Precambrian marine carbonate isotope database: Version 1.1



[1] We present a compilation of strontium, carbon, and oxygen isotope compositions of roughly 10,000 marine carbonate rocks of Archean - Ordovician age (3800 Ma – 450 Ma). The Precambrian Marine Carbonate Isotope Database (PMCID) has been compiled from 152 published and 3 unpublished articles and books of the past 40 years. Also included are 30 categories of relevant “metadata” that allow detailed comparisons and quality assessments of the isotope data to be made. The PMCID will be updated periodically as new data and better age constraints come to light. Here we outline the structure of the first published version of the database and its inherent merits and limitations.

1. Introduction

[2] Temporal trends in the isotopic compositions (Sr, C, O, and S) of marine sedimentary rocks have been used to hypothesize tectonic, chemical, and biological change during the Precambrian. Fluctuations in seawater 87Sr/86Sr, which can be retained in well-preserved marine carbonate rocks, reflect changes in the relative contributions of the continental versus mantle chemical reservoirs to ocean composition [Veizer, 1989]. By contrast, the stable isotopes of C and S have generally been used to recognize changes in the biogeochemical cycling of these elements, which may be related to tectonic events, biological innovations, and the oxidation state at the Earth's surface [Schidlowski et al., 1975; DesMarais et al., 1992; Canfield and Teske, 1996; Farquhar et al., 2000; Goddéris and Veizer, 2000]. Recently, attention has also been paid to the potential of Sr and C isotopes in the global stratigraphic correlation of Paleoproterozoic [Melezhik et al., 1999] and Neoproterozoic rock successions [Kaufman and Knoll, 1995; Shields, 1999; Walter et al., 2000].

[3] Here we outline the Precambrian marine carbonate isotope database or PMCID (, which complements the published Phanerozoic isotope database [Veizer et al., 1999] that is freely available at Both current and future versions of these databases will be available from the Global Earth Reference Model (GERM) site under = 48. The PMCID was conceived in the light of increasing amounts of isotope data that were rapidly invalidating published isotope compilations. In addition to ever larger and more numerous isotope studies, there have been continual improvements to the dating and correlation of Precambrian strata, which make necessary a flexible, electronic database that can be periodically updated. It is hoped that the current use of electronic data processing and the international standardization of analytical techniques will make the task of updating the database increasingly less work-intensive. The generosity of those who have so far given of their time and expertise is gratefully acknowledged.

2. Merits of the PMCID

[4] The Precambrian marine carbonate isotope database (PMCID) is believed to contain all relevant, published isotope data. This has been achieved through an exhaustive 2 year literature search and by directing requests for suggestions and contributions to members of the geochemical community. Despite this effort, some published data have almost certainly been overlooked, and these will be incorporated in future versions. The capacity for expansion is an important feature of the PMCID as is its flexibility, which will allow it to evolve in response to feedback from users and contributors.

[5] In addition to compiling Sr, C, and O isotope data from marine carbonates, we have attempted to include as many categories of “metadata” as possible (Table 1), for example, original sample identification, geographic and stratigraphic details, mineralogy, age, trace element contents, and other isotopic data as available. Such metadata provide a context for the isotope data and help toward their interpretation. Metadata can be updated with time as age constraints or palaeoenvironmental interpretations improve or change. It is also hoped that some categories of nonisotopic metadata will prove to be useful in their own rights, for example, when assessing changes in the abundance of carbonate rocks or in the chemical composition of marine carbonates and seawater through time.

