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.Sometimes, a precise date is not needed and pretreatment methods designed to reduce errors will not be necessary.
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.
A high-precision date may involve the lab in more intensive pretreatment and labour and consequently costs are higher.
Submitters should send as much sample as possible because of the destructive nature of certain pretreatment techniques.
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.
A stratigraphical diagram should be drawn to enable the dater to understand completely the site and origin of the material, and to consider the ability of the lab to adequately date the sample in question.
The submitter should also indicate the degree of accuracy and precision required.
This should be reported in the submission forms accompanying samples sent to the laboratory.
Contamination may be artificially or naturally caused.
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.