Jökull - 01.07.2003, Blaðsíða 28

Leó Kristjánsson
MI 0
Skmf
A B&C
Fagr.
Figure 2b. Low-latitude paleomagnetic poles reported in this paper: SkmfA and SkmfB+C: average poles from
two geographically distinct lava groups in the Skálamælifell excursion. Fagr.: mean pole from those sites in
Fagradalsfjall (Figure 4) which have southerly declinations. MI 0, sea-level site SSE of Mikligarður, Reykjavík.
– Staðsetning sýndarsegulskauta sem samsvara meðal-segulstefnum í Skálamælifelli og ýmsum hraunlögum þar
nálægt, í meirihluta Fagradalsfjalls, og í opnu við sjávarmál suðsuðaustan Miklagarðs í Reykjavík.
at Sundahöfn harbour, less than 100 m distant from
the MI outcrops. He reports finding a single reversed
remanence direction (Incl. -61Æ after AF demagneti-
zation) in a lava unit at about 10 m above sea level.
It overlies a sandstone with indistinct shell remains,
and 3–4 other lavas down to a few m below sea level,
and again 30 m of sediments. Richter did not find a
low-inclination lava in his drill core nor evidence of
lignites, and it is not clear how his core may correlate
with the sequence MI 0–2.
Following the discovery of the intermediate-
direction site MI 0, sampling was made near sea level
in its vicinity (ML and SU in Table 1b) to look for
comparable directions but none were found. The most
likely explanation is that the Elliðavogur marine sed-
iments partially filled depressions in a landscape of
early Quaternary lavas; then, depressions in the sed-
iment were in turn filled by units of gray lavas and
lignite- bearing sediments, before the main phase of
emplacement of the gray lavas. The early units of
these lavas and the associated terrestrial sediments
seem to be small in extent, and discontinuous.
General results on remanence directions
As already noted by Kristjánsson et al. (1980), rema-
nence directions in the gray basalts are quite clustered:
if the site MI 0 is not included, the between-flow an-
gular standard deviation for the 32 site groups of Table
1 is only 11Æ, i.e. about half of the uppermost Ceno-
zoic value quoted above. If MI 0 is included, the a.s.d.
will obviously increase but its magnitude will depend
on the extent to which the directions from other flow
units in Table 1 have been grouped. In addition to MI
0, those directions of Table 1 and Figure 2a which lie
farthest away from the central axial dipole field are
those with rather low inclinations (<65Æ) and easterly
declinations (RE 22–23, KA 0–2, KC 1, MI 1). How-
ever, the distances between these outcrops are so great
that correlation on the basis of only the magnetic di-
rections would not be realistic.
26 JÖKULL No. 52, 2003