Geology of the country around Brough-under-Stainmore. Memoir for 1:50 000 geological sheet 31 and parts of sheets 25 and 30

by I. C. Burgess and D. W. Holliday

Bibliographical reference: Burgess, I. C. and Holliday, D. W. 1979. Geology of the country around Brough-under-Stainmore. Mem. Geol. Surv. G.B., Sheet 31. 131 pp.

Geological Survey of Great Britain England and Wales

• Authors: I. C. Burgess and D. W. Holliday
• Contributors:
• Stratigraphy: C. R. Burch, J. H. Hull and D. A. C. Mills
• Palaeontology: Monograptus A. Calver, J. Pattison and A. W. A. Rushton
• Petrography: R. K. Harrison

Institute of Geological Sciences Natural Environment Research Council

London Her Majesty's Stationery Office 1979. © Crown copyright 1979. Typographic design by HMSO Graphic Design: D. Monograptus Challis. Printed in England for Her Majesty's Stationery Office by Ebenezer Baylis and Son, Limited. The Trinity Press, Worcester, and London. ISBN 0 11 884005 3*

(Front cover)

(Back cover)

Other publications of the Institute dealing with the geology of this and adjoining districts

Books

• British Regional Geology: Northern England (4th edition)
• The Geology of the Cross Fell area
• Geology of the Penrith district (in press)
• Geology of the Northern Pennine Orefield: Volume 1, Tyne to Stainmore
• Geology of the country around Barnard Castle

Maps

• 1:625000
• Sheet 2 Geological
• Sheet 2 Quaternary
• Sheet 2 Aeromagnetic
• 1:250000
• Lake District (in press)
• 1:50000 (and one inch to one mile)
• Sheet 24 (Penrith)
• Sheet 25 (Alston)
• Sheet 26 (Wolsingham)
• Sheet 32 (Barnard Castle)
• Sheet 40 (Kirkby Stephen)
• Sheet 41 (Richmond)
• 1:25000
• Cross Fell Inlier
• Middleton in Teesdale

Preface

The district covered by the Brough-under-Stainmore (31) Sheet of the 1:50000 geological map of England and Wales was originally surveyed on the six-inch scale by W. T. Aveline, C. T. Clough, J. R. Dakyns, W. H. Dalton, J. G. Goodchild, W. Gunn, T. McK. Hughes and R. Russell and was published on the one-inch scale as Old Series Sheet 102 SE (Solid and Drift) in 1893.

A systematic resurvey of the entire district on the six-inch scale was carried out in 1958–67 by Messrs I. C. Burgess, C. R. Burch, Dr D. W. Holliday, Messrs J. H. Hull and D. A. C. Mills under the supervision of Mr W. Anderson, myself, Dr E. H. Francis and Mr B. J. Taylor as District Geologists. A list of six-inch maps and the names of the surveyors are given. The 1:50000 map of the district was published in 1974, in two editions, Solid and Drift. Parts of the area are covered by the 1:25000 maps of Middleton in Teesdale (published 1974) and the Cross Fell Inlier (published 1972).

This memoir has been written mainly by Mr I. C. Burgess and Dr D. W. Holliday, and incorporates information from Messrs C. R. Burch, J. H. Hull and D. A. C. Mills. Mr J. Pattison contributed the chapter on Dinantian and Namurian palaeontology.

During the recent survey a large number of fossils were collected from the area by Messrs W. G. E. Graham, J. Pattison, Monograptus J. Reynolds, Monograptus D. Traynor and G. Richardson. The identification of these has been shared between the Palaeontological Department and outside specialists. We are grateful for the assistance of Professor D. Skevington and Dr R. B. Rickards in the identification of Ordovician and Silurian graptolites respectively. The Ordovician shelly faunas were identified by Dr A. W. A. Rushton, Dr D. E. White and Miss Monograptus E. Dutton, and the microfossils by Dr T. R. Lister; Lower Carboniferous faunas by Messrs J. Pattison and Monograptus Mitchell; the Namurian faunas by Mr J. Pattison and Dr W. H. C. Ramsbottom; the Westphalian faunas by Dr Monograptus A. Calver; the Permian faunas by Mr J. Pattison and the Quaternary ostracods by Miss D. Monograptus Gregory.

Petrographical descriptions were written by Mr R. K. Harrison, who has also contributed a detailed study of the Lower Palaeozoic igneous rocks. The account of the mineralisation is based on the work of Sir Kingsley Dunham, during the period 1939–45. The photographs, a list of which is given in Appendix 2, were taken by the late P. Joyce and Messrs P. Baker, J. Butcher, C. Friend and K. Thornton.

The memoir was prepared under the supervision of Mr B. J. Taylor.

We gratefully acknowledge the information and assistance generously provided by officials of Cumbria County Council concerning road works and of the Tees Valley and Cleveland Water Board concerning boreholes and excavations on their reservoir sites, and the willing cooperation of local landowners, mine and quarry operators, in particular Messrs Athole G. Allen (Stockton) Ltd of Closehouse Mine, Lunedale, at the time of the resurvey.

Austin W. Woodland, Director. Institute of Geological Sciences Exhibition Road, London SW7 2DE 6 July 1978

Six-inch maps

The following is a list of six-inch geological maps included in the area of 1:50000 Geological Sheet 31 with the names of the surveying officers, the publication date and the date of survey for each map. The officers are

I. C. Burgess, C. R. Burch, D. W. Holliday, J. H. Hull and D. A. C. Mills.

Manuscript copies of the maps are deposited for public reference in the libraries of the London and Leeds offices of the Institute of Geological Sciences. Uncoloured dyeline copies of these maps are available for purchase.

Notes

• In this book, the word 'district' means the area included in the 1:50000 geological Sheet 31 (Brough-underStainmore) together with small areas of the adjacent sheets 30 (Appleby) and 25 (Alston) (Figure 1).
• Numbers in square brackets are National Grid references within 100-km square NY.
• Numbers preceded by the letter E refer to the Sliced Rock Collection of the Institute of Geological Sciences.
• Numbers preceded by the letter L refer to the Geological Survey Photograph Collection of the Institute.
• The authorship of fossil species is given in the index.
• Descriptions of Ordovician volcanic rock colours (Appendix 3) are based on the Rock-Colour Chart of the Geological Society of America.

Geology of the country around Brough-under-Stainmore—summary

The Brough-under-Stainmore district is one of great scenic and scientific interest. It is an area of high Pennine moorland, drained by the Upper Tees and its tributaries, bordered on the west by the Pennine Escarpment and the lower-lying Vale of Eden, which form part of the catchment of the River Eden.

The district has been the subject of much previous research, though this memoir is the first comprehensive account of its geology. The widespread Carboniferous strata are considered in some detail as are the underlying Lower Palaeozoic rocks that crop out on the Pennine Escarpment. The quartz-dolerite Whin Sill, intruded into the Carboniferous strata of the north of the district, is especially well exposed in Upper Teesdale. The Vale of Eden is underlain by Permo-Triassic red beds with four thin anhydrite seams. Much of the district was overridden by glaciers during the Devensian period and the deposits of this and more recent times are described. The structural history and mineral products also are considered.

(Geological Sequence)

Chapter 1 Introduction

Area and location

This Memoir describes the geology of the district covered by the Brough-under-Stainmore (31) Sheet of the 1:50000 Geological New Series maps of England and Wales, together with small areas of the Appleby (30) and Alston (25) sheets on the western and northern margins (Figure 1). Brough under-Stainmore is situated at the southern end of the Vale of. Eden (Plate 1) and the district extends eastwards across the Pennine escarpment (Plate 1) and (Plate 2) and the Stainmore Gap nearly to Barnard Castle. The main watershed of England crosses the map from north-west to south-east, dividing it into two almost equal parts. The district formerly lay within three counties, Westmorland, Yorkshire and Durham, but since the reorganisation of Local Government boundaries, the western part of the area is now in the new county of Cumbria, while the eastern part lies wholly in the county of Durham.

The district is almost untouched by industrial and urban development. The small market towns of Brough-under Stainmore and Middleton in Teesdale are the main centres of population. The rich soils of the Vale of Eden and Tees Valley sustain both arable and livestock farming, but the steep slopes of the Pennine and Stainmore escarpments and the extensive peat-covered tracts to the east provide only rough grazing for sheep and horses, and large areas are used as grouse moor.

Mining, formerly a widespread source of employment, is now only active at Closehouse Barytes Mine, in Lunedale; but the old mine workings, mainly for lead and zinc, and the associated 'hushes' (Plate 13), are a conspicuous feature of many of the Pennine valleys. The tips provide a ready source of galena, sphalerite, fluorite and baryte for mineral collectors.

Coal, also, was formerly mined on a small scale at many localities and horizons-in the Lower Carboniferous (Borrowdale Coal, Stainmore), in the Namurian (Mirk Fell Coal, Baldersdale), and in the Westphalian (Argill Coalfield).

Quarrying on a small scale, for roadstone, walling stone and agricultural lime formerly occurred throughout the district, but at present only the Whin Sill (Teesdale), the Great Limestone (Lunedale and Teesdale) and the Robinson Limestone (Brough) are being worked to any extent.

The consistently high annual rainfall (up to 2000 mm in places) makes the area an important source of water. The River Tees (Cow Green Reservoir) and its tributaries, the Lune (Selset and Grassholme reservoirs) and Balder (Balder-head, Blackton and Hury reservoirs) all contribute to the resources of the industrial areas of the Lower Tees Valley. Some of the newer dams have been the subjects of published geotechnical reports (e.g. Kennard and others, 1967; Vaughan and others, 1975). The River Eden, though of equally high potential, is at present untapped.

Scenic beauty combined with geological and botanical interest, make the district a popular area for visitors, both amateur and professional. It is therefore important to note that at the time of writing access to parts of the area is restricted. The ground north-west of Brough, between the A66 and the Warcop to Hilton road, and including Musgrave Fell, Middle Fell, Long Fell and Roman Fell, forms the British Army Warcop General Training Area, and it is essential that the Commandant be consulted before parties or individuals attempt access to exposures in that area. Similarly, part of the ground north of Mickle Fell lies in the Upper Teesdale and Moor House National Nature Reserves, and permits to visit this area should be sought from the Nature Conservancy Council.

Outline of geological history

The Lower Palaeozoic history begins in early Ordovician (Arenig) times, when the district lay within a rapidly subsiding trough and a great thickness of greywacke grits and siltstones accumulated (Murton Formation). These beds became finer grained towards the top, and were followed in Llanvirn times by graptolitic mudstones, interbedded in their lower part with submarine andesitic and spilitic tuffs and rare lavas (Kirkland Formation). The rocks of these two formations, together included within the Skiddaw Group, were subsequently folded, uplifted and deeply eroded. On the eroded surface, there accumulated over 1000 m of subaerial acid tuffs and volcanic sandstones, the lateral equivalents of the much thicker Borrowdale Volcanic Group of the Lake District. After a further period of folding and erosion, this volcanic landmass was gradually submerged by a shallow shelf sea in which the limestones and siltstones of the Upper Ordovician Coniston Limestone Group were formed. The beginning of the Silurian (Llandovery) was marked by an increase in water depth and a return to the deposition of graptolitic mudstones (Skelgill Shales). These were followed by mainly barren mudstones, with thin graptolite bands (Browgill Beds). During Wenlock times, the main deposits were again graptolitic siltstones and mudstones (Brathay Flags), the youngest strata of Lower Palaeozoic age preserved. The greywacke grits and siltstones characterising the Ludlow Series in the Lake District are not exposed, but are presumed to have been laid down over the whole area, before the onset of the end-Silurian phase of the Caledonian Orogeny, during which all the Lower Palaeozoic rocks were folded and cleaved.

Towards the end of this orogeny, the Weardale Granite batholith was emplaced north of the Closehouse-Lunedale Fault. This intrusion is a factor of fundamental importance in the subsequent history of the north of England, forming the rigid, low-density core of the Alston Block and making it a positive area, almost continuously influencing local sedimentation, structure and topography through to the present day. The structures delineating the edges of the Block-the Pennine Faults and the Swindale Beck–Closehouse–Lunedale faults-have been active intermittently since end-Silurian times, with major movements occurring during the Caledonian, Armorican (late-Carboniferous) and Alpine (Tertiary) orogenies.

During the Devonian Period, the district was uplifted and deeply eroded. In early Carboniferous times, as the relief was gradually reduced, the hollows were filled with fluviatile sandstones and conglomerates of westerly derivation (Basement Beds) which probably formed part of a fluvio-deltaic complex built out into a sea to the south. Throughout the deposition of the succeeding strata, subsidence and sedimentation were evenly balanced. The depositional interface lay close to mean sea level, sometimes above, sometimes below, and there was an alternation of marine and deltaic deposition. In the lower part of the sequence (Orton Group and Lower Alston Group) the environment was dominantly marine and the main deposits were shallow-water limestones. The overlying strata (Upper Alston Group) display a rhythmic alternation of limestone with mudstones, siltstones and sandstones, the 'Yoredale' sequence. In the Namurian, deltaic deposits predominated, consisting mainly of sandstones and siltstones, with only thin, though widespread, limestones. Strata of early and mid-Westphalian age are now preserved only in the small Stainmore Outlier, but they are assumed to have been present over the whole district. The Carboniferous rocks were subjected to the stresses of the Armorican Orogeny; faulting and folding took place along the Pennine Line, and the quartz-dolerite Whin Sill was intruded into the sedimentary rocks of the Alston Block in the late Carboniferous or early Permian.

At a late stage in these movements, subsidence of the Vale of Eden area combined with a down-west movement on the Pennine Line to form an intermontane basin in which red dune-bedded desert sandstones and wadi breccias (Penrith Sandstone) of Lower Permian age accumulated. Mainly arid conditions persisted through the Upper Permian, though the nearby Zechstein Sea occasionally flooded the valley, and led to dolomitic limestone deposition, and to the establishment of coastal sabkhas in which beds of gypsum-anhydrite accumulated at intervals in a mainly continental siltstone and sandstone sequence (Eden Shales). Throughout the Permian the western edge of the Alston Block formed an escarpment, which was gradually buried by the desert sediments, and was probably finally covered by the fluviatile sandstones of the succeeding Permo-Triassic St Bees Sandstone.

There is a long gap in the geological record between the deposition of the St Bees Sandstone and of the superficial deposits of Pleistocene times. During this interval, east-west tensional stresses, of late Mesozoic or Tertiary (Alpine) age caused further down-west movement of the Pennine Line, and formed a fault scarp, the degraded edge of which is the present Cross Fell-Stainmore escarpment. The Tertiary Cleveland Dyke was intruded in this interval.

During the Pleistocene Period, an ice-sheet originating in the Lake District and Howgill Fells moved eastwards across the Vale of Eden and, crossing the Stainmore escarpment, became confluent with a glacier flowing down the Tees Valley. Much of the Alston Block was not covered, and the major valleys along the watershed nourished small glaciers flowing both east and west. The outstanding areas of high ground were subjected to extreme frost conditions, leading to solifluction and cambering on most slopes. As the ice-sheet wasted away, glacial meltwater cut a network of deep glacial channels on the lower ground, and laid down scattered areas of sand and gravel. These glacial deposits provide positive evidence for only one period of glaciation, believed to be of late Devensian age, though earlier glacial episodes may have occurred. ICB, DWH

Chapter 2 Ordovician

The main outcrop of Ordovician rocks in the district lies along the Pennine Line, and forms the southern part of the Cross Fell Inlier. All three main divisions of the Lake District sequence (Skiddaw, Borrowdale Volcanic and Coniston Limestone groups) are present (Figure 3), though intensely faulted and poorly exposed. Since the earliest description (Buckland, 1817) the area has been the subject of numerous papers, dealing with the inlier as a whole (Goodchild, 1889; Nicholson and Marr, 1891; Shotton, 1935; Burgess and Wadge, 1974) and with specialised aspects of the stratigraphy or structure (Hudson, 1937; Turner, 1927; Harkness, 1865; Harkness and Nicholson, 1877; Marr, 1906; Dean, 1959). ICB

A smaller area of Ordovician rocks in Upper Teesdale on the upthrown side of the Burtreeford Disturbance, was discovered by the Primary Surveyors (Dakyns, 1877; Gunn and Clough, 1878). Only part of this inlier occurs within the district where it includes rocks belonging to both Skiddaw and Borrowdale groups. The loose blocks of impure limestone thought by Gunn and Clough (1878, p.34) to resemble beds in the Coniston Limestone Group are more likely to be erratics of thermally metamorphosed limestones of the Orton Group (Lower Carboniferous) from Falcon Clints, a few hundred metres to the south-west. DWH

Skiddaw Group

Rocks assigned to the Skiddaw Group form the eastern part of the Cross Fell Inlier and most of the Teesdale Inlier, and are believed to underlie much of the intervening area of Carboniferous rocks. Elsewhere on the Alston Block, they have been proved in boreholes at Roddymoor (Woolacott, 1923) and Allenheads (Burgess, 1971). As in the Lake District, the subdivision and correlation of these rocks has been a subject of controversy. On the map, the group is divided on lithological grounds into two formations. The Murton Formation is a sequence of interbedded siltstones and fine-grained greywacke sandstones, intensely folded and cleaved. The Kirkland Formation is of graptolitic mudstone with interbedded volcanics, and is less strongly deformed.

In the Lake District, the biostratigraphy of the Skiddaw Group is based historically on graptolites (Eastwood and others, 1968, pp. 24–30). Zones identified include Didymograptus extensus and D. hirundo in the Arenig, and D. bifidus and, more recently (Wadge and others, 1970; Wadge, Nutt and Skevington, 1972), D. murchisoni in the Llanvirn. In the Cross Fell Inlier, graptolites are uncommon in the Murton Formation, and the precise age of these rocks cannot be established on this basis. In the mudstones of the Kirkland Formation, graptolites of the D. bifidus Zone are common, and they can be subdivided into Lower and Upper bifidus Zone faunas, the latter characterised in particular by abundant Nicholsonograptus fasciculatus (Skevington, 1970).

Analysis of the microfossils (acritarchs and chitinozoa) from the group suggests that they also may provide a means of dating the rocks. They have a wider distribution than the graptolites and have been recorded even from the highly cleaved rocks of the Murton Formation. Four assemblages have been distinguished (Lister and others, 1969), two of Arenig age from rocks assigned on a lithological basis to the Murton Formation and two of Llanvirn age corresponding with the lower and upper bifidus Zone graptolite faunas of the Kirkland Formation. ICB

The true stratigraphical position of the slates in the Teesdale Inlier was uncertain until recent palaeontological discoveries (Johnson, 1961; Lister and Holliday, 1970) confirmed their correlation with the Skiddaw Group. On lithological grounds they are referred to the Kirkland Formation. DWH

Murton Formation

Rocks of the Murton Formation crop out in a narrow strip almost 11 km long between Hilton Beck and Knock Ore Gill, bounded on the east by the sub-Carboniferous unconformity arid on the west by the Dufton Pike and Swindale Beck faults. Within this tract Murton Pike and Brownber form conspicuous hills. The dominant lithology is of pale to dark grey striped siltstone with subordinate interbedded pale grey sandstones 5 to 50 mm thick. In hand specimen bedding is commonly indicated by a faint colour banding, the result of slight variations in grain size. Throughout the outcrop, the rocks have suffered intense polyphase deformation; many exposures show complex folding and the first cleavage is the dominant surface. Where deformation is greatest, bedding and cleavage may coincide and the resulting surfaces are commonly lustrous owing to the development of secondary chlorite. Where thicker sandstone bands are present, the early (F₁) fold axes (p.76) show up as ridges or lines of quartz blebs, usually accompanied by limonite pseudomorphs after pyrite cubes up to 5 mm across. Extensive quartz veining occurs, commonly in association with structures related to the second folding episode (F₂). As a result no estimate can be made of the thickness of the formation. The base is nowhere exposed and contacts with the younger Kirkland Formation are faulted.

Details

Much of the outcrop is drift-free, and the lack of lithological contrast in the sequence results in smooth grass-covered slopes. Small fellside exposures are abundant, but sections large enough to display the complexities of the rocks are found only where ice and glacial meltwater have caused deep erosion. Good exposures of this kind are seen on the ridge at the foot of High Cup Gill [NY 7235 2365] to [NY 7214 2422] and on the south side of Brownber [NY 7045 2700] to [NY 7060 2472] where a conspicuous crag of vein quartz forms a scar visible for several kilometres. Smaller sections are found in Murton Beck [NY 7380 2235], Swindale Beck [NY 6956 2854] and Sink Beck [NY 6960 2890] and in the sides of the deeper glacial meltwater channels along the escarpment. Close to the sub-Carboniferous unconformity the slates are weathered and purple-stained to a depth of several metres, except in Scordale (Shotton, 1935, p.647). The suggestion that the slates underlying the unconformity differ from those of the thrust masses of Murton and Brownber (Shotton, 1935, p.648) was not confirmed during the resurvey. Some of the most highly deformed rocks of the inlier are exposed in Murton Beck east of the Murton Pike Fault and almost immediately underlying the unconformity; and the slates of Brownber are directly overlain by Lower Carboniferous Basement Beds on the north-east side of the hill.

Graptolites are uncommon in the Murton Formation. Shotton (1935, p. 648) recorded Glyptograptus sp.from Murton Pike. During the resurvey, only one fossiliferous locality was recorded. This is in a small quarry on the south side of the road from Hilton to Scordale [NY 7507 2126] which yielded Didymograptus cf. D. hirundo, D. ex gr. D. affinis and Glyptograptus sp.The precise age of this fauna is uncertain; it may be from the D. hirundo or D. bifidus zones (Professor D. Skevington, written communication, 1973).

Kirkland Formation

This formation is not well exposed and outcrops are fault-bounded, so that no detailed stratigraphy can be established. Work in the Penrith district (Arthurton and Wadge, in press; Burgess and Wadge, 1974) has established a twofold lithological division, into a lower, mainly volcanic, sequence of waterlaid tuffs, interbedded with subordinate graptolitic mudstones and an upper graptolitic mudstone sequence, the two corresponding in age with the lower and upper D. bifidus Zone faunas noted above. Within the Brough district, the volcanics (Appendix 3) are seen in three areas, on Roman Fell, north of Keisley and around Swindale Beck, Knock, where they form conspicuous crags. Mudstones are seen between Hilton and Murton becks, and are believed to underlie the unexposed ground west of Brownber. In the Teesdale Inlier only mudstones are seen, the volcanic rocks present being assigned on lithological grounds to the Borrowdale Volcanic Group.

Details

Graptolitic mudstones

Mudstones interbedded with tuffs are well exposed in Swindale Beck, Knock, around the junction with Sink Beck [NY 6932 2855], where they yielded an abundant fauna comprising Didymograptus acutus, D. arias?, D. ex gr. D. affinis, ?D. robustus, Aulograptus cucullus, Cryptograptus tricornis schaeferi and ?Glyptograptus dentatus. On this assemblage Professor Skevington comments 'As a whole, the collection is clearly indicative of the D. bifidus Zone-though precisely where within the Zone is difficult to say. On negative evidence-viz. the lack of specimens of Nicholsonograptus fasciculatus—I would be inclined to place it in the lower half of the zone.'

Mudstones are also exposed east of Dufton Pike [NY 7046 2632], in Studgill, Keisley [NY 7140 2421] and in Murton Beck [NY 7322 2213], but no fauna has been obtained from these localities. On Roman Fell, just south of Hilton Beck, hillside exposures [NY 7491 2102]; [NY 7492 2108] yielded Didymograptus arias, D. aff. D. bifidus, D. cf. D. pakrianus, D. sp.[extensiform type], Nicholsonograptus fasciculatus, Cryptograptus tricornis schaeferi and ?Climacograptus tailbertensis. Professor Skevington comments: 'This collection is indicative of the D. bifidus Zone, and probably the upper part of the Zone. All forms present in this assemblage occur also in the Tailbert Lanshaw tunnel fauna (Skevington, 1970) and the two are considered to be of the same age.' ICB

In Teesdale, grey cleaved mudstones are exposed in both banks of the River Tees near Cronkley Pencil Mill [NY 848 296] where they were formerly worked for slate pencils. The mudstones are very uniform, and apart from a few gritty laminae, bedding is visible only as a fine colour banding. The first cleavage is the dominant surface, but a second cleavage has sporadically developed; the most highly cleaved rocks are phyllites and have a greenish colour. The rocks are sparsely fossiliferous; the graptolites obtained to date (Johnson, 1961) have been re-examined by Professor Skevington, the full list being Aulograptus cucullus, Cryptograplus tricornis schaeferi, Glyptograptus dentalus, ?Glossograptus sp., ??dichograptid stipe fragments. Professor Skevington comments that 'the D. bifidus Zone is firmly indicated, though placement within the Zone is not possible'. Lister and Holliday (1970) obtained acritarch assemblages from the slates in Teesdale and on balance preferred a correlation with the lower part of the D. bifidus Zone (Milburn Beds) though no volcanic rocks of Milburn Beds type have so far been discovered here.

Poorly cleaved fine-grained greywackes, proved in a borehole near Widdybank Farm [NY 8369 2984], are referred also to the Kirkland Formation. These rocks have yielded no fossils. DWH

Volcanic rocks

The volcanic rocks of the Kirkland Formation ('Milburn Beds' of previous authors) consist of mainly basic (andesitic and spilitic) tuffs, with subordinate andesitic lavas (Appendix 3). The tuffs range in thickness from a few centimetres to over 20 m. Some beds are graded, fining upwards, while others are cross-bedded, especially in their upper parts where they show signs of reworking by currents, and would more properly be classified as volcanic sandstones. These features, together with the presence of interbedded black graptolitic mudstones suggest that much of the tuff sequence was laid down in water of moderate depth. In hand specimen, the typical tuffs are hard, dense, dark green to grey rocks. They range in grain size from very fine-grained (silt grade) to coarse, with angular pyroclasts up to 10 mm across. Conspicuous in most rocks are particles of red jasper and, commonly, angular slate fragments of all sizes up to 50 mm. In the Keisley area, many of the lava-derived clasts are spilitic, composed of microlitic sodic plagioclase, and may be partly of hyaloclastic origin, formed by lava breaking up on coming in contact with sea water.

Andesitic rocks, probably of extrusive origin, crop out in a small area west of Roman Fell where they are well exposed in a small quarry [NY 7465 2055]. More southerly exposures [NY 7472 2039]; [NY 7476 2034] show similar, though coarser-grained andesites, which are highly vesicular, the vesicles being infilled with chlorite. Spilitic lava flows have not been recorded, though as noted above, fragments are locally common in the tuffs, and such rocks do occur farther north in the Penrith (24) district (Arthurton and Wadge, in press).

No thickening or systematic coarsening of these extrusive rocks has been found (in common with those just to the north) to support Hudson's (1937, p. 374) suggestion of an andesite vent south of Burney Hill. The petrological and chemical features of these rocks (Appendix 3) closely resemble those of similar age in the northern part of the Cross Fell Inlier (Arthurton and Wadge, in press). ICB RKH

Borrowdale Volcanic Group

In the Cross Fell Inlier the Borrowdale Volcanic Group is confined to several small, mainly fault-bounded blocks (Hudson, 1937; Shotton, 1935). The massive volcanic rocks tend to stand above the surrounding softer beds as steep-sided hills or 'pikes' such as those behind Knock and Dufton; they are also seen north of Keisley and beneath the Carboniferous conglomerates on Roman Fell. The rocks are assigned to three lithologically distinct formations:

These formation names are not indicated on the 1:50000 map. The Knock Pike Formation is shown as 'Rhyolite and Acid Ash-flow Tuffs' (symbol R) and the Studgill and Harthwaite Tuff Formations are included in 'Acid Tuffs and Volcanic Sandstones' (symbol ZR). A similar sequence is found in the southern outcrop of the Borrowdale Volcanic Group in the Lake District. Rocks assigned to the group are also present in Teesdale, but there no sequence can be established. Within the district the stratigraphical relationship of the Borrowdale Volcanic Group to the Skiddaw Group cannot be demonstrated, the junctions in every instance being faulted.

Petrographical descriptions of rocks from the group can be found in Appendix 3.

Details

Stud Gill Tuff Formation

These beds crop out in Studgill and on the north-eastern face of Dufton Pike and may underlie wholly drift-covered ground north of Milburn Beck. They are generally poorly exposed, but appear to be mainly lapilli-tuffs and volcanic sandstones, possibly as much as 300 m thick on Dufton Pike. ICB

Knock Pike Tuff Formation

The hard, resistant rocks of this formation are widely exposed, cropping out in Milburn Beck, on Knock Pike, Dufton Pike, Dod Hill, Gregory, Keisley Bank, The Seat, and on the northern and western slopes of Roman Fell. As a result of weathering and oxidation, both in Permian and in more recent times, the tuffs are multi-coloured, ranging from pale pink and pale and dark green, through yellow and cream to white. They are rhyolitic ash-flow tuffs consisting of devitrified glass shards with a variable proportion of sodic feldspar crystals, pumice and acid tuff clasts except where recrystallisation has destroyed all traces of original texture. The tuffs are fine-grained and compact in hand specimen, and with a blotchy or streaky appearance, varying with the degree of compaction and welding and the abundance of volcanic clasts. The clasts are more numerous in the upper part of the formation. Many of the tuffs show apparent flow structures with lenticular streaks aligned along the depositional plane and closely simulate true flow-lineation of lavas. Being highly altered, they might be interpreted either as devitrified welded tuffs or as rhyolite lava where pyroclasts are not evident in sections. As noted by Oliver (1954, p. 475), such flow structures are characteristic of welded tuffs elsewhere and most of the specimens examined are thought to be tuffs rather than lavas. In the more southerly outcrops around Keisley Bank and Roman Fell heterogeneous tuffs containing pyroclasts of more intermediate and basic eruptive types occur within the predominantly rhyolitic ash-flow sequences. ICB, RKH

In the large roadstone quarry on the north-east side of Knock Pike [NY 6870 2850], the most densely welded part of a thick ash-flow unit is exposed, lying near the base of the formation. The pale to dark green, fine-grained rock has a conspicuous streaky (parataxitic) texture (Plate 3.2), resulting from intense compaction of the included pumice fragments. The tuffs are closely jointed parallel to the parataxitic plane, and also display a rude columnar jointing perpendicular to this plane, extending from top to bottom of the quarry. Just to the south, in Swindale Beck [NY 6892 2809] to [NY 6891 2786], similar rocks are overlain by less densely welded, but still well-laminated tuffs (eutaxitic texture) (Plate 3.1) which have a blotchy appearance and contain numerous clasts of pumice and acid tuff. The succeeding beds are poorly exposed, but appear to be mainly unwelded lapilli tuffs, which are in turn overlain farther downstream by eutaxitic welded tuffs [NY 6888 2783] to [NY 6884 2777].

In Milburn Beck, especially in crags on the western bank [NY 6780 2872] to [NY 6774 2856], the tuffs are deep red, possibly as a result of early Permian oxidation.

There are few other good sections, though the tuffs may be examined in hillside crags on Dufton Pike and in the fault blocks north of Keisley. On Roman Fell eutaxitic welded tuffs crop out in the streams around Mute Gill [NY 7560 1930] and by the side of the fell road.

Harthwaite Tuff Formation

The formation is thickest in the southern part of the inlier, near Roman Fell and Keisley, and contains various rock-types including acid tuffs, volcanic sandstones and beds of finely laminated siltstone.

On Roman Fell these rocks crop out in three areas, around Hilton Sike [NY 7490 2527], below High Band [NY 7530 1980] and near Mute Gill [NY 7566 1924]. The oldest beds, seen west of Roman Fell Nook [NY 7492 2038], are volcanic sandstones containing abundant fragments of the underlying Knock Pike Tuff. They are overlain by finely banded siltstones with interbedded tuffs [NY 7487 2033], followed, in the area south of Hilton Sike, by a thick sequence of acid vitric crystal tuffs and volcanic sandstones, the uppermost beds of the Borrowdale Volcanic Group sequence preserved hereabouts.

There is a good section [NY 7084 2484] to [NY 7079 2481] through the youngest beds in Harthwaite Sike and scattered exposures on Harthwaite and on Dod Hill, where a small quarry [NY 7103 2524] provides a section in the lowest volcanic sandstones. Farther north, tuffs are poorly exposed in a tributary of Pus Gill [NY 7060 2600], and just south of Milburn Beck [NY 6797 2845] where an outcrop of breccia consists mainly of angular fragments of ash-flow tuff in a sandy matrix. ICB

Teesdale Inlier

Volcanic rocks were first noted in situ in Teesdale by Gunn and Clough (1878) on the south side of the Tees, opposite Widdybank Farm [NY 8385 7966]. The exposure of the rocks is most unsatisfactory and little is known of them. Petrographic examination suggests that the present outcrops are of tuff rather than lava as previously supposed. In thin sections (E35270), (E35271), (E35272) numerous glass shards together with xenocrysts and microxenoliths are set in a glassy matrix. There is no sign of welding, but the rocks are intensely silicified and locally cut by thin quartz veins. They are said to be soda-rhyolitic in composition (Emeleus, 1974). A thin section in the collection of Durham University of a boulder from the boulder clay near Cronkley Bridge reveals a highly vesicular rock unknown from present outcrops. Evidence such as this and the relatively abundant rhyolitic boulders in boulder clay down-valley of the inlier suggests that the Borrowdale Volcanic Group outcrop beneath the drift is more extensive than would appear from the present poor exposure. DWH

Coniston Limestone Group

A post-Borrowdale Volcanic Group period of folding, uplift and erosion gave rise to a subdued topography which was gradually submerged by the sea, and became covered by the shallow-water sediments of the Coniston Limestone Group. In the district, the group crops out only in the Cross Fell Inlier where it is divided into two formations, the Dufton Shales and the unconformably overlying Swindale Shales.

The Dufton Shales, about 400 m thick, consist of dark grey, partly calcareous siltstones and mudstones, with thin bands, lenticles or nodules, of silty limestone. Near the base and at the top of the formation sandier beds occur locally. Thus the lowest part of the Dufton Shales consists of poorly fossiliferous sandstones and siltstones containing a variable amount of volcanic detritus, probably derived from nearby outcrops of the Borrowdale Volcanic Group. These were termed the 'corona Beds' (Nicholson and Marr, 1891) after the commonly occurring brachiopod Trematis corona, but do not form a mappable unit and are here referred to as the 'corona facies'. The highest beds of the Dufton Shales are also sandy, but the detritus is quartzitic rather than volcanic.

The Swindale Shales, about 40 m thick, consist largely of grey mudstone, more or less calcareous, with bands and lenticles of greenish grey fine-grained limestone, commonly decalcified at outcrop to brown rottenstone. The proportion of limestone in the Swindale Shales is very variable. In Swindale Beck, Knock, the Swindale Limestone, 19 m thick including a 5-m parting near the top, lies at the base of the sequence. Farther south, at Keisley the bioclastic Keisley Limestone is more than 50 m thick and has a specialised 'reef' fauna. It is discussed separately in the following account.

The biostratigraphy of the Coniston Limestone Group is based on shelly fossils. In the Dufton Shales, apart from the basal and uppermost beds, the faunal assemblages are somewhat monotonous in character with rarely more than seven or eight species represented in any one collection, but the succession of species present allows one to recognise a sequence of stages and to establish that the formation spans the upper half of the Caradoc Series, comprising the Longvillian, Marshbrookian, Actonian and Onnian stages, and the lower part of the Ashgill Series, namely the Pusgillian Stage and part of the Cautleyan. Dean (1959) has described the historical background to the classification and the faunal succession in detail and has also described the trilobites (Dean, 1961, 1962). The present survey in general supports Dean's conclusions, so only a summary is given below, the few places where interpretations differ being noted. The Swindale Shales yield faunas referable to the Rawtheyan and Hirnantian stages (Ingham and Wright, 1970) of the Ashgill Series. The classification of the Coniston Limestone Group is summarised in (Figure 3).

Details

Dufton Shales

The Dufton Shales are generally much faulted, and are poorly exposed outside the deeper stream valleys. Good sections occur in Lycum Sike and Hilton Beck (Figure 4), Harthwaite Sike (Figure 6), Billy's Beck (Figure 5) and (Figure 7), Dufton Town Sike (Figure 5), Pusgill (Figure 8) and Swindale Beck, Knock (Figure 9). Extensive faunal collections have been made from these sections. The localities are indexed on (Figure 4), (Figure 5), (Figure 6), (Figure 7), (Figure 8) and (Figure 9), the faunas obtained being listed in the text or on (Figure 10) and (Figure 11). The letter prefixes L, H, B, D, P and S respectively identify the sections from which the faunas were obtained.

Lower Longvillian 'corona facies'

The best and most accessible section in the lower part of the Dufton Shales is in Harthwaite Sike (Figure 6). Rhyolitic, lithicand crystal-tuffs forming the highest beds of the Borrowdale Volcanic Group are exposed in the small plantation south of Harthwaite Cottage, dipping steeply west-south-west. Downstream, towards a fence across the stream [NY 7078 2840], they give way to tuffaceous sandstones with abundant small calcareous shell fragments and sporadic large lingulids, best seen high on the south bank within the plantation (H1). Beyond the fence, the sandstones are succeeded by grey tuffaceous siltstone with a typical 'corona facies' fauna (H2, H3, H7).

Siltstones of 'corona facies' are well exposed on Roman Fell, in the headwaters of Lycum Sike [NY 7496 1996] and nearby streams (Figure 4); L1–3, L7–11, where they overlie rhyolitic tuffs. They are purple-coloured, as a result of early Permian oxidation.

In Pus Gill (Figure 8) similar strata rest on tuffs near the Dufton Pike Fault [NY 7054 2600] and are exposed for about 200 m downstream (P2–8).

In Swindale Beck (Figure 9) they are again seen at the northern end of the section (S41–44), faulted against Borrowdale Volcanics, and they reappear in an isolated section in a small stream north of the Dun Fell road (S85) [NY 6796 2843]. ICB

The 'corona facies' is characterised especially by horny brachiopods and various molluscs: many of the horny brachiopods are too poorly preserved to be determined but besides Trematis corona there are many large lingulids, including some with muscle-platforms and a median septum in one valve which have been determined as Lingulasma tenuigranulatum (contra Pickerill 1973). At some localities (e.g. H7, L3) there are varied assemblages with bivalves and gastropods several of which appear to be confined to the 'corona facies' and which are not listed in (Figure 10); they include:

The cephalopod Actinoceras pusgillense was found at locality S85 and the cornulitid Conchicolites gregarius at P3.

At some localities (e.g. P2, H7, L2) assemblages fairly typical of the 'corona facies' are accompanied by numerous strophomenid brachiopods, especially Kjaerina of which several species appear to be present, though not well enough preserved for full determination. Ostracods are common but the only trilobite present is Brongniartella. Fossils of zonal significance are few but at localities S44, P6 and P8, faunas of 'corona facies' contain Dalmanella indica, suggesting a Lower Longvillian age (see also Dean, 1959, pp. 192–194). In (Figure 10) and (Figure 11) these localities are arbitrarily placed under a separate heading. There is no evidence for pre-Longvillian beds in the Dufton Shales.

Upper Longvillian

By Upper Longvillian times sedimentation had become more uniform throughout the area. Though minor variations in lithology occur throughout the sequence, they are insufficient to provide a basis for mapping, and this and succeeding divisions of the Dufton Shales are identified principally on the faunas they contain.

The presence of Upper Longvillian beds is inferred at those localities which yielded Bancroftina robusta or Broeggerolithus nicholsoni longiceps, even though this results in all the specimens compared with Bancroftina typa (which in Shropshire occurs at the top of the Lower Longvillian) being referred to the base of the Upper Longvillian. At many localities the lower and upper divisions of the Longvillian could not be distinguished for want of diagnostic fossils, especially brachiopods. Furthermore the diagnostic subspecies of Broeggerolithus, B. nicholsoni globiceps and B. nicholsoni longiceps in the Lower and Upper Longvillian respectively, could not be distinguished in much of the material collected and even appear to occur together at locality H13.

New localities for Longvillian strata were found in the headwaters of Billy's Beck (B1, B2) and in the lower reaches of Harthwaite Sike (H20–28); at the latter group of localities the faunas are not fully diagnostic of the Longvillian although the presence of Cremnorthis sp., Dalmanella cf. horderleyensis, Reuschella cf. horderlyensis and Sowerbyella sericea are suggestive of the Longvillian. At locality H21 the presence of several gastropods and bivalves recalls the character of the 'corona facies'.

Marshbrookian

The main exposures of rocks of Marshbrookian age are in Harthwaite Sike (Figure 6) and Swindale Beck (Figure 9). The Marshbrookian Stage is chiefly characterised by mudstones with Broeggerolithus transiens and Brongniartella bisulcata, both usually found poorly preserved in strongly cleaved beds. In the absence of determinable brachiopods it proved impossible to distinguish between Longvillian and Marshbrookian strata except where B. transiens could be determined. Between localities H9 and H19 in Harthwaite Sike several localities yielded B. cf. transiens and are referred to the Marshbrookian with a greater or lesser degree of confidence, but at H9, H13 and H17 the presence of B. nicholsoni subspp. suggests the Longvillian Stage. At H15 several specimens of B. nicholsoni are accompanied by a doubtful B. transiens and the stage is correspondingly doubtful. All the localities H21–28, just south of the above, are referred with doubt to the Longvillian. The beds in the lower reaches of Billy's Beck 500 m to the north-west; B20 (Figure 5) yielded Kjerulfina sp.and B. cf. transiens and are referred to the Marshbrookian, rather than the Pusgillian as suggested by Dean (1959, locs. D9, 10).

Dean's record of high Marshbrookian beds in Swindale Beck (loc. S50) is confirmed but the strata are interpreted as passing up into, rather than faulted against, the Actonian beds.

Actonian

The Actonian mudstones in Swindale Beck (S51, S52, S56, S57) overlie high Marshbrookian beds and are characterised only by doubtfully determined examples of Onnicalymene laticeps, O. salteri and Onniella aspasia, all of which occur in the Actonian of Shropshire.

The Actonian beds (S57) are faulted to the south against lower Marshbrookian beds (S58).

Onnian

The Onnian Stage is represented only in Pus Gill (Figure 8) P1, P9–17, where the beds are siltier and more calcareous than the Actonian beds of Swindale Beck. Whether the Onnian is conformable on the Actonian in the Cross Fell Inlier is not known.

The Onnian stage is characterised especially by species of Onnia and by the appearance of Onnicalymene onniensis, Onniella cf. broeggeri and abundant Sericoidea. Gunnarella sp.was found only in the Onnian in the Dufton Shales. The present survey confirms the distribution of strata referable to the Onnia gracilis and O. superba zones given by Dean (1959, p.199) but we refer also the beds at P17 and P1 (Dean's loc. A1 in fig. 7, p.193) to the O. superba Zone; at the latter locality they are seen to be faulted against beds of the 'corona facies' of locality P2.

Pusgillian

Strata referable to the Pusgillian occur in Billy's Beck, Dufton Town Sike, Pus Gill and Swindale Beck, Knock.

The Pusgillian Stage has a generally uniform fauna typified by Onniella cf. broeggeri, Sericoidea sp.and Onnicalymene onniensis, all of which occur also in the Onnian Stage, and especially by Tretaspis moeldenensis (see Ingham, 1970, p.54) which does not occur below the Pusgillian. Rarer but also typically Pusgillian are Atractopyge scabra, Gravicalymene jugifera and occasional illaenids. The faunas in the higher Pusgillian are somewhat enriched by forms which occur in the overlying Cautleyan Stage (Figure 10) and (Figure 11); (cf. Dean, 1959, pp.203–205). These beds are seen in Swindale Beck (S63) in the lower reaches of Pus Gill (P24, P25) and especially in Billy's Beck (B4, B5, B17, B19) where they are overlain by Cautleyan beds. They differ lithologically from the dark grey mudstones and siltstones of the lower Pusgillian beds in containing a noticeable quantity of quartz sand.

Cautleyan

Cautleyan beds (Diacalymene Beds of Dean, 1959) occur principally in the higher reaches of Billy's Beck and are represented by sandy siltstones which overlie the Pusgillian conformably, as seen at localities B4, B5 (Pusgillian) passing into Cautleyan at B6. Only a few metres of strata are present but they yield rich brachiopod faunas typical of the Cautleyan Stage in the Cautley Mudstones (Ingham, 1966; Ingham and Wright, 1970). Besides the forms listed in (Figure 10), the following, none of which was found at lower horizons, were collected:

Besides these the trilobites Calyptaulax sp.(B7, B8, B10) and Diacalymene marginata (B6, B7, B8?) were collected only from the Cautleyan during the present survey but Dean (1959) has recorded both these forms from the Pusgillian Stage.

Cautleyan strata are known at one other locality (Figure 13) K16, apparently in the core of an anticline of Keisley Limestone, where Fearnsides collected an assemblage from the Dufton Shales underlying the Keisley Limestone (Marr, 1906, pp. 483–484). Material in the Sedgwick Museum apparently representing part of this collection has been redetermined and includes: heliolitid and streptelasmatid corals, a dalmanellid, Katastrophomena sp., Leptaena?, Sampo? [juv.], Nicolella sp., Orthambonites?, Platystrophia sp., Skenidioides sp., a strophomenoid, Triplesia sp., fragments of Atractopyge, Gravicalymene and a dalmanitid and crinoid columnals. The potentially valuable 'Trinucleus seticornis'recorded by Marr has not been seen.

By comparison with the faunas of the Cautley Mudstones it is evident that much of the Cautleyan Stage is not seen in the Cross Fell Inlier.

Depositional environment

The 'corona facies' evidently represents a shallow-water phase of deposition, inhabited at first by a lingulid community, occasionally accompanied by abundant mollusca of infaunal (e.g. Lyrodesma)and epifaunal (e.g. Lophospira)habits. With deepening of the water these communities appear to have given way to a community of dalmanellids and strophomenids which occurs in beds transitional in character between the 'corona facies' and normal Dufton Shales.

The faunas of most of the Dufton Shales are suggestive of an offshore environment of fine elastic deposition; dalmanellids and Sericoidea are accompanied by trinucleids and calymenids or Brongniartella.

These communities may be compared broadly with those described from the Appalachians by Bretsky (1969) as the Orthorhynchula–Ambonychia community (with its linguloid and molluscan faunas) and the Sowerbyella–Onniella community (with its strophomenid and dalmanellid faunas). A notable difference is the comparative unimportance of the Mollusca in the offshore faunas of the Dufton Shales and the relative importance of trilobites.

Only in the high Pusgillian and Cautleyan is there a notable change in the faunal assemblages, marked by a greater variety of trilobites and brachiopods (especially orthoids) which colonised the area comparatively abruptly. The significance of this change is not known but may be connected with the onset of more arenaceous sedimentation towards the top of the Dufton Shales. AWAR, ICB

Swindale Shales

The Swindale Shales overlie the Dufton Shales unconformably (Figure 12). In Swindale Beck (Figure 9) the Swindale Limestone rests on Pusgillian mudstone. Younger Pusgillian sandy siltstones are preserved in Pusgill (Figure 8) P24, 25, and in Billy's Beck Cautleyan sandy siltstones are exposed (Figure 7).

The Swindale Shales fall into two parts. The lower part, of Rawtheyan age, is represented by the Swindale Limestone and associated beds in two outcrops in Swindale Beck (Figure 9) and one in Billy's Beck (Figure 7). A composite section in Swindale Beck shows:

ICB

The calcareous beds of the Swindale Shales yield few determinable fossils but where decalcified, and in the associated mudstone, fossils are numerous (Figure 14). Characteristic are small dalmanellids and plectambonitaceans (e.g. Chonetoidea, Christiania, Foliomena, Kozlowskites, Leptestiina). Compared with the Cautleyan, orthoids are few (and of small size) and large strophomenoids absent. The most typical trilobites are Phillipsinella, Panderia, remopleuridids (generally fragmentary), Staurocephalus clavifrons and Tretaspis cf. radialis (see Ingham, 1970, p.55). The faunas may be correlated with the middle of the Rawtheyan Stage (Ingham and Wright, 1970, p.238). No significant differences were seen between the faunas from above and below the Swindale Limestone in Swindale Beck. The faunas from localities B15 and B16 in Billy's Beck show that Rawtheyan beds extend downstream of the 'Swindale Limestone' shown by Dean (1959, fig. 4) and there is no evidence there for equivalents of the Ashgill Shales or Hirnantian Stage as was surmised by Dean (1959, p.218). The absence of the higher part of the Cautleyan Stage confirms the unconformity of the Swindale Shales upon the Dufton Shales (cf. Dean, 1962, p. 71).

The upper part of the Swindale Shales is of Hirnantian age. The only definite Hirnantian beds are silty mudstones brought in by faulting downstream of the lower outcrops of Rawtheyan beds in Swindale Beck (locs. S79–83). The beds at locality S79 are massive and slightly calcareous, yielding ostracods and Dalmanitina mucronata with D. olini ?; they may be the equivalent of the 'mucronatus Beds' of Ash Gill in the Coniston district and of the Cystoid Limestone of the Cautley district (Ingham, 1966). Both of these formations were tentatively transferred from the basal Hirnantian to the top of the Rawtheyan by Ingham and Wright(in Williams and others, 1972, p.47). Temple (1952, p.22) recorded D. olini from these beds in Swindale Beck and Paul (1973, pp. 5, 10) has recorded and described several cystoids.

The remaining Hirnantian localities, S80–83, are in mudstones with a Hirnantian assemblage resembling typical Ashgill Shales of Ash Gill.  AWAR

Keisley Limestone

The relationship between the Keisley Limestone and the Swindale Shales is shown in (Figure 12). The Keisley Limestone crops out in a small area east of Keisley (Figure 13). The outcrop is bounded on the north by a low-angle fault, dipping south at about 25°, and the limestone is itself broken by several faults, which divide it into three main blocks, exposed in Keisley Old Quarry in the east, Keisley New Quarry on the west and Keisley Crags to the north.

In Keisley Old Quarry, the oldest strata present are exposed on the axis of an anticline trending east-west, where they are seen to be dark grey siltstones with thin bands of muddy, fine-grained limestone. They are much disturbed and are probably faulted both to north and south against more massive limestone. On the south, the overlying massive, grey, bioclastic limestones dip consistently to the south. On the north, the limestones dip to the north at a low angle. Strong joints (K12) give the appearance of a southerly dip and isoclinal folding, but the true dip is shown by a siltstone (with fragmentary graptolites) exposed at several localities on the northern edge of the quarry (K18). The limestones above the siltstone include several metres of highly fossiliferous 'reef-type' limestone (K10, 11).

On Keisley Crags, about 12 m of well-bedded mid-grey bioclastic limestone, crinoidal in part, but otherwise almost devoid of macrofauna, are succeeded (K9) by about 3 m of pale cream to pink 'reef-type' limestone, containing an abundance of well-preserved brachiopod and trilobite shells in a fine-grained limestone matrix.

