The Structural Evolution of the Barmer Basin, Northwest India, and the Regional Context of the Rift: Insights From Linked Outcrop and Subsurface Investigations

Abstract

The structural evolution of the Barmer Basin and the context of the rift within the northwest Indian region are poorly understood, despite the rift being a prolific oil and gas province (7.3 BBL of STOIIP). Situated at the northern end of the West Indian Rift System, a substantial subsurface dataset acquired during hydrocarbon exploration within the Barmer Basin provides an unrivalled tool to investigate Barmer Basin rift evolution and the tectonic evolution of the northwest Indian region. In this work we present a structural and stratigraphical analysis of the Barmer Basin covering the outcrop and seismic scales to investigate the structural evolution of the Barmer Basin, and to place the findings within the context of the northwest Indian region. Two non-coaxial extensional structural regimes are exposed at outcrop on opposing rift margins of the Barmer Basin. Rift-perpendicular (≈ NE-SW) extension exposed along the western rift margin is demonstrably Paleocene in age and corresponded to the main episode of rifting within the Barmer Basin. However, a previously unrecognised rift-oblique (≈ NW-SE) extensional event exposed along the eastern rift margin is poorly age constrained, and is suggested to have occurred during the mid-Cretaceous. Expansion of the investigation into the subsurface substantiates that rift-oblique extension preceded rift-perpendicular Paleogene extension. The present day structural architecture of the Barmer Basin, therefore, resulted from the superimposition of two non-coaxial extensional events. Our results demonstrate active rifting throughout northwest India prior to the Cretaceous-Paleogene boundary and eruption of the Deccan Traps. Although, poorly age constrained, extensional events observed in the Barmer Basin can be correlated with regional tectonic processes. Mid-Cretaceous NW-SE 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 NE-SW extension throughout northwest India. The presence of Mesozoic rift-oblique sub-basins obscured beneath the Barmer Basin, and the improved understanding of structural geometries with proven trapping potential, are important considerations for ongoing hydrocarbon exploration within the Barmer Basin.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015