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Abstract

Part of the earth's crust surrounded by three pre-Paleozoic platforms (East European, Mid-Siberian, and Greenland-Canadian) was the site of origin and development of the Arctic Ocean. Arctic Ocean structures are discordant with the structures of the coast and continental shelf. According to tectonic data, present shelf regions represent vast parageosynclinal basins of nearly isometric shape filled with varied sedimentary sequences. Sedimentary history of the shelf is closely related to development of megablocks of the earth's crust in this region. The Barents-Kara, Laptev, East Siberian-Chukotsk, and Alaska megablocks are recognized on the basis of geophysical data. Sequential rejuvenation of the megablocks and sedimentary cover seems to have occurred in a west-east direction.

Rocks of the central Arctic basin are unconsolidated sediments (first layer) with seismic velocities of 1.6–2.5 km/sec, consolidated sediments (second layer) with velocities of 3.0–4.5 km/sec, pre-oceanic folded base-ment (third layer) with velocities of 5.0–6.2 km/sec, and crystalline basement (fourth layer) with velocities of 5.7–6.3 km/sec for granitic composition and 6.4–6.7 km/sec for basalts. In the western part of the Arctic basin, the second and third layers are usually found only in the periphery; in the central parts, unconsolidated sediments lie directly on basaltic basement. In most of the eastern part of the basin, a continuous section is present. In both sectors, thickness of unconsolidated sediments is less on uplifts and ridges (0.1–0.5 km) than in adjacent troughs (1–2 km). Thickness distribution of the second layer generally does not conform to the present structural configuration. Thus, the most significant vertical movement in the inner Arctic Ocean basin occurred mainly in late Mesozoic-Cenozoic time, during deposition of the sediments of the first layer. During that time the present configuration of the Arctic Ocean basin was attained.

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