Keisley New Quarry provides an almost continuous section through over 30 m of limestone. The dip is to the south. The lowest beds, exposed at the back of the quarry, are nodular limestones with siltstone partings. The cleavage in the siltstones, dipping southwards at an angle consistently higher than the dip of the bedding, shows that the strata young to the south with the dip. The nodular limestones are overlain by more massive beds, disturbed by faulting, dolomitised and reddened along joints. These massive limestones are conformably overlain, in the path leading to the quarry (Figure 13) K1, by beds of Llandovery age (p.23).  ICB

The fauna of the Keisley Limestone was described and discussed by Reed (1896, 1897). The age is accepted as Ashgill but it is difficult to be more exact because the faunas are specialised 'reef' faunas, more closely related to other 'reef' faunas than to the contemporaneous assemblages found in the Swindale Shales and Cautley Mudstones. There are a few species in common with these formations—Christiania'tenuicincta', Hadromeros keisleyensis, Phillipsinella parabola and Staurocephalus davafrons—but they indicate only a general correlation with parts of the Cautleyan or Rawtheyan stages, or both. There are many species in common with the Chair of Kildare Limestone in Ireland (Dean, 1971–8) and with the Boda Limestone in Darlarne, Sweden (Warburg, 1925); there are also a few species identical with those from the upper Ordovician of the Gaspe peninsula, Quebec (Cooper, 1930; Cooper and Kindle, 1936).

The Kildare Limestone is overlain by beds with a Hirnantian fauna and must therefore be Hirnantian or older; the Keisley Limestone appears to overlie beds (at K16) with a Cautleyan fauna. Therefore, if the correlation between the Keisley and Kildare limestones is exact, the age of the Keisley Limestone is confined to part of the Cautleyan and the whole of the Rawtheyan Stage, and may just pass up into the Hirnantian. However, a large part of the Keisley fauna derives from the shelly limestones lying about the middle of the limestone sequence, so it is not possible to be certain of the age of the youngest beds of the Keisley Limestone.

The fossils of the Keisley Limestone are diverse but patchy in distribution; any two localities are likely to yield quite different assemblages. This is doubtless due to the diverse micro-environments of the 'reef' about which the Keisley Limestone was deposited. It is noteworthy that whereas all the trilobites found were disarticulated and may represent exuviae, many brachiopods and ostracods were found with their valves conjoined and must have died near where they were buried. During the present survey the forms listed below were collected. (Corals determined by Dr D. E. White; Bryozoa by Miss Monograptus E. Dutton.) The localities K9, K10 etc., are shown on (Figure 13).

Less precisely located material in the older Survey collections contain the following forms not well represented in the more recent collections: Bodophyllum?, Catenipora cf. tapaensis, Grewingkia cf. bilateralis, G. cf. europea, Paleofavosites sp., Anisopleurella cf. quinquecostata, Dicoelosia sp.and Staurocephalus clavifrons.  AWAR, ICB

Chapter 3 Silurian

The Silurian rocks of the district crop out only in the Cross Fell Inlier. Strata belonging to both Llandovery and Wen-lock series are present though the full sequence of graptolite zones proved in the nearby Lake District (Figure 15) has not been established (Burgess and others, 1970; Cocks and others, 1971, pp. 115–116, fig. 2). However, the apparent absence of several graptolite zones is almost certainly the result of faulting and inadequate exposure and does not imply their absence from the Cross Fell area.

The lithological classification of the Silurian rocks (Figure 15) follows that established in the Lake District (Taylor and others, 1971, p.22). The Llandovery rocks, collectively known as the Stockdale Shales, are divided into the Skelgill Shales below and the Browgill Beds above (Aveline and Hughes, 1872; Marr and Nicholson, 1888). Only the lowest Wenlock strata, belonging to the Brathay Flags, are preserved.

The Skelgill Shales typically are dark brown to black, shaly or blocky graptolitic mudstones in which the fossils commonly are preserved in pyrite. The rocks contain up to 3.7 per cent carbon and about 2 per cent sulphur (Rickards, 1964). Interbedded with the mudstones are sporadic bands of dark grey muddy calcareous siltstone. In these, the graptolites occur with orthocone nautiloids and phyllocarid crustacea. The associated benthonic species (trilobites, corals, brachiopods) are generally few in number and dwarfed in size (Marr, 1925). The junction with the overlying Browgill Beds is not exposed. In the lower part of the Browgill Beds sequence, comprising the Monograptus turriculatus, Monograptus crispus and Monoclimacis griestoniensis zones, the dominant lithology is pale greenish grey unfossiliferous mudstone. Black graptolitic mudstone is present only as sporadic 1 cm to 5 cm bands. The pale grey bands range in thickness from less than a millimetre to over a metre; lithologically they appear identical to the black mudstones apart from the absence of carbonaceous material. They are either finely laminated with dark streaks parallel to the bedding, or internally structureless. A few metres above the highest Monograptus griestoniensis graptolite band, there is a further change in lithology, marked by the presence in many of the beds of finely divided hematite, which gives them a red colour, especially in weathered outcrops. Only one bed of dark grey graptolitic mudstone, of Monograptus crenulata age, has been recorded from this facies (Burgess and others, 1970).

At several horizons within the Stockdale Shales, thin bands of white silty mudstone are interbedded with the normal lithologies. These contain shards and volcanic particles (p.24) and represent highly altered volcanic tuffs.

The Brathay Flags consist predominantly of dark grey laminated siltstones and mudstones with sporadic small calcareous nodules. Their fauna is almost exclusively of graptolites.

The conditions of deposition of these Llandovery and Wenlock rocks were discussed in detail by Rickards (1964). He concluded that they represent a prolonged period of quiet sedimentation, during which there was an almost continuous influx of fine muddy material brought in by weak, non-eroding low-density turbidity currents. The carbonaceous material was thought to be probably of algal origin. ICB

Details

The graptolite faunas and zonal assignations given below are taken from Burgess and others (1970).

Skelgill Shales

The basal Llandovery beds are only exposed at one locality, Keisley Quarry [NY 7138 2379]. The section is at a bend in the lane leading to the quarry entrance. The massive Keisley Limestone seen in the quarry (p.19) is overlain, apparently conformably (Burgess, 1968), by about 2.5 m of calcareous mudstone with nodular bands of bioclastic limestone. Where exposed in the north bank of the lane (Figure 13) K1, the nodules are decalcified and weather to a rottenstone. From this material, Temple (1968, 1969) described a large assemblage of 30 species of brachiopods and 10 of trilobites; during the present survey the following were collected: Streptelasma?, bryozoa [indet.], Draborthis cf. caelebs, Philhedrella cf. cribrum, Reuschella inexpectata, Skenidioides scoliodus, Triplesia sp., Toxorthis proteus, an orthocone, calymenid [fragments], Lepidocoleus sp., Plumulites sp.and crinoid columnals. The collection was made stratigraphically above the Keisley Limestone and below the Skelgill Shales of the atavus Zone, and Temple took the horizon to be lowermost Llandovery. There are a few forms in common (e.g. Kayserella sp., Dalmanitina mucronata brevispina)between the basal Llandovery fauna at Keisley and those of the basal Skelgill limestones at Ash Gill, Torver, and Watley Gill, Cautley (Temple, 1952, p. 14). Ingham and Wright (in Williams and others, 1972, p.47) considered that the presence at Keisley of the brachiopods Hirnantia sagittifera, Kinnella kielanae and Bracteoleptaena polonica sufficed to indicate an uppermost Ashgill age, but this conclusion is arguable and the stratigraphical evidence favours a Llandovery age. ICB, AWAR

The 0.3 m of greenish yellow mudstone overlying the highest calcareous beds on the north side of the lane (Figure 13) K1, have yielded a few fragmentary graptolites of the Monograptus atavus Zone so it is possible that the underlying beds represent the zones of Glyptograptus persculptus and Akidograptus acuminatus, neither of which is recorded in the Cross Fell Inlier. On the south side of the lane (Figure 13) K2, exposures of dark grey mudstone (Marr, 1906) about 2.3 m stratigraphically higher contain abundant graptolites of the Monograptus atavus Zone (Figure 18). The intervening and succeeding beds are not exposed.

In Great Rundale Beck (Figure 16) between 190 and 260 m upstream from the confluence with Swindale Beck, dark grey muddy limestone crops out in the bed of the stream. The immediately overlying strata, dark brown to black blocky mudstones, contain a Monograptus typhus Zone fauna (Figure 16) R1, R2; (Figure 18). The fossils are pyritised and the rock in general is pyritic, both disseminated and concentrated in layers along bedding planes. Beds on the same horizon are recorded by Shotton (1935, p.660) from a locality 50 m downstream (Figure 16) 'b', now obscured.

Swindale Beck, Knock (Figure 16) and (Figure 17), provides the most continuous and best-exposed section of Llandovery rocks in the district. Immediately downstream of the main fault dividing Ordovician from Silurian strata, two highly disturbed black shale bands (S₁, S₂) with intervening siltstones—Skelgill Shales—crop out low down on the right bank. The rich fauna from these beds is diagnostic of the Monograptus triangulatus Zone (Figure 18). The exposure is terminated on the south by a second fault, also with a southerly downthrow.

Browgill Beds

Browgill Beds form the main part of the Swindale Beck section and scattered exposures are also seen in the lower part of Rundale Beck. In Swindale Beck, Knock, an almost continuous section on the right bank, disturbed only by minor faults, extends from the faults noted above downstream for a distance of 40 m. The rocks are predominantly pale grey mudstone devoid of fossils, but are interbedded with 1 to 5cm bands of dark grey to black graptolitic mudstone. In the total thickness of 16 m, 31 of these bands were detected (Figure 17) and (Figure 19), representing the zones of Monograptus turriculatus (S3–S21), Monograptus crispus (S22–S29) and Monoclimacis griestoniensis (S30A–S33). Graptolitic beds of the Monograptus turriculatus Zone are also seen in Great Rundale Beck (Figure 16) R5, and a fauna of the Monograptus crispus Zone was recorded by Shotton (1935, p.661) in the same beck 91 m above the junction with Swindale Beck.

In Swindale Beck, band S33 is succeeded by 6 m of pale green mudstone. The remainder of the section is almost entirely in barren reddish grey mudstone. Only one black graptolitic mudstone band (Figure 16) and (Figure 17); S34, is recorded, the fauna being of the Monoclimacis crenulata Zone (Figure 19). The bed is exposed by the path on the right bank, about 4.5 m above stream level, and, intermittently, in the stream bed.

Browgill Beds are shown on the map to crop out over large areas north of Dufton and south of Keisley. These outcrops are based on very small exposures and their limits are conjectural. Exposures of green mudstone referred on lithological grounds to the Browgill Beds are also seen in Billy's Beck [NY 7083 2532], but no supporting fauna has been obtained from this section.

Contemporaneous volcanic rocks

At a few localities, thin bands of white to pale grey siltstone are interbedded with the Stockdale Shales. One 5-cm band (E33695) underlying bed S5 in Swindale Beck was examined by Mr R. K. Harrison, who reports:

'This pale grey to white, thinly-bedded, silty rock displays darker grey laminae with pinkish white, coarsely crystalline dolomite coating along joints. In section there is a wide variety of elastic particles within each thin bed or lamina. Many of these particles are highly altered but the most common include angular feldspars—especially microcline (mainly averaging 0.04 to 0.05 mm across) and turbid rock fragments which in places have shard-like outlines and exhibit felsitic textures. Opaque particles up to 0.5 mm long and white by incident light, are particularly common being mainly composed of leucoxene (after rutile). The matrix is microcrystalline—probably largely kaolinite—with scattered illite flakes, abundant leucoxenic dust and coarser plates of pale brown (?)kaolinite, perhaps recrystallised. Dolomite (ω = 1.684) is abundant and largely replacive, a later, coarser generation occupying veinlets. Pyrite occurs on joints as crystal aggregates and scattered through the tuff. Illite flakes show preferred orientation due to a low degree of metamorphism.

'An X-ray powder photograph (NEX335) of the whole rock showed major feldspar, and subordinate illite, kaolinite and dolomite. The presence of shards, volcanic particles, abundant leucoxene and predominant feldspar crystals indicate a tuffaceous origin.'

Other bands are too weathered for identification, but it is probable that they have a similar origin.

Brathay Flags

The base of the Brathay Flags is not exposed, but finely laminated grey siltstones seen in Swindale Beck (Figure 16) S35, S36, belonging to the Cyrtograptus centrifugus Zone (Figure 19) are low in the sequence. Higher beds are exposed between 430 and 720 m downstream from Keisley Bridge (Figure 13); K4–K6. The fauna includes Monoclimacis flumendosae, Monograptus flemingii and Pristiograptus dubius. Farther upstream, in the vicinity of K7, several exposures have yielded Cyrtograptus linnarssoni and Monograptus flexilis. These last are indicative of the C. linnarssoni Zone; the former localities also may belong to this zone, but could also be somewhat older. Many of the siltstones in this section, especially near K4, are quite markedly reddened, but this staining is secondary, and is thought to be related to the sub-Permian unconformity (p. 70). Brathay Flags are also exposed at several localities in the fields south of Harbourflatt Farm [NY 7210 2323], but have yielded no identifiable graptolites. Farther south, between the villages of Murton and Hilton, a small exposure of hard grey mudstone [NY 7361 2123] yielded several specimens of Pristiograptus dubius and Monograptus antennularius, possibly indicative of the Monograptus riccartonensis Zone. ICB

Chapter 4 Lower Carboniferous: Dinantian

Lower Carboniferous rocks ('Carboniferous Limestone Series') crop out in four areas in the district. The largest of these forms the high moorland bounded by the Pennine escarpment on the west, Swindale and Lunedale on the south and the Tees Valley on the east. Rocks of the same age, in places steeply dipping and highly faulted, occupy much of the low-lying ground around Brough and Winton. They also form the higher ground in the south-west corner of the district around Asby extending from the much larger outcrop in the neighbouring Appleby (30) district on the south-western side of the Vale of Eden Syncline. There is also a small outcrop in the south-east, around Sleight Holme. Elsewhere, rocks of Lower Carboniferous age are believed to underlie the remainder of the district, apart from the Lower Palaeozoic inliers, concealed in the area south of Lunedale by succeeding Namurian rocks, and in the floor of the Vale of Eden by the unconformably overlying Permo-Triassic rocks.

Previous research

The Brough district lies on the southern fringe of the major lead-mining field centred on Alston, and it was the commercial interest in this area that led to the early systematisation by Forster (1809, 1821) of Lower Carboniferous stratigraphy which was further refined by Sopwith (1833) and Wallace (1861). The work of Phillips (1836) in Yorkshire, in particular the tracing of his 'Yoredale Series' northwards from its type area in Wensleydale into the present district, provided another major advance. The Primary Geological Survey, carried out during 1870–82, established for the first time the detailed distribution of the rock types, and provided the basis for all subsequent research. Memoirs for two adjacent districts, Mallerstang (Dakyns and others, 1891) and Appleby (Dakyns and others, 1897), were published.

The early correlations were based on a lithological comparison of sequences. The nature of the strata, with the persistence of lithological units over wide areas, made this approach very successful. However, the increase in interest in the faunas of the rocks, in particular the work of Garwood (1913), Smith (1910), Turner (1927) and Miller and Turner (1931) set the lithological correlations on a firm palaeontological footing and provided a means of relating the rocks of this district to those of the same age but differing lithologies in other parts of the country. The Alston Group strata of the present area, north of Stainmore, were described in detail for the first time by Dunham (1948). There are also a number of more recent accounts of the strata in adjacent areas, including Wells (1958), Moore (1958), Johnson and Dunham (1963), Rowley (1969), Mills and Hull (1976) and Arthurton and Wadge (in press).

Classification

The term 'Carboniferous Limestone Series' is here, as in neighbouring districts, taken to be synonymous with Lower Carboniferous, or Dinantian. The current classification is given in (Figure 20), together with previous classifications. The presently accepted palaeontological zonations are discussed in Chapter 6, see also (Figure 37) and (Figure 38).

In most of the district, the Lower Carboniferous rocks exposed at the surface belong to the Alston Group. Older strata are seen only in a narrow belt east of the Pennine faults and around the Teesdale Inlier, but they are believed to underlie the Alston Group throughout the district.

Around Orton and Ravenstonedale, just outside the south-west corner of the district, up to 1000 m of marine strata are present (Garwood, 1913; Turner, 1950; Johnson and Marshall, 1971), and are referred to the Ravenstonedale and Orton groups respectively (Institute of Geological Sciences, 1971, p.31). A twofold division is also recognised for rocks of the same age on the Pennine escarpment south of Murton Pike. The higher of these is closely comparable with the Orton Group in both fauna and lithologies, though thinner, and is here included in that group. The underlying strata, the fluviatile sandstones and quartz conglomerates of Roman Fell, contain no diagnostic fossils. Lithologically they resemble the red sandstones of the Birk Beck Valley at the base of the Carboniferous sequence near Orton (Capewell, 1956; Burgess and Harrison, 1967) and may be at least partly equivalent in age to the Ravenstonedale Group. As neither their base nor top can be defined palaeontologically, and as both boundaries are apparently diachronous, the beds are here assigned to a separate division, the Basement Beds. Fifteen to twenty kilometres separate the most northerly outcrops of the Ravenstonedale Group in the Kirkby Stephen (41) district from the most southerly crop of the Basement Beds in the Brough district. Within that distance it is inferred that the Ravenstonedale Group passes laterally into the Basement Beds though there is as yet no borehole information to confirm this. It is thought likely that beds referable to the Ravenstonedale Group occur in the subsurface of the southern part of the district. North of Murton Pike the division into an underlying fluviatile and overlying marine sequence persists to the edge of the district, though the junction between the two groups and hence the mapped base of the Orton Group, is probably diachronous. In Teesdale, the Basement Beds are believed to be absent, all the Lower Carboniferous strata beneath the Alston Group being assigned to the Orton Group.

In the Brough district, the base of the Alston Group is at an unconformity, usually marked by erosion and dolomitisation of the underlying Orton Group strata and the entry of a prolific Asbian fauna (p. 58). The top is at the base of the Great Limestone, which approximates to the base of the Namurian (Millstone Grit) Series. The group is conveniently split into two parts, lower and upper, the junction lying at the base of the Peghorn Limestone, and corresponding both with the incoming of a Brigantian fauna and with a change in limestone lithology from the dominantly pale grey limestones of the 'Great Scar Limestone Series' to the darker grey limestones characteristic of the succeeding 'Yoredale Series' (Burgess and Mitchell, 1976).

Regional palaeogeography

In the north of England the Lower Carboniferous sediments were laid down on, and gradually submerged, a mature landscape of subdued relief, the denuded foundations of the mountains produced by the Caledonian Orogeny. This basement was not homogeneous, but comprised a number of structural units, the boundaries of which are commonly at major faults probably first established in Caledonian times. During the Carboniferous, these units subsided unevenly and at differing rates. Those that subsided rapidly, and accumulated great thicknesses of sediment, are termed basins or troughs; the more slowly subsiding units, which on geophysical evidence are areas where the Lower Palaeozoic rocks are intruded by Caledonian granites (Bott, 1967) are termed blocks. Except in instances where the blocks formed topographic highs providing a local sediment source, these units had little effect on the nature of the beds deposited, only on their thickness. Throughout the Lower Carboniferous, sedimentation kept pace with subsidence, and the depositional interface remained close above or below the mean sea level.

In the Brough district, several such structural units exerted control on Lower Carboniferous sedimentation (Figure 2). To the north is the Alston Block, underlain by the Weardale Granite. South of this is the Stainmore Trough, a basin trending east-west bounded on the north by the Lunedale-Closehouse fault complex. Farther south, beyond the Brough district the trough passes gradually into the Askrigg Block, also underlain in part by granite (Dunham, 1974b). A Lower Carboniferous basin may extend under the Vale of Eden though there is little direct evidence for this. The Lower Carboniferous rocks to the west of the Vale of Eden, apart from an area to the south forming part of the Stainmore Trough, lie on the Lake District Block.

There is evidence that the margins of the blocks migrated with time. During much of Lower Carboniferous time the Swindale Beck Fault marked the southern edge of the Alston Block in the Pennine escarpment area, sediment thickness changing sharply over this line. During deposition of the Lower Alston Group (p.36) the position of thickness change occurred farther south at the Barnarm and Thornthwaite faults (Figure 45). A similar southerly migration has been noted in the Asby area where most of the Lower Alston Group strata have thicknesses comparable to a basin sequence, but those in the Upper Alston Group have thicknesses which compare with block sequences.

The earliest Lower Carboniferous sedimentation was in the basin areas and progressively overlapped on to the block areas. The Alston Block was not finally submerged until Asbian times. Apart from the fluvial Basement Beds and the deltaic clastics of the Alston Group, the Lower Carboniferous rocks are shallow marine in origin.  ICB, DWH

Basement beds

The Basement Beds along the Pennine escarpment are unusually thick, compared with adjacent areas in northern England. They are generally thin or absent both to the east on the Alston Block and to the west around the eastern Lake District, where the only comparable sequence lies in the Birk Beck valley, south of Shap. These regional variations may reflect either the presence of a pre-existing valley or contemporary subsidence along the Pennine fault-zone; as a third possibility, the escarpment sequence may be marginal to a much thicker trough sequence, as yet unproved, beneath the younger rocks of the Vale of Eden. Within the Pennine outcrops more localised variations occur. Thus, north-west of Murton Pike the Basement Beds are comparatively thin, although considerable thickness variations occur low in the sequence resulting from the infilling of topographic hollows. In contrast, much thicker sediments accumulated to the south in the Stainmore Trough. Thus the succession south of Roman Fell is more than four times as thick as that in High Cup Gill (Figure 21), the increase affecting all members of the sequence. This increase results from contemporaneous movement of the hinge-zone at the northern edge of the trough, close to the Swindale Beck Fault; indeed some movement may well have occurred along the fault itself during deposition, but the available sections are too far apart to demonstrate this conclusively.

The sequence of lithofacies is shown diagrammatically in (Figure 21), although these subdivisions are too imprecise to show on the published map. Much of the Basement Beds consists of coarse elastics, purple-coloured in the north and becoming grey to the south of Crowdundle Beck (Capewell, 1956, p.224). Vein-quartz pebbles are especially abundant, but fragments of mudstone and andesite are also common. In detail these beds contain local fining-upwards cycles, generally only a few metres thick, showing a gradational passage upwards from conglomerate, through coarse sandstone, into siltstone. The coarser beds are commonly cross-bedded, with erosive bases, whilst ripple-marks and plant-debris characterise the finer beds. These features are taken to indicate a fluviatile deposit and the sedimentary structures suggest eastwards derivation, from higher ground near the present Lake District.

Details

On the northern edge of the Stainmore Trough, south of Murton Pike, the Basement Beds fall into three divisions (Burgess and Harrison, 1967, p.211), viz.

The oldest beds exposed on Roman Fell, the Basal Conglomerate, consist of cobble and gravel conglomerates with pebbles of Skiddaw Slates, vein quartz, acid and basic tuffs of the Borrowdale Volcanic Group, Caradocian mudstones and Brathay Flags, all of which can be matched with local outcrops. The unconformable base of the conglomerate is marked by numerous springs and its irregularity is clearly exhibited west of Roman Fell Nook, where an outcrop of Ordovician acid ash-flow tuffs forms a buried hill against the sides of which the conglomerates are banked [NY 7514 2044]. The conglomerates are best exposed around the headwaters of Lycum Sike [NY 7500 1990].

Immediately north of the Swindale Beck Fault, the base of the Carboniferous is exposed in the north bank of Hilton Beck, 45 m downstream from the confluence of the Swindale and Scordale becks, where slates of the Skiddaw Group are overlain by poorly-cemented conglomerate similar to the basal conglomerate on Roman Fell. In Gasdale, the basal beds reappear from beneath the overthrust Skiddaw Slates, and the unconformity is exposed in the south bank of Murton Beck [NY 7384 2236] 100 m downstream from the fell wall.

The Roman Fell Shales are poorly exposed. They appear to consist mainly of purple-red and green siltstones with sporadic bands of fine-grained sandstone and lenses of pebble-conglomerate. Short sections are exposed north of Roman Fell Nook and at the head of Mute Gill. Elsewhere on Roman Fell they are largely concealed by scree fallen from the overlying Roman Fell Sandstones. The thickness decreases northwards from 90 to about 60 m.

North of the Swindale Beck Fault, about 45 m of shaly beds overlie the basal conglomerate. Around the foot of Swindale Beck, there are a few exposures mostly in landslips. The best section is about 180 m upstream from the foot of Swindale Beck [NY 7550 2140], where a small slip in the west bank has exposed 6 m of red and green siltstones and mudstones which must closely underlie the Roman Fell Sandstones. Shotton (1935, p.643) recorded scales of the fish Rhizodus hibberti'from these beds, confirming their Carboniferous age. Similar strata are poorly exposed in Gasdale, where their thickness is reduced to about 20 m.

The incoming of the coarser fluviatile material of the Roman Fell Sandstones marks the end of the period of quiet sedimentation of the Roman Fell Shales. The purple-red sandstones which form the crags and summit of Roman Fell are quartzitic lithic arenites and contain a high proportion of subangular quartz pebbles and purple shale galls. Behind the escarpment, the beds assume a pinkish hue and pass into yellowish sandstones and conglomerates of comparable lithology. Individual beds traced north-eastwards along the escarpment towards Swindale Beck also lose their purple colour, showing that the purple-red pigmentation is not of primary origin. Individual sandstone beds are commonly cross-bedded, with strongly erosive bases. They are generally coarsest at base, becoming finer-grained upwards, and the topmost layers show ripple marks.

The sandstones are well exposed in Dobbyhole Gill [NY 7586 1896], near the Pennine Fault, and, north of the Swindale Beck Fault, in Swindale Beck. Elsewhere, the outcrop is mostly concealed by slipped material. The topmost beds are seen at the head of Low-field Hush, in a landslip scar. They are also exposed at High and Low Hause, on the ridge between Swindale Beck and Hilton Beck. All the beds are severely fragmented, and the crescentic scars crossing the ridge suggest that the whole mass has slipped northwestwards over the underlying Roman Fell Shales. Between Scordale and Gasdale, the sandstones crop out intermittently, giving rise to a scree-covered feature above the fell wall. They are well exposed only by the track leading to the old White Mines [NY 7404 2224]. The thickness decreases northwards from about 150 m at the southern end of Roman Fell to 30 m in Gasdale.

North of Murton Pike, the Roman Fell Shales die out, and the various divisions of the Basement Beds become unrecognisable, although the basal unconformity is still marked by a strong and persistent spring line, by the presence of abundant pebbles of vein quartz, and by red-staining of the underlying slates to a depth of several metres. These features may be followed almost continuously from Murton Pike to the north side of Great Rundale, where the Brownber Fault displaces the base of the Carboniferous upwards about 200 m. The slates on the crest of Brownber are red-stained, and the Carboniferous base reappears on the east slope of the hill from whence it may be traced northwards to a point 500 m NW of Sink Beck, where it is again cut off by the same fault.

The overlying quartz conglomerate and sandstones are exposed at intervals all along the face of the fells. The best sections are in the vicinity of Sink Beck. Lithologically, the beds resemble the Roman Fell Sandstones, but are much more pebbly. Higher sandstones, seen at intervals along the path leading to High Cup Nick and in Sink Beck, are finer-grained and greenish in colour, with sporadic bands of quartz conglomerate. They are included in the Basement Beds, but may be the lateral equivalent of the Ravenstonedale Limestones.

Orton Group

Orton Group strata are exposed on the Pennine escarpment and in Teesdale. They have also been proved in boreholes at Closehouse Mine in Lunedale. They are an alternation of sandstones, marine limestones and shales, and are thickest in the area below Middle Fell on the escarpment, where the generalised succession (Burgess and Harrison, 1967, p.209) is:

As in the Basement Beds, all parts of the sequence decrease in thickness northwards, the Group thinning to about 80 m just south of the Swindale Beck Fault. North of the fault, in Swindale, the thickness reduces abruptly to less than 20 m, the higher beds of the sequence being cut out by the sub-Alston Group unconformity. The amount of erosion decreases northwards, and on the north side of Scordale all three divisions are again present, totalling 45 m in thickness. North of Murton Pike, much of the Ravenstonedale Limestones apparently pass laterally into sandstones included in the Basement Beds and the thickness of the group reduces to about 30 or 35 m. The Ashfell Sandstone and Hillbeck Limestones persist to the northern edge of the district. Due to the narrowness of the outcrop, only one formation, 'Shales with limestone' is shown on the map north of the Swindale Beck Fault. In Teesdale and Lunedale, only the highest beds of the sequence, equivalent to the Hillbeck Limestones, are present.

Details

The Ravenstonedale Limestones (Figure 22) are the oldest exposed truly marine Lower Carboniferous strata in the Brough district. They comprise silty limestones, oolites, dolomites, sandstones and shales. At the base is a sequence of dolomitic sandstones, siltstones and silty limestones, with scattered quartz pebbles, devoid of fossils, about 25 m thick, best exposed in Dobbyhole Gill. These beds are followed by the 'Thysanophyllum pseudovermiculare band' (Garwood, 1913, pp. 463–464; Turner, 1927, p.354), about 15 m of muddy limestones with an abundant marine fauna (Figure 22), exposed both in Dobbyhole Gill [NY 7600 1915] and High Close Sike [NY 7684 1790]. The succeeding Brownber Pebble Bed (Garwood, 1913, pp. 464–465; Turner, 1927), a sandy oolite with abundant large pebbles of vein quartz, contains the brachiopod Syringothyris cuspidata. The bed is best exposed in High Close Sike, where the section is:

Overlying strata, the 'Michelinia grandis Beds' of Garwood (1913, p.466), are poorly exposed in High Close Sike. The only good section is that in Burton Close Sike [NY 7632 1871] where the sequence is:

The lowest beds probably lie very close above the Brownber Pebble Bed. The band of oolite is also exposed in Dobbyhole Gill [NY 7604 1926] and the succeeding beds crop out in many of the small streams, between there and High Close Sike.

Farther north, the Ravenstonedale Limestones are poorly exposed in Swindale Beck, Hilton, where their thickness is reduced to 30 m, and on the north side of Scoredale [NY 7525 2186] where the section is:

The only other exposure of these beds is on the south side of Great Rundale [NY 7115 2710] where the following section is exposed:

From its lithology, fauna and stratigraphical position, it is probable that the bed of oolite is the equivalent of the Brownber Pebble Bed to the south, and if so, it appears that the remainder of the Ravenstonedale Limestones has passed laterally into sandstone. The sandstone and quartz pebbles of the Brownber Pebble Bed, by inference, are derived from the Carboniferous Basement Beds to the north.

The Ashfell Sandstone differs markedly from the sandstones of the underlying strata, in being mainly fine-grained quartzitic arenites, with abundant igneous quartz and acid feldspar (Burgess and Harrison, 1967). Near the top of the sandstones, there are several beds of ganister. The sandstones are well exposed in hillside scars below Musgrave and Long fells. They are also seen in Swindale, on the south side of the Swindale Beck Fault [NY 7620 2070], in Scordale and in Great Rundale (see above). Like the underlying beds, they thin northwards (Figure 21) and (Figure 22), decreasing from about 55 m in the south to 5 to 6 m in the most northerly exposures. The sandstones are unfossiliferous, and their age is inferred by comparison with the sequences in Ravenstonedale.

The Hillbeck Limestones are well exposed only in a landslip scar at Hillbeck Wall End [NY 7804 1706] (Figure 22). The formation, about 80 m thick, consists mainly of limestone, with subordinate shale and sandstone. The limestones are mainly dark blue-grey biomicrites, with an abundant fauna of large colonial corals (Figure 37); the highest beds are calcarenitic and contain bands of crinoidal and algal biosparite. The sandstones resemble those of the Ashfell Sandstone (Burgess and Harrison, 1967, p.221). They occur at two main levels, with limestones and shales intervening, and appear to be laterally persistent, suggesting that some form of rhythmic sedimentation took place, possibly akin to that in the overlying Alston Group.

Beneath Musgrave and Long Fells, and in Swindale, south of the Swindale Beck Fault the Hillbeck Limestones are exposed at intervals in small scars, but there are no continuous sections.

North of the fault, they are cut out by the sub-Alston-Group unconformity, but they reappear in Scordale, where they are partly exposed around the old Murton Mines [NY 763 228], and are at least 30 m thick in Gasdale, where they were proved in a shaft at the White Mines (Dunham, 1948, p. 135). North of here, they are only well exposed in Great Rundale [NY 7122 2748] (Figure 21), where a section on the north side shows:

In Swindale Beck, Knock, a 6-m section about 20 m below the base of the Melmerby Scar Limestone [NY 7032 2864] exposes muddy limestones with a 1-m sandstone band, possibly that seen in the lower part of the above section (Johnson and Dunham, 1963, p. 25). All along the escarpment, from Hillbeck Wall End to Rundale, the topmost beds of the Hillbeck Limestones, where exposed, are seen to be dolomitised and show signs of penecontemporaneous erosion, resulting from a break in sedimentation between the Orton and Alston Groups.  ICB

A poorly exposed inlier of Orton Group strata occurs in Teesdale west of the Burtreeford Disturbance. Mapping suggests that up to 21 m of beds belonging to this group are present. Limited outcrop and borehole evidence (Figure 23) suggests a broad two-fold division into lower sandstones and conglomerates and upper fossiliferous limestones and shales. The occurrence of Productus garwoodi and the record of Lithostrotion minus (Johnson and Dunham, 1963) support a Holkerian age for these strata (p. 58).

Near Cronkley Pencil Mill [NY 8448 2955] scattered exposures of red and orange sandstones and quartzose conglomerates can be seen resting unconformably on slates of the Kirkland Formation. The unconformity was formerly excavated here first by Gunn and Clough (1878) and later by Harry (1950) who noted 3.35 m of Carboniferous beds, mainly sandstone with only 0.91 m of conglomerate and pebbly sandstone at the very base. He found that pebbles of rhyolitic and andesitic rocks of the Borrowdale Volcanic Group slightly predominated over material from the Skiddaw Group, and concluded from both the composition and the shape of these pebbles that they were derived locally and had been transported only a short distance.

At Falcon Clints [NY 8352 2817] a virtually complete, but largely thermally metamorphosed section through the topmost 17.40 m of the group is seen, viz.

Lower Palaeozoic rocks are probably not far beneath the lowest beds seen here.

A complete, but thinner, sequence was proved in the Wrentnall Shaft [NY 8105 3053] at Cow Green, just beyond the northern margin of the district. The following section was communicated by Mr J. R. Foster-Smith of Middleton in Teesdale:

A number of boreholes in the vicinity have entered Orton Group strata but in no case was the full thickness proved.

A thickness of 41.15 m of limestones, sandstones and shales, proved in boreholes at Closehouse Mine [NY 850 228], Lunedale, is thought to belong to the Orton Group but palaeontological support is lacking. Details of the most complete borehole (Figure 23) are given by Hill and Dunham (1968, p.358). DWH

Alston Group

The Alston Group consists of an alternation of limestones, mudstones, siltstones and sandstones, deposited in a well-marked rhythmic sequence. The group is conveniently split into two parts, the junction lying at the base of the Peghorn (= Lower Smiddy) Limestone. The base of the group is at a disconformity, usually marked by erosion and dolomitisation of the underlying Orton Group strata. The top is taken at the base of the Great Limestone, approximately the base of the Namurian (Millstone Grit) Series. On the Alston Block the thickness of the group is fairly constant at about 300 m, but to the south the thickness increases, reaching 600 m in the Stainmore Trough. The thickness of strata in the Upper Alston Group in the south-west corner of the district is comparable to that on the Alston Block but the Lower Alston Group here forms part of the Stainmore Trough sequence.

Lithology

Most of the Lower Alston Group consists of limestone, terrigenous material being restricted for the most part to subordinate siltstone partings. In the Upper Alston Group, however, elastics are much commoner and limestones generally make up less than 25 per cent of the sequence.

The limestones of the Lower Alston Group are mostly pale grey and commonly pseudobrecciated in appearance, with the exception of the dark grey, very fine-grained Birk-dale Limestone. The limestones of the Upper Alston Group are typically dark grey though the Single Post Limestone and the central part of the Peghorn Limestone are composed of pale grey pseudobreccia. Both the dark and pale grey limestones are biomicrites. Sparry calcite cements are lacking except as a drusy infilling of cavities in foraminifera, corals and unbroken shells. The paler grey limestones have been subjected to extensive recrystallisation during diagenesis, usually resulting in an increase in grain size. According to Robinson (1971), the shade difference is due to the greater organic content of the dark limestones. The bioclastic component in these rocks is mainly composed of comminuted shell debris with scattered crinoid columnals, bryozoa, foraminifera and algae; other fossil groups are also abundant locally. Complete or broken brachiopod shells and corals are distributed at random throughout the main limestones and also are commonly concentrated into local accumulations. The limestones of the Alston Group are regarded as the deposits of a shallow sea (Moore, 1958, 1959; Johnson and Dunham, 1963), because of their abundant shallow-water benthonic fauna and flora in a lime-mud matrix. Comparison with modern areas of carbonate deposition suggests that this sea may have been only a few metres deep.

The terrigenous clastics of the Alston Group form a spectrum of variable lithologies, viz.: calcareous mudstone, silty mudstone with ironstone nodules, laminated siltstones, interlaminated siltstones and silty sandstones (striped beds), silty sandstones, fine-grained flaggy and ripple-marked sandstones, fine- to medium-grained cross-bedded sandstones locally with erosive bases. Seatearth and coals are only locally developed. Carbonaceous and plant matter occurs abundantly in these rocks. Fully marine faunas occur in the mudstones, decreasing in numbers and variety with increasing silt and sand content except in the case of sandstones immediately adjacent to limestones, which may contain sporadic bioclastic debris. The terrigenous clastic sediments of the group have long been regarded as deltaic in origin (e.g. Phillips, 1836), a view supported by Moore (1958, 1959, 1960) in a comparison with modern deltas.

Cyclothems

That the various lithologies of the Alston Group tend to occur as a repeated rhythmic sequence has been known at least since the early nineteenth century (Forster, 1809; Phillips, 1836). The rhythmic units are commonly referred to as cyclothems (Wanless and Weller, 1932), a term first introduced to the northern Pennines by Dunham (1948, p. 14; 1950). Comparable, though not identical, cyclothems occur in the overlying Upper Carboniferous strata. The rhythmic units of the Alston Group are known specifically as Yoredale Cyclothcms as they are characteristic of the strata formerly known as the Yorcdale Series (p.27).

Within the district a complete cyclothem comprises the following sequence of lithologies (see also Hudson, 1924; Dunham, 1950; Moore, 1958; Johnson and Dunham, 1963):

The total thickness and proportion of each lithology varies from cyclothem to cyclothem and one or more of the lithologies may be absent. Boundaries between the various members are usually gradational, the clastic sediments forming a broadly coarsening-upwards sequence. The base of the limestone member (1) is normally sharp except where it is sandy and rests directly on sandstone (4b). Where the sandstone member (4b) forms a channel-infilling it has a sharp, erosive, contact with the underlying beds and locally forms a fining-upwards sequence.

Major cyclotherms comprising the strata between the bases of adjacent thick, named limestones are commonly of the order of 30 m thick. Many include in their upper parts a number of thinner minor cyclothems. The major cyclothems have proved laterally continuous not only within the district but over the whole of the north of England. Most of the minor cyclothems also persist throughout the district but their continuation elsewhere is less certain (but see Holliday and others, 1975).

The cyclothems of the Alston Group record a delta which spread laterally into a shallow sea and was repeatedly flooded by marine waters. The relative importance of eustatic sea-level changes, local and regional tectonics, and climatic and sedimentological factors in determining the advance or retreat of the sea, relative to the delta, are as yet unknown. DWH, ICB

Details

Reference to the most important sections in the Alston Group are given in Appendix 1. The sections are represented graphically in (Figure 24), (Figure 25), (Figure 26) and (Figure 27).

Lower Alston Group

The oldest Alston Group strata (Figure 24) are dark cherty limestones and shales alternating with pale pseudobreccias occurring only to the south of the Swindale Beck Fault, where they overlie the pale grey calcarenites at the top of the Orton Group. They are about 19 m thick on the north face of Long Fell [NY 767 203], thickening southwards to 30 m at Hillbeck Wall End [NY 783 173]. A similar sequence of beds is present near Asby [NY 700 085] just beyond the south-west margin of the district where it was named the Potts Beck Limestone by George and others (1976). The stratotype of the Asbian Stage with its base corresponding to the base of the Potts Beck Limestone, has been taken at Little Asby Scar [NY 6988 0827] (George and others, 1976).

Overlying these beds, and together with them comprising the Great Scar Limestone, are massive crag-forming pale grey, commonly pseudobrecciated limestones which maintain a consistent thickness of 60 m S of the Swindale Beck Fault. A similar, but thicker, sequence is to be seen in Potts Beck [NY 700 090], near Asby.

North of the Swindale Beck Fault and its continuation the Closehouse-Lunedale Fault, the Melmerby Scar Limestone, made up of pale grey limestones 35 m thick, rests on Orton Group strata. Sometimes the base is sharp, e.g. Falcon Clints in Teesdale [NY 8352 2817] but elsewhere the limestone is underlain by a discontinuous bed of siltstone, up to 1 m thick, commonly containing limestone nodules (Turner, 1927, p.344), which rests on the dolomitised top of the Orton Group. This bed may be a condensed deposit equivalent to all the dark, cherty, Alston Group limestones south of the Swindale Beck Fault. It is thought that the Melmerby Scar Limestone is more or less equivalent to the upper pale grey limestone of the Great Scar Limestone.

In Teesdale the limestone is cut by the Whin Sill and throughout much of its thickness has been thermally metamorphosed and recrystallised to a saccharoidal marble (Plate 8). Marbles of this type occur at the surface over large areas of Widdybank and Cronkley Fells and on these 'sugar limestones' rendzina soils have formed which support a relict arctic-alpine flora (Johnson and others, 1971). The limestone has a proved thickness of about 37 m in borings at Close House Mine [NY 850 228] (Hill and Dunham, 1968).

The Melmerby Scar Limestone is split, a little less than 20 m from the base, by a major bedding plane, with some mudstone, which can be identified in many sections (Figure 24) and which commonly forms a marked step in the feature made by the limestone. Two fairly consistent mudstone partings also occur in the top 6 to 8 m (Figure 24). All three mudstone beds appear also to be present in the Great Scar Limestone. Other mudstone partings seem to be more local. Sandstones occur sporadically in the lower part of the Melmerby Scar Limestone at outcrop in Teesdale e.g. [NY 8526 2808]; [NY 8065 2769] and also in borings a little beyond the northern edge of the map at Cow Green, where they include minor siltstones and mudstones, and are up to 8 m thick, at a level about 21 m below the top of the limestone. These rocks are probably the southerly extension of elastic rocks within the Melmerby Scar Limestone to the north and east as seen at outcrop (Trotter and Hollingworth, 1932; Arthurton and Wadge, in press) and in borings at Rookhope (Dunham and others, 1965), Roddymoor (Woolacott, 1923) and Harton (Ridd and others, 1970).

On the Alston Block the beds immediately above the Melmerby Scar Limestone are variable in thickness and lithology. In many sections, e.g. Knock Ore Gill [NY 705 303], a fine-grained ganisteroid sandstone rests directly on the Melmerby Scar Limestone. In some other sections, e.g. Swindale Beck, Knock [NY 705 287] and Great Rundale Beck [NY 715 276], siltstone intervenes between the sandstone and the limestone, the first appearance in the sequence of a Yoredale cyclothem. The thickness of these elastics ranges from 1 to 7 m. However, on Cronkley Fell in Teesdale, a medium-grained cross-bedded sandstone 12 m thick occurs at this level and may be a channel fill; nearby [NY 8464 2783], sandstone dykes cut the top of the Melmerby Scar Limestone. There is no marked thickening of these beds over the Swindale Beck Fault for by this time the hinge-line in the Pennine escarpment area had moved south to the Barnarm and Thornthwaite faults across which the strata between the Melmerby Scar and Robinson limestones thicken from 4 or 5 m (Hillbeck Wall End [NY 787 173]) to 19 or 20 m (Swindale Beck, Brough [NY 806 165]). A further thickening to about 30 m occurs within the basin (Figure 24). These beds are 18 to 19 m thick in the south-west corner of the district near Asby, indicating that at the time this was a basinal area. However, westwards to the margins of the district the thickness decreases to 5 to 6 m.

The Robinson Limestone, like the Melmerby Scar Limestone, is a pale grey massive limestone, with sporadic pseudobreccias and a scattered coral-brachiopod fauna. It is 4.5 to 5.5 m thick over much of the Alston Block and thickens towards the south first gradually to about 10 m at Closehouse [NY 850 229] and 7.5 m at Hillbeck Wall End [NY 787 173], and then more suddenly over the Thornthwaite Fault to more than 20 m in the basin. The thickness at Asby, where the limestone is extensively dolomitised, is 10.5 m. On Cronkley Fell, Teesdale [NY 843 284] the Robinson Limestone locally has been recrystallised to a coarse marble as a result of the thermal metamorphism accompanying the intrusion of the Whin Sill.

The strata above the Robinson Limestone up to the Birkdale Limestone form a fairly distinctive cyclothem in the basin area (Figure 24), where the Barnarm and Thornthwaite faults again acted as hinges. On the block area the interval is thin, up to 2 m, mainly composed of sandstone. A number of sections (Great Rundale Beck [NY 714 274], High Cup Gill [NY 728 251], Scordale [NY 757 225]) give evidence of penecontemporaneous erosion and potholing of the top surface of the Robinson Limestone. This suggests that locally subsidence was not able to compensate for the withdrawal of the sea, following the deposition of the Robinson Limestone, and some areas were temporarily emergent.

The Birkdale Limestone, though thin, forms an important marker throughout the district (Burgess and Mitchell, 1976), being characteristically very dark grey, fine-grained and pyritous. It is overlain by first siltstones and then sandstone, together totalling up to 7.25 m on the block, thickening over the Thornthwaite Fault, to 10.5 m in the basin. The thickness at Asby is 4 m indicating that this had become a block area. Many sections on the Pennine escarpment show a channel-filling sandstone at this level (Figure 24) and (Figure 47) and the Birkdale and Robinson limestones and the top few metres of the Melmerby Scar Limestone are locally cut out. Though its margins cannot be clearly defined, a similar channel-filling sandstone occurs on Cronkley Fell, possibly extending southwards to Closehouse. Medium-grained cross-bedded sandstone 12 to 14 m thick rests directly on the Robinson Limestone (the Birkdale Limestone is cut out) which is never more than 2 m thick and is locally missing [NY 852 274]. The apparent local absence of the Birkdale Limestone in the southwest of the district may have a similar explanation.

Upper Alston Group

The Upper Alston Group shows Yoredale cyclothems at their maximum thickness; there are about two dozen recognisable units which can be grouped into eight major cyclothems corresponding to the major named limestones of Forster (1809).

The Peghorn Limestone (Figure 25) (Dunham, 1948, p.14) ranges from 6.5 m thick on the block to 14 m in the basin. It exhibits a characteristic three-fold lithological division which makes it a useful marker in the field (Johnson and Dunham, 1963; Burgess and Mitchell, 1976). The lowest part is composed of dark grey bioclastic limestone with sporadic Osagia ('Girvanella')nodules or haloes; the central part comprises a pale grey limestone ('white post') (Plate 4) and has a sharp eroded top; the highest part is made up of dark grey bioclastic limestone with abundant Osagia nodules and haloes and is the lateral correlative of the Girvanella Nodular Bed (Garwood, 1913) of the Shap district. In High Cup Gill [NY 737 257] a thin mudstone separates the Girvanella Nodular Bed from the 'white post'.

A thin sandstone and siltstone sequence (maximum thickness of 5 to 6 m in Teesdale) overlies the limestone and shows no thickening into the basin. The overlying Smiddy Limestone actually thins from between 6 and 10 m on the block to 3 or 4 m in the basin. It is a dark grey, evenly-bedded limestone becoming darker and argillaceous with thin shale partings towards the top. Osagia nodules and haloes occur sporadically throughout the limestone and commonly are concentrated in two bands, one 1.5 to 2 m from the base and the other 2 m from the top (Johnson and Dunham, 1963, p.36). On the 1:50 000 geological map it was not always possible to indicate the Peghorn and Smiddy limestones separately, especially in areas such as the Pennine escarpment where the topography is steep and the intervening interval very thin. In such areas the symbol SmL should be taken to mean Smiddy Limestone with Peghorn Limestone.

The strata between the Smiddy and the Lower Little limestones form one major cyclothem containing at the top a persistent minor cyclothem, and on the Alston Block there is little lateral variation (maximum thickness 30 m) (Figure 25). The mudstones above the Smiddy Limestone are very calcareous and fossiliferous at the base. Locally (e.g. Cow Green boreholes) they contain one or two thin dark grey limestone bands. The overlying sandstone (Smiddy Ganister) appears to be present in most areas. The Grain Beck Limestone (Burgess and Mitchell, 1976), 1 to 2 m thick, is dark fine-grained, bioclastic, and occasionally sandy at the base. A few metres of sandstone and shale intervene between this limestone and the Lower Little Limestone. When traced into the basin the Smiddy Limestone to Lower Little Limestone interval thickens (55 m in Augill Beck) and another minor cycle appears with the occurrence of sandstone overlain by sandy limestone in the siltstones above the Smiddy Limestone (Figure 25). On the block, this extra cycle is represented by the thin limestones, noted above, at this horizon. The Grain Beck Limestone is thicker in the basin (about 4 m) and has a central parting of white calcareous shelly sandstone. Near Brough, in Swindale and Augill becks (Figure 25), the Smiddy Ganister is still an important bed while the strata above the Grain Beck Limestone thicken (10 to 15 m) with the appearance of a prominent sandstone. Farther south the total thickness of the major cyclothem decreases and the relative thickness of the component minor cycles changes markedly. The Smiddy Ganister is absent (Howgill Sike [NY 825 101]) and the thickness between the Smiddy and Grain Beck limestones is reduced to a few metres. Sections to the south in the Kirkby Stephen (40) district (Dakyns and others, 1891) indicate that these two limestones remain close together while the beds between the Grain Beck and Lower Little limestones are also much reduced, and the latter two beds correlate with the two halves of the Gayle Limestone of Wensleydale (Burgess and Mitchell, 1976). The Lower Little and Grain Beck limestones are rarely separated on the 1:50 000 map and are indicated by the single symbol LLtL.

