Provenance signature and tectonic setting of the Pliocene Tipam Sandstone Formation from the Chittagong Tripura Fold Belt of the Bengal Basin

The Pliocene Tipam Sandstone Formation is widely exposed in various structures of the Chittagong Tripura Fold Belt in the Bengal Basin. Petrography and major element geochemistry of sandstones from this formation have been examined to infer their provenance signature and tectonic setting. The average modal (Q 77 F 11 L 12 ) composition and geochemical results reveal that the Tipam sandstones are classified as litharenite to sublitharenite and lithic subarkose. The higher ICV (> 1) values and the negative correlation between SiO 2 /Al 2 O 3 and total quartz (Qt) indicate that the investigated sandstones are compositionally immature. The petrographic and geochemical provenance discriminant diagrams suggest a recycled sedimentary provenance, with sediments derived predominantly from felsic igneous sources. The weathering indices, including the CIA (Chemical Index of Alteration), PIA (Plagioclase Index of Alteration), CIW (Chemical Index of Weathering), and A–CN–K [Al 2 O 3 − (CaO * + Na 2 O) − K 2 O], (A–K)–C–N [(Al 2 O 3 –K 2 O) − CaO * − Na 2 O)], A–CNK–FM [Al 2 O 3 –(CaO * + Na 2 O + K 2 O) − (Fe 2 O 3 + MnO)], and MFW [Mafic–Felsic–Weathering] models, indicate a weak to moderate degree of chemical weathering. The paleoclimate model reflects a sub-humid climate condition in the source area. The results imply that the Tipam Sandstone Formation accumulated in an active continental margin context, with the majority of sediments sourced from the Lesser Himalayan Sequence and a smaller portion from the Higher Himalayan Crystalline Sequence, Sub-Himalaya, and Indo-Burma Ranges during the Pliocene.