首页 | 本学科首页   官方微博 | 高级检索  
     检索      

东北四海龙湾玛珥湖沉积物纹层计年与137Cs、210Pb测年
引用本文:储国强,顾兆炎,许冰,刘强,孙青,汉景泰,刘嘉麒.东北四海龙湾玛珥湖沉积物纹层计年与137Cs、210Pb测年[J].第四纪研究,2005,25(2):202-207.
作者姓名:储国强  顾兆炎  许冰  刘强  孙青  汉景泰  刘嘉麒
作者单位:1. 中国科学院地质与地球物理研究所,北京,100029
2. 国家地质实验测试中心,北京,100037
基金项目:中国科学院知识创新“中国玛珥湖高分辨率古气候环境记录研究”项目 (批准号:KZCX3-SW-145),国家自然科学基金项目 (批准号:40171098和 40302023)资助
摘    要:对东北四海龙湾玛珥湖SHLF6孔纹层沉积物的137Cs放射性测量表明:137Cs比活度的最大值出现在55cm处,对应于1963年世界原子弹试爆高峰期。纹层计年表明0~6cm共有35个纹层层偶。从75cm到65cm,137Cs比活度从256±009dpm/g急剧增加到1868±017dpm/g,可能65cm对应于1954年。通过测量226Ra子核214Pb和214Bi(能量为295keV,352keV和609keV)放射的光子数获得226Ra比活度数据,然后求得过剩210Pb比活度(210Pbuns)。210Pbuns比活度随深度增加而呈指数衰减,其异常波动可能与人类活动以及沉积速率变化有关,例如55cm处210Pb比活度较高,与137Cs的峰值对应,这可能与1963年前后人工核实验的高峰有关,因为核试验不仅产生137Cs,而且可以产生208Pb和210Pb;45cm处210Pb比活度较低,而226Ra较高,可能与人类活动加剧,导致沉积速率增加有关。根据210PbunsCRS模式,SHLF6孔0~19cm的平均沉积速率为20mg/cm2·a,或约为011cm/a。210Pb测年数据与137Cs时标及纹层计年均有很好的一致性。四海龙湾玛珥湖发育的纹层为年纹层,可以建立高分辨率时间序列。

关 键 词:四海龙湾玛珥湖  年纹层  137Cs、210Pb测年
文章编号:1001-7410(2005)02-202-06
收稿时间:2004-11-29
修稿时间:2004年11月29

VARVECHRONOLOGY AND RADIOMETRIC DATING (137Cs, 210Pb) FROM THE SIHAILONGWAN MAAR,NORTHEASTERN CHINA
CHU Guoqiang,Gu Zhaoyan,Xu Bing,Liu Qiang,Sun Qing,Han Jingtai,Liu Jiaqi.VARVECHRONOLOGY AND RADIOMETRIC DATING (137Cs, 210Pb) FROM THE SIHAILONGWAN MAAR,NORTHEASTERN CHINA[J].Quaternary Sciences,2005,25(2):202-207.
Authors:CHU Guoqiang  Gu Zhaoyan  Xu Bing  Liu Qiang  Sun Qing  Han Jingtai  Liu Jiaqi
Institution:1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029;
2. National Research Center for Geoanalysis, Beijing 100037
Abstract:Sediments from maar lakes in the Longgang volcanic filed have been demonstrated to contain high-resolution nature archives for paleoclimatic and paleoenvironmental research. In 1998, freezing cores were recovered using a freeze-coring system by scientists from our institute and Geo-science Center in Germany. A frozen core (SHL-F6) was sawed into sediment slabs, freezing-dried, and then impregnated with epoxy resin and manufactured as thin sections. Based on the study of thin sections from core SHL-F6 under microscope, varve couple appears as dark-coloured layer and light-coloured layer. The dark-coloured layer mainly consists of valves of diatoms and organic matter, and with less variation in thickness. The light-coloured layer consists of clastic and organic matter, and with large variation in thickness. The dark-coloured layer is an important mark to identify annually interface. Radiometric dating shows that the highest 137Cs activity appears at 5.5cm depth of core SHL-F6, assumed to correlate to the 1963 maximum of emission due to the nuclear bomb testing. Base on varve counting, 35 couples were found in the upper part of the core (0~6cm). It well corresponds with the highest 137Cs activity at 5.5cm. 137Cs activities increase quickly from 2.56±0.09dpm/g at 7.5cm to 18.68±0.17dpm/g at 6.5cm, and may correlate to the 1954. The short-lived 226Ra activity was measured from daughter nuclides 137Cs and 214Bi (295 keV, 352keV and 609keV). Unsupported 210Pb activity exponentially attenuated as the increasing of the core depth. The abnormal variations of 210Pb activity can be found in the profile. The relative high value of 210Pb at the depth of 5.5cm may be also linked with the 1963 maximum due to the nuclear bomb testing for nuclear bomb testing producing both 137Cs and 208Pb and 210Pb. The relative low value of 210Pb and relative high value of 226Ra at the depth of 4.5cm may due to human activity that induced high sediment input. 210Pb (CRS) and 137Cs dating result show a good agreement with the varve-chronology. Varved sediments in the Sihailongwan maar are annually laminated and high-resolution records for paleoclimatic and paleoenvironmental research.
Keywords:the Sihailongwan maar  varve        137Cs and    210Pb dating
本文献已被 CNKI 万方数据 等数据库收录!
点击此处可从《第四纪研究》浏览原始摘要信息
点击此处可从《第四纪研究》下载免费的PDF全文
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号