Brule Formation

Brule Formation
Stratigraphic range: Rupelian
~33–30 Ma
↓
Brule Formation in Badlands National Park
TypeGeological formation
Unit ofWhite River Group
UnderliesSharps Formation, Arikaree Formation
OverliesChadron Formation
Thickness6–65 metres (20–213 ft)[1]
Lithology
PrimaryFine grained clastic rocks
OtherFreshwater limestone, Tuff, Sandstone
Location
RegionSouth Dakota, Nebraska, North Dakota, Colorado, Wyoming
CountryUnited States

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.

It is a sequence of fine grained clastic rocks (claystones, mudstones, siltstones) interbedded with freshwater carbonates, volcanic ash (tuff), and sandstone.[1]

Historical description

The 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

The 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]

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

Fauna reported from the Brule Formation
Genus Species Location Stratigraphic position Material Description Images

Proscalops[5]

Proscalps tertius[5] Numerous, including upper incisor and molar.[5] Species holotype likely located here.[5]
Hesperocyon H. gregarius
Hyaenodon H. horridus
Hyracodon
  • H. nebraskensis
 SD, ND, NE Jaw fragments, skulls Early rhinoceros
Subhyracodon
  • S. occidentalis
 NE, SD, ND, WY Teeth and skulls Early rhinoceros
Eporeodon
  • E. major
 SD Incredibly rare Large oredodont
Leptauchenia
  • L. decora
 SD, NE Teeth and skulls Small Oreodont
Merycoidodon
  • M. culbertsoni
  • M. gracilis
 SD, ND, NE, WY Skulls, limb bones, and skeletons Oreodont
Poebrotherium
  • P. wilsoni
 SD, ND, NE, WY Bones, jaw fragments Early camel
Leptomeryx SD, NE, WY Teeth Deer-like mammal
Archaeotherium
  • A. mortoni
 WY Teeth and skulls Entelodont

See also

References

  1. ^ a b c "Lithostratigraphy, Paleontology, and Biochronology of the Chadron, Brule, and Arikaree Formations in North Dakota". Retrieved 28 February 2013.
  2. ^ "Geologic Formations". nps.gov.
  3. ^ 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 Public Domain This article incorporates text from this source, which is in the public domain.
  4. ^ 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.
  5. ^ 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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