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

We have mapped the transition from the continental Faroe block (the Faroe I slands and surrounding shelf) to the thickened oceanic crust of the Faroe-I celand Ridge in the North Atlantic using the results of a detailed sea-to-l and seismic profile with wide-angle to normal-incidence recordings of explo sive and airgun shots fired at sea along the Faroe-Iceland Ridge. Interpret ation of all available seismic and gravity data indicates that this aseismi c ridge is composed of 30 +/- 3-km-thick oceanic crust, with a gradual tran sition to ancient continental crust from 100 to 40 km northwest of the Faro e Islands, close to the shelf edge. This confirms that the crust beneath th e Faroe Islands, which may be up to 46 km thick, comprises continental mate rial in agreement with previous seismic and geochemical results. Results su ggest that the upper 5.2 +/- 0.7 km of the Faroe crust consists of Tertiary basalts generated during continental breakup, overlying the continental cr ust 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 underplati ng or intrusion by mafic melts during continental breakup in the early Tert iary. (C) 1998 Elsevier Science B.V. All rights reserved.