Diagenesis and genesis of clay minerals in the Triassic sandstones of the Panchet and Parsora formations, Damodar–Son Basin, India

Abstract

The Triassic sandstones of the Panchet and Parsora formations are deposited in the Damodar and Son basins of the Peninsular India. Though both the formations have similarity in depositional and lithification processes, their diagenetic history and authigenic clay minerals formation have little differences. To improve understanding of diagenesis and associated clay minerals, the present study examined in Triassic sandstones. The Lower Triassic Panchet sandstones are poorly sorted arkose and originate from nearby granitoid terrain. The early diagenetic assemblages of the sandstones are kaolinite–iron oxide, montmorillonite, quartz and cement in the sandstones formed in oxy-acidic environment under shallow burial condition. Authigenic chlorite and recrystallised interstitial components such as orthomatrix are the main late diagenetic products formed, respectively, at oxy-acidic and reducing alkaline conditions where carbonate and allogenic iron cements were emplaced as the latest events. The Panchet and the Parsora formations are the riverine Triassic deposits and have almost identical early diagenetic assemblages. The kaolinisation in sandstone is loss of feldspar and is more pronounced in the Parsora Formation. The late diagenetic products in both the formations essentially similar and differ only in their relative chlorite content, which was formed under elevated temperature as an effect of tectonic activity. Allogenic iron and carbonate cements are post-tectonic.