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Cited by 152Paleontology and Stratigraphy of FossilsGeochemistry and Elemental AnalysisGeological and Geochemical Analysis

Massive formation of early diagenetic dolomite in the Ediacaran ocean: Constraints on the "dolomite problem"

Open access
Chang, Biao, Li, Chao, Liu, Deng, Foster, Ian, Tripati, Aradhna, Lloyd, Max K., Maradiaga, Ingrid, Luo, Genming +8 more·2020·Proceedings of the National Academy of Sciences
DOI 10.1073/pnas.1916673117PMC PMC7321997
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Abstract

Significance Massive Paleozoic and Precambrian dolostone successions have long puzzled geologists in light of the kinetic barriers that inhibit low-temperature dolomite nucleation and precipitation (i.e., the “dolomite problem”). Significantly, the widely accepted hypothesis that such massive dolomites are the product of burial–hydrothermal dolomitization challenges their validity as archives of Earth surface environments. Here, we place constraints on the formation of massive dolomicrite deposits of the Ediacaran Doushantuo Formation (South China), demonstrating their syndepositional (i.e., early diagenetic) formation over a >63-My interval. Our findings suggest that the “dolomite problem” may be a product of specific conditions common if not persistent in Paleozoic and Precambrian oceans, and that massive dolostone successions may be faithful recorders of environmental conditions in the early oceans.

AI snapshot

Written from the paper’s full text.

TL;DR

Clumped-isotope temperatures for Ediacaran Doushantuo dolomicrites in South China indicate most formed below 100°C, and thermal modeling suggests many formed below 60°C, challenging burial-hydrothermal origin for these massive dolostones. The authors argue early diagenetic dolomitization of seawater-derived precursors in rock-buffered, microbially active settings can explain the “dolomite problem” and preserve surface-environment signals.

Key findings

  • TΔ47 values from two drillcores range 50–155°C, with 87% below 100°C. After modeling solid-state reordering under a short (~2,000 y) hydrothermal event with peak ~270°C, initial TΔ47 for 93% of samples falls between 0 and 60°C.
  • REE+Y patterns—positive Y, negative Ce, light REE depletion, and no Eu anomaly—resemble modern seawater and Holocene microbialites rather than hydrothermal fluids, supporting seawater or near-surface pore fluids.
  • δ18O fluid calculations, corrected for Ediacaran seawater, and petrography (fine dolomicrite, spherulitic crystals, microbial fossils, organic matter/apatite associations) point to early diagenetic, rock-buffered dolomitization, possibly via sabkha-like or organogenic pathways.
  • The authors conclude massive Precambrian/Paleozoic dolostones may reflect early-ocean conditions and can retain primary marine geochemical signals.

Methods

  • High-resolution clumped isotope (Δ47) paleothermometry on shallow-marine dolomicrites from Doushantuo Formation drillcores ZK312-P312 and ZK407, Zhangcunping area, Hubei; samples span >63 My and Members I–IV.
  • 45 samples from ZK312-P312 were used for petrology, isotopes, elements, and mineralogy; 15 from ZK407 were analyzed for isotopic and grain-size reproducibility. Analyses included Δ47 at UCLA and CUG-W, δ18O/δ13C, Mn/Sr, REE+Y, XRD, Raman, SEM/EDS, and grain-size measurement.
  • Thermal-history and solid-state reordering modeling used reconstructed burial/tectonic history, equivalent vitrinite reflectance and Raman peak temperatures, and dolomite reordering kinetics to estimate initial TΔ47.

Limitations

  • Stated: kinetic parameters for reordering models carry intrinsic uncertainty; the preferred 2,000-y scenario is one of many possible solutions, and other parameterizations/models can also fit the data. Calibration choices (acid fractionation factor, dolomite calibration, single-standard bias correction) are not optimal and may introduce bias.
  • Stated: some lower-core samples show Mn/Sr >3 and/or δ18O down to -7.3‰, indicating late-stage recrystallization; coarse dolomite patches and veins have higher TΔ47 and lower δ18O, so secondary alteration could not be completely avoided.
  • Evident from the text: conclusions rely on two nearby drillcores and extrapolation via regional correlation; the hydrothermal event timing is uncertain, and no direct modern analogue for massive early diagenetic dolomite is demonstrated.

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

Integrity signals

Registry

Crossref · 10.1073/pnas.1916673117

Cites

69 of 69 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

19 of 71 cited sources checked · 4 supported · 1 flagged · accuracy not yet measured

  • Premisecitation

    No geological process is known to reduce TΔ47 values.

    “Because no geological process is known to reduce T Δ47 values (7, 23-25)”
    Quote in the paperSubstantial claim3 of 4 sources checked
    • cites [7] 7. U. Ryb, J. M. Eiler, Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem. Proc. Natl. Acad. Sci. U.S.A. 115, 6602-6607 (2018). source

      The Significance section (p. 3) says solid-state isotopic reordering, if it occurred in the calcites discussed, would shift clumped-isotope temperatures toward higher values. That supports the point for this process, but the paper does not establish the broader claim that no geological process can reduce TΔ47 values. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [23] 23. T. F. Bristow, M. Bonifacie, A. Derkowski, J. M. Eiler, J. P. Grotzinger, A hydrothermal origin for isotopically anomalous cap dolostone cements from South China. Nature 474, 68-71 (2011). source
    • cites [24] 24. S. J. Loyd et al., Evolution of Neoproterozoic Wonoka-Shuram Anomaly-aged car- bonates: Evidence from clumped isotope paleothermometry. Precambrian Res. 264, 179-191 (2015). source

      Section 5.3 discusses burial heating and solid-state reordering as processes that can alter Δ47 values, while section 5.1 describes a trend toward higher clumped-isotope temperatures during burial. Neither passage states that no geological process can reduce TΔ47 values. Searches for lower clumped-isotope temperatures and the claimed absence of such a process did not find that assertion in our copy. (LLM, conf=0.70)

      Experimental — accuracy not yet measured
    • cites [25] 25. D. A. Stolper, J. M. Eiler, The kinetics of solid-state isotope-exchange reactions for clumped isotopes: A study of inorganic calcites and apatites from natural and ex- perimental samples. Am. J. Sci. 315, 363-411 (2015). source

      In “Modeling and Interpretation of Apparent Equilibrium Blocking Temperatures During Cooling” (page unavailable), the paper models calcite initially equilibrated at 350 °C and then cooled, predicting recorded apparent equilibrium temperatures of 145–235 °C. It also compares those predictions with natural carbonatites. Cooling is therefore a geological process the paper describes as reducing recorded TΔ47, contrary to the claim. (LLM, conf=0.88)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    Laboratory experiments indicate that the difficulty of dolomite synthesis under Earth surface conditions is likely due to hydration effects that hinder incorporation of Mg2+ into the dolomite crystal lattice.

