284 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



It was to be expected that the same formations would soon be found also on the west side of 

 Cache Valley, in the Wasatch Range proper. As exposed on the crest of the range, there is, 

 between the Ordovician quartzite and the identifiable part of the Mississippian limestone, a 

 succession of dark limestones, with some ash-gray brittle dolomites having a thickness of 

 1,000 to 1,500 feet. In the lowest beds there are corals such as Halysites and Favosites. At a 

 slightly higher horizon there are abundant shells, which Eandle thiaks are the same as his 

 Pentamerus fauna of the Bear River Range. All the specimens, however, are poorly preserved, 

 and show best upon the weathered surfaces. Between the Silurian horizon and the fossiliferous 

 Mississippian there is a thick, dark limestone which corresponds satisfactorily with Kindle's 

 Devonian Jefferson formation east of Cache Valley. Further search may be expected to 

 reveal the Jefferson fauna in these beds. 



Kindle "^''' *^®'' examined the sections in several canyons south of Logan Can- 

 yon, in the northern part of the Wasatch Mountains. He distinguishes 1,000 to 

 1,200 feet of dark magnesian hmestones as Devonian, the equivalent of the Jefferson 

 limestone of Montana. The formation lies between Silurian and Mississippian 

 limestones. (See p. 320.) 



In the Uinta Range the Devonian is not present, the Ordovician quartzite 

 being immediately overlain by limestones of lower Mississippian age. 



In the Grand Canyon section, Arizona, a limestone 94 feet thick is classed as 

 Devonian by Walcott.^^^ It rests on Cambrian rocks, as does the Ouray lime- 

 stone in some areas in Colorado, and is overlain by the RedwaU limestone (Carbon- 

 iferous), 962 feet thick. In Gilbert's original account ^^"^ of the RedwaU he says: 

 "The base of the system is arbitrarily assumed at the first marked lithological 

 change, and it is not impossible that it has been placed so low as to include Devo- 

 nian, or even Upper Silurian, if those formations are represented in the series." 



B. S. Butler" has recently found Devonian underlying Mississippian hmestone 

 in the Star Range, Beaver County, Utah. 



J-K 12-13. WYOMING AND COLORADO. 



In western Wyoming the Devonian is represented by the Jefferson limestone. 

 It is not present in the Bighorn Range, according to Darton, and does not occur 

 near Rawlins, according to Kindle. Blackwelder says that it probably occurs 

 in the Teton and Gros Ventre mountains and perhaps in the northwestern part 

 of the Wind River Range. 



In southwestern Colorado the Devonian is represented by the Elbert formation 

 and the lower part of the Ouray limestone. The Elbert consists of calcareous 

 shales, thin limestones, and local quartzite beds, characterized in many places 

 where shaly by casts of salt crystals and carrying at several horizons fish remains 

 of Upper Devonian age (Bothriolepis and Holoptychius) . It usually rests uncon- 

 formably upon the Cambrian (Ignacio quartzite) . It is conformable to the overly- 

 ing Ouray limestone, the division between the two being marked by a band of red 

 shale, the top of the Elbert. The Ouray limestone is in greater part dense and com- 

 pact, yellowish, somewhat sandy in the lower layers, and in places coarsely crystal- 

 Une in the upper ledge. It is 100 to 250 feet thick. The lower part contains a 

 Devonian fauna and the upper part a Mississippian (lower Carboniferous) fauna. 



" Personal communication. 