Table 1. Structure of the PMCID – Version 1.1(a)
Column NameContent of Column
Sample ID numberunique sample number taken from original publication
Sample descriptionadditional relevant information - incomplete
Formationformation name occasionally including groups, members, etc.
Locationname of section, borehole and/or region
Countryname of country
Depth, mdepth in borehole
Height, mstratigraphic height in section
MineralC, calcite; D, dolomite; M, magnesite; S, siderite; A, ankerite; R, rhodocrosite; CH, chert
EraA, Archean; PP, Paleoproterzoic; MP, Mesoproterozoic; NP, Neoproterozoic; Ph, Phanerozoic
Intervalera subdivision from Eoarchean to Cenozoic
Geon100 Ma intervals or “Geons” from 0 to 37 [Hofmann, 1999]
Age, Mawell-constrained ages (less than ±50 Ma)
Age, Mapoorly constrained ages (greater than ±50 Ma)
Uncertainty, Mapublished age constraints
Source: dataliterature reference for isotopic data (see appendix)
Source: ageliterature references for age constraints (incomplete)
Dating techniquedating technique, e.g., U-Pb single zircon, biostratigraphy, etc.
Fe, ppmiron concentration in carbonate phase, ppm
Mg/CaMg/Ca ratio of carbonate phase
Mg, ppmmagnesium concentration in carbonate phase, ppm
Ca, wt %calcium concentration in carbonate phase, weight%
Mn, ppmmanganese concentration in carbonate phase, ppm
Sr, ppmstrontium concentration in carbonate phase, ppm
δ13Ccalcite PDBcarbon isotope composition of calcite, ‰ PDB
δ13Cdolomite PDBcarbon isotope composition of dolomite, ‰ PDB
δ13Cothers PDBcarbon isotope composition of other carbonate minerals, ‰ PDB
δ18Ocalcite PDBoxygen isotope composition of calcite, ‰ PDB
δ18Odolomite PDBoxygen isotope composition of dolomite, ‰ PDB
δ18Oothers PDBoxygen isotope composition of other carbonate minerals, ‰ PDB
87Sr/86Srreported strontium isotope composition of carbonate phase
87Sr/86Srnorm.87Sr/86Sr normalised to NBS 987 = 0.71025
δ13Corganic PDBcarbon isotope composition of kerogen, ‰ PDB
Corg (wt.%)total organic carbon content (TOC) of bulk rock, weight%
H/CH/C ratio of kerogen
δ34Ssulphate CDTsulphur isotope composition of sulphate, ‰ CDT
δ34Ssulphide CDTsulphur isotope composition of sulphide, ‰ CDT
Rb (ppm)rubidium concentration in carbonate phase, ppm
Δδ13Cδ13C of carbonate phase - δ13C of kerogen, ‰ PDB
Commentsproblems with data, e.g. altered, poor age constraints, etc.

3. Limitations of the PMCID

3.1. General Limitations

[6] The usefulness of any database is limited not only by the quantity, i.e., the statistical significance, of the data, but also by the quality. The PMCID comprises isotope data of highly variable degrees of usefulness due to the following:

3.1.1. Poor quality of metadata

[7] Some isotope data cannot be assigned specific geographic locations or stratigraphic positions. This may be due to the intentions of the original authors, which may have been quite different from those of isotope stratigraphers or may be due to tectonic complications. In either case, assigned ages may be poorly constrained and are unlikely to improve with time, thus severely restricting the usefulness of the isotope data. In some studies, the mineralogy or paleoenvironmental setting (e.g., marine versus nonmarine setting) of the measured samples is unclear, in which case, depending on the importance of this information, some isotope data may need to be disregarded for the purposes of interpretation.

3.1.2. Poor age constraints

[8] Most Precambrian isotope data suffer from poor age resolution due to the scarcity of reliable radiometric ages coupled with the inherent difficulties in stratigraphic correlation in the Precambrian. This problem will undoubtedly improve with time as more ages are obtained for important sections. Substantial improvements have already been made during the last decade in the dating of entire rock successions, for example, the McArthur basin of Australia and the Belt/Purcell Supergroup of the USA/Canada, which have led to considerable changes in the age assignments of published isotope data.

