Late Quaternary glacial history, flow dynamics and sedimentation along the eastern margin of the Antarctic Peninsula Ice Sheet

摘要

Geological and geophysical data from the NE Antarctic Peninsula continental shelf are used to reconstruct the glacial history, flow-dynamics and sedimentation of the Antarctic Peninsula Ice Sheet (APIS) along its eastern margin during the Late Quaternary. Ice advanced to the shelf edge during the Last Glacial Maximum (LGM) and deposited a stiff till across the shelf. The presence of highly attenuated bedforms indicates that fast-flowing outlets drained the APIS through cross-shelf troughs to the outer shelf after this ice advance. The bedforms are formed in deformation till in response to deforming bed processes. Deglaciation of Robertson Trough and the troughs of Prince Gustav Channel, Larsen-A and Larsen Inlet was continuous (and possibly rapid) on account of the absence of ice-margin recessional features. In contrast, grounding-zone wedges across the shelf of Northern Larsen-A and south of Prince Gustav Channel indicate that ice retreat was gradual and was punctuated by stillstands. The transition from a grounded ice sheet to ice shelf conditions was completed before 11-12 (14)Cka BP on the shelf south of Prince GustavChannel, and is marked across the shelf by a change from subglacial till to a transitional heterogeneous unit dominated by coarse-grained facies. Transitional sediments record mainly sub-ice shelf rain-out and restricted bottom current and sediment-laden plume activity, as well as localised debris flows. Meltwater-derived facies are largely absent indicating that release of meltwater was not significant beneath polar ice shelves, or during deglaciation of the APIS. In the broader context, the colder, eastern side of the APIS was extensive and was drained mainly through fast-flowing outlets (palaeo-ice streams). Therefore, the eastern APIS would have been an important contributor to sediment and iceberg flux to the Weddell Sea Embayment during the LGM and subsequent deglaciation. (c) 2004 Elsevier Ltd. All rights reserved.