Lakota Formation
The Lakota Formation is a sequence of rocks of early Cretaceous age from Western North America. Located in South Dakota, the name of the formation is derived from the Lakota Native American tribe.
There are two units of the Lakota Formation, the Chilson Member and the underlying Fuson Member. A Berriasian-Valanginian age for the Chilson Member has been extrapolated by means of ostracods and charophytes.
The Fuson Member takes its name from rock exposures in Fuson Canyon, a valley on the eastern side of the Black Hills.