Testing the Utility of Detrital Zircon Provenance Analyses: Neogene Drainage Capture and the Snake River Plain-Yellowstone Hot Spot

测试碎屑锆石物源分析的有效性：新近纪水系捕获和蛇河平原-黄石热点：本提案将利用蛇河平原-黄石热点系统周围河流系统中碎屑锆石颗粒的分布，建立碎屑锆石作为河流系统物源指纹的置信度限。在落基山脉北部，晚中新世（17 Ma）至今，黄石-蛇河平原热点及其地形凸起向东北方向迁移。在这段时间里，北美西部大陆板块沿着迁移地形隆起的波峰移动。因此，中新世中期从爱达荷州中部大陆分水岭向东的区域性排水系统，被中断为从地形凸起处流出的径向北向和向南流动的溪流。在经过热点地区和斯内克河平原的下沉后，向西流动的斯内克河逐渐捕获了几条溪流的片段，使它们向西流动，而不是向北、南或向东流动。迁移热点模型对中新世至新近期的排水捕获进行了可验证的预测。本项目将检验碎屑锆石物源方法在准确记录流域物源中的实用性。PI将使用SHRIMP（敏感高分辨率离子探针）对来自北落基山脉的现代溪流和新近纪陆相沉积物的约50个样品进行60个颗粒的U-Pb地质年代学分析。他将研究混合开始掩盖独特锆石特征的河流系统的尺寸阈值。

Testing the Utility of Detrital Zircon Provenance Analyses: Neogene Drainage Capture and the Snake River Plain-Yellowstone Hot SpotPaul Karl Link, Idaho State UniversityEAR-0125756This proposal will use the distribution of detrital zircon grains in stream systems surrounding the Snake River Plain-Yellowstone hotspot system to establish confidence limits on the use of detrital zircons as a fingerprint of provenance in fluvial systems. In the northern Rocky Mountains the Yellowstone-Snake River Plain hotspot and its associated topographic bulge have migrated northeastward from the late Miocene (17 Ma) to the present. During this time, the western continental divide of North America has followed the crest of the migrating topographic bulge. Thus, regional drainage, which in middle Miocene time was to the east from a continental divide in central Idaho, was disrupted to radial north- and south-flowing streams draining away from the topographic bulge. Following passage of the hot spot and subsidence of the Snake River Plain in its wake, the west-flowing Snake River has progressively captured segments of several streams, causing them to flow west, rather than north, south, or east. The migrating hotspot model makes testable predictions about Miocene to Recent drainage capture. This project will test the utility of the detrital zircon provenance method to accurately record drainage basin provenance. PI will use SHRIMP (Sensitive High-Resolution Ion Microprobe) U-Pb geochronologic analyses of 60 grains each, from about 50 samples from modern streams and Neogene terrestrial sediments from the northern Rocky Mountains. He will investigate the size threshold of fluvial systems where mixing begins to mask distinctive zircon signatures.