The fold belts of northern Greenland, Arctic Canada, northern Alaska, Chukotsk, and the Siberian Arctic coast (up to the mouth of the Lena River) form the latitudinal Arctic belt of the Baykalides, Caledonides, Hercynides, and Mesozoides. Its location was influenced by the presence of the Hyperborean and Greenland-Canadian platforms, as well as by the central Yukon, Anadyr'-Seward, and Kolyma massifs, at the close of the Proterozoic and the beginning of the Paleozoic. It is suggested that the fold belts of the Arctic be considered as a special geostructural zone--the Arctides--in contrast to the structures of the Pacific and the Atlantic--the Pacifides and the Atlantides. The Arctides are mainly characterized by a miogeosynclinal regime of sedimentation, and the Pacifides are characterized by a eugeosynclinal regime.

The Arctides may be divided into two segments: American (from eastern Greenland to the Mackenzie River) and Amerasian (from the Mackenzie River to the Lena River); these systems differ by age of folding. The Caledonian and Hercynian fold systems developed in the American segment. The Mesozoic geosynclinal cycle was most important in development of the Amerasian segment (the Mesozoides of North Alaskan and Novosibirsk-Chukotsk fold systems).

The juncture of the Arctides and Pacifides occurs along the zone of the Mackenzie-Lena latitudinal and sublatitudinal deep faults. The nature of the Arctides juncture with the fold systems of Taymyr, Severnaya Zemlya, Novaya Zemlya, and Spitsbergen is not clear. Hypothetically, this deep-lying border may be drawn from the continental slope of Greenland to the mouth of the Lena River.

The great Kolyma megablock, limited by zones of deep-seated faults, is an area of mutual influence of Arctides and Pacifides types of development. It is suggested that this megablock be considered as a transitional geostructural area--the Arcto-Pacifides.

It is suggested that the Taymyr-Severnaya Zemlya and Novaya Zemlya fold area; structures of Timan, Spitsbergen, and East Greenland bordering the Barents Sea platform; and the Kora Sea massif are spatially and genetically associated with the Atlantic segments and occupy an intermediate position between the Atlantides and the Arctides. They may be called the "Arcto-Atlantides."