Archaeologica.org

Rokcet Scientist wrote: And a look at the list of impact craters in North America corroborates that, because it strikes me that, with the exception of just one, none of the others is dated any more recent than a million years minimum. None at 12,900 BP! And wouldn't the youngest craters be the most easily identifiable?

http://en.wikipedia.org/wiki/List_of_im ... th_America

Minimalist wrote:Would an air burst over a mile thick ice sheet leave much of a crater in the ground? Probably made a hell of a hole in the ice but that would melt with everything else.

Johnny wrote: Surely there would be corresponding markers in the soil and artifact records.

In the 1990s, W. Topping (14) discovered magnetic microspherules and other possible ET evidence in sediment at the Gainey PaleoAmerican site in Michigan (see also ref. 15), and Lougheed (16) and Bi (17) reported that late Pleistocene glacial drift contained similar cosmic spherules. We now report substantial additional data from multiple, well dated stratigraphic sections across North America supporting a major ET airburst or collision near 12.9 ka. Directly beneath the black mat, where present, we found a thin, sedimentary layer (usually <5 cm) containing high concentrations of magnetic microspherules and grains, nanodiamonds, iridium (Ir) at above background levels, and fullerenes containing ET helium. These indicators are associated with charcoal, soot, carbon spherules, and glass-like carbon, all of which suggest intense wildfires. Most of these markers are associated with previously recorded impacts, but a few are atypical of impact events. We identify this layer as the YD boundary (YDB), and we refer to this incident as the YD event.

dannan14 wrote:

Johnny wrote: Surely there would be corresponding markers in the soil and artifact records.

Nanodiamonds

It has become fashionable to speculate that Clovis may have vanished as a result of an impact from an extra-terrestrial body (comet, meteor, asteroid, etc.). That is of course not reconcilable with the fact that no signs of extinctions of other fauna in that same era have been found.

As little as forty years may divide the end of the Pleistocene from the start of the Holocene. Half of the worldwide warming took place in a span of only fifteen years . . . The fact that Clovis expansion roughly corresponds with the extinction has been used to argue for Clovis cultures hunting megafauna out of existence [but] in fact, remarkably few sites show a clear correlation between humans and even a fraction of the 34 species that went extinct. Whether humans were partially responsible for the extinctions or not, changes in climate, flora, and fauna were unavoidable. After the shift, many environments completely disappeared, leaving adapted animals nowhere to survive.

Prior to melting, the Canadian ice sheet stood about a mile high from ocean to ocean and blocked the jet stream from pulling frigid arctic air southward. The resulting climate, although six to eight degrees Fahrenheit cooler than now, caused less severe winters. Without strong seasonal fluctuations, ecological zones of the north intermingled with those of the south, creating conditions for lush, tall grasses on the North American plains and mixed conifers and hardwoods in an open mosaic through the Midwest. No comparable ecology exists anywhere on earth today.

E.P. Grondine wrote:If it was an ice impact, the only sign may be a circular uprise caused when the overlying ice sheet was blown away.