- Radiocarbon Dating -
Dates the moment of death of an organism by measuring the residual 14C or the last CO2 absorption content within it.
dating
morphology
technology
origin
composition
alteration
Mortar
Wood
Mortar & Plaster
Charcoal in mortar from lime burning process (routine method).
Calcium carbonates in mortars (method in progress).
Lime lumps occur in mortars when the mixing, during the mortar production, has not been done well. The presence of too many lime lumps in a mortar is actually an indication of a bad quality mortar,although it is very useful for dating because lumps are pure CaCO3. However, lime lumps are not always present in lime-mortars. Mortar dating attempts to date the calcium carbonates (also called calcite), nonetheless their separation from the rest of the mortar aggregates is complicated (method in progress).
Wood
Wood beams (routine method)
The principle of the method can be explained by the analogy of a constantly full bottle during the life, which starts to leak progressively after the death of the organism, following a known trend of leakage. The longer the organism has died, the emptier the bottle is.
The method is based on the fact that radioactive 14C is part of any living organism and that its content, stable during life, starts to decrease after the death of organisms, following a known physical law which acts like a sand hourglass. As time passes, the amount of radioactive carbon in the dead organism decreases. It is therefore possible to date the moment of death of an organism by measuring the residual 14C content within it.
accuracy
time
cost
in situ
invasive
destructive
Quickly oxidized to carbon dioxide are incorporated into plants during photosynthesis. When an organism dies, the integration of 14C stops and its content immediately starts decreasing, forming 14N and emitting beta particles*. The physical law which governs this decay is well-known; which means it is possible to determine when the organism died by measuring the residual 14C content. Indeed, the more residual 14C there is, the more recently the organism has died, and inversely, the smaller the amount of residual 14C the longer ago its death has occurred.
The same process occurs during non-hydraulic lime-mortar hardening. Indeed, the lime mortar, freshly embedded in masonry, absorbs atmospheric CO2 to produce calcium carbonate CaCO3. Once the mortar has hardened there is no more CO2 exchange with the atmosphere and the content of 14C starts decreasing. Therefore, the older a mortar is, the lower the amount of 14C within its contained calcium carbonates.
