Early atmosphere and hydrosphere oxygenation: Clues from Precambrian paleosols and chemical sedimentary records of India

A number of Precambrian sedimentary basins of the Indian subcontinent offer scope for tracking early oxygenation history of atmosphere and hydrosphere. Available studies, though certainly not exhaustive, record signatures of pre-great oxygenation event (GOE) whiffs of atmospheric oxygenation between 3.29 and 3.02 Ga. Besides, available geochemical signatures . from Precambrian sedimental.) , rocks (BIE sulfides, sulfates, argillaceous sediments and phosphorites) suggest a generally sub-oxic shallow marine and bipartite oxicsulfidic condition in late Paleoproterozoic and Mesoproterozoic time, respectively. In this backdrop, occurrence of phosphorites in several late Paleoproterozoic basins possibly indicates formation of local oxygen oasis in presence of cyanobacterial community. From heavy to very heavy delta S-34 values in sulfides (pyrite) present in a number of Mesoproterozoic basins and Mo, Mo/TOC values from argillaceous intervals of the Vindhyan Supergroup, it is inferred that the deep hydrosphere was, in general, anoxic and, at times, euxinic.