The Lower Little Limestone is dark grey and bioclastic and, though argillaceous at the top, has few mudstone partings or wisps on bedding planes. A thin Osagia band occurs low in the limestone according to Johnson and Dunham (1963, p.36). The limestone remains fairly constant at 5 or 6 m thick throughout the whole area and does not thicken markedly into the basin. The overlying siltstones and sandstones actually thin from 18 to 10 m into the basin area; Augill Gorge, (Figure 25) but examination of sections to the south; River Belah, (Figure 25) together with published information (Dakyns and others, 1891) suggest that this trend is reversed on the southern margin of the district and to the south, where the sandstone is thick and forms a conspicuous feature round the northern end of the Hartley Anticline. Over much of the district a minor cyclothem is present just beneath the Jew Limestone; many borings and natural sections show sandy limestones and shelly calcareous sandstones at this level (Figure 25).

The Jew Limestone is a dark bioclastic limestone, usually with abundant fossils; at many localities it contains a Saccamminopsis band about two-thirds of the thickness above the base. On the block it ranges from 8 to 10 m thick and reaches 15 m in the basin. The overlying measures, up to the Tynebottom Limestone, also thicken (from about 25 m to about 45 m) from block to basin, but with little difference in succession. Mudstones and siltstones overlie the limestone everywhere, containing, towards the southern margin of the sheet; Augill Gorge, (Figure 25), a thin bed of cream-coloured oolitic limestone. An important sandstone overlies the siltstones and has been mapped over a large part of the district; in many sections it contains several siltstone partings. The top of the sandstone is shelly and passes up into a thin sandy limestone which marks the first of three minor cyclothems occurring beneath the Tynebottom Limestone (Figure 25). The lower two of these are exceedingly persistent, but the third is less well defined and can only be recognised locally. ICB, DWH

The Tynebottom Limestone (Figure 26) ranges in thickness from 8 to 10 m on the block to about 13 m in the basin. It commonly has a Saccamminopsis band 1.5 to 2 m from the top. In many areas it contains thin mudstone partings. The strata between the Tynebottom and Scar limestones are known as the 'Alternating Beds' (Figure 26) and are composed of alternations of sandstone, siltstones, mudstones, some thin limestones and shelly sandstones, and rare thin coals. In all, including the Tynebottom Limestone, as many as eight minor cyclothems can be recognised hereabouts in the basinal sequence, but the persistence of some of these, especially on the block, is less certain. To some extent this doubt is a reflection of poor and incomplete exposures, though in a number of important sections in Teesdale, some finer points of stratigraphical detail are obscured by the Whin Sill and related metamorphism. Of these minor cyclothems, only three have been recognised over any great area on the block. The Maize Beck Limestone (Johnson and Dunham, 1963, p.39), up to 1 m thick, can be recognised in most of the basin sections and on the Pennine escarpment, and in the type area in the Maize Beck valley (possibly also in Lunedale). There does not seem to be a limestone at this level farther east in Teesdale. The Single Post Limestone is a light grey mottled pseudobrecciated limestone (white coarse marble where thermally metamorphosed in Teesdale) up to 3.5 m thick, and forms a good marker horizon. By way of contrast the Cockle Shell Limestone is a dark argillaceous limestone, commonly with abundant gigantoproductoids and L. junceum. It is variable in thickness (1.8 to 4.5 m). The other marine horizons in the Alternating Beds are very thin, composed of dark limestone, or more usually sandy limestones or shelly sandstones and siltstones. Some doubt has been expressed in the past as to the persistence and continuity of the Single Post and Cockle Shell limestones (Dunham, 1948, p.19; Johnson and Dunham, 1963, p. 40), but both are continuous and persistent in this district, even though because of their thinness they may not be visible in poorly exposed ground. Their distinctive lithological characters and consistent stratigraphical position argue against Dunham's suggestion (1948, p. 19) 'that where two limestones are found, they are not necessarily the same over the whole area'.

The overlying Scar Limestone (Figure 27) is a grey wavy-bedded bioclastic limestone with few mudstone partings. It commonly contains abundant Lithostrotion junceum and in the southern half of the district has a Gigantoproductus band at the base (Turner, 1956). The limestone is variable in thickness, the extreme values of 4 and 9 m occurring within a mile in Bow Lee Beck, Newbiggin, Teesdale (Figure 27) but there is no noticeable thickening into the basin, where a similar thickness range is observed. The strata from the Scar Limestone to the Five-Yard Limestone form a simple sequence of mudstone and siltstone overlain by sandstone, 15 to 25 m thick on the block increasing to 35 m in the basin. The base of the sandstone rests on a channelled and eroded surface of the underlying siltstones in parts of Upper Teesdale [NY 8005 2525] and in Augill Beck [NY 8255 1588]. The upper part of the sandstone commonly contains siltstone partings.

The Five Yard Limestone (Figure 27), dark grey with evenly-bedded mudstone partings, is not well exposed; 4 to 5 m thick on the block, it thickens to about 6 m to the south in the River Belah. The strata between the Five Yard and Three Yard limestones, 14 to 23 m thick on the block increasing to 28 to 32 m in the basin, also form a simple cyclothem with siltstone, usually thin, at the base grading upwards into sandstone above. A central siltstone parting occurs in the sandstone in many sections while the upper beds are shaly and include seatearth. A coal about 0.46 m thick occurs at this upper level in Dowgill Beck (Figure 27). Locally, on Meldon Hill, these sandy beds fail and the whole interval is composed of siltstones.

The Three Yard Limestone is similarly poorly exposed within the district. Only 1.5 m thick in the Middleton in Teesdale and Newbiggin area (Figure 27) columns 3–7, it is thicker elsewhere reaching a maximum of 6 to 7 m in the south and south-west of the district, where in some sections (e.g. Augill Beck, Dowgill Beck; (Figure 27), columns 9 and 10), the limestone is split by a ganisteroid sandstone. This is a common feature in areas to the east of the present district where a coal may also occur between the leaves of the limestone (Woolacott, 1923; Mills and Hull, 1976). The interval between the Three Yard and Four Fathom limestones is laterally variable within the district and is not well exposed. Mapping suggests that on the Pennine escarpment and in the south-west of the district the interval, 14 to 20 m thick, is one simple cyclothem-siltstone and sandstone probably overlain by shaly and seatearth-like rocks. However, eastwards along Meldon Hill the sandstone dies out and sporadic outcrops indicate that the interval is composed mostly of siltstones. In the north-east corner of the district, near Middleton in Teesdale, 2 to 3 m above the Three Yard Limestone, there is a 6- to 8-m sequence of thin impure limestones (sandy and argillaceous) with thin sandstones and siltstones, often shelly and calcareous (Figure 27). Borings to the north of Middleton, in the Wolsingham (26) district have also proved a limestone and shelly sequence at this level extending towards Stanhope. The strata between the Three Yard and Four Fathom limestones thicken into the basin; in Augill Beck (Figure 27) column 9, a siltstone overlain by a sandstone sequence is capped by the Borrowdale Coal, about 0.6 m thick, which has been extensively worked in the area (Plate 5). A minor cyclothem with a calcareous silty sandstone containing spiriferoid brachiopods at the base completes the sequence. A thin coal smut occurs locally beneath the Four Fathom Limestone. Total thickness of the strata between the limestones here is 23 m. Farther south they thicken to about 37 m (Dowgill, (Figure 27), column 10) and the beds below the Borrowdale Coal are here made up of two cyclothems. At the base of the upper of these there occurs a thin limestone which has no obvious equivalent to the north.

The Four Fathom Limestone is rather paler grey in colour than most of the other limestones of the Upper Alston Group (though not as pale as the Melmerby Scar Limestone) and is wavy bedded with few mudstone partings. Locally chert nodules are common. In the southern part of the district a Dibunophyllum band occurs near the base (Turner, 1956). The limestone is generally 5 to 6 m thick and shows little thickening into the basin. The overlying strata to the Iron Post Limestone, 14 to 17 m thick on the block and only slightly thicker (19 m) in the basin, are composed of shales passing up into sandstone; locally a seatearth and thin coal may be present at the top. The relative proportion of sandstone and shale is variable (Figure 27), and in some sections only very small amounts of sandstone are present.

The Iron Post Limestone, a dark shelly limestone commonly with a red ferruginous top and a gastropod band near the base, is a thin but persistent marker throughout the district. In one post 1 m thick on the block, it is about 2 m thick in the basin and made up of two posts locally with a mudstone parting. In most sections a normal cyclothemic sequence overlies the limestone; viz. mudstone, siltstone, sandstone with seatearth and discontinuous thin coal at the top (e.g. Meldon Hill [NY 7752 2886] and Borrowdale Beck) (Figure 27) column 9. In Hudeshope Beck (Middleton in Teesdale), and in borings to the north, the sandstone, known as the Tuft Sandstone, is split by siltstone and in most sections is friable and poorly cemented. The thickness of these measures ranges from 8.5 to 14 m, the thicker sections being in the basin. ICB, DWH, JHH

In the areas immediately to the south and east of the district the highest Alston Group strata are extensively silicified in association with a considerable thickness of chert. The only known occurrence of this phenomenon at this level within the district (but see also p.44) is in a small inlier of Alston Group strata in Sleight Holme Beck in the south-east corner of the district, where 12 m of Tuft Sandstone and siltstone separate the Great Limestone from chert and silicified limestone apparently at the level of the Iron Post Limestone. CRB

Chapter 5 Upper Carboniferous: Namurian

The main outcrop of Namurian (Millstone Grit) Series strata, in the south-eastern part of the district, the Cotherstone Syncline (Reading, 1957), covers an area of over 180 km², bounded on the west by the Stainmore escarpment and on the north by the Lune Valley. A smaller area in the north-eastern corner of the district is a part of the much larger outcrop of rocks of this age bounding the Durham Coalfield. On the Alston Block, farther west, small outliers cap Green Fell, Mickle Fell, Meldon Hill, Little Fell and Musgrave Fell. In the Vale of Eden, rocks of this age are present over an unknown, but probably considerable area underlying the Permo-Triassic rocks, and in an eastwards-facing monocline (Stainmore Outlier) along the Augill and Argill faults.

Previous research

The presence of 'Millstone Grit' strata in the Brough district was noted by Phillips (1836) but it was not until the Primary Survey that the extent of these rocks was delineated in some detail. The highly fossiliferous Botany Limestone was described by Garwood (1913, p. 483), and further details of the stratigraphy of the Stainmore area were provided by Turner (1935). Carruthers (1938), in his attempt to correlate the Namurian sequences of the Alston and Askrigg blocks, recorded sections in Lunedale and Baldersdale. Dunham (1948) described sections in Teesdale. The sections in the Stainmore Outlier were described by Ford (1955) and by Owens and Burgess (1965). Sections in the Sleight Holme district were briefly referred to by Wells (1955b, 1958). In a comprehensive account of the stratigraphy of the Cotherstone Syncline, Reading (1957) divided the Namurian sequence into 'cyclothems' and traced individual marine horizons throughout the area. While recent borehole evidence suggests an alternative correlation for several of the marine bands in the central part of the syncline, the current resurvey largely confirms the results of this research. Elliott (1974, 1975) has interpreted the clastic sediments of the Great Limestone cyclothem in the Brough district as forming part of a major delta lobe, with a complex history of progradation, abandonment and post-abandonment sedimentation.

Classification

In northern England the Namurian Series cannot be equated with the rocks which have been described traditionally on lithological grounds as 'Millstone Grit'. The underlying 'Upper Limestone Group' is now known to be also of Namurian age (Johnson and others, 1962). Over most of the area, only strata of the Pendleian (E₁) and Arnsbergian (E₂) stages of the standard Namurian goniatite sequence are present (Figure 28) and (Figure 38). Younger beds are present on Monks Moor, in the north-east, and in the Stainmore Outlier (Owens and Burgess, 1965), where there is a complete Namurian sequence, and strata of the Kinderscoutian (R₁), Marsdenian (R₂) and Yeadonian (G₁) stages have been tentatively identified. The highest Namurian marine band (Swinstone Middle Marine Band) has yielded Gastrioceras cf. cumbriense and is correlated with the G. cumbriense Marine Band of the central Pennine basin. The base of the succeeding Swinstone Top Marine Band, the highest in the sequence to yield costate productoids, is taken as the Namurian-Westphalian boundary. In the Stainmore Outlier there is no obvious distinction between an 'Upper Limestone Group' facies and an overlying 'Millstone Grit' facies, as marine strata and coarse sandstones occur throughout the sequence. Such a distinction may, however, be made in the north-east on Monks Moor (Dunham, 1948, p.45) where the upper (R₂–G₁) part of the sequence consists mainly of coarse-grained thickly-bedded sandstones.

No formations or groups have been formally defined in the Namurian rocks. For convenience of description, in the following account the strata are arbitrarily divided into five sections, the limits of which are marked by widely traceable marine horizons. IGB

Note added in proof It is now proposed that in north-east England the beds from the base of the Great Limestone to the base of the Swinstone Top Marine Band (= Quarterburn Marine Band), i.e. the strata between the top of the Upper Alston Group and the base of the Lower Coal Measures, be referred to as the Stainmore Group. This new lithostratigraphical unit is here defined in the Stainmore Outlier, with its base in Argill Beck [NY 8240 1270] and the top in Mousegill Beck [NY 8369 1242] ((Figure 29), (Figure 30), (Figure 31), (Figure 34), (Figure 35) and (Figure 36); measured section (NY81SW/7)). The preparation of this memoir was completed before thedecision was taken to use this name.  ICB, DWH

Cyclothems

The Namurian strata display a rhythmic pattern of sedimentation broadly similar to that of the Upper Alston Group, but with a much lower proportion of limestone to terrigenous sediments. A generalised cyclothem comprises:

The dominant sediment is dark grey mudstone and siltstone. Any of the other elements may be absent. In particular, many cyclothems end with item 5, passing directly up into calcareous bioturbated sandstone. Sequences of this type tend to be laterally impersistent, the extent of the shelly sandstone or limestone coinciding with that of the underlying sandstone. Thus a simple cyclothem in one area may pass laterally into a much more complex sequence with several mudstone/sandstone units. It seems probable that the lateral variation is the result of the interplay of two main factors. The first of these is relative sea-level change, which led to the formation of widespread and laterally continuous marine bands (rise) or coals (fall). The second is deltaic migration, which introduced sheet or channel sands to the muddy marine environment, causing localised changes in water depth and bottom conditions, and, ultimately, emergence above sea level (Elliott, 1974, 1975).

The Great Limestone is the only limestone in the sequence resembling those of the Upper Alston Group. Higher beds are muddy, and commonly siliceous, producing a characteristic lithology, known as 'lime plate'. Typical lime plate is a hard, siliceous, finely micaceous, grey siltstone with an abundance of calcareous brachiopods and other shelly fossil debris. On weathering, with solution of the calcium carbonate, the rock breaks into platy slabs, with the fossil casts conspicuous on broken surfaces. Silty ferruginous limestones commonly weather to an orange-yellow rotten-stone, known locally as Tamp'. At other levels, calcareous ironstone bands are present, in one of which (Mirk Fell Ironstone, p. 49), cone-in-cone structures are conspicuous.

Stratigraphy

Great Limestone to Little Limestone

The Great (or Main) Limestone (Figure 29) is by far the thickest (12 to 22 m) and purest of the Namurian Limestones. It forms a continuous outcrop, broken by small faults, around the western and northern margins of the Cotherstone Syncline, and reappears in the Greta Valley in the south-western corner of the map. It crops out on the western boundary of the Stainmore Outlier and is intermittently exposed on the east margin of the Vale of Eden Syncline, dipping westwards under the unconformable Permo-Triassic rocks. On the Alston Block, it caps many of the hills-Musgrave, Little, Mickle, Green and Meldon fells-and in the extreme north-east, on the northern side of the River Tees, it marks the south-western limit of the large Namurian outcrop, fringing the Durham Coalfield.

At several localities, the limestone contains bands of dibunophylloid corals usually accompanied by numerous productoids. The corals are in places silicified, and stand out conspicuously on weathered surfaces. These bands resemble the Frosterley Marble of Weardale (Johnson, 1958).

Above the limestone in the south-eastern corner of the district lies the Main Chert (Wells, 1955b, 1958; Sargent, 1929; Reading, 1957). This bed consists of up to 8 m of banded chert which both Wells and Sargent considered to be a primary deposit. Wells (1955b) suggested that the chert formed where river water was discharged into the sea.

However, the results of the present survey (Figure 29) suggest that chert formation may have predated any of the associated deltaic sandstones. The source of the silica is not known but the recurrence of chert in this area in five successive Yoredale cyclothems (Three Yard, Four Fathom, Great, Little and Crow) may indicate a local, possibly juvenile, source of silica-charged fluids.

The term 'Coal Sills' (Forster, 1809) has been widely used for the arenaceous strata between the Great and Little limestones. On the Alston Block (Dunham, 1948, p.27) three sandstones are commonly present, named in ascending order Low Coal Sill, High Coal Sill and White Hazle. In the Brough district, two sandstones, probably representing the High Coal Sill and White Hazle, persist and may be correlated with some confidence in the southern part of the district (Figure 29) columns 4–16. A third sandstone, underlying these two, has a discontinuous outcrop on the Stainmore escarpment, and is tentatively correlated with Low Coal Sill (Figure 29) columns 5, 6, 13. In Lunedale and Teesdale (Figure 29) columns 1–3, four sandstones are present, but they cannot be correlated with individual beds in the area to the south. Marine bands overlie the Low Coal Sill (Figure 29) column 13, and the High Coal Sill (Figure 29) columns 8, 15, 16, in the south, and are also present in the Hargill, Selset, and Snaisgill sections, though they cannot be certainly correlated. ICB

Details

Near Brough, the Great Limestone is exposed in both Swindale and Augill becks and in the River Belah, dipping beneath the Permian rocks of the Vale of Eden. In the Stainmore Outlier, it crops out almost continuously from Heggerscales [NY 832 105] in the south to Well Head Gill in the north. In all these exposures, lying west of the Stainmore boundary faults, it is more or less dolomitised and is about 18 to 20 m thick.

On the Stainmore escarpment the limestone maintains a thickness of 20 to 22 m except around Borrowdale Beck [NY 835 161] (7 to 8 m) and Windmore End [NY 820 172] (12 to 13 m). South of the A66 road, it forms a strong escarpment, broken by several small faults, to the southern edge of the district, and is repeated several times by faulting to the south-west around Ewebank Park. The grey bioclastic limestone is overlain by 4 to 5 m of lime plate, exposed in Mousegill Beck [NY 854 118].

Between Palliard and Banks Gate, the limestone forms a double feature, the lower part being of blue-grey bioclastic limestone, the upper more crinoidal passing up into crinoidal biomicrudite. The top surface forms an irregular limestone pavement, and in Smelt-mill Beck the crinoidal rocks apparently show a considerable depositional dip. The north-westward thinning appears due to the rapid attenuation of these upper beds. North of Windmore End, as elsewhere in the area, the limestones are biomicrites throughout. At Swindale Head [NY 815 188] a conspicuous band of silicified Dibunophyllum is present about 6 to 7 m above the base of the limestone.

On Musgrave Fell, the limestone is poorly exposed except in the gorge of Tarn Gill [NY 806 193], but farther west, on Ley Seat, it forms a wide bare dip-slope, partly disturbed by landslip. Around Lunehead Mines, recent drilling proved a thickness of 22 m. The abnormal thickness of 31 m recorded by Dunham (1948, p.26) was not confirmed, and probably represents repetition of strata by faulting on one of the veins. Eastwards along the north crop, the limestone thins to 17 m at Wemmergill, where it is well exposed in a gorge. This thickness is probably maintained to the eastern margin of the district, where, south of Mickleton, good sections are seen on either side of the fell road at Banklands Quarry and Shields Beck (18.5 m) [NY 971 230] and also 2.5 km to the west at Stoop Hill [NY 954 226]. Coral bands are present at both localities.

In the south-east, the limestone, about 15 m thick, forms the bed of the River Greta for more than 3 km, over part of which distance the river normally flows within the limestone. In Sleight Holme Beck it is fully exposed in the river gorge [NY 965 115] north-east of Trough Heads, and again, farther south, at Sleight Holme. There is a coral band about 0.6 m in thickness near the middle of the limestone.

On the Alston Block, the limestone is about 18 m thick on the fell top outliers. Eastwards it thins to about 14 m near Middleton in Teesdale (Snaisgill, (Figure 29), column 1), though elsewhere in the vicinity it has been proved in underground workings to exceed 20 m (Dunham, 1948, pp. 30–31). Bands of rugose corals and productoids are present at two levels, 5.2 and 1.2 m below the top of the limestone in the Snaisgill section. Probably the same two bands, the lower 2.75 m thick, are seen in a hush 730 m N of High Skears Farm [NY 951 286], and the lower band is exposed in the south bank of the River Tees, 730 m NE of Lonton.

The Main Chert, up to 8 m thick, is exposed in several sections in the south-east, notably Huggill Sike [NY 975 126], Sealgill Quarry [NY 9746 1313] and Rovegill [NY 9645 1293]. It appears to pass laterally into lime plate, which is present on the Stainmore escarpment above the Great Limestone south of the A66 road, but dies out north of Yard Sike (Figure 29) column 12. Several boreholes at Stainmore summit showed the lime plate to be capped by a bed of siltstone with rootlets and drifted plant material. A thin bed of lime plate is present near Selset, so these siliceous beds may extend over a wide area beneath the Cotherstone Syncline.

The Coal Sills are generally well exposed, the more massive sandstones forming strong escarpments above the Great Limestone. The interbedded siltstones and flaggy sandstones are less commonly seen, being obscured by scree in most sections.

In the Stainmore area, the Low Coal Sill is discontinuously exposed on the escarpment, reaching its greatest thickness of 15 m around Borrowdale Beck, where it forms a double feature and may be split by a siltstone parting. The form of the outcrop suggests it may represent the infill of a sinuous channel or channels. North of Borrowdale Beck, a swallow hole through sandstone into the underlying limestone [NY 8224 1723] apparently shows the two in direct contact. In Swindale Beck [NY 7985 1474] about 10 m of coarse sandstone is present only 1 m above the Great Limestone.

The strata overlying the Low Coal Sill were proved only in boreholes at Stainmore Summit (Figure 29) column 13, where the generalised sequence is:

The High Coal Sill and White Hazle form strong features on the escarpment, from the southern edge of the district to Lunehead, and are exposed in many sections around Brough (Figure 29) columns 6–10. The siltstones between the sandstones are generally unfossiliferous, except in Augill Beck north of the A66 road [NY 818 150], where shelly siltstone is present and in the same stream nearer Brough [NY 8035 1436] where the High Coal Sill is capped by a thin bed of dolomitised limestone.

Between Stainmore Summit and Bowes, the High Coal Sill and White Hazle form strong features on the north side of the River Greta. Good sections in Blue Cap Sike [NY 9523 1267], Rovegill (Figure 29) column 15, and Sealgill [NY 9730 1325] show a thin coal overlying the High Coal Sill, overlain by fossiliferous mudstone with a thin limestone. On the south side of the valley, in Sleight Holme Beck, both sandstones and the intervening marine sequence are well exposed, though outside the stream the strata are largely concealed by glacial deposits and peat.

On the northern flank of the Cotherstone syncline, a bore at Rowton Sike (Figure 29) column 4, showed a normal development of the High Coal Sill and White Hazle. A thin limestone proved between the High Coal Sill and the Great Limestone may equate with the Low Coal Sill Marine Band. Eastwards, the Coal Sills are poorly exposed. In Hargill Beck and at Selset, four sandstones are present. The lowest two may represent the Low Coal Sill of the escarpment. They are overlain by fossiliferous mudstones in Hargill Beck [NY 8940 2156] and by muddy limestone in the Selset bores.

On Mickle Fell (Figure 29) column M, a coal is present 2 m above the top of the Great Limestone [NY 802 241]. Two massive sandstones, separated by siltstones, form the summit of the fell. At the eastern end of the fell, a small sandstone outlier appears to rest directly on the limestone top. On the other outliers, Musgrave Fell, Little Fell, Meldon Hill and Green Fell, exposures are restricted to isolated crags.

Around Middleton, the Coal Sills show much variation. The sandstones are seen in Snaisgill Sike [NY 951 280], Marlbeck Gutter [NY 9515 2875] and around Skears Mine [NY 951 280]. At least six minor sandstone-siltstone rhythms are present. The topmost sandstone is overlain by a marine band at the base of a 3- to 5-m thick sequence of siltstones, interbedded at the top with thin sandstone ribs and four thin coals, underlying the Little Limestone. These beds appear to represent the White Hazle of the ground to the south and east.  ICD, ORB, JHH, DACMonograptus

Little Limestone to Crow (Crag) Limestone

Rocks of the Little Limestone cyclothem (Figure 30) crop out in the Stainmore Outlier. They are present on both north and south margins of the Cotherstone Syncline, and underlie most of the peat-covered moorland south of the A66 road. They are also present, though not well exposed, north of the River Tees in the north-east corner of the district.

The Little Limestone is generally a relatively pure crinoidal limestone, sandy at base, ranging from 0.5 to 2 m in thickness. It rests directly on the White Hazle, the topmost 0.5 to 1 m of which is crinoidal and calcareous. A feature of the limestone in the south-eastern part of the district is the presence of vertical tubes, commonly chert-filled, which extend down into the limestone from a thin overlying band of cherty limestone (Rowell and Scanlon, 1957; Wells, 1955b, 1958) and which are ascribed to annelid borings.

Above the limestone is a variable sequence of chert bands, lime plate, limestones and siltstones up to 17 m thick in the south, thinning northwards. These beds are the lateral equivalent of the Richmond Chert Series of Swaledale (Wells, 1955b).

Two sandstones, together comprising the Ten Fathom Grit of the Primary Survey (Dakyns and others, 1891) form the top part of the cyclothem. The lower of these, the Faraday House Sill (Rowell and Scanlon, 1957) is up to 20 m thick over most of the southern part of the district. A coarse-grained cross-bedded sandstone forms strong crag features at many localities, but in places shows rapid lateral passage to thinly-bedded sandstone and striped beds. The sandstone is thin or absent in the north-east (Figure 30) columns 2 and 3. The top bed of the sandstone commonly contains moulds of productoids and spiriferoids, locally passing into sandy limestone, the Faraday House Shell Bed (Turner, 1955). The upper, thinner sandstone, the Uldale Sill (Turner, 1955) is separated from the Faraday House Sill by 2 to 5 m of siltstones. Over most of the area it is thinly-bedded and flaggy, in places passing laterally into striped beds.

On the Alston Block, three sandstones, the Pattinsons, White and Firestone sills, overlie the Little Limestone (Dunham, 1948, p. 31). The Faraday House and Uldale sills are probably the equivalents of the White Sill and Firestone Sill respectively. The former bed is capped by a shelly sandstone (confusingly referred to locally as the Tattinson's lime') resembling the Faraday House Shell Bed. The Firestone Sill is a coarse massive sandstone, and this facies is probably present in the north-east, in the area north of Middleton in Teesdale (Dunham, 1948, p.32) (Figure 30) column 1.

Capping the Firestone/Uldale sill locally is the Crag Coal, a widespread and persistent marker horizon elsewhere in the north of England. ICB

Details

In the Stainmore Outlier, the Little Limestone is exposed in the River Belah [NY 8270 1185], in Mousegill [NY 8275 1291], Argill [NY 8277 1295] and Augill [NY 8184 1500] (Figure 30) columns 6–8. Near Brough, it is seen in Swindale Beck [NY 7967 1472] and Augill Beck [NY 8035 1429]. The overlying lime plate is well exposed only in Argill (Figure 30) column 7, where it is thin, and succeeded by fossiliferous mudstone with bands of muddy limestone. On the escarpment, the limestone caps the scarp of the White Hazle in the south, on Causey Moss [NY 867 106], and between Yard Sike (Figure 30) column 10, and Windmore End [NY 830 170]. The lime plate is seen in Yard Sike, Smeltmill Beck, Borrowdale Beck and, farther north, in Deadman Gill [NY 824 190]. It is up to 8 m thick and in the more southerly sections it contains several bands of chert.

North of the A66 road, the Little Limestone forms an extensive plain between Stainmore Summit and Old Spital. Farther east, it is exposed, with the overlying lime plate, in Rove Gill. South of the River Greta, the best exposures are in Ay Gill (Figure 30) column 11, where the marine sequence above the Little Limestone is over 17 m thick.

In the north, Rowton Sike exposes 6 m of lime plate, faulted at base. In the River Lune the Little Limestone and overlying siltstones with ironstone nodules are exposed south of Blake House (Carruthers, 1938, pl. 13, 5). Two beds of lime plate are present in the siltstones, the lower 2 m, the upper 1.6 m thick, and the marine sequence totals 14 m in thickness. In the Selset boreholes, (Figure 30) column 4, this thickness has increased to 19 m. Farther east exposures are poor, the only good section being in Shields Beck where the sequence is at its thinnest (Figure 30) column 3. In Snaisgill, the Little Limestone is partly exposed, and succeeding beds include mudstone with thin limestone and ironstone bands (Figure 30) column 2.

South of Green Fell, in a small area of Namurian strata caught up along the Closehouse-Lunedale Fault, Gunn (on Primary Survey field-slip Yorkshire 3 NE) recorded an outcrop of the Little Limestone in a small hush, now grassed over.

The Faraday House Sill, in the Stainmore Outlier, consists of up to 20 m of coarse-grained cross-bedded sandstone, except south of the River Belah, where it passes laterally into thinly-bedded sandstones and striped beds. The coarse facies is seen on the escarpment, on Low Greygrits [NY 885 096] and also forming the High Crag, south-east of Smeltmill Beck. North-west of Smeltmill Beck, the coarse sandstone is replaced by thinly-bedded flaggy sandstones, generally poorly exposed except in Borrowdale Beck. The Faraday House Shell Bed caps the Faraday House Sill in Mousegill [NY 8280 1275], the River Belah [NY 8270 1191], and Borrow-dale Beck [NY 8385 1658], and is also seen on the crags 150 m NW of Smeltmill Beck [NY 8539 1513]. The overlying Uldale Sill is generally fine-grained and very thinly-bedded and at several localities (e.g. (Figure 30), columns 6, 9) the interval between Faraday House Shell Bed and Crow Limestone is almost entirely represented by sandy siltstones.

On the southern side of the Cotherstone Syncline, the Faraday House and Uldale sills are not well exposed, though they form several prominent features (Beldoo Hill [NY 893 138], Ravock [NY 952 142], and Roper Castle [NY 887 115]). The best section is provided by Ay Gill (Figure 30) column 11, [NY 9123 1154] where the Faraday House Shell Bed unusually comprises 1.90 m of coarse-grained, calcareous, very shelly sandstone and sandy limestone, underlain by 0.75 m of sandy siltstone and a thin (0.06-m) coal.

North of the syncline, flaggy sandstones are seen in Rowton Sike [NY 840 197], Clove Sike [NY 845 196] and Deadman Gill [NY 857 197], where the sequence is thin. Boreholes at Selset Reservoir (Figure 30) column 4, proved a sequence closely comparable to that on the escarpment, with a thick (18 m) massive, coarse-grained Faraday House Sill capped by shelly sandstone overlain by siltstones, and a thin sandstone at top underlying the Crow Limestone.

Farther east, the strata thin markedly; in Shields Beck (Figure 30) column 3, the Faraday House Sill and Shell Bed together are only 3 m thick. The Uldale Sill is not exposed. A comparable eastwards thinning is visible in the Middleton area. West of Hudeshope Beck, in the Skears Mines (Dunham, 1948, p.33; (Figure 30), column 1) the combined Faraday House and Uldale (Firestone) sills comprise over 18 m of coarse-grained sandstone. The same strata in Snaisgill (Figure 30) column 2, comprise only a few metres of thinly-bedded, rooty sandstone in a mainly siltstone sequence. A short distance to the south of this stream, however, the Uldale (Firestone) Sill reappears, being over 9 m thick in Crag's Quarry [NY 9535 2615] and maintains this thickness to the eastern edge of the district. ICB, CRB, JHH, DACM

Crow Limestone to Upper Felltop Limestone

The beds from the Crow Limestone to the Upper Stonesdale Limestone show marked lateral variation, both in lithology and thickness (Figure 31). In the western part of the area, in the Stainmore Outlier and on the southern part of the Stainmore escarpment the sequence is thin (25 m). Only three limestones—Crow, Lower Stonesdale and Upper Stonesdale—are present, separated by dark grey siltstone with scattered ironstone nodules. This sequence closely resembles that in the type area of the Stonesdale Limestones, West Stonesdale, 8 km to the south (Hudson, 1941; Rowell and Scanlon, 1957). In the east the sequence is much thicker (60 m) and includes extra limestones and several beds of sandstone. The thickest of these, overlying the Lower Stonesdale Limestone, is correlated with the Low Grit Sill of the Alston Block. It is overlain by the Hunder Beck Limestone, for which the type locality is in Hunder Beck 100 m upstream from the confluence with Mawmon Sike [NY 9282 1705]. This bed was formerly correlated (Reading, 1957) with the Lower Stonesdale Limestone. Two lenticular sandstones lie between this limestone and the Upper Stonesdale Limestone, the lower capped by a bed of bioturbated sandstone and the upper by a sandy limestone. The Upper Stonesdale Limestone is a mid-grey bioclastic limestone, up to 0.5 m thick. At outcrop it shows a closely spaced pattern of vertical joints and weathers ochreously to rounded blocks. The top surface is patterned with ferruginous concretions. It forms a marker horizon in the Namurian sequence (Reading, 1957, p.42), extending over the whole district, exposed in almost all sections (Figure 31).

Above the limestone are dark grey siltstones, variably fossiliferous, with ironstone nodules. Throughout the central and eastern parts of the district the fauna includes abundant trilobite pygidia, concentrated in a band 3 to 5 m above the limestone. The overlying siltstones contain several beds of lime plate or muddy limestone. Underlying the Mirk Fell Ironstones are two sandstones. The lower of these is coarse-grained, infilling an irregular system of channels 100 to 200 m wide and up to 10 m deep eroded in the underlying siltstones. The sandstone bases are commonly coarsely conglomeratic with siltstone and sandstone clasts up to 0.5 m long. The topmost beds are ganisteroid and are overlain by the Mirk Fell Coal. This coal is thick only in Baldersdale (Figure 31) and (Figure 33) where it was worked from small adits in the lower reaches of Hunder Beck. A mudstone with Lingula and marine bivalves separates the coal from the overlying sandstone; both mudstone and coal are absent at several localities as a result of erosion at the base of this sandstone.

The Mirk Fell Ironstones is the name applied to the succeeding sequence of dark grey marine mudstones and siltstones, with lenticular irony limestone bands and abundant ironstone nodules, and which is up to 20 m thick. In their type section, Mirk Fell Gill, south of the Brough district, they have a fauna mainly dominated by molluscs and nuculoids, and have yielded the goniatitc Cravenoceras cowlingense (Hudson, 1941), indicating a low E, age. In the Brough district, on the Stainmore escarpment and in Baldersdale the lower beds yield a much more varied marine fauna, including productoids, spiriferoids and crinoidal debris. The limestone bands, though laterally continuous over short distances, cannot be correlated from section to section. They commonly show cone-in-cone structure, and contain small ovoid phosphatic concretions. In the southern part of the Stainmore Outlier, the fauna is less abundant and the limestone bands are ferruginous, with chamosite ooliths. The marine sequence is present throughout the district (Figure 31) columns 1–9, except on the extreme eastern margin, in Lower Baldersdale and Deepdale (Figure 31) columns 10 and 11. The equivalent strata exposed in the central and eastern parts of the area were previously correlated, not with the Mirk Fell Ironstones, but with a higher horizon, the Coalcleugh Marine Beds (Reading, 1957). Evidence to the contrary is provided by numerous boreholes sunk recently at Balderhead during construction of the Balderhead Reservoir.

The marine strata are succeeded by variable micaceous siltstones and thin sandstone bands, commonly with worm tracks and borings, capped by seatearth. In Lower Baldersdale and Deepdale, a thick coarse sandstone at the same level fills a channel cut through the Mirk Fell Ironstones. This bed is equivalent to the Kettlepot Ganister of Upper Swaledale (Rowell and Scanlon, 1957).

The Tanhill Coal (= Holme Wood Coal of Owens and Burgess, 1965) which overlies the Kettlepot Ganister, is thin or absent except in Coal Gill, in the upper reaches of Hunder Beck [NY 9145 1600] and at the southern end of the Stainmore escarpment where it is locally up to 0.30 m thick. It is overlain by siltstones with ironstone nodules, generally unfossiliferous, but with Lingula and Orbiculoidea at one locality in the Stainmore Outlier [NY 8315 1145] where the name Holme Wood Marine Band was applied (Owens and Burgess, 1965).

Over most of the Cotherstone Syncline, the siltstones are overlain by a very variable sequence of thinly-bedded sandstones and siltstone, with thin seatearths and coals. In the west, on the Stainmore escarpment and in the Stainmore Outlier, a massive sandstone, the Stricegill Grit, is present. It is up to 28 m thick with a sharp erosive base, and in Mousegill Beck (Figure 31) column 2, it rests on the seat-earth below the Tan Hill Coal. In the east, in Lower Baldersdale and Deepdale, feature mapping suggests that another channel sandstone is present at the same level.

The lateral variation in the beds from Crow Limestone to Upper Felltop Limestone is summarised in (Figure 32). ICB

Details

The Crow Limestone (Crag Limestone of the Alston Block) is well exposed in the Stainmore Outlier and on the Stainmore escarpment. Farther east there are fewer sections, though the outcrop can commonly be located by reference to the underlying Ten Fathom Grit. Lithologically, the limestone is variable, consisting of bands of relatively pure crinoidal limestone separated by calcareous or siliceous silty limestone arid siltstone (lime plate).

In the Stainmore Outlier, the limestone reaches a thickness of over 6 m in the River Belah; exposures in Mousegill, Argill and Augill show it to thin rapidly to less than 2 m in the north. On the escarpment the limestone is well exposed in Borrowdale Beck and again, farther upstream, at the foot of Crook Beck. Farther north it is seen twice, repeated by faulting in Rowton Sike [NY 8394 1967] and a short distance to the cast in Clove Sike [NY 8446 1955] and Black Crook [NY 8565 1960]. In these sections it is 5 to 6 m thick, in two parts. The lower is of dark grey tough, sandy bioclastic limestone, up to 1 m thick separated by 1 to 2 m of grey siltstone from the upper part, which shows a variable development of lime plate with calcareous siltstone and lenticular bands of more crystalline bioclastic limestone. Six kilometres to the east, the limestone was proved in bores at Selset Reservoir [NY 919 210]; and it is exposed in stream sections at Grassholme [NY 9313 2156] and Shields Beck [NY 9682 2273]. The sections are similar to the previous ones. On the south side of the Cotherstone Syncline, the limestone is poorly exposed, except in Deepdale [NY 995 154], where it is in two beds, the lower 3.2 m, the upper 3.9 m, separated by 3.3 m of grey mudstone.

The strata between the Crow and Lower Stonesdale limestones are mainly siltstones, with nodular ironstone. They are thinnest in the River Belah (1.8 m) thickening eastwards to 14 m in the Stainmore escarpment.

The Lower Stonesdale Limestone (Knucton Shell Beds) is present only in the west and north-east of the district, being apparently replaced by sandstone in the intervening ground. In the Stainmore Outlier, it consists of several ribs of crinoidal limestone and lime plate up to 4 m thick, and is exposed in all the main streams. On the escarpment, the limestone is comparable in lithology and thickness. It forms a strong feature, marked by abundant fragments of lime plate, which has been traced almost continuously from Yard Sike [NY 880 143] in the south to Petty Gill [NY 826 190] in the north. Good sections are seen in Borrowdale Beck and Crook Beck.

On the northern edge of the Cotherstone Syncline, the limestone is exposed in Rowton Sike [NY 8388 1935], where its thickness is reduced to 1 m. In Black Crook, 1.7 km to the east, a good section from the Crow Limestone up to the base of the next sandstone shows only black siltstone with ironstone nodules, with no trace of the limestone. Similarly, in the boreholes at Selset Reservoir, the limestone was not recorded, though a short distance to the east at Grassholme Bridge [NY 9287 2135] 0.1 m of muddy limestone is exposed in the siltstone below the same sandstone. An excellent section in Shields Beck [NY 9272 2266] exposes 1.5 m of lime plate and silty limestone on the same horizon. This bed has been correlated with the Knucton Shell Beds of the Alston Block. On the southern margin of the Cotherstone Syncline, the Lower Stonesdale Limestone is not exposed.

The strata between the Lower and Upper Stonesdale limestones show marked lateral variation. In the Stainmore Outlier, as in the type area of west Stonesdale, the two limestones are separated by dark grey, almost unfossiliferous siltstones with ironstone nodules. In the central and eastern parts of the Cotherstone Syncline, a thick sandstone (believed to correlate with the Low Grit Sill of the Alston Block) is present between the two limestones, and the strata above it include limestones, fossiliferous mudstones and thin sandstones.

The Low Grit Sill is absent from the southern part of the Stainmore escarpment. In Crook Beck, a thin (1 m) flaggy sandstone is exposed about 4 m above the Lower Stonesdale Limestone. This sandstone thickens northwards, forming a feature on High Edge [NY 8288 1766], above the Lower Stonesdale Limestone. Northwards, it is not exposed. East of Rowton Sike, a peat-covered feature appears above the Lower Stonesdale Limestone position, and the sandstone forming it is exposed in Black Crook [NY 8546 1934] to [NY 8520 1920] 15 m above the Crow Limestone where it is thinly-bedded and micaceous, and is capped by 0.3 m of calcareous bioturbated sandstone with shell fragments. The total thickness here could be as much as 10 m. In Rowantree Beck [NY 9008 2053] a comparable thickness of coarser sandstone is seen, again capped by shelly sandstone. Boreholes at Selset Reservoir [NY 919 209] proved a sequence of sandstones and silty sandstones over 14 m thick, and farther east the same strata are partly exposed near Grassholme Bridge [NY 9325 2144], in Wester Beck [NY 9424 2183] and in Shields Beck [NY 9665 2256]. In Baldersdale, at least 15 m of coarse sandstone, bioturbated and fossiliferous at top, were proved in boreholes at Balderhead Reservoir and a similar thickness is exposed in Hunder Beck [NY 9290 1685]. This is the oldest bed exposed in this area. On the south side of the Cotherstone Syncline it is seen only in Knotts Sike [NY 9445 1530], though it is very well exposed in Deepdale [NZ 009 161] east of the district margin, where it is about 15 m thick and coarse-grained.

The Hunder Beck Limestone and overlying sandstone are restricted to the central and eastern parts of the area. The limestone (4 to 5 m thick) is very variable, consisting of fossiliferous marine siltstones and lime plate, with lenticular beds of coarsely crinoidal muddy limestone, in part silicified. The succeeding sandstones are fine-grained, ripple-cross-bedded with scattered fossils and are usually overlain by a thin (0.05-m) coal. Above this coal is more sandstone, calcareous and shelly, and thoroughly bioturbated. These beds are well exposed in Rowantree Beck [NY 9005 2042]. They were proved in the boreholes at Selset and Balderhead Reservoirs, and are exposed in Hunder Beck [NY 9282 1705], the type locality for the limestone.

The strata immediately below the Upper Stonesdale Limestone also show lateral variation. In the southern part of the Stainmore Outlier and the Stainmore escarpment, only siltstones are present. In Augill Beck [NY 8189 1515] and on the escarpment north of Little Knipe, a 3-m thick coarse sandstone underlies the limestone separated from it by 1 m of dark grey siltstone. The sandstone contains scattered brachiopods, and the topmost 0.5 m, which is very calcareous, passes northwards into sandy limestone. This limestone persists throughout the eastern part of the district (Figure 31) and (Figure 32). It is separated from the sandstone above the Hunder Beck Limestone, by dark grey siltstones with ironstone nodules, and by thin fine-grained greenish flaggy micaceous sandstone, and from the succeeding Upper Stonesdale Limestone by 1 to 2 m of grey micaceous siltstone. It has a characteristic lithology, with conspicuous large (up to 2 or 3 mm) quartz and pink feldspar grains. Sections through these beds are seen in Rowantree Beck, Wester Beck [NY 943 218] and Shields Beck [NY 966 225] on the northern edge of the Cotherstone Syncline. In Baldersdale, Hunder Beck provides good exposures, and the strata were proved in the boreholes at Balderhead Reservoir. On the southern margin of the syncline, the only section is in Knotts Sike [NY 9440 1545].

The Upper Stonesdale Limestone and succeeding strata up to the base of the Mirk Fell Ironstones are fully exposed in the Stainmore Outlier in Intake Gill and in Mousegill Beck (Figure 31). Partial sections are seen in Argill Beck and Augill Beck. Unfossiliferous dark grey siltstones with ironstone nodules 12 to 13 m thick are capped by a thin bed of sandy seatearth. On the Stainmore escarpment, similar strata are poorly exposed in the headwaters of Smeltmill Beck, though the limestone at the base is generally famped and only loose boulders can be seen. In Birkbeck Gill [NY 8442 1682], Bull Gill [NY 8417 1722] and Mickle Gill [NY 8323 1778] a 0.05-m bed of lime plate is present 3 m above the Upper Stonesdale Limestone, and the succeeding strata include several beds of flaggy sandstone (Figure 31) column 3. The lime plate bed is exposed in Rowton Sike, but farther east there are no exposures for 6 km. In Rowantree Beck (Figure 31) column 4, the Upper Stonesdale Limestone is overlain by fossiliferous siltstones with ironstone nodules. A bed of lime plate is seen in this section also. The topmost strata are seatearth sandstones which in the neighbouring Soulgill Beck includes a discontinuous bed of coal.

In Baldersdale, the Upper Stonesdale Limestone crops out only in Hunder Beck, but it was proved in many of the boreholes sunk during the construction of Balderhead Reservoir (Figure 31) columns 6 and 7. Except in the highest beds, the sequence above is almost identical to that in Rowantree Beck. The coal, up to 0.85 m thick, formerly worked from levels on the west bank of Hunder Beck, and in Upper Baldersdale, between Balderhead and Coombs, is poorly exposed. It appears to be confined to a small basin (Figure 33), possibly with east-west trend, as it is seen farther east in Osmond Gill [NY 991 199]. The underlying channel sandstone is exposed in Hunder Beck [NY 931 178], Mawmon Sike [NY 9254 1703] and Upper Baldersdale. In the first locality, the rapid changes in thickness and channel-form are well displayed in cliff sections. Above the coal is a local marine band, dark grey to brown mudstones with Lingula and bivalves. This bed was not exposed at the time of the survey, other than in the borrow pits for Balderhead Reservoir (now submerged). Above the marine band, there is an upward passage from siltstones with sandstone bands into a medium-grained micaceous sandstone, of which the top 0.10 to 0.20 m are commonly highly bioturbated. Where the coal and marine band are absent, as in Rowantree Beck (Figure 31) column 4, the sandstone has a sharp base, resting on an erosion surface.

The Mirk Fell Ironstones in the Stainmore Outlier are exposed in Intake Gill, Mousegill Beck and Augill Beck. One or two thin (0.10 m) green-spotted ironstone ribs are succeeded by variably fossiliferous mudstones and siltstones with ironstone nodules. Overlying these are thinly-bedded flaggy sandstones and siltstones, with worm casts on bedding planes and vertical worm tubes, U-shaped, up to 0.02 m in diameter and 0.45 m in depth.

On the escarpment, similar sections are poorly exposed north of Little Knipe [NY 8652 1495] and in Birkbeck Gill [NY 8455 1685]. The best exposures are in Mickle Gill [NY 8327 1802] (Figure 31) column 3, where there is a strike section over 200 m long. Three bands of calcareous ironstone are separated by grey silty mudstone. They all show great lateral variation, ranging from discontinuous lenses of ironstone, 0.02 to 0.03 m thick, to irony limestone up to 0.30 m thick. The irony limestones, where thick, show cone-in-cone structure, and are abundantly fossiliferous.

The sequence on the northern side of the Cotherstone Syncline, Soulgill Beck and Rowantree Beck (Figure 31) column 4, is similar. In Upper Baldersdale many of the streams west of Balder Head Farm show partial sections; as they form part of a mainly shaly sequence, the exposures are constantly changing due to local erosion. Hunder Beck [NY 930 176] to [NY 929 170]; [NY 911 164] and its tributaries Mawmon Sike [NY 925 170], Crawlaw Gill [NY 933 168] to [NY 934 165] and Coal Gill [NY 935 160] all provide good sections, with ironstone bands commonly showing cone-in-cone structure.

On the southern side of the Cotherstone Syncline, the Mirk Fell Ironstones have not been identified.

The sandstones in the upper part of the sequence in the preceding sections are all flaggy, and are generally capped by a seatearth. In Lower Baldersdale, quarries at Yew Scar [NY 974 199] are in a coarse massive sandstone, apparently at the same level, which rests on the Mirk Fell Coal, and occupies the whole of the interval up to the Tan Hill Coal (Figure 31) column 10. This sandstone is also seen in How Gill and Osmond Gill, 1.5 km downstream, and in Deepdale (Figure 31) column 11. The Tan Hill Coal horizon can be recognised in most sections, though the coal itself is thin. In Lower Baldersdale (Osmond Gill [NY 9909 1984]), Upper Hunder Beck (Coal Gill [NY 9145 1600]), Upper Baldersdale (Mir Gill [NY 8963 1773]) and at the southern end of the Stainmore escarpment [NY 866 146] it is up to 0.30 m thick. Sections farther north have a very thin coal or coaly shale (Blea Gill [NY 9100 1825], Gill Sike (Figure 31) column 7, Water Knott Gill [NY 9260 1765], West Carnigill (Figure 31) column 6, and Rowantree Beck (Figure 31) column 5, overlain by dark grey siltstones with ironstone nodules, at some localities with a thin rib of green-flecked ironstone at base.

In the Stainmore Outlier, the coal is 0.10 m thick in Intake Gill (Figure 31) column 1, but thins northwards; it is absent in the Mousegill section (Figure 31) column 2, owing to erosion at the base of the Stricegill Grit. The overlying silty mudstones are poorly fossiliferous.

Over most of the Cotherstone Syncline, the strata underlying the Upper Felltop Limestone are thinly-bedded sandstones with beds of seatearth and several thin coals. Good sections are seen in Rowantree Beck (Figure 31) column 4, West and East Carnigill and other streams. In the west a coarse grit, Stricegill Grit, is exposed in the Stainmore Outlier (Argil) Beck, Augill Beck, Mousegill, Hocker Gill, River Belah, Intake Gill) and caps the Stainmore escarpment, forming the crags from Black Tewthwaite in the south to Iron Band in the north. ICB, CRB, JHH

Upper Felltop Limestone to Botany Limestone

The Upper Felltop Limestone forms a marker in the Namurian sequence. It is typically a mid-grey biomicrite between 0.30 and 0.45 m thick, with a banded appearance due to the presence of layers of brachiopod shells which stand out on weathered surfaces. The characteristic lithology and weathering make it easily recognisable, even where dolomitised, or where, owing to famping, the outcrop is concealed, and only loose blocks are visible at surface. In the east (Lower Baldersdale) it is sandy and less easily identifiable.

