Morphotectonics of the southwestern continental margin of India and the adjacent deep offshore regions
BIJESH C. M.*, Yatheesh V., John Kurian P., Twinkle D., Tyagi A.
National Centre for Polar and Ocean Research, Goa
National Centre for Antarctic and Ocean Research VASCO DA GAMA, GOA, India Pincode: 403804 Mobile: 9962876370 E-mail: email@example.com
The Arabian Sea was formed by rifting and drifting among India, Seychelles and Madagascar, along with the microcontinental blocks of the Laxmi Ridge, Laccadive Plateau and Saurashtra Volcanic Platform, since the Late Cretaceous. The relative motions among these continental blocks created the Mascarene, Laxmi, Gop, Arabian, Eastern Somali and Laccadive basins and all these regions were affected by the subsequent geodynamic events such as volcanism caused by the Marion and Rèunion hotspots, and India-Eurasia collision. Therefore, a detailed understanding on the morphotectonics of these ocean basins is important as it appears to carry the imprints of these events. In this perspective, we carried out a detailed marine geophysical investigation in the southwestern continental margin of India and the adjacent deep offshore regions consisting of the Laccadive Basin, Laccadive Plateau and the Arabian Basin to understand the morphotectonic signatures, distribution and probable genesis of the bathymetric high features, using multibeam bathymetry data complemented by sea-surface gravity and magnetic profiles and multi-channels seismic reflection sections. Our updated high-resolution bathymetric map of the study area reveals the presence of large number of distinct bathymetric high features that can be classified as seamounts, hills, knolls, guyots and plateaus. Among these, the prominent are: (a) a total number of 33 bathymetric high features mapped on the southwestern continental margin of India and the adjacent Laccadive Basin; (b) two seamounts connected with structural high/ridge like features, together representing a large circular bathymetric high complex in the Arabian Basin; and (c) the distinct bathymetric highs associated with the Laccadive Plateau. All these features are associated with characteristic gravity highs superimposed over regional negative anomalies and complex negative and positive magnetic anomalies. Interpretation of the multichannel seismic reflection sections suggests that some of these identified features are extrusive in nature, while others are intrusive. In light of the present understanding on the plate tectonic evolution of the study area, we attribute Marion hotspot volcanism for the genesis of features on the southwestern continental margin of India and the Réunion hotspot volcanism for the genesis of features in the Laccadive Basin, Laccadive Plateau and the Arabian Basin.