Creationist FAQ

Are There Things That Can't Be Carbon-Dated?

Yes. The method doesn't work on things which didn't get their carbon from the air. This leaves out aquatic creatures, since their carbon might (for example) come from dissolved carbonate rock. That causes a dating problem with any animal that eats seafood. We can't date things that are too old. After about ten half-lives, there's very little C14 left. So, anything more than about 50,000 years old probably can't be dated at all. If you hear of a carbon dating up in the millions of years, you're hearing a confused report.

We can't date oil paints, because their oil is "old" carbon from petroleum.

We can't date fossils, for three reasons. First, they are almost always too old. Second, they rarely contain any of the original carbon. And third, it is common to soak new-found fossils in a preservative, such as shellac. It is also standard to coat fossils during their extraction and transport. Acetone is sometimes used while extracting fossils, because it dissolves dirt. In short, unless you have evidence to the contrary, you should assume that most of the carbon in a fossil is from contamination, and is not originally part of the fossil.

We also can't date things that are too young. The nuclear tests of the 1950's created a lot of C14. Also, humans are now burning large amounts of "fossil fuel". As the name suggests, fossil fuel is old, and no longer contains C14. Both of these man-made changes are a nuisance to carbon dating.

If you hear of a living tree being dated as a thousand years old, that is not necessarily an example of an incorrect dating. Trees only grow on the outside. Wood taken from the innermost ring really is as old as the tree.

Polonium Halos prove a young earth.

Halo FAQ
http://www.talkorigins.org/faqs/po-halos/gentry.html

Summary/Conclusions
Gentry's polonium halo hypothesis for a young Earth fails all tests