W. Cross — Denver Tertiary Formation. 



263 



Eldridge in studying the older groups. These two papers 

 were published in full in the " Mining Industry " of Denver, 

 July 13, 20, 27 and August 3 and 10, 1888. The monograph 

 on the Denver Coal Basin, by Mr. S. F. Emmons, is now in 

 preparation. 



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 below Laramie 



1. Description of the Formation. 



The area occupied. — By reference to the accompanying map 

 the surface distribution of the Denver beds may be readily 

 seen. Upon that map the eastern limit of the Archaean rocks 

 marks the line of the foot-hills. In the narrow zone between 

 the Archeean and the Denver area are the upturned strata of 

 the Trias, Jura, Cretaceous, and the Willow Creek Tertiary. 



The area of Denver beds represented is somewhat less than 

 400 scmare miles. Its western boundary is determined by the 

 upturning of the strata along the great fold and by the subse- 

 cment erosion. On the north and northeast the line apparently 

 expresses the original limitations of the basin at this level. To 

 the south and southeast the Denver beds disappear under the 

 horizontal strata of the Monument Creek Tertiary, which are 



