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TJ. S. NATIONAL MUSEUM BULLETIN 21' 



deep and warm Pacific Ocean. The soutliem foot of the ice cover 

 of the Wisconsin age was at about latitude 60° IST. in central Alaska, 

 while the midcontinental ice fields extended 15° farther southward. 



In the late Wisconsin age continuous ice fields discharged glaciers 

 north of the Alaska Eange to form moraines along the southern sides 

 of the Kuskokwim and Tanana Valleys (Pewe, 1953). North of the 

 Brooks Range, the Wisconsin age glaciers also extended just beyond 

 the mountains. In general it appears that in Alaska north of about 

 latitude 64° extensive lowland areas were not then covered by ice and 

 that the continuous ice cap m central Alaska extended farther south- 

 ward across only about 5° of latitude (see map, fig. 3). McComiell 

 (1890) first remarked that the northern part of Yukon Territory 

 appeared to have been free from the continuous ice which covered 

 the country far to the southward and which probably extended over 



SEA-LEVEL ISOTHERMS : JANUARY (° Q 



Figure 2.— Sea-level isotherms for January (left) and May (right). (From C. F. Brooks, 



Univ. Press, 1936, 



