Study on long-term geomagnetic field variations during the last 10 million years

• Project/Area Number: 16H02233
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geology
• Research Institution: The University of Tokyo
• Principal Investigator: Yamazaki Toshitsugu 東京大学, 大気海洋研究所, 教授 (80344125)
• Co-Investigator(Kenkyū-buntansha): 堀内 一穂 弘前大学, 理工学研究科, 助教 (00344614) ; 山本 裕二 高知大学, 教育研究部総合科学系複合領域科学部門, 教授 (00452699) ; 中村 教博 東北大学, 高度教養教育・学生支援機構, 教授 (80302248)
• Research Collaborator: Kumagai Yuho
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥43,940,000 (Direct Cost: ¥33,800,000、Indirect Cost: ¥10,140,000); Fiscal Year 2018: ¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000); Fiscal Year 2017: ¥10,920,000 (Direct Cost: ¥8,400,000、Indirect Cost: ¥2,520,000); Fiscal Year 2016: ¥28,470,000 (Direct Cost: ¥21,900,000、Indirect Cost: ¥6,570,000)
• Keywords: 古地磁気 / 古地磁気強度 / 伏角異常 / IODP / ベリリウム同位体 / ベリリウム同位体比 / 古地磁気学 / 海洋地質学 / 地球電磁気学 / 海洋地質

Outline of Final Research Achievements

A continuous geomagnetic paleointensity record during the last 8 million years was obtained uising marine sediment cores. Influence of sediment lithology variations on relative paleointensity estimations was evaluated and corrected. No discernible relation was found among mean paleointensity, polarity length, and polarity for this time interval. From inclination anomaly averaged over each polarity chron, the presence of a small polarity bias was confirmed for the last 5 million years. A shift of the sign of the inclination anomaly may have occurred before about 6 million years.

Academic Significance and Societal Importance of the Research Achievements

過去約800万年間の古地磁気強度変動及び伏角異常の連続的な記録を得たのは世界で初めてであり、学術的意義が大きい。また、現在当該分野で大きな問題となっている、相対古地磁気強度推定への堆積物岩相変化の影響について、それを見積もり補正する道をひらいたことで、今後、相対古地磁気強度記録の統計解析に基づいた、古地磁気強度と地球軌道要素の関係、逆転間隔との関係などの理解が進むと期待される。

