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

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

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.

Citation

Callard, S. L., Ó Cofaigh, C., Benetti, S., Chiverrell, R. C., Van Landeghem, K. J., Saher, M. H., …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, Article 106087. https://doi.org/10.1016/j.margeo.2019.106087

• Journal Article Type: Article
• Acceptance Date: Nov 21, 2019
• Online Publication Date: Nov 26, 2019
• Publication Date: Feb 28, 2020
• Deposit Date: Nov 26, 2019
• Publicly Available Date: Nov 26, 2020
• Journal: Marine Geology
• Print ISSN: 0025-3227
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 420
• Article Number: 106087
• DOI: https://doi.org/10.1016/j.margeo.2019.106087