辽宁金牛山遗址牙釉质样品的电子自旋共振(ESR)测年研究

ELECTRON SPIN RESONANCE DATING OF TEETH ENAMEL SAMPLES FROM JINGNIUSHAN PALAEOANTHROPOLOGICAL SITE

本文报告金牛山五个牙化石样品的ESR法和铀系法对比测年的结果,两者很接近,为23万年左右。文中着重讨论了ESR测年中的:简单指数拟合求累积剂量的困难,α射线相对效率和氡逸失系数的实验测定以及选择关于铀加入模式的指导思想等问题。最后探讨了牙釉质样品ESR测年的可靠性与应用前景。

Our early work on Uranium-series dating had assigned an age range of 230- 300 ka for the Palacoanthropological site of Jingniushan. In this work five more tooth samples from this site were dated with both elcctron-spin-resonance (ESR) and Uranium-series techniques. Enamel layers were separated for ESR dating. The accumulated dose(AD) was normalized with alanine dosimeter. As the AD value based on the exponential extrapolation much depends on the highest irradiated dose, linear extrapolation going with high correlation coefficiants was implemented. A value of 0.23 for alpha-effectiveness has been empirically determined, which differs somehow from the commonly accepted value of 0.15. Tentative efforts were made to determine the radon emanation and moisture coefficients. To keep the necessary consistency with the U-dating method on the U-uptake assumption, the ESR ages were calculated on the basis of 'early U-uptake model'. The closed-system assumption of the U-series dating was cheched and confirmed by comparing the Th-230 / U-234 and Pa-231 / U-235 activity ratios for every dentine sample. The ESR ages, ranging from 197-241 ka, are in fairly good agreement with the U-dates for each of these samples. The average ESR age of these 5 samples is 229 ± 28 (ka), which matches the lower end of the published U-series age range.