NEOGENE PLANKTIC FORAMINIFERAL BIOCHRONOLOGY OF THE CENTRAL INDIAN-OCEAN DSDP SITE-237 AND SITE-238

Qualitative and quantitative planktic foraminiferal analyses of the Central Indian Ocean DSDP Sites 237 and 238 provided 34 important events during the Neogene. A comparison of the chronological succession of these planktic foraminiferal events, with the other tropical Indian Ocean and Southwest Pacific DSDP Sites reveals remarkable similarity. Therefore, these Neogene foraminiferal 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. tumida flexuosa, Gr. crassaformis FAD, Gr. truncatulinoides FAD, and Gs. obliquus LAD, 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 have also been recorded at abo ut the same stratigraphic intervals in several deep sea sections in the Pacific and represent an important oceanographic event, useful for interoceanic correlation.