Date of this Version
General geology and stratigraphy of the Niobrara River drainage basin in Nebraska and adjacent parts of South Dakota generally west of the Missouri River is reviewed. Of particular importance are the correlation of the Long Pine Formation of Pliocene age in Nebraska with the Herrick Gravels in South Dakota, the recognition of the members of the Ogallala Group named by Skinnner, Skinner and Gooris (1968) and by Skinner and Johnson (1984) in the basin, the acceptance of the relationships of the Miocene and older Tertiary units in the basin to those in the part of the study area in South Dakota as proposed by Skinner and Taylor (1967), Skinner, Skinner and Gooris (1968) and by Skinner and Johnson (1984), and the recognition of the Rosebud Formation of the Arikaree Group (Skinner, Skinner, and Gooris, 1968) in the basin. Rocks now included in the Rosebud were placed previously in the White River Group by the Conservation and Survey Division (Burchett , 1986). A refined geologic map of the area shows the currently known distributions of all of the major units, including the Long Pine/Herrick, the Rosebud, and the Chadron formations. none of which has been shown on a map of the study area previously.