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TitleDistribution of crustal types in Canada Basin, Arctic Ocean
AuthorChian, D; Jackson, H R; Hutchinson, D R; Shimeld, J W; Oakey, G N; Lebedeva-Ivanova, N; Li, Q; Saltus, R W; Mosher, D CORCID logo
SourceTectonophysics vol. 691, pt. A, 2016 p. 8-30, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20150409
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthern offshore region
AreaCanada Basin
Lat/Long WENS-180.0000 -130.0000 80.0000 70.0000
Subjectsgeophysics; general geology; marine geology; oceanographic surveys; seismic surveys, marine; seismic velocities; crustal studies; continental crust; oceanic crust; magnetic anomalies; seismic reflection surveys; crustal models; ocean - continent boundary (OCB); Alpha Ridge; Northwind Ridge; High Arctic Large Igneous Province (HALIP)
Illustrationslocation maps; schematic cross-sections; tables; graphs; seismic reflection profiles
ProgramDelineating Canada's Continental Shelf Under UNCLOS
AbstractSeismic 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.
Summary(Plain Language Summary, not published)
An interpretation based on velocity analysis of 70 sonobuoy instruments deployed in Canada Basin has been developed to discriminate between continental, oceanic and transitional crust. The most significant result is that only the central part of the Canada Basin is likely underlain by oceanic crust, and this region is flanked by either transitional crust (magma-rich or poor depending on location) or thinned continental crust. These results support a hypothesis for the opening of the Canada Basin by counterclockwise rotation of Alaska away from the Canadian Polar margin, but also underline the complexity of the region's tectonic history.

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