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A table of optimum and minimum sample sizes is provided below.Please feel free to contact our lab staff to discuss the specific details of your samples.Bioturbation by crabs, rodents, and other animals can also cause samples to move between strata leading to age reversals.Shell may succumb to isotopic exchange if it interacts with carbon from percolating ground acids or recrystallization when shell aragonite transforms to calcite and involves the exchange of modern calcite.We also offer liquid scintillation analysis using an extra low background Quantulus 1220 for high precision measurements on benzene.
Alone, or in concert, these factors can lead to inaccuracies and misinterpretations by archaeologists without proper investigation of the potential problems associated with sampling and dating.
Regardless of the particular 14C technique used, the value of this tool for archaeology has clearly been appreciated.
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.
The method takes advantage of the natural occurrence of a radioactive isotope of carbon (C in samples of ancient carbon compounds and comparing this with the amount in modern materials, it is possible to determine the time of cessation of carbon exchange with the atmosphere.
The radiocarbon lab at Geochron uses gas proportional counters to measure methane derived from relatively small samples. Please read our pages on sample weight requirements, and if you are unsure about the suitability of your sample please contact us.