Tutorial:Burial Processes

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Processes of change in the burial environment
Diagenetic processes that operate in the burial environment include:

Organic matter decomposition
Even if a deposit is isolated from the surface, the ubiquitous nature of soil micro-organisms means that they will still be present in some form, and hence can attack organic materials. Even in anoxic conditions there are many micro-organisms capable of oxidising organic remains (Hopkins, 2004). Hence, although burial favours organic preservation by slowing the process of decomposition it rarely stops it altogether.

Chemical weathering
Chemical processes in the burial medium are largely mediated by the chemistry of the soil water(Pollard, 1998). Dissolved element concentrations, pH, and redox potential all affect the corrosivity of the soil water. Dissolution, oxidation, hydrolysis and corrosion are typical chemical weathering reactions in the burial environment. These processes can affect the preservation of inorganic archaeological artefacts.

Iron redistribution
Iron redistribution is a common process in buried deposits subjected to either seasonal or permanent anoxic conditions. In such conditions iron in the soil is reduced and thus mobilised in the soil water. The iron can then be leached out of the profile altogether or is deposited as reddish brown nodules, mottles and pans in areas where there is more oxygen and/or higher pHs.

Clay eluviation
Physical disruption, compression, organic matter decomposition, and iron removal can result in the breakdown of pre-existing soil structures (peds). This can destabilise clays and other fine particulates, which may be washed down through the soil profile to be deposited as coatings around pores and coarse grains lower down in the profile.

Compression
Physical pressures exerted by the overlying deposits can be considerable. The response of the buried archaeology to compression depends on the depth of burial (weight of burying material) and the texture and water-content of the buried deposit. For example, Sidell et al. (2004) found that silt deposits are more susceptible to compression than sandy silts.

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