Fossil bacterial magnetite in deep-sea sediments from the South Atlantic Ocean

Petersen, N.; Dobeneck, Tilo von; Vali, Hojatollah

doi:10.1038/320611a0

Cited by 342 publications

(210 citation statements)

References 17 publications

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“…We deduce that they have an authigenic origin. Both biogenic and chemical formation of authigenic magnetic minerals are possible in lacustrine and marine sediments [20][21][22][23][24][25][26][27][28], but it was not possible to discriminate between those mechanisms on the basis of magnetic properties in this study.…”

Section: Discussionmentioning

confidence: 99%

Mineral-magnetic record of Late Quaternary climatic changes in a high Alpine lake

Lanci

Hirt

Lowrie

et al. 1999

Earth and Planetary Science Letters

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The magnetic properties of a sediment core from a high altitude lake in the Swiss Alps were compared with palynological and geochemical data to link climatic and mineral magnetic variations. According to pollen data, the sediments extend from the present to the Younger Dryas, i.e., they cover more than 10,000 years of environmental change in the Alps. The major change in magnetic properties corresponds to the climatic warming of the early Holocene. High-coercivity magnetic minerals that characterize the late-glacial period almost disappeared during the Holocene and the concentration of ferrimagnetic minerals increased sharply. The contribution of superparamagnetic grains also decreased in the Holocene sediments. Similar variations in SP content and coercivity, of smaller magnitude, are found in the Holocene and are interpreted to represent minor climatic variations. Comparison with the historical record of the last 1000 years confirms this interpretation. The magnetic mineralogy, the superparamagnetic contents, and the IRM intensity in the coarse-grained, late-glacial sediments are similar to those measured in the catchment bedrock. This indicates a detrital origin. The different properties and the higher concentration of magnetic minerals in the Holocene sediments are due to authigenic phases. Magnetic properties provide a high resolution record of climatic change. They are sensitive even to small variations that are not recorded in the pollen or LOI data. Magnetic parameters show fine-scale variation and constitute a valuable supplement to conventional climatic indicators.

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Section: Discussionmentioning

confidence: 99%

Mineral-magnetic record of Late Quaternary climatic changes in a high Alpine lake

Lanci

Hirt

Lowrie

et al. 1999

Earth and Planetary Science Letters

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“…[15] Magnetic separates were extracted from clay mineral samples dispersed in distilled water using a magnetic finger [Petersen et al, 1986], transferred onto C-coated 300-mesh Cu TEM grids and studied using a JEOL JEM-2000FX TEM and a JEOL-JEM 2100F FE-TEM, the latter equipped with an Oxford INCA microanalytical system. Highresolution lattice-fringe images and diffraction patterns were obtained at 200 kV accelerating voltage.…”

Section: Transmission Electron Microscopymentioning

confidence: 99%

“…[18] TEM and energy dispersive X-ray spectroscopy analysis of magnetic separates [Petersen et al, 1986] from suspended clay reveals abundant elongate prismatic and bullet-shaped, SD-size crystals of stochiometric magnetite (Figures 4 and 5) that resemble magnetite present within a variety of bacteria [Kopp and Kirschvink, 2007;Vali and Kirschvink, 1991]. Equidimensional cuboidal particles are present but less common than elongate particles.…”

Section: Characterization Of Magnetic Particlesmentioning

confidence: 99%

“…Common in both freshwater and marine environments, the bacteria are most abundant under suboxic conditions, both in sediments and in the water column. Although magnetofossils are common magnetic components of Quaternary sediments [Petersen et al, 1986], reports of magnetofossils from older rocks are scarce [Evans and Heller, 2003;Kopp and Kirschvink, 2007]. Kent et al dismissed the possibility that the magnetic properties of the New Jersey PETM clay were produced by magnetofossils because they imaged only isolated, equidimensional magnetite under transmission electron microscopy (TEM).…”

