• 14C Age Measurements of Single-Year Tree Rings of Old Wood Samples 22,000 14C Years BP

      Sato, Taiichi; Sakurai, Hirohisa; Suzuki, Kayo; Takahashi, Yui (Department of Geosciences, The University of Arizona, 2010-01-01)
      Radiocarbon ages of single-year tree rings were measured for Kaminoyama wood samples using accelerator mass spectrometry (AMS) in 2 Japanese facilities, MALT and JAEA, in order to investigate the periodic variation of 14C concentrations relating to the 11-yr solar cycle near 26,000 yr BP. Eight sequential measurements of 14C ages were carried out for a set of 13 alternate single-year tree rings covering 26 yr. Averages of the 5 data sets in MALT and 3 data sets in JAEA were 22,146 +/- 50 and 22,407 +/- 58 14C yr BP, respectively, indicating an offset of 260 +/- 77 14C yr. Multiple sequential measurements are advantageous for evaluating offsets. The standard deviation of the residuals of 14C ages from the averages in each data set was 118 14C yr, in contrast to that of 234 14C yr for the combined data sets due to an elimination effect in the offsets. The profiles of weighted mean values for the residuals of 14C ages showed similar enhancements with a width of ~12 yr for measurements in the 2 facilities. This indicates the reproducibility of the multiple sequential measurements. In the profile for the combined 8 data sets, the 14C enhancement was 73 +/- 36 14C yr from the average.
    • Comparison of 14C Ages between LSC and AMS Measurements of Choukai Jindai Cedar Tree Rings at 2600 cal BP

      Takahashi, Yui; Sakurai, Hirohisa; Suzuki, Kayo; Sato, Taiichi; Gunji, Shuichi; Tokanai, Fuyuki; Matsuzaki, Hiroyuki; Sunohara, Yoko (Department of Geosciences, The University of Arizona, 2010-01-01)
      Radiocarbon ages of Choukai Jindai cedar tree rings growing in the excess era of 14C concentrations during 2757-2437 cal BP were measured using 2 types of 14C measurement methods, i.e. liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS). The difference between the 2 methods is 3.7 +/- 5.2 14C yr on average for 61 single-year tree rings, indicating good agreement between the methods. The Choukai data sets show a small sharp bump with an average 14C age of 2497.1 +/- 3.0 14C yr BP during 2650-2600 cal BP. Although the profile of the Choukai LSC data set compares well with that of IntCal04, having a 14C age difference of 4.6 +/- 5.3 14C yr on average, the Choukai LSC 14C ages indicate variability against the smoothed profile of IntCal04.