Shock finding: P-T mass extinction was due to an ice age, and not to warming

From the UNIVERSITÉ DE GENÈVE

The cold exterminated all of them

Through age determinations that are using the radioactive decay of uranium, scientists have discovered that one of the greatest mass extinctions was due to an ice age and not to a warming of Earth temperature

Permian-Triassic boundary in shallow marine sediments, characterised by a significant sedimentation gap between the black shales of Permian and dolomites of Triassic age. This gap documents a globally recognized regression phase, probably linked to a period of a cold climate and glaciation. CREDIT © H. Bucher, Zürich

The Earth has known several mass extinctions over the course of its history. One of the most important happened at the Permian-Triassic boundary 250 million years ago. Over 95% of marine species disappeared and, up until now, scientists have linked this extinction to a significant rise in Earth temperatures. But researchers from the University of Geneva (UNIGE), Switzerland, working alongside the University of Zurich, discovered that this extinction took place during a short ice age which preceded the global climate warming. It’s the first time that the various stages of a mass extinction have been accurately understood and that scientists have been able to assess the major role played by volcanic explosions in these climate processes. This research, which can be read in Scientific Reports, completely calls into question the scientific theories regarding these phenomena, founded on the increase of CO2 in the atmosphere, and paves the way for a new vision of the Earth’s climate history.

Teams of researchers led by Professor Urs Schaltegger from the Department of Earth and Environmental Sciences at the Faculty of Science of the UNIGE and by Hugo Bucher, from the University of Zürich, have been working on absolute dating for many years. They work on determining the age of minerals in volcanic ash, which establishes a precise and detailed chronology of the earth’s climate evolution. They became interested in the Permian-Triassic boundary, 250 million years ago, during which one of the greatest mass extinctions ever took place, responsible for the loss of 95% of marine species. How did this happen? for how long marine biodiversity stayed at very low levels ?

A technique founded on the radioactive decay of uranium

Researchers worked on sediment layers in the Nanpanjiang basin in southern China. They have the particularity of being extremely well preserved, which allowed for an accurate study of the biodiversity and the climate history of the Permian and the Triassic. “We made several cross-sections of hundreds of metres of basin sediments and we determined the exact positions of ash beds contained in these marine sediments,” explained Björn Baresel, first author of the study. They then applied a precise dating technique based on natural radioactive decay of uranium, as Urs Schaltegger added: “In the sedimentary cross-sections, we found layers of volcanic ash containing the mineral zircon which incorporates uranium. It has the specificity of decaying into lead over time at a well-known speed. This is why, by measuring the concentrations of uranium and lead, it was possible for us to date a sediment layer to an accuracy of 35,000 years, which is already fairly precise for periods over 250 million years.”

Ice is responsible for mass extinction

By dating the various sediment layers, researchers realised that the mass extinction of the Permian-Triassic boundary is represented by a gap in sedimentation, which corresponds to a period when the sea-water level decreased. The only explanation to this phenomenon is that there was ice, which stored water, and that this ice age which lasted 80,000 years was sufficient to eliminate much of marine life. Scientists from the UNIGE explain the global temperature drop by a stratospheric injection of large amounts of sulphur dioxide reducing the intensity of solar radiation reaching the surface of the earth. “We therefore have proof that the species disappeared during an ice age caused by the activity of the first volcanism in the Siberian Traps,” added Urs Schaltegger. This ice age was followed by the formation of limestone deposits through bacteria, marking the return of life on Earth at more moderate temperatures. The period of intense climate warming, related to the emplacement of large amounts of basalt of the Siberian Traps and which we previously thought was responsible for the extinction of marine species, in fact happened 500,000 years after the Permian-Triassic boundary.

This study therefore shows that climate warming is not the only explanation of global ecological disasters in the past on Earth: it is important to continue analysing ancient marine sediments to gain a deeper understanding of the earth’s climate system.

