Fróðskaparrit - 01.01.1976, Page 5

Seismic Refraction Measurements around the Faeroe Islands 13
over the islands with values between +17 mgal and +40 mgal
(1 mgal = 10~5 m/s2). The general trend is an increase in an
easterly direction with a wide minimum in the northwest.
A few other geophysical works on the Faeroe Islands can
be mentioned: Abrahamsen (1967), Saxov and Abrahamsen
(1964, 1966), Schrøder (1971), and Hansen and Søndergaard
(1973).
7he shelf around the Faeroe Islands.
A relatively broad shelf surrounds the islands, this shelf
including the islands will be called the Faeroe Block. Towards
northeast the shelf is bounded by the deep Norwegian Sea.
Towards southeast the shelf is separated from the British Shelf
by the Faeroe — Shetland channel with depths of more than
1 km. To the south the channel divides into two channels,
one continues into the Rockall trough after crossing the Wy-
ville Thomson rise, the other channel terminates between the
Faeroe Islands and the Faeroe Bank. Between Iceland and the
Faeroe Islands there is the aseismic Iceland—Faeroe ridge,
from which the Faeroe Block is separated by a short scarp.
The crest of the ridge is a plain with depths around 400 m,
whereas the Faeroe Block is characterized by depths not signifi-
cantly greater than 250 m.
The Iceland—Faroe ridge has been found underlain by ano-
malous oceanic crust of the Icelandic type (Bott et al. 1971,
Johnson & Tanner 1971), whereas the Rockall plateau to the
southwest of the Faeroe Islands seems to be underlain by conti-
nental crust (Scrutton 1972, Roberts, Ardus & Dearnley 1973).
It is therefore of importance for the understanding of the deve-
lopment of the North Atlantic Ocean to know whether the
Faeroe Islands are underlain by continental crust or not; the
assumption that the Faeroes are continental seems to improve
the model for the opening of the Atlantic Ocean (Bott & Watts
1970).
A key to structural questions of this kind is the gravitational