[M-IS14] 古気候・古海洋変動

[MIS14-P29] Radiocarbon Dating of Fossil Pollen for Lacustrine Sediment Chronology: A Case Study from Lake Kawaguchi

*常岡 廉^1,2、横山 祐典^1,2、宮入 陽介¹、山本 真也³、中村 淳路⁴、藤原 治⁴、Aurélia Hubert-Ferrari⁵、Vanessa Heyvaert^6,7、Marc De Batist⁷、the QuakeRecNankai Team (1.東京大学 大気海洋研究所、2.東京大学大学院 理学系研究科 地球惑星科学専攻、3.山梨県 富士山科学研究所、4.国立研究開発法人 産業技術総合研究所 地質調査総合センター、5.Department of Geography, University of Liège、6.OD Earth and History of Life, Royal Belgian Institute of Natural Sciences, Geological Survey of Belgium、7.Ghent University, Department of Geology)

キーワード：放射性炭素年代測定法、花粉化石、フローサイトメトリー、湖底堆積物、河口湖、富士五湖

Lacustrine sediments serve as valuable archives of past environmental conditions in terrestrial ecosystems. To reconstruct paleoenvironmental changes, it is crucial to establish precise sediment chronologies, enabling accurate comparisons with global climatic and environmental records. Radiocarbon (¹⁴C) dating is one of the most widely used methods for determining the age of these deposits, covering timescales of up to 55,000 years. However, in lake environments, carbon from various sources is incorporated into the sediment, complicating age determinations. This study explores the use of fossil pollen to improve dating accuracy of lacustrine sediments. Recent advancements in ¹⁴C dating techniques and pollen extraction using flow cytometry have facilitated sediment dating based on the ¹⁴C ages of fossil pollen. For example, Ota et al. (2024) successfully extracted fossil pollen from sediments in Lake Motosu (one of the Fuji Five Lakes) and determined the lake's reservoir age using fossil pollen ¹⁴C ages.
In this study, we applied fossil pollen ¹⁴C dating to establish a high-resolution chronology for the sediment of Lake Kawaguchi, which shares similar catchment characteristics and climatic conditions with Lake Motosu but differs in sedimentary environment. Unlike the deep (max. 121.2 m) and isolated Lake Motosu, Lake Kawaguchi is shallower (max. 14.0 m) and receives riverine inputs, leading to different sedimentary dynamics. This contrast allows us to assess the applicability of fossil pollen ¹⁴C dating under varying depositional conditions.
In this presentation, we will report the results of ¹⁴C analysis on fossil pollen extracted from a sediment core obtained from Lake Kawaguchi (KAW15-2), which spans the late Holocene, to evaluate the applicability of fossil pollen ¹⁴C dating in this lake.