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131 thoughts on “Shock finding: P-T mass extinction was due to an ice age, and not to warming

  1. “This study therefore shows that climate warming is not the only explanation of global ecological disasters in the past on Earth”

    OK – point out one case where that was true? Otherwise it is just the PC blather of climate non-science.

    • Just look up above YOUR post Dinsdale.

      I think you will find a report of …. one case ….

      Satisfied now ??

      G

      • The case listed in the article, which is what I assume you meant by “above your post” details an instance where cold caused a mass extinction.

        If I read him right, he’s asking for an example of a case where global warming has caused an extinction event.

      • This article will never stand up under intense Mannian examination.

        The inconvenient truth here is that the hammer in the photo above is clearly upside down. This can only mean that the entire stratigraphic series itself is also 180 degrees upside down and that advanced Tiljanderization techniques must once again be employed before the proper conclusions can be drawn.

        Which are…

        Global warming occurred first killing everything off and evaporating the oceans before the ice age set in.

        It’s beyond debate.

      • No MarkW he asked for one case that …… shows that climate warming is not the only explanation of global ecological disasters in the past on Earth.

        Doesn’t mean that cold is the only alternative to warming; but it is one of them.

        G

      • The question is when, what extinction was caused by warming? Do you have any such examples?
        And no, the current post just prove this one was not the case.

      • The quote was weak in that it could be read in several ways.
        george as is his wont, decided to read it in a way that makes no sense and is clearly not what the poster intended.

    • It’s warming or it’s cooling to blame for sure. And that’s not all. Now that we are either warming or cooling the planet much faster now using the magical CO2 molecule, disaster is neigh! Without the dreaded human beings, this beautiful big blue marble would have to wait thousands of years until the next mass extinction, instead of just eighty years or so.

  2. Dang regressions. Always stealing sediment. Dang ice sheets…always stealing water. Note that their resolution of 35,000 years is pretty darned good over a span of 250,000,000. Good enough to resolve the reasons for the extinction. Amazing how climato-alarmists get all wound up over 150 years, in their rush to apply uniformitarian ideas.

    • I agree, 35,000 years resolution compared to 250,000,000 is like finding a single page in a 7142 page book.

  3. I wonder just how thick the sediment layer, or lack of sediment, actually was if it was only two or so (80 K years) errors in dating (35 K years) “thick”.

    • So Tom, this is a rhetorical question? There is no absolute or standard thickness for 35,000 years of sedimentation. And in the case where there is an ABSENCE, the thickness is zero. Transgression/regression in the sedimentary record is very common. There is no need to assume that a regression in the Permo-Triassic boundary region is any different. +/-35,000 years in 250 million is basically nothing, as far as errors go. So your rhetoric over such precision is pointless, really. A regression happened. In the boundary region.

    • “The period of intense climate warming..”

      Are they talking about accelerated back to normal warming from the ice age?

  4. Some say the world will end in fire,
    Some say in ice.
    From what I’ve tasted of desire
    I hold with those who favor fire.
    But if it had to perish twice,
    I think I know enough of hate
    To say that for destruction ice
    Is also great
    And would suffice.
    ~ Robert Frost

  5. This gets so frustrating, concerning the Permian extinctions, and other mass extinctions for that matter. First it was it was the Siberian Faults that caused all this. Now it is due to an ice age. Earth to intellectuals, what happens to this planet is almost always due to some action that is celestial in nature. Consequently, it helps to understand what caused this Siberian vulcanization, and also ice age.

    Its almost certainly due to IMPACTORS. Can you all think Comet/s for a change? What is so hard for so many to not understand that Impactors have this ability to shake things up so quickly?

    Its the Comets Stupid!

    • You may be correct; a comet could have produced the mini ice age.

      Their thesis is that the ” ice age ” is what caused the ” extinctions “.

      A comet landing (or watering) in the oceans, is not going to kill 95% of everything in the oceans.

      The waves would die out in a couple of days at most.

