Detrital zircon U-Pb geochronology of the Oligocene Huagang Formation in the East China Sea Shelf Basin

Researchers have long suspected a source-to-sink link between the Yangtze Block (and/or North China Block) and Eocene-Miocene passive margin strata in Taiwan, and various models have been proposed to explain similarities in provenance and the presence of Archean grains. The East China Sea Shelf Basin (ECSSB), whose evolution has been neglected in most models, resides between potential mainland China source regions and the sediment sink in Taiwan, and occupies the corridor through which sediment would have been transported. Here we present 378 new concordant detrital zircon U-Pb ages from the Oligocene Huagang Formation in the Xihu Sag, eastern ECSSB. We also present a compilation of published detrital zircon data from major rivers across mainland China to evaluate potential sediment source regions. Detrital ages in the Huagang Formation range from 33 ± 0.4 to 2842 ± 43 Ma, with major clusters at 100-300 Ma and 1600-2200 Ma and small early-middle Paleozoic, Neoproterozoic, and Paleoproterozoic to Archean peaks. Visual and statistical comparison of age distributions suggest close relationships between the Min River and Eocene-Oligocene samples from western Taiwan and between the Oligocene Huagang Formation and Miocene strata in western Taiwan. Combined with the tectonic and depositional evolution of the region, these observations suggest Eocene-Oligocene sediment in Taiwan were mainly sourced from the Min River or similar drainage in the Cathaysia Block. However, the similarities between the Huagang Formation and Miocene strata are best explained by reworking of the Oligocene sediment in the Xihu Sag and transportation to western Taiwain during Miocene tectonic inversion of the ECSSB.