Study of Plio-Pleistocene Foreland Basin Provenance and Orogenic Exhumation History in Central Taiwan: Fission-Track and U-Pb Dating Analyses of Detrital Zircon from Western Foothills

In this study, we employed low-temperature thermochronology to investigate the depositional source and exhumation rates of the mountain belt in central Taiwan. We collected four sedimentary rock samples from the Chiunkongliao River and one sample from Wuxi. Utilizing zircon fission-track (ZFT) dating and uranium-lead (U-Pb) dating, we observed an increase in the percentage of partially reset zircon from the Chinshui Shale to the Toukoshan Formation. Additionally, we identified total reset zircon in the Toukoshan Formation. Furthermore, the probability density of U-Pb dating in the Toukoshan Formation leans more towards the Oligocene than the Miocene. Through double-dating, we determined that ZFT ages less than 65 Ma are not the result of Cenozoic volcanic activity. These findings suggest a change in the origin of the depositional source from the Cholan Formation to the Toukoshan Formation. According to the lag time curve, the exhumation rate accelerated during the time period from 1.1 Ma to 0.5 Ma. Comparing our results with previous studies in the Western Foothills of central Taiwan, we observed that the annealing zone was exposed earliest in the middle part than in the southern one. This may indicate that, in central Taiwan, the exhumation rate in the middle part was the fastest.