Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: inferences from [sup.40]Ar/[sup.39]Ar and (U-Th)/He thermochronology

[1] High topography in central Asia is perhaps the most fundamental expression of the Cenozoic Indo-Asian collision, yet an understanding of the timing and rates of development of the Tibetan Plateau remains elusive. Here we investigate the Cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the Sichuan Basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed. Temperature-time paths inferred from [sup.40]Ar/[sup.39]Ar thermochronology of biotite, multiple diffusion domain modeling of alkali feldspar [sup.40]Ar release spectra, and (U-Th)/He thermochronology of zircon and apatite imply that rocks at the present-day topographic front of the plateau underwent slow cooling (30 [degrees] - 50 [degrees] C/m.y.) coincident with exhumation from inferred depths of ~8-10 km, at denudation rates of 1-2 mm/yr. Samples from the interior of the plateau continued to cool relatively slowly during the same time period (~3 [degrees] C/m.y.), suggesting limited exhumation (1-2 km). However, these samples record a slight increase in cooling rate (from