Lakota Formation
The Lakota Formation is a sequence of rocks of early Cretaceous (Berriasian to Barremian) age from Western North America. Located in South Dakota, the name of the formation is derived from the Lakota Native American tribe.
| Lakota Formation | |
|---|---|
| Stratigraphic range: | |
| Type | Geological formation |
| Sub-units | Chilson Member. Fuson Member |
| Underlies | Fall River Formation |
| Overlies | Morrison Formation |
| Thickness | 200 to 500 feet (60 to 150 m) |
| Lithology | |
| Primary | Sandstone |
| Other | Shale, Coal, Conglomerate |
| Location | |
| Region | North America |
| Country | United States |
| Type section | |
| Named for | Lakota Native American tribe |
| Named by | Darton |
| Year defined | 1899 |
There are two units of the Lakota Formation, the Chilson Member (upper Berriasian to Valanginian) and the underlying Fuson Member (upper Valanginian to early Barremian). A Berriasian-Valanginian age for the Chilson Member has been extrapolated by means of ostracods and charophytes.
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