Flagg Ranch exposure of the Lava Creek Tuff with quartz-hosted melt inclusions

Photo of ash-fall deposit of the Lava Creek Tuff overlying the lower “unknown” ignimbrite (an ash-flow unit, denoted by light yellow box).  Images of quartz-hosted melt inclusions show fully “baked” (dark) melt inclusions in the lowest ash fall layers (1–2). Layers 3–6 contain glassy melt inclusions (clear in appearance), while layers 7 and 8 only have predominantly “baked” melt inclusions.  The baked nature of the melt inclusions in the lower layers indicate that the ash fall occurred while the underlying “unknown” ignimbrite was still hot and that there was no significant time gap between the two events. Photo of deposit by Stacy Henderson (Ph.D. student in Montana State University’s MOnSTER lab). Melt inclusion photos courtesy of Bryana McKay (M.S. student in Montana State University’s MOnSTER Lab).