Climate change by global soot dimming may have killed off the dinosaurs and ammonites

From TOHOKU UNIVERSITY

A new hypothesis on the extinction of dinosaurs and ammonites at the end of the Cretaceous Period has been proposed by a research team from Tohoku University and the Japan Meteorological Agency’s Meteorological Research Institute.

Global climate change caused by soot aerosol at the K-Pg boundary. CREDIT Kunio Kaiho

Global climate change caused by soot aerosol at the K-Pg boundary. CREDIT Kunio Kaiho

The researchers believe that massive amounts of stratospheric soot ejected from rocks following the famous Chicxulub asteroid impact, caused global cooling, drought and limited cessation of photosynthesis in oceans. This, they say, could have been the process that led to the mass extinction of dinosaurs and ammonites.

The asteroid, also known as the Chicxulub impactor, hit Earth some 66 million years ago, causing a crater more than 180 km wide. It’s long been believed that that event triggered the mass extinction that led to the macroevolution of mammals and the appearance of humans.

Tohoku University Professor Kunio Kaiho and his team analyzed sedimentary organic molecules from two places – Haiti, which is near the impact site, and Spain, which is far. They found that the impact layer of both areas have the same composition of combusted organic molecules showing high energy. This, they believe, is the soot from the asteroid crash.

Soot is a strong, light-absorbing aerosol, and Kaiho’s team came by their hypothesis by calculating the amount of soot in the stratosphere estimating global climate changes caused by the stratospheric soot aerosols using a global climate model developed at the Meteorological Research Institute. The results are significant because they can explain the pattern of extinction and survival.

While it is widely accepted that the Chicxulub impact caused the mass extinction of dinosaurs and other life forms, researchers have been stumped by the process of how. In other words, they’d figured out the killer, but not the murder weapon.

Earlier theories had suggested that dust from the impact may have blocked the sun, or that sulphates may have contaminated the atmosphere. But researchers say it is unlikely that either phenomenon could have lasted long enough to have driven the extinction.

The new hypothesis raised by Kaiho’s team says that soot from hydrocarbons had caused a prolonged period of darkness which led to a drop in atmospheric temperature. The team found direct evidence of hydrocarbon soot in the impact layers and created models showing how this soot would have affected the climate.

According to their study, when the asteroid hit the oil-rich region of Chicxulub, a massive amount of soot was ejected which then spread globally. The soot aerosols caused colder climates at mid-high latitudes, and drought with milder cooling at low latitudes on land. This in turn led to the cessation of photosynthesis in oceans in the first two years, followed by surface-water cooling in oceans in subsequent years.

This rapid climate change is believed to be behind the loss of land and marine creatures over several years, suggesting that rapid global climate change can and did play a major role in driving extinction.

Kaiho’s team is studying other mass extinctions in the hopes of further understanding the processes behind them.

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80 thoughts on “Climate change by global soot dimming may have killed off the dinosaurs and ammonites

  1. More interesting than this, is the possibility that the Deccan Trapps in India were formed as a result of the Chicxulub impact. Such a large impact would create shock waves that travel through the Earth, which could possibly converge on the opposite side where the Deccan Trapps are located. Could a focused shock wave like this cause a plume of magma to rise in the mantle?
    R

    • ralfellis Worth exploring. For spherically “focused” I would expecte it to have the opposite latitude. However, both are about 21N.
      Deccan Traps: 17°–24°N, 73°–74°E
      Chicxulub crater: 21°24′0″N 89°31′0″W

      • David, the Indian Subcontinent has moved quite a lot since the End Cretaceous. Reunion Island is near the remnant hot spot that created the Deccan Traps.

