Collision tectonics of the Central Indian Suture zone as inferred from a deep seismic sounding study

The Central Indian Suture (CIS) is a mega-shear zone extending for hundreds of kilometers across central India. Reprocessing of deep seismic reflection data acquired across the CIS was carried out using workstation-based commercial software. The data distinctly indicate different reflectivity characteristics northwest and southeast of the CIS. Reflections northwest of the CIS predominantly dip southward, while the reflection horizons southeast of the CIS dip northward. We interpret these two adjacent seismic fabric domains, dipping towards each other, to represent a suture between two crustal blocks. The CIS itself is not imaged as a sharp boundary, probably due to the disturbed character of the crust in a 20 to 30-km-wide zone. The time sections also show the presence of strong bands of reflectors covering the entire crustal column in the first 65 km of the northwestern portion of the profile. These reflections predominantly dip northward creating a domal structure with the apex around 30 km northwest of the CIS. There are a very few reflections in the upper 2–2.5 s two-way time (TWT), but the reflectivity is good below 2.5 s TWT. The reflection Moho, taken as the depth to the deepest set of reflections, varies in depth from 41 to 46 km and is imaged sporadically across the profile with the largest amplitude occurring in the northwest. We interpret these data as recording the presence of a mid-Proterozoic collision between two micro-continents, with the Satpura Mobile Belt being thrust over the Bastar craton.