350 THE CAMBRIAN. [bull. 81. 



although no organic remains were found. In the vicinity of the head- 

 waters of the Niobrara River he measured a section as follows : 



Feet. 



(1) Quartzose sandstone, some parts filled with pebbles , 22 



(2) Red argillaceous slate 5 



(3) Sandstone, dull reddish ferruginous, like bed 1, above 37 



(4) A series of strata more or less inclined, composed of gneiss with silvery mica 



in large plates, micaceous and talcose slates, white quartz, etc. 



He states further that he has no doubt the Potsdam sandstone 

 occurs in the form of an outcropping belt all along the Laramie range 

 of mountains, although he was unable to discover any organic remains. 

 He correlated it with the Potsdam on the evidence afforded by the 

 Black Hills section of Dakota. The occurrence of the sandstone at 

 this horizon is noted by him at numerous localities ,on the flanks of the 

 Laramie Mountains. 1 In opposition to the view of Dr. Hayden may 

 be cited that of Mr. Arnold Hague, who states that all paleontological 

 evidence obtained from the beds associated with the quartzite and 

 above them tend to show that they belong to the Coal-Measure lime- 

 stone. 2 



In 1871 Dr. Hayden found Obolella and a Lingula in a considerable 

 thickness of Potsdam sandstone on the south side of the Sweetwater 

 River, near the southeastern termination of the Wind River Mountains, 

 thus establishing by paleoutologic evidence the Upper Cambrian or 

 Potsdam age of the sandstone referred to that horizon in 1861. 3 



A small area of paleozoic rocks on the northwestern end of the Wind 

 River range has, according to Prof. Orestes St. John, a sandstone at 

 the base that rests on the Archean. It is coarse grained, grayish, buff, 

 reddish stained, thin bedded, with oblique laminated layers and locally 

 quartzitic. The greatest exposed thickness of this bed probably does 

 not exceed 50 feet. Its exact relation to the underlying Archean rocks 

 and to the superjacent strata referred to the Quebec was not deter- 

 mined. 4 On the diagrammatic section accompanying the report forma- 

 tion No. 2, or the Potsdam, is represented as resting un conformably 

 upon the Archean and conformably subjacent to limestones referred to 

 the Quebec. 



The Cambrian strata of northwestern Wyoming are contained within 

 the district of the Teton range, Gros Ventre range, and the Buffalo 

 Fork Mountains, all of which are reported upon by Prof. St. John. He 

 quotes Prof. Bradley in relation to the lower quartzite, stating it to be a 

 very compact ferruginous quartzite, with a thickness of from 50 to 75 

 feet. Above this occurs about 300 feet of sandstone strata on the 



1 Hayden, F. V. : The Primordial Sandstone of the Rocky Mountains in the Northwestern Territories 

 of the United States. Am. Jour. Sci., 2d series, vol. 33, 18G2, pp. 70, 71. 



2 Descriptive Geology. TJ. S. Geol. Expl. of the Fortieth Par. ; vol.2. Washington, 1877, p. 76. 

 'Report of F. V. Hayden (on the geological survey of Wyoming). U. S. Geol. Surv. of the Terr., 



4th Ann. Rep., 1871, p. 33. 



4 Report on the geology of the Wind River district, U. S, Geol. Surv. of the Terr., 12th Ann. Rep., 

 1883, p. 253. 



