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Cited by 312Paleontology and Stratigraphy of FossilsOrigins and Evolution of LifeGeological and Geochemical Analysis

Reappraisal of hydrocarbon biomarkers in Archean rocks

Open access
French, Katherine L., Hallmann, Christian, Hope, Janet M., Schoon, Petra L., Zumberge, J. Alex, Hoshino, Yosuke, Peters, Carl A., George, Simon C. +4 more·2015·Proceedings of the National Academy of Sciences
DOI 10.1073/pnas.1419563112PMC PMC4434754
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Abstract

Significance: The advent of oxygenic photosynthesis set the stage for the evolution of complex life on an oxygenated planet, but it is unknown when this transformative biochemistry emerged. The existing hydrocarbon biomarker record requires that oxygenic photosynthesis and eukaryotes emerged more than 300 million years before the Great Oxidation Event [∼2.4 billion years ago (Ga)]. We report that hopane and sterane concentrations measured in new ultraclean Archean drill cores from Australia are comparable to blank concentrations, yet their concentrations in the exteriors of conventionally collected cores of stratigraphic equivalence exceed blank concentrations by more than an order of magnitude due to surficial contamination. Consequently, previous hydrocarbon biomarker reports no longer provide valid evidence for the advent of oxygenic photosynthesis and eukaryotes by ∼2.7 Ga.

AI snapshot

Written from the paper’s full text.

TL;DR

New ultraclean Archean drill cores from the Pilbara Craton contain hopanes and steranes at or below blank/femtogram levels, whereas exteriors of conventionally drilled equivalent rocks are contaminated by these biomarkers. The authors conclude that previously reported Archean hydrocarbon biomarkers cannot be used as evidence for oxygenic photosynthesis and eukaryotes by ∼2.7 Ga.

Key findings

  • In AIDP-2 and AIDP-3 rock extracts, hopanes and steranes were typically at or below femtogram detection limits; when detectable, total hopane was <37.9 pg per gram of rock and total sterane was <32.9 pg per gram of rock, comparable to blanks and negative controls. In hydropyrolysates, neither total hopane nor total sterane exceeded cumulative blank concentrations (<20 pg per gram of rock).
  • In contrast, exteriors of conventionally drilled and curated RHDH2A rocks of stratigraphic equivalence reached 389.5 pg per gram of rock total hopane and 1,039 pg per gram of rock total sterane in the abstract; Table 1 lists RHDH2A sawed surfaces at 250 and 259 pg per gram hopane and 1,092 and 509 pg per gram sterane.
  • PAHs and diamondoids exceeded blank concentrations, with individual concentrations up to 80 ng per gram of rock in rock extracts and up to 1,000 ng per gram of rock in hydropyrolysates from the ultraclean cores; the results text reports hydropyrolysate individual PAH concentrations up to 1,039 ng per gram of rock.
  • The authors conclude that previously studied Archean samples host mixtures of biomarker contaminants and indigenous overmature hydrocarbons, so existing lipid biomarker evidence cannot support the emergence of oxygenic photosynthesis and eukaryotes by ∼2.7 Ga; no currently known Archean strata lie within the appropriate thermal maturity window for syngenetic hydrocarbon biomarker preservation.

Methods

  • Multilaboratory study of new Archean drill cores from the Pilbara Craton, Western Australia, drilled during the 2012 Agouron Institute Drilling Program using hydrocarbon-clean protocols; AIDP-1 provided negative control samples, while AIDP-2 and AIDP-3 recovered organic-rich sedimentary rocks.
  • Rock extracts and hydropyrolysates were analyzed by gas chromatography–mass spectrometry in full scan and metastable reaction monitoring modes, with compound-specific carbon isotopic analyses and PAH/diamondoid measurements; interiors and exteriors of 10 biomarker target samples from AIDP-2 and 2 from AIDP-3 were analyzed for extractable hydrocarbons, and hydropyrolysates were analyzed from eight samples.
  • Approximately 10–40 g of rock powder were extracted per sample; results were compared with blanks, negative controls, and a conventionally drilled RHDH2A core to assess contamination versus syngeneity.

