Fróðskaparrit - 01.01.1996, Side 116

120 IMAGING OF BASALT AND UNDERLYING STRUCTURES IN THE FAROESE OFFSHORE AREA
Introduction
The Faroe Islands form part of the Faroe
Platform area, a region of the North Atlan-
tic Ocean beween the United Kingdom,
Norway, and Iceland which is characterized
by a voluminous Paleocene-Eocene basalt
cover. This basalt consists mainly of sub-
aerially extruded plateau basalts (Rasmus-
sen and Noe-Nygaard, 1970; Waagstein,
1988). It is believed that this early Tertiary
volcanism is associated with lithospheric
extension which preceded the continental
breakup between the Faroe-Rockall
Plateau and Greenland (Smythe et al, 1983;
Roberts, Morton, and Backman, 1984) by
the opening of the North Atlantic Ocean
(Fig.l) and therefore forms part of the
Northeast Atlantic volcanic passive mar-
gin.
The presence of Tertiary oceanic crust
can be observed to the north and west of the
Faroe Islands (Figs. 1 and 2) ie, the Faroe-
Iceland Ridge. (Nunns, 1983; Andersen,
1988) The oceanic basalt - a different age
and type from that forming the Faroe Is-
lands Platform - has formed since magnet-
ic Chron 24 (Fig. 2) and has the age of ear-
ly Eocene and younger (Nunns, 1983.)
Oceanward dipping reflectors, or steeply
dipping piles of subaerially erupted basalt
flows which may be interbedded with sedi-
ments, are also found to the north and west
of the Faroes, before the contact of oceanic
crustal rocks. These oceanward dipping re-
flectors are thought to be indicative of the
transition from oceanic to continental cru-
stal rocks (Smythe et al, 1983; Roberts,
Morgan, and Backman, 1984; Spence et al,
1989) .
To the east and south the Faroe Platform
is bounded by a broad, deep, structural
basin known as the Faroe-Shetland Chan-
nel (Fig. 1). The basalt cover thins substan-
tially into this basin and apparently vanish-
es before the basin axis is reached. To the
south and west the Platform is bordered
again by a broad, deep structural basin
called the Faroe Bank Channel and Basin
which appear to have basalt cover through-
out (see Interpretation and Discussion).
This basin is bounded on its southern and
westem edges by the Wyville-Thompson
and Ymir Ridge systems, which are
thought to represent Tertiary compression-
al features (Boldreel and Anderson, 1993,
1995).
Another particularly prominent feature
of the area is the Munkagrunnar Ridge,
which extends the Faroe Platform south-
wards from the Island archipelago (Figs. 1
and 2). This Ridge has bathymetric, mag-
netic, and gravity expression (R. Morgan,
personal communication) but its origin re-
mains enigmatic.
The primary challenges to geophysical
investigations within the area have been to
explore beneath this substantial Tertiary
basalt cover, which acts as a barrier to ex-
ploration and effectively masks the under-
lying features which have controlled the
genesis of the area. The purpose of this
study has been to attempt to »see« through
the basalts, utilizing primarily the seismic
method, to determine what geological and
structural elements lie below