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Requiem for the Younger Dryas impact hypothesis?

Filed under: — gavin @ 1 March 2011

This is the strong conclusion of a new paper in the Earth Science Reviews by Pinter et al (via Scribd). From their abstract:

The Younger Dryas (YD) impact hypothesis is a recent theory that suggests that a cometary or meteoritic body or bodies hit and/or exploded over North America 12,900 years ago, causing the YD climate episode, extinction of Pleistocene megafauna, demise of the Clovis archaeological culture, and a range of other effects.

The physical evidence interpreted as signatures of an impact event can be separated into two groups. The first group consists of evidence that has been largely rejected by the scientific community and is no longer in widespread discussion…. The second group consists of evidence that has been active in recent research and discussions:…. Over time, however, these signatures have also seen contrary evidence rather than support.

In summary, none of the original YD impact signatures have been subsequently corroborated by independent tests. Of the 12 original lines of evidence, seven have so far proven to be non-reproducible. The remaining signatures instead seem to represent either (1) non-catastrophic mechanisms, and/or (2) terrestrial rather than extraterrestrial or impact-related sources.

The YD impact hypothesis made a big splash at AGU in 2007, and we’ve written about it a few times since. Our assessment was (in 2007), that this would need a lot of confirmatory evidence to get accepted, and even if it was, it did not provide much explanation for other, very similar, abrupt changes in the record. In 2009, we were still skeptical and noted that “the level of proof required for this extraordinary idea will need to be extraordinarily strong”. Unfortunately, as this paper makes clear, neither a lot of confirmatory evidence nor extraordinarily strong proofs have been forthcoming.

This paper is unlikely to the very last word on the subject, but it is likely to be the last time the mainstream paleo-climatologists are going to pay this much heed unless some really big new piece of evidence comes to light.

However, while the specifics of this particular hypothesis and its refutation are interesting in many ways…

The YD impact hypothesis provides a cautionary tale for researchers, the scientific community, the press, and the broader public.

Let’s be specific…

… since there are indeed lessons that can be drawn here:

  • ‘Bold’ ideas can get published and get serious people to pay attention. The claims about the YD impact were entirely at odds with mainstream views, yet taken seriously and looked at by a wide variety of other researchers.
  • Like most bold ideas that initially raise skeptical eyebrows, the evidence for this one decreased with time. This is not inevitable, but it is not unusual.
  • Science is self-correcting because other scientists take the time to look for new evidence backing up or refuting initial ideas, and go back and re-interpret what was previously done.
  • Even eventually discarded ideas can provide abundant directions for good science to get done. For instance, a fair amount of research into nanodiamonds has occurred because of the interest in this idea.
  • The media loves the ‘radical new idea’ presented by ‘outsider’ scientists (3 documentaries on this so far, a big NYT piece). It fits a lot of the romantic archetype of what science is supposed to be about. It has controversy, narrative and outsize personalities. Whether the ideas are good or not is barely relevant.
  • The Feynmanian ideal of a single scientist both proposing and refuting their own new idea is very rare. In practice, the roles of proposing and refuting are far more often done by the scientific community as a whole, not an individual.
  • Scientists gain credibility for doing careful work and not going beyond the evidence in interpreting it. This is opposite to what gains readership on blogs. :-)

The Younger Dryas, an extremely abrupt, and still mysterious, interval of climate change, will no doubt continue to excite people across the field of paleo-climate, but we hypothesize that the impact hypothesis has had all the impact it’s going to.


80 Responses to “Requiem for the Younger Dryas impact hypothesis?”

  1. 1
    Joseph O'Sullivan says:

    This was another great RC post that took a specific issue and used it to show how science works.

    Other than the K-T impact are there other well supported extraterrestrial impact events that caused major climatic or ecological changes?

  2. 2
    David B. Benson says:

    SMALL ROUNDED BASIN AT CHARITY SHOAL

    Charity Shoal
    A small equidimensional circular depression 1000 meters in diameter, with a continuous encircling rim, coincides with the feature referred to as Charity Shoal on nautical charts. An elongated ridge extends southwest from the feature, resembling the tail of a crag-and-tail feature common to some drumlin fields. The basin is slightly deeper than 18 meters and the rim rises to depths of 2-6 meters. The origin of the feature remains unknown. Although a sinkhole in the limestone terrane is a possibility, an origin related to a meteor crater, that was subsequently glaciated, seems more likely. Aeromagnetic mapping by the Geological Survey of Canada revealed a negative magnetic anomaly over Charity Shoal, which is a characteristic feature of simple impact craters (Pilkington and Grieve, 1992).
    from
    http://www.ngdc.noaa.gov/mgg/greatlakes/lakeontario_cdrom/html/gmorph.htm#a8
    appears to remain undated.

