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Re: orion-list Radiocarbon

On Thu, 26 Aug 1999 13:47:54 +0200, gd@teol.ku.dk writes:

   [... snip ... noted ...]

>   There are indeed, of the nineteen Qumran texts which have 
>   been radiocarbon dated, five which gave AMS measurements 
>   whose two-sigma ranges are completely later than 63 BCE, 
>   even at their earliest end, according to the most current 
>   Seattle-Belfast calibration.  

   That leaves fourteen samples dated earlier.  If a First C CE date
   for the deposit is hypothesized, that argument is dead on its
   face.  Howover, any argument for a First C BCE deposit can only
   be made if contamination of the samples was not taken into
   account or can be shown to have occurred.  

   That argument has been made.  We have no clear record of what
   samples were contaminated with modern oils ands what were not. 
   Also, it appears that adequate decontamination protocols were not
   followed.  Professor Jull suggests that for a clear answer more
   tests are necessary.  I agree.

   [... snip ... noted ...]

   To add to the discussion, let me give a layman's view of how
   strongly modern contamination from oil or smoke can affect
   ancient meterials:

     Consider a fiber such as a strand of papyrus,
     diameter 1/1000th inch and coated with a film of
     smoke 1/10,000th inch thick:

        If a slice of the fiber is made, the area of
        the diameter of the fiber plus its coating is:
        Pi x (0.001 + 2 x 0.0001)Squared.  (Remember
        that the film is on all of the surface of the

        The area of the fiber itself is:
        Pi x (0.001)Squared.

        So, the ratio of contamination to fiber is:

        Pi x (0.001 + 2 x 0.0001)Squared - Pi x (0.001)Squared
        ------------------------------------------------------ =
                      Pi x (0.001)Squared

        Pi x (0.0012)Squared - Pi x (0.001)Squared
        ------------------------------------------  =
                      Pi x (0.001)Squared

        Pi x 0.00000144  -  Pi x 0.00000100
        ----------------------------------- =
                      Pi x 0.00000100

          Pi may be factored out, so we have

        0.00000144 - 0.00000100    0.00000044     44
        ----------------------- =  ---------- =  --- = 44%!!
             0.00000100            0.00000100    100

     44% is no small figure.
>   Greg Doudna
>   Copenhagen  

    Instructive?  See why taking contamination into account can 
    be so important?

Tom Simms 

For private reply, e-mail to Tom Simms <tsimms@mailserv.nbnet.nb.ca>
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