Jökull - 01.01.2001, Blaðsíða 46

Leó Kristjánsson and Ágúst Guðmundsson
Figure 8. Simplified polarity columns for the Skarðsheiði profiles SI, SJ, SS (present paper), SH (Kristjánsson
and Sigurgeirsson, 1993) and C (Wilson et al., 1972), and the Akrafjall profiles FA, FB of Kristjánsson et al.
(1980), aligned at the onset of the polarity zone N5 of Einarsson (1957). Polarity time scale of Cande and
Kent (1995) on the right hand side, including assumed correlations with polarity zones (Franzson 1978, and
others). Black is normal polarity. C = conglomerate, PF = mostly porphyritic flows, CP = mostly compound
flows. – Einfaldaðar jarðlagasúlur úr sniðunum SI, SJ og SS (í þessari grein), SH og C (úr eldri greinum) í
Skarðsheiði. Til vinstri er sýnd samsvarandi súla úr sniðum FA og FB í Akrafjalli. Til hægri er tímakvarði
umsnúninga jarðsegulsviðsins skv. Cande og Kent (1995), með áætlaðri samsvörun segulskeiða við hraunlaga-
syrpur. Súlurnar eru teiknaðar þannig, að neðstu lög í N5 standast á. C = völuberg, PF = dílabasalt ráðandi,
CP = dyngjusyrpur.
The R5–N5 boundary is also thought to appear
in profile FA (Kristjánsson et al., 1980) in Akra-
fjall, at about 350 m altitude. The stratigraphic col-
umn here is in some respects different from that in
Skarðsheiði. No transitional flows have been demon-
strated at this boundary locality and it has not been
dated, but the upper part of R5 is largely composed of
feldspar–porphyritic flows as in Skarðsheiði and may
thus belong to the same phase of volcanism. These re-
sults also support the view of Franzson (1978), Geirs-
dóttir (1991) and others that conspicuous conglom-
erate beds at the top of these mountains are essen-
tially contemporaneous. Beds of the same or simi-
lar age can also be found in the valleys northeast of
Borgarfjörður. The present study and previous de-
tailed mapping in the Hvítársíða area of Borgarfjörður
(McDougall et al., 1977) may be built on in fur-
ther mapping work elsewhere in the Borgarfjörður–
Hvalfjörður area.
46 JÖKULL No. 50