post- Cretaceous Mountain-making along its course. 183 



"branches of the protaxis. The Rocky Summit region, men- 

 tioned above, is situated accordingly between two protaxial 

 branches, the Front Range branch and the Wasatch. Moreover, 

 the former, although much the higher and most complete, was 

 of least stratigraphical significance. The Wasatch line reaches 

 a height between 11,000 and 12,000 feet ; but the most of it 

 is under a cover of later rocks. The western ouline of the 

 Cretaceous areas shows its course, from the Wasatch range, 

 west of south, to the crossing of the parallel of 37° N. by the 

 meridian of 115° W. 



2. The Mountain-making along the Rocky Mountain Protaxis at 

 the close of the Cretaceous period. 



1. In British America. — The results of the summit post 

 Cretaceous disturbance in British America for a few degrees 

 north of the United States boundary have been studied and 

 described by Dr. Gr. M. Dawson and Mr. R. G-. McConnell, and 

 are reported upon in the Canada Geological Reports for 1885 

 and 1886. According to the accounts, a north-south belt 

 seventy to seventy-five miles wide, between the parallels of 

 49° N. and 52° 1ST., was shoved up into flexures and as dis- 

 placed blocks. The western boundary of the disturbed region 

 is the protaxial Archaean mountains along the Columbia River ; 

 the eastern reaches out some miles into the great central Creta- 

 ceous area of the Continent. It comprises the region of grand 

 mountain scenery along the summit pass of the Canadian 

 Pacific Railway which is there called the Rocky Mountains. 



A transverse section along the parallel of 51° 15', showing 

 the flexures and displacements, is described and figured by Mr. 

 McConnell. Through the western two-thirds of the range, 

 belts of Cambrian rocks, Lower and Upper Silurian, Devonian 

 and Carboniferous alternate, as a consequence of overthrust 

 flexures and an occasional fault. In the eastern third — about 

 twenty-five miles across — Cretaceous belts are comprised in the 

 series, and the strata are partly in flexures but mostly in steep 

 monoclinal uplifts along seven upthrust faults, the thrusts all 

 inland in direction of movement. One north-south Cretaceous 

 belt follows the course of the Cascade River Valley, or the 

 "Cascade Trough." 



The thickness of the Paleozoic formations in the region is, 

 according to Mr. McConnell's estimates in the Bow and Wapta 

 Valleys, about 29,000 feet ; and to this the Cretaceous, to the 

 eastward, adds 5000, making in all 34,000. Out of the 34,000 

 feet of beds in the section at least a third is referred to the 

 Cambrian, and more than half is included within the Cam- 

 brian and Lower Silurian series. The Upper Silurian and 

 Devonian are relativelv thin formations. 



