• High-Precision Calibration of the Radiocarbon Time Scale, 3930-3230 Cal BC

      De Jong, A. F. M.; Becker, Bernd; Mook, W. G. (American Journal of Science, 1986-01-01)
    • Multiple Dating of a Long Flowstone Profile

      Geyh, Mebus A.; Hennig, G. J. (American Journal of Science, 1986-01-01)
      Dense 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.
    • Radiocarbon Calibration Data for the 6th to the 8th Millennia BC

      Kromer, Bernd; Rhein, Monika; Bruns, Michael; Schoch-Fischer, Hildegard; Münnich, Karl Otto; Stuiver, Minze; Becker, Bernd (American Journal of Science, 1986-01-01)
      14C 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.
    • University of Lund Radiocarbon Dates XIX

      Håkansson, Sören (American Journal of Science, 1986-01-01)