| Anomalously high uranium contents and U-238/Th-232 activity ratios deposited during the oxygen isotope stages 2 to 4 are observed in the MD962085 core from the Benguela Current upwelling area. In conjunction,vith the activity ratio of U-234/U-238, the high uranium contents found in this core cannot be considered as detrital; instead, they must be of authigenic origin. The high biological productivity in the overlying seawater may have induced a high flux of organic matter resulting, directly or indirectly, in a reducing environment, and may have led to the addition of authigenic uranium to the sediments during the last glacial period. The correspondence between the variations in authigenic U content, %TOC, and Th-230(ex)-normalized TOC flux supports this... |
