A 220,000‐Year Climatic Record for the East Equatorial Atlantic Ocean and Equatorial Africa: Evidence from Diatoms and Opal Phytoliths in the Zaire (Congo) Deep‐Sea Fan

Abstract

Accumulation rates of microfossil associations are independent of each other and, in addition to percentages, give indispensable information about the significance of micropaleontological data. Marine diatoms reveal that coastal upwelling in the Zaire fan region was strong during glacial stages and weaker during interglacial stages. Oceanic upwelling was intense in stages 6 and 2 and at the stage 5d–5c transition but not in stage 4. The Benguela Current did not penetrate into the Gulf of Guinea during the last 220,000 years. The PhFD index, based on the contribution of freshwater diatoms and phytoliths, is a measure of aridity in equatorial Africa. The production in the low‐salinity river plume was high in the most humid periods on land and low when the continent was arid. On the long term, nutrient supply of the Zaire River to the ocean was probably larger in humid than in arid periods. Periods of strong seasonal variability in river fluxes and coastal upwelling coincide with arid intervals, except in the very humid interval with strong seasonal contrasts 35,000–20,000 years B.P.