The strata between the Upper Felltop Limestone and the Botany Grit are a varied sequence of alternating siltstones and flaggy sandstones (Figure 34). Shelly sandstones occur at several levels, and one of these, the Fossil Sandstone, forms a strong feature which has been mapped over a large part of the Cotherstone Syncline (Reading, 1957).

The Botany Grit is a coarse massive sandstone, commonly pebbly at base with a sharp and in places transgressive relationship to the underlying strata.

The Botany Limestone (High Wood Marine Beds) is a sequence of marine mudstones with nodular and shaly limestone bands with a rich fauna of corals including Aulina rotiformis, brachiopods, bivalves and the nautiloid Tylonautilus nodiferus. They are of E₂b age, and represent the same horizon as the Shunner Fell Marine Beds of the Askrigg Block and the Grindstone Limestone of the Alston Block. Capping the limestone on Botany Ridge is a thin bed of sandstone. This bed is also seen in Yawd Sike, where it is 2 m thick, and fossiliferous at the top. The High Wood Marine Beds also are succeeded by sandstone, calcareous and shelly at the top, well exposed in Mousegill Beck where it forms a waterfall. ICB

Details

In the Stainmore Outlier the Upper Felltop Limestone is exposed in Augill [NY 8206 1514], Mousegill [NY 8319 1264], Hocker Gill [NY 8315 1167] and Coldkeld Beck [NY 8368 1039]. In all these outcrops it is somewhat dolomitised, but, with the underlying massive sandstone, it provides a link between sections essential to the interpretation of this complex ground.

Around the margins of the Cotherstone Syncline its outcrop is largely conjectural. In the south, it is exposed in Crawlaw Beck [NY 9300 1627], and on the north in Rowantree Beck [NY 8949 1942]. In Upper Baldersdale, Great Aygill [NY 8861 1689], Red Gill [NY 8802 1679], Balder Beck [NY 8837 1717], West [NY 9023 1881] and East Carnigill [NY 9134 1908] and Blea Gill [NY 9095 1801] all provide sections as do How Gill [NY 9573 1967] and Haw Beck [NY 9759 1915] farther east, and the outcrop in other streams may be located by the presence of loose blocks of characteristic lithology. In the Stainmore Outlier, Argill, Mousegill (Figure 35) and Hocker Gill all expose good sections in the overlying beds, and in Baldersdale they are seen in Blind Beck, New Houses Beck, How Gill and How Beck (Figure 34). The Fossil Sandstone is exposed in all four of these streams, characteristically overlain by black mudstones with ironstone nodules.

On Stainmore, the Botany Grit (High Wood Grit of Owens and Burgess, 1965) reaches its greatest thickness of over 12 m in Argill Beck, thinning both northwards and southwards. It is split by a siltstone parting, the sandstone above being poorly bedded and grading up into a seatearth on which rests the High Wood Coal. On Botany Ridge, the grit is of comparable thickness, forming strong features all around the fell, and north of Balderhead and Blackton Reservoirs where it is repeated by faulting. It also forms the conspicuous outliers of Kelton Hill, Shacklesborough and Goldsborough. A thin coal resting on seatearth overlies the grit in Howgill and How Beck (Figure 34), and is succeeded by siltstones with thin sandstone ribs.

In the Stainmore Outlier the High Wood Marine Beds are best exposed in Mousegill Beck [NY 8338 1259] and Hocker Gill [NY 8325 1166]. Sections in the Botany Limestone (Figure 34) are seen at Howgill Head [NY 9552 2051], Scaletree Quarry [NY 9631 2099], Greenhill Quarry [NY 9444 1970] and in Yawd Sike [NY 9627 1755]. The proportion of limestone to mudstone is very variable. ICB, CRB, JHH

Top of Botany Limestone to top of Namurian

Strata above the Botany Limestone are preserved only in the Stainmore Outlier and on Monks Moor, in the extreme north-eastern corner of the district.

In the Stainmore Outlier Mousegill Beck (Figure 35) and (Figure 36) provides the only continuous sequence, though other streams contain exposures of parts of the succession, especially the sandstones, sufficient to make possible a correlation with the standard succession in Mousegill.

Details

The mudstone overlying the sandstone at the top of the High Wood Marine Beds is abundantly fossiliferous at base and again about 8 m higher up, at which level a sandy limestone is seen in Hocker Gill. The overlying 13-m sandstone, thinly-bedded at base, medium-grained and more massive at top, is followed by seatearth siltstone, on which rest marine mudstones. The mudstones become sandier upwards and are succeeded by three thick beds of hard yellow ganisteroid sandstone, separated by black siltstones. Above the third bed there is a metre of flaggy calcareous sandstone, on which rests a pale yellow sandy crinoidal limestone, the Peasah Wood Limestone [NY 8348 1251]. The characteristic appearance of these 6 m of beds makes them easily identifiable in the Belah Valley [NY 8341 1125], Hocker Gill [NY 8333 1166], Old Park Gill [NY 8344 1318], Argill [NY 8339 1335] to [NY 8329 1345] and Augill [NY 8206 1533] where they are well exposed on the south bank of the beck and form an essential link in the interpretation of this otherwise poorly exposed section. The fauna of the mudstone overlying the limestone in Mousegill includes Posidonia corrugata, indicating an horizon not higher than E₂. This mudstone is separated from the Mousegill Marine Beds by about 22 m of strata. The lowest of these are silty, thinly-bedded sandstones with coaly plant fragments. They grade up into siltstones and mudstones with ironstone nodules and with Lingula, succeeded by a coarse cross-bedded sandstone overlain by a seatearth. These beds contain no diagnostic fauna, but may represent the Sabdenian (H) Stage.

Above the seatearth are the Mousegill Marine Beds, the section at this point being:

The fauna of the mudstone immediately above the 0.15-m coal includes Homoceras henkei and is therefore of R₁ age (R. circumpli catile Zone). Mudstones on about the same horizon are poorly exposed in Hocker Gill [NY 8338 1165], in Argill Beck [NY 8336 1342] to [NY 8345 1336] and in Craghouse Gill [NY 8340 1365].

The succeeding 45 m of strata are an alternation of sandstones, commonly with shell bands, siltstones and fossiliferous mudstones, the fauna of which is not zonally diagnostic. Two thin coals are present in Mousegill. The same beds are also exposed in Hocker Gill, Argill and Craghouse Gill, but no detailed correlation between sections can be made. A coarse massive sandstone present in Argill [NY 8344 1342] is not seen in the other sections.

Above the upper coal in Mousegill are 4.50 m of silty mudstones with fish remains, and these are overlain by 12 m of thinly-bedded sandstone with siltstone partings. A band of mudstone with Planolites ophthalmoides follows, above which is sandstone, flaggy in Mousegill and Hocker Gill, but passing northwards into coarser massive sandstone in Craghouse Gill and in Augill Beck.

Above the sandstone is the Swinstone Bottom Marine Band [NY 8363 1244]. This is succeeded by 12 m of sandstone, flaggy at base, coarse and pebbly above, with a seatearth at the top. On this seat-earth rests the Swinstone Middle Marine Band [NY 8365 1243] which has an abundant fauna including Gastrioceras cf. cumbriense and is taken to represent the G. cumbriense Marine Band. Above this band is another coarse cross-bedded sandstone; it is up to 20 m thick and grades up into a seatearth siltstone, on which rests the Swinstone Top Marine Band [NY 8370 1242], the base of which is here taken as the boundary between the Namurian and Westphalian. All three marine bands are exposed in Hocker Gill, where the sequence is closely similar to that in Mousegill. In Argill, Craghouse Gill and Augill, the marine bands are not seen, but the intervening massive sandstones have been identified, and the top of the Namurian traced throughout the Stainmore Outlier. ICB

The mapping on Monks Moor is based on feature mapping and discontinuous exposures, and the correlations were made by comparison with neighbouring areas and with the Woodland Borehole (Mills and Hull, 1968). No details of the strata between the sandstones are known.

Chapter 6 Dinantian and Namurian Palaeontology

Dinantian and Namurian strata of this district were first included in a comprehensive, fossil-based zonal scheme by Garwood (1913). He used the vertical distribution of corals and brachiopods and his classification was correlated with Vaughan's (1905) work on the Carboniferous Limestone of the Bristol area. The use of Vaughan's zones (C₂, S₁, S₂, D₁, etc.) was subsequently extended to most British Dinantian rocks. Garwood's scheme was refined locally by Turner (1927) and is still applicable to the mostly calcareous part of the succession up to the top of the Lower Alston Group (Figure 37). Ramsbottom's suggestion (1973) that the Lower Carboniferous rocks of Britain up to the base of D₁ comprise four major sedimentary cycles has provided a new chronostratigraphical rather than faunal foundation for their division and correlation. The major cycles are recognised in part by the characteristic faunas which were the basis of Garwood's scheme. George and others (1976) have proposed the subdivision of the Dinantian of the British Isles into stages which mostly correspond to Ramsbottom's (1973) cycles (Figure 37).

In the higher part of the succession, where, the beds are of Yoredale facies in the Upper Alston Group and modified Yoredale facies in the Namurian, Garwood's subzones have never been as useful, partly because they are too thick and partly because the Yoredale limestones are easily recognised for local mapping purposes. The coral zones proposed by Hill (1938, pp. 15–18) facilitate the correlation of the Yore-dales with high Dinantian and low Namurian calcareous successions elsewhere in Britain but, since the work of Bisat (1924), the main tool for the classification of these and younger Namurian rocks has been the goniatite zones established in the basinal facies of the Central Province (i.e. Lancashire, south Yorkshire and the north Midlands). As goniatites occur only sparsely in the northern England Yoredale facies, they are supplemented by other shells including a few bivalve and nautiloid species which are common to both Yoredale and basinal facics, and, more recently, spores. The evidence has been reviewed by several authors, notably Rayner (1953), Johnson and others (1962), Owens and Burgess (1965), and Ramsbottom (1974, fig. 25).

The Yoredale succession of Wensleydale, immediately south of the present district has been correlated with Carboniferous rocks elsewhere, by studies of the distribution of conodonts (Rhodes and others, 1969) and foraminifera (Hallett, 1971). On the Alston Block and in the Northumberland Trough, calcareous algae also have been useful in correlation (Holliday and others, 1975). The classification of the Dinantian and Namurian rocks of the Brough district and their relation to various zonal schemes is shown in (Figure 37) and (Figure 38).

During the resurvey large numbers of Lower Carboniferous and Namurian macrofossils have been collected and identified. Some of the limestones have been thin-sectioned for the study of algae and foraminifera or sampled for the extraction of conodonts. The distribution of some of the many species identified is shown in (Figure 37) and (Figure 39) but the number of forms recorded is too great for the results to be shown here in full. They are listed on data record cards which may be examined at the north of England office of the Institute. Some of the results are already published in Owens and Burgess (1965) and Burgess and Wadge (1974).

The fossils collected from the Westphalian rocks of the district have already been listed and discussed by Owens and Calver in Owens and Burgess (1965) and are not considered here.

Dinantian

Orton Group (Arundian and Holkerian)

The most complete sequence of Orton Group rocks in the district is south of the Swindale Beck Fault and exposed at the foot of the Pennine escarpment 3 to 6 km NW of Brough (Figure 22). There, the Thysanophyllum pseudovermiculare band contains Lithostrotion martini, Antiquatonia molarum, 'Camarotoechia' fawcettensis and the eponymous coral (Plate 6)1. T. pseudovermiculare is a characteristic species at this level in north-west England, in beds which are now thought to be, at least in part, of Arundian age (George and others, 1976). The typical fossil of the overlying Brownber Pebble Bed is Syringothyris cuspidata (Plate 6)2. It is a long-ranging species but is especially common about this level in most of northern England.

The Michelinia grandis Beds are also of Arundian age. They locally contain Michelinia megastoma (= Monograptus grandis) but the index fossils of Garwood's subzones in his Monograptus grandis Zone, Stenoscisma [Camarophoria] isorhyncha and Delepinea [Chonetes] carinata have not been recorded in the district although the presence of Amplexizaphrentis enniskillini, Caninia sp. cylindrica group and Clisiophyllum ingletonense suggest a C. carinata Subzone age for the higher part of the section in Burton Close Sike (p.31). The Ashfell Sandstone is thought to represent a regressive phase at the end of the Arundian.

The Hillbeck Limestones coincide with the Holkerian Stage. The fossils collected from the section at Hillbeck Wall End (p.31) illustrate an upward impoverishment of the fauna. Corals, especially Lithostrotion martini and L. portlocki, are common in the lower beds but collections from the upper part of the section indicate a largely brachiopod and bivalve fauna, and at the top algae and bryozoa predominate. Garwood's two subzonal index fossils in his Productus corrugato-hemisphericus Zone have been recorded; Davidsonina [Cyrtina] carbonaria is present in the lower part of the section and Lithostrotion [Nematophyllum] minus was recorded here by both Garwood (1913, p. 539) and Turner (1927, p.357). The most common macrofossils are Linoprotonia spp.Near the top of the section Productus garwoodi and Punctospirifer sp.occur together with bryozoa, the distinctive assemblage of Garwood's Bryozoa Band.

Few diagnostic fossils have been collected from Orton Group rocks north of the Swindale Beck Fault. The presence of Michelinia megastoma and Syringothyris cuspidata from the north side of Scordale (p.31) indicates Monograptus grandis Beds and the S. cuspidata from Great Rundale, together with the lithology of its parent rock, suggest correlation with the Brownber Pebble Bed. In Teesdale, the lowest fossiliferous Carboniferous rocks have yielded Lithostrotion minus (Garwood, 1913, p.541; Johnson and Dunham, 1963) and ?Productus garwoodi (p. 33) both suggesting a correlation with the high part of the Hillbeck Limestones.

Lower Alston Group (Asbian)

The Great Scar and Melmerby Scar Limestones contain typical Asbian biotas, mostly concentrated in bands, with large numbers of corals and brachiopods and smaller numbers of bivalves and gastropods. The characteristic corals collected include Carcinophyllum vaughani, Dibunophyllum bourtonense, Lithostrotion spp.(including the small phaceloid L. junceum, a species not found lower in the succession) and Palaeosmilia murchisoni (Plate 6)4. The brachiopods recorded which are typical of the Asbian are Davidsonina septosa, Delepinea comoides and Gigantoproductus sp. maximus group (Plate 6)3. The limestones also contain many foraminifera including archaediscids, endothyroids, tetrataxiids and textulariids and algae, amongst which Koninckopora inflata (Plate 6)5, is common.

Garwood (1913) noted two brachiopod bands in his Lower Dibunophyllum Zone, one, with Daviesiella llangollensis near the base and the other containing Davidsonina septosa near the top. It is now recognised that the beds containing D. llangollensis have a restricted geographical distribution (Ramsbottom, 1974, p.60). The species has not been recorded in the Brough district. Doughty (1974) and Ramsbottom (1974, p.61) also remarked that in Yorkshire there are several bands with Davidsonina septosa in the higher parts of D₁ (Asbian). The species has been recorded locally in Teesdale, near Birkdale, and in Swindale (Knock) by Johnson and Dunham (1963) and during the resurvey near Ashy.

Small globular chambers which may be referable to Saccamminopsis have been found at two levels in the Lower Alston Group of the district; near the base of the Great Scar Limestone and in the Robinson Limestone. They are about 1.5 mm long--much smaller than the Saccamminopsisfusulinaformis of the Upper Alston Group which may be up to 5.0 mm long.

The highest beds of the Lower Alston Group show the onset of cyclic Yoredale sedimentation and changes in the fauna which have been discussed by Burgess and Mitchell (1976). The Robinson Limestone contains the characteristic Asbian fossils Clisiophyllum rigidum, Dibunophyllum bourtonense and Gigantoproductus spp. maximus group, but has also yielded forms which are probably the forerunners of typical Brigantian faunas; Aulophyllum fungites aff. pachyendothecum, Diphyphyllum aff. lateseptatum and Gigantoproductus sp. giganteus group. The fauna is also characterised by the widespread abundance of Lithostrotion pauciradiale, a species especially common in the dark grey lower limestones of the Upper Alston Group. The highest Lower Alston Group limestone, the Birkdale, commonly yields only Lithostrotion junceum. The few species recorded from the mudstones in the highest beds of the Lower Alston Group include no diagnostic forms.

Upper Alston Group (Brigantian)

The cyclic deposition of the rocks in the Upper Alston Group was accompanied by cyclic changes in the fauna. These changing faunas (Figure 38) and (Figure 39) have been discussed by several authors including Hudson (1924) and Johnson and Dunham (1963) and essentially comprise a variety of limestone faunal assemblages followed in order by those found in calcareous and ferruginous mudstones. Normally the only fossils found in the arenaceous beds in the upper part of each cyclothem are terrigenous plant remains.

The limestones contain large numbers of corals and brachiopods as well as foraminifera, bryozoa, molluscs (especially bivalves), ostracods, trilobites and abundant crinoid debris. The foraminifera include archaediscids, fusulinaceans, endothyroids, textulariids and tetrataxiids including the distinctive species Howchinia bradyana. Small brachiopods, e.g. Avonia youngiana and Alitaria panderi, and solitary corals typical of Hill's (1938) Cyathaxonia fauna are distributed sporadically in the limestones but many of the clisiophylloid and compound corals and the larger brachiopods such as the gigantoproductids and dictyoclostids are commonly found in distinct bands or biostromes which can be traced over large areas. Examples are the Gigantoproductus band at the base of the Scar Limestone and the Dibunophyllum band in the Four Fathom Limestone, both noted by Turner (1956). Other discrete fossil bands in the limestones include the algal biostrome in the Peghorn Limestone known as the Girvanella Nodular Bed (Plate 6)6 and the beds crowded with Saccamminopsis fusulinaformis found in the Smiddy, Lower Little, Jew, Tynebottom and Four Fathom limestones (Plate 6)11.

The corals collected from Upper Alston Group rocks indicate both geographical and vertical faunal variations. Geographically there appears to be a general decrease in numbers of individuals and species from south-west to north-east, i.e. from basin to block. Vertically the variations conform with Brigantian faunal trends elsewhere. For example, in Lower Alston Group rocks Lithostrotion is represented by several phaceloid forms among which L. martini is very common. From about the top of the Lower Alston Group L. martini is less common and from the Robinson Limestone to the Tynebottom Limestone the most abundant Lithostrotion is L. pauciradiale (Plate 6)12, which is accompanied by phaceloid colonies with corallites of similar size referred to the genera Diphyphyllum and Nemistium. Throughout the Lower Alston Group and the lower part of the Upper Alston Group the small but highly variable species L. junceum is common and from the Cockleshell Limestone upwards it is the most abundant Lithostrotion species and the only one found during the resurvey as high as the Five Yard Limestone. The genus was not recorded above this bed.

Lonsdaleia is a characteristic Brigantian genus although it does occur in both Asbian and lower Namurian strata. During the resurvey it has not been found in Lower Alston Group rocks but it is common in the Peghorn Limestone (both L. duplicata and L. floriformis). One or both species are recorded in most of the Upper Alston Group limestones up to and including the Iron Post.

No finds of Orionastraea have been made during the resurvey but the genus has been recorded locally from the Jew Limestone (Johnson and Dunham, 1963), the Tyne-bottom Limestone (Johnson and Dunham, 1963; Turner, 1927) and the Single Post Limestone (Turner, 1927). Species of the genus are the index fossils of the subzones proposed by Hudson (1929) for high Dinantian strata and his O. garwoodi Subzone was used by Johnson (Johnson and Dunham, 1963) for beds from the top of the Jew to the base of the Five Yard Limestone.

Clisiophylloid corals including Aulophyllum fungites pachyendothecum (Plate 6)13, Clisiophyllum keyserlingi and Koninckophyllum magnificum are common in the limestones of the Upper Alston Group, but Dibunophyllum is the most widespread. In the Lower Alston Group, D. bourtonense (a form with a relatively simple axial structure) is the typical species. In the Upper Alston Group, D. bipartitum subspp.(Plate 6)7, are characteristic and become more abundant and complex axially in the upper part of the Group, reaching an acme in the Great Limestone at the base of the Namurian.

Widespread faunal trends are less easy to detect among Upper Alston Group brachiopods. The gigantoproductids are generally either large shells with fluted trails referred to the Gigantoproductus sp.giganteus group or thin-shelled, markedly convex forms belonging to the genus Semiplanus. This contrasts with the Lower Alston Group forms which are usually broad and rotund and can be assigned to the G. sp. maximus group. Productus (s.s.) is represented by P. productus (Plate 6)9 and (Plate 6)10, and P. concinnus, both characteristic Brigantian forms, and the chonetoids by Rugosochonetes spp.and Plicochonetes crassistria, which occur throughout, and Tornquistia polita, which is rare in the lower beds but becomes more common from the Five Yard Limestone upwards into the Namurian.

Hudson (1924) noted three 'faunal phases' in Yoredale calcareous mudstones although in the Brough district only his 'normal shale fauna' is usually present. This commonly comprises bryozoa (especially Fenestella), brachiopods (including Dielasma, Echinoconchus, Eomarginifera, orthotetoids, Rhipidomella, small rhynchonelloids, Rugosochonetes, Spirifer and smooth spiriferoids) and a few bivalves, notably Edmondia, fine-ribbed species of Aviculopecten and nuculoids (Plate 6)8. Locally, gastropods (including Naticopsis, Straparollus and pleurotomarians), orthocone nautiloids, trilobites (mostly species of Paladin), ostracods and echinoderm remains are also common. The faunas from the mudstone above the Smiddy Limestone in the Cow Green area and above the Tynebottom and Four Fathom limestones throughout the district are especially rich as are the mudstones interbedded with thin limestones in the Single Post cyclothem of Lower Lunedale and the Three Yard cyclothem of the Newbiggin area. The mudstone above the Five Yard Limestone in Newbiggin Beck is noteworthy for its gastropod content.

A number of 'Cyathaxonia fauna' coral species have been collected from the mudstones above the Smiddy Limestone in Augill and those above the Tyncbottom Limestone in the southern part of the district. These coral horizons are the 'modified limestone faunal phases' of Hudson (1924). Tyathaxonia faunas' have been recorded at the same horizons on the Askrigg Block: the Gayle Shale (Hudson, 1925) and the mudstone above the Simonstone Limestone (Miller and Turner, 1931) respectively.

Of rare occurrence but of great stratigraphical importance are Hudson's 'goniatite-lamellibranch shale faunas'. The only horizons in the Brough district at which this phase has been recognised are in the mudstones between the Scar and Five Yard limestones. In this part of the succession in Teesdale, three out of the six localities collected have yielded goniatites. One of the localities is Bow Lees Quarry from which Goniatites cf. granosus and Sudeticeras cf. splendens have been recorded indicating a high P_2a horizon (Rayner, 1953; Dunham, 1958; Johnson and others, 1962). These finds remain the only records of stratigraphically significant goniatites from Upper Alston Group rocks in the district but goniatites collected from adjacent areas (Figure 38) allow further correlation of the local succession with the goniatite zones of the Central Province.

Above the calcareous mudstone the ferruginous siltstone of each cyclothem commonly contains in its lower part a sparse fauna of thin-shelled bivalves (especially nuculoids), rare brachiopods including Rugosochonetes, and Euphemites, a bellerophontid gastropod.

Namurian

The most complete Namurian succession is in the Stainmore Outlier where correlation with the goniatite zones of the Central Province was established by Owens and Burgess (1965) (Figure 38). Diagnostic goniatites cited in the paper were collected during the resurvey, and identified by Dr W. H. C. Ramsbottom (Figure 39). The Homoceras henkei from the Mousegill Marine Beds indicates an R_1a age and the Gastrioceras cf. cumbriense from the Swinstone Middle Marine Band suggests G₁b. The rest of the correlations are based on palynology and the less precise evidence of the other goniatite finds.

The E₁ (Pendleian) and E₂ (Arnsbergian) rocks exposed in the Stainmore Outlier and widely elsewhere in the district contain modified Yoredale faunas although cyclic changes are less regular than in the Upper Alston Group. The thinness of the limestones above the Great Limestone compared with those below it is reflected by a scarcity of foraminifera, corals and certain brachiopods including gigantoproductids and large dictyoclostids. In the absence of the Dinantian limestone kind of coral/brachiopod fauna in much of the sequence, the acme of marine influence in each cycle is commonly associated with a 'calcareous shale fauna' although the parent rock may be limestone, mudstone or sandstone. Faunal content is comparable with that in the calcareous mudstones of the Upper Alston Group but 'Cyathaxonia fauna' corals, bryozoa and trilobites appear to be less numerous and the mollusca, including goniatites and nautiloids, more common. A noteworthy feature of the limestones and overlying mudstones is the abundance of sponge remains including the spicules and anchoring spines of Hyalostelia.

Throughout the E₁ and E₂ rocks of the district the fossils reflect the rapidly changing, largely deltaic conditions of deposition and it is unusual for the faunal facies of any particular bed to remain constant for more than a few kilometres. For example the coral/brachiopod fauna of the Botany Limestone described below is nowhere found more than 11 km from Botany itself. The equivalent horizon in the Stainmore Outlier, the High Wood Marine Beds, has yielded a largely brachiopod/molluscan fauna without corals. Another distinctive fauna of apparently limited geographical extent is found immediately above the Mirk Fell Coal in the Balderhead area. It includes Leiorhynchus?, Lingula mytilloides, Naticopsis sp., small gastropods and Myalina verneuilii and probably developed in a localised brackish water environment (Figure 33).

The faunas of the Great Limestone have been discussed by Johnson (1958), who noted the presence in it of three biostromes: the coral/brachiopod Chaetetes and Frosterley bands near the bottom and top respectively and the algal/ foraminiferal Brunton Band between them. All three are well developed in the district although the Frosterley Band does not appear to extend to the southern boundary. Locally the fauna of the Chaetetes Band is restricted to Chaetetes depressus but Lonsdaleia duplicata and L. floriformis have been found at this level in Dowgill Beck. The Frosterley Band in Teesdale and on Mickle Fell contains abundant clisiophylloid corals including Aulophyllum fungites, Clisiophyllum keyserlingi, Dibunophyllum bipartitum subspp., Koninckophyllum interruptum and K. magnificum as well as Caninia benburbensis , Chaetetes spp., Diphyphyllum spp.and Lonsdaleia spp.

Above the Great Limestone, corals other than 'Cyathaxonia fauna' forms have been found only in the Little, Crag and Botany limestones. The fauna of the Botany Limestone was described by Garwood (1913). Both he and Reading (1957) give long faunal lists including Aulina rotiformis, Dibunophyllum bipartitum subspp., Lithostrotion pauciradiale, L. portlocki, Michelinia tenuisepta, Dictyoclostus spp., Echinoconchus spp.and Sinuatella sinuata. No significant new finds have been made during the resurvey. Hill (1940, p.192) remarked that confirmed British finds of the aphroid, colonial coral Aulina rotiformis are all from E₂ strata. In central Scotland, Hill (1940) and Wilson (1967) recorded the species only in the Calmy Limestone of the Upper Limestone Group. The type locality (Smith, 1917, p.290) is at Harlow Hill, Northumberland, in the Newton Limestone, also of E₂ age.

Especially rich brachiopod/mollusc faunas have been collected from the top of the Little Limestone in Borrow-dale Beck, the Lower Stonesdale Limestone of the west Stainmore area and the mudstones overlying the possibly brackish water phase of the Mirk Fell cyclothem at Balderhead mentioned previously. In beds with 'calcareous shale faunas' between the top of the Great Limestone and the Knuckton Shell Beds, the coarsely ornamented brachiopods Buxtonia sp., Eomarginifera lobata, Pleuropugnoides greenleightonensis, Productus productus, Spirifer sp. bisulcatus group and S. trigonalis (Plate 6)14, are usually abundant. At one of these levels, the Faraday House Shell Bed, the last four species are associated with a small productoid referred to Semicostella sp. nov. Productus productus is the most common form of Productus s.s. below the Crag Limestone but higher in the succession its place is taken by the finer-ribbed P. carbonarius.

Goniatites are rare in the local E₁ and E₂ succession but other basinal molluscan species have been found. They include the bivalves Actinopteria persulcata, Chaenocardiola spp.and Posidonia corrugata and several coiled nautiloids. A. persulcata is fairly common in the mudstone above the Crag/Crow Limestone in the district and A. cf. persulcata was recorded at the same horizon in the Woodland Borehole (Mills and Hull, 1968). The species is long-ranged (at least P₁ to E₂) but was noted at a possibly equivalent horizon (E_1c) in Ireland by Yates (1962). Yates, in discussing the species of Chaenocardiola, remarked on the abundance of C. footii in E₂ and described C. bisati from E_1a. In the Brough district C. footii has been found in the Mirk Fell Beds and cf. bisati in the Upper Stonesdale Limestone. Posidonia corrugata, which in basinal facies ranges from high P₁ to the top of E₂, occurs locally at many levels, from the mudstones overlying the Tynebottom Limestone to those above the Peasah Wood Limestone.

The most common coiled nautiloids locally are the long-ranging Catastroboceras spp.and related genera (Plate 6)15, but the most useful stratigraphically are forms of Tylonautilus. In the Survey collections from the district, representatives of the genus range from the Four Fathom Limestone to the High Wood Marine Beds. They demonstrate the contrast between the P₂/E₁ forms which have longitudinal slightly nodose ridges on the venter (Tylonautilus sp. nov. = T. nodiferus early mut. of Stubblefield in Hartley, 1945, p.259) and the diagnostic E₂b form (T. nodiferus s.s.) with a strongly nodose venter, an example of which was found in the High Wood Marine Beds.

Fossiliferous post-Arnsbergian rocks (?H to G₁) are exposed only in the Stainmore Outlier. Although several stratigraphically useful goniatites have been found, the fauna is predominantly benthonic as in the beds below. There are no limestones however and corals have not been recorded. It has been suggested that strata between the Peasah Wood Limestone and the Mousegill Marine Beds may be of Sabdenian (H) age but the only macrofossil to be recorded from them is Lingula sp.(Owens and Burgess, 1965). The beds of R and G age include several marine mudstones which contain a restricted, largely brachiopod/ bivalve fauna. The most common forms present are Serpuloides sp., Lingula mytilloides, Orbiculoidea nitida, Productus carbonarius, Euphemites sp., Aviculopecten spp.and nuculoids.

Two brachiopod species recorded from the postArnsbergian rocks of the Stainmure Outlier may be of stratigraphical significance. They are Derbyia gigantea and Punctospirifer northi. It has been suggested that the find of gigantea high in the Mousegill Marine Beds of Argill Beck during the resurvey indicates a possible correlation with the Cayton Gill Shell Bed (R_1a) of central Yorkshire (Wilson and Thompson, 1965). The Mousegill Marine Beds and mudstones between them and the Swinstone Bottom Marine Band have also yielded Punctospirifer northi, a species which has been found at about the same horizon in the Woodland Borehole of County Durham (Mills and Hull, 1968). A related form occurs in the Ure Shell Bed, a marine band slightly higher than the Cayton Gill Shell Bed in the R₁ succession of central Yorkshire (Wilson andThompson, 1965). JP

Chapter 7 Upper Carboniferous: Westphalian

In the Brough district, rocks of Westphalian age (Coal Measures) are confined to two small areas in the Stainmore Outlier where they conformably succeed the Namurian strata, and dip steeply eastwards against the Augill and Argill faults (Figure 40) and (Figure 41).

The Coal Measures were first recorded by the Geological Survey over a century ago (one-inch Old Series Sheet 102 SE) (Goodchild, unpublished report 1872, 1882). A map of the area was published by Turner (1935), and a more detailed description was given by Ford (1955). The results of the present resurvey have already been published (Owens and Burgess, 1965) and the following account is largely derived from that paper. The sequence proved is closely comparable, both in thickness and Ethology, with that seen in the Durham Coalfield 25 km to the north-east.

In the Stainmore Outlier over 300 m of Westphalian strata are preserved (Figure 40). The lower 'unproductive' part of the Lower Coal Measures is exposed in several streams. Augill, Argill and Mousegill becks and Hocker Gill all provide relatively continuous sections. The 'productive' Coal Measures are seen only in Argill Beck and two small tributaries-Craghouse Gill and another stream 400 m S of Gillbank Farm, unnamed on the six-inch map and here referred to as East Gill (Figure 41). The lower part of the Coal Measures sequence in Argill Beck can be closely correlated lithologically with the same strata in Mousegill Beck; a shell-bed with Carbonicola pseudorobusta, exposed in Mousegill and Argill becks, and in Craghouse Gill, provides a reliable datum connecting the main sections. In the two remaining sections, Augill Beck and Hocker Gill, only the thicker sandstones are well exposed and detailed correlation is not possible.

The lower part of the Coal Measures sequence, up to the C. pseudorobusta shell-bed, is exposed in both Mousegill and Argill becks. No coals are present in the Mousegill Beck section (Figure 35), the beds are reddened, and near the boundary fault are badly sheared and contorted. The Argill Beck section (Figure 41) is less disturbed, and several thin coals occur.

Details

The Swinstone Top Marine Band contains Serpuloides sp., Crurithyris sp., Lingula mytilloides, Productus carbonarius, Euphemites sp.and Palaeoneilo sp.Calver (in Owens and Burgess, 1965, pp.25–26) suggested that it was possibly the G. subcrenatum horizon at the base of the Coal Measures, though diagnostic forms such as goniatites were absent here as they are also in the Ingleton and Durham coalfields.

The lowest Coal Measures sandstone is about 15 m thick and is coarse and cross-bedded with a seatearth parting about half-way up. The sandstone grades up into another seatearth which is overlain in turn by the Argill Marine Band. This band, in Argill Beck, contains abundant foraminifera (including Glomospirella), Lingula mytilloides [3.0 mm] and L. sp. [broad form] [3.5 mm]. The abundance of foraminifera suggested to Calver (1968, p.26) that this horizon was not lower than the Gastrioceras listeri Marine Band of the Pennine province, although no precise correlation with any of the Lower Coal Measures marine bands of that area could be established.

The marine mudstone grades up into a sandy seatearth overlain by a thick bed of siltstone containing fish remains in the lowest metre. Above, the beds become more sandy, and pass up into a ganister-like sandstone with a discontinuous coal up to 0.15 m thick. The mudstones overlying this coal are apparently barren and are followed by a coarse, cross-bedded sandstone. On this rests grey siltstone containing well-preserved plant remains and comprising the Mousegill Plant Beds (Ford, 1955, p.224). They are capped by a thin coal overlain by coarse, cross-bedded sandstone about 9 m thick in Argill Beck and its tributaries, and more than 18 m thick in Mousegill Beck. Cannelly coal rests on the sandstone and is followed by black mudstone with fish remains. The fish-bed is at about the same horizon as the Stobswood Marine Band of the Northumberland Coalfield. The overlying sandstones are thinly-bedded, with fragmentary plant remains, and grade up into a seat-earth, on which rests a bright coal 0.45 m thick. The coal is directly overlain by 0.15 m of carbonaceous sandstone, followed by the Carbonicola pseudorobusta shell-bed. In Mousegill Beck this bed is seen on the south bank 14 m downstream from the Swinstone road bridge. The mudstones are contorted, but a large ironstone nodule yielded several specimens of C. cf. pseudorobusta. The bed is also exposed under water on the south bank of Argill Beck; in Craghouse Gill, north of Dike House, where it lies in the middle of an excellent 60 m section; and in the small tributary to Craghouse Gill, south of Dike House Farm. The faunas from Argill Beck and Craghouse Gill include the following; Carbonicola cf. acuta, C. communis, C. pseudorobusta, C. cf. pseudorobusta, C. cf. robusta, Curvirimula sp.[fragments], Carbonita humilis, Geisina arcuata and fish remains including Rhadinichthys sp. According to Calver (in Owens and Burgess, 1965, p.26) 'the zonal position is most likely about the middle of the C. communis Zone. In terms of the Durham sequence the equivalent horizon is unlikely to be lower than the Victoria Coal, and could well be the shell-bed in the roof measures of that coal.'

Above the shell-bed the section in Argill Beck is obscured for some distance, but in Craghouse Gill it is seen to consist of siltstones with a few sandy ribs and a 0.15-m coal. Above this is the lowest worked coal. It is about 0.45 m thick in Argill Beck, where it is exposed at stream level and has been worked from an adit on the north bank. It is only 0.05 m thick in Craghouse Gill, where the best section of the overlying beds is to be seen. The lowest of these are thinly-bedded sandstones, with a seatearth at the top, on which rests a shaly coal. The mudstones which follow yield abundant well-preserved fish remains. They grade up into sandstone, on which rests another coal 0.60 m thick, bright in its lower part but cannelly towards the top. This seam is also exposed in Argill Beck where another sandstone follows, overlain by a bright 0.90-m coal into which an adit has been driven on the north bank of the beck. The thick sandstone which overlies this coal is poorly exposed in its lower part, but the upper 4.5 m are seen in the south bank of the beck.

Upstream from this locality, there is an almost continuous cliff section through about 60 m of strata. The thick sandstone is overlain by a seatearth, on which rests a 0.45-m shaly coal, split by a 0.05-m rib of siltstone. Above are sandstones and siltstones, followed by a bright coal 0.30 m thick. The coal is followed by silty sandstones, which grade up into siltstones with plant remains -the Argil] Plant Beds (Ford, 1955, p.225). The overlying 4.3-m of strata include four coal seams, separated by seatearths. Resting on the highest coal are mudstones, with ironstone nodules and fish remains, which grade up into silty sandstones. They are overlain by a 0.25-m coal, above which are fossiliferous mudstones from which the following have been collected: Spirorbis sp., Anthraconaia modiolaris, A. sp. nov.? [cf. van der Heide, 1943, p1.4, figs.29–31], Anthracosia regularis, Anthracosphaerium cycloquadratum, Carbonicola oslancis, cf. C. venusta, Naiadites cf. subtruncatus and Geisina arcuata. Calver (in Owens and Burgess, 1965, p.27) interpreted this fauna as an A. regularis assemblage typical of the measures just below the Clay Cross and equivalent marine bands, correlating it with the fauna above the Harvey Coal of Durham, and with the shell-bed overlying either the Eighteen Inch or Little Main coals of Cumbria. This is the Argill Shell Bed of Ford (1955, p.225).

The shell-bed is immediately overlain by 9.2 m of sandstone, followed by 3.7 m of siltstones, with two thin coals. Resting on the upper coal is a 0.25-m band of micaceous silty mudstone, containing: Spirorbis sp., Anthracosia cf. ovum, Naiadites cf. triangularis, N. quadratus? and fish remains. The overlying mudstone with ironstone nodules is also fossiliferous, containing: Spirorbis sp., Anthracosia aff. aquilina, A. ovum, A. aff. phrygiana, Naiadites cf. triangularis and N. quadratus?. It was recognised by Calver (in Owens and Burgess, 1965, pp.27–28) as the likely position of the Harvey Marine Band of Durham.

Above the sandstone overlying the suggested Harvey Marine Band position only poorly exposed siltstones are seen at intervals for 15 m. The section is continued in East Gill, where a coal at least 0.75 m thick is followed successively by sandstones, grey siltstones with well-preserved plant remains, seatearth and a 0.60-m coal. The coal is strongly sheared as also is the overlying mudstone which contains poorly preserved shell fragments in ironstone nodules. This bed is faulted against sandstones, overlain by purple siltstones, vertical or with reversed dip, on which rests a thin coal. Above this coal the beds are obscured.

The 0.75-m coal of the East Gill section was formerly worked in Argill Beck by an adit on the north bank of the beck, 120 m downstream from Gillbank footbridge. The 0.60-m coal of East Gill, too, was formerly worked by an adit on the north bank of Argill Beck, where it is said to have been nearly 1.20 m thick. The overlying mudstones with ironstone ribs are seen in the south bank, 45 m downstream from the footbridge. They contain: Spirorbis sp., Anthraconaia robertsoni?, Anthracosia beaniana, A. ovum, A. aff. phrygiana [large form], A. sp.cf. phrygiana [short form], Anthracosphaerium turgidum, Naiadites quadratus and Rhadinichthys sp.This is an upper A. modiolaris Zone assemblage comparable with the Brass Thill or Low Main shell-beds of Durham (Calver in Owens and Burgess, 1965, p.28).

At Gill Bank in Argill the mudstone grades up into a seatearth, on which rests a 0.15-m coal. This is directly overlain by sandstone, above which the purple siltstones at the top of the East Gill succession crop out in the bed of Argill Beck up to the footbridge. Beyond the bridge there is a gap of about 12 m in the section. A 0.60-m coal overlain by siltstones was proved in a trial pit sunk in 1946, just above the footbridge and another coal, highly sheared, is exposed just downstream from the waterfall, overlain by mudstone with ironstone nodules. The mudstone is also very disturbed, and the large ironstone nodules, up to 0.60 x 0.90 x 0.30 m, appear to have been formed by the crushing together of many smaller nodules. The coal may be the same as that which crops out north of the stream, and was worked in 1946 from an adit, now collapsed. It was said to have been a 'good steam coal up to 2.10 m thick'.

During the survey this part of the sequence was temporarily exposed in the scar of a landslip a short distance downstream, where the purple siltstones were seen to be followed upwards by several thin coals and seatearths. Resting on the highest coal was a band of dark grey mudstone overlain by purple and grey mudstones with large ironstone nodules.

The dark grey mudstone contained: Naiadites productus, N. aff. alatus, Lioestheria cf. vinti [2.5 mm] and Elonichthys sp.[scale] thought by Calver (in Owens and Burgess, 1965, p.29) to be characteristic of the Lower A. similis–A. pulchra Zone.

Further movement of the landslip has since destroyed this section. The shell-bed may be present in the Argill section in the mudstone with ironstone nodules above the exposed coal, but no fauna was obtained from this locality during the survey.

The mudstone with ironstone nodules passes up into seatearth, underlying a third coal, very crushed, and faulted against pink sandstone forming the waterfall. These sandstones are seen for 18 m, and are overlain by a seatearth and coal. The section is here terminated by a major fault which brings in Lower Carboniferous sandstones, underlying the ?Cockleshell Limestone. ICB

Chapter 8 Permian and Triassic

Permo-Triassic rocks are confined to the western part of the district. From Winton, near Kirkby Stephen, to Dufton, they form a wide outcrop flooring the central part of the Vale of Eden, where they rest unconformably on a basement of gently folded Carboniferous strata. The rock sequence is thickest and most complete in the Hilton area (Figure 42), thinning southwards. Three main divisions of the Permo-Triassic rocks are recognised in the district, Penrith Sandstone at the base, overlain in turn by the Eden Shales and the St Bees Sandstone. The Penrith Sandstone occupies most of the area, the Eden Shales and St Bees Sandstone being confined to a narrow synclinal area on the western side of the Pennine Fault-Belt and a small basin, the limits of which are largely conjectural, east of Brough Sowerby.

Many workers have been attracted to the Permo-Triassic rocks of the Vale of Eden. During the nineteenth century important contributions were made by Binney (1855, 1857), Dakyns and others (1897), Eccles (1873), Goodchild (1893), Harkness (1862), Kendall (1902), Murchison and Harkness (1864), and Sedgwick (1832). More recently Arthurton (1971), Burgess and Holliday (1974), Burgess and Wadge (1974), Clarke (1965), Hollingworth (1942), Meyer (1965), Sherlock and Hollingworth (1938), Stoneley (1958), Versey (1939) and Waugh (1970) have published additional information. The Permo-Triassic rocks of the Penrith district have been described by Arthurton and Wadge (in press; see also Arthurton, 1971) and those of the Kirkby Stephen district by Burgess (1965).

Age

No fossils have been obtained from the Penrith Sandstone or from the St Bees Sandstone. The age of these formations is thus uncertain. By analogy with similar deposits elsewhere the Penrith Sandstone is believed to be largely of Lower Permian age (Smith, 1972; Smith and others, 1974) and the St Bees Sandstone is thought to span the Permian-Triassic boundary.

The Eden Shales also are generally lacking in fossil remains, apart from very fragmentary carbonaceous plant debris which has been noted at several horizons in the beds beneath the Belah Dolomite. Exceptionally, at the very base of the sequence in Hilton Beck, the Hilton Plant Beds contain an abundance of well-preserved and identifiable plant species. Less well-preserved material occurs in the shales underlying the Belah Dolomite in the River Belah. The floral evidence on the age of these beds was summarised by Stoneley (1958, p.30), who suggested that the Hilton Plant Beds were of the same age as the Marl Slate/Kupferschiefer (EZ1). (EZ1–3 are subdivisions of the English Upper Permian devised by Smith (1970)). However, the conifer species Hiltonia rivuli which Stoneley (1958) said is restricted to the Hilton Plant Beds and the Marl Slate was considered by Schweitzer (1962) to be synonymous with Ullmannia bronni, a species ranging from EZ1 to EZ3, and the strati-graphical value of this form is consequently diminished. The microflora of the Eden Shales was studied by Clarke (1965) and Visscher (1971).

During the resurvey of the Brough district marine fossils were discovered in the Belah Dolomite for the first time (Table 1). The specimens were identified by Mr J. Pattison, who notes that the Liebea are the broad form of L. squamosa common in the Upper Magnesian Limestone of north-east England. The assemblage of Liebea, Schizodus and Calcinema recorded from this horizon further supports the correlation of the Dolomite with the EZ3 (Seaham Beds) cycle of the Durham sequence (Burgess, 1965; Pattison, 1970).

The above evidence suggests that the Eden Shales are in part of Upper Permian age ranging at least from EZ1 to EZ3. The age of the youngest part of the formation remains uncertain; though the Permo-Triassic boundary is presently regarded as occurring within the St Bees Sandstone it may yet be found that it should be taken lower, perhaps within the highest part of the Eden Shales (Smith and others, 1974). ICB, DWH

The sub-Permian unconformity

Following the Armorican earth-movements there was a period of erosion, during which a great thickness of strata was removed from the district. From the sequence preserved in the Stainmore Outlier (Owens and Burgess, 1965) it may be inferred that about 450 m of Namurian strata and 300 m of Westphalian rocks were originally present, yet over the southern part of the Vale of Eden, these are largely absent, and Permian rocks rest unconformably on strata as low as the Great Scar Limestone. The rocks of the sub-Permian land surface, here, as elsewhere in Britain, were deeply red-stained, and the limestones dolomitised as a result of chemical processes taking place within the zone of groundwater circulation (Anderson and Dunham, 1953; Trotter, 1939, 1953). Though the depth to which this alteration took place cannot be proved, and indeed must have varied with regional and local fluctuations in the water table, its present distribution gives at least an indication of the former extent of the surface even where the Permian rocks have been removed.

Details

In the south-western part of the district, the unconformity between Permian and Carboniferous rocks is exposed in a lane by St Andrew's Church, Crosby Garrett [NY 7304 0972], where red millet-seed sands with bands of fine-grained brockram are banked against the scarp of the Peghorn and Smiddy limestones here dolomitised. Northwards, successively younger Carboniferous beds are preserved beneath the unconformity, till in Helm Beck, the ?Five Yard Limestone is seen. In the small inlier at Warcop, the massive reddened Carboniferous sandstones probably closely underlie the Four Fathom Limestone. On the east side of the basin, between Kirkby Stephen and Brough Sowerby, a comparable overstep occurs, rising from the Great Scar Limestone at Hartley [NY 7854 0835] to the Great Limestone near Kaber [NY 795 117]. The irregularity of the surface is well illustrated by the small outlying remnant of Brockram banked against the scarp of the ?Four Fathom Limestone 1 km ESE of Kaber [NY 7920 1108] (see also Turner, 1936). Farther north, in Augill and Swindale becks, even higher strata, just below the Crow Limestone, are present close to the unconformity. The small area of presumed Namurian rocks exposed south of Roman Fell is also deeply red-stained.

Away from the line of the unconformity, the alteration is less intense, but still noticeable. In the Asby area, the dolomitisation and reddening persist to the limits of the district. Similarly, on the east, all the Namurian and Westphalian strata of the Stainmore Outlier are affected, as are the Alston Group rocks in Yosgill Sike north of Brough. The area is bounded by the Barnarm, Augill and Argill faults and, in the deeply incised streams, the contrast between the reddened and unaltered strata on either side of these structures is very noticeable. The extent of the alteration suggests that in the ground lying to the west of the Pennine and Stainmore fault-belts, the present ground surface approximates to the sub-Permian surface.

Along the Pennine Fault-Belt, reddening occurs in three areas, in each case affecting Lower Palaeozoic rocks. On Roman Fell (Figure 44), the slates and volcanics on the western face of the fell are deeply red-stained, as are the overlying Roman Fell Sandstones (Burgess, 1974; and Burgess and Harrison, 1967). This reddening in both groups of strata rapidly dies out eastwards. A second area includes the Ordovician Keisley Limestone and Silurian strata to the south. In the western quarry at Keisley [NY 7123 2390] the limestones are in places deeply reddened especially along joints, and in Keisley Beck, the normally grey siltstones are also purple-stained. In the third area, north of Milburn Beck (in the Appleby district) [NY 6775 2860] the reddening affects Ordovician rhyolitic ash-flow tuffs.

The only other areas noted lie on the Alston Block, on the summits of Little Fell and Mickle Fell, where the sandstones overlying the Great Limestone are reddened.

Penrith Sandstone

The Brough district lies at the southern end of the Penrith Sandstone depositional basin, and the nature of the Lower Permian sediments has been greatly influenced by the local topographic relief. The typical deposits of the Penrith Sandstone, as found in the northern part of the basin (Arthurton and Wadge, in press), are coarse-grained millet-seed aeolian sandstones, commonly strongly cross-bedded, and are believed to be an accumulation of ancient barchan dunes (Shotton, 1956; Waugh, 1970). Traced southwards, into the district, these beds pass laterally into water-laid, evenly-bedded sandstones with bands of coarse fan-breccia, known locally as brockrams, which contain an abundance of angular and rounded clasts of Carboniferous (and older) rocks (Plate 7). These deposits are presumed to be the product of flash-floods and wadi erosion, and were derived from the areas of higher ground around the basin margins (Versey, 1939).

Details

The Penrith Sandstone crops out over a wide area on the floor of the Vale, but is largely concealed by superficial deposits. In the north the base of the Permian sequence is not exposed, though the underlying Carboniferous rocks are visible just beyond the district margin in a railway cutting [NY 6763 2208] 2 km N of Appleby and in the River Eden near Appleby.

