north-west England.JOHNSON, R H (editor). (Manchester: Manchester University Press.)

SPENCER, H E P, and MELVILLE, R V. 1974. The Pleistocene mammalian fauna of Dove Holes, Derbyshire. Bulletin of the Geological Survey of Great Britain, Vol. 48, 43–49.

WALSH, P T, BOULTER, M C, IJTABA, M, and URBANI, D M. 1972. The preservation of the Neogene Brassington Formation of the southern Pennines and its bearing on the evolution of upland Britain. Journal of the Geological Society of London, Vol. 128, 519–559.

WALSH, P T, COLLINS, P, IJTABA, M, NEWTON, J P, SCOTT, N H, and TURNER, P R. 1980. Palaeocurrent directions and their bearing on the origin of the Brassington Formation (Miocene–Pliocene) of the southern Pennines, Derbyshire, England. Mercian Geologist, Vol. 8, 47–62.

WALTHAM, A C. 1974. Limestone and caves of north west England. (Newton Abbot: David and Charles.)

Chapter 9 Structure

FRASER, A J, and GAWTHORPE, R L. 1990. Tectono-stratigraphic development and hydrocarbon habitat of the Carboniferous in northern England. 49–86 in Tectonic events responsible for Britain’s oil and gas reserves. HARDMAN, R F P, and BROOKS, J (editors). Geological Society of London, Special Publication, No. 55.

HOLLIDAY, D W. 1993. Mesozoic cover over northern England: interpretation of apatite fission-track data. Journal of the Geological Society of London, Vol. 150, 657–660.

KIRBY, G A, BAILEY, H E, CHADWIECK, RA, EVANS, DJ, HOLLIDAY, DW, HOLLOWAY, S, HULBERT, AG, PHARAOH, TC, SMITH, NJP, AITKENHEAD, N, and BIRCH, B. 2000. The structure and evolution of the Craven Basin and adjacent areas. Subsurface Memoir of the British Geological Survey.

LEEDER, M R. 1982. Upper Palaeozoic basins of the British Isles — Caledonide inheritance versus Hercynian plate margin processes. Journal of the Geological Society of London, Vol. 139, 479–491.

MOSELEY, F. 1972. A tectonic history of north-west England. Journal of the Geological Society of London, Vol. 128, 561–598.

SMITH, K, SMITH N J P, and HOLLIDAY, D W. 1985. The deep geology of Derbyshire. Geological Journal, Vol. 20, 215–225.

Chapter 10 Geology and Man

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COOPER, A H. 1986. Subsidence and foundering of strata caused by the dissolution of Permian gypsum in the Ripon and Bedale areas, North Yorkshire. 127–139 in The English Zechstein and related topics. HARWOOD, G M, and SMITH, D B (editors). Geological Society of London Special Publication, No. 22.

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DOWNIE, C. 1960. The area around Sheffield. Geologists’Association Guide, No. 9.

DOWNING, R A, and GRAY, D A (editors). 1986. Geothermal energy — the potential in the United Kingdom. (London: HMSO for the British Geological Survey.)

DUNHAM, K C. 1983. Ore genesis in the English Pennines: a fluoritic subtype. 86–112 in Proceedings of International Conference on Mississippi Valley-type lead-zinc deposits: Rolla, Missouri, KISVARSANYI, G, GRANT, S K, PRATT, W P, and KOENIG, J W(editors).(Rolla:University of Missouri.)

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EDWARDS, K C (editor). 1966. Nottingham and its region. British Assocation for the Advancement of Science. (Nottingham: Derry and Sons Ltd.)

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FERRARI, C R. 1988. Subsidence effects on working the eleventh seam, Leeds and Liverpool Canal — Leigh branch, Peacock seam — Bickershaw colliery. Second International Conference on Construction in Areas of Abandoned Mineworkings (1988, Edinburgh).FORDE, M C (editor). (Edinburgh:Technics Press.)

FORD, T D. 1976. The ores of the South Pennines and Mendip Hills, England — a comparative study. 161–195 in Handbook of strata-bound and stratiform ore deposits, II. Regional studies and specific deposits, Volume 5, regional studies. WOLF, K H (editor). (Amsterdam: Elsevier.)

FORD, T D, SARJEANT, W A S, and SMITH, M E. 1993. The minerals of the Peak District. Bulletin of the Peak District Mines Historical Society, Vol. 12, 16–55.

FRASER, A J, and GAWTHORPE, R L. 1990. Tectono-stratigraphic development and hydrocarbon habitat of the Carboniferous in northern England. 49–86 in Tectonic events responsible for Britain’s oil and gas reserves. HARDMAN, R F P, and BROOKS, J (editors). Geological Society of London, Special Publication, No. 55.

FRASER, A J, NASH, D F, STEELE, R P, and EBDON, C C. 1990. A regional assessment of the intra-Carboniferous play of northern England. 417–440 in Classic petroleum provinces. BROOKS, J (editor). Geological Society of London, Special Publication, No. 50.

GLOVER, B W, HOLLOWAY, S, and YOUNG, S R. 1993. An evaluation of coalbed methane potential in Great Britain. British Geological Survey Technical Report, WA/93/24.

GODWIN, C G. 1984. Mining in the Elland Flags: a forgotten Yorkshire industry. British Geological Survey Report, Vol. 16, No. 4.

GODWIN, C G, and CALVER, M A. 1974. A review of the Coal Measures (Westphalian) of Leeds. Journal of Earth Sciences of the Leeds Geological Assocation, Vol. 8, 409–432.

HARRISON, C, and PETCH, J R. 1985. Ground movements in parts of Salford and Bury, Greater Manchester—aspects of urban geomorphology. 353–371 in The geomorphology of north-west England.JOHNSON, R H (editor). (Manchester: Manchester University Press.)

