Controls of allogenic factors on the development of fluvial sequence stratigraphic architecture: A case study
ABHIRUP SAHA BIPLAB BHATTACHARYA
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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.
ABHIRUP SAHA BIPLAB BHATTACHARYA1
Volume 132, 2023
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