CANADIAN ARCTIC 



647 



i Fig. 40.10. Taylor's view of continental drift toward the equator. Reproduced fron 

 Waterschoot van der Gracht (1928). 



Van 



basin is underlain by simatic crust. This is the seismic velocity layer con- 

 sidered today to be made up of a silicate of gabbroic composition. 



In 1937 Du Toit presented a theory of origin of the Arctic and North 

 Atlantic basins using the concept of continental drift facilitated bv one 

 or two major strike slip faults. The blocks bounding the Arctic basin are 

 presumed to have rotated apart and the movement to have been accom- 

 modated by strike-slip along faults. 



Fig. 40.11. Carey's (1958) concept of the origin of the Arctic basin. 



Elaborating on the ideas of Du Toit, Carey | 1958, pp. 195-216) pre- 

 sents the following theory: 



1. Scissors-like drifting apart to form the Arctic basin, hinging at a 

 point in south central Alaska in what the present writer recognizes as the 

 Nevadan otogenic belt. See Fig. 40.11. 



2. The triangularly shaped basin is a tension rift with two sides being 

 the radii from the hinge point and the third side a "megashear" or strike- 



