Evidence of extension at the southwest continental margin of India and opening of the Laccadive Basin: Constraints from geophysical data

Abstract. Previous geophysical investigations of the Western Continental Margin of India (WCMI) confirm the double breakup history of the margin with the first breakup taking place between India and Madagascar in Late Cretaceous, and the second breakup event in early Paleocene with Seychelles separation from India. Despite numerous geoscientific studies along the WCMI, the southern part of the margin, which is known to be the conjugate segment of the Madagascar, has been least studied. In this study, we evaluate the multi-channel seismic reflection and gravity anomalies at the margin to identify the early rift signatures in conjunction with the magnetic anomaly identifications in the Mascarene Basin. The analysis led to the identification of two extensional directions, a ENE-WSW oriented extension over the Laccadive Ridge north of Tellicherry Arch, and the NW-SE extension in the Laccadive Basin region towards south. Plate reconstruction models of the Mascarene Basin suggest the ENE-WSW extension observed over the Laccadive Ridge could be related to the India-Madagascar separation. However, the sediment deposition pattern and the presence of Paleocene trap associated with the NW-SE extensional grabens observed in the Laccadive Basin region has been attributed to the post-breakup extension between the Laccadive Ridge and the West coast of India. We further propose that the anti-clockwise rotation of India and the passage of the Reunion plume have facilitated the opening of the Laccadive Basin.