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Re: Theories on the extinction of dinosaurs



At 10:54 AM 11/16/99 -0500, Dinogeorge@aol.com wrote:
>
>Actually, we don't need a precise timing; all we need is to note that below 
>K-T boundary clay there are plentiful dinosaur fossils, and above K-T 
>boundary clay there are only reworked dinosaur fossils if any. 

Actually, to distinguish some of the hypotheses one *does* need a certain
degree of precision.  Multicausal extinction could well show a pattern very
like this as long as the impact was *one* of the causes.  Indeed, relying
on this pattern ignores the slight possibility that the local dinosaur
extinction somewhat *preceded* the impact, as that, also, would produce
this gross pattern of observed fossils.

Thus, this pattern, without more precise timing, does NOT address the issue
of simultaneity of the extinctions.  It still allows considerable leeway
*prior* to the impact for the extinction in each local basin to occur.
Variations of up to about a million years in the timing of the extinctions
are not yet ruled out by the data.  (And a multicausal process *might*
result in subtle differences in timing from one basin to the next).

>This is what 
>is found everywhere in the world so far, and it strongly suggests the 
>boundary clay had something to do with dinosaur extinction.

Yep.  This is why the impact is included as *one* of the causes in all
multicausal models.

--------------
May the peace of God be with you.         sarima@ix.netcom.com