Long & Medium Term Research: Geochronological Applications of Cosmogenic Isotopes

中长期研究：宇宙成因同位素的地质年代学应用本奖项是在“国外卓越中心中长期研究计划”下推荐的。该项目旨在使美国科学家和工程师能够在国外被证明卓越的研究机构进行长期研究。该奖项为开展联合研究以及利用国外独特或互补的设施、专业知识和实验条件提供了机会。该奖项将支持埃里克·布朗博士对法国进行为期12个月的访问，与巴黎大学奥赛校区核与质量光谱中心（C.S.N.S.M.）的Franoise Yiou和Grant M. Raisbeck博士一起研究“宇宙成因同位素的地质年代学应用”。我们对地球气候历史的了解依赖于过去冰川作用的陆地残留物，以及深海沉积物和极地冰中保存的化学和生物记录。关于过去温度变化、海洋环流型态、海平面和冰川作用范围的资料已经从这些资料中得到，但是将地球一个地区的数据与另一个地区的数据联系起来的绝对定年方法还有待充分发展。许多测年技术涉及使用宇宙产生的放射性同位素（例如碳-14、铍-10、铝-26），这些同位素是宇宙射线使地球物质原子核碎裂的产物。拟议的研究将侧重于开发两种不同的地质年代学方法，分别使用铍-10和铝-26。其中之一是通过使用矿物格内原位产生的宇宙成因同位素来确定岩石表面的暴露年龄。这将使沉积物（如终末冰碛）的年代测定成为可能，为解释冰川历史提供了一个重要工具。第二种方法通过在35000年前和60000年前的雪的冰芯中观察到的铍-10浓度的一对峰值，提供了沉积和冰芯记录之间的绝对联系。如果在深海沉积物中也能发现同样的异常，它们就可以用来将沉积和冰芯记录联系起来，从而将海洋和大气的历史联系起来。

Long & Medium-Term Research: Geochronological Applications of Cosmogenic Isotopes This award recommendation is made under the Program for Long & Medium-Term Research at Foreign Centers of Excellence. The program seeks to enable U.S. scientists and engineers to conduct long-term research abroad at research institutions of proven excellence. Awards provide opportunities for the conduct of joint research, and the use of unique or comple- mentary facilities, expertise and experimental conditions in foreign countries. This award will support a twelve-month visit by Dr. Erik Brown to France to work with Drs Franoise Yiou and Grant M. Raisbeck at the Centre de Spectrometrie Nuclear et de Spectrometrie de Masse (C.S.N.S.M.) of the Orsay campus of the University of Paris on "Geochronological Applications of Cosmogenic Isotopes." Our understanding of Earth's climatic history is dependent on terrestrial remnants of past glaciation, and on chemical and biological records preserved in deep-sea sediments and in polar ice. Information regarding past changes in temperatures, oceanic circulation patterns, sea level and extent of glaciation has been derived from these sources, but absolute dating methods with which to tie data from one area of the globe to those from another have yet to be fully developed. Many dating techniques involve the use of cosmogenic radioisotopes (e.g. carbon-14, beryllium-10, aluminum-26) which are products of the spallation of nuclei of terrestrial material by cosmic rays. The proposed research will focus on developing two separate geochronological methods using beryllium-10 and aluminum-26. One of these is the determination of exposure ages of rock surfaces through the use of cosmogenic isotopes produced in situ within mineral lattices. This will allow the dating of deposits such as terminal moraines, providing an important tool for interpreting glacial history. A second provides an absolute link between sedimentary and ice core records through the use of a pair of spikes in beryllium-10 concentrations observed in ice cores in snow laid down 35,000 years and 60,000 years ago. If the same anomalies can be found in deep-sea sediments, they can be used to link the sedimentary and ice core records, thus correlating oceanic and atmospheric histories.