Lower crustal foundering drove the uplift of southern Tibet during the Paleocene

The growth of the Tibetan Plateau is traditionally attributed to the India-Asia collision and subsequent convergence. However, recent paleo-elevation reconstructions suggest that Gangdese arc in southern Tibetan Plateau reached >4.0 km before or alongside the collision. Here we reconstruct the crustal thickness evolution of the Gangdese arc during the Late Cretaceous-Cenozoic using a machine learning model and investigate the thermal evolution by analyzing the metamorphic temperature-pressure-age properties of crustal rocks. Isostatic calculations are performed to constrain the crustal density evolution. Our results show that crustal thickness decreased from ~60 to ~40 km between 80 and 55 Ma, with an increase in lithosphere geotherm and a drop in average crustal density (from ~2.97 to ~2.70 g/cm3). These results suggest the removal of a 20 km thick dense lower crust during that period. Combined with numerical modeling and geological evidence, we propose that lower crustal foundering drove the uplift of the Gangdese arc during the Paleocene, independent of the India-Asia collision. Uplift of the Gangdese arc in the southern Tibetan Plateau occurred independently of the India-Asia collision and was driven instead by lower crustal foundering, according to a geodynamic model developed with machine learning.