The Brule Formation was deposited between 33 and 30 million years ago, roughly the Rupelian age (Oligocene).[2] It occurs as a subunit of the White River Group in South Dakota, Nebraska, Colorado, North Dakota, and Wyoming.
| 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)[1] |
| Lithology | |
| Primary | Fine grained clastic rocks |
| Other | Freshwater limestone, Tuff, Sandstone |
| Location | |
| Region | South Dakota, Nebraska, North Dakota, Colorado, Wyoming |
| Country | United States |
It is a sequence of fine grained clastic rocks (claystones, mudstones, siltstones) interbedded with freshwater carbonates, volcanic ash (tuff), and sandstone.[1]
Historical description
editThe formation was named by N. H. Darton "for the Brule Indians, who once roamed over Pine Rldge Ind. Res. in southern S. Dak., where the fm. covers large areas, and that it is not present in Brule Ind. Res., which occurs farther NE In S. Dak." Darton's first description stated, "The White River beds In their extension from S. Dak. Into Nebr. present some differences in strat. range and relations. They expand considerably and include, at top, beds which appear not to be represented in the typical regions. Accordingly, to afford distinct definitions for the members in Nebr. I have Introduced the designation Brule clay and separated the underlying Titanotherium beds as Chadron fm. The Brule consists mainly of a hard, sandy clay, of pale-pink color. Thickness about 600 ft. In vicinity of Wyo. line, but diminishes greatly eastward; in vicinity of 103° mer. in NW. comer of Nebr. it is 320 ft. Has not been recognized E. of long. 101°30', where it appears to sink beneath the surface In Platte Valley. Extends far to NB. in So. Dak. Is upper fm. of White River group." N. H. Darton, 1898 (D, 8, G, S, 19th Ann, Eept., p t 4, pp. 736, 766–759). (Abbreviations are in source document.)[3]
Fossil record
editThe sandstones layers, which are up to 3 metres (9.8 ft) thick, can contain mammalian fossils (e.g. the Fitterer bed). The most important fossils sites are:[1]
- Fitterer Ranch
- Obritsch Ranch
- M&M Ranch
- Little Badlands in Stark County, ND
- Chalky Buttes (including White Butte) in Slope County, ND
Prehistoric catfish, several mammals such as nimravids and Hesperocyon, and sunfish fossils are known from the Brule Formation in Badlands National Park.[4]
Notable among the local fauna are Bathornithid birds, ranging from the highly varied wetland-dwelling Bathornis species to the gigantic Paracrax.
Fauna
edit| Fauna reported from the Brule Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Description | Images |
| Proscalps tertius[5] | Numerous, including upper incisor and molar.[5] | Species holotype likely located here.[5] | ||||
| Hesperocyon | H. gregarius | |||||
| Hyaenodon | H. horridus | |||||
| Hyracodon |
|
SD, ND, NE | Jaw fragments, skulls | Early rhinoceros | ||
| Subhyracodon |
|
NE, SD, ND, WY | Teeth and skulls | Early rhinoceros | ||
| Eporeodon |
|
SD | Incredibly rare | Large oredodont | ||
| Leptauchenia |
|
SD, NE | Teeth and skulls | Small Oreodont | ||
| Merycoidodon |
|
SD, ND, NE, WY | Skulls, limb bones, and skeletons | Oreodont | ||
| Poebrotherium |
|
SD, ND, NE, WY | Bones, jaw fragments | Early camel | ||
| Leptomeryx | SD, NE, WY | Teeth | Deer-like mammal | |||
| Archaeotherium |
|
WY | Teeth and skulls | Entelodont | ||
See also
editReferences
edit- ^ a b c "Lithostratigraphy, Paleontology, and Biochronology of the Chadron, Brule, and Arikaree Formations in North Dakota". Retrieved 28 February 2013.
- ^ "Geologic Formations". nps.gov.
- ^ Lexicon of Geologic Names of the United States, Part 1, A-L. United States Department of the Interior, Geological Survey Bulletin 896, USGS Bulletin 896, 1
This article incorporates text from this source, which is in the public domain.
- ^ 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.
- ^ a b c d Bjork, Philip R. (1975). "Observations on Proscalops tertius (Mammalia: Insectivora) of the Upper Oligocene of South Dakota". Journal of Paleontology. 49 (5): 808–813. JSTOR 1303274.
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