This is not the original post that I wanted to write. I wanted to specifically cover my rant on YAGUMETs. Or as the rest of you have seen me call them 'Yet Another Grand Unified Mass Extinction Theory', but in the plural. However, since Dr Keller - ever the anti-bollide guerrilla - sent out yet another press release in support of vulcanism as the culprit for the KT Mass Extinction killer, I thought I would shift gears and try to do a comparison of the PT Extinction and KT Extinction events to try to make a point. Since Dr Keller favors vulcanism, I am going to make the assumption for this post that the Permian Extinction, which has been pretty strongly linked to the effects of massive vulcanism, is a 'proven' fact and its signature is the gold standard for vulcanism being the cause. Even though I am thoroughly convinced that the KT Extinction was caused by Chicxulub. I am going to assume we're unproven here and compare the evidence and signatures of the KT to the PT. I will return to the YAGUMETs post for my next big paleo post, but for now, let's get on with the show.
The Permian Extinction was not a pretty picture. I sketch it out here at least moderately well. It was almost certainly caused by the prolonged and quite nasty eruptions of the Siberian Traps, a truly terrifyingly large and prolonged flood basalt eruption. The evidence that supports this had a very distinctive signature: certain events happened and we think we know why. If we use this signature as a baseline for comparing other extinctions to the PT Extinction we really ought to be able to see if that other signature fits the same profile. If it does, then it seems very likely that the extinction was caused by the same mechanism. With that in mind, we'll approach and compare the KT to the PT!
Extinction Pulses
One of the very distinctive and confusing items about the PT Extinction was that it seemed like it was a very long term affair. This was because careful collections and biostratigraphy had not been done until relatively recently. The reason for appearing to be a very drawn out affair was there were actually multiple pulses of mass death. The pattern of pulses looks something like a drum beat that gets louder and fades. In fact, the last pulses take place actually after most of the dying took place and end up geochronologically in the Triassic[1]. It's very, very distinctive and almost certainly a result of the eruptions and their resultant ecological complications tripping past some thresholds. The the multi-pulse extinction attribute seems to be a very important one for vulcanism caused extinctions and makes perfect sense given how it kills. How does this compare to the KT Event's pattern of extinction? The fact of the matter is that it doesn't match at all. There seems to have been a minor mass extinction ten million years prior to the KT Boundary, but it does not seem to have reduced the number of dinosaur genera present and even had the effect of the mammals diversifying. That might be argued that the prior minor extinction might be the first pulse of the KT, but...there's no subsequent pulses into the Cenozoic! The KT Extinction was a quick and bloody affair: there appears to be only a single pulse involved.
Biotic Recovery
The Permian Extinction killed a lot of everything. By some counts as much as 90% of everything died. That included plants, animals, etc. As a result, and also as a consequence of what was changed environmentally because the the Siberian Traps, life took a very long time to recover. There were sections that have no fossils at all. While the extinction was less nasty in the terrestrial environment - approximately 70% of everything died there - beds of the Karoo in South Africa, one of the best places for chronologically uninterrupted PT Event sections, there are no fossils at all for over 5 million years. Life would not recovery the diversity of the Late Permian for a very long time. Delayed biotic recovery would be another good attribute for identifying vulcanism induced extinctions. The KT Extinction had, at the most, a 300k year recovery period. For something that killed 70% of everything, this is remarkably fast and completely unlike the PT Event. The diversity of life would increase very, very fast after the KT Event. This would also lean towards the idea that the KT Extinction had a different mechanism for the root cause.
Climatic Changes
During the PT Event, it appears that the Siberian Traps belched tons of carbon dioxide. This caused a massive upswing in temperature especially with the addition of the forcing caused by methane as well. The upswing appears to have been in the ten Celsius range. While the temperature dropped down, it remained high throughout the Triassic and into the Jurassic. This is supported by the isotope measurements and mineral deposits. On the other hand, the climate that crosses the KT Boundary as geologically recorded seems to be pretty stable. It was warm and stayed warm. There doesn't seem to have been a wild change over a prolonged period as it was with the PT Extinction.
