Caledonian igneous rocks of Great Britain

Compiled and edited by D. Stephenson British Geological Survey, Edinburgh; R.E. Bevins National Museum of Wales, Cardiff; D. Millward British Geological Survey, Edinburgh; A.J. Highton British Geological Survey, Edinburgh; I. Parsons University of Edinburgh, Edinburgh; P. Stone British Geological Survey, Edinburgh; And W.J. Wadsworth University of Manchester, Manchester

GCR Editor: L.P. Thomas

Joint Nature Conservation Committee

Published by the Joint Nature Conservation Committee, Monkstone House, City Road, Peterborough, PE1 1JY, UK

First edition 1999

Typeset in 10/12pt Garamond ITC by JNCC

Printed in Great Britain by Hobbs the Printers Ltd. on 100 gsm Silverblade Matt.

ISBN 1 86107 471 9.

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Contributors

Acknowledgements

Access to the countryside

Foreword P.E. Brown

1 Caledonian igneous rocks of Great Britain: an introduction

Introduction D. Stephenson

Site selection D. Stephenson

Tectonic setting and evolution D. Stephenson

Origin of the late Caledonian magmas D. Stephenson and A.J. Highton

2 Early Ordovician volcanic rocks and associated opholitic assemblages of Scotland

Introduction R Stone and D. Flinn

The Shetland Ophiolite

The Punds to Wick of Hagdale D. Flinn

Skeo Taing to Clugan D. Flinn

Qui Ness to Pund Stacks D. Flinn

Ham Ness D. Flinn

Tressa Ness to Colbinstoft D. Flinn

Virva D. Flinn

The Highland Border Complex

Garron Point to Slug Head C.W. Thomas

Balmaha and Arrochymore Point J.R. Mendum

North Glen Sannox D.J. Fettes

The Ballantrae Complex

Byne Hill P. Stone

Slockenray Coast P. Stone

Knocklaugh P. Stone

Millenderdale P. Stone

Knockormal P. Stone

Games Loup P. Stone

Balcreuchan Port to Port Vad P. Stone

Bennane Lea P. Stone

Southern Uplands

Sgavoch Rock P. Stone

3 Mid-Ordovician intrusions of the North-east Grampian Highlands of Scotland

Introduction W.J. Wadsworth and D. Stephenson

Hill of Barra W.J. Wadsworth

Bin Quarry W.J. Wadsworth

Pitscurry and Legatesden quarries W.J. Wadsworth

Hill of Johnston W.J. Wadsworth

Hill of Creagdearg W.J. Wadsworth

Balmedie Quarry W.J. Wadsworth

Towie Wood W.J. Wadsworth

Craig Hall W.J. Wadsworth

4 Lake District and northern England

Introduction D. Millward

Eycott Hill D. Millward

Falcon Crag B. Beddoe-Stephens

Ray Crag and Crinkle Crags M.J. Branney

Sour Milk Gill M.J. Branney

