Constraining the age of the last geomagnetic reversal from geochemical and magnetic analyses of Atlantic, Indian, and Pacific Ocean sediments

Valet, Jean‐Pierre; Bassinot, Franck; Simon, Quentin; Savranskaia, Tatiana; Thouveny, Nicolas; Bourlès, Didier; Villedieu, A.

doi:10.1016/j.epsl.2018.11.012

Cited by 35 publications

(28 citation statements)

References 50 publications

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“…(1) The tektite event is said to occur at the beginning of interglacial period M19, i.e., at a time a paleosol was developing. This is not in agreement with the most recent work of Valet et al (2019) on Indian Ocean deepsea cores that clearly put the tektite event at the very end of glacial period M20 or at the beginning of the transition to M19; i.e., at a time paleosol was not yet forming. It is unwise to use Chinese loess stratigraphy for precise chronology, as done by Mizera, as loess sequences do not follow a simple sedimentation pattern: paleosol may develop on materials that were deposited during a cold period due to down-going pedogenesis (see, e.g., Zhou and Shackleton, 1999).…”

contrasting

confidence: 97%

10Be in Australasian microtektites compared to tektites: Size and geographic controls: REPLY

Rochette¹,

Braucher²,

Folco³

et al. 2019

Geology

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contrasting

confidence: 97%

10Be in Australasian microtektites compared to tektites: Size and geographic controls: REPLY

Rochette¹,

Braucher²,

Folco³

et al. 2019

Geology

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“…7h). Considering the recently determined Be-proxy age constraints on the M-B boundary (~ 772 ka at midreversal: Simon et al 2018 andValet et al 2019), the age delay of ~ 22 ka may indicate lock-in depths of ~ 8 cm below the mixing layer for the M-B boundary in the studied core.…”

Section: Age Controlmentioning

confidence: 88%

“…The two polarity changes at ~ 578 cm and ~ 677 cm in NPGP1401-2A provide an age framework as the M-B boundary of ~ 785-772 ka (e.g., Channell et al 2010;Sagnotti et al 2016;Mark et al 2017;Valet et al 2019) and the upper Jaramillo boundary of ~ 991-990 ka (Gradstein et al 2012;Simon et al 2018), respectively. In a sequence with such a low sedimentation rate (~ 677/990 cm/ka), surficial mixing and post-depositional remanent magnetization (pDRM) lock-in effects could affect the paleomagnetic age delay (e.g., Suganuma et al 2010;Simon et al 2016Simon et al , 2018.…”

Section: Age Controlmentioning

confidence: 99%

Wavelet-based verification of a relative paleointensity record from the North Pacific

Shin

Kim

2019

Earth Planets Space

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We present a relative paleointensity (RPI) record for the last ~ 1.1 Myr estimated from a sediment core in the central North Pacific, with quality verification using wavelet analysis. Rock magnetic analysis reveals that a stable remanence is carried mainly by single-domain (SD) biogenic magnetite and pseudo-SD detrital magnetite and that concentration-and grain-size-related bulk magnetic parameters vary by a factor of 3, initially meeting a conventional standard for RPI estimation. However, a further test using wavelet spectra of RPI proxies normalized by anhysteretic remanent magnetization (ARM) or isothermal remanent magnetization (IRM) shows intermittent orbital contamination at period of 100 kyr. A part of the 100-kyr orbital frequency in ARM-normalized RPI has a coherence and physical relationship with the normalizer. For the same time interval, a prominent 100-kyr cycle in the ARM/IRM wavelet spectra is also coherent with RPI, indicating that relative changes in biogenic and detrital magnetite were not well compensated by ARM normalization. For the selected RPI proxy using IRM normalization, a significant physical relationship with the lithology of magnetic minerals was not detected in the wavelet analysis, and thus, its intermittent orbital cycles could be of climatic origin, probably induced by non-magnetic factors. Nevertheless, our RPI record is consistent with global RPI stacks and provides a successful reconstruction of paleointensity with geomagnetic field origin in the North Pacific.

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“…773 ka (with a duration of 4.4 ka) from a set of highresolution paleomagnetic and oxygen isotope data from marine sites in the northern Atlantic Ocean (Channell et al, 2010), and at ca. 772 ka from a combination of 10 Be, paleomagnetic and oxygen isotope analyses (Valet et al, 2019). The volcanic records are characterized by more scattered ages.…”

Section: Introductionmentioning

confidence: 99%

“…The apparent discrepancies between the ages derived from marine records and from terrestrial lava sequences could be caused by multiple factors: (1) non-dipole structures recorded by lava flows but smoothed out in sediments; (2) potential offset between the two signals due to delayed magnetization resulting from locking depth in some sediments; and (3) uncertainties inherent to radiometric dating (Channell et al, 2010;Singer, 2014) and orbital tuning techniques (Valet et al, 2019). It has been proposed (Valet et al, 2012) that geomagnetic reversals could be described by three successive phases: a precursory event, a 180 • polarity switch and a rebound.…”

Section: Introductionmentioning

confidence: 99%

Volcanic Record of the Last Geomagnetic Reversal in a Lava Flow Sequence From the Azores

et al. 2020

Self Cite

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We present paleomagnetic and geochronological data of twenty-five stacked lava flows from São Miguel Island (Azores) that were emplaced during the last geomagnetic reversal (Matuyama-Brunhes, M-B). The characteristic direction of natural remanent magnetization was isolated through alternating field and/or thermal demagnetization. From bottom to top, the directional changes display a first phase with reverse, transitional and normal directions which is followed by a second phase with transitional and normal directions. Dating by Potassium-Argon (K-Ar) of fresh separated groundmass provide ages of 768 ± 5 ka and 765 ± 5 ka (1σ) for the first and second transitional episodes, respectively. We infer that this sequence recorded the last reversal and reveal the presence of a rebound that occurred soon after the transition. The age of the transition is 5-15 kyr younger than at other volcanic localities, but in agreement with astronomical ages that were recently proposed for the transitional interval. The reversal is characterized by weak field intensity during the transition, a recovery phase and a subsequent decrease during the rebound. The two transitional virtual geomagnetic poles (VGPs) that characterize the transition are found above the South Atlantic and the North Pacific. When compared to other M-B records, no VGP is found above preferred locations.

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Constraining the age of the last geomagnetic reversal from geochemical and magnetic analyses of Atlantic, Indian, and Pacific Ocean sediments

Cited by 35 publications

References 50 publications

10Be in Australasian microtektites compared to tektites: Size and geographic controls: REPLY

10Be in Australasian microtektites compared to tektites: Size and geographic controls: REPLY

Wavelet-based verification of a relative paleointensity record from the North Pacific

Volcanic Record of the Last Geomagnetic Reversal in a Lava Flow Sequence From the Azores

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