Conductivity and Magnetometer Survey of the Carty Site

Cultural Resource Analysts, Inc., conducted a conductivity and magnetometer survey of the Carty Site (33PI646) near Columbus, Ohio. The Carty survey, which used both gradiometer and earth conductivity meter, is a nice example of how even a survey of a limited area can produce very interesting results. It also indicates how the use of two survey instruments can enhance interpretation.

The work was done at the request of the Ohio Historical Society, one of several steps in their efforts to record this interesting Woodland site damaged by construction. In the following figures, note that the squares are only 10-x-10. Because the survey area was limited, high-density readings were made. Using the gradiometer, nT was measured at .125 cm intervals along transects 50 cm apart. With the conductivity meter, mS/m was collected at 25 cm intervals along transects 50 cm apart.

Cutting across the surveyed area was a low “ridge.” There was some suggestion that this might be a fragment of an earthwork. The magnetic survey indicates that there is a magnetic “high” below this ridge (cutting across the figure from east to west). Roughly at right angles to this ridge (and running north to south) was a lesser ridge. The magnetics suggest that this may be a series of metal signals, possibly iron fragments from an old fencerow. A prominent magnetic “high” is on the western margin of the figure.

In the conductivity survey figure, the magnetic feature under the ridge appears as a conductivity “low.” Taken together, the two data sets suggest that this may well be a burned feature below the ridge, perhaps an earlier “fence” or enclosing feature. At the same time, the lesser ridge indicates several intense conductivity “lows” strongly suggesting metal targets; however, the magnetic feature on the western margin also shows up in the conductivity data as a “low.” In this case, the conductivity signal might suggest a burned feature rather than a metal target.

Limited test excavation and the liberal use of a metal detector could establish the nature of these anomalies and allow the Historical Society to concentrate on a research strategy for this interesting site.

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