Archaeo-Physics, LLC - geophysical survey and subsurface mapping

Case Study

Tell Ahmar (Til Barsib)

City Wall and Suspected Gate

See also: - Summary page - Urban Zone - City Wall & Monumental Architecture - Isolated Farmstead

City wall and gate - lectrical resistance image with magnetic overlay
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The image above shows a shade plot of electrical resistance data showing the city wall and a number of adjacent structures. Magnetic field gradient data has been overlaid as colored contours. Corelation between the two data sets can greatly aid in their interpretation.

  • Orange - magnetic anomalies associated with city wall
  • Red - resistance anomalies associated with city wall
  • Dark blue - other magnetic anomalies
  • Light Blue - low resistance anomalies
  • Green - high resistance anomalies

Mud brick walls are thought to appear as diffuse low-resistance anomalies, generally linear. Low resistance anomalies might also be caused by organically enriched features or a variety of other cultural or natural features.

High-resistance anomalies may be caused by concentrations of stone or fired brick. Where a resistance high is spatially correlated with high amplitude bipolar (both positive and negative) anomalies, basalt or fired brick is suspected. Where resistance highs are correlated with weak magnetic lows, we suspect limestone to be the origin of the anomaly.

To date there has been no invasive testing of the geophysical survey results within this area. The identification of the city wall can be made with some confidence by interpolation of ground truthing results and by large-scale patterning in the survey data. Limited excavation would greatly inform our interpretation of this data.

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