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orion Castor oil impact on C14 tests
Two comments regarding P. Sodtke's post:
Firstly, I absolutely agree that the quote below (by Taylor) assumes that
the site itself strongly suggests a single date for articles under
examination. A good example would be dating the stack of plates
in Qumran's "dining room". Here's a situation when one can safely
reject outliers.
However, this supposition of a single date is precisely not true for the
situation of a "cache", such as Qumran's caves, a situation which could
easily group items comming from very different periods of time.
> > "Little reliance should be placed on an individual 14C date to
> > provide an estimate of age for a given object, structure, feature, or
> > stratigraphic unit. A critical judgment of the ability of 14C data
> > to infer actual age can best be made with a suite of determinations .
> > . . Concordance of values on different sample types . . . from
> > well-defined stratigraphic contexts provides one of the strongest
> > arguments for the accuracy of age assessments based on 14C values"
> > (R. E. Taylor, _Radiocarbon Dating_, 1987, p. 105).
>
Secondly, regarding the meaning of present tests of oil contamination, P.
Sodtke says:
> a. These tests will attempt to control for possible castor oil
> contamination and to determine how much such contamination might have
> thrown previous 14C dates off.
>
> b. By adding to the database of reliable 14C dates of DSS, these tests
> will increase the statistical confidence of conclusions that might be
> drawn. For example, if the deposit date of the collection were later
> than most of the 14C dates that we have, then, the larger the database,
> the more likely that more than one or two of these later dates would
> turn up. If, on the other hand, as the database grows larger, more later
> dates do not turn up, then it is more *probable* that the isolated
> values are, in fact, outliers.
Well, it's not clear to me how the present tests will "control" for oil
contamination or how would they be able to "add to the databse of of
reliable 14C dates of DSS". As long as no determination can be made
whether a particular manuscript was oil-contaminated, all the tests will
do is force us to conclude that the C14 in this case are less reliable
than everybody assumed. That is surely equivalent to deleting from the
database of reliable dates, not the other way round. The best thing that
can happen in terms of precision of dates is for the test to discover that
castor oil makes not difference it terms for C14, and that I understand is
unlikely. Not that this a criticism of the tests - they are clearly
necessary and interesting.
Best regards, Asia Lerner