THE CRETACEOUS PERIOD 



249 



North America since pre-Cam- 

 brian time. Over the Rocky 

 Mountain district there had 

 been more or less deposition of 

 sediments (both marine and 

 continental) throughout Pale- 

 ozoic and Mesozoic times. 

 Toward the close of the Cre- 

 taceous, there was vigorous 

 deformation, including both 

 folding and dislocations of the 

 strata, not only throughout the 

 Rocky Mountain district in 

 North America from the Arctic 

 Ocean to Central America, but 

 also even along the line of the 

 Andes Mountains to Cape Horn 

 — altogether more than one- 

 fourth of the way around the 

 earth. This great crustal dis- 

 turbance has been called the 

 "Rocky Mountain Revolu- 

 tion." While the folding was 

 usually not nearly as intense as 

 at the time of the "Appalach- 

 ian Revolution," nevertheless 

 there were very considerable 

 uplifts accompanied by moder- 

 ate folding of the strata in 

 many parts of the district (Fig. 

 154). That portion of the 

 Rockies north of the United 

 States (so-called Laramide 

 Range) suffered the severest 

 deformation where strata esti- 

 mated at 40,000 to 50,000 feet 

 thick were folded and faulted 

 into a range which was prob- 

 ably no less than 20,000 feet 

 high. The Rocky Mountains 