Differences in Marine Biotic Extinctions
One of the most profound differences in the KT and PT Extinctions can be found in what died first and what was most effected in the oceans. During the PT Extinction, the benthic organisms - those that live on the seabed - were effected first AND most severely. As you rose up from the depths of the sea, the extinction got less and less severe - though, truthfully, that's something of a hair's difference, the PT Extinction was just damnably horrible - until you reached the terrestrial environment where it was the least severe. The key point though here is that the benthic environment & ecology was mopped across the floor. The reason for this is that the oxygen level dropped down to a anoxic state and full of hydrogen sulfide: the chemical analyses of the PT sediments support this. The KT Extinction couldn't be more different. The organisms effected the most were those that were those that were living in the euphotic zone: photoplankton, ammonites, the great marine reptiles, etc. The benthic organisms were far less impacted. This is a VERY strong indication that something different happened at each extinction event.
Extinctions in the Terrestrial Realm
In the terrestrial environment the Permian Event seems to have been a little uncertain as to what allowed organisms to survive the Great Dying. Truthfully, not enough research has gone into trying to find some sort of common theme that might unite what survived and what did not here. From the point of view of what is currently known, there is no common theme. It appears currently that the killing didn't favor one type of organism over another. This would be what Raup called a 'Field of Bullets' scenario. It truly remains to be seen though. On the other hand, it appears that at least for KT Event this was rather different. There was a definite pattern involved. At first it was thought that it was a weight limit: no more than 50 kg survived the KT Extinction. That hasn't quite turned out to be true: the cut off wasn't mass or weight, but metabolic requirements. Rather it was a metabolic requirement. If your required more calories than a certain amount - the exact amount uncertain right now - then you got whacked for sure. The prime example of this is the Sebecosuchidae, a form of Mesosuchia (or Mesoeucrocodylia, if you're more accurate). the Sebecosuchidaes were largish terrestrial carnivores that made the cross-over from the Mesozoic to the Cenozoic. IIRC, they were over 6m in length (Darren Naish has an excellent article on the subject at Tetrapod Zoology). This means that there is a definite and solid pattern. The KT Extinction was more selective in what died than the PT Extinction. However, there was still an element of randomness to the groups that were within the surviving criteria; frex, 50% of mammals died out and they were well within the metabolic requirements for survival. Lady Luck still had her due. However, this is still very different than in the PT Extinction as far as the research so far has indicated.
Omega: In the End
Now, I have run out of time. I hope that by detailing some of the differences between the KT Mass Extinction and the PT Mass Extinction. I have tried to avoid the usual arguing points: evidence of impact, charcoal traces, geochronology of the Deccan Traps, etc. I have been trying to point out the other diagnostic characteristics that are often overlooked. The fact of the matter is that these two extinctions killed in very different ways. These two extinctions effected organisms of different types. They cannot be caused by the same mechanism. Extinction events are not just something that has a geochronologically convenient 'explanation.' That explanation has to fit the pattern of that extinction as well as the time frame.
I will do a detailed KT Mass Extinction post in the relatively near future, but that will come after the YAGUMETs post. Now let's see if anyone comes along and beats me with a big stick.
1. Which makes me wonder why it's, well, the Triassic if we are defining the extinction event as the demarker, but I am not a geologist.
27 comments:
Monty said...
Couldn't it be that the Deccan Traps weakened the ecosystem somewhat, and the Chixulub impact sealed the Cretacious' fate?
It's possible, Monty, but I wouldn't bet on it.
IIRC, there were sediments and fossils of dinosaurs found between the different layers of the lava flows that comprise the Deccan Traps. This means two things.
