RED BEDS BETWEEN WICHITA FALLS AND LAS VEGAS 247 



Sagerton. The stream runs between steep walls of clay with abun- 

 dant gypsum. On the east side of the stream near the crossing 

 is a bluff from 60 to 70 feet high composed very largely of gypsum 

 with thin intervening beds of gypsiferous clay. No pure selenite 

 was found in this bluff but almost every other form of gypsum occurs : 

 layers of splendid satin spar, impure gypsum in thin and bifurcating 

 irregular seams, as described by Cummins, heavy beds of granular 

 gypsum, and equally heavy beds of clusters of imperfectly formed 

 crystals. From the dip of the beds this is evidently higher than 

 the beds at Sagerton but it is very probable that the increase in 

 the amount of gypsum occurs not only in the rise of the beds but 

 also in their western extension. 



Beyond the Double Mountain Fork the surface rock is a loose 

 sandstone of considerable thickness which readily breaks down into 

 a poor sandy soil with very few exposures on the sides of the gentle 

 but pronounced swells. There is considerable gypsum in this sand- 

 stone, as shown by the frequent efflorescence and beds of pulverent 

 calcium sulphate. True beds of gypsum do not appear again until 

 the hills beyond Aspermont are reached; here at a much higher 

 level than the gypsum on the banks of the Double Mountain Fork, 

 there occur layers, several feet in thickness, of pure granular gypsum, 

 so soft that it is deeply marked by grooves due to rills of rainwater. 



At Double Mountain, a few miles southwest of Aspermont, the 

 following section was made by Dumble and Cummins: 



[ Caprina limestone 40 feet 



Lower Cretaceous \ Comanche Peak series 55 



I Trinity 25 



Triassic 3a. Dockum 35 



Shaly clay underlaid by red or terra cotta 



sandstone 105 



Permian \ Upper gypsum beds 60 



Middle gypsum beds 75 



Lower gypsum beds 135* 



* Am. GeoL, 1892, p. 348. 



The author's section agrees in only a general way with the por- 

 tion marked Permian, unless it be understood that the gypsum 

 beds be considered to mean red clay with much interspersed gyp- 

 sum. Double Mountain is an outUer of the Staked Plains and 