    • Quite interesting indeed. Two rare events happened at the KT boundary, the Chicxulub Impact and the Deccan Traps.
      Not only did a large igneous province appear nearly antipodal to the impact, but the entire Indian microcontinent moved north at unusual rates for the next 20 million years until it began to collide with Asia.
      This also agrees better with the hypothesis that hotspots are caused by tectonics in the upper mantle and crust, not by deep mantle convection plumes.
      http://www.mantleplumes.org/WebDocuments/Antip_hot.pdf
      http://geology.about.com/od/platetectonics/a/nohotspots.htm
      http://www.nature.com/article-assets/npg/srep/2015/150212/srep08407/images_hires/m685/srep08407-f1.jpg

      • There’s no direct connection between the Deccan Traps eruptions and the Chicxulub impact apart from the fact that, from this distance in time, they seem contemporaneous.
        In addition both have been invoked to explain the K-T extinctions.
        The Chicxulub impact was a specific event with both immediate and long term consequences.
        The eruption of the Deccan Traps basalts was a long term event with little immediate effect but probably significant long term consequences.
        A number of researchers believe that the main phase of the Deccan eruptions started about 250,000 years before the Chicxulub impact and continued for 750,000 years.
        http://science.sciencemag.org/content/347/6218/182
        https://www.princeton.edu/main/news/archive/S41/89/26O49/index.xml?section=topstories
        Others accept that the commencement of the Deccan eruptions predated the impact but propose that the meteorite impact triggered the largest eruptions.
        http://gsabulletin.gsapubs.org/content/early/2015/04/30/B31167.1.abstract
        Whatever was the case there certainly would have been some soot floating around at the time.
        And different researchers have suggested that they have found undeniable evidence of global warming, or global cooling [depending on your research bias] immediately after the Chicxulub impact.
        It’s reasonably clear the combination of events would have made conditions very uncomfortable for most animals and plants. No large land animals made it through. Why some large marine animals got through and others didn’t is not certain. Pure carnivores didn’t get though. Omnivores/scavengers had a better survival rate. Ammonites, for instance, may have been too specialised. Uniquely fitted to their ecological niches but in great trouble when their ecological niche disappeared.
        All grist for the research mill

      • This graph looks like an abstract painting: seven female heads in hijabs of various colors are looked upon by a couple of lecherous ghosts and two or three black-and-white young male heads.

    • Didn’t have to be focussed at the antipode, and Deccan Traps weren’t at that time. But the mantle plume was already there as evidenced by phase 1 of the Deccan eruption. Chicxulub likely initiated, or less likely strongly enhanced, phase 2. The chemistry of phase 2 flood basalts is different than phase 1, just part of the geological evidence. Discussed here on a previous thread. There is a 2015 paper from UC Berkeley that lays out all the evidence for the Chicxulub/Deccan hypothesis. Richards et. al. in GSAbulletin. Google chicxulub deccan 2015. First hit. Not paywalled. Well worth a read. Very interesting.

    • The antipodal of the Chicxulub impact at 66 million years ago was somewhere north of where Australia was at the time in the far east Indian Ocean – likely 2000 kms away from where the Deccan Traps area was at the time.
      Can we just keep repeating this post every time the antipodal Deccan Traps idea comes up because it is just wrong and needs to be squelched once and for all.
      http://www.scotese.com/images/066.jpg

      • The “Shiva Crater” is extremely dubious. I happen to know the man who “found” it, he has what you might call a vivid imagination.

  2. Certainly enough energy was imparted into an oil rich region but would that have burned the hydrocarbons? Explosives are used to put out oil well fires. Perhaps the massive energy of impact was also anaerobic?

    • How could they be oil rich regions – I thought that all our oil was formed from dinosaur remains.

      • Rhoda, Nope. Most oil is formed from marine algal remains (kerogen) that has subsequently gone through the thermal/pressure window known as catagenesis. Medium produces oil. Hot produces natural gas. Some oil is formed from extrudates of terrestrial plants. Norway’s offshore Haltenbanken reservoirs are an example. Dinos not at all. Perhpaps you forgot a /sarc.

      • Beyond what ristvan states. The Chixclub impact marks the end of the dinosaur reign. They had been around for some 100 million years prior to that point.

  3. It looks like all the land masses were closer together 66Mya, can they simulate the atmospheric circulation of the planet then?
    @ralfellis, in light of the above was India actually opposed to Chicxulub at the time?
    http://www.scotese.com/K/t.htm

  4. That actually makes sense. Aerosols in the lower atmosphere are subject to natural attenuation from wind, gravity and meteorological events but, from what I’ve read in the past, once those particles are in the stratosphere and beyond they do not attenuate nearly as fast. A 180 km diameter “crater” is an enormous impact area — that would be enough energy to send a lot of soot high into the stratosphere. Maybe there are methods whereby they can confirm this hypothesis. It would seem to me that such a soot blanket in the stratosphere might have significantly blocked UV or other light frequencies for enough time to have left a fingerprint.

