The denudation of the eastern margin of the Qinghai-Xizang Plateau since the Late Cenozoic: Evidence from the fission-track ages

The denudation rates of the eastern margin of the Qinghai-Xizang Plateau since the Late Cenozoic are examined for the third-order geomorphological units western Sichuan plateau,Longmen Mountains and Sichuan Basin on the basis of the fission-track ages for the samples from different blocks in the study area.The findings show that there are gradations of denudation from slow processes before the Miocene to rapid ones after the Miocene.The mean denudation rate is 0.26 mm/yr for the western Sichuan plateau, 0.72 mm/yr for the Longmen Mountains,and 0.20 mm/yr for the Sichuan Basin.It can be seen that the mean denudation rate for the Longmen Mountains is about 2.8 times than that for the western Sichuan plateau,implying that the uplift of the marginal mountain ranges does not means that of the Plateau;the former may be combination of tectonic uplift and denudational uplift.