176 THE ROYAL SOCIETY OF CANADA 



from near sea-level to very near its present elevation. But there is 

 presumptive evidence that an area in the north was uplifted earlier 

 than the central part of the continent, that it was above sea during 

 early Carboniferous time and was again elevated before the retreat 

 of the Cretaceous sea took place in the south. It seems possible, 

 therefore, that mountain building took place earlier in the north than 

 in the south. Had all three* of these mountain groups formed con- 

 temporaneously it is unlikely that the existing diversity of align- 

 ment and break in continuity would have resulted. 



The Geosyncline 



The region of the Great Plains and the eastern border of the 

 Cordillera previous to the formation of the mountains of the Eastern 

 Belt as disclosed in the sections of the now deformed strata was an 

 area in which deposition, mainly marine, persisted from early geological 

 time. In places, especially in the southern section, there is evidence 

 of a pre-Cambrian deposition comparable in amount to that of the 

 eastern margin of the continent as found in the Gold-bearing series 

 of Nova Scotia. Some of this material may have come from the east, 

 but the increasing thickness of the deposits westward points to 

 derivation from a long continental mass, the remains of which now 

 form the Central mountain belt. These early sediments were followed 

 by Palaeozoic limestones and Mesozoic sediments which also display 

 characters that point to a western source of origin but were spread out 

 in more even sheets than the earlier strata. 



The Older, Western Division of the Rocky Mountains 



The early sediments which appear in the géosynclinal region 

 in such enormous masses were probably restricted in their area of 

 deposition and may have produced a local overloading which probably 

 would contribute to the downwarping of the geosyncline and the 

 presumably long continued upwarping of the land mass to the west 

 from which the sediments were derived. Other causes of the upwarp 

 of the western land area were of a different order. Thus the batho- 

 lithic intrusions credited to Jurassic time and represented by the 

 granitic masses in southern British Columbia and along the coast 

 would probably accompany differential movements productive of 

 normal faulting in the land area. This period may reasonably be 

 assumed to be the one in which commenced the advance of the earliest 

 Cretaceous sea. A second period of granitic intrusion^ in southern 

 JCamsell, Fraser Valley, Trans. R.S.C., Vol.. XIV, 1920, Sec. IV, p. 45. 