Limitations

  • Stated: only a single compound-specific isotopic measurement was possible for the 116.09 m sample, so analytical uncertainty and reproducibility are not well constrained; future studies are required to test the possible mixing observation; the biomolecular precursors of the PAHs and diamondoids are unknown; and duration of heating and organic matter type complicate direct conversions between vitrinite reflectance, H/C ratio, and burial temperature.
  • Stated: no currently known Archean strata lie within the appropriate thermal maturity window for syngenetic hydrocarbon biomarker preservation, so future exploration should screen for rocks with milder thermal histories.
  • Evident from the text: the study focuses on the Pilbara Craton and specific AIDP/RHDH2A cores, so the absence of detectable syngenetic hopanes and steranes in these samples does not by itself rule out their preservation in all Archean rocks; the authors acknowledge this by calling for future exploration of less mature archives.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1073/pnas.1419563112

Cites

43 of 43 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 91 cited sources checked · 0 supported · 0 flagged

  • Findingcitation

    Hopane and sterane concentrations in the RHDH2A sample are more compatible with concentrations reported in earlier Archean biomarker studies of the Mount Bruce and Transvaal supergroups.

    “Furthermore, the hopane and sterane concentrations measured in our analysis of the RHDH2A sample are more compatible with the concentrations reported in earlier Archean biomarker studies of the Mount Bruce and Transvaal supergroups (7,21)”
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  • Findingown data

    The two alkane-bearing samples had the least thermally altered kerogens according to atomic H/C ratios and pyrolysate PAH ratios.

    “The two samples containing alkanes also hosted the least thermally altered kerogens according to their atomic H/C ratios and pyrolysate polycyclic aromatic hydrocarbon (PAH) ratios.”
    Quote in the paperSubstantial claim
  • Findingown data

    Extractable acyclic isoprenoids and a homologous series of n-alkanes (C10-23+) were below detection limits or cumulative laboratory blank concentrations in the AIDP samples.

    “Moreover, extractable acyclic isoprenoids and a homologous series of extractable n-alkanes (C 10-23+ ), both of which were prominent in previous Archean biomarker studies (1-3, 5, 7, 22, 23), were also below detection limits or cumulative laboratory blank concentrations in the AIDP samples.”
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  • Findingown data

    The two alkane-bearing samples had the highest abundance of alkylated relative to nonalkylated PAH in their pyrolysates.

    “The same two samples also have the highest abundance of alkylated relative to nonalkylated PAH in the pyrolysates (SI Appendix, Table S10).”
    Quote in the paperNot a substantial claim
  • Findingown data
    § Reappraisal of hydrocarbon biomarkers in Archean rocks

    In the new ultraclean cores, hopanes and steranes in rock extracts and hydropyrolysates were usually at or below femtogram detection limits.

    “Hopanes and steranes in rock extracts and hydropyrolysates from these new cores were typically at or below our femtogram detection limit”
    • Also stated in: § Results and Discussion · plain
      “Hopanes and steranes in the rock extracts from AIDP-2 and AIDP-3 were typically at or below femtogram detection limits”
    Quote in the paperSubstantial claim
  • May combine two claims. 26
  • Classified as probably not a substantial claim. 11

  • May combine two claims.

    Findingown data
    § Reappraisal of hydrocarbon biomarkers in Archean rocks

    When hopanes and steranes were detectable in the new cores, total hopane was below 37.9 pg per gram of rock and total sterane below 32.9 pg per gram of rock, similar to blanks and negative controls.

    “when they were detectable, they had total hopane (<37.9 pg per gram of rock) and total sterane (<32.9 pg per gram of rock) concentrations comparable to those measured in blanks and negative control samples.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    C10-20 n-alkanes, methylalkanes, and alkylcyclohexanes were detected in hydropyrolysates from two carbonate-rich Carawine Dolomite rocks at 116.09 m and 170.40 m in AIDP-2, while acyclic isoprenoids were not detected in any hydropyrolysate.

    “However, a series of C 10-20 n-alkanes (with a maximum abundance at C 13 ), methylalkanes, and alkylcyclohexanes were detected in hydropyrolysates from two carbonate-rich rocks at 116.09 m and 170.40 m in the Carawine Dolomite of AIDP-2 (SI Appendix, Fig. S6), yet acyclic isoprenoids were not detected in any of the hydropyrolysates.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the RHDH2A sample, n-alkanes, hopanes, and steranes were enriched on the exterior relative to the interior, with exterior total hopane and total sterane exceeding interior and blank concentrations by one to two orders of magnitude.

