Palaeo-depositional Environment of the Rewa Group of rocks of Vindhyan Supergroup in light of Microbial Induced Sedimentary Structures (MISS)

Abstract

In India, Vindhyan Supergroup of rocks is one of the thickest polycyclic sedimentary sequence of limestone, sandstone, siltsone and shale, which was deposited during the Neo-Proterozoic age. The Rewa Group exposed at Sohagi Ghat and Duari areas having a polycyclic succession of sandstone, siltstone and shale are suitable locales for such microbial-induced sedimentary structures-MISS, an indicator of microbial coloniza¬tion at the time of deposition. These are the records of their growth, destruction, decay, and diagenesis, which inter alia include sand cracks, mat chips, remnant gas domes, pyrite patches and iron laminae. The presence of preserved microbial mats in the Rewa Group sediments reflects the simultaneous depletion of carbon-dioxide and increase in oxygen due to life processes. After photosynthesis began, it led to changes in the environment of archaic life forms. Plankton, blue-green algae and photo-synthetic bacteria decompose atmospheric carbon dioxide and reduce it to produce atmospheric oxygen. These associated structures are strong indicators of the slow sedimentation in transgressive, tide-influenced, shallow marine, supratidal conditions are being comprehensively evaluated and interpreted in this study.