wA.con I SUMMARY UTAH AND NEVADA. 313 



section, aud the upper portion is almost entirely argillaceous. In the 

 viciuity of Quebec, sandstones and shales make up the section, and 

 along the Lower St. Lawrence, shales, sandstones, and limestones. 



Asa whole, the Appalachian Province is one of varied sedimentation, 

 and, from the character of the sediments and determined fossils now 

 found in them, they were largely accumulated along a gradually sinking 

 coast line. The northern and western shore line exhibits only the con- 

 tact of the sandstones of the Upper Cambrian that overlap upon the 

 pre-Oambrian rocks. Erosion has removed them to a large extent, and 

 south of the Adirondacks the western coast line is unknown. (Fig. 2.) 



ROCKY MOUNTAIN PROVINCE. 



* For the purpose of description the area of Cambrian rocks in the 

 Rocky Mountain Province includes the Cambrian outcrops of northern 

 and western Utah, Nevada, eastern Idaho, the Gallatin River district 

 of Montana, and the Canadian extension. 



UTAH AND NEVADA. 



The Cambrian rocks of Utah and Nevada are considered together, 

 owing to their having a common base in the presence of the Olenellus 

 zone, the strata of which rests conformably upon a great series of sili- 

 ceous and arenaceous shales and sandstones, and massive quartzites. 

 In Nevada the section is much more complete and reaches a far greater 

 development both in amount of sedimentation and the presence of 

 organic remains. The section studied by Messrs. Hague and Walcott 

 in the Eureka district may be considered typical of the Cambrian rocks 

 of central Nevada. It embraces five formations, all of which are 

 described by Mr. Arnold Hague in the abstract of his report on the 

 Geology of the Eureka district. 1 



The Prospect Mountain quartzite that lies at the base of the series 

 has a thickness of 1,500 feet on Prospect Peak. It is distinctly bedded 

 and comformably subjacent to a band of arenaceous shale, in which the 

 Olenellus fauna occurs. It is referred to the Cambrian by Mr. Hague, 

 and I am now of the opinion that this should be done, although I have 

 held the view that the Olenellus zone should be considered the base of 

 the Cambrian, and the Prospect Mountain quartzite I tentatively re- 

 ferred to an Algonkian formation. The subjacent band of arenaceous 

 shale is mentioned by Mr. Hague in his report of 1881, 2 but not in the 

 more complete description of 1882. In the review of the Eureka section 

 by Mr. C. D. Walcott in 1886 this formation is spoken of as follows : 



At the summit of 1 the quartzite becomes more thinly bedded and passes into an 

 arenaceous shale which is more or less calcareous and, in its exteusion northward, is 

 replaced by limestone. This belt of shale and limestone is from 100 to 200 feet in 

 thickness and carries numerous fragments of fossils, among which we have determined 



1 U. S. Geol. Surv., .°d annual report, 1881-'82, 1883, pp. 254-259. 



•Report (on work in Eureka District). TJ. S. Geol. Surv., 2d Ann. Rep., 1880-'81, p. 29, 1882. 



