Articles written in Journal of Earth System Science
Volume 131 All articles Published: 3 June 2022 Article ID 0134 Research article
Evidence of the Permian marginal marine sedimentation recorded in sub-surface drill cores, Lower Gondwana successions, southern India
ABHIRUP SAHA SNEHASIS CHAKRABARTY BIPLAB BHATTACHARYA
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.
$\bullet$ 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.
Volume 132 All articles Published: 2 February 2023 Article ID 0025 Research article
Controls of allogenic factors on the development of fluvial sequence stratigraphic architecture: A case study
ABHIRUP SAHA BIPLAB BHATTACHARYA
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.
$\bullet$ 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.
Volume 132, 2023
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