Gigantism in unique biogenic magnetite at the Paleocene–Eocene Thermal Maximum
- Dirk Schumanna,b,
- Timothy D. Raubc,
- Robert E. Koppd,
- Jean-Luc Guerquin-Kerne,f,
- Ting-Di Wue,f,
- Isabelle Rouillerb,g,
- Aleksey V. Smirnovh,
- S. Kelly Searsb,g,
- Uwe Lückeni,
- Sonia M. Tikooc,
- Reinhard Hessea,
- Joseph L. Kirschvinkc, and
- Hojatollah Valia,b,g,1
- aDepartment of Earth and Planetary Sciences, McGill University, 3450 University Street, Montréal, QC, Canada H3A 2A7;
- bFacility for Electron Microscopy Research, and
- gDepartment of Anatomy and Cell Biology, McGill University, 3640 University Street, Montréal, QC, Canada H3A 2B2;
- cDivision of Geological and Planetary Sciences, California Institute of Technology, MC 170-25 1200 East California Boulevard, Pasadena, CA 91125;
- dDepartment of Geosciences and Woodrow Wilson School of Public and International Affairs, Princeton University, 210 Guyot Hall, Princeton, NJ 08544;
- eImagerie Intégrative de la Molécule à l'Organisme, Institut National de la Santé et de la Recherche Médicale, Unité 759, Institut Curie, 91405 Orsay, France;
- fLaboratoire de Microscopie Ionique, Institut Curie, 91405 Orsay, France;
- hDepartment of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, MI 49931-1295; and
- iNanobiology Marketing, FEI Company, Eindhoven, 5600KA, Eindhoven, The Netherlands
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Edited by James Zachos, University of California, Santa Cruz, CA, and accepted by the Editorial Board August 29, 2008 (received for review April 15, 2008)
Abstract
We report the discovery of exceptionally large biogenic magnetite crystals in clay-rich sediments spanning the Paleocene–Eocene Thermal Maximum (PETM) in a borehole at Ancora, NJ. Aside from previously described abundant bacterial magnetofossils, electron microscopy reveals novel spearhead-like and spindle-like magnetite up to 4 μm long and hexaoctahedral prisms up to 1.4 μm long. Similar to magnetite produced by magnetotactic bacteria, these single-crystal particles exhibit chemical composition, lattice perfection, and oxygen isotopes consistent with an aquatic origin. Electron holography indicates single-domain magnetization despite their large crystal size. We suggest that the development of a thick suboxic zone with high iron bioavailability—a product of dramatic changes in weathering and sedimentation patterns driven by severe global warming—drove diversification of magnetite-forming organisms, likely including eukaryotes.
Footnotes
- 1To whom correspondence should be addressed. E-mail: vali{at}eps.mcgill.ca
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Author contributions: D.S. and H.V. designed research; D.S., J.-L.G.-K., T.-D.W., I.R., S.K.S., U.L., and H.V. performed research; D.S., T.D.R., R.E.K., I.R., A.V.S., S.M.T., R.H., J.L.K., and H.V. analyzed data; and D.S., T.D.R., R.E.K., S.M.T., J.L.K., and H.V. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission. J.Z. is a guest editor invited by the Editorial Board.
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See Commentary on page 17595.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0803634105/DCSupplemental.
- © 2008 by The National Academy of Sciences of the USA
