Archaeological sites may be occupied on surfaces with active deposition, erosional surfaces, or stable surfaces undergoing soil formation. If a site is located in an environment of active deposition, it is likely that the site will be buried and incorporated into the stratigraphic unit. If the sedimentation rate is rapid, there will be a clear distinction between this occupation level and overlying units or subsequent occupations. If the sedimentation rate is slow, archaeological materials from successive occupations could become mixed together since they would not be separated by depositional units.
Soils
Soils in stratigraphy are important to archaeology because they indicate a significant period of stability when a landscape surface was stable and not undergoing significant deposition or erosion. Soils may take many years to form and therefore these surfaces would be exposed to potential human occupation during these periods of stability as with modern landscapes. In addition, buried soils (i. e., buried paleosols) provide geoarchaeologists with valuable information about surface topography and past landscape conditions. In addition, their physical and chemical characteristics aid in reconstructing past climates.
However, soils can cause problems for the preservation of an archaeological site. Soil formation processes can have a direct influence on the preservation of archaeological material. Such processes include the shrinking-swelling of clay, mineral oxidation-reduction, the accumulation and decay of organic matter, translocation or removal of salt, eluviation, iluviation, as well as bioturbation. Organic material such as plant, shell, and bone can deteriorate from leaching, oxidation, and biogenic degradation in soils. Downward translocation of carbonates promotes bone deterioration in leached horizons. Eluvial horizons become more prone to erosion and the stratigraphic context can be destroyed for a site located in that soil horizon. Bioturbation is often more common in soils and can translocate artifacts to the surface. Soils do provide some benefits for preserving the archaeological record. For example, the translocation of salts in calcic horizons can promote the preservation of shell and bone.
Site Preservation
There are many different formation processes which play a role in the preservation of the archaeological record. Some preserve cultural material better than others. In an ideal situation, a site would be rapidly buried by sediments with little disturbance and be minimally affected by postdepositional processes. In essence, such an environment would seal an archaeological deposit into the stratigraphy, for example, many cave sites have this level of preservation. However, well-preserved archaeological sites can be later threatened by postdepositional processes and landscape destruction. In reality, a majority of archaeological sites are affected by some type of postdepositional process and geoarchaeological studies are necessary to evaluate the impact of these processes on interpretations of past human behavior.
World History
