Sunday, 3 February 2013

Probably News to No One By Now. The Younger Dryas Impact Does A Crash 'n' Burn. Marco Langbroek: This One's For You!

One rendition of the putative [and now forever debunked] Younger Dryas Impact theory.
Kathleen Nicoll (U. Utah) alerted me to this yesterday when she sent a reprint. Tip o' the hat, Kathleen. She's second author on this paper. The news is all over the science pages on the web, too. So, I'm certain that you all prolly know evrything 'bout it. Still, there may be one or two. Well, this one's for you!
M. Boslough, K. Nicoll, V. Holliday, T.L. Daulton, D. Meltzer, N. Pinter, A.C. Scott, T. Surovell, P. Claeys, J. Gill, F. Paquay, J. Marlon, P. Bartlein, C. Whitlock, D. Grayson, and A.J.T. Jull (2012), Arguments and evidence against a Younger Dryas impact event, in Climates, Landscapes, and Civilizations, Geophys. Monogr. Ser., vol. 198, edited by L. Giosan et al. 13–26, AGU, Washington, D. C., doi:10.1029/2012GM001209.
A Clovis 'point'
[or double-edged sword, if you prefer]
This paper exposes the fanciful nature of claims made for an extraterrestrial body that was supposed to have created an environmental cataclysm at the beginning of the latest of the Pleistocene glaciations---the Younger Dryas. Alongside these claims was the argument that this would have spelled doom for the so-called Clovis people who inhabited North America between about 14 and about 12 kyr ago.

Boslough et al. first give lie to the various scenarios that the Younger Dryas impact proponents have erected to explain a) an impact with no impact crater, and b) the impossibility of an 'airburst' of sufficient magnitude to have spread its destructive energy across North America south of the ice margin. Put simply, even if a sufficiently large object had made contact on the waning Laurentide Ice Sheet there would have been impact evidence on the ground in the present. No such exist. As for the 'airburst' idea, physical principles tell us that to have been large enough to create a continent-wide cataclysm it needed to have broken up well above Earth's atmosphere [i.e. in space, fer gawd's sake!] and unless there had been a gigantic explosion inside the offending celestial body, and that even if had broken up through some mysterious, previously unheralded physical laws, such a missile would simply have continued on its course, with the various bits in close formation, and have had the same 'footprint' as if it had been all one piece.

Planet Jupiter. The four brown patches are, give or take, the impact points 
of four fragments of the Comet Shoemaker--Levy 9, in 1994. This was the 
first time a human being had witnessed the collision of two celestial bodies.
If that weren't enough to put the YD impact idea in the circular file, the authors go on to point out the shortcomings of the sedimentary and chronological record that YD enthusiasts claim amounts to de facto evidence of an extraterrestrial impact: specifically, the so called Black Mats that in places occur around the time of the Younger Dryas. They occur at other times, and far enough away from the lower half of North America that they can't be used as a time marker, much less as evidence---in and of themselves---for such impacts. The authors also find erroneously identified materials used as evidence, contaminated samples, poorly dated sediments, and on and on. Read it. This paper eviscerates the YD impact theory. And, although we're not treated to the actual physics computations I think we can be fairly certain that the counter-claims made in this article will stand up in the court of archaeological opinion. That's because Boslough is the guy who accurately predicted the effects of the break up and impact on Jupiter of the comet Shoemaker-Levy 9 in mid 1994, and whose model won out against the prognostications of the rest of the scientists in the field.

(CREDIT: Photograph courtesy of Claudio Latorre.)
The team that put this paper together comprise the glitteratti of a half-dozen scientific disciplines, including our own. Not that I'm appealing to authority here [everyone knows THAT's fallacious]. I'm merely pointing out that this is no *cough*cflash-in-the-pan, slash and *cough, cough* burn, criticism. They dismantle the YD impact theory. Full stop.

This is the kind of scrutiny that needs to be applied to every [and I mean every] one of the claims of the kind the Subversive Archaeologist is determined to overturn. I've been going to say this for a few weeks now, but couldn't find the right platform. Now I can. With independent and non-partisan examination, could we not---for example---once and for all, address the possibly erroneous early dates for modern human behaviour from the caves of southern Africa? I focus on this one simply because I'm not a physicist. Neither were the YD impacts proponents. And, although the OSL daters of those south African caves are physicists, too, I think their technique [or more correctly, their method] is due for a thorough going over.

As for the other kind of issue---e.g.purposeful burial in the Middle Palaeolithic. I think these can be dealt with just fine, thank you, by unblinkered archaeologists [with a little informed help from geologists]. Early claims for fire use, however, can't be dealt with by us archaeologists alone. Even the much touted record of presumed 'hearths' at Kebara Cave could do with a re-visit [I believe]. Patrick Randolph-Quinney, one of the SA's staunchest supporters, is ready, willing and quite able, I think, to apply forensic science approaches to the early fire question. [Hope ya don't mind me singling you out, Patrick!]

