Via the American Geophysical Union:
... New findings challenge a theory that a meteor explosion or impact thousands of years ago caused catastrophic fires over much of North America and Europe and triggered an abrupt global cooling period, called the Younger Dryas. Whereas proponents of the theory have offered “carbonaceous spherules” and nanodiamonds—both of which they claimed were formed by intense heat—as evidence of the impact, a new study concludes that those supposed clues are nothing more than fossilized balls of fungus, charcoal, and fecal pellets...
