Relationship between continental rise development and palaeo-ice sheet dynamics, Northern Antarctic Peninsula Pacific margin

摘要

Acquisition of swath bathymetry data west of the North Antarctic Peninsula (NAP), between 63 degrees S and 66 degrees S, and its integration with the predicted seafloor topography of Smith and Sandwell [Global seafloor topography from satellite altimetry and ship depth soundings. Science 277, 1956-1962.] reveal the links between the continental rise depositional systems and the NAP palaeo-ice sheet dynamics. The NAP Pacific margin consists of a wide continental shelf dissected by several troughs, tens of kilometres wide and long. The Biscoe Trough, which has been almost entirely surveyed with rnultibeam sonar, shows spectacular fan-shaped streamlining sea-floor morphologies revealing the presence of ice streams during the Last Glacial Maximum. In the study area the continental rise comprises the six northernmost sediment mounds of the NAP Pacific margin and the canyon-channel systems between them. These giant sediment mounds have developed since the early Neogene by southwest flowing bottom currents, which have redistributed along the margin the fine-grained component of the turbiditic Currents flowing down canyon-channel systems. The widespread evidence of shallow slope instability within the sediment mounds has been identified from both swath bathymetry and topographic parametric sonar seismic reflection profiles. Bathymetric data show that the heads of all the rise canyon-channel systems coincide geographically with the mouths of the major glacial troughs on the continental shelfed. This suggests a close genetic link between these morphological features and allows considering a glacio-sedimentary model for the western NAP outer margin seascape development. This model considers the availability of depositional space on the continental rise as the limiting factor for Mound development. The depositional space, in turn, is controlled by the spacing between glacial maxima shelf-edge reaching ice streams. This model takes into account both glacial and interglacial scenarios and gives new insights on evaluating the palaeoenvironmental record of the continental rise sediment mounds. (c) 2005 Elsevier Ltd. All rights reserved.