Canadian Basin

The Canadian Basin is the largest and oldest sub-basin of the Arctic Ocean and stretches for about 1100 km from the Beaufort Sea shelf to the Alpha-Mendeleev Ridge, which divides the Canadian Basin from the Makarov Basin (see the bathymetric map in Arctic Ocean). The two basins are sometimes referred to together as the Amerasian Basin. The basin has a complex bottom topography with several uplift regions. Ocean depth in the deepest abyssal plain reaches 3800 m, and its area exceeds 250,000 km2.

The width of the continental slope varies from 100 to 400 km, the shelf being steepest and narrowest in the southern basin. The continental slope has terraces at depths of 2600-3000 m and 3200-3400 m, and is divided by canyons, which form the radial-centripetal system of the basin. The abyssal plain at the foot of the continental slope is reached between 3600 and 3800 m. The surface of the abyssal plain is mainly flat, complicated with isolated raisings from 600 to 800 m high located in immediate proximity to Northwind Ridge.

The deep crustal structure in the area of the Canadian Basin is oceanic crust 5-7 km thick of an unexplained age; however, there is no active spreading ridge today in the Canadian Basin, and spreading must have ceased by the early Tertiary. The Northwind Ridge, part of a complex Chukchi Borderland region of ridges and plateaus that projects into the basin, is probably a high-standing fragment of continental crust. The basin now has a deep sedimentary layer up to 1-2 km thick.

The sedimentary cover of the abyssal plain is made up of old terrigenous sediments. The clays, silts, and fine-grained sands are devoid of foraminifers and were brought by sea ice materials, evidently originating from onshore river systems. On the bottom of the Canadian Basin, the process of accumulating atmosphere dust (possibly transported by snow) is ongoing at a slow rate of 1 mm or more per 1000 years. Such a slow accumulation continues on Lomonosov and other ridges, but is not typical for abyssal plains, where mudflows along with deep-sea sources of sedimentary accumulation are more common.

At the surface, the anticyclonic Beaufort Gyre covers the whole of the Canadian Basin. At intermediate depths, the Canadian Basin has warm, saline Atlantic water, but deep waters are Pacific in origin.

Valery Mit'ko

See also Alpha Ridge; Beaufort Gyre; Chukchi Plateau

Further Reading

Gorbatskiy, G.V., Physicogeographical Zoning of Arctic, Volume 3, Arctic Basin, Leningrad: Leningrad University Publishing House, 1973 Gramberg, I.S. (editor), Orographic Map of Arctic Basin.

1:5000000, Helsinki: Karttaneskus, 1995 Gramberg, I.S. & G.D. Naryshkin, Peculiarities of the Arctic Deep-Water Basin's Ground. SPb, VNII Okenologiya, 2000 Grantz, A., D.L. Clark, R.L. Phillips & S.P. Srivastava, "Phanerozoic stratigraphy of Northwind Ridge, magnetic anomalies in the Canada Basin, and the geometry and timing of rifting in the Amerasia Basin, Arctic Ocean." Geological Society of America Bulletin, 110 (1998): 801-820

Lawver, L.A. & C.R. Scotese, "A review of tectonic models for the evolution of the Canadian Basin." In The Arctic Ocean Region. The Geology of North America, edited by A. Grantz, L. Johnson & J.F. Sweeny, Volume L, Boulder, Colorado: Geological Society of America, 1990, pp. 593-617 Weber, J.R., Exploring the Arctic Seafloor in Selected Lorex Contributions, Ottawa, 1985

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