Downslope processes and products on the Wilkes Land compared to other Antarctic margins: Relevance to glacial history
Abstract
Sediment cores collected from the Wilkes Land margin show slope and base-of-slope sedimentation dominated by gravity flow processes during Pleistocene glacial times. Slumps and initial debris flow products dominate the upper slope. Sediments of the lower slope and upper continental rise contain crudely stratified to laminated intervals, which represent the transition between an end member of a debris flow and a turbidity current deposit. Some of the laminated intervals in cores from the continental rise represent sediment deposited from turbidity currents traveling through a complex network of channels. Based on the sedimentary facies, the numerous hiatuses present in piston cores collected from the base of the slope, in which the base of the core extends into the Miocene, are attributed to erosion by consecutive mass wasting events on the slope. On the continental rise, massive and laminated sediment records Pleistocene sedimentation attributed to more continuous sedimentation in the levees bounding the channel and/or in the interchannel areas. Both, the geometry and thickness of the sedimentary unit containing the Pleistocene section as imaged in seismic reflection profiles, and the minimum sedimentation rates calculated from sediment cores, suggest that downslope processes during the Quaternary and remaining part of the unit (Pliocene?) are several orders of magnitude less important in volume than they were in previous times (Miocene?). Decreased sediment supply to the rise correlates with deposition of thick progradational wedges on the outer continental shelf. This indicates that the decrease in sediment supply to the continental rise results from a shift of sedimentary depocenters. Similar geometries in the sedimentary section and decrease in sedimentation rates at about 2.5 Ma have been reported from ODP Sites 1095, 1096 and 1101, drilled during Leg 178, and from ODP Site 1165, drilled during Leg 188 in Prydz Bay. In these two Antarctic margins, the time of decreased sediment supply in the continental rise also corresponds with the development of thick progradational wedges on the continental shelf and upper slope. The similarities in the geometries of the depositional units and the changes in sedimentation rates of these depositional units found on the Antarctic Peninsula, Wilkes Land and Prydz Bay, suggest that this correlative shift in sedimentary depocenters on the Antarctic margins may be controlled by changes in the evolution of the Antarctic Ice Sheet possibly caused by the transition from water-dominated to cold-ice dominated glacial regime.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....11696E