The Five Mass Extinctions and how they Preclude a Global Flood

​​Let's talk about the major extinctions, shall we? Because they are quite problematic if you are a Young Earth Creationist.
In conventional science, there are typically 5 recognized Mass Extinction events. Extinction events can be defined as "widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the rate of speciation." (Wikipedia, Extinction Event)
These five extinctions events are written, saturnine, in the rocks. We can imagine a rich fossil shelf like the Burges Shale, immediately followed by a barren strip of sparse layering as biodiversity has plummeted. This is of course, what we find. Five times, actually, and each with additional identifiers that tell us part of the story of "what happened" to these organisms and their formerly flourishing ecosystems.
Now, many Creationists have differing opinions on many different things. But one connecting factor (to my knowledge, a universal one in this ideology) is that all of the rock layers and fossils above the Vishnu Schist (the lowest granite layer of the Grand Canyon) were deposited by the global Noachian Deluge which occurred somewhere between 4000 BCE and 2000 BCE in approximately one year's time.(depending on the used YEC chronology).
What can be inferred then, is that the cause of death of nearly every fossil we find is impact from the wall of water or drowning.
But the nature of how layers are deposited and the taphonomy behind the deaths of these organisms present issues, especially in the light of those found in death assemblages during mass extinction events.
Let's tackle the glaring issues first.
The Extinction Events: An Overview
1) Ordovician-Silurian
444 mya, approx. 86% species lost.
Likely cause: a short, severe ice age that lowered sea levels, possibly triggered by the uplift of the Appalachians. The newly exposed silicate rock sucked CO2 out of the atmosphere, chilling the planet.
How do we know this?: Isotope analysis of Oxygen in brachiopods and conodonts show us that this period experienced a serious cooling event! It turns out Isotopes can reveal climate. Similar to runaway greenhouse effects, this "mini" Ice Age entered into a feedback loop as more exposed silicate cooled the planet, freezing more water and exposing more silicate.
YEC Problems: Isotope analysis alone is problematic for YEC site Answers in Genesis, which proposes a single Ice Age post-Flood. But logistically this is a problem for all YEC's. The organisms that died in the Ordovician Extinction littered the seafloor as they perished, supposedly representing the first to die in the Noachian Deluge en masse. But their own shell's isotopes indicate they died due to the ice that was beginning to creep down from the poles.
Walt Brown, YEC producer of the Hydroplate Hypothesis, invokes supercritical fluids to explain the deposition of so many layers of rock. Supercritical fluids occur at HIGH temeratures, not the more chilled waters the millions upon millions of sordid shells indicate.
Added is the obvious looming problem of "ecologic sorting". If habitat is to blame for the layering of the fossil record, why do we find ANY seafloor dwellers fossilized past this point? Why are the cetaceans and mosasaurs and MAJORITY of trilobites so much higher in the record?
2) Devonian-Carboniferous
375 million years ago, 75% of species lost.
Likely cause: Colonization of land by plants allows roots to stir up the earth, releasing nutrients into the ocean. This might have triggered algal blooms which sucked oxygen out of the water, suffocating bottom dwellers like the trilobites.
How do we this?: So vascular plants have risen to the land and doomed their distant eukaryotic brethren in the sea (including the poor trilobites). Sapping the oxygen from the sea, they created mass anoxia which can be seen int eh chemical analysis of laminated black shale and in the lack of free O2 in the sediment.
YEC Problems: Anoxia is usually caused by algal blooms (due to eutrophic conditions) of organic-walled plankton and the like. Anoxic death in marine organisms is resultant from the lack of O2 in the water. There is no means by which to suggest that a flood can correlate or cause Anoxic Conditions, as the rough seas would discourage algal growth and destroy any land plants. The marine organisms should show cause of death linked to blunt force or burial, and the entire ocean would certainly not become anoxic in the conditions described in Genesis 6-7.
3) End of Permian “The Great Dying”
251 million years ago, 96% of species lost.
Likely cause: A perfect storm of natural catastrophes. A cataclysmic eruption near Siberia blasted CO2 into the atmosphere. Methanogenic bacteria responded by belching out methane, a potent greenhouse gas. Global temperatures surged while oceans acidified and stagnated, belching poisonous hydrogen sulfide. “It set life back 300 million years,” Rocks after this period record no coral reefs or coal deposits.
How do we Know This?: Each of the factors are documented in the fossils and the rock and are abjectly not copacetic with a global deluge as the cause. First is the magma/igneous residue from the eruption of the Siberian Traps. We can track this also through the rapid introduction of isotopically light carbon found in the marine system. Second, we see the anoxia again. And finally is the fact that after these two events subside geochemically the biodiversity in the fossil record is absolutely decimated. Again, no ancient coral.
