On Fri, 14 Jan 2000 15:36:47 -0500 Michael Weinert
<[log in to unmask]> wrote:
> So I suppose I would even remove the coffin from the whole equation
> and ask the question of whether or not it's possible for the woman's
> lead isotopes from her tooth enamel to be related to N-W Iberian ore
> deposits?
Dear Michael,
In this case, the question of provenance is complicated, not
surprisingly, by the problem of contamination from the coffin. We are
rather pleased that we managed to recover at least some of the biogenic
lead which the woman ingesed during childhood. We know this because
what we measured is isotopically distinct from the coffin lead (which
has typical UK lead ore values). The problem is that, even though her
biogenic signal has not been totally swamped by contamination, we
cannot rule out some diagenesis. Indeed, we think this is highly likely
because she has quite a lot more lead in her tooth enamel than we would
expect - even for a high status Roman.
This means that we do not know for sure the isotope ratios of her
childhood lead. Logic suggests however that this must lie on a mixing
line, the gradient of which is determined by the relative positions of
the coffin lead and the tooth ratio we measured. Exactly where on this
line the true childhood ratio lies depends on how much lead we think
she was exposed to in early life. This is obviously guesswork.
Having said this, the mixing line takes us away from the growth curve
and into a region of isotope ratio space in which we would not expect
to find the great majority of lead ores. No UK ores plot on this line
and these are reasonably well characterised so the balance of
probability suggests a non-UK origin. However, so far, we have not been
able to suggest a source region with isotope ratios which plot on, or
sufficiently near to our mixing line. No Iberian ores (that I know of)
plot close to the line, but of course not all ore sources have been
sampled by a long way.
Sorry if the situation remains somewhat ambiguous, but this is why we
also routinely measured strontium and oxygen isotopes as well. The Sr
was ambiguous in this case. The oxygen results (not undertaken by us in
this case) were discussed on the programme. By the way, there was some
discussion on the Brit-arch mailing list about possible Christian
associations with the iconography back in the summer when it first came
to light. You might like to check their archives.
Best wishes,
Paul.
----------------------
Dr Paul Budd
Department of Archaeological Sciences
University of Bradford
Bradford
BD7 1DP, UK
Tel: +44 (0)1274 233554
Fax: +44 (0)1274 235190
E-mail: [log in to unmask]
Web: http://www.brad.ac.uk/staff/pdbudd/personal.html
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