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The primary goal for this study is to reconstruct the Quaternary history of the Benguela Current and its associated upwelling regimes off western coast of the Africa. Nine deep-sea cores ( Sites 1075 ~ 1082 and 1084 ) were collected during the ODP Leg 175 in October 1997. Variations of surface productivity are deduced based on the d13Corg , biogenic opal, organic carbon and carbonate contents, and X-ray mineral diffraction for the last 1,600,000 years.
According to the carbon isotopic analyses of organic matter, relatively light d13Corg values are found at Sites 1078 ~ 1079, revealing larger land-derived contribution than marine-derived input. On the contrary, marine-derived source are found at Sites 1081 ~ 1084 ( 19o S ~ 25 o S ). Notably high mass accumulation rates ( MAR ) of biogenic opal are recorded at Sites 1075 ~ 1077, 1079, and 1081 ~ 1084. The high surface productivity at Sites 1081 ~ 1084 agree nicely with high OPAL MAR at these three sites. Othe other hand, high OPA MAR at Sites 1075 ~ 1077, and 1079 probably is the result of terrigenous inpt from Zaire River and continent according to the X-ray diffraction analyses.Variations of CaCO3 and TOC MAR at Sites 1075 ~1077 can also be linked to thedilution caused by terrigenous input and deep water dissolution based on the X-ray diffraction and the d13Corg analyses. Distribution pattern of surface productivity with respect to age and latitude shows that high surface productivity are recorded around 1100, 200, and 7 ka at northern of 19 o S. Those high surface productivity could have been related to the variation of the Benguela Current.
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