FIGURE 4 in Geochronology of the middle Eocene Purple Bench locality (Devil's Graveyard Formation), Trans-Pecos Texas, USA

FIGURE 4. Comparison of new and published age estimates for the Devil's Graveyard Fm. and the Purple Bench tuff. Walton (1992) placed the Purple Bench tuff at the C20R-C20N chron transition (43.43 Ma; recalibrated to GST2012; Gradstein et al., 2012), while Prothero (1996) placed the Purple Bench tuff within the C18R chron (41.15- 40.14 Ma; recalibrated to GST2012; Gradstein et al., 2012).