CHAPTER XL 



SILVER AND GOLD, CONTINUED. THE REGION OF THE GREAT 

 BASIN r IN UTAH, ARIZONA, AND NEVADA. 



UTAH. 



2.11.01. Geology. The eastern half of Utah, terminating 

 with the western front of the Wasatch, is in the Colorado Pla- 

 teau, but the western is within the limits of the Great Basin. 

 The plateau portion consists largely of Mesozoic strata, quite 

 horizontal and more or less carved by erosion. The east and west 

 arch of the Uintah Mountains, in the northern part, has upheaved 

 them, so that where the Green River has cut a channel across, the 

 Paleozoic is exposed in great strength. The Wasatch range rises 

 with a gradual ascent from the east, and then terminates with a 

 great fault line having a steep westerly front. This line of weak- 

 ness-was developed in the Archaean and has been a scene of move- 

 ment even to recent times. It is a very important structural feat- 

 ure. West of the Wasatch, which is a fine example of block 

 tilting in mountain-making, the .mountains belong to the Basin 

 ranges, which are more typically developed in Nevada. The 

 Wasatch section was shown by the Fortieth Parallel Survey to in- 

 volve 12,000 to 14,000 feet of the Upper Archaean and nearly 

 30,000 feet of the Paleozoic. In southern Utah the Triassic rocks 

 are important and contain some rich mines. 1 



1 G. F. Becker, Tenth Census, Vol. XIII., 38. C. E. Dutton, Rep. on 

 the High Plateaus of Utah, Washington, 1880. A. Geikie, "Archaean 

 Rocks of the Wasatch Mountains," Amer. Jour Sci., iii., XIX. 363. G. K. 

 Gilbert, ' Contributions to the History of Lake Bonneville," Second Ann. 

 Rep. Director U. S. Geol. Survey, 169-200, and Monograph II. "The An- 

 cient Outlet of Great Salt Lake," Amer. Jour. Sci., iii., XV. 256, XIX. 341; 

 see also A. C. Peale, Ibid., XV. 439. The Henry Mountains, Washington, 

 1877. Hague, King-, and Emmons, Fortieth Parallel Survey, Vols. I. and 

 II. O. C. Marsh, "On the Geology of the Eastern Uintah Mountains,"' 

 Amir. Jour. Sci., iii., I. 191. B. Silliman, "Geological and Mineralogical 

 No.es on Some of the Mining Districts of Utah Territory," Amer. Jour. 



