Tectonic evolution of the seismically active western continental margin of the Indian plate: Implications for kinematic history and fluid flow

The deformation history along the E-W trending Kachchh rift basin at the western continental margin of the Indian plate located in the state of Gujarat, India, has been controlled by activation of NW-SE, NE-SW and E-W trending, 0.25–50 km long oblique-slip and dip-slip faults.

The study is an attempt to establish the kinematic framework along sub-parallel, NW-SE striking group of intra-uplift, striated, high-angle reverse faults, consisting of, Vigodi Fault (VF) and its bifurcation – West Vigodi Fault (WVF), Gugriana Fault (GUF) and its bifurcation – Khirasra fault (KHIF) from the western part of the Kachchh basin in the northern part of Gujarat state in western India. They meet the E-W trending master faults – the Kachchh Mainland Fault (KMF) to the north and the Katrol Hill Fault (KHF) to the south at an acute angle.

Fault-slip data consisting of fault plane and slickenside attitudes along with other kinematic indicators were recorded along the faults at 69 structural stations. A total of 1258 fault-slip data were used to carry out paleostress analysis using Win-Tensor (v.5.8.8) and T-Tecto Studio X5 by executing the Right Dihedral Method.

The NW-SE trending fault system exposes highly porous and permeable deformed sandstones belonging to the Jhuran and Bhuj Formation. The pure compaction bands, cataclastic deformation band clusters, slipped deformation bands and deformation band faults are documented. These tabular structures are densely populated in the fault damage zones of VF, WVF, GUF and KHIF. The field observations related to fluid flow conduits are discussed. We also present the field characteristics and petrographic evidences of chemical bleaching caused by fluid-rock interaction found in the Bhuj and the Jhuran sandstones. The change in the coloration pattern of deformation bands in comparison with the host rock color, presence of iron concretions, iron rinds and liesegang rings are important records of the diagenetic control over the fluid flow. The study is an attempt to the link the tectonic activity and simultaneous chemical reactions that affect the fluid flow transport.

We attribute the deformation history in the western continental margin of the Indian plate has been dominantly controlled by intraplate compressional stresses induced by anticlockwise rotation and collision of the Indian plate with the Eurasian plate at ~55 Ma. This correlates well with the Kachchh basin where rifting aborted during the Late Cretaceous, accommodated syn-rifting extensional component in the intra-uplift VF, GUF and KHIF. It has then undergone inversion phase due to onset of compressive stresses during the Post-Deccan Trap time up to the present. The NW-SE trending intra-uplift faults reactivated multiple times and generated deformation bands having high porosity contrast with the host Bhuj sandstone.