  5. There was a lot of talk a few years ago about a glancing meteorite strike knocking rocks off of Mars and into space, where they eventually fell to earth.
    Now if the Chicxulub impact was strong enough could it have sent a significant amount of particulates into low earth orbit where it would take decades for them to attenuate as they were captured and fell back to earth?

  6. AN impact would not be enough to put burning oil soot into the stratosphere for such a long period. The ejecta would not be enough to sustain burning soot that high unless somehow there were huge eruptions thereafter for a sustained period.
    There is enough to suggest that the Dinosaurs faced a number of challenges and it was a culmination of stresses on the ecosystems. You need amazing evidence to claim a single event caused a global wipeout.

  7. It has been known for a long time that there are significant amounts of fusain (=soot) in the impact layer. This is presumably from forest fires caused both by the ultra-hot shock wave near the impact and from heat released by debris ejected by the impact and then re-entering the Earth’s atmosphere at speeds up to 11 kms^-1 for several hours after the primary impact.
    That the impact would have created significant amounts of soot from hydrocarbons in the impact zone seems extremely unlikely. The temperature in the primary impact cavity was high enough to “cook out” CO2 and SO2 from the carbonate and sulfate rocks. Any hydrocarbons would have been turned into CO2 and H2O.

    • There is some marine soot per CPI. So crude oil was probably burning somewhere. Could have been Athabasca, for all we know. The paper fails logically for a reason related to your last paragraph, explained summarily below. The longer version is a set of comments to Vukavic’s link to this paper on a recent thread.

    • To cook hydrocarbons into CO2 and H2O, you need lots of O2. Was there enough in the immediate are of the impact?

  8. Only one explanation for large animal wipeout, an increase in gravity, the brontosaurus in the room

    • Been reading James Hogan, Max? He didn’t invent the theory, but he did use it in a couple of his books. The idea that Earth’s gravity shifted.

    • Yes, surface gravity on the Earth increased near Pangea causing the extinctions. This is explained by the Gravity Theory of Mass Extinction, a book. A summary of the theory is:

    • If you can come up with a method by which gravity can fluctuate, there is a Nobel with your name on it.

      • I guess you didn’t view the video. If you did and you know a little physics you would know that if the Earth’s core elements moved off-center, by definition, there would be a gravitational gradient around the globe. What caused the offsetting? Study the Conservation of Angular Momentum and ponder why the spinning ice skater’s angular velocity changes as it’s arms move closer and further from it’s body. Then apply the that concept to the Earth when continental mass moves closer and further from the axis of rotation when it moves to higher and lower latitudes. Only the Earth’s angular velocity didn’t change, the core elements moved off-center in lieu of a change in angular velocity.

  9. A better explanation is atmospheric pressure drop- high atmospheric pressure makes the flying dinosaurs and other make physical sense. Its clear that many dinosaurs survived thousands of years past the cataclysm.

    • Just what is it that caused this pressure drop? Computer simulations have shown pterosaurs could fly with present day atmospheric pressures.

  10. Read this paper and commented on it to Vuk on another thread. The paper is logically flawed. Summary. Used CPI to determine that some of the K-Pg boundary layer soot was of marine rather than terrestrial origin. OK. (That biomarker has been used for thismsince 1961.) Said the marine soot would have been from crude oil (which is usually but not always of marine origin; Norway’s Haltenbanken fields are an exception example). Ok. Said terrestrial soot from forest fires caused by the Chicxulub impact would have only been in the troposphere, wash out in weeks, and not be an extinction ‘nuclear winter cause. Ok. (Volcanic troposphere dwell time is < 4 weeks.) Said the oil soot would have been injected into the stratosphere, lasted for years, and caused 'nuclear winter' extinction. NOT Ok.
    The ejecta from the Chicxulub impactor certainly reached the stratosphere; the iridium rich K-Pg layer is found globally. But this study inferred 'global' from just two sample sites, Haiti (proximal) and Spain (distal). Nothing remotely global. So here's the flawed logic. Chicxulub was discovered during oil exploration. But we know from that exploration that there are neither crude reservoirs nor source rocks in the craters proximity, which is where the ejecta would have formed. The nearest are several hundred miles away (the paper cites Mexico's Cantarell field, whose reservoir rock is in fact formed from Chicxukub ejecta).
    So their hypothesis is impossible. The Kuwaiti oil fires from Gulf War 1 reached plume heights of 3000-6100 meters, no where near the stratosphere. The lesser amount of Spain marine soot than in Haiti (paper figure 1) washed out there from the troposphere. And the paper said troposphere soot was not a big part of the extinction. Logic fail.
    The likely global cause of extinction beyond the immediate impact influenced zone was the initiation or exacerbation of stage 2 of the Deccan Traps flood basalt eruption, covered in a previous thread.