    “The n-alkanes, hopanes, and steranes were enriched on the exterior of the RHDH2A core compared with the interior, where the total hopane and total sterane concentrations in the exterior exceeded the interior and blank concentrations by one to two orders of magnitude (Table 1 and Fig. 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In rock extracts from AIDP-2 and AIDP-3, hopanes and steranes were usually at or below femtogram detection limits, and when detected their total concentrations were comparable to blanks and negative controls.

    “Hopanes and steranes in the rock extracts from AIDP-2 and AIDP-3 were typically at or below femtogram detection limits, but if they were detectable, the total sterane and total hopane concentrations were comparable to blank and negative control concentrations (Table 1 and Fig. 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Most samples had H/C ratios of 0.19-0.35, while the two alkane-bearing samples had the highest H/C ratios of 0.54 and 0.46.

    “Most samples had H/C ratios of 0.19-0.35 (SI Appendix, Table S5), but these two samples have the highest H/C ratios of 0.54 and 0.46.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Reappraisal of hydrocarbon biomarkers in Archean rocks

    PAHs and diamondoids in the ultraclean core extracts and hydropyrolysates exceeded blank levels, with individual PAH concentrations up to 80 ng per gram in extracts and up to 1,000 ng per gram in hydropyrolysates.

    “Polycyclic aromatic hydrocarbons and diamondoids, which exceed blank concentrations, exhibit individual concentrations up to 80 ng per gram of rock in rock extracts and up to 1,000 ng per gram of rock in hydropyrolysates from the ultraclean cores.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In AIDP-2 and AIDP-3 hydropyrolysates, individual hopanes and steranes were usually at or below detection limits, and when detected neither total hopane nor total sterane exceeded cumulative blank concentrations of less than 20 pg per gram of rock.

    “As in the rock extracts, individual hopanes and steranes in the AIDP-2 and AIDP-3 hydropyrolysates were usually at or below detection limits, but when they were detected, neither the total hopane nor the total sterane concentrations exceeded cumulative blank concentrations (<20 pg per gram of rock).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Total n-alkane concentrations in these hydropyrolysates were two orders of magnitude higher than laboratory blanks of less than 10 ng per gram of rock, in which methylalkane and alkylcyclohexane series were not detected.

    “The total n-alkane concentrations in these hydropyrolysates were two orders of magnitude higher than in laboratory blanks (<10 ng per gram of rock), in which methylalkane and alkylcyclohexane series were not detected.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The 133.55 m sample is a 10-cm pyrobituminous stylocumulate in stylolitic to brecciated dolarenite of the upper Carawine, where dark insoluble matter concentrated through pressure solution and carbonate dissolution.

    “This anomously 13 C-enriched sample was a 10-cm pyrobituminous stylocumulate occurring in stylolitic to brecciated dolarenite of the upper Carawine where dark insoluble matter concentrated as a result of pressure solution and carbonate dissolution (SI Appendix, Fig. S3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Many AIDP samples contain extractable PAHs and diamondoids at concentrations up to 80 ng per gram of rock and 4 ng per gram of rock, respectively.

    “Many AIDP samples, however, host extractable PAHs and diamondoids with concentrations up to 80 ng per gram of rock and 4 ng per gram of rock, respectively (SI Appendix, Fig. S4).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    PAHs and diamondoids were also detected in hydropyrolysates, where individual PAH concentrations reached 1039 ng per gram of rock and were significantly higher than HyPy blanks of less than 1 ng per gram for phenanthrene and pyrene.

    “PAHs and diamondoids were also detected in the hydropyrolysates, where individual PAH concentrations were up to 1039 ng per gram of rock, and their concentrations were significantly higher than their corresponding HyPy blank concentrations of less than 1 ng per gram of rock for phenanthrene and pyrene (SI Appendix, Table S10).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Sawing can add significant but variable hydrocarbon contaminants to the substrate, yet cumulative blanks in previous studies did not record the contribution from sawing.

