An isotopic analysis of two mass extinction events

Dec 10, 2013 by Geoff Vivian
An isotopic analysis of two mass extinction events
An impression of the supercontinent Pangea at the end of the Permian epoch, about 252 million years ago. Credit: Wikimedia Commons

An international research team has analysed two of the earth's mass extinction events, finding markedly similar conditions between the two.

Curtin University's Kliti Grice says both the Permian-Triassic and the Triassic-Jurassic events began when increasing atmospheric – which ultimately reached at least four times the current level – triggered massive global warming.

There was a single continent, Pangea, at the end of the Permian epoch, about 252 million years ago.

She says high volcanic activity released , and the melting of frozen methane probably released more.

During the Permian-Triassic event there were no polar ice caps.

The oceans were warm and sluggish, with very little movement between the upper and lower water columns, and there was a massive algal bloom.

"There was too much biomass to be recycled by bacteria which existed through the water column and the algae died, so the bottom waters became anoxic ," Professor Grice says.

Green sulfur bacteria proliferated, resulting in toxic toxic levels in the upper water body.

Ninety per cent of marine and seventy per cent of terrestrial species died, producing some of the earth's present-day petroleum reserves.

This includes the oil in Western Australia's Perth Basin.

"What we found are molecular fossils, indicative of the organisms that use hydrogen sulfide instead of water as an electron donor to fix CO2 in light to do photosynthesis," she says.

"Those molecules were found in the shales which gave rise to the oil.

"They were also found in the oils of the Perth Basin, so we have a nice correlation of oil to the rock which generated it."

To see into the past with such detail, the team used compound-specific isotope analysis to measure biomarkers in mixtures.

"So if you've got a mixture of compounds – say there are some from algae, some from plants – you can actually measure them individually to get their individual signals."

Prof Grice says similar carbon dioxide levels 200 million years ago triggered a less-severe extinction event at the end of the Triassic period.

As there are similarities between conditions that produced at least two of the five known , the team has been investigating two of the others, looking for the same characteristics.

She says the end-Cretaceous extinction, which killed most of the dinosaurs about 65 million years ago, was probably related to a bolide, such as a comet or large meteorite, impacting the Earth.

"What prompted this was the similarity or the potential similarity of events which are associated with the deposition of petroleum," Prof Grice says.

Explore further: Reef fossil find sets new age limit

More information: geology.gsapubs.org/content/ea… 10/G34183.1.abstract

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User comments : 12

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Maggnus
5 / 5 (4) Dec 10, 2013
CO2 driven warming, for anyone keeping score.
Mr_Ed
4 / 5 (5) Dec 10, 2013
Only difference this time is the possible use of fossil fuels to create future fossil fuels.
Hooray for 'global warming'!
Humpty
3.8 / 5 (4) Dec 10, 2013
We can recycle the errors from the Triangle Error, the Plasticene Error, and now the Extinction Error.... and in a few hundred million years, we can do it all again.

Bonus.
Paulw789
1 / 5 (6) Dec 11, 2013
These two extinctions occurred during the two largest volcanic events that we know about in Earth history.

Temperatures fell during the events, they did not go up because of CO2, they fell.

If you were around during these volcanoes, it would have been a very bad day.

Maggnus
5 / 5 (5) Dec 11, 2013
Temperatures fell during the events, they did not go up because of CO2, they fell.


Are you reading the same article?
events began when increasing atmospheric carbon dioxide – which ultimately reached at least four times the current level – triggered massive global warming.
It's like you just decided to make up your own conclusion, which is the polar opposite of what the author's of the study concluded! That's some serious denial you got going on there.
Paulw789
1.3 / 5 (4) Dec 12, 2013
Maggnus, here is the CO2 and temperature data.

http://s17.postim...m_In.png

http://s22.postim...m_In.png
Maggnus
5 / 5 (3) Dec 12, 2013
Paul, linking to two graphs says nothing. Provide a link to the source so we can put those graphs into context.

For what its worth, it has been found that the initial eruptions associated with the Siberian traps would probably have caused an initial cooling affect, due to the release of sulfur compounds into the atmosphere. These are relatively short term effects. (See Black et al 2011, here: http://home.dtm.c...012.pdf)
The temperature then soars due to the release of CO2 and other GHG's. These remain in the atmosphere over a much longer timescale. See here: http://palaeo.gly...aps.html
and here: http://www.scienc...931/1179 for example.
Paulw789
1 / 5 (3) Dec 12, 2013

Veizer's dO18 isotope/temperature database has an estimate about every 50,000 years covering these periods. You're not going to find anything better.

http://www.scienc...2004.xls

The CO2 data comes from: Berner GeoCarb III, Pagani 2005, Pagani 1999, Royer 2006 Composites, Pearson 2000, IPCC AR4 2007 - Royer 2008 Composites, Pearson 2009, Tripati 2009, Bao 2008, Hoenisch 2009, Beerling Royer 2011, Bartoli 2011, Seki 2010

I have the biggest database of these numbers of anyone I guess.

Maggnus
5 / 5 (2) Dec 12, 2013
Paul you're not making any sense. Your throwing out a bunch of random numbers in an excel program you've linked to, and you follow that up with a bunch of random cites with no context and no explanation of what you think they mean.

For instance, in Berner GeoCarb III they say:
Revision of the GEOCARB model (Berner, 1991, 1994) for paleolevels of
atmospheric CO2, has been made with emphasis on factors affecting CO2 uptake
by continental weathering.
What does that have to do with CO2 driven radiative forcing? SImilarily, and chosing only names I recognize, Barbel Hoenish at Columbia note:
Some of my projects include:
•Testing Geochemical proxy relationships under variable paleo-seawater chemical conditions
•Reconstructing surface ocean acidification at the PETM
•Validating the boron isotope proxy in deep-sea corals and tracing anthropogenic CO2 invasion
His words. Do you understand the term gish-gallop?
Maggnus
5 / 5 (2) Dec 12, 2013
As for Veizer's dO18 isotope/temperature studies, to say there is a lot of controversy regarding his findings is being generous. His is the one of the only studies I'm aware of that attempts to replace CO2 radiative forcing with solar/cosmic-ray induced warming, and he has been roundly criticized for both his methods and the means by which he arrived at his conclusions. Even he admits that even if he is correct in his conclusions, that the amount of solar/cosmic ray flux would not, by itself, be enough to explain the warming we have seen. Of more importance, in my mind, is that he stands almost alone. This is not the place to argue the nuances of his findings, but to suggest his theory is the end all regarding paleoclimate is disingenuous at best.
Paulw789
1 / 5 (4) Dec 13, 2013
Maggnus, I guess you missed the point that there is 17,000 datapoints in Veizer's dO18 database. These can be turned into global temperature estimates with the proper formulae. My charts above did not use Veizer's 50 million year smooth of the data or Berner/Royer's 50 million smooth of the data. It is the highest resolution of the basic data that one can get without having to run a modern computer for a week.

The CO2 database comprised of the papers mentioned above has 2750 CO2 estimate datapoints.

One can go on believing what one believes or one can default to what the data actually says.

Maggnus
5 / 5 (1) Dec 14, 2013
One can go on believing what one believes or one can default to what the data actually says.
Well there's the rub, isn't it? What the data actually says (according to this study) is that the extinction event occurred during a period of intense global warming brought about by the release of massive amounts of CO2 during the volcanic event that formed the Siberian Traps. You have provided a bunch of numbers and unreferenced cites which, apparently, you think counters this data.
I'd like to know what "formulae" you are using.