The crustal structure of the Lofoten continental margin, off Norway, has been obtained from multichannel seismic reftection data and wide-angle Ocean Bottom Seismograph (OBS) data. The shallow sedimentary sequences on the shelf are well imaged on the seismic reftection data, whereas deeper structures are mapped with confidence from the OBS-data. The area west of the shelf edge is covered with flood-basalts, associated with the Paleocene/Eocene break-up between Norway and Greenland. The flood-basalts, which are essentially opaque on conventional multichannel reftection data, can be penetrated with the OBS-method. A total thickness of up to 4.0 km of pre-opening sediments is indicated below the 1.0-2.5 km thick basalts. The crust is inferred to be of continental origin from the shelf to a sequence of seaward dipping reftectors (SDR) seaward of the Vøring Escarpment (VE). Gradual decrease in crustal velocities from 'oceanic' beneath the SDRs to 'continental' at the Vøring Escarpment is interpreted in terms of landward decrease in the content of magmatic intrusions in the crust, and the presence of a lower crustal magmatic body terminating close to the escarpment.
R. Mjelde, S. Kodaira & M. A. Sellevoll, Institute of Solid Earth Physics, Allégt. 41, University of Bergen, N-5007 Bergen, Norway;
S. Kodaira, on leave from: Laboratory for Ocean Bottom Seismology, Hokkaido University, Sapporo 060, Japan.