    “Laboratory experiments have demonstrated that the difficulty of dolomite synthesis under Earth surface conditions (3) is likely due to hydration effects that hinder incorporation of Mg 2+ into the dolomite crystal lattice (4).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [3] 3. J. D. Rodriguez-Blanco, S. Shaw, L. G. Benning, A route for the direct crystallization of dolomite. Am. Mineral. 100, 1172-1181 (2015). source

      The ‘Nature and stability of the Mg-ACC precursor’ section links magnesium to higher water content and dehydration energy, and suggests that the precursor partly dehydrates before crystallizing. The Results show that dolomite did not form at 25 °C in these inorganic experiments. Neither passage establishes that hydration hinders Mg²⁺ incorporation into the dolomite lattice or identifies that effect as the likely cause of the difficulty at Earth-surface conditions. (LLM, conf=0.77)

      Experimental — accuracy not yet measured
    • cites [4] 4. F. Lippmann, "Sedimentary carbonate minerals" in Minerals, Rocks and Inorganic Materials (Monograph Series of Theoretical and Experimental Studies, Springer, Berlin, 1973), vol. 6, p. 228. source
  • Premisecitation

    Original TΔ47 signatures are subject to secondary alteration via meteoric diagenesis, recrystallization, and solid-state reordering during geological burial, all of which shift values to higher-than-original TΔ47 values.

    “Original T Δ47 signatures are subject to secondary alteration via meteoric diagenesis, recrystallization, and solid-state reordering during geological burial, all of which result in shifts to higher-than-original T Δ47 values (7,(23)(24)(25).”
    Quote in the paperSubstantial claim3 of 4 sources checked
    • cites [7] 7. U. Ryb, J. M. Eiler, Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem. Proc. Natl. Acad. Sci. U.S.A. 115, 6602-6607 (2018). source

      The Significance section (p. 3) says burial-related diagenetic alteration can record elevated clumped-isotope temperatures and that solid-state reordering, if it occurred, would shift those temperatures higher. But the paper does not establish that meteoric diagenesis and recrystallization necessarily shift TΔ47 higher; it discusses meteoric water as a possible cause of changes in δ18O. It also expects the dolomites selected for this study to retain their crystallization temperatures (p. 2). (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [23] 23. T. F. Bristow, M. Bonifacie, A. Derkowski, J. M. Eiler, J. P. Grotzinger, A hydrothermal origin for isotopically anomalous cap dolostone cements from South China. Nature 474, 68-71 (2011). source
    • cites [24] 24. S. J. Loyd et al., Evolution of Neoproterozoic Wonoka-Shuram Anomaly-aged car- bonates: Evidence from clumped isotope paleothermometry. Precambrian Res. 264, 179-191 (2015). source

      Section 5.2 says solid-state reordering can produce higher clumped-isotope temperatures, and §5.4.2 links high temperatures to burial recrystallization. But §5.4.1 treats meteoric diagenesis as a possible earlier signal, not as a process that necessarily raises TΔ47; §5.3 also finds evidence against pervasive reordering in the studied carbonates. The claim overstates the paper by saying all three processes shift values higher than the original temperature. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [25] 25. D. A. Stolper, J. M. Eiler, The kinetics of solid-state isotope-exchange reactions for clumped isotopes: A study of inorganic calcites and apatites from natural and ex- perimental samples. Am. J. Sci. 315, 363-411 (2015). source

      The paper’s Modeling and Interpretation of Apparent Equilibrium Temperatures During Heating section reports that solid-state isotope exchange during burial can raise apparent TΔ47 above formation temperature. Its introductory discussion also identifies recrystallization as a way to alter an original clumped-isotope signature, but does not establish that recrystallization or meteoric diagenesis invariably shifts TΔ47 higher. The burial effect is itself conditional on thermal history, rather than an inevitable increase. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
  • Premisecitation

    The burial-hydrothermal dolomitization model is supported by petrographic observations and geochemical evidence from Phanerozoic and Proterozoic dolostones.

    “This model is supported by many petrographic observations (e.g., coarse dolomite cements, saddle dolomites) and geochemical evidence (e.g., elemental and isotopic compositions) from both Phanerozoic (7) and Proterozoic dolostones (8).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [7] 7. U. Ryb, J. M. Eiler, Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem. Proc. Natl. Acad. Sci. U.S.A. 115, 6602-6607 (2018). source

      The cited paper reports isotopic evidence from Phanerozoic dolostones and concludes that its data are consistent with dolomitization during deep circulation of seawater (Significance, pp. 2, 5). It does not provide the cited petrographic evidence of coarse cements or saddle dolomites. In the citing sentence, the separate citation (8) is attached to Proterozoic dolostones, so that portion is not attributed to this source. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [8] 8. A. M. Shuster, M. W. Wallace, A. van Smeerdijk Hood, G. Jiang, The Tonian Beck Spring Dolomite: Marine dolomitization in a shallow, anoxic sea. Sediment. Geol. 368, 83-104 (2018). source
  • Premisecitation

    The extent of C-O bond reordering is a function of the temperature-time history of a sample.

    “The extent of C-O bond reordering is a function of the temperature-time history of a sample (25).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [25] 25. D. A. Stolper, J. M. Eiler, The kinetics of solid-state isotope-exchange reactions for clumped isotopes: A study of inorganic calcites and apatites from natural and ex- perimental samples. Am. J. Sci. 315, 363-411 (2015). source
  • May combine two claims. 40
  • The quote only partly states this claim. 2
  • Classified as probably not a substantial claim. 20

  • May combine two claims.

    Interpretationreasoning

    Most of the studied dolomite samples must have formed at temperatures below 100 °C, which is inconsistent with an origin via the widely accepted burial-hydrothermal dolomitization model.

