Extraterrestrial impact kills megafauna?

  1. I'm still working on the last glacial transition. The other week I drafted this comment:

    Any questions?
     
  2. jcsd
    Earth sciences news on Phys.org
  3. (necropost) Meanwhile it looks like the comet lost its sparkle.

     
  4. Another necropost (but the previous posts have not lost any significance).

    While the impact idea waned, several scholars pursue an extraterrestrial event of another kind, solar activity.

    Paul A. LaViolette (2011) Evidence for a Solar Flare Cause of the Pleistocene Mass Extinction, February 18, 2011. Radiocarbon, vol. 53, No. 2 (June 1, 2011): 303 - 323

    Abstract

    I also recommend reading The mysterious onset of the Younger Dryas of an author who is well known to some of us :wink:

    There are however other devellopments on which I will report later that give some substantiation to Richard Muller's favorite quote of Josh Billings:

     
    Last edited: Jun 3, 2011
  5. Notice that Laviolette (2011) builds his case around a 14C carbon spike in the atmospheric CO2 around 12900 years ago that correlates with the onset of the Younger Dryas.

    Notice the dating problems mentioned in the OP:

    Finally notice also that Fiedel (2011) in the previous post recognises this dating problem and mentions for calibration purposes a new calibration table INTCAL09.

    Would a comparison of the calibration tables INTCAL04 and INTCAL09 shed some light on these issues?

    I wondered that too and the result was ...erm, remarkable. I think that is worth a seperate thread.

    Oh if anyone wants to have the cited papers for scrutiny, please pm me.
     
    Last edited: Jun 3, 2011
  6. After some consultation, it may be better to keep the narration in this thread, but I need to elaborate on carbon dating techniques and calibration to demostrate how and why things went wrong here with the extrateresstrial hypothesis, the 14C spike and the dating of the lower (older) Younger Dryas boundary.

    Now you could read the wiki about carbon dating which is excellent or take it to the detailed level with Reimer et al 2009. But let me elaborate about that in the next post.
     
  7. Okay so a quick overview of carbon dating then, which is based on the amount of nuclear unstable carbon-14 with a half value time around 6000 years.

    Carbon-14 is produced due to interaction of cosmic rays in the atmosphere in which neutrons interact with 14Nitrogen atoms as follows:

    [​IMG]

    The 14C oxidizes and mingles with the atmospheric CO2 entering the carbon cycle. As the 14C decays again with time, the ratio of 14C to normal 12C decreases and this says something about the age of the mechanism. If the starting ratio was constant, dating would have been rather simple

    However since these processes are highly variable we do not know the initial 14C/12C ratio. So we would need to calibrate the dating with something that can both be carbon dated and dated otherwise.

    Far out the best calibration is done with things that due have some annual accumulation; tree rings, annually layered deposits in deep lakes (varves), speleothems and coral.

    Of these tree rings are the most accurate as the 14C changing processes are the simplest, the wood is made directly from atmospheric CO2 and can obviously be carbon dated directly. The problem however is that good treering assemblies go only back as far as about 12,500 years

    Annual lake varves can also be counted very accurately, the problem is that it does not contain a lot of carbon datable macro fossils.

    annual Speleothem- and Coral rings can also both be counted and carbon dated (carbonates), however there is also a problem here as the carbon is not directly coming from the atmosphere.

    That's where the biological fertilizer comes in contact with the rotating vanes of a machine that produces a high speed low pressure airflow.

    More later
     
    Last edited: Jun 4, 2011
  8. I am reading and taking all this in - honest

    So thanks for posting.

    :smile:
     
  9. Thanks for the feedback. I appreciate that greatly. I'm just trying to illustrate where certain parts of earth science stands now and how important it is to try and think of everything that can affect the 'whodunit'-reconstruction.

    Anyway, to get back to the problems with coral or any marine carbon dating, it's the mixture of carbon sources. For air sources we dont mind a few weeks or even years between the formation of the 14C in the higher atmosphere and the time it got fixed by photosynthesis, entering the biologic part of the carbon cycle. But for the sea/ocean is different. Some carbon did indeed enter the water recently but it is mixed with dissolved carbonates that have been in the water for a long time, like dissolved limestone etc, and hence depleted from 14C, decreasing it's ratio. This is called the "basin effect".

    Now if you have overlapping calibration series of land and marine data, you can calibrate the basin effect (calibrate the calibration) and it is found in some instances that the basin effect is rather constant and amounts for a few hundred years carbon dating.

    But if you find a couple of instances where this is true, is it also always true?
     
  10. Dotini

    Dotini 724
    Gold Member

    Fascinating investigation of a good mystery, Andre. I've been interested in this for a long time, ever since I marveled at the saber-tooth tigers of the La Brea tar pit museum, so I appreciate your posts very much.

    If there was a super-CME which wiped out megafauna in the Americas, how might it be that the megafauna of Africa were spared?

    Respectfully,
    Steve
     
  11. Evo

    Staff: Mentor

    Is there anything you would like me to ask Stuart?
     
  12. Maybe advise him to take note of this thread. There is an issue coming up with his paper. Maybe, we could have a good discussion.
     
  13. Excellent question Steve, One could probably to electromagnetic cosmic influence to be redirected towards the poles like the aurora borealis and aurora australis, but I don't think there is a reason for such audacities.

    Anyway, to continue, as I said earlier

    So having some carbon dating calibration back ground now, it's maybe time for the wow.

    data sets: Intcal09, Intcal04.