    “the analyses of the saw blade (before it was heat treated) and the sawed surfaces of the RHDH2A quarter-core highlight that sawing can contribute significant but variable hydrocarbon contaminants to the substrate, yet the cumulative blanks reported in previous studies did not record the hydrocarbon contribution from sawing (1,4,6,7).”
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  • May combine two claims.

    Findingcitation

    PAH and diamondoid distributions together with H/C ratios confirm that the studied rocks are overmature and fall within the prehnite-pumpellyite metamorphic facies.

    “the PAH and diamondoid distributions in tandem with the H/C ratios confirm that these rocks are overmature and are within the prehnite-pumpellyite metamorphic facies (12,15,17,(36)(37)(38).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites 12,15,17,(36)(37)(38)

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  • May combine two claims.

    Findingcitation

    Low molecular mass aromatics (≤C16) predominate over high molecular mass PAHs (>C16), and nonalkylated parent PAHs are more abundant than alkylated PAHs in the AIDP samples and in previous Archean reports.

    “Like the PAHs and diamondoids that previous studies reported in Archean rock extracts and hydropyrolysates (3,21,24,28), the low molecular mass aromatics (≤C 16 ) predominate over high molecular mass PAHs (>C 16 ), and nonalkylated parent PAHs are in greater abundance compared with alkylated PAH (SI Appendix, Figs.S4 and S5 and Tables S8 and S10).”
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  • May combine two claims.

    Findingown data

    Hydropyrolysate PAHs are the most 13C-depleted organic molecules reported from Archean rocks, ranging from -42.6‰ to -45.9‰.

    “and they are the most 13 C-depleted organic molecules reported from Archean rocks, ranging from -42.6‰ to -45.9‰ (SI Appendix, Table S7).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The hydrocarbons must have been present in, or added to, the RHDH2A quarter core before laboratory preparation.

    “Clearly, the hydrocarbons must have been present in, or added to, the RHDH2A quarter core before laboratory preparation.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Each laboratory analyzed a chert or igneous negative control from AIDP-2 or AIDP-1 before analyzing the biomarker target samples.

    “Each laboratory analyzed either a chert or igneous negative control sample from AIDP-2 or AIDP-1 for extractable hydrocarbons before the analyses of the biomarker target samples.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Results from all participating laboratories agreed with the results reported here.

    “However, all results from all laboratories are consistent with the results described here.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    AIDP-2 and RHDH2A intersect the same Carawine Dolomite and Jeerinah Formation, so they sample the same stratigraphy and underwent the same regional metamorphism.

    “Spatially separated by less than 1 km, AIDP-2 and RHDH2A both intersect the Carawine Dolomite (<2.63 Ga) of the Hamersley Group and the Jeerinah Formation (2.63-2.67Ga) of the Fortescue Group (20), so they sample the same stratigraphy and have experienced the same regional metamorphic effects (Fig. 1).”
    Quote in the paperSubstantial claim0 of 1 sources checked
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  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation
    § Reappraisal of hydrocarbon biomarkers in Archean rocks

    The interpretation of the Archean biomarker record is controversial, with recent arguments that the hydrocarbons are not syngenetic.

    “However, the interpretation of the Archean biomarker record has become controversial, with recent arguments for a nonsyngenetic origin of these hydrocarbons (10,11).”
    Quote in the paperSubstantial claim0 of 2 sources checked
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  • May combine two claims.

    Premisecitation

    Those zones are in the prehnite-pumpellyite metamorphic facies and anthracite coal rank, implying maximum burial temperatures of 200-300 °C and pressures below 7 kbar.

    “According to previous studies of mineral assemblage and organic matter reflectivity, these zones are within the prehnite-pumpellyite metamorphic facies and anthracite coal rank, implying maximum burial temperatures and pressures of 200-300 °C and <7 kbar (1 bar = 100 kPa), respectively (15)(16)(17)(18).”
    Quote in the paperSubstantial claim0 of 1 sources checked
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  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation
    § Reappraisal of hydrocarbon biomarkers in Archean rocks

    Hopanes and steranes in Archean rocks have been put forward as major evidence for an early emergence of oxygenic photosynthesis and eukaryotes, but whether they are syngenetic is debated.

