Dating Mammalian Tooth Enamel using 4He

在美国国家科学基金会的支持下，Thure Cerling博士将研究测量化石牙釉质中4He浓度作为绝对年龄测定方法的潜力。he是铀的衰变产物，如果he保留在牙齿中，并且没有混杂变量存在，那么he的含量应该与时间有关。初步工作产生了两个非常有趣的结果。首先，铀的含量和氦的含量之间没有密切的关系。其次，对已知年龄样品的分析表明，4He的含量与年龄密切相关。这种明显异常的原因尚不清楚，尽管Cerling博士假设，虽然U在埋葬后被牙齿吸收，但最终的4He并没有紧密地结合到基质中，因此丢失了。他将试图阐明4He产生和损失的机制。为了实现这一目标，他将分析来自许多具有不同沉积学和温度历史的地点的已知年龄的牙齿。他要量一量氦和氦在这些样品中的分布。他将比较给出准确日期和异常日期的样本，以确定是否可以建立选择标准。牙齿的横截面将被自动放射照相以确定铀的分布。为了了解铀在牙釉质中的吸附和溶解度，还将进行浸出试验。这项研究很重要，因为如果成功，它将导致一种广泛应用于古人类学以及地质和生物科学的年代测定技术。

With National Science Foundation support Dr. Thure Cerling will examine the potential of measuring the concentration of 4He in fossil tooth enamel as a method for absolute age determination. 4He is a decay product of Uranium and if 4He is retained in the tooth, and no confounding variables are present, the amount should be time dependent. Preliminary work has yielded two very interesting results. First, there is no close relationship between the amounts of uranium and 4He present. Secondly, analysis of samples of known age indicates that the amount of 4He is very closely related to age. The cause of this apparent anomaly is not understood although Dr. Cerling postulates that although U is taken up in teeth after burial, the resultant 4He is not tightly bound into the matrix and is thus lost. He will attempt to illuminate the mechanisms of 4He production and loss. To accomplish this he will analyze teeth of known age from a number of sites with different sedimentological and temperature histories. He will measure the distribution of 4He as well as 3He within these samples. He will compare samples which give accurate vs. aberrant dates to determine if selection criteria can be established. Cross sections of teeth will be autoradiographed to determine the distribution of uranium. In order to understand the adsorption and solubility of uranium in enamel, leaching tests will also be conducted.This research is important because, if successful, it will lead to a dating technique of widespread use in paleoanthropology as well as geological and biological sciences.