The DTs took a long time to happen and went through periods of cessation enough that critters would inhabit former lava flows. In fact, the DTs took 6 million years to erupt. That's a nontrivial time frame when compared to the Siberian Traps which did more boom for a mere million years. The Deccan Traps also had an order of magnitude less lava erupted than the Siberian Traps. If you do a quick BoE calculation, you can see the amount of energy, chemical nastiness, and lava spewed over was an average of 1/80th (or 1.25%) of the STs.
Finally, and tying back to something I said in the first point, India was an island at the time. The DTs were not even nasty enough to kill off the dinosaurs on India! That would make them suspect for poisoning the whole biosphere if it was insufficient for poisoning the DTs' ground zero, so to speak.
All in all, it doesn't seem likely that the DTs had much at all to do with the KT Event. At one time I thought differently, that the biosphere was strained already, that doesn't appear to be the case at all. It appears based on everything I've found today that the KT Event was purely a good Yucatanian rock'n'roll party. :)
Good summary. I've always been fascinated by the pick 'n' choose extinction aspect of the KT extinction (I think everybody is). For example, why did enantiornithines go completely under, as did hesperorniformes, but crown-group water birds survived?
I'm pretty convinced that the Siberian Traps can account for the PT event, but I'd be lying if I said that one big impact knocked the dinosaurs out of the ballpark in one fell swoop. North America took the brunt of the impact debris, but what about the thriving Gondwanna ecosystem? What about titanosaurs and abelisaurs?
I'm pretty convinced that the Siberian Traps can account for the PT event, but I'd be lying if I said that one big impact knocked the dinosaurs out of the ballpark in one fell swoop. North America took the brunt of the impact debris, but what about the thriving Gondwanna ecosystem? What about titanosaurs and abelisaurs?
heh. heh. heh. That is where I say that I will address this in the KT Extinction post that I will put up in the relatively near future. YAGUMETs first. That's a boojum I've been hunting first. ;)
PS: I was trying to disprove the vulcanism hypothesis more than prove the impact theory. I'll do the proof aspect in the KT post.
Nice analysis, but I was amused by the place where you said that the siberian traps outgassed "tons" of carbon dioxide.
Tons? On a geologic scale, mere "tons" is essentially the same as nothing at all.
Hey Geoffrey,
The tons in this case is meant figuratively rather than literally.
Current studies of Dinosaur diversity in Alberta find that diversity starts to decline 10-15 million years before the KT.
Overall numbers of animals appear to be roughly the same, but for example where at tminus-12 million years there were in the order of 5-7 hadrosaurs, 5 million there were 2-3, and by 1-2 million there was only 1 (and it had been surplanted as top herbivore by the ceratopsians which themselves more successful and numberous also experiences a similar decline in diversity).
There was definately some sort of major environmental change going on. This is supported by Alberta's micro fossils showing a major botanical shift during this period. As we all know the inland seas were drying up during this stretch too.
Everything I've seen suggests that at least in North America a major cooling trend was progress. This is most likely were the Deccan traps fit in. Producing enough greenhouse gases to block solar energy from entering the atmosphere is my postulation.
There are just too many extraterrestrial elements in the clay boundary of the KT to discredit a bollide impact. The Deccan traps do provide and excellent weakening of the Cretaceous environment though, and more study should go into how the two worked in unison to snuff out the cretaceous...
Oh and as for North America taking the brunt compared to elsewhere like South America there are no fossil remains to support the Titanosaurs or Abelisaurs making it past the KT...
If anything due to the impact site I'd say SA probably took it as much if not slightly more than NA (though to my knowledge there is no KT exposure known in South Amer to compare to... or am I wrong on this?)
The Royal Tyrrell conducted field work 2ish years ago in Northren China looking for a KT exposure further from the impact site to see what evidence and debris traces they could find in Asia. Sadly no KT boundary strata could be found (they think they got some 3-4 million years just before the KT... BOO), but it was an interesting venture that might have helped shed more light on things.
Asia or Africa might prove to be the place where some dinosaurs manage to survive a little beyond the KT as their further from the impact site, but I'd put out there only small theropods and ornithopods were likely to these survivors, and of course sadly not for too long after that.
