70 GEOLOGY OF THE EUKEKA DISTRICT. 



probably belongs to the genus Aneimites, but no trace of the pinnae can be seen. The 

 evidence, so far as it goes, would indicate the Upper Devonian (or Brian, as I prefer 

 to call it,) rather than the Middle Devonian or the Lower Carboniferous. 



It will be seen that this determination as to the age of the plants is 

 quite in accord with the geological position of the beds above the Nevada 

 limestone of the Devonian and directly below the Diamond Peak quartzite 

 of the Carboniferous. 



Notwithstanding the great development of the black shales they have 

 as yet been recognized only in the two localities already mentioned, Eureka 

 and White Pine. On the east side of the Eureka District, if they are repre- 

 sented at all, it is only by 100 feet more or less of dark shaly beds, highly 

 arenaceous, and passing into sandstones and quartzites of the Diamond 

 Peak beds. There seems to be no doubt that the Diamond Peak forma- 

 tion in the Pinon Range rests conformably upon the Nevada limestone, 

 without the interposition of any great thickness of White Pine shales, 

 although there are a few black sandstones and narrow chert bands which 

 apparently represent the intervening argillaceous epoch. The evidence in 

 favor of this correlation is strengthened by the presence of poorly preserved 

 fragments of vegetable life wherever the black belt comes in. These inter- 

 vening beds have yielded one single species, Discina minuta, which, accord- 

 ing to Mr. C. D. Walcott, corresponds closely with typical specimens from 

 the Marcellus shale of New York. The fact that the White Pine shales are 

 Avanting over large areas, where both the Devonian and Carboniferous are 

 found together, renders it highly probable that these shallow water deposits, 

 although developed to a great thickness, form exceptional occurrences, 

 and that the Nevada limestone passes over abruptly into sandstones of 

 Carboniferous age. On the map (atlas sheet v) these intervening beds on 

 both sides of The Gate are included in the Nevada limestone. 



Fauna of the Devonian. As already mentioned, no subdivisions in the Nevada 

 limestone have been made. Geology as yet fails to furnish sufficient evi- 

 dence for drawing any sharp demarcation, sedimentation having gone on too 

 uniformly under similar conditions to form any marked change in the char- 

 acter of the beds. From the sections already given it will be seen that this 

 epoch was essentially a limestone-making one, the amount of sandstone de- 



