RE: Hell Creek (long)

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

As an aside: I will reply to David's reply to my "[VERY LONG]" post of a
few days ago at a later time (I need to concentrate on some other work
for awhile).  The reply will need more time than I have available.  Just
remember that 99% of my post was originally written in 1998 (actually
pieces of it go back to the mid-80's).  


Concerning the Oxygen levels found in amber:  When I first heard of
this, it seemed to be THE ANSWER - something big hit the earth and
ruined the atmosphere!  The change would have been sudden. The numbers
I've quoted were from an article in the Dino Fest 1996 Symposium
publication (published for the 1998 symposium).  (If someone needs the
ref, I'll try to dig it up).  If they are accurate, then they imply
DRASTIC changes, especially at the K-T border.  (35% down to 28%).  

Tommy Tyrberg said: " Extant animals certainly have a fairly
high tolerance in this respect... Birds are _incredibly_ tolerant ..."
While extant animals can handle lower O2 levels - THAT'S THE POINT.
Those that COULDN'T handle the change DID NOT SURVIVE THE K-T.  (Note
that according to the Amber bubbles, mid-Miocene mammals (etc.) survived
an O2 level as low as 14%).   

HOWEVER: Even the most vociferous advocates of the Amber bubble Oxygen
ratios have all backed off.  Amber DOES have certain levels of porosity,
which seem to be variable - based on what kind of tree it originates
from, how much moisture there was originally, age of the amber, clarity
of the amber, etc.  These variables can not currently be correctly
determined (and no one has any suggestions how to "roll-back" through
them).  Amber is NOT reliable - I mentioned it in my earlier posts as a
way to explain one of the possible means of the K-T extinctions.  (The
levels MAY have been affected, but Amber bubbles won't tell us).   Amber
is not now the means to determining ancient O2 levels.  Perhaps in
conjunction with other fossils and techniques, we can verify (or
dispute) the Amber bubble levels.  (I'm thinking of lignite fossils, and
other gas ratios that may be determinable by some destructive
chromatography and other processes).  


I want to remind everyone that nearly ALL THE ANIMALS THAT WEIGHED MORE
THAN 30 KG DISAPPEARED!  I'm not sure of the numbers of small
(non-avian) dinosaurs that existed in the late Maastrictian, perhaps
someone can supply this info.  My current understanding is that dinosaur
genera had reduced drastically prior to K-T - mostly the larger sized
animals (_T. rex_, _Triceratops_, etc.).  It seems like all the small
dinosaurs were birds!

Before everyone starts yelling "What about the small pterosaurs? What
about the [fill in your favorite small dino]?"  - Consider this: There
are extant animals today who will die if they cannot have a specific
food to eat (e.g. Pandas - bamboo, Koalas - eucalyptus, etc.).  We don't
know how well a pterosaur would fair if the only fish that it eats were
all dead, with no replacements. With major groups of animals killed off
by the other effects of the bolide impact (and "collateral damage"),
some animals would go extinct due to their only food source
disappearing.


Last piece of this post: Concerning the sulfuric acid creation in the
upper atmosphere - If acid rain did occur (as seems likely), then how
much would it affect the preservation of fossils.  Is it possible that
there was enough acid rain to account for the lack of fossils prior to
the K-T (i.e. the acid rain sufficiently changed the soils, that no
(major) fossils were preserved in the underlying layers).

Enjoy

Allan Edels

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] On Behalf
Of Steve Brusatte
Sent: Saturday, June 01, 2002 7:48 PM
To: dinosaur@usc.edu
Subject: Re: Hell Creek (long) 

On Sat, 01 Jun 2002 23:21:42  
 Tommy Tyrberg wrote:
>I don't think that any credible decrease in atmospheric oxygen would
have a
>very significant effect on animals. Extant animals certainly have a
fairly
>high tolerance in this respect... Birds are _incredibly_ tolerant. Many
species
>regularly migrate at altitudes up to 25-30,000 feet which means that
they
>can not only survive but also sustain intense and prolonged physical
>activity at oxygen pressures that will kill most mammals within a few
>minutes. 
>This is usually explained as being due to their "stream through"
breathing
>system in contrast to the "dead-end" mammalian breathing apparatus. 

Most definitely.  First, we have to remember the most of the oxygen
evidence comes from amber bubbles, which was mentioned onlist a few days
ago.  I don't know how reliable these estimates are.  And, even if they
are reliable, an oxygen decrease isn't a very convincing extinction
mechanism when we are talking about dinosaurs, some of which likely had
avian-style respiratory systems, and many bird groups.  Plus, if these
changes were gradual, evolution would have likely "created" survival
strategies in some of the other groups (such as some mammals and
reptiles) that may have been more adversely affected.

>Another aspect that I think hasn't been mentioned in this thread is
that
>the Chixculub bolide impacted on partly dolomitic rock. This means that
>large amounts of sulphur were injected into the stratosphere. This may
have
>had a very significant effect on climate. Microscopic sulfuric acid
>droplets in the stratosphere are the most important component in the
"dust
>veil" from volcanic eruptions and since they are so small it takes two
or
>three years before they settle out. Unfortunately there is no consensus
on
>how much dolomite there really was in the Chixculub target rock. 

Yes, good point.  Everything I've read has said that the bolide likely
impacted a sulfur-rich carbonate platform/shelf.  Sulfur injected into
the atmosphere will not only create dust veils, but will also form
sulfur dioxides, which eventually and easily combine with water to form
sulfuric acid.  This may explain (as Paul briefly mentions in DA) why
the Chixculub impact was especially deadly, while other impacts (such as
the one that created Chesapeake Bay) were not. These "other" impacts,
which included one possible one at the TJ boundary and others in the
Jurassic, Cretaceous, and Tertiary, might have either hit in the ocean
or in other sulfur-poor areas.

Steve

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