Geoarchaeology:Geophysics
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[edit] Geophysics and Geoarchaeology
Geophysics employs a range of survey techniques to detect subtle changes in soil properties (principally moisture, magnetics and density) that can be indicative of buried archaeological features. Spatial survey highlights patterns that may relate to the presence of buried remains. A vast range of electrical, magnetic and acoustic techniques have been tried, but the most commonly used techniques are:
- Resistivity and resistivity profiling - resistivity is linked to soil moisture content, but is also affected by soil structure, texture, density, salinity and temperature.
- Magnetometry - measures the magnetic characteristics of the mineral grains in the soil which can be enhanced by burning. However, the mineralogy of the soil and the presence of modern iron artefacts can create a high, noisy background.
- Ground penetrating radar - detects changes in density through measuring the reflection of radio waves. The attenuation and scattering of the beam is also affected by soil moisture content, soil texture and salinity or conductivity of the soil solution.
No matter what the technique some basic knowldge of the soil conditions is a prerequisite for understanding and interpreting any patterns that emerge. Soils knowledge can also help in the interpretation of poor or negative geophysical results by helping to predict areas where good geophysical results might be expected and other areas where the soil conditions might interfere with the results of the survey, potentially giving negative results in areas of buried archaeology.
A case study example of the use of soils data to help interpret geophysical survey is:
- Lithics scatter site at Boncyn Ddol, Gwynedd, Wales – a spatial topsoil survey of phosphate and magnetic susceptibility.
- Bronze Age cairn at Carneddau, Powys, Wales – investigation of old ground surface and cremation fills through complementary phosphate and magnetic susceptibility analyses.
- Archaeological prospection at Oakham, Leicestershire – use of fractional conversion in the interpretation of field magnetic susceptibility survey data.
[edit] External websites
- British Archaeological Jobs Resource, Archaeological Geophysics: a short introduction
- Archaeology Data Service, Geophysical Data in Archaeology: a guide to good practice, by Armin Schmidt
- Wikipedia, Archaeological Geophysics