    • Soot has long been know from the KT boundary. It has been presumed to be from burning the vegetation on land. While much of the crude oil produced in the Gulf region is from Cretaceous rocks, at the time of the impact they wouldn’t have been buried deeply enough to to ‘cook’ the hydrocarbons present. What we are pumping today seems to have characteristics of Cretaceous vegetation, but it was still largely confined to the Cretaceous rocks and hadn’t yet been pyrorolyzed and mobilized to traps to concentrate it. This link might be of interest: http://news.stanford.edu/pr/94/940804Arc4170.html
      I’m personally dubious of the claims in the paper.

    • I’m not sure that “rainout” would work in the aftermath of a big impact. Re-entry of ejecta would heat the stratosphere, so you would have a very abnormal situation with a large downward heat-flow in the atmosphere. The tropopause (=temperature minimum) would be strongly depressed, perhaps all the way to the surface and convection and precipitation would be more or less completely suppressed until most of the heat had radiated away, probably only after several days.
      Though if there was very large fires on the surface these may have produced enough heat to keep convection going at least locally, as would the heat in the crater area itself.

  11. i still don’t buy the asteroid impact killed the dinosaurs theory. Mammals survived, and there were plenty of large reptiles. Why weren’t crocodiles, snakes, turtles and tortoises also killed off?
    I think a global epidemic better explains it, and also why some dinosaurs survived as birds, since bird populations on remote islands would be safe from infection.

    • India was an island at the time and so was Madagascar. Both with dinosaurs that did not survive.
      And it was absolutely not only dinosaurs (except birds) that became extinct. Many other reptile groups did (e. g. mosasaurs, plesiosaus, pterosaurs) and as a matter of fact so did most (but not quite all) mammals and birds. And a huge proportion of all life in the ocean as well, from single-cell foraminifera to rudist mussels, ammonites and fish.

    • Snakes and lizards were hammered…
      http://www.pnas.org/content/109/52/21396.abstract
      No large mammals survived. There weren’t very many to start with.
      Competition from dinosaurs kept them small. The survivors were mostly rat sized or smaller.
      Their descendants increased in size rapidly after the removal of their competitors.
      Animals like crocodiles can survive food shortages as they can survive for a year on one good meal.
      They may not like it but they can do it. And no large crocodiles survived.

      • The dietary needs of crocodiles drops when the temperature drops as well. I’ve read that zoos and such do not feed the crocs when the temperature drops below (I believe) 70F. At those temperatures, digestion is so slow that food rots before it can be digested, making the croc very sick.

  12. Never convinced by these mechanisms which are suggested as a cause of the extinctions. I recall a programme on the theory televised in the UK years ago now, in which the only Chicxulub-denier given a slot, a very short slot, was Stephen Jay Gould. He simply held up to the camera a large Frog, and said, more or less, “Explain this!” Any climate disruption which would have led to the extinction of Dinosaurs and others would, surely, have caused the extinction of amphibians, reptiles and nautiloids among others. Has anyone ever addressed this problem?
    It’s about as silly as Warmistas prattling on about the threats to the biosphere of an average increase in temperature, even were it to happen of a couple of degrees Celsius. No organism I’ve ever read about lives in an average temperature, or any other average physical factor come to that. As a case in point of how insignificant climate is to species distribution I give the following anecdote.
    Just about a year ago I holidayed in a Germany undergoing a heatwave. We flew from an English Midlands with a temperature of around 19C, and landed in Frankfurt with a temperature in the high 30s. Over the course of the next 10 days, with temperatures at times hitting 40C, the only bird Species I saw which I have not seen in the wild in the UK was a Pelican, and that must have escaped from a Zoo.
    Changes in animal and plant distributions are almost invariably due to competition with other living organisms. I feel sure these extinctions will have had the same cause.

