LETTERS Putative greigite magnetofossils from the Pliocene epoch (original) (raw)

2008

Abstract

Magnetotactic bacteria produce chains of magnetite1,2 and/or greigite3–5 crystals within their cell bodies called magnetosomes that are permanently magnetized6. They use these magnets to navigate along geomagnetic field lines to reach their preferred habitat7. Greigite magnetosomes have been well documented in modern sedimentary environments, but their identification in the fossil record remains controversial. Here we use transmission electron microscopy, electron diffraction patterns and rockmagnetic analyses to assess the origins of nanometre-scale greigite crystals found in Pliocene claystones from the Carpathian foredeep of Romania. We find that, like modern magnetosomal greigite grains, the crystals are single domain8, with few crystallographic defects and an overall shape consistent with an intracellular origin. We suggest these crystals are magnetosomal in origin, which would place them among

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