Oxygen levels in the Triassic

[MigL]

A paper from Jul 2013 'Stable Carbon isotopes of C3 plant resins and ambers record changes in atmospheric oxygen since the Triassic', available for free as a PDF, suggests that O2 levels were much lower than previously thought, and only about 10-15 % concentration in the atmosphere.    
This seems to go against the commonly held belief that higher O2 levels allowed Dinosaurs to grow to such large sizes.

Volcanic activity was much higher in that era, the seas much shallower and CO2 concentration in the atmosphere 5 to 10 times higher than current levels; And, on the face of it, this seems an argument against RUNAWAY global warming, because global temps came down from a level approx. 7 deg higher than current levels, instead of a runaway increase.

Is this paper factually wrong ?
Is it drawing the wrong conclusions from the findings ?
Or am I drawing the wrong conclusions ?

Tappert_GCA_2013.pdf

[Moontanman]

16 minutes ago, MigL said:

A paper from Jul 2013 'Stable Carbon isotopes of C3 plant resins and ambers record changes in atmospheric oxygen since the Triassic', available for free as a PDF, suggests that O2 levels were much lower than previously thought, and only about 10-15 % concentration in the atmosphere.    
This seems to go against the commonly held belief that higher O2 levels allowed Dinosaurs to grow to such large sizes.

Volcanic activity was much higher in that era, the seas much shallower and CO2 concentration in the atmosphere 5 to 10 times higher than current levels; And, on the face of it, this seems an argument against RUNAWAY global warming, because global temps came down from a level approx. 7 deg higher than current levels, instead of a runaway increase.

Is this paper factually wrong ?
Is it drawing the wrong conclusions from the findings ?
Or am I drawing the wrong conclusions ?

Tappert_GCA_2013.pdf

Actually I've read that the low oxygen levels were the "cause" that dinosaurs evolved superior breathing/circulatory system. This allowed them to go one to dominate the world... 

[studiot]

This is consistent with this graph from Beerling.

 

Note the age of the triassic 250 - 205 MYA, long before the end of the dinosaurs at about 60MYA

[T. McGrath]

On 7/23/2017 at 2:37 PM, MigL said:

A paper from Jul 2013 'Stable Carbon isotopes of C3 plant resins and ambers record changes in atmospheric oxygen since the Triassic', available for free as a PDF, suggests that O2 levels were much lower than previously thought, and only about 10-15 % concentration in the atmosphere.    
This seems to go against the commonly held belief that higher O2 levels allowed Dinosaurs to grow to such large sizes.

Volcanic activity was much higher in that era, the seas much shallower and CO2 concentration in the atmosphere 5 to 10 times higher than current levels; And, on the face of it, this seems an argument against RUNAWAY global warming, because global temps came down from a level approx. 7 deg higher than current levels, instead of a runaway increase.

Is this paper factually wrong ?
Is it drawing the wrong conclusions from the findings ?
Or am I drawing the wrong conclusions ?

Tappert_GCA_2013.pdf

I found the paper to be an accurate representation of what I have read from other sources.  Toward the end of the Carboniferous and the formation of Pangaea, combined with our fourth ice-age at that time, the atmospheric oxygen levels began to decline.  When that ice-age ended approximately 270 million years ago atmospheric oxygen levels were already down to ~18% with atmospheric carbon dioxide levels between 250 and 350 ppmv.  That is also when temperatures began to rise, reaching between 35°C and 40°C.  Contrary to popular belief, there were three main extinction events between 270 and 250 million years ago, and each of those three Permian extinction events (spaced between 9 and 11 million years apart) were larger than the extinction event that killed the dinosaurs.

When the Siberian Traps began erupting 248 million years ago the particulates in the atmosphere helped cool off the planet and increased carbon dioxide levels significantly (by as much as 1,200 ppmv according to some sources), but atmospheric oxygen levels would take longer to increase.

