Campbell, S., Scourse, J.D., Hunt, C.O., Keen, D.H. & Stephens, N. 1998. Quaternary of South-West England. Geological Conservation Review Series No. 14, JNCC, Peterborough, ISBN 0 412 78930 2.
The original source material for these web pages has been made available by the JNCC under the Open Government Licence 3.0. Full details in the JNCC Open Data Policy
S. Campbell, Countryside Council for Wales, Bangor
C.O. Hunt, Huddersfield University
J.D. Scourse, School of Ocean Sciences, Bangor
D.H. Keen, Coventry University
and
N. Stephens, Emsworth, Hampshire.
GCR Editors: C.P. Green and B.J. Williams
Chapman & Hall
The comparatively small land area of Great Britain contains an unrivalled sequence of rocks, mineral and fossil deposits, and a variety of landforms which encompass much of the Earth's long history. Well-documented ancient volcanic episodes, famous fossil sites, and sedimentary rock sections, used internationally as comparative standards, have given these islands an importance out of all proportion to their size. The long sequences of strata and their organic and inorganic contents have been studied by generations of leading geologists, giving Britain a unique status in the development of the science. Many of the divisions of geological time used throughout the world are named after British sites or areas; for instance the Cambrian, Ordovician and Devonian systems, the Ludlow Series and the Kimmeridgian and Portlandian stages.
The Geological Conservation Review (GCR) was initiated by the Nature Conservancy Council in 1977 to assess and document the most scientifically-important parts of this rich heritage. The GCR reviews the current state of knowledge of key earth-science sites in Britain and provides a firm basis upon which site conservation can be founded in years to come. Each GCR volume describes and assesses networks of sites of national or international importance in the context of a portion of the geological column, or a geological, palaeontological, or mineralogical topic. The full series of 42 volumes will be published by the year 2000.
Within each individual volume, every GCR locality is described in detail in a self-contained account, consisting of highlights (a précis of the special interest of the site), an introduction (with a concise history of previous work), a description, an interpretation (assessing the fundamentals of the site's scientific interest and importance), and a conclusion (written in simpler terms for the non-specialist). Each site report is a justification of a particular scientific interest at a locality, of its importance in a British or international setting, and ultimately of its worthiness for conservation.
The aim of the Geological Conservation Review series is to provide a public record of the features of interest in sites being considered for notification as Sites of Special Scientific Interest (SSSIs). It is written to the highest scientific standards but in such a way that the assessment and conservation value of the sites is clear. It is a public statement of the value placed upon our geological and geomorphological heritage by the earth-science community that has participated in its production, and it will be used by the Joint Nature Conservation Committee, the Countryside Council for Wales, English Nature and Scottish Natural Heritage in carrying out their conservation functions. The three country agencies are also active in helping to establish sites of local and regional importance. Regionally Important Geological/Geomorphological Sites (RIGS) augment the SSSI coverage, with local groups identifying and conserving sites which have educational, historical, research or aesthetic value, enhancing the wider earth-science conservation perspective.
All the sites in this volume have been proposed for notification as SSSIs; the final decision to notify or re-notify sites lies with the governing councils of the appropriate country conservation agency. Information about the GCR publication programme may be obtained from:
GCR Unit, Joint Nature Conservation Committee, Monkstone House, City Road, Peterborough, PE1 1JY.
