Geological features are commonly discussed in the boundary debate (see, for example, Whitmore and Garner [2008]), but a number of arguments have been made using fossils to support the Flood/post-Flood boundary at different positions in the stratigraphic record. The validity of an argument rests on the reliability of the evidence (the premise of an argument), transparency of all assumptions, and whether the conclusion logically follows.

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There have been several cases, for example, where authors have asserted that fossil data fits within their Flood Model, thereby ‘confirming’ their Flood Model — but ignoring the fact that the fossil data also fits within competing Flood Models. That is poor argumentation.

Here I review and summarize paleontological arguments that argue for a Lower Cenozoic Flood Model or against an Upper Cenozoic Flood Model. In a Lower Cenozoic Flood Model, the Flood/post-Flood boundary may vary a bit by location, but is often indicated as near the K-Pg boundary in most terrestrial deposits. Grouped arguments may share a similar structure, but focus on different specific elements to make a case.

Arguments relating to the Ark Kinds as baraminic lineages

1. If two or more living members of the same unclean terrestrial kind are found in the same fossil deposit, that fossil deposit represents a post-Flood environment.

In my first paper related to this topic, I noted (Arment 2014) that a Late Miocene fossil site in Knox County, Nebraska, included fossils of five living North American snakes: Pantherophis guttatus (cornsnake), Pantherophis obsoletus (ratsnake), Lampropeltis getula (kingsnake), Lampropeltis triangulum (milksnake), and Pituophis melanoleucus (bullsnake). These three genera are all capable of hybridization, so we know that all five species are part of the same Created Kind.

If the Genesis Flood narrative is to be taken as historically accurate, we must take seriously the multiple statements within those passages that only one pair of every unclean terrestrial kind was taken on the Ark. This means that only one pair of this colubrid kind (however broadly it may encompass living colubrid snakes) on the Ark. T

here were not two separate pairs of different Pantherophis species, there were not two separate pairs of different Lampropeltis species, and there were not separate pairs of all three of these genera. There was only one pair of a colubrid snake which was ancestral to all three of these genera. This means that any fossil site with more than one of these species must represent a post-Flood environment.

This argument can be made with any unclean terrestrial Created Kind where multiple living species are found in a fossil deposit (Arment 2020b). It is most effective when there is available hybridization data to securely place different species or genera in the same Created Kind.

2. If two or more members of the same unclean terrestrial kind are found on both sides of a proposed Flood/post-Flood boundary, that boundary is refuted.

This is very similar to Argument 1, except that it does not require the animals in question to be extant, or to be in the same location. Fossil animals that are reasonably asserted to be within the same Created Kind (supported by statistical baraminology or other evidence) may be used (Arment 2020b). As Lynx, Puma, Felis, and Caracal are all known from Pliocene deposits around the world, and are still living today, this argues against a Pliocene-Pleistocene boundary.

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Arguments relating to the continental placement of fossils

3. The extremely high percentage (a statistical improbability) of animals which would have had to migrate from their original landforms to the Ark, then back to the location where their ancestors were buried in Flood deposits, argues against an Upper Cenozoic Flood Boundary.

This original argument was made by Ross (2012a), noting that 27 North American mammal families demonstrated Pliocene-Pleistocene boundary crossing, with 70 genera being found both below and above the boundary. Ross noted that “these data are more naturally interpreted as representing time-sequential recolonization of the post-Flood world by diversifying terrestrial mammal baramins.”

Closely following the argument above, in my investigation of the Australian marsupial fossils, I examined the likelihood of a Flood/post-Flood boundary on that continent at three separate stratigraphic locations (Arment 2020a). Numerous boundary-crossing genera were found for each. Within any Flood model, the original organisms discovered in Flood sediments could have originated on different pre-Flood landforms which may or may not still be in existence.

So, the marsupial fossils found in Australia may not have originated in Australia, if they were carried there by Flood sediment. But why would so many living marsupial genera now be living solely on the continent where their pre-Flood relations were buried? For the most commonly suggested Upper Cenozoic boundary (Pliocene-Pleistocene), the probability of the same marsupial genera showing up above and below the boundary in Australia, was calculated to be 4.42×10^-45. That is a ridiculously low probability, but Australian marsupials are not alone in this issue.