HARRISON, D J, and ADLAM, K A MCL. 1985. The limestone and dolomite resources of the Peak District of Derbyshire and Staffordshire. Description of parts of 1:50 000 geological sheets 99, 111, 112, 124 and 125. Mineral Assessment Report of the British Geological Survey, No. 144.

HARRISON, D J, HUDSON, J M, and CANNELL, B. 1990. Appraisal of high-purity limestones in England and Wales. Part 1. Resources. British Geological Survey Technical Report, WF/90/10.

HEALTH AND SAFETY EXECUTIVE. 1985. The Abbeystead explosion. (London: HMSO.)

HEMINGWAY, J E. 1974. Ironstone. 329–335 in The Geology and mineral resources of Yorkshire. RAYNER, D H, and HEMINGWAY, J E (editors). (Leeds:Yorkshire Geological Society.)

HIGHLEY, D E. 1977. Silica. Mineral Dossier, Mineral Resources Consultative Committee, No. 18. (London: HMSO.)

HIGHLEY, D E. 1982. Fireclay. Mineral Dossier, Mineral Resources Consultative Committee, No. 24. (London: HMSO.)

HOLT, A (editor). 1923. Merseyside. British Association for the Advancement of Science. (University Press of Liverpool Ltd and Hodder and Stoughton Ltd, London.)

HUDSON, P. 1989. Old mills, gritstone quarries and millstone making in the Forest of Lancaster. Contrebis, Vol. 15, 35–64.

JONES, D G, PLANT, J A, and COLMAN, T B. 1994. The genesis of the Pennine mineralisation of Northern England and its relationship to mineralisation in Ireland. 198–218 in Sediment-hosted Pb-Zn ores. FONTBOTE, L, and BONI, M (editors). Society for Geology Applied to Ore Deposits, Special Publication, No. 10. (Berlin: Springer-Verlag.)

JONES, R C B. 1947. The geology of South Lancashire and North Cheshire and its relationship to industry. 105–113 in An advisory plan: Manchester, South Lancashire and North Cheshire Advisory Planning Committee.NICHOLAS, R (editor).

KING, R J, and FORD, T D. 1968. Mineralisation. 112–137 in The geology of the East Midlands. SYLVESTER-BRADLEY, P C, and FORD, T D (editors).(Leicester:Leicester University Press.)

KIRKHAM, R V. 1989. Distribution, settings and genesis of sediment-hosted stratiform copper deposits. 3–38 in Sediment-hosted stratiform copper deposits.BOYLE, R W, BROWN, A C, JEFFERSON, C W, JOWETT, E C, and KIRKHAM, R V (editors). Geological Association of Canada, Special Paper, No. 36.

LAKE, R D, NORTHMORE, K J, DEAN, M T, and TRAGHEIM, D G. 1992. Leeds: a geological background for planning and development. British Geological Survey Technical Report, WA/92/1.

LEGGET, R F. 1978. Cities and geology. (New York: McGraw-Hill.)

LINTON, D L. 1956. Sheffield and its region. British Association for the Advancement of Science.

LOTT, G K, and RICHARDSON, C. 1997. Yorkshire stone for building the Houses of Parliament (1839-c. 1852). Proceedings of the Yorkshire Geological Society, Vol. 51, 265–272.

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MITCHELL, W R. 1985. The exploitation of the Horton Flags — considered as an example of industrial archaeology. Field Studies, Vol. 6 , 237–251.

MITCHELL, W R. 1994. A piece of glorious Dales marble. The Dalesman. November 1994 Issue.

MONKHOUSE, R A, and RICHARDS, H G. 1979. Groundwater Resources of the United Kingdom. Final Report for the Director of the Environment and Consumer Protection Studies. European Community, Central Water Planning Unit.

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NEVES, R, and DOWNIE, C. 1967. Geological excursions in the Sheffield region. (University of Sheffield: J.W.Northend Ltd.)

NORTON, M G, ROWLATT, S M, and NUNNY, R S. 1984. Sewage sludge dumping and contamination of Liverpool Bay sediments. Estuarine, Coastal and Shelf Science, Vol. 19, 69–87.

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PLANT, J A, and JONES D G (editors). 1989. Metallogenic models and exploration criteria for buried carbonate-hosted ore deposits — a multidisciplinary study in eastern England. (Keyworth, Nottingham: British Geological Survey; London: Institution of Mining and Metallurgy.)

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Memoirs of the British Geological Survey

British Geological Survey memoirs and maps have been used as reference sources throughout this book.The memoirs are listed by sheet number and the latest edition of the 1:50 000 series map is shown in italics. Subsurface memoirs, offshore memoirs and geochemical atlases are also listed. Memoirs, maps and other BGS publications are available from BGS offices, and information on BGS products and data is available at http://www.bgs.ac.uk..

Onshore memoirs

Sheet No. and name Date memoir map Memoir title and authors

Economic memoirs

Subsurface memoirs

Offshore memoir

Other publications

Geochemical atlases

Figures, plates and tables

Figures

(Figure 1) Topography of the region.

(Figure 2) Geology of the region (see also map in pocket).

(Figure 3) Palaeogeographical sketches showing continental movements from the early Ordovician to the Middle Devonian (based on Torsvik, 1998). British Isles in red.

(Figure 4) Pre-Carboniferous rocks of the Craven inliers.

(Figure 5) End-Ordovician–early Silurian palaeogeography and location of boreholes proving basement rocks.

(Figure 6) Sketch maps illustrating the generalised palaeogeography of the region and surrounding areas from the late Devonian to early Westphalian.

(Figure 7) Outcrops of Dinantian rocks and principal features of the Dinantian palaeogeography of the region.The main structures are described in Chapter 9.

(Figure 8) Generalised vertical sections of the Dinantian strata of the Askrigg Block, Craven Basin and Derbyshire Dome.

(Figure 9) Sketch illustrating the main environments of carbonate deposition in the Dinantian (not to scale). For the purpose of this book, the whole elevated mass of carbonate rock is termed the ‘platform’.

