VOLUME XXVII NUMBER 4 



THE 



JOURNAL OF GEOLOGY 



MAY-JUNE 1919 



THE BUILDING OF THE COLORADO ROCKIES 



ROLLIN T. CHAMBERLIN 



The University of Chicago 



PART II 

 THE LYONS-GRAND RIVER SECTION 



After a consideration of alternative locations for the contem- 

 plated study of the Colorado Rocky Mountain diastrophism, a 

 section across the folded belt between the Great Plains north 

 of Denver and the Uinta Basin west of Glenwood Springs was se- 

 lected as offering the most promise. Among the advantages thus 

 offered, it may be noted that this section would bring in the char- 

 acteristic en echelon structure of the eastern foothills, here specially 

 declared;^ it would cross the Front Range where strongly devel- 

 oped; it would embrace the wide area of sedimentary rocks in 

 Middle Park; it would traverse a typical section of the Park 

 Range, and finally beyond this it would extend across the most 

 representative strip of the slightly disturbed sedimentary belt to 

 the Grand Hogback which terminates the Rocky Mountain folding 

 on the west. Such a section, furthermore, would be across one of 

 the wider portions of the Colorado Rockies. There was a further 

 advantage growing out of the fact that the Colorado Rockies 



'This has recently been described by Victor Ziegler, "Foothills Structure in 

 Northern Colorado," Jour. Geo!., XXV (1917), 715-40. 



225 



