Browsing Radiocarbon, Volume 28, Number 2B (1986) by Subjects
Now showing items 1-10 of 10
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High-Precision 14C Measurement of Irish Oaks to Show the Natural 14C Variations from AD 1840-5210 BCHigh-precision measurement of dendrochronologically dated Irish oak at bidecade/decade intervals has continued in the Belfast laboratory, extending the 14C data base from ca AD 1840 to 5210 Bc. The dendrochronology is now considered absolute (see Belfast dendrochronology this conference) (Brown et al, 1986) and a continuous detailed curve is presented, showing the natural variations in the atmospheric concentration of 14C over >7000 years. Each data point has a precision of <2.50 per mil, and some 4500 years have now been compared with Seattle, giving excellent agreement. Discussion of this data base and the justification of the claimed accuracy is given together with a comparison of other chronologies. Some of the advantages and limitations of the above are discussed.
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High-Precision Radiocarbon Dating of Bristlecone Pine from 6554 to 5350 BCNew results of radiocarbon dating of ca 100 decadal bristlecone pine samples from 6554 to 6084 BC and from 5820 to 5350 BC are presented. Using 3 new 2.5L counters filled to ca 3atm with carbon dioxide, high-precision dating has been performed by this laboratory for more than two years. Demonstration of the precision and accuracy of these counters is presented using +/2 per mil measurements from the Spörer minimum period. For the older samples, +/3 per mil measurements were made using ca 12-day counting times. Results are presented both as 14C age BP vs dendro-year BC, particularly for calibration purposes, and as Delta-14C vs time.
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Radiocarbon Calibration Data for the 6th to the 8th Millennia BC14C calibration curves derived from South German oak tree-ring series are presented. They cover the interval between 4400 and 7200 BC complementing existing data sets and extending them to older periods. The atmospheric 14C level before 6200 BC no longer follows the long-term sinusoidal trend fitted to the bristlecone data. This observation is supported by a tentative match of the Main 9 series.
