Sentinel Butte Formation
| Sentinel Butte Formation | |
|---|---|
| Stratigraphic range: Thanetian ~ | |
Bentonite (Big Blue Bentonite) in the Sentinel Butte Formation (North Dakota) | |
| Type | Formation |
| Unit of | Fort Union Formation |
| Underlies | Golden Valley Formation |
| Overlies | Bullion Creek Formation |
| Location | |
| Region | North Dakota |
| Country | United States |
The Sentinel Butte Formation is a geologic formation of Paleocene age in the Williston Basin of western North Dakota. It preserves significant assemblages of non-marine plant and animal fossils.