Mesozoic-Cenozoic Exhumation of the Northern Margin of the Qinling Mountains: Constraints from Low-Temperature Thermochronology of Modern River Sands

Reconstructing the exhumation history of the Qinling Mountains is crucial for understanding plate tectonics-driven surface deformation processes within continental interiors and revealing the formation of China's present-day geomorphic framework. This study employs thermochronological analysis using detrital zircon and apatite fission track dating on modern river sands from the Laoyu River in the central Qinling Mountains.The results reveal three dominant peak ages of 91.0–82.0 Ma, 54.4–41.9 Ma, and ca. 24.9 Ma in the samples. These peak ages indicate three potential rapid uplift-exhumation phases in the Qinling Mountains since the Late Mesozoic to Cenozoic: The Late Cretaceous (91–82 Ma) age peak indicates rapid uplift-exhumation of the northern margin of the Qinling influenced by the late Yanshanian intracontinental orogeny. The Eocene (54.4–41.9 Ma) rapid cooling phase reflects extensional faulting along the northern margin of the Qinling under tectonic regimes of Pacific subduction or initial India-Eurasia collision, consistent with the initial rifting timing of the Weihe Basin. The latest Oligocene to early Miocene (ca. 24.9 Ma) rapid cooling episode, widely documented in the northern Qinling region, is likely associated with westward subduction of the Pacific plate, which accelerated extensional deformation along the northern Qinling margin.