Current studies of Dinosaur diversity in Alberta find that diversity starts to decline 10-15 million years before the KT.
IIRC, that's outdated info that keeps running around on the internet as fact. There has been multiple very extensive, very detailed studies refuting the 'declining diversity' claim at least at Hell's Creek. I'll have to go dig it up the cite, but it was a question of doing the sustained field work (not cheap nor glamorous).
BTW, we also have to be very, very careful about claiming declines in species:
http://en.wikipedia.org/wiki/Signor-Lipps_effect
Everything I've seen suggests that at least in North America a major cooling trend was progress. This is most likely were the Deccan traps fit in.
That's just it. Vulcanism doesn't kill by cooling.
Producing enough greenhouse gases to block solar energy from entering the atmosphere is my postulation.
Greenhouse gases don't block the sun. The volcanic forcing needed to do the climate shift you're talking about would be of the wrong sort for the DTs too: they were a flood basalt erruption, not a cinder cone. AFAIK, there's no documented evidence for a cinder cone eruption to be prolonged enough, frequent enough to cause even close to that amount of forcing. By their nature they beltch and are largely done.
The Deccan traps do provide and excellent weakening of the Cretaceous environment though, and more study should go into how the two worked in unison to snuff out the cretaceous...
That's just it. The Dts weren't even toxic enough to expunge the recently found mammals at 66 my ago[1] or even the dinos on the Indian island continent.
If I may ask, where have you seen a 'general cooling' taking place neat the end of the KT? I haven't seen that in the literature at all! The Paleocene and Eocene were rather hot. Just like the Cretaceous.
PS. Yes, more KT Boundary terrestrial sections would be VERY welcome in helping to sort out what happened to the dinosaurs. We have too few as it is and only a mere handful that are largely in NorAm are not that helpful in globally characterizing the KT Extinction.
That said, the 'fern spike' has been found in NZ which was emphatically a part of the southern hemisphere at the time. :)
The disappearance of the inland seas is a direct indicator of the cooling trend as I understood it. As ocean's don't receide on that magnitude unless you have some major glaciation going on, and that needs cold.
Now in fairness Geo is not my area of knowledge (dinosaurs are), but everyone I've talked to about the dropping of the ocean level towards the end of the Cretaceous has stated it was due to cooling of the overall temp.
As for Dinosaur field work I'm NOT talking about Montana and the Hell Creek for the reference on cretaceous diversity. It represents just the end of the cretaceous. Not knowing much about their field practises down state side I can't comment on the quality of their field work, but from the people I have talked to wouldn't take pot shots at it.
I'm talking about the extensive geologic units of the Red Deer River Valley in Alberta which cover some 15-20 million years of the end of the Cretaceous (with a few gaps in the middle). Of which I do know from personal experience the field work has been extensive and cross disiplinary between the various curators of the Royal Tyrrell Museum, University of Alberta, and Uni of Calgary.
Now one thing the researchers were aware of (I was a technician at the time) is that this was only one environmental context. However the drastic changes caused in Alberta due to the draining of the Bearpaw sea were extensive, and very detectable. Additional research going on in a number of localities along up the western interior seaway from Alberta down to Mexico is showing this was a constant trend for the whole subcontinent of western NA as of 2005 and the dinosaur park synposium.
In Alberta there was a constant decrease in both Hadrosaur and Ceratopsian diversity from the Dinosaur Park formation (75 million years ago) to horseshoe canyon (79 million) final to scollard (65 million).
hadrosaurs experience a fall due to very detectable changes in the botanic realm that favour ceratopsians. yet the ceratopsians themselves show the greatest decrease in genus (sorry I shouldn't have said species. habit of talking to the public) from the dinosaur park to horseshoe canyon.
Now granted I'd always tied this into the Hell Creek findings of reduced diversity, but to say that my entire assertion is based on anything but internet fact isn't true.
