Radiocarbon dating sample processed
The lab also offers C: N, %C and %N measurements on collagen extracted from non-cremated bones in addition to δ15N and δ13C at no additional cost for samples sent for radiocarbon dating.The lab also provides stable isotope analyses on a standalone basis.
Amongst the artefacts that have been found are ancient moa bones.1 Bayliss et al 2004)" src=" width="350" height="272" /C) is a naturally occurring isotope of carbon that is formed in the upper atmosphere when cosmic radiation interacts with nitrogen atoms (Figure 1). Once produced, it mixes rapidly across each of the hemispheres, quickly entering the terrestrial food chain through photosynthesis, with the result that the C is an unstable (radioactive) isotope, with a half-life of 5730±40 years, the proportion of radiocarbon in the deceased organism decreases over time. It is by measuring the amount of radiocarbon that remains that scientists are able to estimate the amount of time that has passed since the organism’s death. The naturally occurring concentration of C that was part of the organism when it died is measured. 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.
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.
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.
Once they know that there is sufficient protein remaining, they clean the surface of the bone to remove contaminants like dirt, charcoal or, in some cases, glue that the archaeologists have used to mend the bone fragments The cleaned bone sample is then ground up into smaller pieces to speed up chemical reaction with the acid in the next stage.
The ground-up bone is treated with hydrochloric acid, which dissolves out the hard part of the bone.
For the first 40 years or so, conventional radiocarbon dating involved converting the purified sample into either a gas (COC atoms in the samples, by either gas proportional or liquid scintillation counting, respectively.