Sedimentary Facies and Paleoenvironments of Deposition of the Tipam Sandstone formation, Chandraghona-Boraichari Area of the Sitapahar Hill Range, Chittagong Hill Tracts, Bangladesh

The Mio-Pliocene Tipam Sandstone Formation is well exposed in the Sitapahar Hill Range in Chittagong Hill Tracts, Bangladesh. Stratigraphically the rock sequence along the Chandraghona to Boraichari road-cut section consists of alteration of yellow to brownish yellow, very fine sandstone, siltstones,silty shale and gray to bluish gray shale with occasionally decomposed layers in varying proportion. Two facies associations recognized in the area are (a) medium to fine grained sandy-silty facies association FAS and (b) the silt-clay facies association or heterolithic facies association, FAHL. The facies characteristics suggest that the deposition was restricted within estuary to tidal channels in FAS and very shallow water condition as well as mainly tidal flat to tidal marsh environment in FAH. The dominantly bi-directional and bi-polar paleocurrent charactenstics strongly support presence of tidaI action in the Tipam Sandstone Formation in the study area.