摘要
石笋凭借其准确的年代学和对洞穴外界环境的敏感响应,已经成为第四纪研究的重要力量。亚洲季风区轨道-千年尺度石笋δ18O指示亚洲季风强弱的变化,但是在更短的时间尺度上,石笋δ18O则可能受到其他因素的影响,因此近现代、能与器测记录进行对比的石笋记录研究是衔接现代气候与古气候的关键环节。而这关键环节中的关键问题就是确定石笋的沉积年代。寻找一种适合于无生长纹层、低U含量石笋样品的年代方法对于解决石笋沉积年代有着重要的推动作用。本研究选择广西桂林茅茅头大岩一正在生长的年轻石笋。由于低U含量、高232 Th含量,U系-230 Th定年不成功。利用210Pb定年计算出平均沉积速率为1.96±0.23mm/a,但由于多层晶间孔隙的存在,计算结果偏小。由于石笋中14 C基本为核爆产生,AMS 14 C测试结果计算石笋平均沉积速率为2.10mm/a,但由于未测量到核爆前14 C数据,其值可能仍偏小。由于前人研究指出桂林地区石笋记录能记录夏季风降水,结合桂林多年降水数据,综合计算出该石笋平均沉积速率为2.44mm/a,生长时限为2009—1968年。平均沉积速率和沉积时代的确定,为后续的石笋现代气候研究,进而与古气候衔接提供了重要的研究基础。
Based on high precise dating and the proxies sensitively response to the climate and environment change outside of cave,speleothem（mainly stalagmite）is now an important pillar for Quaternary research.Orbital and millennial-scale variations of stalagmiteδ18 O were reported as a recorder of Asian summer monsoon intensity in the Asian monsoon area.But stalagmiteδ18 O is more complex in centennial to decadal-scale for other factors besides summer monsoon intensity will affect.Hence,the young stalagmite which can compare with meteorological record study is the key link for modern climate and paleoclimate for stalagmite research.Moreover,the key problem for young stalagmite study is determining the growth age.And it becomes very important to find suitable methods to determine the non-growth banding and low uranium stalagmite samples.In this study,an active stalagmite was chosen.For the low uranium and high232 Th concentration,the U-230 Th dating failed.The average growth rate was 1.96±0.23mm/a determined by 210 Pb dating,but for existing of multi-layers intercrystal pores,the real growth rate may be higher.The 14 C after bomb 14 C yielded the average growth rate of 2.10mm/a,no pre-bomb 14 C data indicates the growth rate may be faster.The previous study found the oxygen isotope of stalagmite in Guilin can record the summer monsoon precipitation,so according the meteorological data in the Guilin station reveals the growth rate of DY-2is 2.44mm/a,and the whole stalagmite growth from 1968 and stopped in 2009 when we collected.This fundamental work is the base of future stalagmite modern climate study,but this method can be a case for young stalagmite study.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2015年第10期1884-1891,共8页
Acta Geologica Sinica
基金
中国地质科学院基本科研业务费项目(编号:YWF201414)
岩溶地质研究所基本科研业务费项目(编号:2014025
201319)
中国地质调查局地调项目(编号:12120113006700)联合资助的成果
