Miocene changes in SW-African climate and ocean circulation: inferences from silt analysis and carbonate preservation studies

Abstract

Deep-sea sediments from the SE Atlantic at ODP Sites 1085, 1087 and 1265 off the continental margin SW African and the Walvis Ridge were investigated using sedimentological, mineralogical and geochemical analyses in order to paleoenvironmental and paleoclimatic signals in the Neogene. The variation of carbonate and terrigenous deposition from the Miocene sediment records were associated with changes in the atmospheric circulation pattern. The results showed that the driving process of what so called 'Carbonate Crash' event was complex and differed compared to previous investigation in the other regions. The event in the study area represents a more regional phenomenon. The terrigenous grain-size distribution reveals that the establishment of the wind-driven Benguela Upwelling system and close timing of aridification in South Africa was related to the expansion of the Antarctic ice-sheet and intensification of Southern Hemisphere winds. Variability in carbonate contents are related to the global changes in deep-water chemistry and the variations in southern component of dee-water producing during the interglacial and glacial conditions.