Collaborative Research: Identifying Sediment Sources and Routing of Transcontinental Drainages During Intraplate Deformation

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The largest rivers in the world often start in mountain ranges on one side of a continent and bring sediment to deltas on the opposite side of the continent. The factors that allow these long-lived rivers to maintain or re-establish their courses in the face of changing geological conditions are largely unexplored. This project will study how transcontinental rivers change with time in response to the formation of mountain ranges or basins in the rivers' pathways. Understanding how rivers respond: whether they find a way through or around the developing mountains or basins, and how quickly they re-establish their prior courses, is critical to accurately interpreting the sedimentary record in their deltas. In addition to providing greater insight into continental-scale rivers, this project will provide STEM training for graduate and undergraduate students and support research infrastructure and analytical facilities at a large state university and a small private university. Further, the project will provide an opportunity for hands-on STEM training for ~30 middle school students per year under the guidance of a university professor. Research will focus on the "Ancestral Rocky Mountains" (ARM) and associated basins, which developed primarily in Utah, Colorado, Texas, and New Mexico 320-280 million years ago. These basins archive changes associated with disruption and reintegration of a continental-scale river in response to ARM evolution. This project will combine traditional and cutting-edge methods including field observations of sedimentary strata, U-Pb radiometric dating, analysis of Hf isotopes, and (U-Th)/He radiometric dating of zircons and monazite minerals in sandstones and igneous rocks to determine where sediment came from and how it changed through time. In addition, (U-Th)/He radiometric dating on zircon minerals in igneous rocks will be used to determine when the mountain ranges developed. These data will link changes in sediment sources to mountain and basin development through time. This will be augmented by development of new software to help determine the sources, and proportion of each source, for sediment based on radiometric dating of minerals in sandstones.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.