An exceptionally weak Devonian geomagnetic field recorded by the Viluy Traps, Siberia

Hawkins, Louise; Anwar, Taslima; Щербакова, В. В.; Biggin, Andrew J.; Kravchinsky, Vadim A.; Shatsillo, A. V.; Павлов, В. Е.

doi:10.1016/j.epsl.2018.10.035

Cited by 42 publications

(34 citation statements)

References 44 publications

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“…Absolute palaeointensity data over that same period of time are only partly documented, with hardly any data available during the Cambrian (e.g., Tauxe & Yamazaki 2007). However, they hint at a low value of the field after ⇠ 500 Ma, extending to the better documented Devonian (⇠ 419-359 Ma) when the field displayed an unusually low intensity and was less dipolar (e.g., Shcherbakova et al 2017;Hawkins et al 2019). Starting from the Carboniferous, many more data are available and they testify for a field becoming stronger again.…”

Section: Discussionmentioning

confidence: 97%

Impact of inner-core size on the dipole field behaviour of numerical dynamo simulations

Lhuillier

Hulot

Gallet

2019

Geophysical Journal International

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From a suite of 56 chemically-driven dynamo simulations with aspect ratio (inner to outer core radii) ranging from 0.10 to 0.44, we conduct the first systematic investigation of the impact of inner-core size on the reversing behaviour of dynamos. We show that the growth of the inner core leads to a transition between a "small inner-core" regime ( 0.18), when the field produced is intermediately strong and dipolar, and a "large inner-core" regime (> 0.26), when the field is stronger and more dipolar. During that transition the field is weaker and slightly less dipolar. For aspect ratios 0.20   0.22, reversal frequencies may be more sensitive to changes in the vigour of the convection, allowing high frequencies to be reached much more easily. Although other factors than the size of the inner core likely contribute to controlling the reversal frequency of the Earth's dynamo, we hypothesise that the occurrence of such a transition for the Earth's core between the end of the Precambrian and the end of the Devonian could possibly account for the manifestation of an unusual long-lasting episode of predominantly reversal hyperactivity and complex low intensity fields during that still poorly documented period of time.

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Section: Discussionmentioning

confidence: 97%

Impact of inner-core size on the dipole field behaviour of numerical dynamo simulations

Lhuillier

Hulot

Gallet

2019

Geophysical Journal International

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“…In sharp contrast, the VDM value determined for the Deccan eruption is lower than that of ~130-135 Ma (Fig. 2) and much lower than that in mid-Jurassic (for ex., a VDM of 3.27 ± 0.49 ×10 22 Am 2 at 166 Ma 9 ) and the late Cenozoic (for ex., ~5×10 22 Am 2 in Miocene 43 ); thus the comparison does not support inverse relation between reversal frequency and dipole moment at all times despite the coincidence of low dipole moments and high reversal frequency during mid-Jurassic 10,25,44 and Devonian 45,46 .…”

Section: Discussionmentioning

confidence: 81%

Low geomagnetic field strength during End-Cretaceous Deccan volcanism and whole mantle convection

Radhakrishna

Mohamed

Venkateshwarlu

et al. 2020

Sci Rep

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Knowledge about long-term variation of the geomagnetic dipole field remains in its nascent stage because of the paucity of reliable experimental data over geological periods. Here, we present the first robust experimental data from the largest Cretaceous flood basalt province on Earth, the ~65-66 Ma Deccan basalt within a thick (1250 m) unbiased stratigraphic section down to the basement, recovered from a drill hole of the Koyna Deep Scientific Drilling Project in the Western Ghats, India. Critical analysis of the result along with similar results of the Cretaceous age find that (i) the dipole moment during the end Cretaceous Deccan eruption is the lowest in whole of Cretaceous (ii) dipole moment at the onset/termination of the Cretaceous Normal Superchron is apparently lower relative to that in midsuperchron, however, such differences cannot be deciphered in shorter polarities probably because of insufficient time to develop recognizable variations (iii) inverse relation between dipole moment and reversal rate is lacking and (iv) a cause and effect relation between core-mantle boundary heat flux and low dipole moment that appears to be the principle governing factor in forming the Large Igneous Provinces on the surface of earth. Long-term variability of Earth's early Dipole magnetic field (palaeointensity; PI) is a complex internally driven phenomenon. Numerical simulations apart, geological materials are the only source for direct experimental estimates. However, large failure rate, prolonged duration of experiments and increased complexities in deciphering magnetic field at early periods have become a serious hindrance for this experimental approach; therefore, a vast number of studies have focused over the period of one million year, where the determinations are relatively more straight forward. Yet, in recent years, there have been compilations of PI data over the geological period with an objective to develop a robust global database (for example, PINT15 database: http:// earth.liv.ac.uk /pint/). The Mesozoic period has drawn a special attention with the proposal of a period of relatively low field, one-third of the Cenozoic value, known as the Mesozoic Dipole Low (MDL) 1. Whereas some investigations argue that the MDL proposal is not tenable 2-6 , the hypothesis has gained wider support 7-9 although many disagreements exist on the duration of the low field. The MDL was suggested to confine to the Jurassic Quiet Zone (~145-165 Ma) 10 , and some others extend it into early Cretaceous 11-13 .The low field strength is also variably described with respect to the Cretaceous Normal Superchron (CNS); some argue that the MDL extended into the CNS 14,15 , some others, mostly from China, report a low field at the onset of CNS 16-18 and some works find it at the end of the CNS 19-22. Likewise, the low fields are correlated with high reversal frequency 9,23-26 , but there are arguments decoupling the two 21,27,28. The fluctuation in geomagnetic field strength is intricately linked to core-mantle boundary (CMB) heat flo...

