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TitreSeismic stratigraphic inferences regarding late-phase volcanism and subsidence history along southern Alpha Ridge
AuteurShimeld, J W; Jackson, H R; Chian, D; Mosher, D C; Hutchinson, D; Lebedeva-Ivanova, N N
SourceL'Association géologique du Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 35, 2012 p. 127
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110353
RéunionJoint Annual Meeting, Geological Association of Canada and Mineralogical Association of Canada; St. John's; CA; mai 27-29, 2012
Documentpublication en série
ProvinceRégion extracotière du nord
Sujetsdorsales sous-marines; levés sismiques; profils sismiques; levés de reflexion sismiques; roches ignées; géophysique; stratigraphie; géologie marine
ProgrammePreparation of a submission for an extended continental shelf in the Atlantic and Arctic Oceans under UNCLOS, Délimitation du plateau continental du Canada en vertu de la Convention des Nations Unies sur le droit de la mer (UNCLOS)
Résumé(disponible en anglais seulement)
The Alpha-Mendeleev ridge complex is a submarine mountain system extending in an arcuate trend across the Arctic Ocean Basin from the Canadian margin, northwest of Ellesmere Island, to the Siberian margin north of Wrangel Island. Ranging in elevation from about 3500 to 250 m below sea level, and covering an area of 7.5E5 sq km, the ridge complex exhibits highly variable morphologies. It is generally interpreted to be a large igneous province that possibly includes domains of continental crust. However, the nature and origin of the Alpha-Mendeleev complex are actively debated because of the sparseness of geological and geophysical data and the complexity of the tectonic framework. Modern 16-channel seismic reflection data collected from icebreakers over the southernmost flanks of the ridge complex reveal a distinctive unit deposited immediately on top of presumed igneous crust (inferred from acoustic basement). The unit comprises high amplitude, continuous, parallel to sub-parallel internal reflections. Its base forms a angular unconformity that extends southward into Canada Basin until it is eventually obscured by deep burial. The top of the unit is an onlap surface that also exhibits pronounced truncation along regions of Nautilus Spur. Modelling of wide-angle reflection and refraction sonobuoy data demonstrates a range of seismic velocities within the unit. For burial depths of less than 1.0 km, velocities range from 2.0 to 3.3 km/s. At deeper burial depths velocities are between 4.1 and 4.6 km/s. High impedance contrasts indicate the presence of indurated lithologies such as calcareous or siliceous sediments, or possibly volcanics. Ranging up to about 600 m in thickness, the unit appears to be concordant with basement topography. Faulting is generally minor, but normal offsets at several locations indicate that deposition of the unit predates the most recent phase of significant extension in Canada Basin. The distinct onlap of the overlying sedimentary succession indicates that the extension was associated with rapid subsidence followed by tectonic quiescence. Throughout the northern reaches of Canada Basin, the unit onlaps the flanks of several large basement structures interpreted to be volcanic edifices, suggesting a temporal and possibly genetic linkage to late-phase volcanism. Samples have not yet been obtained, but a working hypothesis is that the unit consists of high-velocity siliceous oozes interbedded with hemipelagic and pelagic sedimentation.