Letter | Published:

Reassessing evidence of life in 3,700-million-year-old rocks of Greenland

Naturevolume 563pages241244 (2018) | Download Citation

Abstract

The Palaeoarchean supracrustal belts in Greenland contain Earth’s oldest rocks and are a prime target in the search for the earliest evidence of life on Earth. However, metamorphism has largely obliterated original rock textures and compositions, posing a challenge to the preservation of biological signatures. A recent study of 3,700-million-year-old rocks of the Isua supracrustal belt in Greenland described a rare zone in which low deformation and a closed metamorphic system allowed preservation of primary sedimentary features, including putative conical and domical stromatolites1 (laminated accretionary structures formed by microbially mediated sedimentation). The morphology, layering, mineralogy, chemistry and geological context of the structures were attributed to the formation of microbial mats in a shallow marine environment by 3,700 million years ago, at the start of Earth’s rock record. Here we report new research that shows a non-biological, post-depositional origin for the structures. Three-dimensional analysis of the morphology and orientation of the structures within the context of host rock fabrics, combined with texture-specific analyses of major and trace element chemistry, show that the ‘stromatolites’ are more plausibly interpreted as part of an assemblage of deformation structures formed in carbonate-altered metasediments long after burial. The investigation of the structures of the Isua supracrustal belt serves as a cautionary tale in the search for signs of past life on Mars, highlighting the importance of three-dimensional, integrated analysis of morphology, rock fabrics and geochemistry at appropriate scales.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Data availability

The datasets generated during and/or analysed during the current study are available from the corresponding authors upon reasonable request.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

  1. 1.

    Nutman, A. P., Bennett, V. C., Friend, C. R. L., Van Kranendonk, M. J. & Chivas, A. R. Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures. Nature 537, 535–538 (2016).

  2. 2.

    Allwood, A. et al. Conference summary: life detection in extraterrestrial samples. Astrobiology 13, 203–216 (2013).

  3. 3.

    Allwood, A. C., Walter, M. R., Kamber, B. S., Marshall, C. P. & Burch, I. W. Stromatolite reef from the Early Archaean era of Australia. Nature 441, 714–718 (2006).

  4. 4.

    Allwood, A. C., Walter, M. R., Burch, I. W. & Kamber, B. S. 3.43 billion-year-old stromatolite reef from the Pilbara Craton of Western Australia: ecosystem-scale insights to early life on Earth. Precambr. Res. 158, 198–227 (2007).

  5. 5.

    Allwood, A. C. et al. Controls on development and diversity of Early Archean stromatolites. Proc. Natl Acad. Sci. USA 106, 9548–9555 (2009).

  6. 6.

    Sugitani, K. et al. Biogenicity of morphologically diverse carbonaceous microstructures from the ca. 3400  Ma Strelley pool formation, in the Pilbara Craton, Western Australia. Astrobiology 10, 899–920 (2010).

  7. 7.

    Walter, M. R., Buick, R. & Dunlop, S. R. Stromatolites 3,400–3,500 Myr old from the North Pole area, Western Australia. Nature 284, 443–445 (1980).

  8. 8.

    Mojzsis, S. J. et al. Evidence for life on Earth before 3,800 million years ago. Nature 384, 55–59 (1996).

  9. 9.

    Rosing, M. T. 13C-depleted carbon microparticles in >3700-Ma sea-floor sedimentary rocks from West Greenland. Science 283, 674–676 (1999).

  10. 10.

    Schidlowski, M., Appel, P. W., Eichmann, R. & Junge, C. E. Carbon isotope geochemistry of the 3.7 × 109-yr-old Isua sediments, West Greenland: implications for the Archaean carbon and oxygen cycles. Geochim. Cosmochim. Acta 43, 189–199 (1979).

  11. 11.

    van Zuilen, M. A., Lepland, A. & Arrhenius, G. Reassessing the evidence for the earliest traces of life. Nature 418, 627–630 (2002).

  12. 12.

    Lindsay, J. F. et al. The problem of deep carbon—an Archean paradox. Precambr. Res. 143, 1–22 (2005).

  13. 13.

    Shields, G. & Veizer, J. Precambrian marine carbonate isotope database: version 1.1. Geochem. Geophys. Geosyst. 3, 1–12 (2002).

