Carbon 12 and carbon 14 dating sexintheuk dating
[A Conventional Radiocarbon Age or CRA, does not take into account specific differences between the activity of different carbon reservoirs.
A CRA is derived using an age calculation based upon the decay corrected activity of the absolute radiocarbon standard (1890 AD wood) which is in equilibrium with atmospheric radiocarbon levels (as mentioned previously, 1890 wood is no longer used as the primary radiocarbon standard, instead Oxalic Acid standards I and II were correlated with the activity of the original standard).
Plants which grow in the vicinity of active volcanic fumeroles will yield a radiocarbon age which is too old. (1980) measured the radioactivity of modern plants growing near hot springs heated by volcanic rocks in western Germany and demonstrated a deficiency in radiocarbon of up to 1500 years through comparison with modern atmospheric radiocarbon levels.
Similarly, this effect has been noted for plants in the bay of Palaea Kameni near the prehistoric site of Akrotiri, which was buried by the eruption of the Thera volcano over 3500 years ago (see Weninger, 1989).
One of the most commonly referenced reservoir effects concerns the ocean.
The average difference between a radiocarbon date of a terrestrial sample such as a tree, and a shell from the marine environment is about 400 radiocarbon years (see Stuiver and Braziunas, 1993).
Hans Suess (1955) discovered the industrial effect (also called after him) in the 1950's.
The reason for this anomaly is that the limestone, which is weathered and dissolved into bicarbonate, has no radioactive carbon.
Since about 1955, thermonuclear tests have added considerably to the C14 atmospheric reservoir.
This C14 is 'artificial' or 'bomb' C14, produced because nuclear bombs produce a huge thermal neutron flux.
The presence of bomb carbon in the earth's biosphere has enabled it to be used as a tracer to investigate the mechanics of carbon mixing and exchange processes.
Ellen Druffel has called this the silver lining in thermonuclear bomb testing.