利用宇宙成因核素10Be,26Al估算流域侵蚀速率的原理与应用
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国家自然基金项目“玉门砾岩、酒泉砾石层的宇生核素埋藏测年及其记录的流域侵蚀速率研究”(40871011)


Calculating Erosion Rate of Drainage Basin by 10Be and 26Al Measurements:Theory and Application
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    摘要:

    地表侵蚀是地貌演化的外营力。定量估算地表侵蚀速率,探讨其与构造活动,气候变化的响应和反馈是地学研究的重要课题之一。利用河流阶地沉积物或盆地沉积物宇宙成因核素(10Be 26Al)可获取流域万年尺度平均侵蚀速率时间序列,弥补了热年代学获得的百万年平均剥露速率和水文观测获得的年代级侵蚀速率之间的环节。地表及其附近岩石中的矿物的原子核受到来自外层宇宙空间的高能宇宙射线粒子的轰击,发生核反应而产生放射性核素,然后被快速埋藏,不再接受宇宙射线辐射。总体上,它们在地表的暴露时间短暂,宇生核素含量低,埋藏后宇生放射性核素随时间流逝而衰减。利用10Be和26Al估算流域古侵蚀速率基于此原理,通过测试河流沉积物或盆地沉积物的年代,结合10Be浓度,进而估算流域的平均侵蚀速率。应用宇生核素方法研究流域侵蚀速率,具有采样简便,精确度高,应用范围广等优势,可以反映更大时间尺度和更广空间尺度上的侵蚀速率变化情况,利用10Be和26Al等核素方法对第四纪至全新世的地表演化进行研究正成为一种重要的研究方法。

    Abstract:

    Erosion is an exogenic agent of landscape evolution.Quantitatively calculation of erosion rates and the reveal of the climate-erosion-tectonics feedback system are important research subjects in Geosciences.The average rates of exhumation can be obtained from thermochronology on time scale of millions of years,and erosion rates from hydrological measurement on time scale of tens of years.As a supplement,erosion rates on time scale of ten thousands of years can be calculated by measuring cosmogenic nuclide(10Be and 26Al)from river terrace deposits or basin sediments.Cosmogenic nuclides were primarily generated by reaction of quartz grains exposed near earth surface by galactic cosmic radiation,which were then suddenly and deeply buried to shield off cosmicrays after exposure of short time on the ground surface.Generally,the quartz grains have a short time exposure and low cosmogenic nuclide concentration.In addition,the cosmogenic nuclide decreases over time after burial.Quantitatively calculation of erosion rates from 10Be and 26Al is a concept based on dating river terrace deposits or basin sediments by determination of 10 Be concentration.Combining 10Be and 26Al measurements,surface exposure ages or erosion rates can then be calculated.The method is precise,easily accessible and widely applicable.It can be used for longer time scales and broader spatial scales,and it is a new method important to landscape evolution research from Quaternary to Holocene.

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胡二伢,李颍,赵志军.利用宇宙成因核素10Be,26Al估算流域侵蚀速率的原理与应用[J].水土保持通报,2011,(3):103-107

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  • 收稿日期:2010-10-26
  • 最后修改日期:2010-11-01
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  • 在线发布日期: 2014-11-26
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