  13. When ALL the ejecta returned to Earth in the 72 hours after the impact, the meteorites (ejecta) falling back to the surface heated up the atmosphere so much that anything that could burn, did burn. Everywhere on the planet, the atmospheric temperature rose to 400C or so and everything burned. Everything. Trees, vegetation, animals, dinosaur eggs, mammals, birds, lakes, everything that did not have a good burrow to be in or someway to escape died from fire and heat. “Everything” burned.
    If it happened today, you might be okay if you could hold out in the fourth level of a parking garage or in a salt mine but otherwise, you are going to burn to death wherever you are. Your house is going to burn to the ground as well as everything that can burn.
    After the funeral pyre of everything around you, then it gets dark and it gets cold for a decade. You would have to have the most extreme luck to the tune of one in a billion to survive a 10 km asteroid impact.
    There have only been two of them that we know about. The other beyond Chicxulub was Vredefort, 2 billion years ago.
    This also says that the Earth has never been hit by a large comet either. Comets have much more speed than an asteroid and any comet at 10 kms width would have melted the entire crust and killed off all life.
    The Earth is one lucky planet. Same story as the “Surface Composition …” article of a day ago.

    • You, and most others considering the effects of the asteroid impact, commonly ignore its effects on the oceans which are probably as significant. The firestorm would have been global and heated up the surface layer of the ocean making it buoyant and preventing much gas transport across it. Couple that with weeks of darkness and phytoplankton would be toast (pun intended). As would be much of the ecosystem that depended upon it (especially giant marine reptiles and ammonites). With the demise of the oceans phytoplankton every single biogeochemical cycle would have been disrupted. I don’t think we need the Deccan Traps.
      Dying phytoplankton would release hydrocarbons. You don’t need geological conditions. Even living trees emit small amounts – hence L.A.’s inability to eliminate photosmogs.

  14. Yes, surface gravity on the Earth increased near Pangea causing the extinctions. This is explained by the Gravity Theory of Mass Extinction, a book. A summary of the theory is:

  15. I once attended a talk by Amy Mainzer, definitely the hottest astrophysicist on the face of the earth…but I digress. She was talking about near earth objects as an existential threat. In her discussion of the Chicxulub impact, she did a little aside. She said that there is evidence of a great deal of carbon after the time of the impact. Her conclusion was that worldwide fires burned all of the surface vegetation to the ground, releasing huge amounts of CO2 into the atmosphere, causing global warming. And THAT was what killed the dinosaurs.
    Now, as hot as she was (and I still am in love), I thought at the time that if all of the surface vegetation burned to the ground, the immediate effect would be death by starvation of all herbivores, followed by death by starvation of all carnivores. Whatever effects temperature might have would have been on a longer time scale. Starvation only takes a month. Global warming takes a long time.
    In any event, this science is not settled.

  16. I’d like to know what didn’t kill of the dinosaurs. The list of things that did seems endless.

  17. ‘May have’ or ‘could have’ is just assumptions not ‘hypothesis’. Hypothesis is powerful scientific conclusion based on known science but could not be proven experimentally e.g. Avogadro’s Hypothesis. So above claim is ‘Rubbish”.

    • The lack of any dinosaur fossils at the KT boundary is significant in my eyes – the fact that paleontologists struggle to find any even close to the boundary tells me dino numbers were waning fast prior to the impact.

    • My 1st comment seems lost in the ether – The lack of fossils at the KT is telling, at least to me. Paleontologists keeping discovering fossils/footprints closer to the boundary, but the numbers obviously begin a big drop prior to the impact event, else there would be an abundance of fossils found within a few centimeters of it
      David Weber

      • Google “Signor-Lipps effect”.
        Or think of it like this: Dinosaurs existed for more than 150,000,000 years. After 200 years of searching we have, possibly, found remains of 100,000 of them (that is a very optimistic figure by the way, even including footprints). That is, on average, one per 1,500 years. So what is the probability of one turning up exactly at the K/Pg boundary? There are several intervals of millions of years with no dinosaur fossils by the way, particularly in the Early Jurassic. Does that mean that they became extinct and rose from the dead?

