In article (Richard A. Schumacher

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Organization: Mitre Corporation From: (James W. Meritt) Message-ID: <2boh26$> Newsgroups: In article (Richard A. Schumacher) writes: }The Teen Mission conveniently ignores the fact that you don't }need a single live tree to get a continuous record, just an }overlapping sequence. The existing overlapping records of }(mostly dead) trees go back about 20,000 years. Here are tree rings for 11,000 years, 5000 years, 7272 years, 8000 years, 9000 years, 9400 years, .................................................................... "Detailed records of atmospheric 14C/12C have been obtained for the last 11,000 years from the measurements of carbon in wood, where annual tree rings provide an independent chronology for the establishment of variations in the atmospheric 14C/12C ratio (2-4)." 2. M Stuiver and R S Kra, Eds., Radiocarbon 28, 805 (1986). 3. B Becker and B Kromer, ibid. p 961. 4 ___, P Trimborn, Nature 353, 647 (1991). (For older samples, carbonates for example, the 14C/12C ratio can be measured and the 230Th dating used to determine age.) All of the above from Science, Vol 260, 14 May 1993, 962. .................................................................. Scientists Hope Tree Rings Will Answer Questions About Past BY: CATHERINE DRESSLER DATELINE: PITTSBURGH PRIORITY: WEEKDAY ADVANCE WORD COUNT: 571 THE ASSOCIATED PRESS DATE: June 16, 1988 12:44EDT Experts hope a boat found near a pharoah's pyramid will answer questions about ancient Egypt, but they're not studying the way it was built - they're looking at the wood it's made of. ''There are 2 1/2 centuries of information in one piece of wood from that boat,'' says Peter I. Kuniholm, a Cornell University archaeologist and tree- ring expert who is studying pencil-like cores drilled out of the planks of the 30-foot-long boat probably buried more than 3,800 years ago in Dashur. It and three similar boats were buried near the pyramid complex of Senwosret III so he could use them in the afterlife, says Diana Craig Patch, the Carnegie Museum of Natural History Egyptologist. Industrialist Andrew Carnegie bought the boat in 1901 and shipped it from Egypt to Pittsburgh. Two of the others are at the Egyptian Museum in Cairo and the third is at the Field Museum of Natural History in Chicago. Kuniholm hopes rings in the samples will pinpoint the boat's age and create a framework to help date Egyptian objects and determine when events occurred. Dendrochronology, the science of tree ring dating, was established in 1930 when Andrew E. Douglass of the University of Arizona studied rings in wooden artifacts to determine the age of a prehistoric Indian site. Though the technology has existed for decades, scientists have been limited by a lack of old wood samples from certain parts of the world, Kuniholm says. Only in recent years have scientists collected enough wood from medieval ruins, ice layers, artifacts and other sources to date objects more than 5,000 years old, said Michael G.L. Baillie of Queen's University in Belfast, Ireland. Archaeologists first studied tree rings only to determine the age of objects, but the science increasingly is revealing more useful information about the past, like the weather or environment 5,000 years ago. ''The trees are recording some form of environmental information,'' Baillie said in a telephone interview from Kuniholm's laboratory in Ithaca, N.Y. ''The trick is going to be to try and get some of that back.'' The spacing of rings represents time intervals when trees were alive and growing. The width of each ring reflects the weather each growing season, and comparison of many samples from one region gives a climate pattern. Scientists can check ring patterns against radiocarbon analysis, which is used to calculate the age of once-living objects. Living things absorb carbon from the environment, some of it radioactive carbon-14. When a plant or animal dies, carbon-14 decays at a measurable rate. To determine the age of ancient wood, scientists must build chronologies dating back for thousands of years in unbroken sequences. One, finished in 1984 in Ireland, established an unbroken record of tree rings in oak trees from the present to 7,272 years ago, Baille said. ''You take living trees of a particular species in a particular area, and you measure the pattern of wide and narrow rings,'' he said. ''You can then go back to ancient timbers from buildings, for example, and measure the ring patterns, and if they overlap in time, you should be able to link those patterns together. ''You're basically piecing together this master pattern, which is anchored at the present day.'' .................................................................. And provided from Chris: The oldest trees are bristlecone pines, between 4500 and 5000 years in age. Dead trees have been matched with live ones, extending the scale of bristlecone pine tree rings of known age back about 8000 years before the present. [_Scientists Confront Creationism_, L. Godfrey, Ed.; New York: Norton, 1983. p. 35] Contains no references to additional literature. The dendrochronological scale of bristlecone pines extends back nearly 9000 years. Trees in the same area share bountiful and lean years which result in wide or narrow rings, respectively. Two important applications of dendrochronology are calibration of the [14]C dating method and study of past changes in climate in the locality. [_Timescale_, N. Calder; New York: Viking, 1983. pp. 28-29, 224, 271-273] Contains references to several articles and a few books. Use of fossil fuels lowered the [14]C balance of the atmosphere by about 2% (this is called the "Suess effect"). Explosion of nuclear devices in the atmosphere, operation of reactors, and particle accelerators have increased the [14]C balance of the atmosphere since about 1945. The variation of [14]C level of the atmosphere in past years can be measured by dendrochronology. Dendrochronology is useful to about 8000 years before the present. For years previous to that, one must rely on varve chronologies (varves are annual layers deposited in glacial lakes). [_Principles of Isotope Geology_, G. Faure; New York: Wiley, 1986. pp. 390-393] Contains many references of a more technical nature. Trunks of dead bristlecone pines have been matched to live ones, creating a scale which extends back about 9000 years before the present. A graph of dendrochronological age versus [14]C age shows that the [14]C balance of the atmosphere has changed over time, which causes [14]C dates to be wrong if calculated from today's level of atmospheric [14]C. From this chart, corrections to [14]C dating have been obtained. [_Science and Earth History_, A. N. Strahler; New York: Prometheus, 1987. pp. 155-158] Contains several references. Variations in the [14]C level of the atmosphere have been measured by dating tree rings of known age. Both giant sequoias and bristlecone pines are used, having a dendrochronology which extends to about 5400 BC. Creationists argue that trees can grow multiple rings - or none at all. Dendrochronologists insure reliability by limiting scales to about three dozen genera of trees (which do not produce multiple rings) and certain geographical areas. "Tree ring dating is complicated but very reliable when properly done." [_Radiometric Dating, Geologic Time, And The Age Of The Earth: A Reply To "Scientific" Creationism_, Dalrymple, G. B.; USGS Open-File Report 86-110, 1986. pp. 39-41] Contains several references. ................................................................ provided from Bill Hyde: Recently a dendrochronological record in subfossil german oak has been established going back 9928 years (Nature, vol 353, page 647). The authors also have a 1600 year old pine chronology which overlaps the end of the oak chronology. As interspecies comparison is difficult they have not yet fixed an absolute age for the pine chronology. If they are able to we will probably have a chronology going back 11,500 years. This will cover the whole of the Younger Dryas with even better resolution than provided by ice cores. A good reference to Dendrochonology and Dendroclimatology is "Quaternary Paleoclimatology", by R.S. Bradley (Unwin Hyman, 1985). ..................................................................... No mention of a flood....


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