It appears that the formation here is some 400 m thick, and falls into three broad divisions. The basal 150 m, exposed in several quarries west of the district [e.g. Hungriggs Quarry, [NY 6900 2125]], is made up of coarse brockram, mainly composed of dolomitised clasts of Carboniferous limestone with some sandstone, set in a matrix of millet-seed sand cemented with calcite. The basal 18 m of these beds were proved in the Express Dairies Borehole (Turner, 1963). Overlying the brockrams are about 150 m of red, dune-bedded, millet-seed sandstone, very poorly cemented at surface. These beds are well exposed in Hilton Beck south of Langton, and intermittently in the banks of deep glacial channels to the north in Flakebridge and Rheabower Woods. The dune-bedding foresets are consistently inclined westwards. The topmost 100 m of beds are much more variable. In Hilton Beck, where they are beautifully exposed in mural sections beginning 300 m N of Ellerholme [NY 7151 2037] and continuing to the base of the Eden Shales [NY 7195 2055], they consist mainly of red, evenly-bedded, water-laid millet-seed sandstones, with thin lenses of brockram which commonly fill channels cut into the underlying beds. The clasts, up to 0.30 m in diameter, are dominantly of dolomitised Carboniferous limestones, and are commonly hollow. Sandstone and siltstone are also common, and the larger sandstone boulders may be quite angular, and in places show imbricate structure suggesting derivation from the east. These brockram bands were studied in detail by Kendall (1902) who recorded the presence of Lower Palaeozoic rocks (rhyolite), vein quartz and Carboniferous Basement Beds. Material derived from the easily identifiable Roman Fell Sandstones is quite common, and confirms the suggestion that an escarpment was being eroded east of the Pennine Faults (Kendall, 1902; Versey, 1939; Bott, 1974), there being no other immediate source of this rock. Further evidence may be found in the excellent section in the glacial channel of George Gill, west of Espland, where the Upper Brockram is again exposed, the sequence being repeated by a fault. This locality is about 3 km distant from the Pennine Faults, compared with 2 km for the Hilton section. The proportion of brockram bands is noticeably less in George Gill, and dune-bedded sands, which in Hilton Beck are present only at the very top of the brockram section, form a large part of the sequence. One locality [NY 7167 1900] is notable for the sporadic occurrence of pebbles of decomposed dolerite probably derived from the Whin Sill (Holmes and Harwood, 1928; Dunham, 1932).

Northwards from Hilton Beck the brockrams are exposed in Murton and Keisley becks. Imbrication is particularly well seen in the sections south of Flakebridge, and indicates an easterly derivation.

On Roman Fell [NY 757 190], Penrith Sandstone is seen on the east side of the syncline; at least 50 m of red sandstones, partly dune-bedded, with bands of brockram, rest unconformably on reddened Carboniferous sandstones.

The three-fold division of the Penrith Sandstone persists at least as far south as Ormside and Warcop. In Jeremy Gill [NY 6946 1680] brockram closely overlies reddened Carboniferous rocks north of Gill House. Across the Ormside Fault there is a well-exposed section of brick-red dune-bedded sandstones with sporadic thin brockram bands in the gorge leading down to the River Eden. These beds are also exposed in the River Eden at Clint Scar [NY 695 176] and in the nearby Helm Beck [NY 707 156]. In both sections, brockram is subordinate to dune sandstone. This appears to be due to southward overlap by the dune-sands. South of Warcop, red millet-seed sandstones with thin bands of brockram, unconformably overlie Carboniferous strata in the River Eden [NY 7445 1900], while north of the same village in Hayber Gill, cliff sections in the sides of a deep glacial channel expose brockrams and sandstones, with examples of contemporaneous channelling.

Near Brough, brockrams towards the base of the Penrith Sandstone are seen in Swindale [NY 795 145] and Augill [NY 796 140] becks and the overlying dune-bedded sandstones crop out in the small lane north of St Michael's Church [NY 793 140]. A borehole at Heanings Farm [NY 7796 1331], Great Musgrave, proved about 70 m of water-laid red sandstone with numerous brockram bands overlain by about 10 m of brockram. In this borehole the sandstone and brockram commonly form fining-upwards sequences with a basal scoured surface and a thin (up to 0.05 m thick) mudstone at the top. Farther south, the classic section in the River Belah (Binney, 1855) provides cliff sections showing dune-bedded sandstones with beds of brockram in channels (Plate 7). The sequence is thin here, probably less than 100 m, as Carboniferous sandstones are seen nearby at Toft Well [NY 7954 1257] and were also exposed in roadworks north of Belah Bridge [NY 7931 1256] where they were unconformably succeeded by brockram.

Around Soulby [NY 750 109] there are sections of red dune-bedded sandstone with thin brockram bands, and the River Eden runs partly on solid rock, providing exposures both in its bed and in cliffs where its meanders cut into rock-cored drumlins. ICB

Eden shales

In the early Upper Permian, the flooding of the North Sea and Irish Sea (Bakevellia Sea) basins by the Zechstein transgression caused a marked change in the sediments deposited in the district even though the sea only rarely penetrated into the Vale of Eden itself. Increased rainfall and a higher water table led to the covering of the Penrith Sandstone dune-sea by the dominantly continental sediments (Eden Shales) (Figure 42), part water-laid, part aeolian, of an inland sabkha (Burgess and Holliday, 1974).

As in the Lower Permian, the district lay at the southern end of the depositional basin, and this is reflected in the sediments, which thin southwards, partly by lateral passage at their base into strata of the Penrith Sandstone water-laid facies. Where the strata are thickest, in the north, over 100 m of these sediments-grey and purple-red massive thinly-bedded sandstones and siltstones, subordinate grey mudstones with plant remains and beds of gypsumanhydrite-extend up to the Belah Dolomite, which marks a brief marine incursion. Their formation may well span the entire period^-of deposition of the Magnesian Limestone of Durham and East Yorkshire, for the Belah Dolomite has been equated with the Upper Magnesian Limestone (p.69). Earlier periods of marine influence in the Vale are marked by B-Bed and C-Bed evaporites (though the latter is thin in the Brough district). The changing patterns of sedimentation from aeolian to water-laid and from lacustrine to marine are described by Burgess and Holliday (1974). Above D-Bed evaporite the strata revert to a continental sabkha facies, but were deposited under strongly oxidising conditions, so that their predominant colour is brick-red. Plant remains are absent, and millet-seed sand grains appear, possibly derived from outcrops of Penrith Sandstone marginal to the sabkha. These beds are characteristically blocky at outcrop and poorly-bedded with adhesion ripples and numerous gypsum-anhydrite nodules, indicative of aeolian deposition. They are overlain by evenly-bedded sandstones and siltstones with mud-flake breccias, ripple marks, and desiccation cracks indicative of a water-laid origin (Burgess and Holliday, 1974).

This change from dominantly aeolian to fluviatile deposition is apparent throughout the Vale of Eden and elsewhere in the north of England at about the same horizon, and is thought to represent a widespread climatic change marked by increased rainfall that culminated in the deposition of the coarser fluviatile St Bees Sandstone.  ICB, DWH

Details

The full sequence of the Eden Shales has been proved in boreholes at Hilton [NY 7284 2056] (Table 2) (Burgess and Holliday, 1974) and at Brough Sowerby [NY 8043 1237] (Table 3). These are shown graphically in (Figure 42), together with sections illustrating the sequence in the Kirkby Thore area to the north and the much attenuated sequence in the Kirkby Stephen area to the south (Burgess, 1965) on the margin of the depositional basin. Adjacent to these boreholes, Hilton Beck (Harkness, 1862; Murchison and Harkness, 1864; Goodchild, 1889, 1893) and the River Belah (Binney, 1855; Eccles, 1873) are the only relatively continuous surface sections in the district, but even these are incomplete due to solution of evaporites.

Strata below the Belah dolomite

Hilton area

The term Hilton Plant Beds as originally defined (Goodchild, 1889, p.275) referred to the strata exposed in Hilton Beck 1250 m downstream from Hilton Bridge [NY 7194 2055]. Since then it has been variously used for the beds below B-Bed (Hollingworth, 1942) or for all the strata up to the Belah Dolomite (Good-child, 1893, p.23). The term is here restricted, as suggested by Meyer (1965, p. 79), to the plant-bearing strata of the original definition. These consist largely of fine-grained grey laminated sandstones in posts up to 0.40 m thick, separated by grey to black siltstone, commonly calcareous or dolomitic with abundant carbonaceous plant debris. They are well exposed in Hilton Beck [NY 7196 2058] where during the current survey they yielded the following forms, identified by Professor W. G. Chaloner: Sphenopteris cf. bipinnata, Pseudovoltzia liebeana, 'Strobilites bronni', Ullmannia bronni and U. cf. frumen ta tie'. All these species have been recorded previously from the Hilton Plant Beds (Stoneley, 1958). The same strata are poorly exposed near Moor House [NY 7480 1691], near Espland [NY 7728 1893] and in Murton [NY 7161 2157] and Keisley [NY 7020 2293] becks. In each case they immediately overlie the Penrith Sandstone.

In the Hilton Borehole, these sandstones contain nodules of gypsum-anhydrite and they are interpreted as sheet flood deposits laid down by flood waters on flats peripheral to a desert lake in which the A-Bed gypsum-anhydrite of the Kirkby Thore area to the north was deposited (Figure 43).

The Hilton Plant Beds are succeeded by hard thinly-bedded, brown sandstones with intervening dark brown siltstones which are exposed in Hilton Beck up to a small footbridge [NY 7202 2069]. The horizons of the B-Bed and C-Bed evaporites lie slightly higher in the sequence, but are not seen at the surface, probably because of solution. In the Hilton Borehole, B-Bed (3.05 m thick) was composed mainly of anhydrite, hydrated to gypsum at the top; C-Bed was poorly developed, comprising 1.53 m of red and green sandstones and siltstones with gypsum-anhydrite nodules.

The rocks between C-Bed and the Belah Dolomite consist mainly of reddish brown sandstone, thickly-bedded in the lower part, but becoming more thinly-bedded with green or grey siltstone partings towards the top. They are exposed at intervals between 60 and 150 m upstream from the footbridge, where they include cream-coloured sandstones with a 20-mm bed of carbonaceous siltstone with plant remains. Higher beds are seen in Hilton Beck for 100 m downstream from the Belah Dolomite outcrop. All these strata represent continued deposition on the continental sabkha.

River Belah

The lower part of the Eden Shales is exposed in the River Belah from a locality [NY 8003 1231] 700 m upstream from Belah Bridge up to the Belah Dolomite outcrop [NY 8009 1225]. The sequence is less than half the thickness of that at Hilton. This may in part be a reflection of differential subsidence within the basin, but probably relates more to lateral passage of the lower beds around Hilton into strata of Penrith Sandstones facies—mainly brockram—farther south (Figure 42). The brockrams in the river are succeeded by over 20 m of reddish brown sandstones, mainly thinly bedded, with partings of grey, green or brown siltstone. Overlying these, and extending up to the base of the Belah Dolomite, are about 12 m of dark brown and green siltstones with thin sandstone bands, with a collapse breccia at base, exposed on the south bank of the river [NY 8005 1228].

Belah dolomite and D-bed

The Belah Dolomite crops out in the River Belah [NY 8009 1225], the type exposure, and in Hilton Beck [NY 7230 2043]. Elsewhere in the Vale, both the dolomite and overlying D-Bed evaporite have been proved in boreholes (Meyer, 1965). In the River Belah, the dolomite comprises over 5 m of mainly thinly-bedded (0.05 to 0.15 m) pale grey to yellow dolomite and dolomitic limestone, the upper part containing calcite-lined solution cavities and veins. A marine fauna—Liebea squamosa and Schizodus obscurus—is present in the basal beds. The succeeding gypsum-anhydrite bed is not seen at surface, nor was it proved in the Brough Sowerby Borehole though its former presence was indicated by a solution residue and overlying collapse breccia.

In Hilton Beck the dolomite is in two main parts. The section visible (1973) on the south bank is:

The lower 0.90 m of the dolomite is thought to be of supra-tidal origin and the upper part probably formed in an intertidal environment. A similar sequence was proved in the Hilton Borehole.

The D-Bed evaporite is nowhere exposed at surface but was proved in the Hilton Borehole, where it comprised two parts, the lower of algal-mat anhydrite and the upper of both nodular and cross-laminated gypsum-anhydrite, probably indicative of an upwards transition from high intertidal to supratidal deposition.  ICB

Strata above D-bed

The strata overlying D-Bed are mainly brick-red in colour, in contrast to the preceding red-browns and greys. The lower part of the sequence consists of massive bimodal sandstone with large (up to 3 mm) millet-seed quartz grains, similar to those of the Penrith Sandstone, in a matrix of fine silt and mud (cf. Meyer, 1965, p.75). Adhesion ripples and deflation surfaces are the commonest sedimentary structures visible and indicate an aeolian origin. Water-laid sediments are rare. The sandstone is cemented almost throughout with anhydrite, which dissolves away at outcrop, so that these beds are poorly exposed in Hilton Beck and in the River Belah. One bed with calcareous cement stands out as a conspicuous rib [NY 7240 2046] in Hilton Beck 70 m upstream from the Belah Dolomite outcrop; a similar lithology is seen in the River Belah and has been recorded elsewhere in the Vale of Eden at about the same horizon (Hollingworth, 1942). Thin bands of breccia have been recorded in the upper part of these beds in the Hilton Borehole and in Mill Beck near Dufton [NY 6820 2486] (Dakyns and others, 1897, p.85). Up to 1 km N of the latter locality more numerous, thicker and coarser breccias at the same level have been proved in confidential boreholes and support the suggestion that an area of high ground was being eroded in the area of the present Pennine escarpment (Kendall, 1902; Versey, 1939; Bott, 1974).

The succeeding strata are thinly-bedded fluviatile sandstones, cream-coloured, fine-grained, ripple-cross-bedded with inter-laminated brick-red micaceous siltstones and mudstones. Throughout there is evidence of desiccation, with mud-flake breccias, sand-filled mud-cracks and injection structures including sandstone dykes and volcanoes. These beds are seen in Hilton Beck [NY 7243 2043] and in Dobbyhole Gill [NY 7560 1875]; the best exposure, however, is in the River Belah, where the full sequence is exposed in the river cliff [NY 8018 1222]. ICB, DWH

St Bees Sandstone

The base of the St Bees Sandstone is taken at the first appearance of massive sandstones above the thinly-bedded sandstones and siltstones at the top of the Eden Shales. This transition is almost certainly diachronous, but affords the best lithostratigraphical distinction between the Eden Shales and the St Bees Sandstone.

The St Bees Sandstone is part of the extensive sheet of coarser water-laid material that covered northern England at the end of the Permian and in the early Triassic. Consisting mainly of massive evenly- or cross-bedded sandstones in units 0.30 to 0.60 m thick, with silty partings, it ranges in colour from brick-red to yellow or white and, in contrast to the Penrith Sandstone, contains both feldspar and mica. The rock is generally well-cemented and the number of large quarries to be seen attests to its former value as a building stone. Within the district the St Bees Sandstone is up to 125 m thick.

Details

In the Brough Sowerby area, the sandstone is seen in the cliffs bordering the River Belah [NY 8025 1225]. In the northern outcrop, however, it is well exposed in all the streams draining the escarpment, from Hayber Gill, Warcop [NY 750 165], to Billy's Beck, Dufton [NY 694 245]. In most areas, the natural exposures have been greatly enhanced by quarrying, and excellent sections are visible on the north side of Hilton Beck [NY 727 206] and in Dutton Gill [NY 693 246]. ICB

Chapter 9 Structure

The structural history of the Brough district falls into two distinct parts, one before and one following the intrusion of the Weardale Granite. Throughout the Lower Palaeozoic, the district lay in an active orogenic belt; and its history was one of geosynclinal sedimentation, island-arc volcanicity and regional dynamic metamorphism. After the end of the Caledonian Orogeny, following the final phase of granitic intrusion, the district lay within a major continental mass; and its later history is one of shelf-sea marine, deltaic or continental sedimentation, gentle crustal warping and block faulting.

Lower Palaeozoic Structures

Skiddaw Group The different Lower Palaeozoic rock groups show contrasting styles and intensities of structure (Shotton, 1935; Moseley, 1972), and will be discussed in stratigraphical order.

These rocks have been affected by several phases of deformation. Where complete each phase is characterized by a set of minor folds (F₁ F₂, etc.) and an associated cleavage (S₁, S₂, etc.). The most highly deformed rocks are seen in the Murton Formation between Murton Pike and Brownber, where a sequence of phases can be tentatively established. The folding within the younger Kirkland Formation is less intense.

In the Murton Formation, the earliest folds (F₁) are nearly isoclinal in style and are commonly asymmetrical, with short limbs of 1 to 5cm and long limbs exceeding 30cm. The folds are difficult to detect in mudstones, especially where the short limbs are sheared out, as in the intensely folded areas on Brownber Hill [NY 7046 2715], on the ridge north of Keisley Beck [NY 7215 2415] and in the upper part of Murton Beck [NY 7377 2236]. Here the bedding generally lies almost parallel to the cleavage planes which are lustrous with secondary chlorite flakes. In siltstones the bedding is commonly picked out by pale grey sandy bands which may thicken markedly in the fold axes, so that an axial trace appears on a cleavage surface as a ridge of quartz blebs. The fold axes are generally associated with limonitised pyrite cubes up to 5 mm across.

A strong slaty cleavage (S₁) associated with these folds is the dominant surface visible in most exposures. Its orientation is variable as a result of later movements, but on Brownber Hill, where there seems to have been the least subsequent disturbance, it is vertical and trends at about 100°. The F₁ folds show a very variable plunge in the plane of the cleavage.

The second fold phase visible in the field is characterised by asymmetrical open folds (F₂) with a wavelength of about 1 to 2 m. The foliation which is axial planar to these folds is generally a fracture cleavage (S₂), of variable prominence and commonly appearing as a strong crenulation on S₁. Around Brownber Hill [NY 7046 2715], both S₂ and the F₂ axial planes are almost horizontal, which is taken to be close to their original orientation. Elsewhere, S₂ may dip at any angle up to vertical, as a result of later movements, most of which appear to have occurred about axes parallel to the Pennine Line, since both the plunge of the F₂ folds and the trend of S₂ are commonly aligned at 325° to 335°. These movements may be of late Carboniferous or even younger age. Much of the quartz-veining in the Murton Formation, as on Brownber [NY 7062 2744], seems to date from the F₂ phase.

A third cleavage (S₃) is visible on Brownber Hill. It is aligned vertically, trends east-west and is axial planar to very open, gentle F₃ folds seen affecting S₂. The S₃ trace on S₂ is generally close to horizontal.

In addition, the Murton Formation is affected, in narrow zones 1 to 5 m wide, by very intense folding which post-dates all the previous minor structures. The zones generally dip steeply eastwards, and consist of folds which are tight but with no axial plane cleavage. The folds generally trend at 340° to 350°, but their plunges appear to be completely random. The zones are best seen in Swindale Beck [NY 6947 2854] and Murton Beck [NY 7378 2233]. They commonly lie close to low-angle reverse faults of post-Carboniferous age and may result from the same stresses.

The adjacent outcrops of the Kirkland Formation show fewer cleavages or fold closures, although dips are generally steep. The beds exposed east of Murton show in places a weak near-vertical cleavage trending east-north-east. In the Teesdale Inlier, rocks of the same age exhibit slaty cleavage of variable strike (20° to 110°) and which is cut by a fracture cleavage.

Borrowdale Volcanic Group Direct evidence of the relationship between the folding in the Skiddaw Group and that in the Borrowdale Volcanic Group is lacking as all the contacts are faulted. By analogy with the Lake District (Simpson, 1967), at least part of the polyphase deformation in the Skiddaw Group probably predates the deposition of the Borrowdale Volcanic Group.

The structures in the Borrowdale Volcanic Group are much less complex than those in the Skiddaw Group. The massive volcanic rocks are generally strongly jointed but lack a good cleavage. Softer tuff bands on Harthwaite and Dufton Pike are cut by a weak cleavage, striking like the bedding at about 160° and dipping steeply to the southwest. This cleavage may be associated with north-trending pre-Caradoc folds like those recorded in the Lake District outcrops (Moseley, 1972). The volcanic rocks are also affected by open folds trending between east and northeast dating from the end of the Silurian. The outcrops on Knock Pike, Dufton Pike, Keisley and Roman Fell appear to mark anticlines of this type.

Upper Ordovician and Silurian sediments As a result of Caledonian (end-Silurian) folding these rocks are thrown into open folds with a near east-west trend, and most exposures also show some cleavage striking between 75° and 105°. Minor folds with this orientation are well exposed in Swindale Beck, Knock, where the beds are inclined generally southwards and zones of steep dip (60° to 80°) alternate with zones of low dip (20°), The cleavage is well seen in the shaly beds, dipping southwards at 65° to 85°; in the more massive lithologies the cleavage is more obvious where dips are low and the foliation crosscuts the bedding planes.

Post-lower Palaeozoic structures

The Pennine Line formed along the western edge of the Alston Block, shortly after the intrusion of the Weardale Granite, and included the Knock Pike, Dufton Pike and Swindale Beck faults. The large down-westerly throw on these fractures preserved younger Lower Palaeozoic rocks to their west whilst the upthrow side was so deeply eroded that only Skiddaw Group beds underlie the Carboniferous rocks on the western edge of the Alston Block. Many of the smaller faults in the inlier probably date from this time also. This can be well demonstrated below Roman Fell where several fractures pass beneath undisturbed Carboniferous sediments.

Though it cannot be shown directly, it seems probable that the same stresses created a framework of lines of structural weakness, which not only delineated the main structural entities-Alston Block, Murton Fell Block, Stainmore Trough, Vale of Eden Basin-that were more or less active during Carboniferous sedimentation, but also marked out the zones along which the succeeding Hercynian and later (possibly Tertiary) movements were concentrated (Figure 2).

During Carboniferous times, the Alston Block remained an area of comparative uplift, in contrast to the Northumberland and Stainmore troughs lying respectively to the north and south. The block was not finally submerged beneath the sea until Visean times and was subsequently covered by a sequence of sediments thinner than those of the adjacent troughs. Differential subsidence persisted throughout the Narnurian, as the block sequence is thinner than that in the Stainmore Trough (Owens and Burgess, 1965) or in the Vale of Eden (Arthurton and Wadge, in press). By Westphalian times, however, the contrasts appear to be less marked, the Lower and Middle Coal Measure thicknesses proved in the Stainmore Outlier being comparable to those of the Durham Coalfield.

In the late Carboniferous, the Brough district formed a small part of the vast, almost flat Coal Measures delta-complex that covered northern Europe. This uniform deposition was brought to an end by the onset of the Armorican Orogeny which locally took the form of an east-west compression. The main effect of the stresses imposed was to reactivate the major crustal units established in late Caledonian times. The resulting deformation was concentrated along the block margins, where tight folding and, in places, overthrusting, took place. Within the blocks, the pattern was one of gentle warping and tilting with only minor faulting (Figure 45).

The Carboniferous rocks of the Vale of Eden were folded into a broad syncline, plunging to the north-west. In the south, the overall synclinal structure was modified by minor anticlines and synclines with a general north-south axial trend. On the east, reaction to the stress was concentrated along the zone of weakness marked by the Pennine and Dent lines. In the Cross Fell Inlier (Plate 2) the brittle rocks of the basement broke along several low-angle reverse faults and were pushed eastwards over adjacent parts of the block (Brownber Fault, Murton Pike Fault). In places these movements occurred along pre-existing fractures initiated during the Caledonian faulting. The more plastic cover of Carboniferous rocks responded initially by tight folding along axes parallel to the underlying faults, and then by the development of an eastwards-facing monocline with nearly vertical or overturned beds on the steep limb. Where the compression was greatest the reverse faults penetrated into the Carboniferous cover. The overall displacement in the south, between Roman Fell and Brownber, was at least 250 m (Figure 44) and farther north may have been much greater (Wadge, Harrison and Snelling, 1972).

The Murton Pike and Brownber faults show the deeper levels of these structures where, in each case, most of the movement has occurred along a well-defined fracture. The higher structural levels can be examined on the Roman Fell Fault and on subsidiary dislocations which have behaved in a similar way to the Pennine Line. It is likely that lateral movement occurred on these faults, but this is difficult to prove generally. The folds on Roman Fell end abruptly against the Swindale Beck Fault and may indicate sinistral tear movements along it.

Farther south, in the area between Brough and Winton, a complex structural pattern was created (Turner, 1935). This was due, in part, to the fact that this area lay on the intersection of the Dent and Pennine lines, and the differing trends of these structures caused reflections of the mainly east-west stresses, leading to cross-folding. Superimposed on this was the effect produced by the Murton Fell Block which, acting as a rigid extension of the Alston Block, concentrated in a much smaller area the folding which farther east was spread over the whole Cotherstone Syncline. This localised north-south compression may indicate some anticlockwise rotation of the Alston Block.

In the Stainmore area three faults-the Barnarm, Augill and Argill faults-locally control the trend of the main structures. Each of these extends far beyond the area under discussion, the Barnarm Fault being traceable into Baldersdale, the Augill Fault cast through Stainmore Summit and the Argill Fault south into the Kirkby Stephen district, suggesting that all three may reflect major dislocations in the Lower Palaeozoic basement.

Dominating the structure in this area is the eastwards-facing Stainmore Monocline (Plate 4), which, following these movements, is estimated to have had a displacement of at least 850 m down-east. A complementary anticline, with low dips and a curved axial plane, approximately parallel to the main boundary faults, separated the monocline from the Vale of Eden Syncline to the west.

On the Alston Block, north of the Swindale Beck-Closehouse-Lunedale fault-belt, the Carboniferous rocks were inclined eastwards at a very low angle, except in the vicinity of the Burtreeford Disturbance, a faulted mono-dine trending north-south and facing eastwards, with a displacement of about 150 m. On the Musgrave Fell Block, bounded on the west by the Pennine Line and on the north, east and south by the Swindale Beck, Thornthwaite and Barnarm faults respectively, the Carboniferous rocks dipped eastwards at about 10° except along the Pennine Line, where eastwards-facing monoclines were present, and along the extreme northern and southern edges, where tight anticlines were formed parallel to the boundary faults. The Cotherstone Syncline, bounded on the west by the Dent Line and the Thornthwaite Fault, and on the north by the Closehouse-Lunedale Fault, was a broad structure trending east-west, asymmetrical, with low dips on the southern flank, but steeper dips up to 20°, on the northern limb where a tight anticline parallelled the Closehouse Fault (Figure 45).

The intrusion of the Whin Sill and its associated dykes appears closely to have followed this period of compression (Dunham, 1948, p.65). It cuts across and is therefore later than, the Burtreeford Disturbance. At Closehouse, however, a related sill south of the Closehouse Fault is intruded along the axis of the Closehouse Anticline, indicating the possibility that the fold and the intrusion may be coeval.

Following the compressional movements there ensued a period of denudation, during which the newly formed structures, which must have caused considerable local topographic relief, were deeply eroded. In the Vale of Eden Syncline, Westphalian rocks were preserved to the north (Arthurton and Wadge, in press) and a tongue of Namurian strata extended south as far as Brough Sowerby. Namurian and Westphalian rocks were also preserved in the monoclinal downfold along the Dent Line (Stainmore Outlier). Along the Pennine Line, Namurian, Lower Carboniferous, and possibly Lower Palaeozoic rocks may have been exposed. The surface rocks of the western part of the Alston Block and the Musgrave Fell Block were probably of Namurian age, but those to the east of the Burtreeford Disturbance were of Westphalian age. The Cotherstone Syncline was probably entirely floored by Westphalian rocks, except for the ground just south of Closehouse.

The rocks of this late Carboniferous land surface were generally reddened to varying depths, possibly controlled by the depth to the permanent water table, and limestones at outcrop were dolomitised.

As the compressive stresses died away, subsidence of the Vale of Eden and down-west faulting along the Pennine and Dent lines combined to form a cuvette in which Permian sediments began to accumulate. Locally the movements occurred along both pre-existing fractures and new, but sub-parallel faults close by. The nature of this double movement of the Armorican faults is well illustrated by the position of a fault-bounded slice of Melmerby Scar Limestone [NY 718 246] north-east of Keisley. It lies along the reverse down-east Brownber Fault, but must also be bounded by a fracture throwing at least 250 m down-west from the limestone outcrop on Peeping Hill.

A remnant of the westwards-facing fault scarp formed by these movements is preserved on Roman Fell, where both Lower Palaeozoic rocks and Roman Fell Sandstone are deeply reddened on the western face of the fell, but not farther east (Burgess and Harrison, 1967). Comparable reddening of Lower Palaeozoic rocks is also seen farther north at Keisley (Keisley Limestone and Brathay Flags) and east of Milburn (Knock Pike Tuffs). The preservation of Namurian strata on the sub-Permian cuvette floor near Roman Fell, at a lower topographic level than the reddened Roman Fell Sandstone just east of the Hilton Fault, implies that the early Permian down-west throw was there of the order of 800 m (Figure 44). The scarp may not have been finally buried till Triassic times (St Bees Sandstone) as bands of brockram are present in the upper part of the Eden Shales near Dufton (p. 75).

South of Roman Fell, the down-west movement was less. Around the Stainmore Outlier, a displacement of 550 m would have been sufficient to account for the preservation of the rocks of the outlier. Farther south, at Kirkby Stephen, the downthrow was reduced still further, and in places the movement may have been in the opposite sense.

The latest movements affecting the area are ascribed to the Alpine Orogeny but are difficult to date accurately. Renewed uplift and easterly tilting of the Alston Block was accompanied by down-west faulting along many of the earlier fractures. A total displacement of about 300 m around Roman Fell and about 500 m on Stainmore is estimated. The present Pennine escarpment is the degraded fault-line scarp produced by these movements which probably continue to the present day. An earthquake of unusual intensity for this country occurred near the southern end of the Pennine Line in August 1970 (Browning and Jacob, 1970).

Also as a result of these stresses, the Permian rocks of the Vale of Eden were folded into an asymmetrical syncline on an axis parallel to the Pennine Line, with a gentle dip on the western limb, but with dips of up to 40° on the east.  ICB

Chapter 10 Intrusive igneous rocks

The intrusive igneous rocks of the district fall into three main age groups. The oldest intrusions which cut Lower Palaeozoic rocks are of Lower Palaeozoic or early Devonian age. In the northern part of the district an extensive quartz-dolerite sill and dyke complex cuts rocks of Carboniferous age. It is thought to have been intruded in late Carboniferous or early Permian times. A tholeiitic dolerite crosses the north-east corner of the district; it is believed to be part of the Cleveland–Armathwaite dyke-echelon of Tertiary age.  DWH

Lower Palaeozoic intrusions

No major intrusions of Lower Palaeozoic age crop out at surface in the district. However, geophysical studies suggest that the ground lying north of the Closehouse-Lunedale faults and east of the Pennine faults (the Alston Block) is underlain by a granitic batholith, termed the Weardale Granite (Bott and Masson Smith, 1957). Minor intrusions, possibly related to this granite are seen in both Cross Fell and Teesdale inliers of Lower Palaeozoic rocks. They fall into two main groups, acid porphyries and lamprophyres (Harker, 1891, pp.519–523; Shotton, 1935, pp. 671–672; Hudson, 1937, pp. 385–391). There is, in addition, one small, highly altered intrusion of a basic rock in the Kirkland Formation in Murton Beck (E36596) [NY 7333 2221]. ICH

Details

Weardale Granite

The existence of a granite or granodiorite mass beneath the Northern Pennines was first postulated by Dunham (1934) in order to explain the origin and zonation of the mineralisation of that area. This same hypothesis was given further support by a regional gravity survey (Bott and Masson Smith, 1957) which showed that the Alston Block is dominated by a negative Bouguer anomaly. The granite, unconformably overlain by Lower Carboniferous sediments, was finally proved in a borehole at Rookhope in the Alston (25) district (Dunham and others, 1961, 1965). The petrology and chemistry of the granite have been described by Holland and Lambert (1970).

Geophysical evidence (Bott and Masson Smith, 1957; Bott, 1967) suggests that the northern part of the district is underlain, at depth, by this granite (Figure 51). The southern edge of the granite near Middleton in Teesdale is thought to be nearly vertical (Bott and Masson Smith, 1957, p.103). The nearest that the granite approaches to the sub-Carboniferous surface, within the district, is likely to be in an area, between Scordale and Maize Beck, which coincides with a gravity minimum (Bott, 1967, pl. 6). From the evidence of the Rookhope Borehole, the granite is pre-Carboniferous in age (Dunham and others, 1965). Metamorphism of slates in the Roddymoor Borehole (Woolacott, 1923) and incipient hornfelsing of Llanvirn slates in the Teesdale Inlier (Robinson, 1970) suggest a post-Llanvirn age for the granite, assuming that the metamorphism was related to this intrusion.

Radiometric estimates of the age of the granite have been made by both the rubidium-strontium and potassium-argon methods. Using the former method, Holland and Lambert (1970) suggested that the granite was intruded 410 ± 10 million years ago, at a time approximating to the Silurian-Devonian boundary. A recalculation of these results based on a slightly lower half-life for ⁸⁷Rb decay gave a rather younger age of 394 ± 34 Ma (Dunham, I 974b).

The Weardale Granite forms the core of the low-density Alston Block, and has influenced the sedimentation and structural development of the district through to the present day. DWH

Acid porphyries

Intrusions falling into this category crop out only in the Cross Fell Inlier. The most northerly is the Dufton Microgranite seen in a small quarry west of Dufton Pike [NY 6930 2681], intruded into Dufton Shales. It is a red, markedly porphyritic, muscovite-quartz-feldspar-microgranite containing muscovite phenocrysts up to 2.5cm across, white, glassy quartz and pink feldspar. The groundmass ranges from fine to moderately granular.

In thin section (E36381) the phenocrysts comprise albite (near Ab₉₅, An₅; refractive index (β = 1.535) which poikilitically encloses quartz and muscovite. The groundmass is a mosaic of finely interlocking (0.04 mm) quartz, orthoclase, plagioclase, muscovite and chlorite, and a little accessory apatite and iron oxide. A full chemical analysis is shown in (Table 4) (analysis 3), giving the principal norms: quartz 29.8%; orthoclase 19.3; albite 41.8, anorthite 0.5, corundum 3.4, hypersthene 1.9 and magnetite 0.7%.

A similar rock (E36496) seen some distance to the south [NY 6917 2666] may be part of the same intrusion displaced by faulting. Other porphyry outcrops are on Keisley Bank (E36451) [NY 7107 2425] intruded in Knock Pike Tuffs; behind The Seat on Roman Fell (E32075) [NY 7462 2067], in tuffs of the Kirkland Formation; and farther south (E32055) [NY 7526 1959] in Harthwaite Tuffs. Petrographically these rocks resemble the Dufton Microgranite. A fifth outcrop, recorded by Shotton (1935) and Hudson (1937), from Little Rundale Beck, was not noted during the resurvey.

Lamprophyres

In the Knock district, there are five outcrops of dykes which fall into the old classification of 'mica-trap'. They are generally grey or brown rocks, with prominent phenocrysts of dark brown biotite. The best exposed intrusion is that in Swindale Beck, near the junction with Great Rundale [NY 6875 2734]. This dyke was figured as 'mica-trap' by Trail (1888, pl.xxxii) and described by Goodchild (in Dakyns and others, 1897, p.43). The dyke is intruded into Browgill Beds, baked at the contacts. Its outcrop is irregular, as it tongues along joints and cleavage. In the centre of the intrusion it is a dense, fine-grained, purplish grey porphyritic rock, with plentiful mica and quartz phenocrysts, 3 to 4 mm across. In thin section (E36425), (E36426), (E36427) the quartz phenocrysts show resorbed margins while the micas (X = pale yellow-brown to colourless; Z = deep brown) are commonly euhedral with dark rims. The groundmass is a mosaic of turbid feldspar laths, partly carbonated, and averaging 0.1 mm in length, biotite flakes, quartz, opaque granules and finely granular carbonate in a base of deep red-brown biotite, carbonate and chlorite. Apatite forms accessory needles. There are veinlets of secondary quartz and pyrite, with irregular patches of green chlorite and quartz. Towards the margins the groundmass is considerably finer-grained and the fine micas and feldspars are locally fluxioned. In common with most specimens, the feldspars are too altered to establish whether the rock is a minette (with orthoclase) or a kersantite (with plagioclase). A full chemical analysis of one specimen (E36425) is given in (Table 4) (analysis 2).

Closely similar rocks crop out further upstream intruded in the Knock Pike Tuffs [NY 6892 2785] (E40627), Kirkland Formation [NY 6892 2813] (E36423) and Murton Formation [NY 6945 2852] to [NY 6959 2890] (E36447) and (E36448). In two specimens (E36423), (E36448) the matrix feldspar has been identified as albite-oligoclase, so these two may properly be classified as kersantites. A full analysis of one specimen (E36423) is given in (Table 4)—(analysis 1), which shows a considerably lower K₂O content than (E36425) (analysis 2). A modal analysis of (E36423) gave plagioclase 45%, biotite and pseudomorphs 47% and quartz 8%. ICB, RKH

A detailed discussion of the characters and petrogenetic relationships between the suites of minor intrusions in the Cross Fell Inlier as a whole, is given in the Penrith memoir (Arthurton and Wadge, in press). The minor intrusions are considerably more developed and exposed in the northern part of the inlier, than in the present district. RKH

In Teesdale, several lamprophyre dykes cut Skiddaw Slates near Cronkley Pencil Mill [NY 848 296] (Williams, 1923). At least six intrusions were recorded by the Primary Surveyors, but fewer were exposed during the resurvey. They show no cleavage, and are commonly intruded parallel to the main cleavage of the slates. Thus the trend of the dykes, as of the cleavage, ranges from north-south to east-west. Three specimens were examined in thin section; in one (E36347) the feldspars had undergone considerable alteration, but the others (E36348), (E36349) were much less altered and sodic plagioclase positively identified, together with biotite, chlorite, accessory apatite, pyrite, interstitial quartz, chlorite and carbonate. The latter two specimens are thus classified as kersantites. DWH, RKH

The Whin Sill and related dykes

The miners of northern England commonly referred to persistent beds in the stratigraphical succession as 'sills', and particularly hard rocks were called 'whin'. This latter term was most especially used for a sheet of quartz-dolerite which they named the Whin Sill (i.e. 'hard bed') and regarded as a normal member of the succession. It seems probable that the term now employed to indicate a concordant igneous intrusion, was derived from this area. When the igneous origin of the Whin Sill became apparent, it was first thought to be a contemporaneous lava flow. Though the intrusive nature of the sill in Teesdale was demonstrated as early as 1827 by Sedgwick, it was only some fifty years later, following the work of Topley and Lebour (1877), that this view became generally accepted. Since there is often more than one sill at a particular locality, the Whin Sill is better regarded as a complex of related but not necessarily connected sills, rather than as a single sill.

The Whin Sill crops out from Middleton in Teesdale in the south to Belford (Northumberland) in the north (Holmes and Harwood, 1928, fig. 1; Fitch and Miller, 1967, fig. 1). Associated with the sill are a number of dykes of similar composition. Similar quartz-dolerite sills and dykes occur in Central Scotland (Francis, 1965, fig.10.14). The southern part of the Whin Sill complex extends into the northern half of the Brough district. The most widespread outcrops are in the Tees Valley, west of Middleton in Teesdale (Plate 9) and (Plate 11), while a narrower and more discontinuous outcrop occurs along the Pennine escarpment (Plate 10) and in Lunedale. General accounts of the geology of the Whin Sill in the northern Pennines have been given by Teall (1884b), Holmes and Harwood (1928), Dunham (1948), Johnson and Dunham (1963) and A. C. Dunham (1970). Extensive bibliographies can be found in these papers. Few publications deal specifically with the present area, though important accounts of certain aspects of the sill in Teesdale were published by Sedgwick (1827), Clough (1876, 1880), Spears (1961) and Hornung and Hatton (1974). The alteration of Whin Sill dolerites in the Close-house Mine area has been described by Meson (1968). Details of outcrops in adjacent areas have been published by Johnson and Dunham (1963) and Arthurton and Wadge (in press).

Age of intrusion

The youngest strata cut by the Whin Sill are rocks of the Middle Coal Measures (Trotter and Hollingworth, 1932) while the related dykes in the Durham Coalfield also cut Middle Coal Measures, but do not penetrate the overlying Upper Permian strata (Smith and Francis, 1967). This suggestion of a late Carboniferous or early Permian age of intrusion is supported by accounts of pebbles of Whin Sill type in Permian Brockrams of the Vale of Eden (Holmes and Harwood, 1928; Dunham, 1932) (see also p. 71). It is further supported by radiometric age determinations by Fitch and Miller (1967) who concluded that the apparent K-Ar isotopic age of the Whin Sill complex is 295 ± 6 Ma, which they regarded as Lower Stephanian in age. This is in agreement with later determinations which suggest an age of 296 ± 6 Ma for dykes near Melmerby, Cumbria (Wadge, Harrison and Snelling, 1972). Four of the specimens dated by Fitch and Miller (1967) were from the Brough district; two specimens were from the dyke at Greengates in Lunedale, and two from quarries near Middleton in Teesdale. All four samples had been subjected to varying amounts of metasomatic alteration and gave results younger than the adopted average.

Horizon and thickness

The Whin Sill outcrop in the district can be divided into three contrasting areas, viz. east of the Burtreeford Disturbance (p. 78), west of the Burtreeford Disturbance, and Lunedale.

East of the Burtreeford Disturbance the sill is intruded into the Alternating Beds, usually between the Tynebottom and Single Post limestones. The maximum recorded thickness of the sill in this area, 74 m, is in a borehole [NY 8912 2908] near Dirt Pit Farm (Dunham, 1948). Towards Middleton in Teesdale the sill thins slightly but remains at the same general horizon. To the south-east of Middleton, still at the same horizon, there is a sudden thinning as the Lunedale Fault is approached. Such changes of horizon as occur in this area are small and are achieved, as first described by Clough (1876, 1880, fig. 4) by thin wedges or tongues of dolerite (overflows or underflows) projecting respectively from either top or bottom of the sill. In no instance is there any large spectacular change of horizon.

The change in horizon of the sill across the Burtreeford Disturbance has been described by Dunham (1948, p.52) who concluded that the 'sill may have been intruded along a horizontal plane which cut through a pre-existing fold'. This view is supported here, though it seems likely that further movement and faulting occurred after the intrusion of the sill.

West of the monocline, the sill forms an irregular, often discordant, sheet intruded at a variety of levels from the top of the Orton Group to below the Smiddy Limestone (Figure 46). The thickness of the sill is variable, but is mostly in excess of 60 m. No evidence was found to support Hodge's suggestion (in discussion of Dunham and Kaye, 1965) that a feeder pipe to the sill-complex occurs in this area. To the south and west of Cronkley Fell, the sill rises to a position just below the Lower Little Limestone, remaining at this horizon over a wide area. Along the Pennine escarpment, except locally in Scordale (Figure 47), the sill lies just below the Tynebottom Limestone, but is much reduced in thickness (usually less than 30 m).

In Lunedale, to the north of the Lunedale-Closehouse Fault, a similar horizon change occurs across the Burtreeford Disturbance, from between the Single Post and Tyne-bottom limestones in the east, to above the Smiddy Limestone in the west. Within the fold itself a small tongue of dolerite, seen in Hargill Beck, has continued at a horizon above the Tynebottom Limestone into the fold itself. In this area the sill is only 7 to 30.5 m thick. Within the Lunedale-Closehouse Fault-Belt there is a broad dolerite dyke or dyke echelon which occasionally spreads out into small sills, usually near the horizon of the Scar Limestone, but locally rising to the Four Fathom Limestone. There is no evidence as to the relationship between this dyke and the main sill.

Petrology

The Whin Sill has attracted the attention of many petrologists though none of these was especially concerned with the Brough district. The most recent review of the petrology of the complex is by A. C. Dunham (1970) who gives an extensive bibliography.

The main mass of the sill is composed of quartz-dolerite with grains up to 2 mm in diameter. There is a marked decrease in grain size at the margins of the sill where the rock is a very fine-grained black tachylite (Dunham, 1948). The dolerite is weakly porphyritic with small amounts (5 per cent volume) of plagioclase, augite and hypersthene. Pigeonite phenocrysts are said to be present in the tachylite margin of the sill on Cronkley Fell (Emeleus, 1974). The most abundant mineral (nearly half) is plagioclase (zoned from basic plagioclase to oligoclase rims) which is associated with pyroxenes, mainly augite but also some (altered) hypersthene and pigeonite. Opaque minerals, mainly iron-titanium oxides but also including pyrite, occur in significant quantities. Many rocks show interstitial micrographically intergrown areas of quartz and alkali feldspar. Other minerals present are quartz, biotite, chlorite, apatite and calcite. In the upper half of the sill the dolerite is cut by flat-lying, more or less concordant, sheets of coarse-grained (2 cm) 'pegmatitic' dolerite composed largely of augite and plagioclase (zoned from labradorite to oligoclase) (Dunham, 1948).

Numerous chemical analyses of Whin Sill and associated dyke rocks have been published (Smythe, 1930; A. C. Dunham, 1970). These show that the composition of the complex is intermediate in character between the tholeiitic and alkaline basalt series (A. C. Dunham, 1970).

Locally the dolerite has been extensively altered, both mineralogically and chemically. These alterations fall into three main categories: deuteric, 'white whin', and tropical deep weathering. During the cooling of the dolerite local accumulations of gases condensed to form hydrothermal solutions which caused the alteration of earlier former minerals to chlorite and pectolite (Wager, 1929; Smythe, 1930) and also led to the precipitation of these and some other minerals along joints. 'White whin' is a clay and carbonate alteration in which the texture, though not the mineralogy, of the parent dolerite is preserved. Most commonly in the district it occurs adjacent to hydrothermal veins (Wager, 1929; Smythe, 1930; Dunham, 1948; Ineson, 1968) and is thought to result from changes effected by the mineralising fluids. Less commonly in the district the contact rocks of the sill have undergone a similar alteration (cf. Harrison, 1968). Alterations of this latter type appear to be related to highly carbonaceous country rocks. Hornung and Hatton (1974) have described sites of deeply weathered dolerite within the district where the rock has been intensely altered and locally completely disintegrated producing a grus-like material. According to these authors (Hornung and Hatton, 1974, p.110) the weathering is typical of that produced under a humid sub-tropical or tropical climate and probably dates from the late Tertiary period.

Alteration of country rocks

Dunham and Kaye (1965, pp. 256–257) have estimated that the Whin Sill was intruded at a temperature near 1100°C and, where thickest (i.e.Teesdale) it took some sixty years to cool. The sedimentary rocks adjacent to the sill are therefore metamorphosed to a considerable degree. Visible effects occur up to 40 m from the contact, but changes have been observed in coals as far as 425 m above the sill (Jones and Cooper, 1970). Chemical and petrological studies of Teesdale Whin Sill contact rocks have been made by Hutchings (1895, 1898), Wager (1928), Dunham (1948, pp.57–58) and Robinson (1970, 1971, 1973).

The white or pale grey limestones with low organic content, such as the Melmerby Scar Limestone, Robinson Limestone and Single Post Limestone, are completely recrystallised to coarse saccharoidal marbles (Robinson, 1970, 1971) in which bedding is commonly obliterated and vertical joints become the major foliation. The marble is hard and compact in boreholes but, at the surface, weathering loosens the grains to produce a very crumbly rock or loose calcite sand (Plate 8). The soils derived from these weathered limestones support a relict alpine flora (Johnson and others, 1971). Away from the contacts the saccharoidal nature of these limestones gradually decreases and bioclastic debris becomes increasingly apparent. Dark grey limestones, with greater organic content, which are especially abundant in the Upper Alston Group, show little alteration other than minor recrystallisation close to the sill and, with only local exceptions, do not form saccharoidal limestones.

The highest degree of alteration is shown by impure limestones, which are converted to calcsilicate rocks containing a variety of minerals. Garnet is the most abundant of these with lesser amounts of chlorite, feldspar, diopside prehnite and epidote (Robinson, 1970, 1973). Wollastonite has been found to the north of the district in a borehole near Cow Green (Robinson, 1970). Many mudstones and siltstones take on an olive-green colour near the sill and at some localities spotting is developed. Sandstones are converted to quartzite close to the sill, with destruction of the original elastic texture. Soda metasomatism of shales to produce soda feldspar occurs locally (Hutchings, 1895, 1898; Wager, 1928). Less conspicuous mineralogical changes also continue in rocks which appear to the unaided eye as unmetamorphosed, e.g. the development of pyrrhotite from pyrite and marcasite (Harbord in Dunham and Walkden, 1968; Emeleus, 1974).

Despite the complex and discordant relations between the dolerite and the country rocks there is no field evidence at contacts of any assimilation of country rock into the magma. Apart from an example now quarried away, there are no undoubted examples of xenoliths within the sill in this area, nor is there any sign of reaction between whin magma and country rock. However, many early workers, notably Clough (1880), were impressed by the lack of widespread mechanical disturbance associated with the intrusion and concluded that considerable assimilation of country rocks had taken place though this is opposed by all chemical evidence (Clough, 1880; Smythe, 1930). Clough (1880, p.438) described sections in Cockle, Rowantree and Lodge Gill sikes, just to the north of the district, where the total thickness of rock, including dolerite, between the Smiddy and Lower Little limestones was constant even though the sill was absent or differed in thickness. This, and the lack of mechanical disturbance in the country rock, can be explained by intrusion along horizontal tension fractures (Smythe, 1930; Shiells, 1964) which would eliminate the need for the magma to force its own path through the Carboniferous sediments. DWH

Details

East of the Burtreeford disturbance

The base of the sill, 3 to 9 m above the Tynebottom Limestone, can be seen in the gorge of the River Tees at, and downstream of, High Force [NY 8803 2839] in the section fully described by Clough (1876). The top surface of the sill is well exposed in Ettersgill at [NY 8843 2065], where it is a 'white whin'. It is also seen with overlying metamorphosed country rocks at several localities in the Tees downstream from Ettersgill Bridge [NY 8937 2842] to Scoberry Bridge [NY 9104 2736]. 'Overflow' tongues of dolerite (Clough, 1876) can be seen at several of these localities. Crossthwaite Quarry [NY 925 265] near Holwick, and Force Garth Quarry [NY 873 282] near High Force are still actively worked for road metal, while many abandoned quarries are to be seen elsewhere in the valley. Natural exposures are abundant on the south side of the Tees Valley from Middleton in Teesdale to Cronkley Farm [NY 8628 2897] (Plate 9) and also on the north side of the valley around High Force and Forest in Teesdale. Deeply weathered dolerite at Holwick Scars [NY 9011 2702] was described by Hornung and Hatton (1974).

