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 summarizes the results of a stratigraphic and sedimentologic study of outcrops of one unit of the sequence, the Gueydan (Catahoula) Formation, from south of the Colorado River, Texas, to the Rio Grande. It is one phase of a study of middle Tertiary volcanism in southern Texas and northeastern Mexico.

Papers in this volume were presented at the Fourth Forum on Geology of Industrial Minerals sponsored by the Bureau of Economic Geology, The University of Texas at Austin, on March 14 and 15, 1968. The program and meetings were organized and directed by co-chairmen W. L. Fisher and P. U. Rodda, Bureau of Economic Geology. Papers in this volume are arranged in the order of presentation at the meetings; contributions have been edited only as necessary to present a standard format. Mr. James Macon, Cartographer, and Mrs. Elizabeth T.

Geologic map that depicts surface geology of Swisher, Briscoe, Hall, and Childress Counties and parts of Randall, Armstrong, Donley, Collingsworth, Hale, Floyd, Motley, and Cottle Counties. This map was published as a memorial to William Fletcher Cummins, who pioneered in mapping West Texas geology and specialized in the study of Permian rocks of West Texas and New Mexico. These rocks are depicted in the eastern two-thirds of the Plainview Sheet.