Late Quaternary history of continental climate and the Benguela Current off South West Africa

Abstract

Late Quaternary sediments from the southwest African continental slope were analyzed for their coarse fraction, diatom and clay mineral content and composition. Changes in the flow pattern of the Benguela Current were inferred from the abundance and preservation of opaline microfossils and diatom species composition. The Benguela Current turned westward in the general latitude of 24°S during oxygen isotope stages 1 and 3; this flow pattern caused transportation of opaline microorganisms from the near shore area to the continental slope area or caused increased upwelling phenomena further offshore. During oxygen isotope stage 2, on the other hand, the westward deflection of the Benguela Current was moved further to the north. Two sources of terrigenous material were determined: one is local with supply from the Namib desert, the other one is distant with supply from the Orange River mouth; material from the Orange River mouth might have been transported to the north by the Benguela Current. The local terrigenous supply from the Namib desert increased during oxygen isotope stage 2 as evidenced by the increased amounts of terrigenous matter, by an increase of illite and by greater grain sizes. Occurrence of wood fibres in oxygen isotope stage 3 indicates a denser continental vegetation over the present Namib desert.