As stated previously, carbon dating cannot be used on artifacts over about 50,000 years old.
These artifacts have gone through many carbon-14 half-lives, and the amount of carbon-14 remaining in them is miniscule and very difficult to detect.
Nuclear tests, nuclear reactors and the use of nuclear weapons have also changed the composition of radioisotopes in the air over the last few decades.
This human nuclear activity will make precise dating of fossils from our lifetime very difficult due to contamination of the normal radioisotope composition of the earth with addition artificially produced radioactive atoms.
Once our geologist had the “index fossil” that was found approximately in the same layer as the newly discovered fossil, he would then see where in the geologic column it came from and presto, he now had a date for his newly discovered fossil.
He would simply go to a chart that listed the geologic column by ‘ages’ and find the place where the index fossil appears, and thereby the geologists could tell the paleontologist how old his fossil was.
These isotopes have longer half-lives and so are found in greater abundance in older fossils.
This restriction extends to animals that consume seafood in their diet.
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.
Scientists attempt to check the accuracy of carbon dating by comparing carbon dating data to data from other dating methods.
Other methods scientists use include counting rock layers and tree rings.