      G

      • The waves would, but not the ejecta. Either way, the science isn’t settled!

      • George, its not the water that really matters. Its the flexible crust, which is floating on top of an inner molten mantle. When something of great mass punches through that thin crust, it causes terrible geologic ripples that make the oceans look like chicken feed. That’s what causes all the plates to suddenly turn loose, volcanoes spew out like crazy, and all that ejecta thrown out into the upper atmosphere. Instant nuclear winter times a thousand.

      • I think I just said that a comet landing in the ocean is not going to kill 95% of everything In the oceans; like in a couple of days or even weeks.

        but !

        Yes a resulting nuclear winter a thousand times over could do that. I think the comet landing in the oceans did not kill everything (95%). But the resulting freeze could have.

        Maybe I’ll rewrite that in Maori; might be more intelligible then !

        G

    • Unlikely on the prevailing view of comets as dirty snowballs, or (a distinction with doubtful difference) snowy dirtballs.

      • As Niven and Pournelle point out in Lucifer’s Hammer, when you’re talking about that much mass at that speed, what it’s made of really doesn’t matter much. Only the first few meters are going to notice the atmosphere anyways.

      • I don’t think so Chimp. A huge crater under the Antarctic ice has been attributed to the guilty impactor. In 249 million years the continents have shifted and this impact site would have been almost precisely on the other side of the Siberian area where all the vulcanism occurred. This fits exactly because the ripple effect of the crust would radiate out and around, coming together at once and greatly magnifying the effect of the impact.

      • John,

        The alleged Wilkes Land “crater”, if it is a crater, which is still in doubt, cannot be dated any better than between 100 and 500 Ma.

        The total absence of a well-defined impact ejecta layer at the Permian–Triassic boundary where it crops out in Victoria Land and the central Transantarctic Mountains argues against there having been any impact capable of creating a crater the size of the hypothesized Wilkes Land crater within Antarctica at the Permian–Triassic boundary.

        As I said, debunked.

      • Just because it is so old that ‘in your face’ evidence is not present, does not mean it is “debunked”. The latest thing is that Siberian Traps as the reason. But totally overlooked is what would cause the traps to go nuclear. Well Duuh! In fact, I contend that there was most probably more than one Impactor. There is something that goes on about every 32 million years, out in the Oort that is shaking loose all those comets, and they are making the inner system a shooting gallery. If you and others can’t use logic and conclude this probable, that’s not my problem. Out here.

  6. Did it occur to them that a “gap in sedimentation, which corresponds to a period when the sea-water level decreased” could also be caused by a local uplift of land mass?

    • And then it went right back down again, and continued sedimentating after only 80,000 years.

      Works for me.

      G

      • It would be nice to back up claims by sources.

        Other than that, suppose that for some unknown reason, dealing with different precession trends of solid and fluid earth cores and earth mantle caused different pressures on the lithosphere, causing the bulge of the equator to either grow or shrink, what might that do to equatorial and arctic sea levels?

  7. I’ve noted before that the dO18 isotopes show a large temperature drop right at the Permian Extinction event. Now these isotopes have no hope of getting to 35,000 year time resolution but the cooling was general over a few million years with a big drop right at the extinction timeline.

    These Siberian Traps volcanoes were big enough and lasted long enough to cause deep cooling across the planet. This does not fit the global warming explanation that climate science likes to use lately.

    • Not to mention that over much of the world during the Permian, prior to the extinction, there were signs that seaways dried up and much of the surface was desertified. The Permian evaporative basin the the US contains over 1,000 feet of salt, and it also contains thousands of feet of highly oxidized paleosols, with stringers of gypsum and anhydrite — it was very very dry. A warm global climate generally does not coincide with an aridity. Not only did aerosols from volcanoes play a role, airborne dust in the atmosphere probably didn’t help matters either.

