258 Tertiary. 



He estimated the thickness of this Pliocene lake strata, which he 

 called the Niobrara Pliocene exposed in Wyoming, at from 1,200 to 

 1,500 feet. 



The beds are found lying unconformably upon the older uplifted 

 ^ strata, and overlapping the area of the Miocene basin. South of the 

 Union Pacific Railroad, they occur abutting against Mesozoic forma- 

 tions; just north of Granite Canon, they lie next the Archaean mass ; 

 and a short distance beyond, at the mouth of Crow Creek canon, are 

 found essentially horizontal against nearly vertical Palaeozoic lime- 

 stones. From Crow creek, northward, they ma}^ be seen resting direct- 

 ly upon every formation, from the Archaean to the Fox Hills Group. 



The strata consists of marls, clays, coarse and fine sandstones, con- 

 glomerates, with some nearly pure limestones. Fine, marly sand- 

 stones are the predominant beds. 



Overlying the Pliocene lake deposits on Sybille creek and its tribu- 

 taries, and in the region of Chugwater and Pebble creeks, there occur 

 beds of coarse and fine conglomerate, having a thickness of 300 or 400 

 feet. These beds have been called the Wyoming Conglomerate. 



In North Park, Pliocene beds lie unconformably upon the older 

 rocks, resting in places against every formation from Archaean to the 

 top of the Cretaceous, and are seen in undisturbed condition resting 

 against the basalts. They extend over the entire Park basin, giving 

 it the level, prairie-like aspect, which it presents from all the higher 

 elevations. 



He referred the Tertiary beds in the eroded basins and valleys worn 

 out in the rhyolite in the Toyabe range of the Nevada basin, and 

 noticable on Silver and Boone creeks to the Truckee Miocene. 



S. F. Emmons found the same formation in the valley of Reese 

 river, near Ravenswood Peak, along the foot hills, both to the east 

 and west of the Soldier's Spring Valie}' basin, in the low depression of 

 Indian valley, and in the re-entering ba^' north of Black Canon, with 

 a thickness of over 700 feet. 



The Truckee Miocene is so named from Truckee range, Nevada, 

 which extends in a north and south line for 72 miles, and consists, for 

 the greater part of the distance, of a single narrow ridge, barely more 

 than 5 miles from base to base, but widening considerably at the 

 southern end, where it is made up of broad fields of Tertiary eruptive 

 rocks. 



Alfred R. C. Selwyn said* that between Blackwater and Stewart's 



■•' Geo. Sur. of Canada. 



