Re: Radiometric Dating Techniques

Arthur V. Chadwick (
Wed, 11 Feb 1998 08:58:49 -0800

At 03:57 PM 2/10/98 -0500, Chris wrote:

>The only assumptions in the analyses I've read are that: (1) trees
>growing near each other experienced roughly the same climate (i.e.,
>the pattern of wide and narrow rings corresponding to years with good
>or poor growing conditions can be matched up); and (2) rings grown
>in the same year on different trees would date to approximately the
>same age. These assumptions are certainly reasonable, and alone they
>are sufficient to match up rings between living and recently dead
>trees, and then between those trees and ones which have been dead
>for a longer time.

As one who has taught dendrochronnology, I have a few opinions on this
particular subject. Also, one of my graduate students went to work for
Ferguson in his lab at U of A, and in fact was the curator of his work
after his death, and is presently probably the only one who know anything
about how he produced the bristlecone chronology. Another of my graduate
students gave a seminar to the lab on dendrochronology of fossil trees and
had ample opportunity to analyze the procedures there, and to work with
Ferguson for a while. I can say on pretty firm grounds that the
Bristlecone chronology before 4000bp is fraught with problems and
unanswered questions. While Ferguson was alive, he never allowed anyone to
analyze his original data or the bases for the many suppositions that went
into the establishment of the chronology. Thus the cronology was not
subjected to the normal rigors of science. This is regrettable, because I
believe he was a careful and sincere scientist. Of course one could always
excuse Ferguson for not revealing the bases of his decisions (for example,
the most important rings in any chronology are the "missing rings" which
have to be added by the investigator). But suffice to say the chronology
before 4000bp is entirely dependent on C14 dates of the wood, and is thus
tautologous. This does not mean it is meaningless or necessarily wrong,
just that I wouldn't base too much on it.