PostFlood boundary lower than Pliocene?

Last year at Origins 2011 in Rapid City, Marcus Ross of Liberty University presented a paper on the Flood/postFlood boundary as it relates to North American mammal stratigraphy, and the latest Journal of Creation has the full paper (which is currently not online, so you'll have to get the paper edition to read it).  The idea is pretty simple: Given that the Flood account in Genesis appears to require absolute extinction of terrestrial mammals globally and then repopulation of the earth from animals coming off the Ark in the Middle East, we should expect to see a pretty big stratigraphic and geographic discontinuity.  Otherwise, we have to make ad hoc assumptions about animals migrating to the Ark, surviving the Flood, then migrating back to the exact spot they lived before the Flood.  One such example would be hard to swallow.  Many such examples would suggest we've misinterpreted which sediments are really post-Flood.

For North American terrestrial mammals, Ross found that 23% of genera and 96% of families cross the Pliocene/Pleistocene boundary, a commonly assumed post-Flood boundary.  If that really is the Flood boundary, then a surprising number of mammal baramins migrated right back to where their pre-Flood ancestors were buried, which strikes me as really weird.  If the mammal family is the created kind, then near all of them migrated right back to where they lived before the Flood.

Ross concludes,
The biostratigraphic analysis presented here for North American mammalian families makes placement of the Flood/post-Flood boundary untenable.  Rather, these data are more naturally interpreted as representing time-sequential recolonization of the post-Flood world by diversifying terrestrial mammal baramins. Given the biostratigraphic break expected to characterize the Flood/post-Flood boundary, a lower location for the boundary must be sought.  At present, the Cretaceous/Paleogene boundary appears to be the stratigraphically highest and most prominent biostratigraphic break ... though a similarly thorough analysis must be completed in order to strengthen its claim to the Flood/post-Flood boundary.
I hope that "similarly thorough analysis" on the Cretaceous/Paleogene boundary is already in the works!

Those of you who don't have access to Journal of Creation can read a detailed abstract of this work in last year's Creation Geology Society proceedings.  His abstract starts on page 6.

Ross, MR.  2012.  Evaluating potential post-Flood boundaries with biostratigraphy - the Pliocene/Pleistocene boundary.  Journal of Creation 26:82-87.
