Radiocarbon dating lab exercise
Desmond Clark (1979:7) observed that without radiocarbon dating "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation." And as Colin Renfrew (1973) aptly noted over 30 years ago, the "Radiocarbon Revolution" transformed how archaeologists could interpret the past and track cultural changes through a period in human history where we see among other things the massive migration of peoples settling virtually every major region of the world, the transition from hunting and gathering to more intensive forms of food production, and the rise of city-states.
However, as with any dating technique there are limits to the kinds of things that can be satisfactorily dated, levels of precision and accuracy, age range constraints, and different levels of susceptibility to contamination.
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.
The resulting overall background is, however, almost similar.
Multiple measurements on 2 wood samples of known calendar age yield consistent and accurate 14C ages in both laboratories.
For example, rootlet intrusion, soil type (e.g., limestone carbonates), and handling of the specimens in the field or lab (e.g., accidental introduction of tobacco ash, hair, or fibers) can all potentially affect the age of a sample.
Bioturbation by crabs, rodents, and other animals can also cause samples to move between strata leading to age reversals.
We did find differences between the 2 laboratories in the contributions of chemical preparation, graphitization, and measurements to the overall background.
This resource is designed to provide online information concerning the radiocarbon dating method.
We hope it will be of occasional use to radiocarbon users and interested students alike.
The introduction of "old" or "artificial" carbon into the atmosphere (i.e., the "Suess Effect" and "Atom Bomb Effect", respectively) can influence the ages of dates making them appear older or younger than they actually are.
This is a major concern for bone dates where pretreatment procedures must be employed to isolate protein or a specific amino acid such as hydroxyproline (known to occur almost exclusively in bone collagen) to ensure accurate age assessments of bone specimens.