Paleomagnetic, radiolarian, and foraminiferal studies of piston cores from the Ross Sea, Antarctica, reveal the existence of a widespread disconformity separating sediments of Gauss age (t > 2.4 m.y.) from a thin discontinuous layer of Brunhes sediments (t < 0.7 m.y.). Climatic cooling, expansion of the Ross Ice Shelf, and the resultant increased circulation of bottom water in late Gauss or early Matuyama time probably caused the extensive erosion and (or) nondeposition responsible for the disconformity. Ross Ice Shelf expansion may also have caused a reduction in the number of outlet glaciers discharging debris-laden ice directly into the sea resulting in the observed decrease in glacial-marine sediment deposition since the Gauss. Increased circulation under an expanded ice shelf and an associated increase in the concentration of dissolved carbon dioxide is implied by a late Gauss–early Matuyama rise from > 1,800 to < 350 m in the calcium-carbonate compensation depth within the Ross Sea. The distribution of reworked Gauss age fossils in Brunhes deposits in submarine channels on the Ross Sea Shelf and continental slope and on the nearby abyssal plain further indicates that substantial amounts of resuspended sediment have been transported out of the Ross Sea by bottom currents during the Brunhes.

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