    “Hopanes and steranes found in Archean rocks have been presented as key evidence supporting the early rise of oxygenic photosynthesis and eukaryotes, but the syngeneity of these hydrocarbon biomarkers is controversial.”
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  • Classified as probably not a substantial claim.

    Study design and conductown data

    PAHs and diamondoids were identified by comparison with published mass spectra, published relative retention times, and parallel analysis with standards.

    “PAHs and diamondoids were identified by comparison with published mass spectra, published relative retention times, and parallel analysis with standards.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    Only one compound-specific isotopic measurement was possible for the 116.09 m sample, so analytical uncertainty and reproducibility are not well constrained.

    “Only a single compound-specific isotopic measurement was possible for this sample, so the analytical uncertainty and reproducibility are not well constrained.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Contamination is the only explanation for the reproducible surficial hopanes and steranes in conventionally drilled and curated Archean samples and for the undetectable or blank-level hopanes and steranes in the ultraclean AIDP cores.

    “Instead, contamination is the only explanation for the reproducibility of the detectable surficial hopanes and steranes in conventionally drilled and curated Archean samples (3,6,7,11) and the undetectable or blank level-equivalent hopane and sterane concentrations in samples from the ultraclean AIDP drill cores.”
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  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Two hypotheses have been proposed for surficial biomarker enrichments in Archean drill core: contamination and the live oil effect.

    “Two hypotheses have been proposed to explain surficial biomarker enrichments in Archean drill core: contamination and the live oil effect (i.e., the outward migration of hydrocarbons due to drill core depressurization during recovery) (11).”
    Quote in the paperSubstantial claim0 of 1 sources checked
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  • May combine two claims.

    Interpretationcitation

    Extractable PAHs could be syngenetic but heavily altered by reactions between hydrothermal fluids and bitumen, but this mechanism may not account for the full >10‰ 13C enrichment.

    “Lastly, the extractable PAHs could be syngenetic but heavily altered by reactions between hydrothermal fluids and the bitumen (28), but this mechanism may not be able to account for the full >10‰ 13 C enrichment.”
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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Previous work suggests the Jeerinah Formation and other organic-rich Archean shales generated and expelled petroleum.

    “Previous work suggests that the Jeerinah Formation and other organic-rich Archean shales generated and expelled petroleum (17)”
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  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationnone given

    This is a critical proof of concept for Precambrian organic geochemistry that had never been directly demonstrated before this work.

    “which is a critical proof of concept for Precambrian organic geochemistry that had never been directly demonstrated before this work, to our knowledge.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Previous work suggests the Pilbara Craton, including Ripon Hills, experienced multiple episodes of hydrothermal fluid flow, particularly around peak regional metamorphism at ~2.1 Ga.

    “and that the Pilbara Craton, including the Ripon Hills region, has experienced multiple episodes of hydrothermal fluid flow, particularly around the time of peak regional metamorphism at ∼2.1 Ga (18,41).”
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  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    Hydrothermal fluids could account for PAH migration from its original source, where a second generation of migrated overmature hydrothermal PAHs would have diluted or replaced primary bitumens.

    “Therefore, hydrothermal fluids could account for PAH migration from its original source, where this second generation of migrated overmature hydrothermal PAHs would have diluted or replaced the primary bitumens.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The lack of covariation suggests kerogens of the Jeerinah Formation and Carawine Dolomite may not be the primary source of cooccurring extractable PAHs, despite strong evidence of indigeneity.

    “suggesting that the kerogens of the Jeerinah Formation and Carawine Dolomite may not necessarily be the primary source of the cooccurring extractable PAHs, despite strong evidence of indigeneity.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The carbon isotopic anomaly at 2.6–2.7 Ga is a reliable stratigraphic marker for comparing AIDP bulk organic δ13C.

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based).

    Interpretationnone given

    Lateral oil migration before peak metamorphism could have introduced extractable organic matter with isotopic compositions distinct from associated kerogen.

    “Alternatively, lateral oil migration before peak metamorphism could have introduced the extractable organic matter with isotopic compositions distinct from the associated kerogen.”
    Quote in the paperNot a substantial claim
33 of 33

  • The paper relies on this without support.

    Laboratory blanks and negative controls capture all hydrocarbon contamination relevant to the AIDP samples.