    Been busted once for making my own graphs, but nobody else does it, so I take that risk:

    [​IMG]

    Ideally, both graphs should overlap with only tiny abbarations, but the difference in our time frame of interest is huge, notice that the calibration of ~10,900 14C years, the approximate boundary of the Younger Dryas, (yellow line) used to calibrate roughly to something like 12,870 calendar years BP with Intcal04, but it calibrates now, with Intcal09, to something like 12720 Calendar years.

    That is major and far fetching, but why is that so?
     
    Last edited: Jun 4, 2011
  14. Oh, before we concentrate on the why, remember that Laviolette (2011) mentions a radio carbon spike in this time frame:

    We see in the intcal data sets linked to in the previous post that there is also a column "Delta 14C permil". That looks like the ratio of radiocarbon. So we can plot that too for both Intcal tables:

    [​IMG]

    Sure enough Intcal04 shows a significant radiocarbon spike corresponding with the mentioned Caracio Basin varve record, but look what happened with Intcal09. It's gone, only a little spike remains, hardly outstanding against other local spikes, but some 250 years later.

    That is even more far fetching.
     
  15. So for the why question, we need to scrutinize the original publication Reimer et al 2009. (I see that I mutilated the earlier link in my previous post yesterday and it doesnt work, but nobody noticed :cry: What is that guys? Don't you care reading the science behind all this? )

    Anyway considering this discrepancy we just discovered, Reimer et al write:

    But the result of that decision is far fetching
     
  16. lisab

    Staff: Mentor

    I'm a noob on this topic, but that 'basin effect'...I'm not getting a lot of info on that term. I tried looking up 'lake effect' but that's a meteorological term about snow formation.
     
  17. Right Lisa, good catch, my bad. Mea culpa. :redface: I meant to say 'reservoir effect', the same mentioned as 'reservoir age' in Reimer et al:

    So there is the whole problem, changes in the ocean flows, whcih were disrupting the expectation that the reservoir effect caused a more of less constant age different. But this assumption produced a spurious 14C spike that sent future researchers on a tangent in an attempt to explain that. Hence LaViolette 2011 loses it's principle cause, no more big radiocarbon spike at the onset of the Younger Dryas.

    Obviously we can also say something more about the timing of the mysterious onset of the Younger Dryas now next.
     
  18. Anyway, that decision in Reimer et al (2011) keeps bugging me:

    If a scientist 'could, in theory,' solve a problem, he will, I would think. Moveover it would be pretty important to know the reservoir age devellopment. So why not here?

    It gets more intruging if you look at the graphs of the original Hughen et al 2000 in science, particurly the line up with the Younger Dryas in the GISP2 icecore, also showing the -now- spurious 14C spike.

    [​IMG]

    This has always looked like a pretty solid base to establish the onset of te Younger Dryas at 12,900 Cal years BP. But now these data between "12,552–12,944 cal BP' are essentially voided by that decision.
     
  19. I promissed issues wth Fiedel (2011):

    I observe that his analysis is accurate most of the time, except however.., and maybe I may quote the following:

    I dont understand the boldface (mine). The orginal dating of the periglacial oscilations is publiced in Brauer et al (2001) Lateglacial varve chronology and biostratigraphy of lakes Holzmaar and Meerfelder Maar, Germany Boreas 30 pp 83 - 88. There is no mentioning of any ice core in that publication, just the correlating of the varve stratigraphy without external calibrations and it finds for the Younger Dryas 11 590–12680 varve years BP in the Meerfelder maar and for the Holzmaar, 11600–12 606 varve years, independently of any other dating. The difference is discussed.

    ----

    Fiedel then mentions multiple research results, including the 14C spike problems, all suggesting that the onset of the Younger Dryas -in Europe- was around 12,700, but nevertheless he concludes:

    Unfortunately, with the deletion of exactly those Cariaco data in INTCAL09, much of the substantiation for that assessment has disappeared.
     
    Last edited: Jun 6, 2011
  20. Anyway, the Cariaco problem keeps bugging me. This is what Muscheler et al (2008) (Cited by Reimer et al 2009) propose:

    While Hughen et al (1998) found originally:

    But maybe we are looking at the wrong problem. As Fiedel (2011) sums up, there exist several annually counted geologic records for the whole younger dryas. European lake varve records and the GRIP ice core tend to count ~1050 years, whereas the GISP-II ice core and the Cariaco basin foraminifera varves counted ~1300 years. So maybe it is not a reservoir age problem but a year counting problem?
     
  21. That counting problem could be supported by the work of the Polish Quartenary geologist Tomas Goslar in Goslar et al 1999, Variations of atmospheric 14C concentrations over the Allerod-Younger Dryas transition, Climate Dynamics (1999) 15 : 29Ð42

    It compares the carbon dating versus annual varve counting of the Swedish lake Madtjarn and the Polish lake Gosciaz
    (Sorry Borek, my keybord does not produce all those random outcrops on the letters) against marine counts of corals and sure enough the Cariaco basin.

    [​IMG]

    The caption:

    The area of interest is obviously the red oval where the spline function goes down steeply while the Cariaco crosses go almost horizontal. I guess that could have been the hypothetical result if the Cariaco varves count was too high.

    Notice also that Goslar et al place the older Younger Dryas boundary around 12650 Cal year BP.

    But the Cariaco chronology was selected for the INTCAL tables while the other were not. It's a choice I guess. But objective?
     
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