GEOLOGICAL SUEVEY OF THE TEREITOEIES. 



35 



and thirty miles from east to west, underlaid by tlie Pliocene deposit?, 

 inclining gently northwest, influenced probably by the Black-tailed Deer 

 Eange. 



The country about these 

 sources or branches of the Jef- 

 ferson fork is very fine, and 

 api^ears most attractive to the 

 eye, with a fertile soil, excel- 

 lent water, and well adapted for 

 settlement, except that the win- 

 ters must be very severe. The 

 elevation of the valleys is from 

 6,000 to 7,000 feet, 'involving 

 early and late frosts, and deep 

 winter snows. About a mile be- 

 fore Wild Cat Caiion opens into 

 the valley, the variegated por- ; 

 phyries commence, a dull purj)- ' 

 lish color prevailing, though y el- \ 

 low and mottled are not un- [ 

 common. The porphyries ap- i 

 jDear to have been poured out ; 

 over the metamorphic rocks; > 

 from the south side of the Black- •= 

 tailed Deer Valley they project | 

 out from the hills in beds much I 

 like basalt. The configuration • 

 of the surface where the por- \ 

 phyries prevail is quite pecu- \ 

 liar — sharp, rounded, conical ; 

 l)eaks, with deep ravines or i 

 gorges. These peaks are all j 

 capped with the porphyries. | 

 Immense quantities of the | 

 broken fragments or debris lie ; 

 on the summits and sides of ; 

 these hills. On the east side of j 

 the valley the Pliocene beds ; 

 reach a thickness of 500 to 1,000 i 

 feet, and are composed of pud- | 

 ding-stones, yellow marls, gray I 

 and white fine-grained sand- ' 

 stones, weathering into singular 

 columnar and other architect- 

 ural forms. All the rocks con- 

 tain more or less lime. Both 

 Black-tailed Deer and Stinking 

 Water Creeks have their sources 

 in a high range of limestone 

 mountains, 9,000 to 10,000 feet 

 above the sea level, the highest 

 peaks rising at least 2,000 feet 

 above the valleys of these 

 streams, where they are crossed 

 by the road. High up on the 

 sides of these ridges, reaching 



