STRUCTURAL EVOLUTION OF THE KULU-RAMPUR AND LARJI WINDOW ZONES, WESTERN HIMALAYA, INDIA |
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| Authors: | Anand Kumar Pandey |
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| Institution: | Anand Kumar Pandey 1,N.S.Virdi 2,V.K.Gairola 3,J.P.Burg 1 |
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| Abstract: | The Kulu\|Rampur and Larji windows in the western Himalaya make a window in window structure in the Lesser Himalaya between the Main Boundary Thrust (MBT) and Main Central Thrust (MCT). The former constituted of late Archean Rampur Group with middle Proterozoic intrusive Bandal Granite Complex has been thrusted on to the younger Larji Group (Riphean) along a splay thrust making the latter a window in window structure. Both the sequences have recorded multiple deformation during the Himalayan orogeny. Five sets of Himalayan structures have been recognised. The first deformation event (D 1) was responsible for large isoclinal, (recumbent) folds (F 1) which are older than the onset of Himalayan thrusting. Presently, the Rampur Group constitutes the antiform and the Larji Group occupies a synformal position of F 1 folds. The parautochthons of the window zone has been covered by the Chail and Jutogh nappes along the Chail and Jutogh thrusts during D 2. Thrusting was followed by F 3 folding during D 3 deformation. This fold can be recognised in form of Rampur Antiform and corresponding Nirath\|Pandoh Synform with NW—SE axial trend. The Chail and Jutogh nappes are folded along with the parautochthonous rocks of window zone by this folding event. The out\|of\|sequence imbrication and the splay thrusts in the hanging wall of the MBT were initiated during D 3. The F 3 are overprinted by cross folding (F 4) of D 4 deformation, which is responsible for the doubly plunging character of the window zones. Cross folding was followed by D 5 extensional faulting and collapse of the hanging wall in out\|of\|sequence shear zones. The D 5 extensional fabrics are attributed to gravity collapse in the hanging wall of the MBT. |
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| Keywords: | tectonic windows Himalayan deformation MBT hanging wall splay thrust |
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