Planktic foraminiferal biogeography and ocean circulation in Southwest Pacific during last 3.3 My

Abstract

Biogeographic patterns of significant tropical to cool subtropical planktic fomminiferfl from Leg 90 Deep Sea Drilling Project (DSDP) sites have been quantitatively mapped for the last 13. my in the Southwest Pacific. Marked differences are apparent in (he biogeographic distribution of the Menarddk and Globoconella groups before and after 1.77 Ma reflecting changes in surface water circulation. Spatial distribution of Neogloboquadrina pachydermia changed very little in the last 3,3 my except that its frequency increased around 2.58 Ma and again, at 0.78 Ma. The Menardella group established its present day distribution pattern in the Southwest Pacific al 1.77 Ma (Top of Olduvai) and Chbigerinoides spp. at 0.78 Ma (Base of Brunhes).The distribution pattern of Ghbigeriim bulbides shows an interval of intense upweiling at 2.58 Ma.