Understanding the Flood / post-Flood Boundary Issue

The Problem with an Upper Cenozoic Flood/post-Flood Boundary

Chad Arment (2021)

Within creation science, there are numerous subjects where creationists may hold diverse, often very different, opinions. The biblical narrative is more specific on certain points than it is on others. Our understanding of the natural world is like a puzzle: the Biblical Creation account and Flood narrative offer us edges and corners as a framing reference, and we figure out the rest of the pieces using science and logic. Much of creation science comes from collaborative work, as different researchers investigate problems in astronomy, physics, geology, atmospheric science, biology, and more. They publish, debate, and discuss. Sometimes there are less-collaborative researchers who are more interested in pushing their own agendas. Overall, though, creation science tends to move forward.

One of the few true schisms in creation science is the debate over the Flood/post-Flood boundary. We know that there are sedimentary layers and a fossil record that exists because of a global flood. Almost every creationist agrees that fossils below the K-T boundary are Flood fossils (with perhaps the ‘earliest’ representing pre-Flood fossilization). Most creationists who have studied the paleontological record have suggested that fossils above the K-T boundary (Cenozoic fossils) are mostly the result of post-Flood events that involved localized flooding, volcanic ash fall events, lake sedimentation burials, or other fossilizing phenomena.

Recently, a few creationists have argued that almost the entire fossil record is Flood deposit, and that the upper boundary of the Flood record is in the Upper Cenozoic (for example, between Pliocene and Pleistocene layers). This position makes a significant departure in how we discern the differences between the pre- and post-Flood worlds, in how we understand the biological changes possible within biblical kinds, and in how we grasp the theological underpinning of the Flood narrative. More concerning is that these creationists don’t actually seem to understand the issues and use hand-waving tactics to dismiss and minimize the problem.

Unlike certain areas where a researcher may speculate and theorize broadly, we actually have guidance here from Scripture regarding the position of the Flood/post-Flood boundary. It doesn’t come from the day-by-day narrative of the Flood action, though. Instead, it comes from the number of animals that God brought onto the Ark. Specifically, the Bible tells us that only one pair of each unclean, terrestrial animal kind was saved on the Ark.

So, What’s a Biblical Kind?

The Biblical kind is a concept in creation science derived from Genesis 1: God created plants and animals ‘according to their kinds.’ While there is some debate over the details, the traditional view within creation biology has been that organisms created during the first week were organized (whether by pairs or even groups) by kind. Two different kinds would not have a common ancestor, nor would they be able to hybridize together. Descendants of a kind would be able to diversify and adapt as they ‘filled the earth.’ This means new species or genera (or even higher levels) within those kinds appeared after the Creation Week. No new kinds would appear, of course. Some species within the same kind might be able to hybridize, while others might not. But if two species could hybridize, this has traditionally denoted that those species are in the same kind. Today, creation biologists recognize that a Biblical kind may encompass many related species and genera (including extinct ones), all descended from the original created kind. Often, the kind is associated with the taxonomic level of the family, but in certain cases it may include even higher levels of taxa.

Kinds on the Ark

Only terrestrial and flying creatures were taken aboard the Ark. The Hebrew phrasing of Genesis 7 tells us that seven pairs of each clean terrestrial animal kind and seven pairs of each flying creature kind were brought onto the Ark. For unclean terrestrial animal kinds, however, only one pair was brought onto the Ark. So, seven pairs of the cattle kind and seven pairs of gallinaceous birds were brought onto the Ark, but only one pair each of the feline kind, the monitor lizard kind, or the kangaroo kind would have been on the Ark.

So what’s the significance of this? If only one pair of an unclean kind was saved from the pre-Flood world, then we should not find multiple species and genera from the same kind, that were living in the pre-Flood world, also living today. If we were to find fossil remains of lions, leopards, caracals and servals (all felines living today) in the same African sedimentary deposit, we would know that those fossils were formed after the Flood. Only one pair of felines were on the Ark, which diversified into the various genera and species we have today. Those species are not going to be the same as the felines that may have lived before the Flood. They have their own distinct genetic trajectories, influenced by very different environments.

This is a traditional model of a single unclean, terrestrial kind, showing A) species before the Flood (several lineages would have gone extinct with the Flood); B) one pair surviving the Flood; and C) post-Flood diversification into new species/genera as the kind adapted to new habitats spreading across the earth.

Proponents of an Upper Cenozoic Flood/Post-Flood Boundary are pushing (knowingly or not) this model. A) shows a variety of pre-Flood species and genera within a single unclean, terrestrial kind; B) indicates one pair surviving on the Ark; while C) shows numerous pre-Flood species and genera within that same kind magically showing up in the post-Flood fossil record. As just one example, with the Clarey Flood Model's assertion that the boundary is between the Pliocene and Pleistocene, seventeen of the same fossil kangaroo genera can be found both before and after that alleged boundary.


There are a number of arguments that can be made, using this Biblical constraint, showing that fossils below the Pleistocene layers (Pliocene and Miocene) are part of post-Flood faunal deposition. They were living in the period after the Flood as the earth was recovering. We can see this in fossils around the globe. For specific details, please see below for links to the papers I’ve written on this subject.

If the Flood/post-Flood boundary is in the Upper Cenozoic, then more than one pair of unclean terrestrial kinds survived the Flood, and Genesis 7:2 cannot be correct. The question for creationists who argue for an Upper Cenozoic boundary is simple: do you intend to protect your model at all costs? Or, are you willing to agree that the Bible is true, even if it means revising your model?


Arment, C. 2020. To the Ark, and Back Again? Using the Marsupial Fossil Record to Investigate the Post-Flood Boundary. Answers Research Journal 13(April 8): 1-22 [pdf]

Arment, C. 2020. Implications of Creation Biology for a Neogene-Quaternary Flood/Post-Flood Boundary. Answers Research Journal 13(Nov. 4): 241-257 [pdf]