Ice-stream retreat and ice-shelf history in Marguerite Trough, Antarctic Peninsula: sedimentological and foraminiferal signatures

• Published in: Geological Society of America Bulletin
• Main Authors: Kilfeather, A.A., Cofaigh, C.O., Lloyd, J.M., Dowdeswell, J.A., Xu, S., Moreton, S.G.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2011
• Subjects: Antarctic; Antarctic Peninsula; Inner Bay; Marguerite; Weddell; Weddell Sea; Antarc*; Ice Sheet; Ice Shelf; Ice Shelves
• Online Access: http://eprints.gla.ac.uk/70904/

The timing, nature, and causes of grounded ice-sheet retreat following the Last Glacial Maximum (LGM) in Marguerite Trough, west Antarctic Peninsula, and subsequent early Holocene ice-shelf decay, are presented in this paper. We use sedimentological, foraminiferal, geotechnical, and accelerator mass spectrometer (AMS) radiocarbon data from marine cores from the mid-continental shelf, together with previously published AMS dates, to establish a sedimentological and chronological model. Initial ice-sheet retreat through the outer- and mid-shelf sectors of Marguerite Trough was under way by ca. 14 ka B.P., was rapid, and coincided with the sea-level rise of meltwater pulse 1a. An ice shelf formed during this retreat, and fine-grained, laminated muds reflecting meltwater-derived suspension settling and/or tidal pumping were deposited. During this time the ice sheet remained grounded on the inner shelf. Ice-shelf breakup and retreat of the calving front, from ca. 13.2 to 12.5 ka B.P., was slow (∼100 m a−1) across the outer- and mid-shelf, with calving bay conditions remaining for at least 3.5 ka. We interpret this ice-shelf decay to have been driven by an incursion of Weddell Sea Transitional Water onto the shelf. In contrast, grounding-line and ice-shelf retreat in the inner bay occurred from ca. 9.3 ka B.P. and was driven by Circumpolar Warm Deep Water encroaching onto the continental shelf. At this time the mid-shelf was an open-marine environment characterized by hemipelagic deposition. These findings highlight the importance of oceanographic controls in the breakup of Antarctic Peninsula ice shelves during the Holocene.