PLANKTIC FORAMINIFERAL BIOSTRATIGRAPHY AND BIOCHRONOLOGY OF THE POST-MIOGYPSINA NEOGENE OF BOMBAY OFFSHORE BASIN

Neogene planktic foraminiferal events and biostratigraphy of four deep well sections viz D1-A-1, SS-1, R-13-1 and D-4-1 in the Bombay Offsho re Basin have been established A pronounced and regional unconformity separates the post-Miogypsina (post Zone N10 or N12, Middle Miocene) c lay/claystone succession from the underlying carbonates. In most of th e studied wells the hiatus covers a time span of 6.5 Ma (or 9.7 Ma) in volving part of Middle Miocene and entire Late Miocene except in well D-4-1 where its span is greatly reduced. Three planktic foraminiferal datums viz LAD of Globigerina nepenthes (3.78 Ma), LAD of Dentoglobige rina altispira (2.6 Ma) and LAD of Globigerinoides fistulosus (1.6 Ma) have been demarcated in the Pliocene. A comparison of these biochrono logic datums with those recorded from the DSDP sites in northern India n Ocean is made. The delayed Last Occurrence of Globoquadrina dehiscen s in Bombay Offshore is attributed to its reworking in Pliocene.