Characteristics of paleoflood deposits archived in unit T0403 of Yuxi site in the Three Gorges reservoir areas, China

Based on the detailed analyses, multi-proxies such as AMS 14C dating, grain size, component and morphology of heavy minerals, micromorphology of zircon, magnetic susceptibility, Rb/Sr and Hg content are used to research the paleoflood sediments archived in the Yuxi Site. The research indicates that, since 7.6 kaBP, at least 16 times of paleoflood with water level above Wusong Elevation 147.024 m (a.s.l.) left deposits in the Neolithic layers of unit T0403 from the Yuxi Site. The results are induced from the following aspects: (1) The plaeoflood sediments take on great similarities with modern flood sediments in the Yuxi Site and Zhongba Site in probability cumulative curves which mainly show a pattern of 3 segments in fluvial pattern. (2) There is some resemblance between the heavy mineral components and the zircon shape characteristics of paleoflood deposits and those of modern flood deposits. (3) Magnetic susceptibility values (40.44–70.10SI) are lower than those of sediments from cultural layers (59.59–188.68SI). (4) Hg values (290.71–742.51 ng/g) are lower than those of sediments from cultural layers (344.16–10518.17 ng/g). (5) Rb/Sr values are higher than those of sediments from cultural layers, while those of the 4th, 5th, 6th, 7th, 8th cultural layers are high, which shows that they are inundated by paleoflood. The reason for many flood deposits existing is related to the site situated on the first terrace where the Yuxi River joins with the Yangtze River. As there are some similarities between the plaeoflood sediments and those of the Zhongba Site, it is feasible to confirm the existence of paleoflood sediments based on the above points.