How is C-14 used?
Carbon 14 is used to date recent human buildings, artifacts and remains of dead organisms.
Carbon 14 has a half life of approximately 5,700 years. This makes dating of items that are less than 5,700 years very accurate. After two half lives there is 25% left still very good values at 11,400 years. After 7 half lives at 40,,000 years there is only 1/128 or .007 or 0.7 percent left. That is less than 1% which makes the values very uncertain. After 57,000 years there is only 1/1054 parts left that is ,00009 or less than .01 percent, making Carbon 14 essentially useless as a dating tool.
Carbon14 is useful in archeology but of no value in the study of fossils. A textbook I taught from stated that the dinosaurs extinction of 65 million years had been determined by Carbon 14
After 65 million years there should be no Carbon left let alone Carbon 14. (Note there have been empirical evidences of Blood like substances found in the center of fossilized dinosaur bones.)