Geological Study of the Mardi River Section from Upallo Dip to Ramche, Lesser Himalaya, Western Nepal

Abstract

Geological mapping and petrographic study were carried out along the Mardi River from the Dip to Ramche. The area is covered by the rocks of the Lesser Himalaya in the south and the Higher Himalaya in the north separated by the Main Central Thrust (MCT). The Kuncha Formation consists of chlorite-phyllite and metasandstone, which is underlain by the Fagfog Quartzite. The Fagfog Quartzite consists of white quartzite and two band of amphibolite intrusion, above this lies the Marble and Schist having medium grained garnet. The Black Schist and Quartzite lies over the Marble and Schist. All these terminate over the garnet and kyanite bearing schist and gneiss namely the Kyanite banded Gneiss. The lower boundary of the formation is supposed to be the Main Central Thrust (MCT). Hence in the area the Lesser Himalaya contains four units and the Higher Himalaya contains one unit. The biotite grade zone starts from the Dip, lowest part of the area which is underlain by the garnet zone. The garnet grade zone starts from the Saiti Ghatta Khola and terminates in the MCT, from that kyanite grade zone is initialized. The foliation in the area mostly dips towards NE except in the areas of local folding. Foliation is less prominent and usually parallel and sub parallel to the bedding. The area contains folds, thrust, stretching lineation and boudinage in the lesser Himalaya rocks. From the petrographic study, it is depicted that the metamorphism in the area is the inverse prograde type. The higher grade metamorphic mineral is found stratigraphically high.