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Extraterrestrial impact caused Younger Dryas?

  1. Jan 18, 2008 #1
    Some earlier threads have been dedicated to the Younger Dryas and a possible connection to an impacter. Here is the full paper about it.

    Firestone et al 2007, Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling, PNAS Vol 104, no 41, 9 Oct, pp16016–16021

    Firstly I'm interested in the dating ~12,9 ka:

    That's pretty clear. Open and shut case? Let's have a look here.

    This picture clearly shows this transition. Consequently:

    Lücke, A.; Brauer, A. 2004 Biogeochemical and micro-facial fingerprints of ecosystem response to rapid Late Glacial climatic changes in varved sediments of Meerfelder Maar (Germany),Palaeogeography, Palaeoclimatology, Palaeoecology, 211, 1-2, 139-155 p.

    So what is it? 12,9 ~ 0.1 Ka or 12,690-12,670 counted years BP and what are those relatively warm YD summer temperatures doing there?
  2. jcsd
  3. Jan 18, 2008 #2
    So how about getting the ice cores here to see when the Younger Dryas started.

    We plot the stable isotope data of the three main cores, the European NGRIP, GRIP and the American GISP-2.

    So if we plot those for the time frame of interest, we get this.

    Note NGRIP is a bit curious giving two values per 50 years (grey). So I averaged that (blue). Even more curious is that the timescale started at 2000AD, while the standard is 1950, which would have caused a mismatch. So I corrected for that.

    Now, if we assume that the Younger Dryas started halfway the last spike down then NGRIP (blue) and GRIP (black) agree nicely between 12,650 and 12,700 counted annual ice layers. GISP2 (red) is definitely the outlier around 12,850 years ago.

    How about yet another source, Isarin and Bohncke 1999 have made an extensive compilation of paleo flora records in Europe and wrap it up thus:

    For carbon dating calibrating is used the INtcal04 calibration tabel

    It's starting to look like we have two Younger Dryases, one phase starting around ~12,850 calendar years BP according to the American and European carbon dating and the GISP-II ice core and one starting around 12,670 calendar years BP according to European annual layer counted records and the GRIP and GISP-II ice cores, the latter with warm summers? What is going on here?

    Attached Files:

    Last edited: Jan 18, 2008
  4. Jan 19, 2008 #3
    Not interesting? Nagging about a mere 200 years dating discrepancy on a scale thousands of years? It should be though, when it appears to challenge one of the most important fundamentals of climate science.

    Let's see what is the likely correct time frame of that isotope spike going down, the supposed start of the Younger Dryas. it seems that the mentioned number of records suggesting a time frame of 12,900 - 12,850 are at par with the records for the 12,700 - 12,650 time frame. However this is only optical, since all the calibrated carbon dates are now reflecting the age of the counted layers, as the INTCAL04 calibration table is generated from comparing the annual layer count with the carbon date of the same specimen.

    Note also here that the stable isotope records (d18O) from the Ammersee in Germany and lake Gosciaz in Poland concur with high accuracy with GRIP. There is very little doubt that the isotopes dropped in the period 12,700 - 12,650 Cal BP.

    That would mean that the single outlier is now the GISP-2 ice core only.

    But what about all those reports on the cold starting at 12,900 cal BP. Take this one for instance:

    Van’t Veer R., G.A. Islebe, H. Hooghiemstra, 2000; Climate change during the Younger Dryas chron in Northern South America: a test of the evidence. Quartenary Science Review Vol 19 (2000) pp 1821 - 1835

    (all carbon date calibrations and emphasis mine)

    To me that's a wow! So they seem to see the same cold period in Columbia as Isarin and Bohncke 1999 in Europe as mentioned before and also some warming after 12,590 Cal BP versus 12,640 Cal BP respectively. Pretty close to the 12,700 - 12,650 Cal BP d18O isotope drop.

    So we tested the hypothesis if the Extraterrestrial impact did cause the Younger Dryas and the result is that it would depends on your definition of when the Younger Dryas started, the North American events around 12,900 Cal BP could be related to the widespread cooling noted around that period. But it does not concur with the 12,700 Cal BP drop in the stable isotopes ratio (d18O).

