Has radiocarbon dating been invalidated by unreasonable results?

What about the stories of ridiculous radiocarbon dates?

A number of stories are commonly circulated about a shell, or a piece of coal, or some other sample which supposedly yielded a radiocarbon date which could not possibly be correct. Such stories misrepresent the truth and do a disservice to science and public knowlege. Presented here are a few examples, exposing the truth about these stories.

Example 1: "Pennsylvanian" Coal

Coal from Russia from the "Pennsylvanian", supposedly 300 million years old, was dated at 1,680 years. (Ham et al., page 73.)

Dr. Aardsma investigated this claim and noted:

A brief look at the original reference [Vinogradov et al., page 319.]...immediately reveals that the sample was not Pennsylvanian coal at all. This is evident first of all by the fact that it is part of a date list which is broken into three parts: "geologic samples", "archaeological samples", and "fossil animals". Clearly, Pennsylvanian coal would be listed as a geologic sample, but this sample of "coal" is listed as an archaeological sample.

... In the original reference the sample is described as "scattered coals in a loamy rock in deposits of a 26-m [river] terrace". This Radiocarbon reference must originally have been translated from Russian and it is not unreasonable to suppose that there was some loss of descriptive clarity as a result. But it seems pretty clear that what is being described here is certainly not "Pennsylvanian coal". There is, in fact, no indication anywhere in the original reference that these samples were from the "Pennyslvanian"; nor is there any hint that they were expected to be "300 million years old"; these appear to be purely apocryphal embellishments to the original account. Surely, what the Russians intended to convey (and what nearly everybody would understand), is that these samples were charcoal from a not too ancient campfire. (Aardsma, 1994, page 2.)

Dr. Aardsma also noted that the date on these samples was in line with the archaeologists' expectations. The radiocarbon date, in this instance, was in no way unreasonable.

Example 2: Natural Gas

Natural gas from Alabama and Mississippi (Cretaceous and Eocene, respectively) should have been 50 million to 135 million years old, yet ¹⁴C gave dates of 30,000 to 34,000 years, respectively. (Ham et al., page 73.)

Dr. Aardsma investigated this claim also, and noted:

The original reference [Trautman and Willis, page 200.] in the second case (natural gas) immediately reveals that both Whitelaw and The Answers Book have, unfortunately, neglected several very important ">" (strictly greater than) signs. The "dates" in this case are given in the original publication as ">30,000" and ">34,000". Thus, these natural gas samples were not dated to "30,000 to 34,000 years" at all. In fact, the original reference plainly notes "infinite age as expected". (Aardsma, 1994, page 2.)

The sensitivity of the equipment used to make the radiocarbon measurements on these natural gas samples was limited to 30,000 to 34,000 years---the equipment was unable to measure back further. Here again the radiocarbon dates were as expected.

Example 3: Living clams which died 2,000 years ago?

In this example, old radiocarbon dates from living clams or snails are given as evidence which discredits the reliability of radiocarbon dating. Dr. Aardsma addressed this issue in a 1989 article:

The shells of freshwater clams can, and often do, give anomalous radiocarbon results. However, the reason for this is understood and the problem is restricted to only a few special cases, of which freshwater clams are the best-known example. It is not correct to state or imply from this evidence that the radiocarbon dating technique is thus shown to be generally invalid.

The problem with freshwater clams arises because these organisms derive the carbon atoms which they use to build their shells from the water in their environment. If this water is in contact with significant quantities of limestone, it will contain many carbon atoms from dissolved limestone. Since limestone contains very little, if any, radiocarbon, clam shells will contain less radiocarbon then would have been the case if they had gotten their carbon atoms from the air. This gives the clam shell an artificially old radiocarbon age.

This problem, known as the "reservoir effect", is not of very great practical importance for radiocarbon dating since most of the artifacts which are useful for radiocarbon dating purposes and are of interest to archaeology derive from terrestrial organisms which ultimately obtain their carbon atoms from the air, not the water. (Aardsma, 1989, page 2.)

Conclusion

Other such stories have been circulated, but these examples make clear the nature of such stories. The truth is that radiocarbon dating is a very effective and valuable tool in the hands of competent chronologists. As with any physical measurement, things can go wrong and mistakes can be made. But this just means that one should not hang their whole confidence on a lone radiocarbon date. In actual practice, it is the amassed evidence of multiple radiocarbon dates, generally on different materials by different investigators using different measurement apparatus, which is applied to a given chronological question. Stories of the sort above, which are obviously meant simply to discredit radiocarbon dating, are very far from the truth.

References:

1. Aardsma, Gerald E. "Myths Regarding Radiocarbon Dating" Impact No. 189 El Cajon, CA: Institute for Creation Research. 1989.
2. Aardsma, Gerald E. "A Search for Radiocarbon in Coal" Proceedings of the Third International Conference on Creationism. Pittsburgh: Creation Science Fellowship, Inc. 1994.
3. Ham, Ken; Andrew Snelling; and Carl Weiland. The Answers Book El Cajon, CA: Master Books, 1992.
4. Trautman, Milton A. and Eric H. Willis, "Isoptopes, Inc. radiocarbon measurements V", Radiocarbon 8 (1966) 161-203 [sample #s I-1149 & I-1150, page 200].
5. Vinogradov, A. P.; A. L. Devirts; E. I. Dobinka; and N. G. Markova. "Radiocarbon Dating in the Vernadasky Institute I-IV" Radiocarbon 8 (1966) 292-323 [sample # Mo-334, page 319].