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Brule Formation

Brule Formation
Stratigraphic range: Rupelian
Brule Formation Badlands NP.jpg
Brule Formation in Badlands National Park
Type Geological formation
Underlies Sharps Formation, Arikaree Formation
Overlies Chadron Formation
Thickness 6 to 65 m.
Lithology
Primary Fine grained clastic rocks
Other Freshwater limestone, Tuff, Sandstone
Location
Region North Dakota, South Dakota
Country United States

The Brule Formation was deposited between 34 and 30 million years ago, roughly the Rupelian (Oligocene). It is a sequence of fine grained clastic rocks (claystones, mudstones, siltstones) interbeded with freshwater carbonates, volcanic ash (tuff), and sandstone.

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:

Cat fish, several mammals such as nimravids and hesperocyon and sunfish fossils are known from the Brule Formation in Badlands National Park. Notable among the local fauna are bathornithid birds, ranging from the highly varied wetland-dwelling Bathornis species to the gigantic Paracrax.



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