GEOLOGICAL SURVEY OF THE TERRITOEIES. 



35 



and tliirty miles from east to west, underlaid by the 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 

 appears 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 Oat Canon opens into 

 the valley, the variegated por- 

 13hyries commence, a dull purp- 

 lish color prevailing, though yel- 

 low and mottled are not un- 

 common. The porphyries ai)- 

 pear to have been poured out 

 over the metamorphic rocks j 

 from the south side of the Black- 

 tailed Deer Valley they project 

 out from the hills in beds much 

 like basalt. The configuration 

 of the surface where the por- 

 phyries prevail is quite pecu- 

 liar — sharp, rounded, conical 

 peaks, with deep ravines or 

 gorges. These peaks are all 

 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 

 the valley the Pliocene beds 

 reach a thickness of 500 to 1,000 

 feet, and are composed of pud- 

 ding-stones, yellow marls, gray 

 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-tailied 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 



