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Re: orion-list Radiocarbon discussion

On Thu, 19 Aug 1999 14:14:48 -0700, ajtjull@physics.arizona.edu writes:
>To the list:
>I was asked to comment on some statements made by Greg Doudna and
>maybe others on the question of the radiocarbon measurements of the

   Thank you for your lucid comments, Dr. Jull.  

>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 dating.

   These discussions were never raised on the List until just
   recently.  As a result, we've been flying blind.

>Since I am coming at this problem from the dating end, I will con-
>centrate on that angle.
>I would comment specifically on some assertions made on the Orion list
>by Doudna and Simms.

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

>In my opinion,
>this result should be considered skeptically because of the wide
>difference in ages reported by Bonani et al (195) in their table 2 on
>this scroll and so has a suggestion of some problems with pretreat-

   Which was my point, inter alia.

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

>I agree that in this case the unusual result precipitated the retest-
>ing to some extent.  However, you will note that this sample also was
>one of those listed as being contaminated with perspex glue.  If it
>were not removed, this glue would be expected to be 14C-free, from
>petroleum, and hence give an apparent "old" age.   However, one might
>also consider that those scroll fragments which have been glued to
>rice backing paper may also have had other things done to them.   The
>sample of 4Q171 pPs was considered to be cleaner in our report (Jull
>et al., 1995)

   Cleaner?  See my next comment.

>> The second
>> > > sample gave a dating in agreement with the other Qumran
>> > > texts.  There are now two reported C14 dates for 4QS(d),
>> > > and both cannot be correct.  There is no reason to reject
>> > > the 2nd century CE dating other than that it is outside
>> > > the pattern of other Qumran text radiocarbon datings, as
>> > > well as outside of expectations on other grounds.>
>I think this indicates that we need to develop better criteria for
>cleaning these samples.

   Until such standards are developed then are all bets off?  C-14
   technicians need to show these caveats plainly in their reports.

>> >    In the earlier discussion noted, we learned that the
>> >    modern text examiners often brushed the fragments with
>> >    modern oil to highlight the writing.  No consistent
>> >    record of who did this exists other than that it DID
>> >    occur.  IOW, we have no consistent record of the type
>> >    of handling of the fragments.>
>True, this would be helpful.

   More than helpful.  Until you have set out your contamination
   removals protocols precisely, not having such is fatal to any
   precise conclusions, right?  (as your caveat below...?)

>> >    There is a further explanation not discussed the first
>> >    time around.  Some fragments may have been shielded
>> >    from the ambient contamination of the centuries.  No
>> >    review that I know of has addressed this issue for it
>> >    can easily account for the width of the distibution
>> >    curve of results.
>I find it hard to believe that this is a problem.  If by ambient
>contamination you mean physical, then these should be removed on
>pretreatment.  If you mean chemical contamination (e.g. by oils) we
>can use solvent extraction to remove these.

   In the dozen years since I ceased being a flat fifty a day
   smoker, I've become quite conscious of how insidious and serious
   ambient contamination can be.  In my lifetime, I moved from a
   wood and coal burning society to an oil burning one.  I can see
   meaningful contamination occurring just as I hypothesized during
   the cave clearances.  

   Let me point out the cigarette butt and package contamination
   found in Reeves & Martin's Nov/Dec '99 clearance under my "X" and
   next to KV-62 all lying on and between the 12th C BCE workers'
   hut foundation stones.  This was evidence of how far down the
   Valley of the Kings Davis's 1907 clearance went.  Only when they
   cleared deeper into virgin soil below did they learn where that
   earlier work stopped.  

   No proper journals of any of Davis's work then were ever publish-
   ed.  But then, anti-smoking protocols did not exist in the 1940's
   either.  That's when I started smoking.  That's when the Caves
   were mostly cleared.

>>  But it is wholly
>> > > inappropriate to assume no regional offset until proven
>> > > otherwise.  It is appropriate to assume lack of knowledge
>> > > on this point until there is knowledge.
>You make a true statement, but it hides the fact that no regional
>effects in this kind of radiocarbon sample has been observed with an
>offset in radiocarbon age of more than 20 yrs.  Indeed (and this is an
>important point) this is about the uncertainty in the calibration
>curve itself.
>> > > In fact, the existence of a regional offset, possibly
>> > > significant (i.e. up to the 20 years estimated possible),
>> > > might already be suggested by existing Scrolls data.
>> > > I refer to the five dates on the Bar Kochba texts.
>> > > The distribution of dates was Zurich had two one way
>> > > from the Seattle-Belfast curve, the Seattle-Belfast
>> > > curve was in the middle, and all three of Tucson's dates
>> > > were in the _other_ direction.  Making sense of those
>> > > Bar Kochba dates is very difficult.
>All of these samples were papyrus and not parchment.  I think this may
>be important to understand these differences.

   Papyrus and also linen are very different writing surfaces to
   clean from skins.  It's good thing too, or we'd all be very
   liable to many more infective invasions... <g>.  Woven fabrics
   are highly permeable.  You point out the hazard of cleaning a 
   sample to destruction.  That concern should be carved on all
   our foreheads.

>> >    The variability noted above would convince most re-

   [... snip ... noted & agreed ...]

>There is in such things no substitute for more measurements, which if
>they agree allow us to reduce the error, and if they do not, should
>tell us that there is some problem.  Also, better sample preparation
>protocols might be developed for this type of material.


>I hope these comments are helpful,
>Timothy Jull
>Research Scientist, University of Arizona
>and Editor, Radiocarbon

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