Collaborative Research: Improved Geochronology-Based Sediment Provenance Analysis Through Physico-Mechanical Characterization of Zircon Transport

风和水流产生和移动的沉积物是数十亿年来塑造地球表面的基本地质过程。通过这些过程，风化和侵蚀从高海拔地区移走的物质被机械地输送到低海拔地区(即盆地)，从而使地形高点(如山脉)变得平坦。对这些过程的定量研究和理解为地球科学家提供了关于地理、演化、人类迁徙、气候、构造和重要经济沉积盆地发展的基本信息。研究现代和古代沉积系统(如河流、沙漠)中沉积物运移的最有力的方法之一是测量锆石等抗风化矿物的地质年龄，这些矿物含有放射性母体和子体同位素。通过研究远行的锆石的年龄模式，地球科学家可以找到与年龄相当的潜在来源地区的联系，并重建古代沉积物路线系统。作为该项目的一部分，学生们将接受研究方法方面的培训，并将为本科生开发一门新的创造性探究课程。通过碎屑矿物的年龄测定来研究沉积物的运移并不是没有复杂性和潜在的偏见。虽然牵引力流携带的颗粒的机械分选和分馏过程在沉积学中已经被熟知了一个多世纪，但我们对沉积物运移如何影响碎屑锆石种群和影响U-Pb年龄谱的了解仍然严重不足。利用河流系统作为天然实验室，该项目将量化锆石的物理特征，如颗粒大小、形态和累积的辐射损害，在运输过程中系统地偏向碎屑锆石年龄谱的影响。该项目将：1)收集运输过程中碎屑锆石分馏的可靠年龄和物理性质信息，2)应用统计推断方法量化这些物理特征对观测年龄谱的潜在影响。这些洞察力将使地球科学家能够进行更多“地质信息”的样本间比较，提高构造重建、定量物源模型和从碎屑锆石U-Pb数据得出的沉积物迁移路径的准确性。开发的代码将是用户友好的，并可供其他研究人员使用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The generation and movement of sediments by wind and water currents are fundamental geologic processes that have shaped the surface of our planet for billions of years. Through these processes, material removed from higher elevation areas by weathering and erosion is mechanically transported to lower elevation regions (i.e., basins), thereby leveling topographic highs (e.g., mountains). Studying and understanding these processes in a quantitative way provides Earth Scientists with fundamental information about geography, evolution, human migration, climate, tectonics, and the development of economically important sedimentary basins. One of the most robust ways to study sediment transport in modern and ancient sedimentary systems (e.g., rivers, deserts), is by measuring the geologic ages of weathering-resistant minerals such as zircon that contain radioactive parent and daughter isotopes. By studying the age patterns of far-travelled zircons, Earth Scientists can draw linkages to potential source areas with comparable ages and reconstruct ancient sediment routing systems. Students will be trained in the research methods and a new Creative Inquiry course for undergraduates will be developed as part of the project.Studying sediment transport through age-dating of detrital minerals is not without complexities and potential biases. Although the mechanical sorting and fractionation of particles carried by tractive currents have been well-known processes in sedimentology for well over a century, our knowledge of how sediment transport affects detrital zircon populations and influences U-Pb age spectra remains critically inadequate. Using fluvial systems as natural laboratories, this project will quantify the effects that the physical characteristics of zircon, such as grain size, morphology, and accumulated radiation damage, have in systematically biasing detrital zircon age spectra during transport. This project will: 1) collect robust age and physical-properties information of detrital zircon fractionation during transport, and 2) apply methods of statistical inference to quantify the latent effects these physical characteristics have in biasing the observed age spectra. These insights will allow Earth Scientists to perform more ‘geologically informed’ inter-sample comparisons, enhancing the accuracy of tectonic reconstructions, quantitative provenance models, and sediment-transport pathways derived from detrital zircon U-Pb data. The code developed will be user friendly and available to other researchers.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.