Cenozoic Sedimentation and Paleo-Water Depths of the Weddell Sea Basin Related to Pre-Glacial and Glacial Conditions of Antarctica

Abstract:

The Weddell Sea basin is of particular significance for understanding climate processes, including the generation of ocean water masses and their influence on ocean circulation as well as the dynamics of the Antarctic ice sheets. Seismic stratigraphic and drill data from the Weddell Sea and the margin have provided much direct evidence concerning ice sheet evolution and sediment transportation processes. More than 250 seismic lines and ODP Leg 113 drilling sites are applied to gain the age control of the sedimentation. Using these constraints, we calculate grids to depict the depths, thicknesses and sedimentation rates of pre-glacial (145-34 Ma), transitional (34-15 Ma) and full-glacial (15 Ma to present) units. These grids allow us to compare the sedimentary regimes of the pre-glacially dominated and glacially dominated stages of Weddell Sea history. We further calculate paleobathymetric grids at 15 Ma, 34 Ma, and 120 Ma by using a backstripping technique. The paleobathymetric grid of 15 Ma has been applied for the climate model test, which shows that the Weddell gyre centre was southward shifted. This result is consistent with the warm period of the middle Miocene with relatively less see ice and higher temperature in the Weddell Sea.

A case study has been focused on a series of iceberg erosional and current reworked features like the giant elongate mounded sediment drifts and mass transporting deposits (MTDs) along the continental margin of the southeast Weddell Sea from the middle Miocene to the present. The giant sediment drifts are ascribed to the large catchments area with the fast (paleo) ice streams associated with Filchner Ronne Ice Shelf and bottom water. A remarkable increase in MTDs in the late Miocene and middle Pliocene strata is related to ice dynamics, overpressure of rapid sediment accumulation and the steep topographic gradients. Our studies and data also provide the significant contribution for the future drilling plans in the Weddell Sea.