Research Products

• [Journal Article] In-situ and meteoric 10Be and 26Al measurements: Improved preparation and application at the University of Tokyo (2019)
  • Author(s): Yokoyama, Y., Yamane, M., Nakamura, A., Miyairi, Y., Horiuchi, K., Aze, T., Matsuzaki, H., Shirahama, Y., Ando, Y.
  • Journal Title: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Volume: 印刷中 Pages: 260-264
  • DOI: 10.1016/j.nimb.2019.01.026
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Relative paleointensity and inclination anomaly over the last 8 Myr obtained from the Integrated Ocean Drilling Program Site U1335 sediments in the eastern equatorial Pacific. (2018)
  • Author(s): Yamazaki, T., Yamamoto, Y.
  • Journal Title: Geophys. Res. Solid Earth Volume: 123 Pages: 7305-7320
  • Peer Reviewed
• [Journal Article] A Geomagnetic Paleointensity Record of 0.6 to 3.2 Ma From Sediments in the Western Equatorial Pacific and Remanent Magnetization Lock-In Depth (2017)
  • Author(s): Sakuramoto Yukihiro、Yamazaki Toshitsugu、Kimoto Katsunori、Miyairi Yosuke、Kuroda Junichiro、Yokoyama Yusuke、Matsuzaki Hiroyuki
  • Journal Title: Journal of Geophysical Research: Solid Earth Volume: 122 Issue: 10 Pages: 7525-7543
  • DOI: 10.1002/2017jb014450
  • Peer Reviewed
• [Journal Article] Paleomagnetic inclination variations during the last 200 kyr in the Okhotsk Sea and their relation to persistent non-axial-dipole field. (2016)
  • Author(s): Yamazaki, T., Shimono, T., and Inoue, S.
  • Journal Title: Earth Planets Space Volume: 68 Issue: 1
  • DOI: 10.1186/s40623-016-0561-7
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Presentation] Paleointensity variation around 30 Ma obtained from Ethiopian Large Igneous Province (LIP) (2018)
  • Author(s): Yoshimura, Y., Yamazaki, T. Yamamoto, Y., Ahn, H.-S., Kidane, T., Otofuji, Y., and Ishikawa, N.
  • Organizer: EGU General Assembly 2018
  • Int'l Joint Research
• [Presentation] Preliminary report on sedimentary structure and magnetostratigraphy of IODP Site U1490 (2018)
  • Author(s): 熊谷祐穂、中村教博、Hatfield Robert、山崎俊嗣、山本裕二、国際深海科学掘削計画第363次 乗船研究者
  • Organizer: 日本地球惑星科学連合2018年大会
• [Presentation] 地磁双極子モーメントの平均値を求めるには何個の絶対古地磁気強度が必要か？ (2018)
  • Author(s): 吉村由多加、山崎俊嗣
  • Organizer: 日本地球惑星科学連合2018年大会
• [Presentation] Paleointensity variation around 30Ma obtained from Ethiopian Large Igneous Province (LIP) (2018)
  • Author(s): Yoshimura, Y., Yamazaki, T., Yamamoto, Y., Ahn, H.-S., Kidane, T.B., Otofuji, Y., Ishikawa, N.
  • Organizer: 2018 AGU Fall Meeting
• [Presentation] Preliminary report on sedimentary structure and magnetostratigraphy of IODP Site U1490 (2018)
  • Author(s): 熊谷祐穂，中村教博，Hatfield, R. G.，山崎俊嗣，山本裕二，Expedition 363 Scientists
  • Organizer: 地球電磁気・地球惑星圏学会第144回講演会
• [Presentation] 10Beから見た過去の宇宙線変動 (2018)
  • Author(s): 堀内一穂
  • Organizer: 宇宙線考古学研究会
• [Presentation] IODP Site U1490の古地磁気層序 (2018)
  • Author(s): 熊谷祐穂，中村教博，山崎俊嗣
  • Organizer: 平成29年度高知大学海洋コア総合研究センター共同利用・共同研究成果発表会
• [Presentation] Paleointensity variation at 30 Ma obtained from Ethiopian Large Igneous Province (LIP) (2018)
  • Author(s): Yoshimura, Y., Yamazaki, Y., Yamamoto, Y., Ahn, H.-S., Kidane, T., Otofuji, Y., Ishikawa, N.
  • Organizer: 平成29年度高知大学海洋コア総合研究センター共同利用・共同研究成果発表会
• [Presentation] Initial report for magnetostratigraphy of IODP Site U1490 (2017)
  • Author(s): Kumagai, Y., Hatfield, R. G., Nakamura, N., Yamazaki, T., and Expedition 363 Scientists
  • Organizer: American Geophysical Union 2017 Fall Meeting
  • Int'l Joint Research
• [Presentation] 東部赤道太平洋堆積物（IODP Site U1335）から得られた過去800万年間の相対古地磁気強度および伏角異常 (2017)
  • Author(s): 山崎俊嗣、山本裕二
  • Organizer: 日本地球惑星科学連合2017年大会
• [Presentation] A relative paleointensity record of the last 3.2 m.y. from western equatorial Pacific and remanent magnetization lock-in depth (2017)
  • Author(s): Sakuramoto, Y., Yamazaki, T., Miyairi, Y., Kimoto, K., Yokoyama, Y.
  • Organizer: JpGU-AGU Joint Meeting 2017
  • Int'l Joint Research
• [Presentation] Paleolatitudinal constraints from Eocene to Recent sediments cored in the equatorial Pacific on IODP Expeditions 320 and 321 (2016)
  • Author(s): Acton, G., Richter, C., Yamamoto, Y., Ohneiser, C., Yamazaki, T., Channell, J. E. T., Evans, H. F., Petronotis, K. E., Guidry, E. P.
  • Organizer: 2016 AGU Fall Meeting
  • Place of Presentation: 米国、サンフランシスコ
  • Year and Date: 2016-12-12
  • Int'l Joint Research
• [Presentation] ストロンチウム安定同位体比から探る第四紀の化学風化・炭酸塩収支の変化 (2016)
  • Author(s): 吉村寿紘、若木重行、黒田潤一郎、山崎俊嗣、高木悠花、木元克典、櫻本晋洋、石川剛志、大河内直彦
  • Organizer: 第２回地球環境史学会年会
  • Place of Presentation: 早稲田大学、東京都
  • Year and Date: 2016-11-26
• [Presentation] Chronostratigraphic constraints for cryptochron C18n.1n-1 observed in Eocene sediments cored in the paleoequatorial Pacific on IODP Expedition 320 (2016)
  • Author(s): Acton, G. D., Evans, H., Ohneiser, C., Richter, C., Yamamoto, Y., and Yamazaki, T.
  • Organizer: 2016 GSA Meeting
  • Place of Presentation: 米国、デンバー
  • Year and Date: 2016-09-25
  • Int'l Joint Research
• [Presentation] アイスコアと堆積物の10Beが示す17～20万年前の長周期太陽変動 (2016)
  • Author(s): 堀内一穂、鎌田佳苗、前島舜、佐々木祥、佐々木宣欣、山崎俊嗣、藤田秀二、本山秀明、松崎浩之
  • Organizer: 日本地球惑星科学連合2016年大会
  • Place of Presentation: 幕張メッセ国際会議場、千葉県、千葉市
  • Year and Date: 2016-05-22
  • Invited