Distribution of calcareous nannofossils in sediments cores in the western South Atlantic

Calcareous nannofossil assemblages recovered in four Islas Orcadas piston cores along the northern margin of the Maurice Ewing Bank on the eastern Falkland Plateau are correlated with lower Oligocene and middle Eocene sections at Deep Sea Drilling Project Sites 511 and 512, respectively. Results indicate that the Paleogene section near the piston core stations is generally more calcareous and complete than at the Leg 71 drill sites and could provide a valuable highlatitude biostratigraphic reference locality if drilled at some future date.

Sedimentation rates and geochemical analysis of surface sediments from the South Atlantic

Extensive investigations of sedimentary barium were performed in the southern South Atlantic in order to assess the reliability of the barium signal in Antarctic sediments as a proxy for paleoproductivity. Maximum accumulation rates of excess barium were calculated for the Antarctic zone south of the polar front where silica accumulates at high rates. The correspondence between barium and opal supports the applicability of barium as a proxy for productivity. Within the Antarctic zone north of today's average sea ice maximum, interglacial vertical rain rates of excess barium are high, with a maximum occurring during the last deglaciation and early Holocene and during oxygen isotope chronozone 5.5. During these periods, the maximum silica accumulation was supposedly located south of the polar front. Glacial paleoproductivity, instead, was low within the Antarctic zone. North of the polar front, significantly higher barium accumulation occurs during glacial times. The vertical rain rates, however, are as high as in the glacial Antarctic zone. Therefore there was no evidence for an increased productivity in the glacial Southern Ocean.