  3. 3
    Isotopious says:

    IMO the climate system ‘bit off more than it could chew’ during the Bølling/Allerød interstadial.

    The climate released a huge amount of energy during this time, the energy melted the ice.

    The state of the climate then shifted and began to store energy as opposed to releasing it, and the resulting surface cooling was then amplified by very cold melt water.

  4. 4
    chris colose says:

    I never thought this was popular anyway in the YD literature, just something you hand-wave quickly in the introduction of a paper to establish you actually read what’s out there.

  5. 5
    Russell says:

    It was a charming just so story while it lasted.

    The account of finding mammoth tusks with their upsides peppered with nickel-iron micrometeorites like so much bird shot was as seductive ( if true) as the carbon nano-mineralogy was suspect.

    What became of the smoking tusks?

  6. 6
    wili says:

    From the quote above: “The remaining signatures instead seem to represent either (1) non-catastrophic mechanisms, and/or (2) terrestrial rather than extraterrestrial or impact-related sources.”

    What exactly would terrestrial impact-related sources be?

    On another OT point, the PTRS just had an issue devoted to discussions about what a 4 degree hotter world will look like.

    http://rsta.royalsocietypublishing.org/content/369/1934.toc

    Any chance that there would be a thread here to talk about the findings?

  7. 7
    Jim Prall says:

    I’ll second the motion by Will in#6 for a post on the Four Degrees themed issue. i’ve downloaded all the papers and I’ve begun working my way through them. Sobering stuff.

    - Jim P.

  8. 8

    So, you’re saying that bloggers gain readership for doing haphazard work and reaching beyond the evidence when offering interpretation. What’s your evidence for that?

  9. 9
    tamino says:

    Re: #8 (John D. Wilson)

    So, you’re saying that bloggers gain readership for doing haphazard work and reaching beyond the evidence when offering interpretation. What’s your evidence for that?

    Anthony Watts.

  10. 10
    Richard Kerr says:

    I may have already written the requiem for the YD impact, see my Science news story, http://www.sciencemag.org/content/329/5996/1140.full .

  11. 11

    Tell us when you are going to retract your statements that the nanodiamonds in YD sediments don’t exist, when we now have a credible published report that they do, in fact, exist in YD sediments in great abundance, here. Take your time. Thanks in advance.

    [Response: What statements are you referring to? Who are you even talking to? - gavin]

  12. 12
    Hank Roberts says:

    for Richard Kerr, is the text of your story available online anywhere?
    The MP3 is available (thank you!): http://www.sciencemag.org/content/suppl/2010/09/02/329.5996.1140.DC1/1140.mp3 — can you give us more references to sort out the dozen lines of evidence?
    Typing as I listen: “they don’t see any evidence of an impact, and they’ve had 30 years or more to work out what constitutes evidence of an impact … three years ago there were 12 lines of evidence … rejecting … a particular type of nanodiamond that everyone agrees could only be generated in a massive impact … fails …. proponents are not giving up … and … more evidence coming out in papers in coming months ….”

    So I’m guessing the dozen lines of evidence have some physical evidence for something; that evidence may or may not be holding up; if so something other than a huge climate-changing impact may have produced the evidence.

    For example as others asked, the nickel-iron bits — if confirmed, in a small number of tusks — could those indicate a smaller closer airburst? What process could imbed metal fragments in tusks to match whatever they’ve described as of last year, http://adsabs.harvard.edu/abs/2009AGUFMPP31D1385H

    And what are the other dozen lines? Pointers to papers most welcome.

  13. 13
    Lazarus says:

    Re: #8

    “Anthony Watts”.

    Nail – head.

  14. 14
    Hank Roberts says:

    Oh, I guess I ought to wait til the actual paper’s available–looking at the abstract (link in the first line at the top of the page ) my questions will be answered there and by the footnotes and references. (I’m not a subscriber so I’ll have to wait for a library copy or one of the authors to share a copy).

  15. 15
    seamus says:

    Humans probably killed off the megafauna. We’ve never been very good at sustainable resource management.

  16. 16

    If you were genuinely interested in and following this story with any due diligence, Gavin, you would know that I am speaking directly to Richard Kerr and his comments in Science Magazine here :

    http://www.sciencemag.org/content/329/5996/1140.summary

    which he just linked to, and which now have been DEFINITIVELY REFUTED in the article I just linked.

    I was just wondering when he was going to retract his statements. I think a retraction would be in order, but who am I to say what Richard Kerr can or should say or do.

