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Txu-Oclc-2551832.Pdf BUREAU OF ECONOMIC GEOLOGY The University of Texas Austin 12, Texas John T. Lonsdale, Director Report of Investigations—No. 39 Correlation of the Ogallala Formation (Neogene) in Western Texas With Type Localities in Nebraska By JOHN C. FRYE AND A. BYRON LEONARD August 1959 Contents Abstract 5 Generalities 5 Depositional history .... 6 Previous work 7 Acknowledgments 11 Physical stratigraphy 12 Lithologic types within the Ogallala 12 Stratigraphic and geographic variations in lithologies 14 Physical criteria of correlation 16 Stratigraphic paleontology 18 Vertebrate faunas 18 Molluscan faunas 20 Fossil plants and floral zones 21 Geographic range of fossil seeds 21 Stratigraphic range of fossil seeds 23 Valentine floral zone 23 Ash Hollow floral zone 24 Kimball floral zone 26 Summary and conclusions 27 Measured sections 30 References 33 Index 43 Illustrations FIGURES 1. Graphic correlation of the Ogallala formation in western Texas with type localities in Nebraska 8-9 2. Known geographic range of some significant Ogallala fossil seeds from Texas to Nebraska 22 3. Known stratigraphic ranges of some significant fossil seeds in the Ogallala formation 23 PLATES I. The Ogallala formation (Ash Hollow floral zone) in central western Texas 38 11. Distinctive lithologies of the Ogallala formation in Texas 41 Correlation of the Ogallala Formation (Neogene) in Western Texas with Type Localities in Nebraska JOHN C. FRYE 1 AND A. BYRON LEONARD 2 ABSTRACT The Ogallala formation extends from the The lithology of the formation from north side of the Pecos Valley northward Nebraska to central western Texas is dis- across western Texas, Oklahoma, Kansas, cussed, criteria for correlation are con- and Nebraska into southern South Dakota. sidered, and the work on fossil vertebrates, With its southern limit within the Edwards mollusks, and fossil plant seeds is briefly Plateau, it underlies the upland surface of reviewed, with the purpose of correlating much of the High Plains section of the the Ogallala formation of central western Great Plains Province. The extensive flu- Texas with previously recognized type vial deposits of Neogene age are widely localities in Nebraska. Classification prob- exposed throughout the dissected plateau lems are discussed and it is concluded that region that flanks the Rocky Mountains on rock-stratigraphic subdivision of the Ogal- the east. The deposits have yielded large lala of Texas is not usable regionally, faunas of fossil vertebrates and mollusks whereas floral zones are recognizable and an abundance and variety of fossil throughout the High Plains. Three floral plant seeds. Relief on the sub-Ogallala zones recognized in the Texas Ogallala are erosion surface accounts for the range in correlated with the Valentine, Ash Hollow, thickness of the formation from a feather and Kimball ofKansas and Nebraska. edge to more than 500 feet. GENERALITIES The Ogallala formation displays the established across Kansas. The correlation greatest geographic extent of outcrop area of the Texas Ogallala with the Nebraska of all the nonmarine (pre-Pleistocene) for- types therefore will serve to produce a mations of the United States. The forma- uniform frame of reference throughout the tion is almost continuous throughout a Great Plains. region extending more than 800 miles from From a practical standpoint the outcrop north to south and 300 miles from east to area of the Ogallala formation is coexten- west, and adequate exposures are generally sive with the High Plains physiographic available for study. For this widespread section. The intimate dependence of topo- depositional unit a relatively uniform stra- graphic expression on the Ogallala is most tigraphic framework, accompanied by strikingly displayed in Texas and New basic correlation, should be effected Mexico where the High Plains surface is through the region. The stratigraphic sub- sharply terminated on both the east and divisions of the formation, as well as the west sides by Ogallala scarps (PI. I,A). formation itself, are based on type localities However, the High Plains are gradational in Nebraska, and correlations have been with the Edwards Plateau to the south where the formation thins and eventually ¹ Chief, Illinois Stale Geological Survey, Urbana. ² Department of Zoology, University of Kansas, Lawrence. feathers out. 6 Report of Investigations—No. 39 In and north of the Texas Panhandle Plains, primarily because it constitutes the area, the scarps that bound the High Plains largest and most extensive groundwater become discontinuous and even where reservoir of the region. It also is a major present are less dependent upon the Ogal- source of sand and gravel and road metal lala. For example, in central and north- (caliche) and contains less