      • “A warm global climate generally does not coincide with an aridity.” It depends on how warm. Evaporite basins form in torrid climate conditions, as evaporation outstrips water supply. Also, Pangaea was extant at the time…

      • RWturner: It would be great to see that map of Permian evaporative basins on a reconstruction of the continental setup at that time, like one of Scotese’s reconstructions. Do you know of one?

        The Siberian traps, in places at least, erupted through sulfate-rich beds. That likely is the reason the nickel deposits of Norilsk formed – sulfur taken into the basaltic magma to extract nickel, PGMs and copper as sulfide minerals (otherwise, the nickel goes into minerals such as olivine). It also could have given rise to sulfuric gases being expelled into the atmosphere. This article makes a compelling case for the conditions that brought around the P-T extinction event. Now, to find another place or two singing the same story.

      • Alarmists don’t so much explain the P-T using global warming, more the case they use the supposed runaway warming of the P-T to wail about runaway global warming just a few decades away. The P-T is a central plank of their scary argument. No P-T, no runaway, then why are we wasting trillions on an energy transition?

    • Bill Illis March 6, 2017 at 10:31 am

      The blue line suggests an event or development that started at 262 million years BP and (after a little stop at 255) ended (!) around the Permian Extinction Event. After that there is a quick recovery to the point from where there was a more gradual lowering of the blue line, in accordance with the top at 262 BP. Between 262 and 248 BP there is a gap. About 14 million years.

  8. So many things could affect sediment deposition. I am skeptical of anyone being able to narrow the cause to only one thing some 250 million years after the fact.

    • A regression that lasts for only c. 100,000 years is almost certainly due to glaciation. There is no other mechanism that is that fast.

  9. 35,000 year resolution.

    That is not a trifling number. I find it incomprehensible. 10 years ok… 40 years ok. 100 years ok.

    But 35,000 years? What is 35,000 years? Then to use that number as a gradation of a 250,000,000 year event makes the whole exercise an abstraction for me. (the uranium angle is very cool.)

    So what am I to think? Big changes happen over very long time periods. Human life is a twinkling of an eye.

  10. This ice age was followed by the formation of limestone deposits through bacteria, ………” ?

  11. Supporting Information has the details of the uncertainties in timing.

    https://dl.dropboxusercontent.com/u/75831381/Baresel%20SI.pdf

    The authors make the point in the main text that their theory (initial cooling as the main cause of the P-T extinction) now agrees with the Triassic-Jurassic explanation, although in one case it may have been volcanos and in the other case it may have been an asteroid impact:

    “Abrupt drop down of sea surface temperature, shrunken habitats on shelves resulting from a global low stand, and short-term acidification may all have synergistically triggered the PTBME. In many aspects, the environmental
    upheavals linked with the PTBME (i.e. short-lived cooling followed by longer term warming) tend to parallel the most recent model proposed for the Triassic-Jurassic boundary mass extinction event, thus leading to a more unifying view of causes and effects of large igneous provinces.”

    • Sea level normally falls when you have a super-continent, or let’s say the ocean actually gets deeper than a normal Earth scenario.

      Once you have crashed all the continents together and they have built big mountain chains all over the place and have finally fused together, you have less land mass as a percent of the total Earth. It only takes a few percent less.

      Then you also have mature ocean basins. Mature ocean basins sink into the mantle from when they are formed as Rift Valleys on land a few metres deep until they are a full-fledged Oceans 100 millions later and they are now 5,000 metres deeper. So, once a Pangea is in place, the average depth of the ocean is probably 300 or 400 metres deeper than today.

      So, what you have is NO continental shelf area below sea level like today. Basically, you just have a deep drop-off from the shore to 2,000 metres which then falls just as fast to 5,000 metres.

      It looks as though sea level has actually fallen or that a deep ice age has started up, but it is really just the “age” of the ocean basins and the fact that the land has compacted slightly.

      This leaves little room for continental shelf type dwelling sea-life organisms and on the eastern side of Pangea, I imagine it often got too hot for complex life in the PaleoTethys sea. And then on the super-continent, you have huge mountain chains and huge deserts leaving little room for land-based life.

