During March of 1991, Stephen Ball and personnel from the Glenn A. Black Laboratory of Archaeology conducted a magnetic survey of the Clampitt site. The survey was carried out using with a Geoscan FM36 fluxgate gradiometer designed to detect subsurface magnetic anomalies. Past research at prehistoric sites in Indiana has shown that this instrument was useful for detecting prehistoric "excavations," such as hearths, cooking pits, refuse pits, etc., containing oxidized materials (e.g. fire-cracked rock, heat-altered soils, or fired-clay ceramics) (Ball 1993a, 1993b).
Readings of magnetic intensity were taken at 25 cm intervals within 20 meter by 20 meter grid squares. A total of eight adjoining grid squares, which were aligned west to east, were surveyed over a period of three days. The completed (20 meter by 160 meter) survey transect covered what was, at that time, believed to be the midline of the site (Figure4).
The magnetic readings were mapped using computer graphics software in an attempt
to reveal areas of varying intensities across the survey transect. The results
immediately revealed a number of distinctive dipolar anomalies (closely spaced
very high and very low intensity readings) which were interpreted as historic
metal. Of greater interest were a large number of high intensity anomalies which
appeared as discrete circular and ovoid "spots" which measured between 0.5 and
1.0 meter in diameter (Figure
13). It was hypothesized that these locations represented buried prehistoric
features containing oxidized materials. The largest concentration of these "feature"
anomalies were located in the easternmost grid square (Grid 8), but scattered
anomalies of this type occurred all along the surveyed transect. After a consideration
of the results of the magnetic survey, it was decided to "ground-truth" several
of the anomalies during the 1991 excavation season. A detailed discussion of
the methods and results of this investigation are described in Appendix A.
