Extensional tectonics in the Himalayan orogen, Zanskar, NW India

Abstract

Large-scale nappes of the deformed Higher Himalayan Crystallines (HHC) were thrust southward over the Lesser Himalayan Proterozoic foreland during the Late Cenozoic. Critical evaluation of shear fabrics, reveals that the HHC underwent an earlier phase of ductile shearing with top-to-southwest overthrust-type sense of movement. On which was superposed layer-parallel NE-trending extension. As a consequence, the Zanskar Shear Zone (ZSZ) along the northern boundary of the HHC is re-interpreted as a complex ductile shear zone with an initial top-to-southwest sense of thrusting followed by the later superposition of top to northeast-directed extension. This period of extension is recognized across the whole of the HHC and is the result of the uplift and exhumation of the HHC by southwestward directed thrusting and ramping along numerous thrusts including the Main Central Thrust (MCT). © 1993 The Geological Society.