  14. 14.

    Nutman, A., Van Kranendonk, M. Sampling of the World’s Oldest Stromatolites from Isua (Greenland): Damage to a Globally-Unique Locality. Technical Report (2017).

  15. 15.

    Fedo, C. M., Myers, J. S. & Appel, P. W. U. Depositional setting and paleogeographic implications of Earth’s oldest supracrustal rocks, the >3.7 Ga Isua Greenstone belt, West Greenland. Sediment. Geol. 141–142, 61–77 (2001).

  16. 16.

    Machel, H. G. Concepts and models of dolomitization: a critical reappraisal. Geol. Soc. Spec. Publ. 235, 7–63 (2004).

  17. 17.

    Bau, M. & Dulski, P. Distribution of yttrium and rare-earth elements in the Penge and Kuruman iron-formations, Transvaal Supergroup, South Africa. Precambr. Res. 79, 37–55 (1996).

  18. 18.

    Nutman, A. P., Friend, C. R. L., Bennett, V. C., Wright, D. & Norman, M. D. ≥3700 Ma pre-metamorphic dolomite formed by microbial mediation in the Isua supracrustal belt (W. Greenland): simple evidence for early life? Precambr. Res. 183, 725–737 (2010).

  19. 19.

    Planavsky, N. et al. Rare earth element and yttrium compositions of Archean and Paleoproterozoic Fe formations revisited: new perspectives on the significance and mechanisms of deposition. Geochim. Cosmochim. Acta 74, 6387–6405 (2010).

  20. 20.

    Qing, H. & Mountjoy, E. W. Rare earth element geochemistry of dolomites in the Middle Devonian Presqu’ile barrier, Western Canada Sedimentary Basin: implications for fluid–rock ratios during dolomitization. Sedimentology 41, 787–804 (1994).

  21. 21.

    Heirwegh, C. M., Elam, W. T., Flannery, D. T. & Allwood, A. C. An empirical derivation of the X-ray optic transmission profile used in calibrating the Planetary Instrument for X-ray Lithochemistry (PIXL) for Mars 2020. Powder Diffr. 162–165 (2018).

  22. 22.

    Elam, W. T. et al. A new atomic database for the X-ray spectroscopic calculations. Radiat. Phys. Chem. 63, 121–128 (2002).

  23. 23.

    De Andrade, V. et al. The sub-micron resolution X-ray spectroscopy beamline at NSLS-II. Nucl. Instrum. Methods Phys. Res. A 649, 46–48 (2011).

  24. 24.

    Chen-Wiegart, Y. C. K. et al. Early science commissioning results of the sub-micron resolution X-ray spectroscopy beamline (SRX) in the field of materials science and engineering. In Proc. 23rd International Conference on X-Ray Optics and Microanalysis (eds Thieme, J. & Siddons, D. P.) (ICXOM23, American Institute of Physics, 2016).

  25. 25.

    Li, L., Yan, H., Xu, W., Yu, D. & Heroux, A. PyXRF: Python-based X-ray fluorescence analysis package. Proc. 10389 X-Ray Nanoimaging, Instruments and Methods III 103890U (SPIE Optical Engineering & Applications, 2017).

Download references

Acknowledgements

Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). Funding for the work was provided by the NASA Mars 2020 PIXL flight project. We thank the Government of Greenland, Ministry of Mineral Resources for provision of access to the field sites, sampling permits and specifically geologist A. Juul-Nielsen for accompanying us on the field expedition, participating in discussions to determine an acceptable sampling strategy, and approving the final sample collection; T. Elam for providing the PIQUANT quantification code and descriptions of its architecture for the PIXL prototype; J. Thieme and E. Fogelqvist for assistance with data collection and reduction at the SRX beamline; T. Rasbury and K. Wooton for assistance with sample digestion and REE + Y analysis; I. Burch for field assistance including sample acquisition; K. Bourke for cutting and polishing the rock samples; and I. Fast for assistance in the field. J.A.H. acknowledges partial support from the Stony Brook University-Brookhaven National Laboratory Seed Grant program.

