Fróðskaparrit - 01.01.1977, Síða 72

80 Complementary gravity observations in the Faroe Islands
In Fig. 8 we present for area IV the Bouguer anomalies in-
cluding the topographic correction according to the figures
given in the last column in the table. Isogals are drawn with
an equidistance of 1 mGal. It has been preferred to give the
anomalies with one tenth of a milligal. That does not mean
that the anomaly values are correct to this unit due to the
topographic correction. Repeated calculations of this correction
for a number of stations have given divergences up to 0.3
mGals. It has to be pointed out that in area IV are included
areas I, II and III presented previously (Saxov 1971). An
inspection of the anomaly picture in Fig. 8 gives occasion for
the following remarks. Firstly, the anomaly curves from + 31
mGals to + 22 mGals at the southern part of Mykines, Vágar,
Koltur and Hestur must run along the western edge of Sandoy
in order to fit into the anomaly picture of SuSuroy. Secondly,
the minimum in the northern part of Streymoy which was
suggested at the former gravity map (Saxov 1969) appears
now more clearly, and there is reason to believe that the +21
mGal curve closes in the water westwards. Thirdly, a comment
concerning the changing features of Streymoy. It was remarked
(Saxov 1971) that it was a surprise to locate a gravity mini-
mum northwest of Kirkjubøur. The new measurements have
only emphasized this minimum, and they have also given rise
to several local features, e. g. the minimum north of Kaldbak.
Finally, it may be remarked that the gravity picture seems to
indicate that the geology of Streymoy may not be so simple
as previously believed. In this connection it can be mentioned
that there are inconsistencies in the seismic records in the Tórs-
havn region (Casten 1974; Bott et al. 1976). Also in the in-
vestigation by Pálmason (1965) an unsolved problem remained
at Kollafjørður along the profile Tórshavn—Hvalvík. This
problem could equally well be due to inconsistencies in the
Tórshavn region.
Anyway, the seismic surveys in 1969, 1972, and 1975 have
all given reliable records from the northern part of Streymoy
as well as from Vágar and the northern part of Eysturoy