Looking for the climatic signal in sediment composition : lessons from equatorial to sub-littoral southwest Africa

Abstract

The Atlantic margin of southwestern Africa is characterized by a strong latitudinal climatic gradient, being an excellent natural laboratory to investigate the effects of climatic on sediment composition. The mineralogy and geochemistry of fluvial and coastal samples are strongly affected by the source area lithology and recycling processes. Consequently, weathering parameters display complex patterns of variation, especially for sand samples. Among all mineralogical and chemical parameters, those that correlate best with rainfall in the drainage areas are some αAlE values (estimating the degree of depletion in element E relative to the UCC standard) and clay mineralogy. These proxies seem to be better climate estimators than the classical weathering indices, although the relatively good results may be somewhat fructiferous”.