      Now throw in the biggest volcanoes in Earth history (enough to cover the entire US in 1 km of magama) lasting for several million years and what do you get?

      A very bad place for life to survive. Extinctions were inevitable.

      • The surface waters of these oceans must have also been pretty opaque with settling volcanic dust.
        Photosynthesis must have virtually ceased in this ash soup and the whole food chain would have collapsed.

      • Along with crashing the continents, just throw in a little expansion of the planet – would play merry hell with sea levels.

      • There clearly was a sea level low stand. The question is whether an “ice age” was the cause. I am not aware of any tillites from that time frame.The standard notion is that temperature was recovering from the Carbo-Permian ice age (which has tillites) and it was rather hot.

        Another interesting feature of the extinction is that it was a VERY bumpy ride to recovery in the early Triassic.

        This is a very interesting and important paper. If there was a “flash freeze” at the end of the Permian we definitely need to know about it.

      • gymnosperm March 7, 2017 at 9:05 am

        Gymnosperm, is there any explanation for the contrary movement of Sea Level and Temperature Anomaly around 250 Ma?

    • Wim,

      No. That is a mystery. Locking water up in ice would explain that, but there are other possibilities. According to largeigneousprovinces.org, volcanic activity was also unusually low. This runs counter to the usual notion that the skies were blackened by volcanoes.

      During the Cretaceous it was equally warm but sea level was high. Much of the extremely high volcanic activity was under water in the Pacific, possibly lifting the basin floor and flooding the continents.

      The Siberian volcanism in the Permian was on land, and there are indications it was particularly nasty.

      • 250 Million years ago, all continents were unified in Pangea. I can imagine that the colliding together made a compact land surface with high rising ‘Himalaya’s’ in between the colliding parts. If the total land surface diminished by a ten percent but ‘land’ was on the average higher, then the lower sealevel could be explained as well, at least for a part. More space for the oceans, resulting in a lower sea level.

      • One must be careful because Pangea stuck around for a long time. Most collisional orogeny from its formation was 100 million years earlier. We might presume that the continents were pushed into a pile by active ocean ridges, but questions remain.
        The astonishing Cenozoic migration of India to form the Himalayas is difficult to reconcile with “push”. One wonders if it may be related to the gravity low that still pervades the area.

  12. I’m perplexed. This is news ?

    Back when the world face mass extinction due to Global Thermonuclear War, “nuclear winter” was the widely accepted outcome. Same for asteroid and comet events.

    I guess what might be news is that there haven’t been any Global Warming mass extinction events within record.

    • Especially during the Carboniferous Era, a pungently prolific period of lush everything.

      • Which was actually a global ice-age with CO2 about as low as today. The coal deposits were directly caused by the frequent regression/transgression cycles caused by glaciations.

    • “nuclear winter” was the widely accepted outcome

      Widely accepted among a tiny group of deep green fanatics. Ignored by everyone else.

      • After Carl Sagan claimed that, if Iraq were to ignite the Kuwaiti oil wells, there would be a regional cooling in Pakistan/India … the glimmer wore off when the regional cooling didn’t happen.

  13. Read the paper and SI. The brief cold spell ‘ice age’ is inferred from a gap (cessation) in shallow sea sedimentation implying a drop in sea level implying ice sheet formation. This gap is overlain by a bacterial limestone (stromatolyte) implying the sea level rose again. This is explained by sulphate aerosols from the earliest stage eruption of the Siberian traps. The cold does NOT explain the mass extinction of marine organisms since the seas did not freeze and have about 1000 times the heat capacity of the atmosphere. But ocean acidification from the sulphates as they settled out of the stratosphere could be an explanation.
    Debunks the CO2 from the Siberian Traps caused the end Permian extinction theory via ocean acidification. Never made much sense anyway, for two reasons: the seawater carbonate system is highly buffered, and flood basalt eruptions like the Siberian Traps are sulphate rich and relatively CO2 poor. It is subduction zone volcanism that is CO2 rich, from recycling of carbonate rock like marine limestones. No different than CO2 from making cement.

