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Re: extinction by suffocation?! - Long Reply



Jessi, et al:

    I had posted some things relating to this idea some time ago - and here
is part of one long post that I sent to a science writer off-list.

RE-POST FOLLOWS:
****************************************************************************
****************
A specific reference:
"Plate Techtonics and the Radiations/Extinctions of Dinosaurs, the Pele
Hypothesis" by Robert E. Sloan (Dept. of Geology and Geophysics, University
of Minnesota, Minneapolis, MN 55455),  from "DinoFest International:
Proceeding of a Symposium sponsored by Arizona State University"
pp.533-539.  This was originally presented at the DinoFest in 1996, and
published for the DinoFest in 1998 (March).

    The overall thrust of the paper is that changes in oxygen levels caused
an extinction of dinosaurs (64%)  by the early Cretaceous, with 100%
(excluding birds) at the end of the Cretaceous.

    Just a few quotes:
-------

    "A few of the arguments that the gas in amber bubbles is really fossil
air are given here, for the others see Landis and others 1996.

*    Gases released from deep and surface bubbles of the same piece of amber
are the same.
*    Gas in primary bubbles in highly fractured amber is the same as from
unfractured amber from the same locality.
*    Primary bubbles must be present to yield air.
*    Argon 39 produced by neutron irradiation doesn't leak out in 3 years at
VERY high vacuum.
*    All Cretaceous ambers show high oxygen.  Miocene and Late Eocene ambers
are low in oxygen with respect to modern air.  Oxygen doesn't leak through
unfractured amber.  Modern resin shows modern air."

-------

    "1.  A high carbon dioxide generated extinction at the end of the
Jurassic and beginning of the Cretaceous with the introduction of large
amounts of carbon dioxide released from the mantle which triggered the onset
of the Cretaceous greenhouse and, 2. Falling oxygen levels, in the presence
of elevated carbon dioxide, cause respiratory stress in the exact time
interval when metabolic needs were increasing because of falling global
temperatures.  The second type may have been the ultimate cause for most of
the terminal Cretaceous extinction."
-------

"    Hengst and others (1993, 1996) demonstrated that a large long necked
sauropod suchas the Tithonian _Apatosaurus_ required an oxygen content in
the atmosphere of about 35% to function at any level above a very slow walk,
slower than the rates deducted from trackways.  Our measured levels of
Narremian and Aptian oxygen are 28% and 29% respectively.  It thus is not
very surprising that our only surviving Aptian sauropods are both small, and
short-necked, clearly adaptations to these low Early Cretaceous oxygen
levels.

        THE LATE CRETACEOUS DINOSAUR RADIATION

    There are four major factors involved in the Late Cretaceous radiation
of dinosaurs, all are important.  The first is the breakup of Pangea
documented in Figure 1, which permitted the development of endemic faunas.
The second was the great increase in carbon dioxide and oxygen in the
atmosphere (to 35%), the former favored plant production and diversity, the
latter permitted an increase in dinosaur size.  The third was the Angiosperm
radiation which greatly increased the food supply.  Lastly, the superplumes
and continental breakup caused a high sea level, and more importantly a
great variation  in sea level. ..."

------

"*    The increased Carbon Dioxide (up to 6 times the present value) caused
the Cretaceous Greenhouse effect, and major global warming."

------

"        WHY DID DINOSAURS AND NOT MAMMALS GO EXTINCT?

    Hengst has shown that Dinosaurs could not venilate their lungs as easily
as Birds or Mammals (Hengst et al '93, '96).  FIgure 3 diagrams these
differences.

*    Dinosaurs required 40 breaths to fully replace the air in their lungs.
*    Mammals and Birds only require 7 breaths to completely replace the air
in their lungs.
*    Large Dinosaurs required elevated levels of O2 in the air to
diversify."

-------

Some additional notes:

    The paper indicates that the O2 level during the Permian was 14%, 35%
during the Pennsylvanian (and most of the Cretaceous), and is currently 21%.

    Barremian                                    130 mya            28%
    Aptian                                           115 mya            29%
    Cenomanian                                  95 mya            35%
    Turonian                                         88 mya            33%
    Judith River Formation                 75 mya            35%
    Basal Hell Creek                           70 mya            35%
    Hell Creek (Maastrictian)             68 mya            35%
    Top-most Hell Creek                    65.2 mya         31%

    AFTER K/T Boundary                  65 mya             29%

    Eocene                                          50 mya             16%
    Miocene                                        20 mya             14%

    NOW                                                NOW              21%

    Hope this proves useful.
****************************************************************************
***************
RE-POST ENDS.

    Of course, some recent work (using new techniques) indicates that the O2
levels in amber may have been equal to current levels.  If the higher O2
rates ARE CORRECT, then dinosaurs might have grown large simply because
their muscles would allow them to lift more (because they are easily
replenishing their O2).

    In effect, Jessi, your mom's BF was more or less right.  Of course, we
could argue what CAUSED the Oxygen levels to drop so drastically....

    Allan Edels


-----Original Message-----
From: James R. Cunningham <jrccea@bellsouth.net>
To: rtravsky@uwyo.edu <rtravsky@uwyo.edu>
Cc: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Tuesday, December 22, 1998 11:01 AM
Subject: Re: extinction by suffocation?!


>There is a really good article on this subject in J. Exp. Biol.
201,1043-1050 (1998),
>Atmospheric Oxygen, Giant Paleozoic Insects And The Evolution Of Aerial
Locomotor
>Performance by Robert Dudley.
>
>Dudley reports that oxygen peaked at 35% at the very end of the
Carboniferous and
>declined precipitously into and through the Permian, with a double minimum
in the
>Jurassic and early Triassic, then rose to another, lower maximum at the end
of the
>Cretaceous and early Tertiary, before declining gradually to the present
day levels.
>It's interesting to note that spontaneous combustion of the biosphere might
be possible
>at 35% oxygen concentration. Wonder where all those coal deposits came
from? Also, the
>higher oxygen partial pressures might allow oxygen and carbon dioxide
exchange in the
>trachea of long-necked animals.  Both thoughts are highly speculative.
Take them with a
>grain of salt, if at all.
>JimC
>
>Richard W Travsky wrote:
>
>> On Tue, 22 Dec 1998 Ccookk@aol.com wrote:
>> >       I just happened to see a partial of what you are talking about.
Evidently
>> > some gas trapped in amber was analyzed to be approximately 35% oxygen.
This
>> > was from the time of the dino's, Jurassic I beleive. So the theory goes
that
>>
>> I saw most of this, and I'm pretty sure they said cretaceous. (Oh
dear...)
>>
>> > [...]
>> >       I can see how some of this may be viable as a concept, but really
need to get
>> > more info on this. One thing is may explain, is how the large sauropods
were
>> > able to get enought oxygen through those large necks. A greater percent
of
>>
>> I've been curious whether or not any absorption through the skin was
>> possible (I doubt it, tho).
>>
>> > [...]
>>
>> rich
>
>
>
>