How stuff works carbon 14 dating
It is produced in the upper atmosphere by radiation from the sun.(Specifically, neutrons hit nitrogen-14 atoms and transmute them to carbon.) Land plants, such as trees, get their carbon from carbon dioxide in the air. The same is true of any creature that gets its carbon by eating such plants. Suppose such a creature dies, and the body is preserved.That causes a dating problem with any animal that eats seafood. After about ten half-lives, there's very little C14 left.So, anything more than about 50,000 years old probably can't be dated at all.It is also standard to coat fossils during their extraction and transport.Acetone is sometimes used while extracting fossils, because it dissolves dirt.As the name suggests, fossil fuel is old, and no longer contains C14.
We can't date oil paints, because their oil is "old" carbon from petroleum. And third, it is common to soak new-found fossils in a preservative, such as shellac.See below for details about the 45,000 annual varves in Lake Suigetsu. For example, polar bears that eat seals aren't getting their carbon from an atmospheric source.The second kind are datings on contaminated samples, or on samples which are a mixture.For example, Stonehenge suddenly became older than the Pyramids, instead of younger.Since then, several other calibrations have been done, which confirm and extend the tree-ring one.