Geodynamic events leading to formation of passive western continental margin of India

Abstract

The geodynamic events of continental breakup and origin of northwest Indian Ocean led to the development of passive continental margin, off western India. However, causal mechanisms and relative chronology of these geodynamic events are not clearly known because of complex regional-scale ridges-basin physiography, multi-stage rifting in a short-time span and thick sediment cover. The Laxmi and adjacent Gop basins constitute key tectonic elements and geophysical investigations on them have come up with sharply divergent explanations of continental rifting and ocean spreading. We present geochemical results of the Laxmi Basin (LB) basement, recovered by the International Ocean Discovery Program Expedition-355 and interpreted in light of existing geophysical results. The basement is identified as continental rift basalt, different from the Deccan/Madagascan basalts. We suggest the basement eruption at ~75 Ma causing igneous underplating which triggered the extension/rifting in Laxmi and Gop basins. The rifting translated into ocean spreading only in the Gop Basin and not in the Laxmi Basin. The geodynamic events echoed soon with similar relative chronology in western India with Reunion plume impact and the Deccan eruption followed by second extension/rifting that culminated in India-Seychelles breakup.