Record of emergent continental crust ∼3.5 billion years ago in the Pilbara craton of Australia

Buick, Roger; Thornett, J. R.; McNaughton, Neal J.; Smith, J.B.; Barley, Mark; Savage, M.D.

doi:10.1038/375574a0

Cited by 262 publications

(134 citation statements)

References 21 publications

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“…Quartz sands at the base of this formation were deposited during the earliest stage of a marine transgression across Earth's oldest known unconformity surface (33). Associated grains of rounded detrital pyrite show no signs of oxidation, nor do localized coatings of pyrite around rounded quartz grains (7).…”

Section: The Gunflint Chert: New Analytical Techniquesmentioning

confidence: 99%

Changing the picture of Earth's earliest fossils (3.5–1.9 Ga) with new approaches and new discoveries

Brasier

Antcliffe

Saunders

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

145

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New analytical approaches and discoveries are demanding fresh thinking about the early fossil record. The 1.88-Ga Gunflint chert provides an important benchmark for the analysis of early fossil preservation. High-resolution analysis of Gunflintia shows that microtaphonomy can help to resolve long-standing paleobiological questions. Novel 3D nanoscale reconstructions of the most ancient complex fossil Eosphaera reveal features hitherto unmatched in any crown-group microbe. While Eosphaera may preserve a symbiotic consortium, a stronger conclusion is that multicellular morphospace was differently occupied in the Paleoproterozoic. The 3.46-Ga Apex chert provides a test bed for claims of biogenicity of cell-like structures. Mapping plus focused ion beam milling combined with transmission electron microscopy data demonstrate that microfossil-like taxa, including species of Archaeoscillatoriopsis and Primaevifilum, are pseudofossils formed from vermiform phyllosilicate grains during hydrothermal alteration events. The 3.43-Ga Strelley Pool Formation shows that plausible early fossil candidates are turning up in unexpected environmental settings. Our data reveal how cellular clusters of unexpectedly large coccoids and tubular sheath-like envelopes were trapped between sand grains and entombed within coatings of dripstone beach-rock silica cement. These fossils come from Earth’s earliest known intertidal to supratidal shoreline deposit, accumulated under aerated but oxygen poor conditions.

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Section: The Gunflint Chert: New Analytical Techniquesmentioning

confidence: 99%

Changing the picture of Earth's earliest fossils (3.5–1.9 Ga) with new approaches and new discoveries

Brasier

Antcliffe

Saunders

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

145

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“…The Coonterunah rocks come from the ∼6.5-km-thick, 3.518 Ga (19) Coonterunah Subgroup in the East Strelley Belt, the oldest supracrustal rocks in the Pilbara Craton of northwest Australia ( Figs. 1 and 2).…”

Section: Samples and Site Geologymentioning

confidence: 99%

Evidence for reactive reduced phosphorus species in the early Archean ocean

Pasek

Harnmeijer

Buick

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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167

170

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It has been hypothesized that before the emergence of modern DNA-RNA-protein life, biology evolved from an "RNA world." However, synthesizing RNA and other organophosphates under plausible early Earth conditions has proved difficult, with the incorporation of phosphorus (P) causing a particular problem because phosphate, where most environmental P resides, is relatively insoluble and unreactive. Recently, it has been proposed that during the Hadean-Archean heavy bombardment by extraterrestrial impactors, meteorites would have provided reactive P in the form of the iron-nickel phosphide mineral schreibersite. This reacts in water, releasing soluble and reactive reduced P species, such as phosphite, that could then be readily incorporated into prebiotic molecules. Here, we report the occurrence of phosphite in early Archean marine carbonates at levels indicating that this was an abundant dissolved species in the ocean before 3.5 Ga. Additionally, we show that schreibersite readily reacts with an aqueous solution of glycerol to generate phosphite and the membrane biomolecule glycerol-phosphate under mild thermal conditions, with this synthesis using a mineral source of P. Phosphite derived from schreibersite was, hence, a plausible reagent in the prebiotic synthesis of phosphorylated biomolecules and was also present on the early Earth in quantities large enough to have affected the redox state of P in the ocean. Phosphorylated biomolecules like RNA may, thus, have first formed from the reaction of reduced P species with the prebiotic organic milieu on the early Earth.origin of life | prebiotic chemistry | phosphorylation | astrobiology | exobiology P hosphorus (P) is the limiting nutrient in many ecosystems; its scarcity is linked to the insoluble nature of phosphate minerals (1, 2). Phosphorus species may have been important reagents during prebiotic chemical evolution, but their presumed low abundance has presented a problem in understanding the origin of key phosphorylated biomolecules, such as RNA (3, 4). This was recognized early in the study of prebiotic chemistry, and a possible role for more reduced P compounds was suggested because these are more soluble than phosphate (5, 6). However, no potential source of reduced P was known at the time, leaving phosphate as the only available P species under typical geochemical conditions (7).Phosphide minerals such as schreibersite (Fe,Ni) 3 P are ubiquitous minor constituents of meteorites (8) and are potential sources of reduced P (9-12). Schreibersite reacts with water to release P compounds that are reduced relative to the geologically abundant P 5+ phase phosphate PO 4 3− , including P 3+ phosphite HPO 3 2− and P 1+ hypophosphite H 2 PO 2 − (9-14). Both of these compounds are significantly more soluble than phosphate in waters of neutral pH and rich in the divalent cations Ca 2+ and Mg 2+ , such as modern seawater (5). Schreibersite reaction rates indicate complete phosphide dissolution when submerged in water over about 10 y (12), implying rapid reaction with w...

