Skull Creek Shale  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Mesozoic
 ...Cretaceous
 ....Lower Cretaceous
 .....Skull Creek Shale
RTWyoming
 Montana
 North Dakota
 South Dakota
 Colorado Group
SNNE Wyoming, Montana, North Dakota and South Dakota. Added to Thesaurus in 1985.