3.1.3. Difficulties in stratigraphic correlation

[9] Although there has been a marked improvement in the number of radiometric age constraints on Precambrian successions, it is unlikely that there will ever be enough data to assign firm ages to most samples on this basis alone. Therefore other techniques of global stratigraphic correlation need to be applied. For the Neoproterozoic-Cambrian interval, schemes of global stratigraphic correlation have been consulted that use fossil, isotopic, and other information [e.g., Kaufman and Knoll, 1995; Shields, 1999; Walter et al., 2000]. However, in cases where age assignment has involved carbon or strontium isotope stratigraphy in isolation a generous margin of error has been chosen because of the potential dangers of circular reasoning.

3.2. Element Specific Limitations

3.2.1. Sr isotopes

[10] Published Sr isotope data (Figure 1) for carbonate rocks are generally reported relative to the NBS 987 standard or can, by means of reported standard values from the same laboratory of the Elmer Amend standard or modern ocean water, be recalculated against expected values of the NBS 987 standard. Today, the most commonly cited value for the standard NBS 987 is 0.71025 [McArthur, 1994], and this was used as the standard value for normalization of all reported Sr isotope ratios (Table 1, 87Sr/86Srnorm column). Although laboratories may produce different systematic errors in their measurement of this standard, this only becomes a significant problem for high-resolution Sr isotope stratigraphy in the late Phanerozoic [McArthur, 1994].

Figure 1.

Strontium isotopic evolution of seawater based on published analyses of marine carbonate rocks and Phanerozoic calcitic fossils from Veizer et al. [1999]. Poorly time-constrained samples (greater than ±50 Ma) are shown as open circles.

[11] The biggest problem in Precambrian Sr isotope stratigraphy is postdepositional alteration. Of the ∼1000 Precambrian carbonate samples that have been analyzed for Sr isotopes, almost all have suffered alteration of their 87Sr/86Sr ratios to some degree. Alteration by a radiogenic source, by interaction with clay minerals, for example, will tend to increase 87Sr/86Sr, while alteration by fluids affected by a juvenile volcanic source or by dissolution of older, less radiogenic authigenic minerals will tend to decrease 87Sr/86Sr. In practice, postdepositional alteration nearly always causes an increase in 87Sr/86Sr, which leads to the rule-of-thumb that lowest 87Sr/86Sr ratios represent our best maximum estimate of seawater 87Sr/86Sr at any particular time [Veizer and Compston, 1974; Burke et al., 1982]. This is certainly the case on the scale of the Precambrian (Figure 1) but should be demonstrated on a case-by-case basis as postdepositional decreases in 87Sr/86Sr have been reported, although these are generally of a relatively minor magnitude.

[12] Analytical techniques and reporting of Sr isotope data vary greatly. Sample dissolution techniques have generally become more carbonate-selective, while sampling techniques have become more component-selective, both of which have led to lower, more seawater-like 87Sr/86Sr ratios. Nowadays, carbonate samples are generally prepared by leaching with a weak acid, such as acetic acid, after initial washing in water or a buffer solution [McArthur, 1994]. Some research groups systematically carry out corrections of their 87Sr/86Sr ratios for radiogenic 87Sr, which derives from the in situ decay of 87Rb. However, well-preserved, pure carbonate components should not normally contain sufficient Rb to necessitate such correction, while Rb corrections usually involve unjustifiable assumptions that are likely to result in significant errors. For example, some leaching of clays during sample preparation is frequently inevitable and so measured Rb/Sr ratios could relate, in part, to clay minerals, which might have changed their trace element compositions during diagenesis. Clay minerals suffer preferential loss of radiogenic Sr from their lattices relative to the parent Rb, something which can occur during diagenesis or sample preparation, resulting in the overcorrection of initial 87Sr/86Sr ratios. Last the ages of most samples are not known with sufficient accuracy to carry out corrections for Rb decay, causing additional errors. Lastly, for these reasons, 87Sr/86Sr data in the PMCID have been left uncorrected for 87Rb decay.

3.2.2. C isotopes

[13] Generally, analytical techniques, data reporting, and diagenetic alteration rarely present major problems for C isotope data (Figure 2) on the scale of the Precambrian. Nevertheless, some questions need to be asked of individual case studies, such as whether the presence of organic matter in Corg-rich samples has affected the analysis of δ13Ccarb and whether diagenetic or primary components were selected in the original study.