The point is: the work is there to be done. And although several people have asked me to work with them on some of the issues, I truly believe my mind is best applied to my activities at the Subversive Archaeologist. I'm happy pointing you in the right direction.

With that in mind. Get busy! Great things are afoot!

Oh. And. I still have work to do on the "Out of Africa, Out of Africa Again, and Yet Again Out of Africa" business recently posited by Boivin et al.

Thanks for making my day!

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  1. Good to see another debunking. By now, no sensible scientist should remain in support of the hypothesis. But I fear the impact proponents nevertheless will not budge.

    As one of the Authors has stated, quite rightfully:

    "“The theory has reached zombie status,” said Professor Andrew Scott from the Department of Earth Sciences at Royal Holloway. “Whenever we are able to show flaws and think it is dead, it reappears with new, equally unsatisfactory, arguments"

  2. What is this radiocarbon evidence of modern contamination that they're talking about? Which site is this? And who did the dating?

  3. Hey, Spawn.
    Verbatim. The MB refers to the lead author M. Boslough.
    "Finally, one of us (MB) acquired carbon microspherules (Figure 4) collected from the Gainey site in Michigan from one of the original YD impact proponents (A. West). Gainey is one of the nine key YD sites, and one of the undated ones, presented by Firestone et al. [2007]. To verify the age of the samples, we submitted one set of spherules for accelerator mass spectrometry radiocarbon dating at the University of Arizona. Only one microspherule has been dated thus far and is 207 ± 87 years BP (AMS lab number AA92197). This result suggests that there are geochronology problems. One key problem is that particles identified as diamond-containing carbon microspheres and presumed to be related to the pur- ported YD impact may actually be younger than the YD, unrelated to the YD or to an impact, and might be modern contaminants."

  4. Oops. The carbon spherule itself is a modern contaminant. It's not that the 14C estimate was contaminated with modern carbon.

  5. Are they going on to tackle the ice free corridors? I could never understand them.

  6. I'm not surprised. The stratigraphy and the chronology at many of these sites leave a lot to be desired; though the same can be said about many paleoindian sites. Carbon spherules aren't unique to impact processes, you get them from normal wildfires, hearths, etc. Since they are so small they're mobile in the soil.

  7. Iain S, this may help.

    Dixon, E. J. (2013). Late Pleistocene colonization of North America from Northeast Asia: New insights from large-scale paleogeographic reconstructions. Quaternary International, 285(0), 57-67. doi:

    Iain (D)

  8. So you guys are fawning over a paper that claims to refute a hypothesis based on the dating of a single particle? That figures.

    This is an easily ignorable paper even given the numerous problems with the impact hypothesis. He could have gotten thousands of particles from Le Compte to date, and he apparently is claiming he was unaware of the spherule results via Le Compte, that they are ubiquitous and terrestrial.

  9. @kT: I'm personally not fawning over anything. You're correct that one date is not definitive, especially at an essentially unstratified site like Gainey. Better work has to be done. The Lake Quitzeo chronology from last year is horrible, and it's another example of the impact proponents shooting themselves in the foot by ignoring the importance of chronology. Having said that, Boslough's group includes Marlon, Bartlein et al.(PNAS 2009), with a charcoal/bio-mass burning database built on calibrated dates ranging from the 1986 Praetoria curve through Stuiver et al. 1993, Intcal98, Intcal04, etc, which each give different calibrated ages across the Younger Dryas Boundary. So of course there's no charcoal spike at 12.9ka. There's no single timescale. Any spike in it is smeared out over a millennium. But because of the poor
    chronology, we also can't say there WAS a spike.

    Neither "side" (if they are sides, anyway) is approaching the question correctly. And if you don't have the chronology worked out any cause and effect argument is moot since you haven't even established the order of events.

    To me this remains an open question until the chronology is adequately resolved.

  10. Well said, Spawn. I'd, for one, like to hear what Boslough says about airbursts and the spread of damage after the meteorite that blew up over the Urals the other day.

  11. Statistically it didn't happen, because the likelihood of the event coinciding within 24 hours of the passage of an unrelated near-Earth asteroid, an airburst over San Francisco, and another one over Cuba, all coming at different trajectories, is infinitesimally low. The people in Chelyabinsk just have the wrong a priori assumptions about the event, and therefore they suffer the posteriors.

  12. Personally I don't believe that an impact of any large magnitude occured at the Younger Dryas boundary. It doesn't fit into any hydrogeological models of the event and the only known hydrogeological explanation of the event that I can imagine that would involve a large impact points to a feature near Lake Nipigon that has other more prosaic explanations and does not exhibit classical impact features at all. So either the impact was non-classical, or very small, or it didn't happen. My best guess is still Corossol but that feature remains undated and unexplored.

    What I am interested in is the developing field of microscopic impact proxies. It's a shame the Russians were not able to get an aircraft up quickly into the impact plume to collect some particles while they were still concentrated. That would have helped immensely. But it is still possible to collect some of the impact plume particles from that event, but they will be greatly diluted by time and distance.


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