Magnetic fabric and geomorphic characteristic of Neotectonic activity along strike direction of North Almora Thrust,Kumaun Lesser Himalaya,India

Structurally,the North Almora Thrust(NAT),is placed in the northern proximity of the Almora Nappe(AN)in the Kumaun Lesser Himalaya.The NAT is characterized by the presence of a zone of mylonitic rocks of basal Saryu Formation(1800±100 Ma)in the hanging wall and the metasedimentaries of Inner Lesser Himalayan rocks as the footwall block.The NAT has been dextrally offset by two estabilished maj or faults i.e.Saryu River Fault(SRF)in Saryu Valley and Dwarahat-Chaukhutia Fault(DCF)in Ramganga valley.In present study,we identified four new faults,based on field study,geomorphic landform and magnetic fabric analysis.These faults are N-S trending Pancheshwar Fault,NE-SW Rameshwer Fault,NNE-SSW trending Kosi Fault,and NNE-SSW trending Gagas Fault(GF).Our results show that the zone is bound by cross cutting relation with NAT and these fault zones are comparatively more active than other regions.Furthermore,we suggest that the steep and NW-SE orientation of magnetic foliation within the NAT zone is a result of NE-SW oriented progressive regional compression.The magnetic foliations represent the unseen internal foliations in the rocks developed due to preferred alignment of magnetic minerals and can be found through the Anisotropy of magnetic susceptibility(AMS)study.Variation in the alignment of the field and magnetic foliations are developed due to superimposed brittle deformation along the faults over the pre-existing field foliations.Magnetic foliations represent the impact of last stage deformation and significant to find brittle deformation and finite strain in the rocks of the study area.The lowering of anisotropy(Pj)away from the fault zone represents distribution of strain across the NAT zone.AMS fabric confirms the presence of faults developed across the NAT zone and also explains the deformation pattern along these faults.The geomorphic anomalies and steepness changes across the NAT zone are correlated with active deformation along the NAT and associated transverse faults.