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Contributors
Acknowledgements
Access to the Countryside
Preface
1 Introduction to the Quaternary S. Campbell and J.E. Gordon
Introduction
The character of the Quaternary
Climate change in the Quaternary
The deep-sea record
Subdividing the Quaternary
The history of the ice ages
British Quaternary environments
The challenge for Quaternary science
2 The geomorphological evolution and Quaternary history of South-West England: a rationale for the selection and conservation of sites
The principles and methodology of the Geological Conservation Review S. Campbell and J.E. Gordon
Introduction
Site selection guidelines and site networks
The geomorphological and Quaternary evolution of South-West England: a synthesis S. Campbell
The pre-Quaternary inheritance
Quaternary events prior to the Devensian Stage
The Devensian Stage
The Devensian late-glacial and Holocene
3 Pre-Quaternary and long-term landscape evolution
The pre-Quaternary inheritance C.P. Green and S. Campbell
Beer Quarry S. Campbell
St Agnes Beacon S. Campbell and R.A. Shakesby
Contents
4 Granite landscapes
Introduction S. Campbell
Granite landforms and weathering products S. Campbell, A.J. Gerrard and C.P. Green
Merrivale S. Campbell
Believer Quarry S. Campbell
Two Bridges Quarry S. Campbell
Devensian late-glacial and Holocene environmental history J.D. Scourse
Hawks Tor S. Campbell and N.D.W. Davey
Dozmary Pool S. Campbell
Blacklane Brook S. Campbell
Black Ridge Brook S. Campbell and R. Cottle
5 Pleistocene cave sequences
Introduction S. Campbell
Kent's Cavern D.H. Keen
Tornewton Cave A.P. Currant
Chudleigh Caves S. Campbell and S. Collcutt
Joint Mitnor Cave S. Campbell and Al Stuart
6 The Quaternary history of the Dorset, south Devon and Cornish coasts
Introduction D.H. Keen
Portland Bill D.H. Keen
Hope's Nose and Thatcher Rock D.H. Keen
Start Point to Prawle Point D.H. Keen
Pendower S. Campbell
Porthleven S. Campbell
Boscawen S. Campbell
Porth Nanven S. Campbell
Godrevy S. Campbell
Trebetherick Point S. Campbell
7 The Quaternary history of north Devon and west Somerset
Introduction N. Stephens
Brannam's Clay Pit S. Campbell and D.G. Croot
Fremington Quay S. Campbell and D.G. Croot
The Croyde–Saunton Coast S. Campbell and A. Gilbert
Westward Ho! S. Campbell
The Valley of Rocks S. Campbell
Doniford S. Campbell
The Chains S. Campbell and R. Cottle
8 The Quaternary history of the Isles of Scilly
Introduction J.D. Scourse
Porthloo, St Mary's J.D. Scourse
Watermill Cove, St Mary's J.D. Scourse
Old Man, Gugh, St Agnes J.D. Scourse
Peninnis Head, St Mary's J.D. Scourse
Porth Seal, St Martin's J.D. Scourse
Bread and Cheese Cove, St Martin's J.D. Scourse
Chad Girt, White Island, St Martin's J. D. Scourse
Northward Bight, St Martin's /D. Scourse
Battery (Castle Down), Tresco J.D. Scourse
Castle Porth, Tresco J.D. Scourse
Higher Moors, St Mary's J.D. Scourse
9 The Quaternary history of the Somerset lowland, Mendip Hills and adjacent areas
Introduction C.O. Hunt
(A) Sites relating to the extra-glacial development of the Somerset lowland and adjacent areas
Langport Railway Cutting C.O. Hunt
Greylake (No. 2 Quarry) C.O. Hunt
Hurcott Farm C.O. Hunt
Portfield C.O. Hunt
Low Ham C.O. Hunt
Broom Gravel Pits S. Campbell, N. Stephens, C.P. Green and R.A. Shakesby
(B) Colluvial and fan-gravel sites in Mendip and adjacent areas
Middle Hope C.O. Hunt
Brean Down C.O. Hunt
Bourne C.O. Hunt
Wookey Station C.O. Hunt
10 The Quaternary history of the Avon Valley and Bristol district
Introduction C.O. Hunt
(A) Glaciation of the Bristol district
Court Hill C.O. Hunt
Bath University C.O. Hunt
Nightingale Valley C.O. Hunt
Bleadon Hill C.O. Hunt
Kennpier C.O. Hunt
Yew Tree Farm C.O. Hunt
Kenn Church C.O. Hunt
Weston-in-Gordano C.O. Hunt
(B) River terraces and landscape development
Ham Green C.O. Hunt
Newton St Loe C.O. Hunt
Stidham Farm C.O. Hunt
Hampton Rocks Cutting C.O. Hunt
Holly Lane C.O. Hunt
References
Index
S. Campbell Countryside Council for Wales, Plas Penrhos, Ffordd Penrhos, Bangor, Gwynedd LL57 2LQ.
S. Collcutt Oxford Archaeological Associates Limited, Lawrence House, 2 Polstead Road, Oxford OX2 6TN.
R. Cottle English Nature, Norman Tower House, 1–2 Crown Street, Bury St Edmunds, Suffolk 1P33 1QX.
D.G. Croot Department of Geographical Sciences, University of Plymouth, Drake Circus, Plymouth, Devon PL4 8AA.
A.P. Currant Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD.
N.D.W. Davey GCR Publications Unit, Joint Nature Conservation Committee, Monkstone House, Peterborough PE1 1JY.
A.J. Gerrard Department of Geography, Birmingham University, P.O. Box 363, Edgbaston, Birmingham B15 2TT.
