ALASKA AND THE YUKON 



61 I 



BROOKS RANGE 



SOUTHERN FOOTHILLS. 



NORTHERN FOOTHILLS 



ARCTIC COASTAL PLAIN 



5000' 



-5000'- 



C OLVIL LE 



BASIN 



BARROW 



ARCH 



CREEK 



\SCHRADER 

 \ BLUFF 



V^\ 



LOWER JURASSIC 

 Vpp £R~~T~RTVssi c 



PRECAMBRIAN (?) 

 AR6ILLITE 



Fig. 39.6. Cross sections of Arctic Foothills, and Coastal Plain. A-A', existing section; B-B', et a/., 1951; somewhat altered after Grye et a/., 1956. Black is "inland facies"; stippled is 

 restored to close Cretaceous showing facies of Nunushunk and Colville groups, after Payne "coastal facies"; blank is "offshore facies." Kot, Torok fm.; Knc, Nanushuk group. 



so widespread that much of Alaska must have been under water and 

 receiving sediments during Cretaceous times. Certainly large parts of 

 the Triassic and Jurassic geanticline were covered. Mertie (1930) states 

 that, at least at one time or another during the Cretaceous, all Alaska 

 was subjected to sedimentation. But, it seems evident that a number 

 of long linear uplifts rose and separated the basins of sedimentation in the 

 manner shown on Fig. 39.4. The Cretaceous sediments are everywhere 

 very thick and are almost entirely clastic. They probably have been 

 studied most under the Arctic Coastal Plain and in outcrop in the 



Foothills Belt under the auspices of the U. S. Navy Department in Naval 

 Petroleum Reserve No. 4. Cross sections A-A' and B-B' of Fig. 39.6 show 

 the beds and structure there approximately as they are today and as 

 restored to pre-Laramide time, respectively. 



The discovery of the Barrow arch of Precambrian (?) rocks under the 

 northern edge of the Coastal Plain was unexpected, but it points to a 

 positive region there, and to a northern source of sediments in mid- and 

 late Paleozoic times ( Dutro, 1960 ) . 



In the Kuskokwim distict Cady et al. (1955) describe Upper Creta- 





