干旱区生态环境知识资源中心

Palynological investigation of a marine piston core GeoB 1008-3 (6 degrees 35'S/10 degrees 19'E) from the highly productive area off the Congo fan provides a dinoflagellate cyst record reflecting marine surface water conditions during the last 190 ka and a pollen record of the vegetation changes in Central Africa induced by climatic fluctuations for the same period. The freshwater discharge of the Congo river is related to the intensity of the West African monsoon. During warmer and more humid phases, dinoflagellate cyst flux decreased in relation to lower productivity and increased freshwater input in the eastern South Atlantic. At the same time on the continent, the rain forest expanded. During the cooler interstadials of Stage 5, the Afromontane forest represented by Podocarpus pollen expanded to lower altitudes and occupied former areas of rain forest during periods showing intermediate levels for sea surface temperatures and river discharge. During the colder and more arid phases of glacial Stages 6 and 2, when freshwater run-off into the Gulf of Guinea decreased, dinoflagellate cysts were much more abundant. However, Stage 4 shows high levels of river discharge and a moderate dinoflagellate cyst flux coupled to low sea-surface temperatures of the eastern South Atlantic, while Stage 3 shows moderately high pollen percentages of the rain forest during phases with fluctuating fresh-water discharge and very low sea-surface temperatures. High sea levels at the beginning of the Last Interglacial and the Holocene favoured the expansion of mangroves.