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Séquence d'activité des failles et dynamique du prisme himalayen : apports de la thermochronologie et de la modélisation numérique

Abstract : The influence of erosion on the location of deformation in mountain ranges has been demonstrated by numerical modelling. However, few relevant geological data in favour of this hypothesis exist. Thus, demonstrating a temporal or spatial evolution of the deformation/kinetics in the frontal units of the Himalayan range would provide a key observation to test the interactions between erosion and the location of the tectonic deformation at the scale of a mountain belt. We test this effect by the acquisition of low-temperature thermochronological data (apatite fission-track) and forward and inverse thermo-kinematic numerical modelling. The southern flank of the Himalaya, situated above a major crustal detachment, is well adapted to test the interactions between erosion and tectonics because it is submitted to convergence that is spatially continuous and homogeneous through time, and its rheology is invariable through time. However, it is submitted to a climatic gradient from east to west, perpendicular to the convergence direction. This gradient is moreover variable through time. We show that 1) in central Nepal, there is a well-expressed crustal ramp on the Main Himalayan Thrust (MHT) below the physiographic transition, out-of-sequence thrusting is not required by the data, 2) the geometry of the MHT varies from east to west, from a linearly dipping detachment to a well-expressed crustal ramp, and 3) the lateral variations of the kinetics or the initiation of the Main Frontal thrust are limited at the scale of the entire orogen.
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Submitted on : Tuesday, January 13, 2009 - 1:53:51 PM
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Xavier Robert. Séquence d'activité des failles et dynamique du prisme himalayen : apports de la thermochronologie et de la modélisation numérique. Géologie appliquée. Université Joseph-Fourier - Grenoble I, 2008. Français. ⟨tel-00352596⟩

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