    “these results suggest that most of our dolomite samples must have formed at temperatures below 100 °C, which is inconsistent with an origin via the widely accepted burial-hydrothermal dolomitization model (5,7).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [5] 5. J. M. Gregg, D. L. Bish, S. E. Kaczmarek, H. G. Machel, C. Hollis, Mineralogy, nucleation and growth of dolomite in the laboratory and sedimentary environment: A review. Sedimentology 62, 1749-1769 (2015). source
    • cites [7] 7. U. Ryb, J. M. Eiler, Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem. Proc. Natl. Acad. Sci. U.S.A. 115, 6602-6607 (2018). source

      The source supports a deep-burial account of dolomite formation: it says pre-Cenozoic dolomites mostly formed above plausible shallow-sediment temperatures (p. 4) and concludes that its data are consistent with dolomitization at kilometer-scale burial depths (p. 5). It does not establish 100 °C as a cutoff that rules out burial dolomitization; its reported mean crystallization temperatures for Paleozoic and Mesozoic dolomites are both below 100 °C (p. 3). The temperature inference about 'our dolomite samples' belongs to the citing authors, not this source. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • The quote only partly states this claim.

    Findingcitation

    The TΔ47 records from the Zhangcunping drillcores differ from earlier Doushantuo dolostone studies at Huajipo and Jiulongwan, which yielded generally low Δ47 values corresponding to significantly higher temperatures up to 224 °C.

    “We note that the T Δ47 records from the Zhangcunping drillcores differ from results for Doushantuo dolostones in earlier studies of the Huajipo (23) and Jiulongwan (23,24) shelf sections in the Yangtze Gorges area”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [23] 23. T. F. Bristow, M. Bonifacie, A. Derkowski, J. M. Eiler, J. P. Grotzinger, A hydrothermal origin for isotopically anomalous cap dolostone cements from South China. Nature 474, 68-71 (2011). source
    • cites [24] 24. S. J. Loyd et al., Evolution of Neoproterozoic Wonoka-Shuram Anomaly-aged car- bonates: Evidence from clumped isotope paleothermometry. Precambrian Res. 264, 179-191 (2015). source

      The Results (section 4) report clumped-isotope temperatures for South China carbonates, and Table 1 lists Doushantuo dolomite samples. But our copy does not identify Huajipo or report a temperature of 224 °C for those samples; it gives a South China range of 38–164 °C. It also does not compare either named shelf section with Zhangcunping drillcores. (LLM, conf=0.83)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    The high temperatures in earlier Doushantuo studies are inferred to reflect postdepositional hydrothermal alteration of host rocks and loss of original Δ47 signals.

    “These high temperatures are inferred to reflect postdepositional hydrothermal alteration of the host rocks and loss of original Δ 47 signals (23,24)”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [23] 23. T. F. Bristow, M. Bonifacie, A. Derkowski, J. M. Eiler, J. P. Grotzinger, A hydrothermal origin for isotopically anomalous cap dolostone cements from South China. Nature 474, 68-71 (2011). source
    • cites [24] 24. S. J. Loyd et al., Evolution of Neoproterozoic Wonoka-Shuram Anomaly-aged car- bonates: Evidence from clumped isotope paleothermometry. Precambrian Res. 264, 179-191 (2015). source

      Section 5.1 (page unavailable) says the South China carbonate temperatures are consistent with burial heating and interprets the rocks as recrystallized and reequilibrated; §5.4.2 links high clumped-isotope temperatures to burial recrystallization. The paper does not identify hydrothermal alteration as the cause of those temperatures or specifically establish loss of the original Δ47 signals in earlier Doushantuo studies. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductcitation

    Raw Δ47 values were calculated using the 17O calibration parameters reported in ref. 53, which have been shown to improve interlaboratory data consistency.

    “Due to the possible large uncertainties related to Assonov 17 O calibration parameters (50-53), we calculated raw Δ 47 values using the 17 O calibration parameters reported in ref. 53, which have been shown to improve interlaboratory data consistency (54).”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [53] 53. W. A. Brand, S. S. Assonov, T. B. Coplen, Correction for the 17 O interference in δ 13 C measurements when analyzing CO 2 with stable isotope mass spectrometry (IUPAC Technical Report). Pure Appl. Chem. 82, 1719-1733 (2010). source
    • cites [54] 54. S. M. Bernasconi et al., Reducing uncertainties in carbonate clumped isotope analysis through consistent carbonate-based standardization. Geochem. Geophys. Geosyst. 19, 2895-2914 (2018). source

      In “Calculation of Δ47 and the Effect of the 17O Correction” (page unavailable), the paper says the revised parameters reconcile inconsistencies within individual laboratories and possibly across laboratories. But “Does Use of the Brand Parameters Solve All Interlaboratory Inconsistencies?” (page unavailable) questions whether comparability across laboratories has improved and reports remaining differences. The claim presents an improvement in interlaboratory consistency as established, which is stronger than the paper supports. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Study design and conductreasoning

    The interlaboratory bias correction of the dolomite temperature calibration based on a single standard may not be optimal, but it is still better for Δ47 temperature calculations than direct use of the original calibration in ref. 50.

    “The preceding interlaboratory bias correction of the temperature calibration for dolomites based on a single standard may not be optimal, but it is still better for Δ 47 temperature calculations than direct use of the original calibration in ref. 50, which was not given in the Brand parametric framework nor calibrated to the ETH standard values reported in ref. 53.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [50] 50. M. Bonifacie et al., Calibration of the dolomite clumped isotope thermometer from 25 to 350 °C: And implications for a universal calibration for all (Ca: Mg: Fe)CO 3 carbonates. Geochim. Cosmochim. Acta 200, 255-279 (2017). source
    • cites [53] 53. W. A. Brand, S. S. Assonov, T. B. Coplen, Correction for the 17 O interference in δ 13 C measurements when analyzing CO 2 with stable isotope mass spectrometry (IUPAC Technical Report). Pure Appl. Chem. 82, 1719-1733 (2010). source

      The Summary and Practical Implementation section (pp. 1729–1730) describes a framework for correcting and calibrating CO₂ isotope measurements. It does not address dolomite Δ47 temperature calibrations or compare a single-standard interlaboratory correction with direct use of an original calibration. Searches for those terms found no passage that evaluates the claimed comparison. (LLM, conf=0.75)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Study design and conductreasoning

    The temperature calibration of ref. 50 was used because it is based on 12 samples exhibiting a stronger correlation (R2 = 0.997), whereas the calibration of ref. 62 was based on only five samples with a modest correlation (R2 = 0.864).

