Gridded isopach maps from the South Pacific and their use in interpreting the sedimentation history of the West Antarctic continental margin

Abstract

We model sediment isopach grids for the southern Pacific margin of West Antarctica on the basis of a compilation of more than 10,000 km of single‐channel and multichannel seismic reflection data and correlations with ocean drilling sites. Following recent seismic stratigraphic models, we differentiate two main sequences, the upper of which alone is defined by seismostratigraphic indications for frequent grounded ice advances to the shelf edge off West Antarctica. The subsequent modeling of sediment thickness grids allows us to compare the pre‐glacially dominated and glacially dominated sedimentary development of the study area. On the basis of available age constraints from drilling sites, we assume the onset of accumulation of sediments on the continental rise that were supplied by frequent advances of grounding ice on the continental shelf to have occurred at about 10 Ma. The thickest glacial sediment accumulations occur in front of major glacial drainage outlets, i.e., Marguerite Trough on the western Antarctic Peninsula margin, Belgica Trough in the Bellingshausen Sea, and a depression on the inner and middle shelves off Pine Island Bay in the Amundsen Sea. Glacially dominated sedimentation rates of between 140 and 170 m/m.y. are calculated for these sites.