Abstract Collisional fold-and-thrust belts are characterized by foreland-verging thrusts. Conversely, structures with hinterland-ward vergence, known as the back-thrusts, also exist. Strain intensification, critical taper deformation and the presence of thrust ramps generate back-thrusts. This study focuses on the exposure-scale brittle and ductile structures showing hinterland-ward vergence (back-structures) from a part of the Garhwal Lesser Himalaya, NW India, mainly along the Bhagirathi river section. In our field-traverse, back-structures were found at 31 locations. Towards the north, in the Outer Lesser Himalaya, the back-structures are located on the inverted limb of the Mussoorie Syncline (Group 1). The Tons Thrust is a south-dipping thrust (i.e. back-thrust). Hence, the Tons Thrust and nearby areas show intense back-structures (Group 2). In the Inner Lesser Himalaya, back-structures have been generated by shearing related to the folded Berinag Thrust (Group 3). The back-structures at and near the Main Central Thrust Zone (MCTZ) (Group 4) can be correlated with the presence of the Delhi–Haridwar Ridge. In this way, this study establishes the back-structures to be an integral part of the Garhwal Lesser Himalaya and provides the genesis of those structures by correlating them with the (local) tectonic settings.

Abstract Indian basement faults, which bound three orogen-perpendicular palaeotopographic ridges of Precambrian Indian basement south of the Himalaya, extend to the base of the Indian lithosphere and to the northern extent of the Indian lithosphere underneath Tibet. In the eastern Himalaya, the active orogen-perpendicular Yadong–Gulu graben is aligned with an earthquake-generating strike-slip fault in the high Himalaya. We argue that the graben results from crustal necking during reactivation of the underplated basement fault. In the central Himalaya, along-strike diachronous deformation and metamorphism within the Himalayan metamorphic core, as well as lateral ramps in the foreland thrust belt, spatially correspond to the Lucknow and Pokhara lineaments that bound the subsurface Faizabad Ridge in the Indian basement. Analogue centrifuge modelling confirms that offset along such deep-seated basement faults can affect the location, orientation and type of structures developed at various stages of orogenesis and suggests that it is mechanically feasible for strain to propagate through a melt-weakened mid-crust. We suggest that inherited Indian basement faults affect the ramp-flat geometry of the basal Main Himalayan Thrust, partition the Himalayan range into distinct zones, localize east–west extension resulting in the Tibetan graben and, ultimately, contribute to lateral variability in tectonic evolution along the orogen's strike.