Soil Clay Minerals in Namibia and their Significance for the Terrestrial and Marine Past Global Change Research

Abstract

We delineated seven soil clay mineral provinces in Namibia. Many individual clay mineral assemblages occur in fluvial, pan, cave and other environments. Previous researchers have used clay mineral compositions as evidence for palaeoenvironmental reconstructions, often without analyzing the formation, the transport and the deposition of these clay minerals. In Namibia, rates of erosion and denudation by water and wind have been very small since early Quaternary times. During the Quaternary, the clay mineral assemblages of the seven provinces and of individual clay mineral deposits did not change significantly. Palaeoenvironmental reconstructions have to consider these small rates of erosion, especially if clay minerals were transported by water and/or wind from their source area to distant regions (e.g., the ocean). Changes in marine clay mineral compositions may not reflect climate change, but can be caused by changes in the ratio of fluvial to aeolian transport. If the changes in the transport mode are known, these changes can be interpreted palaeoenvironmentally. Future researchers have to decipher quantity and quality of the fluvial and aeolian dust transport (clay minerals, pollen, etc.) over southwestern Africa and the Benguela Current area.