From: Technotranscendence (neptune@mars.superlink.net)
Date: Tue Jun 26 2001 - 14:19:26 MDT
Sorry it took so long to answer this. Work projects got in the way, then I
forgot about it.:/
On Saturday, May 12, 2001 10:06 AM CurtAdams@aol.com wrote:
> > I admit, I have some problems with it. What!?! The usual way the
scenario
> > is put, it's hard to believe anything above bugs and bacteria would
> survive.
> > There has to be a reason why crocodiles, mammals, lizards, toads, and
birds
> > made it, but T. rex didn't. A big asteroid hit would seem to be more
> > egalitarian in its affects, taking out all major groups -- not
specifically
> > targeting nonavian dinosaurs
>
> The above groups all differ from dinos in that they
> can take refuge underground or underwater*.
What of smaller dinos?
> If the
> earth was put on "bake" for 1 day, as one estimate of
> tecktite heat delivery has it, the dinos would indeed
> be all gone and the above groups still there.
Archibald does cover this in _Dinosaur Extinction and the End of an Era_.
> * it wasn't all birds. Actually birds were almost
> entirely wiped out. Only one group of shore birds
> survived. They then radiated to current bird niches.
> The near-elimination of birds *may* have provided the
> opportunity for bats to emerge.
I was not aware of this.
> I just heard yesterday of a discovery of a suspicious
> carbon layer at the Triassic/Jurassic mass extinction
> boundary.
This might support a global wildfire resulting from an impact.
> An interesting point is that the end-
> Cretaceous and end-Permian extinction match up with
> *both* massive bolide impacts *and* bogglingly large
> flood basalts.
Yeap. Archibald does not dispute this, though there is some disagreement
over timing. On page 145 of the book, he even charts the level of eruption,
but argues on 144 that the "eruptions... were episodic -- not continuous."
The flood basalts range in age from 69 to 65 million years old. If the
impact is placed at 65 million years ago, this means a good portion of high
level volcanic activity was already happening before the impact. This does
not completely rule out an impact as the [nonavian] dinosaur killer, though
it might point to an accomplice.
> > Archibald points out the myriads effects of sea level changes and how
> >this correlates well with the fossil evidence -- much better than an
impact
> >or massive volcanism.
>
> I don't get that. Sea level changes happen all the time. I just saw
> a palentologist talk about the 300-meter drop at the end of the Miocene
> oscillation. The graph of late Tertiary sea levels looks like the path
> traced by a yoyo as its operator walks on uneven ground.
According to Archibald -- see his chart on page 148 ibid.; he's relying on
Smith & Co.'s _Atlas of Mesozoic and Cenozoic Coastlines_ -- nonmarine area
was at its highest just before the K/T boundary.
The Tertiary certainly has had its share of sea level and land area changes,
though these appear small in comparison to the changes during the
Cretaceous -- again, according to Archibald.
All of these does not speak completely against an impact, IMHO, though it
does mean there is some more explaining to do.
Cheers!
Daniel Ust
http://uweb.superlink.net/neptune/
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