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Source Rock Properties, Depositional Environment and Kerogen Degradation Kinetics of Lower Permian Shales from the Ib River Sub‐Basin, Mahanadi Basin, Eastern India.

Organic-rich borehole samples from the Talabira mine, Ib River Vevaluate their source rock potential and depositional environment. The study indicates high TOC content (>5 wt%), Type II–III kerogen, and strong hydrocarbon generation potential, though the rocks remain thermally immature (Tmax < 435°C). The Barakar Formation reflects periodic marine incursions and climatic fluctuations, with higher gammacerane index (GI ~0.29) suggesting greater water column stratification and salinity than the Karharbari Formation.

Based on geochemical evidence and regional context, two marine interaction scenarios are proposed: either a widespread marine embayment covered the basin, or marine waters entered along a NW–SE slope, affecting the Rewa region in the NW.

Schematic showing the progression of marine embayment into the Indian peninsula: a) marine embayment region suggested by Ghosh (2003), b) extended marine embayment region covering Ib sub-basin, c) inter-basinal marine incursion towards Ib sub-basin from Rewa region.

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