海螺沟现代冰碛物中的宇生核素10Be浓度分析

尽管许多学者都意识到继承性宇生核素对冰碛物暴露年代测量可能会带来一定的误差,然而影响究竟有多大,还缺乏对现代冰碛物宇生核素浓度的研究。对采自贡嘎山海螺沟冰川现代冰碛物碎屑和冰碛砾石的本地生宇生核素 10 Be 浓度的分析表明,即使是海洋性冰川(暖底冰川),其冰碛物碎屑和冰碛砾石都残留一定量的本地生宇生核素; 即使是具有明显磨蚀痕迹的现代冰碛砾石表面,也残留一定量的本地生宇生核素。因此,进行宇生核素测年时要给予充分的重视。当然,其冰碛物基质和具有明显磨蚀痕迹的现代冰碛砾石表面的本地生宇生核素 10 Be 浓度比较低,一般不大于2×104atoms/g。对暴露年代的影响一般不大于0.61ka。尽管其适用范围还有待于更多的研究结果的进一步证实,但是却为残留影响的研究提供了一个研究的实例和一组可以参考的数据。

INHERITED COSMOGENIC NUCLIDE 10Be IN MODERN MORAINE OF HAILUOGOU GLACIER IN THE GONGGA MOUNTAINS,SICHUAN PROVINCE, CHINA

The effect of the inherited cosmogenic nuclide 10 Be concentration on determining of exposure time of moraine is an important problem,but how many is the effect is not clear.This is mainly because lack of study on this concentration in modern moraines.In the paper,we collected samples of fine component and boulder from modern moraine of Hailuogou Glacier of the Gongga Mountains,Sichuan Province,China to determine their cosmogenic nuclide 10 Be concentrations.Our results indicated that a certain quantity of in situ cosmogenic isotope 10 Be was usually remained in fine components and boulders of modern maritime glaciers(warm-bottom glacier)and even in surface materials of moraine boulders with abrasion traces.In such surface materials,the inherited nuclide 10 Be concentration is relatively low,lower than 2×104atoms/g,and its effect on determining of the exposure time of moraine is generally less than 0.61ka.