The purpose of this discussion is to carry the section from the top of the Jackson (where Patterson’s paper stopped) through the Frio, Catahoula, and Oakville formations; to make a subdivision of the Catahoula; and to point out the occurrence of the Oakville formation in this area. The distribution of the formations is shown on the aerial map.

For convenience of mapping, an oyster bed at or near the top of the Jackson (Fayette) is accepted as the base of the Frio. There are 550–600 feet of red and green clays with thinly bedded sands, assigned to the Frio formation. Two prominent sandstone beds occur in the upper 200 feet of the formation.

The Catahoula is subdivided into three members: Fant, 75 feet; Soledad, 200 feet, and La Chusa, 1,000 feet thick (Thomas L. Bailey, Univ. Texas Bull. 2645).

Approximately 200 feet of pinkish chocolate-colored clays with globules of soft limestone overlies the La Chusa tuffs. These clays are distinctly different from Catahoula deposits, and are referred to the Oakville formation, due to their lithologic character and position in section.

The Catahoula and Oakville are overlapped by Lissie or post-Pleistocene conglomerate throughout north and northeastern Starr County.

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