    “Because the temperature calibration of ref. 62 was based on only five samples exhibiting a modest correlation (R 2 = 0.864), we used the calibration of ref. 50, which is based on 12 samples exhibiting a stronger correlation (R 2 = 0.997).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [50] 50. M. Bonifacie et al., Calibration of the dolomite clumped isotope thermometer from 25 to 350 °C: And implications for a universal calibration for all (Ca: Mg: Fe)CO 3 carbonates. Geochim. Cosmochim. Acta 200, 255-279 (2017). source
    • cites [62] 62. I. A. Müller et al., Calibration of the oxygen and clumped isotope thermometers for (proto-) dolomite based on synthetic and natural carbonates. Chem. Geol. 525, 1-17 (2019). source

      Section 3.3 reports R² = 0.864, as claimed, but says the calibration used 289 measurements of 20 samples formed at five temperatures—not five samples. The cited paper does not establish the stated sample count or R² for ref. 50. (LLM, conf=0.90)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingown data

    Coarse-grained dolomite patches and veins show generally larger crystal sizes, lower δ18O carb values, and higher TΔ47 values than the fine-grained matrix.

    “generally larger crystal sizes, lower δ 18 O carb values, and higher T Δ47 values (Fig. 2).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The samples mostly yielded Mn/Sr below 3 and δ18O above -7‰, suggesting only limited fluid-buffered diagenetic alteration.

    “Our samples mostly yielded Mn/Sr < 3 and δ 18 O > -7‰, similarly suggesting only limited fluid-buffered diagenetic alteration.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The samples show no significant δ13C-δ18O covariation for ZK312-P312 (r = +0.14) or moderately negative covariation for ZK407 (r = -0.57), suggesting fluid-buffered diagenesis did not significantly affect the studied samples.

    “In contrast, our samples show no significant covariation (r = +0.14 for ZK312-P312) or moderately negative covariation (r = -0.57for ZK407) (SI Appendix, Fig. S5), suggesting that fluid-buffered diagenesis did not significantly affect our studied samples.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Some samples from the lower parts of the two study cores yielded Mn/Sr above 3 and/or relatively low δ18O values down to -7.3‰, suggesting a degree of late-stage recrystallization.

    “However, some samples from the lower parts of the two study cores yielded Mn/Sr >3 (Fig. 1C and SI Appendix, Table S4) and/or relatively low δ 18 O values (down to -7.3‰; Fig. 1D), suggesting a degree of late-stage recrystallization also indicated by microscopic and cathodoluminescence images”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The ZK312-P312 and ZK407 drillcores yielded similar TΔ47 values ranging from 50 to 155 °C, with 87% of samples having TΔ47 below 100 °C.

    “The ZK312-P312 and ZK407 drillcores yielded similar T Δ47 values, ranging from 50 to 155 °C with 87% of samples having T Δ47 < 100 °C”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Varying the initial temperature from 0 to 50 °C yields final modeled TΔ47 values of 55 to 99 °C, corresponding well to measured TΔ47 values of 50 to 106 °C in well-preserved samples.

    “Based on this simulation, we then varied the initial temperature from 0 to 50 °C, yielding a range of 55 to 99 °C for the final modeled T Δ47 values, which corresponds well to the range of measured T Δ47 values (50 to 106 °C) in our well-preserved samples (Fig. 4D).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    Raman spectroscopy showed that both spherulitic and nonspherulitic dolomitic crystals are surrounded by organic matter and apatite, both of which are linked to biological processes.

    “Raman spectroscopy showed that both spherulitic and nonspherulitic dolomitic crystals are surrounded by OM and apatite (Fig. 7 C and D), both of which are linked to biological processes (41).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [41] 41. C. Ohtsuki, H. Kushitani, T. Kokubo, S. Kotani, T. Yamamuro, Apatite formation on the surface of Ceravital-type glass-ceramic in the body. J. Biomed. Mater. Res. 25, 1363-1370 (1991). source

  • May combine two claims.

    Findingown data

    Both bulk-rock and carbonate fractions of all samples display a positive Y anomaly, a negative Ce anomaly, light REE depletion, and lack of a Eu anomaly.

    “Both the bulk-rock and carbonate fractions of all samples display a positive Y anomaly, a negative cerium (Ce) anomaly, light REE depletion, and lack of a europium (Eu) anomaly”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The REE+Y features are similar to modern seawater and Holocene microbialites but distinctly different from hydrothermal fluids and related dolomites.

    “These features are similar to the REE+Y compositions of modern seawater and Holocene microbialites, which are likely to be similar to the patterns in ancient equivalents (35), but they are distinctly different from those of hydrothermal fluids and related dolomites (summarized in ref. 36).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [35] 35. G. E. Webb, B. S. Kamber, Rare earth elements in Holocene reefal microbialites: A new shallow seawater proxy. Geochim. Cosmochim. Acta 64, 1557-1565 (2000). source
    • cites [36] 36. A. P. Nutman, C. R. L. Friend, V. C. Bennett, D. Wright, M. D. Norman, ≥3700 Ma pre- metamorphic dolomite formed by microbial mediation in the Isua supracrustal belt (W. Greenland): Simple evidence for early life? Precambrian Res. 183, 725-737 (2010). source

  • May combine two claims. The quote only partly states this claim.

    Findingcitation

    The result is robust to choice of dolomite-based solid-state reordering models; similar results are obtained using alternative models, although those require heating durations of 4,000 to 70,000 y at a peak temperature of 270 °C.

    “We note that this result is robust to choice of dolomitebased solid-state reordering models; similar results are obtained using the alternative dolomite-based”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [33] 33. B. H. Passey, G. A. Henkes, Carbonate clumped isotope bond reordering and geo- speedometry. Earth Planet. Sci. Lett. 351-352, 223-236 (2012). source
    • cites [34] 34. G. A. Henkes et al., Temperature limits for preservation of primary calcite clumped isotope paleotemperatures. Geochim. Cosmochim. Acta 139, 362-382 (2014). source

  • May combine two claims.

    Findingown data

    The Doushantuo dolomite consists of many similar-sized spherical to ellipsoidal crystals, consistent with a possible microbial origin.

