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

• Published in: Marine Geology
• Main Authors: Callard, Sarah Louise, O'Cofaigh, Colm, Benetti, Sara, Chiverrell, Richard, Van Landeghem, Katrien, Saher, Margot, Livingstone, S.J., Clark, Chris, Small, David, Fabel, Derek, Moreton, Steven
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Grounding Zone Wedges; British -Irish Ice Sheet; Ice Shelf; Glacimarine; Last Glacial Maximum; Ice -Sheet Retreat; Continental Shelf; Porcupine Bank; Ice Sheet
• Online Access: https://research.bangor.ac.uk/portal/en/researchoutputs/oscillating-retreat-of-the-last-britishirish-ice-sheet-on-the-continental-shelf-offshore-galway-bay-western-ireland(041d1a4e-b839-43ba-8caf-eee53058450e).html; https://doi.org/10.1016/j.margeo.2019.106087; https://research.bangor.ac.uk/ws/files/26681600/1_s2.0_S0025322719302245_main.pdf

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.