Tracing exhumation and drainage dynamics in Taiwan's orogenic belt using detrital zircon U–Pb geochronology

Abstract The convergence between the Eurasian continental margin and the Philippine Sea plate has led to the rapid exhumation of the Taiwan orogen and the formation of a foreland basin in western Taiwan since approximately 6.5 Ma. Over 5 km of foreland basin deposits have accumulated in central Taiwan and have been linked to the rapid exhumation of the Hsüehshan Range and the western fold-and-thrust belt. Detrital zircon U–Pb dating was conducted within the orogenic belt and the foreland basin in central Taiwan to investigate the unroofing process of the orogenic belt and the resultant sedimentation. The zircon U–Pb date spectrum from Hushan Dam indicates that the sediments have been sourced from the Yushan area, which has experienced a higher exhumation rate. Compared with the age spectrum from the Chi-Chi area, this reflects the westward transport and progressively northward migration of the Chenyulan River, eventually merging with the Choshui River system. The age spectrum, ranging from the Chinshui Shale to the Toukeshan Formation, corresponds to the unroofing process of the Miocene to Eocene strata in the Hsüehshan Range. Additionally, the youngest foreland basin deposits and modern river sediments reflect the activity of the fold-and-thrust belt, which is associated with exposure to the Miocene strata.