INTRUSIVE AND EXTRUSIVE IGNEOUS ROCKS--Composition ranges from hornblende
     monzonite to basalt.  In Yellowstone area includes andesite and basalt of Emerald
     Lake (age about 2 Ma), rhyolite of Broad Creek, Pliocene Junction Butte Basalt, and
     gravel of Mount Everts.  Age of basalt on Crescent Mountain 3.6 Ma. Tii
CALDWELL CANYON VOLCANICS--Dacitic volcanic rocks; obsidian gravel at base. Tcv
SALT LAKE FORMATION--White, gray, and green limy tuff, siltstone, sandstone, and 
     conglomerate. Tsl