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The pre-glacial to glacial development of Antarctica: Footprints in deep-sea sediments

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Lindeque, A. , Gohl, K. , Martos, Y. M. and Uenzelmann-Neben, G. (2012): The pre-glacial to glacial development of Antarctica: Footprints in deep-sea sediments , 72. Jahrestagung der Deutschen Geophysikalischen Gesellschaft, Hamburg, 5 March 2012 - 8 March 2012 .
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The pre-glacial to glacial development of Antarctica and the processes that eroded, transported and deposited sediments onto the shelf, slope and abyssal plane are archived in the deep-sea sedimentary record. Expanding ice sheets erode unconsolidated sediments of pre-glacial river systems, resulting in a high sediment supply over a relatively short period of time, however, once grounded on the shelf, sediment supply decreases in response to bedrock erosion. Local scale studies around Antarctica reported some sediment deposition variations, but a margin-wide seismic stratigraphy model and identification of pre-glacial (PG), transitional (T) and full glacial (FG) sequences are still lacking. Such a correlation is necessary to build circum-Antarctic sediment thickness grids that are needed for past topography and bathymetry reconstructions, which in turn constrain paleoclimate models. We present (i) a ~3200 km long Weddell Sea - Scotia Sea transect comprising 23 seismic reflection profiles from the Seismic Data Library System, and (ii) a ~2000 km long Amundsen Sea - Ross Sea transect of multichannel seismic data collected on the RV Polarstern cruise in 2010. Sequences interpreted to represent PG, T and FG processes were identified based on varying seismic properties. FG and T-units partly correlate to similar units in local studies but PG-units in the Weddell Sea were re-interpreted. Sparse borehole data provide age control for the FG sequences and magnetic anomalies constrain basement ages. Each sedimentary unit and its associated discontinuity vary laterally in age but represent the same process. The pre-glacial Weddell Sea sediment units suggest a Cretaceous proto-Weddell Gyre. The 0.5-1 km thick unevenly distributed T-unit indicates high sediment supply and Eocene East Antarctic ice sheet expansion with ice caps and smaller ice sheets preceding Miocene Antarctic Peninsula ice sheet and the West Antarctic ice sheet development. Pliocene/Pleistocene FG-deposits are thinner and more evenly distributed, indicating lower sediment supply due to bedrock erosion, and intensified ocean bottom currents. This work contributes the first margin-wide scale seismic stratigraphy for the Weddell and Amundsen Seas and identified continuous PG, T and FG sediments, which are significant steps towards the circum-Antarctic sediment thickness grid constructions.

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