Brule Formation

Brule Formation
Stratigraphic range: Rupelian
Type Geological formation
Underlies Sharps Formation, Arikaree Formation
Overlies Chadron Formation
Thickness 6 to 65 m.[1]
Primary Fine grained clastic rocks
Other Freshwater limestone, Tuff, Sandstone
Region North Dakota, South Dakota
Country United States

The Brule Formation was deposited between 34 and 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]

Cat fish, several mammals such as nimravids and hesperocyon and sunfish fossils are known from the Brule Formation in Badlands National Park.[3] Notable among the local fauna are bathornithid birds, ranging from the highly varied wetland-dwelling Bathornis species to the gigantic Paracrax.


  1. 1 2 3 "Lithostratigraphy, Paleontology, and Biochronology of the Chadron, Brule, and Arikaree Formations in North Dakota". Retrieved 28 February 2013.
  2. "Geologic Formations".
  3. Hunt, ReBecca K., Vincent L. Santucci and Jason Kenworthy. 2006. "A preliminary inventory of fossil fish from National Park Service units." in S.G. Lucas, J.A. Spielmann, P.M. Hester, J.P. Kenworthy, and V.L. Santucci (ed.s), Fossils from Federal Lands. New Mexico Museum of Natural History and Science Bulletin 34, pp. 63-69.

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