RE: Hell Creek [VERY LONG]

["Allan Edels" <edels@msn.Com>]

David, et al:

A reply, finally, to your reply to my very long missive :-).   

Note that I originally wrote most of that posting nearly 4 years ago.  I
did very little editing before sending it out.  (Also, parts of it had
originated 15 years ago!)

I've prefixed my responses with "===>".

Thanks.
 
Allan Edels 

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] On Behalf
Of David Marjanovic
Sent: Thursday, May 30, 2002 5:34 PM
To: The Dinosaur Mailing List
Subject: Re: Hell Creek [VERY LONG]

----- Original Message -----
From: "Allan Edels" <edels@msn.Com>
Sent: Thursday, May 30, 2002 8:37 AM

>     Facts are:
>
> [...]
>     2)    The object hit the earth around 65 mya.

_At_ 65 Ma ago, to be precise, at 64.98 +- 0.05 Ma ago.

===> There was some question of the precise dating when I originally
wrote this.

>     3)    Lots of things changed on earth around 65 mya - climate,
land
> vs. sea ratios, etc.

"Around". I'll ask Rampino next Monday on the last word on those climate
change issues; the (milder than thought for long) regression that's seen
in
the Western Interior Seaway may not have been a global phenomenon
either,
and cannot have lead to global extinctions in any case.

===> There were reports of some seas receding over 200 feet - rather
quickly, by geological standards.

> 2)    There were a lot of different survivors, including birds,

Hardly any birds.

===> Yes, but they made it!

> crocs,

Not the turtle-eating ones. Someone please find :-> a good record of LK
Notosuchia which aren't known from the Cenozoic.

> mammals,

Suffered quite some losses, though it's for most groups unclear exactly
when. The Asian clade of Eutheria (Zalambdalestidae, *Kennalestes*,
*Ukhaatherium*, maybe Zhelestidae), the deltatheroid, stagodontid and
most
or all pediomyid metatherians, the last docodont (*Reigitherium*), the
last
triconodontid (*Alticonodon*), maybe a relative of that
(*Austroconodon*)
and IIRC some "symmetrodonts" are known from the Campanian and/or
Maastrichtian but not the entire Cenozoic. Only one dryolestoid,
*Peligrotherium*, has so far been found in Paleocene layers. There are
stagodontids and pediomyids in the Hell Creek Fm. Many multituberculates
snuffed it IIRC, but I really know too little about them.

===> Once again, they had major groups survive.  I never said that any
of these groups passed through the K-T boundary unscathed.

> frogs

Well, they survived Mt. St. Helens, I've read in the archives.

===> If the frogs were hibernating (if it was winter or if the "Nuclear
Winter" scenario triggered hibernation).

> 3)    Pterosaurs had all disappeared prior to the Maastrictian
(possible
> exception - _Quetzalcoatlus_).

Outdated. *Hatzegopteryx* and the Spanish beast are end-Maastrichtian.
How
old are *Bennettazhia* and *Montanazhdarcho*?

===> Unknown at the time I originally posted.  I haven't kept up with
all the pterosaurs. 

> 4)    Ichthyosaurs had all disappeared several million years prior to
> K-T.

Not just several Ma, but apparently in the Cenomanian-Turonian
catastrophe.
And before that (since the beginning of the K), there was only one
genus,
*Platypterygius* (whatever a genus is... don't know how many species
have
been described for it).

===> Nonetheless, that genus disappeared millions of years before K-T.

> 5)    Many of the dinosaurs were in a decline (in terms of numbers of
> genera and species).

Now is this a fact, or is it just the Signor-Lipps effect? (So far what
once
was the 3 m gap shrinks every time someone looks more closely.) Is it
known
from outside the Hell Creek Fm? (AFAIK not.)

===> The problem is that we do not have a lot of late Maastrichtian
terrestrial formations to test this with.  Hell Creek is a really good
place to look (Leave it to Jack to get into that prime piece of real
estate.  [Thanks to Nathan, I think?]).  I'm assuming that the decline
is real.  It doesn't matter to my way of thinking.  Either the dinosaurs
were in a decline - which I believe they would have recovered from
(except for that nasty bolide!).  OR they were just damned unlucky,
along with a whole bunch of other animals. 

> 7)    The climate changed drastically (geological time) - from very
warm
> and humid to much cooler and drier.

Isn't that an old factoid?

===> Actually, it is based on the changes in the Foraminifera -
indicating global changes.  The only thing that might be old is the
humid vs. drier.

> 8)    Foraminifera changed at the K-T, indicating the climate change
> (They went from very complex forms, usually indicative of warm water,
to
> very, very simple forms, usually indicative of cold water).

>From a very _diverse_ array of simple and complex forms to a
monoculture of
small and simple forms -- a part of the plankton extinction. Strangelove
ocean.

===>Yes.

> 9)    The Deccan Traps (of India) had been flowing for several million
> years prior to K-T, and seem to have continued several thousand years
> after it.

Several million years after it IIRC.

===> I wasn't sure of the end date when I originally wrote this.

>     h)    If the Ozone layer was damaged or removed,

Probably it was. The impact must have created large amounts of nitric
oxides
and blasted them far upwards. Should destroy the ozone layer immediately
according to apparently unpublished calculations. :-} BTW, nitrogen
dioxide
(and the monoxide becomes dioxide pretty soon) is deeply reddish-brown
[FREEZE], while dinitrogen monoxide = laughing gas is a powerful
greenhouse
gas [BAKE]. :-)

===> If the angle of the impact path with the ground was between 10 and
20 degrees, then the bolide (which was large enough for this scenario)
could strip off a large percentage of the Ozone layer.  Adding in the
effects from the NOx should really reduce the Ozone layer to nearly nil.

