The morphostructure and relief of the Arctic were formed chiefly by modern warping movements. The magnetic anomaly patterns of the Eurasian and the Scandic subbasin may be the result of successive inversions of strips of continental crust through time. To determine the total amount of warping which has occurred one must study the continental slope structure, where maximum warping may have taken place, and where the pre-Holocene section of the Arctic Basin may be studied.

Nonuniformity of neotectonic processes explains the various degrees of oceanization of the Arctic Ocean bottom. Oceanization has proceeded in orderly succession from the more ancient stabilized Atlantic to the young Pacific rim. The margins of the oceanized areas are the Laptev Sea, the East Siberian Sea, the Chukotsk and Beaufort Seas, the Canadian-Greenland shelves, and the Barents and Kara Seas. These surround the Amerasian subbasins that comprise the Arctic. The main feature contributing to the development of the Eurasian and the Scandic subbasins, in particular, has been the formation of the mid-ocean ridge, which extends through the Scandic basin and Eurasian basin.

A principal feature in the development of the modern continental structures has been the regular and repeated shift or orogenesis from the Atlantic Ocean to the Pacific through the areas of the present American and Eurasian basins. This repeated shift of orogenesis has formed symmetric chains in succession, from the ancient activated platforms of the Atlantic-Eurasian area to the modern Pacific geosyncline which is characterized by seismic activity and volcanism. The location of the zone of the Atlantic riftogenesis (Mid-Atlantic and Mid-Arctic Ridges) in the area of the most ancient stabilization (not younger than Caledonian) may account for the anomalous tectonic activity in this area during the latest stage of oceanization. The fact should be noted that the most active orogenesis o curred in areas of epi-Mesozoic platforms.

The main features of the modern morphostructural framework in the American and Eurasian continental structures also are inherited from Paleozoic morphostructures in the Atlantic (Scandic) coastal zone and Mesozoic morphostructures in the central Arctic (West Siberia, Central Siberia, northern Canada). The most recent morphostructures are (1) those inherited from the geosynclinal framework in Pacific coastal zones of epiplatform orogenesis and (2) the superimposed riftogenic activity which is outlined most clearly in the zones of oceanization.

The process of oceanization is observed in studies of the shelves, on Barents Sea-Kara Sea shelves in particular. Here, in the zones of ancient Paleozoic mobile belts, structural reconstruction is taking place. The ancient mountain ranges are being inverted into sags, grabens, and epicontinental troughs.

The concentric arrangement of the main elements of the modern Arctic geostructure with relation to the geographic pole may be related to the rotational regime of the earth. Considering the fact that this concentricity dates back at least to Mesozoic time, it is doubtful that significant migration of the poles can have taken place from late Mesozoic time to the present.

Another factor affecting the modern structures was the superimposition of glacial and ocean-water loads. The specific effect on the modern structures is determined by the structural features of the substrate.

The established directional regularity through time of the development of modern structure of the Arctic and the concepts regarding the Neogene-Quaternary riftogenesis and other activity, in particular, are based mainly on data from the Eurasian side of the Arctic. However, the similarity of the structure in the American Arctic provided a basis for extrapolating our observations to the whole Arctic region.

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