The Upper Ordovician of the central Appalachians may be subdivided into (1) three formations (Reedsville, Bald Eagle and Juniata) based largely on rock color, and (2) six clastic lithofacies, based on lithology only. The two methods of subdivision frequently disagree, and lithofacies are often contained in different formations. This phenomenon is caused by a nonsystematically fluctuating drab-red color boundary; areally, the drab Bald Eagle Formation is of irregularly variable thickness. Fossiliferous lithofacies constitute the Reedsville Formation, drab unfossiliferous lithofacies constitute the Bald Eagle Formation, and red unfossiliferous lithofacies make up the Juniata Formation.

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