Subsidence and isostasy along a sheared margin—Cauvery Basin, Eastern Continental Margin of India



We have applied a process-oriented method to a seismo-geological section across Cauvery Basin, a sedimentary basin along the southern part of the Eastern Continental Margin of India (ECMI) to examine the isostatic mechanism operating beneath the margin. The evolution of the ECMI appears to be within a shear-rift tectonic setting, mainly driven by the difference in the relative motions of India and East Antarctica and the subsequent direction of spreading and the Cauvery Basin seems to have formed in this pull-apart tectonic setting. Shearing along the southern ECMI is modeled with gravity anomalies and the resultant crustal configuration, through various models of isostasy. Backstripping analysis suggests a very low Te of 3 km beneath the basin. The shelf edge gravity anomaly reflects a strong contrast across a wrench fault parallel to the coast inferred from gravity forward modeling, denoting coast-parallel transform motion in the initial stages of continental separation prior to rotation and spreading.