THE CAMBRIAN PERIOD. 



255 



In some other places, Cambrian outcrops are surrounded by older 

 formations. This is the case, for example, in some places in the prov- 



Fig. 103. — Diagram showing the positions of outcrops as determined by folds. The 

 anticline at the right is represented as having been truncated in such a way as to 

 expose the Cambrian, €, in a single belt. The anticline to the left has been cut- 

 so as to expose pre-Cambrian formations, A, beneath, and the Cambrian, €, outcrops 

 in two belts, one on either side of the older formation. 



inces of Mackenzie and Athabasca in Canada. 1 In such cases the 

 Cambrian outcrops presumably represent remnants which have escaped 

 erosion. Theoretically, they might occupy depressions in the surface 

 of pre-Cambrian formations, or they might constitute hills (Fig. 104). 



Fig. 104. — Figure to illustrate the occurrence of Cambrian in isolated areas surrounded 

 by older formations. The diagram illustrates two ways in which such isolated 

 areas may occur. 



Again, more or less circular areas of exposed Cambrian are locally 

 surrounded by the outcrops of younger formations, as at some points 



Fig. 105. — Diagram illustrating how an isolated area of Cambrian may be surrounded 

 or bordered by younger formations. 



west of Hudson bay. An explanation of such areas is suggested by 

 Fig. 105. 



1 Geological map of the Dominion of Canada, Western sheet, edition of 1901 



