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.

研究者们长期以来一直怀疑长江地块（以及/或华北地块）与台湾的始新世-中新世被动大陆边缘地层之间存在源-汇联系，并提出了各种模型来解释物源相似性和太古宙碎屑颗粒的存在。在大多数模型中，被忽视的东海大陆架盆地（ECSSB）位于可能的陆源区与台湾的沉积汇之间，占据着沉积物可能运输的走廊。在此，我们展示了来自东部ECSSB西湖凹陷奥陶纪华冈组的378个新的同步碎屑锆石U-Pb年龄。我们还汇总了来自中国大陆主要河流的已发表碎屑锆石数据，以评估潜在的沉积源区。华冈组的碎屑年龄范围在33 ± 0.4至2842 ± 43百万年之间，主要聚集在1亿至3百万年和1600至2200百万年，以及较小的早中寒武纪、新元古代、古元古代直至太古宙峰值。年龄分布的视觉和统计分析表明，闽江与台湾西部始新世-奥陶纪样品之间存在密切关系，以及奥陶纪华冈组与台湾西部中新世地层的密切关系。结合该地区的构造和沉积演化，这些观察结果暗示台湾的始新世-奥陶纪沉积物主要来源于闽江或类似位于华南地块的流域。然而，华冈组与中新世地层之间的相似性最好通过西湖凹陷奥陶纪沉积物的重新作用以及在ECSSB中新世构造反转期间向台湾西部的运输来解释。