> 13)    Amber gas inclusions (air bubbles) indicate a variation in
oxygen
> and carbon dioxide levels.

Is amber reliable? I mean, is it reliable to store oxygen in a material
that
can burn? Won't that produce more and more carbon dioxide over time and
(in
relation) slightly decrease the amount of oxygen?

===> As I indicated in an earlier post this week, Amber is NO LONGER
considered reliable.

> Both were at their highest levels during the
> end of the Cretaceous (last 20 my).
>     a)    O2 levels:
> Permian  - 15%,
> Late Jurassic  -  28%,
> Late Cretaceous (Pre-K-T)  - 35%,
>              After K-T  -  28%,
> Mid-Miocene  -  14%,
> Late Eocene - 15%,
> Current Levels - 21%.
>     b)    THERE REMAINS SOME QUESTION AS TO THE VALIDITY OF THESE
> LEVELS.  Some other techniques seem to show the same level as
currently
> (i.e. 21%) throughout all these eras.

What I've read in New Scientist 3 or 4 years ago --

Carboniferous: 35 %
then "normal" (around 21)
Middle Jurassic -- Eocene: 28 %
since then: "normal"

===>  I'm not sure where their figures come from.  They are similar to
the percentages that I posted.

In the Paleo- and Eocene, when there neither deserts nor grasslands nor
inland ice (hm... probably I'm oversimplifying), I'd personally expect
higher oxygen levels than today.

===> Actually, there were no grasslands before the end of the
Cretaceous.  (Someone can check on this).  It may be that the K-T
extinction not only fostered the growth of the mammals, but the grasses
as well.  [This is speculation - with assumptions galore].

> 14)    If large firestorms occurred, due to a large bolide impact,
much
> of the atmospheric oxygen would have been converted into carbon
dioxide,
> with insufficient vegetation remaining to pump O2 back into the
> atmosphere quickly enough.

But after that, both oxygen and carbon dioxide levels should, I think,
have
remained pretty constant for quite some time -- both photosynthesis and
respiration were largely shut off.

===> If photosynthesis and respiration were mostly shut off, then the O2
level would be lower, and the CO2 level would be higher - and remain
that way for some time.  The surviving animals were able to continue at
the lower O2 level.

> This would have made it impossible for the
> larger animals to survive, because they had evolved to take advantage
of
> the higher O2 content.

I don't think so. I mean, many if not all dinosaurs apparently had
bird-style respiration systems. Furthermore, there are very simple
things to
do when there's less oxygen in the air -- to breathe more often, and to
boost the production of red blood cells. Both of these methods are
unavailable to insects, and therefore oxygen content seems to limit
insect
size. I don't know of any monster K insects, though, while the gigantic
Permian insects are famous (not to mention the Carboniferous
*Arthropleura* -- it also had trachaeae, right?).

===>  I had thought that if the O2 level was higher during the Jurassic
and Cretaceous, that it might help explain how some dinosaurs were able
to grow to such enormous sizes.  (i.e. They were able to exploit the
increased O2, by pushing the limits).  HOWEVER - your mention of the
lack of monster K insects would seem to argue against that.  (Although,
maybe some of the dinosaurs were VERY effective insectivores).

> NOTE ALSO: The Signor-Lipps effect. The effect is analogous to the
> Heisenberg Uncertainty Principle - the closer you get to examining
your
> subject, the more likely you are to introducing errors, or not
noticing
> important info.

Actually not. What it is about is the simple fact that rare fossils are
unlikely to be found in _any_ thin layer, therefore their exact
extinction
date -- which must coincide with the deposition of a thin layer -- won't
coincide with their last (known) appearance. Ways to reduce it are to
sample
more intensively (gee...) and to sample more sites. Frequently forms
that
disappear quite some distance below some boundary in one site last to
the
bitter end just a few kilometers away and vice versa (there are
published
examples for the K-T and the P-Tr boundaries, ask me for refs for the
latter).

===> I should have said that the Signor-Lipps effect was VAGUELY
analogous to the Heisenberg Uncertainly Principle.   My understanding of
the effect is that if you set an arbitrary boundary, then the closer to
this boundary that you get, the less likely you are to find some
particular fossil.

Some more facts...

-- At every mass extinction investigated so far, there's a _sharp_ shift
in
the 12C/13C ratio in the (marine) sediments, indicating that
photosynthesis
was switched off.
-- The K-T has the famous fern spore spike. The P-Tr has a fungal spore
spike ?instead -- looks like the whole world went moldy. A marine K-T
site
in New Jersey has lots of brachiopods instead -- brachiopods had evolved
when there still was hardly any plankton and have the lowest metabolism
of
all plankton eaters or something like that; ref: William Gallagher &
Luther
Young: Dinosaurs of the East Coast, publisher forgotten, 1995.

===> I don't own a copy of this, but I had read parts of it.  (I know
Bill).  I like the idea that the whole world went moldy.

-- At the K-T, sedimentation rates dropped _sharply_ at the K-T and
remained
down for several thousand years in a site where most of the sediment is
composed of plankton shells. Strangelove ocean again.
-- There's a site in India where the boundary layer lies in an
intertrappean
bed. Right up to the boundary there are dinosaur remains, but not above,
showing that at least dinosaur extinction was unconnected to at least
the
lava flow pattern in that place.