5. Detecting
the Shriver Circle Earthwork, Ross County,
Ohio by Jennifer Pederson
and
Jarrod Burks
Ephraim Squier and Edwin Davis surveyed the
Mound City Group area over 150 years ago. Although
primarily interested in this earthwork complex,
with its more than 20 mounds surrounded by a
low embankment, their map also depicted an oblong
circular enclosure located less than 1,500 feet
from Mound City’s southern embankment wall.
Named after Henry Shriver, owner of the surrounding
farmland in the mid-1800s, the Shriver Circle
consists of a large circular embankment flanked
by an exterior ditch (Figure 1).
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Six gateways break the circumference of
the circle, which has a diameter exceeding
1,000 feet. In the 1840s, the embankment
measured 5 feet high and 25 feet wide at
the base, while the ditch was 4 feet deep
and 20 feet wide (Squier and Davis 1848:Plate
XIX).
Near the enclosure’s center, Squier
and Davis mapped a low mound 40 feet across
and 5 feet high. Excavation into the mound’s
center uncovered a large altar containing
burned bones, 10 copper bracelets, and 2
plates of mica, leading Squier and Davis
(1848:55) to conclude that the mound was “clearly
a place of sacrifice.” |
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 Figure
1. The Shriver Circle, the survey
area, and selected contemporary features.
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Artifacts found within this
mound coincide with materials found in quantity
at Mound City (e.g., mica). However, some
of the artifacts, namely the copper bracelets,
look similar to those found in mounds attributed
to the Adena culture.
Today the earthwork has all but disappeared
from the ground surface. Even prior to Squier
and Davis, the earthwork was impacted by
nearly 50 years of agriculture, bisected
by a main thoroughfare, and trenched for
the construction of the Ohio and Erie Canal.
Since the mid-1800s, the Shriver Circle has
suffered through a number of additional disturbances,
including continued agricultural plowing,
grading to make way for parade grounds associated
with the WWI Camp Sherman training facility,
the construction of a large prison, and the
expansion of State Route 104. Each of these
disturbances, joined by a healthy community
of ground hogs, has chipped away at various
parts of the earthwork. Until recently, no
intensive archeological research had been
conducted at the site.
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| In spring
2001, archeologists from Hopewell Culture
National Historical Park began geophysical
testing of the site in an effort to relocate
its southern limit.This research was driven,
in
part, by a proposal to widen State
Route 104. We conducted a survey of
a 60-x-60-m area using a Geoscan Research
fluxgate gradiometer, the FM-36. This
survey clearly located a 60-m-long
section of a ditch and embankment that
correlate very closely to the measurements
given by Squier and Davis in 1848 (Figure
2). |
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 Figure
2. Magnetic survey data from the
Shriver Circle collected during the
Archeology for Teachers
Workshop, June 2001. Crew included J. Pederson, P. Castro, L. Davis, E. Karshner,
and J. Burks.
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Furthermore, the linear
bands of magnetic high and low readings
over the ditch suggest that it was
partially in-filled by organically
rich soils,
especially along the outer edge,
and partially in-filled by less- magnetic
soils along the interior edge, perhaps
eroded down from the embankment.
Whether
this signature is the result of rapid
in-filling from agricultural plowing
subsequent to Squier and Davis’s
visit or a backfilling event during
construction of Camp Sherman remains
to be discovered. Spurred on by these results, we enlisted
the help of teachers enrolled in the
park’s 2001 Archeology for Teachers
Workshop. Over the course of a week,
the teachers collected magnetic, resistivity,
topographic, and GPS data. The additional
magnetic data included several anomalies
with the potential for being cultural
features.
The transect of resistivity data was
collected with off-the-shelf components
(i.e., a digital multimeter, barbecue
skewers, and a six-volt lantern battery)
arranged in a Wenner array of four
probes with one-meter spacings. Even
this simple geophysical test (Figure
2), which we conducted to demonstrate
the accessibility of geophysics for
pre-college teaching, revealed useful
information about the Shriver Circle.
Not only did it produce a classic double-peak
signature over the ditch, but it also
seems to have detected the inside edge
of the embankment -- as did the magnetic
survey.
While other projects now dominate
our summer agenda, we plan to return
to the Shriver Circle to test the western
portion of the site using these same
techniques. By using geophysical testing
and accurate mapping techniques, we
can efficiently document subsurface
features covering large areas without
excavation. In addition, these techniques
clearly show that earthworks, without
surface expression, can still be successfully
located even after 200 years of historic
and modern disturbance.
Reference Cited
Squier, E. G., and E. H. Davis
1848 Ancient Monuments of the Mississippi Valley.
Contributions to Knowledge No. 1. Smithsonian Institution, Washington, D. C.
About the Authors
Jennifer Pederson is Park Archeologist
and Jarrod Burks is Archeological Technician,
both at Hopewell Culture National Historical
Park. Both authors are Ph.D. candidates
at Ohio State University. |
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