Younger Dryas impact event

The Younger Dryas impact event is the name of a hypothesized impact event at the beginning of the Younger Dryas cold spell about 10,900 BCE. The impact seems to have occurred near the North American Great Lakes; the bolide may have disintegrated in the air.

Evidence

The evidence for such an impact event is a layer of unusual materials (Nanodiamonds, magnetic grains, carbon spherules, magnetic spherules, charcoal, soot, fullerenes enriched in Helium 3, etc.) at the very bottom of the "black mat" of organic material that marks the beginning of the Younger Dryas.cite journal
first = Rex
last = Dalton
title = Archaeology: Blast in the past?
journal = Nature
volume = 447
pages = 256–257
date = 2007-05-17
doi = 10.1038/447256a News article in "Nature" ]

It is hypothesized that this impact event brought about the extinction of many North American large mammals. These animals included camels, mammoths, the giant short-faced bear and numerous other species. The markers for the impact event also appear at the end of the Clovis culture.cite web
url = http://www.agu.org/cgi-bin/sessions5?meeting=sm07&part=PP41A&maxhits=400
title = Session Information, 2007 Joint Assembly, Paleoceanography and Paleoclimatology
publisher = American Geophysical Union
accessdate = 2007-05-22 Includes links to abstracts.]

2007/2008 meetings

Scholars have actively debated the controversial theory. On May 24, 2007, a session at the spring 2007 joint assembly of the American Geophysical Union in Acapulco, Mexico was held to discuss this hypothesis and reveal the evidence.The theory also drew new scrutiny in March 2008 at the annual meeting of the Society for American Archaeology in Vancouver, Canada. In August 2008, independent verification of Firestone and West's identification of ET material in Clovis stratigraphy was presented by Mustafa Fayek and Sharon Hull of the University of Manitoba at the annual Pecos Archaeological Conference [Fayek and Hull, Pecos Archaeological Conference, Flagstaff, Arizona, August 10, 2008] . Allen West, a lead proponent of the Clovis Comet theory, and Ted Bunch, a co-author of the original PNAS paper and former NASA chief of exobiology, presented new evidence, and participated in a panel discussion of the findings with Sandia Laboratory asteroid impact modeler, Mark Boslough, and comet hunter Carolyn Shoemaker [ [http://www.youtube.com/view_play_list?p=91566C328E999E76 Video of the August, 2008, Pecos Conference presentations on the Clovis Comet] ] .

PNAS publications, pro and contra

On September 27, 2007, a paper presenting the findings of the Acapulco group was pre-published online at the Proceedings of the National Academy of Sciences website. According to the study, the impact event may have led to an immediate decline in human populations in North America at that time.cite web
url = http://www.pnas.org/cgi/content/abstract/0706977104v1
title = Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling
publisher = The National Academy of Sciences
accessdate = 2007-09-30 ]

Less than year later substantial support for the synchronous nature of the black mat was provided by leading Clovis archaeologist, C. Vance Haynes, also in the Proceedings of the National Academy of Sciences.

Says Haynes,

Further analysis is in progress and other Clovis sites need independent study and verification of this evidence. Until then I remain skeptical of the ET impact hypothesis as the cause of the YD onset and the megafaunal extinction. However, I reiterate, something major happened at 10,900 B.P. that we have yet to understand. [ [http://georgehoward.net/Vance%20Haynes%27%20Black%20Mat.htm Younger Dryas “black mats” and the Rancholabrean termination in North America, C. Vance Haynes, Jr.,PNAS May 6, 2008 vol. 105 no. 18 6520-6525] ]

Almost a year after the first publication, a study published in August 2008 states "The results of the analyses were not consistent with the predictions of extraterrestrial impact hypothesis. No evidence of a population decline among the Paleoindians at 12,900 ± 100 calBP was found. Thus, minimally, the study suggests the extraterrestrial impact hypothesis should be amended." [B Buchanan, M Collard & K Edinborough 2008. "Paleoindian demography and the extraterrestrial impact hypothesis " "PNAS" August 19, 2008 vol. 105 no. 33 11651-11654 doi: 10.1073/pnas.0803762105 [http://www.pnas.org/content/105/33/11651.abstract?sid=9d193f91-add8-4105-b36f-d39804b70daa] ]

See also

* Pleistocene megafauna
* Holocene extinction event

References

External links

* [http://www.youtube.com/watch?v=oZsa1uvyOVE&feature=PlayList&p=91566C328E999E76&index=17 Hayek and Hull present independent verification at the annual Pecos Conference]
* [http://www.youtube.com/view_play_list?p=741568C2D58A9793 Video of the AGU Press Conference announcing the discovery]
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