(Figure 10) Sketch reconstruction of a framework community from the late Visean apron reefs (this example from Stebden Hill, North Yorkshire).The matrix is fine-grained limestone showing microbial lamination and the associated fauna is a specialised community of sponges, bryozoans and shelly forms that lived in the shallowest parts of the reef complex. (after Mundy in McKerrow, 1978, fig. 44). Tabulate corals a Michelinia; b Sutherlandia; c Cladochonus. Rugose coral d Cyathaxonia. Bryozoans e Fistulipora and Tabulipora; f Fenestella. Lithistid sponge g Haplistion. Pseudomontid bivalve h Pachypteria. Brachiopods i ‘Reticularia’, j Stenocisma, k Streptorhynchus; l Leptagonia. Ostracod m Entomoconchus. Geopetal infillings of shell (n) and a growth cavity (o) Surfaces of fill were horizontal at time of deposition.

(Figure 11) Schematic cross-section of the Askrigg Block (after Wilson, 1992, fig. 4).The limestones on the Askrigg Block are collectively termed the Great Scar Limestone Group. See (Figure 8) for succession below the Ashfell Sandstone in the Raydale Borehole; see (Figure 12) for configuration of strata across the Middle Craven Fault.

(Figure 12) Simplified geological map and cross-section of the Craven Reef Belt.The once-continuous apron reef topography was buried by the onlapping Bowland Shale Group, and the present-day outcrops represent an exhumed pre-Namurian surface.

(Figure 13) Two contrasting cyclothems of Brigantian age. Note different scales. a The Five Yard Cyclothem of the Wensleydale Group recorded in the Gunnerside Borehole [SD93850126] near Muker, Askrigg Block (after Dunham and Wilson,1985,fig.3). b Cyclothem in the Monsal Dale Limestones of the Derbyshire Block at Crich (after Bridges, 1982, fig. 3). The Askrigg Block was subjected to repeated progradation and drowning of a river delta, whereas the Derbyshire Block was beyond the reach of terrigenous clastic input, but subject to the same eustatic sea-level oscillations.

(Figure 14) Some generalised composite sections of areas in the Craven Basin to illustrate the Dinantian stratigraphy (after Riley, 1990).

(Figure 15) Distribution of igneous rocks in the Peak District Dinantian outcrop.

(Figure 16) Schematic section across the region showing the main Namurian sandstone units and stage boundaries. Inset map shows the centre points and names of the BGS 1:50 000 sheets, the generalised vertical sections of which were used to compile the section. Abbreviations AsG Ashover Grit; BB Brooksbottom Grit; BrG Brennand Grit; CG Chatsworth Grit; CoSS Cocklett Scar Sandstones; DuCS Dure Clough Sandstones; EdG Eldroth Grit; ElCr Ellel Crag Sandstone; ES Edale Shale Group; FB Fletcher Bank Grit; FCS Five Clouds Sandstones; GG Grassington Grit; GGt Gorpley Grit; GtG Greta Grits; HB Holcombe Brook Grit; HG Hazel Greave Grit; HHb Heysham Harbour Sandstone; HM Helmshore Grit; HR Huddersfield White Rock; KG Kinderscout Grit; LFG Lower Follifoot Grit; LH Lower Haslingden Flags; LoS Longnor Sandstones; LvS Laverton Sandstone; ML Main Limestone; Mp Marchup Grit; Not Nottage Crag Grit; PG Pendle Grit; PS Parsonage Sandstone; PH Pule Hill Grit; R Rough Rock; RoG Roaches Grit; RSG Red Scar Grit; SG Shale Grit; SlvS Silver Hills Sandstone; SnS Sheen Sandstones; ToD Todmorden Grit; UBS Upper Bowland Shale Formation; WrSt Ward’s Stone Sandstone; WWG Warley Wise Grit

(Figure 17) Abbreviations UBS Upper Bowland Shale Formation Marine bands  Ca Cancelloceras cancellatum; Cgi Cayton Gill Shell Bed; Cc Cravenoceras cowlingense; Hm Hodsonites magistrorus; Bg Bilinguites gracilis;    Cl Cravenoceras leion; Sb Subcrenatum; Is Isohomoceras subglobosum Sandstones AC Alum Crag Grit; AD Addlethorpe Grit; AlmG Almscliff Grit; BB Brooks Bottom Sandstone; BBG Brocka Bank Grit; BG Bramhope Grit; BHF Beacon Hill Flags; CCG Caley Crag Grit; EC East Carlton Grit; G Guiseley Grit; GG Grassington Grit; FB Fletcher Bank Grit; HB Holcombe Brook Grit; HG Hazel Greave Grit; HM Helmshore Grit; HMS High Moor Sandstone; HR Heyden Rock; Hro Harrogate Roadstone; KG Kinderscout Grit; LFG Lower Follifoot Grit; LK Lower Kinderscout Grit; LM Lindley Moor Grit; LPG Lower Plompton Grit; MgG Midgley Grit; Mn Middleton Grit; Mp Marchup Grit; NS Nesfield Sandstone; PG Pendle Grit; PS Parsonage Sandstone; R Rough Rock; RD Readycon Dean Formation; RF Rough Rock Flags; SF Scotland Flags; SG Shale Grit; TG Todmorden Grit; UFG Upper Follifoot Grit; UH Upper Haslingden Flags; UK Upper Kinderscout Grit; UPG Upper Plompton Grit; WR Huddersfield White Rock; WWG Warley Wise Grit (Figure 17) Comparative generalised vertical sections of Namurian strata in a north-east–south-west transect across the region. Inset shows centre points of the BGS 1:50 000 sheets, the generalised vertical sections of which were used to compile the sections.  See opposite for abbreviations

