Home > Carbon 14 Dating > An Abstract for Today

An Abstract for Today

October 4, 2014

clip_image001

The chronology of long Upper Pleistocene loess sequences in Eurasia is based on combined pedostratigraphy and radiocarbon dating of high-quality charcoal. The accuracy of such a chronology depends on the reproducibility and precision of the 14C dates. However, certain dates may show discrepancies with regard to their chronostratigraphic context based on series of coherent dates. In order to evaluate the consistency and variation in the 14C dates obtained from small charcoal pieces, this question was tested on a set of spruce wood remains with well-preserved tree rings found in the Middle Pleniglacial loess-loam sequence of Kurtak (central Siberia). Tree-ring analysis of five fairly large wood pieces from three successive layers, dated to about 30.0, 30.8, and 32.2–32.5 ka BP previously, was done by continuous sampling of 90–150 rings on each wood piece. This enabled direct comparison of the succession of tree rings with the 14C dates. A total of 133 dates was obtained for the five wood pieces. The results show fluctuations in the 14C dates within a time range between 1000 and 2000 yr. Four possible causes for such variation will be discussed herein: (1) internal variability of the AMS dating method; (2) outliers; (3) variations in the 14C background; and (4) external factors such as past atmospheric 14C variations.

The paper is Variability in Radiocarbon Dates in Middle Pleniglacial Wood from Kurtak (Central Siberia) by P Haesaerts, F Damblon, N Drozdov, V Checha, J van der Plicht appearing in Radiocarbon, Vol 56, No 3 (2014).

Tell me again about how reliable carbon dating always is.

Hat tip to Joe Marino

Categories: Carbon 14 Dating Tags:
  1. October 4, 2014 at 5:36 am

    One cannot compare the dating of the Shroud with the dating of a 30,000 years old wood remain.

    • Dan
      October 4, 2014 at 5:50 am

      Why is that?

      • October 4, 2014 at 6:11 am

        The calibration of these ancient dates has always offered problems, often because the problems of contamination over so many years is more acute. I recall reading quite a lot about the distinct problems when you reach 50,000 years (50 ka) BP. Adjustments of these dates, here it appears one to two thousand years in 30,000 are significant and ,rightly,are taken seriously here but unless the specific reasons for the discrepancy relate to the Shroud testing I cannot see the relevance. Even it they were it would only shift the Shroud dating at the most forty years one way or the other ( and remember that it could be one way or the other so it might place the Shroud later not earlier – it does not fundamentally discredit the testing process as such.)

      • October 4, 2014 at 8:34 am

        Consider that the 30,000 years old wood has been left with about 2 percent of modern standard. The Shroud has over 90 percent modern standard. The less the amount of C14 left, the more difficult is measuring it exactly. Moreover the same amount of possible inquinating atoms shifts the 2 percent ratio much more than the 90 percent ratio.

        • Dan
          October 4, 2014 at 8:35 am

          Thanks.

  2. October 4, 2014 at 6:55 am

    In a nutshell, the ancient wood dated to 30000 years, plus or minus 3%. The shroud dated to 1300 years, plus or minus 4%. That’s how reliable radiocarbon dating is. The paper was not written in disappointment at how inaccurate radiocarbon is, but as research into making an accurate and reliable dating method even more so.

    • Dan
      October 4, 2014 at 7:00 am

      Thanks.

  3. Max patrick Hamon
    October 4, 2014 at 7:18 am

    Hugh wrote, “That’s how reliable radiocarbon dating is”.
    When it comes to direct AMS 14C dating of artifacts such as the TS, do not forget the human factor involved in terms of sampling and possible unknown contamination(s) (for lack of complete history of its conservation and cleared-up archaeological context), please.

  4. daveb of wellington nz
    October 4, 2014 at 4:08 pm

    I first encountered the theory of statistics and probability during my engineering degree around 1960. Following graduation I followed it up with several supplementary papers in the topic during the following 20 or so years. My first formal text was by Paul G Hoel, Professor of Mathematics, University of California in L.A. published in 1962, It was an excellent work, and despite other subsequent texts I often had cause to refer back to it, and occasionally still do. Towards the end of my career for some ten years during the 1990s I was advising the Internal Audit of a major NZ Corporate on the design of their sampling systems for audit purposes.