YEC Problems: Here we also see the death of the majority of the Synapsids, Dicynodonts, Pelycosaurs etc. These animals occupied the same niches the dinosaurs would come to takeover, meaning their habitats are the same and the fossils are in the same location but separated by geologic time. Some of these guys outwieghed some of the dinosaurs. So why are they so deep below them in the sediment? Hydrologic sorting cannot explain why a tyrannosaur would be above a gorgonopsid, as the former SHOULD sink below if they are indeed killed at the same time. And as I mentioned, their habitats are nearly identical, so Ecologic sorting cannot either.
Equally as problematic is the notion of the anoxia (again) and the severe volcanism. You see, the noxious output by the Siberian Traps encouraged methanogenic bacteria to flourish. Today, modern methanophiles live in harsh conditions such as under the permafrost or in the soil of arid deserts.
They do NOT thrive in floodwaters, or in a global inundation.
The coral are problematic as well. After this geochemical marker in time, they dissapear and the taxa which are killed off never make a reappearance. However, they are succeeded in the SAME habitats by different coral (soft corals) which survived the Permian Event thanks to the lack of their calcareous parts. So the Flood Geologist must come up with a hydrologic sorting method which can model why the waters patterned the corals as such, since no modern floodwaters have been observed sorting SOME organisms by size/weight/habitat, and not others.
4) End of Triassic
200 million years ago, 80% of species lost.
Likely cause: As of 2017, Volcanism is suggested, but this is a more contended issue. The disappearance of 80% of known life in the fossil record is abrupt and left few clues, but a 2017 paper examines one of the larger ones: Mercury.
How do we Know This?: Mercury Levels! These coincide with enormous volcanic events, suggesting another potential anoxic event.
YEC Problems: You may be noticing a pattern of anoxia here. Before you entertain the hypothesis that the flood triggered this O2 sap somehow and attribute it as another unifying Flood condition, allow me to present an issue. The Geological history of Oxygen on the planet shows fluctuations. The most damning to this particular idea is the fact that insects enjoyed insanely high O2 numbers in the Carboniferous... which is seated between two periods of mass anoxia.
The volcanistic nature of the End-Triassic is problematic due to the ash residue, which is terrestrial in nature. Meaning the volcanoes were not acting up underwater, but belching cinders into the air.
5) Cretaceous-Cenozoic
66 million years ago, 76% of all species lost.
Likely cause: Impact event that left the ) Chicxulub crater in the Gulf of Mexico. Killed all the dinosaurs, and all tetrapods over 55 lbs.
How do we know This?: The Iridium Layer! Iridium is an element that is supremely rare on Earth, but notably common in meteors and asteroids. There is a global band of this element found at the K-T boundary, the same layer that the Chixulub crater is found in. This layer is quite unique, as it represents a fuzzy border between the time of the dinosaurs and the time after them. This has always been the prevailing theory, but a recent hubub has been made over supposed further confirmation thanks to a new dig site.
YEC Problems: The nature of meteorite impacts is well known. We can tell by the size of a crater how large the object was, how fast it was going and it's composition. The crater at Chixulub is not indicative of a meteor which would have to penetrate sea levels higher than the Himalayas.
There are arguments of course that the Himalayas are a result of the flood and perhaps the waters were lower at the time of the Chixulub impact. The question then becomes something a bit more problematic.
The layers that make up the Jurassic and Cretaceous would have been laid down late in the Flood. This means The Chixulub impact was also late during the flood. Since we find the Jurassic dino fossils right underneath the Iridium Anomaly, we now face some issues. If the dinosaurs died this late in the flood, what did they eat while swimming for nearly a year? What about the dinosaurs not capable of swimming (looking at you carnotaurus)? if they were dead and simply not deposited yet, why are they all articulated together? Submergence in water lends a body to breakdown and the bones would be separately buried, not in a death-pose.
Thus the dead dinos must have been terrestrial at the time of death. This final issue on the last extinction alone precludes the Global flood based solely on principles of Taphonomy, let alone in the light of everything else.
Summary + Closing
While these events clearly create enormous problems for a Global Flood, little was said specifically on the Young Earth Nature. I am hopeful that seeing these events in tandem makes it clear that they could not have all occurred in 6000-10000 years simply due to the required ecologic recovery time. Additionally is the simple argument of radiometric datingon the rocks formed during these time periods.
The Mass Extinctions are incredibly displays of the fickle nature of our world. They rely on of an often chance event that spirals out of control while the hapless denizens of the planet struggle to survive. It is AFTER these horrific cataclysms that we see the biggest events of radiative evolution occur, proving that most relentless disasters till the soil for forms of life great and small to take Life's grand stage.
TL;DR: Various lines of evidence provide a basis for five mass extinctions, the natures of which preclude a global deluge from having occurred at that time geochemically and taphonomically.

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