Section: Introductionmentioning

confidence: 99%

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Magnetofossil spike during the Paleocene‐Eocene thermal maximum: Ferromagnetic resonance, rock magnetic, and electron microscopy evidence from Ancora, New Jersey, United States

et al. 2007

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Previous workers identified a magnetically anomalous clay layer deposited on the northern United States Atlantic Coastal Plain during the Paleocene‐Eocene thermal maximum (PETM). The finding inspired the highly controversial hypothesis that a cometary impact triggered the PETM. Here we present ferromagnetic resonance (FMR), isothermal and anhysteretic remanent magnetization, first‐order reversal curve, and transmission electron microscopy analyses of late Paleocene and early Eocene sediments in drill core from Ancora, New Jersey. A novel paleogeographic analysis applying a recent paleomagnetic pole from the Faeroe Islands indicates that New Jersey during the initial Eocene had a ∼6°–9° lower paleolatitude (∼27.3° for Ancora) and a more zonal shoreline trace than in conventional reconstructions. Our investigations of the PETM clay from Ancora reveal abundant magnetite nanoparticles bearing signature traits of crystals produced by magnetotactic bacteria. This result, the first identification of ancient biogenic magnetite using FMR, argues that the anomalous magnetic properties of the PETM sediments are not produced by an impact. They instead reflect environmental changes along the eastern margin of North America during the PETM that led to enhanced production and/or preservation of magnetofossils.

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“…None, however, display the unique, elongate 'bullet'-or 'boot'-shaped crystals that unequivocally de¢ne an intracellular, biogenic origin for such grains (e.g. Petersen et al, 1986;Vali et al, 1987) and the concatenation is likely to have occurred postdispersion and -extraction.…”

Section: Mineralogical Analysis Of Magnetic Extractsmentioning

confidence: 99%

Magnetic mineralogy of soils across the Russian Steppe: climatic dependence of pedogenic magnetite formation

Maher

Alekseev

Alekseeva

2003

Palaeogeography, Palaeoclimatology, Palaeoecology

187

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Formation of ferrimagnets in well-drained, buffered, unpolluted soils appears to be related to climate, and especially rainfall. If robust, this magnetism/rainfall couple can be used to estimate past rainfall from buried soils, particularly the multiple soils of the Quaternary loess/soil sequences of Central Asia. However, dispute exists regarding the role of climate vs. dust flux for the magnetic properties of modern loessic soils. Here, we examine the mineralogical basis of the magnetism/rainfall link for a climate transect across the loess-mantled Russian steppe, where, critically, dust accumulation is minimal at the present day. Magnetic and independent mineralogical analyses identify in situ formation of ferrimagnets in these grassland soils; increased ferrimagnetic concentrations are associated with higher annual rainfall. XRD and electron microscopy show the soil-formed ferrimagnets are ultrafinegrained ( 6 V50 nm) and pure. Ferrimagnetic contributions to Mo « ssbauer spectra range from 17% in the parent loess to 42% for a subsoil sample from the highest rainfall area. Total iron content varies little but the systematic magnetic increases are accompanied by decreased Fe 2þ content, reflecting increased silicate weathering. For this region, parent materials are loessial deposits, topography is rolling to flat and duration of soil formation effectively constant. The variations in soil magnetic properties thus predominantly reflect climate (and its co-variant, organic activity)ŝ tatistical analysis identifies strongest relationships between rainfall and magnetic susceptibility and anhysteretic remanence. This magnetic response correlates with that of the modern soils across the Chinese Loess Plateau. Such correlation suggests that the rainfall component of the climate system, not dust flux, is a key influence on soil magnetic properties in both these regions. ß

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Fossil bacterial magnetite in deep-sea sediments from the South Atlantic Ocean

Cited by 342 publications

References 17 publications

Mineral-magnetic record of Late Quaternary climatic changes in a high Alpine lake

Mineral-magnetic record of Late Quaternary climatic changes in a high Alpine lake

Magnetofossil spike during the Paleocene‐Eocene thermal maximum: Ferromagnetic resonance, rock magnetic, and electron microscopy evidence from Ancora, New Jersey, United States

Magnetic mineralogy of soils across the Russian Steppe: climatic dependence of pedogenic magnetite formation

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