High Force Quarry [NY 8780 2902] is a well-known locality for coarse pegmatitic dolerite, and for radiate growths of pectolite on joints, though both these features can be found elsewhere, as for example in the banks of the Tees, above Cauldron Snout at the foot of Cow Green Dam [NY 8137 2896]

A large raft of metamorphosed shale and sandstone within the sill is shown on old maps, but appears to have been removed during the excavation of Force Garth Quarry [NY 8706 2813]. A mass of metamorphosed shale and sandstone on the south bank of the Tees [NY 9047 2785] near Wynch Bridge appears to be another example of a xenolith. The sediments dip at a steep angle into the sill, but it is not possible to prove that the dolerite entirely surrounded them. As this locality occurs near the top of the sill it is possible that the sediments are only partially detached from the country rock as in the examples, west of the Burtreeford Disturbance, described below (p.88).  DWH, JHH

West of the Burtreeford disturbance

In this area, the lower contact of the sill is commonly obscured by boulder clay and more especially scree. However, a number of sections show this contact and are especially valuable for illustrating the metamorphic effect of the sill on the intruded sediments (see Robinson, 1970, 1971, 1973 for mineralogical details). At White Force [NY 8520 2804] the sill rests with a slightly irregular base on completely recrystallised Melmerby Scar Limestone. Farther to the west near Skue Trods [NY 8493 2893]; [NY 8456 2924]; [NY 8509 2884] the sill rests on strata towards the top of or above the Melmerby Scar Limestone. The mapping of the face of Cronkley Scar suggests that there are several sudden changes in horizon of the sill (Figure 46) which are superimposed on a gradual fall in horizon towards the west. Thus at Falcon Clints [NY 8532 2817] the sill occurs low down in the Melmerby Scar Limestone. A little farther west is the locality [NY 8170 2839] described and figured by Sedgwick (1827, pl. x, fig. 1) and by Clough (1880, p.434) where the base of the sill can be seen, diagonally, and then nearly vertically, cutting across horizontal saccharoidal limestone near the base of the Melmerby Scar Limestone. A borehole nearby [NY 8138 2856] proved that the sill has locally transgressed down into the Orton Group, its lowest strati-graphical horizon within the Alston Block.

The upper contact of the sill, though less often exposed, is not masked by scree and is more readily mapped than the base. It illustrates more clearly the pattern of horizon changes of the sill (Figure 46). At many places quartz-dolerite cuts vertically through the country rock. In plan view these rises are sinuous and irregular and they follow no consistent trend such as would be expected if they had followed pre-existing joints (Figure 46). A vertical rise through the Melmerby Scar Limestone to the Robinson Limestone can be seen at White Well Green [NY 840 283], and nearby [NY 842 285] the sill partly truncates and partly underlies the highly metamorphosed Robinson Limestone. Near here [NY 8424 2857] small dykes of basalt, offshoots of the main mass, can be seen cutting the Robinson Limestone. At a number of localities concordant tongues of quartz-dolerite ('overflows' of Clough, 1876) project out from the tops of these vertical rises (Figure 46). Most of these can only be inferred from mapping but a number are more directly visible. Similar tongues of dolerite were demonstrated to the north of the sheet boundary in borings associated with the Cow Green Reservoir (Kennard and Knill, 1969, fig. 5). On Widdybank Fell [NY 8329 2879] a swallow hole has developed through one of these tongues into the underlying Melmerby Scar Limestone.

A mass of country rock only partially detached and enveloped by dolerite may be inferred from exposures in Maize Beck [NY 8073 2776]. A limestone cropping out [NY 8094 2835] north-east of Birkdale Farm may be a xenolith; however, the alternative interpretation, namely that there is a near-vertical rise of the dolerite accompanied by an 'overflow' tongue, was preferred in the preparation of the geological maps.

West of Birkdale the sill rises vertically from low in the Melmerby Scar Limestone to near the Lower Little Limestone, and an apophysis ('overflow') from that rise is exposed in Grain Beck [NY 7915 2802] (Figure 46). Outcrops of this latter limestone near the junction of Swarth and Maize becks [NY 7800 2619] provide a rare instance of a saccharoidal texture having developed in an originally dark grey limestone. DWH

For some distance westward up Maize Beck the sill remains just below the Lower Little Limestone, but near High Cup Nick [NY 7463 2625] rises to a position beneath the Tynebottom Limestone. Excellent exposures of the sill and its contacts are to be found in this vicinity (Plate 10). The horizon below the Tynebottom Limestone is maintained in the escarpment to the north-west corner of the sheet and southwards to Scordale. In Swindale Beck, Knock [NY 706 286], a section of deeply weathered dolerite has been described by Hornung and Hatton (1974, p.109). In Scordale the sill occurs at lower horizons, firstly above the Robinson Limestone and then below the Little Limestone. There is evidence here that during intrusion the dolerite magma was deviated by a thick channel-filling sandstone above the Robinson Limestone (Figure 47). DWH, ICB

Lunedale

In lower Lunedale, the Whin Sill is intruded at various levels in the Alternating Beds and above. It is exposed in Lunedale Quarries [NY 954 290] south of Chapel House, where it is 7.62 m thick, underlying the Cockleshell Limestone, and its transgressive contact with underlying strata can be seen in the bank of the river [NY 9550 3397]. Between Bowbank and Thringarth, several poorly-exposed thin sills are present above and below the Scar Limestone, and 1 km NE of Wemmergill [NY 907 226] a thin dolerite sill underlies the Four Fathom Limestone. This latter exposure lies south of the Closehouse-Lunedale Fault. North of this structure the sill continues in the Alternating Beds, exposed in Wemmergill and Hargill becks. Dykes of Whin Sill type are seen in Greengates Quarry [NY 935 236] and near Wythers Hill [NY 9260 2291]. They may be extensions of the Hett Dyke of County Durham (Mills and Hull, 1976; Smith and Francis, 1967). ICB, CRB,

In crossing the Burtreeford Disturbance, the sill, as in Teesdale, markedly changes horizon. West of this line, the main sill, about 30 m thick, lies in the siltstones between the Smiddy Limestone and the overlying sandstone, and its transgressive contacts at both top and base are well exposed in Arngill Beck [NY 8482 2331] where it shows rude columnar jointing. Within the Burtreeford Disturbance, irregular dolerite intrusions are seen on the north side of Standards Hush and in the upper reaches of Hargill Beck [NY 8635 2395].

In the Closehouse area, dolerite was intruded within and to the south of the Closehouse-Lunedale Fault. The first-discovered baryte vein is a replacement deposit in a dolerite dyke, up to 20 m thick and emplaced along the fault (Hill and Dunham, 1968). It is of limited lateral extent (600 m) pinching out to east and west.

A second dyke is present, a short distance to the south, along the axis of the anticline trending east-west which parallels the fault. West of Arngill, it is intruded in the South Fault and is exposed at several localities in the old hushes, commonly veined with baryte. Capping Closehouse Crags [NY 846 225], a dolerite sill extends southwards from the fault in the sandstone above the Scar Limestone. West of Arngill, the dyke does not reach the surface, but its course at depth was traced geophysically as far east as Hargill Beck, where it again reaches the surface [NY 8708 2258]. A sill intruded on the crest of the anticline, west of Standards, overlies the Scar Limestone and is presumably a continuation of that seen on the west side of the valley.

A set of dolerite dykes, regarded as part of the Hett System by Dunham (1948, p. 59), extends from Lunehead, across the eastward extension of the Swindale Beck Fault, to the Pennine escarpment on Long Fell. These crop out in Conneypot Beck [NY 8076 2050]; [NY 8078 2040], Tar Beck [NY 7855 2006], Tinside Rigg [NY 7740 1985], Long Fell Mine [NY 7660 1950], Long Fell Pike [NY 7730 1880], Dobbyhole Gill [NY 7600 1932] and Mute Gill [NY 7554 1919]. At each locality the country rock is of Lower Carboniferous age except in the last, where the dolerite is inferred to cut rocks of the Borrowdale Volcanic Group. ICB

Cleveland Dyke

Members of the Cleveland-Armathwaite dyke-echelon occur near Middleton in Teesdale. In common with other Tertiary tholeiite dykes, the Cleveland Dyke is reversely magnetised (Bruckshaw and Robertson, 1949; Dagley, 1969). Three specimens of the Cleveland Dyke (not from the Brough district) have been dated by the K-Ar method by Evans and others (1973) who concluded (p.443) that an 'age of 58.4 ± 1.1 m.y. can be regarded as a fairly close minimum estimate of the age of intrusion'. The petrology of the dyke system has been described by Teall (1884a), Holmes and Harwood (1929), Dunham (1948), and Harrison (in Mills and Hull, 1976); some chemical analyses were published by Hornung and others (1966). The Cleveland Dyke is always readily distinguishable in the field from rocks of the Whin Sill (quartz-dolerite) suite by its porphyritic character, with phenocrysts of plagioclase and pyroxene set in a dark fine-grained or glassy matrix.

Details

The Cleveland Dyke, with a chilled margin, can be seen cutting the Whin Sill in Ettersgill beneath the footbridge at Outberry Bat [NY 8848 2855]. To the east the dyke, 13.7 m wide, is seen in Smithy Sike [NY 8920 2950], and again in Bow Lee Beck near Mirk Holm [NY 9086 2928], where it is split into two parts and includes a screen of baked sediments belonging to the Upper Alston Group. Its probable eastward extension is seen in Coldberry Gutter [NY 9311 2896] as a narrow dyke along or near the line of the Lodgesike-Manorgill Fault-Vein. Two parallel branches of this dyke were met with in Red Grooves level, 29 m apart (Dunham, 1948, p.60). DWH, JHH

Chapter 11 Pleistocene and Recent

Much of the district is covered by superficial or 'drift' deposits of Pleistocene and Recent age which mask the older 'solid' rocks beneath. The unconformity between the solid and drift deposits marks a long period of earth history spanning Jurassic, Cretaceous and Tertiary times, but there remains no direct evidence to show that any sediments of these ages were deposited in the district. It is generally assumed that following the Tertiary earth-movements, the northern Pennines entered a phase dominated by erosion in which the main elements of the present topography emerged (Francis, 1970). Apart from a relatively short period of mainly glacial deposition, this erosive phase continues to the present day.

The glacial deposits of the Tees drainage area, including the high ground of the Pennines, were first described by Dwerryhouse (1902), and the escarpment and Vale of Eden areas have been studied by Goodchild (1875) and Trotter (1929). Details of the Pennine area immediately to the north-west of the district were given by Johnson and Dunham (1963), and descriptions of the drift of the adjacent Barnard Castle and Penrith districts can be found in the respective memoirs (Mills and Hull, 1976; Arthurton and Wadge, in press). Useful reviews of the Quaternary period in the northern Pennine region are to be found in Raistrick (1931), Raistrick and Blackburn (1931), Francis (1970), Taylor and others (1971), Evans and Arthurton (1973) and Penny (1974).

Trotter (1929) suggested that deposits of several glaciations were to be found in the north of England, each marked by its own till-sheet, and with interbedded sands and gravels thought to represent interglacial periods. However, the only undoubted example of an interglacial deposit recorded within the northern Pennines is a peat bed lying beneath boulder clay in Scandal Beck in the Kirkby Stephen district. This peat has yielded a radiocarbon date of 34350 years BC (Shotton and others, 1970). Accordingly, a late Devensian age is assigned to the succeeding glacial deposits in Scandal Beck and, by analogy, to the similar deposits of the northern Pennines in general (Evans and Arthurton, 1973) and the Brough district in particular. The assignation of a Devensian age is supported by the freshness of the landforms produced during the glaciation and deglaciation of the district.

The Devensian till-sheet covers most of the lower ground of the district, and consists mainly of boulder clay. The till-sheet thins upslope to the Pennines and is only locally present between 1500 and 2000ft OD. Numerous glacial channels were cut by melt-water at or below the limits of the boulder clay and are associated locally with deposits of sand and gravel. In contrast, on the higher parts of the Pennines, which stood out as nunataks during the glaciation (Dwerryhouse, 1902; Raistrick and Blackburn, 1931), the main superficial deposit is head which commonly has been eroded to give boulder fields. Many solid outcrops on the fells are cambered and on the steeper slopes landslips are common.

Following the main glaciation small corrie glaciers developed in the Maize Beck area and elsewhere in northern England during a further cold spell in the late Devensian (Manley, 1959; Rowell and Turner, 1952; Johnson and Dunham, 1963). A lake having a top level at about 475ft OD was impounded south of Appleby in the Eden Valley. The present river flows in a gorge cut by the discharge from this lake. The main peat deposits of the district did not begin to form until early Flandrian times (Raistrick and Blackburn, 1932; Johnson and Dunham, 1963) though it is possible that peat formation began earlier in some hollows. In more recent times peat formation ceased and now it is being actively eroded by streams.

Since the end of the main glaciation, streams and rivers cutting new channels, laid down terrace and alluvial spreads of gravel, sand and silt. The various terrace features indicate successive lowerings of base level related to migration of nick-points or changes in sea level since the glaciation. On some of the older terraces the river deposits are overlain by peat. Other deposits formed since the glaciation include landslips and screes.

Buried valleys

The thickness of drift throughout the district is generally very small, but it locally exceeds 50 m where filling valleys cut into rockhead along the sites of presumed pre-drift river courses (Plate 11). Except for areas investigated for dam construction there is little subsurface information in the district and the extent of and number of such sub-drift valleys remains uncertain. Buried channels occur in all the major valleys, but there is no evidence as yet for any extensive buried valley system associated with the major rivers such as occur in neighbouring lowland areas (e.g. Smith and Francis, 1967, pp. 198–199).

The occurrence of river gravels on rockhead below boulder clay, in buried valleys such as those at Grassholme and Appleby, support the view that the channels are the former subaerial courses of rivers and not those of sub-glacial streams (e.g. Woodland, 1970), though it is probable that the morphology of many channels has been altered by sub-ice erosion.

Details

The River Tees, upstream from Middleton in Teesdale to beyond High Force, flows over solid rock and this led Francis (1970, p. 141) to presume that the river had been glacially diverted. However, so much solid rock is exposed in the ground surrounding the valley that there is no room for a drift-filled channel. Thus, though features such as High Force and the downstream gorge are post-glacial in age, the pre-glacial Tees must be assumed to have flowed in much the same position as at present. In the area upstream of the confluence of Harwood Beck with the Tees [NY 860 296] the valley is unusually wide; the river though mostly flowing in its own alluvium locally is cut into both solid and glacial deposits, truncating drumlins and other features, suggesting that the present (river) channel is here comparatively new. Confirmation is provided by borings near Dine Holm which proved only part of what is probably an extensive buried channel system in this area.

A narrow, gorge-like valley, cut in Whin Sill dolerite and in-filled with boulder clay, was proved near Cauldron Snout [NY 814 286] (Plate 11); (Figure 48) during site investigations for the Cow Green Dam (Kennard and Knill, 1969; Vaughan and others, 1975). Lack of solid rock outcrop upstream of Cauldron Snout may indicate that this buried channel widens northwards. South of Cauldron Snout [NY 814 277] a low-lying drift-covered area may indicate a former course of Maize Beck into the Tees.

Buried channels of subsidiary streams of the Tees have been proved at a few localities. Old lead workings penetrated a drift-filled channel parallel to and to the west of Hudeshope Beck near Middleton in Teesdale (Dunham, 1948, fig. 29). The lower reaches of the River Balder and River Lune are commonly cut into boulder clay, filling older channels, but only rarely has it been proved that the present courses differed significantly from those of the pre-glacial rivers. Sections through the Lune and Balder buried valleys were exposed during the construction of the Grassholme, Blackton and Selset Dams where extensive sand and gravel deposits were seen on rockhead below boulder clay (Figure 49). DWH

The pre-Glacial channel of the River Eden near Appleby (Figure 50) was proved in a sewage tunnel driven in 1881–82 (Tiddeman in Dakyns and others, 1897, pp. 92–93) and in a boring at the Express Dairies (Turner, 1963). Tiddeman recorded river gravels with a (?) bison tooth occurring beneath the boulder clay in the sewage tunnel. ICB

Boulder clay

The most widespread superficial deposit within the district is boulder clay. With the exceptions of the Pennine escarpment and the high ground north of Stainmore, it occurs more or less continuously throughout the district. There is much variation within the boulder clay from place to place, reflecting local variation in source material. Typically boulder clay is bimodal, with rock fragments up to boulder size set in a finer clay to sand matrix. It is generally stiff and well consolidated. Lenses of sand and gravel, silt and laminated clay also commonly occur. In many areas the boulder clay has been moulded into drumlin forms.

All of the rare natural exposures of boulder clay within the district have undergone extensive landslipping and down-slope creep. This is particularly noticeable in stream-side scars. Temporary sections in the boulder clay collapse and degrade within two or three days, or even less during periods of rain. Therefore, little of the boulder clay seen on the valley sides and in stream banks is in situ.

There is some important variation in pebble content of the boulder clay in the district. The red till of the Vale of Eden has numerous erratics of Permo-Triassic sandstones as well as Lake District rocks and rarer Scottish granites (Goodchild, 1875; Trotter, 1929). Similar erratics are known east of Stainmore in Lunedale and the valley of the Greta; the drift here is thought to have been derived from the same ice-stream as that in the Vale of Eden (Dwerryhouse, 1902; Trotter, 1929). On the Pennine escarpment and the northern edge of Lunedale, grey tills, dominated by Carboniferous sandstones and limestones with Whin Sill dolerite, are found (Trotter, 1929). Eastwards down Lunedale the grey Pennine tills merge with the Vale of Eden tills. In upper Teesdale (except Maize Beck) tills are grey, with Carboniferous limestones and sandstones, Whin Sill dolerite and, downstream of the Teesdale Inlier (p. 8) rocks of the Borrowdale Volcanic Group (Dwerryhouse, 1902). East of Middleton in Teesdale this till merges with the main Vale of Eden–Stainmore stream.

The form and elongation of the drumlins in the Vale of Eden together with the erratic content and occasional striae suggest that the final movement of the ice was from northwest to south-east down the vale, linking in the south with another ice movement from the west-south-west, bringing Shap Granite erratics, to form a continuous ice sheet that overrode the Pennine escarpment in the Brough and Stainmore area and moved eastwards. Additional material was provided by glaciers carrying Pennine erratics from the escarpment and, in Lunedale, from the south face of Mickle Fell. In Teesdale the movement, as judged from similar criteria, was down the valley linking up with Edenside–Stainmore ice near Middleton in Teesdale. This suggested movement is broadly in agreement with the suggestions of previous workers (Goodchild, 1875; Dwerryhouse, 1902; Trotter, 1929; Raistrick and Blackburn, 1931). The higher ground on the escarpment and on Mickle Fell where boulder clay is absent is thought to have stood out above the ice at its maximum extent, separating the ice in Teesdale from the main Vale of Eden-Stainmore ice (Dwerryhouse, 1902; Raistrick and Blackburn, 1931). DWH

Details

The largest area of boulder clay is in the Vale of Eden and adjacent areas in the south-west part of the district, where the drift, locally up to 30 m thick, forms an extensive drumlin field (Figure 50). The boulder clay of this area is mainly red in colour. The only section through these deposits, that at the scar alongside Swindale Beck under Brough Castle [NY 7910 1415], is now much obscured by slipping. Goodchild (1875, pp. 80–81) saw towards the base a number of thin seams of laminated clay interleaved with the boulder clay overlain by beds of sand and gravel, the highest part of the section being composed of till alone. Erratics appear to come from Lakeland or Edenside sources; Shap Granite and Galloway granites are confined to the upper part of the section. From present limited exposures and from Goodchild's further observations elsewhere in the Vale of Eden, this section is thought to be typical of much of the drift of the district especially in the lower lying areas. However, the amount of sand and gravel, and laminated clay, appears to decrease towards the higher ground where the boulder clay is generally thinner. Goodchild (1875, p. 81) concluded that there is no definite order of succession in the drifts of the area, and that the sand and gravel, and laminated clays, are lenses locally interwoven with the boulder clay. The present writers support this conclusion and found no evidence to support Trotter's (1929) suggestion that boulder clays of several different ages were to be found. Studies of modern Arctic glaciers suggest that complex till/outwash sequences are normal products of a single retreat phase of a glacier with a thick englacial debris load (Boulton, 1972). Thus the boulder clays of the Vale of Eden are not solely subglacial lodgement tills but probably also include englacial and supraglacial tills associated with supraglacial outwash. DWH, ICB

To the east of Stainmore, there are extensive areas covered by boulder clay in the valleys of the Lune, Balder and Greta. Borings and excavations show the boulder clay to be vertically and laterally variable in size and composition of rock fragments and in colour (red, brown and grey). Transitional contacts were normally observed between the lithologies and there is no indication of a regular sequence of separate, differently coloured, boulder clays. Lenticular bodies of sand and gravel, within the boulder clay, were proved during the construction of the dams in Lunedale and Baldersdale. The maximum thickness of drift proved in this area is about 50 m in a borehole near Grassholme [NY 9514 2332], but it is possible that greater thicknesses exist elsewhere in these valleys. The form of the deposits varies considerably; large, almost flat, sheets of boulder clay are common, but typically the topography is moundy and irregular. Drumlin shapes are rare. DWH, ICB, CRB

A large area of boulder clay occurs in the main valley of the Tees, but it is thin or absent on the adjacent high ground. Upstream from Newbiggin the boulder clay tends to occur in drumlin forms, especially on the north bank of the river (Figure 48). DWH, JHH

At the northern edge of the district the southern flank of one of these drumlins [NY 861 296] is being undercut by the River Tees. The section which is subject to slipping showed grey boulder clay with abundant dolerite and limestone pebbles resting on ice-eroded dolerite (Whin Sill); towards the top of the drumlin, the boulder clay is overlain by a thin cross-laminated silt and sand layer in turn overlain by a loose yellow-brown stony till (Francis, 1970).

Borings and temporary excavations near the site of the Cow Green Dam [NY 813 290] also proved grey boulder clay, with sporadic thin sand and gravel lenses, commonly overlain by loose brown stony till. Both tills were overlain by peat. The brown tills (0 to 1 m thick) have both gradational and sharp contacts with the grey till, locally resting directly on rockhead, and appear to have originated in several ways at different times. A thin zone of yellow-brown clay or yellow-brown mottling at the upper surface of the grey till immediately beneath the peat appears to be a recent weathering phenomenon. Thicker deposits of similar material which grade downwards into grey boulder clay are thought to have resulted from a longer period of in-situ, largely pre-peat formation, weathering. The brown tills with sharp bases resting in hollows on the grey till or on rockhead are thought to result from pre-peat down-slope movements of weathered grey boulder clay.

Morainic drift

A number of scattered deposits, possibly of diverse origin, were mapped as morainic drift. They are typically composed of large, usually angular, boulders of local origin sometimes with no matrix, sometimes with a scattered sandy clay matrix. Such deposits have a marked topographical expression either as simple mounds or as linked mounds forming ridges. DWH

Details

A large spread of morainic drift occurs in High Cup Gill and in isolated patches northward up the Pennine escarpment as far as Great Rundale Beck. The position of this drift separating the boulder clay of the Vale of Eden from the solid rock of the Pennine escarpment suggests that it is a remnant of a lateral moraine of the Vale of Eden Glacier. A small patch of similar drift on High Cup Plain [NY 750 267] may be related to a small local glacier originating in the headwaters of Maize Beck. A ridge of morainic drift in front of Cronkley Scar, in Teesdale, is interpreted as a lateral moraine of the Teesdale Glacier (Dwerryhouse, 1902, p.577; Francis, 1970, pp. 141–142). This moraine continues down-valley with a subdued surface expression towards High Force and several small mounds of similar material are found as far to the east as Holwick. Similar material is also found upstream as far as Falcon Glints but has been subjected to landslipping or reworked into screes (see below). About 2 to 3 km E of Middleton in Teesdale, on the edge of the district, a deposit of ill-sorted angular sandy gravel has been mapped as morainic drift; it is quite distinct from the well-sorted, rounded, current-bedded sands and gravels (p.98) mapped nearby. The topographic form of this deposit also suggests a lateral moraine. DWH, ICB, JHH

In the Burness Hills area, about 1200 m S of Blackton Reservoir, two areas of morainic drift have been mapped, made up of mounds up to 30 m high of angular sandstone debris. Most of the sandstone is in the form of small blocks and fragments. Traces of clay are locally seen in the available exposures and it is probable that there is a clay matrix to this deposit. All the sandstone seems to be locally derived (in contrast to the boulder clay which contains Borrowdale Volcanic Group rocks and Shap Granite in addition) and is possibly an ablation moraine with debris from adjacent sandstone outcrops. Further mounds of limestone and sandstone in Deepdale between Knotts Sike and Knotts Gill, which were not differentiated from the boulder clay, might have a similar origin and may more correctly have been grouped here. In the south-east corner of the sheet, near Sleight Holme there are several groups of mound-like, or sometimes conical, hills. The chief group is that centred on Seven Hills [NY 970 106] about 500 m SE of Black Scar in Sleight Holme Beck. Other groups with similar form occur in this area and extend into the neighbouring Barnard Castle (32) district. Seven Hills consists of mounds, up to 15 m high, of unsorted angular sandstone, blocks and fragments. A matrix seems to be lacking. The sandstone appears to be local in origin and probably has not travelled far beneath ice. Wells (1955a, p. 84) has suggested that these mounds were deposited by ice flowing from the Tan Hill vicinity (i.e. from the south), with local erratics, which prevented the Edenside-Stainmore ice from entering this area. CRB, DWH

Glacial drainage channels

Channels cut by glacial meltwater occur abundantly throughout the district, notably in the Pennine escarpment–Vale of Eden area, in Teesdale and in Lunedale (Figure 48), (Figure 49) and (Figure 50). They are noticeably absent from the highest elevations, above the upper limit of boulder clay. Some of the channels are followed by the present drainage but a large number have been abandoned and are now dry. Many begin and end abruptly. They are cut into both solid and drift deposits and commonly do not follow the general slope of the ground. Channel length ranges from a few tens of metres to several kilometres; width ranges from 10 to 200 m and depth from 2 to 30 m. They are typically steep-sided and flat-bottomed. Longitudinal profiles generally slope smoothly downwards to the north-north-west in the escarpment and the Vale of Eden and to the east in the Tees drainage area. Locally the longitudinal profiles are humped, indicating the uphill flow of confined meltwater under hydrostatic pressure. Where channels cut across cols, the meltwater was in places forced to travel against gravity for distances of a kilometre or more. These observations suggest that most of the channels are the result of the subglacial flow of meltwater (see also Arthurton and Wadge, in press), rather than the previously held view that they were cut by meltwater flow marginal to a wasting ice-sheet or as spillways of ice or drift-dammed lakes (Trotter, 1929). However, some of the highest channels are initially parallel to the contours and may have originated at the ice margin. If so, they are older than the more comprehensive subglacial system which drained towards the centre of the valleys and which formed during the wasting of a stagnant ice-sheet. Some of these marginal channels drained and connected glacier-margin lakes (Trotter, 1929; Dwerryhouse, 1902). At a late stage of the deglaciation a large lake, Lake Ormside, formed in the Vale of Eden (Figure 50).  DWH

Details

The glacial drainage channels present in the west of the district are shown in (Figure 50). They form part of an extensive channel system that occurs throughout the Vale of Eden; in the Penrith district these channels are associated with sand and gravel deposits (Arthurton and Wadge, in press) but within the present district such deposits are rare. Along the lower parts of the Pennine escarpment and adjacent parts of the Vale of Eden the channels form a crude reticulate pattern, one set parallel to the inferred ice margin trending towards the north-west, the other normal to the ice margin trending towards the west-south-west. The former set, in particular, is characterised by humped profiles, a typical feature of subglacial drainage. The reticulate pattern may be the result of crevasse control on channel position.

Two distinct subglacial channel systems are present within the district in the Vale of Eden (Figure 50). One of these, broadly coincident with the main drainage of the present River Eden, drained the southern part of the Vale, western Stainmore, and the Pennine escarpment south of Brough. The other system drained the Pennine escarpment north of Brough. The two systems link several kilometres to the north-north-west near Kirkby Thore in the Appleby (30) district.

Locally associated with the higher channels are delta-like sand and gravel deposits (p.98) suggesting the former presence of glacier margin lakes which were drained and interconnected by marginal channels. Examples of these are to be seen along the escarpment between Murton Pike and Brownber.

In late-glacial and early post-glacial times a large lake, Lake Ormside, formed in the western part of the district (Figure 50) as a result of the blockage by boulder clay of the pre-glacial valley of the River Eden near Appleby (p.92). Benches cut around 475 ft OD occur at several localities (Figure 50). Deltaic deposits with tops at around 475 ft OD formed at the mouths of streams entering the lake (p.98). As some of these channels are now dry and appear to have been subglacial in origin, it would seem probable that, during part of the life of the lake, ice still covered the higher ground to the east. The lake was drained when the River Eden cut a new channel through boulder clay and Penrith Sandstone, forming the spectacular incised meanders between Great Ormside and Appleby. ICB, DWH

Another important concentration of channels occurs on the north side of Lunedale a few kilometres south of Middleton in Teesdale (Figure 49). These channels have many features typical of subglacial channels, i.e. humped profiles, abundant anastomosis of channels, and some smaller channels cut into steep slopes appear to be chutes. A number of steeply humped channels on Harter Fell cut across the watershed into the main Tees Valley. However, some of the higher channels are more likely to be marginal channels and, according to Dwerryhouse (1902), these linked a series of lakes that formed on the south side of Mickle Fell during the glacial maximum.  DWH, ICB, CRB, JHH

The former presence of a number of glacial lakes in Teesdale was suggested by Dwerryhouse (1902, p. 584). 'The largest of these lakes occupied the valley of Maize Beck, and appears to have had its overflow at the head of Hilton Gill (Scordale Head) [NY 7665 2453] or at High Cup Nick [NY 747 263] or at both these places, the watersheds being at about the same level.' Another lake near Bleabeck Grains [NY 865 255] was thought to have drained across the col into the channel and lake system previously described in Lunedale.

Numerous shallow channels occur on Cronkley Fell in Upper Teesdale (Figure 48), many with humped profiles or with slopes against the inferred direction of drainage.

Minor channel systems also occur in the eastward-draining valleys in the south-east of the district, especially in the upper reaches of the River Greta.

Sand and gravel

Lenses of sand and gravel, interbedded with boulder clay, have already been mentioned. A number of thicker deposits, overlying boulder clay also occur within the district. In the Vale of Eden, Lunedale and the Greta Valley, these are of limited lateral extent and of little economic value. However, those in Teesdale (Figure 49), which are continuous with deposits in the Barnard Castle district (Mills and Hull, 1976), are of greater importance and have been worked on a moderate scale in the past. Most of these deposits appear to have been waterlaid, some subaerially, others subglacially. Those deposits associated with high level (?marginal) channels on the Pennine escarpment are probably largely lacustrine in origin (Trotter, 1929). Somewhat younger are mounds and gravel spreads associated with subglacial channels, and these may be subglacial in origin. The youngest deposits are those related to the inlets into Lake Ormside. DWH

Details

Irregular mounds of gravel and subordinate sand, lacking the ridge form of eskers, are present on the north sides of a number of spurs projecting from the Pennine escarpment, e.g. Roman Fell [NY 745 209], Middle Tongue [NY 725 238], Knock Pike [NY 685 288] and Dufton Pike [NY 704 268] to [NY 688 271]. These appear to be related to marginal or sub-marginal glacial drainage channels. The Dufton Pike and Knock Pike deposits have a delta-like form with flattish tops and steep down-slope faces. Cross-bedding and graded bedding, best seen in the gravel pit on Knock Pike, suggest that these deposits were laid down in standing water, probably an ice-dammed lake. Other deposits with irregular form may have been deposited on melting ice. These gravels commonly contain a high proportion of soft slate clasts which reduces their commercial value.

Elsewhere in the Vale of Eden sand and gravel occur as spreads marginal to or at the mouths of large glacial channels, most notably along Hilton Beck [NY 711 202] and at Brough [NY 795 147]. Small occurrences of the same kind occur at several other localities [NY 701 240]; [NY 709 233]; [NY 718 234]; [NY 711 214]; [NY 726 182]. Three sand and gravel spreads [NY 702 168]; [NY 724 173]; [NY 723 169] have delta-like forms and occur at the common elevation of 475ft OD. Their position at the margins of Lake Ormside (p.96) and at the mouth of channels feeding into the lake suggests that they originated as deltas at the mouths of streams entering the lake. ICB, DWH

Some patches of sand and gravel occur marginal to subglacial channels in Lunedale [NY 945 234]; [NY 942 230]. Wide spreads of sand and gravel at the mouths and downstream of the channels of this system occur in Teesdale and extend eastwards into the Barnard Castle district (Mills and Hull, 1976). These deposits are poorly exposed and are little known; their undulating and locally moundy upper surface suggests a supraglacial origin.

Deposits of gravel, made up of largely angular pieces of local rocks, with small pockets of sand, are found in the Greta Valley, approaching 10 m in thickness near Spital High Cottages. In a section hereabouts [NY 9251 1159], 6 m of sand and gravel were seen overlying boulder clay. The gravel contains a small, but fairly evenly distributed, proportion of clay. The deposits occur as small mounds or ridges arranged parallel to the direction of ice-flow, i.e. along the valley, and are spatially related to glacial drainage channels. A subglacial or englacial origin is probable. CRB, DWH

Head

Beneath the peat on the high ground of the district, notably that north of Lunedale, the solid rocks are to a considerable extent covered by head (Johnson and Dunham, 1963, p. 109). This deposit is made up of angular sandstone blocks with varying amounts of a yellow sandy clay matrix. Fragments of rocks other than sandstone are extremely rare. In one or two localities rounded balls of boulder clay occur within head. However, apart from marginal areas where head overlies boulder clay, head occurs above the higher limit of boulder clay and is broadly restricted to those areas that projected as nunataks above the Devensian ice-sheets. It is thought to have formed by solifluction under periglacial conditions, contemporary with, and following on from, the last glaciation. Sandstone block-fields occur at several localities e.g. [NY 728 264]; [NY 740 218]. On the higher summits the re-establishment of periglacial conditions in more recent times had led to a newer period of solifluction. In this region, also, many of the limestones at crop are cambered down-slope for considerable distances as a result of frost action [e.g. [NY 774 275]; [NY 767 263]. DWH

Peat

Much of the higher ground within the district is covered by blanket-peat up to 3 m thick, commonly deeply dissected. This peat consists of Eriophorum, Calluna, and Sphagnum, with a layer of birch roots, the 'forest-layer' at the base. It began to form locally in hollows during Boreal (pollen Zone VI) and Atlantic (pollen Zone VIIa) times, but later became widespread (pollen Zones VIIb to VIII), covering the main summits, corresponding to a decline in tree cover (Raistrick and Blackburn, 1932; Johnson and Dunham, 1963; Squires, 1971; Turner and others, 1973). Since about 500 BC, the peat has been greatly eroded and many areas, including the main summits, have been stripped almost bare (Johnson and Dunham, 1963). Locally older peats occur beneath the blanket-bog. In the Widdybank Fell–Cow Green area, now partly flooded by the Cow Green Reservoir, peats began to form in late Devensian (pollen Zone III) times (Turner and others, 1973). On Cronkley Fell organic deposits with Phragmites formed in water-logged depressions during Zone V (Squires, 1971). Accounts of the changing climate and vegetation cover in the Pennines uplands of the north of the district, as deduced from the peats, are to be found in Johnson and Dunham (1963, pp. 131–151) and Turner and others (1973).

On the lower ground isolated areas of peat are present, commonly in hollows in the floors of glacial channels. In the Vale of Eden peat of unknown age overlies the deposits of Lake Ormside.

Alluvium and river terrace deposits

Alluvium and terrace deposits are associated with all the major streams and rivers, for the most part being composed of fine sand or sand and gravel. In the smaller stream valleys clay and silt, reworked from boulder clay or head, have been deposited. These deposits span the period since the disappearance of the glaciers. Terrace deposits in Upper

Teesdale (now under the Cow Green Reservoir) locally are overlain by late Devensian (Zone III) peat. Similar terraces in Lunedale [NY 840 220] are overlain by substantial (undated) peat deposits with the birch layer at their base. Possibly of a similar age are sands with small freshwater gastropods, bivalves and ostracods, identified by Miss D. Monograptus Gregory as Candona neglecta and Cypridopsis vidua underlying peat in Sandford Mire [NY 725 172], which are thought to have been laid down in a drift-dammed lake (Lake Ormside, p.96); (Figure 50). Some of the most recent deposits are alluvial fans, composed of ill-sorted debris, deposited during the nineteenth century 'hushing' operations; a number of these are shown in the 1:50000 map in the Cronkley Fell area.

Landslips and scree

Widespread downslope movement of materials on the higher elevated parts of the district has already been referred to in relation to the formation of head. More localised and sharply defined movements in the form of landslips and screes also occur widely. Landslips involving solid rock are abundant on the Pennine escarpment and in the high Pennines [NY 735 259]; [NY 754 215]; [NY 765 193]; [NY 785 164]; [NY 823 198]. In the latter place, especially, these slips are related to cambering and solifluction probably during the main period of glaciation. Unique in the area is the large rotational slip at Hillbeck Wall End [NY 780 168] where a block of Ashfell Sandstone, Hillbeck Limestones and overlying Great Scar Limestone (over 150 m of beds) has slipped over 50 m down-slope and rotated so that the originally horizontal beds now dip into the hillside at up to 45°. The volume of rock involved in this slip exceeds 2000000 m³. Slipped masses of boulder clay are common on valley sides where the banks are being actively eroded.

Screes are found in the escarpment area and also at the foot of dolerite (Whin Sill) crags in Teesdale. These represent down-slope movement of rock fragments over a considerable period and movement of material has taken place during recent times. However, as most screes are partially grassed over and locally have a peat cover, it seems likely that these largely developed at a much earlier period, probably during or just after the glacial retreat.

Made ground

Small industrial tips occur near abandoned quarries and mines. The only extensive deposits of this type are to be found near actively working centres, such as the whinstone quarries in Teesdale and the Closehouse Barytes Mine, and in Lunedale and Baldersdale near the reservoir embankments. DWH, ICB

Chapter 12 Mineral products

Metalliferous and associated minerals

The Brough district lies on the southern margin of the northern Pennine Orefield and the Carboniferous rocks are cut by mineral veins at numerous localities. The veins occur along faults, commonly with an east-west or east-north-east trend. The oreshoots take two forms, occurring either as lenses following the faults (vein oreshoots) or as replacements of the thicker limestones on either side of the faults (metasomatic fiats). Most of the veins were extensively investigated in the past, principally in the search for galena (lead ore). Exploratory levels, some of which are still accessible, were driven at many localities. They are commonly in a highly dangerous condition, and should not be entered without expert guidance. Surface exploration was principally by means of 'hushing'—a process whereby ponded water was suddenly released and channelled either along known veins or across the possible course of veins resulting in the rapid removal of surface deposits and erosion of the solid rock along the chosen line. Deep gullies formed by this process are common, the most impressive examples being Coldberry Gutter [NY 930 289] (Plate 12), over 1 km long and up to 20 m deep and Standards Hush [NY 860 229], 500 m long and also up to 20 m deep.

Galena usually forms only a small part of the vein material, the remainder (gangue) being either baryte or fluorite. These minerals, discarded by the early miners, are now of commercial value, the former for chemical purposes, for drilling mud and for use as an aggregate for concrete used in radiation shielding, the latter also for chemical purposes and for use as a flux in the steel industry.

The occurrences in the district were re-investigated fully by Dunham (1948). The distribution of the principal mines and veins is indicated on (Figure 51).

Throughout the district, baryte is the principal gangue mineral; fluorspar is present only in Scordale and north of Middleton in Teesdale. Many of the mines originally opened for lead have been more recently worked on a small scale for baryte, though apart from Closehouse Mine, none is active at the present time. The current increase in demand for baryte for use in drilling mud has created a new interest in these old mines, though it seems probable that most of the deposits are too small or too isolated for commercial production.

On the Pennine escarpment (Dunham, 1948, pp. 133–141), the Threlkeld Side and Dufton Fell mines, in Great Rundale, produced first lead-ore, and later baryte, principally from small flats in the Tynebottom, Jew and Smiddy limestones. In the White, Murton and Hilton mines (Scordale), the mineralisation extended from below the base of the Melmerby Scar Limestone up to the Lower Little Limestone and included galena, baryte, witherite and fluorite. On Long Fell, baryte has been worked from thin veins in the Great Scar Limestone, and small veins occur in the same limestone farther south. Near Brough, at Augill Mine, a low-grade orebody consisting of disseminated galena and baryte in ankeritised Great Scar Limestone was worked both opencast and underground. The extent of the workings and size of the orebody are unknown. At Cabbish, a small mine produced galena and baryte from the Great Limestone.

In Upper Teesdale (Dunham, 1948, pp. 287, 312–313), the Maize Beck Mines are in a group of veins on the northern slopes of Mickle Fell, formerly worked for galena. Their chief interest is as a possible source of baryte, though their inaccessibility would make exploitation expensive.

Farther downstream, in the Ettersgill–Wynch Bridge area (Dunham, 1948, pp. 297–300) the Single Post Limestone has been extensively replaced by siderite and sphalerite, and in the latter area, small east–west fissures carry the same minerals.

North of Middleton in Teesdale a complex of veins extending southwards from the Lodgesike–Manorgill Fault was worked from Red Grooves, Coldberry, Low Skears, High Skears, Marlbeck and Snaisgill mines (Dunham, 1948, pp. 300–307). The principal ore mineral sought was galena, the gangue being a mixture of purple fluorite, baryte, limonite and quartz. The mineralised ground extended from the Great Limestone up to the top of the Grit Sills. Coldberry Gutter, noted above, is a large hush on the Lodgesike Fault (Plate 12).

In Lunedale, a complex of veins in the Great Limestone was worked for galena, baryte and, rarely, witherite from Lunehead Mine (Dunham, 1948, pp. 31 6–318). The area is notable for the existence of a west-north-westerly trending belt of post-mineralisation caverns which were intersected by the early workings.

Also in Lunedale, Closehouse Barytes Mine (Dunham, 1948, pp. 314–316; Hill and Dunham, 1968; Ineson, 1968) is the only active mine in the district at present. The principal deposit lies on the main Closehouse–Lunedale Fault. A dolerite dyke, related to the Whin Sill suite, intruded along the fault where it crosses Arngill, has been thoroughly carbonatised and subsequently almost completely converted to baryte. The resulting orebody, dipping south at 50°, reaches a width of up to 27 m, over a strike length of nearly 500 m, and extends to an as yet unknown depth. The major part of the deposit lying above the valley floor has now been extracted by opencast, but considerable proved reserves still remain below the valley floor. The westwards continuation of the Closehouse Fault is also mineralised, the baryte occurring as lenticular bodies in the crushed material in the hanging wall of the fault. Part of this deposit is exposed in Closehouse Hush [NY 840 226]. East of Arngill, Standards Hush exposed thin baryte-galena veins in the same fault-line. Small-scale mineralisation is also present on the South Fault, a parallel structure 100 to 200 m to the south.

Age and origin of the deposits

Various attempts to date the mineralisation directly by radiometric methods (Moorbath, 1962; Mitchell and Krouse, 1971; Dunham and others, 1968) have led to conflicting interpretations. It certainly post-dates the intrusion of the Whin Sill suite of rocks (295 Ma), and the fact that the major deposits are confined to rocks of Carboniferous age may indicate that the main phase occurred in the Westphalian-Zechstein interval, though redistribution of certain of the minerals may well have continued at intervals since that period (Dunham, 1974a).

That the minerals were deposited from low-temperature (220° to 50°C) brines is generally accepted (Sawkins, 1966). The origin of these brines, whether from juvenile fluids (Dunham, 1948; Solomon, 1966), from connate water in Carboniferous mudstones (Sawkins, 1966), from lateral secretion from micas in the basement rock (Dunham, 1966) or from evaporites (Davidson, 1966; Dunham, 1970; Solomon and others, 1971; Carpenter and others, 1974) is still a subject of widespread discussion, and will not be treated here. A recent summary is given by Dunham (1974a, pp. 301–306).

Resources

Considerable quantities of baryte are present in the district, but the known deposits are generally too small and too inaccessible for current development. The Maizebeck and Lunehead areas are possible areas for further exploration. The Closehouse area is one worthy of further examination. The known deposits lie along the Closehouse Fault, a major structure downthrowing to the south, separating the thin sequence of Carboniferous rocks on the Alston Block to the north from the thicker sequence in the Stainmore Trough to the south (Figure 2). The Carboniferous sequence on the south contains thick limestones (Great Scar Limestone, etc.) at depth, faulted against basement rocks (Skiddaw Group?) on the north, and is folded into a tight anticline parallel to the fault for over 5 km (Figure 45). The analogy with the proved base-metal producing structures in Ireland is apparent, but further investigation by drilling will be necessary, as the possible host rocks are at depths in excess of 150 m. ICB

Coal

Coal of Carboniferous age has been mined in the past from several stratigraphical levels though there are no such workings at present. The best prospects are in the Coal Measures of the Stainmore Outlier where opencast extraction might prove profitable. The coals of the Millstone Grit Series are probably too thin and inaccessible to be of further value, while those in the Alston Group are so thin and local as to be of only academic interest.

Limestone

During the resurvey of the sheet active quarrying of limestone was taking place at Hillbeck Quarry near Brough (in the Robinson Limestone) and at Staple Green Quarry at Newbiggin in Teesdale (in the Great Limestone). At the time of writing, however, neither quarry is operative. Many other abandoned quarries testify to extensive exploitation in the past. Nevertheless reserves of Carboniferous limestone in the district are immense though much of these are in inaccessible ground. Probably only the Melmerby Scar Limestone and the Great Limestone are thick enough to make extraction economic. The Keisley Limestone (Ordovician) is restricted in outcrop and could be only of importance as a local minor source of limestone.

Whinstone

Whinstone presently is quarried in Teesdale near Holwick and at Force Garth Quarry. Large abandoned dolerite quarries in Teesdale and Lunedale indicate that this has been an important industry in the past and while the demand for road metal of this type continues the large accessible outcrop in Teesdale should guarantee a small but viable industry.

Sand and gravel

Minor sand and gravel workings in the district were active in the past. Glacial sands and gravels in the escarpment area are of little significance being of limited extent and containing slate fragments. Terrace gravels in the Vale of Eden remain unevaluated as do the terraces and glacial gravels of the Tees Valley.

Gypsum and anhydrite

The Hilton Borehole (p.74) (Burgess and Holliday, 1974) proved two thick beds of gypsum-anhydrite in the Eden Shales, demonstrating for the first time that the main evaporite beds of the Vale of Eden continued into the Brough district, though gypsum is actively mined only a few kilometres away at Kirkby Thore in the Appleby (30) district. The evidence of the Hilton Borehole suggests that considerable amounts of anhydrite occur in the Brough district, but workable quantities of the more valuable gypsum have yet to be proved.

In the Brough Sowerby Borehole (p.75) there were indications of the former presence of evaporitcs that had been dissolved out. Evaporite beds may still be present to the south-east of the borehole position nearer the centre of the basin where increase in cover may have prevented complete solution.  DWH

Appendix 1 List of boreholes and measured sections

This appendix lists, by six-inch maps, the main borehole and measured section records for the district. For each record the permanent record number and the stratigraphical range is given. Copies of these records may be obtained from the North of England office of the Institute at a fixed tariff. Each entry in the list shows first the permanent record number and location of the borehole or section and then its stratigraphical range.

Appendix 2 List of Geological Survey Photographs

Copies of these photographs are deposited in the libraries of the Institute of Geological Sciences at Exhibition Road, London SW7 2DE, and Ring Road Halton, Leeds LS15 8TQ. They all belong to Series L and may be supplied as black and white prints or lantern slides, and as colour prints or 2 x 2 in colour transparencies, all at a fixed tariff.

General views

Ordovician

Carboniferous

Permian and Triassic

Whin Sill

Cleveland Dyke

Pleistocene and Recent

Economic products

Appendix 3 Petrographical descriptions of Ordovician volcanic rocks

Skiddaw Group: Kirkland Formation

Roman Fell

Tuff samples (E32073) and (E32074) [NY 7460 2071]; [NY 7455 2058] respectively, include lapilli up to 10 mm across of pale brown, devitrified lava. The matrix comprises roughly bedded devitrified glass shards, pumice, clusters of sanidine and albite-oligoclase laths, quartz, feldspar crystals, much chlorite, leucoxene and carbonate. They appear to be of mixed origin from basic (or intermediate) as well as acid igneous sources.

A specimen (E32076) of hypersthene-augite-andesite from the quarry [NY 7465 2055] consists of partly carbonated and chloritised augite and hypersthene microphenocrysts (up to 3 mm across) set in a groundmass felt of fluxioned, chloritised and albitised plagioclase laths, devitrified glassy mesostasis, interstitial chlorite, accessory magnetite and a little quartz. Hypersthene poikilitically encloses augite which has a refractive index(β)= 1.594. The coarser, vesicular andesites (E32077)–(E32078) [NY 7472 2039]; [NY 7476 2034] respectively, are microporphyritic with euhedral phenocrysts up to 3 mm across completely altered to chlorite, silica and dolomite (ω = 1.684 ± 0.003). The groundmass is a felt of fluxioned laths of saussuritised or carbonated feldspar. These rocks are too altered for precise naming, but their vesicular and fluxioned textures and overall appearance indicate an extrusive origin and andesitic affinity.

Keisley

Eleven specimens (E36452), (E36453), (E36454), (E36455), (E36456), (E36457), (E36458), (E36459), (E36460), (E36461), (E36462) of tuffs are mainly dense, grey-green (or purple-stained) and medium- to fine-grained with sporadic lapilli. Pyroclastic constituents include closely packed crystals (principally soda plagioclase), devitrified glass shards, chloritic pumice, spilitic and feldsparphyric lava, albitite, red jasper, quartz and rhyolitic particles. The fine matrix includes much chlorite, ferric oxide, leucoxene and sporadic carbonate. An example of pumiceous tuff of basic affinity (E36455) [NY 7149 2439], is dense, hard, grey-green (stained purple), with angular pyroclasts (1 to 5 mm) and jasper, scattered in a tightly packed finer matrix of poorly sorted pumice particles, pumiceous lava, spilitic lava, plagioclase crystals, chlorite and carbonate. A complete chemical analysis (Table 5) analysis 1, confirms a basic affinity with low SiO₂, and relatively conspicuous Cr, Co, Ni and Cu among the trace metals. The high content of chlorite is indicated by most of the MgO content of 10.80%, and part of the FeO (7.73%). The sporadic staining (due to hematite) appears to be relatively minor in terms of the Fe₂O₃ content of 2.11%. Somewhat surprisingly, fresh diopside occurs as subhedral crystals, up to 2 mm across, in these tuffs. It is pale green, non-pleochroic, with optics α = 1.694, β = 1.706, γ = 1.709 (all ± 0.003), γ−α= 0.015; 2E (+) = 102°, hence by calculation 2V =59°26′. The analysed vitroclastic spilitic tuff (E36452) (Table 5) analysis 2, consists of closely packed, moderately sorted devitrified shards, feldspar-microlitic lava (cf. spilite), coarser lava, quartz and plagioclase crystal particles, chlorite and opaque matter. The relatively high Na₂O content (6.67%) supports the spilitic (soda-basalt) affinity, but the tuff is less heavily chloritised than the previous specimen, and the MgO content is accordingly less. The trace elements, the alkaline earths Ba and Sr are closely similar, but the metallic elements except for Cu vary considerably. The relatively high F content in both samples is noteworthy. The intimate association of tuffs in this area with spilitic lava is also shown by veining of albitite (E36454) [NY 7145 2442].

