Further application of the deconvolution method of post-depositional DRM to the precise record of the Matuyama-Brunhes reversal in the sediments from the Boso Peninsula, Japan

Tsunakawa, Hideo; Okada, Makoto; Niitsuma, Nobuaki

doi:10.1186/bf03352221

Cited by 13 publications

(8 citation statements)

References 17 publications

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“…The directional changes obtained in this study (Figure 6a) are more complicated than those of Chauvin et al [1990], who report a single directional reversal from the southern side of Punaruu Valley (Figure 6b). A similar oscillatory remanence change at the M‐B transition was reported from a lava flow sequence on Maui [ Coe et al , 2004] and also from several sedimentary records [e.g., Tsunakawa et al , 1996, 1999; Yamazaki and Oda , 2001]. Complex directional behaviors were clearly observed in the high‐deposition‐rate sediment drifts [ Channell and Lehman , 1997].…”

Section: Paleodirectionssupporting

confidence: 78%

Paleointensity variation across the Matuyama-Brunhes polarity transition: Observations from lavas at Punaruu Valley, Tahiti

et al. 2011

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[1] We have conducted a paleointensity study of the Matuyama-Brunhes (M-B) polarity transition recorded in 34 successive lava flows of Punaruu Valley on Tahiti. A reversed polarity is obtained from the lower part of the record, major directional changes are derived from the middle part of the record, and a normal polarity is recorded in the upper part of the record. These paleomagnetic directions and five 40 Ar/ 39 Ar ages yielding a weighted mean of 771 ± 8 (1s) ka indicate that 30 lava flows recorded the geomagnetic field across the M-B transition. The 215 specimens from 32 flows were subjected to the double-heating technique of the Shaw method combined with low-temperature demagnetization (LTD-DHT Shaw method), yielding 73 successful results from 18 flows. For the reversed polarity period just prior to the major directional changes, paleointensity shows an oscillation-like variation between 3 and 38 mT corresponding to virtual dipole moments (VDMs) between 0.9 × 10 22 and 9.6 × 10 22 Am 2 . For the major directional changes, a weak paleointensity of 5 mT is obtained, which gives a VDM of 1.0 × 10 22 Am 2 . For the normal polarity period, paleointensities are 14-21 mT, giving VDMs of 3.5-5.2 × 10 22 Am 2 . For the reversed polarity period just prior to the major directional changes, a linear relationship with a correlation coefficient of 0.96 is recognized on the diagram of VDM versus virtual geomagnetic pole latitude. This linear relationship may be a precursory feature of the geodynamo at the onset of the M-B transition.

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Section: Paleodirectionssupporting

confidence: 78%

Paleointensity variation across the Matuyama-Brunhes polarity transition: Observations from lavas at Punaruu Valley, Tahiti

et al. 2011

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“…1c). These pioneering studies identified the M-B boundary approximately 2 m below the Byk-E tephra bed using alternating field (AF) demagnetization, which removes secondary remanences by exposing a specimen to an alternating magnetic field (Niitsuma 1971;Okada and Niitsuma 1989;Tsunakawa et al 1995Tsunakawa et al , 1999Aida 1997).…”

Section: Previous Paleomagnetic Studies In the Kokumoto Formationmentioning

confidence: 99%

A full sequence of the Matuyama–Brunhes geomagnetic reversal in the Chiba composite section, Central Japan

