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TitleStructural characteristics of the ocean-continent transition along the rifted continental margin, offshore central Labrador
AuthorKeen, 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
Year2018
Alt SeriesNatural Resources Canada, Contribution Series 20170217
PublisherElsevier
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceEastern offshore region
AreaLabrador Sea
Lat/Long WENS -61.0000 -52.0000 59.0000 54.0000
Subjectstectonics; marine geology; seismic surveys, ship; seismic surveys, marine; continental margins; continental margins, atlantic; deformation; structural analysis; oceanic crust; continental crust; offshore areas; seismic reflection surveys; seismic velocities; rifting; magnetic anomalies; magma-poor; extension history
Illustrationslocation maps; seismic reflection profiles; graphs; geophysical images; schematic cross-sections
ProgramBaffin Petroleum Systems, GEM2: Geo-mapping for Energy and Minerals
AbstractStudies 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.
Summary(Plain Language Summary, not published)
Offshore of Labrador, new industry seismic reflection data provides enhanced images of the deep basement structure where the rocks of the continental margin thin and transition into oceanic crust underlying the central part of the Labrador Sea. This transition is important to understand in regional basin studies as it provides tectonic context and age constraints for the overlying sediments and their petroleum potential. Three previous major structural zones are described and extrapolated laterally along the margin for over 200 km. We show the seismic and potential field characteristics of these zones and further define a ¿proto-oceanic¿ domain of early, thin oceanic crust. The results are compared to the conjugate West Greenland margin and other regions with notable similarities to those off Iberia and Newfoundland.
GEOSCAN ID306045