Detrital zircon geochronology of river sands from Taiwan: Implications for sedimentary provenance of Taiwan and its source link with the east China mainland

Cenozoic sedimentary strata of the continental margin are well-preserved on Taiwan Island thus providing an excellent geological window into the tectonic and environmental changes that occurred in East Asia during this interval. In this study, we report U-Pb ages of detrital zircons from sandy sediments of the Lanyang River in east Taiwan and the Zhuoshui River in west Taiwan. Detrital zircons from the two rivers display seven major age groups: 200-100 Ma, 300-200 Ma, 550-360 Ma, 850-700 Ma, 1.1-0.9 Ga, 2.0-1.8 Ga and 2.6-2.4 Ga. However, significant differences in zircon age distributions exist between the two rivers, showing a high proportion of Phanerozoic zircons in the Lanyang River sediments and a more complex age population and more Precambrian zircons in the Zhuoshui River sediments. This suggests that both rivers must be sampling sedimentary rocks with different zircon age populations and provenances. By comparing the detrital zircon geochronology between Taiwan and three major tectonic blocks in the east China mainland, the Cenozoic sedimentary provenance of Taiwan and its source link with mainland China are revealed. The Eocene-upper Oligocene strata of the Hsuehshan Range and the Miocene turbidites of the west Central Range are mainly sourced from the Cathaysia Block, while the Miocene-Pleistocene strata in the Western Foothills are primarily derived from the Yangtze Block and the North China Block. We infer that the sedimentary evolution of Taiwan is closely related to the interacting processes between the drainage reorganization in East China and the paleogeographic evolution and sedimentary environmental changes in the continental margin. Furthermore, a detailed scenario combining multistep sediment transport with post-depositional migration is proposed to decipher this evolution.