The Provenance of Eocene Tuff Beds in the Fossil Butte Member of the Green River Formation of Wyoming: Relation to the Absaroka and Challis Volcanic Fields

alteration in volcanic rocks , Fossil Butte National Monument , Green River Formation , Fossil Basin , Fossil Butte Member , Absaroka volcanic field , Challis volcanic field , Greater Green River Basin , Absaroka , Eocene volcanic rocks , Challis , Wyoming , Lake Gosiute , Fossil Lake , altered tuff bed , slab window