    But we seem to have tested also another hypothesis here.

    Alley R.B. 2000, The Younger Dryas cold interval as viewed from central Greenland
    Quaternary Science Reviews Volume 19, Issues 1-5, 1 January 2000, Pages 213-226.

    As said, it appears that the comparison of relevant records is showing that the summer temperature in Europe and the general temperature in Colubia rose in about the same period that the stable d18O isotopes of the European lakes and the GRIP-2 ice core dropped. So if the European lake isotopes did not reflect the rise in summer temperatures why would the Greenland isotopes do so?
    Last edited: Jan 19, 2008
  5. Jan 19, 2008 #4
    okay, let's see if we can wrap this up in reasonable English.

    early research of all kind of geologic records, mostly based on remains of plants, shows that there was a sudden cold period not too lang ago, an apparant return to ice age conditions, which was named the Younger Dryas after abundant pollen of the near arctic Dryas flower. As soon as carbon dating was invented the period was determined to be between 11,000 and 10,000 years Before Present - BP - (=1950).

    But with the maturing of counting techniques like annual tree ring series (dendrochronology) and annual individually visible sediment layers in lake sediments annual coral growth it became apparant that something was wrong with the carbon dating technique, notably the start concentration of radioactive carbon isotopes. But this problem could be solved by comparing carbon dating with counting. This meant that the radiocarbon dates of 11,000 - 10,000 BP calibrated to 12,910 cal BP and about 11,400 Cal BP counted years

    Parallel to those devellopments there was the research to the ice cores of Greenland and Antarctica, which also allowed for layer counting to determine age to a certain extend. Moreover using the heavy to light isotope ratios of the ice it was thought that the temperatures could be reconstructed. So the Dye cores and the GISP cores made the news by showing the distinct isotope ratio drop, the younger dryas, concurring with the geologic records of plant remains?

    So things looked like a pretty convincing proof that isotopes are indeed a good paleo thermometer. There had been several challenges to that assumption.

    But there was a glitch. several counted records insisted that the Younger Dryas begun after 11,700 cal BP while the plant remains and the GISP-2 ice cores suggested before 11,850 cal BP. So with the evidence suggesting an extra terrestrial impactor, emphasis was given again to the return to cold conditions around 11,900 Cal BP. However, several individually and independently counted records agreed on the isotope drop after 11,700 Cal BP. But -I did not mention this before- the cooling of 11,900 years ago concurs with the rise of the isotopes in the ice and European lake cores, suggesting that it warmed.

    Meanwhile the plant remains of the different geologic records suggest that after 11,650 the climate in Europe and in the north part became drier and warmer in summer time but this concurs with the drop in isotope values which suggest a drop in temperature.


    Isotopes: warming
    geologic record: cooling and wet

    Isotopes: Cooling
    geologic record: warmer summers and arid.

    So which records do you want to believe?

    To confirm the confusion have a look here:


  6. Feb 12, 2008 #5
    Another player in this field not mentioned before is the Laacher see in Germany. It's actually a Maar,
    This eruption was the largest of the late Pleistocene in Europe and produced an ash or tephra layer which is widely visible in Europe. It's eruption date? 12,900 years ago as dated by several independant method. Litt et all count the Laacher See tephra at 12,880 annual sediment layers (varves) in the sediments of the Meerfelder Maar but that is also 200 varve years before the onset of the Younger Dryas.

    See in the OP that Firestones extraterestrial event is also dated at 12,900 years ago. How big is the coincidence of an extreme rare big impact event codating within a few years with an extreme rare mega eruption? Could the eruption of the Laacher see be responsible for any of the evidence that Firestone finds or could the impact have triggered the eruption of the Laacher See?
  7. Mar 7, 2008 #6
    meanwhile, today Science magazin, features an article, debunking the comet impact.

