“…Some source areas host deposits of obsidian with multiple geochemical signatures, reflecting complex histories of eruption and the geochemical evolution of magma chambers between eruptive events (e.g. Ericson & Glascock, 2004;Brown, Reid, & Negash, 2009;Morgan et al, 2009;Poupeau et al, 2010;Glascock, 2011;Argote-Espino et al, 2012;Knight et al, 2017). Obsidian from Glass Buttes in central Oregon, for example, can be assigned to as many as nine geochemical source groups, all found within a 200 km 2 area (Ambroz, Glascock, and Skinner 2001;Frahm 2014;Frahm and Feinberg 2015).…”