Moat Rhyolites, young
Moat Rhyolites, young
late to middle Pleistocene
Consists of a cluster of five rhyolite domes, flows, and lesser fragmental ejecta in Long Valley caldera west of the resurgent uplift. Domes are typically steep-sided with up to 240 m relief and are partly covered by pyroclastic ejecta (map unit v-y) from Inyo Domes (map unit mic). Composed of subalkaline rhyolite containing 20-35% phenocrysts of plagioclase, sanidine, quartz, biotite, hornblende, and other trace minerals (Hildreth, 2014; Hildreth and Fierstein, 2016). Rhyolites are compositionally similar except in SiO2 and Ba, which distinguish two clusters (Hildreth, 2004). Total volume estimated to be ~3-5 km3, most of which is the West Moat Coulee flow that is up to 5 km long and 574 m thick based on boring logs (Hildreth, 2004; Hildreth and Fierstein, 2016). Ar-Ar sanidine ages range from 163 ± 2 ka (Mahood and others, 2010) to 101 ± 8 ka (Heuman and others, 2002).