    [Response: Neither I, nor any other reader, is psychic, so you might be better off explicitly stating what comment or person you are addressing in future. But returning to your actual point, Kerr was reporting results from Daulton et al (2010) who indeed reported finding no nanodiamonds in a particular set of sediments, and indicated that previous assessments likely mistook signatures of graphene for nanodiamonds. Kennett (as quoted by Kerr) clearly does not agree. The Tian et al (2011) study, did find nanodiamonds in their samples (from Lommel YDB layer in Belgium), but not of the kind highlighted by Kennett et al originally as providing evidence of an impact. (Lonsdaleite). Kerr even mentioned the AGU presentation from these same authors, and so there is no new information on the topic. Having read Kerr's piece carefully, I don't see any reason why he needs to retract anything. (PS. I have no dog in this fight, so please just stick to science rather than attacks on me, Kerr or anyone else). - gavin]

  17. 17
    Hank Roberts says:

    From the MP3 podcast, I also at first had the impression someone said nanodiamonds didn’t exist — I was mistaken, the point was that those found aren’t the kind that would be impact markers. They’re real; but they’re not evidence for an impact — not tied to one particular stratum, not the right type of crystal form.

  18. 18
    E.P. Grondine says:

    Hi Earl –

    The “smoking tusks” are now realized to have been produced by an earlier iron asteroid impact, and the peppered Siberian musk ox skull by yet another iron impact that occured even earlier. A search is on for the impact craters, but as usual suffers from a lack of funds.

    As far as the YD impacts goes, few outside of the impact community realize how hard it is to find impact signatures – in other words, locating the YD layer, sampling it, and then processing the samples is non-trivial.

    For example, at the recent known impact site at Tunguska, it took more than 3 years of field expeditions, sampling, and sample processing to nail down the type of impactor, and the impact process is still under investigation.

    For what it is worth, it appears that the peoples living in North America at the time of the YD impacts remembered them for some 13,000 years, and those impacts had a profound effect on their world view.

    E.P. Grondine
    Man and Impact in the Americas
    (while the book has hundreds of pages of small type, too many typos, and not enough pictures, it does have a correction sheet pasted inside the front cover)

  19. 19

    Hank, ANY nanodiamonds, whether cubic or hexagonal or otherwise, found in large quantitites in YD sediments along large amounts of fullerenes and graphene fragments, is a clear indication that something extraordinary happened at the TD boundary. Nanodiamonds are not created by wildfires, they are either the result of the natural influx of extraterrestrial material, or if they concentration is spiked or elevated, some sort of carbon and volatile rich atmospheric or surface impact. Big impacts create hexagonal nanodiamonds in situ. Smaller impacts deposit existing extraterrestrial nanodiamonds in large amounts.

  20. 20
    E.P. Grondine says:

    Hi Richard –

    I don’t think you want to take credit for breaking that story:

    http://cosmictusk.com/vindication

    We’re working with data some 13,000 years old, and it is difficult.

    A good model to keep in mind as regards impact research is the Chicxulub/Shiva research and coverage.

    E.P. Grondine
    Man and Impact in the Americas

    [Response: If you want to comment here and be taken seriously, please read the papers you are referencing: "Because no hexagonal diamond (Lonsdaleite) could be identified a shock-induced mechanism is unlikely to be involved in the formation of the crystalline carbon material in the present layer." and "As a final conclusion it should be stated that the present variety of crystalline structures observed in the black Younger Dryas boundary in Lommel does not provide sufficient evidence to conclude an exogenic impact as the origin of these structures." Far too much discussion occurs on issues that are not actually relevant and on misquotes and misrepresentations of what people are claiming. I don't see any contradiction between Claeys' quote in the Science piece "There is nothing, no meteoritic signal." with what is in the Tian et al paper and what was presumably presented at AGU. - gavin]

  21. 21
    Chris Colose says:

    A review discussing the evidence against the impact hypothesis was done before this too, discussing lack of sufficient chemistry changes in Greenland ice cores, as well as the non-uniquenes of a YD-like event (as I talked about in my post) implying that a random catastrophic event probably wasn’t what was going on.
    http://www.geology.wisc.edu/~acarlson/Other/carlson_2010_geology_YD.pdf

  22. 22
    Hank Roberts says:

    Wili above quoted
    >> (2) terrestrial rather than extraterrestrial or impact-related sources.”
    and then asked
    > What exactly would terrestrial impact-related sources be?

    Wili, you misread that; “or” connects. What you quoted means:

    [terrestrial sources] rather than [extraterrestrial or impact-related sources]

  23. 23
    Slioch says:

    Oh, what a shame! I enjoyed relating the various aspects of the 2007 PNAS Firestone et al paper to anyone unwise enough to listen … But, I suppose, therein lies the danger: it was such a lovely idea.

    But, I assume, the evidence that there was, at some time, an impact in Bladen County, North Carolina still stands: this aerial photo (Fig. 7) is astonishing:

    http://www.pnas.org/content/104/41/16016/suppl/DC1

  24. 24
    Edward Greisch says:

    The print is too fine in the article at http://www.scribd.com/doc/45791500/Lommel-Diamonds-in-Younger-Dryas-Boundary-Claeys#open_download
    and some sentences are redacted.

