The sandstone-shale-coal succession of the Barakar Formation (early Permian) of the Raniganj Basin, India hosts low-diversity ichnoassemblages, containing ichnogenera Arenicolites, Chondrites, Diplocraterion, Monocraterion, Ophiomorpha, Palaeophycus, Planolites, Skolithos, Taenidium, and Thalassinoides, produced by shallow marine infaunal invertebrates. Sedimentary facies architecture depicts a transgressive, fluvio-tidal (with a minor wave) interactive estuarine depositional setting. The fluvial deposits, lying beyond the zone of tidal encroachments, record absence of trace fossils, which is attributed to a low colonization window caused by high fluvial discharge and frequent channel migrations. Tidal interactions with high fluvial discharge led to bay-head deltas in the inner-middle estuary with the dominance of suspension-feeding and deposit-feeding ichnotaxa in coarser- and finer-dominated sediments, respectively, suggesting a mixed Skolithos–Cruziana ichnofacies. Increasing tidal influence with very less fluvial input allowed opportunistic colonizers and deposit feeders of the Cruziana ichnofacies to flourish in the central estuarine setting. Intermittent low-oxygenated restricted conditions marked by the chemosymbiotic ichnoassemblages of the Zoophycos ichnofacies indicate very low energy conditions. The outer estuary with increasing wave dominance is inhabited by suspension-feeding, domicile ichnotaxa of Skolithos ichnofacies, frequently mixed with the ichnotaxa of the Cruziana ichnofacies. The recurrent juxtaposition and lateral distribution of the Seilacherian marginal marine ichnofacies is attributed to complex sediment–organism interaction patterns in response to prevalent energy conditions, sediment discharge and substrate conditions in different zones of the fluvio-tidal estuarine setting. The integrated sedimentological-ichnological model signifies marine transgressions that affected the palaeogeography of the Permian continental Gondwanaland.

$\bf{Highlights}$

$\bullet$ Sedimentological–ichnological analysis signifies marine encroachment in Barakar Formation in peninsular India.

$\bullet$ Ichnoassemblages point to complex pattern of sediment–organism interactions with gross energy distribution.

$\bullet$ Sustained marine transgression event within the continental Gondwanaland during early Permian is visualized.

Evidence of marine influences within the Permian Barakar Formation of the Pranhita–Godavari (P–G) Basin and its age equivalent, the Kommugudem Formation of the Krishna–Godavari (K–G) Basin, are previously investigated from the outcrop studies. The present work carefully documents the signatures of tidal and wave influences from the Early Permian rocks, solely based on excellently preserved subsurface drill core samples from both the basins. Tidalites, represented by laterally accreted tidal bundles, tidal rhythmites, tidal beddings, oppositely directed strata bundles, and double mud drapes, are preserved within the sandstone–mudstone heterolithic rocks, signifying deposition predominantly in an upper subtidal–intertidal setting. Association of wave-generated structures with the tidalites are indicative of open marine waves, interacting with the tides in the upper subtidal to intertidal region. Records of such tidal and wave processes unambiguously point to the significant marine influence within the continental setup during the Lower Gondwana sedimentation in both the P–G and the K–G basins during the Early Permian time, which indicates a regional encroachment of the sea onto the land.

$\bf{Highlights}$

$\bullet$ A unique approach to study the tidal and wave signatures within the Early Permian sediments from the Pranhita–Godavari Basin and the Krishna–Godavari Basin using subsurface drill core samples.

$\bullet$ The presence of tidal features such as tidal bundles, tidal rhythmites, tidal beddings, with occurrence of the spring–neap tidal cyclicity within the thinly bedded sandstone–mudstone heterolithic rocks signify sedimentation in upper subtidal-intertidal settings.

$\bullet$ The intercalation of tidal deposits with combined flow and wave-generated structures indicates an open tidal flat setting.

$\bullet$Such features unambiguously point to the presence of marine influence within the continental riftogenic basins during the Early Permian time.

The consideration of events of marine invasion within the continental Gondwanaland in the Indian subcontinent during the Permian is often doubted due to lack of appropriate fossil record. The Permian Barren Measures Formation within the Lower Gondwana Supergroup in eastern India is considered as deposited in a fluvio-marine estuarine setting, interpreted mostly based on sedimentological signatures in terms of marine tide and wave imprints within the so-called continental fluvial deposits. Fossilized shells of marine Gastropoda genus Baylea DeKoninck, 1883, are reported here from the siltstone beds of the prodeltaic sediments of the Barren Measures Formation, West Bokaro Basin. The in-situ preservation of the marine invertebrate fossils Baylea sp. provides definite proof of marine link of the West Bokaro Basin during the Barren Measures sedimentation. The present fossil record, when combined with sedimentological attributes, clearly signifies a marine inland encroachment event during the Permian time.

Control of allogenic mechanisms in the development of stratal architecture within upstream-controlled fluvial depositional systems is poorly understood. The present research examines the scope of the allogenic factors in controlling the stratal stacking patterns in fluvial systems from the siliciclastic succession of the Barren Measures Formation (Permian), Pranhita–Godavari (P–G) Valley, peninsular India. The succession is characterised by a river deposit, with minor tidal influences in the upper part, indicating a fluvial–tidal interactive depositional system. Abundant tidal influences near the top part of the succession suggest landward encroachment of the tidal limit, causing frequent flooding and rising of the fluvial base level. The characteristic stratal stacking pattern resulted in two High Amalgamation Systems Tracts (HAST-1 and -2), indicating autogenic upstream-controlled low-accommodation conditions, each followed by a Low Amalgamation Systems Tract (LAST-1 and -2), indicating low rates of channel amalgamation under higher accommodation space, caused by an interplay of varying rates of tectonic subsidence within a rift basin along with flooding by the encroaching tidal currents. Thus, the prevalent sequence architecture is attributed to the alternate phases of autogenic mechanisms followed by the allogenic mechanisms, including the syn-rift tectonic subsidence and the encroaching tidal currents, in the upstream controlled fluvial depositional systems.

$\bf{Highlights}$

$\bullet$ High-energy river with minor tidal influences within an inland fluvial-tidal system.

$\bullet$ Allogenic process mediated stratigraphic architecture in upstream controlled settings.

$\bullet$ Varying rates of tectonic subsidence created net accommodation space.

$\bullet$ Encroaching tidal currents modified accommodation to sediment supply ratio.