Magnetic Characteristics of ZK145 Borehole Sediments in Wuhan Area and Its Records of Paleoflood

The middle reaches of the Yangtze River are the most severely affected areas in China, and the Wuhan section is the key to flood control in the middle reaches of Yangtze River. It is of great significance to study the paleoflood of the Yangtze River in Wuhan area so as to prolong the record of the paleoflood. In this study, ZK145 borehole was selected in a typical lake behind the dam of Wuhan section of the Yangtze River. Based on the analysis of sedimentary lithology and sedimentary facies, magnetic characteristics and particle size characteristics of the core were analyzed, and AMS¹⁴C dating was used to study the occurrence period of holocene paleoflood in wuhan section of the Yangtze River. The borehole is divided into five sedimentary stages based on the mass magnetic susceptibility(χ) and the frequency susceptibility (χ_fd%) curve.Combined with the median particle size and sand content, nine paleoflood events were identified, with the age:10 580-10 510, 10 280-10 200, 9 690-9 670, 9 530-9 500, 8 660-8 450, 7 700-7 500, 6 270-5 910, 4 850-4 800, 3 560-3 500 cal.a BP, paleofloods occurred frequently at 9 700-4 800 cal.a BP among them. Through analysis of temperature-dependent magnetic susceptibility (κ-T curve), the heating curve of the paleoflood sediments shows a more obvious peak near 510℃ in paleoflood sediments, and Magnetite is the dominant magnetic mineral. The research shows that the high mass magnetic susceptibility, the low frequency susceptibility and the coarser particle size are the identification marks of the paleoflood deposition in the lakes behind the Yangtze River embankment in the Yangtze River.