    Has anybody tested impacts into ice? The bolide would be the only source of carbon if it hit a miles-thick glacier. The bolide composition would control the carbon found.

    If it wasn’t Lake Agassiz or an impact, what did cause the YD?

  25. 25
    Edward Greisch says:

    If a bolide hit, say, the Greenland glacier, wouldn’t the glacier melt at that spot and wouldn’t the water flow into the ocean? Was there still a continental glacier in northern Europe at that time? Could the water flow have concentrated the nanodiamonds in Belgium?

  26. 26
    bigcitylib says:

    As to the shrapnel pelted mammoths, paleontologist GS Paul gave this notion a thumbs down:

    “Some in this discussion still seem to imagine that sand sized blast debris can be imbedded in bone surfaces or skin at substantial range from an meteoritic explosion. Tiny particles can travel at high velocities if they are being carried along by air that is itself an equally fast moving part of the supersonic shock wave (shock waves are shock waves because they move faster than sound) produced by the explosion, which are limited to the region immediately surrounding the point source. Anything hit by high velocity microdebris in this zone will be so severely damaged by even more obvious shock and heat that the sand impact will be incidental. The supposedly impacted tusks and bones should be shattered and scorched. Any living animal will be killed outright, the debris will not be the killing agent. Once the micro-debris hits stable air it slowsdown to harmless terminal velocity in well under a kilometer. Even pebble sized objects will slow down to a 100 mph in a few kilometers. That is why being hit by a round musket ball or grape shot at long range was not lethal.”

    Allen West, one of the theory’s first proponents, responded to this. You can read his response through the link below.

    http://bigcitylib.blogspot.com/2008/07/comets-over-canada-part-ii.html

    #18 and Mr. Grondine. Yes, some of the “peppered” carcasses were dated to times earlier than the YD. I believe the response to that from West and Co. was that they might have been already dead and partially exposed at the surface when the YD event occured.

  27. 27
    E.P. Grondine says:

    Hi bigcitylib –

    I am pretty sure that GS Paul is no expert on the mechanics of iron impacts, otherwise he would not have made such stupid statements. Some of the paricles take a ballistic trajectory, which is why you have peppering without death.

    On further examination, some of the bones were found to have healing.

    As far as “shattered and scorched” remains from YD impacts go, Ken Tankersley’s data from Sheriden Cave should move this debate on whenever they are formally published.

  28. 28

    I don’t see any contradiction between Claeys’ quote in the Science piece “There is nothing, no meteoritic signal.” with what is in the Tian et al paper and what was presumably presented at AGU

    Apparently one of the co-authors thought otherwise in a previous paper here, which remarkably is not referenced by Lommel et al., and completely ignored by both Pinter et al., and Tian et al., except as an afterthought. Both of those papers pronounce the premature death of the hypothesis while ignoring the crucial evidence, and offering no explanation of how both nanodiamonds and a wide variety of unusual carbon fragments made their way preferentially into the Younger Dryas sediment layers in Europe and Greenland.

    Wildfires do not explain this data. Impacts do. I would be more than willing to give up this hypothesis except for the fact that hydrogeology and geomorphology in the Lake Nipigon basin supports it, as well as carbonaceous anomalies in the Younger Dryas Sediments in Greenland and Europe, both downwind of the hypothesized impact.

    Clearly Firestone’s original scenario of a massive firestorm and conflagration was an overreach, but to pronounce any impact hypothesis dead this prematurely is not good science. Impacts happen all the time. They will continue to occur whether you admit their existence or not. Whether or not an impact occurred, or not, or contributed to the YD transition, or not, remains to be demonstrated, but it’s still a valid hypothesis, not refuted and but not yet confirmed.

    [Response: Since one can never prove a negative, this situation will last for ever. But without replicated and confirmatory evidence the posterior probability for it being significant decreases markedly. (PS. Lommell is a place, not an author). - gavin]

  29. 29
    E.P. Grondine says:

    Hi Gavin –

    I doubt that the YD deposits will be uniform globally, and I don’t see any reason why they should be expected to be uniform globally.

    [Response: Who suggested such a thing? - gavin]

    Gavin, whatever occured triggered a substantial change in the Earth’s climate. I think that I’ve stated before that my current hypothesis is that cold water from the Artic mixed with the Pacific Current after the sudden event, and that is what accounted for the end of the Ice Age: colder water off the west coast of North America resulted in less snow falling in Northern North America, and more of the Sun’s heat being absorbed.

    Since you seem very interested in this sudden climatic change, could I ask you to briefly state your own hypothesis, or to state if you do not have one?

