Jökull - 01.01.2001, Page 37

Paleomagnetic studies in Skarðsheiði, SW-Iceland
Figure 2. Topographic contours of the Skarðsheiði mountain. Our main paleomagnetic sampling profile is com-
posed of profiles SI (in the hillslope Stóra–Brattatorfa to the Litlahorn peak) and SJ (in Skarðshyrna and the
Skarðshyrna–Heiðarhorn ridge), see Figure 3. SS (Figure 5) and SW are short supplementary profiles. The
location of profile SH (Kristjánsson and Sigurgeirsson, 1993) as well as the estimated location of the upper
part of profile C (Wilson et al., 1972) are also shown. – Hæðarlínukort af Skarðsheiði, með samsetta sýna-
söfnunarsniðinu SI–SJ í Litlahorni, Skarðshyrnu og Heiðarhorni, og styttri sniðum SS og SW. Staðsetning fyrri
sýnasöfnunarsniða í Villingadal sést einnig.
glomerate between FA 51 and 52. Geirsdóttir (1991)
referred to the sediment FA 51/52 as “diamictite unit
1”, indicating contemporaneous sediment formation
in the Akrafjall area and in the Borgarfjörður area
some 30 km to the northeast (the NP 319/320 sedi-
ment and NT 3/4 sediment, both occurring one or two
flows above the base of the Mammoth subchron in the
profiles of McDougall et al. (1977)). These sedi-
ments were for many years considered to herald the
onset of cold climate in South–Western Iceland, but
the sedimentological analysis of Geirsdóttir (1991)
indicates that glacial conditions did not prevail until
about 0.5 M.y. later.
Paleomagnetism – methods
Sampling and measurements followed procedures
used in many previous paleomagnetic surveys in Ice-
land. 2.5 cm cores were collected by a portable drill
and oriented with respect to the Sun or by sightings on
distant geographical features. Generally, four samples
were collected from each unit, spread over a distance
of 1 m to several m laterally. Flows SI 24–27 and SJ
1 were thin and crumbly, so that SI 27 and SJ 1 were
omitted, and the unit numbered SI 24+ in Table 1 rep-
resents two samples from flow 24 and two from 25.
Exposures of flow interiors are very good, and not dis-
turbed by block movements, dikes, chemical weather-
ing or other such factors. Remanence measurements
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