Active Faulting and Deformation of Quaternary Landform Sub-Himalaya, India

Abstract

Landforms developed across terrain defining boundary the Main Boundary Thrust (MBT) have imprints of recent tectonic activity. Depositional landforms such as colluvial fan bear signatures of later phases of tectonic activity in the form of faulting of colluvial fan deposits and development of fault scarps. Tectonic geomorphology applied to the MBT zone suggests recent subsurface activity along the MBT and its splay thrusts. Present day tectonic activity of MBT is indicated by ground creeping, thrusting of Lower Siwalik rocks over recent colluvial fan deposit, aligning of series of lakes along splay faults and laterally along a fault, deflected streams, fault scarps and waterfalls. In the present paper we are addressing the tectonic situation in the foothill region of southeastern Kumaun Sub-Himalaya, India based on detailed field work carried out in the region which brought forward some outstanding morphotectonic evidence of neotectonic activities in the MBT zone.

A review on out-of-sequence deformation in the Himalaya

“…Banerjee et al (1999), in the Kumaun Himalaya, reported out-of-sequence thrust activity in the Nainital region at c. 40 ka at the Nainital Fault and the Sleepy Hollow Fault, and at the MBT c. 70 ka. Around 10 -30 m vertical displacement of terraces was observed in the Nainital region (see also Kothyari et al 2010). The Bhikiyasain Fault is a steeply dipping/sub-vertical transverse neotectonic fault from the Almora region of unknown exact timing (Goswami & Pant 2008b).…”

Quaternary extensional and compressional tectonics revealed from Quaternary landforms along Kosi River valley, outer Kumaun Lesser Himalaya, Uttarakhand

“…In the Himalaya, the localized normal faulting is reported from various terrains of the Himalaya from the Higher Himalaya up to the HFT zone, where HFT is the youngest crustal boundary where at present is the zone of maximum convergence (Thakur 2004;Thakur et al 2009). In the MBT zone, recent movement along this intra-crustal boundary is characterized by thrusting of the older bedrocks over the younger sediments (Thakur et al 2009;Kothyari et al 2010). In the frontal part, the compressional characteristic of the HFT is defined by thrusting of the Siwalik rocks over the Gangetic alluvia, uplift terrace, tilted terrace and fault scarps.…”

Evaluation of neotectonic variability along major Himalayan thrusts within the Kali River basin using geomorphic markers, Central Kumaun Himalaya, India

“…Uplift and incision of bedrock and formation of strath terraces, fill terraces, debris‐flow terraces, and fossil valleys associated with epigenetic gorges are the common morphotectonic features observed within the different thrust zones along the Kali River valley. The morphotectonic setting together with the earthquake activities suggests that the study area is tectonically active and the drainage patterns are a consequence of ongoing tectonic activity associated with the MCT, AT, BjT, BT, NAT, MBT, and HFT (Kothyari, ; Kothyari et al, ; Kothyari et al, ; Luirei et al, ; Pant et al, ). Furthermore, Mukul, Jaiswal, and Singhvi (); Wobus, Heimsath, Whipple, and Hodges (); and Wobus et al () believed that the hinterland thrusts are active ~30 km south of the MCT within the Lesser Himalaya, which is marked by the abrupt elevation changes.…”

“…Further downstream, the Kali River flows across the Main Boundary Thrust (MBT) zone. The steeply inclined thrust plane has brought Lesser Himalayan rocks upon the Cenozoic sedimentary terrain of the Outer Himalaya (Kothyari et al, ; Kothyari, Pant, Joshi, Luirei, & Malik, ; Valdiya, ). However, towards the Himalayan front, the river flows across the Himalayan Frontal Thrust (HFT), which defines the southern limit of the Himalaya against the Indo‐Gangetic Plains of Quaternary age.…”