Late Devensian and Holocene relative sea level changes on the Isle of Skye, Scotland Selby, K. Submitted version deposited in CURVE June 2010 Original citation: Selby, K. (1997) Late Devensian and Holocene relative sea level changes on the Isle of Skye, Scotland. Unpublished PhD Thesis. Coventry: Coventry University. Note: This is volume 1 of 2 – please see https://curve.coventry.ac.uk/open/items/0e151cae- 7151-0ae4-e4f3-99a45f12ce84/1/ for volume 2. Copyright © and Moral Rights are retained by the author. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This item cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder(s). The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders. CURVE is the Institutional Repository for Coventry University http://curve.coventry.ac.uk/open Late Devensian and Holocene Relative Sea Level Changes on the Isle of Skye, Scotland Katherine Selby A thesis submitted in fulfilment of the University's requirements for the degree of Doctor of Philosophy August 1997 Volume 1: Chapters 1-11 and References Statement of copyright The copyright of this dissertation rests with the author. No quotation from it should be published without prior written consent. Any information derived from it should be acknowledged. Declaration This dissertation is the result of the author's own work. Data or information from other authors, which are referred to or quoted in the text, are acknowledged at the appropriate point in the text. 2 Abstract Five coastal sites have been studied on the Isle of Skye to investigate Late Devensian and Holocene relative sea level changes. In the field, detailed stratigraphical work, geomorphological mapping and levelling were undertaken and representative cores were sampled. Detailed pollen and diatom analyses were undertaken in the laboratory and samples were submitted for radiocarbon assay where distinct pollen, diatom or lithostratigraphical changes were recorded. Loss on ignition analysis was also undertaken to ascertain the carbon content of the samples. The investigations have revealed that during the Late Devensian marine transgressions were experienced at two sites in southern Skye. These are thought to relate to readvances of the ice that arrested the isostatic recovery of the land, caused renewed isostatic depression and upon deglaciation, allowed marine waters to penetrate the sites. At Inver Aulavaig the transgression is thought to relate to the Wester Ross Readvance recorded in Wester Ross, Coli and Tiree and at Point of Sleat the transgression is thought to relate the Loch Lomond Readvance recorded extensively in Scotland. Relative sea level at Point of Sleat (southern Skye) then fell below an altitude of 4.13m0D at 10460±50 BP and remained low during the early Holocene until the Main Postglacial Transgression occurred. This transgression is recorded at three of the sites: at Inver Aulavaig (southern Skye) at 885o±70 BP where it had attained an altitude of at least 5.10m0D, at Peinchorran (eastern Skye) where it is thought to have been underway by 7980±70 BP and attained an altitude of 4.49mOD and at Talisker Bay (western Skye) at 7790±100 BP where it had attained an altitude of -2.18m0D. At Ardmore Bay (northern Skye), it is thought that the Main Postglacial Transgression did not reach an altitude of 3.34mOD. It is possible that barrier formation at some of the sites accompanied the early stages of the Main Postglacial Transgression. It is thought that regression of the sea occurred between circa 6600 BP and circa 5400 BP and remained low until circa 4200 BP when a later rise in relative sea level took place at Peinchorran attaining a maximum altitude of 4.90mOD. A late Holocene transgression is also recorded at Point of Sleat at between circa 3800 BP and circa 2900 BP where it attained an altitude of greater than 4.13m0D and at Inver Aulavaig after circa 3200 BP where it attained an altitude of between 5.10-6.01mOD. It is unclear whether this episode of high relative sea level represents the diachronous nature of one late Holocene transgression or several fluctuations in relative sea level during the late Holocene. Following the late Holocene transgression, relative sea level fell until the present day. Comparison of the data obtained from Skye with the isobase maps and rheological models suggests that the isobases for the Main Lateglacial Shoreline (Firth et al., 1993) show a good fit in age and altitude but the rheological model of Lambeck (1993b) for 10500 BP requires modification. The isobases for the Main Postglacial Shoreline appear to lie circa 4m too high for the sites studied on Skye and the isobases produced for a late Holocene shoreline appear to be greatly in error (Firth et al., 1993). It is possible that the build up of ice during the Loch Lomond Stadial may have had a greater effect on crustal movements than previously thought and this may account for discrepancies identified in the isobase maps. The study of isolation basins and back-barrier environments has allowed an assessment of their potential in recording relative sea level changes. The use of isolation basins in areas devoid of estuarine sedimentation has been particularly demonstrated. The vegetation reconstruction undertaken, suggests that variations do occur in coastal locations compared to sites further inland, although these are subtle. The dates obtained for the increase in taxa such as Corylus avellana and Alnus and the recording of anthropogenic indicators on the vegetation, agree with those previously obtained for Skye. The use of pollen analysis in verifying the radiocarbon dates obtained, particularly for the Late Devensian, has been recognised and combined with diatom analysis has provided a comprehensive data base from which to reconstruct past relative sea levels. 3 Acknowledgements I wish to extend my gratitude to Professor David Smith and Dr. Alastair Dawson for providing me with the opportunity to undertake this research. I have acquired many skills and had the opportunity to visit and study a spectacular island whose beauty was a constant inspiration. None of this would have been possible without the commitment of David and Alastair. I would also like to thank Dr. Timothy Mighall and Dr. Andrew Haggart for their supervisory contribution to this research. Funding for this research was provided by the European Commission on relative sea level changes and extreme flooding events around European coasts (PL910044). Many people have assisted me with fieldwork on Skye, often providing essential bodymass to push down the coring equipment. They remained good-natured despite the inevitable Scottish west coast downpours and infamous midges and their help was invaluable. They are Hazel and Brian Bird, Jim Campbell, Robin Cullingford, Alastair Dawson, Chris Gleed-Owen, SHin Hender, James Lewis, David Smith and James Wells. David's reserve in this department must also be acknowledged as several pieces of coring equipment now "rest in peace" beneath a peat moss in southern Skye. Several sites were studied in Skye and permission to work on the land was obtained from the following people; Neil Campbell at Talisker Bay; Roger and Georgie Bidwell at Point of Sleat; David Bryant at Ardmore Bay. My thanks are extended to these people for their interest and willingness to allow me to undertake research on their land. Finally, I would like to thank my family and friends for their support, advice and encouragement with work in the field, in the laboratory and especially on the computers, which displayed logic several dimensions removed from mine at times. 4 Late Devensian and Holocene Relative Sea Level Changes on the Isle of Skye Statement of copyright and declaration......................................... 2 Abstract.................................................................................... 3 Acknowledgements.................................................................... 4 Contents................................................................................... 5 List of Tables........................................................................... 9 Section A Context of the research Chapter 1.0 Introduction 1.1 Introduction ....................................................................... 11 1.2 Objectives......................................................................... 11 1.3 Location of the Isle of Skye..................................................... 12 1.3.1 Geology.................................................................... 12 1.3.2 Climate..................................................................... 13 1.3.3 Vegetation.................................................................. 13 1.4 Location of sites studied......................................................... 14 1.5 Structure of the dissertation..................................................... 15 1.6 Glossary of abbreviations and terms........................................... 16 Chapter 2.0 Literature review 2.1 Introduction ...................................................................... 17 2.2 The Late Devensian in Scotland ............................................... 17 2.3 The Late Devensian on Skye ................................................... 20 2.4 Relative sea level changes in Scotland ........................................ 24 2.5 Late Devensian