For a radiocarbon value measured in a sample S (Fs), bomb radiocarbon delivers two possible calendar dates (T1 and T2), indicated by the grey boxes (Hua, 2009).Details C concentrations are mainly due to variations in the rate of radiocarbon production in the atmosphere, caused by changes in the Earth's magnetic field and variability in solar activity, and changes in the carbon cycle.Radiocarbon is a naturally occurring radioactive isotope of carbon.Atoms of radiocarbon behave in the same way as any other carbon atoms except that they weigh slightly more and, after an average of some 5000 years decay to nitrogen.Terrestrial (Int Cal04) and Marine (Marine04) radiocarbon calibration curves for the past 26,000 cal yr BP. Calibrated ages are shown for 1σ and 2σ (68.2% and 95.4% confidence levels, respectively). Details Calibration of a radiocarbon age of 6550 ± 40 BP of a terrestrial sample from the Northern Hemisphere, using Int Cal04 calibration curve and Ox Cal program version 3.10.For the remaining period 12,400-26,000 cal yr BP, the curve is derived from independently dated marine samples such as foraminifera and corals.
To understand radiocarbon dating, you first have to understand the word Although an element’s number of protons cannot change, the number of neutrons can vary slightly from each atom.Atoms of the same element that have different numbers of neutrons are called isotopes. Most carbon on Earth exists as the very stable isotope carbon-12, with a very small amount as carbon-13.Here’s an example using the simplest atom, hydrogen. Carbon-14 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-12.These neutrons react with nitrogen atoms in the atmosphere by the first of the reactions shown above: C Because the rate at which cosmic rays strike the earth does not vary greatly, the overall quantity of radiocarbon in the atmosphere is fairly constant.It is, however, only a very small proportion of the total carbon present: The fact that these ratios are fairly constant is important in using radiocarbon as a dating tool.