    I believe a scientist seeks to obtain an absolute rigorous truth, which in theory is actually unattainable. He has to be satisfied with building a theory which is as close to the truth as the evidence will take him at that particular time. But he knows that ultimately it will be surpassed as new knowledge comes to hand. The history of scientific progress adequately demonstrates that.

    In engineering, the engineer is expected to deliver within an acceptable time frame, he has little time available to him for research, and he has to be content with an acceptable economic solution that his knowledge can take him at that particular time. In our Law courts the attempt to arrive at the truth is one notch lower than that of the scientist, and persons are condemned or liberated on the balance of reasonable probabilities, and a weight of circumstantial evidence may be sufficient. In Audit, the quest is one notch lower again, and the auditor is content to give his assurance on such evidence as he may judge is sufficient according to the various tests he can economically apply.

    Hoel discusses the question of the validity of sampling tests at length as early as Chapter 3 ‘Nature of Statistical Methods’. “A statistical hypothesis is an assumption about the frequency function of a random variable.” “A test of a statistical hypothesis is a procedure for deciding whether to accept or reject the hypothesis.”

    He then distinguishes between two types of error. The Type I Error occurs when the hypothesis is actually true, but the sample falls into the critical area when the hypothesis is therefore falsely rejected. The Type II Error occurs when the hypothesis is actually false but the sample falls within the true area, and so the hypothesis is falsely accepted. Sampling therefore does not yield an absolute truth, but only a relative truth, it is no more than one particular method for making a decision. It is an underlying assumption of course that the samples will also pass standard tests for being adequately representative, and there must be a sufficient number of samples which adequately demonstrate the amount of dispersion.

    In the case of the 1988 C-14 samples on the Shroud, there was in fact only one small sample taken, and there have been several valid questions raised that it was not in fact truly representative of the whole. This single sample was split three ways, and the individual laboratories split their shares of the sample again so they could each run three individual tests on their share. The control pieces have been criticised as inadequate, and of a different type from the sample and not comparable to the parent cloth. Their results have been reported as apparently failing even a standard chi square test. Even so, it might be asserted that the tests could be a valid result as far as the original sample was concerned. However it cannot be asserted that the tests have been sufficiently rigorous to make any definitive statement about the age of the original cloth. It is certainly not an absolute truth, it hardly passes as any kind of relative truth, I would not pass it even as an adequate audit test, and scientists ought not to hang on to it as passing any kind of worthwhile authentic scientific test!

  5. October 4, 2014 at 6:01 pm

    How very complicated. In practice, you find an artifact which has a historical provenance to the middle of the 14th century, snip off an inconspicuous corner, and find that it dates to about 50 years before its provenance. Not a big surprise. Of course it may be wrong, but so far, inadequate evidence has been provided to convince me that it is, in spite of my earnest attempts to discover some. Neither Remi van Haelst’s or Riani & Atkinson’s statistical analysis detract from the overall medieval date, and nor do Garza-Valdez’s bioplastic coating nor Marino & Benford’s invisible patch stand up to investigation. There is a faint hope that the mysterious cotton, or the even more mysterious vanillin, might save the day, but this is inadequately researched and until it is there is little scientific reason to challenge the published date.

    • daveb of wellington nz
      October 4, 2014 at 6:39 pm

      There is all the reason in the world to challenge it as I’ve described above, and set out in some detail, only for the benefit of those whose understanding of proper sampling procedures and what they can and cannot imply is so clearly deficient!

      • October 5, 2014 at 3:01 am

        We don’t get very far by challenging what is some evidence from the 14 dating and the earliest documentation that we should be looking in the medieval era unless a better method of dating is proposed. I was fascinated with the way in which a number of ‘ respectable ‘papers published the Fanti ratings, cleverly placed to appear before Easter, without checking them and then the story faded completely as soon as everyone realised he had three different dates, of which only one at the most may have been correct, adjusted one but not the two others and then averaged them to produce his answer. The radiocarbon date wins out over this any day.
        But I agree that we must build a raft of other evidence if we wish to support a medieval date. The earliest documentation is certainly helpful as I know a number of other cases where the earliest documentation and the date of the object concerned are similar. There is still a mountain of work to be done on the earliest descriptions and depictions of the Shroud and for conservationists to see whether what we are actually looking at is an image that has now faded from what it was originally.
        The sceptics have the immense advantage in that ANY date other than between,say BC 20 and AD 33, means that the Shroud is not the authentic burial cloth.

