Archaeology Case Studies: Grad601 Gradiometer
These six case studies, courtesy of Oxford University, illustrate the Grad601 Single Axis Magnetic Gradiometer system's ability to detect and provide important information on underground archaeological features. The surveys demonstrate the effectiveness of a magnetic survey over a range of geological conditions.
Iron Age and Romano-British features, in sand and limestone:
- Archaeological Survey 1 - Noah's Ark Inn
- Archaeological Survey 2 - Cherbury Camp
- Archaeological Survey 3 - Hinton Waldrist
Romano-British settlements, in Kimmeridge Clay:
Banjo enclosures and Roman villa, in upper greensand and chalk:
A geophysical survey can detect archaeological features which have been cut through the subsoil and which have later filled with topsoil and other material. Examples of such features are ditches, gullies and pits, detected as positive magnetic anomalies and represented by dark areas on the images. Surveys 1 and 5 also demonstrate the ability to detect surviving masonry foundations within the subsoil, which are negative magnetic anomalies, appearing as lighter areas on the images.
The success of magnetic surveys depends on the difference in magnetic susceptibility between the topsoil and subsoil. Human habitation and activity can increase the magnetic susceptibility of the topsoil. Surveys in these areas produce excellent results.
We are very grateful to William Wintle, Paula Levick and Dr David Griffiths of Oxford University for allowing us to reproduce their results.