Ice-dammed lateral lake and epishelf lake insights into Holocene dynamics of Marguerite Trough Ice Stream and George VI Ice Shelf, Alexander Island, Antarctic Peninsula

Bethan Davies, Michael J. Hambrey, Neil F. Glasser, Thomas Holt, A. Rodes, John L. Smellie, Jonathan L. Carrivick, Simon Blockley

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We present new data regarding the past dynamics of Marguerite Trough Ice Stream, George VI Ice Shelf and valley glaciers from Ablation Point Massif on Alexander Island, Antarctic Peninsula. This ice-free oasis preserves a geological record of ice stream lateral moraines, ice-dammed lakes, ice-shelf moraines, epishelf lake shorelines and valley glacier moraines, which we dated using cosmogenic nuclide exposure ages. We provide one of the first detailed sediment-landform assemblage descriptions of epishelf lake shorelines. Marguerite Trough Ice Stream imprinted lateral moraines against eastern Alexander Island at 120 m at Ablation Point Massif. During deglaciation, lateral lakes formed in the Ablation and Moutonnée valleys, dammed against the Marguerite Trough Ice Stream in George VI Sound. Exposure ages from boulders on these lake shorelines yielded ages of 13.9 to 9.7 ka. Following recession of the ice stream, George VI Ice Shelf formed in George VI Sound. An epishelf lake formed at 15-20 m asl in Ablation and Moutonnée valleys, dated (by 10Be exposure and OSL ages) from 9.4 to 4.6 ka, suggesting that the lake was stable and persistent for some 5000 years. We find no evidence of ice-shelf collapse, and argue that the epishelf lake was a persistent feature throughout the Holocene. Further work is required to test this hypothesis. Lake-level lowering occurred after this, with the lake level at 12 m at 3.1 ± 0.4 ka and at 5 m asl today. A readvance of the valley glaciers on Alexander Island at 4.4 ± 0.7 ka is recorded by valley glacier moraines directly overlying epishelf lake sediments. We speculate that the glacier readvance, which occurred during a period of relative warmth, may have been caused by a dynamic response of the glaciers to a lowering in surface elevation of George VI Ice Shelf.
Original languageEnglish
Pages (from-to)189–219
Number of pages31
JournalQuaternary Science Reviews
Early online date5 Nov 2017
Publication statusPublished - 1 Dec 2017

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