Exhumation and landscape evolution in eastern South China since the Cretaceous: New insights from fission-track thermochronology

摘要

Widespread extensional half-/grabens with red bed sedimentation, dome structures, and magma intrusions/eruptions with polymetallic mineralization within South China during the Cretaceous-Cenozoic provide a natural laboratory to understand intracontinental deformation and plate tectonics. In order to decipher the tectonic and landscape evolution of eastern South China, this study presents new low-temperature thermochronology from a broad region covering major tectonic units including the Xuefeng, Jiuling, Nanling, and Wuyi mountains. Zircon and apatite fission track dates, length distribution, and thermal history modeling reveal a prominent and rapid cooling phase during similar to 125-80 Ma across the paleo-highland in eastern South China. A synthesis of existing thermochronologic data and geological observations suggests that NE/NNE-striking syn-sedimentary faults system with half-/graben basins, rapid exhumation of Cretaceous magma and pre-Cretaceous basement, and final extension of dome structures were all initiated in a back-arc setting during this period (similar to 80-125 Ma). Eastern South China during the Paleogene was characterized by a tectonic quiescence during which insignificant exhumation, peneplanation, and local sedimentation occurred, forming regional low-amplitude, long-wavelength topography. Accelerated regional cooling commenced in the late Oligocene or early Miocene in response to the far-field effect of the India-Asia continental convergence. Additionally, the termination of red-colored gypsum-salt-bearing sediment in the Neogene suggests a paleo-environmental change within South China, from an arid to a monsoonal climate; such change was likely the result of the topographic uplift of the Tibetan Plateau and its margins.