Archaeo-Physics, LLC - geophysical survey and subsurface mapping

Case Study

Tell Ahmar (Til Barsib)

City Wall and Monumental Architechture

See also: - Summary page - Urban Zone - Isolated Farmstead - City Wall Resistance Data With Magnetic Overlay

Tell Ahmar - city wall and monumental architecture

City wall and monumental architecture - interpretations of geophysical data

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Until this survey, the location of the western portion of the city wall was unknown. This shade plot shows the city wall and a zone typified by monumental architecture just within the wall.

On the smaller image, anomalies associated with architectural features are indicated with colored lines. The wall (yellow)is thought to be constructed mainly of large basalt blocks. Buildings in this zone are large, and often incorporate basalt or fired brick (orange) in their construction. Mud brick or limestone (dark blue) are also used. An isolated linear low (light blue) appears outside the city wall. This type of feature is often associated with presumed farmsteads outside the city wall.

Basalt building stone, fired brick, and rather massive pottery are all common components of the archaeological deposits at Tell Ahmar. These materials have a remanent, or permanent magnetic field which appears in the data as a bipolar (having both a positive and negative component) anomaly. The magnetic signatures can be confused with that of ferrous metal. It is therefore not possible to always distinguish bipolar features of ancient origin, but the pattern or configuration of many of these anomalies indicates that they are ancient in origin.

Mud brick or limestone architecture appears as subtle magnetic lows, because these materials have a lower magnetic susceptibility than the surrounding soil.

Because the soils have a high magnetic susceptibility, small scale topographic variation can produce rather strong anomalies. Irrigation ditches and alternating rows and furrows cause anomalies in this survey area which are often stronger than those associated with ancient architectural features, but can be distinguished by their patterning.

 

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