Deformational Structures in Ladakh Molasse and their Significance in Interpreting the Collision Scenario

Unconformably resting over the Ladakh magmatic arc complex, the molassic sediments (Ladakh molasse) have been thrust over mainly by Dras and Indus formations within the Indus-Suture Zone of Ladakh Himalaya. The convergence between the Indian plate and Tibetan microplate initially produced NW-SE trending cylindrical folds, but the continued NE-SW compression ultimately led to the collision between the two plates and resulted in northeast translated thrusting in molassic sequence. Indentation of Indian plate around the northwest corner during collision led to the accumulation of high compressive strain in the plate boundary i.e. along the Indus Suture Zone. This strain not only caused the intervening material to get escaped laterally eastwards in this zone but also activated the various NW-SE trending thrusts with simultaneous dextral strike slip movement. The latter movement produced many N-S oriented secondary fractures (faults) in the crystalline arc complex and subsequently forced them to undergo strike slip activation. In this manner the blocks formed by these two sets of faults were rotated dextrally together with overlying folded molassic sediments.