    • Actually I would think it extremely lucky to actually find a dinosaur fossil that close to the boundary, considering the utterly minuscule proportion of all dinosaurs that once lived that have been found.

    • Yet there are other scientists who claim that there are dinosaur fossils that can be found after the Chicxulub event.

  18. “While it is widely accepted that the Chicxulub impact caused the mass extinction of dinosaurs and other life forms, researchers have been stumped by the process of how. In other words, they’d figured out the killer, but not the murder weapon.”
    If they were detectives, they would fired instantly. The murder weapon was a 10 km wide asteroid with an impact energy equal to 3 billion Hiroshima atomic bombs. These detectives inspected the totally destroyed Hiroshima and concluded it must be the soot that killed these people.

    • Maybe they can’t find how because most dinosaurs were gone by the time of the impact – as you approach the KT boundary (geologically speaking), there is a sever dwindling of fossils, as one would expect from thinning numbers

      • Surely the long dead dinosaurs before the impact could not have been killed by the asteroid. But that’s not what they are trying to establish in their study. They said the dinosaurs died after the impact because of the soot. The shockwave of 3 billion atomic bombs didn’t kill them, the firestorms inferno did not, it was soot and climate change. Are these dinosaurs from IPCC?

      • There is a second, but related problem. We are usually presented with this picture of the exctinction of the dinosaurs —- Up until the day when the rock from up there slammed into Chicxullub, there were millions, if not billions, of dinosaurs having a whale of a time, doing whatever dinosaurs did. Then the rock from up there wiped them out in the blink of an eye.. If this picture were true, then the KT boundary layer should have more dinosaur fossils per cubic meter than any other geological stratum. Just think about it. Millions, if not billions, of dinosaurs killed in a few hours. Then their bodies would have been covered by the iridium dust falling out the sky. The iridium rich KT boundary layer should be jam packed with dinosaur remains. And what is the reality ? There are very few fossils of any description to be found in the KT boundary layer. Nobody has found any dinosaur fossuls in the KT boundary layer. The great Cretaceous mass extinction took place before the rock from outer space fell on Chicxulub. This has been known for ages.

      • It takes extremely rare circumstances for a body to get itself fossilized.
        The biggest criteria is that it must be buried before it can be weathered away.

  19. First image released from world’s super radio telescope
    “When fully up and running in the 2020s, the SKA will comprise a forest of 3,000 dishes spread over an area of a square kilometre (0.4 square miles) across remote terrain around several countries to allow astronomers to peer deeper into space in unparalleled detail.
    It will have a discovery potential 10,000 times greater than the most advanced modern instruments and will explore exploding stars, black holes, dark energy and traces of the universe’s origins some 14 billion years ago.”
    http://phys.org/news/2016-07-image-world-super-radio-telescope.html

  20. One possible problem with this particular hypothesis is that they state:

    when the asteroid hit the oil-rich region of Chicxulub

    I understood that the big oil fields of Mexico were composed of debris that filled the Chicxulub crater. I.e. they post-dated the impact and that the region’s “oil-rich” character is a consequence of the event. The unusual origin of the carbonate breccias is what gave them the high porosoity and high permeability that make the Cantarelli oil field so productive.

  21. Here’s another thing that bothers me, as someone who has spent a lot of time looking at rocks and trying to learn what they can tell you.
    There’s this famous photo of the Alvarez’s standing at a rock face where the K-T boundary is exposed. It’s an unbroken sequence of what look like shallow marine sediments. The transition from Cretaceous to Tertiary has presumably been determined by palaeontology.
    The sceptic in me says: if a 10 km diameter asteroid or comet impacted the earth, the seismic activity would have been colossal, beyond anything we can visualise from our personal or vicarious experiences.. There should have been world-wide tsunamis that would (ought to have?) disrupted the process of calm, orderly sedimentation in shallow seas. Some scouring of subjacent layers with redeposition, some coarser material washed in from nearby land areas, something – anything – that disrupts what appears to be an uninterrupted sedimentary sequence.
    Marine sediments would not necessarily show much evidence of land-based extinction, but a lot of marine species went extinct at the same “time” (especially ammonites). If all the ammonites died in a very short interval (as postulated in this “soot” hypothesis), wouldn’t there be a sedimentary layer with an exceptionally high number of ammonite shells at the K-T boundary? As opposed to what one might expect if the “Deccan Traps caused the extinction” hypothesis were correct, which would have resulted in a progressive decrease in ammonite shells as the boundary is approached from below. Which seems to be the case.
    Not saying that the hypothesis is wrong, just that the postulated event is so apocalyptic that there ought to be more evidence of it in sedimentary rocks laid down at the time. More than just a bit of soot and an enrichment in iridium.
    Geology is a very inexact science, far more than most of its practitioners care to admit. Too often, hypotheses that are intellectually attractive, are based on scattered bits of hard evidence (e.g. chemical and isotopic analyses) dropped into a matrix of generally soft, rather pliable evidence (looking at the rocks), without adequate consideration of possible alternatives.
    I really like that term I just came up with “pliable evidence”. I think I’ll be using it a lot from now on. In reference to Climate “Science”.

