GONDWANA SEDIMENTATION IN THE CHINTALAPUDI SUBBASIN GODAVARI VALLEY, ANDHRA-PRADESH

A 3000 m thick Gondwana lithic fill consisting of multifacies associat ions were preserved in a NW-SE oriented intracratonic Chintalapudi sub -basin set across the Eastern Chat Complex (EGC). Sedimentation commen ced with the deposition of diamictite-rhythmite sequence of the Talchi r Formation in glacio-lacustrine environment. The succeeding sandstone -coal cyclothems of the Barakar Formation were formed in fluvial-coal swamp complex. The fluvial streams flowed across the EGC, originating somewhere in the southeast beyond the East Coast of India. Phase wise upliftment of the EGC during Mesozoic imparted changes to the Permian intercontinental drainage system which started supplying increased amo unt of detritus to the basin. Basin marginal faults were first formed at the beginning of Triassic. Alluvial fans originated in the east and southeast and northwesterly flowing braided streams deposited the con glomerate sandstone sequence of the Kamthi Formation. The Early Jurass ic uplift of the Mailaram high in the north imparted westerly shift to the braided rivers during the Kota sedimentation. Due to prominence o f Kamavarapukota ridge in the south by Early Cretaceous, the drainage pattern became centripetal and short-lived high sinuous rivers debouch ed into the basin. The silting up of the Chintalapudi sub-basin with t he sandstone-claystone sequence of the Gangapur Formation marks the cu lmination of the Gondwana sedimentation, perhaps, coinciding with the breakup of India from the Gondwanaland.