    E.P. Grondine
    Man and Impact in the Americas

    [Response: The evidence that most of the climatic effects are related to a slowdown/shutdown in the North Atlantic thermohaline circulation is very strong. The trigger for this THC change (and for the multitude of other similar events during Stage 3 and during other terminations) is likely to be meltwater/iceberg discharge related. This will likely be related to ice sheet/shelf instability/variations in runoff routing/lake drainage events etc. which for the most part are very poorly constrained (with the one exception of the 8.2kyr event). I have a pretty open mind about how any of this went down, but all I ask is that people discuss these things clearly and not conflate apples and oranges in a rush to support their preferred story. - gavin]

  30. 30

    Since one can never prove a negative, this situation will last for ever.

    No it won’t. It will last until somebody (anybody) adequately explains the geomorphology of the Nipigon basin, and the cubic nanodiamond formation, synthesis and deposition mechanism, well as the carbonaceous anomalies in the Lommel sediments (sorry about the confusion). Clearly Tain et al. and Pinter et al. have not done that, and nobody seems to want to address the Nipigon problem at all, which is the most glaring anomaly imaginable in all of this. I’m all for hypothesis falsification, as there is something to be learned even with falsification in both of these cases, and I would be the first person to jump on the bandwagon once the origins of these pesky little artifacts are cleared up. But until then, I’m skeptical of any claims of the death of the Younger Dryas impact hypothesis.

  31. 31
    E.P. Grondine says:

    Hi Gavin –

    Ah yes – but what caused that melting in the first place?

    I think your scenario is suffering from an observational bias, in other words, while we have plenty of data from the Atlantic we have damned little from the Pacific coast of North America.

    Of course, the oil companies have multiple cores from that area, but they are proprietary.

    I think we can both agree that climate is a global system. Thus in my view, without that data any model of the transition is tentative.

    All that I want to add is that impact science is evolving, with substantial revisions made – a look at Chicxulub/Shiva will show what I mean.

  32. 32

    30, Thomas,

    You are defining Nipigon as a “problem,” and I’m not saying someone shouldn’t consider it, but I find nothing at all to date the crater. Has anyone done so, or confirmed that it is in fact an impact crater and not something else?

    My point being that, while it certainly appears to be an impact crater, to assume that it is, and more pointedly that it formed 12,900 years ago, is a leap.

    1) Printer et al found no evidence (signatures) of an impact in the period in question.

    2) Nipigon appears to be an impact crater.

    QED) Any Nipigon impact did not occur in the time period in question, and so is unrelated to the YD.

    The first step to proving otherwise (and a giant step forward in in the YD impact hypothesis) would be to find some method of dating that impact crater.

    Correct?

  33. 33

    30, Thomas,

    After briefly studying the Earth Impact Database, I’m not even sure that it is an impact crater, and if it is, it must be far more ancient than 12,900 years old. At least, I need to withdraw my own statement that it at least looks like one. It actually looks to me more like a flood basin, or a now dried out lake bed, or something else.

    First, it lacks a serious degree of depression compared to the surrounding land — most impact craters appear to be deep enough to form large bodies of water, and given the number of lakes in that region, that fact that it doesn’t is rather surprising. Second, it lacks a central “rebound” feature. Third, it has too many other features which suggest geologic processes that would require millions of years — a crater that young, I would think, would look a whole lot more like a crater. The existence of a large lake which cuts across what should be the rim of the crater, and large gaps in that rim, seem like a very unlikely features to have formed in just the past 13,000 years.

    In addition to that, as an impact crater, it would rank as huge — 20 km across. The effects of such a recent impact would, I’d think, be pretty obvious (rather than lacking any clear signatures), and such large bodies do not appear to strike the Earth all that often.

    Again, I know little of this, but as a layman, glancing at a database of hundreds such craters… it seems that first the case must be made that it is a crater, and then what the date of impact is, before it can be put forth as a serious cause in the YD scenario.

    Do you have any evidence other than “it looks like” a crater?

    Wait a minute… am I acting like an ignorant denier? Or a skeptic? Oh, shoot, I have to go take a shower… iccck!

  34. 34

    Here is the list of anomalies and my general reasoning.

    Just south of Lake Nipigon is a large anomalous 25 km diameter geomorphism consisting of a heart shaped basin, lying across a fault line that delineates harder Canadian shield rock in the east from softer glacial till areas to the west, which was discovered, within a few minutes of searching Google earth maps, after deducing that this area must have been unusually hydrogeologically active at a time when ice covered the area 13000 years ago. Two cores in the area reveal highly disordered regolith down to the basement. Anomalous salt licks appear across the entire area which appear to originate from the basement regolith interface. All of the lake sediments in the area reveal elevated heavy metal concentrations. A smaller depression appears just to the northwest of the heart shaped depression. Other depression like areas appear to the east of this area, where dramatic cliff and channel systems appear to indicate some kind of intense megaflooding during and after Laurentide ice sheet disintegration.

