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BUREAU OF ECONOMIC GEOLOGY The University of Texas Austin, Texas 78712 l'eter T. Flawn, Director Report of Investigations—No. 51 Relation of Ogallala Formation to the Southern High Plains in Texas By John C. Frye and A. Byron Leonard March 1964 Contents Page Abstract 5 Introduction 5 Regional physiography 8 The Ogallala Formation and the High Plains surface 10 Fossil seeds of the Ogallala Formation 11 Pleistocene dissection of the High Plains margin 14 Abandoned Panther Valley 15 Lake Lomax 17 Fossil molluscan assemblages 18 Conclusions 20 References 20 Index . 24 - Illustrations Figures Page Index of central-western Texas location 1. map showing of profiles and fossil localities . 7 2. Regional profiles in central-western Texas 9 abandoned Panther the 3. Profiles across Lake Lomax and Valley in of and Glasscock counties - 16 Big Spring area Howard, Martin, Plate I. Field views 22 Relation of Ogallala Formation to the Southern High Plains in Texas JOHN C. FRYE 1 and A. BYRON LEONARD^ ABSTRACT Studies along the southern and south- Pliocene and Pleistocene valley is de- scribed of Edwards Plateau eastern borders of the High Plains have across a prong the of outliers of south of and the drainage of demonstrated presence Big Spring, Lake Lomax is de- fossiliferous Ogallala Formation in Borden the late Pleistocene in and Scurry counties and have documented termined to have occurred pre-Bradyan Wisconsinan lime. A the occurrence of Pliocene deposition as far meaningful physio- be- The limit of cannot be drawn southeast as Sterling County. graphic boundary southern limits of the characteristic Ash Hollow seed floras is ex- tween the High Plains and the Edwards Plateau. tended to the southeast. An abandoned INTRODUCTION the limits of the Plains are less firmly The High Plains surface is the dominant High here the surface of the physiographic feature of central-western fixed because upper Formation does stand as the and northwestern Texas (Sellards, Adkins, Ogallala not above the It is layer of a plateau adja- and Plummer, 1933, fig. 3). a high capping the cent terrain, nor does the truncated edge of plateau, sloping generally toward terminated the Formation a prominent southeast. This plateau is Ogallala cap In fact, in the region north of toward the east by a striking escarpment, escarpment. Pecos (Leonard and Frye, 1962) and its western extent is likewise abruptly Valley and of it is indeed diffi- terminated in eastern New Mexico. North- west Sterling City, cult to draw a meaningful line of separa- ward, the High Plains surface is transected Ed- tion between the High Plains and the by the trench of the Canadian River valley, wards Plateau subdivi- but the upland surface extends through the as physiographic the Oklahoma sions based on topographic expression (PL Texas panhandle, across Kansas into I, B) and, as physiographic units, they panhandle and western western the be even ar- Nebraska. cannot differentiated, by of the feather edge of Since the early work by Johnson (1901; bitrary acceptance the Formation as the dividing 1902) and Darton (1905; 1920), the High Ogallala feature has been line. Plains as a physiographic southeast from the coextensive with the Furthermore, High regarded as virtually Borden and and the Plains particularly in deposits of the Ogallala Formation, scarp, there outliers of the west and Scurry counties, are Ogal- Plains are terminated to east, forma- lala that coincide with the projected gra- north at the truncated limits of this dient of the High Plains surface; these tion. To the south and southeast, however, the if such areas should be pose question Geological Survey, Urbana. 1 Chief, Illinois Stale as outliers of the High Plains, of Kansas, Lawrence. regarded 2 Department of Zoology, University 6 Report of — Investigations No. 51 even within though the Osage Plains re- and southeastern gion. An additional limits. complicating factor is Il is the the of this presence of extensive Pleistocene purpose report to de- lake s< rihe the basins within the regional relations of the southern area of the Ogallala extremities of the Texas formation (Evans and High Plains, to list Meade, 1945) and fossd within seeds from the the that has Ogallala Formation in region generally been classed some of the outliers and from as near its High Plains. Therefore this southern and to limit, describe the exten- physiographic feature, so clearly recog- late sive Pleistocene lake nizable farther north in that existed Texas and in west- in southwestern ern Kansas Howard and (Frye and adjacent Leonard, 1952) counties. becomes difficult to define at its southern Relation of Ogallala Formation. Southern High Plains 7 locations of Figure 1. Map of central-western Texas showing cross sections on figures 2 and 3 and locations of Pleistocene fossil snail faunas and Ogallala fossil seed floras used in this