    • 80,000 years is a long time for oceans to cool during.
      Beyond that, lots of aerosols in the atmosphere would have cut down the amount of sun light resulting in the loss of plants and plankton, which in turn means the loss of those animals that feed on them.

  14. I highly recommend “Is Genesis History?” I saw it and it was very good.

    One more showing tomorrow night (March 7th) here is a list of theaters.

  15. Funny the number of people attacking this paper as being an attempt to debunk a global warming hypothesis as being the cause of the Permian Extinction. Or at least that is what the rhetoric is suggesting.

  16. It’s commonly stated that crocodiles have existed for 300 million years. How and where could they have survived such an ice age? If 95% of marine animal species were eradicated, surely the percentage of large land animals must have been even greater? Could it be that the appearance of crocodiles has been mis-dated by 50+ million years?

    Hopefully a more precise measurement than “abrupt” of the onset of this ice age can soon be obtained, together with the intensity of the initial cooling. Certainly, this is a powerful incentive for accelerating the development of safe technologies that would permit humanity and at least some appreciable segment of earth’s flora and fauna to survive an effectively endless winter of polar proportions.

    Mars flights and solar gliders certainly won’t help us in this scenario.

    • “It’s commonly stated that crocodiles have existed for 300 million years.”

      Nope. The oldest crocodylomorphs are late Triassic c. 20 million years after the P/Tr extinction.

      • Thanks for the heads up.

        I thought briefly that I had confused the shark fossil record with that of crocodiles, but no. Sharks have been around for more than 400 million years. I guess I’ve been watching nature documentaries too uncritically.

        OTOH, on looking online today, I found an ancestor of the crocodiles of considerable size (Xilousuchus, three feet long. 5-10lbs) dated at 250 million years.

        https://www.preceden.com/timelines/44419–evolution-of-crocodiles-

  17. I think that the average surface temperature determines if we are in a ice age or not and this will also decrease if a lot of the surface of the earth is well above sea level as it is today. The climate sensitivity is also lower today because there is less radiation from a cooler surface than a warm surface. I think that the interglacial period we are in could be defined by the fact that the surface temperature never falls below freezing in the mid latitudes at sea level in an average year even at the coldest part of winter (which in the northern mid latitude is the middle of January) . I think the idea proposed in the article is plausible but who knows what happened 250 million years ago.

  18. Scientists from the UNIGE explain the global temperature drop by a stratospheric injection of large amounts of sulphur dioxide reducing the intensity of solar radiation reaching the surface of the earth.

    Sulphur dioxide is a greenhouse gas. It absorbs in the IR region.

    BTW, the tiny double peak at around 2500 cm-1 is due to CO2.

    • How much energy does the earth radiate in those regions? I had a chart for that but couldn’t find it.
      Regardless, sulfur dioxide makes clouds brighter which reflects more sunlight before it can reach the earth’s surface.

      • Doesn’t sulphur dioxide make rain (acid) as well as lots of clouds before the rain.

        And by the way, at 288 K the LWIR peaks at about 10.1 microns. That little blip around 1000 is one micron; tail end of solar spectrum, not LWIR.

        G

      • I dont know. Water also absorbs at around 1500 cm-1. I just wanted to point out that, like H2O, SO2 is also a v-shaped triatomic molecule with a permanent dipole moment, so is should be more efficient at absorbing IR radiation than CO2, which is a lineal triatomic molecule without permanent dipole moment.

        SO2 combines with water and forms sulphurous acid, which is oxidized to sulphuric acid. It produces aerosols with a cooling effect.

        I just was wondering why nobody in the field takes into account that SO2 also absorbs IR radiation.

