REVIEW AND CONCLUSION 271 



the Dakota. The relationship with the Comanche in Kansas, southern 

 Colorado, and eastern New Mexico and with the overlying Upper Creta- 

 ceous rocks throughout its extent is too intimate. It is true that the 

 Comanche fauna as a whole is very distinct from the Upper Cretaceous 

 fauna as a whole, but the change from the Kiowa or Denison fauna to' 

 the Woodbine or from the Woodbine to the Benton shows little if any 

 oreater contrast than is found between the Niobrara and Carlile faunas, 

 or between the Carlile and the Greenhorn, or even between some of the 

 zones in the Carlile. And yet these faunal changes within the Upper 

 Cretaceous were certainly not caused by the complete retreat and a suc- 

 ceeding advance of the sea. The restricted distribution of the Woodbine 

 sand and its absence from central and southern Texas suggest an uncon- 

 formity at the base of that formation or at the base of the Eagle Ford, 21 

 but recent workers consider it unimportant if present. Stephenson 22 has 

 presented evidence in favor of an erosion interval between the Eagle Ford 

 and the Austin chalk, a suggestion which is also supported by the varying 

 thickness of the Eagle Ford. It is probable, however, that all of these 

 unconformities, so far as they actually exist, represent only local and 

 temporary uplifts whose influence was not felt over a wide area. 



The proposal to elevate the Comanche series to the rank of a system, 

 under the name Comanchean, which was made in Chamberlin and Salis- 

 bury's Geology in 1906, has never seemed to me justified by the facts 

 known at that time, and the arguments then advanced for it have been 

 much weakened by subsequent investigations. Both the physical break and 

 the faunal change at the top of the Comanche now seem much less impor- 

 tant. In arguing for the importance of the division, it was assumed that 

 the Comanche series has approximately the same upper limit as the Euro- 

 pean Lower Cretaceous — that is, the base of the Cenomanian — but many 

 European paleontologists have long referred the Washita to the Ceno- 

 manian, and of late the paleobotanists have become insistent on that 

 correlation on account of the character of the flora of the Cheyenne sand- 

 stone. I have often stated 23 in print that the Washita may be in part at 

 least Cenomanian, when explaining that "the whole of the Comanche 

 soi-ies is treated as Lower Cretaceous, because in the Texan area the top 

 of the Comanche is the only natural and satisfactory major plane of 

 division in the Cretaceous." Some of those who accept the correlation 

 of the Washita with the Cenomanian and wish to recognize two systems 



21 University of Texas, Bulletin 1916, no. 44, p. 72. 



22 U. S. Geol. Survey, Professional Paper 120, p. 149. 



23 See, for example. Jour, of Geology, vol. 5, 1897, pp. 583 and 006; idem. vol. IV, 1909. 

 p. 416: F. S. Geol. Survey, Monograph 44, 1903, p. 14. 



