In the Arun and Barun valleys the upper portion of the Lesser Himalayan section is made up by the Num orthogneiss. It is a 3-4 km thick unit of granitic augen gneiss with bands of kyaniteflogopite schists (Lombardo et al. 1993). It records a noncoaxial deformation related to its involvement within the Main Central Thrust zone that produced an heterogeneous mylonitic deformation with rotated feldspar porphyroclasts, bookshelf structures and localized shear bands with a prominent top-to-the SW sense of shear. The base of the Num orthogneiss is the Main Central Thrust I.
