Oxidizable carbon ratio dating
Published: 20 July 2014 (GMT+10)
MM from Australia asked about a new dating method called “oxidizable carbon ratio” (OCR) dating, which was brought to his attention by a friend.1
It is important to understand the simple, fundamental principle behind all dating methods, and why they are not able to produce objective, absolute dates (see article How dating methods work). The fatal flaw is that all scientific measurements are made in the present, whereas a date relates to a time in the past. We cannot go back into the past to measure all the parameters we need in order to do the dating calculation.
Hence, all these parameters must be assumed—always. There is no other way. Further it must be assumed that the parameters have not varied over the ‘life’ of the sample. Because these are assumed, we cannot have any confidence that the calculated age is correct. Thus, scientists always compare their calculated result with what they think the answer should be. If their calculated age does not agree with expectations they will explain it away and look for something else to give them the age they need. The article How dating methods work gives one example of how unwanted dates are explained away. Radioactive dating anomalies gives other examples.
All dating methods depend on something that is changing with time, plus they need a plausible initial condition. In the case of OCR dating, the variable that is changing with time is the ratio of oxidizable carbon to organic carbon.2 On earth, carbon is continually recycled by biological processes. Some forms, such as fresh organic matter, are quickly recycled, but more resistant forms, such as charcoal, are recycled more slowly. The assumption is that when a sample is freshly burned, there will be no oxidizable carbon because it has been removed by the combustion process. Over time biological activity will cause the amount of oxidizable carbon to increase.
As you can imagine, the rate of change of carbon ratio due to biological activity will depend on many factors including the location of the sample and the environmental conditions. The OCR dating method was developed by Douglas Frink, who included six significant variables which he considered would affect the carbon ratio: oxygen, moisture, temperature, carbon concentration, and the soil reactivity (by means of texture and pH). However, there would be many more variables that affect biological activity that these parameters do not account for.
Frink analysed dozens of archaeological samples from North America and East Africa. He developed a statistical relationship between a sample’s OCR and its published age based on cultural or carbon-14 dates. The following is the equation he developed: 3
OCRAge = OCR x (depth x mean temperature x mean rainfall) / (mean texture x pH0.5 x %C0.5 x 14.4888)
Frink warns in his paper that you can’t accept a calculated OCR date without question, but that each date had to be examined to see if it is acceptable. He presents this word of caution:
“While the OCR procedure provides good age estimates for many archaeological samples, it cannot be applied to all situations. Specific environmental conditions must be met before meaningful age estimates are possible. The change in the oxidizable C ratio through time and the formulation of the OCR-date equation, were derived from samples obtained from moderately to well drained aerobic soils. Results from the analyses conducted on samples obtained from poorly drained anaerobic soils yielded spurious data, suggesting that OCR-date equation pertains to an O2 dependent system. Soil samples affected by long-term saturation (reducing conditions) returned age estimates much older than expected.” 4
In other words, you have to know what the conditions were in the past before you can be sure that the method is likely to work. How can you know what the conditions were unless you were there? Further, what other factors are likely to upset the result that are not included in the formula and are not known about.
The paper discusses four samples from Connecticut and West Virginia that gave results that were spurious. On further investigation it was found from people involved who witnessed the procedures that there was a problem with the storage of the samples after they were collected. The reason the results were considered spurious was that they contradicted the dates obtained by other methods. The reason they identified the cause was because people had observed what had happened.
Also mentioned in the paper is one soil sample from Somalia that deviated significantly from its expected age based on its stratigraphic position (and not on radiocarbon dating). The reason suggested for this discrepancy was that rodent activity may have disturbed the soil, or the sample’s low carbon content may have distorted the result. Without eyewitnesses the suggested cause can only be “may have”.
OCR dating was critiqued in the Society for American Archaeology Bulletin in 1999 by Killick, Jull, and Burr.5 They questioned the accuracy and precision of the method as well as highlighting the problems with site-specific environmental factors. Frink in his reply6 discussed these criticisms as well as acknowledging that much work was needed to improve and develop the method.
Since it was developed, the OCR method has been used in many studies of archaeological and geomorphological situations. However, every calculated date must be evaluated to decide whether it fits within the accepted chronological framework, or whether it needs to be explained away. Consequently, the OCR method still needs careful stratigraphic observations and separate carbon-14 ‘dates’ as a check. One example of the method in use is on cultural artefacts at a site in Australia.7 The method was checked independently against other methods before concluding that it seemed to be giving consistent results at this particular site.
The other important point is that the OCR method is calibrated against carbon-14 dating. In other words, OCR dating does not provide objective evidence for long ages. Its long ages are derived from the long ages of carbon-14 results. Carbon-14 dating assumes that the ratio of 14C to 12C has been constant for hundreds of thousands of years. The problem with that assumption is that the 14C to 12C ratio was disrupted by the global Flood, so all carbon-14 ages need to be corrected for the resultant atmospheric carbon imbalance (see What about carbon dating?).
In summary, the OCR dating method is neither independent nor objective. It may have a limited application in certain situations but the results will always need to be checked with other dating information. Because it is tied to mainstream carbon-14 procedures OCT dating does not provide fundamental evidence for long ages for the earth. Any age result over 3000 or 4000 years will require downward correction to take account of the effects of Noah’s Flood.
References and notes
- This dating method was presented on a Rational Wiki page entitled Evidence against a recent creation, but it actually is not such evidence, as the main article here shows. Return to text.
- Oxidizable carbon is measured by measuring the loss of carbon by combustion. Organic carbon is measured by a wet oxidation method, i.e. the loss of carbon when mixed with water and oxidized by introducing air or oxygen. Return to text.
- Frink, D.S., Application of the oxidisable carbon ration (OCR) dating procedure and its implications for pedogenic research, Pedological Perspectives in Archaeological Research, SSA Special Publication 44, Soil Science Society of America, Madison, WI: 1995; http://www.eprida.com/hydro/ecoss/background/applicationofocr.pdf Return to text.
- In this quote I changed OCRDATE to OCR-date for ease of reading. Return to text.
- Killick, D.J., Jull, A.J.T., and Burr, G.S., A failure to discriminate: Querying Oxidizable Carbon Ratio (OCR) Dating; http://www.saa.org/Portals/0/SAA/publications/SAAbulletin/17-5/saa18.html, Accessed 26 June 2014. Return to text.
- Frink, D.S., The scientific basis of Oxidizable Carbon Ratio (OCR) Dating; http://www.saa.org/Portals/0/SAA/publications/SAAbulletin/17-5/saa18.html, Accessed 26 June 2014. Return to text.
- Harrison, R., and Frink, D.S., The OCR carbon dating procedure in Australia: New dates from Wilinyjibari Rockshelter, southeast Kimberley, Western Australia, .Australian Archeology 51:6–15, 2000; https://www.library.uq.edu.au/ojs/index.php/aa/article/download/792/791 Return to text.