Gammon Ferruginous Member  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Mesozoic
 ...Cretaceous
 ....Upper Cretaceous
 .....Gammon Ferruginous Member
RTWyoming
 Montana
 South Dakota
 Pierre Shale
SNOf Pierre Shale. NE Wyoming, SE Montana and NW South Dakota. Added to Thesaurus in 1985.