Locations of Lava Creek Tuff samples and their barium compositions in the Yellowstone National Park area

Locations of Lava Creek Tuff samples in the Yellowstone National Park area. Colored rings show the relative abundance of sanidine crystals with different barium (Ba) concentrations, measured in parts per million (ppm), at each site. Letters inside the rings indicate whether the deposit was mapped as member A or member B, and “n” is the number of sanidine grains analyzed for each sample. Deposits assigned to both members contain many of the same Ba populations, suggesting the two members are not as distinct as previously thought. Adapted from Henderson and others (2026), https://doi.org/10.1016/j.jvolgeores.2026.108753.