    “The Doushantuo dolomite consists of many similar-sized spherical to ellipsoidal crystals (Fig. 7B), consistent with a possible microbial origin.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Solid-state reordering in the preferred 2,000-y alteration scenario would have caused an increase in TΔ47 of 42 to 55 °C, consistent with initial TΔ47 values between 0 and 60 °C for 93% of samples.

    “Our results indicate that solid-state reordering in the preferred 2,000-y alteration scenario would have caused an increase in T Δ47 of 42 to 55 °C, which is consistent with initial T Δ47 values between 0 and 60 °C, as calculated for 93% of our samples”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Given heating on 10^4-y and 10^3-y timescales, modeled TΔ47 values vary from 0 to 91 °C and 0 to 68 °C, respectively.

    “Given heating on 10 4 -y and 10 3 -y timescales, the modeled T Δ47 values vary from 0 to 91 °C (Fig. 4B) and 0 to 68 °C (Fig. 4C), respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Additional petrological observations under SEM revealed well-preserved microbial fossils and abundant mycelia and mycetomes associated with organic matter in the Doushantuo samples.

    “Additional petrological observations of our samples under a scanning electron microscope (SEM) revealed well-preserved microbial fossils (Fig. 7E) and abundant mycelia and mycetomes associated with OM (Fig. 7F)”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    The burial-hydrothermal dolomitization attribution raises doubt about the validity of massive dolostones as archives of Earth surface environments.

    “thus raising doubt about the validity of these deposits as archives of Earth surface environments.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisenone given

    The genesis of massive Paleozoic and Precambrian dolostones is usually attributed to burial-hydrothermal dolomitization of primary limestones at temperatures above 100 °C.

    “Accordingly, the genesis of these dolostones is usually attributed to burial-hydrothermal dolomitization of primary limestones (CaCO 3 ) at temperatures of >100 °C”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    The two TΔ47 profiles show generally similar stratigraphic patterns, confirming reproducibility of TΔ47 measurements at least within the Zhangcunping area.

    “The two T Δ47 profiles show generally similar stratigraphic patterns (Fig. 1F), confirming the reproducibility of the T Δ47 measurements, at least within the Zhangcunping area.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    The authors minimized secondary alteration influences by microdrilling only fine-grained dolostone suitable for Δ47 analysis, avoiding coarse dolomite grains typically ascribed to deep burial or high-temperature processes.

    “we minimized such influences by microdrilling only fine-grained dolostone (i.e., dolomicrite) [grain size: 20 ± 15 μm (mean ± SD, n = 37); Fig. 1 A and B] suitable for Δ 47 analysis (SI Appendix, Fig. S4), avoiding the coarse dolomite grains that are typically ascribed to deep burial or hightemperature processes.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The fine-grained dolomicrite is the component least altered by late diagenesis and potentially best preserves the original TΔ47 signatures of the study units.

    “These patterns indicate that the fine-grained dolomicrite is the component that was least altered by late diagenesis and the one that potentially best preserves the original T Δ47 signatures of the study units.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Mn/Sr values below 3 and δ18O values above -10‰ are indicative of less altered samples.

    “with values of Mn/Sr < 3 and δ 18 O > -10‰ indicative of less altered samples (26).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [26] 26. A. J. Kaufman, A. H. Knoll, Neoproterozoic variations in the C-isotopic composition of seawater: Stratigraphic and biogeochemical implications. Precambrian Res. 73, 27-49 (1995). source

  • May combine two claims.

    Premisecitation

    Zircon U-Pb ages indicate the Doushantuo Formation was deposited from about 635 to 551 Ma, with carbonate deposition mainly during about 614 to 551 Ma.

    “Zircon U-Pb ages indicate that the Doushantuo Formation was deposited from ∼635 to 551 Ma (20), with carbonate deposition occurring mainly during the ∼614to 551-Ma interval (20,21).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [20] 20. D. Condon et al., U-Pb ages from the neoproterozoic Doushantuo Formation, China. Science 308, 95-98 (2005). source
    • cites [21] 21. P. Liu, C. Yin, L. Gao, F. Tang, S. Chen, New material of microfossils from the Ediacaran Doushantuo Formation in the Zhangcunping area, Yichang, Hubei Province and its zircon SHRIMP U-Pb age. Chin. Sci. Bull. 54, 1058-1064 (2009). source

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

    Premisecitation

    The sabkha model hypothesizes early diagenetic dolomitization of calcite or aragonite precursors at temperatures below 60 °C in evaporative settings via reflux of Mg-rich seawaters.

    “Major early diagenetic mechanisms invoking seawater as the dolomitizing fluid include the sabkha model, which hypothesizes early diagenetic dolomitization of calcite or aragonite precursors at temperatures of <60 °C in evaporative settings (such as hypersaline ponds associated with sabkhas) via reflux of Mg-rich seawaters (1,9).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [1] 1. J. Warren, Dolomite: Occurrence evolution and economically important associations. Earth Sci. Rev. 52, 1-81 (2000). source
    • cites [9] 9. L. S. Land, The origin of massive dolomite. J. Geol. Educ. 33, 112-125 (1985). source

  • May combine two claims.

    Premisecitation

    The Doushantuo Formation was deposited immediately after the Marinoan glaciation at paleolatitudes of about 30 °N.

    “The Doushantuo Formation of the Yangtze Platform (South China) is a succession of marine carbonate (mainly dolomite), siliciclastic, and phosphatic sedimentary rocks deposited immediately after the global-scale Neoproterozoic Marinoan (or Nantuo in South China) glaciation at paleolatitudes of ∼30 °N (19)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [19] 19. S. Zhang et al., New paleomagnetic results from the Ediacaran Doushantuo Formation in South China and their paleogeographic implications. Precambrian Res. 259, 130-142 (2015). source

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

    Premisecitation

    The organogenic dolomite model involves direct precipitation of very high-Mg calcite and nonstoichiometric or stoichiometric dolomite from seawater or near-surface porewaters through microbial-organic mediation, followed by transformation to ordered dolomite during early marine burial.

