Intermittent non-axial dipolar-field dominance of twin Laschamp excursions

• Published in: Communications Earth & Environment
• Main Authors: Hyodo, M., Nakagawa, T., Matsushita, H., Kitaba, I., Yamada, K., Tanabe, S., Bradák, B., Miki, M., McLean, D., Staff, R., Smith, V., Albert, P., Bronk Ramsey, C., Yamasaki, A., Kitagawa, J., Schlolaut, G., Gotanda, K., Tsumura, K., Inagawa, K., Kumazawa, K., Abe, H., Sugo, S., Takahashi, K., Kitamura, A.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2022
• Subjects: Geomagnetic Pole
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5015121; https://gfzpublic.gfz-potsdam.de/pubman/item/item_5015121_1/component/file_5015208/5015121.pdf

Geomagnetic excursions represent the dynamic nature of the geodynamo. Accumulated palaeomagnetic records indicate that such excursions are dominated by dipolar-fields, but exhibit different structures. Here we report a palaeomagnetic record from the varved sediments of Lake Suigetsu, central Japan, which reveals fine structures in the Laschamp Excursion and a new post-Laschamp excursion that coincides with the Δ14C maxima. The record’s high-resolution chronology provides IntCal20 mid-ages and varve-counted durations. Both excursions comprise multiple subcentennial directional-swings. Simulations of filtering effects on sediment-magnetisations demonstrate that this high-resolution record replicates most of the features in existing, lower-resolution Laschamp excursion records, including the apparent clockwise open-loop of the virtual geomagnetic pole pass. The virtual geomagnetic poles during the ‘swing’ phases make four clusters centred in hemispherically-symmetric regions, three of which encompass the virtual geomagnetic poles associated with the Laschamp Excursion recorded in lavas at various locations. The stationary dipolar-field sources under each cluster should have intermittently dominated one after another during the excursions.