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“…In addition this basal sandstone contains two populations of detrital zircons dated at 3.502 Gyr G3 Myr (nZ33) and 3.479 Gyr G8 Myr (nZ5) (Nelson, personal communication) and at the sample site lies unconformably on basaltic volcanics and cherts of the ca 3.515 Gyr Coucal Formation of the Coonterunnah Group (Buick et al 1995;Van Kranendonk 2000). The unit is 1-5 m thick here, resting on an unconformity surface that records the earliest preserved episode of subaerial exposure and deep chemical weathering ca 3.45 Ga in the rock record (Buick et al 1995). The occurrence of low angle cross-bedding and channel bedforms, plus the relatively high textural and compositional maturity of the sandstone, indicates deposition during a relatively high energy, shallow marine transgression (Lowe 1983).…”

Section: Endoliths and The Warrawoona 'Microtubes'mentioning

confidence: 99%

A fresh look at the fossil evidence for early Archaean cellular life

Brasier

McLoughlin

Green

et al. 2006

Phil. Trans. R. Soc. B

256

154

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The rock record provides us with unique evidence for testing models as to when and where cellular life first appeared on Earth. Its study, however, requires caution. The biogenicity of stromatolites and 'microfossils' older than 3.0 Gyr should not be accepted without critical analysis of morphospace and context, using multiple modern techniques, plus rejection of alternative non-biological (null) hypotheses. The previous view that the co-occurrence of biology-like morphology and carbonaceous chemistry in ancient, microfossil-like objects is a presumptive indicator of biogenicity is not enough. As with the famous Martian microfossils, we need to ask not 'what do these structures remind us of ?', but 'what are these structures?' Earth's oldest putative 'microfossil' assemblages within 3.4-3.5 Gyr carbonaceous cherts, such as the Apex Chert, are likewise self-organizing structures that do not pass tests for biogenicity.There is a preservational paradox in the fossil record prior to ca 2.7 Gyr: suitable rocks (e.g. isotopically light carbonaceous cherts) are widely present, but signals of life are enigmatic and hard to decipher. One new approach includes detailed mapping of well-preserved sandstone grains in the ca 3.4 Gyr Strelley Pool Chert. These can contain endolithic microtubes showing syngenicity, grain selectivity and several levels of geochemical processing. Preliminary studies invite comparison with a class of ambient inclusion trails of putative microbial origin and with the activities of modern anaerobic proteobacteria and volcanic glass euendoliths.

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Record of emergent continental crust ∼3.5 billion years ago in the Pilbara craton of Australia

Cited by 262 publications

References 21 publications

Changing the picture of Earth's earliest fossils (3.5–1.9 Ga) with new approaches and new discoveries

Changing the picture of Earth's earliest fossils (3.5–1.9 Ga) with new approaches and new discoveries

Evidence for reactive reduced phosphorus species in the early Archean ocean

A fresh look at the fossil evidence for early Archaean cellular life

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