How is carbon dating used
Carbon-14 cannot be used to date biological artifacts of organisms that did not get their carbon dioxide from the air.
This rules out carbon dating for most aquatic organisms, because they often obtain at least some of their carbon from dissolved carbonate rock.
Also, many fossils are contaminated with carbon from the environment during collection or preservation procedures.
As stated previously, carbon dating cannot be used on artifacts over about 50,000 years old.