1. Uri A. Grunder
Capstone – Tuesday 10-12
Geophysical Indicators of Culturally Emplaced Soils and Sediments Review
This article, published in 2002, is representative of pioneering efforts to use non-invasive
geophysical sub-surface testing methods to delineate between naturally deposited soils and
culturally deposited soils. Particular interest is claimed towards the identification of what is
below the surface. A multitude of geophysical tools are used to help examine the effectiveness of
various geophysical testing on archaeological sites. These methods included seismic surveys,
radar surveys, magnetic susceptibility measurements, conducting and resistivity soundings.
These methods were drawn to record which method would most effectively distinguish the
Anisotropy (physical direction which magnetic elements within the sediment align during
deposition that may be related to the magnetic pull of the Earth at a given time) of sediments
(Dalan pg. 786). The actual tools used to conduct these observations were equally diverse. This
study was performed at three separate sites within known Mississippian mound building areas as
the research revolved aroundthe identification of differences between naturally and culturally
deposited soils. These sites included: The Cahokia Mounds State Historic Site, Effigy Mounds
National Monument, and the Hopeton Earthwork.
Three assumptions were made prior to fieldwork which heavily leaned on Anisotropy.
The first was that there would be a difference in Anisotropy between naturally and culturally
deposited soils and that this difference may be observed during any or all of the methods
mentioned above. The second assumption asserted the location of naturally deposited soils which
were tested and compared against the data from known culturally deposited mounds.The final
assumption held that naturally deposited soils would retain a consistent Anisotropy while
culturally deposited soils would be muddled or at least starkly different than their surrounding
natural soils (Dalan pg. 807).
The results of this investigation were muddled to say the least with results that revealed
different tests proved effective at different locations. Magnetic susceptibility and resistivity
soundings were noted to have proven effective at the Cahokia Mounds site – though inconsistent
with the seismic tests that were conducted in the same area. Several seismic tests, radar (ground
penetrating radar), coring samples, and resistivity tests were conducted at the Effigy Mounds site
with Seismic refraction techniques being distinguishing features from other techniques and tests
at the Hopeton Earthwork site leaned heavily on magnetic susceptibility soundings rather than
other tests carried out in the area.
The recorded methods section of this document was very well detailed which is fantastic
for any other groups looking to repeat the experiment. I would also assert that using this
document as a guide, incoming investigators may test the same location and return with the same
results or alter the research design and test their luck with new results. I say this because many of

2. the methods being used are non-destructive and often (except for the occasional coring samples)
are composed of sticking electromagnetic poles into a small section of the earth or striking a
metal platform on the surface of the earth. I appreciate the value of exploring new and non-
invasive ways of identifying anthropogenic landscapes.
My main concern is that no diagnostic fingerprint can be identified that may be relied on
using one instrument or amongst modified landscapes in general (Dalan pg. 781). I don’t believe
that it would be practical to arm archaeological teams with the wide array of geophysical testing
units for each and every project and without the diversity of tests the margin of error seems too
high. I would agree that geophysical testing is useful to the identification of culturally modified
soils however it very much does need to grow and expand into the archaeological field. I would
also be interested in testing the Anisotropy of soils further away from the sites themselves that
may be suspected of being naturally deposited using the same geophysical tests.