i6i 



strata of the Rocky mountains; upon those the Jurassic 

 and Cretaceous lie with apparent conformity. In the 

 general absence of Mesozoic sediments in the Middle 

 ranges of British Columbia, it is a delicate, still unsolved 

 problem as to how far the western part of the Eastern 

 Belt was mountain-built during the Jurassic. Perhaps 

 the information will be found along the new Grand Trunk 

 Pacific Railway line. 



The late Jurassic folding in the Western Belt was 

 immediately followed by granitic intrusion on a grand 

 scale, whereby the enormous Coast Range batholith was 

 outlined, if not largely completed. Many smaller batho- 

 liths and stocks were simultaneously intruded into the 

 older rocks of Vancouver island and of the broad tract 

 between the Coast range and the Selkirks. 



From that time to the present both Eastern and Western 

 belts of the Cordillera have witnessed subaerial erosion. 

 Near the line of the present Pacific shore and also in the 

 eastern foot-hill zone of the Rockies, local geosynclinals 

 of great depth were formed in the Cretaceous, Examples 

 are: the Pasayten geosynclinal, stretching from west- 

 central Washington to and beyond the Fraser valley at 

 North Bend and Lytton; the Queen Charlotte geosyn- 

 clinal, west of the Coast range; and the Crowsnest geosyn- 

 clinal of the Eastern Rockies. Sediments of both Lower 

 and Upper Cretaceous age occur in these local downwarps 

 of Cordilleran trend. 



With the completion of the thick Cretaceous prisms, 

 the conditions were ripe for renewed mountain-building 

 and the Laramide revolution deformed most of the Canadian 

 Cordillera. As in the more limited Jurassic revolution, 

 the major thrusts were directed from the Pacific side 

 but they were now, for the first time since the pre-Beltian 

 period, of pronounced effect at the extreme eastern limit 

 of the Eastern Cordilleran Belt. All observers agree 

 that the major deformation of the Rocky Mountain Front 

 ranges took place at this time. Opinions differ as to the 

 date of the great overthrust by which those ranges have 

 advanced outwards, over the Great Plains. Willis has 

 postulated a mid-Tertiary date for the Lewis thrust at 

 the International Boundary, but the present writer is 

 inclined to regard it and the similar thrust in Alberta as 

 incidents of the Laramide revolution [6, p. 340; and 11, 

 Part I p. 94]. 



