ORDOVICIAN AND CARBONIFEROUS 437 



Cambro-Ordovician limestones. It is overlaid by 200 to 300 feet of 

 Silurian and Devonian limestones, at least in the Cache Valley region, 

 as shown by fossils collected by the writer in 1906 and determined by 

 Messrs Ulrieh and Kindle. In the Uinta range the Ogden quartzite rests 

 upon the Lodore shales, considered to be Cambrian in age, and is imme- 

 diately overlaid by limestones of Lower Mississippian age. This forma- 

 tion was not differentiated by the 40th Parallel geologists in the Uinta 

 region. 



Description. — The formation is well exposed along the south side of the 

 range from Kamas creek to Whiterocks creek. The basal beds are green- 

 ish sandstones, above which are several beds of fine-grained conglomerate 

 and cross-bedded sandstone. These are succeeded by 200 feet of white 

 quartzites. The upper part of the formation contains beds of conglom- 

 erate and a prominent band of calcareous sandstone two to three feet in 

 thickness, which grades into buff weathering limestone of the overlying 

 Mississippian series. 



ISTo representative of the Ogden quartzite was determined on the north 

 side of the range, as the Lodore shales appeared to pass directly into the 

 Mississippian limestones. This seems a peculiar circumstance, since the 

 quartzite is 1,200 feet in thickness in Ogden canyon, 1,000 feet or more 

 in Weber canyon, and 800 to 1,000 feet in Big Cottonwood and American 

 Fork canyons, in the Wasatch mountains, which are not more than 25 to 

 40 miles from the western end of the Uinta range. 



CARBONIFEROUS 



Mississippian series — Nomenclature and correlation. — The 40th Par- 

 allel geologists recognized that the great quartzite-sandstone series .of 

 the Uinta range were the oldest sediments and conformably succeeded by 

 the overlying beds, but by correlating the series with the Weber quartzite 

 of the Wasatch mountains it necessitated the correlating of the Missis- 

 sippian limestones with the strata above the Weber quartzite; conse- 

 quently they did not recognize the presence of the Wasatch limestone. 



Wherever fossils have been found in the lower and upper members of 

 the Wasatch limestone, they show the former to be of. Mississippian age 

 and the latter of Pennsylvanian age. This is also true of the Uinta 

 range. The precise line of division has not yet been determined. In the 

 Uinta range about 600 feet of the 1,070 feet of beds that have been corre- 

 lated with the Wasatch limestone are certainly of Mississippian age. 

 Powell correlated the beds of the Wasatch limestone with his Grand Can- 

 yon section. They correspond in general to the Eed Wall group. 



