Pliocene - Pleistocene Benthic Foraminifera and Abyssal Circulation Changes at Arabian Sea DSDP Sites 220 and 223

Pliocene-Pleistocene benthic foraminifera were analysed from arabian Sea Deep Sea Drilling Project (DSDP) sites 220 and 223. At site 220 the most dominant taxon is Nuttallides umbonifera showing peak abundances in the Early Pliocene, Early and latest Pleistocene possibly representing intervals of highly carbonate-undersaturated bottom waters. The species diversity [H(S)] and equitability (E') trends show inverse relationship with N. umbonifera percentages. At relatively shallower site 223, the benthic assemblage is dominated by Cibicides wuellerstorfi, Oridorsalis umbonatus and Uvigerina hispido-costata through Plio-Pleistocene. N. umbonifera shows peak abundances only in the beginning of the Pliocene. This species shows an abrupt decrease to near extinction near the Plio-Pleistocene boundary and occurs very rarely and sporadically in the Pleistocene at site 223. C. wuellerstorfi and O. umbonatus show increased percentages in the earliest Pliocene, late Early Pliocene, and a short lived peakin the Early Pleistocene (samples 2-5), indicating presenceof relatively warm, oxygenated, and less corrosive bottom water at this site. The peaks of U.hispido-costata at site 223 are inferred to reflect intervals of high surface productivity due to intense upwelling off the Arabian coast.