Mesoscopic, magnetic and petrofabric study of the High Himalayan gneisses and leucogranite along oblique and frontal ramps of the Vaikrita Thrust in Satluj and Bhagirathi valleys: Thrust locking and superposed folding

Abstract

Field, microstructural and anisotropy of magnetic susceptibility (AMS) studies were performed along the oblique thrust ramp of the Satluj river valley and frontal thrust ramp of the Bhagirathi river valley. The presence of asymmetric and sheath folds indicates intense shearing near the thrust. The simple shear gradually decreases with an increase in distance from the thrust and pure shear with upright folds becomes prominent. The AMS studies suggest slightly higher pure shear in the frontal ramp region as compared to the oblique ramp region where oblique slip was predominant. The sense of shear criteria and orientation of superposed folds indicate locking of the thrust. Normal faults are the youngest structure.