Fluorine absorption dating is a method used to determine the amount of time an object has been underground. Fluorine absorption dating is based on the fact that

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

contains fluoride ions. Items such as

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

that are buried in soil will absorb fluoride from the groundwater over time. From the amount of absorbed fluoride in the item, the amount of time that the item has been buried can be estimated. However, since different sites have different levels of fluorine in the groundwater, fluorine absorption dating can only be used to determine the relative age of bones from the same site. It cannot give how old a bone actually is, only whether it is younger, older, or the same age as other bones from the same site. Many instances of this dating method compare the amount of fluorine and uranium in the bones to results from

nitrogen dating Nitrogen dating is a form of relative dating Relative dating is the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining their absolute age (i.e., estima ...

, allowing more accurate estimations of date. Older bones have more fluorine and uranium, with less nitrogen. Because

decomposition Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ess ...

happens at different speeds in different places, it is not possible to compare bones from different sites. As not all objects absorb fluorine at the same rate, the accuracy of fluorine dating is somewhat limited. Although this can be compensated for by including the estimated rate of absorption in calculations, such accommodations tend to have a rather large

margin of error The margin of error is a statistic expressing the amount of random sampling error in the results of a Statistical survey, survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of ...

. In 1953, this test was used by

Kenneth Oakley Kenneth Page Oakley (7 April 1911 – 2 November 1981) was an English physical anthropologist, palaeontologist and geologist. Oakley, known for his work in the Fluorine absorption dating of fossils by fluorine content, was instrumental in ...

to easily identify that the ' Piltdown Man' was forged, almost 50 years after it was originally 'unearthed'. It was also used to disprove the validity of the Calaveras Skull, the first use of fluorine dating on human bone.

References

* Göksu, H. Y., M. Oberhofer and D. Regulla, editors, ''Fluorine dating'' in ''Scientific Dating Methods,'' Springer, 1991, pp 251 – 270 {{DEFAULTSORT:Fluorine Absorption Dating Dating methodologies in archaeology