Brule Formation
| Brule Formation | |
|---|---|
| Stratigraphic range: Rupelian ~ | |
Brule Formation in Badlands National Park | |
| Type | Geological formation |
| Unit of | White River Group |
| Underlies | Sharps Formation, Arikaree Formation |
| Overlies | Chadron Formation |
| Thickness | 6–65 metres (20–213 ft) |
| Lithology | |
| Primary | Fine grained clastic rocks |
| Other | Freshwater limestone, tuff, sandstone |
| Location | |
| Region | South Dakota, Nebraska, North Dakota, Colorado, Wyoming |
| Country | United States |
The Brule Formation was deposited between 34 and 30 million years ago, roughly the Rupelian age (Oligocene). It occurs as a subunit of the White River Group in South Dakota, Nebraska, Colorado, North Dakota, and Wyoming.
It is a sequence of fine grained clastic rocks (claystones, mudstones, siltstones) interbedded with freshwater carbonates, volcanic ash (tuff), and sandstone.