      • daveb of wellington nz
        October 5, 2014 at 3:57 am

        The Fanti methods are as yet in their infancy, and probably need more refinement. But they will probably remain indicative only, as relying on mechanical properties, they will always suffer from the problem of the artefact’s subsequent history, such as folding etc.

        There’s not a great deal wrong with the principle of radio-carbon dating, but the sampling of heterogeneous materials must be representative, and not singular. Otherwise like any other method it’s GIGO! Garbage In, then it’s Garbage Out! The known failures never get written up.

    • Max patrick Hamon
      October 4, 2014 at 6:58 pm

      How come then you still cannot you tell us how exactly the image was created? Historically, archaeologically, iconographically and scientifically speaking, inadequate evidence has been provided to convince dozens and dozens of experts it dates back to the middle of the 14th CE. How very simplistic.

    • daveb of wellington nz
      October 4, 2014 at 8:14 pm

      “Snipping off an inconspicuous corner” from an artifact whose homogeneity can be so easily challenged is so very amateurish. It’s like looking for a ‘magic bullet’ by following a magic ritual. For a more time-honoured and established formal approach, inspection of animal entrails would provide no less a worthless result!

      • October 5, 2014 at 5:04 am

        On the contrary, the homogeneity of the Shroud is well established. As a single piece of cloth woven at one time, with no evidence of anything but the minutest extraneous matter, it is far more homegenous than, say, a piece of wood, whose C14 has been acquired over hundreds of years, or an artifact made of different materials assembled. It has not been steeped in water or buried in soil, and the STuRP team thoroughly attested to the lack of extraneous material ten years previously. As I said above, there are possibilities that evidence against the C14 dating could be strengthened, but until it is, comparison with entrails is wishful thinking, not science.

      • daveb of wellington nz
        October 5, 2014 at 6:03 am

        Raes sample 1973:
        Piece 1, main cloth: warp – 38.6 threads / cm, 16.3 tex (gm / km); weft – 25.7 threads / cm; 53.6 tex (gm / km);
        Piece 2, side strip: warp – 18 tex (gm / km); weft – 25.7 threads / cm; 73.1 tex (gm / km).
        The two pieces were not homogeneous.
        Homogeneity has not been established; There are three separate sets of water stains.
        Benford, Raes, & Rogers considered the C-14 sample not representative. You may dismiss them if you will, but the doubts must still remain. Consequence of only a single non-representative sample!

        • PHPL
          October 5, 2014 at 6:50 am

          ” … but the doubts must still remain.” The only indisputable thing that remained following the C 14 dating was a date tallying perfectly with skeptics’ forecast. The worst possible date for the “shroudies”.

    • PHPL
      October 4, 2014 at 11:21 pm

      ….You forgot to mention Stephen E. Jones’ magnificent KGB conspiracy theory Hugh.

  6. daveb of wellington nz
    October 4, 2014 at 10:13 pm

    A fundamental principle of sampling theory, is that the choice of samples should be mutually independent. Usually this can be achieved using a table of random numbers, or a random number generating algorithm. Coming from the very same swatch as they did, all nine tests carried out by the three laboratories were necessarily all mutually interdependent, breaking this fundamental principle. There can be no surprise at the alleged similarity of results which are meaningless! I’m uncertain about the sampling methods involving animal entrails, but I’ve heard they should be killed by the light of the full moon. Werewolves need not apply!

  7. Max patrick Hamon
    October 5, 2014 at 5:09 am

    Methinks Hugh can do without good Field Archaeology and reliable History to dating any artifact. This is BAD history and archaeology.

  1. No trackbacks yet.
Comments are closed.
%d bloggers like this: