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The Alpha Ridge-Mendeleev Rise (AMR) is the major bathymetric feature in the Amerasia Basin of the Arctic Ocean. Its tectonic history is controversial due to its remote location in ice covered waters making data acquisition difficult, resulting in the lack of diagnostic data. Analysis of the wide-angle reflection/refraction data based on the compressional waves (P-waves) from the AMR indicates that its velocity/depth structure is typical of large igneous provinces (LIPs). LIPs can form on either oceanic or continental crust and can exhibit complex history of development. Here converted shear waves (S-wave) on the Alpha Ridge have been used to calculate Poisson's ratios and many of measured values are within the felsic range in the upper crust. They are comparable to published S-waves from the Mendeleev Rise. They are also consistent with the results of Rayleigh-wave group-velocity analysis that indicate the Alpha Ridge in adjacent northern Canada has an intermediate composition. Based on magnetics, pseudogravity and volumetric considerations the High Arctic Large Igneous Province (HALIP) most closely resembles the Kerguelen Plateau, a LIP with a continental component. The geophysical characteristics of the AMR are compatible with a number of other LIPs that have continental affinities. A variety of offshore information from dredges and cores and onshore geological data support continental fragments incorporated in the AMR. [ABSTRACT FROM AUTHOR]

Seismic velocities determined from 70 sonobuoys widely distributed in Canada Basin were used to discriminate crustal types. Velocities of oceanic layer 3 (6.7–7.1 km/s), transitional (7.2–7.6 km/s) and continental crust (5.5–6.6 km/s) were used to distinguish crustal types. Potential field data supports the distribution of oceanic crust as a polygon with maximum dimensions of ~ 340 km (east–west) by ~ 590 km (north–south) and identification of the ocean–continent boundary (OCB). Paired magnetic anomalies are associated only with crust that has oceanic velocities. Furthermore, the interpreted top of oceanic crust on seismic reflection profiles is more irregular and sometimes shallower than adjacent transitional crust. The northern segment of the narrow Canada Basin Gravity Low (CBGL), often interpreted as a spreading center, bisects this zone of oceanic crust and coincides with the location of a prominent valley in seismic reflection profiles. Data coverage near the southern segment of CBGL is sparse. Velocities typical of transitional crust are determined east of it. Extension in this region, close to the inferred pole of rotation, may have been amagmatic. Offshore Alaska is a wide zone of thinned continental crust up to 300 km across. Published longer offset refraction experiments in the Basin confirm the depth to Moho and the lack of oceanic layer 3 velocities. Further north, toward Alpha Ridge and along Northwind Ridge, transitional crust is interpreted to be underplated or intruded by magmatism related to the emplacement of the High Arctic Large Igneous Province (HALIP). Although a rotational plate tectonic model is consistent with the extent of the conjugate magnetic anomalies that occupy only a portion of Canada Basin, it does not explain the asymmetrical configuration of the oceanic crust in the deep water portion of Canada Basin, and the unequal distribution of transitional and continental crust around the basin. [ABSTRACT FROM AUTHOR]