GEOGRAPHY OF THE TRIASSIC PERIOD. 379 



formations contain an abundance ofTriassic fossils. They form an arch 

 over the spur to both ravines, down which they extend far enough to 

 appear in the lower section of figure 2. The strike of the Carboniferous 

 strata on the lower part of the spur carries them directly and uncon- 

 formably beneath the Triassic arch. 



The Carboniferous and Trias arc exposed near together for some dis- 

 tance along the Genesee anticlinal, but northwest of the divide between 

 Genesee valley and Hosselkus creek they arc so folded and eroded as 

 to render their unconformity indistinct. 



Mr. King has shown that there was probably an upheaval at the close 

 of the Carboniferous, making a land area in eastern Nevada, and felt 

 altogether assured in the belief that the Trias and Carboniferous were 

 unconformable further westward.* 



Professor Hyatt has shown that the Trias of Taylorville is upper Trias, 

 later than that of the Aspen mountains, Idaho, or of the Star Peak range, 

 Nevada. The Trias-Carboniferous unconformity, therefore, apparently 

 represents a rather long time interval. The absence of the earlier Trias 

 may be taken either as an indication that the northern Sierra region was 

 a land area during that epoch or that the earlier Trias was eroded before 

 the deposition of the later Trias. It is not impossible that the earlier 

 Trias occurs yet undiscovered in the northern Sierra Nevada. 



Dr. George M. Dawson reports that the Nicola Triassic rocks rest un- 

 conformably op the Carboniferous in the southern portion of the interior 

 of the province of British Columbia.f 



Jura-Trias Unconformity. — One and one-half miles southeast of Peters', 

 in the southwestern branch of the ravine which heads near the Taylor dig- 

 gings, at an altitude of nearly 5,000 feet, the Mormon sandstone (Jurassic) 

 may be seen resting directly and unconformably upon the Hosselkus 

 Limestone (Triassic). Both formations contain their characteristic fossils, 

 and Professor Hyatt, who visited this locality with me, agrees that there 

 can be no doubl as to the identification of the rocks concerned. Their 

 exposed areas are rather small, confined to the central portion of the 

 ravine, and limited on all sides by eruptives. They have been traced 

 along the ravine for about one-half mile, with a difference of nearly 1 ,000 

 feet in the altitudes of the terminal p'ortions. 



The angle between the strikes of the two formations is 62°, and their 

 dips are at right angles to each other. In different portions of the area 

 the strike varies considerably in direction, hut it is evident near their 

 contact that t he t rem I of t he Limestone carries it unconformably beneath 

 the sandstone. Their relation- are indicated in the accompanying 



Geological Exploration of the Fortieth Parallel, vol. i, s logy, pp. 249-357. 



British Columbia : Geol. Magazine, decade ii, vol, viii, April and May, 1881, p, IT. 



