Detailed analysis of three sections of the Late Cretaceous Mancos Shale at Black Mesa in northeastern Arizona demonstrates that sufficient data are preserved within the thick, seemingly monotonous, fine-grained clastic sequences of the western foreland basin to develop a conceptual framework comparable to that developed for the carbonate-dominated central Western Interior Seaway. The Mancos Shale ranges from 146 m in southwestern Black Mesa to form 200 to 210 m in northern and eastern Black Mesa and is herein divided into four members in ascending order: lower shale member, middle shale member, Hopi Sandy Member, and upper shale member, of which...