A. Gilbert Department of Geographical Sciences, University of Plymouth, Drake Circus, Plymouth, Devon PL4 8AA.
J.E. Gordon Scottish Natural Heritage, 2 Anderson Place, Edinburgh EH6 SNP.
C.P. Green Department of Geography, Royal Holloway and Bedford New College, University of London, Egham, Surrey TW20 OEX.
C.O. Hunt Department of Geographical and Environmental Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH.
D.H. Keen Centre for Quaternary Science, School of Environmental and Natural Sciences, Coventry University, Priory Street, Coventry CV1 5FB.
J.D. Scourse School of Ocean Sciences, University College of North Wales, Menai Bridge, Bangor, Gwynedd LL59 5EY.
R.A. Shakesby Department of Geography, University College Swansea, Singleton Park, Swansea, West Glamorgan SA2 8PP.
N. Stephens 8 Christopher Way, Emsworth, Hampshire P010 7QZ.
A.J. Stuart Castle Museum, Norwich NR1 3JU.
B.J. Williams Earth Resources Centre, University of Exeter, North Park Road, Exeter EX4 4QE.
The short-listing and selection of the GCR sites contained in this volume began with a widespread consultation exercise, in the early 1980s, co-ordinated by John Gordon, Bill Wimbledon and Chris Hunt. Between 1987 and 1990, preparatory work for compiling the volume, involving field visits and site descriptions, was begun by Stewart Campbell. The writing of this volume was initiated by the Nature Conservancy Council in 1990, and has been seen to completion by the Joint Nature Conservation Committee on behalf of the three country agencies, English Nature, Scottish Natural Heritage and the Countryside Council for Wales. Each site account bears the name of its author(s). Draft text was produced by the named contributors from 1990 to 1994. All the draft site descriptions, introductory passages and figures were edited and unified into the designated format of this publication series by Stewart Campbell between 1994 and 1997. Within this volume, all published source material is duly referenced. In addition, the authors of the volume have contributed their own personal knowledge of sites, and numerous extra notes, concepts and descriptions have been incorporated from unpublished thoughts and discussions: several sites are described in detail for the first time here.
The selection of the 63 GCR sites described in this volume involved the assessment of several hundred potential localities. In addition to the named contributors, many members of the earth-science community assisted with information or advice during site selection and documentation. Without their assistance, the volume could not have been produced. The help of the following colleagues is therefore gratefully acknowledged: J. Alan, A. Bolt, D.Q. Bowen, D. Brunsden, C. Caseldine, J.A. Catt, R.A. Cullingford, D.C. Davies, K.H. Davies, D.D. Gilbertson, N. Glasser, A.B. Hawkins, A. Heyworth, S.A.V. Hill, C.E. Hughes, H.C.L. James, C. Kidson, M. Macklin, D. Maguire, D. Mottershead, N. Perkins, H. Prudden, J. Rooke, J. Rose, P. Sims, A. Straw, A.J. Sutcliffe, N. Thew, R.S. Waters, R.C. Whatley and R. Wolton.
Several sites required excavation prior to assessment, and the members of the Creswell Natural History and Archaeology Society and I.P. Brooks, G. Coles, D. Francis and J. Rooke kindly helped with these site investigations.
Stewart Campbell is particularly grateful to David Keen and Brian Williams for reviewing the entire text in detail and on several occasions, and also to the following for reviewing or revising substantial parts of the text: Simon Collcutt, John Gerrard, John Gordon, Chris Green, Chris Hunt, Les James, James Scourse, Nick Stephens and Anthony Sutcliffe. Professors David Bowen and Nick Stephens kindly provided much published and unpublished data, and have given constant support for the project: John Gordon and Bill Wimbledon provided guidance and encouragement throughout its long gestation.
It is a pleasure to acknowledge the help of the GCR publication production team: Neil Ellis (Publications Manager), Valerie Wyld (former Sub-editor) and Nicholas Davey (former Editorial Assistant), Carolyn Davies, Tania Davies, Mark Diggle, Caroline Mee and Margaret Wood also provided invaluable bibliographic, scientific and administrative support.
The various topographic and geological maps, which make up many of the figures in the volume, have been compiled from numerous, individually acknowledged, sources. Many rely, at least in part, upon the high-quality maps produced by the British Geological Survey and the Ordnance Survey, whose underpinning contribution is gratefully acknowledged. All the diagrams were drawn by Dave Williams of Lovell Johns, St Asaph, Clwyd.
