Monsoon Pattern Changes along PETM Recorded in the Barmer Basin, Rajasthan, India

Multiple short-term (<105 years) global warming events ("hyperthermals") occurred throughout the early Eocene. Chemical weathering of continental silicate rocks is considered to have played a key role in recovery from these transient global warming events via consumption of excess atmospheric CO2. However, although evidence of this negative feedback has been reported for the Paleocene-Eocene Thermal Maximum (PETM), the effectiveness of chemical weathering during other transient hyperthermals remains poorly constrained. Compared with marine records, continental sedimentary records of the PETM are very limited therefore need to explore in detail to better constrain climatic and environment changes during this interval. Here, we newly report the first detailed record of the PETM in the Barmer Basin, India to identify the environment and hydrological changes across the PETM. This study presents carbon isotope, geochemical and clay mineral analysis results of the biostratigraphically constrained continental lignite bearing sediments from the Barmer Basin, India to identify the environmental and hydrological changes across the PETM. The carbon isotopic (δ13C) values show large negative excursions -29.00 ‰ observed in grey shale lying in the middle part of the section and the least -24.03‰ value noticed in the grey shale towards the terminal end of the sedimentary sequence. The most negative δ13C values and lower TOC suggest an intense warm period. A gradual increase in chemical index of alteration (CIA), Rb/Sr ratio and further increase/expansion of smectite mineral due peaks are possibly associated with the PETM, indicating an intensified silicate weathering in the catchment region in response to warmer and more humid climate. Our results corroborate the general understanding that an accelerated continental chemical weathering served as a negative feedback to sequester carbon and lower the atmospheric greenhouse-gas level during the PETM.