report. REGIONAL PHYSIOGRAPHY In central-western Texas the Plains High a of little slope a more or loss than 2 feet is an extensive table-land on of the top per mile from SW and modified to NE, therefore, if upper surface of the late Tertiary we ignore structural plain of coalescent subsequent movement, alluviation, defined by the suggested initial the slope is from lop of the Ogallala Formation. slightly Pleisto- west of NW to slightly east of SE and is at cene veneers of sheet Hood eolian or de- a rate of 10 feet approximately per mile. posits occur on large parts of the The surface; character of the sediments in the in upper some areas the upland plain is indented part of the Ogallala Formation by Pleistocene lake suggests basins; and locally the that the gradients on which they were High Plains are notched by Pleistocene and less deposited were than this, and the flora be cent canyons. However, the surface and pre- invertebrate fauna of the formation serves in the initial general depositional that suggest during most of the time of its slope of the Ogallala sediments as it has the deposition region was at a lower alti- been modified by subsequent regional tilt- tude and received more precipitation than ing, and, perhaps, very gentle it warping. now does and The (Frye Leonard, 1957; general character of this surface is 1959). However, below the surface shown by the upper generalized profiles, located of the Ogallala sediments there developed m figure 1 and in presented figure 2. The an extensive thick zone of soil caliche that present of the gradient surface is about 5 has been modified several feet by cycles of per mile from north to south, 6 to 8 brecciation and recementation feet mile from (Swineford, per west to east, and 8 9 to Leonard, and Frye, 1958) and that feet mile from now per NW to SE. At right serves as a resistant capping layer. Inter- angles to the direction of maximum gra- spersed the throughout upper part of the dient shown in figure 2, the profiles show lormation are other zones, wherein the Figrue 2. Generalized schematic physigraphic profiles in central-western Texas (plotted from 1:250,000 Arm Map Servie Sheets). A. From west-central Hale County south to north-central Midland County, and then southest along the western limit of the Ewards Plateau to the Pecos River in southwest Crane County, showing the southern feather edge of the High Plains, the Cretaceous bedrock divide, and the Pecos Valley. B. West-east from southwestern New Mexico to western Nolan County, showing the eastern com- ponent of High Plains slope. Lake Lomax basin, and the Osage Plains standing above the pro- jection of the High Plains surface. C. Southwest from Farwell, at the New Mexico line in Parmer County, to northwestern Nolan County, showing the Haigh Plains (Ogallala Formation) slope along its maximum gradient, its eastern escarpment in Garza County, the prominent outliers in northeastern Borden an dnorht- western Scuŕy counties, the Pleistocene veneered upland in the snyder area, and the bedrock surface of the Osage Plains rising above the projected slope of the High Plains in northwestern Nolan County. D. Southwestward from the New Mexico line in Cochran County to central Howard County, and thence southward to central Reagan County. showing the regional slope of the High Plains surface, and the position of the Edwards Plateau (Cretaceous) standing above the projected slope of the high Plains surface. E. Northeastward formt he New Mexico line in Andrews County to central Motley Country showing the High Plains surface, at right angles to the direction of its major regional slope, and the High Plains escarpment at the Floyd-Montley Country line. Relation of Ogallala Formation, Southern High Plains 9 sediments are cemented with of the limestones of Cretaceous irregularly ception age calcium carbonate and locally silica, that (Fredericksburg). Therefore, it is in the the help to give Ogallala Formation the region where the Ogallala pinches out resistance greatest to erosion of any of the against the resistant limestone, or feathers pertinent stratigraphic units, with the ex- out onto gently sloping surfaces developed 10 Report of Investigations—No. 51 on these that limestones, the limits of the oepted limits of the Hi Plains. High Plains are indistinct. Where upland 1 he major of rock that has surfaces underlain body long by limestones of the keen considered an isolated outlier of the Fredericksburg Group stand distinctly Ogallala Formation above the (Sellards, Adkins, and surface of the Ogallala Forma- Plummer, 1933) is in the NW to SE elon- tion, a differentiation between the Edwards gate belt shown on the of Plateau and the geologic map High Plains is clear. lexas as from the lh 0 extending northeastern e gallala Formation and the r High corner of Borden County to south of Roscoe ! lams —It is surface.

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