Beyond that timespan, the amount of the original C formed by irradiation of nitrogen by neutrons from the spontaneous fission of uranium, present in trace quantities almost everywhere.For these samples, other dating methods must be used.Furthermore, if a sample has been contaminated, scientists will know about it.Ironically, given how supposedly useless carbon dating is claimed to be, Creation Ministries International rests part of their "101 Evidences" on carbon dating being a useful method for within several thousand years.This is meaningless because dinosaur fossils are not dated using carbon dating; dinosaurs became extinct 66 million years ago, more than a thousand times farther back than carbon dating can be used.The level of atmospheric C is not constant due to human activity, in part because of human combustion of fossil fuels and in part because of above-ground testing of the largely defensive weapon of the thermonuclear bomb.Therefore dates must be calibrated based on Indeed, this results from a unique decay mode known as "cluster decay" where a given isotope emits a particle heavier than an alpha particle (radium-226 is an example.) This fact is extremely inconvenient and is therefore usually omitted in creationist literature. Carbon dating has a certain margin of error, usually depending on the age and material of the sample used.
This of course contradicts claims that the Great Flood messed up how carbon was deposited, destroying their own argument.
Less astute creationists often conflate carbon dating with other forms of radiometric dating, attempting to "disprove" the true age of dinosaur fossils by "refuting" carbon dating.