This volume is not intended for use as a field guide. The description or mention of any site should not be taken as an indication that access to a site is open or that a right of way exists. Most sites described are in private ownership, and their inclusion herein is solely for the purpose of justifying their conservation. Their description or appearance on a map in this work should in no way be construed as an invitation to visit. Prior consent for visits should always be obtained from the landowner and/or occupier.
Information on conservation matters, including site ownership, relating to Sites of Special Scientific Interest (SSSIs) or National Nature Reserves (NNRs) in particular counties or districts may be obtained from the relevant country conservation agency headquarters listed below:
Countryside Council for Wales, Plas Penrhos, Ffordd Penrhos, Bangor, Gwynedd LL57 2LQ.
English Nature, Northminster House, Peterborough PEI 1UA.
Scottish Natural Heritage, 12 Hope Terrace, Edinburgh EH9 2AS.
This book contains scientific descriptions of 63 localities
The individual GCR site descriptions form the core of the book. In the following chapters, sites are arranged and described in broad geographic areas and by research topic. This is necessitated by the widely disparate nature of the field evidence in South-West England: sites demonstrating the full range of Quaternary and geomorphological features are not evenly and conveniently dispersed throughout the region, and some areas have significant gaps. Neither do the individual chapters contain sites that necessarily equate with particular site selection networks. Rather, the chosen chapter headings provide the least repetitive means of describing the sites and background material. Where possible, a chronological approach, from oldest to youngest, has been used to describe sites within a given chapter. Again, this approach is not always possible, and a group of sites may show variations on landform or stratigraphic evidence broadly within one major time interval or chronostratigraphic stage; inevitably there are many overlaps.
Each chapter introduction provides an overview of the region or topic, highlighting the particular aspects of Quaternary or geomorphological history which are of special significance. The individual site reports each contain a synthesis of currently available documentation and interpretations of the site evidence. A key part of each site account is the 'Interpretation' section, which explains the site's importance in a regional, national or international context, and justifies its conservation. Where sites were chosen as part of a closely related network, cross-reference is made to the related sites to provide a fuller understanding of their respective attributes and the justification for their selection. Where sites are of particular historical significance, the history of study at the site is presented in detail.
There is currently no universally agreed system of terminology for the subdivision of Quaternary deposits in Britain. Mitchell et al. (1973b) proposed a correlation scheme based on standard stages. Since that date, however, not only has there been a great increase in knowledge of the Quaternary succession, so that the 1973 system is now incomplete, but also certain of the stage names proposed at the time have been questioned as to their suitability or even the existence of the sediments to which they refer.
The most recent attempt to correlate Quaternary deposits across Britain (Bowen, in prep.) has been based on lithostratigraphy and a time-frame founded on oxygen isotope stages. This scheme has been applied to South-West England (Campbell et al., in prep.) and, wherever possible in this volume, site evidence is referred to the oxygen isotope framework. The basis of such a chronology is the oxygen isotope signal recognized in deep-sea sediments. This signal has been shown to be a function of the Earth's orbital parameters (Hays et al., 1976), and astronomical data have been used to 'tune' the geological timescale (cf. Imbrie et al., 1984; Prell et al., 1986; Ruddiman et al., 1986, 1989; Martinson et al., 1987). For the period back to about 620 ka, the timescale is that developed by Imbrie et al. (1984), which has been substantiated by later work (Prell et al., 1986; Shackleton et al., 1990). For the earlier part of the Quaternary, the revised timescale of Shackleton et al. (1990) is adopted.
The correlation of the selected GCR sites for South-West England
Where radiocarbon 'dates' (age estimates) are cited, they are quoted in radiocarbon years before present (AD 1950), with laboratory reference number and associated standard error if available. It should be noted that the radiocarbon timescale diverges from the calendrical one, and although calibration is available back to 9 ka in detail (cf. Pilcher, 1991) and to 30 ka in outline (Bard et al., 1990), the interpretation of radiocarbon measurements, particularly during parts of the Late Devensian, is additionally complicated (cf. Ammann and Lotter, 1989; Zbinden et al., 1989).
Where possible, modern taxonomic nomenclature has been used and the Geological Society's 'Instruction to Authors' guidelines for taxonomic quotation followed. Nomenclature for marine Mollusca follows Seaward (1982); for freshwater and brackish Mollusca it follows Kerney (1976a); and for land Mollusca it follows Kerney and Cameron (1979).