Improvements In Radiocarbon And Archaeomagnetism Dating Techniques

放射性碳对我们了解世界史前史的贡献是真正革命性的。 然而，60多年过去了，仍然存在弱点（由于该方法的基本物理学无法解决），限制了其在人类历史某些关键时期的有效性。 一种较新的测年方法，考古磁学，已经证明了它在解决其中两个弱点方面的有效性。一个是大的标准差（日期的+/-范围），往往比人们希望的日期的开始和结束时间更长，另一个是周期性的平坦化，或高原化，放射性碳校准曲线（由此得出日历日期），因此在公元前800年至公元前400年之间（公元前）可以更精确地追溯到400年（地球仪周围的史前史学家诅咒的所谓“哈尔施塔特高原”）。 公元前的最后一千年正是世界历史核心的许多创新-国家和城市的起源，手工艺和金属加工的出现-具有爆炸性的开始和快速的演变。 耶鲁大学考古磁学实验室于2013年开放，致力于在全球范围内应用该方法。目前的项目是实验室发展的下一阶段不可或缺的一部分，该阶段不仅将对考古材料进行高精度测年，而且还将开发从考古背景中获取有关地球磁场强度变化的数据的方法，这些数据对于考古学家试图了解磁场产生背后的基本机制至关重要。 耶鲁大学考古磁学实验室的成立，显然是为了解决令人担忧的滞后，在生产的考古科学数据在美国相比，这些结果的涌出来自欧洲（美国考古学中所谓的“安静危机”）。高精度考古磁力年代的精确化和迄今为止独特的磁场强度数据的产生依赖于发现具有深度分层沉积物的考古遗址，具有丰富的燃烧特征（壁炉，熔炉，燃烧房屋），由正确矿物学的地球建造，以便这些特征记录燃烧时地球的磁信号。 沿着西非的中塞内加尔谷，在非洲最早的铁冶炼（公元前第一个千年）和非洲大陆最早的“国家”（塔克鲁尔，公元第一个千年）的遗址上，项目小组已经有了20年的挖掘经验，这些特征正是这些特征。 这个为期两年的项目不仅将产生推动科学发展的数据，而且还将培训六名塞内加尔学生和研究人员进行采样（因此可以在NSF资助的两年之后继续约会）。 塞内加尔达喀尔大学新近翻修的放射性碳实验室将使用在这些地点采集的放射性碳样本以及考古样品，作为其更新的必要组成部分，这是一个在因缺乏样本而延迟近30年后恢复服务的过程。最后，但并非最不重要的是，如果没有比传统放射性碳更精确的年代，人们根本无法回答非洲史前史上最具创新性的时期之一的核心问题。这一时期发生在沿着中塞内加尔河的两千年里。

Radiocarbon has been truly revolutionary in its contribution to our knowledge of world prehistory. However, over 60 years on, there are still weaknesses (irresolvable due to the basic physics of the method) that limit its effectiveness when applied to certain key periods in the human past. A newer dating method, archaeomagnetism, has proven its effectiveness in resolving two of these weaknesses. One is the large standard deviation (the +/- range of dates) that often extends longer than the beginning and end of the event one wishs to date, and the other is the periodic flattening, or plateau-ing, of the radiocarbon calibration curve (by which one derives calendar dates) such that nothing between 800 and 400 BCE (before the common era) can be dated more precisely than 400 years (the so-called "Hallstatt Plateau" cursed by prehistorians around the globe). The last millennium BCE is precisely when many innovations at the core of world history - beginnings of states and cities, emergence of crafts and metalworking to name just a few - had their explosive beginning and rapid evolutions. The Yale Archaeomagnetism Laboratory, opened in 2013, is dedicated to application of the method worldwide. The present project is integral to the next stage of the lab's development which will feature not only high-precision dating of archaeological materials, but also the development of methods to derive data from archaeological contexts on changes to the intensity of the Earth's magnetic field data critical to geophysicist's attempts to understand the fundamental mechanics behind the generation of the magnetic field. The Yale Archaeomagnetism lab was founded explicitly to address the worrying lag in the production of archaeological scientific data in America compared to the outpouring of those results coming from Europe (the so-called "Quiet Crisis" in American archaeology).The refinement of high-precision archaeomagntic dates and the generation of heretofore unique magnetic intensity data rely upon finding archaeological sites with deeply stratified deposits, with an abundance of burnt features (hearths, furnaces, fired houses), built of earth of the correct mineralogy so that those features record the Earth's magnetic signal at the time of burning. Along the Middle Senegal Valley in West Africa, at sites with evidence of Africa's earliest iron smelting (first millennium BCE) and of the continent's earliest "state" (Takrur, first millennium CE), the project team already has two decades of experience excavating features with exactly those characteristics. This two-year project will result not only in the generation of data to push the science forward, but also in the training of six Senegalese students and researchers in sample-taking (so the dating can continue beyond the two years of NSF funding). The newly refurbished radiocarbon laboratory at the University of Dakar, Senegal, will use radiocarbon samples taken at these sites in tandem with the archaeomagentic samples as a necessary part of its renewal, a process of returning it to service after nearly thirty years that has been delayed for lack of samples. Lastly, but not least, one simply cannot answer core questions about one of the most spectacularly innovative periods in the prehistory of Africa, taking place along the Middle Senegal during those two millennia, without dates of higher precision than conventional radiocarbon can provide.