AMS 14C dating of deglacial events in the Irish Sea Basin and other sectors of the British–Irish ice sheet |
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| Institution: | 1. School of Biological and Environmental Science, University of Ulster, Coleraine BT52, Northern Ireland;2. Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA;1. British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK;2. Scottish Association for Marine Science, Scottish Marine Institute, Oban PA37 1QA, UK;3. Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK;1. Department of Geography, Durham University, Durham, DH1 3LE, UK;2. Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John''s, Newfoundland, A1B 3X7, Canada;3. Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, 47907-2051, IN, USA;4. Department of Physical Geography, and Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden;5. United States Geological Survey, 12201 Sunrise Valley Drive, VA 20192, USA;6. Department of Environmental Sciences, MS 604, University of Toledo, Toledo, OH 43606-3390, USA;7. Department of Geological Sciences, Stockholm University, 106 91 Stockholm, Sweden;8. British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, UK;9. Department of Earth Science, University of Bergen, and Bjerknes Centre for Climate Research, 5007 Bergen, Norway;10. Department of Geography, University of Sheffield, Sheffield, S10 2TN, UK;11. Department of Geography, University of Sussex, Brighton, BN1 9QJ, UK;12. The University Centre in Svalbard (UNIS), 9171 Longyearbyen, Norway;13. Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S 1A7, Canada;14. Lamont Doherty Earth Observatory, Palisades, NY 10964, USA;15. NASA/Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA;p. Geological Survey of Canada Atlantic, Bedford Institute of Oceanography, Dartmouth (Nova Scotia), B2Y 4A2, Canada;q. Institute of Earth and Environmental Sciences – Geology, University of Freiburg, Albertstr. 23b, 79104 Freiburg, Germany;r. Faculty of Earth and Life Sciences, Vrije University Amsterdam, Amsterdam, Netherlands;s. Laboratoire des Sciences du Climat et de l''Environnement (LSCE), CEA/CNRS-INSU/UVSQ, Gif-sur-Yvette Cedex, France;t. Department of Geological Sciences, University of Manitoba, Winnipeg, R3T 2N2, Canada;1. OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale), Borgo Grotta Gigante 42C, Trieste, 34010, Italy;2. Maynooth University Department of Geography, Maynooth, Co. Kildare, Ireland;3. British Geological Survey, Murchison House, West Mains Road, Edinburgh, Scotland, EH9 3LA, UK;4. Department of Geography, Durham University, Durham, DH1 3LE, UK;5. Geological Survey of Ireland, Beggars Bush, Haddington Road, Dublin, Ireland;6. Department of Geography, Trinity College Dublin, Ireland;1. School of Ocean Sciences, Bangor University, Menai Bridge, LL59 5AB, UK;2. School of Environmental Sciences, University of Liverpool, Liverpool, L69 7ZT, UK;1. School of Geography and Environmental Sciences, University of Ulster, Cromore Road, Coleraine, BT52 1SA, Northern Ireland, UK;2. Department of Geography, Durham University, Durham, DH1 3LE, UK;3. Natural Environment Research Council, Radiocarbon Facility, East Kilbride, Scotland, G75 OQF, UK;4. School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland;5. Department of Geography, University of Sheffield, Sheffield, S10 2TN, UK |
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| Abstract: | Sedimentary sequences deposited by the decaying marine margin of the British–Irish Ice Sheet (BIIS) record isostatic depression and successive ice sheet retreat towards centres of ice dispersion. Radiocarbon dating by accelerator mass spectrometry (AMS) of in situ marine microfaunas that are commonly associated with these sequences constrain the timing of glacial and sea level fluctuations during the last deglaciation, enabling us to evaluate the dynamics of the BIIS and its response to North Atlantic climate change. Here we use our radiocarbon-dated stratigraphy to define six major glacial and sea level events since the Last Glacial Maximum. (1) Initial deglaciation may have occurred ?18.3 kyr 14C BP along the northwestern Irish coast, in agreement with a deglacial age of ～22 36Cl kyr BP for southwestern Ireland. Ice retreated to inland centres and areas of transverse moraine began to form across the north Irish lowlands. (2) Channels cut into glaciomarine deglacial sediments along the western Irish Sea coast are graded to below present sea level, identifying a fall of relative sea level (RSL) in response to isostatic emergence of the coast. (3) Marine mud that rapidly infilled these channels records an abrupt rise in global sea level of 10–15 m ～16.7 14C kyr BP that flooded the Irish Sea coast and may have triggered deglaciation of a marine-based margin in Donegal Bay. (4) Intertidal boulder pavements in Dundalk Bay indicate that RSL ～15.0 14C kyr BP was similar to present. (5) A major readvance of all sectors of the BIIS occurred between 14 and 15 kyr 14C BP which overprinted subglacial transverse moraines and delivered a substantial sediment flux to tidewater ice sheet margins. This event, the Killard Point Stadial, indicates that the BIIS participated in Heinrich event 1. (6) Subsequent deposition of marine muds on drumlins 12.7 14C kyr BP indicates isostatic depression and attendant high RSL resulting from the Killard Point readvance. These events identify a dynamic BIIS during the last deglaciation, as well as significant changes in RSL that reflect a combination of isostatic loading and eustatic changes in global sea level. |
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