Late Quaternary submarine bedforms and ice-sheet flow in Gerlache Strait and on the adjacent continental shelf, Antarctic Peninsula

摘要

Geophysical data from Gerlache Strait, Croker Passage, Bismarck Strait and the adjacent continental shelf reveal streamlined subglacial bedforms that were produced at the bed of the Antarctic Peninsula Ice Sheet (APIS) during the last glaciation. The spatial arrangement and orientation of these bedforms record the former drainage pattern and flow dynamics of an APIS outlet up-flow, and feeding into, a palaeo-ice stream in the Western Bransfield Basin. Evidence suggests that together, they represent a single ice-flow system that drained the APIS during the last glaciation. The ice-sheet outlet flowed northortheastwards through Gerlache Strait and Croker Passage and converged with a second, more easterly ice-flow tributary on the middle shelf to form the main palaeo-ice stream. The dominance of drumlins with low elongation ratios suggests that ice-sheet outlet draining through Gerlache Strait was comparatively slower than the main palaeo-ice stream in the Western Bransfield Basin, although the low elongation ratios may also partly reflect the lack of sediment. Progressive elongation of drumlins further down-flow indicates that the ice sheet accelerated through Croker Passage and the western tributary trough, and fed into the main zone of streaming flow in the Western Bransfield Basin. Topography Would have exerted a strong control on the development of the palaeo-ice stream system but subglacial geology may also have been significant given the transition from crystalline bedrock to sedimentary strata on the inner-mid-shelf. In the broader context, the APIS was drained by a number of major fast-flowing outlets through cross-shelf troughs to the outer continental shelf during the last glaciation. Copyright (C) 2004 John Wiley Sons, Ltd.