If the correct location is in the Late Cenozoic, then the paleontological evidence would suggest a slower and less dramatic post-Flood diversification.
The number of animals spreading out from the ‘mountains of Ararat’ would need to be explained only by the variety we see today and during the Ice Age.
Thus, the boundary placement affects the burgeoning subfield of baraminology. Did it begin immediately after the Flood in favorable locations, such as the mountains of Scandinavia, eastern and central Canada, the Greenland mountains, and Antarctica, or was it delayed for several centuries by large-scale post-Flood catastrophism?
Three positions were argued in Reed and Oard: The third position is mine, and I believe it to be a middle ground between the two, based on field evidence I have studied.
For more information, I recommend reading the cited literature.
Many of these people believe there is little or no evidence for the Flood.
For example, anti-creationist geologist, Arthur Strahler proclaimed: Strahler at least grudgingly admits we have a little evidence.
Perhaps the most important is to show the presence of the Flood in the rock record to those who do not believe it ever occurred.
These include uniformitarians, theistic evolutionists, and other old-earth creationists.
In addition to these apologetic reasons, the boundary constrains the part of the rock record caused by the Flood, a crucial component of any Flood model.
Third, it also allows a geologically-based understanding of post-Flood processes and events, providing a context for the times between the Flood and the founding of the Mesopotamian empires, which can be forensically studied by archaeology.
I discovered a large body of evidence against the Flood/post-Flood boundary being at the K/T boundary, especially geomorphological evidence—a field often ignored by both secular geologists and creationists.
There are many surficial features that can only be explained by Floodwater drainage.
Any creationist who assumes an incorrect boundary will likely be wrong about events after the Flood and during the late Flood period.