Dendrochronology: The Plasticine Effect

The Plasticine Effect

The problem with dendrochronologists is that they never know when to stop.
Every gap they encounter is a challenge that must be bridged.
Every floating chronology is an orphan waiting to be crossmatched.

Unfortunately, dendrochronologists haven’t read a Bridge Too Far.

A Bridge Too Far, a non-fiction book by Cornelius Ryan published in 1974, tells the story of Operation Market Garden, a failed Allied attempt to break through German lines at Arnhem across the river Rhine in the occupied Netherlands during World War II in September 1944.

The title of the book comes from a comment made by British Lt. Gen. Frederick Browning, deputy commander of the First Allied Airborne Army, who told Field Marshal Bernard Montgomery before the operation, “I think we may be going a bridge too far.”

Prior to Ryan’s book, Market Garden had been a classic example of victors writing the history.

Popular histories of World War II of the time usually tended to not mention the battle at all, mentioned it in passing or put Montgomery’s spin on it as being a “partial success”.

A Bridge Too Far was responsible for bringing to the general public’s attention the full extent of this massive operation, including a catalogue of errors and miscalculations, whilst highlighting the extreme bravery of the participants.

Unfortunately, dendrochronologists don’t remember the The Plasticine Effect .

The Plasticine Effect
If you mix all three primary colours you get BROWN.

Not pleasant-warm-new-conker brown, or deep-dark-mysterious-nearly-black brown, but yucky-sludgy-just-come-out-of-the-wrong-end-of-a-cow brown.

Shitty brown in simple terms.

The colour your Plasticine always ended up. So never mix three colours together, in similar quantities, as they will always tend towards the more unpleasant variety of brown.

The Unstuck Diaries – John Coombes

Sadly, dendrochronologists [and most Earth Scientists] don’t remember that if you Mix and Mash your data too much you will simply end up with a brown smelly turd.

It may be a bright and sparkling.
It may have taken man years of effort to prepare.
But it will still be a turd.
It will not be an insightful, value-added, sate-of-the-art repository of knowledge.

The first big unanswered question is: How many samples should to be collected at a site to ensure the dendrochronologist has a representative population sample?

The usual non-specific answer appears to be “numerous” and the associated illustration suggests 16 samples from 10 trees is sufficient.

Great Sand Dunes

The Principle of Replication
This principle states that the environmental signal being investigated can be maximized, and the amount of “noise” minimized, by sampling more than one stem radius per tree, and more than one tree per site.

Obtaining more than one increment core per tree reduces the amount of “intra-tree variability”, in other words, the amount of non-desirable environmental signal peculiar to only tree.

Obtaining numerous trees from one site, and perhaps several sites in a region, ensures that the amount of “noise” (environmental factors not being studied, such as air pollution) is minimized.

Principles of Dendrochronology

The second big unanswered question is: What strategy is used to ensure a representative selection of samples is collected from the site population?

The usual non-specific answer appears to rely upon the experience of the dendrochronologist when they are sampling living trees.

When it comes to floating archaeological chronologies the strategy seems to be based upon including whatever they find [because they have no knowledge of the overall population] provided it has 40, or more, tree rings.

213-year oak tree-ring chronology first-millennium AD Constantinople

A 213-year oak tree-ring chronology has been constructed from timbers from several sites from first-millennium AD Constantinople, in particular, from the study of over 2000 samples from harbour installations at Yenikapı (Figure 1), Istanbul (Pekin & Kangal 2007) (Figure 2). A tentative dendrochronological placement of the 213-year sequence against other tree-ring series suggests an absolute date range of AD 398–610 for the time-series (Pearson et al. submitted).

Dendro-wiggle-match placement of an oak tree-ring chronology from mid-first millennium AD Constantinople
Sturt W. Manning, Charlotte L. Pearson, Carol B. Griggs & Bernd Kromer
Antiquity Volume 086 Issue 331 March 2012

This is in sharp contrast to the sub-fossil floating chronologies that still had gaps in 1983 after collecting 2,200 samples [again from an unknown population].

The Hohenheim Tree-Ring Laboratory has extended the Holocene oak tree-ring chronology back to prehistoric times by analyses of subfossil tree trunks from gravel deposits along the rivers of central Europe.

Hundreds of subfossil oaks can be collected each year because of widespread gravel quarrying.

Despite this nearly continuous source of samples (at present, 2200 trees are analyzed), even within these deposits some limitations do exist in linking together a Holocene tree-ring sequence.

The main problem is the relatively short growth period of the Holocene valley oaks, reaching only 100 to 400 treerings.

This requires a close temporal sequence of tree trunk deposits over thousands of years.

However, while phases of increased flooding accumulated large numbers of eroded trees, there also have been periods of low fluvial activity, which left only few buried wood remains.

Unfortunately, such a phase of reduced floodings occurred during the first millennium BC, a period from which wood samples from prehistoric settlement constructions, the other source of dendrochronology, are rarely found in southern Germany.

