Landform evolution of the Qilian Shan since 120 Ma revealed by apatite fission track data

The Cenozoic uplift of the Qilian Shan mountain range is intimately connected with the collision of the Indian and Eurasian plates, although the mechanism of deformation is still unclear due to the large distance between the Qilian Shan and the plate collision boundary. The first requirement if we are to determine this mechanism is to obtain the uplift process of the Qilian Shan range, which remains a matter of debate. We compiled apatite fission track data from previous studies of the Qilian Shan range to investigate the spatial and temporal disparities or similarities of the exhumation process. Most of the age-evolution profiles and thermo-modelling results show a low exhumation rate from 80 to 20 Ma, corresponding to shorter apatite fission track lengths, indicating a lower rate of erosion and lower relief across the whole Qilian Shan region. The results also reveal two stages of rapid exhumation: during the Cretaceous (120–80 Ma) and since the Miocene (20–0 Ma). The exhumation history of the Qilian Shan range shows no significant spatial difference and outward growth was limited at the southern and northern edges after 5 Ma. This temporal and spatial pattern for the exhumation of the Qilian Shan range suggests that there was probably no obvious uplift at the time of the initial collision of the Indian–Tibetan plates and support the proposal that the whole Qilian range has uplifted synchronously since 20 Ma.