C05_07

A pollen ¹⁴C stratigraphy of Lake Suigetsu from 12 to 20 ka BP

Omori T¹, Yamada K², Kitaba I², Nakagawa T²

¹The University Museum, The Uiniversity of Tokyo, Tokyo, Japan, ²Research Centre for Palaeoclimatology, Ritsumeikan University, Shiga, Japan

A radiocarbon stratigraphy of terrestrial fossil pollen grains extracted from Lake Suigetsu’s varved sediment has been established from 12 ka to 20 ka cal BP in multi-decadal resolution. The obtained curve showed i) an overall good agreement with that of terrestrial macro fossils (Bronk Ramsey et al. 2012), and ii) significantly smoother decadal trends than those of the terrestrial macro fossils. These results indicate that the fossil pollen grains are i) as good indicator of the atmospheric radiocarbon concentration as terrestrial leaf fossils, and ii) picking up decadal signals of the atmospheric radiocarbon variability, free from inter-annual scatters which are inevitable with terrestrial leaf fossils. Because pollen grains fix the contemporary atmospheric radiocarbon, the smoothness of the curve should be a good indication of the true radiocarbon variability, rather than the terrestrial radiocarbon reservoir effects. The fact that curve is relatively free from the influence of inter-annual variability, which has been proved to be more significant than was previously believed (Bronk Ramsey et al. 2020, Miyake et al. 2017), implies that the radiocarbon datasets of fossil pollen grains are likely to have stronger power to constrain ages, when used as a radiocarbon calibration model.