Reviewer information

Nature thanks M. M. Tice, M. van Zuilen and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information

Affiliations

  1. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

    • Abigail C. Allwood
    • , David T. Flannery
    •  & Christopher M. Heirwegh
  2. Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark

    • Minik T. Rosing
  3. Department of Geosciences, Stony Brook University, Stony Brook, NY, USA

    • Joel A. Hurowitz

Authors

  1. Search for Abigail C. Allwood in:

  2. Search for Minik T. Rosing in:

  3. Search for David T. Flannery in:

  4. Search for Joel A. Hurowitz in:

  5. Search for Christopher M. Heirwegh in:

Contributions

A.C.A. led the research and field expedition, determined analytical strategy for samples, interpreted data, analysed the structures and wrote the manuscript. M.T.R. coordinated field logistics, including sampling permits and inclusion of Greenland government staff in the fieldwork and sampling operations, made field observations, interpreted metamorphic history, provided regional geologic context and contributed to manuscript writing. J.A.H. performed synchrotron X-ray fluorescence analyses, REE + Y analyses and interpreted geochemical data, contributed to manuscript writing and helped to write the Methods. D.T.F. acquired and analysed PIXL maps, performed thin section petrography and contributed to manuscript revisions. C.M.H. processed the PIXL data used in elemental maps and helped to write the Methods.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Abigail C. Allwood or Joel A. Hurowitz.

Extended data figures and tables

  1. Extended Data Fig. 1 Satellite image showing the approximate outline and location of the Isua Structural Belt and the study area.

    The satellite image of the study area. The image was obtained from Google Maps.

  2. Extended Data Fig. 2 Putative stromatolites of the ISB at site A.

    Yellow arrows point to triangular shapes with apices mostly pointing down relative to layering. Note, the stratigraphy was inverted, as the layers have been overturned1. Each of the triangles is approximately 4 cm across. The blue box shows the approximate outline of the sample acquired for the present study. The yellow box shows the area shown in Fig. 1.

  3. Extended Data Fig. 3 Breccia at site C.

    a, Close-up view of breccia, from the previous study1. Ch, chert; dol, dolomite. b, Larger field of view showing the same breccia block as in a, showing the location of the elongated rod-like fabric (rodding) on the upper right side of the rock. c, Top view of the breccia-containing block from a—note the contrasting appearance of the rock fabric.

  4. Extended Data Fig. 4 Photographs of details from the deformation fabrics of site A.

    The photographs show details of the observed deformation fabrics on the cut and polished faces of all three pieces of the columnar sample that we collected from site A. Each piece was cut to show rock fabrics on orthogonal faces. a, Largest piece, which includes one of the ‘stromatolites’ on the right face. Note contrasting fabrics on adjacent faces. be, Additional pieces of the rock sample, showing further examples of the contrasting rock fabrics. Green arrows on all images indicate the orientation of the spaced cleavage.

  5. Extended Data Fig. 5 Petrographic context of samples that were digested for REE + Y analyses.

    a, Slab sample before cutting. b, Slab sample after cutting. ‘M’ denotes the subsample from which analyses ‘M3M’ and ‘M3C’ were derived. ‘C’ denotes the subsample from which analyses ‘C3M’ and ‘C3C’ were derived. Scale bar, 10 mm.

  6. Extended Data Fig. 6 Synchrotron XRF element maps of the ISB sample.

    The distribution of trace elements relative to minerals is shown. a, Photograph of the sample. White squares show map locations. Scale bar, 10 mm. b, Distribution and X-ray intensity of detected elements for map 1. c, Distribution and X-ray intensity of detected elements for map 2. b, c, X-ray intensity variations were used to colour the element maps. Blue, zero X-ray intensity; red, maximum X-ray intensity. X-ray intensity ranges (counts per second (cps)) are shown beneath each map. All maps are for K-shell X-rays except for Ba, which was detected using L-shell X-rays.

  7. Extended Data Table 1 REE + Y concentrations (p.p.m.) from acid digestion and ICP-MS analysis

Supplementary information

  1. Supplementary Information

    This file contains Supplementary Text: Interpretation of synchrotron micro-XRF element map data and Supplementary Table 1: Key evidence presented in support of biogenic interpretation of stromatolites in the 3,450 Ma Strelley Pool Formation.

  2. Reporting Summary

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/s41586-018-0610-4

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.