Fróðskaparrit - 01.01.1982, Page 13

Um dýpdarboringina í Vestmanna og í Lopra
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was divided into a lower basalt series (about 900 m); a coal bearing sedi-
ment series (about 10—15 m); a middle basalt series (about 1250 m) initi-
ated by explosive volcanism producing agglomerates and tuffs, the tuff-
agglomerate zone; and an upper basalt series (about 675 m). Minor intru-
sions occur in form of dikes, sills and irregular intrusive bodies. The pla-
teau has a low-angle easterly dip and the lavas of the lower basalt series
are updomed in two areas, Vágar—Mykines and Suðuroy.
Geological and geophysical investigations were continued out on the
shelf around the islands and on the Faeroe bank, Bill Baily bank and
Lousy bank to the west.
Further geological information was obtained from two bore holes, one
drilled in the summer 1980 at Vestmanna on Streymoy and the second in
the summer and autumn of 1981 near the village of Lopra on Suðuroy
(Fig. 1).
The faeroese government organized, and was economically responsible
for the drill project, which was carried out in collaboration with the Geo-
logical Survey of Denmark. The drilling work was entrusted to the ice-
landic »National Energy Authority« (Orkustofnun). The drilling project
was supported by the Carlsberg Foundation because of its scientific signi-
ficance.
The bore hole at Vestmanna was drilled to determine if the lower basalt
series and the coal bearing sediment series from Vágar could be traced down
dip below sea level as far east as Streymoy, and to get information on the
regional thermal gradient.
The bore hole at Vestmanna (Fig. 2) was drilled from just above sea
level with full core to a depth of 660 m (Fig. 3).
The coal bearing sedimentary series from Vágar was found at 556 m.
Here it was 3 m thick and contained basaltic sand and pebbles, but not
coal. The tuff-agglomerate zone did not occur at the drill site in Vest-
manna. The drilling continued 101 m into the upper part of the lower
basalt series. The thermal gradient was 40°C/km.
The Lopra bore hole was planned to penetrate at least 2 km into the
unknown sequence below the known part of the lower basalt series and to
obtain further thermal gradient data.
The drill site was located west of the village Lopra a few m above sea
level, as low in the known part of the lower basalt series as possible (Fig.
4). A section through the bore hole reaching 2178 m below sea level is
shown on Fig. 5. Six cores were taken (one core lost) at different levels
and cuttings collected for each two m drilled. The drilled sequence consist
of about 120 subaerially erupted lava flows indicating a subsidence of more
than 2000 m. The lava flows average about 20 m in thickness while the
intercalated sediments are up to 5 m. The drilled sequence consists of
aphyric to feldsparphyric tholeiitic basalts and must be considered as a