Evidences of Late Quaternary Neo-Tectonics at Kirtinagar in Alaknanda Valley of Garhwal Himalaya, India

Abstract

       Formation of river terraces, transverse faults along with the major thrusts, deformation of quaternary sediment, and mass movement results from the combined effect of the tectonic and climatic process, tectonic landforms developed across defining the boundary of North Almora Thrust (NAT) have imprints of late Holocene tectonic activities. The reactivation of thrust and faults has greatly influenced the topography of the Himalayan region. Considering this a series of geomorphic evidence of the Quaternary period has been reported along the strike-slip transverse fault near NAT at Kirtinagar in Lower Alaknanda valley of the Lesser Himalaya. Present tectonic landforms of the transverse fault indicated by various cutting of host rock, V-shaped valley, epigenetic gorge, unpaired river terrace, deflecting river course, offset drainage pattern, triangular facet, incision with higher uplift along with tectonic upheaval, and immature topography. The neo-tectonic sites were identified along with the road cut section and Kirtinagar terrace scarp. The tectonic structures and nature of sediments were analyzed and photographed during the field study. The minor structural features of Quaternary sediments are folding, faulting, thrusting, warping, and tilting. The samples of optical chronology were collected from discrete sand horizons. The OSL date was obtained using the single aliquot regeneration. The Optical Chronology of terraces sediments shows that the T2 and T3 levels of terraces are deposited around 4.6 Ka in the Holocene periods. Based on existing data it is assumed that the Lesser Himalayan thrust and faults were tectonically active during the early Holocene period. After that, the role of tectonic decreases and incision increases due to the climatic variability. The conclusive results of the study indicate that the neo-tectonic movements along NAT were more active in recent past times. It is concluded that the transverse strike-slip fault along NAT in the study section has been reactivated from time to time

Keywords- Neo-tectonics; Deformation; North Almora Thrust; Transverse fault; Quaternary period.