Abstract The primary objective for this study is to determine the variations of germanium (Ge) to silicon (Si) ratios in diatom shells from down core sediments off the southwestern coast of the Africa. Because Ge behaves like Si in the ocean and the major source of these two elements is rivers, Ge/Si ratios of the diatom are thus expected to record the intensity of weathering on continents. Two sediment cores (Site 1081 and 1084) were collected during the ODP Leg 175 in August, October 1997 and were analyzed for intervals between 3.1 and 1.9 Ma. Generally, the (Ge/Si)diatom ratios in this study show the similar trend with those reported from the Antarctic Ocean. The decline of Ge/Si ratios after 2.5 Ma is caused by the high opal mass accumulation rate, indicating the increasing rivers input of silica to the ocean. Relatively high Ge/Si ratios of diatom shells during warm periods shown by the depleted benthic foraminiferal £_18O values from the North and Equatorial Atlantic, suggesting a scenario of intensified chemical weathering on continent. Cold periods signified by £_18O-enriched values are associated with lower Ge/Si ratios. Very likely the reduced Ge/Si values reflect the prevailing weathering on continents was less chemical-dissolving due to the dry weather in cold stages.

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