黄龙洞年轻石笋的^210Pb测年研究  

^(210)Pb Dating of Young Stalagmite from Huanglong Cave

作　　者：杨勋林[1,2] 张平中[2] 袁道先[1,3] 程海[4] 

机构地区：[1]西南大学地理科学学院,三峡库区生态环境教育部重点实验室,中国重庆400715 [2]兰州大学资源环境学院,西部环境教育部重点实验室,中国兰州730000 [3]中国地质科学院岩溶地质研究所,国土资源部岩溶动力学重点实验室,中国广西桂林541004 [4]美国明尼苏达大学地质与地球物理系,美国明尼苏达,MN55455

出　　处：《地质论评》2010年第4期543-548,共6页Geological Review

基　　金：国家自然科学基金创新群体项目(编号40421101),国家自然科学基金项目(编号40471137);重庆市自然科学基金(编号CSTC,2009BB7107);中国博士后科学基金(编号20090460713);国土资源部岩溶动力学重点实验室开放基金(编号桂科能0842008,kdl2008-07);西南大学博士基金(编号SWUB2007043)的成果

摘　　要：利用210Pb测年法对来自亚洲季风系统相互作用的青藏高原边缘区、高海拔的黄龙洞两根年轻石笋进行了测年研究,数据分析结果显示黄龙洞石笋顶部的210Pb放射性活度随距离呈指数衰变,衰变的趋势逐渐减缓,表明所研究的石笋中含有过剩的210Pb,样品顶部年龄小于100a。对黄龙洞石笋过剩210Pb数据进行非线性拟合,计算出两根石笋的平均沉积速率分别为0.104mm/a和0.143mm/a,与利用230Th测年法得到的沉积速率在定年误差范围之内一致,表明黄龙洞的210Pb测年数据是可靠的,通过计算石笋的沉积速率,可以建立近百年的石笋记录。研究表明,利用210Pb测年方法可以判断石笋(或石笋顶部)是否为100a内沉积的年轻石笋,弥补230Th法测定年轻石笋年龄的不足,有利于建立更加精确的石笋年代标尺,对探讨洞穴现代沉积记录和现代气象数据之间的相关性,明确洞穴石笋δ18O值所指示的气候环境含义具有重要意义。This paper presents the 210^Pb dating of two young stalagmites from the Huanglong Cave which is located at the east margin of the Qinghai—Xizang（Tibet） Plateau influenced by the interaction of the southwest monsoon and the East Asian monsoon.The determination of 210^Pb age and the calculation of stalagmite growth rates are based on the 210^Pb activity decay with time.The 210^Pb activity is plotted against the depth and exhibits an exponential decay with the depth,which indicates that the sample is younger than 100 years and the 210^Pb activity comes mostly from the excess 210^Pb of the stalagmite.The average growth rates of the two stalagmites determined by excess 210^Pb activity are 0.104mm/a （HL021） and 0.143mm/a （HL021）,respectively,which is almost in agreement with that from the 230Th dating data,with the average growth rates of 0.105mm/a for HL021 and 0.145mm/a for HL022.The study proves the reliability of the 210^Pb dating results of stalagmite in Huanglong Cave and demonstrates that 210^Pb dating could be applied in dating of the stalagmite younger than 100 years while 230Th dating could not.This has also great significance in investigating correlation between stalagmites δ^18O records and meteorological data,which will provide more definite interpretation on oxygen isotope records of cave stalagmites as environmental indicators.However,the sampling method of large-size drilling with larger dating errors to some extent limits the use of 210^Pb dating method in the study of cave stalagmites.

关 键 词：210Pb测年 年轻石笋 沉积速率 黄龙洞 

分 类 号：P597.3[天文地球—地球化学]