THE LAST GLACIATION OF SHETLAND Hamish Ross A Thesis Submitted for the Degree of PhD at the University of St Andrews 1997 Full metadata for this item is available in St Andrews Research Repository at: http://research-repository.st-andrews.ac.uk/ Please use this identifier to cite or link to this item: http://hdl.handle.net/10023/15278 This item is protected by original copyright The Last Glaciation of Shetland Hamish Ross University of St Andrews 1996 ProQuest Number: 10171081 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10171081 Published by ProQuest LLC(2017). Copyright of the Dissertation is held by the Author. All rights reserved. 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Box 1346 Ann Arbor, Ml 48106- 1346 Abstract Evidence of the last glaciation of the Shetland Islands, UK, is re-examined and combined with new data on terrestrial glacigenic deposits and recent offshore data from the continental shelf to produce a dynamic, integrated model of the history of the whole ice cap. • It is shown that evidence which has previously been attributed to last glacial, or earlier, Scandinavian ice incursion, might be explained by the eastwards migration of local ice sheds. • At its maximum, the ice sheet reached the continental shelf edge to the west of the islands, at least 75 km east, at least 50 km north and might be seen as a peninsular extension of the Scottish ice sheet to the south. • The changing patterns of ice flow during deglaciation are reconstructed, implying an early phase of deglaciation at the west and northwest margins (possibly accounting for the suggested eastern migration of the ice shed), followed by retreat at more northern, then eastern, then southern margins. • It is suggested that the above pattern reflects tidewater calving controlled by bathymmetric variation around the ice sheet. • During a later phase of deglaciation, the margin of the ice cap may have grounded at around the current -100m bathymmetric contour and from there retreated terrestrially. • The importance of topographic control on patterns of deglaciation as ice retreated towards the island group is clearly established. • Some minor moraines in parts of Shetland are due to active ice margins but their age is unknown. • Radiocarbon dates reported here show that the last glaciation was Late Weichselian and that the maximum northern extent was at least 50 km north of the islands. • The concepts of an eastwards migrating ice shed and an early, extensive ice cap retreating to a grounding point, could have parallels elsewhere in Scotland during the last glaciation. • The methodology applied in this study of Shetland - integrating onshore and offshore data, and developing a dynamic picture of the whole ice cap - needs to be applied to the last Scottish ice sheet also. Declarations 1, Hamish Ross, hereby certify that this thesis, which is approximately 60,000 words in length, has been written by me, that it is the record of work carried out by me and that it has not been submitted in any previous application for a higher degree. I was admitted as a research student in January 1993 and as a candidate for the degree of Doctor of Philosophy in January 1993; the higher study for which this is a record was carried out in the University of St Andrews between 1993 and 1996. -2/50S I hereby certify that the candidate has fulfilled the conditions of the Resolution and Regulations appropriate for the degree of Doctor of Philosophy in the University of St Andrews and that the candidate is qualified to submit this thesis in application for that degree. z/ In submitting this thesis to the University of St Andrews I understand tWt I am giWig permission for it to be made available for use in accordance with the regulations of the University Library for the time being in force, subject to any copyright vested in the work not being affected thereby. I also understand that the title and abstract will be published, and that a copy of the work may be made and supplied to any bona fide library or research worker. 2/^ Acknowledgements The advice, enthusiasm, time and humour of the following individuals are much appreciated. Jack Jarvis, Adrian Hall and Alan Stevenson. Doug Peacock and Graeme Whittington. John Ball, Colin Ballantyne, Doug Benn, Jackie Birnie, Andrew Black, George Bremner, Colin Cameron, Peter Cundill, Rob Duck, Dan Evans, John Gordon, Helen Grew, Rhona Gow, Doug Harkness, Stuart Harvey, Richard Holmes, Derek Flinn, Mike Livesy, Dave Long, Florence McAndie, John McManus, Brian Miller, Janet Mykura, Graham Sandeman, Martyn Stoker, Graham Tulloch, John Walden, Alan Werritty, Rob Whiteman, Frances Wilson and Malcolm Woodstock. The following organizations are also thanked for their assistance: The Natural Environmental Research Council The British Geological Survey, Mercliison House, Edinburgh The School of Geography and Geology, University of St Andrews Contents Contents CONTENTS.........................................................................................................................................5 LIST OF FIGURES........................................................................................................................... 8 LIST OF PLATE FIGURES........................................................................................................... 11 1. INTRODUCTION........................................................................................................................ 13 1.1. Background and aims...............................................................................................................13 1.2. Limitations................................................................................................................................. 13 1.3. Conclusions............................................................................................................................... 16 2. THE LAST GLACIATION OF NORTHWEST EUROPE.................................................. 17 2.1. The last glaciation of Scotland..........................................................................................17 2.1.1. Glacial build-up (englaciation) and maximum extent...................................................... 17 2.1.2. Deglaciation............................................................................................................... 19 2.1.3. Chronology.......................................................................................................................... 20 2.2. Northwest European and Scandinavian Glaciation...................................................... 22 2.2.1. Englaciation and maximum extent.....................................................................................22 2.2.2. Deglaciation...............................................................................................................23 2.3. The North Sea Basin............................................................................................................... 24 2.4. Mechanisms................................................................................................................................26 2.5. Conclusions...............................................................................................................................28 3. THE LAST GLACIATION OF SHETLAND......................................................................... 30 3.1. Solid geology, topography and bathymmetry................................................................30 3.2. Previous work........................................................................................................................... 32 3.2.1. The last terrestrial glaciation.............................................................................................32 3.2.2. The last offshore glaciation................................................................................................34 3.2.3. Chronology.......................................................................................................................... 35 3.3. Conclusions...............................................................................................................................36 4. THE LAST GLACIATION OF FAIR ISLE........................................................................... 38 4.1. Solid Geology, topography and bathymmetry................................................................ 38 4.2. Previous work........................................................................................................................... 38 4.3. Outstanding issues...................................................................................................................39 4.3.1. Multiple or single glaciation..............................................................................................40 4.3.2. East-west and west-east ice movement...............................................................................40 4.3.3. Western and north-western ice sheds.................................................................................43 4.3.4. Nature of englaciation