Tectonics and Geodynamics of a Narrow Continental Rift: Barmer Basin, Rajasthan, India

The Barmer petroliferous basin in W Rajasthan (India) is ~ 50 km wide and ~ 200 km long trending NNW. The Barmer basin experienced a two-phase (NW–SE followed by NE–SW) extension during Early Cretaceous and Late Cretaceous-Paleocene times. It consists of fluvial to shallow marine sediments deposited between Jurassic to Miocene, with some distinct hiatus in between. Late Proterozoic Malani igneous suite/Malani rhyolite is the basement rock. The western margin rift shoulder consists of Malani basement isostatic flexural uplifts, while the eastern margin comprises thick sedimentary cover and is fault-bound. The objective is to understand the rift kinematics, structural inheritance and the type of deformation from field based studies. We carried out structural field studies along the rift margins that helped in deciphering the two-phase (NW–SE followed by NE–SW) extension through brittle shear tectonics. Cross-cutting relation among the NW and NE fault planes connotes the relative timing of the two extension phases. Other key observations from field studies are (1) presence of mega-scale transfer zones along the N margin of the basin, (2) NW trending rift faults inherited the pre-existing structures, (3) variation in strike and crosscutting nature of fault planes in eastern and western rift margins. Paleostress analysis further interprets the stress regime and relative timing of the tectonic events. Thus, the analysis helps in deciphering the rift evolution and the type of extensions related to tectonic inheritance.