Based on need for convenient, small-scale cartographic units, the basal Cretaceous rocks in Texas from Red River to Burnet County and on the Callahan Divide are herein divided into three distinctive lithologic sequences.

The wedge-shaped Black Gap area in southern Brewsier County, Texas, occupies approximately 4,50 square miles east of the Big Bend National Park.

Geologic map that depicts the surface geology of Lamar, Red River, Bowie, Delta, and Titus Counties and parts of Fannin, Hunt, Camp, Cass, Hopkins, Franklin, and Morris Counties, Texas. The 6-page booklet indicates geologic formations, abbreviations, and ages.

At five places along the outcrop of the Wellborn Formation in Lee and Burleson counties, Texas, anomalously high gamma radiation is associated with concentrations of heavy minerals. The most abundant heavy minerals are ilmenite, magnetite, and zircon.

Hye quadrangle includes part of the southeastern Llano region and part of the eastern margin of the Edwards Plateau where most of the Plateau surface has been destroyed by erosion.

Stonewall quadrangle includes part of the southern margin of the Llano region and part of the eastern margin of the Edwards Plateau where most of the plateau suriace has been destroyed by erosion.

This volume presents the texts of papers presented at a Symposium...sponsored by the Southwestern Federation of Geological Societies and The University of Texas in Austin, January 29, 1965.