>Since there are no trees that have 10,000 continuous rings, I would be
>willing to bet that there is some tautological analysis involved in that
>extrapolation. Although the picture of tree ring variation appears to be
>pretty well closed for about 4000 years, I wouldn't stake my life on dates
>older than that. Brown has done some interesting analysis on trends older
>than 4000 years that is revealing.
Some of R.H.Brown's best articles are more recent ones:
See especially Origins 21(2)66-79 (1994) in which he distinguishes the
equilibrium inventory of C-14 in the Lower Biosphere (the ocean below about
300 ft, with its associated sediments) from that of the Upper Biosphere,
and gives a model for relatively rapid accumulation of the present total
biosphere C-14 inventory. He corrects deficiencies in previous articles
that used published estimates for the formation of C-14 which were based on
the assumption that the total biosphere is in C-14 equilibrium. He
presents evidence for questioning this assumption.
See also Origins 22(1)47-52 (1995) discussing statistical methods assessing
the reliability of using tree rings to calibrate radiocarbon dates.