    Kerr R.A 2008 Experts Find No Evidence for a Mammoth-Killer SCIENCE VOL 319 7 MARCH 2008

    The article claims that the comet related phenomena can be explained differently.
  8. Jun 8, 2008 #7
    Andre, you will have to travel to ai-Jane to read my reply to your astute thread. Unfortunately the moderator/admin here is not open minded enough to allow me to make my 15 posts in order to link to important sites.

    Sorry, but I am gone, to find some other venue.

  9. Aug 20, 2008 #8
    Meanwhile a new paper has been publised in PNAS:

    Buchanan, Briggs, et al 2008 Paleoindian demography and the extraterrestrial impact hypothesis, PNAS August 19, 2008 vol. 105 no. 33 pp 11651–11654

    That's surprise as it was generally assumed that the Clovis culture disappeared without a trace to be replaced by the Folsom several centuries later with distinct differences in fluted points.


    John Maynard Keynes
  10. Dec 30, 2008 #9
    I saw a programme on TV about the Rick Firestone suggestion of a comet airburst event around 12.9 ka and the evidence of a black mat and magnetic sphericules etc. http://www.newscientist.com/article/dn11909. However, I found the explanation of the resultant dramatic cooling very unconvincing. Also the absence of impact craters was explained by laboratory test firings into sheets of ice, but even these showed some shallow craters. It seemed to me that the evidence pointed towards that of a supervolcano, especially the drop in temperature due to the release of SO2 gas. An underwater supervolcano would explain the unusual sphericules perhaps? What do you think?

    Here is an extract from the 2007 book 'Supervolcano' by John Savino and Marie D. Jones:

    "While extremely active, there are no known supervolcanoes on the mid-ocean ridge system or in the deep ocean basins. The reason for this is the relatively thin oceanic crust, as opposed to the thicker continental settings and rhyolitic compostions for the land-based volcanoes." (emphasis is mine)

    The oceanic supervolcano seems a better fit for a mass extinction than a comet event in my opinion.
  11. Dec 30, 2008 #10
    If there was a release of SOx, then that must be visible in volcanic sulfate tracers in the Ice Cores. We see a spike (369 ppb) at 12,932 yrs but a bigger spike (524 ppb) at 13,033 years. However we know that one of the biggest Volcanic events at that time was the Laacher See Eruption, and there is something strange with the timing of that event. It's counted 200 annual sediment layers (varves) years in the Meerfelder maar before the onset of the Younger Dryas (Lücke and Brauer 2004)
  12. Dec 30, 2008 #11
    Was this the size of a supervolcano event? How could the ash deposits reach the North American great lakes area? In the same TV series I mentioned above, it was shown that the Indian subcontinent was covered in ash and caused a mass extinction around 74,000 years ago by the Mt Toba eruption which lasted for days. This was a supervolcano event bigger in size than Yellowstone. Due to the wind direction the debris drifted over India. They reported that the human population must have been reduced to something like 600, to account for their low genetic diversity. They estimated that the emission of SO2 reduced the temperature by 5-6 degrees for several years. The North American cause for the estimated 10 degree temperature drop and continental mass extinction implies an eruption even larger than this. The evidence of such an event from Laacher See would be obvious if this was the case. The size of the eruption makes me dubious because of this.
    Last edited: Dec 31, 2008
  13. Dec 30, 2008 #12
    The Mt Toba event appears to be visible in the aforemention GISP-II volcanic sulpor tracers at 71058 years with 466 ppb Volcanic sulphur, alternately it could be concealed in the frequent volcanic tracers between 72.5 Ky and 74 Ky. An unusual active period.

    About the Laacher see eruption, this is the crater of the explosion, the Laacher See, a volcanic "maar", not a small boy, the biggest in the Eifel in Germany:

    http://www.esys.org/rev_info/laachsee.jpg [Broken]

    The ashes (Tephra) did not reach America but the aerosols disperse world wide of course.
    Last edited by a moderator: May 3, 2017
  14. Dec 31, 2008 #13
    I'm feeling a bit confused Andre, are you suggesting that the Laacher See eruption is responsible for the evidence Rick Firestone attributes to a comet impact/airburst event? I presume not of course.

