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Kinematic, Metamorphic, and Age Constraints on the Miyar Thrust Zone: Implications for the Eohimalayan History of the High Himalayan Crystalline of NW India
Author(s) -
Robyr Martin,
Lanari Pierre
Publication year - 2020
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2020tc006379
Subject(s) - geology , continental collision , foreland basin , main central thrust , nappe , seismology , subduction , paleontology , collision zone , metamorphic rock , fold and thrust belt , fold (higher order function) , shear zone , thrust , mountain formation , tectonics , mechanical engineering , engineering , physics , thermodynamics
NE‐vergent folds and thrust faults are an enigmatic feature of the High Himalayan Crystalline in the NW Indian Himalaya, as these structures are in marked contrast to the SW‐directed thrusts and fold vergences that predominate in the rest of the Himalaya since the continental collision between India and Asia. However, it is controversial whether these unusual NE‐vergent structures reflect local heterogeneities in strain during the main SW‐vergent deformation or whether they are associated with a postulated NE‐directed early Eocene deformation phase. In this study, microstructural analysis and monazite geochronology across the SW‐dipping Miyar Shear Zone (Miyar Valley, NW India) reveal that these NE‐verging structures result from a NE‐directed propagation of crustal deformation that was initiated before 40 Ma, likely slightly after continental collision at ca. 55 Ma. The new data presented in this study identify that the kinematic evolution of the High Himalayan Crystalline in NW India was initially controlled by an early Eocene NE‐directed crustal thickening phase. Consequently, the SW‐verging kinematic evolution widely accepted for the High Himalayan Crystalline in the central and eastern Himalayan sections should be reconsidered for the western part of the Indian Himalaya. In a broader sense, these results reveal that crustal shortening during the initial stage of continental subduction is not exclusively accommodated by foreland‐directed folding and thrusting but may also be adapted by deformation involving opposite‐directed vergence.