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.

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.