Abstract

The Mumbai Offshore Basin, records a complex tectono-sedimentary evolution from the Paleocene to the Oligocene. Traditionally, the Mumbai High platform was interpreted as remaining emergent until the Late Oligocene. However, this study integrates wireline log motifs, high-resolution seismic mapping, microfacies analysis, and biostratigraphic age data from 38 key wells to reevaluate the submergence history of this structural high. Three stratigraphic intervals—Paleocene-Early Eocene (Panna/Devgarh), Middle Eocene (Bassein), and Early Oligocene (Mukta)—show wedge-out geometries against the platform slopes. In contrast, the Late Early Oligocene Heera Formation exhibits continuous onlap from peripheral lows onto the Mumbai High crest, demonstrating that full marine inundation of the platform occurred earlier than previously understood, during the Late Early Oligocene rather than the Late Oligocene. Well log and seismic horizons (H3G) correlated with diagnostic Early Oligocene benthic foraminifera (Nummulites fichteli) and dinocysts (Areoligera semicirculata, Fibrocysta axialis, Operculodinium divergens) confirm the age and spatial continuity of Heera carbonates across the high. This revised timeline significantly refines the paleogeographic and sequence stratigraphic framework of the basin, offering new insights into transgressive-regressive dynamics, platform drowning, and reservoir heterogeneity.