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The Brule Formation was deposited between 34 to 30 million years ago, roughly the Rupelian (Oligocene).〔(【引用サイトリンク】url=http://www.nps.gov/badl/naturescience/geologicformations.htm )〕 It is a sequence of fine grained clastic rocks (claystones, mudstones, siltstones) interbeded with freshwater carbonates, volcanic ash (tuff), and sandstone.〔(【引用サイトリンク】url=https://www.dmr.nd.gov/ndfossil/Research/Short%20Papers/white_river.asp )〕 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:〔 *Fitterer Ranch *Obritsch Ranch *Little Badlands in Stark County *Chalky Buttes (including White Butte) in Slope County Cat fish and sunfish fossils are known from the Brule Formation in Badlands National Park.〔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.〕 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Brule Formation」の詳細全文を読む スポンサード リンク
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