While atmospheric oxygen levels has certainly determined the size of arthropods, I am not sure the same thing applies to reptiles or dinosaurs.  We have evidence of large arthropods during the Carboniferous, when atmospheric oxygen levels were as high as 33%.  Even during the Silurian and Devonian, when oxygen levels spiked to 24%, there were 3 meter long arthropods.  The atmospheric oxygen levels would drop again towards the end of Devonian, which is also when the giant eurypterids went extinct.

What seems to matter more, with regard to the size of reptiles, dinosaurs, and even mammals, is the amount of space they have, not the amount of oxygen.  Reptiles, dinosaurs, and mammals get bigger and bigger the more space they are given, irrespective of the amount of atmospheric oxygen that is available.

During the Triassic the massive Pangaea continent was beginning to break up, but the super-continents of Gondwanaland and Laurasia still existed so they could start getting large during this period.  When Gondwanaland and Laurasia started to break apart into South America, Africa, North America, and Eurasia about 100 million years ago it also ended the rein of the large sauropods.  Life on land would never again get that large, and it had nothing to do with atmospheric oxygen levels.

See also "The Silurian-Devonian: How An Oxygen Spike Allowed The First Conquest of Land", from The National Academies of Sciences, Engineering, and Medicine, Chapter 5 - https://www.nap.edu/read/11630/chapter/7

 

[Area54]

On 19/08/2017 at 3:17 PM, T. McGrath said:

What seems to matter more, with regard to the size of reptiles, dinosaurs, and even mammals, is the amount of space they have, not the amount of oxygen.  Reptiles, dinosaurs, and mammals get bigger and bigger the more space they are given, irrespective of the amount of atmospheric oxygen that is available.

During the Triassic the massive Pangaea continent was beginning to break up, but the super-continents of Gondwanaland and Laurasia still existed so they could start getting large during this period.  When Gondwanaland and Laurasia started to break apart into South America, Africa, North America, and Eurasia about 100 million years ago it also ended the rein of the large sauropods.  Life on land would never again get that large, and it had nothing to do with atmospheric oxygen levels.

This seems a very tenuous correlation and a highly suspect inference. If you consider probable grazing/predation range for such beasts one does not need a supercontinent to provide the space for a viable populations of each. If you dispute this could you provide citations or a well-reasoned argument to justify the claim.

[T. McGrath]

6 hours ago, Area54 said:

This seems a very tenuous correlation and a highly suspect inference. If you consider probable grazing/predation range for such beasts one does not need a supercontinent to provide the space for a viable populations of each. If you dispute this could you provide citations or a well-reasoned argument to justify the claim.

What is tenuous or suspect about making valid observations?  Were there not large reptiles, dinosaurs, and mammals on the large landmasses?  Did they not get smaller as the landmasses got smaller?  In extreme cases, when the landmass was so small we have examples of dwarf species adapting to that environment.  Atmospheric oxygen levels were between 12% and 13% during the Triassic and Jurassic, and dropped to between 10% and 11% during the Cretaceous, so atmospheric oxygen levels could not have been the cause for the size of the reptiles and dinosaurs during this period.  What part of this line of reasoning is "highly suspect" to you?

 

 

Edited August 21, 2017 by T. McGrath

[Area54]

Firstly, you are confusing correlation with causation.

Secondly, dwarf species are well known as a response to severely restricted environments. The splitting apart of Gondwanaland and Laurasia still left extremly large continental lands. To suggest that an area many times the probable range of these "giants" was insufficient is a "highly suspect" speculation. If you wish it to be taken seriously you need to produce something more substantive than an inapplicable evolutionary trait, observed thus far only on islands.  You may be correct, but your suggestion is at odds with established evolutionary biology. You need to make a proper case, or acknowledge that it nothing more than a wild assed guess.

[T. McGrath]

2 minutes ago, Area54 said:

Firstly, you are confusing correlation with causation.