For the record I'm still in the asteriod boat on the KT. there is just too much support for it even just again in the clay
I'll call myself Anonymous99.
I'm not in the Asteroid boat nor the Volcano boat. I don't believe either caused a mass extinction...here's why:
P-T extinction
The best explanation, IMO, is the so-called clathrate gun hypothesis. Methane released from the sea bottom would devastate benthic life the most, and that's what happened. Terrestrial life would also be affected, less so, and animals with robust lung structure should be the survivors, they were. But what caused the methane release? Was it the Siberian Traps? Probably not, because the P-T extinction was preceded by the end-Guadalupian extinction that seemed to be similar. Benthic life was hit the hardest and the massive negative carbon isotope (C13) swings occurred during both extinctions. And, it is commonly believed that the clathrate gun hypothesis is the only known mechanism that could account for the size of the C13 swings. If the above is true, then the Siberian Traps was too late to be the perpetrator.
Another recent revelation is that the marine survivors of the P-T extinction found refuge near the coast of northwest Canada. Since that area and the Traps were in a relatively high northern latitude, one would think that the highest devastation would also be there.
Finally, two of the largest flood basalt eruptions, the Ontong Java Plateau and the Kerguelen Plateau, are not known to have caused any extinctions. So, the question that has to be answered is "What caused the methane to be released?"
At K-T, I have similar doubts about the Asteroid Impact Theory. I'll describe them in my next post.
I don't believe that the K-T extinctions were the result of flood basalt volcanism nor asteroid impact. My prior post on the P-T extinction gives the reasons why I don't think volcanism is the cause or any other one. The killing mechanism for both of these methods is basically the same except for the time duration.
There seems to be only one thing about the asteroid impact theory that's verifiable....and that is that an asteroid struck the Earth and left a worldwide iridum rich clay layer. Some even doubt that it was deposited by impact because we know that volcanism (e.g. in the current Hawaiian Island volcano) produces iridium.
The survival of so many creatures that should have been destroyed by the asteroid scenario: snakes frogs, lizards, crocs, birds, bees, etc., didn't happen. In the news recently is the story of the New Zealand Tuatura, a lizard that has existed for at least 200my. Itis now facing extinction because of the rapid climate warming due to temperature related skewing of male/female egg ratios.
Apparently gradual temperature change in the past has allowed it to evolve survival strategies. The K-T impact should have
produced extreme, short-term swings in temperature yet the Tuatura managed to survive that.
Then we have the polar dinosaurs which, if they were still around at K-T, should have been better prepared to survive those same temperature swings....but they didn't.
There were also burrowing dinosaurs......they didn't survive either.
There appears to have been some other stress(es) operating over millions of years which caused the dinosaurs to diminish in both physical size and numbers and that their extinction was inevitable. So, the question is whether the gradual decrease in physical size/metabolic requirement can be
shown to agree with the fossil record. And, any claim of increasing diversity toward the end of the Cretaceous is not relevant. Increasing diversity could be an indication of stress which is driving that diversity.
The record seems to show the K-T extinctions occurred in the following pattern:
1. Larger land vertebrates gave way to smaller, lower metabolic ones over millions of years.
2. Larger marine reptiles die out near and up to K-T boundary.
3. Many smaller marine amd micro-marine animals die out very near and after the K-T.
When I use the term "K-T boundary" I'm referring not to the impact date but to the transition from Cretaceous to Teriary micro-marine fossils. This is currently believed to be at least 300,000 years after the impact.
I believe extinction scientists need a "mental clearance sale" and must take a fresh look at the K-T extinctions.
Anonymous99
Extensive reply later, Dave. I'm a tad bit busy at the moment and on something of an online hiatus.
I wouldn't call the temnospondyl and nonarchosaurian diapsid survivors as examples of superior lung development though in PT Extinction leftovers.
