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<p>The Pliocene Tipam Sandstone Formation in the Eastern Fold Belt (EFB) of the Bengal Basin, provides critical insights into fluvial depositional systems within an active foreland basin setting. This study provides a detailed analysis of lithofacies to reconstruct depositional environment and tectonic controls on sedimentation. Nine lithofacies were identified, and grouped into three facies associations: (1) fluvial channel sand bodies (FA 1), dominated by large-scale trough (St) and planar cross-bedding (Sp), indicative of braided river systems; (2) channel fill deposits (FA 2), characterized by ripple cross-lamination (Sr) and laminated fine sandy-silty mud (Fl), reflecting waning flow conditions and channel abandonment; and (3) floodplain deposits (FA 3), consisting of laminated sandy-silty mud (Fl) and massive mudstone (Fm) with desiccation cracks, suggesting overbank deposition with intermittent drying phases associated with a monsoon-controlled climatic regime. The predominance of high-energy fluvial facies, coupled with coarse lag deposits and erosional bases, points to a proximal sediment source and rapid subsidence associated with the uplift of the Himalayas and the IBR. The absence of deltaic influences indicates a fully terrestrial depositional environment during the Pliocene, marking a significant shift from the earlier Miocene shallow marine-deltaic conditions. These findings underscore the role of tectonics in shaping fluvial depositional systems in the Bengal Basin and contribute to a broader understanding of foreland basin evolution in collisional settings.</p>

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Fluvial depositional systems of the Pliocene Tipam Sandstone Formation in the Eastern Fold Belt of the Bengal Basin (Bangladesh): Insights from lithofacies analysis

  • 期刊论文

  • 发表日期：

    2026年4月11日

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  • Abu Sadat Md. Sayem

摘要

The Pliocene Tipam Sandstone Formation in the Eastern Fold Belt (EFB) of the Bengal Basin, provides critical insights into fluvial depositional systems within an active foreland basin setting. This study provides a detailed analysis of lithofacies to reconstruct depositional environment and tectonic controls on sedimentation. Nine lithofacies were identified, and grouped into three facies associations: (1) fluvial channel sand bodies (FA 1), dominated by large-scale trough (St) and planar cross-bedding (Sp), indicative of braided river systems; (2) channel fill deposits (FA 2), characterized by ripple cross-lamination (Sr) and laminated fine sandy-silty mud (Fl), reflecting waning flow conditions and channel abandonment; and (3) floodplain deposits (FA 3), consisting of laminated sandy-silty mud (Fl) and massive mudstone (Fm) with desiccation cracks, suggesting overbank deposition with intermittent drying phases associated with a monsoon-controlled climatic regime. The predominance of high-energy fluvial facies, coupled with coarse lag deposits and erosional bases, points to a proximal sediment source and rapid subsidence associated with the uplift of the Himalayas and the IBR. The absence of deltaic influences indicates a fully terrestrial depositional environment during the Pliocene, marking a significant shift from the earlier Miocene shallow marine-deltaic conditions. These findings underscore the role of tectonics in shaping fluvial depositional systems in the Bengal Basin and contribute to a broader understanding of foreland basin evolution in collisional settings.