Rosthwaite Fell M.J. Branney

Langdale Pikes M.J. Branney

Side Pike M.J. Branney

Coniston D. Millward

Pets Quarry M.J. Branney

Stockdale Beck, Longsleddale D. Millward

Bramcrag Quarry S.C. Loughlin

Bowness Knott D.J. Fettes

Beckfoot Quarry B. Young

Waberthwaite Quarry B. Young

Carrock Fell D. Millward

Haweswater D. Millward and B. Beddoe-Stephens

Grainsgill, Caldew Valley S.C. Loughlin

Shap Fell Crags S.C. Loughlin

5 Central England

Introduction D. Millward

Croft Hill J.N. Carney and T.C. Pharaoh

Buddon Hill J.N. Carney and T.C. Pharaoh

Griff Hollow J.N. Carney and T.C. Pharaoh

6 Wales and adjacent areas

Introduction R.E. Bevins

Rhobell Fawr R.E. Bevins

Pen Caer R.E. Bevins

Aber Mawr to Porth Lleuog R.E. Bevins

Castel Coch to Trwyncastell R.E. Bevins

St David's Head R.E. Bevins

Cadair Idris D. G. Woodhall

Pared y Cefn-hir D.G. Woodhall

Carneddau and Llanelwedd D. G. Woodhall

Braich to du M. Smith

Llyn Dulyn M. Smith

Capel Curig M. Smith

Craig y Garn M. Smith

Moel Hebog to Moel yr Ogof M. Smith

Yr Arddu M. Smith

Snowdon Massif M. Smith

Cwm Idwal M. Smith

Curig Hill M. Smith

Sarnau M. Smith

Ffestiniog Granite Quarry M. Smith

Pandy P.J. Brenchley

Trwyn-y-Gorlech to Yr Eifl quarries T.P. Young and W. Gibbons

Penrhyn Bodeilas T.P. Young and W. Gibbons

Moelypenmaen T.P. Young and W Gibbons

Llanbedrog T.P. Young and W Gibbons

Foel Gron T.P. Young and W Gibbons

Nanhoron Quarry T.P. Young and W Gibbons

Mynydd Penarfynydd T.P. Young and W Gibbons

Skomer Island R.E. Bevins

Deer Park R.E. Bevins

7 Late Ordovician to mid-Silurian alkaline intrusions of the North-west Highlands of Scotland

Introduction I. Parsons

Alkaline plutonic complexes

Loch Borralan Intrusion I. Parsons

Loch Ailsh Intrusion I. Parsons

Loch Loyal Syenite Complex I. Parsons

Alkaline minor intrusive rocks

'Grorudite' (peralkaline rhyolite, comendite)

Glen Oykel south L Parsons

Creag na h-Innse Ruaidhe I. Parsons

The Canisp Porphyry (porphyritic quartz-microsyenite)

Beinn Garbh I. Parsons

The Laird's Pool, Lochinver I. Parsons

Cnoc an Leathaid Bhuidhe I. Parsons

'Hornblende porphyrite' (microdiorite, spessaritite)

Cnoc an Droighinn I. Parsons

Luban Croma I. Parsons

Vogesite (hornblende-rich lamprophyre)

Allt nan Uamh I. Parsons

Glen Oykel north I. Parsons

'Nordmarkite' (quartz-microsyenite)

Allt na Cailliche L. Parsons

'Ledmorite' (melanite nepheline-microsyenite)

