Composition of Smectites in the Lameta Sediments of Central India: Implications for the Commencement of Deccan Volcanism

The studies on the structural formulae of smectites in the Larneta sediments indicate that they are rich in octahedral Fe, Mg and tetrahedral Al. Identical patterns of Mg, Fe and Al abundances in the octahedral and tetrahedral layers respectively, were also observed in the smectites of intertrappean sediments and weathered Deccan Basalts. The thermodynamic components and charge configurations of smectites in the Lameta, intertrappean and Deccan Basalt indicate that they fall within the compositional plane of smectite solid solution. The compositional commonality of smectite in the Lameta sediments with those in the intertrappeans and weathered Deccan Basalt suggests, Smectites in the Lameta sediments are derivatives of Deccan volcanic products. This implies the commencement of Deccan Volcanism during the Maastrichtian Lameta sedimentation or prior to it.