The Talchir Formation of Permian age is the lowermost lithostratigraphic unit of the Indian Gondwana successions preserving a record of the Late Paleozoic glaciation that affected the whole Gondwanaland.The formation unconformably overlies the Precambrian basement in all the Gondwana basins of India,and marks initiation of sedimentation after a long hiatus since the Pro- terozoic.The Talchir Formation of the Satpura Gondwana basin of central India shows features diagnostic of deposition under glacial regime such as the presence of diamictites,boulder pavements, bedding plane striation,faceted/striated gravels,bullet-shaped clasts,dropstone,cryoturbation, etc.The Talchir strata of the Satpura basin,in addition to tidal signatures,contain marine bivalve and trace fossils.A proglacial marine environment is thus inferred for their deposition.The dominant lithologies are conglomerate,pebbly sandstone,sandstone and shale with little limestone, which can be classiﬁed into the following major facies:
The conglomerates are interpreted as deposits of a spectrum of sub-aqueous sediment gravity lows including debris flow, hyperconcentrated/concentrated density flow and grain flow. The crossstratified pebbly sandstone bodies, on the other hand, represent braidplain delta deposits of glacial outwash origin. Hummocky, swaley, low-angle cross-stratified sediment bodies were deposited by storm-generated combined flows in a shoreface setting. In contrast, the sheet sandstone bodies are products of turbidity currents and storm-induced density currents in an inner shelf setting below fair weather wave base. The claystone facies is interpreted as a product of suspension fallout from hypopycnal sediment plumes in the outer shelf domain below storm wave base. All the lithofacies described above occur repetitively in the succession. Three facies-associations have been recognized in the Talchir Formation, representing ice-contact fandelta, outwash braidplain delta and a virtually ice-free, non-deltaic open marine realm. The different marine facies of the Talchir Formation define a number of shallowing-upward packages, which are arranged in the succession with a retrogradational trend to result in an overall fining- and deepening-upward succession. The overlying coal-bearing Barakar Formation has been interpreted to have formed in a tide-wave influenced deltaic setting with a marine, prodeltaic part. The strata that are transitional between Talchir and Barakar Formations show preservation of abundant plant materials suggesting gradual warming. The three facies-associations of the Talchir Formation also point towards progressive decrease in the intensity of glacial activity, inducing changes in the paleogeography from ice-contact depositional environment to an eventually relatively ice-free, open marine condition.
Volume 131, 2022
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