Facies Analysis, Petrography, heavy mineral analysis of paleo-Mesozoic sediments of Eastern India: Implications on provenance and basin evolution

Gondwana Basins of eastern India preserves sediment record from Carboniferous to Triassic, which were possibly sourced partially from Antarctica through a radial drainage system. This study attempts to test the hypothesis regarding source of sediments based on petrographical and mineral chemical analysis of siliciclastic Paleo-Mesozoic sediments of eastern India. We present an integrated provenance and paleodrainage analysis on the sediments of Bokaro and Raniganj basins, outcrops of which occur along E-W trend along eastern part of India. The sedimentation in these Gondwana basins initiates with basal Talchir Formation, consisting of alternation between conglomerate and fine- to medium-grained sandstones, and is succeeded by Barakar-Barren Measures-Raniganj and Panchet Formation with sandstone-mudstone alternation, with or without coal.  Petrographic study of sandstones reveals moderate sorting, with angular to sub-rounded quartz and feldspar and rounded to well-rounded lithic fragments; however, the abundance of lithic fragments drastically reduces from Talchir to Panchet formation. Feldspar grains shows the dominance of K-feldspar over plagioclase.  Most of the sandstones are classified as feldspatho-quartzose arenite. The Qm-F-Lt plot indicates that these sandstones were derived primarily from transitional continental sources. Heavy minerals in sandstones include garnets, tourmaline, epidote, rutile, zircon, monazite in order of decreasing abundance. Mineral chemistry of garnet in sandstones points their source to metasedimentary amphibolite facies rocks and granitoid. The tourmaline mineral chemistry suggests the derivation of sediments from various sources, including Li-poor granitoids associated with pegmatites, aplites and Ca-poor metapelites. Rutile chemistry in sandstones indicates the predominance of metapelitic source over metamafic source. Insights from heavy mineral analysis indicates that the Gondwana sediments were derived from multiple sources, and such variation in sources bears information about paleogeographic and paleotectonic evolution of the depositional basin.  The mineral composition of source rocks and paleocurrent data tracks the source of sediments to Eastern Granulite-Schist belt and the Eastern Ghat mobile belt, situated to the east and southwest parts of the Gondwana succession.  This study when integrated with geochronological data would reveal the extent to which a particular source provided sediments to these basins, evolution of sediment sources from bottom to top and ultimately will lead to a refined understanding of timing and evolution of East Gondwana assembly.