Archaeologia Islandica - 01.01.2002, Síða 13

Geophysical Techniques
archaeological monuments and land-
scapes.
General principlcs of geophysical
prospection
For the prospection of archaeological
sites a great number of different geo-
physical techniques and instruments
exist, each with their own capabilities
and limitations. Most techniques work by
detecting a contrast in the material prop-
erties of the subsurface, producing a geo-
physical anomaly. On an archaeological
site each method can have different
potential depending on the nature of the
buried archaeology, geology and possibly
climate and land-use.
Following data-collection it is then
necessary to determine the causative
body, and to interpret this as an archaeo-
logical feature (Horsley 1998, 17).
Geophysical surveys suffer from an
inherent ambiguity in the conclusions
that can be drawn, as many dififerent sub-
surface configurations could reproduce
the same observed measurements
(Kearey and Brooks 1984, 8-9). It is
often the case that processing is required
to aid in the identification and interpreta-
tion of anomalies in a survey, but altering
the raw data in any way must be under-
taken with care.
Much has been written about the differ-
ent geophysical techniques routinely
employed in archaeological surveying, in
particular the two methods employed for
this evaluation: fluxgate gradiometry and
earth resistance methods (see Clark,
1975; 1990; Keary & Brooks, 1984;
Scollar et al., 1990, Telford et al. 1976,
among others). A full background to the
techniques and theoretical details will not
be given here, and the reader is advised
to look at these works, and to the guide-
lines for the use of geophysical tech-
niques in archaeological field evaluations
provided by David (1995) and Gaffney et
al. (1991).
Archaeological prospection in Iceland
In recent years, Fornleifastofnun Islands
(FSI) has undertaken an interdisciplinary
investigation of the settlement of Iceland,
including topographical surveys of extant
earthworks, chemical surveys and exca-
vation (Friðriksson & Vésteinsson,
1998a, 1998b). However, geophysical
prospection as an additional technique
for site location and interpretation has
never been systematically applied in
Iceland, either on its own or as part of an
integrated strategy.
Archaeological features are not
always represented on the surface, but
even where earthworks do exist, their
morphologies may appear ubiquitous and
defy attempts at qualification or charac-
terisation (Dockrill and Gater, 1992).
Geophysical surveys would be an effec-
tive and unique tool in aiding this multi-
disciplinary research in Iceland, in the
non-destructive characterisation and
interpretation of archaeological sites
identified by other methods, or in locat-
ing new sites in its own right.
Before this can happen however, a
proper and systematic assessment of the
techniques in this new environment is
necessary to allow an understanding of
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