| Group or Formation |
Period |
Notes |
| Alan Mountain Limestone | Carboniferous | |
| Amsden Formation | Carboniferous | |
| Arikaree Formation | Neogene | |
| Bear Formation | Paleogene | |
| Bearpaw Formation | Cretaceous | |
| Bearpaw Shale | Cretaceous | |
| Benton Shale | Cretaceous | |
| Big Snowy Formation | Carboniferous | |
| Big Snowy Group/Heath Formation | Carboniferous | |
| Blackleaf Formation | Cretaceous | |
| Blacktail Deer Creek Formation | Cretaceous | |
| Cameron Creek Formation | Carboniferous | |
| Castle Reef Dolomite | Carboniferous | |
| Claggett Formation | Cretaceous | |
| Claggett Shale | Cretaceous | |
| Climbing Arrow Formation | Paleogene | |
| Cloverly Formation | Cretaceous | |
| Cody Shale | Cretaceous | |
| Colorado Group/Belle Fourche Formation | Cretaceous | |
| Cook Ranch Formation | Paleogene | |
| Deadwood Formation | Ordovician, Cambrian | |
| Dearborne Limestone | Cambrian | |
| Deep River Formation | Neogene | |
| Dell Beds Formation | Paleogene | |
| Dinwoody Formation | Triassic | |
| Dunbar Creek Formation | Paleogene | |
| Eagle Formation | Cretaceous | |
| Ellis Formation | Jurassic | |
| Flaxville Gravels Formation | Neogene | |
| Fort Union Formation | Paleogene, Cretaceous | |
| Fort Union No. 3 Beds (Melville) Formation | Paleogene | |
| Fort Union Group/Tullock Formation | Paleogene | |
| Fox Hills Sandstone | Cretaceous | |
| Graneros Shale | Cretaceous | |
| Greyson Shale | United States | |
| Heath Formation | Carboniferous | |
| Heath Shale | Carboniferous | |
| Hell Creek Formation | Paleogene, Cretaceous | |
| Hepburn's Mesa Formation | Neogene | |
| Horsethief Formation | Cretaceous | |
| Jefferson Formation | Devonian | |
| Judith River Formation | Cretaceous | |
| Kishenehn Formation | Paleogene | |
| Kootenai Formation | Cretaceous | |
| Lance Formation | Cretaceous | |
| Lebo Formation | Paleogene | |
| Livingston Formation | Paleogene | |
| Lodgepole Limestone | Carboniferous | |
| Ludlow Formation | Paleogene | |
| Ludlow? Formation | Paleogene | |
| Madison Group/Lodgepole and Mission Canyon Formation | Devonian | |
| Madison Valley Formation | Neogene | |
| Madison Valley Equivalent Formation | Neogene | |
| Madison Group/Allan Mountain Limestone | Carboniferous | |
| Madison Group/Lodgepole Formation | Carboniferous | |
| Madison Group/Lodgepole Limestone | Carboniferous | |
| Marias River Shale | Cretaceous | |
| Meagher Formation | Cambrian | |
| Melville Formation | Paleogene | |
| Montana Formation | Cretaceous | |
| Montana Group/Eagle Sandstone | Cretaceous | |
| Montana Group/Hell Creek Formation | Cretaceous | |
| Montana Group/Judith River Formation | Cretaceous | |
| Montana Group/Two Medicine Formation | Cretaceous | |
| Morrison Formation | Jurassic | |
| Mowry Shale | Cretaceous | |
| Otter Formation | Carboniferous | |
| Pagoda Formation | Cambrian | |
| Park City Formation | Permian | |
| Passamari Formation | Paleogene | |
| Passamari Formation | Paleogene | |
| Pentagon Formation | Cambrian | |
| Phosphoria Formation | Permian | |
| Pierre Shale | Cretaceous | |
| Pilgrim Formation | Cambrian | |
| Polecat Bench Formation | Paleogene | |
| Renova Formation | Paleogene | |
| Ruby River Basin Group/Renova Formation | Paleogene | |
| Sage Creek Formation | Paleogene | |
| Sappington Formation | Carboniferous, Devonian | |
| Sawtooth Formation | Jurassic | |
| Shedhorn Formation | Permian | |
| Shell Creek Shale | Cretaceous | |
| Sixmile Creek Formation | Neogene | |
| Snowy Range Formation | Cambrian | |
| St. Mary River Formation | Cretaceous | |
| Telegraph Creek Formation | Cretaceous | |
| Thaynes Formation | Triassic | |
| Thermopolis Shale | Cretaceous | |
| Three Forks Formation | Devonian | |
| Three Forks Shale | Devonian | |
| Tongue River Formation | Paleogene | |
| Toston Formation | Paleogene | |
| Tullock Formation | Paleogene | |
| Two Medicine Formation | Cretaceous | |
| Upper Hell Creek Formation | Cretaceous | |
| Virgelle Sandstone | Cretaceous | |
| White River Formation | Paleogene | |
| Willow Creek Formation | Cretaceous | |
| Wiota Gravels Formation | United States | |
| Wolsey Formation | Cambrian | |
| Wolsey Shale | Cambrian | |
|