Secondly, dwarf species are well known as a response to severely restricted environments. The splitting apart of Gondwanaland and Laurasia still left extremly large continental lands. To suggest that an area many times the probable range of these "giants" was insufficient is a "highly suspect" speculation. If you wish it to be taken seriously you need to produce something more substantive than an inapplicable evolutionary trait, observed thus far only on islands.  You may be correct, but your suggestion is at odds with established evolutionary biology. You need to make a proper case, or acknowledge that it nothing more than a wild assed guess.

I am not suggesting anything, I am reporting factual information.  When Gondwanaland and Laurasia broke apart during the beginning of the Cretaceous the large sauropods became extinct.  This is a fact, not a suggestion.  That didn't mean all other large life forms ceased to exist, they just never got as big.  I'm sorry you find fossil evidence to be "highly suspect."  There is nothing I can do about that.

 

[Area54]

You made these statements:

Quote

During the Triassic the massive Pangaea continent was beginning to break up, but the super-continents of Gondwanaland and Laurasia still existed so they could start getting large during this period.  When Gondwanaland and Laurasia started to break apart into South America, Africa, North America, and Eurasia about 100 million years ago it also ended the rein of the large sauropods. 

Your argument appears to run thus:

• Sauropods were able to get large because Gondwanaland and Laurasia were large.
• When those continents had split apart they were too small too allow for large sauropods.

If that is not your argument it would be helpful if you had been clearer.

If that is your argument then it appears to be a fatuous one. I am giving you the benefit of the doubt - that you have evidence or an argument to support the contention. Without either of those you are simply blowing hot air.

Edit: I am not disputing the fossil evidence that they became smaller. I am disputing your claim that this is because the land masses were smaller.

Edited August 21, 2017 by Area54

[studiot]

59 minutes ago, T. McGrath said:

I am not suggesting anything, I am reporting factual information.

Atmospheric oxygen levels were between 12% and 13% during the Triassic and Jurassic, and dropped to between 10% and 11% during the Cretaceous,

Your figures are very different from the widely accepted graph I posted and therefore need substantial backing so please explain.

Edited August 21, 2017 by studiot

[Moontanman]

3 hours ago, T. McGrath said:

 

So why do reptiles tend to be larger in small isolated habitats ie Islands, and mammals tend to get smaller in similar habitats? 

I will repost this since it seems to have been misinterpreted: 

Quote

Actually I've read that the low oxygen levels were the "cause" that dinosaurs evolved superior breathing/circulatory system. This allowed them to go one to dominate the world...

From what I've read of this thread so far there seems to be an idea that the size of dinosaurs was due to high oxygen and that my post supported this. Not at all, in fact it was low oxygen environments that provided the stressor dinosaurs needed to evolve their superior circulatory/breathing systems. One reason such large birds as geese can fly at very high altitudes. The lower oxygen levels impacted the proto mammals more than the proto dinosaurs possibly because their circulatory systems had already started down the road to that breathing system due to the way reptiles breath as opposed to mammals.  

 

Well except for turtles, many of them breath through their anus...

 

Edited August 22, 2017 by Moontanman

[Area54]

@T.McGrath, I really do hope you are not one of those posters who seem to jump ship when asked to justify an assertion when they realise it is indefensible. I am looking forward to your response. You clearly have an interest in and knowledge of science, so it would be a pity if you left the forum over this. I'm hoping it's because you really only have time available on forums at the weekend. See you Saturday.

[T. McGrath]

On 8/21/2017 at 2:14 PM, studiot said:

Your figures are very different from the widely accepted graph I posted and therefore need substantial backing so please explain.

Stable Carbon Isotopes of C3 Plant Resins & Ambers Record Changes in Atmopsheric Oxygen Since the Triassic - https://www.eas.ualberta.ca/wolfe/eprints/Tappert_GCA_2013.pdf

On 8/21/2017 at 4:42 PM, Moontanman said:

So why do reptiles tend to be larger in small isolated habitats ie Islands, and mammals tend to get smaller in similar habitats? 

