In a message dated 5/12/01 7:27:59 AM Pacific Daylight Time,
neptune@mars.superlink.net writes:
[re bolide theory of end-Cretaceous extinction]
> 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*. 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.
* 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 just heard yesterday of a discovery of a suspicious
carbon layer at the Triassic/Jurassic mass extinction
boundary. An interesting point is that the end-
Cretaceous and end-Permian extinction match up with
*both* massive bolide impacts *and* bogglingly large
flood basalts.
> 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.
This archive was generated by hypermail 2b30 : Mon May 28 2001 - 10:00:04 MDT