Jökull - 01.01.2010, Page 158

L. Kristjánsson
holt, Gaukshöfði and Skriðufell, some 30 lava units in
total). However, magnetic results obtained from these
are not reported here, as they have not yet been fitted
into a common stratigraphic scheme. The remanence
directions given in Appendix 1 have been corrected
for tectonic tilt which is estimated to average 5◦ with
a down-dip direction of 30◦ east (Friðleifsson et al.,
1980; Á. Guðmundsson, pers. comm. 1992; Khoda-
yar and Franzson, 2004).
A short description of some features of the two
sampled profiles, based on unpublished information
kindly supplied by Á. Guðmundsson, Á. Geirsdótt-
ir and Th. Thordarson (pers. comm. 1992–2001), is
as follows (Figure 8). According to the numbering
of Friðleifsson et al. (1980), the Stratigraphic Units
HR 5, 7, 9 and 11 consist mostly of lavas of tholeiitic
lithology, while their Units 6, 8, 10 and 12 are rather
heterogeneous tuffaceous sediments not differentiated
in Figure 8. The bottom one-third of the composite
column is composed of the series HR 5A through 5V,
i.e., Unit 5 of Friðleifsson et al. (1980) which can be
traced across several kilometers in the area. 11 out
of over 20 mostly thin flows were sampled, 5A to
5H south of the Þverá stream and 5I to 5V along it.
All were reversely magnetized except the top one 5V
which is a lava lake. Nearby flows FO 20 and FO 21
on the east side of Þverá are also of normal polarity.
Then we find sandstone and diamictite, a couple of re-
versely magnetized flows FO 22, 23, and FO 24 with
a transitional direction on the boundary with another
normal-polarity series of medium-grained basalts FO
25–32. It is not certain where some of the HR flows
(sampled west of the stream above HR 5V) fit into the
FO profile east of the stream, but HR 7A probably be-
longs to the same reverse zone as FO 22 whereas the
normal-polarity units HR 9A,B,C,E correspond to the
top part of FO 25–32. Although no faults are shown
crossing the stream in maps accompanying the reports
of Friðleifsson et al. (1980) and Khodayar and Franz-
son (2004), a fault zone may lie between flows FO 32
and 36B. Repetition in the lava sequence at this level
is inferred from the similarity of the remanence direc-
tions in the reverse flows FO 33 and 34 with those in
FO 35 (and HR 9D) and 36A respectively. At least
two normal-polarity flows FO 36B, 37 are also found
here. Finally, sediments containing the reversely mag-
netized FD 38 (a picrite) and HR 11A,B is in turn
overlain by the normal-polarity lavas FD 39,40.
158 JÖKULL No. 60