Age determination for the Matuyama-Brunhes geomagnetic reversal boundary and comprehensive calibration of geologic ages

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04068
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Stratigraphy/Paleontology
• Research Institution: Ibaraki University
• Principal Investigator: Okada Makoto 茨城大学, 理工学研究科(理学野), 教授 (00250978)
• Co-Investigator(Kenkyū-buntansha): 菅沼 悠介 国立極地研究所, 研究教育系, 准教授 (70431898) ; 堀江 憲路 国立極地研究所, 研究教育系, 助教 (00571093)
• Research Collaborator: Haneda Yuki ; Kameo Koji ; Konishi Takumi ; Kubota Yoshimi
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 古地磁気学 / 地磁気逆転 / 古海洋学 / 氷期ー間氷期変動 / 年代層位学

Outline of Final Research Achievements

Based on detailed paleomagnetic and oxygen isotope measurements in the Chiba Composite Section, the age of the Matsuyama-Brunhes boundary was determined as 773 ka which is 10,000 years younger than the official age of the International Stratigraphic Commission. Furthermore, the Be-10 measurements succeeded to reconstruct the earth’s dipole moment variation during and across the boundary. On the other hand, as a result of investigation of other geomagnetic reversals necessary for comprehensive calibration of geologic ages, we succeeded in obtaining six geomagnetic reversal records in the period between 3.0 and 4.6 Ma.

Free Research Field

地質学

Academic Significance and Societal Importance of the Research Achievements

千葉複合セクションで得られた本研究の結果を最大限活用することで,日本初のGSSP候補である「千葉セクション」のGSSP申請を行い,ライバルのイタリアを退け,第2次審査を突破し，第3次審査へと進むことができた．さらにBe-10測定では，磁場逆転中にどこまで地磁気強度が弱まるかについて定量的な結果を得ることができた．この結果は，磁場逆転が人間社会に与える影響を評価する上で必要不可欠なデータを提供すると考えられる．