The lab must consider the possibility of contamination in each sample it dates and depends upon information supplied by the submitter and collector of the material for its assessment.
The submitter should supply information detailing the type of environment from which the sample was obtained and commenting on the presence of rootlet intrusion and contaminants.
Nevertheless, there are certain laboratory procedures which are associated with specific sample types and environments, and a number of accepted and often repeated pretreatment methods. The laboratory decides on the most effective pretreatment procedure through a careful examination of each submitted sample.
A number of variables feature in this consideration, one of the most important concerns the environment within which the sample was deposited.
This is particularly relevant for laboratories which use conventional methods of dating.
Bone dating, for example, requires large amounts of sample because the fractions which are usually extracted comprise a small percentage of the total material and the target fractions decompose rapidly.
He predicted that charcoal would be the most effective, shell, the least.The following types of sample have been commonly radiocarbon dated: Since the 1950's, a number of researchers have concentrated on investigating and reducing the effects of this post-depositional contamination.This field of inquiry is known as sample pretreatment and it is concerned with removing post-depositional contaminants by isolating sample fractions containing carbon which is autochthonous and therefore accurately dates the event in question.Natural contamination occurs in the post-depositional environment.Samples may be contaminated by material which make any radiocarbon result either too old or too young.