I will repost this since it seems to have been misinterpreted: 

From what I've read of this thread so far there seems to be an idea that the size of dinosaurs was due to high oxygen and that my post supported this. Not at all, in fact it was low oxygen environments that provided the stressor dinosaurs needed to evolve their superior circulatory/breathing systems. One reason such large birds as geese can fly at very high altitudes. The lower oxygen levels impacted the proto mammals more than the proto dinosaurs possibly because their circulatory systems had already started down the road to that breathing system due to the way reptiles breath as opposed to mammals.  

 

Well except for turtles, many of them breath through their anus...

 

Except that your assumptions are not supported by the evidence.  Atmospheric oxygen levels during the Triassic and Jurassic were between 12% and 13%, and dropped even further to between 10% and 11% during the Cretaceous.  At the end of the Cretaceous the oxygen levels spike back up to 18%, but are still lower than today's level.  Hence, atmospheric oxygen levels played absolutely no role in determining the size of the dinosaurs.

Stable Carbon Isotopes of C3 Plant Resins & Ambers Record Changes in Atmopsheric Oxygen Since the Triassic - https://www.eas.ualberta.ca/wolfe/eprints/Tappert_GCA_2013.pdf

 

[Area54]

2 hours ago, T. McGrath said:

Except that your assumptions are not supported by the evidence.  Atmospheric oxygen levels during the Triassic and Jurassic were between 12% and 13%, and dropped even further to between 10% and 11% during the Cretaceous.  At the end of the Cretaceous the oxygen levels spike back up to 18%, but are still lower than today's level.  Hence, atmospheric oxygen levels played absolutely no role in determining the size of the dinosaurs.

I don't see any assumptions in Moontanman's post. Where do you think they are?

Nowhere does Moontanman claim that atmospheric oxygen played any role in determining dinosaur size. Indeed, his post was a direct effort to clarify that he was not claiming that.

When do you plan to acknowledge and respond to my post from Monday? As it stands you are left defending a silly position. It would be nice for you to acknowledge that so we can get on to matters of substance.

Edited August 26, 2017 by Area54
correct spelling of defending

[Moontanman]

1 hour ago, T. McGrath said:

Stable Carbon Isotopes of C3 Plant Resins & Ambers Record Changes in Atmopsheric Oxygen Since the Triassic - https://www.eas.ualberta.ca/wolfe/eprints/Tappert_GCA_2013.pdf

Except that your assumptions are not supported by the evidence.  Atmospheric oxygen levels during the Triassic and Jurassic were between 12% and 13%, and dropped even further to between 10% and 11% during the Cretaceous.  At the end of the Cretaceous the oxygen levels spike back up to 18%, but are still lower than today's level.  Hence, atmospheric oxygen levels played absolutely no role in determining the size of the dinosaurs.

Stable Carbon Isotopes of C3 Plant Resins & Ambers Record Changes in Atmopsheric Oxygen Since the Triassic - https://www.eas.ualberta.ca/wolfe/eprints/Tappert_GCA_2013.pdf

 

It would appear I am correct, you do not understand what I am saying... 

[studiot]

6 hours ago, T. McGrath said:

On 21/08/2017 at 11:14 PM, studiot said:

Your figures are very different from the widely accepted graph I posted and therefore need substantial backing so please explain.

Stable Carbon Isotopes of C3 Plant Resins & Ambers Record Changes in Atmopsheric Oxygen Since the Triassic - https://www.eas.ualberta.ca/wolfe/eprints/Tappert_GCA_2013.pdf

Thank you for your reference, no I was not aware of that work.

However I noted that your figures are very different from the Berner and Canfield curve I posted.
In particular Tappert's works appears to follow only one source of information, whereas the B & C curve was constructed from several corroborating independent sources of data.
One of those sources is noted as the 'atomic abundance' on my post. Not only where isotopes of carbon used as with Tappert but also isotopes of Sulphur.
However their assessment method was different in that it was the relative abundance in various sedimentary facies that was taken rather than abundance in observed fossil resins.
It should be noted that there is considerably more rock than resin and correspondingly more data that way.

