640 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



Fig. 40.4. Belts of deformation of northern North America. The fold belts of the Arctic 

 Archipelago are after Fortier ef a/., 1954. A, Ellesmere-Greenland fold belt; B, Eureka Sound 

 fold belt; C, Parry Island fold belt; C, northern Ellesmere fold belt (in eugeosynclinal sedi- 

 ments); D, Coastal Plain. For details of the Cordilleran belts of deformation see Fig. 39.2. 



below the Late Pennsylvanian strata and the older formations is common 

 in both regions and draws them together in a common province. 



The northern Ellesmere fold belt in rocks of eugeosynclinal character, 

 parts of which are probably Precambrian, may relate to the Paleozoic 

 positive area of northern Alaska. The latter's rocks are only known in well 

 cores and are identified as argillite, probably Precambrian in age. Again, 

 the continental shelf is fairly narrow from Ellesmere Island to Alaska, 

 and not much room is available under it to connect the Precambrian 

 terranes. Certain authors have presumed the lands to have extended 

 northward into areas now of deep water, and imagined subsidence in 

 the order of 10,000 feet to have occurred, but as we shall see, this is 

 probably not possible. 



The Laramide structures of Alaska extend to the Arctic shoreline in 

 northeastern Alaska and northern Yukon, as if perhaps, they once con- 

 tinued northeastward under the continental shelf. See Fig. 40.4. Structures 



of the same age in the Eureka Sound Fold Belt suggest that the two 

 may have been continuous. There seems no way, however, to prove or 

 demonstrate this postulate. 



The subject of possible connections will be pursued farther on follow- 

 ing pages when the origin of the Arctic Basin is considered. 



PLEISTOCENE EPEIROGENY AND CLIMATIC CHANGES 



Washburn (1947) reports that Victoria Island has emerged at least 

 500 feet since the last glaciation, as demonstrated by raised strand lines 

 and marine fossils. In addition he believes the whole of the Arctic 

 Archipelago has suffered comparable movements. Elevated beaches are 

 reported by G. M. Stanley (personal communication) up to 900 feet 

 above sea level along the east coast by Hudson Bay. 



Continental ice sheets formerly covered all Arctic Canada east of the 

 Cordillera except some of the western Queen Elizabeth Islands (Craig 

 and Fyles, 1960). The elevated strand lines represents an isostatic ad- 

 justment following the melting of the ice, and such emergence was 

 almost complete before the final eustatic rise of the sea. 



Numerous Tertiary deposits have been found in the Arctic region, and 

 fortunately most of them carry coal beds and fossil plants. By recon- 

 structing the character and distribution of the Tertiary flora from the 

 Arctic to the temperate regions of the northern hemisphere, with par- 

 ticular reference to the redwood Sequoia, Chaney (1940) concluded as 

 follows (Fig. 40.5); the Arctic cooled gradually from late Eocene to the 

 Pleistocene with a slight reversal in mid-Miocene (personal communica- 

 tion, E. Dorf), and the temperate rain forests shifted southward across 

 60° of latitude incident to the cooling. He postulates that the gradual 

 cooling was caused by and was coincident with a gradual uplift of the 

 continent. 



OROGENIC BELTS OF GREENLAND 



Paleozoic 



East Greenland north of 70° N. Lat. is marked by a belt of Caledonian 

 ( Late Silurian and Early Devonian ) orogeny, and another belt of orogeny 



