Marine geophysical studies off Karwar, West Coast of India

Abstract

Geophysical studies of the southwestern continental margin revealed significant surface and subsurface topographic highs (ridges) trending NNW-SSE to NW-Se beyond the shelf break. Residual magnetic anomaly map depicts prominent NNW-SSE, NW-SE and E-W trends. The magnetic anomaly map also reveals three different provinces, A, B and C, based on magnetic signatures, confined to inner shelf, outer shelf and lower shelf. A prominent E-W trending structural lineament with a NW-SE trending offset is observed cutting across the inner shelf and the lower shelf. Model studies of the geopotential data over the topographic rise indicate about 18 km thick mafic basement of continental origin at a shallow depth (~800 m). The gravity model studies indicate a thick consolidated sediment layer deposited over the horst and grabenlike features within the granitic layer. The occurrence of ridges parallel to the shelf edge shows the similarity of the western Indian continental margin with the outer typical and extensively studies passive margins