Travertine sample from Yellowstone National Park

Travertine sample from the Hillside Springs Group in Upper Geyser Basin, sampled under permit YELL-2020-SCI-8030. (Left) Cut and polished sample slab showing the different layers of travertine; dashed circles indicate where subsamples were taken for geochronology analysis. (Middle) Sample viewed under shortwave infrared light, where the bright green layers indicate higher uranium concentrations. (Right) Travertine slab post sampling shows how much material was excavated for each analytical aliquot—each of those pits results in the age that the layer of travertine formed. Scale is in millimeters.