The Long-Term Radiocarbon Trend of the Absolute German Oak Tree-Ring Chronology 2300 to 800 BC – 1983 – Bernd Becker
Radiocarbon, Vol 25, No. 2, 1983, P 197-203

However, these unanswered questions and three inconsistent groupings [living tree chronologies, archaeological floating chronologies and sub-fossil floating chronologies] are then Mixed and Mashed into higher level chronologies where The Plasticine Effect ensures the final product is the dendrochronological equivalent of a brown plasticine turd.

One of the better examples of The Plasticine Effect can be found in the 12,460-year Hohenheim Oak and Pine Tree-Ring Chronology for Central Europe.

Compilation of the central European Holocene oak chronologies of the Hohenheim laboratory. The blocks represent replicated regional chronologies which were linked dendrochronologically to each other. The chronology from the river Main consists of an unbroken record from 8239 BC to AD 1100. The chronology of oaks from archaeological sites, historical timbers, and living trees connect the prehistoric chronologies to the present. The numbers at the left-hand end of the bars give the calendar year (cal BC) of the oldest oak tree ring in the respective region.

Regional chronologies which were linked dendrochronologically

The 12,460-year Hohenheim Oak and Pine Tree-Ring Chronology
Michael Friedrich, Sabine Remmele, Bernd Kromer, Jutta Hofmann, Marco Spurk, Klaus Felix Kaiser, Christian Orcel, Manfred Küppers
Radiocarbon, Vol 46, Nr 3, 2004, p 1111–1122 – 2004

The Hohenheim oak chronology begins reasonably enough with the “Historical Oak Chronology” which tracks back from the modern era to about 1000 AD where the sample count plummets from [around] 50 down to [about] 1 or 2 samples by 800 AD.

Then the fun really begins because all the remaining oak chronologies [from “archaeological sites”, “historical timbers” and “subfossil oaks”] are floating chronologies that are bridged together by only 1 or 2 samples in many places.

These sparsely populated bridges are clearly Bridges Too Far which, in turn, means the dating of the floating chronologies are statistically invalid and unsubstantiated.

The combined oak and pine tree-ring chronologies of Hohenheim University - 50 samples
The 12,460-year Hohenheim Oak and Pine Tree-Ring Chronology
Michael Friedrich, Sabine Remmele, Bernd Kromer, Jutta Hofmann, Marco Spurk, Klaus Felix Kaiser, Christian Orcel, Manfred Küppers
Radiocarbon, Vol 46, Nr 3, 2004, p 1111–1122 – 2004

However, the Hohenheim chronology then adds another twist to The Plasticine Effect by combining the oak and pine chronologies.

Dendrochronological linkage of Preboreal pine to Holocene oak

The 12,460-year Hohenheim Oak and Pine Tree-Ring Chronology
Michael Friedrich, Sabine Remmele, Bernd Kromer, Jutta Hofmann, Marco Spurk, Klaus Felix Kaiser, Christian Orcel, Manfred Küppers
Radiocarbon, Vol 46, Nr 3, 2004, p 1111–1122 – 2004

The Plasticine Effect then moves on to a higher level of abstraction.

The German oak chronologies from the Main River [“built independently in the Göttingen and Hohenheim tree-ring laboratories”] are somehow mixed and mashed into the Terrestrial Carbon-14 calibration curve and [the surreal] Marine Carbon-14 calibration curve.

Schematic diagram of IntCal04 and Marine04 calibration data set construction

The Holocene part of the 14C calibration is based on several millennia-long tree-ring chronologies providing an annual, absolute time frame within the possible error of the dendrochronology, which was rigorously tested by internal replication of many overlapping sections.

Whenever possible, they were cross-checked with independently established chronologies of adjacent regions.

The German and Irish oak chronologies were cross-dated until back into the 3rd millennium BC (Pilcher et al. 1984), and the German oak chronologies from the Main River, built independently in the Göttingen and Hohenheim tree-ring laboratories, cross-date back to 9147 cal BP (Spurk et al. 1998).

The North American trees that form part of the 14C calibration curve prior to AD 1320 were cross-dated with either the Sequoiadendron master chronology or with a Pacific Northwest Douglas fir chronology (Stuiver 1982).

Paula J Reimer1, Mike G L Baillie, Edouard Bard, Alex Bayliss, J Warren Beck, Chanda J H Bertrand, Paul G Blackwell, Caitlin E Buck, George S Burr, Kirsten B Cutler, Paul E Damon, R Lawrence Edwards, Richard G Fairbanks, Michael Friedrich, Thomas P Guilderson, Alan G Hogg, Konrad A Hughen, Bernd Kromer, Gerry McCormac, Sturt Manning, Christopher Bronk Ramsey, Ron W Reimer, Sabine Remmele, John R Southon, Minze Stuiver, Sahra Talamo, F W Taylor, Johannes van der Plicht, Constanze E Weyhenmeyer
Radiocarbon, Vol 46, Nr 3, 2004, p 1029–1058

Libby's Ring

Gallery | This entry was posted in Catastrophism, Dendrochronology, History, Radiocarbon Dating. Bookmark the permalink.

1 Response to Dendrochronology: The Plasticine Effect

  1. Pingback: Deranged Dating: Double Vision | MalagaBay

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