The same low probability arises when we look at many different Ark kinds around the world. For example, I looked at endemic North American terrestrial reptiles, and found at least 29 genera that are found both above and below the Pliocene-Pleistocene boundary (Arment 2020b).

In looking more broadly at terrestrial mammals around the globe, endemic Pliocene-Pleistocene boundary crossers included Africa (96 genera), Asia (35 genera), Australia (66, including bats and monotremes), Europe (30 genera), North America (60 genera), and South America (55 genera) (Arment 2025). So at least 342 mammal genera crossed that boundary, being found only on a single continent. That is incredibly implausible.

4. The very low percentage of animals from Old World Neogene deposits showing up in North American Pleistocene deposits, is evidence against a Pliocene-Pleistocene boundary.

This argument emerges from Ross’ (2012a) evaluation of North American boundary-crossing mammals, being the ‘flip side’ of the previous argument. In a ‘sweepstakes’ route within post-Flood dispersal, there would be no reason to expect that only animals with near relations in the North American Paleogene-Neogene record would show up in North America. We can, of course, broaden this argument to include both South America and Australia, as they also rely on ‘sweepstakes’ routes rather than ‘open bridges’.

As I noted (Arment 2025), “If it is just random chance that positions a genus solely above its ancestors of the same genus, on the same continent, then we should also see many other genera solely on a single continent after the Flood, while all their pre-Flood buried ancestors of the same genera are solely on a different continent. Where are all those genera?”

Arguments relating to boundary placement in the stratigraphic record

5. The sheer number of genera within the same families (putative Created Kinds, or at least monobaramins) found both above and below Upper Cenozoic boundaries make those boundaries highly improbable for a Flood model.

An excessive number of genera crossing the Pliocene-Pleistocene (also known as the Neogene-Quaternary) boundary explicitly demonstrates the unlikelihood of that boundary for Flood models. Within the Canidae, at least ten genera cross that boundary, while at least thirteen genera of the Felidae do so (Arment 2020b). This means that there would have been at least ten pairs of canines and thirteen pairs of felines on the Ark.

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That turns the Ark’s ‘clean kinds’ and ‘unclean kinds’ into meaningless phrases — why bother saying that only one pair of every unclean kind was on the Ark, when Noah had to deal with ten pairs of wolf- and fox-like canids? Beyond that, extrapolation of genus-survivorship to all the other Ark Kinds would require an armada of Arks to save all those animals. Note, this particular argument does not rely on stratigraphic ordering of the fossils themselves, beyond placement above or below a proposed boundary.

6. A biostratigraphic break should be expected if a given stratigraphic position is to be considered for the Flood/post-Flood boundary placement.

A proposed boundary lacking a distinctive biostratigraphic break is probably incorrect. Ross (2012b) evaluated forty-three North American tetrapod families (247 genera) at the K-Pg boundary, noting 14.2% survivorship (though these were not strictly terrestrial animals). In comparison, a higher percentage of survivorship was noted in mammal families at the Pliocene-Pleistocene boundary. Ross noted that this was a preliminary analysis, but it has potential for further investigation.

7. The fossil record in the immediate aftermath of the Flood/post-Flood boundary deposition is likely to demonstrate higher diversity in families and lower diversity in genera and species.

This argument derives from Whitmore and Wise (2008), and their observations in the Green River Formation. Within this Eocene formation, which would be very near the boundary in a Lower Cenozoic Flood Model, there are some 120-154 species in 85 genera of terrestrial mammals, in 41 families. This averages to 2.1 genera/family, 1.4-1.8 species/genus.

If this fossil site represents a post-Flood dispersal site within decades of the Flood, that suggests ‘low diversity’ dispersion initially, with higher speciation further along the dispersal trajectory, or as the authors suggest “at the termini of post-Flood dispersion paths.” This suggests a possible test for boundary placement: do comparable Paleogene fossil sites demonstrate similar levels of diversity in family, genus, and species?