Oxidizable carbon ratio dating
is a method of dating
that can be used to derive the age of charcoal
samples up to 35,000 years old. The method is still in the experimental stage and not universally accepted and rarely used (as compared with well establish methods like carbon dating
. Successful usage by has been demonstrated for relative dating
. Its accuracy for establishing an abolute date
depends on calibration of within the context of the archaeological site.
The technique was first introduced by the Archaeology Consulting Team from Essex in 1992.
This dating method works by measuring the ratio of oxidizable carbon to organic carbon. If the sample is freshly burned there will be no oxidizable carbon because it would have all been removed by the combustion process. Over time this will change and the amount of organic carbon will decrease to be replaced by oxidizable carbon. By measuring the ratio of oxidized carbon to organic carbon (the OCR) and applying it to the following equation the age of the sample can be determined with a very low standard error
Accuracy and criticism
Although OCR dating has been claimed to be accurate by several studies by Douglas S. Frink, it has been critizized for depending on careful calibration with an arbitrary constant and to contain too many variables to determine ages with the level of accuracy required by modern archeology.
Douglas S. Frink has published studies according to which OCR dates correlate extremely well with radiocarbon dates
; in several dozen samples dated using both methods the largest degree of error was 3%..
Other researchers in archeology use the methods for relative dating when carbon dating is inconclusive. This use of OCR as an alternative dating mechanisms is backed by the theoretical mechanism underpinning OCR dating. The change in oxidizable carbon ratio is assumed to be mostly due to interaction of the sample with organic matter from the environment (bacteria or organics seeping with ground water). As a result carbon with a new carbon date and old carbon often mix in the sample making carbon dating unreliable. Criticism to the method are not to its general usefulness but rather to the attempt to compare it directly to carbon dating and to use it for absolute dating.
Many independent archologists have had good results with OCR dating but some others have experinced erroneous age measurements.
It is important to note that while OCR dating has been well established in humid regions it has not undergone testing in hyper arid environments.