Research Projects

The mid-Proterozoic period, spanning from 1.8 Ga to 0.8 Ga, is known for environmental stability and biological stasis on Earth. The atmospheric oxygen concentration was low during this period, with the ocean basin being largely anoxic. Wide spread oceanic euxinia caused scarcity of essential micronutrients in the surface ocean, limiting biological nitrogen fixation and hindering eukaryotes' evolution. A muted global carbon-cycle with a near uniform δ¹³C of marine dissolved inorganic carbon (DIC) suggests a weaker biological pump. Geochemical modelling on S-isotope composition indicates a low, less than 1mM dissolved SO4 concentration of Mesoproterozoic ocean. Recent studies document dynamic oceanic redox conditions and higher biotic diversification during the Mesoproterozoic. Several episodes of increased oxygenation are now recognized at 1.57–1.54 Ga, 1.4 Ga, and 1.1 Ga. The Cumbum Formation of Nallamalai Group, Cuddapah basin hosts the world's largest and earliest known bedded barite deposit, with an estimated reserve of 70 Mt barite. Precipitation of such a huge marine sulphate deposit requires much higher dissolved SO4 than currently suggested, requiring more detailed work. The proposed work aims to conduct detailed petrographic and elemental geochemical studies on systematic samples for screening, devise a suitable sequential step leaching technique, and directly date the barite and black shale by Rb-Sr and Pb-Pb isotopic study of the leachates. High resolution δ¹³C, δ³⁴S, ⁸⁷Sr/86Sr, and redox-sensitive-element chemo-stratigraphy will be carried out to understand biogeochemical cycling of carbon and sulphur and their bearing on redox-structure and paleo-oxygenation of the ocean.

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