HOLOCENE ICE RETREAT FROM THE LAZAREV SEA SHELF, EAST ANTARCTICA

Distinct facies types, classified in radiocarbon-dated sediments from the shelf of the Lazarev Sea, East Antarctica, reveal a detailed histo ry of processes that have controlled sedimentation during the deglacia tion over the last 10,000 yr. The ice retreat on this part of the Anta rctic shelf started 9500 yr BP, marked by the deposition of laminated sediments, deposited from a floating ice shelf. These laminites, which occur on top of diamictons laid down from a grounded ice sheet, are t he basal sediments of the postglacial sequence; The intensity of the A ntarctic Coastal Current (ACC), directed by shelf morphology, controll ed sedimentation of the postglacial facies. A residual glaciomarine se diment with the fine fraction winnowed by strong currents developed fr om 9000-8000 yr BP in the western part of the investigation area and f rom 9000-5000 yr BP in the eastern part, closer to the prominent 'Fenn o Deep' trough. Current velocities apparently decreased between 8000 a nd 2000 yr BP due to a deflection of the ACC by advancing ice tongues to the east of the investigation area during the 'Hypsithermal'. This led to a deposition of fine-grained sediments, and clay mineralogy sug gests a continental source, possibly near the grounding line of the Ni vl Ice Shelf, rather than a winnowing of sediments near the shelf brea k or advection from deeper water. Current velocities intensified after 2000 yr BP, removed fine material from these sediments and led to a r elict sediment, consisting of coarse bryozoan and molluscan debris. Co pyright (C) Elsevier Science Ltd.