Re: S&L+ Where Do We Go From ...

[Tompaleo@xxxxxxx]

As one who has a great interest in the study of mass extinctions versus
gradual or stepwise extinctions (and their causes), it would seem to me that,
judging by the exchanges on this list, the S-L effect is not useful in
determining weather or not a particular extinction mode occurred. This is
especially so where the Hell Creek is concerned. Was not this "1 meter gap"
once a "three meter gap"? 
Thanks to more detailed srutiny the gap has narrowed to less than one meter
as Peter has shown. The result of such resolution to date then seems to
concur that there is a taphonomic bias  (assuming near perfect resolution as
far as sampling is concerned) as would be expected in highly variable
depositional settings such as at Hell Creek from the latest Cretaceous
through the Tertiary.
 In conclusion then it seems that the S-L effect is a valuable statistical
tool for the number crunchers but can be convincingly used to argue for (as
Peter has) or against (as in a paper by Michael Williams ; March 1994 Journal
of Paleontology). The remaining phenomena to deal with is the Iridium anomaly
and this remains as the most direct evidence  we have that a large bolide(s)
struck the earth ~65Ma and set in motion a domino effect of events that
exterminated the dinosaurs, and numerous other contemporaneous animal and
plant life.

                                                                Tom Lipka
                                                        tompaleo@aol.com