[en] The Pennsylvanian-Wolfcamp section in the Palo Duro Basin includes brine aquifers that are considered to be the most important ground-water flow paths in the deep-basin system. This report is the fifth in a series providing summary documentation of studies that subdivide the section into hydrogeologic units based on their judged relative capacities for transmitting water. This report extends the hydrogeologic study area to the eastern Texas Panhandle, north-central Texas, and southwestern Oklahoma. It includes 37 counties in Texas and Oklahoma. Underground patterns of rock distribution are delineated from a hydrologic perspective and at a level of detail appropriate for numerical modeling of regional ground-water flow. Hydrogeologic units are defined and characterized so that appropriate porosity and permeability values can be assigned to each unit during construction of the numerical models (not part of this study), and so that modelers can combine units where necessary. In this study, hydrogeologic units have been defined as mappable, physically continuous rock bodies that function in bulk as water-transmitting or water-retarding units relative to adjacent rocks. Interpretations are made primarily from geophysical logs. Hydrologic characteristics are assessed on the basis of properties typically associated with certain lithologies (e.g., sandstones are more pervious than shales) and on the basis of gross variations in effective porosity (particularly in carbonate sequences). 44 refs., 32 figs., 1 tab