Cenozoic uplift and exhumation in southern Sichuan Basin—Evidence from low-temperature thermochronology

Based on the model of low-temperature thermochronology (apatite and zircon (U-Th)/He, apatite fission track) and folding in anticlines, we decipher the uplift and exhumation in southern Sichuan basin during Cenozoic time, which is characterized by low-relief and low-slope in topography. The Muchuan and Sangmuchang area underwent rapid uplift and exhumation in Oligocene-Miocene, with a rate of ~0.1 mm/a and a magnitude of 1.0~2.0 km of surface erosion. It indicates that the craton basement has exerted a significant influence on the regional uplift and exhumation. The apatite (U-Th)/He ages range from ~10 Ma to 28.6 Ma in Muchuan anticline, there is a distinct decrease in AHe ages with the increasing depth to show a steady-state uplift and exhumation with a rate of 0.12±0.02 mm/a during this time. However, the apatite fission-track ages range from ~36 Ma to 52 Ma in Sangmuchang anticline, the AFT ages and the track lengths show no distinct change in depth, with a roughly similar value of ~50 Ma in ages and ~12.0 μm in lengths. Temperature-time histories of AFT show that most samples experienced three episodes of evolution. After arriving at the largest depth of subsidence around ~80 Ma, there is a slow uplift and cooling process between 80 Ma to 20 Ma with a rate of ~0.025 mm/a, followed by a rapid uplift and exhumation with a rate of ~0.1 mm/a. The compression between the eastward moving crust in Tibet and the craton basement in Sichuan basin accommodated different kinematic vectors in vertical and horizontal under the control of different boundary faults around the basin. Thus, it had a profound influence on the mount-building in eastern margin of Tibetan plateau and Sichuan basin.