RELATIONSHIP OF THE CAMBAY RIFT BASIN TO THE DECCAN VOLCANISM

The Cambay rift basin in northwestern India is one of the three basins that originated between the early Jurassic and Tertiary, during India 's drift after the break-up of Gondwanaland. The thickness of the Quat ernary and Tertiary sediments in some parts of the basin varies betwee n 3000 and 5500 m. These sediments are underlain by the Deccan trap vo lcanics which form the basement of the Tertiary sediments. The presenc e of a high velocity lower crust and crustal thinning across the Camba y basin are in agreement with the geochronological model of volcanic a ccretion for the Deccan traps. The large thickness of volcanics in the Cambay basin, estimated to be between 1000 and 3200 m, and their rapi d eruption suggest that the Cambay rift originated in late Cretaceous. Large post-volcanic subsidence of the rift is evidenced by the presen ce of up to 4000 m thick Tertiary sediments which were deposited in va rious phases of basin development. The first phase of basin subsidence appears to be associated to the rapid withdrawal of the magma from th e Reunion mantle plume due to the proximity of the Cambay rift to the axis of the plume.