How Carbon-14 Dating Works
This effect is accounted for during calibration by using a different marine calibration curve; without this curve, modern marine life would appear to be 400 years old when radiocarbon dated. There are also cases where there is no functional relationship, but the association is reasonably strong: for example, a layer of charcoal in a rubbish pit provides a date which has a relationship to the rubbish pit. The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age.
Rejecting fossil data cannot be supported by proof. Retrieved 9 December 2017. To determine this, a blank sample of old, or dead, carbon is measured, and a sample of known activity is measured. Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.
Accuracy of Fossils and Dating Methods - New York: Columbia University Press.