Geoarchaeology:Soils

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Soils in Geoarchaeology
Soils are formed by the in-situ physical, chemical and biological modification of sediments and/or underlying geology. The parent materials for these soils may be natural or anthropogenic sediments. The scientific study of soil is termed pedology.

During periods of relative stability (i.e. when there is little net deposition or erosion), soils can develop in archaeological and natural sediments. Soil formation alters the properties of these deposits and can destroy evidence of individual depositional events as roots, worms and other soil animals mix (bioturbate) the upper layers of the soil. Soil analysis, therefore, is important in the reconstruction of site formation processes. It can help identify phases of stability and may help to identify where stratigraphy has been lost and any relic traces that remain. This can be particularly important when trying to date deposits.

Soil processes may also change the composition (texture and organic matter content) and colour of deposits. These changes occur in bands or layers (horizons), which are superimposed over the top of depositional stratigraphy and may confuse stratigraphic interpretation. Understanding this post-depositional modification is an important part of deciphering the formation of a site.

The nature of the soil that develops depends very much on environmental conditions. Pre-occupation landsurfaces and other palaeosols can be an important source of environmental evidence elucidating changes in climate, vegetation and soil conditions. Soils are also an important resource as a medium for cultivation. Where buried land-surfaces have been preserved, soil analysis can be used to gain information about former cultivation and land management techniques.

Modern topsoils may also hold information about the presence and nature of former soils. Where sites are not too deeply buried and where modern contamination hasn’t been an issue, concentrations of phosphate and other elements such as lead, zinc, calcium, and copper in the topsoil may be mapped to help identify new sites, target areas for excavation, and identify the extent of a site.

Examples of the study of soils in archaeology include:
 * Buried soil at Pegwell Bay, Kent

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