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Re:



 >
 > >... apparently, at least in North America, the forests
 > >were temporarily removed, since immediately above the Iridium
 > >layer almost all "pollen" is fern spores (for about a centimeter).
 > >swf@elsegundoca.ncr.com             sarima@netcom.com
 >
 > Interesting, since one prediction of the impact theory is regional
 (global?)
 > forest fires. If they were severe enough, the surviving trees might
 take maybe
 > a million years to re-seed themselves populously across the
 devastated areas.

Well, the 1 or so cm of fern spore domination represents, at most,
a few thousand years.  Which is more or less the time it takes
to reestablish climax forest after clear-cutting  (the time
varies from a few hundred to over a thousand years for this).

Also, I believe there is *not* a charcoal layer coordinate with
the Iridium spike in the Hell Creek, which suggests the reason
for the deforestation may *not* have been a fire.
[I have also seen one paper which claimed this deforestation
is not seen in most other parts of the world].

So, a while a fire is one possiblity, the shock wave itself
may also have been the cause.
 >
 > This is also predictable from the impact hypothesis. Global dust
 would shut out
 > the sunlight that planktonic forms need. This would disrupt the food
 chain all
 > the way to the large sea reptiles (plesiosaurs, et al). The
 survivors on land
 > and at sea would be the scroungers (small mammals and fish).

This is predictable on almost *any* extinction model.

It is not a differentiator.  It is expected that forms with
wider tolerances (generalists) and with smaller resource
requirements wouls survive *any* sort of environmental stress
better.

swf@elsegundoca.ncr.com         sarima@netcom.com

The peace of God be with you.