The early-stage structural evolution of the Barmer Basin rift, Rajasthan, northwest India

Abstract

The structural evolution of the Barmer Basin and the context of the rift within the northwest Indian region are poorly understood, despite being a prolific hydrocarbon province. In this work an integrated basin analysis is presented covering the outcrop-, seismic-, and lithosphere-scales. The early-stage structural evolution and the origin of poorly understood structural complications in the Barmer Basin subsurface are assessed. Subsequently, the findings are placed within the wider context of the northwest Indian region and the implications for continued hydrocarbon exploration within the Barmer Basin are discussed.
Two non-coaxial extensional structural regimes are exposed at outcrop. Rift-perpendicular (˜ northeast-southwest) extension is demonstrably Paleocene in age and corresponded to the main episode of rifting in the Barmer Basin. A previously unrecognised, rift-oblique (˜ northwest-southeast) extensional event is poorly age constrained, and is suggested to have occurred during the Lower Cretaceous Epoch. Expansion of the investigation into the subsurface substantiates that rift-oblique extension preceded rift-perpendicular extension. The present day structural architecture of the Barmer Basin, therefore, resulted from the superimposition of two non-coaxial rifting events. Further structural analyses and lithosphere-scale forward modelling demonstrate that structural complications in the Barmer Basin subsurface arise from structural inheritance, and lithosphere flexure may have been substantial during Paleogene rifting.
The results demonstrate active rifting throughout northwest India prior to the Cretaceous-Paleogene boundary and eruption of the Deccan Traps. Lower Cretaceous (northwest-southeast) extension within the Barmer Basin may be an intra-continental manifestation of transtension between the Greater Indian and Madagascan continents during Gondwana fragmentation. Subsequently, relocation of the plate boundary between the Greater Indian and African continents in the wake of the rapidly migrating Greater Indian continent initiated northeast-southwest extension. Mesozoic sub-basins and the improved understanding of structural geometries with proven trapping potential are important considerations for ongoing hydrocarbon exploration within the Barmer Basin.