Intensity of the Earth's magnetic field: evidence for a Mid-Paleozoic dipole low

Hawkins, Louise; Grappone, J. Michael; Sprain, Courtney J.; Saengduean, Patipan; Sage, Edward; Thomas-Cunningham, Sheikerra; Kugabalan, Banusha; Biggin, Andrew J.

doi:10.1002/essoar.10504053.1

Cited by 4 publications

(12 citation statements)

References 33 publications

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“…Until recently, many measurements of the Palaeozoic paleointensity were acquired using techniques that are not considered to meet modern standards of reliability. Several recent studies (Hawkins et al, 2020(Hawkins et al, , 2019Shcherbakova et al, 2017) have, however, confirmed their central observation -the field in the Devonian and early Carboniferous, was unusually weak compared to any subsequent period. Kulakov et al (2019) made a compilation of all paleointensity results from 65-200 Ma.…”

Section: Studies Of Geomagnetic Field Behaviourmentioning

confidence: 84%

“…Paleointensity studies typically provide snapshots of the strength of the magnetic field, and obtaining a continuous record throughout the Devonian will require many studies. All the paleointensity data spanning the interval 200-500 Ma have recently been reassessed by Hawkins et al (2020), who conclude that paleointensities express an extremely weak magnetic field throughout the Devonian, with some outliers during the Early Devonian (around 400 Ma), a time period for which there are both weak and strong paleointensity results. It is possible that the field dropped in strength from weak in the Early Devonian to extremely weak in the Middle and Late Devonian, but many more paleointensity data are needed to verify this.…”

Section: Studies Of Geomagnetic Field Behaviourmentioning

confidence: 99%

“…They determined a longterm average of the field between 65-200 Ma (Cretaceous-Jurassic) at around 40 Z Am 2 (Z equals 10 21), while the modern field is stronger, around 80 Z Am 2 (Thébault et al, 2015). The field in the Devonian is thus much weaker (Hawkins et al, 2019;Shcherbakova et al, 2017), with a median value of 17 Z Am 2 (Hawkins et al, 2020). Hawkins et al (2020) suggest this low field interval extended for at least 80 Myr, from the Early Devonian into the early Carboniferous and named it the Mid-Palaeozoic Dipole Low.…”

Section: Studies Of Geomagnetic Field Behaviourmentioning

confidence: 99%

“…For these reasons, careful selection criteria must be balanced with the desire to maximize the quantity of data included in a description of long-term field behaviour. Hawkins et al (2020) expanded the dataset of field strength estimates for the Devonian and assessed the reliability of paleointensity data. Using the data set compiled by Hawkins et al (2020), we selected sites which met the following criteria for our analysis: 1) directions were not identified as transitional in polarity by authors of the study, 2) there are at least 3 intensity determinations per site, and 3) site data are of reasonable quality (Q PI ≥ 3, following Biggin and Paterson, 2014).…”

Section: Studies Of Geomagnetic Field Behaviourmentioning

confidence: 99%

“…Thus, there is a strong need for new magnetostratigraphic studies in the Paleozoic, and especially the Devonian. Studies on the strength of the magnetic field (paleointensity), show that the Earth's magnetic field during the Devonian was very weak (Hawkins, 2018;Hawkins et al, 2020Hawkins et al, , 2019Shcherbakova et al, 2017). Several studies have also posed the hypothesis that the field was non-dipolar in some time intervals (Shatsillo and Pavlov, 2019;Shcherbakova et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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A Persistent Non-uniformitarian Paleomagnetic Field in the Devonian?

Boon¹,

Biggin²,

Thallner³

et al. 2021

Preprint

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The Devonian, like much of the Paleozoic, has long been a problematic period for paleomagnetism. Devonian paleomagnetic data are generally difficult to interpret and have complex partial or full overprints; problems that arise in data obtained from both sedimentary and igneous rocks. As a result, the reconstruction of tectonic plate motions, performed largely using apparent polar wander paths, has large uncertainty. Similarly, the Devonian geomagnetic polarity time scale is very poorly constrained. Paleointensity studies suggest that the field was much weaker than the modern field, and it has been hypothesised that this was accompanied by many polarity reversals (a hyperreversing field). We sampled middle to upper Devonian sections in Germany, Poland and Canada which show low conodont alteration indices, implying low thermal maturity. We show in this study that there are significant issues with these data, and they are not straightforward to interpret, even though no significant heating and remineralisation was likely to have caused overprinting. We compare our data to other magnetostratigraphic studies from the Devonian and review the polarity pattern as presented in the Geologic Time Scale. Combined with estimates for the strength of the magnetic field during the Devonian, we suggest that the field during the Devonian might have been so weak and in part non-dipolar that obtaining reliable primary paleomagnetic data from Devonian rocks is challenging. Careful examination of all data, no matter how unusual, is the best way to push forward our understanding of the Devonian magnetic field. Paleointensity studies show that the field during the Devonian had a similar low strength to that recently advocated during the Ediacaran. Independent evidence from malformed spores around the Devonian-Carboniferous boundary suggests that the terrestrial extinction connected to the Hangenberg event, was caused by increased UV-B radiation, supporting the weak field hypothesis. A fundamentally weak and possibly non-dipolar field during the Devonian could have been produced, in part, by true polar wander acting to maximise core-mantle heat flow in the equatorial region. It may also have influenced evolution and extinctions in this time period. There is a large-number of paleobiological crises in the Devonian, and we pose the question, did the Earth's magnetic field influence these crises?

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Section: Studies Of Geomagnetic Field Behaviourmentioning

confidence: 84%

Section: Studies Of Geomagnetic Field Behaviourmentioning

confidence: 99%

Section: Studies Of Geomagnetic Field Behaviourmentioning

confidence: 99%

Section: Studies Of Geomagnetic Field Behaviourmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A Persistent Non-uniformitarian Paleomagnetic Field in the Devonian?

Boon¹,

Biggin²,

Thallner³

et al. 2021

Preprint

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Enigmatic well-characterized remanent magnetization of silicified Lower Devonian rocks from the Tadrart area (Murzuq basin, SE Algeria)

Derder

Henry

Maouche

et al. 2022

Int J Earth Sci (Geol Rundsch)

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Analyzing Triassic and Permian Geomagnetic Paleosecular Variation and the Implications for Ancient Field Morphology

Handford

Biggin

Haldan

et al. 2021

Geochem Geophys Geosyst

Self Cite

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The geomagnetic field exists as a consequence of a dynamic system and shows variations across a range of timescales (Johnson & McFadden, 2015). Long-term behavior is often described in terms of the intensity, reversal rate, morphology, and stability of the field. As all of these features are a result of the geodynamo, it follows that their variations should be intrinsically linked and that relationships may exist between them (

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Intensity of the Earth's magnetic field: evidence for a Mid-Paleozoic dipole low

Cited by 4 publications

References 33 publications

A Persistent Non-uniformitarian Paleomagnetic Field in the Devonian?

A Persistent Non-uniformitarian Paleomagnetic Field in the Devonian?

Enigmatic well-characterized remanent magnetization of silicified Lower Devonian rocks from the Tadrart area (Murzuq basin, SE Algeria)

Analyzing Triassic and Permian Geomagnetic Paleosecular Variation and the Implications for Ancient Field Morphology

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