Petrography and Geochemistry of Proterozoic Clastic Sediments of Naragund, Karnataka:Implications for their Provenance and Tectonic Setting

The Proterozoic clastic sediments exposed at Naragund, Karnataka belongs to the Kaladgi Group, which are unconformably under lain (Eparchean unconformity) and surrounded by Archaean gneiss. The rocks are characteristically bedded with individual beds having variable thickness. Based on the color variation, four varieties of quartz arenite have been distinguished as the grey, white, red and pink quartz arenites. The primary sedimentary structure like stratification, ripple marks, current bedding and graded bedding are commonly seen in the study area. The petrographic analysis has revealed that the clastic sediments are quartz-rich and were primarily derived from felsic sources. The chemical composition of 10 quartz arenite samples corroborates the petrographic observations. The provenance and geodynamic studies indicate that the clastic sediments were derived predominantly from felsic source region and were deposited in a passive margin type tectonic setting.