Tectonics of the Bay of Bengal: new insights from satellite-gravity and ship-borne geophysical data

Recently released satellite-derived free air gravity anomalies and the exis ting ship-board geophysical data provide new insights into the tectonics of the Bay of Bengal with respect to the structure and regional extension of the buried 85 degrees E ridge and the tectonics of the Eastern Continental Margin of India (ECMI). The 85 degrees E ridge can be visualized extending inland via the Mahanadi basin volcanics to the Rajmahal Traps. A large volc anic province in eastern India encompassing the Rajmahal and Sylhet Traps a nd volcanics in the Bengal and Mahanadi basins, almost on the scale of the Deccan volcanic province along the west coast, can be envisaged taking into account the occurrences of intrusive and extrusive rocks around the age of 117 Ma. The 85 degrees E ridge represents the deep-ocean volcanic trace of this magmatic activity. Towards the south, the ridge continues in an arcua te manner to the Afanasy-Nikitin seamount at equatorial latitudes in the ce ntral Indian Ocean. Gravity models of the ridge are indicative of hotspot-r elated crustal underplating processes beneath the ridge. The ECMI can be di vided into a southern transform and northern rifted segments on the basis o f gravity and bathymetry data, which bear similarities with the conjugate E ast Antarctica margin. (C) 1999 Elsevier Science B.V. All rights reserved.