Dating Yellowstone Lava Flows using U-Th Geochronology
Category: Community Engagement Poster
Author(s): Roy Davis, Phillip Kondracki
Presenter(s): Roy Davis
Mentors(s): Lauren Harrison
In the 1960's, 13 research wells were drilled in Yellowstone National Park. Stratigraphy was published decades before geologic maps were published and geochronological constraints established. New data has called into question the original stratigraphy and raised the possibility that there are subsurface rhyolite flows with no surficial outcrops. This project aimed to further refine the known dates of rhyolite flows in the Y-2 and Y-3 drill cores using U-Th dating techniques on zircon to interpret eruption ages of the flows present in the drill cores. To this end, three samples were selected from the Y-2 and Y-3 drill cores and selected minerals, zircon and sanidine, were extracted. The zircon was taken to the Sensitive High-Resolution Ion Microprobe-Reverge Geometry (SHRIMP-RG) in Stanford University and analyzed for its U sontent. The ages received indicate a need for further investigation, with the selected samples having similar eruption ages, but more scatter in the deeper flows, suggesting sourcing from a longer-lived magmatic system than shallower flows. Furthermore, zircon samples were U-poor, posing a challenge for high-precision ages. Future work includes more zircon analyses and analysis of Ar-Ar dating in the sanidine samples to corroborate the zircon eruption ages.