Browsing Radiocarbon, Volume 31, Number 2 (1989) by Subjects
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High-Resolution 14C Dating of Organic Deposits Using Natural Atmospheric 14C VariationsThe occurrence of atmospheric 14C variations complicates calibration, ie, the translation of 14C ages into real calendar ages. The procedure of wiggle matching, however, allows very precise calibration, by matching known 14C variations with wiggles in the floating chronology. In principle, wiggle matching can also be applied to a series of 14C dates from organic (peat) deposits. Where, in general, 14C ages are required at short distances and on small samples, dating by 14C accelerator mass spectrometry (AMS) is required.
Problems Associated with the Use of Coal as a Source of 14C-Free Background MaterialMany 14C dating laboratories have established that coal samples exhibit a finite 14C age, apparently caused by contamination of the specimens before any laboratory preparation is undertaken. In this work, the possibility that the contamination is due to microbial and fungal activity in the coal substrate is considered and some suggestions are made for alternative sources of background test materials for 14C dating laboratories. Initial results indicate that geologically formed graphites contain little 14C and are likely to be good background test materials, especially in 14C AMS laboratories.