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User:Awc/Dendrochronology

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Contents

Outline of an article

  • General idea
  • Prerequisites
  • Missing rings
  • Extra rings
  • Building a chronology
  • Tertiary replication
  • Extraordinary (intensive, widespread and brief) events
  • Role of and relation to radiocarbon dating

scientific papers

A 7,272-year tree-ring chronology for western Europe

by J. R. Pilcher*, M. G. L. Baillie*, B. Schmidt† & B. Becker‡, Nature 312, 150 - 152 (08 November 1984); doi:10.1038/312150a0 - just an abstract here, but Nature should be easy to find. Gives refs for "[t]he world's longest continuous tree-ring chronology ... based on the bristlecone pine ... a continuous tree-ring sequence of 8,681 years".

A slice through time: dendrochronology and precision dating

By M. G. L. Baillie

(This looked interesting enough that I went and bought it.)

We would not know the true dates of the Long Chronology until both the remaining gaps were closed with significant tree-ring links. [emphasis in origina] Only then would we know it the radiocarbon suggestions were even remotely correct. After all, if we found that the true placement of the Long Chronology was wildly at odds with the placement suggested by calibrated radiocarbon dates, then we would know that Suess' calibration was not applicable worldwide. Were that to have been the case, the Belfast calibration would become the accepted radiocarbon correction curve for the Old World! If, on the other hand, tree-ring connections were found which were in line with the suggested radiocarbon placement, then this would confirm that the Suess curve was effectively universally applicable. (p.35)

As a basis for dating a section of the Irish Long Chronology this [relying upon a link to a Roman London chronology] was very unsatisfactory, for the following reasons. The 5061-year prehistoric Belfast chronology had been built completely independently - thanks to Swan Carr - and at no point did the Irish chronology depend on any of the German chronologies. Given this situation it was to be hoped that the Irish chronology could be completed independently. This was potentially very important because comparisons between the Irish and German chronologies could then form the third-level replication which would ultimately prove European dendrochronology. Because of this need for independence, we retained misgivings about attempting the Ireland to England to Germany bridging exercises mentioned above. In an ideal world such comparisons should only take place after both chronologies had been completed independently. So the problem with New Fresh Wharf was that it had been dated against German chronologies. Fortunately this situation was later rectified when Ian Tyers constructed a complete Southwark chronology which spanned AD 255-252 BC (Sheldon and Tyers 1983). This chronology cross-dated directly with the older part of the Irish chronology and with Carlisle (Fig. 2.2). (pp.35-36)

Just when it was needed, and unknown to any of the Belfast, Köln or Stuttgart workers, Leuschner and Delorme, at Göttingen, published a note on their completion of a separate German chronology from AD 785 to 4008 BC (Leuschner and Delorme 1984). Here was then the opportunity for an independent test of the Belfast chronology. In the spring of 1985 Hubert Leuschner kindly made available to us a continuous German chronology running, by that time, from AD 928 to 4163 BC. The results of running the various sections of the Belfast prehistoric chronologies against the independent Göttingen chronology confirmed that both prehistoric chronologies were in precise synchronization. Despite the distances involved, the original Long Chronology gave t = 8.8 at 949 BC, Swan Carr gave t = 8.45 at 381 BC and even Garry Bog 2 gave t = 3.6 at 229 BC (Brown et al. 1986). Since that time numerous additional sections of English prehistoric chronology have shown consistent matching against both the Belfast and Göttingen chronologies (see Fig. 1.3 for examples). So the Göttingen chronology provided the ultimate tertiary replication necessary to prove the European oak complex. (pp.39-40)

In an ideal world samples could be plugged into a black box system which would supply totally independent and perfectly precise results. Curiously, radiocarbon in some ways comes closest to this ideal in the sense that any carbon sample submitted to a laboratory guarantees a 'date' even though the relationship of that 'date' to the true age of the sample is often tenuous (see, for example, Baillie 1990a).

Baillie , M.G.L. 1990a, 'Checking back on an assemblage of published radiocarbon dates', Radiocarbon 32, 361-6.

"Apart from two missing rings, at 2142 BC and 2681 BC in the Campito chronology, the two chronologies were in perfect agreement over more than five millennia."

Are there marker events that can be used to verify the consistency between chronologies?

Should be global or continental in scope, and have occurred 8000-20000 BP. The oldest living non-clonal tree, verified by dendrochronology, is "Methuselah" (4,800 years old), a Great Basin Bristlecone Pine in California. If the Flood was in 2348 BC, that would be 4358 years ago, when the tree was 442 years old.

The end of the Younger Dryas has been dated to around 9500 BC (11550 calendar years BP, occurring at 10000 radiocarbon years BP, a "radiocarbon plateau") by a variety of methods, with mostly consistent results:

11530±50 BP — GRIP ice core, Greenland [1]
11530+40−60 BP — Kråkenes Lake, western Norway.[2]
11570 BP — Cariaco Basin core, Venezuela [3]
11570 BP — German oak/pine dendrochronology [4]
11640±280 BP — GISP2 ice core, Greenland [5]

other sources

"The 8,000-year-long BCP chronology appears to be correctly crossmatched, and there is no evidence that bristlecone pines can put on more than one ring per year."
"There presently exist several long dendrochronologies, each comprised of about 10,000 individual growth-rings. These are examined for the possibility of multiple ring growth per year in their earliest portions due to unusual climatic conditions following the Flood. It is found that the tree-ring/radiocarbon data are contrary to the suggestion of multiple ring growth. Since it seems that the Flood must have occurred before the oldest rings of these series grew, the implication is that the Flood must have occurred more than 10,000 years ago."
"In practice, there are a number of problems with this principle: (1) trees occasionally produce more than one ring a year; (2) trees occasionally go a year or more without producing a ring; (3) you have to somehow see the rings to count them, preferably without killing the tree; and (4) how was the tree first established and how fast did it grow in its earliest years? We'll look at these problems in turn, but first, a little information on how a tree grows."

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