Microbial dynamics in an intertrappean lake during the terminal phase of Deccan volcanism

Biogeochemical changes associated with Deccan volcanism and their potential link to the K/Pg extinction event are still debated in Palaeoclimate research. Contemporary terrestrial organosedimentary deposits are important archives for understanding the perturbation in the biogeochemical cycling during this critical episode in Earth's history. Here, we report an intertrappean lacustrine carbonate deposit from the Amba Dongar region in the northwestern part of the Deccan igneous province, formed during the terminal phase of Deccan volcanism. This sedimentary horizon contains two types of biologically induced carbonate deposits: (1) older Type I (fine and discontinuous laminae with uneven boundaries) and younger Type II (thick and regular laminae with well-defined boundaries). Our sedimentological and stable isotope investigation captures evidence of gradual eutrophication of the lake system associated with the Deccan volcanism. Based on the clumped isotope-based temperature estimates (33°-41°C), we propose a “hot and sour soup”-like condition promoting microbial carbonate precipitation.