High-resolution OSL chronology for exploring a regime shift of Quaternary crustal displacement

2021 Fiscal Year Final Research Report

• Project/Area Number: 18H01294
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 17030:Human geosciences-related
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Tamura Toru 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, 上級主任研究員 (10392630)
• Co-Investigator(Kenkyū-buntansha): 納谷 友規 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, 主任研究員 (90549891) ; 熊代 浩子 (岡崎浩子) 千葉県立中央博物館, その他部局等, 研究員(移行) (10250135)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: OSL年代 / 第四紀 / 地殻変動 / 関東平野 / 地層

Outline of Final Research Achievements

This study yielded three major findings. 1) Features of feldspar OSL in the Kanto region were investigated to clarify the optimal measurement temperatures and potential residual doses, which then were used for enhancing the accuracy of the OSL ages. 2) OSL dating and tephra analysis revised the correlation of the marine terrace of the eastern Kanto plain as to MIS 5a-c, not MIS 5e as previously considered, revising up the uplift rate of this region over the last 100,000 years. 3) Marine deposits formed in MIS 6d, a major interstadial period between MIS 5 and 7, yielding the minimum uplift over the last 180,000 years, which is comparable with that over the last 100,000 years. This suggests that the inferred tectonic regime shift, from subsidence to uplift, in the Kanto plain is likely to have occurred before 100,000 years ago.

Free Research Field

地質学

Academic Significance and Societal Importance of the Research Achievements

世界有数の変動帯である日本列島において第四紀の海成段丘や海成層が記録する地殻変動の様式は，巨大地震履歴の解読に有用である上，放射性廃棄物の処分でも重要な情報となる．本研究は，第四紀の海成段丘や海成層の研究手法として，OSL年代測定とボーリングコアとの組み合わせが有効であることを示した．さらにその適用により，過去数十年間信じられてきた海成段丘の対比が見直され，隆起速度の上方修正が行われた．また，従来ほぼ無視されてきたMIS 6の亜間氷期における地質記録が地殻変動の評価に有用であることが見いだされた．