Quantifying magnetite magnetofossil contributions to sedimentary magnetizations

Heslop, David; Roberts, Andrew P.; Chang, Liao; Davies, M. H.; Abrajevitch, Alexandra; Deckker, Patrick De

doi:10.1016/j.epsl.2013.09.011

Cited by 42 publications

(53 citation statements)

References 59 publications

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“…We observe occasional biogenic magnetite crystals below the sulfidic redox boundary (Figures k and l). However, biogenic magnetite crystals within this sample are much less abundant compared to samples from above the boundary and from typical magnetofossil‐rich sediments [e.g., Chang et al ., ; Heslop et al ., ].…”

Section: Resultsmentioning

confidence: 99%

“…Low‐temperature SIRM warming curves after ZFC and FC treatment and corresponding derivatives for samples from (a) the Ria de Vigo, Spain [ Mohamed et al ., ], (b) offshore of Western Australia [ Heslop et al ., ], and (c) offshore of Southern Australia. Green and blue dashed lines in the derivative curves mark the peaks at 100 and 120 K, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…Such organic‐rich sediments host strong magnetic mineral diagenesis [ Roberts , ]. Additional marine sediment samples from offshore of Western Australia [ Heslop et al ., ], Southern Australia, and the Ria de Vigo, Spain [ Mohamed et al ., ], were also analyzed.…”

Section: Methodsmentioning

confidence: 99%

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Discrimination of biogenic and detrital magnetite through a double Verwey transition temperature

et al. 2016

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Magnetite occurs widely in natural environments in both inorganic and biogenic forms. Discrimination of the origin of magnetite has important implications, from searching for past microbial activity to interpreting paleomagnetic and environmental magnetic records in a wide range of settings. In this study, we present rock magnetic and electron microscopic analyses of marine sediments from the continental margin of Oman. Low‐temperature magnetic data reveal two distinct Verwey transition (Tv) temperatures that are associated with the presence of biogenic and inorganic magnetite. This interpretation is consistent with room temperature magnetic properties and is confirmed by electron microscopic analyses. Our study justifies the use of two distinct Tv temperatures as a diagnostic signature for discriminating inorganic and biogenic magnetite. Simple low‐temperature magnetic measurements, therefore, provide a tool to recognize rapidly the origin of magnetite within natural samples. In addition, our analyses reveal progressive down‐core dissolution of detrital and biogenic magnetite, but with preservation of significant amounts of fine‐grained magnetite within sediments that have been subjected to severe diagenetic alteration. We demonstrate that preservation of magnetite in such environments is due to protection of fine‐grained magnetite inclusions within silicate hosts. Our results, therefore, also provide new insights into diagenetic processes in marine sediments.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Discrimination of biogenic and detrital magnetite through a double Verwey transition temperature

et al. 2016

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“…Magnetosome chains have remarkable magnetic properties (5,6,9), which have been used to identify bacterial magnetofossils in sediments. Although previous studies demonstrated that observations by electron microscopy and/or magnetic measurements could detect bacterial magnetofossils in natural samples (9)(10)(11)(12)(13), the chain structure is generally lost during sediment aging owing to degradation of organic matter assembling magnetosomes (9,14). This strongly complicates the identification of the bacterial magnetofossils.…”

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confidence: 83%

Chemical signature of magnetotactic bacteria

Amor

Busigny

Durand-Dubief

et al. 2015

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

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There are longstanding and ongoing controversies about the abiotic or biological origin of nanocrystals of magnetite. On Earth, magnetotactic bacteria perform biomineralization of intracellular magnetite nanoparticles under a controlled pathway. These bacteria are ubiquitous in modern natural environments. However, their identification in ancient geological material remains challenging. Together with physical and mineralogical properties, the chemical composition of magnetite was proposed as a promising tracer for bacterial magnetofossil identification, but this had never been explored quantitatively and systematically for many trace elements. Here, we determine the incorporation of 34 trace elements in magnetite in both cases of abiotic aqueous precipitation and of production by the magnetotactic bacterium Magnetospirillum magneticum strain AMB-1. We show that, in biomagnetite, most elements are at least 100 times less concentrated than in abiotic magnetite and we provide a quantitative pattern of this depletion. Furthermore, we propose a previously unidentified method based on strontium and calcium incorporation to identify magnetite produced by magnetotactic bacteria in the geological record.

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“…Because magnetosomes usually synthesize chains of SD crystals with extremely well-controlled sizes and shapes (Egli et al 2010;Heslop et al 2013), a narrow ridge feature is expected to be presented in our FORC diagrams. We selected four samples for FORC measurements: At 0.59 and 6.91 m core depth, the two samples represented the locations where a higher peak value and a relatively constant value were recorded in the χ ARM /χ and χ ARM /SIRM ratios, respectively (Fig.…”

Section: Detection Of Magnetosomesmentioning

confidence: 99%

Orbital-scale variation in the magnetic content as a result of sea level changes in Papua New Guinea over the past 400 ka

2015

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We describe the orbital-scale environmental variation around Papua New Guinea (PNG) for the last 400 ka based on the environmental magnetism. Six magnetic parameters and the δ 18 O record of the core MD05-2928 are presented in the study. Results of magnetic analyses reveal opposite responses to different environmental conditions: Magnetic minerals were relatively fewer and finer in interglacial periods and were more and coarser in glacial periods. The reason could be suggested: In interglacial periods, sediments coming from central New Guinea were transported by the coastal currents in the northern Coral Sea and then imported to the core site location. Magnetic minerals would be relatively fewer and finer due to this longer transportation process. In glacial periods, the routes of the currents might regress seaward with reduced current intensity because of lower sea level. Main sediment sources would shift to the Papuan Peninsula relatively near the core site, and therefore, the magnetic minerals became more and coarser. Further, period analyses using the eccentricity, tilt, and precession (ETP) curves and the wavelet spectra were applied to the study to analyze the periodicities embedded in the parameters. Results of both period analyses clearly present the Milankovitch periods, indicating the dominance of the orbital forcing in this area. The strongest signal of 100-ka period reveals that sea level change played the dominant role in long-term environmental setting for the past~400 ka. However, influences of 40-and 20-ka periods, possibly related to regional precipitation, should also be considered though they might be second factors affecting the environmental variation around PNG.

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Quantifying magnetite magnetofossil contributions to sedimentary magnetizations

Cited by 42 publications

References 59 publications

Discrimination of biogenic and detrital magnetite through a double Verwey transition temperature

Discrimination of biogenic and detrital magnetite through a double Verwey transition temperature

Chemical signature of magnetotactic bacteria

Orbital-scale variation in the magnetic content as a result of sea level changes in Papua New Guinea over the past 400 ka

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