    “Another proposed mechanism is the organogenic dolomite model, which involves direct precipitation of very high-Mg calcite and nonstoichiometric or stoichiometric dolomite [Ca 2+ + Mg 2+ + 2CO 3 2-→ CaMg(CO 3 ) 2 ] from seawater or near-surface porewaters through microbial-organic mediation (10,11), followed by transformation to ordered dolomite following Ostwald's rule (12) during early marine bur”
    Quote in the paperNot a substantial claim0 of 6 sources checked
    • cites [10] 10. C. Vasconcelos, J. A. McKenzie, R. Warthmann, S. M. Bernasconi, Microbial mediation as a possible mechanism for natural dolomite formation at low temperatures. Nature 377, 220-222 (1995). source
    • cites [11] 11. X. Qiu, H. Wang, Y. Yao, Y. Duan, High salinity facilitates dolomite precipitation mediated by Haloferax volcanii DS52. Earth Planet. Sci. Lett. 472, 197-205 (2017). source
    • cites [12] 12. S. H. Nordeng, D. F. Sibley, Dolomite stoichiometry and Ostwald's step rule. Geochim. Cosmochim. Acta 58, 191-196 (1994). source
    • cites [13] 13. T. M. Smith, S. L. Dorobek, Alteration of early-formed dolomite during shallow to deep burial: Mississippian Mission Canyon Formation, central to southwestern Mon- tana. Geol. Soc. Am. Bull. 105, 1389-1399 (1993).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [14] 14. A. Geske et al., Impact of diagenesis and low grade metamorphosis on isotope (δ26Mg, δ13C, δ18O and 87Sr/86Sr) and elemental (Ca, Mg, Mn, Fe and Sr) signatures of Triassic sabkha dolomites. Chem. Geol. 332-333, 45-64 (2012). source
    • cites [15] 15. A. Bahniuk et al., Characterization of environmental conditions during microbial Mg- carbonate precipitation and early diagenetic dolomite crust formation: Brejo do Es- pinho, Rio de Janeiro, Brazil. Geol. Soc. London Spec. Publ. 418, 243-259 (2015). source

  • May combine two claims.

    Premisecitation

    Only minor amounts of dolomite are formed in modern surface environments, and these are usually embedded in calcitic and aragonitic host sediments.

    “only minor amounts of dolomite are formed in modern surface environments, and these are usually embedded in calcitic and aragonitic host sediments (see review in ref. 5).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] 5. J. M. Gregg, D. L. Bish, S. E. Kaczmarek, H. G. Machel, C. Hollis, Mineralogy, nucleation and growth of dolomite in the laboratory and sedimentary environment: A review. Sedimentology 62, 1749-1769 (2015). source

  • Classified as probably not a substantial claim.

    Premisecitation

    Massive dolostones are usually attributed to slow burial or hydrothermal dolomitization of calcite or aragonite precursors by Mg-rich fluids at temperatures above 100 °C.

    “To resolve the dolomite problem, massive dolostones are usually attributed to slow burial or hydrothermal dolomitization of calcite or aragonite precursors by Mg-rich fluids at temperatures of >100 °C”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] 5. J. M. Gregg, D. L. Bish, S. E. Kaczmarek, H. G. Machel, C. Hollis, Mineralogy, nucleation and growth of dolomite in the laboratory and sedimentary environment: A review. Sedimentology 62, 1749-1769 (2015). source

  • May combine two claims.

    Premisecitation

    The Doushantuo Formation was deposited in a passive continental margin setting from about 635 to 551 Ma, with subsequent maximum burial depths of about 4 km for platform facies and about 7 km for coeval basinal facies.

    “The Doushantuo Formation was deposited in a passive continental margin setting from ∼635 to 551 Ma, with subsequent maximum burial depths of ∼4 km for platform facies and ∼7 km for coeval basinal facies (28).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] 28. G. Jiang, M. J. Kennedy, N. Christie-Blick, H. Wu, S. Zhang, Stratigraphy, sedimentary structures, and textures of the Late Neoproterozoic Doushantuo cap carbonate in South China. J. Sediment. Res. 76, 978-995 (2006). source

  • May combine two claims.

    Premisecitation

    Early-stage formation of organogenic dolomite commonly exhibits weak to no cationic ordering, although it may have a Mg/Ca ratio close to 1:1.

    “The early-stage formation of organogenic dolomite commonly exhibits weak to no cationic ordering, although it may have a Mg/Ca ratio close to 1:1 (5).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] 5. J. M. Gregg, D. L. Bish, S. E. Kaczmarek, H. G. Machel, C. Hollis, Mineralogy, nucleation and growth of dolomite in the laboratory and sedimentary environment: A review. Sedimentology 62, 1749-1769 (2015). source

  • May combine two claims.

    Interpretationown data

    The two early diagenetic mechanisms outlined above agree well with the isotopic and elemental observations and are further supported by the mainly fine-grained dolomicritic nature of the Doushantuo dolostones.

    “Other early diagenetic mechanisms are also possible, but the two early diagenetic mechanisms outlined above agree well with our isotopic and elemental observations and are further supported by the mainly fine-grained dolomicritic nature of the Doushantuo dolostones (SI Appendix, Figs.S4, S6, and S7).”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The extremely low Δ47 values in Doushantuo cap carbonate veins have been interpreted as evidence of high-temperature hydrothermal fluids migrating through the cap carbonate and other permeable layers.

    “These values have been interpreted as evidence of hightemperature hydrothermal fluids migrating through the cap carbonate and other permeable layers in the Doushantuo Formation (23).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [23] 23. T. F. Bristow, M. Bonifacie, A. Derkowski, J. M. Eiler, J. P. Grotzinger, A hydrothermal origin for isotopically anomalous cap dolostone cements from South China. Nature 474, 68-71 (2011). source

  • May combine two claims.

    Interpretationcitation

    The most likely interpretation is that disordered nonstoichiometric proto-dolomites or very high-Mg calcites formed first and were followed by gradual cationic ordering in a rock-buffered environment, as observed under both shallow and slightly deep burial conditions.