Haneda

Okada

Suganuma

et al. 2020

Prog Earth Planet Sci

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Geological records of the Matuyama–Brunhes (M–B) geomagnetic reversal facilitate the development of an age model for sedimentary and volcanic sequences and help decipher the dynamics of the Earth’s magnetic field. However, the structure of the geomagnetic field during the M–B geomagnetic reversal remains controversial due to its complex field behavior. In this study, we conducted paleo- and rock-magnetic analyses of samples from the Chiba composite section (CbCS), a continuous and expanded marine succession in Central Japan, to reconstruct the full sequence of the M–B geomagnetic reversal. We define an average stratigraphic position of the M–B boundary and estimate its age based on three sections in the CbCS and a neighboring drill core, TB-2. The average stratigraphic position of the M–B boundary in the CbCS is established at 1.1 ± 0.3 m above a widespread volcanic ash bed (the Byk-E tephra). Assuming a chronological error associated with orbital tuning of 5 kyr and stratigraphic uncertainty of 0.4 kyr, the M–B boundary in CbCS is at 772.9 ± 5.4 ka (1σ). The virtual geomagnetic pole, which is calculated from the paleomagnetic directions, shows several short fluctuations between 783 and 763 ka, with concomitant decreases in geomagnetic field intensity index. After termination of the field instabilities, the field intensity recovered and became higher than before the M–B boundary, with a stable normal polarity direction. The paleomagnetic records in the CbCS exhibit a field asymmetry between the axial dipole decay and field recovery, providing a full sequence of the M–B reversal, suggesting that the non-axial dipole field dominated several times during periods ca. 20 kyr long across the M–B boundary, due to depletion in the main axial dipole component. Our results provide probably the most detailed sedimentary record of the M–B geomagnetic reversal and offer valuable information to further understand the mechanism and dynamics of geomagnetic reversals. Graphical abstract

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“…However, its influence is also observed in records of older Cenozoic reversals obtained from Australian lavas [Hoffman, 1986;. With regard to the Matuyama-Brunhes, domination of the transitional field by the Australian flux patch extended over a considerable portion of Earth's surface [see Hoffman, 2000], as its apparent effect has been observed in Chilean lavas [Brown et al, 1994[Brown et al, , 2004, Japanese sediments [e.g., Niitsuma, 1971;Tsunakawa et al, 1999], and Chinese loess [Zhu et al, 1994].…”

Section: Reversal Of the Ad-field And Conclusion Of The Dynamo Processmentioning

confidence: 99%

Evidence of a partitioned dynamo reversal process from paleomagnetic recordings in Tahitian lavas

Hoffman

Mochizuki

2012

Geophysical Research Letters

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[1] Lavas erupted at the Society hotspot during the Matuyama-Brunhes (M-B) polarity reversal record transitional field behavior containing two tight paleodirectional groups that when averaged are antipodal at the 95% confidence level, and thus correlate to antipodal clustered virtual geomagnetic poles (VGPs). The occurrence of these observations--data obtained from two published records of the M-B transition from distinct sections of a succession of flows on Tahiti--is associated with a time when the strength of the axial dipole was significantly reduced. One of the clusters was recorded by lavas that were not erupted in succession, suggesting that significant time had passed during this volcanic activity. Time spent during the formation of the antipodal cluster is unknown, although it resides in the same location as VGP clusters associated with four other transitional events obtained from Society hotspot lavas. Calculated VGPs at the Society hotspot for both "polarities" of the averaged historic field--less the axial dipole term--are found in the cluster locations. These findings offer strong evidence for a two-tiered dynamo process in which nearly the entire axial dipole component undergoes both demise and regeneration quasi-independently from that of the remainder of the field, the pattern of which is tied to long-held physical conditions of the lower-most mantle.Citation: Hoffman, K. A., and N. Mochizuki (2012), Evidence of a partitioned dynamo reversal process from paleomagnetic recordings in

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Further application of the deconvolution method of post-depositional DRM to the precise record of the Matuyama-Brunhes reversal in the sediments from the Boso Peninsula, Japan

Cited by 13 publications

References 17 publications

Paleointensity variation across the Matuyama-Brunhes polarity transition: Observations from lavas at Punaruu Valley, Tahiti

Paleointensity variation across the Matuyama-Brunhes polarity transition: Observations from lavas at Punaruu Valley, Tahiti

A full sequence of the Matuyama–Brunhes geomagnetic reversal in the Chiba composite section, Central Japan

Evidence of a partitioned dynamo reversal process from paleomagnetic recordings in Tahitian lavas

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