Terminated Main Himalayan Thrust, evidence of Pre-Siwalik Tertiary rocks beneath and evolution of NW Himalayan foreland basin

Abstract Active seismic study in the Himalayan fold-thrust belt is quite rare due to its rugged topography, inhospitability and fragility. This work has brought out subsurface disposition of several geotectonic features from industry-standard seismic data in the NW Himalayan foreland basin and provided their inter-tectonic relations and geodynamic evolution of the study area. The analysis of seismic attributes, computation of interval velocity and digital amplitude tracing have been performed, and all these show that the Surin-Mastgarh Anticline (SMA) and Medlicott–Wadia Thrust (MWT) are not soled at depth with the Main Himalayan Thrust (MHT). Other important aspects of this study are the delineation of some new subsurface features such as the Duplex-Thrust Complex (DC) of Late Proterozoic formation above the MHT, a Blind Thrust (BT) in between SMA and MWT, and a synform at the east end of the SMA. The study discovered that the MHT is unusually terminated southward below the SMA at a depth of~ 4700 ms two-way time (TWT), and thus not exposed on the surface as the Himalayan Frontal Thrust (HFT), and is underlain by Pre-Siwalik Tertiary formation. This may provide far-reaching prospects for hydrocarbon exploration and implications on seismicity. The regional tectonostratigraphic evolutionary model, presented here, shows that the less competent Siwalik rocks folded into the SMA, and the MWT and BT, which overrun the northern limb of SMA, are broken parts of DC. The model also elucidates how the Pre-Siwalik Tertiary formations went down beneath the MHT and Late Proterozoic rock came out of the Indian plate to constitute the DC, BT and MWT.