Well I got my hands on a copy of the Science article about the North American impact theory I mentioned yesterday. Thanks to a professor at my former university for helping get it to me and so quickly too. You rock, Dr. Mormile!
I think they are onto something but for me they haven't presented enough evidence. They only referenced three areas that they took samples from and only two of those had iridium in them. And all three areas were very widespread. They are right about the ways the nano-diamonds form, but really that is not enough proof.
What I would love to see are sampling from more locales and then some correlation with the pollen and other plant remains from the Younger Dryas Boundary. Something like an impact occurs and it messes with the growing cycles and the botanical zones. The pollen would tell us for sure if something wonky happened. And it sure wouldn't be the first time palynology was used in conjunction with larger fossils and samples. Heck, if undergrads and grad students can do that in the middle of the Missouri Ozarks, surely the PhDs on the projects can call a palynologist up for tea, crumpets, and some collaboration.
And if Dr. Kennett or his wonderful colleagues ever see this, I would happily present my creditials and apply to a master's program to be a research-slave, I mean grad student who stares at pollen all day. Of course I'd have to move to Oregon, California, or Arizona unless something could be worked out with someone more local.