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TitleOceanic crust in the Canada Basin of the Arctic Ocean
AuthorHutchinson, D; Chian, D; Jackson, RORCID logo; Lebedeva-Ivanova, N; Shimeld, J; Li, Q; Mosher, DORCID logo; Saltus, R; Oakey, G
SourceEuropean Geosciences Union, General Assembly 2015; Geophysical Research Abstracts vol. 17, EGU2015-5543, 2015, 1 pages
LinksOnline - En ligne (pdf)
Alt SeriesEarth Sciences Sector, Contribution Series 20160146
PublisherEuropean Geosciences Union
MeetingEuropean Geosciences Union, General Assembly 2015; Vienna; AT; April 12-17, 2015
Mediaon-line; digital
File formatpdf
ProvinceNorthern offshore region
NTS98C; 98F; 98G; 99B; 99C; 99D; 107E; 107F; 107G; 107H; 117E; 117F; 117G; 117H
AreaArctic Ocean; Mackenzie Delta
Lat/Long WENS-180.0000 -120.0000 87.5000 70.0000
Subjectsgeophysics; marine geology; geophysical surveys; acoustic surveys, marine; seismic surveys, marine; seismic reflection surveys; seismic refraction surveys; sedimentary basins; crustal studies; crustal structure; oceanic crust; continental margins; continental shelf; continental slope; gravity interpretations; magnetic interpretations; mantle; geological history; bathymetry; seafloor topography; Canada Basin; Canada Basin Gravity Low (CBGL); High Arctic Large Igneous Province (HALIP); Alpha Ridge; Northwind Ridge; Phanerozoic; Mesozoic
ProgramDelineating Canada's Continental Shelf Under UNCLOS
Released2015 01 01
AbstractCrustal velocities from 85 expendable sonobuoys in the Canada Basin of the Arctic Ocean acquired between 2007 and 2011 distinguish oceanic, transitional, and extended continental crust. Crustal type was based on objective assignments of diagnostic velocities - oceanic from the presence of layer 3 velocities (6.7-7.2 km/s); transitional from the presence of a lower-most, high velocity layer (7.2-7.7 km/s), and continental for velocities typical of continental crust (\'146.6 km/s). Combined interpretations of sonobuoys, coincident multichannel seismic reflection profiles and existing maps of potential field (gravity and magnetic) are used to refine the distribution of oceanic crust. Oceanic crust forms a polygon approximately 320-350 km wide (east-west) by \'18500 km (north-south). The northern segment of the Canada Basin Gravity Low (CBGL) bisects this zone of oceanic crust, as would be expected from the axis of the spreading center. The multichannel profiles also image a prominent bathymetric valley along this segment of the CBGL, similar to axial valleys found on slow and ultra-slow spreading ridges. Paired magnetic anomalies are associated only with crust that has typical oceanic velocities and are interpreted to represent possibly Mesozoic marine magnetic anomalies M0r - M4 (?), for a duration of opening of 8 million years, and a half spreading rate of \'1810 mm/a. The southern segment of the CBGL, where it trends toward the Mackenzie Delta/fan, is associated with transitional velocities that are interpreted to represent serpentinized peridotite (mantle). As a result of being close to the inferred pole of rotation, this southern area may have had a spreading rate too low to support magmatism, producing amagmatic transitional crust. Further north, near Alpha Ridge and along Northwind Ridge, transitional crust is interpreted to be underplated or intruded material related to the emplacement of the High Arctic Large Igneous Province. Seismic reflection profiles across the Canada Basin show the topography of the basement surface varies with the crustal types determined by the velocity data. The top of oceanic crust is generally a weak reflection with a high-relief blocky character, and rare deeper reflections. The top of transitional crust is a low-relief, bright reflection with numerous subparallel bright reflections that extend as much as .5 km deeper. The areas of continental crust show grabens possibly associated with rifting. Previously published longer offset wide-angle reflection/refraction experiments in the southern Canada Basin are consistent with the lack of oceanic layer 3 velocities and the depth to Moho based on our interpretation of the sonobuoy profiles. Our new sonobuoy results show a restricted area of oceanic crust centered within the middle of Canada Basin. This result has implications for plate reconstruction models, which now must close a smaller area and must also account for the poorly known but finite extension in the transitional crust.
Summary(Plain Language Summary, not published)
Measurements of seismic velocity from the rocks beneath the Canada Basin of the Arctic Ocean are used to distinguish three different crustal types: oceanic, transitional, and extended continental crust. Integrating these results with interpretations of seismic reflection data and measurements of the Earth's magnetic and gravity fields allows us to delineate a region of Canada Basin in which oceanic crust was formed by seafloor spreading. This information, which was poorly constrained until the present study, is essential for geological models of how the Arctic Ocean was formed.

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