The field work and detailed mapping which form the basis of this paper are a continuation of previous work done in the general area. The trace of the unconformity at the base of the Custer is shown in detail by a series of county maps. Also one general map shows the change in direction of the trace of the unconformity and the trace of the base of the San Angelo. The length of the area covered by this field work is 300 miles, from Wheeler County, Texas, southward to Coke County, Texas.

Many changes of facies were observed in the field and these have had an important bearing upon the nomenclature as the beds were traced southward from Kansas and Oklahoma into Texas. Because of the loose application of the nomenclature of Kansas and northern Oklahoma to beds in Texas which are only partially equivalent, the writer has quoted the original type descriptions so that the differences may be apparent at once. It is to be hoped that the naming of facies as a formation and the bounding of these formations by chemical deposits will not be perpetuated as only confusion can result from this practice. This method of nomenclature has been and is now widely used, especially in Texas. It is again suggested that the beds occupying the interval between the base of the Dockum and the unconformity mapped be given one formation name, Custer, and the names now in usage be confined to the facies which they represent.

A brief discussion of the field evidence for the alteration of anhydrite to gypsum, and the effect of this hydration upon the inclosing sediments is presented. The lithologic difference between the anhydrites of the Custer and the gypsums of the Blaine is included.

Some unusual problems of erosion now active in this part of Texas are discussed. Due to the presence of wind-blown sand and the escarpment of the Great Plains little is known concerning the stratigraphy of the upper part of the Custer.

Certain physiographic features observed in the field are described, such as karst topography and results of epicycles of erosion. The solution of the gypsum and salt in the Blaine has resulted in the formation of the erratic dips observed in the lower Custer. The exposed part of the Blaine now presents a beautiful example of karst topography. Two epicycles of erosion are now in active process, and badlands are being formed in the older rolling topography.

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