A basic study on remanent magnetization of volcanic ash layer

2021 Fiscal Year Final Research Report

• Project/Area Number: 17K05683
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Kumamoto University
• Principal Investigator: Mochizuki Nobutatsu 熊本大学, 大学院先端科学研究部(理), 准教授 (60422549)
• Co-Investigator(Kenkyū-buntansha): 長谷川 健 茨城大学, 理工学研究科(理学野), 准教授 (00574196) ; 渋谷 秀敏 同志社大学, 研究開発推進機構, 嘱託研究員 (30170921)
• Project Period (FY): 2017-04-01 – 2022-03-31
• Keywords: 火山灰 / 堆積残留磁化

Outline of Final Research Achievements

Remanent magnetization of volcanic ash layers is clearly understood, but the remanent magnetization has the potential to record the paleomagnetic field and to be a new recorder to recover paleomagnetic secular variations. We conducted a fundamental study on remanent magnetizations of volcanic ash layers. Paleomagnetic analyses show that inclinations of the remanent magnetizations are consistent or shallower than that of the paleomagnetic field when the volcanic ash layer formed. On the other hand, declinations of the remanent magnetizations are consistent with the paleomagnetic field. The reasons for the differences between the remanent magnetization and the paleomagnetic field are unclear; the shallow inclination may be related to local magnetic anomaly, sedimentation/compaction processes, etc.

Free Research Field

古地磁気学

Academic Significance and Societal Importance of the Research Achievements

本研究により火山近傍の火山灰が安定な残留磁化を持っていることが確認された。いくつかの火山灰層の残留磁化は地磁気伏角よりもいくらか浅いものがあり，この要因については検討が必要ではあるものの，細粒火山灰層は堆積当時の地磁気方位に平行な残留磁化を獲得しているようだ。古地磁気方位の復元には，火山岩や火砕流堆積物だけではなく，火山灰層も利用できる可能性が見えてきたといえる。