Magnetic Properties of Late Cenozoic Sediments in the Subei Basin: Implications for the Yangtze River Run-through Time

Abstract

ABSTRACT Shu, Q.; Zhao, Z.; Zhao, Y.; Chen, Y., and Zhang, M., 2021. Magnetic properties of late Cenozoic sediments in the Subei Basin: Implications for the Yangtze River run-through time. Journal of Coastal Research, 37(1), 122–131. Coconut Creek (Florida), ISSN 0749-0208. The Subei Basin is situated in the lower reaches of the Yangtze and Huai Rivers. In this study, samples were selected from the XH-2 borehole near the subsidence center of the Subei Basin, and modern sediments from the lower reaches of the Yangtze and Huai Rivers. The aim of this study is to decipher the evolution of the regional river system and the formation of the Yangtze River's Three Gorges through the analyses of paleomagnetism, mass susceptibility, and magnetic minerals. The results show that the river system in the Subei Basin experienced several major upheavals. (1) During 4.76–4.2 million years before present (Ma BP), the Yangtze River flowed through the study area in the vicinity of the XH-2 location; (2) During 4.2–2.2 Ma BP, the Yangtze River had migrated from the study area, and the Huai River flowed through the area; (3) During 2.2–0.55 Ma BP, the Yangtze River flowed through the area again; (4) During 0.55–0.12 Ma BP, the Yangtze River and Huai River alternatively influenced the study area; and (5) Since 0.12 Ma BP, the Yangtze River withdrew from the Subei Basin entirely, and the Huai River flows through the XH-2 position again. The Yangtze River sediment in the bottom of the XH-2 borehole indicates that the time of formation of the Three Gorges of the Yangtze River is probably greater than or equal to 4.76 Ma BP. This estimated time is earlier than the previous conclusions of an Early Pleistocene run-through time for the Yangtze River.