Japan Geoscience Union Meeting 2023

Presentation information

[J] Online Poster

H (Human Geosciences ) » H-QR Quaternary research

[H-QR03] Quaternary, Diachronic dynamics of human-environment interactions

Sun. May 21, 2023 1:45 PM - 3:15 PM Online Poster Zoom Room (5) (Online Poster)

convener:Kazuyoshi Yamada(School of Human Sciences, Waseda University), Kazuaki Hori(Department of Earth Science, Graduate School of Science, Tohoku University), Toru Tamura(Institute of Geology and Geoinformation Geological Survey of Japan, AIST), Atsushi Urabe(Research Institute for Natural Hazards and Disaster Recovery, Niigata University)


On-site poster schedule(2023/5/21 17:15-18:45)

1:45 PM - 3:15 PM

[HQR03-P10] Reassessment of Lagoon-Specific Marine Reservoir Effects in Tongatapu, Kingdom of Tonga, over the Past 3000 Years

*Naoto Fukuyo1, Geoffrey Clark3, Yusuke Yokoyama2 (1.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, 2.Atmosphere and Ocean Research Institute, University of Tokyo, 3.College of Asia and the Pacific, The Australian National University)

Keywords:radiocarbon, sea level change, South Pacific

Lagoon-specific local marine reservoir effects (ΔRlagoon) were introduced as a novel proxy to estimate the radiocarbon (14C) activity change in the lagoon freshwater proportion in Fukuyo et al. (2020). In Tongatapu island, ΔRlagoon values increased linearly between ~2.6 and 0.4 ka, which suggested that ΔRlagoon value increase was caused by the near-closure of the Fanga ‘Uta Lagoon. However, these values still presented large errors. Here, we present 10 new Δ14C and 16 new ΔRlagoon values from G. tumidum combined with the previously published values and a ΔRlagoon value recalculated using Marine20. Moreover, we examined whether the 14C value of G. tumidum reflected that of the dissolved inorganic carbon in the lagoon water. Although the new ΔRlagoon values were similar between 0.4 ka and 1.2 ka, the values increased from 2.6 ka to 1.2 ka. This timing was consistent with geophysical comparisons reported in our previous study and archaeological studies.