Re: EXTINCTION

[stssram@st.unocal.com (Bob Myers)]

On Apr 27, 17:46, Scott wrote:
} Subject: Re: EXTINCTION
>   I had mostly accepted the impact theory based on:
> 1. The presence of iridium at the K/T boundary
> 2. The dinosaur fossil record ending abruptly at the iridium layer
> 3. The Chixulub crater being of more than sufficient size and the correct age
>    (if you find someone standing over a dying body, with a smoking gun in his
>    hand, what conclusion would you come to?)
> 4. There are no other convincing theories to explain the extinction of large
>    reptiles (land, air, and sea) while preserving mammals, birds, amphibians,
>    crodilians.
> 
>   Recent postings on the list have attacked points 2, 3, and 4. I think that
> points 2 and 3 are still controversial. As for point 1, it has been suggested
> elsewhere that iridium could have been produced by volcanic events such as the
> Deccan Traps. That leaves point 4, and I am still not convinced by alternate
> theories. Therefore I find the best solution to be:
> a) suspect that reports of dinosaur dwindling prior to the K/T boundary to be
>    a systematic error
> b) _IF_ the Chixulub crater turns out not to be an astrobleme, consider that
>    the impact occurred in deep ocean (where it would be covered in sand and
>    virtually invisible), or that the impact was a volatile comet (that left no
>    crater)

So if:
1) "Chixulub" is volcanic, not an astrobleme, and still of the same age
and since 
2) The Deccan Traps in India, the largest continental flood basalts of
        the last >100 my, are also of the same age
3) Iridium is known from volcanoes.  Not in the concentrations required in
   the iridium layer, but then again these *were* unusually large and rapid
   volcanic events
naturally, we conclude that  
a) Evidence of dinosaur dwindling prior to the iridium layer is suspect
and 
b) The dinosaurs were killed off by an astrobleme that impacted the deep
   ocean, or that there was a volatile comet that left no crater.

Why?  because of 4)

> 4. There are no other convincing theories to explain the extinction of large
>    reptiles (land, air, and sea) while preserving mammals, birds, amphibians,
>    crodilians.

I really don't think we understand ecosystems and extinction well enough to
postulate a very large astrobleme on the basis of the extinction patterns
alone.  Wouldn't Occam's Razor suggest that massive volcanism is to blame in
that case?


-- 
Bob Myers                               Unocal Energy Resources Division
Internet: Bob.Myers@st.unocal.com       P. O. Box 68076
Phone: [714] 693-6951                   Anaheim, California  92817-8076