The Geology of Besham Area, North Pakistan Deformation and Imbrication in The Footwall of the Main Mantle Thrust
Abstract
The gneisses, granites and metasediments of the northern exposed margin of the Indian plate in the Besham antiform consist of a Precambrian crystalline basement with younger sedimentary cover. These were metamorphosed during the main fabric-forming event of the Himalayan orogeny, a ductile simple shear dominated deformation of the footwall of the MMT during southward overthrusting of the Kohistan Arc. Deformation intensity and ductility decrease southwards. Subsequent thrusting brought together internally imbricated blocks which have different deformation/metamorphic histories. High grade rocks thrust over low grade rocks within each block define an inverted metamorphic gradient produced by post-metamorphic thrusting. Major cross folding producing the Besham antiform, plus brittle faults are expressions of the later N-W directed backthrusting and E-W compression and uplift of the Besham area
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