Precambrian microbe-like pseudofossils: A promising solution to the problem

doi:10.1016/j.precamres.2010.03.003

Precambrian Research

Volume 179, Issues 1–4, May 2010, Pages 191-205

https://doi.org/10.1016/j.precamres.2010.03.003 Get rights and content

Abstract

Of various problems that have hindered progress in documenting the Precambrian history of life, the difficulty in distinguishing between bona fide microbial fossils and nonbiological microscopic pseudofossils has been among the most serious. Though errors in the interpretation of putative Precambrian fossil microbes have diminished greatly over recent years, mistakes continue to be made. We suggest that such errors can be avoided by the use of a multifaceted strategy based on a specified series of biologically definitive characteristics that document the presence of interrelated biological morphology and biologically derived chemistry. To illustrate this promising approach, we use optical microscopy, confocal laser scanning microscopy, and Raman spectroscopy, together, to distinguish between authentic microbial fossils and microscopic “look-alikes,” both coccoidal and filamentous, rock-embedded in five Proterozoic and two Archean geological units: bona fide fossils of the ∼800 Ma Bitter Springs Formation of central Australia and ∼3050 Ma Farrel Quartzite of northwestern Australia; and objects we regard to be pseudofossils from the ∼770 Ma Chanda Limestone of southern India, ∼800 Ma Myrtle Springs Formation of South Australia, ∼1020 Ma Lakhanda Formation of southeastern Siberia, ∼1700 Ma Vempalle Formation of central India, and ∼2629 Ma Marra Mamba Iron Formation of northwestern Australia. The results demonstrate that no single criterion, by itself, is sufficient to establish the biological origin of such objects. Instead, as shown here, this problem appears solvable by the use of an interdisciplinary approach that combines the data and techniques of geology, biology, and chemistry.

Section snippets

Characteristics of bona fide fossil prokaryotes

As has been suggested in earlier publications (Schopf and Walter, 1983, Schopf, 1992a, Schopf, 1993, Schopf, 1999a, Buick, 2001), authentic fossil microbes should be expected to satisfy five criteria: their host rock should be of known provenance and age; they should be indigenous to and syngenetic with the formation of the rock in which they occur; and they should be assuredly biogenic. This last criterion, almost always the most difficult to satisfy, is the focus of this article.

Materials

All illustrated specimens are in petrographic thin sections of Precambrian fine-grained sediments, either siltstone (those of the Lakhanda Formation) or chert (all other specimens), from the following seven geological units: the ∼770 Ma Chanda Limestone of southern India (Bandopadhyay, 2007); ∼800 Ma Myrtle Springs Formation of South Australia (cf., but stratigraphically 100 m above, PPRG sample 1283; Moore and Schopf, 1992, p. 630); ∼800 Ma Bitter Springs Formation of central Australia (PPRG

Results

The optical, CLSM, and Raman images in Fig. 1, Fig. 2, Fig. 3 show bona fide coccoidal and filamentous microbial fossils and microscopic objects interpreted here as pseudofossils from seven Precambrian geological units. Fig. 4, Fig. 5 present, respectively, a summary of the size distributions of the objects studied and the Raman spectra of the kerogenous or mineral materials of which they are composed. The data presented in these figures, taken together, provide the evidence of biological

Summary and conclusions

A long history of the sporadic misintepretation of Precambrian microscopic pseudofossils, coupled with evident differences between the relatively well-documented Proterozoic fossil record and that of more ancient, Archean-age deposits, has raised doubt about early evidence of life, for some workers including all evidence older than ∼1900 Ma (Moorbath, 2005). Such misgivings are unfounded. Not only are microbially laminated stromatolites known from some 50 Archean geological units, bona fide

Acknowledgments

We thank P.C. Bandyopadhyay (Ministry of Mines, Geological Survey of India, Kolkata, West Bengal, India) for the samples from the Chanda Formation studied here, and J. Shen-Miller, C. Shi and I. Foster, for reviews of this manuscript. Work carried out by J.W.S. and A.B.K. was supported by CSEOL (UCLA's Center for the Study of Evolution and the Origin of Life) and the NAI PennState Astrobiology Research Center; K.S. received support from the Japan Society for the Promotion of Science, via the

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Precambrian microbe-like pseudofossils: A promising solution to the problem

Abstract

Section snippets

Characteristics of bona fide fossil prokaryotes

Materials

Results

Summary and conclusions

Acknowledgments

Precambrian Res.

J. Afr. Earth. Sci.

Res. Microbiol.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Rev. Palaeobot. Palynol.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Stromatolite reef from the early Archaean era of Australia

Nature

Evidence of life in seemingly barren Chanda Limestone, Neoproterozoic Penganga Group, south India

The oldest fossils

Scient. Am.

Microorganisms from the late Precambrian of central Australia

Science

Microorganisms from the Gunflint chert

Science

The algal sediments of Andros Island, Bahamas

Phil. Trans R. Soc. London, Ser. B

No “nanofossils” in martian meteorite

Nature

Questioning the evidence of Earth's oldest fossils

Nature

Microfossil-like objects from the Archean of Greenland: a cautionary note

Nature

Microfossil recognition in Archean rocks: an appraisal of spheroids and filaments from a 3500 m.y. old chert-barite unit at North Pole, Western Australia

Palaios

Life in the Archean

Stromatolite recognition in ancient rocks: an appraisal of irregular laminated structures in an early Archean chert-barite unit from North Pole, Western Australia

Alcheringa

Manicosiphoniaceae, a new family of fossil algae from the Sinian System of S.W. China with reference to its systematic position

Acta Palaeontol. Sinica

Raman spectra of a Lower Cambrian ctenophore embryo from SW Shaanxi, China

Proc. Natl. Acad. Sci. USA

Significance of the Gunflint (Precambrian) microflora

Science

Early biogeologic history: the emergence of a paradigm

Microbiotas of the banded iron formations

Proc. Natl. Acad. Sci. USA

Biogenic origin for Earth's oldest putative fossils

Geology

Morphology: an ambiguous indicator of biogenicity

Astrobiology

Self-assembled silica-carbonate structures and detection of ancient microfossils

Science

Morphogenesis of self-assembled nanocrystalline materials of barium carbonate and silica

Science

Evolution of Sedimentary Rocks

Algae believed to be Archean

J. Geol.

Discovery of life in the Archean

J. Geol.

Possible algal microfossils from the Late Pre-Cambrian of California

Nature

Geochemical evidence bearing on the origin of aerobiosis, a speculative hypothesis

The organic geochemistry of Precambrian rocks

Archean stromatolites as microbial archives

Early Proterozoic microfossils