Implications of Late Palaeozoic postglacial marine transgressive‐regressive (T‐R) cycles recorded in the Talchir Formation, Son Valley Basin, peninsular India: A sequence stratigraphic paradigm

Abstract

The signature of Late palaeozoic glaciation, a pan‐Gondwanaland palaeoclimatic event, is recorded in the Talchir Formation (Late Carboniferous to Early Permian), the basal‐most litho‐unit within the Gondwana Supergroup (Late Carboniferous–Early Cretaceous) in peninsular India. About 200 m thick sedimentary succession of the Talchir Formation, exposed in the Hasdeo River section in the Son Valley Basin, Central India, manifests signatures of deposition by melting of glaciers near to the ice‐grounding line. Evidence of glacial influences is prevalent in the lower‐middle part of the succession and represented by glacial tillites with faceted/striated gravels and bullet‐shaped clasts, dropstones and ice‐rafted debris (IRD), associated with various sediment gravity flow deposits. In the middle‐upper part of the succession, records of post‐glacial marine incursions are preserved as thick sandstone and sandstone‐mudstone heteroliths of a shallow marine shore‐shelf depositional regime. These are characterized by abundant tidal and wave signatures, with marine bivalve fossils and trace fossils of marine invertebrates. The upward decrease in size and abundance of the IRDs indicates a gradual decrease in glacial influences, with landward incursion of the marine depositional systems over the proglacial systems. Multiple stacked progradational and retrogradational stratal stacking patterns formed by alternating glacigenic and marginal marine dominated processes signify multiple transgressive‐regressive (T‐R) cycles, manifesting repeated advancements and retreats of the glacier, associated with sea level rise and marine incursions into the land. The top part of the succession, characterized by fine‐grained siltstone/mudstone without any IRD, suggests sedimentation at a relatively deeper part of the basin, indicating the strong influence of the eustatic rise caused by significant melting of the retreating ice sheet. Stacked T‐R cycles bounded by distinct facies architecture define multiple system tracts confined within three major deglaciation sequences within the studied Talchir Formation, suggesting multiple phases of advance‐retreats of the ice sheet and significant marine onlaps within the continental Gondwanaland under the Late Palaeozoic icehouse‐greenhouse climatic change.