    Acoustic soundings in the Lake Superior basin just south of this area reveal sediment layering indicative or Marquette ice sheet advances and retreats, specifically in an area that was supposedly totally covered in ice during the Younger Dryas. A wide variety of nanodiamonds and carbon fragments appear in Greenland ice and European soil samples in a layer of carbon rich sediments that represent the Younger Dryas period. Large water based impacts are now thought to create atmospheric ozone catastrophes which can put unusual extreme stresses on the vegetation and the wildlife.

    Impact simulator results indicate a low grazing angle impact of a volatile and carbon rich impactor of less than a kilometer, impacting on an ice sheet consisting of more or less pure water roughly a kilometer or more thick, could yield an impact feature of this magnitude and shape – a heart shaped blast basin and a smaller vapor impact basin, providing a credible synthesis, deposition and distribution mechanism for a large variety of nanodiamonds and carbon fragments. An ozone collapse would provide additional vegetation and megafaunal stresses on an already overhunted and stressed populations. Residual heavy metals and salts would be distributed into the area, eventually making their way into lake sediments and the water table. A subtle ammonia and nitrate spike would present itself in the ice core data.

    A large disruption of the Laurentide ice sheet would occur in this general area, initiating an instantaneous aas well as a longer term route for Lake Agassiz meltwaters, under and through the Laurentide ice sheet, through Lake Nipigon and down into the exposed lower Great Lakes, creating dramatic waterfalls and channels (the remnants of which are observed everywhere in the area) and eventually out to the Atlantic along the edge of the receding ice sheet. The ice sheet disruption in the area would be filled in by ice sheet advances during the Younger Dryas cooling now thought to be initiated by the long term Laurentide and other world wide ice sheet collapses, which continued throughout the entire Younger Dryas period. Subsequent post Younger Dryas ice sheet collapses would route even more meltwater through this region, scouring clean a great deal of the evidence of any such impact.

    This works for me, but I also admit that there may be even other more conventional and slower long term explanations for the abrupt climate change that we now think (more or less) was initiated by long term LIS meltwater flows into the North Atlantic and Arctic regions. I would be very happy if anyone could explain to me the nature and origin of this unusual geological feature in an area that was literally whacked by ice sheet advances and retreats, followed by periods of intense megaflooding, which also explains the host of the other unusual indicators discovered.

    Such as, for instance, cubic nanodiamods in the Younger Dryas sediments.

  35. 35

    Thomas,

    Impact simulator results

    Cite, please.

  36. 36

    There are a large variety of impact simulator programs available online, Bob – feel free to fiddle with the input parameters any which way you like.

    Remember, the large majority of the impact energy is deposited into a very thick sheet of almost pure water ice in this situation, material that is subsequently catastrophically mobile over a period of several thousand years.

  37. 37

    (PS. I have no dog in this fight, so please just stick to science rather than attacks on me, Kerr or anyone else)

    I have no dog in this fight either, Gavin, but what I do have is an open mind, and I’ve taken the time to speak directly with, or otherwise communicate with or inform, most of those who DO have a dog in this fight, and to dig as deeply as possible into the subject matter, rather than simply dismissing or selectively refuting only certain lines of evidence.

    So when I see phrases in the published literature and commentary like ‘requiem’ or ‘flunks out’ or even worse : ‘physical and statistical impossibility‘ about a subject matter that is capable of producing useful scientific insights even if falsified – I do have certain issues.

    This sort of seesaw, right, no wrong, no maybe right, oops wrong again, occurs on a continual basis in the condensed matter physics literature, and the Younger Dryas is an excellent example of this in geophysics.

  38. 38
    David B. Benson says:

    Edward Greisch @24 & others — The change of drainage of Lake Agassiz from southwards to the northwest (eventually into the Artic Ocean) agrees quite well with the onset of YD. So does the catatropic drainage of proglacial lakes to the east down the Mohawk/Hudson and thence to the Labrador Sea. Less well constrained, but still close to the onset of YD is the drainage of Baltic Ice Lake I.

    I suppose that all three of these ice dammed lakes were about ready to drain i8n any case; all a posited YD bolide does is synchronize the releases, an event not presumed for the similar YD III during termination 3.

    The dating of the drainages around Lake Nipigon places that events as much later. At the time of YD the area was entirely covered with the Laurentide ice sheet.

    Conservative archaeologist C. Vance Haynes, Jr., no proponent of the CLovis Comet nonetheless remarked that while Paleoindians could well have extirpated the megafauna of North America, he stated “but all at once?”

    I went through all the literature I could find and posted on the previous-but-one RC thread on this contentious subject.

