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Thread: Mass extinction without masses of fossils - why?

  1. #1 Mass extinction without masses of fossils - why? 
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    The current popular view of the demise of the dinosaurs is the big rock from outer space at the end of the Cretaceous. Resulting heat shock and subsequent nuclear winter shuts down photosynthesis and lots of things die, leaving behind only those creatures that burrowed or lived in isolated patches of fresh water. This may explain a lot of things, such as why we have mammals and crocodiles, although not why we also have the coelacanth or tortoises, but I can’t help thinking there is something grossly wrong with an explanation appears to owe much of it’s popularity to film and TV companies ability to represent it with special effects. In particular what happens to all the dead dinosaurs?

    Fossilisation is a difficult are fairly rare process that is largely dependent upon the deceased organism being quickly covered with some form of sedimentation, so that most fossils come from ancient river beds or desserts.

    So now take the modern savannah in Africa and an unfortunate wildebeest. Our wildebeest spends its life wandering, looking for grass, hoping that some large feline doesn’t jump on it the moment its back is turned, until it just lies down one day and gives up. If this in the middle of the savannah lions, hyenas, jackals and vultures will descend on the corpse fairly quickly and disperse the remains allowing weathering to breakdown just about everything, maybe except the teeth. By pure chance the wildebeest must give up the ghost near or in water some of the time, providing a nice meal for the crocs. I’m assuming that the same niches existed in the time of the dinosaurs and the same natural waste disposal system was handled by others organisms. So what happens when lots of the animals die? A lot of dead herbivores may be disposed of by lots of living predators/scavengers, but the impact theory suggests that all animal populations should suffer high levels of mortality, even those from species that eventually recovered, so that the world at the time of K-T boundary should have been knee-deep in animal corpses (I overstate the case, but I’m sure you see my point). Even allowing that most dino bodies would ultimately rot and breakdown the number of animals that died in conditions suitable for fossilisation should increase, and these would remain undisturbed because of the number of living, although very well fed, scavengers isn’t sufficient to consume the corpses. Consequently, there should a increase in the number fossils at the time of the K-T event. As far as I know there isn’t.

    Now I’m not suggesting that the mass extinction didn’t happen – obviously there were dinosaurs and there aren’t anymore – nor that the Impact Theory argues for a single cataclysmic day or even week. But the Impact Theory does suggest a crisis period of six months or so in which huge numbers of animals died and this resulted in the extinction of many species, genus, families, and even orders, so where are the fossils?

    Can anybody tell me why I’m wrong?


    Wibble
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  3. #2  
    Forum Professor river_rat's Avatar
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    Simple - things in general do not turn into fossils as you need very specific conditions for bones to fossilise.


    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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    Yes, as I've said. But if there are more bodies there should be more fossils.
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    It depends on a few ideas then - for example the events of the K-T boundary preserved ideal fossilisation conditions (which i doubt) and secondly a tiny probability increased 100 fold is still a relatively tiny probability. Also, to my knowledge the mass extinction events where not 6 week affairs, or 6 month affairs but took a relatively short amount of time in geological terms to play out.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  6. #5  
    Forum Isotope Zelos's Avatar
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    it is as river_rat have said, the porobability is small and thereofr only a small amount did fossilise. lets say tehre were 500 billion dinourse then, and there is a chance of 1/500 million they fosilise, we should have about 1000 fossiles
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  7. #6  
    Forum Professor river_rat's Avatar
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    To first order, every species on earth is extinct and also to first order non of them became fossils
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  8. #7  
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    First of all thanks for the responses.

    I've got no idea what river rat's last post means.

    If the probablility is increased the number of fossils must also increase. To say that increasing the likelihood of event over a large number of trials will not effect the incidence of the event occurring is nonsensical.

    As I've said fossilisation is dependent upon the remains being covered by sediments. This process is disrupted by the actions of others animals, as I've said. If those animals are dead the disruption can not occur and the sedimentation is free to take even longer to preserve the remains.

    And the impact theories do postulate that there is a sudden killing off over or short period attributed, as I've said, to an initial heat-shock followed by a type of nuclear winter that would last up to a year.
    Wibble
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  9. #8  
    Forum Professor river_rat's Avatar
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    Wibble - It meant that it is a good approximation that every species that has every existed on earth is extinct and that it is also a very good approximation that non of the members of those now extinct species became fossils - ie. its very rare for something to become a fossil.

