Re: Carbon dating and flooding

Carbon dating is based on the ratio of Carbon 14 to the total amount of 
carbon in a sample.  The method assumes that, when an organism dies, the 
organism STOPS incorporating carbon into it's structure (body).  This is 
important, because a very small amount of the carbon incorporated into any 
organism is the radioactive isotope Carbon 14 (produced when cosmic rays 
strike nitrogen atoms in the Earth's upper atmosphere, and present as a 
very small percentage of all carbon in the air and on the surface of the 
Earth).  Therefore, because the organism stops incorporating carbon when 
it dies, and because Carbon 14 decays away, the ratio of Carbon 14/Total 
Carbon gets smaller with time.

When dating something with this method, it's important to be able to 
exclude sources of carbon AFTER the death of the organism (contamination 
while the sample is being obtained, for example).  Anything that would 
deposit either "fresh" carbon or very old carbon in the sample would bias 
the results.  

It is possible (although unusual) for floodwaters/groundwaters to deposit 
carbon into an existing, fossilized organism.  Fortunately, procedures 
have been developed to correct for groundwater intrusion (and a host of 
other confounding variables).

An analysis is only as good as the analyst.  When scientists do a good job 
of sampling, and a good job of correcting for anomalies, Carbon 14 dating 
analyses yield very accurate and repeatable results.

You can find more information about Carbon 14 dating techniques, including 
detailed procedural information, from:  http://members.aol.com/dsfrink/ocr/ocrpage.htm

Happy Hunting.