A review and new data on neotectonic evolution of active faults in the Kachchh Basin, Western India: legacy of post-Deccan Trap tectonic inversion

Abstract

AbstractThe Kachchh Basin, located in Gujarat (India) at the western trailing edge of the Indian plate, comprises several east–west trending seismically active faults. The Kachchh Basin evolved in two major stages. The first is the rift stage, which correlates with the break-up and separation of the Indian plate in the Late Triassic–Early Cretaceous and synrift sedimentation. The second is the post-Deccan Trap inversion stage, when the basin was periodically uplifted along the existing east–west trending intrabasinal master faults: the Katrol Hill Fault, the Kachchh Mainland Fault, the South Wagad Fault, the Gedi Fault and the Island Belt Fault. The inversion of basin was initiated by the onset of a compressive stress regime in response to the collision of the Indian plate with the Eurasian plate in the far north during the Early Eocene. This is shown by the tilting of the Deccan Trap lava flows along with the underlying Mesozoic sequence and the associated intrusive bodies that occupy the core portions of domal and anticlinal flexures bounded by major fault lines. Seismotectonic data on the prolonged aftershock sequence after the 2001 Bhuj earthquake (Mw 7.7) reveal continuous low-to-moderate seismic activity along multiple faults covering a large area, now identified as the Kachchh Seismic Zone. This article reviews the neotectonic perspective of the active faults with the prime objective of delineating the post-Deccan Trap inversion phase of the Kachchh Basin, with an emphasis on neotectonism with regard to modern seismic activity. The datasets presented are primarily field-based neotectonic data from active fault zones that cover aspects of the tectonic geomorphology, Quaternary stratigraphy, near-surface fault traces and the nature of the fault in the shallow subsurface based on ground-penetrating radar studies. We also attempt a comparative neotectonic evaluation of each active fault in the Kachchh Basin and discuss the constraints for evolving a viable neotectonic model of the basin.