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

风和水流沉积物的产生和移动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，通过风化和侵蚀从高海拔地区去除的物质被机械地运输到低海拔地区（即盆地），从而平整地形高地（例如山脉）。以定量方式研究和理解这些过程为地球科学家提供了有关地理、进化、人类迁徙、气候、构造以及具有重要经济意义的沉积盆地发育的基本信息。研究现代和古代沉积系统（例如河流、沙漠）中沉积物迁移的最可靠方法之一是测量耐风化矿物（例如含有放射性母同位素和子同位素的锆石）的地质年龄。通过研究遥远的锆石的年龄模式，地球科学家可以将具有可比年龄的潜在源区联系起来，并重建古代沉积物路径系统。学生将接受研究方法方面的培训，并且作为该项目的一部分，将为本科生开发一门新的创意探究课程。通过碎屑矿物年龄测定来研究沉积物迁移并非没有复杂性和潜在偏差。尽管一个多世纪以来，牵引流携带的颗粒的机械分选和分馏一直是沉积学中众所周知的过程，但我们对沉积物迁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。该项目将利用河流系统作为天然实验室，量化锆石的物理特性（例如粒度、形态和累积辐射损伤）对运输过程中碎屑锆石年龄谱的系统性偏差的影响。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）应用统计推断方法来量化这些物理特征对观测到的年龄谱产生偏差的潜在影响。这些见解将使地球科学家能够进行更多“地质信息丰富”的样本间比较，从而提高构造重建、定量起源模型以及从碎屑锆石 U-Pb 数据得出的沉积物传输路径的准确性。开发的代码将是用户友好的并且可供其他研究人员使用。该奖项反映了 NSF 的法定使命，并且通过使用基金会的智力价值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.