Signatures of hyperthermal events in the Late Paleocene–Early Eocene limestone succession of the Jaisalmer basin, India

Abstract

Here, radiogenic strontium isotopes, and stable carbon and oxygen isotopes analyses of the Paleocene-Eocene limestones of the Jaisalmer basin, Western India are carried out to find out the evidences of Paleocene–Eocene thermal maximum and Early Eocene Climatic Optimum. The occurrence of Numulites burdigalensis suggests the succession to be a Paleocene–Eocene interval that is also confirmed by the radiogenic strontium isotope ratios. The low Mn/Sr ratio (< 2) of the studied limestones suggest that they are pristine and can present the original isotopic signatures. The δ13C values of the limestones in the studied succession are negative and there are two prominent shifts in δ13C curve towards the more negative side, one in the lower part and another in the middle of the succession. The lower one represents the Paleocene–Eocene Thermal Maximum and the middle one represents the Early Eocene Climatic Optimum. These two peaks are interpreted as the addition of carbon from the atmosphere or land as a result of the regional tectonics which could be connected with India-Asia collision. Also, the shift in the δ18O (−6.38 to −9.84‰), values can be linked with the Eocene warming events that are coeval with the carbon isotopic stages I and II. The effect of risen temperatures during these two hyperthermal events (PETM and EECO) was such that the succession is rich in larger foraminifera at carbon isotope stage I and carbon isotope stage II.