The mineral resources survey of Erath County included plane table mapping of Pennsylvanian limestones exposed in the northwest part of the county. Most of the work was on the Goen Limestone and the Santo Limestone. The project was terminated before the Brannon Bridge Limestone could be studied. The outcrops were picked up at the Palo Pinto-Erath County line and mapped southwestward to the Pennsylvanian-Cretaceous contact, 7 miles south of Thurber.

Gravel deposits are found in Henderson County in the stream terrace deposits of the Trinity River and its tributary, Cedar Creek. These deposits were examined in detail in the vicinity of Trinidad. It was found that four terrace levels contain gravel. The top of the lowest of these terraces is 10 to 15 feet above the level of the floodplain, and the base of the terrace is below floodplain level. The gravel lies in the lower part of the terrace deposit, with the upper part consisting of loam and silt.

The field work on which this report is based was done during October and November, 1936. It consisted of the mapping by reconnaissance methods of the areas of outcrop of the formations over as large a portion of the county as possible, followed by the detailed mapping of the area west of Elkhart with the plane table. This work was supplemented by coring with hand tools.

A mineral resource survey of Texas has been started by the Works Progress Administration, with the Bureau of Economic Geology of The University of Texas acting as sponsor. The purpose of the survey is to assemble information and make it available to the public. Through a separate project, sponsored by the State Planning Board, the results of the survey, as they are received in Austin, are being assembled for publication.