re:Radiometrics

[Neil Clark <gxha14@udcf.gla.ac.uk>]

>David wrote: 
> > 
> > Anyone with a better reference library than mine:
> > 
> >    I'm having a debate with a local colleague about the validity of
> > biostratigraphic dating vs. sequence stratigraphic dating.  Upshot is,
> > we need a current source of radiometric dates for precise intervals within
> > the Santonian through early Maastrichtian of the Upper Cretaceous.
> > Harland, et al., 1989, _A geologic time scale_ does not give dates more
> > precise than the stadial boundaries.  Anyone know a better source?
> > 
> > David Schwimmer
> > Columbus College
> > schwimm@uscn.cc.uga.edu>[A>[A>[A>[A>[B>[B>[B>[B>[B
> > 
> > 
> 
> I'm afraid that Harland doesn't even give good stadial boundary dates. 
> I would check the source references before using any of Harland's dates.
>  Some of the dates he has used are in the middle of stages and not of
> the boundary giving the impression that some stages are shorter/longer
> than they truly are!
> 
> As for your debate, you cannot compare a biostrat dating scheme with a
> lithostrat or chronostrat scheme as they represent different things.  In
> most instances biostrat, when available and fine enough, is very
> accurate for comparative dating (sometimes more accurate correlations
> than with radiometric means) but does not give dates.  Radiometric
> dating is accurate enough.  Sequence stratigraphy is also useful but has
> problems with diachroneity which biostrat doesn't.
> 
> Neil Clark
> Glasgow University
>