26 THE PERMO-CARBONIFEROUS RED BEDS OP 



from clays in which they first were formed by true concretionary growth. The fre- 

 quent association of sandstone and of these conglomerates with contemporaeous 

 unconformities or local excavations in the clays is significant in this connection. 

 It is known that concretionary growths may form quite rapidly, and on the Gulf 

 coast places may now be found where the waves are beating down banks of recently 

 formed clay, leaving thin layers of calcareous concretions mingled with sand on 

 the beach at the foot of the clay chff . A sandy conglomeration of such concretions, 

 that perhaps was laid down on a beach in this manner, was noted in the breaks 

 about 4 miles south of Electra. The concretions have evidently been embedded 

 in the upper surface of a stratum of sand, to which they adhere in the exposure. 

 The absence of everything but indigenous material in conglomerates which clearly 

 have been produced by currents of considerable strength suggests isolation of the 

 coasts from mountain lands while the Wichita beds of this region were deposited. 

 The underlying beds of the Cisco formation contain pebbles of chert and of granite, 

 which are derived from the Wichita Mountain upKft. Evidently the geographic^ 

 conditions prevailing during the deposition of the Wichita beds were different from 

 those existing during the making of the Cisco beds." 



THE BEAVERBURK LIMESTONE. 



"While the clays and the sandstones of the Wichita formation are too irregular 

 in their development to be individually correlated, at least one limestone was 

 found which it was possible to follow for a dozen miles or more, even though it 

 may not be quite continuous for this distance. We have called this the Beaver- 

 burk limestone, for the reason that it is well developed in the basin of Beaver 

 Creek, and has been traced northeast as far as to Burk Station on the Fort Worth 

 and Denver Railroad. 



"This Kmestone caps the upland bluffs on the north side of the Wichita River 

 in the southwest comer of Wichita County, where it has its greatest thickness and 

 measures about 3 feet. Its outcrops have been traced from this point northeast- 

 ward across the basin of Beaver Creek, and from there northward and eastward 

 to Burk Station, * * *. (See fig. 4, p. 33.) In the Beaver Creek Basin the rock is 

 less than 2 feet thick, and in some places less than a foot. Northeast from the 

 Beaver Creek basin, and in the vicinity of Burk, it is less than 6 inches thick, and is 

 evidently not always present in the section. The horizon where it belongs is, how- 

 ever, marked by a continuation of the dark or greenish-gray shale which underlies. 

 This shale is traceable eastward as far as to the hills 2 miles northwest of Iowa Park. 

 A thin shell of limestone, which may be a continuation of this limestone, was noted 

 at a point on a hillside 3 miles north and i . 5 miles east of Iowa Park. 



"This limestone is mostly a tough, dark gray rock, that effectively withstands 

 weathering. It has been used very generally for building stone and in foundations 

 at the neighboring ranches. It breaks along two main systems of joints into rec- 

 tangular and sometimes diamond-shaped blocks, often in sizes small enough to be 

 handled and hauled away. Where the limestone caps a small slope these blocks 

 creep down on its surface, forming a pavement in which the blocks maintain their 

 arrangement in rows for some distance down the slope. (See figs, i and 2, plate 10.) 

 This is frequently seen in the breaks on the Houston and Texas Central Railroad 

 Company survey 33. * * * 



"In its original form the rock is almost compact and structureless, save for 

 the presence of more or less obscure lamination. Under the microscope the sample 

 * * * exhibited an exceedingly fine and homogeneous granular texture, the granules 



Or climatic— E. C. C. 



