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 is a sequence of fine grained clastic rocks (claystones, mudstones, siltstones) interbedded with freshwater carbonates, volcanic ash (tuff), and sandstonein South Dakota, Nebraska, Colorado, North Dakota, and Wyoming. It was deposited between 34 and 30 million years ago, roughly the Rupelian age (Oligocene). It occurs as a subunit of the White River Group.