UPPEK CRETACEOUS. 677 



The numerous formations listed in the above table are described in detail by 

 Veatch, who states the general relations as f oUows : ^^^^ 



The exact base of the Cretaceous in this region is not known. The lowest fossihferous 

 Cretaceous beds are clearly near the base of the Upper Cretaceous, and the Dakota, as well as 

 the Cretaceous beds which Darton has found beneath the Dakota in eastern Wyoming, if they 

 exist in this region, are thus inferred to be represented in the upper part of the Beckwith forma- 

 tion. The top of the Cretaceous is hkewise in doubt, involYing, as it does in other parts of the 

 Rocky Mountains, rather conflicting lines of stratigraphic and paleontologic evidence. In the 

 present discussion the Cretaceous is made to terminate with the great dynamic revolution which 

 interrupted the period of relative quiescence in this area, which extended without important 

 interruption from the earliest Carboniferous to late Cretaceous time. These disturbances pro- 

 duced important folds and faults, involving the movement of these sediments through thou- 

 sands of feet. This known portion of the Upper Cretaceous series has the enormous thickness 

 of over 20,000 feet. Its fossils indicate that it contains the time equivalents of the Benton, 

 Niobrara, Montana, and Laramie groups of the eastern section, but the natural lithologic subdi- 

 visions do not correspond with these faunal subdivisions and do not agree with those east of the 

 Rocky Mountains. There is in this section an entire new member — the Bear River formation^ 

 characterized by brackish and fresh water forms, which, although attaining a great thickness, 

 is essentially of local development. 



Regarding the division line between the Cretaceous and the Eocene of south- 

 western Wyoming, Veatch *^®^ makes the following statement : 



In the Wasatch group as thus defined by Hayden the field work of the season of 1905 showed 

 three divisions — (1) a basal member composed of reddish-yeUow sandy clays, in many places 

 containing pronounced conglomerate beds, which has been named the Almy formation; (2) a 

 great thickness of light-colored rhyolitic ash beds containing intercalated lenses of white hme- 

 stones "with fresh-water shells and leaves, the Fowkes formation; and (3) a group of reddish- 

 yeUow sandy clays with irregular sandstone beds closely resembling (1) hthologically and 

 separated from (1) and (2) by a pronounced period of folding and erosion. The last group has 

 been called the Knight formation and is the horizon of the Coryphodon remains found in this 

 vicinity. The Alm y and Fowkes formations belong, with the Evanston, in the conformable 

 series separated on the one hand by a pronounced period of folding and erosion from the Laramie 

 beds, and on the other from the Coryphodon Wasatch beds by a period of folding and erosion of 

 grea,t magnitude though of much less importance than the one between the AdaviUe and the 

 Evanston. The fossUs from the Almy and Fowkes have, without exception, been considered 

 Eocene, but the formations are treated with the Evanston because of their very intimate strati- 

 graphic relation to it and the stratigraphic isolation of the Evanston, Almy, and Fowkes from 

 the beds above and below. Whether it can ever be conclusively proved from the hmited 

 paleontologic data available that the line between the Cretaceous and Eocene should be drawn 

 in this section between the Evanston and Almy, so that one great physical break will be thrown 

 into the Cretaceous and the other secondary physical break into the Tertiary, is very doubtful. 

 Stratigraphic geologists wiU, in the absence of very positive paleontologie data to the contrary, 

 and none such exist at present, favor taking one physical break or the other for the hue between 

 the Cretaceous and Tertiary, preferably the earlier and greater one. The Knight formation is 

 not in dispute and has therefore been treated under the Eocene. 



The formations distinguished by Veatch in southwestern Wyoming have been 

 identified and traced northward from the forty-second parallel to the Gros Ventre 

 Range by Schultz." 



In the Wind River Basin, which lies northeast of the western Wyoming area 

 just described and is separated from it by the Wind River Range, the stratigraphic 



" Unpublished manuscript. 



