A 12,900 BP impact in NA? Where is it then?

[Rokcet Scientist]

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.

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

If they can find a 250 mio year old crater under 3 miles of ice in Antarctica (Wilkesland) while not looking for one then surely a 12,900 year old crater under no ice, in north America, should be found? Especially if you know what you're looking for!
Alas, no such thing to date...

[Johnny]

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

I'm not sure I'd call that list exhaustive. As EP would point out, it's missing the Whitecourt impact of 1100 years ago.

[Minimalist]

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]

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.

Interesting point. I wonder what evidence an air burst might leave in the antarctic ice record. If a burst of sufficient size to cause any amount of extinction occurred over NA during the LGM, what could the environmental effects have looked like further south? Surely there would be corresponding markers in the soil and artifact records.

[dannan14]

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

Nanodiamonds

[Digit]

According to a recent UK TV programme such have been found in the ice at about that age.

Roy.

[Minimalist]

http://www.pnas.org/content/104/41/16016.full

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.

[Johnny]

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

Nanodiamonds

http://news.nationalgeographic.com/news ... monds.html

[uniface]

There is more than enough evidence of it in many chert artifacts of the Paleo era from the NCentral USA. They're riddled with tiny holes that are drilled deeply into (sometimes through) them. These are not found on later artifacts of the same materials. This is the one smoking gun that the quibblers avoid in their dismissals. Other anomalies can be argued away through sophistry and suggestion. But the holes in the artifacts (and their radioactive signatures) can only be ignored.

[uniface]

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.

Bob Patten, Peoples of the Flute -- a Study in Anthropolithic Forensics (Denver : Stone Dagger Publications, 2005), pp. 232-233.

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.

ibid., p.41

[E.P. Grondine]

Thanks to all of you here who tried to keep RS on track.

RS - You can go to http://cosmictusk.com for all of the latest research on the YD impact event.
The current working analysis is that it was a shower of Tunguska sized comet fragments from the disintegration of Comet Encke, though the search for one for the remains of one of the larger impacts is on, as you'll see there. If it was an ice impact, the only sign may be a circular uprise caused when the overlying ice sheet was blown away.

[dannan14]

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

Is it likely that such a rise would still be there? i mean, after 13k years it seems there would be a fair chance of it subsiding. Or is this sort of a rise different from the isostatic rebound observed on the islands of the Pacific Northwest?

[Minimalist]

I would expect isostatic rebound to have eliminated that in the ensuing 10,000 years.

[Rokcet Scientist]

Curious that this impact – or airburst, whatever the case may be – chose to wipe out just the Clovis people, and not the ancestors of the 'first nations' we 'recognize' today, nor any other species of fauna.

Apparently racism is, literally, universal...

[Minimalist]

The whole point is that numerous species of megafauna were killed off.

There are far more "clovis" sites in the East than the West. They would have been closest to the blast zone and, as E.P. has discussed on numerous occasions, the secondary effects of the blast would have turned their environment into a wasteland.

We do not know if the ancestors of the 'first nations' were even here yet or if they arrived later, via Beringia or boat.