[Al Simmons]

"and the climate change + increased volcanism theory is regaining lost ground."

You forgot to add "against all logic".

A global extinction of all critters bigger than a dog (except for the cold-blooded reptiles which could 'hibernate' through the global winter without having to eat for a year or more if necessary)is not going to be caused by "climate change" or "increased volcanism".

Actually, it was indeed caused by the temporary "catastrophic climate change" caused by the impact of the Yucatan asteroid (According to an Indian scientist, there may have been another simultaneous impact in Asia, presumably from the original object breaking up before impact, but that has not yet been proven as fact...)

[cogitator]

Based on quick research for my previous reply, the impact-didn't-do-it camp (led by Gerta Keller) still acknowledges the Chicxulub impact. Keller contends that the Cretaceous actually continues for 300,000 years after Chicxulub, and that another (undiscovered) larger impact finished off the familiar Cretaceous biota (dinos), which were under stress from Chicxulub and volcanism.

I have one big problem with that. From what I remember, the K/T iridium layer gets thicker the closer you get to Chicxulub -- and there is only one K/T iridium layer, as far as I know. So if the K/T iridium layer is not due to Chicxulub, why doesn't it thicken in a direction other than toward Chicxulub? I have no idea.

[cogitator]

If you're interested in the controversy, get out a magnifying glass and read this page:

The Chicxulub Impact and Its Relation to the K/T Boundary

The meeting where these papers were presented was last week, so this is hot off the press.