SOUTHEAST ATLANTIC MARINE AND TERRESTRIAL RESPONSE TO MIDDLE PLIOCENECLIMATE-CHANGE

Analysis of planktic foraminifers and pollen from Deep Sea Drilling Pr oject Site 532 located on the continental margin of southwest Africa p rovides information on the link between Pliocene paleoceanographic con ditions and paleoenvironments of southwest Africa. Increased upwelling at Site 532 correlates with southward migration of onshore vegetation regions. Both terrestrial and marine changes can be explained by chan ges in the southern hemisphere surface temperature gradient which affe cted the paleo-position of subtropical high pressure cells and product ivity of water masses during the Pliocene. When the subtropical high p ressure cells were further south, Southern Ocean waters were warmer, c ontained less sea ice, Southern Ocean diatom productivity was high, an d nutrient depleted water upwelled off southwest Africa. When the subt ropical high pressure cells were in a configuration similar to the pre sent, Southern Ocean waters were cooler and contained more sea ice, th e aerial extent of Southern Ocean diatom productivity was limited, and nutrient rich waters upwelled off southwest Africa as the Benguela up welling system migrated closer to the position of Site 532.