Archaeologia Islandica - 01.01.2002, Síða 20

Timothy J. Horsley & Stephen J. Dockrill
structed over a stone foundation (Bruun,
1928; Hermannsdóttir, 1987), and these
results indicate that the magnetometer is
responding to individual, near-surface
igneous rocks.
The results from the area over booths
are at fírst sight not entirely clear,
although with comparison to the aerial
photograph (Figure 2a), many of the pos-
itive anomalies coincide with the high
banks.
The data also indicates quite a clear
difference between the booth area and the
region between this and church earth-
works where no surface features exist.
This might confirm that booths were not
present in this area.
Earth resistance results
Only a small area over the churchyard
was surveyed with the earth resistance
meter, however the results show great
potential for future use of this method at
Gásir. The bank of the churchyard has
been detected as a low resistance anom-
aly, although such a feature might be
expected to produce a high resistance
response due to the better drainage. Low
resistance anomalies over turf banks and
mounds were detected elsewhere in
Iceland in this survey (e.g. Neðri As -
midden, Nes - farm mound), and implies
that the turf used in their construction is
water retentive. This would result in the
thick turf deposits found in such features
to be better electrical conductors than the
surrounding soil. Curiously, there are
bands of very low resistance linear
anomalies within the bank, roughly coin-
ciding with the positive magnetic anom-
alies thought to be due to rocks. However
there are no positive resistance anomalies
indicating buried stones. These lower
resistance anomalies might be due to
bands of more-retentive turfs, although
the underlying cause for these results can
only be confirmed by excavation.
Both survey techniques have been influ-
enced by the presence of frost hum-
mocks, or thufur, a periglacial phenome-
non that distorts the ground surface. They
are visible on the plots as areas of back-
ground noise, although the effect is more
intense in the earth resistance data. At
present the degree to which these hum-
mocks affect the results of an earth
resistance survey is not known.
Conclusion
Geophysical surveys at Gásir have only
been undertaken over a small sample of
the site, yet demonstrate the potential of
these method for providing archaeologi-
cal information for this site and for simi-
lar features elsewhere.
Such prospection could be used to
provide evidence for the use of some of
these booths, and possibly locate areas of
industrial activity. By surveying a much
greater area, it should be possible to
determine the extent of the booths, and
hence defrne the full extent of this impor-
tant site.
Skálholt, Arnessýsla
Situated in the lower part of the
Biskupstungur valley between the rivers
Hvítá and Brúará, Skálholt is one of
Iceland's places of special historical
interest. Within two centuries of the set-
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