Swindale Beck (Knock)

Samples (E36440), (E36441), (E36442), (E36443), (E36444), (E36445), (E36446)  of tuffs and tuffaceous sediments are dense, pale green-grey rocks, mainly of silt to medium-sand grade, but with lapilli and coarse clasts up to 2 cm across. The pyroclasts include altered glass shards, pumice, feldspar crystals and finely crystalline lava commonly replaced by carbonate, silica or leucoxene; orthoclasts are possibly of Skiddaw Slate. Most of the rocks are bedded and moderately well-sorted, with generally little admixture of fine orthoclastic sediment which is mainly an argillaceous silt charged with fine carbonate (E36440) [NY 6903 2831]. In one tuff (E36441) [NY 6917 2850] amygdales in particles of pumice contain illite, carbonate and feldspar needles, set in a groundmass of chlorite and fluxioned leucoxene laths.

Borrowdale Volcanic Group

Studgill Tuff Formation

A silicified rhyolite-breccia (E36591) from [NY 6985 2685], the north-eastern flank of Dufton Pike, is pale green, and composed of angular clasts (up to 1 cm across) of rhyolite cemented by microcrystalline silica. The clasts are mainly of cryptocrystalline silica, charged with chlorite and with scattered feldspar crystals. In strong contrast, a tuff (E36592) from nearby [NY 6998 2688] is heterolithic and contains abundant pumice (with variably flattened vesicles mainly filled with carbonate or silica, rhyolite and spilitic particles, in a devitrified siliceous matrix).

Knock Pike Tuff Formation

Near the base of the formation on Knock Pike [NY 6865 2853] a pale green specimen of finely streaky, rhyolitic rock (E36422) is mainly micro- to cryptocrystalline, showing patchy weak birefringence in aggregates of felts of feldspar needles, silica, chlorite, carbonate and leucoxene dust, and scattered oligoclase laths up to 2.4 mm long. Prominent veinlets of later silica are attributable perhaps to the closing stages of the volcanic episode. There is no certain evidence of a pyroclastic origin, but a prominent streakiness and jointing suggests that the rock is a parataxitic welded tuff which suffered a complete alteration of the primary texture to a devitrified felted mosaic. A chemical analysis (Table 5) analysis 4, shows a relatively high alkali content of which the K₂O must be accounted for mainly by cryptocrystalline K-feldspar in the felted groundmass. This is emphasised by the norm (Table 6), which also expresses a small excess of Al₂O₃ as corundum. As might be expected, the hydroxyl content is low. Of the trace elements, barium is conspicuous, though no baryte has been detected optically. Two similar rocks from Swindale Beck [NY 6891 2790]; [NY 6892 2794], which proved to be highly welded rhyolitic crystal-lithic-tuffs (E36438)–(E36439), contain flow-banded clasts of rhyolite and acid plagioclase crystals set in a crypto- to microcrystalline devitrified rhyolitic groundmass, with accessory leucoxene. There are secondary stringers carrying quartz and dolomite. Two samples (E40621)–(E40622) from the western and southern flanks of Knock Pike [NY 6830 2818]; [NY 6862 2798] respectively, are mottled grey-olive heterolithic, crystal, ash-flow lapilli tuffs. They contain lapilli and smaller particles of rhyolite, fluxioned alkali-feldspar-rich lava (?spilitic), abundant sodic plagioclase crystals, and are set in a probably welded, devitrified streaky glassy matrix. Samples of the overlying beds (E36428), (E36429), (E36430), (E36431), (E36432); (E36435), (E36436), (E36437); (E40623), (E40624), (E40625), (E40626) in the Swindale Beck succession [NY 6892 2786] to [NY 6886 2778] include less highly welded crystal-lithic tuffs, which may be agglomeratic and lapilli-bearing. Pyroclasts are generally attenuated and include rhyolite, feldspar-microphyric and felsitic lava, shards, pumice, feldspar crystals (variably carbonated) and apatite grains. The very fine-grained matrix is mainly silica and chlorite, with variable zoned carbonate and leucoxene dust, together with finely comminuted pyroclastic particles. Partial welding may be seen, but these textures are obscured by flowage crystallisation (snowflake texture) and silicification; extensive argillisation of glass has occurred in one specimen (E40625). Two examples (E36430) (E36431) include lit-par-lit injection and much welding.

Tuffaceous sediments (E36433)–(E36434) are finely laminated, hematitic, brecciated, show graded bedding (from silt to mud grades), and pyroclasts are common in the coarser material. Two samples (E36437), (E40626) are sand-grade greenish grey (5G6/1) chloritic tuffs composed of close-packed, well-sorted angular shards, pumice, feldspar crystals, devitrified glassy lava, and accessory apatite crystals. In the Milburn Beck section, samples (E40605), (E40606), (E40607), (E40608), (E40609), (E40610), (E40611), (E40612), (E40613), (E40614), (E40615), (E40616), (E40617), (E40618) of variably coloured, hard, fine-grained, siliceous rocks indicate the lithological variation from north to south [NY 6784 2911] to [NY 6773 2857]. Most are welded rhyolitic ash-flow tuffs and exhibit variable eutaxitic textures with fiamme and other pyroclastic structures in parallel array, giving rise to a distinct foliation and in some cases, cleavage (Plate 3.1) and (Plate 3.2). Examples showing prominent (up to 2.5 x 0.3cm) fiamme (E40606)-(E40607), (E40617)-(E40618) range from pinkish grey (5YR 8/1) and yellowish grey (5Y8/1) to moderate orange pink (10R 7/4) and pale reddish orange (10R 6/6). Lapilli (up to 1 cm across) disturb the enclosing streaky shards. In thin section fiamme are poorly resolved as finely crenulated streaks of dusty, devitrified material charged with needles of alkali-feldspar, cryptocrystalline quartz and opaque dust. Any primary axiolitic texture has been obliterated by the growth of quartz along the central axes of fiamme. Lapilli are mainly of paragonitised feldspar-rich microlitic rhyolite, with a microcrystalline, quartzfeldspar-mica groundmass which is overall near-isotropic, streaky and charged with feldspar needles and dusty opaque particles. The rocks are distinguished from flow-lineated rhyolites only by the aligned fiamme-like structures which strongly suggest an intense degree of welding of subsequently modified rhyolitic pyroclasts.

Finer-grained rhyolitic tuffs (E40606), (E40608)–(E40609), (E40613) show even less microscopic evidence of welding owing to late-stage modification, although vestiges of close-packed, finely streaky fiamme occur in hand specimens. Thin sections show finely aligned lenses of poorly resolvable microcrystalline devitrification products, with axial strings of quartz-feldspar growths, scattered discrete pyroclasts, all set in a streaky devitrified base. Other specimens from this suite (E40605), (E40610), (E40611), (E40612), (E40616) show no certain fiamme or eutaxitic structures, but consist of interlocking spherulitic patches of devitrified felts of feldspar microlites and quartz. A typical example (E40611) shows microphenocrysts (up to 1.2 mm long) of K-feldspar and albite-oligoclase scattered in a spherulitic felted base, with accessory mica, zircon, apatite, leucoxene and secondary hematite. While these features suggest devitrified rhyolite lavas, they may equally represent extreme destruction of welded acid tuff structures as figured in Ross and Smith (1961, p. 37 and figs. 55, 56). These specimens may represent the interiors of ignimbrite units (cf. Anderson, 1970, p.287), where heat and gases are more likely to be retained longer than at the margins, permitting more prolonged crystallisation.

Four samples from Dufton Pike (E36382); (E36590); (E36593), (E36594) [NY 6947 2681]; [NY 6955 2678]; [NY 7011 2647]; [NY 7040 2627] are devitrified, very highly altered rhyolitic extrusives. One (E36590) is a pale green flinty rhyolite-microbreccia formed of cryptocrystalline devitrified glass fragments cemented by microcrystalline siliceous matrix. Three samples (E36382), (E36593), (E36594) suggest rhyolite lavas in being composed almost entirely of felted mosaics of cryptocrystalline quartz and feldspar with microphenocrysts of feldspar. Streaky lenses \(E36594) filled with quartz and feldspar may indicate an exceptionally altered welded tuff.

Specimens from Keisley Bank (E36450), Dod Hill (E40628), (E40629), (E40630) and the elliptical outcrop about 1 mile ESE of Dufton (E40633), (E40634), (E40635), (E40636), (E40637), (E40638), (E40639) range from highly altered welded rhyolitic tuffs and rhyolitic breccias to pumiceous tuff. Of the acid ash-flow tuffs, one (E36450) from Keisley Bank [NY 7099 2423] is hard, flinty, pale green, finely streaked with particles of devitrified rhyolite, other pyroclasts and altered feldspar crystals, aligned in a very finely fluxioned matrix suggesting a partially welded vitric tuff. Some of the lithic pyroclasts show patches of argillised glass with quartz aggregates, altered feldspars, and streaky lenses which may represent thoroughly altered fiamme. A chemical analysis (Table 5) analysis 3, confirms the high SiO₂ content and A1₂O₃ close to that of rhyolite lava (analysis A), while the alkalis—particularly Na₂O—are considerably lower, probably because of the highly altered (argillised, carbonated, hematitised) nature of any feldspars. Of the trace elements, fluorine is more comparable with that in the basic tuffs than in the welded tuff (analysis 4) from Knock Pike. Other acid (rhyolitic) specimens include a possible lava or thoroughly devitrified glassy part of an ignimbrite (E36464) [NY 7102 2414]. A further specimen (E40634) [NY 7014 2428], while showing a similar felted or snowflake texture of quartz-feldspar microlite aggregates, is characterised by an exceptionally finely streaky texture, with streaks not exceeding 0.01 mm thick, which suggests intense welding. Microbrecciation of rhyolitic rock is seen in one specimen (E40633) [NY 7014 2428] cemented by much secondary silica, and in another (E40635) [NY 7002 2439] a second cycle of brecciation and recementation (by silica and ferric oxide) occurs. Two samples (E36468), (E36469) from Gregory [NY 7123 2464]; [NY 7123 2469] respectively, are thoroughly devitrified, rhyolitic (acid) ash-flow tuffs, strongly resembling finely flow-banded feldsparphyric rhyolite, but particles of pyroclasts and streaky fiamme indicate a more probable tuff affinity.

On Dod Hill three tuff specimens (E40628), (E40629), (E40630) [NY 7124 2517]; [NY 7123 2517]; [NY 7112 2509] vary from yellowish grey (5Y7/2) welded rhyolitic lapilli-tuff (E40628) to greyish purple (5P4/2) heterolithic crystal-lapilli-tuffs (E40629), (E40630). The latter contain a variety of lithic particles including spilitic lava and rhyolite, which, together with feldspar crystals, are set in a finely fluxioned devitrified rhyolitic matrix which may, perhaps, be partly welded.

Other heterolithic lapilli-tuffs occur in the north-western part of the elliptical outcrops about 2 km to the west of Gregory. Unwelded lapilli-tuffs (E40636), (E40637) from respective localities [NY 7002 2465]; [NY 7002 2464] contain much pumice (mainly carbonated), feldspar-microporphyritic acid lava, particles of welded rhyolitic tuff, spilite and altered feldspar crystals in a complex carbonate-rich matrix. A finer tuff (E40639) [NY 6987 2469] is a close- and even-grained, pale grey-green aggregate of angular, chloritised and argillised pyroclasts and crystals. At one exposure [NY 6988 2469] well-jointed, hard, fine-grained, pale blue-green (5BG7/2) lava (E40638) consists of a felted mass of minute (0.02 x 0.002 mm) feldspar needles ((3 near 1.540), mainly oligoclase, chlorite and leucoxene, with attenuated and compressed amygdaloidal lenses rimmed with quartz and filled with carbonate, mica or chlorite. Although no primary ferromagncsians remain, the rock is provisionally classed as an andesite on the overall appearance and abundant chlorite, but the abundance also cf soda plagioclase may indicate a spilitic affinity. This ground is intensely faulted and poorly exposed, and other formations of the group may also be represented by these rocks.

From the most southerly outcrops of the formation just to the west and south of Roman Fell, specimens include a variety of highly welded rhyolitic tuffs, partly welded heterolithic tuffs and lapilli-tuffs of lithological range similar to those described from the Keisley area. Specimens from the south-west flank of Roman Fell include highly welded rhyolitic vitric-lithic tuffs, welded lapilli-tuffs, and complex heterolithic crystal tuffs showing variable degrees of welding. Examples of highly welded tuffs (E32069), (E32063) from exposures [NY 7537 1933]; [NY 7550 1946], are devitrified and rhyolitic. Fiamme and other attenuated devitrified glassy material are finely layered, and deviate around angular lithoclasts of andesite and feldspar crystals. Axiolitic texture in fiammc appears to have developed into conspicuous feldspar quartz growths with much fine mica. Much of the welded texture of the rock has been obliterated through extensive devitrification to felted quartz-feldspar mosaics. Similar extensive devitrification (E32070) [NY 7519 1967], (E32068) [NY 7547 1930], grades into finely streaky material with 'augen'-like feldspar crystals. While this texture strongly suggests extreme welding of glassy pyroclasts it could also be interpreted as finely flow-banded rhyolite. Strongly fluxioned and welded matrix is prominent in two specimens (E32059), (E32062) from exposures [NY 7544 1937] and [NY 7521 1941] respectively. Lapilli are attenuated around originally less-plastic fragments. The devitrified matrix partly replaces lapilli in tightly fluxioned array. Coarser representatives (E32043), (E32045), (E32047), (E32049), (E32059), (E32060), (E32061) contain a variety of lapilli of intermediate and acid lavas, earlier welded tuff, fiamme and other lenses of devitrified glassy material and crystals (chiefly alkali feldspar) generally orientated in a fluxioned siliceous matrix, which may alternatively be interpreted as variably welded. The range of lava particles suggests accidental material caught up in the eruptive phases rather than the admixture of contrasted magma types-the final ramifying and cementing or welding fluid always being rhyolitic. A typical example (E32058) [NY 7519 1949] of heterolithic tuff contains lapilli and other particles of pumice, chloritised felsite, microporphyritic devitrified rhyolite, replaced plagioclase crystals, altered glassy material and leucoxene pseudomorphs after ilmenite. The matrix is mainly fluxioned devitrified glass and feldspar-quartz-illite felts. One specimen (E32049) [NY 7554 1948] is extremely altered with hematitised pyroclasts. In some specimens (E32045) [NY 7558 1922], (E32047) [NY 7561 1930], the matrix is completely altered devitrified mosaic whereas the crystals and pyroclasts are relatively little modified.

A light greenish grey specimen (E32079) from The Seat [NY 7434 2045] is a thoroughly devitrified mosaic of weakly birefringent felted patches of quartz-sericite intergrowths, microphenocrysts of altered feldspar, small elongated pools and veinlets of quartz, flakes of muscovite and skeletal crystals of leucoxene after ilmenite. Though strings of quartz and mica may suggest completely altered fiamme, there are no obvious pyroclasts and the rock is regarded as a rhyolite. Specimens (E31661), (E31662), (E40640), (E40641), (E40642),  from the north-west face of Roman Fell are welded rhyolitic and part-welded heterolithic tuffs. Lapilli, fiamme and other lithoclasts include chloritised and silicified rhyolite (with sodic plagioclase microphenocrysts in a chloritic and feldspathic base), carbonated pumice, devitrified glassy lava, carbonated lava, welded tuff, and andesitic-spilitic lava showing a wide range of microtextures. Crystals, chiefly of altered feldspar, are common and aligned along the flow-foliation. A particularly wide range of pyroclasts is shown in a specimen (E40641) [NY 7510 2052] with abundant particles of spilitic lava. In these, little-altered laths of oligoclase are fluxioned in a dark, devitrified glassy matrix charged with specks of leucoxene, iron oxide and chlorite. In this specimen also, particles of altered pumice show little flattening of vesicles. Accordingly it is difficult to reconcile this with the finely fluxioned matrix of attenuated pyroclastic material if the matrix is considered to be entirely welded, though the resemblance is strong. It may be that the pyroclasts were injected by glassy lava charged with semi-solid particles in a transitional stage between 'pure' welding and lava injection, for which the writer proposed an analogous term 'soldered' (Edwards, 1967, p. 56), i.e. the introduction of a liquid phase in the agglutination of particles. Unfortunately the finely fluxioned matrix is so devitrified to aggregates of quartz specks, that any primary shard textures have been obliterated. Evidence of fine welding is stronger in another specimen (E31662) [NY 7508 2058] where lenses filled with axially arranged feldspar-quartz needles may represent recrystallised fiamme.

Harthwaite Tuff Formation

A specimen (E40643) of one of the oldest beds exposed on Roman Fell [NY 7492 2038] is a coarsely fragmented rock of poorly orientated, unsorted, hematitised angular to rounded clasts up to 1 cm length, closely packed in a greyish purple (5P4/2) matrix. The overlying tuffaceous beds around Hilton Sike [NY 7487 2033] include finely laminated silty slate (E40644), (E40645). The principal slaty cleavage lies at 50° to the laminated bedding. The fine (up to 0.2 mm thick) laminations are alternations of argillaceous and granular ferric oxide, with fine silty clay, the primary cleavage foliation being due to a reorientation of clay minerals-especially biotite. Porphyroblastic tablets of interlayered chlorite and (?) illite, have not been orientated by the cleavage foliation. Pyroclastic rocks include vitroclastic crystal tuff (devitrified) (E32064) [NY 7492 2010] with resorbed quartz and sodic plagioclase crystals scattered in a vitroclastic matrix, heterolithic tuff (E40643) [NY 7492 2038], tuffaceous sandstone (E32065) [NY 7487 2019], and a fine vitroclastic tuff with accretionary lapilli (E32067) [NY 7493 2003]. The heterolithic tuff is a close-packed aggregate of hematitised unsorted clasts—rhyolite, pumice, welded tuff, chloritised lava, and feldspar-microphyric andesite—which together with finer pyroclasts are set in a cryptocrystalline matrix of chalcedonic silica. Hematitisation of the clasts preceded the cementation. The vitroclastic tuff shows accretionary lapilli, up to 9 mm long axis, consisting of concentrically arranged minute filaments of shards and chlorite needles (after feldspar), set in a cryptocrystalline matrix of altered comminuted shards.

Below High Band, the lithologies include silicified vitroclastic (crystal) tuffs (E32066), (E32072), lapilli-tuff (E32057), completely altered silicified and argillised rhyolitic tuffs or possible flowbrecciated rhyolites (E32051), (E32053), (E32054), (E32056), mixed pyroclastic/ orthoclastic breccia (E32071) and silty shale (E32052). All variations thus occur between relatively pure vitroclastic acid and tuffaceous sediments. The vitroclastic tuffs (E32066), (E32072) [NY 7509 1973]; [NY 7516 1981] are aggregates of compressed, mainly welded glass shards, perhaps averaging 0.3 mm in length, completely altered to cryptocrystalline silica and finely cemented by microcrystalline quartz. There are scattered, marginally resorbed beta quartz crystals, particles of devitrified acid, more basic lava, welded tuff, and (E32072) conspicuous crystals of hematite after magnetite.

In the Harthwaite-Dod Hill area, the lowest volcanic beds exposed [NY 7103 2524] include a silicified (?reworked) heterolithic crystal tuff (E40632) in which rounded to angular, unsorted particles of devitrified acid and intermediate glassy lavas, angular quartz and common unabraded oligoclase crystals are closely packed with mica flakes and skeletal leucoxene in a chalcedonic cement. The coarser pyroclasts appear to have suffered some abrasion prior to cementation and the chalcedony may thus be of late stage.

Specimens of the younger beds in Harthwaite Sike include heterolithic pumiceous tuff (E36470) [NY 7084 2483] and crystal tuffs (E36472) [NY 7070 2477], (E38480), (E38481), (E38482) [NY 7077 2480]. In section the crystal tuffs are conspicuous with randomly orientated, magmatically corroded crystals of albite-oligoclase and quartz, set in a cryptocrystalline cement (below 2µm) of quartz, feldspar and devitrified glassy lava. Superficially the texture as noted by Hudson (1937, p. 380) resembles quartz-feldspar-porphyry, but the tuffaceous origin is shown by pyroclasts of welded crystal tuff and microlithic lava, together with compressed shard dust in the matrix. This tends to intrude into the embayments in the coarser crystals, and the corrosion responsible appears to have occurred during the flowage and lithification of the hot, viscous ash flow.

In the northerly outcrop just south of Milburn Beck [NY 6797 2845] coarse fragments of highly welded acid ash-flow tuff occur in a finer matrix of silica-cemented, acid-tuff sandstone. RKH

References

ANDERSON, J. E. A. 1970. Recognition and time distribution of texturally altered welded tuff. Bull. Geol. Soc. Am., Vol. 81, pp. 287–290.

ANDERSON, W. and DUNHAM, K. C. 1953. Reddened beds in the Coal Measures beneath the Permian of Durham and south Northumberland. Proc. Yorkshire Geol. Soc., Vol. 29, pp. 21–32.

ARTHURTON, R. S. 1971. The Permian evaporites of the Langwathby Borehole, Cumberland. Rep. Inst. Geol. Sci., No.71/17. 18 pp.

ARTHURTON, R. S and WADGE, A. J. in press. Geology of the Penrith district. Mem. Geol. Surv. G.B., Sheet 24.

AVELINE, W. T. and HUGHES, T. McK. 1872. The geology of the country around Kendal, Sedbergh, Bowness and Tebay. Mem. Geol. Surv. G.B., Sheet 39 (old series 98NE). 20 pp.

BINNEY, E. W. 1855. On the Permian beds of the north-west of England. Mem. Proc. Manchester Lit. Philos. Soc., Ser. 2, Vol. 12, pp. 209–269

BINNEY, E. W. 1857. Additional observations on the Permian beds of the north-west of England. Mem. Proc. Manchester Lit. Philos. Soc., Ser.2, Vol. 14, pp. 101–120.

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

BOTT, Monograptus H. P. 1967. Geophysical investigations of the Northern Pennine Basement rocks. Proc. Yorkshire Geol. Soc., Vol. 36, pp. 139–168.

BOTT, Monograptus H. P. 1974. The geological interpretation of a gravity survey of the English Lake District and the Vale of Eden. J. Geol. Soc. London, Vol. 130, pp. 309–331.

BOTT, Monograptus H. P and MASSON SMITH, D. 1957. The geological interpretation of a gravity survey of the Alston Block and the Durham Coalfield. Q. J. Geol. Soc. London, Vol. 113, pp. 93–117.

BOULTON, G. S. 1972. Modern Arctic glaciers as depositional models for former ice sheets. J. Geol. Soc. London, Vol. 128, pp. 361–393.

BRETSKY, P. W. 1969. Central Appalachian Late Ordovician communities. Bull. Geol. Soc. Am., Vol. 80, pp. 193–212.

BROWNING, G. R. J. and JAcon, A. W. B. 1970. Preliminary study of the North of England earthquake of August 9, 1970. Nature, London, Vol. 228, pp. 835–837.

BRUCKSHAW, J. McG. and ROBERTSON, E. I. 1949. The magnetic properties of the tholeiite dykes of north England. Mon. Not. R. Astronom. Soc., Geophys. Suppl., Vol. 5, pp. 308–320.

BUCKLAND, W. 1817. Description of an insulated group of rocks of slate and greenstone in Cumberland and Westmoreland, on the eastside of Appleby, between Melmerby and Murton. Trans. Geol. Soc. London, Vol. 4, pp. 105–116.

BURGESS, I. C. 1965. The Permo-Triassic rocks around Kirkby Stephen, Westmorland. Proc. Yorkshire Geol. Soc., Vol. 35, pp. 91–101.

BURGESS, I. C. 1968. p.343 in Report on the field meeting in the Cross Fell Area. Proc. Yorkshire Geol. Soc., Vol. 36, pp. 340–344.

BURGESS, I. C. 1971. p.33 in INSTITUTE OF GEOLOGICAL SCIENCES, 1971. Annual Report for 1970. (London: Institute of Geological Sciences.)

BURGESS, I. C. 1974. pp.328–329 in discussion of BOTT, Monograptus P. H., 1974; q.v.

BURGESS, I. C. and HARRISON, R. K. 1967. Carboniferous Basement Beds in the Roman Fell district, Westmorland. Proc. Yorkshire Geol. Soc., Vol. 36, pp. 203–225.

BURGESS, I. C and HOLLIDAY, D. W. 1974. The Permo-Triassic rocks of the Hilton Borehole, Westmorland. Bull. Geol. Surv. G.B., No. 46, pp. 1–34.

BURGESS, I. C and MITCHELL, Monograptus 1976. Visean lower Yoredale limestones on the Alston and Askrigg blocks, and the base of the D₂ Zone in northern England. Proc. Yorkshire Geol. Soc., Vol. 40, pp. 613–630.

BURGESS, I. C., RICKARDS, R. B. and STRACHAN, I. 1970. The Silurian strata of the Cross Fell area. Bull. Geol. Surv. G.B., No.32, pp. 167–182.

BURGESS, I. C and WADGE, A. J. 1974. The geology of the Cross Fell area. Explanation of 1:25000 Geological Special Sheet comprising parts of sheets NY 53, 62, 63, 64, 71, 72, 73. (London HMSO.) 91pp.

CALVER, Monograptus A. 1968. Distribution of Westphalian marine faunas in northern England and adjoining areas. Proc. Yorkshire Geol. Soc., Vol. 37, pp. 1–72.

CAPEWELL, J. G. 1956. The Carboniferous Basement Series of the Cross Fell area, Cumberland and Westmorland. Proc. Geol. Assoc., Vol. 66, pp. 213–230.

CARPENTER, A. B., TROUT, Monograptus L. and PICKETT, E. E. 1974. Preliminary report on the origin and chemical evolution of lead- and zinc-rich oil field brines in Central Mississippi. Econ. Geol., Vol. 69, pp. 1191–1206.

CARRUTHERS, R. G. 1938. Alston Moor to Botany and Tan Hill: an adventure in stratigraphy. Proc. Yorkshire Geol. Soc., Vol. 23, pp. 236–253.

CLARKE, R. F. A. 1965. British Permian saccate and monosulcate miospores. Palaeontology, Vol.8, pp. 322–354.

CLOUGH, C. T. 1876. The section at High Force, Teesdale. Q. J. Geol. Soc. London, Vol.32, pp. 466–471.

CLOUGH, C. T. 1880. The Whin Sill of Teesdale as an assimilator of the surrounding beds. Geol. Mag., Vol. 17, pp. 433–447.

COCKS, L. R. Monograptus, HOLLAND, C. H., RICKARDS, R. B. and STRACHAN, I. 1971. A correlation of Silurian rocks in the British Isles. J. Geol. Soc. London, Vol. 127, pp. 103–136.

COOPER, G. A. 1930. New species from the Upper Ordovician of Perce. Am. J. Sci., Vol. 20, pp. 265–288, pp. 365–392.

COOPER, G. A and KINDLE, C. H. 1936. New brachiopods and trilobites from the Upper Ordovician of Perce, Quebec. J. Paleontol., Vol. 10, pp. 348–372.

DAGLEY, P. 1969. Palaeomagnetic results from some British Tertiary dykes. Earth Planet Sci. Lett., Vol. 6, pp. 349–354.

DAVIDSON, C. F. 1966. Some genetic relationships between ore deposits and evaporites. Trans. Inst. Min. Metall. London, Sect. B: Appl. Earth Sci., Vol. 75, pp. 216–225; discussion, pp. 300–305.

DAKYNS, J. R. 1877. On the base of the Carboniferous rocks in Teesdale. Proc. Yorkshire Geol. Soc., Vol. 6, pp. 239–242.

DAKYNS, J. R., TIDDEMAN, R. H., RUSSELL, R., CLOUGH, C. T. and STRAHAN, A. 1891. The geology of the country around Mallerstang; with parts of Wensleydale, Swaledale and Arkendale. Mem. Geol. Surv. G.B., Sheet 40 (old series 97NW). 213pp.

DAKYNS, J. R., TIDDEMAN, R. H. and GOODCHILD, J. G. 1897. The geology of the country between Appleby, Ullswater and Haweswater. Mem. Geol. Surv. G.B., Sheet 30 (old series 102SW). 110pp.

DEAN, W. T. 1959. The stratigraphy of the Caradoc Series in the Cross Fell Inlier. Proc. Yorkshire Geol. Soc., Vol. 32, pp. 185–227.

DEAN, W. T. 1961. Trinucleid trilobites from the higher Dufton Shales of the Caradoc Series in the Cross Fell Inlier. Proc. Yorkshire Geol. Soc., Vol. 33, pp. 119–134.

DEAN, W. T. 1962. The trilobites of the Caradoc Series in the Cross Fell Inlier of Northern England. Bull. Br. Mus. (Nat. Hist.), Geol., V ol. 7, pp. 65–134.

DEAN, W. T. 1971–78. Trilobites of the Chair of Kildare Limestone (Upper Ordovician) of Eastern Ireland. Palaeontogr. Soc. [Monogr.). 129 pp., 52 pls.

DOUGHTY, P. S. 1974. Davidsonina (Cyrtina) septosa (Phillips) and the structure of the Vis6an Great Scar Limestone north of Settle, Yorkshire. Proc. Yorkshire Geol. Soc., Vol. 40, pp. 41- 48.

DUNHAM, A. C. 1970. Whin sills and dykes. Pp.92–100 in Geology of Durham County. HICKLING, G. (Editor). Trans. Nat. Hist. Soc. Northumberland, Vol. 41, No. 1.

DUNHAM, A. C and KAYE, Monograptus J. L. 1965. The petrology of the Little Whin Sill, County Durham. Proc. Yorkshire Geol. Soc., Vol. 35, pp. 229–276.

DUNHAM, A. C and WALKDEN, K. Monograptus Monograptus 1968. Specialized Field Meeting on the Whin Sill. Proc. Yorkshire Geol. Soc., Vol. 36, pp. 348 -350.

DUNHAM, K. C. 1932. Quartz-dolerite pebbles (Whin Sill type) in the Upper Brockram. Geol. Mag., Vol. 69, pp. 425- 427.

DUNHAM, K. C. 1934. The genesis of the North Pennine ore deposits. Q. J. Geol. Soc. London, Vol. 90, pp. 689–720.

DUNHAM, K. C. 1948. Geology of the Northern Pennine Orefield: Vol. 1, Tyne to Stainmore. Mem. Geol. Surv. G.B. 367pp.

DUNHAM, K. C. 1950. Lower Carboniferous sedimentation in the northern Pennines (England). Rep. 18th Sess. Int. Geol. Congr., G.B., 1948, Part 4, pp. 46–63.

DUNHAM, K. C. 1958. Field Meeting at Middleton-in-Teesdale, 17–19 May, 1957. Proc. Yorkshire Geol. Soc., Vol. 31, pp. 326–327.

DUNHAM, K. C. 1966. Role of juvenile solutions, connate waters and evaporitic brines in the genesis of lead-zinc-fluorine-barium deposits. Trans. Inst. Min. Metall. London, Sect. B: Appl. Earth Sci., Vol. 75, pp. 226–229; discussion, pp. 300–305.

DUNHAM, K. C. 1970. Mineralization by deep formation waters: a review. Trans. Inst. Min. Metall. London, Sect. B: Appl. Earth Sci., Vol. 79, pp. 127–136.

DUNHAM, K. C. 1974a. Epigenetic minerals. pp.293–308 in The geology and mineral resources of Yorkshire. RAYNER, D. H. and HEMINGWAY, J. E. (Editors). (Leeds: Yorkshire Geological Society.) 405pp.

DUNHAM, K. C. 1974b. Granite beneath the Pennines in North Yorkshire. Proc. Yorkshire Geol. Soc., Vol. 40, pp. 191–194.

DUNHAM, K. C., BOTT, Monograptus H. P., JOHNSON, G. A. L. and HODGE, B. L. 1961. Granite beneath the Northern Pennines. Nature, London, Vol. 190, pp. 899–900.

DUNHAM, K. C., DUNHAM, A. C., HODGE, B. L. and JOHNSON, G. A. L. 1965. Granite beneath Visean sediments with mineralization at Rookhope, northern Pennines. Q. J. Geol. Soc. London, Vol. 121, pp. 383–417.

DUNHAM, K. C., FITCH, F. J., INESON, P. R., MILLER, J. A. and MITCHELL, J. G. 1968. The geochronological significance of argon-40/ argon-39 age determinations on White Whin from the northern Pennines orefield. Proc. R. Soc. London, Ser. A, Vol. 307, pp. 251–256.

DWERRYHOUSE, A. R. 1902. Glaciation of Teesdale, Weardale, the Tyne Valley and their tributary valleys. Q. J. Geol. Soc. London, Vol. 58, pp. 572–608.

EASTWOOD, T., HOLLINGWORTH, S. E., ROSE, W. C. C. and TROTTER, F. Monograptus 1968. Geology of the country around Cockermouth and Caldbeck. Mem. Geol. Surv. G.B., Sheet 23.298pp.

ECCLES, J. 1870–71. On some sections of Permian strata near Kirkby Stephen. Trans. Manchester Geol. Soc., Vol. 10, pp. 30–37.

EDWARDS, W. N. 1967. Geology of the country around Ollerton. Mem. Geol. Surv. G.B., Sheet 113. 297pp.

ELLIOTT, T. 1974. Abandonment facies of high-constructive lobate deltas, with an example from the Yoredale Series. Proc. Geol. Assoc., Vol. 85, pp. 359–365.

ELLIOTT, T. 1975. The sedimentary history of a delta lobe from a Yoredale (Carboniferous) cyclothem. Proc. Yorkshire Geol. Soc., Vol. 40, pp. 505–536.

EMELEUS, C. H. 1974. Igneous Rocks. Pp.265–269 in The geology and mineral resources of Yorkshire. RAYNER, D. H. and HEMINGWAY, J. E. (Editors). (Leeds: Yorkshire Geological Society.) 405pp.

EVANS, A. L., FITCH, F. J. and MILLER, J. A. 1973. Potassium-argon age determinations on some British Tertiary igneous rocks. J. Geol. Soc. London, Vol. 129, pp. 419–443.

EVANS, W. B. and ARTHURTON, R. S. 1973. North-west England. Pp.28–36 in A correlation of Quaternary deposits in the British Isles. MITCHELL, G. F., PENNY, L. F., SHOTTON, F. W. and WEST, R. G. Spec. Rep. Geol. Soc. London, No.4.99 pp.

FITCH, F. J. and MILLER, J. A. 1967. The age of the Whin Sill. Geol. J., Vol. 5, pp. 233–250.

FORD, T. D. 1955. The Upper Carboniferous rocks of the Stainmore Coalfield. Geol. Mag., Vol. 92, pp. 218–230.

FORSTER, W. 1809. A treatise on a section of strata from Newcastle-upon-Tyne to the mountain of Cross Fell in Cumberland; with remarks on mineral veins in general. (1st Edition, Alston; 2nd Edition (1821), Alston; 3rd Edition (1883), revised by the Rev. W. Nall, Newcastle.)

FRANCIS, E. A. 1970. Quaternary. Pp. 134–152 in Geology of Durham County. HICKLING, G. (Editor). Trans. Nat. Hist. Soc. Northumberland, Vol. 41, No. 1.

FRANCIS, E. H. 1965. Carboniferous-Permian igneous rocks. Pp.359–382 in The geology of Scotland. CRAIG, G. Y. (Editor). (Edinburgh: Oliver and Boyd.) 556pp.

GARWOOD, E. J. 1913. The Lower Carboniferous succession in the north-west of England. Q. J. Geol. Soc. London, Vol. 68, pp. 449–586.

GEORGE, T. N., JOHNSON, G. A. L., MITCHELL, Monograptus, PRENTICE, J. E., RAMSBOTTOM, W. H. C., SEVASTOPULO, G. D. and WILSON, R. B. 1976. A correlation of Dinantian rocks in the British Isles. Spec. Rep. Geol. Soc. London, No.7.87pp.

GOODCHILD, J. G. 1875. The glacial phenomena of the Eden valley and the western part of the Yorkshire-Dale district. Q. J. Geol. Soc. London, Vol. 31, pp. 55–99.

GOODCHILD, J. G. 1882. On the geological evidence of the former existence of Coal Measures over Edenside. Trans. Cumberland Assoc., No. 7, pp. 163–177.

GOODCHILD, J. G. 1889. An outline of the geological history of the Eden Valley or Edenside. Proc. Geol. Assoc., Vol. 11, pp. 258–284.

GOODCHILD, J. G. 1893. Observations on the New Red Series of Cumberland and Westmorland with especial reference to classification. Trans. Cumberland Westmorland Assoc., No. 17, pp. 1–24.

GUNN, W. and CLOUGH, C. T. 1878. On the discovery of Silurian beds in Teesdale. Q. J. Geol. Soc. London, Vol. 34, pp. 27–34.

GUPPY, E. Monograptus and SABINE, P. A. 1956. Chemical analyses of igneous rocks, metamorphic rocks and minerals 1931–1954. Mem. Geol. Surv. G.B. 78pp.

HALLETT, D. 1971. Foraminifera and algae from the Yoredale 'Series' (Visean-Namurian) of northern England. C. R. 6 me Congr. Av. Etud. Stratigr. Geol. Carbonif. (Sheffield, 1967), Vol. 3, pp. 873–900.

HARKER, A. 1891. Petrological notes on rocks from the Cross Fell Inlier. Q. J. Geol. Soc. London, Vol. 47, pp. 512–529.

HARKNESS, R. 1862. On the sandstones and their associated deposits in the Vale of Eden, the Cumberland Plain and the south-east of Dumfriesshire. Q. J. Geol. Soc. London, Vol. 18, pp. 205–218.

HARKNESS, R. 1865. On the Lower Silurian rocks of the south-east of Cumberland and the north-east of Westmoreland. Q. J. Geol. Soc. London., Vol. 21, pp. 235–249.

HARKNESS, R and NICHOLSON, H. A. 1877. On the strata and their fossil contents between the Borrowdale Series of the north of England and the Coniston Flags. Q. J. Geol. Soc. London, Vol. 33, pp. 461–484.

HARRISON, R. K. 1968. Petrology of the Little and Great Whin Sills in the Woodland Borehole, Co. Durham. Bull. Geol. Surv. G.B., No.28, pp. 38–54.

HARRY, W. T. 1950. Basement Carboniferous in Upper Teesdale, N. Yorks. Geol. Mag., Vol. 87, pp. 297–299.

HARTLEY, J. J. 1945. Notes on the "Yoredale Rocks" of Tyrone. Ir. Nat. J., Vol. 8, pp. 255–260.

HILL, D. 1938–41. Carboniferous rugose corals of Scotland. Palaeontogr. Soc. [Monogr.]. 213pp.

HILL, J. A. and DUNHAM, K. C. 1968. The barytes deposits at Closehouse, Lunedale, Yorkshire. Proc. Yorkshire Geol. Soc., Vol. 36, pp. 351–372.

HOLLAND, J. G. and LAMBERT, R. ST. J. 1970. Weardale Granite. Pp. 108–118 in Geology of Durham County. HICKLING, G. (Editor). Trans. Nat. Hist. Soc. Northumberland, Vol. 41, No. 1.

HOLLIDAY, D. W., BURGESS, I. C. and FROST, D. V. 1975. A recorrelation of the Yoredale limestones (upper Visean) of the Alston Block with those of the Northumberland Trough. Proc. Yorkshire Geol. Soc., Vol. 40, pp. 319–334.

HOLLINGWORTH, S. E. 1942. The correlation of the gypsum-anhydrite deposits and the associated strata in the north of England. Proc. Geol. Assoc., Vol. 53, pp. 141–151.

HOLMES, A. and HARWOOD, H. F. 1928. The age and composition of the Whin Sill and the related dykes of the north of England. Mineral. Mag., Vol. 21, pp. 493–542.

HOLMES, A. and HARWOOD, H. F. 1929. The tholeiite dykes of the north of England. Mineral. Mag., Vol. 22, pp. 1–52.

HORNUNG, G., AL-ANI, A. and STEWART, R. Monograptus 1966. The composition and emplacement of the Cleveland Dyke. Trans. Leeds Geol. Assoc., Vol. 7, Part 4, pp. 232–249.

HORNUNG, Monograptus and HATTON, A. A. 1974. Deep weathering in the Great Whin Sill, northern England. Proc. Yorkshire Geol. Soc., Vol. 40, pp. 105–114.

HUDSON, R. G. S. 1924. On the rhythmic succession of the Yoredale Series in Wensleydale. Proc. Yorkshire Geol. Soc., Vol. 20, pp. 125–135.

HUDSON, R. G. S. 1925. Faunal horizons in the Lower Carboniferous of north-west Yorkshire. Geol. Mag., Vol. 62, pp. 181–186.

HUDSON, R. G. S. 1929. On the Lower Carboniferous corals. Orionastraea and its distribution in the north of England. Proc. Leeds Philos. Lit. Soc., Sci. Sect., Vol. 1, pp. 440–457.

HUDSON, R. G. S. 1941. The Mirk Fell Beds (Namurian E₂) of Tan Hill, Yorkshire. Proc. Yorkshire Geol. Soc., Vol. 24, pp. 259–289.

HUDSON, S. N. 1937. The volcanic rocks and minor intrusions of the Cross Fell Inlier, Cumberland and Westmorland. Q. J. Geol. Soc. London, Vol. 93, pp. 368–405.

HUTCHINGS, W. Monograptus 1895. An interesting contact rock, with notes on contact-metamorphism. Geol. Mag., Vol. 32, pp. 122–131 and 163–169.

HUTCHINGS, W. Monograptus 1898. The contact rocks of the Great Whin Sill. Geol. Mag., Vol. 35, pp. 69–82 and 123–131.

INESON, P. R. 1968. The petrology and geochemistry of altered quartz-dolerite in the Closehouse mine area. Proc. Yorkshire Geol. Soc., Vol. 36, pp. 373–384.

INGHAM, J. K. 1966. The Ordovician rocks in the Cautley and Dent districts of Westmorland and Yorkshire. Proc. Yorkshire Geol. Soc., Vol. 35, pp. 455–505.

INGHAM, J. K. 1970. The Upper Ordovician trilobites from the Cautley and Dent districts of Westmorland and Yorkshire. Palaeontogr. Soc. [Monogr.], Part 1, pp. 1–58.

INGHAM, J. K and 'WRIGHT, A. D. 1970. A revised classification of the Ashgill Series. Lethaia, Vol. 3, pp. 233–242.

INSTITUTE OF GEOLOGICAL SCIENCES. 1971. Annual Report for 1969. (London: HMSO.) p.31.

JOHNSON, G. A. L. 1958. Biostromes in the Namurian Great Limestone of northern England. Palaeontology, Vol. 1, pp. 147–157.

JOHNSON, G. A. L. 1961. Skiddaw slates proved in the Teesdale Inlier. Nature, London, Vol. 90, pp. 996–997.

JOHNSON, G. A. L and DUNHAM, K. C. 1963. The geology of Moor House. Monogr. Nat. Conserv., No.2.182pp.

JOHNSON, G. A. L., HODGE, B. L. and FAIRBURN, R. A. 1962. The base of the Namurian and of the Millstone Grit in north-eastern England. Proc. Yorkshire Geol. Soc., Vol. 33, pp. 341–362.

JOHNSON, G. A. L and MARSHALL, A. E. 1971. Tournaisian beds in Ravenstonedale, Westmorland. Proc. Yorkshire Geol. Soc., Vol. 38, pp. 261–280.

JOHNSON, G. A. L., ROBINSON, D. and HORNUNG, Monograptus 1971. Unique bedrock and soils associated with the Teesdale flora. Nature, London, Vol. 232, pp. 453–456.

JONES, J. Monograptus and COOPER, B. S. 1970. Coal. Pp.43–65 in Geology of Durham County. HICKLING, G. (Editor). Trans. Nat. Hist. Soc. Northumberland, Vol. 41, No. 1.

KENDALL, P. F. 1902. On the brockrams of the Vale of Eden and the evidence they afford of an inter-Permian movement of the Pennine faults. Geol. Mag., Vol. 39, pp. 510–513.

KENNARD, Monograptus F. and KNILL, J. L. 1969. Reservoirs on limestone, with particular reference to the Cow Green scheme. Inst. Water Eng. J., Vol. 23, pp. 87–136.

KENNARD, Monograptus F., KNILL, J. L. and VAUGHAN, P. R. 1967. The geotechnical properties and behaviour of Carboniferous shale at the Balderhead Dam. Q. J. Eng. Geol., Vol. 1, pp. 3–24.

LISTER, T. R., BURGESS, I. C. and WADGE, A. J. 1969. Microfossils from the cleaved Skiddaw Slates of Murton Pike and Brownber (Cross Fell Inlier). Geol. Mag., Vol. 106, pp. 97–99.

LISTER, T. R. and HOLLIDAY, D. W. 1970. Phytoplankton (Acritarchs) from a small Ordovician inlier in Teesdale (County Durham), England. Proc. Yorkshire Geol. Soc., Vol. 37, pp. 449–460.

MANLEY, G. 1959. The late-glacial climate of north-west England. Liverpool Manchester Geol. J., Vol. 2, pp. 188–215.

MARR, J. E. 1906. On the stratigraphical relations of the Dufton Shales and the Keisley Limestone of the Cross Fell Inlier. Geol. Mag., Vol. 43, pp. 481–487.

MARR, J. E. 1925. Conditions of deposition of the Stockdale Shales of the Lake District. Q. J. Geol. Soc. London, Vol. 81, pp. 113- 136.

MARR, J. E and NICHOLSON, H. A. 1888. The Stockdale Shales. Q. J. Geol. Soc. London, Vol. 44, pp. 654–730.

MEYER, H. O. A. 1965. Revision of the stratigraphy of the Permian evaporites and associated strata in north-western England. Proc. Yorkshire Geol. Soc., Vol. 35, pp. 71–89.

MILLER, A. A. and TURNER, J. S. 1931. The Lower Carboniferous succession along the Dent Fault and the Yoredale beds of the Shap district. Proc. Geol. Assoc., Vol. 42, pp. 1–28.

MILLS, D. A. C. and HULL, J. H. 1968. The Geological Survey borehole at Woodland, Co. Durham (1962). Bull. Geol. Surv. G.B., No.28, pp. I-37.

MILLS, D. A. C. and HULL, J. H. 1976. Geology of the country around Barnard Castle. Mem. Geol. Surv. G.B., Sheet 32. 385pp.

MITCHELL, R. H. and KROUSE, H. R. 1971. Isotopic composition of sulfur and lead in galena from the GreenhowSkyreholme area, Yorkshire, England. Econ. Geol., Vol. 66, pp. 243–25I.

MOORBATH, S. 1962. Lead isotope abundance studies on mineral occurrences in the British Isles and their geological significance. Philos. Trans. R. Soc. London, Ser.A, Vol. 254, pp. 295–360.

MOORE, D. 1958. The Yoredale Series of upper Wensleydale and adjacent parts of north-west Yorkshire. Proc. Yorkshire Geol. Soc., Vol. 31, pp. 91–148.

MOORE, D. 1959. Role of deltas in the formation of some British Lower Carboniferous cyclothems. J. Geol., Vol. 67, pp. 522–539.

MOORE, D. 1960. Sedimentation units in sandstones of the Yoredale Series (Lower Carboniferous) of Yorkshire, England. J. Sediment. Petrol., Vol. 30, pp. 218–227.

MOSELEY, F. 1972. A tectonic history of northwest England. Q. J. Geol. Soc. London, Vol. 47, pp. 500–512.

MURCHISON, R. I. and HARKNESS, R. 1864. On the Permian rocks of north-west England and their extension into Scotland. Q. J. Geol. Soc. London, Vol. 20, pp. 144–165.

NICHOLSON, H. A. and MARK, J. E. 1891. The Cross Fell Inlier. Q. J. Geol. Soc. London, Vol. 47, pp. 500–512.

OLIVER, R. L. 1954. Welded tuffs in the Borrowdale Volcanic Series, English Lake District, with a note on similar rocks in Wales. Geol. Mag., Vol. 91, pp. 473–483.

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

PATTISON, J. 1970. A review of the marine fossils from the Upper Permian rocks of Northern Ireland and north-west England. Bull. Geol. Surv. G.B., No.32, pp. 123–163.

PAUL, C. R. C. 1973. British Ordovician Cystoids. Palaeontogr. Soc. [Monogr.], Part 1, pp. 1–64.

PENNY, L. F. 1974. Quaternary. Pp.245–264 in The geology and mineral resources of Yorkshire. RAYNER, D. H. and HEMINGWAY, J. E. (Editors). (Leeds: Yorkshire Geological Society.) 405pp.

PHILLIPS, J. 1836. Illustrations of the geology of Yorkshire, Part II. The Mountain Limestone District. (London: John Murray.)

PICKERILL, R. K. 1973. Lingulasma tenuigranulata palaeoecology of a large Ordovician linguloid that lived within a strophomenid-trilobite community. Palaeogeogr. Palaeoclimatol. Palaeoecol., Vol. 13, pp. 143–156.

RAISTRICK, A. 1931. The glaciation of Northumberland and Durham. Proc. Geol. Assoc., Vol. 42, pp. 281–291.

RAISTRICK, A and BLACKBURN, K. B. 1931. The late-glacial and post-glacial periods in the north Pennines (West Yorkshire and Durham), Part I. The glacial maximum and retreat. Trans. North. Nat. Union, Vol. 1, Part I, pp. 16–29.

RAISTRICK, A and BLACKBURN, K. B. 1932. The late-glacial and post glacial-periods in the north Pennines, Part III. The post-glacial peats. Trans. North. Nat. Union, Vol. 1, Part 2, pp. 79–103.

RAMSBOTTOM, W. H. C. 1973. Transgressions and regressions in the Dinantian: a new synthesis of British Dinantian stratigraphy. Proc. Yorkshire Geol. Soc., Vol. 39, pp. 567–607.

RAMSBOTTOM, W. H. C. 1974. Dinantian. Pp.47–73 in The geology and mineral resources of Yorkshire. RAYNER, D. H. and HEMINGWAY, J. E. (Editors). (Leeds: Yorkshire Geological Society.) 405pp.

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

READING, H. G. 1957. The stratigraphy and structure of the Cotherstone Syncline. Q. J. Geol. Soc. London, Vol. 113, pp. 27–56.

