dating technique relies on the progressive decay or disappearance of the radioactive parent with time.

This is now a common method for estimating the age of a carbonaceous archaeological artifacts.

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However, its use is still helpful where recognizable products of dateable manufacture are found in undated contexts with no possibility of using a technique.

So in the absence of geochronology, two cultural groups can only be proved contemporary by the discovery of links between them.

The test is used mainly in association with the fluorine test and radiometric assay, as in the cases of Piltdown and Swanscombe Man. The basis of cross-dating is the occurrence of finds in association.

The assumption is that a particular type of artifact, for example a type of sword, when found in an undated context will bear a similar date to one found in a dated context, thus enabling the whole of the undated context to be given a chronological value.

The technique is based on the principle that cations of certain elements are more soluble than others; they leach out of rock varnish more rapidly than the less soluble elements, and their concentration decreases with time.

A cation is an ion carrying a positive charge which moves toward the negative electrode/cathode during electrolysis.

Collagen survives long after death and the collagen content of a bone, measured by the amount of nitrogen present, yields information as to its relative date.

The rate of decay is varies with temperature and other aspects of the environment, but collagen dating can only give relative dates for different bone samples from a particular site.

Aspartic acid is the compound most often used because it has a of 15,000-20,000 years and allows dates from 5,000-100,000 years to be calculated.

However, racemization is very much affected by environmental factors such as temperature change.

If there has been significant change in the temperature during the time in which the object is buried, the result is flawed.