Paleodrainage analysis of Paleozoic—Mesozoic Bokaro Basin, East India: implications for East Gondwana assembly

The north—westerly paleocurrent data, mineral chemistry of rutile, garnet, and tourmaline, besides detrital monazite age populations of primarily 500-400 Ma and 1100-900 Ma populations, tracks the proximal source of the Paleo-Mesozoic sandstones in eastern India to Chhotanagpur Gneissic Complex. The major distal sources supplied material to the Assam Meghalaya Gneissic Complex, besides minor sources in Eastern Ghats, East Antarctica, and southwestern Australia. These Paleo-Mesozoic sediments were deposited in the rifted basins of eastern India following the Cambrian Kuungan orogeny, which saw the last phase of East Gondwana assembly. The basal Talchir Formation of Late Carboniferous age initially accumulated immature glacio-fluvial sediments. Climatic amelioration thereafter enhanced chemical weathering, which led to the maturation of the drainage system from the Permian period onward. Sandstone petrography, rutile, tourmaline, and garnet chemistry imply bulk sediment supply from granitoids and metapelitic rocks. Metamafic rocks supplied occasional sediment during the deposition of Barren Measures and the Early Triassic Panchet Formation. The Cambro-Ordovician monazite ages are absent in the Barren Measures sandstones. Such variation confirms differential sediment input from axial and transverse drainages as a function of paleoclimate and paleotectonism. This study, therefore, establishes that Paleo-Mesozoic sediments of eastern India were transported through the axial and transverse drainage systems from a unified East Gondwana that initiated from the Late Carboniferous and continued till the Early Triassic.