    Incidentally, I've suddenly woken up to the significance of the Allerød dramatic warming event of around 14,000 B.P. Although interstadials are defined by region, the Allerød period is not, being global in its effects; that is, the temperature and sea level rose everywhere, not just in north Europe. The Greenland ice core graph shows this was a sudden increase in temperature by around 10 degrees! What could have caused that? This is the first event before the YD climate variations and therefore could be the most influencial, with the following millenia of climate change still being connected to this initial event. I tentatively propose that an oceanic supervolcano eruption could cause such a rise in temperature by the emission of CO2 gas into the atmosphere. Similarly, an oceanic supervolcano could be the cause of the Devils Hole sudden warming signature. These huge events could be the cause of ice age terminations in general. Perhaps only the gases escape to be released from the surface, whereas the ash is absorbed by the ocean, hence the lack of signatures in the ice cores?

    Attached Files:

    Last edited: Dec 31, 2008
  15. Dec 31, 2008 #14
    No the idea was that a super volcano with cooling sulphur would have left Volcanic tracers in the ice cores. But we see only the Meerfelder maar eruption which may have been in the same order of magnitude of the Tambora eruption that caused the year without summer.

    Also there is something strange about the Bolling Allerod warming as narrated here
  16. Dec 31, 2008 #15
    Okay, you're saying the Meerfelder maar eruption could be responsible for the year without summer. But we still need to explain the Allerod warming and the black mat/extinction event of North America.

    I'm still confused, Andre. With regard to mid-ocean ridge supervolcanoes, I propose that any SO2 gas emissions could be mostly absorbed by the overlying ocean to form sulphuric acid. CO2 emissions could be much greater for a particular supervolcano and therefore be the only significant outpouring. This seems a plausible explanation for dramatic global warming periods in the order of 10 degrees. Do you not think so?
    Last edited: Dec 31, 2008
  17. Dec 31, 2008 #16
    You don't see it, the other evidence as linked to, do not support that dramatic warming. What you actually see is a deamatic shift in isotope ratios, isotope ratios are dependent on temperature, but is the conclusion logically correct that hence there was warming?

    See the affirming the consequent fallacy
  18. Dec 31, 2008 #17
    So what is your explanation for the dramatic shift in isotope ratios then? The earlier link to the 'list' wasn't very convincing, more confusing. Perhaps you could go through each example a bit more slowly. I want to be on your side, but the temperature proxies of the ice cores have a good record, I believe. They won't be perfect of course. Are you saying the Devils Hole proxy data isn't registering an abrupt temperature increase either?
  19. Jan 2, 2009 #18
    Interestingly, here is an article which states that Yellowstone caldera erupted 70,000 years ago http://news.yahoo.com/s/ap/20081230/ap_on_sc/yellowstone_quakes [Broken]. This is a likely candidate for the 71058 date of the volcanic sulphur tracer.
    Last edited by a moderator: May 3, 2017
  20. Jan 2, 2009 #19
    Here is an early warning sign that isotopes do more than tracking temperatures:

    Edwards T.W.D, B.B. Wolfe 1996 Influence of Changing Atmospheric Circulation on Precipitation d18O–Temperature Relations in Canada during the Holocene, Quartenary Research 46, 211–218 (1996)

    with as key sentence:

    Anyway that doesn't say that there was not a comet: Fresh from the press:

    Kennett D.J, et al 2009 Nanodiamonds in the Younger Dryas Boundary Sediment Layer, Science 2 January 2009: Vol. 323. no. 5910, p. 94


  21. Jan 2, 2009 #20
    Very interesting. It shows that changes in oxygen isotopes aren't necessarily measuring a temperature change. The Allerod period is recognised as being a global warming though. Do you dispute this conclusion?

    If nanodiamonds can arrive in an impactor, I don't see how anyone can categorically say they can't arrive from mid-ocean ridge highly explosive volcanic eruptions.
    Last edited by a moderator: Apr 24, 2017
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