    “The most likely interpretation is that the formation of disordered nonstoichiometric proto-dolomites or very high-Mg calcites was followed by gradual cationic ordering in a rock-buffered environment, as observed under both shallow and slightly deep burial conditions (12,14,15).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [12] 12. S. H. Nordeng, D. F. Sibley, Dolomite stoichiometry and Ostwald's step rule. Geochim. Cosmochim. Acta 58, 191-196 (1994). source
    • cites [14] 14. A. Geske et al., Impact of diagenesis and low grade metamorphosis on isotope (δ26Mg, δ13C, δ18O and 87Sr/86Sr) and elemental (Ca, Mg, Mn, Fe and Sr) signatures of Triassic sabkha dolomites. Chem. Geol. 332-333, 45-64 (2012). source
    • cites [15] 15. A. Bahniuk et al., Characterization of environmental conditions during microbial Mg- carbonate precipitation and early diagenetic dolomite crust formation: Brejo do Es- pinho, Rio de Janeiro, Brazil. Geol. Soc. London Spec. Publ. 418, 243-259 (2015). source

  • May combine two claims.

    Interpretationown data

    The massive ordered dolomites of the Ediacaran Doushantuo Formation formed in a low-temperature early-diagenetic environment with seawater-derived fluids and abundant microbial activity.

    “Our T Δ47 records along with cogenerated elemental, isotopic, and petrographic data indicate that the massive ordered dolomites of the Ediacaran Doushantuo Formation formed in a low-temperature early-diagenetic environment with seawater-derived fluids and abundant microbial activity.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Paleogeographic reconstructions suggest shallow-water facies of the Doushantuo Formation were deposited in a semirestricted shelf lagoon at a paleolatitude of about 30 °N.

    “Indeed, paleogeographic reconstructions suggest that shallow-water facies of the Doushantuo Formation were deposited in a semirestricted shelf lagoon (39) at a paleolatitude of ∼30 °N (19).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [39] 39. G. Jiang, X. Shi, S. Zhang, Y. Wang, S. Xiao, Stratigraphy and paleogeography of the Ediacaran Doushantuo Formation (ca. 635-551Ma) in South China. Gondwana Res. 19, 831-849 (2011). source
    • cites [19] 19. S. Zhang et al., New paleomagnetic results from the Ediacaran Doushantuo Formation in South China and their paleogeographic implications. Precambrian Res. 259, 130-142 (2015). source

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

    Study design and conductnone given

    The kinetic parameters upon which the solid-state reordering models are based contain intrinsic uncertainties.

    “We also note that the kinetic parameters upon which these models are based contain intrinsic uncertainties.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Most likely, the sedimentary precursors of the Doushantuo dolomites (e.g., calcite, aragonite, very high-Mg calcite, or nonstoichiometric and disordered protodolomite) precipitated from seawater or marine porewaters and were subsequently transformed to ordered dolomites during early diagenesis in a shallow-burial porewater setting.

    “Most likely, the sedimentary precursors of the Doushantuo dolomites (e.g., calcite, aragonite, very high-Mg calcite, or nonstoichiometric and disordered protodolomite) precipitated from seawater or marine porewaters and were subsequently transformed to ordered dolomites during early diagenesis in a shallow-burial porewater setting.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationnone given

    Whatever the age of the hydrothermal alteration event(s), their effects on TΔ47 values through solid-state reordering would have been similar and do not affect the modeling results.

    “However, whatever the age of the hydrothermal alteration event(s), their effects on the T Δ47 values of our study samples through solid-state reordering would have been similar and thus do not affect the modeling results described below.”
    Quote in the paperNot a substantial claim

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

    Study design and conductown data

    Analytical errors are better than ±6.1% for Mn, ±0.7% for Sr, and ±8.9% for REE based on duplicate analyses of four USGS standards.

    “Analytical errors are better than ±6.1% for Mn, ±0.7% for Sr, and ±8.9% for REE based on duplicate analyses of four USGS standards (AGV-2, BHVO-2, BCR-2, and RGM-2).”
    Quote in the paperNot a substantial claim

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

    Study design and conductown data

    Typical sample precision of the Δ47 data based on replicate measurements of our dolomite samples is 0.010‰ (1 SE).

    “Typical sample precision of the Δ 47 data based on replicate measurements of our dolomite samples is 0.010‰ (1 SE).”
    Quote in the paperNot a substantial claim

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

    Study design and conductown data

    The SDs for replicate analyses of ZK312-317 and ZK312-368 are better than ±4.6 ppm for Mn, ±1.1 ppm for Sr, and ±0.07 ppm for REEs.

    “The SDs for replicate analyses of ZK312-317 and ZK312-368 are better than ±4.6 ppm for Mn, ±1.1 ppm for Sr, and ±0.07 ppm for REEs.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    All Δ47 values are reported on the absolute reference frame (ARF), calculated using CO2 reference gases equilibrated at 10, 25, 50, and 1,000 °C.

    “All Δ 47 values are reported on the absolute reference frame (ARF), which was calculated using CO 2 reference gases equilibrated at 10, 25, 50, and 1,000 °C (49).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [49] 49. K. J. Dennis, H. P. Affek, B. H. Passey, D. P. Schrag, J. M. Eiler, Defining an absolute reference frame for "clumped" isotope studies of CO 2 . Geochim. Cosmochim. Acta 75, 7117-7131 (2011). source

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Prior to microdrilling, the intended sampling points were examined in thin sections to avoid areas of visible late diagenetic alteration.

    “Prior to microdrilling, the intended sampling points were examined in thin sections (ca.2.5 × 4 cm) to avoid areas of visible late diagenetic alternation.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Only microcrystalline areas that best represent the 'primary' phases of the study dolomites were targeted.

    “We targeted only microcrystalline areas that best represent the”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    These conditions may explain why our REE+Y data reflect a seawater signal, and why the δ13C carb values of the Doushantuo and other coeval dolomitic successions were able to capture large perturbations of the oceanic carbon cycle during the Ediacaran.

    “These conditions may explain why our REE+Y data reflect a seawater signal, and why the δ 13 C carb values of the Doushantuo and other coeval dolomitic successions were able to capture large perturbations of the oceanic carbon cycle during the Ediacaran (46).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [46] 46. J. P. Grotzinger, D. A. Fike, W. W. Fischer, Enigmatic origin of the largest-known carbon isotope excursion in Earth's history. Nat. Geosci. 4, 285-292 (2011). source

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Fifteen samples from the Doushantuo Formation at ZK407 were analyzed for isotopic and dolomitic grain size characteristics in order to confirm the reproducibility of measurements from ZK312-P312.