    “Hopanes and steranes in the rock extracts from AIDP-2 and AIDP-3 were typically at or below femtogram detection limits, but if they were detectable, the total sterane and total hopane concentrations were comparable to blank and negative control concentrations”
    “Instead, contamination is the only explanation for the reproducibility of the detectable surficial hopanes and steranes in conventionally drilled and curated Archean samples (3,6,7,11) and the undetectable or blank level-equivalent hopane and sterane concentrations in samples from the ultraclean AIDP drill cores.”

  • The paper relies on this without support.

    Hydropyrolysis releases kerogen-bound organic matter without significant carbon isotopic fractionation.

    “The isotopic match between the AIDP bulk organic matter and the hydropyrolysate PAHs supports a syngenetic origin for the hydropyrolysate PAHs generated by thermochemical cleavage of covalent bonds within the host kerogens.”

  • The paper relies on this without support.

    The carbon isotopic anomaly at 2.6–2.7 Ga is a reliable stratigraphic marker for comparing AIDP bulk organic δ13C.

    “In contrast, the δ 13 C values of extractable PAHs do not covary with the AIDP bulk organic δ 13 C through the carbon isotopic anomaly at 2.6-2.7 Ga”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The earliest organic biomarker evidence for eukaryotic sterol synthesis, previously dated to 2.7 Ga, has been convincingly tied to contamination.

    “Until recently the earliest organic biomarker evidence for eukaryotic sterol synthesis was dated to 2.7 Ga (Brocks et al., 1999), but those records have now been convincingly tied to contamination (French et al., 2015).”

    From Oxygenation, Life, and the Planetary System during Earth's Middle History: An Overview (2021) · cites this paper as French et al., 2015

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • AIDP biomarker concentrations exceed the stated limits

    Minor

    The abstract says detectable hopane and sterane concentrations in the new cores were below 37.9 and 32.9 pg per gram of rock, respectively. Table 1 reports 50.4 and 49.4 pg per gram of rock in the exterior of AIDP-2 197.20 m.

1 of 1

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Authors
French, K. L., Hallmann, C., Hope, J. M., Schoon, P. L., Zumberge, J. A., Hoshino, Y., Peters, C. A., George, S. C., Love, G. D., Brocks, J. J., Buick, R., & Summons, R. E.
Affiliations
  • Massachusetts Institute of Technology (US)
  • Max Planck Society (DE)
  • Australian National University (AU)
  • University of California, Riverside (US)
  • Macquarie University (AU)
  • University of Washington (US)
ORCID
Venue
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences
Published
2015-04-27
Volume
112
Issue
19
Pages
5915-5920
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
DOI
10.1073/pnas.1419563112
PMC
PMC4434754
OpenAlex
W1970132751
Semantic Scholar
0236935f5104a4938fd43e23d9b4f55fa2cefd08
Cited by
307
References
43
Citations by year
2026: 13 · 2025: 23 · 2024: 21 · 2023: 14 · 2022: 38 · 2021: 26 · 2020: 27 · 2019: 41 · 2018: 41 · 2017: 25 · 2016: 26 · 2015: 11 · 2014: 1
FWCI
25.95
Type
journal article
Language
en
Open access
Licence
www.pnas.org/site/misc/userlicense.xhtml (vor, 183 d)
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
  • eSpace (Curtin University) (submittedVersion)
  • ANU Open Research (Australian National University) (submittedVersion)
Funders
  • Agouron Institute (private foundation, no grant number)
  • NSF FESD (1338810)
  • NSF GRFP (DGE-1122374)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Origins and Evolution of Life
  • Physical Sciences › Earth and Planetary Sciences › Geophysics › Geological and Geochemical Analysis
Keywords
Archean rocks, hopanes, steranes, hydrocarbon biomarkers, polycyclic aromatic hydrocarbons, diamondoids, eukaryotic origin, Pilbara Craton, thermal maturity
MeSH terms
Cyanobacteria, Archaea, Australia, Fossils, Hydrocarbons, Oxygen, Paleontology, Photosynthesis, Polycyclic Aromatic Hydrocarbons, Solvents, Temperature, Biomarkers, Geologic Sediments

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-08.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-08.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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