LABRADOR SEA - THE EXTENT OF CONTINENTAL AND OCEANIC-CRUST AND THE TIMING OF THE ONSET OF SEA-FLOOR SPREADING

Regional reflection seismic profiles across the Labrador Sea originally acquired in 1977 have been reprocessed and reinterpreted. Zones of different structural style have been identified. The seismic interpretations have been used to constrain magnetic modelling and oceanic crust has been confirmed from magnetic anomaly 27N and seaward. However, all attempts to model the area landward of magnetic anomaly 27N as a series of remanent magnetizations of alternating polarity have failed. Interpretations which fit the magnetic and seismic data consist of a zone of block-faulted and subsided continental crust on both the Greenland and Canadian sides, which is separated from oceanic crust by zones of continental crust intruded by and in places overlain by magnetized igneous material. It is concluded that seafloor spreading started in the Labrador Sea in the Palaeocene (Chron 27N) and that large areas under deep water formerly thought to be underlain by oceanic crust should now be considered to be continental.