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TitleThe crustal structure of the Alpha Ridge at the transition to the Canadian Polar margin - results from a seismic refraction experiment
AuthorFunck, T; Jackson, H R; Shimeld, J
SourceJournal of Geophysical Research vol. 116, issue B12, B12101, 2011 p. 1-26, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20110132
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthern offshore region
AreaArctic Ocean; Canadian Polar Margin
Lat/Long WENS-100.0000 -90.0000 84.3333 80.0000
Subjectsmarine geology; geophysics; seismic data; seismic profiles; seismic refraction surveys; p waves; crustal models; oceanic crust; Alpha Ridge; Mendeleev Ridge; Lomonosov Ridge
Illustrationslocation maps; seismic profiles; schematic cross-sections; magnetic anomaly maps
ProgramDelineating Canada's Continental Shelf Under UNCLOS
Released2011 12 03
AbstractThe crustal structure of the Alpha Ridge and its connection to the Canadian Polar Margin was studied by a seismic refraction experiment consisting of a 350-km-long line perpendicular to the margin and of a 175-km-long cross line on the ridge. Explosives with a spacing of 22 km were recorded by geophones deployed on the ice (~1.5 km spacing). P wave velocity models were developed by forward and inverse modeling of travel times and by tomographic inversion. The models show a 30-km-thick continental crust with velocities from 5.5-6.6 km/s. The continent-ocean transition zone is characterized by thinned and intruded continental crust; a high-velocity lower crustal body (7.5 km/s) indicates magmatic underplating. An up to 5-km-thick layer with velocities of 4.7-5.4 km/s can be correlated from the transition zone onto the Alpha Ridge, where reflection seismic data indicate the presence of extrusive volcanics. The transition zone is characteristic for volcanic-style continental margins. The crust on Alpha Ridge consists of the volcanics, a 4-km-thick layer with intermediate velocities of 6.1-6.6 km/s and a lower crustal layer with velocities of 6.8 to 7.3 km/s; Moho depth varies between 26 and 32 km. Velocities on the ridge are similar to other oceanic large igneous provinces. The Alpha Ridge and the contiguous Mendeleev Ridge are interpreted to result from interaction between a Cretaceous plume and a seafloor spreading centre parallel to the Canadian Polar Margin with the Lomonosov Ridge acting as a shear margin.

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