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Dates above and below a location provide minimum and maximum age determinations according to the law of superimposition.
Thermoluminescence is a similar technique to optical dating, but uses heat instead of light to stimulate the minerals.
This page has articles skeptical of Carbon-14 dating methods, and an article in defense of the method.
In the Willandra area it is typically used on quartz sand grains which have been buried and have not been exposed to sunlight since burial.
The method also assumes a 'zeroing' event in the life of the material, when it was either last heated or exposed to sunlight.
Over the last decade several dozen direct dates on cave art pigments or associated materials have supplemented more traditional style-based attempts to establish a chronological (and developmental) scheme for cave art.
It uses the fact that natural carbon contains a known ratio of ordinary carbon and the radioactive isotope carbon-14, and that this mix is reflected in carbon taken up by living organic materials such as wood, shells and bones.
When organisms die, the carbon-14 begins to decay at a known rate.