Evolution of the Proterozoic Vindhyan Basin, Rajasthan, India: insights from geochemical provenance of siliciclastic sediments

The Vindhyan Basin of western India is a part of the largest Proterozoic sedimentary basin of the Indian subcontinent. Deposited in a largely shallow marine environment, the sedimentary sequence of the basin, known as the Vindhyan Supergroup, is believed to hold clues to our understanding of the evolution of life and climate during the Proterozoic. Inspite of multiple important paleobiological discoveries from these rocks, our knowledge about the development of the basin and responsible regional tectonics had remained rudimentary. Here, we propose a model for the evolutionary history of the Vindhyan Basin based on quantitative provenance analysis through geochemical and isotopic compositions of siliciclastic sediments. According to our model, the basin opened up in a foreland setting during an event that was contemporaneous with the amalgamation of the supercontinent Columbia. In the Lower Vindhyans, most of the sediments were derived from the basement gneisses (BGC-I & II) and a younger differentiated magmatic arc, whereas the >1.7 Ga rocks of the Aravalli and Delhi supergroups formed the source area for the Upper Vindhyans. In comparison to their counterparts in the eastern sector in the Son Valley, the Semri and Kaimur groups of the western sector had a relatively younger provenance; whereas, the Rewa and Bhander groups of both the sectors appear to have shared geochemically similar provenances. Unlike its counterpart in the eastern sector, the provenance of the sediments in the western sector had remained constant across the supposedly 400 million years break in sedimentation between the Lower and the Upper Vindhyans. However, a change in the provenance is observed during the transition from the Kaimur to Rewa group in the western sector which we infer to be a break in the deposition.