Structure of the Chamba nappe and position of the Main Central Thrust in Kashmir Himalaya

Abstract

The Chamba nappe, composed of an approximately 8 km thick sequence of Late Precambrian to Jurassic age rocks is located between the Higher Himalaya Crystallines (HHC) and the Lesser Himalayan (LH) formations of Panjal Imbricate Zone (PIZ) in the Kashmir Himalaya. To the south, the Panjal Thrust, demarcating the base, brings the Chamba nappe rocks over the Panjal Imbricate Zone. To the north, the Chamba nappe rocks lie over the metamorphic HHC along the south dipping Chenab Normal Fault (CNB). A pervasive stretching lineation defined by a mineral lineation, stretched pebbles and felspar phenocrysts plunges NE-NNE and occurs on the foliation/cleavage surface. This lineation is related to southward displacement of the Chamba nappe. The Chamba nappe is folded by regional scale fold, viz. the Chamba, Tandi and Bharmor synclines and the Tisa anticline. These NW-SE trending folds structures were developed synchronously with southward thrusting of the Chamba nappe. The Chamba nappe results from southwestward sliding of cover rocks from their basement (HHC) due to topographic uplift. The Main Central Thrust (MCT) in Kashmir Himalaya is different from that of the Kumaun and Nepal Himalaya. The MCT (Vaikrita Thrust) does not extend west of the Beas river, but it is exposed in the Rampur Window and the Kishtwar Window separating the HHC from the underlying LH rocks. Southward propagation of the MCT from the window zone, up-cutting the overlying HHC, is transferred to the Panjal Thrust which transports the Chamba nappe to the south over the Lesser Himalayan formations.