Radiometric dating methods

Description

A general designation of dating methods involving the measurement of the radioactivity of certain componants of the artefact, or the measurement of the result of interactions between ionising radiationqs (cosmic rays, natural radioactivity of the environment) and certain components of the artefact. Concerning the cultural heritage area, the more significant methods are:

- Carbon 14 dating (or Radiocarbon dating) dedicated to organic materials, including two different measurement techniques for the concentration of the carbon 14 isotope: liquid scintillation and accelerator mass spectrometry (AMS)

- Measurement of the observed abundance of naturally occuring radioactive isotopes and their decay products (such as potassium 40 / argon, uranium / lead, thorium.), using known decay rates The use of this technique was first published in 1907 by the American radiochemist Bertram Boltwood and is one of the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and can be used to date a wide range of natural or man-made materials

- Luminescence dating methods - Natural sources of ionising radiation in the environment (cosmic rays, natural radioactivity) interact in, say, a piece of pottery. The result of these interactions is an accumulation of electronse in defects in certain material's crystal lattice structure (like quartz, feldspar, zircon). Heating or illuminating the object will release the captured electrons, producing a luminescence. Two different methods are used:

• Thermoluminescence dating (TL) - When the sample is heated, at a certain temperature it will glow from the emission of electrons released from the defects, and this glow can be used to estimate the age of the sample. For instance, the date of a piece of pottery is reset by the heat of the kiln. Typically temperatures greater than 400 °C will reset the "clock".
• Optically stmulated luminescence dating (OSL) – Instead of heating, one uses a laser beam to provoque the luminescence of the irradiated crystalline materials.

- Electron paramagnetic resonance (EPR)- which can be used for Quaternary geochronology, for instance for dating fossil teeth

Synonyms and Related Terms

Radiometrische Datierungsverfahren (Deut.); méthodes radiométriques de datation (Fr.)

Additional information

• M.J. Aitken, Thermoluminescence Dating, Academic Press, London (1985)

• M.J. Aitken, Introduction to Optical Dating, Oxford University Press (1998)

• C. Furetta, Questions and answers on Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL), World scientific publishing, Singapore (2008)

• I. Liritzis, A. K. Singhvi, J. K. Feathers, G. A. Wagner, A. Kadereit, N. Zacharias & S.H. Li, Luminescence dating in archaeology, anthropology, and geoarchaeology: An Overview, Springer (2013)

Authority

• Laboratory for Archaeology and the History of Art, University of Oxford http://www.arch.ox.ac.uk/luminescence.html