Specifically, there are two types of carbon found in organic materials: carbon 12 (C-12) and carbon 14 (C-14).It is imperative to remember that the material must have been alive at one point to absorb the carbon, meaning that carbon dating of rocks or other inorganic objects is nothing more than inaccurate guesswork.Radiocarbon dating is especially good for determining the age of sites occupied within the last 26,000 years or so (but has the potential for sites over 50,000), can be used on carbon-based materials (organic or inorganic), and can be accurate to within ±30-50 years.
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.
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 surrounding environment can also influence radiocarbon ages.
By testing the amount of carbon stored in an object, and comparing to the original amount of carbon Unfortunately, the believed amount of carbon present at the time of expiration is exactly that: a belief, an assumption, an estimate.
It is very difficult for scientists to know how much carbon would have originally been present; one of the ways in which they have tried to overcome this difficulty was through using carbon equilibrium.Compared to conventional radiocarbon techniques such as Libby's solid carbon counting, the gas counting method popular in the mid-1950s, or liquid scintillation (LS) counting, AMS permitted the dating of much smaller sized samples with even greater precision.Regardless of the particular 14C technique used, the value of this tool for archaeology has clearly been appreciated.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. The Radiocarbon Revolution Since its development by Willard Libby in the 1940s, radiocarbon (14C) dating has become one of the most essential tools in archaeology.