The Maximum Date for Carbon-14

It is confusing when the maximum date for Carbon-14 is listed as 60,000 years and 80,000 years in the same article (Chapter 4 Dating Methods by Roger Patterson and the reference article summary 4.2 by Riddle.) and as 50,000 years in another (The Answers Book) as well as 95,000 years in the Creation College lecture by Dr. Andrew Snelling.

– F.G., U.S.

Dear F.G.,

The maximum theoretical age obtainable by radiocarbon dating depends on the instrument used to do the analyses. The older beta counting instrument was stretched to get results of 50,000 years, whereas the AMS instrument should be effective up to 95,000 years. The other factor is what has become known as the "radiocarbon barrier" at around 55,000–60,000 years. This is due to the fact that the AMS instrument has to be calibrated, and yet the organic materials used for calibration (that are supposed to be so old they shouldn't have any detectable radiocarbon left in them) all contain so much radiocarbon that it means samples of unknown age can't yield dates above this radiocarbon barrier.

This is why there is the disparity in the quoted limits to radiocarbon dating, as highlighted by this inquirer. Theoretically, the AMS instrument should obtain ages up to 95,000 years, but practically, 60,000 years or less is the limit. But the radiocarbon detected in diamonds is equivalent to ages of up to 80,000 years.

So you can see why the various age limits have appeared in different publications of ours. Basically, it is correct to suggest 50,000–95,000 years. The former is the practical limit (based on the calibration materials presently used in radiocarbon labs), while the latter is the theoretical limit of the AMS instrument.

I hope these comments are a help.

Yours sincerely in Christ,
(Dr.) Andrew Snelling