THE COMANCHEAN PERIOD. 



117 



times clear enough to allow of the accumulation of impure limestone. The 

 series is made up of alternating beds of clay, limestone, sandstone, etc. 

 In its typical development in Texas, more than half the Comanchean 

 system is calcareous, and chalk, rather than limestone in its ordinary 

 form, prevails. In general, the clastic beds thicken toward the Ouachita 



Fig. 382. — Shows the effects of faulting on outcrops of the various Cretaceous for- 

 mations, near Uvalde, Texas. Ce (Edwards limestone), Cdr (Del Rio clay), 

 and Cb (Buda Lmsstone) are the local subdivisions of the Comanche system 

 Kef (Eagle rord fo: mat ion) is the lower part of the (Upper) Cretaceous. 



Mountains, while the beds of chalk, which point to clearer water, thicken 

 in the opposite direction. Locally the Comanchean system of Texas 

 is deformea and notably faulted (Figs. 381 and 382). 



Westward and northward extension. — The Comanchean forma- 

 tions originally spread westward from Texas over a considerable 

 area in eastern New Mexico, and probably even to Arizona, where the 

 system is 5000 feet thick l and carries the Texan fauna, 2 and north- 



1 Ransome, Professional Paper 21, and Bisbee folio U. S. Geol. Surv. 

 * Stanton, Professional Paper 21, U. S. Geol. Surv. r p. 70. 



