Thin-section and isotope data from the Lakadong Limestone, NE India (eastern Tethys)

The Paleocene Eocene Thermal Maximum (PETM) is associated with major extinction events in the deep ocean, and significant paleogeographic and ecological changes in surface ocean and terrestrial environments. However, the impact of the associated environmental change on shelf biota is less well understood. Here we present a new PETM record of a low paleolatitude late Paleocene-earliest Eocene shallow-marine carbonate platform from Meghalaya, NE India (eastern Tethys). The biotic assemblage was distinctly different to other Tethyan PETM records dominated by larger benthic foraminifera and calcareous algae both in the Paleocene and Eocene. The record is lacking the ecological change from corals to larger foraminiferal assemblages and the Lockhartia dominance, characteristic of other sections in the Tethys. Limestone samples were collected at very high resolution of up to 10 cm from the carbonate successions outcropping in the Mawmluh Cement quarry (25°15.707' N; 91°42.626' E), East Khasi Hills, Meghalaya, NE India. Petrographic thin-sections were prepared from the limestone samples for the light and scanning electron microscopic analysis of the biotic components. In addition to LBF biostratigraphy, carbon isotope analysis was carried out for correlating the shallow benthic zones with the carbon isotope excursion (CIE) for developing a polished record of the PETM. An CIE of ~-3‰ (from 1.96 to -1.08 ‰) tied into the biostratigraphy places the PETM towards the upper part of the Lakadong Limestone from 25.0 to 30.5 m. A change in taxa and forms indicating deeper waters with a concurrent decrease in abundance of shallow water algae suggested a sea-level rise during the onset of the PETM. Oxygen isotope analysis indicated signs of diagenetic overprint in the studied succession