The seismic structure of the Saurashtra crust in northwest India and its relationship with the Réunion Plume



The Saurashtra Peninsula in northwest India, lying at the northern boundary of the Deccan Volcanic Province, is almost entirely covered by these volcanics. Analogue seismic refraction/wide-angle reflection data along a 160 km long profile, from Navibandar to Amreli, were collected during 1977 to determine the crustal configuration. Reprocessing of these data, after digitization, has yielded a crustal model that is significantly different from the earlier model of Kaila et al. The model shows the upper crust down to a depth of 16 km in the west and 13 km in the east and underplating (velocity of 7.20 km s−1) of the lower crust. The Moho is at a depth of ∼36 km in the western part and at 32–33 km in the eastern part; the change of depth is quite sharp almost in the middle of the profile. Similar depth changes are seen in other crustal horizons indicating a deep fault that is in line with the extension of the Proterozoic Aravalli trend in to the Saurashtra Peninsula. The crustal structure in the eastern part is similar to that in the Cambay Basin and indicates that the crust to the east of the proposed fault is uplifted. The uplifted region extends as far as another arm of the Aravalli trend that turns eastwards. Crustal underplating in large parts of western India is confined to the corridors affected by the passage of India over the Réunion Plume in the Late Cretaceous. The shallower Moho appears to be confined to the areas close to the axis (trace of the plume) on Earth's surface of the plume.