Figure 2.

Carbon isotopic evolution of marine carbonate based on published analyses of limestones (circles), dolostones (triangles), and Phanerozoic calcitic fossils from Veizer et al. [1999]. Poorly time-constrained samples (greater than ±50 Ma) are shown as open symbols.

3.2.3. O isotopes

[14] O isotope data (Figure 3) suffer most from inconsistency and ambiguity. δ18O data are often absent from data tables, especially where C isotope stratigraphy has been the authors' prime concern. This is generally because of the relative susceptibility of O isotopes to diagenetic alteration and subsequent difficulty in interpretation. For this reason, previous isotope compilations have not included O isotope data [e.g., Schopf and Klein, 1992] with the exception of the work of Perry and Ahmad [1983].

Figure 3.

Oxygen isotopic evolution of marine calcite based on published analyses of limestones and Phanerozoic calcitic fossils from Veizer et al. [1999]. Poorly time-constrained samples (greater than ±50 Ma) are shown as open circles.

[15] Some reported O isotope data may also be of limited usefulness due to a lack of background information (metadata) on original mineralogy and analytical technique. First, δ18O data need to be mineral-specific to be of use as each carbonate mineral undergoes different degrees of fractionation during its precipitation from solution. The δ18O data are frequently reported without reference to the mineralogy of the carbonate phase analyzed and usually omit mention of whether the authors have determined the mineralogical purity of their samples. This problem is especially acute with older Precambrian sedimentary rocks, which are likely to contain iron, magnesium, and manganese carbonate minerals as well as dolomite and calcite. In cases, where a mixture of dolomite and calcite is known to have been analyzed, it is also desirable to know whether these mineral phases have been cleanly separated before analysis. Where doubts remain about the carbonate mineralogy, these data have been placed within the “other carbonate minerals” column.

[16] Research articles seldom clarify whether the respective corrections have been carried out according to the different equilibrium fractionations experienced during dolomite and calcite dissolution in phosphoric acid. Where dolomite has been analyzed without any correction at 25°C, this leads to a δ18Odol value that is roughly 0.8‰ higher than if the correction had been carried out.

3.3. Effects of Sampling Bias on the Precambrian Sr, C, and O Isotopic Records

3.3.1. Geographic bias

[17] Most sampling for isotope stratigraphy has been carried out in easily accessible areas of developed countries even though most Precambrian rocks derive from ancient cratons, which are frequently poorly exposed and relatively inaccessible. For these reasons, some sections in Australia, USA, and Canada have been resampled many times by different research groups, which may greatly exaggerate the importance of these sections.

3.3.2. Preservation bias

[18] Because of tectonic recycling and sedimentary burial, most potential marine carbonate samples of Precambrian age have been annihilated, either by uplift and erosion or by subduction, or are not exposed. In addition, many Precambrian rocks are highly metamorphosed. Metamorphism frequently alters the chemical and isotopic compositions of carbonate rocks, rendering them of limited usefulness for isotope stratigraphy. Even in cases where metamorphic rocks have preserved their primary isotopic signatures, their tectonic settings can often be too complex to permit adequate dating and correlation.

3.3.3. Sedimentary bias

[19] Most samples represent marginal, shallow-water settings, which represent only a small proportion of the wide range of possible ocean sedimentary settings.

3.3.4. Temporal bias

[20] A disproportionately large number of the samples are of Neoproterozoic-Cambrian (800–500 Ma) and mid-Palaeoproterozoic age (2100–1900 Ma). This may partly be a true reflection of the marine carbonate record and partly a result of sampling bias. This temporal bias appears also when we consider the number of individual studies or data sets (Figure 4) rather than individual samples. One obvious reason for this skewed distribution is that isotopic studies are more often carried out for these two intervals because of the large δ13C excursions during these times (Figure 2).

Figure 4.

