COTTONWOOD REGION. 353 



strike, for which reason it has been difficult, in the absence of palseontologi- 

 cal evidence, to define the position of the Ute limestone. The ore body of 

 the Miller Mine, which is on a shoulder of this spur, is in the line of one 

 of these breaks; the rocks, which enclose it, dipping sometimes a little 

 north, though their general inclination is south. Like the majority of the 

 ore bodies in this region, this deposit is enclosed within, and generally 

 parallel with, the stratification. The hanging-wall is a light-colored quartz- 

 ose rock, which passes into a white quartzite, while the foot-wall is a dark- 

 colored siliceous rock passing into a blue limestone, probably the Ute 

 limestone, which is found on the spur a little north of the mine. This lime- 

 stone forms the head of the upper branch of American Fork, and can be 

 traced across the head of Cottonwood Canon, just below the town of Alta; 

 it is much metamorphosed and singularly barren of fossil remains. 



In the lower part of the Wahsatch limestone, at the head of American 

 Fork Canon, were found: 



Productus punctatus. 



Productus cora. 



Productus semireticulatus. 



Streptorhynclius crenistria. 

 * ' ■ ZapJirentis centralis? 



Spirifer (opimusf). 

 Cottonwood Region. — That portion of the range which is included 

 between Utah Lake and Emigration Canon forms a geological whole, con- 

 sisting of a series of sedimentary formations, flexed around a body of Ar- 

 chaean granite. Here the range no longer consists of a single ridge, as in 

 the southern portion, but forms a broad mountain-mass, about 15 miles in 

 width, and over 10,000 feet in average height, whose surface is deeply scored 

 by a net- work of glacier- worn canons and ravines, now debouching into the 

 plain through narrow gorges, which recent erosion has cut down below the 

 level of the old lake that once covered it. Seen from the valley, the most 

 commanding points of this portion of the range are Twin Peaks and Lone 

 Peak, each over 11,000 feet in height, but within the mass are still higher 

 points, of which there are no less than five on the ridge extending from 

 Lone Peak (11,295 feet) to Clayton's Peak (11,889 feet). The view of this 

 portion of the range from Salt Lake City is well known to western tourists 

 23 D G 



