Application and Ar-Ar Calibration of Uranium-Series Dating at Olorgesailie

在国家科学基金会的支持下，Kenneth Ludwig，Alan Deino和Warren Sharp博士将收集和分析来自肯尼亚南部经典Olorgesailie考古区的氩-氩测年样品，并分析现有的铀系测年样品。 Olorgesailie拥有极其丰富的早期人类文物积累和人类占领的连续记录，已被研究了50多年，最近一次是由史密森学会的Richard Potts和同事正在进行的研究。 由于Deino之前的氩-氩测年，Olorgesailie的60万年前的记录现在已经过时了。 然而，记录的较年轻的部分，包含了从阿舍利技术（一种相对粗糙的石头工业，以相对较小的大脑直立人为特征）到中石器时代技术（与解剖学上的近现代人类有关）的过渡的极少数记录之一，现在才被详细研究。 然而，这一部分的Olorgesailie地层几乎没有任何类型的日期，而且精度也不高。 正是这个空白，我们将填补这项建议的研究，部分是通过应用一个相对较新的，但经过充分验证和极高精度的方法-铀系列热电离质谱法-到新类型的样品，已被证明是常见的Olorgesailie。 这些新类型的样品--其中最有希望的是被蛋白石形式的二氧化硅取代的根模--以前没有用于铀系测年，因此它们的可靠性和准确性未经验证。 幸运的是（也是非常不寻常的），这样的验证可以在Olorgesailie进行，因为铀系测年的样品与氩-氩测年的火山灰样品共同出现，后者是公认的考古测年的“黄金标准”，时间范围从5万年到数百万年。 如果得到验证，铀系测年法可以用来对缺乏适合氩-氩测年的火山灰层的较年轻的Olorgesailie层的那些部分提供年龄控制。 在本研究提供的预期年龄控制下，史密森学会科学家的详细研究（最近获得了为期5年的国家科学基金会资助，继续在Olorgesailie进行研究）东非人类文化和行为的进化将获得一个宝贵的和精确的年龄控制层面，这在长期的单点研究中是前所未有的。人类在过去50万年的进化。 因此，该项目将与其他联邦资助的研究高度协同（特别是考虑到该项目的成本分摊程度），并为考古学和地质学应用高科技方法的勤工俭学学生提供宝贵的经验。

With support from the National Science Foundation, Drs. Kenneth Ludwig, Alan Deino, and Warren Sharp will collect and analyze samples for Argon-Argon dating, and analyze existing samples for uranium-series dating, from the classic Olorgesailie archeological area in southern Kenya. Olorgesailie, with its extremely rich accumulation of early human artefacts and continuous record of human occupation, has been studied for over 50 years, most recently by the ongoing studies or Richard Potts and colleagues at the Smithsonian Institution. The pre-600,000 year record at Olorgesailie is now well-dated, as the result of previous Argon-Argon dating by Deino. However, the younger part of the record, which contains one of the very few records of the transition from Acheulean technology (a relatively crude stone industry characteristic of relatively small-brained Homo Erectus) to Middle Stone Age technology (related to anatomically near-modern humans) of is only now being studied in detail. Few dates of any kind are available for this part of the Olorgesailie stratigraphy, however, and none of high precision. It is just this gap which we will fill with the research of this proposal, in part by applying a relatively new but well-validated and extremely high-precision method - uranium-series by thermal ionization mass spectrometry - to new types of samples that have been shown to be common at Olorgesailie. These new types of samples - of which the most promising is root-casts which have been replaced by the opal form of silica - have not been used before for Uranium-series dating, so their reliability and accuracy are unvalidated. Fortunately (and very unusually), such validation can be carried out at Olorgesailie because of the common co-occurrence of samples for uranium-series dating with samples of volcanic ash for Argon-Argon dating, the latter being the acknowledged "gold standard" for archaeological dating in the time-range of 50,000 years to millions of years. If validated, the uranium-series dates can then be used to provide age control on those parts of the younger Olorgesailie beds that lack ash beds suitable for Argon-Argon dating. With the anticipated age control provided by this research, the detailed studies by Smithsonian Institute scientists (who recently obtained a 5-year National Science Foundation grant to continue their research at Olorgesailie) on the evolution of human culture and behavior in East Africa will gain an invaluable and precise dimension of age control at a level that is unprecedented in a single-site study of long-term human evolution over the past 500,000 years. This project will thus by highly synergistic with other federally-funded research (especially given the significant degree of cost sharing of this project), as well as providing valuable experience to a work-study student in applied high-technology methods in archeology and geology.