Larger benthic foraminiferal response to the PETM in the Potwar Basin (Eastern Neotethys, Pakistan)

Abstract

The Paleocene-Eocene Thermal Maximum (PETM) was the most pronounced global and transient warming event of the Cenozoic and was associated with marked changes in the biosphere, atmosphere and hydrosphere. On the basis of the large benthic foraminiferal (LBF) biostratigraphy coupled with δ13C record, the PETM event and the Paleocene-Eocene boundary are constrained in the Duleram section (Potwar Basin, Pakistan). This shallow-marine carbonate deposit offers a unique opportunity to study in detail the stratigraphic record of the PETM and its effect on LBF assemblages in the eastern Neotethyan Ocean. The ~5‰ negative carbon isotope excursion (CIE) is here used to pinpoint the Paleocene-Eocene boundary corresponding to the base of SBZ 5. The CIE is not directly associated with evident compositional changes in the LBF assemblages that are instead identified during the CIE recovery phase. The prominent LBF assemblages' changes are marked by the disappearance of Miscellanea juliettae, Miscellanea dukhani, Ranikothalia nuttalli, Ranikothalia sindensis, Daviesina tenuis, Daviesina langhami and Orbitosiphon punjabensis and by the appearance of Alveolina ellipsoidalis, Alveolina globula, Alveolina moussoulensis, Alveolina minervensis, Alveolina avellana aurignacensis, Orbitolites biplanus, Nummulites fraasi, Nummulites minervensis and miliolids that correspond to the boundary between SBZ 5 and SBZ 6. The change in the LBF assemblages during the CIE-recovery phase of PETM is attributed to enhanced continental weathering and increased temperature and organic content flux that altered the habitat from oligotrophic to eutrophic conditions. This study provides the first evidence of the PETM at shallow marine deposits in the Potwar Basin and shows that change in the LBF assemblages in response of the PETM warming event affected shallow seas bordering the eastern Neotethyan Ocean.