Asteroid Impacts and the Younger Dryas: New Evidence

The basics of the idea from Science Daily:

West presented on his theory that a large comet or asteroid, believed to be more than a mile in diameter, exploded just above the earth at a time when the last Ice Age appeared to be drawing to a close.
The timing attached to this theory of about 12,900 years ago is consistent with the known disappearances in North America of the wooly mammoth population and the first distinct human society to inhabit the continent, known as the Clovis civilization. At that time, climatic history suggests the Ice Age should have been drawing to a close, but a rapid change known as the Younger Dryas event, instead ushered in another 1,300 years of glacial conditions. A cataclysmic explosion consistent with West’s theory would have the potential to create the kind of atmospheric turmoil necessary to produce such conditions.

(You can find out more about this idea here and here.)
The idea has been somewhat controversial, but Science Daily is reporting new data strong enough to convince one of the skeptics:

Tankersley was familiar through years of work in this area with the diamonds, gold and silver deposits, which at one point could be found in such abundance in this region that the Hopewell Indians who lived here about 2,000 years ago engaged in trade in these items.
Prevailing thought said that these deposits, which are found at a soil depth consistent with the time frame of the comet/asteroid event, had been brought south from the Great Lakes region by glaciers.
“My smoking gun to disprove (West) was going to be the gold, silver and diamonds,” Tankersley says. “But what I didn’t know at that point was a conclusion he had reached that he had not yet made public – that the likely point of impact for the comet wasn’t just anywhere over Canada, but located over Canada’s diamond-bearing fields. Instead of becoming the basis for rejecting his hypothesis, these items became the very best evidence to support it.”

This is what convinced Tankersley:

Samples of diamonds, gold and silver that have been found in the region have been conclusively sourced through X-ray diffractometry in the lab of UC Professor of Geology Warren Huff back to the diamond fields region of Canada.

I must say, I am somewhat skeptical of the idea, but this new evidence looks pretty convincing to me – but then I’m not a geologist. There is no indication of when this would be published, but some of it will find it’s way into specials on PBS (NOVA) and the History Channel. Seems to me to be putting the cart before the horse, more details would be nice, at any rate I guess we will have to wait and see…
M. J. Murphy at BigCityLib Strikes Back has more – including an email exchange with West.

12 Responses

  1. The impact hypothesis is discussed in the recent documentary Journey to 10,000 BC, which also enthuses about the Solutrean speculation.

  2. Makes no sense to me at all. Why would megafauna be obliterated (apparently selectively) by this air burst that thrust NA back into the ice age during which the megafauna thrived in the first place. Seems to me it would have extended their existence. But then, I don’t understand how the events that ended the dinosaurs selectively destroyed all those dinosaurs that weren’t birds…..

  3. I would like to get more details as well. But for now I’ll take their word on the existence of new evidence and wait for the full article

  4. Martin – Yup, I got that DVD too.

  5. I had seen 2 items in Science relating to this: 1) In 2007 Richard Kerr reported on a meeting of the American Geophysical Union where the impact idea was announced. The article said the announcement received a mixed reception. 2) In 2008, Kerr described a PNAS report (October 2007) that claimed there was no evidence for an impact, but that something did happen to bring on the cold (Younger Dryas) about 12,900 years ago.

  6. I’m also not a geologist, but am conversant with at least some of the basic ideas. I was just wondering, is there some reason to think that the traditional posited trigger for the Younger Dryas (a massive freshwater pulse from N. American glacial lakes interrupting the Global Conveyor Belt) either didn’t happen or was inadequate as a trigger? Maybe someone more conversant than I am with this controversy can offer some insight…?

  7. They argue that the impact event was responsible for the freshwater pulse, via melting and altered drainage patterns.

  8. A problem with their evidence is this: there are chunks of native copper from Canada and Upper Michigan found throughout the Midwest and down into Ohio and, I think, Indiana too. How did it get there? Thrown into the air by a meteor strike? Nope. The glaciers carried the copper there. Pieces of native copper were plucked up into the ice, carried south, and left where the glaciers melted and dropped them. The same process could easily have happened for native silver and gold as well as diamond-bearing rocks from up north. Maybe their final publication will address this problem, though. I’m also skeptical of any “sourcing” that done with XRD.

  9. afarensis, thank you.
    Hm. Their argument is interesting, but doesn’t seem adequate in any Bayesian sense.

  10. silver, gold and diamonds? can someone tell me which hopewell sites these were found on? I haven’t heard about that.

  11. Megan, the authors are suggesting, I believe, that a meteor strike in Canada caused gold-, silver-, and diamond-bearing ejecta to land in Ohio and Indiana… not that their occurrence in the region was due to the Hopewell interaction sphere (which is how obsidian, Pacific and Mediterranean shells, and other exotic items made it to the region).

  12. Yes, but Tankersley says that the Hopewell were trading these items, presumably out of Ohio and into other regions, or amongst themselves. I just haven’t heard of any of these items being found on archaeological sites in the region, though Hopewell certainly isn’t my speciality.

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