Number of identifiable stratigraphic units with published carbonate isotope data shown against 100 Ma intervals or geons [Hofmann, 1999].

3.3.5. Sample size bias

[21] Many studies, especially those before 1985, do not report many isotopic values per lithological unit, whereas some more recent studies report hundreds of values from a small part of one unit, which likely represents a much shorter period of time. This kind of bias exaggerates the effect of particular lithological units to the detriment of others and can be reduced by dividing the database into identifiable lithological units. We have carried this out in an alternative version (Table 2) of the PMCID (version 1). This version tends to overemphasise younger, more intensively studied parts of the geological record, while ignoring the obvious fact that not all, identifiable lithological units represent an equal duration. We consider, however, that the coupling of both kinds of database structure will lead to a more complete interpretation of the Precambrian isotopic record.

Table 2. Structure of the Alternative Version of the PMCID Database - Version 1.1(b)
Column NameContent of Column
Formationformation name occasionally including groups, members, etc.
Locationname of section, borehole and/or region
Countryname of country
Eraera subdivision from Eoarchean to Cenozoic
Geon100 Ma intervals or “Geons” from 0 to 37 [Hofmann, 1999]
Age, Marelatively well constrained ages (less than ±50 Ma)
Age, Maassigned ages
maxmaximum age constraint
minminimum age constraint
Durationlikely time equivalent of data range
Source: C,O dataliterature references for stable isotope data (see appendix)
Source: ageliterature references for age constraints (incomplete)
Dating techniquedating technique, e.g., U-Pb single zircon, biostratigraphy, etc.
n° Cnumber of C isotope analyses on all carbonate minerals
δ13Cmeanmean of δ13C values for all carbonate minerals, ‰ PDB
δ13Cmaxmaximum of δ13C values for all carbonate minerals, ‰ PDB
δ13Cminminimum of δ13C values for all carbonate minerals, ‰ PDB
δ13Csdstandard deviation of δ13C values for all carbonate minerals
n° Ocalcitenumber of O isotope analyses on calcite
δ18Omean calcitemean of δ18O values for calcite, ‰ PDB
δ18Omax. calcitemaximum of δ18O values for calcite, ‰ PDB
δ18Omin. calciteminimum of δ18O values for calcite, ‰ PDB
δ18Osd calcitestandard deviation of δ18O values for calcite
n° Odolomitenumber of O isotope analyses on dolomite
δ18Omean dolomitemean of δ18O values for dolomite, ‰ PDB
δ18Omax dolomitemaximum of δ18O values for dolomite, ‰ PDB
δ18Omin dolomiteminimum of δ18O values for dolomite, ‰ PDB
δ18Osd dolomitestandard deviation of δ18O values for dolomite
n° Oothersnumber of O isotope analyses on other carbonate minerals
δ18Omean othersmean of O isotope data on other carbonate minerals, ‰ PDB
δ18Omax othersmaximum of δ18O values for other carbonate minerals, ‰ PDB
δ18Omin othersminimum of δ18O values for other carbonate minerals, ‰ PDB
δ18Osd othersstandard deviation of δ18O values for other carbonates
n° Corgnumber of C isotope analyses on kerogen
δ13Cmean orgmean of δ13C values for kerogen
δ13Cmax orgmaximum of δ13C values for kerogen
δ13Cmin orgminimum of δ13C values for kerogen
δ13Csd orgstandard deviation of δ13C values for kerogen
Δδ13Cδ13C of carbonate minerals - δ13C of kerogen
Δδ18Oδ18O of dolomite - δ18O of calcite
n° Srnumber of Sr isotope analyses on carbonate minerals
87Sr/86Srlowermost or best preserved Sr isotope ratio
Source: Sr dataliterature references for strontium isotope data - see appendix
Commentscomments (incomplete)

4. Interpretation

[22] It is not the purpose of the present article to interpret isotopic trends through the Precambrian in any depth. Nonetheless, we consider it necessary to describe the initial results of the PMCID compilation and to outline major similarities and differences between these results and those of previous compilations.

