A review of biotic signatures within the Precambrian Vindhyan Supergroup: Implications on evolution of microbial and metazoan life on Earth

Abstract

This study presents a review of the wide spectrum of biotic signatures within the Precambrian Vindhyan Supergroup deposited during the 'boring billion' and assesses their biological affinity and age implications. The sedimentation took place in wide-ranging palaeo-environments from fluvial to offshore through shallow marine. While the lower part of the~4500 m thick Vindhyan succession is older than 1650 Ma, the age at its top part is poorly constrained, ranging from 1000 to 650 Ma. Microbial records are abundant in the form of stromatolites in limestone and microbially induced sedimentary structures (MISS) on both siliciclastics and carbonates across the Vindhyan succession. The wide morphological variation of these two features corresponds to depositional processes, early cementation, as well as lithological variations. The stromatolite record, as well as calcified and chertified microbial fossils, attest to the Mesoproterozoic to Neoproterozoic age of the sediments. Although the carbonaceous body fossils do not have age implications, they indicate the proliferation of algal life during the Meso-to Neoproterozoic time. The Ediacaran-like fossils mostly relate either to 'discoidal microbial colony' or detached pieces of microbial mat. Wide-ranging putative metazoan fossil reports remain the focal point of attention for many years. Although most of these reports are found to be microbially originated, some of these features have the potential to highlight the evolution of multicellular life during the Precambrian.