Miocene Subsidence and Surface Uplift of Southernmost Tibet Induced by Indian Subduction Dynamics

Abstract

The Indus ‐ Yarlung suture of southernmost Tibet marks the initial collisional zone, the ongoing India ‐ Asia collision, and yet more than ~30 million years after the onset of collision, a thick detrital sedimentary unit was deposited just north of the suture: the Kailas Formation. The mechanism permitting subsidence of the deep intracontinental Kailas basin in a compressional tectonic regime remains uncertain. We present new apatite (16 – 11 Ma) and zircon (24 – 19 Ma) fi ssion track (AFT and ZFT) ages from the Gangdese batholith just north of the Kailas basin. ZFT analysis of modern ‐ river sand from the northern Gangdese magmatic arc indicates an exhumation at 27.3 ± 1.3 Ma. Thermal modeling indicates that the batholith experienced reheating between 28 and 20 Ma, coeval with deposition in the Kailas basin (between 26 and 21 Ma), followed by overall rapid cooling between 20 and 17 Ma. We interpret this thermal history as a phase of regional Oligocene ‐ Miocene sedimentary burial followed by exhumation. By modeling mantle dynamics in the geodynamic framework of the India ‐ Asia collision, we show that transient dynamic topography over the relative southward folding of the Indian slab is consistent with burial and exhumation of the Gangdese magmatic arc during Oligocene ‐ Miocene time. The northward migration of the Indian continent relative to its own stationary slab created a wave of dynamic topography that caused subsidence in the overriding plate north of the Himalaya, followed by a phase of surface uplift since ~27 Ma of the northern Gangdese magmatic arc. During latest Oligocene ‐ early Miocene time, the dynamic de fl ection center was in the Kailas area, and it progressively relocated southward to its present position at the Ganges basin.