THE CRETACEOUS PERIOD 755 



North America. The Rocky Mountain system may be said to have 

 had its birth at this time. That these mountains are not older is 

 shown by the deformation of the Laramie beds along with those 

 of greater' age. That some of the folding was not younger, is 

 shown by the lesser deformation of the Tertiary beds in the same 

 region. It should be added that most of the western mountains 

 which began their history at this time are unlike the Appalachians, 

 as developed at the close of the Paleozoic. In the first develop- 

 ment of the latter, horizontal movement was the great factor in- 

 volved; in most of the former, vertical movement. 



Faulting. The growth of mountains at the close of the Creta- 

 ceous was accompanied by faulting on a somewhat extensive scale 

 throughout the region of movement, though the faulting of this 

 time cannot always be distinguished from that of later date. In 

 the Rocky Mountains of British Columbia, one overthrust fault has 

 been located which crowded the Cambrian rocks obliquely up over 

 the Cretaceous. The horizontal displacement is estimated to be 

 as much as seven miles/ and the throw 15,000 feet. Near the 

 national boundary, the displacement of what appears to be the same 

 fault crowded the Proterozoic up over the Cretaceous 2 by a move- 

 ment of equal magnitude (Fig. 510). The exact date of these faults 

 has not been determined, but was, perhaps, mid -Tertiary. 



Igneous eruptions. The close of the Cretaceous was marked by 

 the inauguration of a period of exceptional igneous activity, con- 

 tinuing far into the Tertiary. During this period, great bodies of 

 igneous rock, both extrusive and intrusive, were forced up. Erup- 

 tions occurred in other lands at about the same time. 



UPPER CRETACEOUS OF OTHER CONTINENTS 3 



Europe. The distribution of the Upper Cretaceous strata of 

 Europe shows that extensive transgressions of the sea occurred at 

 the beginning of tl^e period, for in some parts of the continent, 

 marine Cretaceous formations overlap all older Mesozoic systems. 



1 McConnell, Geol. Surv. of Canada, Vol. II, Kept. D, p. 33, 1886. 



2 Willis, Bull. Geol. Soc. of Am., Vol. XIII, pp. 307, 331-335. 



3 The term Comanchean has not been applied outside of North America, 

 and the Cretaceous system will therefore be referred to as Upper Cretaceous. 