4.1. Sr Isotope Stratigraphy

[23] As discussed in section 3.2, the lower part of the 87Sr/86Sr band in Figure 1 is likely to represent a maximum constraint on seawater 87Sr/86Sr. These “best estimate” (least altered from seawater) 87Sr/86Sr ratios reveal a deflection away from mantle-like 87Sr/86Sr before ∼2.5 Ga to more radiogenic 87Sr/86Sr after ∼2.5 Ga [Veizer and Compston, 1976]. This switch is consistent with a change from a “mantle”-buffered to a “river”-buffered global ocean around this time and is likely to result from a combination of (1) decreasing heat flux from the mantle and (2) intensified formation of continental crust [Veizer et al., 1982]. A second major increase in 87Sr/86Sr from 0.7052 to 0.7092 took place between ∼1000 and 500 Ma, implying steadily increasing continental influence on ocean chemistry during this time. This is consistent with elevated rates of tectonic uplift and erosion of highly radiogenic crust, possibly related to the birth, break-up, and dispersal of the supercontinent Rodinia [Meert and Powell, 2000]. This second increase is also of potential importance in global stratigraphic correlation, especially when combined with C isotopes [Shields, 1999; Walter et al., 2000].

4.2. C Isotope Stratigraphy

[24] The δ13C values reflect changes in the biogeochemical redox cycling of carbon, with long-term trends (>100 Ma) likely reflecting real shifts in the proportion of carbonate versus organic carbon burial [Schidlowski, 1993]. Published Precambrian δ13C data are relatively numerous with over 10,000 samples measured from 536 distinct lithological units. The compilations shown in Figures 2 and 5 confirm that marine bicarbonate δ13C remained close to 0‰ during much of Precambrian time [Schidlowski et al., 1975]. Two prolonged intervals of anomalously high (greater than +10‰) and variable (range up to 20‰) δ13C can be identified: the mid-Paleoproterozoic (2.3–1.9 Ga) and the mid-Neoproterozoic (0.8–0.6 Ga). The extent to which high marine carbonate δ13C represents truly elevated rates of organic burial is difficult to prove for either period [Melezhik et al., 1999; Shields et al., 2002]. Mean δ13C values reveal a sustained rise over some 108 years during both these times, which is consistent with a real increase in organic carbon burial and storage rates. Atmospheric oxygen concentrations seem likely to have risen as a consequence [DesMarais et al., 1992].

Figure 5.

Carbon isotopic evolution of marine carbonate based on means of published analyses of carbonate rocks (including all carbonate minerals) from identifiable lithological units. Poorly time-constrained samples (greater than ±50 Ma) are shown as open circles. Continuous line represents a running mean through all data points.

4.3. O Isotope Stratigraphy

[25] Despite considerable scatter due to postdepositional alteration, primary variation and analytical inconsistencies, calcite δ18O values are generally depleted throughout the Precambrian relative to most of the Phanerozoic (Figures 3 and 6). Mean δ18O values from both calcite and dolomite increase in parallel through the Precambrian with a roughly constant isotopic discrimination (Figure 6) that probably reflects differences in their equilibrium isotopic fractionations [Land, 1980], either during precipitation from seawater or, more likely, from near-marine, early diagenetic fluids. The low δ18O values of most Precambrian carbonates are consistent with the well-documented increase in marine calcite δ18O during the Phanerozoic, which has been interpreted as resulting from a tectonically controlled, first-order increase in seawater δ18O with higher-order, climate-related fluctuations superimposed [Veizer et al., 2000]. The extent to which seawater δ18O has changed over geological history is still a matter of controversy [Muehlenbachs, 1998; Goddéris and Veizer, 2000], but the observed Precambrian O isotope record is consistent with recent modeling [Wallmann, 2001].

Figure 6.