extensive de- central Kansas the most prominent scarps posits of diatomite (Evans, 1946), vol- are developed on resistant limestones of canic ash (Swineford and Frye, 1946) and Cretaceous age and may or may not be siliceous-cemented rock. capped by Ogallala deposits. Farther north It is our purpose in this paper to present the High Plains surface is commonly evidence, and conclusions drawn there- mantled by a significant thickness of from, concerning the correlation of the Pleistocene deposits, and the upper part of Neogene deposits of the High Plains region the Ogallala has been removed by erosion of Texas with the type localities in Nebras- over large areas. Only in central western ka. The physical stratigraphy (including Texas and adjacent New Mexico is W. D. depositional history and physiographic ex- Johnson's (1901, p. 629) generality, "the pression) of the Ogallala formation is re- High Plains have endured as alluvial pla- viewed in general terms, but detailed de- teaus since Tertiary times," demonstrably scriptions are presented only as illustra- true (Frye, 1946). This physiographic tions, and evidence from fossil vertebrates situation is particularly favorable for stra- is reviewed insofar as these data have been tigraphic work in the High Plains of Texas presented in the literature.The degree and because the re-entrant canyons cut into the extent of utility of fossil mollusks and the scarp afford excellent exposures of virtually widespread occurrence of fossil plant ma- the entire thickness of the local Ogallala terials and their significance in correlation (Frye and Leonard, 1957a; and measured studies are discussed. sections, this publication). Depositional history.—The depositional There is a distinct contrast in the physio- history of the Ogallala is complex. After an graphic relations of the southern and early hypothesis favoring lacustrine origin northern limits of the Ogallala formation. (King. 1878) had been refuted, the con- In the southern area the Ogallala becomes cept of stream deposition was introduced generally thinner southward (fig. 1) and (Gilbert. 1896). Unfortunately, however, is discontinuous south of Howard County, it was thought that the mechanism of feathering out to scattered patches of the stream deposition was alluvial fan build- uppermost part of the formation. In ing (Plummer, 1933, p. 769) and that the Borden, Dawson, and Howard counties plain was developed by coalescence of a the Ogallala controls some scarps but in series of adjacent gigantic fans that spread other places the scarps are controlled by out over an essentially planate surface. It resistant Cretaceous limestones. South of is apparent that if such were the case the these counties the Ogallala is nowhere a oldest deposits in the alluvial complex significant factor of topographic control. should exist in the area of initial deposition In contrast, the northern limit of the for- (presumably relatively near the apical mation in Nebraska and southern South regions of the fans), the occurrences of Dakota is controlled by erosion rather than these oldest deposits should be roughly by stratigraphic pinch-out. It is not known aligned in a north-south direction parallel how far north the Ogallala originally was to the source area, and there should be pro- deposited, for in that region the uppermost gressive overlap of younger beds toward units have been removed and the northern the east. A test of this hypothesis is possible outcrops are typified by the truncated mid- by stratigraphic means once sufficiently de- dle and lower parts of the formation. tailed correlations are made within the The Ogallala formation is of great eco- mass of the deposits. nomic importance throughout the Great Recent work in Kansas (Frye, Leonard, Ogallala Formation Correlation 7 and Swineford, 1956) has led to the con- large mesas protected by resistant Cretace- clusion that the mechanism of deposition ous rocks stood prominently above this was quite different. It was possible to trace alluvial plain that surrounded them. The zones of several ages for considerable dis- Neogene deposits became progressively tances west to east, and to show that the thinner and more discontinuous southward younger units, instead of progressively over the surface of the resistant rocks that overlapping the older deposits to the east, form the surface of the Edwards Plateau. displayed a north and south overlapping The cause of the diminution of the rate relationship on the gently sloping sides of of alluviation and its eventual cessation in broad and relatively shallow pre-Ogallala late Neogene time is not known with cer- valleys. Although figure 1 is not plotted to tainty, but it seems plausible that climatic a uniform geographic scale and the strati- control by progressive
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