Pierre Shale  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Mesozoic
 ...Cretaceous
 ....Upper Cretaceous
 .....Pierre Shale
RTWyoming
 Montana
 Colorado
 Nebraska
 North Dakota
 Minnesota
 South Dakota
 Montana Group
 Gammon Ferruginous Member
 Sharon Springs Member
SNIn Montana Group. E Colorado, W Minnesota, E Montana, Nebraska, North Dakota, South Dakota, and E Wyoming.