For Jeanie, from "why does the science of evolution persist (especially in the face of attempts to portray it as an evil social program or some type of religious faith while ignoring reality) thread:

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I have a tape somewhere buried from when I homeschooled which gets into the sedimentation issues and flaws with carbon dating.
It will be interesting to see you explain the correlation between age and climate if carbon-14 is "erratic" as creationists claim.

Of course another likelihood is that your creationist source (whoever made your tape) is presenting false information about carbon-14, how it is used, what can properly be dated. I can list several cases where creationists have intentionally misused carbon-14 dating, and note that there are several PRATTs associated with this issue. A good source of honest information is Dr. Wiens (from the ASA website):

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Carbon-14 in particular is used to date material such as bones, wood, cloth, paper, and other dead tissue from either plants or animals. To a rough approximation, the ratio of carbon-14 to the stable isotopes, carbon-12 and carbon-13, is relatively constant in the atmosphere and living organisms, and has been well calibrated. Once a living thing dies, it no longer takes in carbon from food or air, and the amount of carbon-14 starts to drop with time. How far the carbon-14/carbon-12 ratio has dropped indicates how old the sample is. Since the half-life of carbon-14 is less than 6,000 years, it can only be used for dating material less than about 45,000 years old. Dinosaur bones do not have carbon-14 (unless contaminated), as the dinosaurs became extinct over 60 million years ago. But some other animals that are now extinct, such as North American mammoths, can be dated by carbon-14. Also, some materials from prehistoric times, as well as Biblical events, can be dated by carbon-14.
Very informative article, and a good place to start.

Enjoy.