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Low-temperature magnetic properties of pelagic carbonates: oxidation of biogenic magnetite and identification of magnetosome chains

Chang, L., M. Winklhofer, A. P. Roberts, D. Heslop, F. Florindo, M. Dekkers, W. Krijgsman, K. Kodama, and Y. Yamamoto (2013), Low-temperature magnetic properties of pelagic carbonates: oxidation of biogenic magnetite and identification of magnetosome chains, J. Geophys. Res., 118, 6049-65, doi:10.1002/2013JB010381.

Abstract
Pelagic carbonates are deposited in much of the world's oceans and provide important records of past environmental change. We carried out detailed low-temperature magnetic measurements on biogenic magnetite-bearing sediments from the Southern Ocean (Ocean Drilling Program (ODP) Holes 738B, 738C, 689D, and 690C) and on samples containing whole magnetotactic bacteria cells. We document a range of novel low-temperature magnetic properties, which reflect previously known effects due to different degrees of oxidation of magnetite, and a new effect that we name the dipole spring mechanism. This effect results from the uniaxial anisotropy that originates from the chain arrangement of biogenic magnetite, which acts like a spring that restores the remanence during low-temperature cycling. We suggest that this magnetic signature can be used as a diagnostic indicator for the presence of intact magnetosome chains. In addition, magnetic measurements through the Eocene section of ODP Hole 738B reveal an interval with distinct magnetic properties that we interpret to originate from less oxidized biogenic magnetite and enrichment of a biogenic "hard" component. Co-occurrence of these two magnetic fingerprints during the late Eocene in the Southern Ocean indicate less oxic conditions, probably due to increased oceanic primary productivity and organic carbon burial. The documented novel low-temperature magnetic properties, which can be rapidly detected using rock magnetic techniques, provide important additional paleoenvironmental information from pelagic carbonates.
Further information
BibTeX
@article{id1923,
  author = {L. Chang and M. Winklhofer and A. P.  Roberts and D. Heslop and F.  Florindo and M. Dekkers and W. Krijgsman and K. Kodama and Y. Yamamoto},
  journal = {J. Geophys. Res.},
  month = {dec},
  pages = {6049-65},
  title = {{Low-temperature magnetic properties of pelagic carbonates: oxidation of biogenic magnetite and identification of magnetosome chains}},
  volume = {118},
  year = {2013},
  url = {http://www.geophysik.uni-muenchen.de/~michael/pdf/Chang{\_}OxidizedMagnetosfossilsCarbonates{\_}JGR.pdf},
  doi = {10.1002/2013JB010381},
}
EndNote
%0 Journal Article
%A Chang, L.
%A Winklhofer, M.
%A Roberts, A. P. 
%A Heslop, D.
%A Florindo, F. 
%A Dekkers, M.
%A Krijgsman, W.
%A Kodama, K.
%A Yamamoto, Y.
%D 2013
%V 118
%J J. Geophys. Res.
%P 6049-65
%T Low-temperature magnetic properties of pelagic carbonates: oxidation of biogenic magnetite and identification of magnetosome chains
%U http://www.geophysik.uni-muenchen.de/~michael/pdf/Chang_OxidizedMagnetosfossilsCarbonates_JGR.pdf
%8 dec
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Printed 15. Dec 2019 22:47