218 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



ward the Paleozoic ocean deepened over a broad basin, which probably 

 continued to a great depth until it reached the western shore, in longi- 

 tude 117° 30'. It is a striking fact that no unconformity has been found 

 in the exposures studied between the members of the series, from the 

 Primordial to the summit of the Coal Measures. 



The author remarks that the key to the subdivision of the whole 

 Paleozoic is obtained in the Wasatch Range, where he observed a 

 siugle section, of about 30,000 feet thickness, of conformable rocks, ex- 

 tending from the Permo-Carboniferous strata, conformably underlying 

 the red sandstones of the Trias, down to low exposures of the Cam- 

 brian, and he notes in their order, from the base of the Cambrian up- 

 ward, the important stratigraphic divisions, with their position in the 

 New York scheme. 



The lowest division of the series is composed of three prominent 

 terranes, the lowest a series of siliceous schists and argillites, from 

 800 to 1,000 feet in thickness ; next is a series of quartzite and quartzo- 

 feldsitic strata, with limited beds of slate interspersed through it, and 

 dark micaceous zones near the top, the whole in Cottonwood Caiion 

 reaching a thickness of 12,000 feet; the third terrane is a narrow zone 

 of variable argillites, calcareous shales, and thin, slightly siliceous 

 limestones, whose extreme thickness is 75 feet. The only fossils found 

 in this division occur in the shaly zone and are of Primordial type. 



The author includes the uppermost beds in the Potsdam epoch of 

 the Primordial period, and considers the whole underlying conform- 

 able series as Cambrian down to the Archean. This Cambrian forma- 

 tion varies in thickness, not reaching an exposure of over 100 feet at 

 the extreme east of the field, while in middle Nevada the uppermost 

 thin, shaly member of this terrane in the Wasatch Range is an im- 

 mense body of dark limestone, 3,000 feet in thickness, carrying Primor- 

 dial fossils throughout. A list of fossils obtained from the Cambrian 

 series is given. 



Above the shales of the Cambrian is a bed of limestone, having a 

 maximum thickness of 2,000 feet in the Wasatch, which the author 

 calls the 4< Ute limestone," and which has yielded only fossilsof the Quebec 

 group. In western Nevada the calcareous shales of the Potsdam and 

 the Quebec limestone have greatly thickened, and represent from 4,000 

 to 5,000 feet of continuous limestone, yielding fossils of the Lower 

 Helderberg, Niagara, Quebec, and Primordial. 



Overlying the Ute limestone is a quartzite from 1,000 to 1,500 feet 

 thick, called by the author the " Ogden quartzite," from its exposure 

 in the Ogden Caiion ; it is seen in western Nevada between the Upper 

 and Lower Helderberg horizons, and is included provisionally within 

 the Devonian system, being considered as the probable equivalent of 

 the Schoharie and Cauda-galli grits. 



Next above is the "Wasatch limestone," reaching 7,000 feet in thick- 

 ness in the Wasatch and over 8,000 in middle Nevada. Its lower 