But a particular stumbling block, as I see it, is your flat assertion that oxygen levels fell below 13%, which is accepted as the charcoal formation threshold.
ref: Nature 290 428 Cope and Challoner.

If oxygen levels fell several points below the charcoal formation threshold, where did the fossil charcoal from those time periods come from?

 

This is not to say that we should reject Tappert's work outright or fail to incorporate it into a revised and hopefully improved paleo atmospheric history. It is, after all, a genuine new method and source of data.

Edited August 26, 2017 by studiot

[Area54]

6 hours ago, studiot said:

But a particular stumbling block, as I see it, is your flat assertion that oxygen levels fell below 13%, which is accepted as the charcoal formation threshold.
ref: Nature 290 428 Cope and Challoner.
If oxygen levels fell several points below the charcoal formation threshold, where did the fossil charcoal from those time periods come from?

For much more recent work in this area consider Belcher and McElwain, Science v321 p1197-100 2008. From experimental work they place the limit at 15%, raising additional doubts. Here is their abstract:

"Several studies have attempted to determine the lower limit of atmospheric oxygen under which combustion can occur; however, none have been conducted within a fully controlled and realistic atmospheric environment. We performed experimental burns (using pine wood, moss, matches, paper, and a candle) at 20°C in O² concentrations ranging from 9 to 21% and at ambient and high CO² (2000 parts per million) in a controlled environment room, which was equipped with a thermal imaging system and full atmospheric, temperature, and humidity control. Our data reveal that the lower O² limit for combustion should be increased from 12 to 15%. These results, coupled with a record of Mesozoic paleowildfires, are incompatible with the prediction of prolonged intervals of low atmospheric O ² levels (10 to 12%) in the Mesozoic."

[T. McGrath]

10 hours ago, studiot said:

Thank you for your reference, no I was not aware of that work.

However I noted that your figures are very different from the Berner and Canfield curve I posted.
In particular Tappert's works appears to follow only one source of information, whereas the B & C curve was constructed from several corroborating independent sources of data.
One of those sources is noted as the 'atomic abundance' on my post. Not only where isotopes of carbon used as with Tappert but also isotopes of Sulphur.
However their assessment method was different in that it was the relative abundance in various sedimentary facies that was taken rather than abundance in observed fossil resins.
It should be noted that there is considerably more rock than resin and correspondingly more data that way.

But a particular stumbling block, as I see it, is your flat assertion that oxygen levels fell below 13%, which is accepted as the charcoal formation threshold.
ref: Nature 290 428 Cope and Challoner.

If oxygen levels fell several points below the charcoal formation threshold, where did the fossil charcoal from those time periods come from?

 

This is not to say that we should reject Tappert's work outright or fail to incorporate it into a revised and hopefully improved paleo atmospheric history. It is, after all, a genuine new method and source of data.

First, it is obvious that you did not read Tappert et. al because he cites numerous sources.  In fact the paper lists five pages of references.  Tappert et. al even includes your prior reference of Berner, multiple times.

Second, they are not my figures any more than your reference to Berner's data is your figures.

If you have an issue with the peer-reviewed paper I provided, take it up with the author.  At least I cited a credible source.  Where is your citation?

 

[studiot]

1 hour ago, T. McGrath said:

First, it is obvious that you did not read Tappert et. al because he cites numerous sources.  In fact the paper lists five pages of references.  Tappert et. al even includes your prior reference of Berner, multiple times.

Second, they are not my figures any more than your reference to Berner's data is your figures.

If you have an issue with the peer-reviewed paper I provided, take it up with the author.  At least I cited a credible source.  Where is your citation?

 

Why so aggresive?

Yes I did read the paper you referenced.

And I thanked you for it.

 

I may have misread Tappert's paper, but I thought he only had one method of assessment, that of resin.

He did indeed append a long list of references to his paper instead of developing his own analysis, as is de rigour these days.

Since you (correctly) say that Tappert includes Berner, why are you quibbling with my sources, instead of progressing the discussion?

Edited August 27, 2017 by studiot