Brule Formation
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| Brule Formation Stratigraphic range: Rupelian | |
|---|---|
| Type | Geological formation |
| Underlies | Sharps Formation, Arikaree Formation |
| Overlies | Chadron Formation |
| Thickness | 6 to 65 m.[1] |
| Lithology | |
| Primary | Fine grained clastic rocks |
| Other | Freshwater limestone, Tuff, Sandstone |
| Location | |
| Region | North Dakota, South Dakota |
| Country | USA |
The Brule Formation was deposited between 34 to 30 million years ago, roughly the Rupelian (Oligocene).[2] It is a sequence of fine grained clastic rocks (claystones, mudstones, siltstones) interbeded with freshwater carbonates, volcanic ash (tuff), and sandstone.[1]
The sandstones layers, which are up to 3 m thick, can contain mammalian fossils (e.g. the Fitterer bed). The most important fossils sites are:[1]
- Fitterer Ranch
- Obritsch Ranch
- Little Badlands in Stark County
- Chalky Buttes (including White Butte) in Slope County
References
- ↑ 1.0 1.1 1.2 "Lithostratigraphy, Paleontology, and Biochronology of the Chadron, Brule, and Arikaree Formations in North Dakota". Retrieved 28 February 2013.
- ↑ "Geologic Formations". nps.gov.
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