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Andrea Caburlotto, OGS, Trieste (Italy)
Renata G. Lucchi, Universitat de Barcelona (Spain)
Raffaella Tolotti, University of Genova (Italy)
Patrizia Macrì, INGV (Italy)
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The Wilkes Land continental rise is characterised by a channel-ridge type depositional system with an approximately north-south elongation, perpendicular to the margin. The channels represent the main sediment drainage pattern, supplied by the continental shelf margin ice-sheet, and feeding the ridge depositional system.
Piston and gravity cores, high resolution echo-sounding (3.5 kHz) and Chirp profiles collected in the frame of the joint Australian and Italian WEGA (WilkEs Basin GlAcial History) project provide new insights into the Quaternary history of the East Antarctic Ice Sheet and the High Salinity Shelf Water behaviour across this margin.
The analysis of sediment cores and high-resolution seismic data in the continental slope and rise demonstrate clearly that downslope flows are the main transport mechanisms of sediment from the continental shelf to the rise. Turbiditic as well as HSSW downflows containing suspended bioclastic material leave their clear print in the sea floor morphology, throughout the formation and maintain of deep channels, channel levees and sediment wave fields. On one of these channels (WEGA), geophysical data indicates a depositional setting change since mid-late Pleistocene. Four sediment cores collected along the channel have been examined in order to better characterise the sedimentary processes change and to relate it to the glacial dynamic. Up to Marine Isotopic Stage 10, the depositional setting on the WEGA channel was related to the supply of material by turbiditic flows and the redistribution of the sediments on the continental rise by contour currents. The sedimentological characteristics observed on the cores collected along the thalweg of the WEGA channel indicate that since that time the WEGA channel has been a low-energy but still dynamic environment. At least during the last 30 kyrs it is characterised by transport of sediment through high salinity water flows (HSSW), originating in the shelf area. The HSSW entrains the fine sediments deriving from the shelf area and redistributes them on the continental rise area.
This trend has been confirmed by preliminary investigations on the 35 meters long Calypso core collected in an adjacent area in the frame of the MDO3 CADO cruise. The sedimentary sequence drilled by this core has a high cronostratigraphic potential, continuous and with a high resolution that could be compared with that one inferring from the ice cores. The comparison and the correlation between the information coming from the glacimarine sediments on the Wilkes Land margin and those inferred from the Dome C ice cores, represent a great opportunity to investigate the relationship between the paleo-climatic changes, the dynamic of the EAIS and the glacimarine depositional environment facing it.
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