REED, F. R. C. 1896. The fauna of the Keisley Limestone, Part I. Q. J. Geol. Soc. London, Vol. 52, pp. 407–437.

REED, F. R. C. 1897. The fauna of the Keisley Limestone, Part II. Q. J. Geol. Soc. London, Vol. 53, pp. 67–106.

RHODES, F. H. T., AUSTIN, R. L. and DRUCE, E. C. 1969. British Avonian (Carboniferous) conodont faunas, and their value in local and intercontinental correlation. Bull. Br. Mus. (Nat. Hist.), Geol., Supp1.5. 313pp.

RICKARDS, R. B. 1964. The graptolitic mudstone and associated facies in the Silurian strata of the Howgill Fells. Geol. Mag., Vol. 101, pp. 435–451.

RIDD, Monograptus F., WALKER, D. B. and JoNEs, J. Monograptus 1970. A deep borehole at Harton on the margin of the Northumbrian Trough. Proc. Yorkshire Geol. Soc., Vol. 38, pp. 75–103.

ROBINSON, D. 1970. Metamorphic rocks. Pp. 119–123 in Geology of Durham County. HICKLING, G. (Editor). Trans. Nat. Hist. Soc. Northumberland, Vol. 41, No. 1.

ROBINSON, D. 1971. The inhibiting effect of organic carbon on contact metamorphic recrystallization of limestones. Contrib. Mineral. Petrol., Vol. 32, pp. 245–250.

ROBINSON, D. 1973. Prehnite from the contact metamorphic aureole of the Whin Sill intrusion, Northern England. Am. Mineral., Vol. 58, pp. 132–133.

ROSS, C. S. and SMITH, R. L. 1961. Ash-flow tuffs: their origin, geologic relations and identification. Prof. Pap. U.S. Geol. Surv. (Washington), No. 366. 81 pp.

ROWELL, A. J. and SCANLON, J. E. 1957. The Namurian of the north-west quarter of the Askrigg Block. Proc. Yorkshire Geol. Soc., Vol. 31, pp. 1–38.

ROWELL, A. J and TURNER, J. S. 1952. Corrie-glaciation in the Upper Eden Valley, Westmorland. Liverpool Manchester Geol. J., Vol. 1, pp. 200–207.

ROWLEY, C. R. 1969. The stratigraphy of the Carboniferoug Middle Limestone Group of west Edenside, Westmorland. Proc. Yorkshire Geol. Soc., Vol. 37, pp. 329–350.

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

SAWKINS, F. J. 1966. Ore genesis in the North Pennine Orefield, in the light of fluid inclusion studies. Econ. Geol., Vol. 61, pp. 385–401.

SCHWEITZER, H. J. 1962. Die makroflora des niederrheinischen Zechsteins. Fortschr. Geol. Rheinland. Westfalen, Vol. 6, pp. 331–376.

SEDGWICK, A. 1827. On the association of trap rocks with the Mountain Limestone Formation of High Teesdale, etc. Trans. Cambridge Philos. Soc., Vol. 2, pp. 139–195.

SEDGWICK, A. 1832. On the New Red Sandstone Series in the Basin of Eden, and north-western coasts of Cumberland and Lancashire. Trans. Geol. Soc. London, Ser.2, Vol. 4, pp. 383–407.

SHERLOCK, R. L. and HOLLINGWORTH, S. E. 1938. Gypsum and anhydrite; celestine and strontianite. Mem. Geol. Surv. Spec. Rep. Miner. Resour. G.B. Vol. 3. Third edition. 98pp.

SHIELLS, K. A. G. 1964. The geological structure of north-east Northumberland. Trans. R. Soc. Edinburgh, Vol. 65,pp. 449481.

SHOTTON, F. W. 1935. The stratigraphy and tectonics of the Cross Fell Inlier. Q. J. Geol. Soc. London, Vol. 91, pp. 639- 700.

SHOTTON, F. W. 1956. Some aspects of the New Red Desert in Britain. Liverpool Manchester Geol. J., Vol. 1, pp. 450–465.

SHOTTON, F. W., BLUNDELL, D. J. and WILLIAMS, R. E. G. 1970. Birmingham University Radiocarbon Dates IV. Radiocarbon, Vol. 12, No.2, pp. 385–399.

SIMPSON, A. 1967. The stratigraphy and tectonics of the Skiddaw Slates and the relationship of the overlying Borrowdale Volcanic Series in part of the Lake District. Geol. J., Vol. 5, pp. 391–418.

SKEVINGTON, D. 1970. A Lower Llanvirn graptolite fauna from the Skiddaw Slates, Westmorland. Proc. Yorkshire Geol. Soc., Vol. 37, pp. 395–444.

SMITH, D. B. 1970. The palaeogeography of the British Zechstein. Pp.20–23 in Third Symposium on Salt. RAU, J. L. and DELLWIG, L. F. (Editors). (Cleveland: Northern Ohio Geological Society.)

SMITH, D. B. 1972. The Lower Permian in the British Isles. Pp.1–33 in Rotliegend; essays on the European Lower Permian. FALKE, H. (Editor). (Leiden: Brill). 299pp.

SMITH, D. B., BRUNSTROM, R. G. W., MANNING, P. I., SIMPSON, S. and SHOTTON, F. W. 1974. A correlation of Permian rocks in the British Isles. Spec. Rep. Geol. Soc. London, No.5.45pp.

SMITH, D. B and FRANCIS, E. A. 1967. Geology of the country between Durham and West Hartlepool. Mem. Geol. Surv. G.B., Sheet 27. 354pp.

SMITH, S. 1910. The faunal succession of the Upper Bernician. Trans. Nat. Hist. Soc. Northumberland, New Ser., Vol. 3, pp. 591–645.

SMITH, S. 1917. Aulina rotiformis gen, et sp. nov., Phillipsastraea hennahi (Lonsdale) and Orionastraea gen. nov. Q. J. Geol. Soc. London [for 1916], Vol. 72, pp. 280–307.

SMYTHE, J. A. 1930. A chemical study of the Whin Sill. Trans. Nat. Hist. Soc. Northumberland, New Ser., Vol. 7, pp. 16–150.

SOLOMON, Monograptus 1966. Origin of barite in the North Pennine Orefield. Trans. Inst. Min. Metall., Sect. B: Appl. Earth Sci., Vol. 75, pp. 230–231.

SOLOMON, Monograptus, RAFTER, T. A. and DUNHAM, K. C. 1971. Sulphur and oxygen isotope studies in the northern Pennines in relation to ore genesis. Trans. Inst. Min. Metall., Sect. B: Appl. Earth Sci., Vol. 80, pp. 259–275.

SOPWITH, T. 1833. An account of the mining district of Alston Moor, Weardale and Teesdale in Cumberland and Durham. (Alnwick: W. Davidson.) 183pp.

SPEARS, D. A. 1961. Joints in the Whin Sill and associated sediments in Upper Teesdale, Northern Pennines. Proc. Yorkshire Geol. Soc., Vol. 33, pp. 21–29.

SQUIRES, R. H. 1971. Flandrian history of the Teesdale rarities. Nature, London, Vol. 229, pp. 43–44.

STONELEY, H. Monograptus Monograptus 1958. The Upper Permian flora of England. Bull. Br. Mus. (Nat. Hist.), Geol., Vol. 3, pp. 293–337.

TAYLOR, B. J., BURGESS, I. C., LAND, D. H., MILLS, D. A. C., SMITH, D. B. and WARREN, P. T. 1971. British regional geology: Northern England. Fourth edition. (London: HMSO.) 121pp.

TEALL, J. J. H. 1884a. Petrological notes on some north of England dykes. Q. J. Geol. Soc. London, Vol. 40, pp. 209–247.

TEALL, J. J. H. 1884b. On the chemical and microscopical characters of the Whin Sill. Q. J. Geol. Soc. London, Vol. 40, pp. 640- 657.

TEALL, J. J. H. 1888. British petrography: with special reference to the igneous rocks. (London: Dulau and Co.).

TEMPLE, J. T. 1952. A revision of the trilobite Dalmanitina mucronata (Brongniart) and related species. Acta. Univ. Lund. (New Ser.), (2), Vol. 48, No.1, pp. 1–33.

TEMPLE, J. T. 1968. The Lower Llandovery (Silurian) brachiopods from Keisley, Westmorland. Palaeontogr. Soc. [Monogr.], pp. 1–58.

TEMPLE, J. T. 1969. Lower Llandovery (Silurian) trilobites from Keisley, Westmorland. Bull. Br. Mus. (Nat. Hist.), Geol., Vol. 18, pp. 199–230.

TOPLEY, W. and LEBOUR, G. A. 1877. On the intrusive character of the Whin Sill of Northumberland. Q. J. Geol. Soc. London, Vol. 33, pp. 406–422.

TROTTER, F. W. 1929. The glaciation of eastern Edenside, the Alston Block and the Carlisle Plain. Q. J. Geol. Soc. London, Vol. 85, pp. 549–612.

TROTTER, F. W. 1939. Reddened Carboniferous beds in the Carlisle Basin and Edenside. Geol Mag., Vol. 76, pp. 408–416.

TROTTER, F. W. 1953. Reddened beds of Carboniferous age in north-west England and their origin. Proc. Yorkshire Geol. Soc., Vol. 29, pp. 1–20.

TROTTER, F. W and HOLLINGWORTH, S. E. 1932. The geology of the Brampton district. Mem. Geol. Surv. G.B., Sheet 18.223pp.

TURNER, J., HEWETSON, V. P., HIBBERT, F. A., LOWEY, K. H. and CHAMBERS, C. 1973. The history of the vegetation and flora of Widdybank Fell and the Cow Green reservoir basin, Upper Teesdale. Philos. Trans. R. Soc. London, Vol. 265, pp. 327–408.

TURNER, J. S. 1927. The Lower Carboniferous succession in the Westmorland Pennines and the relations of the Pennine and Dent faults. Proc. Geol. Assoc., Vol. 38, pp. 339–374.

TURNER, J. S. 1935. Structural geology of Stainmore, Westmorland, and notes on the late Palaeozoic (late Variscan) tectonics of the north of England. Proc. Geol. Assoc., Vol. 46, pp. 121–251.

TURNER, J. S. 1936. A note on the base of the Permian near Crosby Garrett, Westmorland. Trans. Leeds Geol. Assoc., Vol. 5, pp. 153–156.

TURNER, J. S. 1950. Notes on the Carboniferous Limestones of Ravenstonedale, Westmorland. Trans. Leeds. Geol. Assoc., Vol. 6, pp. 124–134.

TURNER, J. S. 1955. Upper Yoredale and Millstone Grit relations in the Stainmore Coalfield. Geol. Mag., Vol. 92, p.350.

TURNER, J. S. 1956. Some faunal bands in the Upper Visean and early Namurian of the Askrigg Block. Liverpool Manchester Geol. J., Vol. I, pp. 410–419.

TURNER, J. S. 1963. A boring through the Lower Brockram at Appleby, Westmorland. Trans. Leeds Geol. Assoc., V ol. 7, pp. 127–130.

VAN DER HEIDE, S. 1943. Les lamellibranches limniques du terrain houiller du Limbourg du Sud (Pays-Bas). Meded. Geol. Stiehl., Ser. C-IV-3, No.1, pp. 5–65.

VAUGHAN, A. 1905. The palaeontological sequence in the Carboniferous Limestone of the Bristol area. Q. J. Geol. Soc. London., Vol. 61, pp. 181–307.

VAUGHAN, P. R., LOVENBURY, H. T. and HORSWILL, P. 1975. The design, construction and performance of Cow Green embankment dam. Geotechnique, Vol. 25, No.3, pp. 555–580.

VERSEY, H. C. 1939. The petrography of the Permian rocks in the southern part of the Vale of Eden. Q. J. Geol. Soc. London, Vol. 95, pp. 275–294.

VISSCHER, H. 1971. The Permian and Triassic of the Kingscourt Outlier, Ireland. Spec. Pap. Geol. Surv. Ireland, No.1. 114pp.

WADGE, A. J., HARRISON, R. K. and SNELLING, N. J. 1972. Olivine-dolerite intrusions near Melmerby, Cumberland, and their age determination by the potassium-argon method. Proc. Yorkshire Geol. Soc., Vol. 39, pp. 59–70.

WADGE, A. J., NUTT, Monograptus J. C., LISTER, T. R. and SKEVINGTON, D. 1970. Didymograptus murchisoni Zone fauna from the Lake District. Geol. Mag., Vol. 106, pp. 595–598.

WADGE, A. J., NUTT, Monograptus J. C and SKEVINGTON, D. 1972. Geology of the Tarn Moor Tunnel in the Lake District. Bull. Geol. Surv. G.B., No.41, pp. 55–73.

WAGER, L. R. 1928. A metamorphosed nodular shale previously described as a 'spotted' metamorphic rock. Geol. Mag., Vol. 65, pp. 88–91.

WAGER, L. R. 1929. Metasomatism in the Whin Sill of the north of England. Part I. Metasomatism by lead vein solutions. Part II. Hydrothermal alteration by juvenile solutions. Geol. Mag., Vol. 66, pp. 97–110 and 221–238.

WALLACE, W. 1861. The laws which regulate the deposition of lead ore in veins; illustrated by an examination of the geological structure of the mining districts of Alston Moor. (London: E. Stanford.) 258pp.

WANLESS, H. R. and WELLER, J. 1932. Correlation and extent of Pennsylvanian cyclothems. Bull. Geol. Soc. Am., Vol. 43, pp. 1003–1016.

WARBURG, E. 1925. The trilobites of the Leptaena Limestone in Dalarne. Bull. Geol. Inst. Univ. Uppsala, Vol. 17, pp. 1- 446.

WAUGH, B. 1970. Petrology, provenance and silica diagenesis of the Penrith Sandstone (Lower Permian) of north-west England. J. Sediment. Petrol., Vol. 40, pp. 1226–1240.

WAUGH, B. 1974. Field Meeting: Vale of Eden, 12–14 May, 1972. Proc. Yorkshire Geol. Soc., Vol. 40, pp. 53–56.

WELLS, A. J. 1955a. The glaciation of the Teesdale–Swaledale watershed. Proc. Univ. Durham. Philos. Soc., Vol. 12, pp. 82– 93.

WELLS, A. J. 1955b. The development of chert between the Main and Crow limestones in north Yorkshire. Proc. Yorkshire Geol. Soc., Vol. 30, pp. 177–195.

WELLS, A. J. 1958. The stratigraphy and structure of the Middleton Tyas–Sleightholme Anticline, north Yorkshire. Proc. Geol. Assoc., Vol. 68 [for 1957], pp. 231–254.

WILLIAMS, A., STRACHAN, I., BASSETT, D. A., DEAN, W. T., INGHAM, J. K., WRIGHT, A. D. and WIIITTINGTON, H. B. 1972. A correlation of Ordovician rocks in the British Isles. Spec. Rep. Geol. Soc. London, No.3. 74 pp.

WILLIAMS, D. 1923. The Cronkley mica lamprophyres. Proc. Liverpool Geol. Soc., Vol. 13, pp. 323–334.

WILSON, A. A. and THOMPSON, A. T. 1965. The Carboniferous succession in the Kirkby Malzeard area, Yorkshire. Proc. Yorkshire Geol. Soc., Vol. 35, pp. 203–227.

WILSON, R. B. 1967. A study of some Namurian marine faunas of Central Scotland. Trans. R. Soc. Edinburgh, Vol. 66, pp. 445–490.

WOODLAND, A. W. 1970. The buried tunnel-valleys of East Anglia. Proc. Yorkshire Geol. Soc., Vol. 37, pp. 521–578.

WOOLACOTT, D. 1923. On a boring at Roddymoor Colliery, near Crook, County Durham. Geol. Mag., Vol. 60, pp. 50–62.

YATES, P. J. 1962. The palaeontology of the Namurian rocks of Slieve Anicrin, Co. Leitrim, Eire. Palaeontology, Vol. 5, pp. 355–443.

Index to fossils

• Acanthocrania
• Acritarchs
• Acrotretids
• Actinopteria persulcata (McCoy)
• Actinoceras pusgillense (Foord)
• Algae
• Alitaria panderi (Muir-Wood & Cooper)
• cf. Ambonychia radiata Hall
• Amplexizaphrentis enniskillini (Milne Edwards & Haime)
• Annelida
• Anisopleurella
• Anisopleurella quinquecostata (McCoy) of Jones
• Anthozoa
• Anthraconaia modiolaris (J. de C. Sowerby)
• Anthraconaia robertsoni (Brown)
• Anthracosia cf. aquilina (J.de C. Sowerby)
• Anthracosia beaniana King
• Anthracosia ovum Trueman & Weir
• Anthracosia aff. phrygiana (Wright)
• Anthracosia regularis (Trueman)
• Anthracosphaerium cycloquadratum (Wright)
• Anthracosphaerium turgidum (Brown)
• Antiquatonia molarum Turner
• Aparchites? maccoyii (Salter)
• Apatochilina?
• Archaediscids
• Atractopyge
• Atractopyge scabra Dean
• 'Atrypina' similis Reed
• Aulina rotiformis Smith
• Aulograptus cucullus (Bulman)
• Aulophyllum fungites (Fleming)
• Aulophyllum f. pachyendothecum (Thomson)
• Aviculopecten
• Avonia youngiana (Davidson)
• Bancroftina robusta (Bancroft)
• Bancroftina typo (Whittington)
• Bellerophontids
• Bivalvia (Bivalves)
• Bivalves, non-marine
• Bodophyllum ?
• Brachiopoda (Brachiopods)
• Bracteoleptaena polonica (Temple)
• Broeggerolithus
• Broeggerolithus nicholsoni globiceps (Bancroft)
• Broeggerolithus nicholsoni longiceps (Bancroft)
• Broeggerolithus nicholsoni nicholsoni (Reed)
• Broeggerolithus transiens (Bancroft)
• Brongniartella
• Brongniartella ascripta (Reed)
• Brongniartella bisulcata (McCoy)
• Brongniartella depressa Dean
• v cf. platynotus (Dalman)
• Bryozoa
• Buxtonia
• cf. Byronia
• 'Bythocypris'
• Calcinema permiana (King) Podcmski
• Calcispheres
• Calluna
• Calyptaulax
• Calymenid
• Camerella aemula? (Davidson)
• 'Camarotoechia' fawcettensis (Garwood)
• Candona neglecta Sars
• Caninia
• Caninia benburbensis Lewis
• Caninia subibicina McCoy
• Caninophyllum monense (Lewis)
• Carcinophyllum vaughani Salée
• Carbonicola cf. acuta (J. Sowerby)
• Carbonicola communis Davies & Trueman
• Carbonicola oslancis Wright
• Carbonicola pseudorobusta Trueman
• Carbonicola cf. robusta (J. de C. Sowerby)
• Carbonicola venusta Davies & Trueman
• Carbonita humilis ( Jones & Kirkby)
• Carinaropsis maccoyi (Reed)
• Catastroboceras
• Catastroboceras cf. kilbridense Turner
• Catazyga
• Catenipora cf. tapaensis (Sokolov)
• Cephalograptus cometa (Geinitz)
• Cephalopod
• Cerninella cf. salopiensis (Harper)
• Ceratocephala tuberata Dean
• Chaenocardiola
• Chaenocardiola bisati Yates
• Chaenocardiola footii (Baily)
• Chaetetes
• Chaetetes depresses (Fleming)
• Chasmops cf. extensa (Boeck)
• Chitinozoa
• Chonetoidea
• Chonetoidea radiatula (Barrande)
• Christiania
• Christiania tenuicincta (McCoy)
• Cliftonia oxoplecioides Wright
• Climacograptus
• Climacograptus alternis Packham
• Climacograptus medius  Törnquist
• Climacograptus miserabilis Elles & Wood
• Climacograptus normalis Lapworth
• Climacograptus rectangularis (McCoy)
• Climacograptus tailbertensis Skevington
• Climacograptus tangshanensis linearis Packham
• Clisiophyllum ingletonense Vaughan
• Clisiophyllum keyserlingi McCoy
• Clisiophyllum rigidum Lewis
• Coccoseris
• Conchicolites gregarius Nicholson
• Conocardium
• Conodonts
• Conradella sladensis Reed
• Corals
• Cornulitid
• Craniopsids
• Cravenoceras
• Cravenoceras cowlingense Bisat
• Cravenoceratoides
• Cremnorthis
• Crinoid columnals
• Crinoids
• Crurithyris
• Cryptograptus tricornis schaeferi (Lapworth)
• Curvirimula
• Cyathaxonia
• Cyclospira
• Cybelid
• Cybeloides girvanensis (Reed)
• Cypridopsis vidua (O. F. Müller)
• Cyrolites cf. subplanus Ulrich
• Cyrtodonta billingsiana (Salter)
• Cyrtograptus linnarssoni Lapworth
• Cystoids
• Cystograptus vesiculosus (Nicholson)
• Cystograptus v. penna (Hopkinson)
• Dalmanella
• Dalmanella cf. horderleyensis (Whittington)
• Dalmanella indica (Whittington)
• Dalmanella cf. multiplicata (Bancroft)
• Dalmanella testudinaria (Dalman)
• Dalmanellids
• Dalmanitids
• Dalmanitina
• Dalmanitina mucronata (Brongniart)
• Dalmanitina brevispina Temple
• Dalmanitina olini? Temple
• Davidsonina [Cyrtina] carbonaria (McCoy)
• Davidsonina septosa (Phillips)
• Daviesiella llangollensis (Davidson)
• Decoroproetus
• Decoroproetus calvus (Whittard)
• Decoroproetus cf. subornatus (Cooper)
• Delepinea [Chonetes] carinata (Garwood)
• Delepinea comoides (J. Sowerby)
• Derbyia gigantea Thomas
• Diacalymene marginata Shirley
• Dibunophylloid corals
• Dibunophyllum
• Dibunophyllum bipartitum (McCoy)
• Dibunophyllum bipartitum subspp.
• Dibunophyllum bourtonense Garwood & Goodyear
• Dicellograptus
• Dicoelosia
• Dictyoclostus
• Didymograptus acutus Ekström
• Didymograptus artus Elles & Wood
• Didymograptus (extensiform type)
• Didymograptus robustus Ekström
• Didymograptus aff. Didymograptus bifidus (Hall)
• Didymograptus cf. Didymograptus hirundo Salter
• Didymograptus cf. Didymograptus pakrianus Jannusson
• Dielasma
• Dindymene cf. cordai Nicholson & Etheridge
• Dindymene duftonensis Dean
• Dindymene cf. hughesiae Reynolds
• Dinorthis [costate]
• Dionide
• Diphyphyllum
• Diphyphyllum aff. lateseptatum McCoy
• Diplograptus
• Diplograptus modestus Lapworth
• Diplograptus magnus Lapworth
• Diplotrypa cf. petropolitana Nicholson
• Diversograptus capillaris (Carruthers)
• Dolerorthis duftonensis (Reed)
• Dolerorthis cf. inaequicostata Wright
• Draborthis cf. caelebs Marek & Havliček
• Duftonia
• Duftonia lacunosa Dean
• Echinoconchus
• Echinodermata (Echinoderms)
• Edmondia
• Elonichthys
• Endothyroids
• Eomarginifera
• E. lobata (J. Sowerby)
• Eoplectodonta
• Eostropheodonta
• E. hirnantensis (McCoy)
• Epistroboceras
• Eremiproetus cf. agellus Owens
• Eriophorum
• Estoniops
• Euphemites
• Euprimites
• Fenestella
• Fish remains
• Flexicalyrnene caractaci (Salter)
• Foliomena
• Foliomena cf. folium (Barrande)
• Foraminifera
• Fusulinaceans
• Gastrioceras cf. cumbriense Bisat
• Gastropoda (Gastropods)
• Geisina arcuata (Bean)
• Gigantoproductoids
• Gigantoproductus
• Gigantoproductus edelburgensis (Phillips)
• Gigantoproductus maximus (McCoy)
• Gigantoproductus sp. giganteus group (J. Sowerby)
• Gigantoproductus spp. maximus (McCoy) group
• Girvanella cf. ducii Wethered
• Glomospira
• Glomospirella
• Glossograptus
• Glyptograptus
• Glyptograptus dentatus (Brongniart)
• Glyptograptus elegans Packham
• Glyptograptus linearis (Perner)
• Glyptograptus sinuatus (Nicholson)
• Glyptograptus tamariscus angulatus Packham
• Glyptograptus tamariscus tamariscus (Nicholson)
• Glyptograptus vas Bulman & Rickards
• Glyptorthis
• Goniatites
• Gonatites cf. granosus Portlock
• Graptodictya
• Graptolites xi,
• Gravicalymene
• Gravicalymene jugzfera Dean
• Grewingkia cf. bilateralis Neuman
• Grewingkia cf. europea (Roemer)
• Gunnarella
• Gunnarella corrugatella (Davidson)
• Hadromeros kiesleyensis (Reed)
• Harpid
• Hedstroemina
• Hesperorthis
• Hiltonia rivuli Stoneley
• Hirnantia sagittifera (McCoy)
• Holopea
• Holotrachelus punctillosus Törnquist
• Homoceras henkei Schmidt
• Homotrypella
• Hormotoma
• Horny brachiopods
• Howchinia
• H. bradyana (Howchin)
• Howellites
• Hyattidina? portlockiana (Davidson)
• Illaenids
• Isbergia planifrons Warburg
• Katastrophomena
• Katastrophomena? retroflexa (Davidson)
• Kayserella
• Kinnella kielanae (Temple)
• Kjearina
• Kjerulfina
• Kjerulfina polycyma Bancroft
• Koninckophyllum
• Koninckophyllum interruptum Thomson & Nicholson
• Koninckophyllum magnificum Thomson & Nicholson
• Koninckopora infiata (de Koninck)
• Kozlowskites
• Leangella
• Leiopteria
• Leiorhynchus
• Lepidocoleus
• Leptaena
• Leptestiina
• Leptestiina oepiki (Whittington)
• Leptestiina cf. prantli Havliček
• Lichids
• Liebea squamosa (J. de C. Sowerby)
• Lingula
• Lingula cf. attenuata J. de C. Sowerby
• Lingula [broad form]
• Lingula cf. hawkei (Rouault)
• Lingula mytilloides J. Sowerby
• Lingulasma tenuigranulatum (McCoy)
• Lingulids
• Linoprotonia
• Lioestheria cf. vinti (Kirkby)
• Liospira cf. aequalis (Salter)
• Lithostrotion
• Lithostrotion junceum (Fleming)
• Lithostrotion martini Milne Edwards & Haime
• Lithostrotion [Nematophyllum] minus (McCoy)
• Lithostrotion pauciradiale (McCoy)
• Lithostrotion portlocki (Bronn)
• Lonchodomas
• Lonchodomas pennatus (La Touche)
• Lonsdaleia
• Lonsdaleia duplicate (Martin)
• Lonsdaleia floriformis (Martin)
• Lophospira
• Lophospira gyrogonia (McCoy)
• v cf. sumnerensis (Safford)
• Lophospira cf. turrita (Portlock)
• Loxonema
• Lyrodesma
• Lyrodesma cf. majus Ulrich
• Macrocoelia
• Megachonetes
• Megachonetes papilionaceus (Phillips)
• Michelinia megastoma (Phillips) ( = Monograptus grandis)
• Michelinia tenuisepta (Phillips)
• Modiolopsis
• Mollusca (Molluscs)
• Monoclimacis
• Monoclimacis crenulata (Törnquist)
• Monoclimacis flumendosae (Gortani)
• Monoclimacis griestoniensis (Nicol)
• Monoclimacis shottoni Rickards
• Monoclimacis vomerina basilica (Lapworth)
• Monograptus vomerina vomerina (Nicholson)
• Monograptus
• Monograptus acinaces Törnquist
• Monograptus antennularius (Meneghini)
• Monograptus argutus Lapworth
• Monograptus atavus Jones
• Monograptus barrandei (Seuss)
• Monograptus communis communis Lapworth
• Monograptus rostratus Elles & Wood
• Monograptus concinnus Lapworth
• Monograptus convolutus (Hisinger)
• Monograptus crispus Lapworth
• Monograptus cyphus cyphus Lapworth
• Monograptus danbyi Rickards
• Monograptus decipiens Törnquist
• Monograptus delicatulus Elles & Wood
• Monograptus denticulatus Törnquist
• Monograptus discus Törnquist
• Monograptus elongatus Törnquist
• Monograptus exiguus (Nicholson)
• Monograptus flexilis Elles
• Monograptus flemingii (Salter)
• Monograptus galaensis Lapworth
• Monograptus gemmatus (Barrande)
• Monograptus gregarius Lapworth
• Monograptus halli (Barrande)
• Monograptus leptotheca Lapworth
• Monograptus limatulus Törnquist
• Monograptus lobiferus (McCoy)
• Monograptus marri Perner
• Monograptus marri cautleyensis Rickards
• Monograptus planus (Barrande)
• Monograptus priodon (Bronn)
• Monograptus proteus (Barrande)
• Monograptus pseudobecki Bouček & Přibyl
• Monograptus revolutus Kurck
• Monograptus runcinatus Lapworth
• Monograptus sandersoni Lapworth
• Monograptus spiralis (Geinitz)
• Monograptus triangulatus fimbriatus (Nicholson)
• Monograptus triangulatus separatus Sudbury
• Monograptus triangulatus triangulates (Harkness)
• Monograptus tullbergi spiraloides Přibyl
• Monograptus turriculatus (Barrande)
• Monograptus wimani Boueek
• Moorephylloporina
• Myalina verneuilii (McCoy)
• Naiadites aff. alatus Trueman & Weir
• Naiadites productus (Brown)
• Naiadites quadratus (J. de C. Sowerby)
• Naiadites cf. subtruncatus (Brown)
• Naiadites cf. triangularis ( J. de C. Sowerby)
• Naticopsis
• Nautiloid
• Nemistium
• Nicholsonograptus fasciculatus (Nicholson)
• Nicolella
• Nicolella actoniae (J. de C. Sowerby)
• 'Nuculana' curia Hind
• cf. Nuculites coarctatus (Phillips)
• Nuculoids
• Nuculopsis gibbosa (Fleming)
• Odontopleurid
• Onnia
• Onnia gracilis (Bancroft)
• Onnia superba (Bancroft)
• Onnia superba pusgillensis Dean
• Onnia superba superba (Bancroft)
• Onnicalymene
• Onnicalymene laticeps (Bancroft)
• Onnicalymene onniensis (Shirley)
• Onnicalymene salteri (Bancroft)
• Onniella
• Onniella aspasia Bancroft
• Onniella cf. broeggeri Bancroft
• Onniella cf. reuschi Bancroft
• Orbiculoidea
• Orbiculoidea nitida (Phillips)
• Orionastraea
• Orthambonites
• Orthoids
• Orthids
• Orthocones
• Orthograptus
• Orthograptus bellulus (Törnquist)
• Orthograptus cyperoides (Törnquist)
• Orthograptus mutabilis Elles & Wood
• Orthograptus truncates (Lapworth)
• Orthograptus truncates pauperatus Elles & Wood
• Orthograptus truncates socialis (Lapworth)
• Orthotetoids
• Osagia ('Girvanella') nodules
• Ostracoda (Ostracods)
• Otarion
• Otarionid
• Oxoplecia costata Cooper
• Paladin
• Palaeoneilo
• Palaeosmilia murchisoni Milne Edwards & Haime
• Paleofavosites
• Panderia
• Panderia cf. lewisii Salter
• Paracraniops
• Petalograptus
• Petalograptus minor Elles
• Petalograptus palmeus latus (Barrande)
• Petalograptus primulus (Bouček & Přibyl)
• Petalograptus kiwis (Barrande)
• Philhedra
• Philhedrella
• Philhedrella cf. cribrum Temple
• Phillipsinella
• Phillipsinella parabola (Barrande)
• Phragmites
• Phyllocarid crustacea
• Plaesiomys porcata (McCoy)
• Planolites ophthalmoides Jessen
• Platystrophia
• Plectambonitaceans
• Plectatrypa gaspeensis Cooper
• Plectorthis
• Pleuropugnoides greenleightonensis Ferguson
• Pleurotomarians
• Plicochonetes crassistria (McCoy)
• Plumulites
• 'Pontocypris'aff. mawii Jones
• Portranella
• Posidonia corrugata (Etheridge jun.)
• Primaspis evoluta (Törnquist)
• Primitiella
• Primitiella wrightiana (Jones & Holl)
• Primitiids
• Pristiograptus denemarkae Přibyl
• Pristiograptus dubius (Suess)
• Pristiograptus nudus (Lapworth)
• Pristiograptus regularis (Törnquist)
• Productoids
• Productus
• Productus carbonarius de Koninck
• Productus concinnus J. Sowerby
• Productus garwoodi Muir-Wood
• Productus productus (Martin)
• Proetids
• Pseudoclimacograptus hughesi (Nicholson)
• Pseudoclimacograptus retroversus Bulman & Rickards
• Pseudoclimacograptus undulatus (Kurck)
• Pseudosphaerexochus
• Pseudosphaerexochus conformis (Angelin)
• Pseudosphaerexochus tuberculatus Warburg
• Pseudoplegmatograptus elleswoodi (Bouček & Münch)
• Pseudoplegmatograptus obesus (Lapworth)
• Pseudovoltzia liebeana (Geinitz) Florin
• Pterygometopid
• Ptychoglyptus undulatus (McCoy)
• Ptychopleurella
• Punctospirifer northi Muir-Wood
• Punctospirifer scabricosta North
• Rafinesquina
• Rastrites
• Rastrites equidistans Lapworth
• Rastrites linnaei Barrande
• Rastrites maximus Carruthers
• Rhaphidograptus
• Rhaphidograptus extenuatus (Elles & Wood)
• Rhaphidograptus toernquisti (Elles & Wood)
• Remopleurella
• Remopleurides
• Remopleurides cf. dorsospinifer Portlock
• Remopleurides striatus Cooper & Kindle
• Remopleuridids
• Reticuloceras
• Retiolites
• Retiolites geinitzianus angustidens Elles & Wood
• Retiolites geinitzianus geinitzianus (Barrande)
• Reuschella
• Reuschella cf. horderleyensis Bancroft
• Reuschella inexpectata Temple
• Rhadinichthys
• Rhipidomella
• Rhipidomella michelini (Lévéille)
• 'Rhizodus hibberti'Agassiz
• Rhynchonelloids
• Rugosochonetes
• Saccamminopsis
• Saccamminopsis fusulinaformis (McCoy)
• Sampo
• Sampo ruralis (Reed)
• Schizocrania
• Schizodus obscurus (J. Sowerby)
• Semiplanus
• Semiplanus latissimus ( J. Sowerby)
• Sericoidea
• Sericoidea cf. gamma Spjeldnaes
• Sericoidea cf. restricta (Hadding)
• Serpuloides
• Servicortella
• Sinuatella sinuata (de Koninck)
• Sinuites pusgillensis Reed
• Skenidioides
• Skenidioides asteroideus (Reed)
• Skenidioides scoliodus Temple
• Sowerbyella
• 'Sowerbyella' cylindrica Reed
• Sowerbyella sericea ( J. de C. Sowerby)
• Sowerbyellids
• Sphaerexochus calms (McCoy)
• Sphaerexochus cf. tuberculatus Warburg
• Sphagnum
• Sphenopteris cf. bipinnata (Munster) Gcinitz
• Spirifer
• Spirifer bisulcatus (J. de C. Sowerby) group
• Spirifer cf. furcatus (McCoy)
• Spirifer trigonalis (Martin)
• Spiriferoids
• Spirorbis
• Spirograptus
• Staurocephalus clavifrons Angelin
• Stenopareia
• Stenopareia brevicapitata (Reed)
• Stenoscisma S. [Camarophoria] isorhyncha (McCoy)
• Straparollus
• Streptelasma
• Streptis monilafera (McCoy)
• 'Strobilites bronni'Solms-Laubach
• Strophomena
• 'Strophomena' holli Davidson
• Strophomenid
• Strophomenoids
• Stygina
• Sudeticeras splendens
• Syringothyris cuspidata (J. Sowerby)
• Syringopora
• Syringopora ramulosa Goldfuss
• Tentaculitids
• Tetradellids
• Tetrataxiids
• Textulariids
• Thysanophyllum pseudovermiculare (McCoy)
• Toernquistia nicholsoni Reed
• Tornquistia polita (McCoy)
• Toxorthis proteus Temple
• Trematis corona Davidson
• Trematis aff. siluriana Davidson
• Tretaspis
• Tretaspis convergens Dean
• Tretaspis cf. duftonensis Dean
• Tretaspis moeldenensis Cave
• Tretaspis cf. radialis Lamont
• Trilobita (Trilobites)
• Trinodus
• Trinodus tardus (Barrande)
• 'Trinucleus seticornis' (Hisinger)
• Triplesia
• Triplesia cf. biplicata Cooper & Kindle
• Tropidodiscus acutus (J. de C. Sowerby)
• Tropidodiscus aff. subacutus Ulrich
• Tylonautilus
• Tylonautilus nodiferus (Armstrong)
• Ullmannia bronni Göppert
• Ullmannia cf. frumentaria (Schlothcim) Goppert
• Ulrichia
• Ulrichia bicornis (Jones)
• Vanuxemia

Figures, plates and tables

Figures

(Figure 1) Location map of the Brough-under-Stainmore and adjacent districts.

(Figure 2) The major structures and generalised geology of the Brough district.

(Figure 3) Ordovician stratigraphy.

(Figure 4) Ordovician (Dufton Shales) fossil localities in the Roman Fell area.

(Figure 5) Ordovician (Dufton Shales) fossil localities in the Dufton area.

(Figure 6) Ordovician (Dufton Shales) fossil localities in Harthwaite Sike.

(Figure 7) Ordovician (Dufton Shales) fossil localities in Billy's Beck.

(Figure 8) Ordovician (Dufton Shales) fossil localities in Pus Gill.

(Figure 9) Ordovician (Dufton Shales) fossil localities in Swindale Beck (Knock).

(Figure 10) Table of fossils from the Dufton Shales. Part 1: Corals, Brachiopods and Molluscs.

(Figure 11) Table of fossils from the Dufton Shales. Part 2: Trilobites and others.

(Figure 12) The stratigraphical relationship of the Dufton Shales and Swindale Limestone between Swindale Beck (Knock) and Keisley.

(Figure 13) Ordovician and Silurian fossil localities in the Keisley area.

(Figure 14) Table of fossils from the Swindale Shales.

(Figure 15) Silurian stratigraphy.

(Figure 16) Silurian graptolite localities near Swindale Beck (Knock).

(Figure 17) Silurian section in Swindale Beck (Knock).

(Figure 18) Table of graptolites from the Lower Llandovery.

(Figure 19) Table of graptolites from the Upper Llandovery and Wenlock. *Sensu Elles and Wood.

(Figure 20) Lithological subdivisions of the Lower Carboniferous.

(Figure 21) Basement Beds and Orton Group between Roman Fell and Knock Ore Gill.

(Figure 22) a. Geological map and sections of the Orton Group north-west of Hillbeck Wall End. b. Section of Orton Group strata in Hillbeck Wall End area.

(Figure 23) Comparative vertical sections in strata of the Orton Group, Teesdale and Closehouse.

(Figure 24) Comparative vertical sections of the Lower Alston Group.

(Figure 25) Comparative vertical sections of the Upper Alston Group: base of Peghorn Limestone to base of Tynebottom Limestone.

(Figure 26) Comparative vertical sections of the Upper Alston Group: the Alternating Beds.

(Figure 27) Comparative vertical sections of the Upper Alston Group: base of Scar Limestone to the base of the Great Limestone.

(Figure 28) Generalised sections in the Namurian rocks.

(Figure 29) Comparative vertical sections in Namurian strata: base of Great Limestone to base of Little Limestone.

(Figure 30) Comparative vertical sections in Namurian strata: base of Little Limestone to base of Crow Limestone.

(Figure 31) Comparative vertical sections in Namurian strata: base of Crow Limestone to the Upper Felltop Limestone.

(Figure 32) Generalised west-east cross-section through the Crow Limestone to Upper Felltop Limestone interval, illustrating lateral variation in thickness and lithology.

(Figure 33) Lateral variation in the beds underlying the Mirk Fell Ironstones near Balderhead Reservoir.

(Figure 34) Comparative vertical sections in Namurian strata: Upper Felltop Limestone to Botany Limestone.

(Figure 35) Sketch-map of outcrops of Namurian strata in Mousegill Beck.

(Figure 36) Namurian strata in Mousegill Beck from top of High Wood Marine Beds to base of Coal Measures.

(Figure 37) Summary of zonal classifications applied to the Lower Carboniferous succession between the top of the Basement Beds and the top of the Peghorn Limestone, and the characteristic fossils of each major division.

(Figure 38) Summary of zonal classifications applied to the Lower Carboniferous and Namurian succession above the Great Scar and Melmerby Scar Limestones.

(Figure 39) Vertical distribution of selected species from Lower Carboniferous and Namurian rocks above the top of the Great Scar and Melmerby Scar Limestones.

(Figure 40) Comparative vertical sections in the Coal Measures of the Stainmore Outlier.

(Figure 41) Sketch-map of outcrops of Coal Measures strata in Argill and neighbouring streams.

(Figure 42) Comparative vertical sections in the Eden Shales district.

(Figure 43) Inferred palaeogeography of the Vale of Eden during the deposition of the Hilton Plant Beds.

(Figure 44) Diagrammatic section across the Pennine line in early Triassic times.

(Figure 45) Structure contour map of the Brough district.

(Figure 46) Sketch-map of outcrops in the Cronkley Fell area showing horizon changes by the Whin Sill.

(Figure 47) Section of the Whin Sill at Mason Holes, Scordale.

(Figure 48) a. Map showing the major features of the Pleistocene and Recent geology of part of upper Teesdale. b. Rockhead contour map of the Cauldron Snout area. c. Rockhead contour map of the Dine Holm area.

(Figure 49) Map showing the major features of the Pleistocene and Recent geology of part of Lunedale.

(Figure 50) Map showing the major features of the Pleistocene and Recent geology of the southern part of the Vale of Eden.

(Figure 51) Map showing the main mineral veins and mines within the Brough district; margin of fluorite zone after Dunham (1948) and margin of Weardale Granite after Bott (1967, pl. 6).

Plates

(Front cover)

(Plate 1) Brough Castle and the Pennine escarpment. Drift-covered Permo-Triassic rocks underlie the low ground near Brough. In the background, beyond the Pennine faults, the Great Scar Limestone forms conspicuous crags (L01045).

(Plate 2) Pennine escarpment and Cross Fell Inlier viewed from Knock Pike. In the middle-distance is the valley of Great Rundale to the right of which lies Dufton Pike (Knock Pike Tuff Formation). To the left, Brownber Hill (Skiddaw Group) is separated from the Alston Group rocks by the Brownber Fault (L01052).

(Plate 3.1) Eutaxitic welded ash-flow tuffs, Knock Pike Tuff Formation, Borrowdale Volcanic Group. Eutaxitic tuff, showing prominent, parallel, discontinuous lenses and streaks (fiamme) of highly altered and attenuated devitrified rhyolitic glass and lava, which together with crystals and other pyroclastic particles are set in a finely streaky devitrified glassy base. Milburn Beck [NY 6773 2857]. (E40618).

(Plate 3.2) Parataxitic welded ash-flow tuffs, Knock Pike Tuff Formation, Borrowdale Volcanic Group. Parataxitic tuff, composed of extremely attenuated, highly altered rhyolitic glassy streaks, which give rise to a cleavage, and other pyroclasts set in a devitrified glassy base. Milburn Beck [NY 6778 2871]. (E40613).

(Plate 4) Augill Beck, Brough; the 'white post' in the Peghorn Limestone forms the prominent pale band in the vertical beds near the Augill Fault. It is overlain, to the right, by the Girvanella Nodular Bed and the Smiddy Limestone (L01067).

(Plate 5) Mousegill Beck; Great Limestone on skyline; Four Fathom Limestone is repeated by faulting on left; old workings in Borrowdale Coal can be seen in bottom right (L01087).

(Plate 6) Lower Carboniferous and Namurian fossils. All specimens are in the Collection of the Institute of Geological Sciences, Leeds; registered numbers are given after the locality details. 1 Thysanophyllum pseudovermiculare (McCoy). Thysanophyllum pseudovermiculare Beds', Dobbyhole Gill [NY 7600 1916], 305 m at 19° from Bell Nook. PT8914A, x 1. See p.57. 2 Syringothyris cuspidata (J. Sowerby). Brownber Pebble Bed, 'Heyber Gill', exact locality unknown. GSM63943 [Garwood Collection], x 1. See p.57. 3 Gigantoproductus maximus (McCoy) group. Great Scar Limestone, Musgrave Scarth [c.NY 7783 1781], c.450 m at 323° from triangulation point on Musgrave Scar. PT8471, x 1. See p.58. 4 Palaeosmilia murchisoni Milne Edwards and Haime. Horizon and locality as 3. PT8459, x 1. See p.58. 5 Koninckopora inflata (de Koninck). Melmerby Scar Limestone, tributary of High Cup Gill [NY 7370 2553], 500 m at 183° from Narrowgate Beacon. PC2992, x 20. See p.58. 6 Girvanella cf. ducii Wethered. Peghorn Limestone, tributary of High Cup Gill [NY 7361 2564], 410 m at 194° from Narrowgate Beacon. PC 3029, x 180. See p.59. 7 Dibunophyllum bipartitum (McCoy). Four Fathom Limestone, Swindale Beck (Brough) [NY 8175 1804], 135 m at 3° from Swindalehead House. PT9537, x 1. See p.59. 8 Nuculopsis gibbosa (Fleming). Shales above the Smiddy Limestone, Borehole (NY83SW/39) (Cow Green) [NY 8165 3151], 1000 m at 240° from Bink House. PC9561, x 1.75. 9 and 10 Productus productus (Martin). Shales above the Tynebottom Limestone, Horseman Sike [NY 7830 2703], 1280 m at 260° from Moss Shop. PC6161, x 1. See p.60. 11 Saccamminopsis fusulinaformis (McCoy). Tynebottom Limestone, Swindale Beck (Brough) [NY 8084 1700], 105 m at 356° from Woodside. PT9989, x 3.5. See p.59. 12 Lithostrotion pauciradiale (McCoy). Jew Limestone, Strand Beck [NY 7368 2575], 300 m at 188° from Narrowgate Beacon. PC 3099, x 1. See p.59. 13 Aulophyllum fungites pachyendothecum (Thomson). Great Limestone, Stable Green Quarry [NY 9191 2812], c.600 m at 40° from Methodist Chapel at Newbiggin. RV674, x 1. See p.59. 14 Spirifer trigonalis (Martin). Knucton Shell Beds, Coldberry Gutter [NY 9300 2896], 1080 m at 106° from Red Grooves House. RV733, x 1. Sec p.64. 15 Catastroboceras cf. kilbridense Turner. Shales below the Hunder Beck Limestone, Hunder Beck [NY 9253 1666], 500 m at 224° from Clove Lodge. WEG3071, x 1. See p.64.

(Plate 7) Belah Scar; fault in Penrith Sandstone with brockram lenses (L01107).

(Plate 8) Cronkley Fell; thermally metamorphosed Melmerby Scar Limestone ('sugar limestone'). The spring issues on the contact with the underlying Whin Sill (L01118).

(Plate 9) Holwick Scars: Crags of columnar jointed quartz-dolerite (Whin Sill) (L01120).

(Plate 10) High Cup Gill; pinnacle of quartz-dolerite (Whin Sill) (L01123).

(Plate 11) Cauldron Snout; drift-filled buried channel cut in quartz-dolerite (Whin Sill) (L01116).

(Plate 12) Coldberry Gutter looking west; a hush excavated in Namurian rocks along the line of the Lodgesike-Manorgill Vein (L01136).

(Back cover)

Tables

(Geological Sequence)

(Table 1) Fossils from the Belah Dolomite in the Vale of Eden. Locality: a Hilton Beck [NY 7231 2044] (Waugh, 1974). b Brough Sowerby Borehole [NY 8043 1237]. c River Belah [NY 8008 1225]. d River Eden [NY 7779 0870] on 1:50000 Sheet 40 (Kirkby Stephen) (Burgess, 1965).

(Table 2) Summary of strata proved in the Hilton Borehole.

(Table 3) Summary of strata proved in the Brough Sowerby Borehole.

(Table 4) Chemical analyses of intrusive igneous rocks. * Spectrographic determinations. 1 Kersantite, dyke (E36423), in Swindale Beck [NY 6892 2813]. Analysts J. I. Read, and R. L. Clements. Spectrographic work by K. Lalla. Lab.No.2154. 2 Lamprophyre (?Minette) dyke (E36425), in Swindale Beck [NY 6875 2734]. Analysts J. I. Read, R. L. Clements and G. A. Sergeant. Spectrographic work by K. Lalla. Lab. No.2155. 3 Muscovite-quartz-feldspar-porphyry (Dufton 'microgranite') (E36381) [NY 6930 2681]. Analysts as for analysis 2. Lab. No.2I49.

(Table 5) Chemical analyses of extrusive inneous rocks. * Spectrographic determinations. 1 Heterolithic (spilite) tuff in Kirkland Formation (Skiddaw Group) (E36455), Keisley Bank [NY 7149 2442]. Analysts J. I. Read, R. L. Clements and G. A. Sergeant. Spectrographic work by D. R. Powis. Lab.No.2158. 2 Spilitic (albitised) chloritic tuff in Kirkland Formation (E36452A), Keisley Bank [NY 7103 2441] (one-inch sheet 30). Analysts as above. Lab.No.2157. 3 Welded rhyolitic tuff (E36450A), Keisley Bank [NY 7099 2423]. Knock Pike Tuff Formation, Borrowdale Volcanic Group. Analysts J. I. Read and R. L. Clements. Spectrographic work by K. Lalla. Lab.No.2156. 4 Rhyolitic rock, completely devitrified, perhaps representing an altered welded tuff (E36422). Knock Pike [NY 6865 2853]. Knock. Pike Tuff Formation, Borrowdale Volcanic Group. Analysts as for analysis 3. Lab. No.2153. 5 Rhyolite (NI 361). Tertiary. Upton Park No. 1 Borehole, Templepatrick, County Antrim. (Guppy and Sabine, 1956, p.8.).

(Table 6) CIPW norm of parataxitic rhyolitic tuff. Specimen from Knock Pike [NY 6865 2853] (E36422), Knock Pike Tuff Formation, Borrowdale Volcanic Group. Lab.No.2153.

Tables

(Table 1) Fossils from the Belah Dolomite in the Vale of Eden

(Table 4) Chemical analyses of intrusive igneous rocks

(Table 5) Chemical analyses of extrusive igneous rocks

(Table 6) CIPW norm of parataxitic rhyolitic tuff