FIGURE 3. Zircon U in Geochronology of the middle Eocene Purple Bench locality (Devil's Graveyard Formation), Trans-Pecos Texas, USA

FIGURE 3. Zircon U-Pb results from tuffaceous sandstones of the Devil's Graveyard Fm. analyzed via LAICP-MS. Results were filtered to exclude single grain ages with>15% discordance between 235U/207Pb age and 238U/206Pb age, or>10% propagated analytical error in 238U/206Pb age. Weighted means were calculated for each sample using Tuff extractor plugin from the ISOPLOT package (Ludwig and Mundil, 2002; Ludwig, 2003). Number of grains used in TuffZirc algorithm displayed as n= # of ages used by TuffZirc / # of ages total for sample. Data are displayed as kernel density estimators (KDEs) with a bandwidth of 1 Myr (Vermeesch, 2018). Individual zircon ages and 2s standard errors are displayed as vertically stacked boxes. Individual ages in red were used in the calculation of the weighted mean. Weighted means and errors are displayed as a grey box with a bar representing the mean.