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BTChronostratigraphic Units
 .Phanerozoic
 ..Mesozoic
 ...Cretaceous
 ....Upper Cretaceous
 .....Montana Group
RTNew Mexico
 Utah
 Wyoming
 Montana
 Colorado
 North Dakota
 Bearpaw Formation
 Kansas
 South Dakota
 Cody Shale
 Eagle Sandstone
 Fox Hills Formation
 Pierre Shale
 Judith River Formation
 Parkman Sandstone
 Two Medicine Formation
SNIncludes Bearpaw Shale, Claggett Shale, Cody Shale (upper part), Eagle Sandstone, Fox Hills Sandstone, Horsethief Sandstone, Judith River Formation, Lennep Sandstone, Parkman Sandstone, Pierre Shale, Trinidad Sandstone, Two Medicine Formation, and Virgell