    The point is that instead of finding say 100 fossils per million years across all land species in the fossil record, at the KT boundary you may have the possibility that 10000 fossils formed, and ignoring normal geological effects that destory fossils its still a minority and it is spread across the entire land surface area of the planet you would hardly notice the difference.

    Other animals effecting the sediment is not the main cause of remains not becoming fossils - you need very specific geological events to occur, over a long time period for a fossil to form.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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    The point is that instead of finding say 100 fossils per million years across all land species in the fossil record, at the KT boundary you may have the possibility that 10000 fossils formed...
    Taking your figures (which I'm aware are only examples) is still a one hundrend fold incease. That would be noticable. i would think that wiping out whole genuses in a relatively short period would give much higher numbers than that.

    Other animals effecting the sediment is not the main cause of remains not becoming fossils - you need very specific geological events to occur, over a long time period for a fossil to form.
    Other animals do not affect the sediment, that is not what I have said.

    All fossils come from sedimentary rocks. They can not be created in igneous rock, and the intense temperatures and pressures resposnible for conversion of metamorphic rock would destroy the fossil. There are no other types of rock. These are indisputable facts. At the time fossils were layed down the sites in which they are found were river beds, or sea floors, or desserts, or near active volcanoes that produced ash. These are environments that meant the remains were covered by sediments before animals could break the body apart and disperse the remains.

    Obviously once the carcass has been covered there is a series a chance events that affect the likelihood of the fossil surviving and being found, but these factors will remain constant, while the likelihood of the first event, the carcass being covered by sediments, must increase if the number of carcasses increase. Therefore, the final number must increase.
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  11. #10  
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    And they do increase Wibble - but it does not mean the increase is noticeable or extreme. Buying one thousand lottery tickets increases your chance of winning quite dramaticly relative to your original chance but a number that is almost zero times another number (within reason) is another number that is almost zero. Add to that the huge geographical areas we are talking about and it is not surprising that you dont see millions of fossils at every fossil bed at the K-T boundary.

    By how much would you hazard to guess all your seperate events increased the chance of a fossilisation event?
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  12. #11  
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    It "all my seperate events".

    A single factor is changing. The base rate of the the number of caracasses. All other factors remain constant.

    Xk = f
    Where k is the constant geological processes, f is the number of fossils and X is the number of dinosaur caracsses.

    The number of fossils is dependent on an proportional to the number of dinosaur carcasses.

    I really don't know the size of the increase, it would depend on the lifespan on dinosaurs, their rate of reproduction, and their population size. But bear in mind it is the entire order of dinosaura and many other species that were killed off, not a single species, so, if impact theories have any validity, there must have been a huge increase. But there isn't. QED impact theories are wrong.
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    I'm not sure you should expect a dramatic increase in fossils. The organisms on earth at any given time are only a small, small fraction of the number that die over larger periods of time. The mass deaths of any 1 set of organisms doesn't seem like a significant number where you'd expect to find any more fossils than you normally do. In fact, with the severe dropoff in offspring that all these dead organisms will no longer be having for thousands of years to come, I wouldnt be surprised if you found less fossils in that time frame.
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    hmm,..i studied about fossilisation and correlation in my science course this year,..and i think actully u r right about that.
    but i studied that,..a huge Sudden Disappearence happend for Dinasours in Paleozoic Era(some of them were lastin to Mesozoic Era ex; Turassic Bird) there was no any clearification about the kind of this disaster,..but i assume that it's kind of Volcanic Eruptions which melt the living bones materials..
    ure basic of fossilisation is totally right, any fossils need 2 conditions 'Bilogical& Geolgoical" if Dinasours satisfy the biological condition (hard skeleton) ..they may didn't satisfiy the geological condition!!
    u see what i mean? some austerallians scienctists reffered this huge disappearence of dinasours to type of Natural process happend in the past which is not repeated in out daily times..i dunnt know what type of disaster they mention, but in all of these cases i do believe that there was a big disaster occured according to the paleozoic Era Events.
    iam weak about this type of study,..but i will look for further information..
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    My first reaction was that a mass extinction due to a meteorite or volcanic eruption should contribute to the conditions for fossilization by burying the bodies in ash.

