Swift Formation  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Mesozoic
 ...Jurassic
 ....Upper Jurassic
 .....Swift Formation
RTWyoming
 Montana
 North Dakota
 South Dakota
SNIn Ellis Group. N central Montana, W South Dakota, North Dakota and E Wyoming. Added to Thesaurus in 1985.