Influence of Antarctic Bottom Water (AABW) and monsoonal activity in the Central Indian Ocean over past 5 million years: benthic foraminiferal record at DSDP Site 238

Abstract

This study quantitatively analyzes Pliocene-Pleistocene benthic f'oraminifcra from DSDP Site 238 in the central Indian Ocean. A Q-mode factor analysis of 28 most abundant species defines three significant faunal assemblages reflecting different environmental characteristics. The Cibicida; witelterstorfi-Oridorsalix umbonatm assemblage (Factor I) represents well oxygenated bottom waters with active currents and intermediate to low supply of organic matter. The Uvigerina proboscidea assemblage (Factor 2) indicates a continuously high flux of organic matters to the sea floor in response to increased surface water productivity. The NititaUides umbonifera assemblage (Factor 3) is associated with Antarctic Bottom Water (AABW) and reflects cold, oligotrophy, increased carbonate corrosiveness and high oxygen concentration.