| [Thread Prev] | [Thread Next] | [Thread Index] | [Date Prev] | [Date Next] | [Date Index] |
> The biases and sampling error inherent in S/L-E account for most >of
>the problem worldwide. What this means, as we tried to explain in >our
>original paper, is that the fossil record per se cannot descriminate
>between sudden extinctions and gradual extinctions; therefore >paleontology
>has little to say about the time period of the extinction event or the
>mechanism. I, too, would argue that all the taxa going extinct >"near" the
>end of the Cretaceous (or any other extinction boundary) tell us >something
>very important. But it's unlikely to be the mechanism itself.
This sounds like the paleontological version of the Heisenberg Uncertainty
Principle! If we have reached a fundamental limit in paleontology whereby we
can't argue definitively as to the mode and timing of an extinction event,
then we must turn to geochemical and geophysical methods to fill in the gaps
or refine what is known.
>Paleontology, for example, could not descriminate between an >impact that
>produced an extinction and a 1000 year change in >paleoceanography that
<snip> <splice>. (Not >too
>silly either, as El Ninos today accomplish much of that in a single
>year--mass mortalities in all those groups, and at least one >extinction; so
>hold one of those for a decade, and you probably can have another >mass
extinction.)
Good point. I seem to remember reading a paper (in Geology?) where someone
attempted to identify paleo-El Ninos in the geologic record and at the time
thought that it could be applied to the K-T. I'will try to dig it up for a
reread.
>What we need to do, it seems to me, is to define carefully (using >the
>entire biota, stable isotopes, and paleobiogeography) the pre- and
>post-extinction environments. That's not been done well enough yet
>(especially the post-) to set limits on the actual mechanism.
I certainly would like to see this come to pass regardless which way the
results go. A concentrated, gloabl effort need to be started whereby pro,
con, and other, share resources and work together in a manner similar to the
Human Genome Project. Look at how successful it has been!
> After >all,
>the asteroid did not clobber each and every individual--it somehow >changed
>the environment and that caused the extinction, if you believe in >killer
asteroids.
We only need to look at the _multiple_ impacts of kilometer sized fragments
of S-L9 on Jupiter earlier this year and the lunar, and planetary cratering
record of the last billion years to see that they do exist!
regards,
Thomas R. Lipka
Paleontological/Geological Studies
Partial index: