Structure and tectonics of the continental margins of India and the adjacent deep ocean basins: current status of knowledge and some unresolved problems

The Indian Ocean and the bordering continental margins are characterized by a number of tectonic features consisting of deep ocean basins, aseismic ridges/submarine plateaus and seamounts. Marine geophysical studies carried out over these regions for the past four decades have led to an increased understanding of the formation and evolution of these features. The present paper synthesizes an up-to-date compilation of the results of the salient inferences of those studies to describe the structure and tectonic evolution of these features as well as the Indian Ocean in general. A review of the existing know ledge on the structure and tectonics of the continental margins of India and the adjacent ocean basins reveal the existence of several unresolved problems, primarily due to the inherent tectonic complexities or the paucity of adequate data. Some of the major problems that need to be addressed/examinedare : the existence and extent of the Prathap and Kori-Comorin ridges; the locations of the continent-ocean boundaries around the continental margins of India; the timing of formation of the deep offshore regions adjacent to the Indian continental margins; the deeper crustal structure and trend of the 85 degrees E Ridge; the crustal configuration as well as the extent of the postulated micro-continental slivers; and the cause of intense seismicity over the Chagos Bank segment of the Laccadive-Chagos Ridge. In addition to addressing these questions, the present paper suggests ways to go forward by acquiring high-resolution and deep penetration multichannel seismic reflection data, seismic refraction data using Ocean Bottom Seismometers (OBS) and closely spaced sea-surface and deep-tow magnetic profiles along with high-resolution seafloor mapping.