This full-color, oversize map, designed for hikers in the park, describes geologic units and features. The text documents the geologic history of the Big Bend Ranch State Park area. Support was provided by the Texas Parks and Wildlife Department and the U.S. Geological Survey.

This report combines borehole core and geophysical log study with porosity and permeability data to define patterns of facies and permeability distribution in a typical upper Clear Fork reservoir in the Permian Basin. Key findings are that permeability, but not porosity, varies markedly with facies and that spectral gamma ray logs are critical for defining facies, facies architecture, and reservoir quality.