Jökull - 01.12.1991, Page 51

Fig. 2. Location of stratigraphic/paleomagnetic profiles in Mosfellssveit. - Staðsetning sniða vegna kortlagningar
og sýnatöku.
nearby Stardalur caldera (Friðleifsson 1985). The
flows are often intercalated with sedimentary beds,
most commonly thin red partings but thicker sedi-
ments are also found, tillites as well as tuffaceous and
silt beds.
In this paper the succession is divided into 8
series (Fig. 4), four predominantly of basalt lavas and
four of hyaloclastite and sediments. The division is
based on the paleomagnetic polarity of the volcanics
as well as on their lithology. It should be noted that
the paleomagnetic polarities of hyaloclastites, given
below, are only based on measurements in the field.
a) The Gufunes hyaloclastite is the lowermost
exposed series in the area. It is found in Gufunes, in a
borehole at the Korpa river (Smárason et al. 1985)
and north of the Kaldakvísl river. It is presumably
reversely magnetized. Its thickness is uncertain, but it
is at least 250 m thick in a borehole in Gufunes (see
Tómasson et al. 1977) and the thickness of corre-
sponding series in Esja ranges from 5 to 300 m (Unit
18 of Friðleifsson 1973). Jóhannesson (1985) sug-
gested that the Gufunes hyaloclastite was a part of the
caldera filling of the Viðey volcano.
b) The Eiðsvík basalt series consists predominant-
ly of coarse-grained compound lava flows at least 20
m thick and normally magnetized. It is exposed at the
head of Eiðsvík as well as at the south coast of
Leiruvogur and along the southern bank of the
Kaldakvísl river. In Esja, this series ranges in thick-
ness from 10 to 200 m (Unit 19 of Friðleifsson 1973).
c) The Korpúlfsstaðir basalt series is reversely
magnetized, and its cumulative thickness is about 350
m. It consists predominantly of tholeiitic lava flows
but includes a pronounced unit of compound lava
flows which ranges in thickness from 30 m in the
western part of the area up to 80 m in Helgafell in the
JÖKULL,No. 41, 1991 49