Dynamic Uplift of the Indian Peninsula and the Réunion Plume.

The Deccan Traps are one of the largest Continental Flood Basalt Provinces in the world. Radiometric dates and magnetostratigraphy of the basalts show that they were emplaced in a remarkably short time across the Cretaceous-Tertiary Boundary. This vast pile of basalt has been studied in much detail, but very little is known about the dynamic effects of the plume on surface elevation. Long wavelength free-air gravity and topographic highs, such as in the southern Indian Ocean are produced by convective upwelling in the mantle beneath. Adjacent sedimentary basins and catchment areas are thought to be sensitive to the dynamic uplift caused by mantle upwelling which can induce hundreds of metres of vertical motion. Here, I analyse the effects of the Deccan plume on sedimentation patterns on the Indian peninsula. At the end of the Cretaceous, the Réunion plume lay beneath the north-western part of the Indian peninsula. Increased mantle temperatures due to the plume and lithospheric thinning as a consequence of the rifting off of the Seychelles Bank caused massive mantle melting, producing the Deccan Traps. Subsidence analysis of well log data from Krishna-Godavari and Cauvery Basins on the east coast and Kutch Basin in the north-west record several hundred metres of transient uplift, from the Maastrichtian until the late Paleocene. Solid-sediment flux measurements from Krishna-Godavari and Cauvery Basins indicate a three- to five-fold increase in sediment input in the Late Campanian - Early Maastrichtian. This is related to an increase in topography across the catchment areas. High sediment yields persisted into the Eocene. Contemporaneously, the sedimentary facies distribution across the basins radically changed. A deep marine regime is replaced by much shallower water conditions and the progradation of the deltas of the proto-Godavari, Krishna and Cauvery Rivers begins. Temporary uplift, synchronous with the extrusion of the Deccan basalts is related to the dynamic doming of the NW Indian peninsula above the Réunion plume. Proximal sedimentary basins indirectly record these epeirogenic events caused by mantle convection.