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The Weddell Sea – Scotia Sea Transect: A stratigraphic correlation of deep sea seismic reflection data along the Atlantic margin of West Antarctica

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Lindeque, A. , Martos, Y. M. , Gohl, K. and Maldonado, A. (2011): The Weddell Sea – Scotia Sea Transect: A stratigraphic correlation of deep sea seismic reflection data along the Atlantic margin of West Antarctica , 11th International Symposium on Antarctic Earth Sciences, University of Edinburgh, Scotland, 10 July 2011 - 16 July 2011 .
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Abstract:

Deep sea sediments in the Weddell Sea and Scotia Sea collectively record ca. 147 million years of interaction between ocean bottom circulation and increased sediment supply before, and after, the first Antarctic ice sheets advanced to the shelf edge. Seismic stratigraphy is a useful tool to decipher past and present dynamics of the Antarctic ice sheets, but existing Weddell Sea – Scotia Sea stratigraphic correlations only use sections of seismic reflection profiles and trace reflectors locally. In order to map the regional stratigraphy, we constructed the first continuous, ca. 5000 km long, seismic transect from 25 multichannel seismic reflection profiles in the Antarctic Seismic Data Library System. The transect starts in the south-eastern Weddell Sea, crosses the Powell Basin near the Antarctic Peninsula, and ends in the western Scotia Sea. We mapped six major, continuous, high amplitude reflectors and interpret these unconformities to represent depositional processes related to pre-glacial, transitional and glacial regimes. Basement ages from published regional magnetic anomaly data, and ODP boreholes in the Weddell Sea and Antarctic Peninsula, provided sparse chrono-stratigraphic control. Our results are consistent with stratigraphic models in the Scotia Sea, but lower horizons in the south-eastern Weddell Sea are re-interpreted. Interestingly reflector WS-4, interpreted to represent the transition from pre-glacial to glacial regime, correlates to the Eocene/Oligocene boundary in the south-eastern Weddell Sea (34 Ma, chron C13), but to the middle to late Miocene (12.6 Ma, chron C5A) near the Antarctic Peninsula and Scotia Sea. Regional age variation of a reflector indicates the extent and duration of the depositional process and as such, our model suggests sediment supply to the deep Weddell Sea increased from east to west, in response to the advancement of the East Antarctic ice sheet, followed by the West Antarctic ice sheet and late Miocene Antarctic Peninsula ice sheet development.

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