Crustal structure beneath the Faroe Islands and the Faroe-Iceland Ridge

We have mapped the transition from the continental Faroe block (the Faroe Islands and surrounding shelf) to the thickened oceanic crust of the Faroe-Iceland Ridge in the North Atlantic using the results of a detailed sea-to-land seismic profile with wide-angle to normal-incidence recordings of explosive and airgun shots fired at sea along the Faroe-Iceland Ridge. Interpretation of all available seismic and gravity data indicates that this aseismic ridge is composed of 30 +/- 3-km-thick oceanic crust, with a gradual transition to ancient continental crust from 100 to 40 km northwest of the Faroe Islands, close to the shelf edge. This confirms that the crust beneath the Faroe Islands, which may be up to 46 km thick, comprises continental material in agreement with previous seismic and geochemical results. Results suggest that the upper 5.2 +/- 0.7 km of the Faroe crust consists of Tertiary basalts generated during continental breakup, overlying the continental crust beneath. The lower crust, where seismic constraint is poor,may exhibit high seismic velocities (7.1-7.6 km s(-1)) which we attribute to underplating or intrusion by mafic melts during continental breakup in the early Tertiary. (C) 1998 Elsevier Science B.V. All rights reserved.