And radiocarbon dating
3.5 decays/gram/minute of carbon would be produced by a sample 11,460 years old.
However, atmospheric testing of nuclear weapons in the late 1950's and early 1960's greatly increased the amount of radiocarbon in the atmosphere, so the decay rate of 14 decays per minute more than doubled.
Most carbon consists of the isotopes carbon 12 and carbon 13, which are very stable.
A very small percentage of carbon, however, consists of the isotope carbon 14, or , which is unstable.
A technique for measuring the age of organic remains based on the rate of decay of carbon 14.
Because the ratio of carbon 12 to carbon 14 present in all living organisms is the same, and because the decay rate of carbon 14 is constant, the length of time that has passed since an organism has died can be calculated by comparing the ratio of carbon 12 to carbon 14 in its remains to the known ratio in living organisms.
Increased rates of deep-water upwelling may responsible for the "too old" radiocarbon ages during the last glaciation. Atmospheric radiocarbon calibration beyond 11,900 cal BP from Lake Suigetsu.
A., Kromer, B., Mc Cormac, G., van der Plicht, J., Spurk, M. INTCAL98 radiocarbon age calibration, 24,000-0 cal BP. The ratios are consistent among species, and the slight (1-3%) differences can also be calculated from the ratio of C) decreases as the radiocarbon decays. Libby determined, one gram of pure carbon should produce about 14 (13.56) radioactive decays per minute.