Eocene Tibetan plateau remnants preserved in the northwest Himalaya

摘要

The northwest Himalaya shows strongly contrasting relief. Deeply incised mountain ranges that are characterized by extremely rapid exhumation(1-3) and some of the highest peaks in the world are in contrast with high-elevation, low-relief areas such as the Deosai plateau in northern Pakistan, which lies at an altitude of 4,000 m. The origin and evolution of such plateau regions at the convergence of the most active continental collision in the world remain elusive. Here we report low-temperature thermochronology data from the Deosai plateau and use thermal history modelling to show that the plateau has undergone continuous slow denudation at rates below 250 m Myr(-1) for the past 35 Myr at least. This finding suggests tectonic and morphologic stability of the plateau since at least Eocene times, only 15-20 Myr after the onset of the India-Asia collision. Our work contradicts the hypothesis that widespread low-relief surfaces in the northwest Himalaya result from efficient kilometre-scale glacial erosion during Quaternary times(4). We show that similarly stable surfaces exist throughout the entire northwest Himalaya and share common morphologic characteristics and denudation histories, which are comparable to those of the western Tibetan plateau. Our results suggest that these surfaces are preserved remnants of an Eocene southwestern Tibetan plateau that was more extensive than today.