Accuracy and precision in radiocarbon dating
It is vital for a radiocarbon laboratory to know the contribution to routine sample activity of non-sample radioactivity.
Obviously, this activity is additional and must be removed from calculations.
Shell may succumb to isotopic exchange if it interacts with carbon from percolating ground acids or recrystallization when shell aragonite transforms to calcite and involves the exchange of modern calcite.
The application of Accelerator Mass Spectrometry (AMS) for radiocarbon dating in the late 1970s was also a major achievement.
This process of decay occurs at a regular rate and can be measured.
By comparing the amount of carbon 14 remaining in a sample with a modern standard, we can determine when the organism died, as for example, when a shellfish was collected or a tree cut down.
Shells of known age collected prior to nuclear testing have also been dated ( to ascertain the effects of old carbon (i.e., local marine reservoir effects). However, the most common materials dated by archaeologists are wood charcoal, shell, and bone. In brief, radiocarbon dating measures the amount of radioactive carbon 14 (14C) in a sample.
Radiocarbon analyses are carried out at specialized laboratories around the world (see a list of labs at: When a biological organism dies, the radioactive carbon in its body begins to break down or decay.