ESR Dating at Archaeological Sites in Europe, Africa and Asia

Drs。Bonnie Blackwell和Anne Skinner将进行一系列的实验室实验，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样本。ESR提供了一种方法来确定牙齿和适当类别的石器文物的年代，这些文物的年代在大约2万年到可能多达400万年之间。由于这两类文物在考古遗址中都很常见，并且由于许多此类事件无法通过其他可用技术确定日期，因此，如果适当发展，ESR可以提供重要的人类学工具。该技术依赖于埋藏的物体从土壤中吸收少量铀的事实，以及由解体副产物产生的内部和外部轰击在样品内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。当剂量率确定后，就可以计算年龄。许多史前人类在将石器制成工具之前对其进行加热，因为加热引起的结构变化使这种材料更容易加工。幸运的是，热量也将电子位移时钟设置为零，从而使热处理件适合ER分析。虽然它在原则上是可行的，并产生了直观合理的日期，但ESR并没有得到很好的发展，并且结果被谨慎对待，这是可以理解的。铀的吸收率很难确定，已经提出了几种不同的模型。Blackwell和Skinner的研究重点是技术发展。他们应进行若干实验，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，以提供更准确的摄取模型；发展一种非破坏性的技术，在不损失有价值的进化信息的情况下测定原始人牙齿的年代；比较等时线分析所得的外剂量率与标准ESR测量所得的外剂量率。他们还将对一系列具有人类学意义的遗址的样本进行测年。

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.