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, RA, Smith, VC, Albert, PG, 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: English
• Published: Springer Nature 2022
• Subjects: Geomagnetic Pole
• Online Access: https://doi.org/10.1038/s43247-022-00401-0; https://ora.ox.ac.uk/objects/uuid:c72a0701-e26f-4705-8857-7cdb02e8772e

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.