A 275 km section of a regional seismic reflection profile from the Greenland side of the Labrador Sea has been reprocessed and interpreted. Three zones of different structural style have been identified, the innermost of which is block-faulted. Magnetic modelling based on the seismic line shows that sea-floor spreading anomalies are confined to the outermost zone and the oldest identified anomaly is 27N. All attempts to model the area landward of anomaly 27N as a series of remanent magnetizations of alternating polarity failed. However a model in which the innermost zone is interpreted as extended and block-faulted continental crust and the intermediate zone as continental crust intruded and overlain by reversely magnetized igneous material fits the magnetic and seismic data. It is concluded that, at least in the northern Labrador Sea, sea-floor spreading started in Palaeocene times (chron 27), and large areas formerly thought to be underlain by oceanic crust should now be considered to be continental. One plate kinematic consequence may be a reduced need to postulate large strike-slip movements along Nares Strait.

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