Archaeologia Islandica - 01.01.2002, Side 33

Geophysical Techniques
effects. Discrete magnetic dipole anom-
alies clearly distinguish individual rocks
from the solid bedrock, and alignments
of these anomalies can reveal buried
walls. Comparison of the magnetometer
results with resistance data has con-
firmed this interpretation.
The geological input is dramatically
reduced on sites where deeper aeolian
deposits lie above the bedrock, as at
Skálholt. In such situations, the geology
is at a greater distance from the instru-
ment, allowing the subtler archaeological
anomalies to be detected. It should there-
fore be possible to assess the potential of
a magnetometer survey at a site by first
measuring the soil depth with an auger,
although this has yet to be tested.
At both Gásir and Þingvellir, booth
remains have produced distinct magnetic
and resistance anomalies, although the
small survey area at both sites prevents
their full understanding at present.
Conclusion
This preliminary study has successfully
demonstrated the effectiveness of routine
archaeological prospection techniques in
Iceland, particularly when undertaken as
part of an integrated study as discussed
here. The benefits of combining earth
resistance and magnetometer surveys has
also been illustrated, and that where pos-
sible earthwork surveys, aerial photogra-
phy and trial trenching should also be
used to better understand the geophysical
results and therefore the archaeology.
Future Work
This assessment of geophysical tech-
niques in Iceland is the fírst step in inte-
grating geophysical surveys with other
forms of archaeological evaluations.
While a number of important questions
have been answered during the course of
this study, many more have been asked,
and further research is necessary to allow
the maximum information to be extracted
from geophysical surveys.
A better understanding of the limita-
tions caused by geology and geomor-
phology is required, so that effects pro-
duced by these features may be discrimi-
nated from archaeological anomalies.
When geophysical surveys are inte-
grated into archaeological evaluations,
the time scale of most projects poses
severe constraints on fíeld geophysicists
(Gaffney et al. 1991, 1). It is therefore
necessaiy that a full understanding of the
viability and limitations of the use of
geophysical techniques in such evalua-
tions be obtained before contract field-
work can be undertaken efficiently.
Acknowledgements
This project was carried out by T.J.
Horsley for an Archaeological
Prospection MSc Dissertation under the
supervision of S.J. Dockrill, at the
Department of Archaeological Sciences,
University of Bradford. The MSc course
was funded with a NERC studentship,
and the author is grateful to NERC for its
help with costs towards the fieldwork.
Fieldwork was undertaken in collabora-
tion with the FSI and thanks are due to
their staff, in particular to Orri
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