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Apatite fission-track dating and thermal-history modeling were carried out on samples from the Dabashan (大巴山), a fold-thrust belt, northeast of the Sichuan (四川) Basin and east of the Tibetan Plateau. A first cooling event in the Late Cretaceous is followed by a prolonged period of thermal stability with exhumation rates of ≤0.025 mm/a, as determined from age vs. elevation relationships. The preservation of age vs. elevations relationships and the lack of distinct age changes across tectonic structures indicate that the Dabashan fold-thrust belt formed prior to the Late Cretaceous, consistent with the current view of Triassic-Early Cretaceous shortening. Relatively short mean track lengths (～12 μm) indicate that the samples remained in the partial annealing zone for a prolonged time. The knick points in the best-fitting temperature-time models suggest that the onset of late-stage accelerated cooling commenced at ≤11 Ma. Related exhumation rates are 0.3-0.2 mm/a assuming geothermal gradients of 20 and 30 ℃/km. We speculate that this late-stage event results from eastward growth of the Tibetan Plateau and overstepping of the Sichuan Basin, it is likely responsible for the youthful morphology of the Dabashan.
Apatite fission-track dating and thermal-history modeling were carried out on samples from the Dabashan, a fold-thrust belt, northeast of the Sichuan (Sichuan) Basin and east of the Tibetan Plateau. A first cooling event in the Late preservation of aging vs. elevations relationships and the lack of distinct age changes across tectonic structures that that the Dabashan fold-thrust belt formed prior to the Late Cretaceous, consistent with the current view of Triassic-Early Cretaceous shortening. Relatively short mean track lengths (~ 12 μm) indicate that the samples remained in the partial annealing zone for a prolonged time. The knick points in the best-fitting temperature-time models suggest that the onset of late-stage accelerated cooling commenced at ≤11 Ma. Related exhumation rates are 0.3-0.2 mm / geothermal gradients of 20 and 30 ° C / km. We speculate that this late-stage event results from eastward growth of the Tibetan Plateau and overstepping of the Sichuan Basin, it is likely responsible for the youthful morphology of the Dabashan.