Bird Spring Formation  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Paleozoic
 ...Bird Spring Formation
RTPennsylvanian
 Lower Permian
 Utah
 California
 Nevada
 Upper Mississippian
SNUpper Mississippian, Pennsylvanian and Lower Permian. In Spring Mountain area, Nevada. Underlies Spring Mountain Formation and overlies Illipah Formation. Indexed with ages as applicable.