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TitleThe ocean-continent transition zone underlying the central Labrador margin, Canada
AuthorKeen, C E; Dickie, K; Dafoe, L T
SourceConjugate Margin Conference, abstracts volume; .
Alt SeriesNatural Resources Canada, Contribution Series 20180095
PublisherAtlantic Geology
MeetingConjugate Margin Conference; Halifax; CA; 2018
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
ProgramGEM2: Geo-mapping for Energy and Minerals, Baffin Petroleum Systems
AbstractThe nature of the ocean-continent transition zone on the central Labrador rifted continental margin, and its conjugate off West Greenland, have been studied for several decades. Geophysical studies and deep drilling have increased our fundamental understanding of the tectonic evolution of this type of magma-poor margin globally. Several elements of the ocean-continent transition zone have been delineated by a refraction survey during a previous experiment on the central Labrador margin, including a zone of extended continental crust under the shelf, a region underlain in part by exhumed and serpentinized mantle, and furthest seaward under the deepest part of the Labrador Sea, is oceanic crust. We show new 2D seismic data and link it to potential field data and a deep seismic crustal velocity profile. The results allow us to: a) extend the previously defined zones laterally for over 200 km, b) show that a zone of hyper-extended continental crust some tens of kilometers wide displays complex basement faulting with possible low-angle detachments and polyphase faulting, c) define a transparent seismic character within the serpentinized basement zone, and d) determine that the oldest oceanic crust is thin and structured with an age of about 70¿65 Ma, similar to the 'proto-oceanic' domain defined on other margins. Therefore seafloor spreading begins at about magnetic chron 31, earlier than the well-defined chron 27. 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 rifts in Phanerozoic terrain off Iberia and Newfoundland, suggesting that a long rift history and/or mantle metasomatism may have weakened the cratonic lithosphere prior to the main rifting event.
Summary(Plain Language Summary, not published)
The basement types underlying the distal Hopedale Basin have been mapped using a modern seismic dataset. These consist of a zone of extended continental crust, a zone of hyper-extended continental crust, a zone of continental mantle which has been serpentinized, a zone of thin oceanic crust and a zone of thicker, normal oceanic crust. We show seismic examples of these basement types and their main characteristics.