332 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



not far from the road. The low ranges farther south, also far beyond our southern 

 route, are formed by the Carboniferous rocks, their yellow color indicating it plainly. 



In the next mountains, on the west side of Buell Valley, we again find a consid- 

 erable development of siliceous limestones and slates, of mostly bluish-gray color, 

 characterized by their fossils as Devonian. They are overlaid in the pass by heavy 

 masses of a coarse siliceous sandstone, and a conglomerate of rounded siliceous pebbles? 

 mostly of a rather dark color, which seem to occupy the position of the Old Red of the 

 Knglish ideologists, between the Devonian and Carboniferous formations. A further 

 proof of this I found near Cho-kup's Pass. Its thickness must be considerable. I 

 observed 300 feet of it in a single exposure. On the west side of the pass eruptive 

 masses protrude, which seem to belong to the basaltic or phonolitic group, and are 

 partly vesicular; other rocks close by may either be allied to them or highly altered 

 slates. I also noticed some tufa, a sedimentary local deposit of tine fragments, or ashe > 

 of eruptive origin. McCarthy's Creek marks the line of contact between these differ- 

 ent rocks. 



In the same range, some miles north of Cho-kup's Pass, on the eastern slope, and 

 again on the west side of the pass, I found a few fossils in gray and bluish limestones. 

 Mr. Meek considers them as Lower Carboniferous. The main body of the range there 

 is composed of si lire. »us conglomerate, flint rock, and a strongly cemented light-colored 

 or reddish sandstone, which formation attains a thickness of at least several hundred 

 feet, It is most probably an equivalent of the conglomerate farther south, and "Old 

 Red." There we have it overlying Devonian strata, here we find it in connection with 

 Carboniferous rocks. Although the latter are found on the side of the mountain, 

 while the sandstone forms the crest, they seem to occupy a higher geological position- 

 The upheaving forces have exhibited a great local intensity in a direction coinciding 

 with the central line of the ridge. The strata at numerous points stand on the edge, 

 having been tilted up at an angle of 90°, or even more. Thus the originally lower 

 sandstones now occupy the most elevated position in the center. No igneous rocks 

 were noticed near the pass, but they appear to form some hills farther north. 



The permanent character of some springs, and the large volume of water, in Pah- 

 hun-nu-pe Valley seems to be, partly at least, the result of the upthrusting of these 

 sandstones and other older strata, which hold a highly elevated position in the neigh- 

 boring Humboldt and Cooper Mountains, and there, at their outcrops, take up a con- 

 siderable quantity of water from the melting snows and summer rains; while it is partly 

 due to the circumstance that this valley receives the drainage of the extensive Kobah 

 Valley. 



The rocks in Swallow Canon, between Pah-hun-nu-pe and Kobah Valleys, are 

 dark-gray and blue impure limestones, with numerous small veins of dolomite, also 

 slates and flinty sandstones. They are characterized by their fossils as Devonian 

 (see Mr. Meek's report). This canon has apparently been eroded by the discharge of 

 the water from Kobah Valley into the less elevated Pah-hun-nu-pe Valley. The 

 former has thus been gradually drained of its lake, the relics of which are still found, 

 not only as marked benches and some tufaceous strata, but as a considerable succes- 

 sion of horizontal layers of shaly sandstones and arenaceous shales, partly calcareous, 