Camas Eilean Ghlais I. Parsons

an Fharaid Mhór I. Parsons

8 Late Silurian and Devonian granitic intrusions of Scotland

Introduction A.J. Highton

Loch Airighe Bheg N.J. Soper

Glen More W.E. Stephens

Loch Sunart A.J. Highton

Cnoc Mor to Rubh' Ardalanish A.J. Highton

Knockvologan to Eilean a'Chalmain A.J. Highton

Bonawe to Cadderlie Burn A.J. Highton

Cruachan Reservoir A.J. Highton

Red Craig S. Robertson

Forest Lodge D. Stephenson

Funtullich W.E. Stephens

Craig More W.E. Stephens

Garabal Hill to Lochan Strath Dubh-uisge W.E. Stephens

Loch Dee W.E. Stephens

Clatteringshaws Dam Quarry W.E. Stephens

Lea Larks W.E. Stephens

Lotus Quarries to Drungans Burn W.E. Stephens

Millour and Airdrie Hill WE. Stephens

Ardsheal Hill and Peninsula I.M. Platten

Kentallen I.M. Platten

9 Late Silurian and Devonian volcanic rocks of Scotland

Introduction D. Stephenson

South Kerrera G. Durant

Ben Nevis and Allt a'Mhuilinn D.W. McGarvie

The Glencoe Volcano — an introduction to the GCR sites

D. W McGarvie

Bidean nam Bian D.W. McGarvie

Stob Dearg and Cam Ghleann D.W. McGarvie

Buachaille Etive Beag D.W. McGarvie

Stob Mhic Mhartuin D.W. McGarvie

Loch Achtriochtan D.W. McGarvie

Crawton Bay R.A. Smith

Scurdie Ness to Usan Harbour R.A. Smith

Black Rock to East Comb R.A. Smith

Balmerino to Wormit M.A.E. Browne

Sheriffmuir Road to Menstrie Burn M.A.E. Browne

Craig Rossie M.A.E. Browne

Tillicoultry M.A.E. Browne

Port Schuchan to Dunure Castle G. Durant

Culzean Harbour G. Durant

Turnberry Lighthouse to Port Murray G. Durant

Pettico Wick to St Abb's Harbour D. Stephenson

Shoulder O'Craig P. Stone

Eshaness Coast D. Stephenson

Ness of Clousta to the Brigs D. Stephenson

Point of Ayre N.W.A. Odling

Too of the Head N.W.A. Odling

References

Glossary

Index

Contributors

Brett Beddoe-Stephens British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Richard E. Bevins Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF1 3NP.

Michael J. Branney Department of Geology, University of Leicester, University Road, Leicester LEI 7RH.

Patrick J. Brenchley Department of Earth Sciences, University of Liverpool, The Jane Herdman Laboratories, Brownlow Street, Liverpool L69 3BX.

Michael A.E. Browne British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

John N. Carney British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG.

Graham Durant Hunterian Museum, University of Glasgow, University Avenue, Glasgow G12 8QQ.

Douglas J. Fettes British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Derek Flinn Department of Earth Sciences, University of Liverpool, The Jane Herdman Laboratories, Brownlow Street, Liverpool L69 3BX.

Wes Gibbons Department of Earth Sciences, University College of Wales, Cardiff, PO Box 914, Cardiff CFI 3YE.

Andrew J. Highton British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Susan C. Loughlin British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Dave McGarvie The Open University, 2 Trevelyan Square, Boar Lane, Leeds LS1 6ED. John R. Mendum British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

David Millward British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Nicholas W.A. Odling Department of Geology and Geophysics, University of Edinburgh, The Grant Institute, West Mains Road, Edinburgh EH9 3JW.

Ian Parsons Department of Geology and Geophysics, University of Edinburgh, The Grant Institute, West Mains Road, Edinburgh EH9 3JW.

Timothy C. Pharaoh British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG

Ian Al. Platten School of Earth and Environmental Science, University of Greenwich, Medway Campus, Pembroke, Chatham Maritime, Kent ME4 4AW.

Steven Robertson British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Martin Smith British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Richard A. Smith British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

N. Jack Soper Gams Bank, Riverside, Threshfield, North Yorkshire BD23 4NP.

W. Edryd Stephens School of Geography and Geosciences, University of St Andrews, Purdie Building, North Haugh, St Andrews, Fife KY16 9ST.

David Stephenson British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Philip Stone British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Christopher W. Thomas British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

W. John Wadsworth Department of Geology, University of Manchester, Manchester M13 9PL.

Derek G. Woodhall British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Brian Young British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA.

Timothy P. Young Department of Earth Sciences, University College of Wales Cardiff, PO Box 914, Cardiff CF1 3YE.

Acknowledgements

This volume is the combined work of the 31 authors listed on pages xi–xii, most of whom, in addition to their own site descriptions, have made valuable comments on other aspects of the work. Individual chapters have been compiled by the authors of the relevant chapter introductions and have been edited by R.E. Bevins (Chapter 6), A.J. Highton (Chapter 8), D. Millward (chapters 1, 4, 5 and 9), D. Stephenson (chapters 3, 7, 8 and 9) and P. Stone (Chapter 2). Overall compilation and editing is by D. Stephenson. The GCR editor, L.P. Thomas provided guidance throughout the writing and compilation and the referee's comments of P.E. Brown were particularly welcome during the final stages of editing. The project has been managed by N.V. Ellis, N.K. Cousins and A.J. Carter for JNCC and D.I.J. Mallick and D.J. Fettes for BGS.

The initial site selection and site documentation for this volume was by R.E. Bevins, I.W. Croudace, B.P. Kokelaar, M.J. LeBas, D.T. Moffat, D. O'Halloran, I. Parsons, J.L. Roberts, W.E. Stephens, R.G. Thomas and W.J. Wadsworth. Since this initial exercise, much new mapping and refined interpretation has taken place, particularly in the Lake District and North Wales, and some revision of the original GCR site list has been necessary. M.J. Branney, M.F. Howells and B.P. Kokelaar have provided much helpful advice on this revision and the necessary amendments to the GCR documentation have been greatly facilitated by S. Campbell (for CCW), T. Moat (for EN) and R. Threadgould (for SNH).