(Figure 18) Sections of the Edale Shale Group representing various palaeogeographical settings. North Staffordshire Basin (Werrington Anticline and Blake Brook): Edale Basin (Alport Borehole and outcrop): condensed successions overlying the Derbyshire carbonate platform (Stoop Farm Borehole, Birchover Borehole SK26SW/37 and Tansley Borehole): Widmerpool Gulf (Carsington composite boreholes, Duffield Borehole and outcrop). Inset map shows outcrop and section locations.  Abbreviations Bb Bilinguites bilinguis; Bg B. gracilis; Bm B. metabilinguis; Cc Cravenoceras cowlingense; Cl C. leion; Cm C. malhamense; Cte Cravenoceratoides edalensis; Ctn Ct. nititoides; Ef Eumorphoceras ferrimontanum; Hm Hodsonites magistrorus; Hdp Hudsonoceras proteum; Is Isohomoceras subglobosum; Nn Nuculoceras nuculum; Ns N. stellarum; Rc Reticuloceras circumplicatile; Rn R. nodosum; Rr R. reticulatum; Rs R.sp. nov.; Rt R. todmordenense; R sp(c) R.sp. (circumplicatile group); Tp Tumulites pseudobilinguis. Abbreviated symbols for the stages are shown to the left of each column (see (Figure 17)).

(Figure 19) Comparative sections of the R1a Zone successions in starved basin (1) and ramp settings (2 and 3). See (Figure 20) for locations. (Plate 12) Mam Tor [SK 128 835] near Castleton, showing the great landslip scar on the east face.This exposes the Edale Shale Group at the base, passing up into the Mam Tor Beds.The latter represent the first turbidite influx of feldspathic sand into this part of the Pennine Basin in late Kinderscoutian times (L211).

(Figure 20) Comparative sections of the Kinderscout Grit and equivalent late Kinderscoutian (R1c Zone) strata. Inset map shows location of sections 1–7; Sections of the Knott Coppy Borehole (KC) and Farnham Borehole (1) and of Salmesbury Bottoms (SB) are shown on (Figure 19).

(Figure 21) Distribution of Westphalian strata in the region.

(Figure 22) Generalised sections of Westphalian strata in the region.

(Figure 23) Washouts in the Top Hard Coal in the East Midlands (based partly on Elliott, 1969, fig. 4).The sandstone is not a single sheet, but a series of superimposed sinuous channel fills. Only the deepest scours have cut down into the coal.

(Figure 24) The Silkstone Rock east of Sheffield (based on Guion et al., 1995). Scales are approximate.The Threequarters Coal splits and increases in ash content towards the sandstone channel before dying out (north side), and has been eroded out locally by a lateral shift of the channel (south side). Despite the width of the channel belt, the Yard Coal is only rarely affected by washout.

(Figure 25) Two kinds of seam split. a Map shows location of split over area of thin sediment (based on Lake, 1999). b Map shows close association between the line of split and the Deerplay Fault (based on Wright et al., 1927, and Broadhurst and Simpson, 1983). Note that the present downthrow of the fault is to the north-east, but that the downthrow must have been to the south-west during coal deposition.

(Figure 26) Schematic sections, based on numerous borehole records, to illustrate lateral variations in the lowest Coal Measures (‘Ganister Coal Series’) across the Pennine region. Above, East Pennines; below, Lancashire and Yorkshire.

(Figure 27) Early Permian environments (after Smith, 1989, 1992; Smith and Taylor, 1992).

(Figure 28) Late Permian (approximately Zechstein Cycle EZ1) environments and generalised Permian successions (after Smith, 1992; Smith and Taylor, 1992).

(Figure 29) Early Triassic (Sherwood Sandstone Group) environments and stratigraphical successions (after Warrington and Ivimey-Cook, 1992).

(Figure 30) Late Triassic environments and generalised successions of the Mercia Mudstone Group (after Warrington and Ivimey-Cook, 1992;Wilson, 1990, 1993; Charsley et al., 1990).

(Figure 31) Correlation of deep-sea oxygen isotope temperature curve (tuned to orbital timescales after Imbrie et al., 1984) with standard British Quaternary stages. Peaks to left of centre shaded black indicate extremely cold tundra and possible glacial conditions, at least in upland Britain. Stadials are denoted by black bars and interglacials by white bars.

(Figure 32) Distribution of pre-Late Devensian relict deposits. For locations of Victoria Cave and Chelford sand pits see (Figure 33). Abbreviations for selected caves and open sites with pre-Late Devensian fossiliferous deposits are: AH Armley (Leeds) hippopotamus site; Au Austerfield interglacial site; Ar Armthorpe interglacial site; BQ Boden’s Quarry; CC Cresswell Crags;DH Victory Quarry, Dove Holes; EB Elder Bush Cave; Et Etches Cave; FH Fox Hole Cave; HF Hazlebadge Fissure; HG Hoe Grange Cave; La Langham interglacial site; Ox Oxbow opencast site, Leeds; RD Raygill Delph;WN Windy Knoll

(Figure 33) Features related to the Dimlington Stadial glaciation. Also shown are isolated earlier deposits lying within the limit of this glaciation and Late glacial cirque glaciers. Names of selected features are abbreviated as follows: CC Calder Channel; CG Cliviger gap; Ch Chelford sand pits; EM Escrick Moraine; FG Foulridge Gap; FM Flaxby Moraine; GG Guiseley gap; H-AE Helperby-Aldwark esker; HE Hunsingore esker; L–S Leeming–Sutton Howgrave esker; LS Linton–Stutton kame belt; N–C Newby Wiske–Cundall esker; PA proto-Aire; PD proto-Don; PI proto-Idle; PO proto-Ouse; PN proto-Nidd; PS proto- Swale; PU proto-Ure; RD Raygill Delph; RE Roecliffe esker; SG Stainmore Gap;TM Tollerton moraine; VC Victoria Cave WC Walsden channel; YM York moraine.

