What factor reduces the accuracy of radiocarbon dating
While American scientists were building bristlecone pine and Douglas fir chronologies, European scientists were actively building a very long tree-ring chronology using oak trees.The more recent part of the chronology was constructed from oak logs used in various historic buildings.Separate dendrochronologies were then developed, also in America, using other types of trees, such as Douglas fir.These separate chronologies did not extend as far back in time because these types of trees are shorter-lived.This is accomplished using wood specimens found preserved, for example, in historic buildings, or on the forest floor, or in peat bogs.The rings in a non-living specimen can be counted to determine the number of years the specimen spans.By matching ring-width patterns in a specimen of known age (starting with living specimens) to ring-width patterns in an older specimen, the proper placement of the older specimen is determined.Tree-ring chronologies have been extended to 10,000 years before present in this way.
In fact, a comparison of the European and American chronologies showed very close correlation.However, they did agree with the bristlecone chronology as far back as it could be checked by the shorter chronologies.That is, rings of the same putative dendrochronological age were found to contain the same amount of radiocarbon, and to give the same pattern of fluctuations over time.The following article is abstracted from The Biblical Chronologist Volume 5, Number 1. The science of constructing chronologies from tree rings is called dendrochronology. Modern trees are known to produce one growth ring per year. (The idea that ancient trees grew more than one ring per year will be discussed below.) Therefore, by coring a living tree and counting rings from the present backwards, it is possible to determine the year in which each ring grew. The bristlecone pines in the White Mountains of California live to extremely old ages, some in excess of 4,000 years.The University of Arizona dendrochronology lab sports a (no longer living) specimen which contains over 6,000 rings.