Similar pages on my web site are
and Here is a site for Anthropology in the News from Texas A & M.
August 29, 2007. A Cretaceous beetle preserved in amber at the moment it was exuding a defensive droplet. Oregon State press release. The paper is in the Journal of Chemical Ecology.
August 8, 2007. Further confirmation of microbial fossils in the Pilbara region of Australia, aged around 3.5 Ga. Terra Daily site
Bodiselitsch, B., et al. 2005. Estimating duration and intensity of Neoproterozoic snowball glaciations from Ir anomalies. Science 308: 239-242 here , and comment, p. 181 here.
Here's what the paper says. A Snowball Earth would accumulate incoming space dust on the ice, loaded with iridium. When it melted, there would be an outwash of all the iridium all at once, which would give an iridium spike in the sediments. Indeed, such a spike occurs after the two main major glaciations linked with the Snowball hypothesis.
I don't see why a Slushball ice sheet on the tropical continents wouldn't also accumulate iridium that would also outwash to give an iridium spike: in other words, I don't see how this study differentiates between Snowball and Slushball. The samples were taken at sites that were along the edge of the tropical continent. So let's do a thought experiment. Antarctica today has been accumulating space dust for 30 m.y. or so. If it melts, as it must some day, won't it produce an iridium spike? Would that imply that Antarctica had been part of a Snowball Earth? I think the answers to these two questions are Yes, and No, respectively. So I'm not going to alter my piece on Slushball Earth (yet).
The paper does NOT address ecological questions. For example, however many clades of mammals there were in the Cretaceous, they were only of marginal importance in ecological terms. Dinosaurs dominated the large-body guilds right up to the KT boundary. And it apparently required the demise of the dinosaurs before mammals could evolve to fill those "dinosaur" guilds (see my Chapter 19).
The paper does have the biggest mammalian supertree yet, so it has its value. It's the TIMING of events that is in question.
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