Absence of evidence for a meteorite impact event 13,000 years ago

Dec 08, 2009
The woolly mammoth was one of the large mammals that became extinct in North America at the onset of the Younger Dryas approx. 13,000 years ago. Credit: Image of Woolly Mammoth at the Royal BC Museum, Victoria, British Columbia courtesy Wikipedia Commons

An international team of scientists led by researchers at the University of Hawaii at Manoa have found no evidence supporting an extraterrestrial impact event at the onset of the Younger Dryas ~13000 years ago.

The Younger Dryas is an abrupt cooling event in Earth's history. It coincided with the extinction of many large mammals including the woolly mammoth, the saber toothed jaguar and many sloths. This cooling period is generally considered to be the result of the complex global climate system, possibly spurred on by a reduction or slowdown of the thermohaline circulation in North America. This paradigm was challenged two years ago by a group of researchers that reported finding high iridium concentrations in terrestrial sediments dated during this time period, which led them to theorise that an impact event was instead the instigator of this climate shift.

A team led by François Paquay, a Doctoral graduate student in the Department of Geology and Geophysics at the University of Hawaii at Manoa (UHM) decided to also investigate this theory, to add more evidence to what they considered a conceptually appealing theory. However, not only were they unable to replicate the results found by the other researchers, but additional lines of evidence failed to support an impact theory for the onset of the Younger Dryas. Their results will be published in the December 7th early online edition of the prestigious journal the .

The idea that an impact event may have been the instigator for this cooling period was appealing because of several alleged impact markers, especially the high iridium concentrations that the previous team reported. However, it is difficult for proponents of this theory to explain why no impact crater of this age is known. "There is a black mat layer across North America which is correlated to the Younger Dryas climatic shift seen in Greenland ice cores dated at 13 thousand years ago by ," explains Paquay. "Initially I thought this type of layer could be associated with an impact event because concentration in the proxies of widespread wildfires are sky high. That plus very high levels of iridium (which is one indicator used to indicate extraterrestrial impact events). So the theory was conceptually appealing, but because of the missing impact site, the idea of one or multiple airburst arose."

To corroborate the theory, Paquay and his colleagues decided to take a three-pronged approach. The first was to replicate the original researchers data, the second step was to look for other tracers, specifically osmium isotopes, of extraterrestrial matter in those rocks, and the third step was to look for these concentrations in other settings. "Because there are so many aspects to the impact theory, we decided to just focus on geochemical evidence that was associated with it, like the concentration of iridium and other platinum group elements, and the osmium isotopes," says Paquay. "We also decided to look in very high resolution sediment cores across North America, and yet we could find nothing in our data to support their theory."

The team includes American, Belgian and Canadian researchers. Analysis of the sediments was done both at UHM and in Belgium, using the same sediments from the same interval and indepedently did the analysis work and got similar results. Both the marine and terrestrial sediment records do not indicate that an impact event was the trigger for the transition into the Younger Dryas cold period. "The marine and terrestrial record both complement each other to support this finding," concludes Paquay. "That's what makes the beauty of this study."

More information: This research will be presented at the American Geophysical Union Fall 2009 Meeting in San Francisco.

PNAS Early Edition, December 7, 2009 www.pnas.org_cgi_doi_10.1073_pnas.0908874106

Source: University of Hawaii at Manoa

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User comments : 13

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deatopmg
not rated yet Dec 08, 2009
Clearly something catastrophic happened to the large animals and Clovis culture. Maybe a nearby gamma ray burst really does fit. But what about all the smaller animals - how did they survive? Was there a contraction in numbers at that time?
Archivis
1.6 / 5 (7) Dec 08, 2009
Now see boys and girls, the wooly mammoth and various other large mammals produced a vast amount of methane gas, leading to an Al Gore calibur greenhouse effect which is where your climate shift came from.

