186 GEOLOGY OF THE EUKEKA DISTRICT. 



bottom. For comparative purposes, therefore, it may be well to introduce 

 here, with more or less detail, some descriptions of the geological structure 

 and occurrences elsewhere in the Great Basin of those portions of the lower 

 Paleozoic horizons that happen to be well represented at Eureka. The sec- 

 tion at Eureka may be taken as a standard. 



The Oquirrh Mountains. In the_ Oquirrh Mountains, the first range west of 

 the Wasatch, the Olenellus horizon has been identified in a thin bed of 

 yellow shale conformably overlying a reddish white quartzite of unknown 

 thickness, above which occur from 3,000 to 4,000 feet of limestone carry- 

 ing Lower Carboniferous and Coal-measure fossils. The geological posi- 

 tion of the shale bed is determined by the following species : Lingulella ella, 

 Olenellus gilberti, and Bathyuriscus prodmta. Mr. S. F. Emmons, 1 while 

 engaged upon the Geological Exploration of the Fortieth Parallel, exam- 

 ined this range and shrewdly suggested, from orographic evidences, that a 

 fault existed between the shales and overlying limestones a structure 

 which would be in accord with the observed facts brought out at Eureka. 



The Highland Range. The Highland Range, about 125 miles south of 

 Eureka, presents a geological structure in many respects similar to Pros- 

 pect Mountain, although by no means as simple or furnishing an unbroken 

 section of equal extent. At Pioche, at one time a nourishing mining town, 

 situated on an eastern spur of the main range, Mr. E. E. Howell obtained 

 two species of the genus Olenellus, which Mr. F. B. Meek' described as 

 0. gilberti and 0. howelli. According to Mr. Howell 3 they occur in a red- 

 dish yellow arenaceous shale about 400 feet in thickness, overlying 1,200 

 feet of quartzite. In the published section the shale is represented as con- 

 formably overlain by gray limestone, which he regarded as of Carbonifer- 

 ous age, although no paleontological evidence was presented. If these 

 strata are conformable it would seem highly probable, from the known 

 sequence of beds at Eureka as well as elsewhere in the Highland Range, 

 that the overlying limestone belongs to the Prospect Mountain epoch. 



'U. 8. Geol. Explor'n 40th Par., vol. 2, Descriptive Geology, p. 444. 



3 Geographical Surveys West of One hundredth Meridian, vol. 3, p. 182. 



3 Op. oit. vol. 3, p. 258. 



