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

Idaho State University, Pocatello ID

Investigators

Abstract

Testing the Utility of Detrital Zircon Provenance Analyses: Neogene Drainage Capture and the Snake River Plain-Yellowstone Hot Spot Paul Karl Link, Idaho State University EAR-0125756 This 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.