(Figure 34) Depth contours (in metres below OD) to the top of Caledonian basement. Note that the main faults are principally subsurface structures, the surface expressions of which are generally minor, or, in some cases, unrecognised.The fault locations are plotted at top basement level and are slightly offset laterally from their positions at outcrop. N–S indicates line of section of (Figure 36)

(Figure 35) Principal early Carboniferous extensional structures (red) and end-Carboniferous (Variscan) inversion structures (black). Note that the extensional structures are mapped in the subsurface at top basement level where they are somewhat offset from their surface location.The Variscan structures are much shallower features and their surface locations are shown. Dashed lines indicate major subsurface structures with only minor or unrecognised surface expression. (see p.123 for abbreviations) Abreviations used on (Figure 35) (opposite) AA Ashover Anticline; AlB Alport Basin; AlF Alport Fault; AsB Askrigg Block; ASF Askern-Spittal Fault; BaF Bakewell Fault; BAF Bolton Abbey Fault; BoA Bolton Anticline; BoL Bowland Line; CaA Catlow Anticline; CBA Calow-Brimington Anticline; CiF Cinderhill Fault; ClA Clitheroe Anticline; CLH Central Lancashire High; CrA Crich Anticline; DeF Dent Fault; DVF Darwen Valley Fault; DiA Dinkley Anticline; EaA Eakring Anticline; EdB Edale Basin; EA Ecton Anticline; EFF Eakring–Foston Fault; EgF Egmanton Fault; EMP East Midlands Platform; EsA Eshton Anticline; GA Greenhow Anticline; GaT Gainsborough Trough; GiA Gisburn Anticline; GrA Grindleton Anticline; GS Goyt Syncline; HaA Harrogate Anticline; HeA Hetton Anticline; HeF Heywood Fault;HMA Hardstoft-Mansfield Anticline; HoA Howgills Anticline; HoF Holme Fault; HoH Holme High; HuB Huddersfield Basin; HuM Hutton Monocline; LEA Longstone Edge Anticline; LoA Lothersdale Anticline; MCF Middle Craven Fault; MiA Middop Anticline;MMA Mixon-Morridge Anticline; MoA Mossley Anticline; MoCF Morley-Campsall Fault; NCF North Craven Fault; NNA Nicky Nook Anticline; PeF Pendle Fault; PeM Pendle Monocline; PFA Plantation Farm Anticline; PL Pennine Line; PM Pennine Monocline; QuT Quernmore Thrust; RoB Rossendale Basin; SA Skyrholme Anticline; SCF South Craven Fault; SeA Sessay Anticline; SkA Skipton Anticline; SlA Slaidburn Anticline; StD Stockdale Disturbance; StF Stockdale Fault; StT Stainmore Trough; SwA Swinden Anticline; SyA Sykes Anticline; TA Thornton Anticline; TaA Taddington Anticline; ThA Thornley Anticline; TSB Todmorden Smash Belt; WeA Wheatley Anticline; WhA Whitewell Anticline; WiG Widmerpool Gulf; WoH Woo Dale High.

(Figure 36) Cross-section through the Pennine region (vertical exaggeration _ 2.5; see ((Figure 34)) and ((Figure 40)) for line of section). ClA Clitheroe Anticline; GrA Grindleton Anticline; HeF Heywood Fault; MCF Middle Craven Fault; NCF North Craven Fault; PeF Pendle Fault; PeM Pendle Monocline; SCF South Craven Fault; StD Stockdale Disturbance; StF Stockdale Fault.

(Figure 37) Simplified cross-section through the Craven Basin illustrating the process of basin inversion. a Late Carboniferous times immediately prior to inversion. b End Carboniferous times, compressive stresses causing crustal shortening and basin inversion. Dashed lines denote strata subsequently eroded to form presentday land surface.

(Figure 38) Seismic reflection profile across the southern margin of the Craven (Bowland) Basin showing major inversion structure. Note thickening of the syn-rift succession across the northerly downthrowing Pendle Fault and the overlying (Variscan) south-facing Pendle Monocline.

(Figure 39) True-scale cross-sections through Variscan inversion structures of the Ribblesdale Fold Belt. a Whitewell and Plantation Farm anticlines near northern margin of the Bowland Sub-basin b Grindleton Anticline c Clitheroe Anticline

(Figure 40) Depth contours (in metres below OD) to the base of the Permo-Triassic succession. N–S indicates line of section of (Figure 36). BrF Brook House Fault; IVF Irwell Valley Fault; PeF Pendle Fault; WBF Western Boundary Fault; WoF Woodsfold Fault.

(Figure 41) Significant oil and gas discoveries in the Pennine region and late Dinantian–Namurian source rock potential (red–oil; green–gas).

(Figure 42) Seismic reflection profile through the Eakring Anticline.The Eakring and Kirklington oilfields are situated on the crest of this anticline. Oil accumulations shown diagramatically.

(Figure 43) Industrial mineral resources of the Pennine region.

(Figure 44) Metalliferous mineral occurrences in the Pennine region.

Plates

(Front cover) Gordale Beck emerging from Gordale Scar, one of the major scenic attractions in the Yorkshire Dales National Park. (Photographer Colin Raw)

(Plate 1) Upper Ordovician (Ashgill) fossils from the Dent Group of the Craven inliers. Brachiopods: i Eremotrema paucicostellatum Mitchell (X3); ii Christiana sp. (X2); iii Dolerorthis inaequicostata Wright (X2); iv Eoplectodonta rhombica (McCoy) (X1.5); vi Strophomena shallockiensis Davidson (X3). Cystoid: v Haplosphaeronis mutifida Paul (X1). Trilobites: vii tail-piece of Pseudosphaerexochus conformis (Angelian) (X1.5); ix Atractopyge scabra Dean (X2). Alga: viii dasycladacean thallus (X2).

