Precambrian microbe-like pseudofossils: A promising solution to the problem
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
References (115)
- et al.
3.43 billion-year-old stromatolite reef from the Pilbara Craton of Western Australia: ecosystem-scale insights to early life on Earth
Precambrian Res.
(2007) The oldest fossils of Africa – a brief reappraisal of reports from the Archean
J. Afr. Earth. Sci.
(2001)- et al.
Archean microfossils: a reappraisal of early life on Earth
Res. Microbiol.
(2003) - et al.
Filamentous fossil bacteria from the Archean of Western Australia
Precambrian Res.
(1983) - et al.
Carbonaceous filaments from North Pole, Western Australia: are they fossil bacteria in Archean stromatolites? A discussion
Precambrian Res.
(1988) Carbonaceous filaments from North Pole, Western Australia: are they fossil bacteria in Archean stromatolites?
Precambrian Res.
(1984)Carbonaceous filaments from North Pole, Western Australia: are they fossil bacteria in Archean stromatolites? A reply
Precambrian Res.
(1988)- et al.
New insights into the nature of Late Riphean Eosolenides
Precambrian Res.
(2009) - et al.
Palynology of Archean microfossils (c. 3.0 Ga) from the Mount Grant area, Pilbara Craton, Western Australia: further evidence of biogenicity
Precambrian Res.
(2009) - et al.
Micro-FTIR spectroscopic signatures of bacterial lipids in Proterozoic microfossils
Precambrian Res.
(2009)
NanoSIMS: insights into biogenicity and syngenicity of Archean carbonaceous structures
Precambrian Res.
Mesoproterozoic Lakhanda Lagerstätte, Siberia: paleoecology and taphonomy of the biota
Precambrian Res.
Modes of fossil preservation
Rev. Palaeobot. Palynol.
Paleontology, microbial
Confocal laser scanning microscopy and Raman imagery of ancient microscopic fossils
Precambrian Res.
Microfossils in Collenia-like stromatolites from the Proterozoic Vempalle Formation of the Cuddapah Basin, India
Precambrian Res.
Evidence of Archean life: stromatolites and microfossils
Precambrian Res.
Diverse microstructures from Archaean chert from the Mount Goldsworthy-Mount Grant area, Pilbara Craton, Western Australia: microfossils, dubiofossils, or pseudofossils?
Precambrian Res.
Taxonomy and biogenicity of Archaean microfossils (c. 3.0 Ga) from the Mount Goldsworthy-Mount Grant area of the northeastern Pilbara Craton, Western Australia
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
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