"If you read it online, it MUST be true..."
AMMBD
not rated yet Dec 08, 2009
Perhaps the airburst, perhaps something else. The question remains WHAT? There's scads of evidence something serious went down 13K ago. Be nice to know what.
andre_chaisson
not rated yet Dec 08, 2009
Balderdash!! I have found the elusive Clovis Comet craters (yes theres 2 of them!). http://www.youtub...Gy8TIinI
Hernan
4.5 / 5 (2) Dec 08, 2009
If the a comet hit a 1 mile thick ice sheet, wouldn't the catastrophic melting also take most of the evidence away? I would search for evidence of catastrophic meltdowns (floods, as in many of the old cultures myths).
rebellionkid
not rated yet Dec 08, 2009
Not relevant to a very interesting article, but:

"Ads by Google
Darwin's errors unearthed - Serious doubts about evolution are evolving. Flawed theory exposed... - www.ucg.org.uk/ad/ev/"

appeared at the top of the page, google doesn't appear to be screening these appropriately.
marjon
3.3 / 5 (3) Dec 08, 2009
"Scientists have long blamed climate change for the mass extinction of animals that took place in North America almost 13,000 years ago. Now some researchers say a comet broke apart and burned the landscape and many of the creatures living on it. The proof is "nanodiamonds," microscopic diamonds they've found in the soil across the continent."
http://www.npr.or...98958270
DragonHunter
4.7 / 5 (3) Dec 08, 2009
The thing to keep in mind is that impact science is very poorly understood. There are many clearly obvious impact structures on this continent that aren't normal craters. And do not fit the standard model in any way.

I've cataloged more than 500 of them. This 8.5 meg PDF has a sampling of 50: http://dl.dropbox...ters.pdf
po6ert
1 / 5 (1) Dec 08, 2009
has anybody considered the impact of excessive carbon sequestion by plants leading to a fall in co2 levels? here to for a warmer planet! :-)) I can do without a return to the ice age in which we are currently living
vidyunmaya
1 / 5 (3) Dec 08, 2009
Sub:Earth Planet-Magnetic Fields-Reversal
Earth Planet Magnetic reversal is around 26,000 Years. Dwapara Tuga must be dated back to 12,000-13,000 Years. The subject is relevant for Cosmological Index-Cosmology Vedas Interlinks
See: Earth Glow Index -Cosmic Signatures and Cosmic Alignment-2012
http://www.scribd...ORMATION
Vidyardhi Nanduri
R_R
1 / 5 (2) Dec 09, 2009
Perhaps the obvious answers are hidden the best. When you start to take logic out of the equation everything becomes complicated. Perhaps these people searching for clues should get in a boat and row themselves 250 miles out to the center of the perfect giant arc at lower right Hudson Bay and take a dive and observe the lava basin from rim to rim. This precision arc certainly could represent an impact crater. So perhaps all these searchers should join forces and grab an orr and hopefully their boat will stay afloat and not take their archaic forms of deduction to the bottem.
Shootist
1 / 5 (1) Dec 13, 2009
The thing to keep in mind is that impact science is very poorly understood. There are many clearly obvious impact structures on this continent that aren't normal craters. And do not fit the standard model in any way.

I've cataloged more than 500 of them. This 8.5 meg PDF has a sampling of 50: http://dl.dropbox...ters.pdf


cinder cones.
Shootist
3 / 5 (2) Dec 13, 2009
Perhaps the obvious answers are hidden the best. When you start to take logic out of the equation everything becomes complicated. Perhaps these people searching for clues should get in a boat and row themselves 250 miles out to the center of the perfect giant arc at lower right Hudson Bay and take a dive and observe the lava basin from rim to rim. This precision arc certainly could represent an impact crater. So perhaps all these searchers should join forces and grab an orr and hopefully their boat will stay afloat and not take their archaic forms of deduction to the bottem.


Hudson Bay is not an astrobleme. Astroblemes that size look more like Sudbury or Vredefort.

http://impacts.rajmon.cz/