Application of this method of age determination is limited to those periods of pottery and fired clay availability ( from about 6000 BC to the present). 50 Denison Drive Guilford, CT 06437 (203) 453-3299 University of Hawai'i Hawai'i Institute of Geophysics and Planetology 2525 Correa Road Honolulu, HI 96822 (808) 956-8761 FAX (808) 956-3188 University of Washington Luminescence Laboratory, DH-05 Seattle, WA 98195 (206) 543-1506 FAX (206) 543-3285 American Council of Independent Laboratories 1629 K Street, NW Washington, DC 20006 (202) 887-5872 FAX (202)887-0021 E-mail: [email protected] of independent testing, research and inspection laboratories. 101 West Edison Avenue, Suite 250 Appleton, WI 54915 (920) 749-3040 FAX (920) 749-3046 Testing and analysis for the pulp, paper, and allied industries. FAO/IAEA International Symposium on Managing Soils for Food Security and Climate Change Adaptation and Mitigation, Vienna, Austria 23-27 July 2012 Hua, Quan. Radiocarbon: A chronological tool for the recent past.
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Carbon-14, or radiocarbon, is a naturally occurring radioactive isotope that forms when cosmic rays in the upper atmosphere strike nitrogen molecules, which then oxidize to become carbon dioxide.
Green plants absorb the carbon dioxide, so the population of carbon-14 molecules is continually replenished until the plant dies.
Radiocarbon dating is especially good for determining the age of sites occupied within the last 26,000 years or so (but has the potential for sites over 50,000), can be used on carbon-based materials (organic or inorganic), and can be accurate to within ±30-50 years.
Probably the most important factor to consider when using radiocarbon dating is if external factors, whether through artificial contamination, animal disturbance, or human negligence, contributed to any errors in the determinations.
Compared to conventional radiocarbon techniques such as Libby's solid carbon counting, the gas counting method popular in the mid-1950s, or liquid scintillation (LS) counting, AMS permitted the dating of much smaller sized samples with even greater precision.
But while the difficulties of single life may be intractable, the challenge of determining the age of prehistoric artifacts and fossils is greatly aided by measuring certain radioactive isotopes.
Desmond Clark (1979:7) observed that without radiocarbon dating "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation." And as Colin Renfrew (1973) aptly noted over 30 years ago, the "Radiocarbon Revolution" transformed how archaeologists could interpret the past and track cultural changes through a period in human history where we see among other things the massive migration of peoples settling virtually every major region of the world, the transition from hunting and gathering to more intensive forms of food production, and the rise of city-states.
However, as with any dating technique there are limits to the kinds of things that can be satisfactorily dated, levels of precision and accuracy, age range constraints, and different levels of susceptibility to contamination.
Because of the somewhat short half-life of 14C, radiocarbon dating is not applicable to samples with ages greater than about 50,000 years, because the remaining concentration would be too small for accurate measurement.
Thermoluminescence dating: this method is associated with the effect of the high energy radiation emitted as a result of the decay or radioactive impurities.