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Chapter 17 Sedimentation in the Papaghni Group of rocks in the Papaghni sub-basin of the Proterozoic Cuddapah Basin, India

Abstract The Gulcheru Quartzite (30–200 m thick) overlies Archaean basement rocks, and comprises an impersistent conglomerate at the base of more widespread quartzites, with shale and ferruginous interbeds. The overlying Vempalle Formation (≤1500 m) comprises mainly stromatolitic carbonates, lesser cherts and mudrocks. Together, these two units make up the Palaeoproterozoic Papaghni Group, which displays an arcuate outcrop belt in the SW Cuddapah Basin, bearing no obvious relationship to the tectonic grain in the basement lithologies. Facies defined in the Gulcheru Quartzite are ascribed to initial alluvial fans, which transitioned into a shallow-marine coastline and shelf, as transgression occurred under overall thermal subsidence, possibly related to post-plume thermal relaxation. The shallow siliciclastic Gulcheru shelf is inferred to have evolved to a stromatolitic ramp that accommodated deposition of the Vempalle chemical sediments. The abrupt vertical transition from clastic to carbonate deposits is ascribed to rapid sea-level rise. Late-stage shoreline progradation during uppermost Vempalle times and concomitant clastic inflows terminated the carbonate factory.