261 / 2022-03-31 09:00:00

Detrital zircon geochronology of Late Cenozoic sediments from the southern Yangtze Delta: Implications for sedimentary provenance and the Yangtze catchment evolution

Detrital zircon geochronology, provenance analysis, Yangtze River, drainage evolution, Late Cenozoic

Eleven samples of different depositional ages were collected from borehole PD-99 in the Yangtze delta. These samples were collected for detrital zircon U-Pb date testing. This testing process was selected to explore the feasibility of the methodology and to reconstruct the evolutionary history of the Yangtze River in the late Cenozoic. The zircon age patterns show some similarities among all the samples. Some similarities include clustering at the periods of 100~300 Ma，350~550 Ma，600~1000 Ma，1400~2000 Ma, and 2200~2800 Ma, but distinct differences have emerged between the 3 samples from the Pliocene and the 8 samples from the Pleistocene, which was also proved by Empirical orthogonal function (EOF) analysis. Besides the appearance of Cenozoic zircons, commonly considered as sourced from the Tibetan plateau in the upper reaches, The 8 samples have fewer Cretaceous zircons, more Late Paleozoic, Early Paleozoic, and Neoproterozoic zircons, conceivably sourced from the lower reaches, ELIP, Qinling tectonic belts, and the Cathaysia Block, and the Yangtze Block, respectively. It was indicated that the sedimentary provenance of the Yangtze delta changed dramatically around the late Pliocene. Sediments were mainly derived from the middle and lower reaches of the Yangtze River before the late Pliocene. Due to the huge area, complex outcropped rocks, and recycled sediments of the Yangtze catchment, using the zircon U-Pb age method could only realize the sediment provenance from partial tributary watersheds.