  39. 39
    E.P. Grondine says:

    Hi Edward

    \Has anybody tested impacts into ice? The bolide would be the only source of carbon if it hit a miles-thick glacier. The bolide composition would control the carbon found.\

    Yes, Dr. Schultz started work on modeling ice impacts at NASA Ames.

    I kind of like the Lloydminster structure as a candidate, where there appears to have been isostatic rebound after an impact removed the ice load. There are several other candidate structures as well; it is entirely likely that there were multiple impacts at the YD. But since Gene Shoemaker’s passing, there is no coherent well funded effort in this field. And as regards larger impacts, you have to remember that hydrocarbons pool in the fractures from them, so a large part of the work remains proprietary.

  40. 40

    36, Thomas,

    There are a large variety of impact simulator programs available online, Bob – feel free to fiddle with the input parameters any which way you like.

    No thanks… I have way too much other work on my plate. What I’m interested in is knowing which program you used, and with exactly what parameters, and most importantly how valid that particular model is and how specific the results are.

    My point is that you saying that you did X, and so X is possible, does nothing whatsoever to prove that the feature you’ve identified is an impact crater, or… much more importantly… that such an impact occurred within the last 13,000 years.

    It could be a perfectly valid hypothesis, but currently “real” evidence points against it, and all that you’ve produced so far appears to be speculation. If you are able to advance your points beyond speculation, please do so.

  41. 41
    E.P. Grondine says:

    Hi Edward –

    “The change of drainage of Lake Agassiz from southwards to the northwest (eventually into the Arctic Ocean) agrees quite well with the onset of YD.

    Yes.

    “So does the catastrophic drainage of proglacial lakes to the east down the Mohawk/Hudson and thence to the Labrador Sea. Less well constrained, but still close to the onset of YD is the drainage of Baltic Ice Lake I.”

    My working hypothesis is that Lake Agassiz overflowed east after the melt triggered by its “sudden” northward drainage. A triggering event of a “tipping point”, if your will –

    “I suppose that all three of these ice dammed lakes were about ready to drain in any case; all a posited YD bolide does is synchronize the releases, an event not presumed for the similar YD III during termination.”

    If you go to http://cosmictusk.com, you can read what appears to be an Assiniboine/some Sioux memory of the drainage of glacial Lake Missoula, and the events surrounding it which I posted there.

  42. 42
    E.P. Grondine says:

    Hi Bob

    “My point is that you saying that you did X, and so X is possible, does nothing whatsoever to prove that the feature you’ve identified is an impact crater, or… much more importantly… that such an impact occurred within the last 13,000 years.’

    I can agree completely with you on your comment to Tom here. It is likely that he used the Purdue impact simulator, which I guess does not include modeling of ice impacts nor of Boslough’s ablative airbursts.

    “It could be a perfectly valid hypothesis, but currently “real” evidence points against it, and all that you’ve produced so far appears to be speculation. If you are able to advance your points beyond speculation, please do so.”

    And here I have to disagree with you, completely. Besides the hydrocarbon markers, there are gross neutron and proton signatures, and we have gross climate change, rapid simultaneous species extinctions, and there is a sudden quarry abandonment, indicating the death of roughly 95% of the population of North America.

    What is quite amazing is that several peoples appear to have remembered these events for some 13,000 years, and further remembered where they were at that time, and thus can be locked onto the archaeological record from 13,000 years ago on.

    E.P. Grondine
    Man and Impact in the Americas

  43. 43

    It could be a perfectly valid hypothesis

    No, it’s a viable hypothesis, nothing more and nothing less. To pronounce it dead, or flunked or scientifically impossible is unhelpful, in my opinion, especially since it continues to provide useful insight into natural nanodiamonds (NDs for the spam filter) origins, occurrence, distribution and synthesis, for instance, a fertile, current, interesting area of research.

    Any number of plausible parameters are capable of reproducing this feature, and hypersonic gun experiments with pellets into ice clearly show fairly plausible methods of producing lateral, subglacial blast waves.

    currently “real” evidence points against it

    Which explains why there are no published reports describing and explaining this unusual Nipigon feature, and what the anticipated forms and distributions might be of the naturally deposited terrestrial surface NDs, and why estimated deposition rates appear nowhere in the literature as far as I can tell. Perhaps Tyrone Daulton or one of the other authors of these papers would be willing to stop by here and give us their estimated cubic ND surface fluxes, and explain to us how relatively pristine cubic NDs arrived in the Lommel sediments, and if those deposition rates are not unusual, what other sediments have they analyzed for cubic ND content to verify surface fluxes, and if we might be able to rely on ice core ND content to track past impactor fluxes, or if they envision some other completely different origin of the cubic NDs.

