172 
STRUCTURAL GEOLOGY 
The Canadian region was made readily accessible by the construc¬ 
tion of two transcontinental lines of railroad. Canyons along the 
Frasier River and the Miette River, the chief headwater of the 
Athabasca River, present unparalleled sections across the Cordil¬ 
lera in walls' 2000 feet high. This superb natural cross-section is 
supplemented again and again by other exposures showing details 
in endless profusion and variety. 
The Cordillera in Jasper Park, as in other parts of the mighty 
mountain chain, is characterized by great thrust-planes, but unlike 
in other parts of the uplift, there is also sharp flexing on a large 
scale (plate ix, from photograph by D. B. Dowling). The espec¬ 
ially notable feature is the Appalachian, or Alpine, structure; and 
the relationships of the various rock members are presented with 
far greater perspicacity than possibly anywhere else throughout the 
Fig. 12. Magnitude of Siouan Fold 