    • The double peak at 2500cm-1 is actually due to SO2, the CO2 peak would be at a slightly lower wavenumber. If it were due to CO2 you’d also expect a peak at 667cm-1 which there clearly isn’t.

  19. Is this one of those “Mandela effect” things I’ve been reading about? ‘Cos, if you’d asked me five minutes ago about the P/T boundary event being a heat wave or a cold spell, I would have said that I thought it was an ice age. And yet this article says we “used” to think it was a temperature rise and they’re only just now “showing” that it was cold?

    My geology degree is from a long time ago. No way to know if it’s my faulty memory, or if the prevailing wisdom back then was P/T boundary = cold. Still, color me surprised. Extremely surprised.

    • “My geology degree is from a long time ago.”

      In the meantime the P/Tr extinction, like virtually everything else, has been blamed on the demon molecule CO2.

  20. Nice to see scientists at work. I took the last statement to be an affirmation that science requires constant debate. Never shouting down.

  21. Whenever there is a mass extinction affecting over 90% of marine species, ocean acidification from volcanic sulfates is the likely cause.

    So the hypothesis they develop is that the mass extinction took place during an ice age caused by unusual volcanic activity. Most species died as a consequence of ocean acidification, acid rain, decrease in insolation, and sudden cooling, because we know that ice ages do not cause mass extinctions by themselves. This is usually describe as a volcanic winter. A very big one.

    However we still don’t know the cause of the unusual volcanic activity. Could it not be due to another asteroid hitting the Earth like in the K-T extinction? Something like that could very well cause unusual volcanic activity.

    And I hate it when they say:

    scientists have discovered that one of the greatest mass extinctions was due to an ice age

    They have discovered evidence that they interpret as due to an ice age in their hypothesis. In science the level of security displayed does not exist. Much less about something that happened 250 million years ago. New evidence could change the way we interpret this event.

    • Thank you, Javier, for your remarks. I was about to ask how an ice age would cause 90% of marine species to go extinct.

    • The putative Wilkes Land Crater was suggested as an impact that could have caused the Siberian Traps eruptions, but this conjecture has been thoroughly debunked.

      That leaves mantle plume or superplume activity, as is the case with most such volcanism, if not all.

  22. An excellent article in many respects. A check on the behaviour of the trace elements from the black shales would indicate a exhalative volcanic regime. This gives rise to a toxic atmosphere. This is all pervasive. and will certainly affect life. If a short term ice age also occurs then the combination would be devastating. In that case hen both marine and terrestrial life is severely affected. It is possible that the mass extinctions at the end of the Ordovician are driven by similar mechanisms. Certainly the work I have done in this age group of black shales point to felsic volcanism as the main driver for unusual sedimentary accumulation possibly leading to mass extinctions. This highly repeatable mechanism also points to the difficulty in having a wandering comet make impact in such a manner as to be the sole cause of mass extinctions.

  23. And if the world cooled, the feedback mechanism that assisted that cooling would have been surface albedo from ice sheets. Surface albedo feedbacks are orders of magnitude greater than CO2 feedbacks, when measured locally.

    R

  24. I have often wondered, could massive oceanic strikes produce deadly-enough concussions, to cause mass fish extinctions?

  25. A very interesting piece of work but there are a couple of points that trouble me. The fact that the report infers that the depositional gap described is stated as representing an interval of 80’000 years might be problematic. Essentially they are saying that there is a discontinuity of 80k years , but it might be more, such things being difficult to be certain of. I admire the confidence to assert intervals of 35k and 80k with accuracy at timescales of 250 my in the past.
    Just a quick reading of all the comments shows how problematic the interpretation of all this is at the vast gap of time involved. IT seems that yet again the writing out of the possibility of a cometary impact is at the heart of this because as we know there is no major impact of any comet or asteroid involved in any disruptive event or extinction ever in the Earth’s history. This is because we live on a magic planet which is wholly immune to th celestial events which have left every other body in the solar system looking like it has been used as a pincushion by collisions, but the only bad things that ever happen to our planet are only ever caused by people (preferably either giving off too much CO2, Methane etc or just fornicating too much for the planets alledged sustainability).
    Yeah right.

