Geological and Geophysical Manifestations of the Reunion Plume-Indian Lithosphere Interactions-Evidence from Northwest India

A number of geological and geophysical features have been recorded in western Rajasthan and in the Kachchh (nee Kutch) region of northern Gujarat, northwest Indian Shield, which evolved during a short span across the K-T boundary. The features include, besides the extensive Deccan Trap related volcanicity, the formation of rift basins, the emplacement of magma plutonism of diverse petrochemical types, the development of the E-W and N-S trending fracture systems, the formation of structural domes due to magma diapirism, and the occurrence of isolated patches of positive Bouguer gravity anomalies and zones of high-heat flow. A critical analysis of all these features point towards a common origin resulting from the impingement of Reunion Plume at the base of the Indian lithosphere. The formation of these interrelated features across the K-T boundary is incidental to the fact that it was around this time that the plume-head remained focussed under this part of the Indian lithosphere. The importance of bolide impact at the K-T boundary lies only in the intensification of the existing plume activities.