(Plate 2a) Turbidite sandstones in Austwick Formation. a Parallel bedded, turbiditic sandstones up to 2 m thick, separated by laminated siltstone, Arcow Wood Quarry [SD 803 703] (L2351).

(Plate 2b) Turbidite sandstones in Austwick Formation. b Flute casts on the base of turbiditic sandstones near Newfield House [SD 800 692].They indicate palaeocurrents from the south-east (right side of photograph) (L2353).

(Plate 3) Sub-Carboniferous unconformity, Combs Quarry [SD 800 701], Foredale, near Horton in Ribblesdale. Subhorizontal Kilnsey Formation rests on an erosion surface cut in steeply dipping Horton Formation (L2360).

(Plate 4) A selection of Carboniferous fossils from the region.Westphalian ammonoid (i), non-marine bivalves (ii, iii), marine—brackish brachiopod (iv), arthropod (v) and plant (vi); Namurian ammoniods (vii, viii, ix) and marine bivalves (x), Dinantian coral (xi) and brachiopod (xii).  i Gastrioceras listeri (x0.34). LZ 238. Bullion Mine, Blackburn. ii Naiadites flexuosus (x0.5 approx). He 1876. Middle Coal Measures. Bolton. iii Anthracosia cf. phyrgiana (x0.36). He 2956. Middle Coal Measures. Manchester. iv Lingula mytilloides (x0.5). GA 234. Oxbow Opencast Site, Leeds. v Euproops rotundata (x0.23). LZ 5543. Oxbow Opencast Site extension, Leeds. vi Neuropteris GSM 76249. vii Gastrioceras cancellatum (x0.42). GSM 54234. Cribden Clough, Lancs. viii Reticuloceras reticulatum (x0.8). GSM 30803. Hebden Bridge, Yorkshire. ix Reticuloceras todmordense (x0.64). GSM 83927. Pendle, Lancs. x Posidonia gibsoni (x0.44). Bd 382. Kirkheaton, Yorkshire. xi Cythoclisia modavensis (x0.5). 5092. Ribblesdale, Lancs. xii Spirifer coplowensis (x0.36). 3261.

(Plate 5) Kilnsey Crag [SD 974 683], Great Scar Limestone Group.The type section of the Kilnsey Formation forms the overhanging cliff and is overlain by the Malham Formation at the top of the crag (L2693).

(Plate 6) Gordale Scar [SD 9153 6404] near Malham.This deep gorge was eroded largely by glacial melt waters cutting through the limestones of the Malham Formation near the southern edge of the Askrigg Block (L2706).

(Plate 7) High Tor, Matlock.A 30m-high knoll-reef in the late Brigantian Eyam (or Cawdor) Limestone Formation dominating the gorge of the River Derwent below Matlock, Derbyshire (MN39751).

(Plate 8) Ravens Tor, Dovedale [SK 1412 5385]. Massive, pale micritic limestones forming the core of a knoll-reef pass laterally into well-bedded crinoidal limestones seen at the right-hand end of the crag (L1606).

(Plate 9) Core from the Hag Farm Borehole. Basal part of the Addingham Edge Grit with prominent fresh pink feldspar crystals (MN2736).

(Plate 10) Excavation in Upper Bowland Shale Formation near Blindhurst [SD 5888 4504] on the southern escarpment of the Bowland Fells near Chipping. It exposes a typical interbedded succession of blocky, yellow-brown weathering, calcareous mudstones and siltstones, and dark grey, fissile mudstones (L14794).

(Plate 11) Sandstones of the Pendle Grit Formation exposed in a 20 m face in a disused quarry [SD 6143 3796] near Longridge.The sandstones are medium to coarse grained, with quartz pebbles and mudstone clasts in some beds.The beds appear to be internally structureless and have sharp bases resting on erosion surfaces cut in the underlying thin, dark grey, shaly mudstone interbeds (A14816).

(Plate 13) Brimham Rocks.Tors of cross-bedded sandstones of the Lower Brimham Grits, of Namurian R1 age at Brimham Rocks, North Yorkshire (L1384).

(Plate 14) Crags, up to 17 m high, on the escarpment formed by the Rough Rock overlooking the Calder valley below Albert Promenade, Halifax [SE 083 234].The crags consist of coarse-grained, cross-bedded, pebbly sandstones, characteristic of the Rough Rock, which crops out over a wide area of the Pennines.The sandstones are interpreted as braided river deposits.The greater part of Halifax lies on the dip slope of this rock, to the right (north-east) of the photograph.The photograph (A3577) was taken in July 1926. A dense cover of trees now extends up to the crags.

(Plate 15) Swillington brickworks near Leeds, 1991.The section illustrates the alternation of sandstone (pale brown) and mudstone (grey) typical of Coal Measures successions.The sandstone at the base is the Thornhill Rock (A15258)

(Plate 16) Cutting for M62 motorway at Lofthouse [SE 322 263], near Wakefield, in 1998. A thin coal seam (Beck Bottom Stone Coal) is directly overlain by a thick sandstone, the Horbury Rock (pale brown colour) (photo J I Chisholm).

(Plate 17) Fenay Bridge brickpit [186 156], near Huddersfield, in 1996.The coal is the Black Bed Coal (Lower Coal Measures) (photo J I Chisholm).

(Plate 18) Elland Edge [SE 120 125], an escarpment near Halifax capped by Elland Flags sandstones (Lower Coal Measures). An old brickpit at the foot of the slope shows a section of grey mudstones from just above the 36 Yard Coal up to the base of the 80 Yard Rock (three pale layers at the top of the face) (photo R Addison).

(Plate 19) The Carboniferous–Permian unconformity at Abbey Crags [SE 3550 5583], Knaresborough Gorge. Large-scale cross-bedded, oolidal limestones of the Cadeby Formation rest unconformably on a buried hill of Namurian Upper Plumpton Grit (L1814).

