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TitreStructural characteristics of the ocean-continent transition along the rifted continental margin, offshore central Labrador
AuteurKeen, C E; Dickie, K; Dafoe, L T
SourceMarine and Petroleum Geology vol. 89, 2018 p. 443-463, https://doi.org/10.1016/j.marpetgeo.2017.10.012
Année2018
Séries alt.Ressources naturelles Canada, Contribution externe 20170217
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.marpetgeo.2017.10.012
Mediapapier; en ligne; numérique
Formatspdf
ProvinceRégion extracotière de l'est
Lat/Long OENS -61.0000 -52.0000 59.0000 54.0000
Sujetslevés sismiques, navire; levés sismiques marins; marges continentales; marges continentales, atlantique; déformation; analyse structurale; croûte océanique; croûte continentale; régions extracôtières; levés de reflexion sismiques; vitesse des ondes sismiques; décrochement horizontal; anomalies magnétiques; tectonique; géologie marine
Illustrationslocation maps; seismic reflection profiles; graphs; geophysical images; schematic cross-sections
ProgrammeSystèmes pétroliers de Baffin, GEM2 : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
Studies of the structural deformation and the nature of the ocean-continent transition zone at the rifted continental margin, offshore central Labrador, and its conjugate off West Greenland have been conducted over several decades and helped to define our understanding of the controlling factors in the development of magmapoor margins globally. New two-dimensional seismic reflection data are now available across the Labrador margin which can help to modify and refine this understanding. In this paper, we describe some of these new seismic data and the corresponding potential field data in relation to earlier studies, including an existing deep seismic crustal velocity profile. These data cross the three major structural and compositional zones below the sedimentary wedge defined in earlier deep seismic experiments as: 1) extended zone of continental crust, including the hyper-extended region, partly underlain by serpentinized mantle; 2) exhumed and serpentinized continental mantle zone; and 3) zone of oceanic crust. We are able to extend these zones laterally over 200 km along the margin. The rifted continental crust is hyper-extended over tens of kilometers landward of the breakup location, where many varieties of normal faults and possible low-angle detachment surfaces are present, some of
which are near or at the base of the crust. Further seaward, mantle was serpentinized and likely exhumed, and possesses a seismic character very different from the continental crust. Basement in this zone may locally form prominent ridges. Within the oceanic zone we define a further sub-division into a 'proto-oceanic' domain with thin, variable oceanic crust of about 70-65 Ma in age (magnetic chrons 27 to 31) and a steady-state seafloor spreading region further seaward. Thus, seafloor spreading starts at about chron 31 time. Potential field data and models are broadly consistent with these zones. A strongly reflective, post-rift volcanic event is present across much of the region, especially over the exhumed mantle zone and parts of the oceanic crust. These results are discussed and compared to earlier studies of the West Greenland conjugate margin and to other well-studied magma-poor margins. Given that this rift occurred in thick, cold cratonic lithosphere, the results are remarkably similar to those off Iberia and Newfoundland, suggesting that a long rift history and/or mantle metasomatism may have weakened the lithosphere prior to the main rifting event.
Résumé(Résumé en langage clair et simple, non publié)
Au large du Labrador, de nouvelles données industrielles d¿observation sismique par réflexion fournissent des images améliorées de la structure du sous-sol profond où les roches de la marge continentale se raréfient et laissent peu à peu place à la croûte océanique sous la partie centrale de la mer du Labrador. Il est important de comprendre cette transition dans le cadre des études des bassins régionaux puisqu¿elle fournit le contexte tectonique et les contraintes d¿âge pour les sédiments qui recouvrent cette couche et leur potentiel pétrolifère. Trois grandes zones structurales antérieures sont décrites et extrapolées latéralement le long de la marge, sur une distance de plus de 200 km. Nous montrons les caractéristiques sismiques de ces zones ainsi que les caractéristiques potentielles du terrain et nous définissons un domaine « proto-océanique » de la mince couche océanique ancienne. Les résultats sont comparés à la marge conjuguée du Groenland de l¿Ouest et à d¿autres régions qui présentent des similitudes avec d¿autres zones au large d¿Iberia et de Terre-Neuve.
GEOSCAN ID306045