Robin,

Check out the refs in this article:

http://www.sciencenews.org/20030906/fob2.asp

Regards,
Paul Kekai Manansala

--- TTT UUU <gymnogoy@...> wrote:
> Paul
> Very interesting. The chances for error in dating is
> high especially in a tropical climate with high
> humidity. Bacteria and fungi moss and algae will
> grow on any wet surface.
> Is anything about the Borneo rock paintings
> published in accessable books?
>
> Robin Day
>
> Paul Kekai Manansala <p.manansala@...>
> wrote:
> Cross dating (Th/U-14C) of calcite covering
> prehistoric paintings in
> Borneo
>
> Quaternary Research, September 2003, vol. 60, no. 2,
> pp. 172-179
> (8)
>
> Plagnes V.[1]; Causse C.; Fontugne M.; Valladas H.;
> Chazine J.-M.;
> Fage L.-H.
>
> [1]Laboratoire des Sciences du Climat et de
> l'Environnement, UMR
> CEA/CNRS 1572, avenue de la Terrasse, 91198
> Gif/Yvette , Cedex,
> France
>
> Abstract:
>
> We present the first application of cross-dating
> (Th/U measured by
> thermo-ionization mass spectrometry (TIMS) and 14C
> measured by
> accelerator mass spectrometry (AMS)) of calcite
> covering prehistoric
> paintings. Th/U age estimates of cave drapery range
> from 9800 to
> 27,300 yr B.P. while conventional 14C age is
> estimated between 9900
> and 7610 yr B.P. depending on the dead carbon
> correction. The age
> discrepancy is attributed to a disturbance of Th/U
> and/or 14C
> geochemical systems, showing the limits of the
> geochronological
> approach applied to this kind of material. For the
> Th/U system, the
> poor consistency of U data (U content, 234U/238U
> activity ratios)
> and apparent ages argue for open system conditions.
> For 14C system,
> variation of the dead carbon fraction (dcf) and a
> possible mixing of
> successive generations of calcite could account for
> age discrepancy.
> Nevertheless, one sample shows concordant ages for
> the two methods.
> Compatible ages through corrections for open system
> conditions are
> assumed for other samples. Then, the cross-dating
> suggests 9900 yr
> as the minimum age of the piece of drapery; the
> underlying painting
> must be older. This study of rock art demonstrates
> the presence of a
> Pleistocene population before 9900 yr in the
> southeast of Borneo,
> whereas previously the only population in evidence
> in this area was
> of Austronesian type from ~5000 to 6000 yrs ago.
>
>
>
>
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