Geochemistry of the Miocene Sandstones of Bhuban Formation of the Surma Group Occurring in and Around Katigorah, Cachar District of Assam, India

Abstract

Geochemical composition (major oxides) of the Miocene Sandstones of Bhuban Formation of the Surma Group exposed in and around Katigorah, Cachar District of Assam was determined to reveal their palaeoweathering, chemical maturity, palaeoclimate, provenance and tectonic setting. Representative samples were analysed for major, minor and trace elements by method. Geochemical classifications show that the sandstones are sublithic to greywacke in composition. The positive correlation between the major elements (oxides) is observed and it suggests the influence of source rock lithology. From the study of palaeoweathering, it is seen that K-feldspar is more in Bhuban Sandstones indicating moderate intensity of chemical weathering in the source area. Regarding chemical maturity, sandstones are slightly matured. The geochemical studies reveal that the climatic condition was arid during that time. It is seen that sandstones are derived mostly from metamorphic and igneous (mostly granite) sources which are present in the adjoining areas. Under tectonic setting, sandstones are mostly of Active continental margin type and Passive margin type and the sediments were deposited in Miocene foreland basin formed due to collision orogen.