For at least the past three decades, creation geologists and paleontologists have analyzed the geologic record in an attempt to determine which layer (or layers) represent the last of those laid down by the global Flood of Noah’s day, and the first of those denoting to the post-Flood period. There are currently two leading positions. One is that the boundary lies at or around the Cretaceous/Paleogene (K-Pg) boundary , roughly coinciding with the impact of a massive asteroid that hit the earth in the Gulf of Mexico. The second suggested boundary roughly coincides with the beginning of the Ice Age . Supporters of both sides have proposed various criteria they feel best advocates the boundary’s location.
Paleontologist Marcus Ross published a rather unique study in 2013 where he tried to establish the Flood/post-Flood boundary using mammal fossils in North America . Our post-Flood diversity of animal life would have diversified since the Flood from the representatives of each created kind of air-breathing land animal that walked off Noah’s Ark. And while we don’t know the pre-Flood world’s biodiversity levels upon its creation, it is likely that the time between Creation and the Flood experienced diversification much like what occurred afterward. Only two (14 of some) of each air-breathing land animal kind survived the Flood, creating a bottleneck. Given that post-Flood climates, environments, continental arrangements, and topography were quite different after the Flood, the chances that any post-Flood variety would be a carbon copy of pre-Flood lineages that did not survive the Flood is incredibly small. Therefore, when we look at the Flood/post-Flood boundary, Dr. Ross argues that we should see a clear break between life forms that died in the Flood and those that lived afterward.
To determine where and if such a break existed in the fossil record, Dr. Ross analyzed 303 genera (that’s the plural form of genus) from 28 families of North American that are found in rock layers dated to the beginning of and just before the Ice Age. The rhinoceros family was the only mammal family that did not cross the pre-Ice Age/Ice Age boundary. Dr. Ross found that 23% of mammal genera and over 96% of mammal families did cross this boundary. Three of these genera, the pronghorn antelope, Megalonyx (a ground sloth), and cotton-tail rabbits not only appear on both sides of the boundary, but they are only found in North America. If the Flood/post-Flood boundary occurs near the beginning of the Ice Age, then these genera would have to leave their habitat to board the Ark, and then leave the Ark in the Middle East after the Flood and only wind up where their pre-Flood predecessors are buried. All this despite the fact that the current continental configurations, climate and topography did not even exist before the Flood! Even more peculiar is the fact that no non-North American mammals are found in North America that are only found in other places in Flood rocks. Why did no koalas, penguins or kangaroos end up migrating to North America?
Dr. Ross argues that the absence of a break between pre-Ice Age and Ice Age North American mammals makes this section of the geologic record an untenable Flood boundary. Instead, he posits that the Flood/post-Flood boundary lies at the K-Pg boundary, and suggests that other researchers contribute by finding similar patterns in mammal biodiversity on other continents, like Australia .
The views expressed in this article reflect those of the author(s) mentioned and not necessarily those of the editorial staff.
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 Clarey, T.L., and D.J. Werner. 2018. Global stratigraphy and the fossil record validate
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 Ross, M.R. 2012. Evaluating potential post-Flood boundaries with biostratigraphy—the Pliocene/Pleistocene boundary, J. Creation 26(2):82–87.
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