TERRIGENOUS PROVENANCE IN THE CAPE BASIN

Evaluating variability in the terrigenous provenance of deep sea sediments is useful for identifying temporal trends in paleo-circulation. Bulk and isotopic geochemistry of deep sea sediments recovered at Site 1089 (41S) during Ocean Drilling Program Leg 177 in the southeastern Atlantic sector of the Southern Ocean reveals several important aspects of paleo-circulation and terrigenous provenance. Site 1089 is a drift deposit located north of the modern-day position of the Antaractic Polar Front. Based on bulk sediment geochemistry, terrigenous sources varied considerably over the past 600 kyr, with clear glacial/interglacial variability in provenance. Al/Ti ratios have maximum values (Al/Ti =20-25) during glacial intervals that decrease through the interglacial with minimum values (Al/Ti=5) near terminations. Furthermore, Nd and Sr isotopes and Sm/Nd ratios of the terrigenous fraction suggest the last glacial maximum and Holocene have geochemically distinguishable provenance. Isotopic data also suggests that the terrigenous fraction is influenced by southern African sources and variability probably reflects changes in the strength of the Agulhas Current. At the MIS 12-11 transition, Fe/Ti ratios permanently decrease from values prior to 420 kyr ranging from 20-25 and values after 420 kyr ranging from 15-20. This suggests that a significant and permanent change in terrigenous deliver occurred near the MIS 12-11 transition, likely resulting from a change in ocean or atmospheric circulation. In order to further investigate provenance variability across this important climate transition, we are in the process of generating Nd and Sr isotopic data for the MIS12-11 transition.