Stable isotopes and larger benthic foraminiferal response to the Paleocene-Eocene Thermal Maximum in the shallow-water carbonates of the Lower Indus Basin (Eastern Tethys, Pakistan)

The Paleocene-Eocene Thermal Maximum (PETM) was the most prominent climatic perturbation of the Cenozoic. Rapid climate warming and ocean acidification resulted in biotic changes including the largest deep-sea extinction event of the last 90 Ma and a marked turnover in larger benthic foraminifera (LBF). While heavily studied as a potential analogue for future climate change, important spatial gaps remain in our understanding of the environmental and biotic impacts of the PETM. Particularly, the expression of the PETM in the shallow marine settings of central Eastern Tethys remains poorly documented because of the scarcity of well-preserved PETM sections in the region. Here we identify the PETM and its biotic impact in shallow marine carbonate ramp deposits of the late Paleocene 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 sidensis , and the disappearances of Glomalveolina levis, Miscellanea juliettae, Azzarolina daviesi, Karsella hottingeri, Kathina pernavuti and Kathina selveri. Microfacies and biofacies analysis suggest shallow marine carbonate environments, ranging from inner to mid ramp settings, demonstrating that the CIE and LBF turnover are associated with the PETM event and not just a result of local sea level change. We conclude that the stratigraphic correspondence between the LBF turnover and the onset of the PETM in the Lower Indus Basin resembles that observed in carbonate settings of Western Tethys. This is distinct from other records from the Eastern Tethys, where it is suggested that LBF turnover occurred well after the onset of the PETM. Our observations confirm that the PETM had an impact on shallow marine benthic foraminifera in the western side of central Eastern Tethys.