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“…During the last decennia, there is a trend towards applying multiple different paleointensity methods to prologue 14 rock samples from a single study (e.g. de Groot et al, , 2015de Groot et al, , 2016Hawkins et al, 2019;Hervé et al, 2017), which can improve the number of reliable paleointensities obtained.…”

Section: Short-term Variation Of the Geomagnetic Fieldmentioning

confidence: 99%

“…De laatste decennia is er een trend om meerdere verschillende paleointensiteitmethoden toe te passen op gesteentemonsters van een enkele studie (bijv. De Groot et al, , 2015Hawkins et al, 2019;Hervé et al, 2017), wat het slagingspercentage van een studie en het aantal betrouwbare paleointensiteitsgegevens kan verhogen. Om de betrouwbaarheid van de verkregen paleointensiteitsgegevens te kwantificeren, wordt het resultaat van een paleointensiteittechniek doorgaans vergeleken met een reeks vooraf gedefinieerde selectiecriteria.…”

Section: Paleointensiteit -De Sleutel Tot Het Begrijpen Van Het Aardmunclassified

“…Several attempts to calibrate pseudo-Thellier results into absolute paleointensities have seen mixed successes over the past years (e.g., Lerner et al, 2017;Paterson et al, 2016). There is also a trend towards applying different paleointensity methods to the same set of samples in a single study (e.g., 2016;Ertepinar et al, 2016;Greve et al, 2017;Hervé et al, 2017;Hawkins et al, 2019;Monster et al, 2015a;. Such a 'multimethod approach' dramatically increases the amount of reliable paleointensities produced for a set of sampled cooling units or sites and has been assigned its own paleointensity quality criterion .…”

Section: Introductionmentioning

confidence: 99%

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Highs, Lows, and Puzzling Intensity Variations of the Earth’s Magnetic Field

Béguin¹

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The Earth's magnetic field has a pivotal role in the Earth Sciences, its applications range from plate tectonics, to magnetostratigraphy. Together with seismology, it is the only window into the deep Earth and the Earth's core. In everyday life, the Earth's magnetic field is important for navigation devices. More importantly, the Earth's magnetic field protects the Earth against harmful solar radiation, and it protects satellites orbiting the Earth. Without the Earth's magnetic field, the atmosphere would have been stripped away and life on Earth would not have been possible. The growth of a stable magnetic field is thought to have been instrumental for the beginning of early life. Understanding the evolution and behavior of the Earth's magnetic field is therefore of great importance. In this thesis I will focus on the study of the strength of the Earth's magnetic field, its intensity. Therefore, I set out to unravel fast and local fluctuations in the direction and strength of the geomagnetic field. Paleointensity-the key to understanding the Earth's magnetic field Methods to derive paleointensity estimates from absolute recorders, e.g. lavas or archaeomagnetic materials, rely on comparing the ancient magnetization of the recorders that was obtained during cooling in the Earth's magnetic field, with a laboratory induced magnetization. As simple as this might sound, obtaining reliable and high quality paleointensity estimates from lavas is notoriously difficult. Besides the laborious effort to obtain paleointensity measurements, there is little consensus on the best approach of interpreting the measurement data and how to distinguish between high and low quality results. The first to propose to obtain information on the past state of the strength of the Earth's magnetic field by studying thermal remanences was Guiseppe Folgheraiter. He proposed that by reheating ancient pottery, the intensity of the ancient magnetization could be compared to the present magnetization (Folgheraiter, 1899). Folgheraiter did find that this method might lead to 'too uncertain results' when the baked vases were reheated several times. Almost forty years later an experimental protocol for estimating the ratio of natural remanent magnetization (NRM) and a laboratory acquired thermal remanence magnetization (TRM) was described by Johann Koenigsberger (1936). Koenigsberger used prologue a comparison of quasi-perpendicular and doubleheating thellier-style paleointensity techniques-towards an optimal protocol 1

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An exceptionally weak Devonian geomagnetic field recorded by the Viluy Traps, Siberia

Cited by 42 publications

References 44 publications

Impact of inner-core size on the dipole field behaviour of numerical dynamo simulations

Impact of inner-core size on the dipole field behaviour of numerical dynamo simulations

Low geomagnetic field strength during End-Cretaceous Deccan volcanism and whole mantle convection

Highs, Lows, and Puzzling Intensity Variations of the Earth’s Magnetic Field

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