Geologic map that depicts the surface geology of Shackelford, Stephens, Palo Pinto, Callahan, and Eastland Counties and parts of Jones, Taylor, Runnels, Coleman, Brown, Comanche, Erath, Parker, and Hood Counties, Texas.

Geologic map that depicts surface geology of Tarrant, Dallas, Kaufman, Ellis, Johnson, Somervell, and Rockwall Counties and parts of Parker, Hood, Erath, Bosque, Hill, Navarro, Henderson, Van Zandt, and Hunt Counties, Texas.

Coal is found in six areas in Texas, including the large North-Central Texas field, a distinctive cannel coalfield in Webb County, and Late Cretaceous-age coals near Eagle Pass.

These are 21 Texas county maps made in cooperation with the American Association of Petroleum Geologists and Society of Economic Paleontologists and Mineralogists, issued between 1929 and 1932 and revised in 1937.

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.

Lower Cretaceous sands have long been important aquifers in Central, North-Central, and North Texas. In recent years these sands also have been sources of high-silica industrial or specialty-purpose sand.

The Fort Worth Basin, in North-Central Texas, is a late Paleozoic foreland basin that was downwarped during the Early to Middle Pennsylvanian Period in response to tectonic stresses that also produced the Ouachita Thrust Belt.