Résumé : Tectonic models for the Oligocene-Miocene development of the Himalayan Mountains are largely focused on crustal-scale processes, and developed along orogen-perpendicular cross sections. Such models assume uniformity along the length of the Himalaya, but significant along-strike tectonic variations occur, highlighting a need for three dimensional evolutionary models of Himalayan orogenesis. Here we show a strong temporal correlation of southward motion of the Indian slab relative to the over-riding Himalayan orogen, lateral migration of slab detachment, and subsequent dynamic rebound with major changes in Himalayan metamorphism, deformation, and exhumation. Slab detachment was also coeval with South Asian monsoon intensification, which leads us to hypothesize their genetic link. We further propose that anchoring of the Indian continental subducted lithosphere from 30 to 25 million years ago steepened the dip of the Himalayan sole thrust, resulting in crustal shortening deep within the Himalayan orogenic wedge. During the subsequent 13 million years, slab detachment propagated inward from both Himalayan syntaxes. Resultant dynamic rebound terminated deep crustal shortening and caused a rapid rise of the mountain range. The increased orography intensified the South Asian monsoon. The asymmetric curvature of the arc – broadly open, but tighter to the east – suggests faster slab detachment migration from the west than from the east.
Lieu : salle Grenat