Expression of the Palaeocene-Eocene Thermal Maximum in shallow-water carbonates of central eastern Tethys (Lower Indus Basin, Pakistan)

The Palaeocene-Eocene Thermal Maximum (PETM) was the most prominent climatic perturbation of the Cenozoic, characterized by rapid warming and ocean acidification. Major biotic impacts include a substantial deep-sea extinction event and a significant turnover in larger benthic foraminifera (LBF). Despite being extensively studied as a potential model for future climate change, there are gaps in understanding its environmental and biotic consequences, especially in shallow marine settings. Here we identify the PETM and its biotic impact in shallow marine carbonate ramp deposits of the late Palaeocene and early Eocene Dungan Formation from the Lower Indus Basin (Eastern Tethys; present day Pakistan). A ~2.5‰ carbon isotope excursion (CIE) identifies the stratigraphic position of the PETM, which coincides with the boundary of shallow benthic zones (SBZ) 4 and 5. The CIE is associated with a major turnover of LBF, including the first appearances of Alveolina ellipsoidalis, Glomalveolina minutula, Assilina dandotica and Ranikothalia sidenesis, and the disappearances of Glomalveolina levis, Miscellanea juliettae, Azzarolina daviesi, Karsella hottinger, Kathina prenavuti and Kathina selveri. Microfacies and biofacies analysis shows only minor changes in depositional environment, spanning inner to mid-ramp shallow carbonate settings, confirming that the observed LBF turnover was indeed associated with the PETM event and not solely due to local sea level changes. Our findings suggest that the PETM had a substantial impact on shallow marine benthic foraminifera in the western side of central eastern Tethys, contrasting with recent findings from sites further to the east but aligning with observations in Western Tethys carbonate settings.