Correlation of the Ogallala Formation (Neogene) in Western Texas with Type Localities in Nebraska

The Ogallala formation extends from the north side of the Pecos Valley northward across western Texas, Oklahoma, Kansas, and Nebraska into southern South Dakota. With its southern limit within the Edwards Plateau, it underlies the upland surface of much of the High Plains section of the Great Plains Province. The extensive fluvial deposits of Neogene age are widely exposed throughout the dissected plateau region that flanks the Rocky Mountains on the east. The deposits have yielded large faunas of fossil vertebrates and mollusks and an abundance and variety of fossil plant seeds. Relief on the sub-Ogallala erosion surface accounts for the range in thickness of the formation from a feather edge to more than 500 feet. The lithology of the formation from Nebraska to central western Texas is discussed, criteria for correlation are considered, and the work on fossil vertebrates, mollusks, and fossil plant seeds is briefly reviewed, with the purpose of correlating the Ogallala formation of central western Texas with previously recognized type localities in Nebraska. Classification problems are discussed and it is concluded that rock-stratigraphic subdivision of the Ogallala of Texas is not usable regionally, whereas floral zones are recognizable throughout the High Plains. Three floral zones recognized in the Texas Ogallala are correlated with the Valentine, Ash Hollow, and Kimball of Kansas and Nebraska.