Abstract

Paleocene-Eocene Thermal Maximum event, occurring around 55.8 million years ago, is one of the most intense global warming event in Earth’s history in Cenozoic. It caused a rapid rise in global temperatures and widespread ocean stratification, which prevented sinking of cooler, oxygen and nutrient-rich waters from higher latitudes. This disrupted deep-water circulation which includes, sinking and movement of waters through deeper ocean, thereby limiting the delivery of essential nutrients to ocean floor and severely impacting deep-water calcareous benthic foraminifera. The breakdown of this nutrient supply, combined with oxygen depletion, hindered their ability to form shells effectively, contributing to the extinction of approximately 50-60% of deepwater calcareous benthic foraminifera during PETM (Thomas, 1998). This study presents the first biostratigraphic evidence of PETM from Mahanadi Basin, India. In deep water well M-1 of Mahanadi basin, a major turnover of deep water calcareous benthic foraminifera is observed across PaleoceneEocene boundary, marked by a sharp decline in calcareous taxa and dominance of agglutinated forms above the boundary. Infaunal forms become prevalent above the boundary, contrasting with predominance of epifaunal forms below it. Assemblages above the boundary indicate hypoxic to suboxic conditions, unlike the oxic assemblages below. Planktic foraminiferal abundance increased significantly, raising planktic/benthic ratios and reflecting enhanced surface productivity. Nannofossil assemblages transitioned from cool water, eutrophic species to warm water, oligotrophic forms, with a notable bloom at P-E boundary. This integrated micropaleontological data points towards PETM event in Mahanadi Basin, contributing important regional insights to global PETM records and biological responses to environmental stress.