Contamination

Materials that are not part of a natural archaeological deposit or assemblage but which have intruded or altered the deposit or assemblage. The term is often applied to samples taken for radiocarbon dating which have been affected by their environment, for example by humus, which also contains carbon, and may be much younger than the sample, thus resulting in an inaccurate age determination.

In general, the term contamination is applied to samples of archaeological deposits or materials which have been affected by contact with other matter. In particular the term is often applied to samples taken for radiocarbon dating which have been affected by their environment. For instance, they may have been contaminated by humus. The humus, which also contains carbon, may be much younger than the sample, thus resulting in an inaccurate date. Samples that have been contaminated in this way can be treated with sodium hydroxide to dissolve out the humus. Dates are then determined for the treated sample and the dissolved ‘humate’ separately. This makes it possible to see how much contamination has occurred. convergence. Term used to describe the appearance of similar traits or techniques in different contexts, as a result of parallel or converging evolution (in contrast to diffusion).