Testing the impact of reworking on the isochronicity of tephras deposited in diverse sedimentary environments

这个项目将改进我们解释和利用记录地球地质历史的沉积物记录的方式。人们将开发新的方法来确定火山喷发产生的沉积物的年龄，并且将使用成熟的方法来更好地了解美国内华达州大盆地的古湖泊水位波动。这将有助于古气候和景观动态的重建，有助于理解现代气候变化，并为减灾提供信息，特别是当它与大盆地和美国西部的干旱和荒漠化有关时。由于它对了解干旱危害的贡献，该项目通过增加应对全球和环境变化所需的知识，为美国的国家健康、繁荣和福利做出了贡献。该项目还将向职业生涯早期和中期的妇女提供培训和支持，并就所调查的主题向感兴趣的利益攸关方，特别是内华达州大盆地的听众进行外联。Tephras是由火山喷发的物质组成的沉积物。利用泥岩准确解释古气候和景观现象的一个突出问题是泥岩沉积时间的确定。该项目将利用发光测年法解决与确定白炽灯沉积时间有关的问题，发光测年法是一种埋葬年龄测年方法，可以找到沉积物最后暴露在光或热下的时间。在这个项目中，将测试关于tephras沉积的地质时间窗口的问题。还将测试沉积后再加工的时间尺度。这些问题对于在沉积记录中使用岩相作为时间标记至关重要。这项研究是在美国大盆地进行的，因为现有的数据使我们能够测试我们的方法，并解决依赖于tephra记录的古湖泊水位的相互矛盾的解释。这项工作将产生一种可靠的测年方法，对年龄超过可靠放射性碳上限35 ka、年龄小于可靠K/Ar和40Ar/39Ar测年技术下限120 ka的岩屑进行测年。这项工作还将有助于改善对古气候的解释和景观动态的重建，如由温度相关性产生的湖泊水位波动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will improve the ways we interpret and utilize the record of sediments that document the Earth’s geologic history. New methods will be developed to define the age of tephras, sediment that originates from volcanic eruptions, and well-established methods will be used to better understand paleolake level fluctuation in the Great Basin of the U.S. in Nevada. This will aid in reconstruction of paleoclimate and landscape dynamics which contributes to understanding modern changes to climate and informs hazard mitigation, particularly as it relates to drought and desertification in the Great Basin and western U.S. Owing to its contribution to understanding drought hazards, the project contributes to the national health, prosperity, and welfare of the U.S. by increasing knowledge needed for resiliency to global and environmental change. The project also will provide training and support to early and mid-career women and outreach on topics investigated to an audience of interested stakeholders, particularly in the Great Basin in Nevada. Tephras are sediments that comprise volcanically erupted material. An outstanding problem in using tephras to accurately interpret paleoclimate and landscape phenomenon is identifying when they were deposited. This project will resolve questions related to defining the timing of tephra deposition using luminescence dating, which is a burial age dating approach that finds the time of the last exposure of sediment to light or heat. In this project, questions about the window of geological time in which tephras are deposited will be tested. The timescales of tephra reworking after deposition will also be tested. These questions are critical to using tephras as markers of time in the sedimentary record. This study is being conducted in the Great Basin of the U.S. because existing data allows us to test our methods and resolve conflicting interpretations of paleo lake-levels that rely on the tephra record. This work will yield a reliable dating methods to date tephras that are older than the 35 ka upper limit for reliable radiocarbon and younger than the 120 ka lower limit of reliable K/Ar and 40Ar/39Ar dating techniques. This work will also contribute to improving interpretations about paleoclimate and reconstructions of landscape dynamics, such as lake-level fluctuations, that are made from tephra correlations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.