Studies of Cenozoic Geology along Eastern Margin of Texas High Plains, Armstrong to Howard Counties

The eastern margin of the High Plains in central western Texas affords particularly good opportunity for study of late Cenozoic geology. The topography of the area is dominated by the southernmost segment of the late Tertiary mantle of fluvial sediments, isolated from the central and northern High Plains by the valley of the Canadian River. The eastern escarpment presents many exposures and the canyons that extend into the plains contain, in addition, a nearly complete sequence of Pleistocene terraces and deposits. The Canadian River, which crosses the Texas Panhandle north of the area under study, flows by way of the Arkansas River to the Mississippi. However, in the Plains to the south are the headwaters of drainage to Red River (which enters the Mississippi just above its delta) and of the Brazos and the Colorado rivers, each of which takes its independent course to the Gulf of Mexico. Therefore, the Pleistocene histories of adjacent High Plains canyons are indicative of independent drainage systems. These geographic relationships that place nearby streams under control of three different base level situations give special significance to late Cenozoic correlations in this region. Field work on which this report is based has been discontinuously distributed over a decade. Several short periods were spent in the field from 1945 through 1949 when work was directed primarily toward correlation of Kansan age deposits with deposits in the northern Great Plains and with the glacial section of the Mid-West. This study was carried on largely by use of the distinctive petrography of the Pearlette volcanic ash bed and by fossil molluscan faunas (Frye, Swineford, and Leonard, 1948), but was accompanied by a reconnaissance of Pliocene and Pleistocene stratigraphy of the region. Field work directed specifically toward the present report consisted of several weeks in the fall of 1954 and summers of 1955 and 1956 under the auspices of the Bureau of EconomicGeology of The University of Texas. It is our purpose here to present the results of the regional integrated attack on the problems of correlation by use of fossil molluscan faunas, fossil seed floras, physiographic history, buried soils, lithology, and previously described volcanic ash petrography. From this approach there has emerged the basis for a framework of stratigraphic classification consistent with other parts of the Great Plains region. The data used are relatively widely spaced along the eastern margin of the Plains, and further detailed work is needed in this region to produce a desirable degree of refinement and certainty.