    I’m always interested to learn of such things. I’d also be interested in any microstructural or compositional analysis of any impurities, and isotopic analysis of any of the detected surface or sediment nanodiamonds.

    So many questions, so little time.

    If you are able to advance your points beyond speculation, please do so.

    Sure, I’ll run right up to Lake Nipigon this weekend and collect and arrange for the international shipment of soil and rock samples, get them analyzed, and have a report ready for you my Monday morning, no problem. I’ll get right on it.

  44. 44
    Douglas Watts says:

    This came out quite recently from UMaine. Thoughts?

    Kurbatov A.V., P.A. Mayewski, J.P. Steffensen, A. West, D.J. Kennett, J.P. Kennett, T.E. Bunch, M. Handley, D.S. Introne, S.S. Que Hee, C. Mercer, M. Sellers, F. Shen, S.B. Sneed, J.C. Weaver, J.H. Wittke, T.W. Stafford, J. J. Donovan, S. Xie, J. J. Razink Jr., A. Stich, C.R. Kinzie, W.S. Wolbach, Discovery of a nanodiamond-rich layer in the Greenland ice sheet. Journal of Glaciology, v. 56, n 199, 749-759

  45. 45
    David B. Benson says:

    Douglas Watts @44 — Thanks. The authors suggest a dating of YD initiation, but conclude their abstract with however, more investigation is needed to confirm this association.

  46. 46
    Hank Roberts says:

    Has anyone tried doing MRI on fossil material or on drill cores?
    http://www.physorg.com/news185737514.html

    “… nanodiamonds have excellent biocompatibility and can be used for efficient drug delivery. This new work paves the way for the clinical use of nanodiamonds to both deliver therapeutics and remotely track the activity and location of the drugs…. the first published report of nanodiamonds being imaged by MRI technology, to the best of the researchers’ knowledge…. Ho and Meade imaged a variety of nanodiamond samples, including nanodiamonds decorated with various concentrations of Gd, undecorated nanodiamonds, and water. ”

    Seems they might bioaccumulate??

  47. 47
    Edward Greisch says:

    43 Thomas Lee Elifritz: “Any number of plausible parameters are capable of reproducing this feature, and hypersonic gun experiments with pellets into ice clearly show fairly plausible methods of producing lateral, subglacial blast waves.”
    Can you tell us any more about the hypersonic gun experiments with pellets into ice? Do you happen to know of any downloadable papers?

  48. 48

    43, Thomas,

    No, it’s a viable hypothesis, nothing more and nothing less. To pronounce it dead, or flunked or scientifically impossible is unhelpful…

    But I did no such thing. I said that as yet you have failed to support the hypothesis with sufficient evidence.

    Sure, I’ll run right up to Lake Nipigon this weekend and collect and arrange for the international shipment of soil and rock samples…

    The sarcasm is lost on me. I didn’t come in here posting my own pet theory without sufficient supporting evidence, expecting others to take my proclamations at face value and without question.

    I’m pretty sure that gremlins caused the YD, and if someone would take the time to engineer a time-vapor-gremlin-ghost-detector, they’d know it. It’s not my fault that no one has taken me seriously enough to build a TVGGD yet. It’s still a valid theory, and to my mind, totally true until someone proves otherwise…

    I’ll say it again. The post said:

    …none of the original YD impact signatures have been subsequently corroborated by independent tests. Of the 12 original lines of evidence, seven have so far proven to be non-reproducible. The remaining signatures instead seem to represent either (1) non-catastrophic mechanisms, and/or (2) terrestrial rather than extraterrestrial or impact-related sources.

    Simplified, there is no evidence of an extraterrestrial impact related cause of the YD. You cannot refute this simply by saying that you’ve found a geological feature which looks like it might be an impact crater.

  49. 49

    42, E.P. Grondine,

    And here I have to disagree with you, completely. Besides the hydrocarbon markers, there are gross neutron and proton signatures, and we have gross climate change, rapid simultaneous species extinctions, and there is a sudden quarry abandonment, indicating the death of roughly 95% of the population of North America.

    I’m not sure what you’re saying here. According to Pinter et al, as per to OP, there are no valid signatures for an impact event. The fact that there was gross climate change, rapid simultaenous species extinctions, and population loss in North America says something happened in the YD, yes, but not that it was impact related. You can’t say something like “there was an effect, so X must have been the cause.” There was an effect, so there must have been a cause, but there is no evidence yet as to what the cause was.

    That said, the paper discussed in this OP seems to say pretty unequivocally that it was not an impact event because the signatures of such an event do not exist. Until evidence is produced to the contrary, that particular option is off the table.

    That’s not to say someone can’t produce evidence tomorrow. If so, we can argue it tomorrow. Today, there is no such evidence.

  50. 50
    Edward Greisch says:

    Several people: Thanks.


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