摘要
长期暴露于地表的石英砂被快速搬入洞穴或埋藏,不再接受宇宙射线辐射,埋藏前所积累的陆地宇生核素26A l和10B e随时间指数衰减。据此用加速器质谱计测定沉积物中石英样品现存的26A l/10B e可计算其埋藏年代。用此方法本文对周口店第一地点的下部地层年代作了初探。此次研究表明自第10层以下的沉积物其年代很可能≥1 M a。
This paper introduces a recently developed dating technique based on the decay of ^26Al and ^10Be. The two radionuclides, with half lives 0. 7 and 1.5 Ma respectively, are in situ produced by secondary cosmic-ray particles in quartz near the ground surface with a stable ratio of production rates. Their concentrations depend on the time of mineral＇s exposure to cosmic rays, which is in turn controlled by the erosion rate of the host rock. If quartz grains, after longtime exposure on the ground surface, are suddenly washed into a cave or deeply buried with at least ten meters of overburden to shield off cosmic rays, the production of ^26Al and ^10Be drastically slows or ceases and the inherited radionuclides decrease exponentially with time. Because ^26Al decays roughly twice as fast as ^10Be, the ^26Al/^10Be ratio decreases also exponentially with time, With a state-of-the-art accelerator mass spectrometry （AMS）, it＇s possible to precisely determine the trace amount of ^26Al and ^10Be in quartz, from their ratio the sample＇s burial time can be deduced. This method is applicable in the range of 0. 3 to 5 Ma, filling thus a ＂blind spot＂ of the Quaternary geochronology.
With this technique, we studied the chronology of the low sediments at Zhoukoudian Location 1. The result indicates that the chronoloies of the Layer 10 may be approach 1 Ma. However, the samples were not purified sufficiently to obtain reliable data, because of the complexity of mines, especially the effect of feldspar.
出处
《中国岩溶》
CAS
CSCD
北大核心
2006年第3期195-200,共6页
Carsologica Sinica
基金
国家自然科学基金资助项目(编号:40073020)
