Archaeo-Physics LLC was contracted by GCM Services,
Inc. to perform a geophysical investigation as part of archaeological
investigations at 48WE917, a Late Archaic site in Weston County,
Wyoming. The geophysical investigation consisted of magnetic field
gradient surveys of several areas within the site, and an electrical
resistance survey of a small area within one of the larger magnetic
survey areas.
Based on artifacts recovered from the surface, the
Huckins site appears to have been repeatedly occupied from at
least the Late Archaic to Late Prehistoric periods. Open air campsites
such as Huckins are often a composite of clusters of features
and artifacts. This type of site may cover hundreds if not thousands
of square meters, but in reality there are large areas within
it that are virtually devoid of cultural remains. The geophysical
survey was undertaken as part of phase II evaluation of the site
in order to identify loci that might be associated with different
occupations and activities. It is unlikely that conventional methods
alone could produce a large enough sample of positive data for
meaningful description and hypothesis testing on a site of this
size and complexity.
Lithic tools and debitage and fire cracked rock were
scattered across the site, and several hearths were visible on
the surface. Very few modern artifacts were found.It was anticipated
that in an archaic cultural context, hearths were likely to be
the most detectable cultural features. Magnetic field gradient
survey was chosen as the principal method of investigation because
the thermally altered mineral grains in rock and soil often create
a strong and distinctive magnetic anomaly.
The magnetic field gradient and electrical resistance
surveys were successful in detecting probable cultural features
all of the areas surveyed. Anomalies of interest appear in discrete
clusters, generally near the edge of the flat top of the landform.
These clusters may represent separate social units or successive
occupations.
Most of the suspected features are thought to be hearths. Correlation
between exposed hearths and magnetic anomalies allows a high degree
of confidence in the interpretation of these anomalies. A number
of other anomalies appear to be culturally patterned, but cannot
be as easily interpreted without ground truthing. Results of the
resistance survey were more ambiguous, but there is some correlation
between resistance and magnetic data sets.
In general, the site had very little magnetic "clutter"
due to modern metal or geologic variance. The standard deviation
of each of the survey areas ranged from 0.16nT to 0.64nT (after
processing). Anomalies thought to be caused by hearths have amplitudes
up to several tens of nanoTeslas and contrast starkly with the
very uniform background. Anomalies thought to be caused by hearths
appear as discrete magnetic highs with values ranging roughly
from 1nT to 50nT. While in-situ hearths often appear as bipolar
anomalies because of remanent magnetic effects, hearths at 48WE917
appear with only a very weak negative component. An explanation
for this is that bioturbation and other small-scale disturbances
may have randomly re-oriented mineral grains in the soil. Remanent
effects are thus largely neutralized, leaving only an induced-field
anomaly caused by enhanced suscuptibity. Other more subtle magnetic
highs appear that may be caused by other types of features, such
as houses and pits.
Related content: Geophysical
survey as an approach to the ephemeral campsite problem
