WHAT CAUSED THE MAJOR BIOTIC TURNOVER IN SHALLOW MARINE SETTINGS DURING THE PETM EVENT: CHANGE IN THE SEA-LEVEL OR SEA SURFACE TEMPERATURES? (INSIGHTS FROM EASTERN NEO-TETHYS)

The Paleocene-Eocene Thermal Maximum event (PETM~ 55.90 Ma) is globally recognized as one of the most intense warming events in the Cenozoic. The shallow-marine Larger Benthic Foraminifera (LBF) are very susceptible to minor changes in the sea-level, Sea Surface Temperatures (SSTs), and nutrient influx. Limited information is however available on sea-level changes during the CIE recovery phase in shallow-marine settings of the Eastern Neo-Tethys. This work provides the first comprehensive record of the PETM event from two shallow-marine sections of the Dunghan Formation in the Baluchistan Basin. A prominent negative CIE of ~ 5.65‰ and ~ 3.11‰ at shallow-marine sections are utilized to accurately constrain the PETM event and pinpoint the P/E boundary in the upper to upper-most part of the SBP 4. During the CIE-onset, the rising sea-level and increased SSTs are associated to a minor LBF turnover that involves the radiation of the large-sized Alveolina (Alveolina vredenburgi) and the local disappearance of Lockhartia spp. and Miscellanea spp. in the upper to uppermost part of the SBP 4. Upwards, during the CIE-recovery phase, a significant drop in sea-level is observed at the boundary between SBZ 5/6. The major biotic turnover at the SBZ 5/6 is marked by the extinction of the key Paleocene LBF assemblages, including Daviesina spp., Lockhartia spp., Miscellanea spp., Orbitosiphon spp., and Ranikothalia spp., and the subsequent proliferation of larger shell-sized early Eocene Alveolina spp., Nummulites spp., Orbitolites spp., and miliolids. The sea-level fall is accompanied by SST cooling during the CIE-recovery phase had detrimental effects on Paleocene LBFs (i.e., Daviesina spp., Lockhartia spp., Miscellanea spp., Orbitosiphon spp., and Ranikothalia spp.) that were replaced by the earliest Eocene LBFs (i.e., Alveolina spp., Nummulites spp., Orbitolites spp.) and miliolids. Hence, the second major LBF turnover observed at the SBZ 5/6 boundary is likely related to the alteration in nutrient input caused by the enhanced continental weathering triggered by the sea-level fall and lowering in SSTs during the CIE-recovery phase. This implies that the environmental and biotic changes can be attributed to a decrease in the relative sea-level and SSTs during the PETM recovery phase.