(Plate 20) Devensian lacustrine sand and gravel overlying pre-Ipswichian cryoturbated glaciofluvial sand and gravel at Austerfield near Doncaster.

(Plate 21) ‘Clint’ (or ‘grike’) karst dissolution in a pavement of limestones of the Gordale Member of the Malham Formation above Malham Cove [SD 896 642] (L2402).

(Plate 22) Satellite image showing the drumlin fields in the north-west of the region.

(Plate 23) Swaintley Hill [SD 586 625], a conical moulin kame, the Haylott meltwater channel and upper Roeburndale, viewed from the north-west. Mallowdale Pike lies in the right middle distance and White Hill in the far distance on the left (A15504).

(Plate 24) Glaciofluvial sand and gravel in a disused gravel pit [around SE 4760 6620] between Tholthorpe and Flawith. About 1.5 m of red-brown, cross-bedded, fine-grained sand with lenses of pebble and cobble gravel forming part of the Helperby–Aldwark esker complex (L3079).

(Plate 25) Sharp, symmetrical, straight-limbed folds, probably caused by valley-bulging under periglacial conditions, in thinly bedded turbidite sandstones and shales in the uppermost Edale Shale Group.They are overlain by a thin layer of head deposits. Bank of the River Ashop at Rowlee Bridge [SK 149 890] (L498).

(Plate 26) Folded turbidite limestones of the Ecton Limestone Formation in roadside quarries near Apes Tor in the Manifold Valley [SK 0990 5867].The structures are minor ones within the Ecton Anticline (L1180).

(Plate 27) Opencast coal working in the Middleton Main Coal and overlying beds (Lower Coal Measures) at Skelton [SE 349 308], near Leeds in 1991 (A15228).

(Plate 28) Dolerite sill in the now-closed Water Swallows Quarry [SK 085 750], near Buxton. Columnar jointing of the dolerite can be seen in foreground, the limestone beneath the sill appears in the centre of the photograph (L239).

(Plate 29) Collapse caused by gypsum dissolution at a house in Ure Bank Terrace, Ripon (MN27922A).

Tables

(Table 1) Geological succession of the rocks and deposits of the Pennine region.

(Table 2) Early Palaeozoic stratigraphy of the Craven inliers. Lithostratigraphical names based on Kneller et al., 1993; Ordovician chronostratigraphy based on revision of Fortey et al., 1995 and ages (in millions of years before present) from Tucker and McKerrow, 1995.

(Table 3) Classification of the Carboniferous rocks.

(Table 4) Summary of the depositional environments and lithologies of some of the principal Dinantian formations and groups in the three main outcrop areas. Boundaries between the environments were commonly gradational and some thicker formations extend laterally and vertically across these boundaries.

(Table 5) Summary of the principal events affecting Dinantian deposition in the Craven Basin (after Riley, 1990).

(Table 6) The age relationships of the Dinantian rock units at outcrop and in deep boreholes in the Derbyshire Dome. Note that the table shows units additional to those represented on (Figure 8), which crop out in the south-west of the Peak District.

(Table 7) Stages, marine bands, biozones and lithostratigraphy of the Namurian.

(Table 8) Names of sandstones in the Millstone Grit and Edale Shale groups used on 1:50 000 scale geological maps of the region.The stratigraphical position of the sandstone is shown in relation to the closest overlying marine band, either present or inferred.

(Table 9) Fossils from the Reticuloceras todmordenense Marine Band (R1a4) from three localities representing basin, lower ramp and upper ramp environments (see also (Figure 18)).

(Table 10) Classification of Westphalian strata in the Pennine Basin.

(Table 11) Formations in the Warwickshire Group.

(Table 12) Representative regional deposits, features and events related to the Quaternary stratigraphical framework and timescale.

(Table 13) Licensed groundwater abstraction and use.

Map

(Map 1) 1:625 000 scale geological map of the region in back pocket

Tables

(Table 4) Summary of the depositional environments and lithologies of some of the principal Dinantian formations and groups in the three main outcrop areas.

Boundaries between the environments were commonly gradational and some thicker formations extend laterally and vertically across these boundaries.

Palaeo– environment Typical lithologies Examples at outcrop in the region
Platform Thickly bedded, pale grey to grey, massive bioclastic limestones (packstones and grainstones), dolomitised limestones and dolomites Great Scar Limestone Group (A),Woo Dale Limestones, Bee Low Limestones and Monsal Dale Limestones (D), Kevin Limestones and Milldale Limestones (S)
Ramp Grey to dark grey, thinly bedded, bioclastic limestones (packstones) commonly with chert nodules and pale grey micritic limestones forming knoll reefs (mud mounds) Clitheroe Limestone (C), Eyam Limestones
(D), Hopedale Limestones and Milldale Limestones (W)
Slope Limestone conglomerates and boulder beds, limestone turbidites commonly showing soft-sediment deformation structures and chert nodules Pendleside Limestone, and limestones in the Hodder Mudstone (C), Ecton Limestones and limestones in the Widmerpool Formation (W)
Basin Dark, thinly bedded, cherty, fine- grained limestones (wackestones) and dark grey to black, fissile and blocky mudstones Hodderense Limestone and Hodder Mudstone (C),Widmerpool Formation (W), Bowland Shale Group (C), with Pendleside Sandstones Member (C)

(Table 8) Names of sandstones in the Millstone Grit and Edale Shale groups used on 1:50 000 scale geological maps of the region.

The stratigraphical position of the sandstone is shown in relation to the closest overlying marine band, either present or inferred.