Happy New Year......1/3/09
If the Clathrate Gun Hypothesis is correct when explaining the P-T extinctions, and I think it is, then the temnospondyl survival makes sense. The comment on P-T survivors with robust lung structure applies to terrestrial vertebrates, such as Lystrosaurus. Peter Ward suggests this in his book 'Gorgon' (page 224) where he suggests the animal's massive rib cage probably evolved because of low oxygen conditions. Excessive atmospheric methane/carbon dioxide is a possibility. Lystrosaurus dominated the early Triassic landscape (95% of terrestrial vertebrates).
Temnospondyl was an amphibian and most likely inhabited inland, shallow fresh water locations which would not have felt the full brunt of methane asphyxiation as the life in and near the epicontinental seas would. Its metabolic requirements also would have been much lower than that of active terrestrial herbivores and carnivores.
Anonymus99
First off, anon (it IS dave, isn't it?), did you read the Permian Extinction post? If you had, you'd see that the calthrates are part of the feedback mechanism that killed so much. It was tickled by the volcanic warming into being released and jacking up the temperature even more. It wasn't a singular kill mechanism for the PT Extinction, but a train wreck set in motion by the Siberian Traps.
As for the Guadelupean Extinction, that is, as I recall, a rather understudied one at present and drawing a conclusion on it as unrecommended: unless you have links to a flurry of papers?
Methane wouldn't have been asphyxiating much of anything in the kill scenarios that I've seen so far. Hydrogen sulfide has been labeled as such, but not methane: methane at room temperature is lighter than air and even with the calthrates having been cold by the time the gas would have breached the surface of the sea, it'd have warmed considerably and in the roaster that the world was at the time, it'd only be able to asphyxiate for a short, short time.
I am troubled by the stats that Gorgon and others give about the lystrosaurus numbers is that the number of sites for the time frame in question is really, really low. Adding another one would probably cause huge changes in percentages. Sampling bias has already reared its head lately with dicynodonts twice: once in Poland for the late rhaetian and once in Australia (maybe) for the Cretaceous.
Gorgon, btw, is largely a travelogue. If you are looking for other books on the subject that cover more of the science, I especially recommend Mass Extinctions and Their Aftermath by Wignall and Hallam. Extinction by Erwin is another good one. When Life Nearly Died isn't bad either by Benton.
More later. Squished with too much to do.
1/06/09
I'm not dave...you can call me Anonymus99 or Anon99.
I'll wait until you have some free time before I present some pretty compelling evidence why the Siberian Traps didn't cause the P-T extinctions.
Anonymus99
Fire away, anon.
I will perpetually be busy. I run HPC assets, building rockets, and being a daddy all in one time. My writing & blog is squeezed between everything else.
If you have compelling evidence, by all means, post away. Citations would be appreciated so that I may go read the primary sources.
1/07/09
Permian carbon isotope analysis is what undermines the current belief that the Siberian Traps was responsible for the P-T extinctions.
A graph of the carbon isotope change (i.e. delta 13C) can be seen at the following website:
http://palaeo.
gly.bris.ac.uk/Palaeofiles/rateanalysis.html
A similar graph can be found in the book Mass Extinctions And Their Aftermath (page 127).
The graphs clearly show a peak in the late Permian (Changxingian) and a steady rise that reaches a peak near the P-T boundary.
Because of the magnitude of the carbon isotope swing, the only explanation is a release of methane (i.e. the Clathrate Gun Hypothesis).
This is explained in the following website:
http://palaeo.
gly.bris.ac.uk/Essays/wipeout/default.html
A quote from that website is "Pulses of carbon-12 in the geological record are usually indicative of a volcanic eruption or a large die-off(plants, animals...."
and "But the carbon-12 pulse is far too big to be explained by these mechanisms alone." The essay goes on to attribute the carbon isotope change to the relaease of methane from the methyl hydrates under the ocean.
Since the graph shows changes long before the Siberian Traps erupted, the methane release would be the logical explanation for the global warming that ensued. Methane is a far more potent greenhouse gas than carbon dioxide and methane transforms to carbon dioxide in a relatively short period of time....I believe 10-20 years.
