Neogene Planktic Foraminiferal Biochronology of the Central Indian Ocean DSDP Sites 237 and 238

Qualitative and quantitative planktic foraminif∼raal nalyses of the Central Indim Ocean DSDP Sites 237 and 238 provided 34 important events during the Neogene. A comparison of the chronoIogica1 succession of ihese planktic foraminiferal events, with the other tropical Indian Ocean and Southwest Pacific DSDP Sites reveals remarkable similarity. Therefore, these Neogene foraminiferai events [First Appearance (FA) and Last Appearance (LA)] are considered as synchronous within the tropical Indo-Pacific except Gq. dehiscens LAD, Gr. margaritae FAD, range of Gr. tumidaflexuosa, Gr. crassaformis FAD, Gr. truncatulinoides FAD, and Gs. obliquusLAD, which are diachronous reflecting their paleobiogeographic control. Stratigraphic ranges of planktic foraminifera enabled recognition of 20 zones from the late Early Miocene to Pleistocene.

Two hiatuses (NH3 at Site 238 and NH4 at Site 237) associated with severe carbonate dissolution were identified. These hiatuses havealsobeen recordedatabout the same stratigraphic intervals in several deep sea sections in the Pacific and represent an important oceanographic event, useful for inreroceanic correlation.