PALEOSTRESS STATES IN PARTS OF CHAKRATA FORMATION, GARHWAL HIMALAYA, EVIDENCE FROM EN-ECHELON VEINS

Abstract

The Krol Nappe of Garwhal syncline is overlain by older Chakrata Formation of the Damtha - Group. The contact between the Blani Formation and the Chakrata Formation is a thrust contact. The study aims at the reconstruction of the paleostress states in parts of Chakrata Formation by analyzing en-echelon veins. Field data on en-echelon veins has been classified into homogeneous sets on the basis of field • criteria and each set has been analyzed by P-T Axis method, Direct 1nversicn Method and Win Tensor. The result shows that the study area had undergone two phases of deformation. - At the first stage an extensional stress were dominant that leads to normal faulting and at the final stage compressive stress having direction NE-SW that is similar to Himalayan orogeny reactivated the fault plane that leads to reverse faulting but the intermediate principal stress direction remain same in both the phases indicating extensional stress changes to compressive stress at tL stage.