In the figure right, the production of radio-active carbon is demonstrated.
Tree ring data has been widely used to calibrate the timescales, as tree rings provide an annual calendar year, and the wood can be radiocarbon dated to provide a calibration.
As shown in the diagram above, the radioactive isotope carbon-14 originates in the Earth's atmosphere, is distributed among the living organisms on the surface, and ceases to replenish itself within an organism after that organism is dead.
This radioactive ), and are then absorbed by living organisms and oceans.
In Antarctica, where organic remains are rare, this usually means dating microscopic marine organisms in glaciomarine muds that overly glacial tills and sediments on the continental shelf[2-4].
Radiocarbon dating works because an isotope of carbon, C, is constantly formed in the atmosphere by interaction of carbon isotopes with solar radiation and free neutrons.
Living organisms absorb carbon (for example, we breathe it in).
Radiocarbon dating marine organisms has added complications in Antarctica, because around the Antarctic continent old deep ocean currents up well.
These currents are contaminated with ‘old’ carbon, meaning that marine organisms alive today have a radio-carbon age of about 1200 years[5, 6].
For the isotopes uranium-235 and uranium-238 to respectively become lead-207 and lead-206, they must first undergo a serious of highly unstable transformations into isotopes with very short half-lives.