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A unifying model for Neoproterozoic–Palaeozoic exceptional fossil preservation through pyritization and carbonaceous compression

Nature Communications volume 5, Article number: 5754 (2014) | Download Citation

Abstract

Soft-tissue fossils capture exquisite biological detail and provide our clearest views onto the rise of animals across the Ediacaran–Cambrian transition. The processes contributing to fossilization of soft tissues, however, have long been a subject of debate. The Ediacaran Gaojiashan biota displays soft-tissue preservational styles ranging from pervasive pyritization to carbonaceous compression, and thus provides an excellent opportunity to dissect the relationships between these taphonomic pathways. Here geochemical analyses of the Gaojiashan fossil Conotubus hemiannulatus show that pyrite precipitation was fuelled by the degradation of labile tissues through bacterial sulfate reduction (BSR). Pyritization initiated with nucleation on recalcitrant tube walls, proceeded centripetally, decelerated with exhaustion of labile tissues and possibly continued beneath the BSR zone. We propose that pyritization and kerogenization are regulated principally by placement and duration of the decaying organism in different microbial zones of the sediment column, which hinge on post-burial sedimentation rate and/or microbial zone thickness.

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Acknowledgements

This research was supported by funding through NASA Exobiology and Evolutionary Biology Program, NASA Astrobiology Institute (N07-5489), National Science Foundation (EAR-0824890, EAR095800, EAR1124062), Chinese Academy of Sciences, National Natural Science Foundation of China (41202006; 41030209; 41272011), Chinese Ministry of Science and Technology, Virginia Tech Institute for Critical Technology and Applied Sciences and China Postdoctoral Science Foundation (2013M531410). We would like to thank K.L. Shelton and J.W. Huntley for insightful discussion.

Author information

Affiliations

  1. Department of Geological Sciences, University of Missouri, Columbia, Missouri 65211, USA

    • James D. Schiffbauer
  2. Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA

    • Shuhai Xiao
  3. Early Life Institute, State Key Laboratory of Continental Dynamics, and Department of Geology, Northwest University, Xi’an 710069, China

    • Yaoping Cai
    •  & Hong Hua
  4. Department of Geological Sciences, University of Delaware, Newark, Delaware 19716, USA

    • Adam F. Wallace
  5. Nanoscale Characterization and Fabrication Laboratory, Institute of Critical Technology and Applied Science, Virginia Tech, Blacksburg, Virginia 24061, USA

    • Jerry Hunter
  6. NASA Astrobiology Institute, Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706, USA

    • Huifang Xu
  7. Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405, USA

    • Yongbo Peng
  8. Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20742, USA

    • Alan J. Kaufman

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Contributions

J.D.S. designed the research with input from S.X. and Y.C. S.X. supervised the research. J.D.S, S.X., Y.C. and H.H. performed the fieldwork. Sample preparation was performed by J.D.S. and Y.C., SEM and EDS analysis was performed by J.D.S., SIMS analysis was performed by J.D.S. and J.H., ultraviolet and XRD analysis was performed by H.X., IRMS analysis performed by Y.C., Y.P. and A.J.K. and geochemical data analysis was performed by J.D.S., S.X. and A.F.W. J.D.S., with significant input from all of the authors, wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to James D. Schiffbauer.

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https://doi.org/10.1038/ncomms6754

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