    • ” There should have been world-wide tsunamis that would (ought to have?) disrupted the process of calm, orderly sedimentation in shallow seas.”
      There was. There are lots of sites with severely disrupted or chaotic stratification for thousands of miles around Chicxulub, but for studying the impact one searches for deep-sea sediments deposited far away in distant oceans, because that is where you will find continuous deposition and an intact fallout layer.
      And remember if all ammonites were killed by Chicxulub, that means that one standing crop was deposited in perhaps a few weeks. Lets say that the average lifetime of ammonites was (optmistically) 50 years, that means that those ammonites were deposited in one year rather than in fifty. That is an indistinguishable difference in the marine fossil record.

  22. Sometimes the truth is right in front of your nose and you don’t see it.
    Take the dinosaur extinction. Every creature we call dinosaur went extinct except those who learned how to fly. Until recent times, flightless birds, aka dinosaurs, lived on islands. As soon as the mammals showed up, human, rats, and dogs, those dinosaurs went extinct.
    Does this suggest a hypothesis to anyone to explain the dinosaur extinction? The cause of their extinction of course is they have to incubate their eggs and otherwise guard their nests from predators, making them and their ground nests highly vulnerable to predation. Reptiles, which can bury their eggs (hide them) and leave the next unattended, have survived. Just like mammals, the dinosaurs had to take to the trees to survive.
    Next question.

    • The question is why the mammals didn’t wipe out the dinosaurs earlier. Placental mammals appeared after the disappearance of dinosaurs and marsupials are just as old as dinosaurs. And ammonites didn’t get wiped off the map by mammals.
      Its more a question of how a family of organism has the potential to evolve into a better competitor but doesn’t seem to get a foot in the door until the population of its competitors is decimated. It happened to a family of reptiles, the synapsida, that ruled the land but died out shortly after the previous Pt event leaving just a small population that couldn’t compete with the offspring of other reptiles, namely the dinosaurs. They were all eventually wiped out except the ancestors of mammals.
      It could be that marsupials were held back by preditation, then it wasn’t so much the die off but the abundance of carcasses that took the pressure off mammals and allowed the population to explode to numbers that kept the dinosaurs from bouncing back.

    • Dinosaurs had been preying on each others eggs for millions of years before the first placental mammal showed up.

  23. It’s all about surface, not universal, gravitation changes around the Earth. At the Triassic-Jurassic boundary a rapid increase in surface gravity on Pangea was responsible for the extinction of the crurotarsi, which held the dinosaurs in check. The reason for their extinction? Almost all of them had a splayed leg structure unlike the vertical leg structure of the dinosaurs which would have been a major handicap when surface gravity increased.
    The ammonites went extinct because the increase in surface gravity affected all marine creatures that moved up and down in the water column. An increase in surface gravity would increase the water pressure per unit depth. The nautilus’s body was better able to deal with this challenge; that’s why it still exists.
    All of this is explained by the Gravity Theory of Mass Extinction.

  24. Back in the late sixties engineers showed that with the sudden improvements demanded by the clean air acts the original Stevenson screen was no longer adequate for producing accurate results and would produce anything up to a degree higher than actual ones compared to the air quality at the turn of the century.
    Yes this was done with actual hardware not computers but it really did warrant proper examination by scientists who were simply not interested in the nuts and bolts of data acquisition.
    Why is this effect so important if it is so irrelevant when considering climate change I wonder?

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