Schumann Dirk, Raub Timothy D, Kopp Robert E, Guerquin-Kern Jean-Luc, Wu Ting-Di, Rouiller Isabelle, Smirnov Aleksey V, Sears S Kelly, Lücken Uwe, Tikoo Sonia M, Hesse Reinhard, Kirschvink Joseph L, Vali Hojatollah
Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montréal, QC, Canada H3A 2A7.
Proc Natl Acad Sci U S A. 2008 Nov 18;105(46):17648-53. doi: 10.1073/pnas.0803634105. Epub 2008 Oct 20.
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 microm long and hexaoctahedral prisms up to 1.4 microm 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.
我们报告了在新泽西州安科拉一口钻孔中富含粘土的沉积物中发现了异常大的生物源磁铁矿晶体，这些沉积物跨越古新世-始新世极热事件（PETM）。除了先前描述的大量细菌磁小体化石外，电子显微镜还揭示了新型的矛头状和纺锤状磁铁矿，长达4微米，以及长达1.4微米的六八面体棱柱体。与趋磁细菌产生的磁铁矿类似，这些单晶颗粒的化学成分、晶格完整性和氧同位素与水生来源一致。电子全息术表明，尽管它们的晶体尺寸很大，但仍为单畴磁化。我们认为，厚的亚氧化带的发展具有高铁生物可利用性，这是由严重全球变暖驱动的风化和沉积模式的剧烈变化的产物，推动了形成磁铁矿的生物的多样化，可能包括真核生物。
