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Inverse Magnetic Susceptibility Fabrics in Pelagic Sediment: Implications for Magnetofossil Abundance and Alignment
- Source :
- Journal of Geophysical Research: Solid Earth. 124:10672-10686
- Publication Year :
- 2019
- Publisher :
- American Geophysical Union (AGU), 2019.
-
Abstract
- 金沢大学理工研究域地球社会基盤学系<br />Single-domain magnetite particles exhibit minimum susceptibility along their elongation, resulting in so-called inverse fabric of the anisotropy of magnetic susceptibility (AMS). We report the discovery of inverse AMS fabrics from pelagic clay recovered by a ∼12m long piston core from the western North Pacific. A previous study identified fossil single-domain magnetite produced by magnetotactic bacteria (magnetofossils) as the dominant ferrimagnetic mineral in the sediment. The inverse AMS fabrics were found in a ∼2m zone. The ∼6 and ∼4m of sediment above and below this zone showed normal, horizontal AMS fabrics. Rock magnetic data and ferromagnetic resonance spectroscopy indicated that magnetofossils account for most of the mean susceptibility regardless of normal or inverse AMS. This was explained by the mixing models where the inverse fabric from magnetofossils is nearly balanced by the normal fabrics of terrigenous minerals. The corrected degree of AMS carried by magnetofossils in the sediment was estimated to be ∼1.01, which is comparable to that of typical pelagic sediment at shallow depth. On the other hand, terrigenous minerals in the sediment were estimated to have higher degree of anisotropy, possibly reflecting burial and subsequent erosion of >80m of sediment, which was also suggested by a subbottom acoustic stratigraphy. This suggests that inverse AMS fabrics due to magnetofossils may be widespread in pelagic clay without strong compaction. ©2019. American Geophysical Union. All Rights Reserved.
- Subjects :
- environmental magnetism
Paleomagnetism
Environmental magnetism
Magnetotactic bacteria
deoformation
paleomagnetism
magnetotactic bacteria
Pelagic sediment
Magnetic susceptibility
Geophysics
Oceanography
Space and Planetary Science
Geochemistry and Petrology
Abundance (ecology)
Earth and Planetary Sciences (miscellaneous)
Geology
Magnetofossil
Subjects
Details
- ISSN :
- 21699356 and 21699313
- Volume :
- 124
- Database :
- OpenAIRE
- Journal :
- Journal of Geophysical Research: Solid Earth
- Accession number :
- edsair.doi.dedup.....99c6eb1b8f8398c54724dc1b6a13a092