Stratigraphy and geochemistry of the Balwan Limestone, Vindhyan Supergroup, India: Evidence for the Bitter Springs δ 13 C anomaly

Abstract The Vindhyan Supergroup of India, deposited in an intracratonic basin, is one of the important Proterozoic marine successions of the world that contains some of the most controversial Precambrian fossil discoveries. Despite their importance, the chronology of the host strata and global correlation of the events that occurred within the basin remain equivocal. Here, we present results of a detailed geological, geochemical and isotopic (Sr-C-O) study of the Balwan Limestone, the youngest carbonate formation of the supergroup, exposed only in the western sector of the basin. Our results suggest that the Vindhyan Basin had become a structurally controlled marginal sea towards the end of its existence and that the limestone was deposited in a subtidal environment that had strong depositional currents. We find evidence for a strong storm event or a tsunami during its deposition. Near primary 87 Sr/ 86 Sr of 0.70676 at the top and 207 Pb- 206 Pb age of 866 ± 90 Ma ( Gopalan et al., 2013 ) of this ∼120 m thick formation suggest its deposition during Late Tonian. δ 13 C stratigraphy reveals the presence of the globally synchronous Bitter Springs anomaly (∼12‰ shift) in the formation, the first such report from India.