GEOLOfiY OF THE DENVER BASIN IN COLORADO. 



By S. F. Emmons, Whitman Cross, and George H. Eldeidge. 



CHAPTER I. 



By S. F. Emmons. 



GENERAL GEOLOGY. 



PHYSIOGRAPHY. 



The area specially treated in this report is the portion of the foothill 

 belt of the Great Plains lying between the meridians of 104° 37' and 

 105° 2D' west longitude and the parallels of :!9 : 30' and 40° 27' north 

 latitude. The extent of the area is about 1,000 square miles. The South 

 Platte River, which debouches from the mountains just beyond the south- 

 ern boundary of the area, crosses it diagonally to its northeastern corner, 

 receiving in its course two tributaries from the mountains on the west and 

 a few from the mesa region to the southeast. 



Not only does the present surface constitute a topographical basin, but 

 as will be seen later, a still better defined basin exists in the rocks which 

 form its substructure. The city of Denver, situated on the banks of the 

 Platte, occupies a central position in this area, and it has therefore been 

 named the Denver Basin. 



In its broader geological and topographical features this area may lie- 

 taken as a type of thai portion of the Great Plains which immediately 

 adjoins the eastern front of the Rocky Mountains within the State of 

 ( lolorado, and which may be denominated the foothill belt. A description 

 mon xxvii 1 i 



