Assumptions used in carbon dating
In most cases, the three methods produced similar results.
Surprisingly, in at least one case the date range given by There may be other examples of systematic variation in isotope decay rates.
The reasonableness of this assumption probably depends on the environment around the sample.
A sample that is sealed from the surrounding environment is more likely to avoid contamination or loss than one in an open environment where materials may be carried into or out of the sample by water or simple diffusion.
Other processes may affect the local concentrations of carbon-14.
These effects are corrected for by comparing samples from different locations.
In practice, there are sufficient variations in these conditions that it is necessary to correct a sample’s raw radiocarbon age by comparing it with the standard calibration curve.
Violations of this assumption occur in the ocean reservoir due to the time required for mixing of surface waters with the deep layers.
It is widely used in dating fossils or archaeological samples containing organic material such as wood, charcoal, bone, shells, etc.
It is not used to date rocks or other inorganic material.
Carbon-14 dating cannot be applied to materials that have no C dates are less than that figure.
It is sometimes thought possible to extend the dating range a few half-lives, so one occasionally sees dates as old as 70,000 years or more.