Idowling] eastern BELT OF THE CANADIAN CORDILLERAS 185 



The Mackenzie mountains extend across a region over which 

 Cretaceous and Carboniferous sedimentation was limited or since 

 destroyed and end in a series of plunging anticlines against a terrace 

 of unconsolidated Cretaceous rocks. To the west across a spur or 

 narrow basin of Cretaceous rocks appears a ridge or fold of Palaeozoic 

 limestones which is the last or northern end of the Rocky Mountain 

 series of folds and overthrusts. If the vigorous folding of the Mac- 

 kenzie Mountains was synchronous with that of the Rockies there 

 would be evidence of reinforcement, but as there seems to be no 

 direct continuity of folding it must be surmised that the eastern 

 mountains were formed earlier than this part of the Rockies at least, 

 and that the gap between the two was not closed on account of the 

 dying away of the stress which built the Mackenzie Mountains. 

 Similarly the strains of the later period within the sphere of maximum 

 stress produced deformations (the outer Rockies) that extended to 

 some distance into the Cretaceous basin, but were restricted in the 

 zone of deformation by the heavy load of incompetent beds of the 

 Cretaceous basin. Northward, where this load decreased, the 

 narrowing of the zone as well as the simplifying of the folds denotes 

 a lessening of the strains. 



As the great ribbing up of the crust denotes a movement, as well 

 as compressive stresses, the building up of mountain ridges would 

 tend to form dams to stay the advance, so that it would seem reason- 

 able to outline the history of this region by assuming that the early 

 ridges appeared to the east of the area under strain. Under that 

 assumption the outer ranges which are on the right bank of the 

 Mackenzie were first formed. These consist of an irregular chain 

 running about directly north and called the Franklin Mountains. 

 These are nearly joined by an east- west series that have a range of 

 over a hundred miles and have really no general name, but may be 

 generally designated as the Norman ranges. The structure as noted 

 already shows pressure and movement of the crust which for the 

 inception of the period appears to have been northeastward. The 

 line represented by the Franklin ranges is the edge of this movement 

 as the ridges are close folds arranged en échelon, while the ridges 

 with east-west alignment indicate folding at right angles to the 

 movement. As these latter terminate eastward in a faulted upthrust 

 and westward in plunging anticlines it is assumed that the formation 

 of the eastern ridges so loaded the crust that outside of the first 

 east-west fold, whose course is not yet fully mapped, simple buckling 

 of the surface occurred until a sheared fault line was developed west 

 of and parallel to the Franklin range. The release of the surface by 



