赣北黄茅潭湖泊沉积记录的240年以来古洪水事件  

A 240-year sedimentary record of paleoflood events from the Huangmaotan Lake, northern Jiangxi Province

作　　者：吴霜 刘倩[1] 曹向明 赖忠平[2] 陈远辉 贾玉连[1,3] 

机构地区：[1]江西师范大学地理与环境学院,南昌330022 [2]中国地质大学地球科学学院,武汉430074 [3]鄱阳湖湿地与流域研究教育部重点实验室,南昌330022

出　　处：《地理科学进展》2017年第11期1413-1422,共10页Progress in Geography

基　　金：江西省重大生态安全问题监控协同创新中心项目(JXS-EW-00);鄱阳湖湿地与流域研究教育部重点实验室(江西师范大学)开放基金项目(ZK2013003)~~

摘　　要：古洪水研究是近几十年来全球变化研究的一个热点,同时也是难点。本文利用赣北黄茅潭的湖泊沉积,建立了小冰期以来全球变暖背景下的区域洪水记录。采用210Pb和137Cs方法厘定了地层年代,基于粒度与元素地球化学指标的对比分析,揭示了器测记录(1950年)以来指标记录的特点与区域日降水超过50 mm天数的关系,认为黄茅潭HMT-01孔粒度(包括粗粉砂+砂/粘土比值、平均粒径)和Zr/Rb、Ti/Rb、Zr/Fe比值可作为洪水指标记录,共识别出1950-2010年期间记载的13次洪水事件中的11次。基于这些指标记录及指标特点,共识别1769-1950年间由历史文献记录的31次洪水事件中的23次,识别率达74.2%。研究表明:(1)湖泊沉积中Zr/Rb、Ti/Rb、Zr/Fe比值和粒度参数(平均粒径、粗粉砂+砂/粘土)作为洪水指标,对洪水事件沉积有较好的指示作用,且Zr/Rb比值对洪水事件的检出率较高;(2)黄茅潭流域洪水发生频率暖期高于冷期;(3)年代际尺度上,1820s-1840s,1860s-1870s为19世纪冷期黄茅潭洪水高频期,这两个阶段对应东亚夏季风偏强,长江中下游地区降雨较多;20世纪赣北黄茅潭洪水基本随1920s-1940s,1980s-1990s两个变暖阶段而高频出现,与长江中下游大洪水演变特点基本一致。研究结果为利用湖泊沉积记录反演过去的洪水变化,延长洪水序列、认识洪水规律提供了一定的科学依据。Paleoflood reconstruction is one of the foci of global change research and in the last decades,increasingly more attention has been paid to investigate lacustrine sediments to identify sedimentary proxies（such as chemical, physical） and extract environmental information of flood events. This article attempts to elucidate the issue based on recent Huangmaotan lacustrine sediments and reconstructs the regional paleoflood records of northern Jiangxi since the Little Ice Age. This investigation, using the 137 Cs and 210 Pb-based chronology, first presents a comparative analysis of grain size parameters, geochemical indices of sediments, and annual number of days with rainfall 50 mm during the last 60 years. It indicates that the particle size parameters, including（coarse silt＋sand）/clay ratios, mean grain size（um）, and ratios of Zr/Rb, Zr/Fe, and Ti/Rb correlated well with 11 of the 13 flood events recorded in historical documents during 1950-2010, which suggests that these indices can be applied to identify flood events from lacustrine sediments. Based on these indices, 23 of the 31 flood events during 1769-1950 recorded in historical documents are identified. The study indicates that：（1） Zr/Rb, Zr/Fe, and Ti/Rb ratios,（coarse silt ＋ sand）/clay ratio, and mean grain size are sensitive to flood-event deposits, especially Zr/Rb ratios. Strong catchment erosion during flooding periods and intensified river discharge, we argue, are favorable conditions for the delivery of more coarse particles to the lake to deposit.This type of horizons, with high Zr and Ti, and low Fe and Rb, contrast with background lacustrine sediments.（2） This study also demonstrates that there were more floods occurred during the recent warm period（1900-2010） compared with the last cold stage of the Little Ice Age（1800-1900）.（3） On multi-decadal time scales,regional floods were high-frequency incidence in the 1820 s-1840 s and the 1860 s-1870 s, when the East-Asian summer monsoon was stronger and rainfall

关 键 词：湖泊沉积 洪水指标 粒度 Zr/Rb 黄茅潭 

分 类 号：P532[天文地球—古生物学与地层学]