Archaeo-Physics, LLC - geophysical survey and subsurface mapping

Case Study


Magnetic Field Gradient Survey

See also: Summary Page - Resistance Survey

Magnetic gradiometer map showing copper-age pit houses

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Correlation between magnetic anomalies (blue) and resistance anomalies (red)

Numerous circular, rectangular, or square magnetic field gradient highs, 6-8m across, appear in the data that are thought to represent semi-subterranean pit house features. Most of these anomalies have a direct correlate in the electrical resistance survey results. This correlation significantly increases the degree of certainty of our interpretations. Many of these positive anomalies are bounded by linear field gradient lows. These lows may represent a building material composed of a lower susceptibility material, or they may simply be a non-cultural negative component of the complex induced magnetic field created by these archaeological features.

Many of the magnetic anomalies interpreted as semi-subterranean pit house features possess an small internal, higher amplitude magnetic high. These may represent internal hearth features within the houses.

Numerous high-amplitude (generally in the red/blue range of the color scale), short wavelength anomalies are visible in the magnetic data. Anomalies with these characteristics usually are created by modern ferrous iron debris at or close to the ground surface.

Numerous small circular magnetic field gradient highs are visible throughout the survey area. These anomalies often seem to appear in pairs, and are often clustered around the perimeter of the apparent semi-subterranean pit houses. These anomalies are interpreted to represent possible storage/refuse pits, burial pits, external hearth features, or similar features.

Many small circular magnetic field gradient highs may form alignments or patterns of significance. These anomalous patterns may represent the remains of structures external to the semi-subterranean pit houses such as corrals or stockades.

Numerous subtle magnetic field gradient highs in the vicinity of N100/E980 form patterns that may be significant. These patterns are often circular, and in some cases have a small central magnetic field gradient high. These anomalies may represent small structures external to the semi-subterranean pit houses. Those with central magnetic highs may have internal fire hearths.


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