On Saturday, both the BBC Science section and Science Daily had a story about a recent study of nanodiamonds at Clovis sites in North America published in Science (abstact below). The jist of the study is that there was a "celestial event" that caused the Younger Dryas and that this led to the demise of Megafauna and the Clovis culture in North America. This event or series of events may have been similiar to the Tunguska explosion in Siberia that occurred in 1908. I haven't read the article yet so I can't comment on it at this point but an interesting hypothesis, nonetheless. I do however, have a problem with extraterrestrial events to explain mass extinctions. There is one evolutionary universal and that is extinction, plus there would appear to be some different rates of demise for the megafauna and the Younger Dryas occurred globally, so it would be interesting to see if other sites of similiar dates from the Old World had similiar sediment layers or even if Tunguska in Siberia had a similiar soil profile.
Nanodiamonds in the Younger Dryas Boundary Sediment Layer
We report abundant nanodiamonds in sediments dating to 12.9 ± 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. N-diamond concentrations range from
10 to 3700 parts per billion by weight, comparable to amounts found in known impact layers. These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America.
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