沉积环境地球化学变化对牙齿ESR-U系联合法测年的影响

Effect of geochemical alteration of depositional environment on combined ESR-U series dating of herbivore teeth

在进行考古测年时,沉积环境的地球化学变化可能会影响野外环境剂量率的测定,从而导致基于辐射暴露原理的测年方法结果的不准确性,如释光和电子自旋共振(ESR)。实验通过对采自法国南部Arago洞穴中三种不同沉积环境下的同层牙齿样品进行ESR-U系联合法年代学分析,探讨了不同沉积环境及沉积环境的不均一性对测年结果产生的影响。其中出自石英矿物环境的样品年龄约为330ka,而另两种不同沉积环境(碳酸盐和磷酸盐)下的样品年龄约480ka,前者比后者年轻约150ka,这一现象可能是由于对石英矿物环境样品野外环境剂量率的高估造成的。

In archaeological dating, the geochemical alteration of depositional environments may affect the measurement of external dose rate, which will cause the inaccuracy of dating result of methods basing on the principle of radiation exposure, such as thermoluminescence （TL） and electron spin resonance （ESR） dating. In this study, tooth fossils from three different depositional environments in Arago cave, south of France, were analyzed by combined ESR-U series method and the potential effects of geochemical alteration and inhomogenous of depositional environment on the dating results were revealed. The study shows that the age of samples from non-altered quartz mineral environment was dated about 330 ka, while the teeth from the other two environments （carbonated and phosphate areas） were dated around 480 ka, the former is about 150 ka younger than the latter. This phenomenon is probably caused by the overestimation of external dose rate in quartz mineral area. The study suggests that the dating researchers should pay much attention to geochemical alteration of depositional environment of samples.