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Re: orion-list Radiocarbon

On Mon, 30 Aug 1999 05:29:44 GMT, cctr114@cantva.canterbury.ac.nz writes:
>> From owner-orion@panda.mscc.huji.ac.il Sat Aug 28 00:09:51 1999
>> >Hence a radiocarbon 
>> >date after 63BC indicates that the material the scrolls are made from 
>> >was still alive after 63BC and thus could not have been deposited
>> >on or before that date. 
>>    Nope.  The dates are the LATEST possible.  Since we have NO 
>>    protocols showing how the effects of contamination were taken
>>    into account we must assume these are the LAST dates possible. 
>>    IOW, tests done on uncontaminated samples would show EARLIER
>>    dates.
>You seem to be questioning the underlying theoretical understanding
>of the method here. In a living system the ratio of C-14 to C-12 
>is in equilibrium with the environment. Once the system is dead
>there is no mechanism to maintain that equilibrium hence the ratio
>of C-14 to C-12 changes as the C-14 decays. But if I understand your
>argument correctly you are saying:-
>(1) The equilibrium state is maintained until deposit.

     Sorry, I'm not saying so.  I've left in above what I wrote.
     Where do you see that?  If I had suggested a papyrus cutting
     spree with hastily dried sheets scribbled on by rushing scribes
     rolling their finished products to crams into hastily prepared
     jars, all at once, you'd be right.  However, I didn't.  

>(2) Contamination in modern times makes the samples appear younger.

     Agreed.  As does contamination along the way.  I can posit no end
     of events that could have filled the caves with smoke over the

>I don't think (1) is right. If this is what you are claiming can you 
>explain a mechanism whereby the C-14/C-12 ratio in the scrolls are 
>kept in equilibrium with the environment after the material is no
>longer living.
>The problem of (2) is supposed to be addressed by the cleaning of the

    Read again Dr. Jull's caveat (my _underlining_).

     "I think it is important that we all understand that the
     radiocarbon dating of the scroll samples was limited by the
     amount of material which could reasonably be removed (as was
     discussed by both Bonani et al 1991 and Jull et al 1995) and
     further by the amount of pretreatment (cleaning) which could
     be done without _destroying_ the small samples we had for

>>    Some, possibly, but each present serious questions.  There are
>>    FOURTEEN others earlier than 63 BC.  Unless you can show evidence
>>    of multiple deposits - which would help explain the dating dif-
>>    ferences - you must consider the whole deposit.
>But this assumes (1) above. I think the *method* of radiocarbon
>dating determines the date of the death of the organic material 
>on which the scrolls were written. A simpler explanation for
>the different dates is that the scrolls were "manufactured" over
>a lengthy period of time.

    Isn't that what I assumed?  Or are you putting YOUR words 
    in MY mouth.?  I don't think that's what you intended.

>>    Irrelevant.
>>    You seem to have ignored my layman's argument showing how rapidly
>>    contamination can skew results.
>>    Again, you fail to consider that the dates reported are the
>>    latest for each artifact, not the earliest.  Until the contamin-
>>    ation issue is fully addressed, you're stuck with what's there.
>I haven't failed to consider this, at this point I don't believe it.
>Provide me with a mechanism to keep the C-14/C-12 ratio in equilibrium
>with the environment and I'll come round to your point of view.

     I had your view from the beginning.  Welcome to the club.

>Yes, the contamination issue is real, but on this I have to bow to the
>superior knowledge and experience of the AMS people.  

    Remember what Dr. Jull said about removing contamination, namely,
    that cleaning _may_ destroy the sample before it can be tested.
    Hence, we may need parallel methods.  As a reminder for a second
    time, the recent pronouncement by an Israeli source on the Shroud
    of Turin on the basis of pollen found being of Levantine Provenance
    and dated before 750 CE shows the decontamination techniques for
    C-14 testing twenty years ago needed improvement.

>Bill Rea, Information Technology Services, University of Canterbury  \_ 
>E-Mail b dot rea at its dot canterbury dot ac dot nz                 </   New 
>Phone   64-3-364-2331, Fax     64-3-364-2332                        /)  Zealand
>Unix Systems Administrator                                         (/' 


Tom Simms, retired  (does not mean I have put new tires on my car. <G>)
For private reply, e-mail to Tom Simms <tsimms@mailserv.nbnet.nb.ca>
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