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在独流减河入海口附近河道之间的盐沼采用人工探坑侧壁连续取样,获得2个站位的沉积物样品。通过~(210)Pb和~(137)Cs定年法建立年代框架,结合粒度分析、有孔虫鉴定和水文数据,探讨了该区的现代洪水事件沉积。结果表明,该区沉积物的~(210)Pb_(exc)比活度-深度剖面中存在2处明显的低值沉积层,分别在3~6cm和10~14cm深度,这2个沉积层分别对应~(137) Cs曲线的次峰和主峰。这两层与上下相邻层位相比呈现粒径较粗、分选较差,有孔虫丰度较低、破损百分比较高的特征。~(210) Pb测年结果显示,~(137)Cs曲线下部的主峰对应的年龄为1963年,与全球性的最大峰值形成时间相对应,而上部的次峰对应的并非1986年切尔诺贝利核泄漏事故形成的次峰。区内水文数据显示,在1963和1996年分别发生了2次较大的洪水事件。因此,推断S4和S5站位剖面中2个特殊的沉积层是由洪水事件造成的。本研究说明高分辨率沉积特征的多指标研究可以较为准确地揭示洪水等灾害性事件发生的年代和频率,这有利于系统地揭露海陆过渡带地区地质历史时期灾害和气候事件的频率和强度,为灾害预防和未来规划提供科学依据。
In the salt marsh between the rivers that flowed into the estuary by the rivers, the sample of sediment at two stations was continuously sampled by using artificial sidewalls. The dating of ~ (210) Pb and ~ (137) Cs dating method was used to establish the framework of the age. Combining with the particle size analysis, foraminifera identification and hydrological data, the deposition of modern flood events in this area was discussed. The results show that there are two distinct low-value sedimentary layers in the ~ (210) Pb specific activity-depth profile of the sediments in the depth of 3 ~ 6cm and 10 ~ 14cm, respectively Corresponding to the 137 Cs curve of the secondary peak and the main peak. Compared with the upper and lower adjacent layers, these two layers showed the features of coarse particle size, poor sorting, low abundance of foraminifera and high percentage of damage. The results of ~ (210) Pb dating show that the main peak at the lower part of ~ (137) Cs curve corresponds to the age of 1963, corresponding to the global maximum peak formation time, whereas the upper secondary peak corresponds not to 1986 Chernobyl Bailey nuclear leakage accident formed the second peak. Regional hydrological data show that two large flood events occurred in 1963 and 1996, respectively. Therefore, it is inferred that two special sedimentary layers in S4 and S5 station profiles were caused by flood events. This study shows that the multi-index study of high-resolution sedimentary features can accurately reveal the age and frequency of disastrous events such as floods. This is conducive to systematically exposing the frequency and intensity of disasters and climate events during the geological history of the transitional zone, Provide a scientific basis for disaster prevention and future planning.