Differential Denudation of the Sichuan Basin since Late Cretaceous: Insights from Low-temperature Thermochronology

Abstract:

The Sichuan Basin is located on the eastern edge of the Tibetan Plateau. Better understanding of its late Cretaceous - Cenozoic geological evolution contributes to explore the process and mechanism of the eastward expansion of the Tibetan Plateau. However, it remains uncertain when and how the denudation had occurred and when the basin reached its maximum burial depth. Here we report a low-temperature study to reconstruct the thermal history of this basin using apatite fission-track and (U-Th-Sm)/He techniques. Inverse temperature and denudation history modeling suggests (1) a mid-Cenozoic phase of cooling (ca. 70 °C since ca. 35±5 Ma), (2) the widespread erosion of ~2 to 4.8 km since Late Cretaceous; (3) the differential denudation of ~2 km between the eastern and western sides of the basin during 80-40 Ma. We interpret the mid-Cenozoic phase of cooling as resulting from eastward expansion of shortening and uplift over a blind detachment fault. The late Cretaceous differential cooling and denudation is likely a response to the formation of Jura-type folds in the eastern Sichuan Basin, which have been interpreted as a far-field effect of Pacific subduction.