Widely used name(s) Other names Overlying Marine Band
 (marine band index in parentheses)
Rough Rock (underlain locally by Upper Haslingden Flags or Rough Rock Flags) Laverton Sandstone Subcrenatum
Lower Haslingden Flags Greta Grits (part) Cancelloceras cumbriense (G1b1)
Huddersfield White Rock; Chatsworth Grit (overlain locally by the Redmires Flags) Wandley Gill Sandstone; Holcombe Brook Grit underlain by Brooks Bottom Grit; Rivelin Grit Cancelloceras cancellatum (G1a1)
Ashover Grit; Roaches Grit (underlain locally by Corbar Grit & Five Clouds Sandstones) Hazel Greave Grit; Beacon Hill Flags; Guiseley Grit Bilinguites superbilinguis (R2c1)
Helmshore Grit†
Fletcher Bank Grit†; Midgley Grit; Revidge Grit		 Greta Grits (part); Gorpley Grit; Woodhouse Grit; Brandon Grit; Pule Hill Grit; Heyden Rock; Sheen Sandstones Bilinguites metabilinguis (R2jBilinguites eometabilinguis (R2b4)
Alum Crag Grit† Greta Grits (part);Woodhouse Flags; Scotland Flags Bilinguites bilinguis (R2b3)
East Carlton Grit Readycon Dean Flags Bilinguites bilinguis (R2b2)
Upper Kinderscout Grit Heysham Harbour Sandstone; Upper Brimham Grit; Upper Plompton Grit; High Moor Sandstone; Longnor Sandstones; Kniveden Sandstones Bilinguites gracilis (R2a1)
Lower Kinderscout Grit underlain by Shale Grit & Man Tor Beds Bramhope Grit;
Doubler Stones Sandstone		 Butterly (R1C5)
Eldroth Grit; Lons Ridge Sandstone; Lower Plompton Grit Reticuloceras coreticulatum (R1C4)
Addingham Edge Grit;Addlethorpe Grit; Caley Crags Grit; Lower Brimham Grit Reticuloceras reticulatum (R1C2)
Knott Coppy Grit†; Blackstone Edge Sandstones Reticuloceras stubblefieldi (R1b3)
Ellel Crag Sandstone Addlethorpe Grit† Reticuloceras dubium (R1a5)
Upper Follifoot Grit†; Brocka Bank Grit Hodsonites magistrorum (R1a1)
Accerhill Sandstone Homoceras undulatum (H2b1)
Lum Edge Sandstones Hudsonoceras proteum (H2a1)
Middleton Grit; Lower Follifoot Grit Silver Hills Sandstone† Isohomoceras subglobosum (H1a1)
Nesfield Sandstone Hurdlow Sandstones; Scar House Beds† Nuculoceras nuculum (E2c2)
Red Scar Grit†;Ward’s Stone Sandstone Minn Sandstones (part) Cravenoceratoides edalensis (E2b1)
Marchup Grit Sapling Clough Sandstone Eumorphoceras yatesae (E2a3)
Cocklett Scar Sandstones Minn Sandstones (part) Saleswheel (E2a2b)
Dure Clough Sandstones Eumorphoceras ferrimontanum (E2a2)
Grassington Grit.Warley Wise Grit Brennand Grit;Almscliff Grit; Minn Sandstones (part) Cravenoceras cowlingense (E2a1)
Pendle Grit Grassington Grit (part) Blacko (E1c2)

(Table 9) Fossils from the Reticuloceras todmordenense Marine Band (R1a4) from three localities representing basin, lower ramp and upper ramp environments (see also (Figure 18)).

Basin
Preston district: River Darwen. Salmesbury Bottoms [SD 6185 2900]		 Lower ramp
Settle district: Knott Coppy Borehole (SD76SE/16) [7698 6449]		 Upper ramp
Harrogate district: Farnham Borehole (SE35NW/27) [3469 5996]
Corals Rotophyllum sp.
Brachiopods Lingula mytilloides Crurithyris sp.
L. squamiformis L. mytilloides
Orbiculoidea sp. Orbiculoidea sp.
Productus carbonarius
Rugosochonetes sp.
Schizophoria sp.
Scaphopods Coleolus sp.
Gastropods Bellerophon sp.
Euphemites sp.
Bivalves Caneyella squamula Caneyella squamula Anthraconeilo
Dunbarella rhythmica Dunbarella rhythmica laevirostrum
Posidonia sp. ‘Modiola’ sp.
Posidonia obliquata
Sanguinolites sp.
Nautiloids orthocones Huangoceras sp.
Ammonoids Reticuloceras Reticuloceras dimorphoceratid
paucicrenulatum paucicrenulatum anthracoceratid
R. todmordenense R. todmordenense Reticuloceras
Vallites sp. R. aff adpressum paucicrenulatum
Anthracoceratids Vallites sp.
Metadimorphoceras sp.
Arthropods Belotelson sp. Cavellina sp. ostracods
Schleesha sp.
Crinoids crinoid ossicles crinoid ossicles

 (Table 11) Formations in the Warwickshire Group.

Warwickshire Pennines
Standard names Standard names Older names in Lancashire
ASHOW FORMATION
KENILWORTH SANDSTONE FORMATION
TILE HILL MUDSTONE FORMATION
SALOP FORMATION ?SALOP
FORMATION		 ARDWICK
HALESOWEN FORMATION HALESOWEN
FORMATION		 LIMESTONES
ETRURIA FORMATION ETRURIA
FORMATION		 ARDWICK MARLS
COAL MEASURES

(Table 13) Licensed groundwater abstraction and use.

Aquifer/Use Total Public
Licensed Supply*
(Mm3/a) (%)		 Industrial
(%)		 Agriculture
(%)		 Other
(%)
CARBONIFEROUS LIMESTONE
Peak District 27.02381 17 1 1
North Pennines 16.40484 4 8 4
Total 43.42782 12 3 2
MILLSTONE GRIT 30.97464 27 9
COAL MEASURES 25.06229 50 2 19
MAGNESIAN LIMESTONES 22.91224 51 23 2
SHERWOOD SANDSTONE GROUP†
East area 260.88273 19 7 1
West area 219.56568 27 5
Total 480.44770 23 6 1