Oversize color geologic map that depicts surface geology of Dimmit, LaSalle, and McMullen Counties and parts of Maverick, Zavala, Frio, Atascosa, Karnes, Wilson, Live Oak, Jim Wells, Duval, and Webb Counties, Texas. The 6-page booklet indicates geologic formations, abbreviations, and ages.

A preliminary study of the Frio sand distribution and formation temperatures and pressures was undertaken in order to define prospective areas in which a more detailed reservoir analysis is necessary prior to the selection of a site for a geothermal well.

Tuff, tuffaceous sand and clay, bentonite, and sandstone containing abundant volcanic rock detritus are present in Gulf Coast Tertiary rocks ranging in age from Eocene to Pliocene.

This report is a compilation of all available data on mineral resources (exclusive of oil and gas) in 39 south Texas counties. Information from published and unpublished sources was checked and supplemented by field investigations.