Characterization of Individual Rock Magnetic Components by Analysis of Remanence Curves, 1. Unmixing Natural Sediments

Egli, Ramón

doi:10.1023/b:sgeg.0000020839.45304.6d

Cited by 241 publications

(409 citation statements)

References 100 publications

Supporting

Mentioning

370

Contrasting

Unclassified

Order By: Relevance

“…The magnetofossil component is correlated to the medium-coercivity component 2 (Table 1) with coercivity values around 40 mT and a small DP (~0.3), similar to the IRM signal of magnetotactic bacteria found in other studies (e.g. Egli, 2004;Chen et al, 2007;Jovane et al, 2012;Roberts et al, 2012 and 52%. The low-coercivity component varies from 5% to 17%.…”

Section: Environmental Magnetismsupporting

confidence: 83%

“…The coercivity distribution has a broad peak between 3 and 25 mT, with a maximum at 15-20 mT (Fig. 7) that falls within the range expected for magnetite magnetosomes (Egli, 2004;Kopp and Kirschvink, 2008;Egli et al, 2010). Outside the 63.2-65.5 msl interval, the magnetic signal of the samples is much weaker and no meaningful FORC distribution could be obtained from these samples (Fig.…”

Section: Environmental Magnetismmentioning

confidence: 65%

“…However, we cannot discount that component 1 represents the coarse end of a distribution of fine-grained, largely superparamagnetic particles, perhaps produced in situ by dissimilatory iron-reducing bacteria (e.g. Egli, 2004). The magnetofossil component is correlated to the medium-coercivity component 2 (Table 1) with coercivity values around 40 mT and a small DP (~0.3), similar to the IRM signal of magnetotactic bacteria found in other studies (e.g.…”

Section: Environmental Magnetismmentioning

confidence: 97%

“…These chains of nanocrystals (40-300 nm) are used by the magnetotactic bacteria to orient themselves relative to Earth's magnetic field (Blakemore, 1975) to find optimal living conditions in strongly chemically stratified aquatic environments (Bazylinski and Frankel, 2004). Magnetosomes can be preserved in sediments and in some cases may account for 20-60% of their bulk magnetization (Egli, 2004;Housen and Moskowitz, 2006;Roberts et al, 2011). Although magnetotactic bacteria are found in various marine environments (e.g.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean

Savian

Jovane

Frontalini

et al. 2014

Palaeogeography, Palaeoclimatology, Palaeoecology

View full text Add to dashboard Cite

Section: Environmental Magnetismsupporting

confidence: 83%

Section: Environmental Magnetismmentioning

confidence: 65%

Section: Environmental Magnetismmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean

Savian

Jovane

Frontalini

et al. 2014

Palaeogeography, Palaeoclimatology, Palaeoecology

View full text Add to dashboard Cite

“…The coercivity distribution of the dominant soft magnetic component (MDF ≈ 20 mT and DP ≈ 0.4) is characteristic of pedogenic magnetite (13,14), which is commonly transported into caves via drip water and preserved in stalagmites (9,11) (Fig. 2).…”

mentioning

confidence: 99%

Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China

Zhu

Feinberg

Xie

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

160

137

View full text Add to dashboard Cite

Extreme hydrologic events such as storms and floods have the potential to severely impact modern human society. However, the frequency of storms and their underlying mechanisms are limited by a paucity of suitable proxies, especially in inland areas. Here we present a record of speleothem magnetic minerals to reconstruct paleoprecipitation, including storms, in the eastern Asian monsoon area over the last 8.6 ky. The geophysical parameter IRMsoft-fluxrepresents the flux of soil-derived magnetic minerals preserved in stalagmite HS4, which we correlate with rainfall amount and intensity. IRMsoft-fluxexhibits relatively higher values before 6.7 ky and after 3.4 ky and lower values in the intervening period, consistent with regional hydrological changes observed in independent records. Abrupt enhancements in the flux of pedogenic magnetite in the stalagmite agree well with the timing of known regional paleofloods and with equatorial El Niño−Southern Oscillation (ENSO) patterns, documenting the occurrence of ENSO-related storms in the Holocene. Spectral power analyses reveal that the storms occur on a significant 500-y cycle, coincident with periodic solar activity and ENSO variance, showing that reinforced (subdued) storms in central China correspond to reduced (increased) solar activity and amplified (damped) ENSO. Thus, the magnetic minerals in speleothem HS4 preserve a record of the cyclic storms controlled by the coupled atmosphere−oceanic circulation driven by solar activity.

show abstract

Magnetotaxis and acquisition of detrital remanent magnetization by magnetotactic bacteria in natural sediment: First experimental results and theory

Mao

Egli

Petersen

et al. 2014

Geochem Geophys Geosyst

View full text Add to dashboard Cite

[1] The widespread occurrence of magnetotactic bacteria (MTB) in several types of marine and freshwater sediment, and the role of fossil magnetosomes (magnetofossils) as main remanent magnetization carriers therein, has important paleomagnetic and paleoenvironmental implications. Despite numerous studies on MTB biology and on magnetofossil preservation in geological records, no detailed information is yet available on how magnetotaxis (i.e., the ability to navigate along magnetic field lines) is performed in sedimentary environments, and on how magnetofossils possibly record the Earth magnetic field. We provide for the first time experimental evidence for these processes. MTB living in sediment are poorly aligned with the geomagnetic field, contrary to what is observed in water. This can explain the seemingly excessive magnetic moment of most MTB. The observed alignment is sufficient for supporting magnetotaxis across the typical thickness of chemical gradients. Experiments with magnetofossil-rich sediment suggest that a natural remanent magnetization (NRM) is acquired by magnetofossils in the so-called benthic mixed layer, where natural MTB populations usually occur. The acquired NRM is proportional to the applied field at least up to $160 mT, and its intensity is compatible with values observed in nature for same sediment types. Therefore, if fossil magnetosome chains are not subjected to further alteration by early diagenetic processes, they can provide useful relative paleointensities. We propose a preliminary model to explain early stages of magnetofossil NRM acquisition as the result of a dynamic equilibrium between magnetic torques and randomizing forces due to sediment mixing.

show abstract

Characterization of Individual Rock Magnetic Components by Analysis of Remanence Curves, 1. Unmixing Natural Sediments

Cited by 241 publications

References 100 publications

Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean

Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean

Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China

Magnetotaxis and acquisition of detrital remanent magnetization by magnetotactic bacteria in natural sediment: First experimental results and theory

Contact Info

Product

Resources

About