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Re: Extinction

At 07:40 PM 3/23/00 +0100, Tommy Tyrberg wrote: 
I wrote:
>The debatable issue is whether the impact was, by itself, a *sufficient*
>cause for the total extinction of non-avian dinosaurs.  (For instance, I
>suspect that the bolide was so effective only because the ecosystems of the
>Earth were already stressed from other causes, and the same bolide striking
>at, say, 34 MYBP would have had little long-term effect).
>
Actually I think it would have had a great deal of effect at 34 MYBP, since
that would be right at the Eocene/Oligocene border, Stehlins "grande
coupure" when earth's ecosystem were probably a great deal *more* stressed
than in the late Maastrichtian.

I may have gotten the target date wrong: I was looking for a time when only background extinction was happening.

But I have a hard time believing it was more stressed: massive flood volcanism, receding oceans, possible oceanic anoxia, and in the middle of THAT a major meteorite strike.

Personally I find it hard believe it is justa coincidental that the P/Tr
extinction happened exactly at the same time as the largest volcanic
episode of the Phanerozoic and the K/T one exactly at the same time as the
largest bolide impact of the Phanerozoic.

Who said it was a coincidence? I merely suggested the impact was not a *sufficient* cause. In fact the coincidence I find hard to believe is the fact that *both* extinctions occurred during major flood volcanism episodes.

[The discovery of dinosaurs in sediments in the middle of the Deccan Traps does not really rule out their contribution to the extinctions, since the effect could have been relatively gradual, and required the additional cause of the impact to *finish* the job].

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