GEOSCAN, résultats de la recherche

Menu GEOSCAN


TitreNew potential field cross sections of the Amerasian Basin
AuteurOakey, G N; Saltus, R W
Source2014 Arctic Days Symposium - iMAGINE Special Session (Integration of Magnetics and Gravity in Northern Exploration); .
Séries alt.Secteur des sciences de la Terre, Contribution externe 20160150
ÉditeurGeological Society of Norway
Réunion2014 Arctic Days Symposium; Tromsø; NO; juin 3-4, 2014
Lang.anglais
Mediapapier
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)
We present 5 new potential field cross sections spanning the Amerasian Basin in the high Arctic region. The two-dimensional models are based primarily on gravity/density modeling constrained by previously published seismic lines on the Canadian margin and new sonobuoy interpretation from joint data collection by the United States and Canada. The new sonobuoy data were acquired as part of seismic investigations in support of the United National Convention on the Law of the Sea (UNCLOS) programs for the definition of regions of extended continental shelf by each country. The potential field cross sections are further constrained to honor the regional magnetic anomalies as defined by the International Polar Year magnetic compilation of Gaina et al.
These cross sections provide the most comprehensive and self-consistent crustal analysis to date for this controversial frontier region. Our models consist of 3 post-rift sedimentary units with increasing density with depth (2000 kg/m3, 2400 kg/m3, and 2500 kg/m3); a basal acoustic basement unit (inferred volcanics and volcaniclastics) with a density of 2600 kg/m3; crystalline upper and lower crust units with densities of 2800 kg/m3, 2900 km/m3,and 3000 kg/m3; a high velocity/density 'anomalous' lower crustal layer with density of 3100 kg/m3; and a uniform mantle (sub Moho) density of 3300 kg/m3.
The cross section models depict marginal regions with typical continental crustal density structure (Canadian Margin, Chukchi Plateau, Lomonosov Ridge); deep-water regions of hybrid crustal character (most of the deep water region); a small zone with oceanic crustal character within the central Amerasian basin; and a large region underlain by high velocity/density lower crust (Alpha Ridge and portions of the Canada basin).
The primary magnetic source layers are a highly magnetic basal volcanic/volcaniclastic layer, moderately magnetic portions of the upper crust (above the inferred Curie temperature depth), and lower susceptibility layers within the crystalline crust. The physical properties for these magnetic layers are based on analogy to the inferred lithologies; we do not have direct physical property measurements for these layers. The moderate amplitude magnetic highs within the Canada basin are primarily caused by variations within the volcanic/volcaniclastic and upper crustal layers; the very high amplitude anomalies within the High Arctic Magnetic High domain result from a combination of shallow and deeper magnetic anomaly sources.
These new profiles provide a useful regional framework both for development and testing of geodynamic models and for refinement by more detailed data collection and interpretation. Taken at face value (i.e., based on the difference in crustal thickness between the margin and basin), our models suggest apparent stretching factors (beta values) of about 4 for the central Canada basin, and about 2 for the Nautilus Spur region. Crustal thickness in the Alpha ridge region is similar to that of the adjacent Canadian islands (resulting in an apparent beta factor of 1) and presumably reflects a combination of stretching offset by extensive intrusion/underplating related to development of the large igneous province.
Résumé(Résumé en langage clair et simple, non publié)
Un volume important de nouvelles données géophysiques de l'Arctique ont été collectées au cours de la dernière décennie au cours de la collaboration canadienne, américaine, et des expéditions de recherche danois pour soutenir prolongée présentation du plateau continental du Canada auprès des Nations Unies. Afin de mieux comprendre la structure géologique de la marge Canadain l'Arctique, la gravité et les modèles magnétiques ont été générées pour plusieurs coupes pour illustrer la variabilité des différents segments de la marge de divergence ainsi que la répartition de la croûte magnétisée et les unités volcaniques.
GEOSCAN ID299147