The fossil record is stratified, that does not seem to be disputed by YEC. The identifiable geological eras from the Cambrian forward are identifiable by geological characteristics but also by their fossil inclusions. The fossil record displays a general progression from more primitive organisms, extinction boundaries, and sorting of creatures into their associated epochs. This is precisely what would be expected given life evolving over a span of hundreds of millions of years.
Given that YEC holds that all the animals that ever breathed coexisted together before the deluge, this presents a challenge - if they lived together why did they not die together? The entire geologic column constituting most of the fossil bearing sedimentary rock found on the planet, would have been laid down roughly over the course of a year.
Flood proponents advance three scenarios, not necessarily mutually exclusive, to explain the segregation of the fossil record. The first runs something along the lines of; all over the world, as the flood waters were rising, animals were attempting to escape to higher ground. The quicker and larger creatures found their way to higher ground and held the valuable real estate until the end. Another is that their carcasses sank into the murky flood waters at different rates.
Finally but foremost, the suggestion that various animals actually lived well separated from each other; as Bodie Hodge of AiG asks, would you want to live with dinosaurs?
Taken separately or together, I cannot imagine anybody offering these explanations without squirming internally, because they are dismal. Most often the question is addressed in terms of why no humans and dinosaur fossils have ever been found together, but that is only the thinnest sliver of the problem. Bear in mind that YEC believes that pretty much every creature that ever lived was present in the days leading to the flood. So we should find not just people with dinosaurs, but trilobites with crabs, dimetrodons with velociraptors, plesiosaurs with whales, triceratops with elephants, pterosaurs with buzzards - one could go on all day.
The question is, why would appealing land not attract the interest of animals associated with every epoch? Why would T. Rex not steal a lion’s kill? Just as there are animals which fill every climate niche available today, the same generally applies to dinosaurs. The YEC dodge that dinosaurs were located remote from other animals betrays a tacit admission, either they lived apart in time - which is the mainstream alternative but YEC rejects; or they lived apart in space - which makes little sense but YEC adopts.
If the animals lived together, perhaps they segregated as the flood waters arose. Could it have been by the size of the animal? Only a minority of dinosaurs grew to the size of large sauropods or T. Rex, most were comparable to elephants and buffalo, and many down to the size of badgers. There is also no reason to believe that dinosaurs moved particularly faster or slower than an assortment of other animals. There are over a thousand identified species of dinosaur of many shapes and sizes; if they lived at the same time there is no reason to expect there would be no inter-sorting between Permian amphibians, cretaceous reptiles, and Holocene mammals. Finally, could they have sunk at different rates? That makes no sense for sorting either, some animals would be tangled up or suffer trauma and not even float to begin, and again, many amphibians, dinosaurs, and mammals are about the same size and would bloat and sink randomly. These things are not like clockwork.
So it makes little sense that if animals from the various epochs were all alive at the time of the flood, that there would be any effective mechanism that would result in any sorting whatsoever. But the fossil record is screaming clear. There has never been a solitary dinosaur found above the KT boundary, and never a modern mammal ever below.
Flood geology holds that the deluge was an extraordinarily violent affair, spreading the continents apart, grinding primal rock to massive sedimentary formations, and jutting mountain ranges skywards. It is inconsistent that all this fury would reshape the planet but placidly lay each animal to rest in peace in some well ordered sequence followed the world over. That would be like, …what would be a good analogy? Well, it would be like a tornado in a junkyard assembling a 737 jetliner without anything out of place or in the wrong order. No Cambrian pieces after Jurassic, no Paleocene pieces before Triassic; nothing at all out of place.
Creationist pitch that the waters of the flood chaotically transported material great distances when it suits them. For instance, Andrew Snelling, proposes the fantastical idea that the Permian fossil forests discovered in Antarctica did not in fact grow there but were uprooted and transported there to be buried in upright[!] positions by entrained sediments of the same flood water. Stumped by Forests Snelling also writes that the flood would be characterized by fast moving, catastrophically powerful water currents and surges which deposit strata layers fully across the continents. Best Flood Evidences
It matters not whether you have an hydraulics degree from MIT or fled from high school science. Try removing your evolutionist glasses and your creationist lenses, and just see for yourself. In your mind’s eye, remember what you personally witnessed at a stream side during a swollen spring runoff, or at the oceanfront during a violent storm, or watching the news footage of a tsunami relentlessly plowing across land without ever seeming to spend its energy. Do not ask Snelling or anyone else what you are supposed to see, what do you see? You are responsible for your own observation. If the answer leads you to believe it is possible that dinosaurs living with modern mammals would never be jumbled and mixed together by the deluge, then peace be upon you. For me, that would require that I unsee what I have personally seen, and to unknow what I know for sure to be true. I take the YEC position here to be untethered from reality.