Additional information and advice were provided by T.R. Astin (Shetland and Orkney sites), D. Gould (NE Grampian Highlands intrusions) and J.E.A. Marshall (Siluro-Devonian biostratigraphy). Diagrams were drafted by S.C. White and C.F. Pamplin (Xipress IT Solutions, Newmarket); photographs were scanned and prepared by T. Bain (BGS, Edinburgh). Photographs from the BGS collection are reproduced by kind permission of the Director, BGS ©NERC; all rights reserved (PR/23–27). The references were compiled by M.W. Kinnear, and the index was prepared by B.J. Amos.

Finally, on behalf of all of the site authors, we would like to record our thanks to the owners and managers of land and quarries who have allowed access to the sites, either during previous work or specifically for the GCR exercise.

Access to the countryside

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 PE1 1UA.

Scottish Natural Heritage, 12 Hope Terrace, Edinburgh EH9 2AS.

Foreword

Britain is exceptional in the continuity of geological history and variety of geological phenomena that are preserved within a comparatively small area. Since the early days of the geological sciences, the area has continued to provide outstanding contributions, theoretical and practical, to the understanding of Earth processes. No section of this long and distinguished history of scientific investigation is more noteworthy than that arising from the outstanding variety and preservation of the Caledonian igneous rocks. This volume describes localities that are regarded as representative of the long and complex evolution of the Caledonian igneous activity. Many of the sites listed have played a key role in interpretations marking major advances in geological thinking. One needs only to recall Hutton's deductions on the origin of granite from observations made in Glen Tilt over two hundred years ago, or the modern realization of the tectonic significance of Caledonian ophiolites. There are many problems remaining and new interpretations to be made, and the descriptions of key localities in this volume will, as well as the basic objective of conservation, provide both a tool and a stimulus for further research.

With regard to further research, one of the features that emerges from a review of the Caledonian igneous rocks and which is brought out in the introduction to the volume, is the breadth of interest these rocks have for different branches of the Earth sciences, including the petrologist looking for plate-tectonic models in explanation of the variety and spatial distribution of the igneous rocks, the structural geologist looking to the igneous rocks for support of his thoughts on ancient plate movements and the isotope geochemist endeavouring to provide a tinie framework for both. To all those interested in the comprehensive review presented, this GCR volume is potentially of great value in providing, as it does, summary access to both the detail and the broader picture of Caledonian igneous activity.

Accurate description and recording of field data is a fundamental aim of the Geological Conservation Review. Interpretations of the observations may vary over time but the role of the field geologist in providing the key data is paramount. In this review of the Caledonian igneous rocks the importance of detailed field observations is particularly well illustrated by the elegant modern interpretations of volcanological phenomena described at GCR sites in the Lake District and Glen Coe. These are outstanding examples of major advances resulting essentially from 'map and observation geology' (hammers nowadays tend to be rather frowned on, particularly at conservation sites). Detailed laboratory examination without adequate field support is always likely to lose much of its value, or at the worst the interpretations will be incorrect. The GCR review of the Caledonian igneous rocks is a welcome re-affirmation of the fundamental importance of field work.

The rocks described occur in Scotland, England and Wales and the variety and importance of the sites covered inevitably have made this a lengthy compilation. Individual site descriptions from thirty one contributors are organized into nine chapters under seven compilers. In most cases the sites have been described by acknowledged 'experts', many of whom have known and worked on the sites for many years. Some have been described by persons with no previous knowledge of the site, but with a background in related igneous rocks, and almost all have been visited by their author. The few exceptions that have not been visited had recent authorative descriptions that could be summarized. Dr D. Stephenson and his team of co-authors are to be congratulated on the clarity achieved and also in preserving the individuality of presentation of the site descriptions whilst ensuring conformity with the overall aims and standard format of the Geological Conservation Review. The resulting volume will be valuable to both the amateur and professional for many years to come.

P.E. Brown FRSE Professor Emeritus University of St Andrews