ODDSIMS, A New Method of Age Dating Hydrated Obsidian by Secondary Ion Mass Spectrometry

在国家科学基金会的支持下，Lee Riciputi博士和他的同事们将进行一项为期三年的研究，以完善黑铁矿水合测年技术。黑玉岩，也被称为“火山玻璃”，史前人类的珍视，因为它同质的玻璃状结构使得它可以相对容易地被剥落，并且可以高度控制。这样产生的锋利的边缘起到了刀和其他工具的作用。黑岩被广泛交易，并在中南美洲、非洲和东半球其他地区的许多考古遗址中被发现。剥落的过程会产生新的外表，随着时间的推移，当它们从大气和土壤中吸收水分时，会产生新的外部表面。表面上可见的水合边缘随着时间的推移而变厚，这种年龄相关性为绝对测年技术提供了基础。科学家们可以切开一片黑铁矿，测量其边缘的厚度，然后尝试将其转换为日期。虽然这项技术已经使用多年，具有巨大的潜力，但效果往往不尽如人意。水化速率似乎与温度和湿度有关。它也可能受到黑铁矿本身的微量元素组成的影响。科学家们在如何模拟扩散速度随时间变化的问题上也存在分歧。里希普蒂博士和他的同事们开发了一种新的黑铁矿水合分析方法。他们将使用更精确的二次离子质谱仪技术，而不是使用光学显微镜来确定水合深度。他们还将通过一系列受控实验来解决水化建模的问题，在这些实验中，来自单一来源的黑铁矿暴露在温度和湿度变化的环境中。为了将结果应用于现实世界，研究人员将分析通过与放射性碳年代测定材料相关联而确定年龄的中美洲黑铁矿文物。这些标本的年龄以及沉积环境的温度和湿度都会有所不同。这项研究很重要，因为如果成功，它将为考古学家提供一个强大的年代测定工具，能够在世界许多地方应用。

With National Science Foundation support Dr. Lee Riciputi and his colleagues will conduct a three year study to refine the technique of obsidian hydration dating. Obsidian, also known as `volcanic glass`, was prized by prehistoric peoples because its homogeneous glass-like structure allows it to be flaked with relative ease and a high degree of control. The sharp edges thus produced functioned as knives and other tools. Obsidian was traded widely and has been recovered in many archaeological sites in Middle and South America, Africa and other parts of the Old World. The process of flaking produces fresh external faces and over time these `hydrate` as they absorb water from the atmosphere and soil. The hydration rim visible on the surface thickens over time and this age dependence provides the basis for an absolute dating technique. Scientists can section an obsidian flake, measure the thickness of the rim and then attempt to convert this to a date. Although the technique has been used for many years and holds great potential, the results are often unsatisfactory. Hydration rate appears to be temperature and moisture dependent. It may also be affected by the trace element composition of the obsidian itself. Scientists also disagree on how to model diffusion rates over time. Dr. Riciputi and his colleagues have developed a new approach to obsidian hydration analysis. Rather than use an optical microscope to determine hydration depth, they will employ a more precise secondary ion mass spectrometry technique. They will also address the issue of hydration modeling through a series of controlled experiments in which obsidian from a single source is exposed to environments which vary in temperature and humidity. To apply the results in a real world context, the investigators will analyze Middle American obsidian artifacts whose age has been determined through association with radiocarbon dated materials. These specimens will vary in age as well as the temperature and humidity of their depositional environment. This research is important because, if successful, it will provide archaeologists with a robust dating tool capable of application in many parts of the world.