September 1, 2010
An alternative theory that a comet impact caused the Younger Dryas period, an ice age that occurred 13,000 years ago and coincided with the disappearance of the Clovis culture, has been challenged by recent sediment studies. Among the evidence presented in favor of the comet impact theory were nanodiamonds, which the theory’s authors claimed were evidence of the shock of a comet impact. However, the sediment studies have found that these nanodiamonds are actually aggregates of the carbon materials graphene, graphane, and their oxides.
The report comes close behind a geoarchaeological study that found that the carbon spherules found at four nanodiamond sites were actually fungal material and fecal matter from arthropods.
For more, see the article in Nature News.