64 A GEOLOGICAL SUBVEY OF LANDS 



terranes is very low and in places even reversed. Mapping this 

 region was out of question, except in a general way. 



Possible Economic Importance. 



The fine texture of the Buda rock would adapt it for use as 

 lithographic stone were it not for the presence of occasional 

 grains and streaks of calcite and numerous barely visible joints 

 or incipient fractures which were seen to affect all the material 

 examined. The joints would without doubt disappear some dis- 

 tance within the rock, if a quarry were opened in a suitable place, 

 and it may be that the calcite grains do not exist in all the ledges, 

 although no such ledges were observed in this survey. 



The purity af the limestone makes it a suitable material for 

 the manufacture of Portland cement. For this purpose similar 

 limestones are mixed with a certain quantity of clay, and for this 

 use the underlying Del Rio clay would answer very well. The 

 limstone would be easy enough to grind, as it is rather less tough 

 than the majority of rocks of similar kinds. Economic conditions 

 limit profitable enterprises of this kind to localities where the raw 

 materials occur in the immediate vicinity of transportation facil- 

 ities, and such locations might readilj'' be found along the South- 

 ern Pacific railroad just east of Del Rio, or between Devil's river 

 and Comstock. 



THE EAGLE FORD BEDS. 



This formation, which takes its name from a locality in North 

 Texas, overlies the Budalimestone. Its lower contact with the Bud a 

 limestone is invariably sharply marked, as already noted, but up- 

 ward it very gradually and quite imperceptibly acquires the char- 

 acter of the overlying chalky limestone. For this reason no 

 definite depth can be a ssigned to it, except when taken with this 

 upper member. For practical purposes we may regard it as 

 measuring 250 feet. Westward it exceeds this figure. 



The main part of the Eagle Ford beds in this region consists 

 of ledges of cream-colored limestone, measuring from a few inches 

 to a foot in thickness. This limestone is not pure, but contains a 

 varying amount of fine sand, which usually appears as bands of 

 yellowish or light brown color on vertical fractures. The entire 

 formation is somewhat regularly thin-bedded. The lower hun- 