    But I think there is some major fallacies in arguments of Wibble. First is about what these mass extinctions consist of. Basically by collecting fossils and dating them by the strata in which they are found we get a rough history of what species were present at what times. The last dated fossil of a particular species indicates an extinction of that species. A mass extinction is where this kind of extinction of a large number of different species are all dated at the same time.

    The enormous fallacy of Wibble's is that the immediate death by the entire population of a species would produce a fossil record that is any different than if they died as they ususally do of the usual causes. These animals lived to ages which were decades long not millenia. And the fosil record does not pinpoint the time of death to the accuracy of decades anyway. Whether the population dies all at once or they die within decades of each other makes absolutely no difference in the fossil record at all, except for the fact that if they die all at once then after that time there are no more fossils of that species. There is not in fact a sudden increase in bodies with which to produce fossils as Wibble supposes, there is only a sudden decrease in bodies with which to produce fossils afterwards. The lifetime of these animals is not a significant interval compared to the frequency of fossilization let alone compared to the resolution of our ability to date the fossils.

    Another thing which Wibble has failed to understand is that fossilization is such a rare event that there is a very small probability that even one member of the entire population of a species at a given time will become a fossil. It only over many generations that we are like to get a fossil representative. Consequently there is no reason to expect that even one of the population that died during the mass extinction would have ended up as a fossil.
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  16. #15  
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    I think I've covered these points already.

    The possibility/probability of fossilisation over time in suitable locations remain the same.

    The variable is whether organisms die in that location and remain in place long enough for their remains to be covered. More bodies with less disturbance must create more fossils.

    Of course the organism will cease to appear after it is extinct, but suggest that fossilisation is so rare as to be non-representive is wrong. Fossilisation across the all environments is rare because many environments do not allow for fossilisation at all, but in locations that go on to produce sedimentary rocks fossilisation is not rare at all. Flint are fossilised sea creatures similar to sponges. Flint are not rare because the environment the animal lived in was conducive to fossilisation. A random distribution of land animals corpses will mean that some die in water or in desserts etc. In normal circumstances most of these corpses would be scavenged and the remians destroyed before they can be covered. BUT if most of the scavengers have also been killed off this will not happen. By reducing the number of all species the number number of scavengers will be reduced and the actions of scavengers will be reduced so the number of carcasses that can be fossilised will be increased.

    The argument that the rate of fossilisation is rare in all environemnts and is unaffected by living organisms is a fallacy.

    Incidently, using the word falacy multiple times does not lend any strength to your argument, rather it it makes it sound like as if you are relying on the intimidatory power of one word instead of solid reasoning. Whether this last point is true or not I don't know, but it sounds like it is.
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  17. #16  
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    Wibble, I think you're just not getting it.

    Fossilization is EXTREMELY rare. The situations you are contemplating will not make a statistically identifiable difference in the composition or number of fossils found. Even under environmental conditions that can yield fossils, fossilization is STILL a rare event. It's not just a matter of undisturbed corpses because there might be fewer scavengers. The particular actions of bacteria and how sediment accumulates will also greatly influence the chances of fossilization. You're by no means guaranteed a fossil just by dropping a bunch of dead animals in an abiotic sediment-forming area even if none of them are disturbed by other animals.

    Even if all the dinos did drop dead in a period of 6 month, the number of dinos that would have died in the previous 1000 years (a period indistinguishable in geological terms) would be maybe 50-300 times more (depending on the average lifespan of the dinos). Over 10,000 years (a timeframe maybe, possibly distinguished in the VERY BEST of strata 65 million years old, the number is 500-3000 times the number of dead dinos. Under your conditions, you really think that there is a 500-3000 fold increase in the chances of fossilization? I think there is not a real possibility of that much of an increase. You'd need an even greater increase in fossilization rates to detect any statistical increase. Do you disagree with these numbers?
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  18. #17 Fossils, or rather, lack thereof 
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    From what I can gather, the odds of anything becoming fossilized are extremely long. Conditions must favor the process.
    I spent some time on the Island of Java. All along the south coast they have one volcano after the other. The prevailing wind is from SW to NE. The northern slopes of Java are all sandstone, compacted volcanic ash. A Paleontologists Dream. In fact, that was where the Missing Link, Pithecanthropus Erectus, "Java Man" was discovered. I met diggers from Holland who had uncovered intact fossils of Pygmy Rhinos and Elephants there.
    There are precious few areas of the World that offer those conditions.
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