132 ANNALS NEW YORK ACADEMY OF SCIENCES 



have overlooked this relationship. They seem to have been prejudiced 

 from the similar relations which they had observed in the range to the 

 north, in Weber and Ogden Canyons. In describing the Big Cottonwood 

 section, King^^ has the following to say : 



"Next above the Cambrian lie 1,000 feet of Ute limestone, which for the 

 most part is very light colored, highly crystalline and characterized by peculiar 

 cloudings of color that extend across the beds near the bottom of the series, 

 and at one or two horizons near the top it is noticeable for containing a 

 large projwrtion of tremolite, and under the microscope it is seen to be highly 

 siliceous, the silica appearing as rounded glass grains of pellucid quartz. The 

 outcrop extends up the hills on both sides of the canyon and to the south is 

 conspicuous upon the divide, from which it descends into Little Cottonwood 

 and in the valley a little way below .Alta exposes a fine precipitous cliff, the 

 result of a fault (the Superior fault of this report). Here again are seen the 

 same highly crystalline, almost marble-like condition and the same prevalence 

 of tremolite and silica. Under these circumstances it is not at all remarkable 

 that the beds contain no fossils, but it is unquestionably Silurian, as will be 

 seen later. 



"Above the limestone occurs the white granular body of Ogden quartzite, 

 which is here reduced in thickness to about 800 feet. It may be traced up the 

 hill to the south and forms an interesting saddle in the ridge top, between the 

 Ute limestone and the bold masses of Wasatch limestone which directly overlie 

 it. Here are but limited traces of the thin body of greenish argillites that far- 

 ther south, in the region of Rock Creek, were found on both sides as bounding- 

 beds to the Ogden body." 



The presence of the "Ogden" quartzite between the "Ute" and '^Wa- 

 satch" limestones in the Big Cottonwood section seems to have been 

 inferred from its prominent appearance on the ridge above Alta. In Big 

 Cottonwood Canyon, no such quartzite member is exposed. The outcrop 

 at the head of South Fork, having the described position between the two 

 limestone members, can be traced northward along the strike of the beds 

 into Big Cottonwood Canyon, where it appears below the lowest lime- 

 stones there exposed. It therefore clearly belongs to the Cambrian. This 

 fact might easily have been discovered had the early geologists attempted 

 to explain the presence of a black shale above the "Ogden" quartzite on 

 the ridge above Alta. For some reason this important horizon marker 

 was overlooked or disregarded altogether. The "limited traces" above 

 referred to are hard to harmonize with the good exposure of this Cam- 

 brian shale at the south end of the Reade and Benson ridge, where it 

 shows its typical thickness, between 150 and 200 feet. The lower occur- 

 rence, below the "Ute" limestone, seems to have been noted, though the 



" C. King : TJ. S. Geol. Expl. 40th Par., Vol. I. Sys. Geol., pp. 167-168. 1878. 



