644 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



NORTH POLE 



BASIN A 



ALASKA OFF 

 POINT BARROW 



ALLUVIATEO PLAIN CHUKCHI CAf 



ALLUVIATEO PLAIN 



ALPHA RANGE, 



MENDELEEV RANGE. 



OR CENTRAL 8ASIN RISE 



LOMONOSOV 



RANGE ALLUVIATED PLAIN REGION OF SEAMOUNTS HANSEN'S SILL SEA 



IOOO 

 J 2000 

 "3000 

 3«000 

 E 5000 



SI 



/ ^"'^4*^^^^^^ ^^ IYl mjfL^m^ ri ^''^—^ 



Fig. 40.7. Bathymetric profile across Arctic basin, taken in August, 1958, by SSN (571) 

 Nautilus. Drafted from chart kindly supplied by Dietz and Shumway. Basin A is called Beau- 

 fort Sea basin by Soviets, and Canada basin by Dietz and Shumway. Basin B is called 



is narrow, but off Eurasia it is very broad. Spitzbergen ( Svalbard ) , Franz 

 Josef Land (Zemlya Frantsa Iosifa), North Land (Severnaya Zemlya), 

 Novaya Zemlya, New Siberian Islands ( Novosibirskiye Ostrova), and 

 Wrangel Island (Ostrov Vrangelya) all rise from the shallow but broad 

 shelf north of Siberia and Norway. 



Spitzbergen was formerly believed to be tied to northern Greenland 

 by the Nansen sill, but recent soundings show that the sill is broken by a 

 transverse trench with a floor 3100 to 3900 meters deep and about 200 

 kilometers wide (Hope, 1959b). 



Deep Basin 



The deep basin is approximately triangular in shape with the base 

 about 1150 miles across and the side from Spitzbergen to Alaska about 

 1650 miles long. On the basis of post-war soundings, principally by the 

 Russians, the large basin is known to be divided by the Lomonosov 

 Range (or Ridge) which extends from the New Siberian Islands to Green- 

 land and Ellesmere Island, a distance of 1800 kilometers. Its peaks rise 

 2500 to 3000 meters above the adjacent ocean floor, and the highest 

 peak yet sounded is 954 meters below the ocean surface. Saddles to a 

 depth of 1500 meters, spurs, and steep slopes are characteristic. 



On the Alaskan side of the Lomonosov Range another range was dis- 

 covered by the United States drifting ice station Alpha. It has pro- 

 visionally been called the Alpha Range by Hope (1959a). Its extent is 

 not known and its relief appears to be less than the Lomonosov Range. 

 Its apparent plateau-like top rises to 2300 meters below sea level. The 



Makarov basin by Soviets and central Arctic basin by Dietz and Shumway. Basin C is called 

 Nansen basin by Soviets and Eurasia basin by Dietz and Shumway. Nansen's Still is called 

 Nansen Ridge by Dietz and Shumway. 



two ranges then divide the major deep basin into three sub-basins which 

 have not yet been named officially. They will be referred to here as 

 basins A, B, and C. The scientists of the U.S.S.R. and of the United States 

 respectively have called them as follows; Basin A, Beaufort Sea Basin 

 and Canada Basin; Basin B, Makarov Basin and Central Arctic Basin; 

 and Basin C, Nansen Basin and Eurasia Basin (personal communica- 

 tion V. N. Sachs and charts prepared by Dietz and Shumway). The 

 Alpha Range is called the Mendeleev Range by the Russian scientists, 

 and on unpublished charts by Dietz and Shumway, the Central Basin 

 Rise. 



Basin C, which lies north of the Greenland, Barents, Kara, and Laptev 

 seas, is the deepest of the three and has a maximum depth of over 5220 

 meters. Basin B on the opposite side of the Lomonosov Range, has depths 

 over 4000 meters. Basin A which lies north of the Chukchi and Beaufort 

 seas has depths up to 3820 meters. 



The sonic depth profile recorded by the submarine Nautilus across the 

 Arctic Ocean, is summarized in Fig. 40.7. It extends from a point north 

 of Point Barrow directly to the North Pole and beyond to the middle of 

 Basin C, and thence southwesterly to Nansen's Sill between Spitzbergen 

 and Greenland. Its features should be noted, and in succeeding para- 

 graphs they will be referred to. 



Seismic studies over the Alpha Range by Hunkins ( 1961 ) indicate the 

 boundary between the 4.7 km/sec layer and the basaltic layer at about 

 5 kilometers which is less than that shown by Demenitsckya. Relief of the 

 rise is rugged and apparently the result of block faulting. The constitution 

 of the crust is similar to that of the Atlantic Ocean floor. 



