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The positions of Paleozoic depositional basins in Antarctica are determined by examining the paleogeographies of other Gondwana continents. However, because of its ice cover, Antarctica's post-Paleozoic paleogeographic settings are more uncertain. Most of the Antarctic continental margin has remained passive since initial rifting. The only exception is the Bellingshausen-Amundsen margin along which the Aluk Ridge was subducted between 53 and 21 m.y.B.P.
The initial breakup of Gondwanaland resulted in a network of narrow ocean basins in which euxinic claystones were deposited. As spreading continued, enhanced circulation resulted in the deposition of biogenic sediments, mostly carbonate beds, in the juvenile ocean basins bordering Antarctica. At the time of separation of Antarctica and South America approximately 23 m.y.B.P., the Circum-Antarctic Current was initiated. The continent was then thermally isolated and the stage was set for a continental ice sheet to develop. By late Miocene time the ice sheet had advanced onto the continental margin and had dominated marginal sedimentation since that time. The importance of glacial erosion and sedimentation on the continental margin has been profound. In the Ross Sea, the only area where he continental margin has been drilled, the waxing and waning Ross Ice Shelf has eroded hundreds of meters into the continental shelf to within a few tens of meters of basement rock. In its retreat, the ice deposited almost 400 m of glacial-marine sediments. Seismic profiles from the Weddell Sea continental shelf reflect similar deep erosion. Hence, although paleogeographic reconstructions suggest that parts of the Antarctic continental margin may contain rich oil and gas reserves, the combined influence of isostasy and glacial erosion may have reshaped the Antarctic continental margin significantly.
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