Also, as mentioned in one of my prior posts, the release of methane would have been most deadly to benthic life in the oceans. On land, the effects would have been to deprive land animals of oxygen and flora of carbon dioxide, causing extinctions in both groups.
Ward's comment about the robust lung structure of Lystrosaurus is important. If Lystrosaurus evolved this attribute, it would have to have been exposed to lowered oxygen levels gradually over a long period of time. The graphs above would indicate that was the case.
Lystrosaurus's main predator, the carnivorous Gorgonopsids did not survive the Permian. As a carnivore, it did not require the stamina-enhanced structure (i.e. lung capacity) that a herbivore would.
Therefore, based on the above, the release of methane was not an after-effect of the Siberian Traps but preceded it and gradually increased to a maximum level near the time of the Traps. In other words, the extinctions would have happened even if there were no flood basalt eruption at the P-T boundary.
Anonymus99
um. server not found.
1/08/09
My typo. There should be "Permian" after the "Palaeofiles/". So let's try again:
http://palaeo.gly.bris.ac.uk
/Palaeofiles/Permian/rateanalysis.html
I split up the URL because the preview doesn't show the entire line....so I wasn't sure if it would post correctly.
Anonymus99
I checked from home and server was available. Perhaops it was down while I was at work. I'll check again a little later.
Last night, the graph didn't seem to be on the server (page not found), but the second link was a section from Benton's book....which was in support of the Siberian Traps with the methane calthrate release caused by the warming of the oceans caused by the release of carbon dioxide by the Siberian Traps.
You are also ignoring the research done with respect to the hydrogen sulfide content of the oceans and atmosphere. The H2S content, generated by vicious little bacteria that live in hypoxic/anoxic conditions, greatly increases the longevity of methane in the atmosphere as well as being an asphyxiant and generally poisonous.
I am going to have to ask for a paper cite for the current understanding of the Lystrosaurus lung structure. Is there a paper (or even a communique) by a anomodont researcher that gives information wrt this? Ward hypothesizes that this is the case, but as of his book, Out of Thin Air and the paper was approximately the same time, the evidence is still equivocal at best...or nonexistent.
ha! Talk about doing the same thing at the same time. Thanx for the correction.
I'll check the link a bit later. I'm recasting nsd server configurations to take advantage of the new 'private' nsd server functionality in GPFS.
1/09/09
I don't know if there is research on Ward's Lystrosaurus observation. I mention it because it supports the Clathrate Gun Hypothesis as it applies to the Permian/Triassic extinctions.
H2S release occurred during the P-T transition but the timing and intensity, as far as I know, has not been established. Most likely, it was the result of the lengthy (according to the Carbon Isotope graph) disassociation of methane. The positive feedback cycle of the methane release would have raised global temperatures and deprived the oceans of oxygen causing anoxic conditions favorable to the production of H2S.
There's no doubt that H2S was a component of the killing mechanism but its magnitude is unknown.
What is interesting about 'Mass Extinctions And Their Aftermath' is that the authors confirm both the pre-Traps marine and terrestrial extinctions:
"The terrestrial tetrapod record appears out of step with that of the marine invertebrates in showing a protracted Lopingian diversity decline." (page 114)
But they don't link the massive carbon isotope swing (shown in their graph on page 127) with the rising levels of methane. In fact, I find only one reference to methane in the entire book (page 137):
"The methane of gas hydrates may also have exsolved as temperatures rose, thus further exacerbating the greenhouse effect (methane rapidly oxidises to CO2 in the atmosphere)." I have to assume that, because the book was published in 1997, they were not aware of the methane/carbon isotope linkage.
Therefore, based on all of the above, in my opinion, the Late Permian and P/T transition extinctions were overwhelmingly the result of the methane disassociation from the oceanic methyle hydrates.
Anonymus99
Response post coming in the next week. It's going to be long and be a top level post. A link will be put in here at a later time.
Hello i need help wat is the permian period.
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