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

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.