    “Fifteen samples from the Doushantuo Formation at ZK407 were analyzed for isotopic and dolomitic grain size characteristics in order to confirm the reproducibility of measurements from ZK312-P312.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    The average Raman spectra of OM were deconvolved into several peaks with a high-fit degree (R2 > 0.99).

    “The average Raman spectra of OM were deconvolved into several peaks (SI Appendix, Fig. S12) using the computer program WITec Project 5 (Gaussian Lorentzian Sum) with a high-fit degree (R 2 > 0.99).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    The results from both laboratories show almost the same values and the same trend, confirming the reliability of our Δ47 data.

    “The results from both laboratories show almost the same values and the same trend (SI Appendix, Fig. S11 and Table S2), confirming the reliability of our Δ 47 data.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    The Δ47 analysis was carried out in duplicate at UCLA and CUG-W to monitor the reproducibility of our results.

    “The Δ 47 analysis was carried out in duplicate at the University of California, Los Angeles (UCLA), and in State Key Laboratory of Geological Processes and Mineral Resources at China University of Geosciences-Wuhan (CUG-W) to monitor the reproducibility of our results.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductown data

    δ18O values were calibrated relative to NBS-19 and GBW04416 and have a precision of better than ±0.1‰ based on duplicate analyses.

    “δ 18 O values were calibrated relative to the international reference standard NBS-19 (δ 18 O = -2.20‰)and Chinese national standard GBW04416 (δ 18 O = -11.59± 0.11‰) and are expressed in standard δ-notation as per mille deviations from the Vienna Pee Dee Belemnite (VPDB) international standard with a precision of better than ±0.1‰ based on duplicate analyses of GBW04416 and selected study samples”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    Nonlinearity corrections were made per standard protocols using water-equilibrated and heated CO2 gases.

    “Nonlinearity corrections were made per standard protocols using water-equilibrated (10, 25, and 50 °C) and heated (1,000 °C) CO 2 gases, as described in ref. 49.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [49] 49. K. J. Dennis, H. P. Affek, B. H. Passey, D. P. Schrag, J. M. Eiler, Defining an absolute reference frame for "clumped" isotope studies of CO 2 . Geochim. Cosmochim. Acta 75, 7117-7131 (2011). source
55 of 55

  • The authors state this as an assumption.

    Diagenetic recrystallization of carbonate, if it occurred, was the dominant influence on measured TΔ47 values.

    “assuming that diagenetic recrystallization of carbonate, if it occurred, was the dominant influence on measured T Δ47 values.”

  • The paper relies on this without support.

    The Doushantuo Formation dolomites from the studied drillcores are representative of massive early-diagenetic dolomite formation in Precambrian oceans.

    “Therefore, our study provides direct evidence for massive early-diagenetic dolomite formation in Precambrian oceans.”
2 of 2

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?

  • Clumped isotope data for carbonates precipitated or altered in the subsurface have placed new constraints on dolomitization and carbonate reservoirs.

    “Clumped isotope data for carbonates precipitated or altered in the subsurface have placed new constraints on dolomitization and carbonate reservoirs (e.g., Ferry et al. 2011, Murray & Swart 2017, Chang et al. 2020, Hu et al. 2022)”

    From Frontiers of Carbonate Clumped Isotope Thermometry (2023) · cites this paper as Chang et al. 2020

    The Abstract (page unavailable) reports clumped-isotope temperatures for Ediacaran dolostones and uses them to constrain when dolomitization occurred, supporting that part of the claim. The studied carbonates are shallow-marine deposits altered during early diagenesis; the paper does not address carbonate reservoirs or establish a reservoir-specific constraint. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

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.

  • ETH standard values are attributed to two different references

    Minor

    The methods attribute the new ETH standard values to reference 54 in one passage, but to reference 53 in a later explanation of the calibration.

  • Analytical standard is listed as both RGM-1 and RGM-2

    Minor

    The methods first identify RGM-1 as one of the four standards run with the samples, then identify RGM-2 as one of the four standards used to assess analytical errors.

2 of 2

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Authors
Chang, B., Li, C., Liu, D., Foster, I., Tripati, A., Lloyd, M. K., Maradiaga, I., Luo, G., An, Z., She, Z., Xie, S., Tong, J., Huang, J., Algeo, T. J., Lyons, T. W., & Immenhauser, A.
Affiliations
  • China University of Geosciences (CN)
  • Institut Universitaire Européen de la Mer (FR)
  • University of California, Los Angeles (US)
  • California Institute of Technology (US)
  • China Geological Survey (CN)
  • University of California, Riverside (US)
  • Ruhr University Bochum (DE)
Corresponding author
  • Li, Chao
  • Huang, Junhua
ORCID
Venue
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences
Published
2020-06-08
Volume
117
Issue
25
Pages
14005-14014
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
DOI
10.1073/pnas.1916673117
PMC
PMC7321997
OpenAlex
W3032974216
Cited by
152
References
69
Citations by year
2026: 13 · 2025: 28 · 2024: 29 · 2023: 30 · 2022: 27 · 2021: 22 · 2020: 3
FWCI
24.10
Type
journal article
Language
en
Open access
Licence
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion, other-oa)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion)
  • CaltechAUTHORS (California Institute of Technology) (submittedVersion)
  • HAL (Le Centre pour la Communication Scientifique Directe) (submittedVersion)
  • Publikationsdatenbank der Fraunhofer-Gesellschaft (Fraunhofer-Gesellschaft) (submittedVersion)
  • OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (submittedVersion)
  • Fraunhofer-Publica (Fraunhofer-Gesellschaft) (submittedVersion)
Funders
  • National Natural Science Foundation of China (41825019, 41821001, 41573099, 41661134048)
  • National Key Research and Development Program of China (2016YFA0601100)
  • Strategic Priority Research Program of Chinese Academy of Sciences (XDB26000000)
  • China University of Geosciences, Wuhan (CUGCJ1710)
  • U.S. Department of Energy (DE-FG02-13ER16402)
  • Laboratoire Excellence LabexMER (ANR-10-LABX-19)
  • NASA Astrobiology Institute (NNA15BB03A)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Geochemistry and Petrology › Geochemistry and Elemental Analysis
  • Physical Sciences › Earth and Planetary Sciences › Geophysics › Geological and Geochemical Analysis
Keywords
dolomite problem, early diagenesis, Ediacaran, Doushantuo Formation, dolomitization, paleoceanography, South China

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Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-11.

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