  26. Can’t be true as I’ve been told by lots of folks the science is settled. Besides they’ve got no tree rings.

    • It largely depends if it’s on the A-list of settled science with politically directed imperatives for revenue reach and the extended list of funded activist groups or if it’s from the B-list of normal science process in overturning conventional understanding. Fortunately medical research is mostly on the B-list.

  27. This direct evidence study blows away the arm waving of presumed mechanisms that typified what came before it. Next step is to study the coral reef fossils of the period with direct core samples.

  28. Wiki says it was the heat that killed off the marine vertebrates when their thermal tolerance was exceeded. Minor discrepancy, sarc

  29. I once attended a talk by Dr. Amy Mainzer, principal investigator on the NEOWISE asteroid-hunting program at JPL. Her talk was fascinating right up the point where she mentioned the Chicxulub meteor strike, widely regarded as the cause of the K-Pg extinction ending the dinosaurs. She said that everyone thinks the blockage of sunlight by the enormous dust cloud put in the atmosphere by the impact caused global cooling. BUT, she said, scientists have found a layer of carbon over the entire globe, all at the geologic time of the asteroid impact. That means that there was a world-wide fire in which all surface vegetation was consumed, putting enormous amounts of carbon dioxide into the atmosphere and causing huge global warming. This, she concluded, means that we need to take global warming seriously.

    I almost stopped listening at that point, because that raised a red flag regarding her scientific judgement. Making the leap from a global fire to CO2 induced global warming as the reason for the K-Pg extinction just seemed bizarre to me, especially since no mechanism for warming killing the dinosaurs was put forth in the chain of argument. Before she made that leap, the first thing I thought of was that a fire that wiped out all surface vegetation immediately and completely cut off the bottom of the food chain, and death by starvation of all life depending on that food chain would be inevitable. I still think that’s more plausible than global warming.

    Full disclosure: I almost stopped listening, but didn’t; not because of the talk, initially, but because Dr. Mainzer is drop-dead gorgeous. Eventually I got back into the talk, and am glad I did.

    • It’s appalling how the Carbonisti have polluted science.

      The global fires were caused by superheated ejecta returning to earth. No need to invoke CO2 to explain extinctions. The K-P wipeout included global cooling, not warming.

      The O-S mass extinction event also was caused by an ice age. No MEE, at least during the Phanerozoic Eon, has been caused by global warming.

      Primary causes of the five biggies:

      Ordovician-Silurian (~439 Ma): Brief but intense ice age.
      Late Devonian (~364 Ma): Volcanism-induced global cooling.
      Permian-Triassic (~252 Ma): Volcanism-induced global cooling, leading to a brief but intense ice age.
      Triassic-Jurassic (~201 Ma): Volcanism-induced global cooling.
      Cretaceous-Paleogene (~66 Ma): Impact- and volcanism-induced global cooling.

      Nor do Precambrian MEEs, such as the Great Oxidation Catastrophe and Ediacaran-Cambrian extinctions, appear to have been caused by global warming. Rather, they’re associated with Snowball Earth intervals, ie the most extreme cooling possible.

  30. I’m with you on this Michael. If there was a global fire the heat blast from the impact must have been colossal and probably would have killed off a good part of the animals that went extinct right off even before we got to tidal waves, vegetation fried, dust screening sunlight for days/weeks/months etc. The CO2 would pale into insignificance after these even assuming it was as high as was being supposed. And let’s not forget the follow on eruptions chucking out SiO2 and acid rain like battery acid.

  31. I’d be interested in re-checking any other mass extinctions popularly ascribed to temperature increase, given the stable upper bound in geologic time and the increased prevalence of life in those warmest times versus now.

    I mean, if life could barely survive at that upper bound and abounded during Ice Ages, that would be different.

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