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The Mancos Shale or Mancos Group is an Late Cretaceous (Upper Cretaceous) geologic formation of the Western United States. The Mancos Shale was first described by Cross and Purington in 1899〔Cross, W. and Purington, C. W. (1899) "Description of the Telluride quadrangle, Colorado" ''United States Geological Survey Atlas, Folio 57''〕 and was named for exposures near the town of Mancos, Colorado. ==Geology== It is dominated by mudrock that accumulated in offshore and marine environments of the Cretaceous North American Inland Sea. The Mancos was deposited during the Cenomanian through Campanian ages, approximately from 95 Ma to 80 Ma. Stratigraphically the Mancos Shale fills the interval between the Dakota Group and the Mesaverde Formation Group.〔Weimer, R. J. (1960) "Upper Cretaceous Stratigraphy, Rocky Mountain Area" ''American Association of Petroleum Geologists Bulletin'' 44: pp. 1-20〕 The Mancos Shale rests conformably on the Dakota and in its upper part grades into and intertongues with the Mesaverde Group. The shale tongues typically have sharp basal contacts and gradational upper contacts. 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「Mancos Shale」の詳細全文を読む スポンサード リンク
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