ESR Dating at Archaeological Sites in Europe, Africa and Asia

Bonnie Blackwell博士和Anne Skinner博士将进行一系列实验室实验，以改进电子自旋共振(ESR)技术，并将其应用于各种重要的古人类学样本。ESR提供了一种方法来确定牙齿和适当类别的石器的年代，这些石器可以追溯到大约20,000年到可能长达4,000,000年前。由于这两类文物在考古遗址中都很常见，而且许多这样的遗迹无法用其他可用的技术确定年代，如果得到适当的开发，ESR可以提供一个重要的人类学工具。这项技术依赖于这样一个事实，即埋藏的物体从土壤中吸收少量铀，解体副产品对内部和外部的轰击在样品中产生随时间变化的电子位移。ESR提供了一种方法来衡量这种情况发生的程度。当确定了剂量率后，就可以计算年龄了。许多史前人类在将石块制成工具之前先将其加热，因为加热引起的结构变化使材料更容易加工。幸运的是，加热也将电子位移时钟设置为零，从而使热处理件适合进行ER分析。虽然它在原则上是可行的，并产生了直观合理的数据，但ESR并不是很好地开发，结果得到了可以理解的谨慎对待。铀摄取率很难确定，已经提出了几种不同的模型。布莱克韦尔和斯金纳的研究重点是技术开发。他们将进行一系列实验，以比较牙釉质与相关的牙本质、牙骨质和邻近沉积物的地球化学特征；了解牙齿如何吸收铀，以提供更准确的吸收模型；开发一种非破坏性技术，使人类牙齿的年代测定不会丢失宝贵的进化信息；比较等时线分析得出的外部剂量率与标准ESR测量得出的剂量率。他们还将对一系列具有人类学意义的遗址的样本进行年代测定。

Drs. Bonnie Blackwell and Anne Skinner will conduct a series of laboratory experiments to improve the electron spin resonance (ESR) technique and apply it to a variety of significant paleoanthropological samples. ESR provides a method to date teeth and appropriate categories of stone artifacts which date between ca. 20,000 and possibly as much as 4,000,000 years old. Because both categories of artifacts are common in archaeological sites and because many such occurrences are not datable by other available techniques, ESR, if properly developed, can provide an important anthropological tool. The technique depends on the fact that buried objects absorb small amounts of uranium from the soil and the internal as well as external bombardment by disintegration byproducts creates time dependent displacement of electrons within the sample. ESR provides a method to measure the extent to which this has occurred. When the dose rate has been determined, it is then possible to calculate age. Many prehistoric peoples heated lithics before they fashioned them into tools because the structural changes caused by heating made the material easier to work. Luckily, heat also sets the electron displacement clock to zero thus making heat treated pieces amenable to ER analysis.While it is feasible in principle and has produced intuitively reasonable dates, ESR is not well developed and the results have been treated with understandable caution. Uranium uptake rates are hard to determine and several different models have been proposed. Blackwell and Skinner's research focuses on technique development. They shall conduct a number of experiments to: compare geochemical characteristics of enamel with associated dentine, cementum and adjacent sediments; learn how teeth absorb uranium to provide more accurate uptake models; develop a non-destructive technique which will allow hominid teeth to be dated without loss of valuable evolutionary information; compare external dose rates derived from isochron analysis with those from standard ESR measurements. They will also date samples from a series of anthropologically significant sites.