Browsing Radiocarbon, Volume 28 (1986) by Subjects
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Multiple Dating of a Long Flowstone ProfileDense speleothem samples are considered as closed systems and are, therefore, possibilities for any dating method. Four dating methods (14C, U/Th, paleomagnetism, and electron spin resonance = ESR) were used for samples up to 1,000,000 yr old and taken along a vertical flowstone profile in the Heggen cave in West Germany. Also delta-18O and delta-13C analyses were carried out. The reliability of the results of each method is dependent on the diagenetic processes that took place during the complex growth history of the flowstone. Speleothem growth was interrupted during glacial periods. During interglacial periods, at least the stalagmite growth rate was greater by one order of magnitude than during interstadial periods. During the periods of low interstadial growth rate various processes might have changed the 14C, 18O, and 13C concentrations, leaching might have removed uranium, recrystallization might have moved thorium several centimeters, and increased content of radon in the cave might have exaggerated the accumulated dose (AD) at the speleothem surface. As a result, 14C ages may be too small and U/Th as well as ESR data may be too large.