Benthic foraminiferal changes across the miocene/pliocene boundary in the Northern Indian ocean: paleoceanographic implications

Abstract

The distribution pattern of deep sea bemhic foraminifera across the Miocene/ Pliocene boundary in the northern Indian Ocean DSDP sites 219, 237 and 238 were examined in order to determine their relationship with the bottom water circulation pattern. Of the 153 species of benthic foraminifera encountered at the Miocene/Pliocene transition Uvigerina spp. [mainly U. probosci-dw): Cibicides wuellerstorfi, C kullenbergi Globoaissidulinn subglobosa, Buli-mina alazanensis, Oridorsalis umbonatus and Stilostomella lepidula show marked changes in their relative abundances. The relative abundance curves of dominant bemhic foramimleral taxa. species diversity; H(SJ and equitahiltty; t' during Miocene/Pliocene transition at the DSDP situs 219, 237 and 238 were taken into account Lo explain bottom water history in the northern Indian Ocean. The latest Miocene and earliest Pliocene in all the examined sites are marked by fagh Uvigerina spp. abundances, bottom water cooling, increased upwellmg and intensified bottom water circulation. However, low abundance of Uvigerina spp. at 5.2 Ma (Miocene/Pliocene boundary) suggests a short interval of relative warming of bottom waters. The intermittent peaks of occurrence of Nuttallides umbonifera at site 238 relied recurrent incursions of Antarctic Bottom WalerjAABW) in this region.