Bathymetric highs in the mid-slope region of the western continental margin of India-Structure and mode of origin

Abstract

Analysis of the multi- and single beam bathymetric, seismic, magnetic and free-air gravity (ship-borne and satellite derived) data from the western continental margin of India between 12°40' N and 15°N had revealed the presence of several flat topped NNW-SSE trending bathymetric highs of considerable areal extent, 256 to 1165 km² area each at base. They are interspersed by bathymetric lows, thereby, forming a chain of horst and graben structures covered by thick sediments. 2-D modeling of the gravity and magnetic anomalies constrained by seismic results (reflection and refraction) had indicated ~23 km thick crust consisting of 2 to 3 km thick sediments, and a thin basaltic and granitic layer. The model has brought into focus the presence of mantle based volcanic plugs. Their geomorphological and geophysical expressions and structural pattern and associated deep-seated faults led to suggest continental crust. These features are inferred as rifted fragments of the western continental margin of India formed during its northward movement. They were subjected to sub-aerial erosion during the Paleogene due to lowered sea levels resulting in flat tops. Subsequently they were submerged to the present depths in the Neogene. The basic tectonic process appears to be regional.