Geology structural and exhumation history of the

Authors: R C Patel Vikas Adlakha Paramjeet Singh Yogesh Kumar Nand Lal

Publish Date: 2011/03/03

Volume: 77, Issue: 1, Pages: 47-72

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Abstract

The crystallines in the Kumaon Himalaya India are studied along Goriganga Darma and Kaliganga valleys and found to be composed of two highgrade metamorphic gneiss sheets ie the Higher Himalayan Crystalline HHC and Lesser Himalayan Crystalline LHC zones These were tectonically extruded as a consequence of the southward directed propagation of crustal deformation in the Indian plate margin The HHC and its cover rocks ie the Tethyan Sedimentary Zone TSZ are exposed through tectonic zones within the hinterland of Kumaon Himalaya The HHC records history of at least one episode of preHimalayan deformation D1 three episodes of Himalayan deformation D2 D3 D4 The rocks of the HHC in Kumaon Himalaya are thoroughly transposed by D2 deformation into NWSE trending Sm S1+S2 The extent of transposition and a welldeveloped NEplunging L2 lineation indicate intense strain during D2 throughout the studied portion of the HHC Ductile flow continued resulting in rotation of F1 and F2 folds due NEdirection and NWSE plunging F3 folds within the HHC The over thickened crystalline was finally superimposed by latetopost collisional brittleductile deformation D4 and exposed the rocks to rapid erosionApatite Fission Track AFT and Zircon Fission Track ZFT studies from the Kumaon Himalaya suggest reactivation of the Main Central/Munsiari Thrust MCT/MT and Vaikrita Thrust VT rapid exhumation and a system that has been in topographic and exhumation steadystate since at least 4 Ma

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