30 THE PERMO-CARBONIFEROUS RED BEDS OF 



' ' In the lower beds red and blue clays predominate, but the upper beds are 

 characterized by an increase in the proportion of arenaceous constituents and also 

 of limestone and gypsum. The sandstones and limestones are friable and, together 

 with the clays, yield readily to eroding agencies and supply a large amount of 

 detritus to the streams, which are heavily charged with the red sediments brought 

 down by their tributaries. In the lower beds the gypsum occurs as thin layers 

 and lenses in the clays. Beds of massive gypsum 2 to 3 feet thick crop out in the 

 hills south of Quanah. At Acme, where the material is quarried, the deposit is 

 from 10 to 20 feet thick. In many places fibrous gypsum fills cracks which cut the 

 alluvial clays in every direction. 



"The massive gypsum does not constitute persistent strata, but thins out or 

 is replaced horizontally by clays or limestones. J. J. Cyrus, a well-driller of Quanah, 

 states that the wells of that city derive their water from a porous limestone stratum 

 at a depth of 75 feet and that no gypsum occurs in the overlying beds, which con- 

 sist mostly of clay. A well put down a mile south of Quanah passed through a bed 

 of gypsum at 40 to 65 feet and another at 75 to 83 feet, the latter apparently the 

 eqmvalent of the limestone found in the city wells. 



"Except where overlain by fluviatile deposits of Quaternary age, the Clear 

 Fork and Double Mountain formations constitute the surface rocks west of the 

 Wichita formation as far as the escarpment that marks the eastern extension of 

 the Triassic in Texas. 



The age of these beds is generally recognized as Permian. Fossils are scarce and 

 are confined chiefly to the limestones. The meager collections thus far made from 

 these beds in Texas are not sufficient to warrant definite conclusions concerning them. 



"Cummins has assigned to these beds a total thickness of 3,900 feet, 1,900 

 feet to the Clear Fork and 2,000 feet to the Double Mountain. Only the lower 

 beds of the formations are exposed in the Wichita region. Red gypsiferous shales 

 and sands, with beds of gypsum and some limestones in the upper part, represent 

 the formations as they appear here. 



"The limestone (No. 3) [section 43 of this paper] is made up of several layers, 

 some of which are composed largely of fragmental remains of vertebrates, including 

 plates, spines, fish teeth, etc. The stratification of the argillaceous and arenaceous 

 sediments is very irregular, the sandstones and shales grading into each other both 

 vertically and horizontally. Moreover, there is a monotonous likeness in both 

 the sandstones and the shales throughout the area, which, in the absence of per- 

 sistent, clearly recognizable strata, renders the correlation of beds, except within 

 very narrow limits, practically impossible. 



"Some of the most prominent limestone divisions of the southern area persist, 

 although in diminished thickness, as far north as Red River, perhaps farther. The 

 Kmestones so well developed on Clear Creek, in the southwestern part of Throck- 

 morton County, extend northward through Seymour, are crossed by Wichita River 

 about 3 miles east of the Seymour- Vernon road, and are last seen on Beaver Creek, 

 in the eastern part of Wilbarger County. The transition of limestone into sandstone 

 is well marked in an exposure in the bluffs of the Salt Fork of Brazos River, about 

 a mile west of Spring Creek post-office, in the northwest corner of Young County. 

 A bed of Hmestone 3 feet thick and an overlying bed of blue shales 5 feet thick, 

 both filled with fossils (chiefly Myalina permiana), are replaced within a distance 

 of 200 yards by a light-colored cross-bedded calcareous sandstone having a maxi- 

 mum thickness of 15 feet. The transition is rather abrupt in appearance, but the 

 sandstone contains much Hme and also some fossils. Farther along the limestone 

 reappears as before. 



