Oscillating retreat of the last British-Irish Ice Sheet on the continental shelf offshore Galway Bay, western Ireland

Louise Callard, Colm Ó Cofaigh, S. Benetti, Richard Chiverrell, Katrien J J Van Landeghem, Margot Saher, Stephen J Livingstone, Chris D Clark, David Small, Derek Fabel, Steven G Moreton

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Abstract

During the Last Glacial Maximum, the British-Irish Ice Sheet extended across the continental shelf offshore of Galway Bay, western Ireland, and reached a maximum westward extent on the Porcupine Bank. New marine geophysical data, sediment cores and radiocarbon dates are used to constrain the style and timing of ice-sheet retreat across the mid to inner-shelf. Radiocarbon dated shell fragments in subglacial till on the mid-shelf constrains ice advance to after 26.4 ka BP. Initial retreat was underway before 24.4 ka BP, significantly earlier than previous reconstructions. Grounding-line retreat was accompanied by stillstands and/or localised readvances of the grounding-line. A large composite Mid-Shelf Grounding Zone Complex marks a major grounding-line position, with the ice grounded and the margin oscillating at this position by, and probably after, 23 ka BP. The continental shelf was ice-free by 17.1 cal. ka BP, but the ice sheet may have retained a marine margin until c. 15.3 ka BP. Retreat occurred in a glacimarine setting and the ice sheet was fringed by a floating ice-shelf. Collectively, this evidence indicates a dynamic and oscillatory marine-terminating ice sheet offshore of western Ireland during the last deglaciation.
Original languageEnglish
Article number106087
JournalMarine Geology
Volume420
Early online date26 Nov 2019
DOIs
Publication statusPublished - 1 Feb 2020

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Keywords

  • British-Irish Ice Sheet
  • Continental shelf
  • Glacimarine
  • Grounding zone wedges
  • Ice shelf
  • Ice-sheet retreat
  • Last Glacial Maximum

Cite this

Callard, L., Ó Cofaigh, C., Benetti, S., Chiverrell, R., Van Landeghem, K. J. J., Saher, M., ... Moreton, S. G. (2020). Oscillating retreat of the last British-Irish Ice Sheet on the continental shelf offshore Galway Bay, western Ireland. Marine Geology, 420, [106087]. https://doi.org/10.1016/j.margeo.2019.106087