Oxygen isotopic evolution of Precambrian and Cambrian marine calcite (circles, n = 318), dolomite (triangles, n = 349) and other carbonate minerals (squares) based on means of published analyses of carbonate rocks from identifiable lithological units. Poorly time-constrained samples (greater than ±50 Ma) are shown as open symbols. Continuous lines represent running means through the dolomite (top line) and calcite (bottom line) data, respectively.

5. Future Work

[26] The Precambrian Marine Carbonate Isotope Database is still unfinished. At the moment of writing, a further 50 recently published articles await incorporation. Also, Precambrian isotope data need to be combined seamlessly with the Phanerozoic isotope record, which is based largely on data from fossil brachiopods and foraminifera [Veizer et al., 1999]. At present, the PMCID contains a large proportion of the published carbonate isotope data for the Cambrian System, and it is hoped that this can be extended to include much of the lower Paleozoic, which will allow direct comparison between the carbonate rock-based data and fossil limestone-based data. Meanwhile, we await feedback from users, so that the PMCID can evolve into a useful tool for the geochemical community at large.

Appendix (Representative Sample).: PMCID Version 1.1 Database References

[27] The full Appendix is available in the HTML version of the article at

Abell, P. I., J. McClory, A. Martin, and E. G. Nisbet, Archaean stromatolites from the Ngesi Group, Belingwe greenstone belt, Zimbabwe: Preservation and stable isotopes-Preliminary results, Precambrian Res., 27, 357–383, 1985a. [C, O, Corg]

Abell, P. I., J. McClory, A. Martin, E. G. Nisbet, and T. K. Kyser, Petrography and stable isotope ratios from Archaean stromatolites, Mushandike Formation, Zimbabwe, Precambrian Res., 27, 385–398, 1985b. [C, O]

Abell, P. I., J. McClory, H. E. Hendry, and K. L. Wheatley, Stratigraphic variations in carbon and oxygen isotopes in the dolostone of the Carswell Formation (Proterozoic) of northern Saskatchewan, Can. J. Earth Sci., 26, 2318–2326, 1989. [C, O; no data table]

Aharon, P., A stable-isotope study of magnesites from the Rum Jungle uranium field, Australia: Implications for the origin of strata-bound massive magnesites, Chem. Geol., 69, 127–145, 1988. [C, O]

Aharon, P., M. Schidlowski, and I. B. Singh, Chronostratigraphic markers in the end-Precambrian carbon isotope record of the Lesser Himalaya, Nature, 327, 699–702, 1987. [C]

Asmerom, Y., S. B. Jacobsen, A. H. Knoll, N. J. Butterfield, and K. Swett, Strontium isotopic variations of Neoproterozoic seawater: Implications for crustal evolution, Geochim. Cosmochim. Acta, 55, 2883–2894, 1991. [Sr, C, O]

Azmy, K., J. Veizer, R. Misi, T. De Olivia, and M. Dardenne, Isotope stratigraphy of the neoproterozoic carbonate of Vazante Formation Saõ Francisco Basin, Brazil, Precambrian Res., in press, 2002. [Sr, C, O]

Baker, A. J., and A. E. Fallick, Evidence from Lewisian limestones for isotopically heavy carbon in two-thousand-million-year-old seawater, Nature, 337, 352–354, 1989a. [C, O]

Baker, A. J., and A. E. Fallick, Heavy carbon in two-billion-year-old marbles from Lofoten-Vesteralen, Norway: Implications for the Precambrian carbon cycle, Geochim. Cosmochim. Acta, 53, 1111–1115, 1989b. [C, O]

Banerjee, D. M., M. Schidlowski, F. Siebert, and M. D. Brasier, Geochemical changes across the Proterozoic-Cambrian transition in the Durmala phosphorite mine section, Mussoorie Hills, Garhwal Himalaya, India, Palaeogeogr., Palaeoclimatol., Palaeoecol., 132, 183–194, 1997. [C, O]

Bartley, J. K., M. A. Semikhatov, A. J. Kaufman, A. H. Knoll, M. C. Pope, and S. B. Jacobsen, Global events across the Mesoproterozoic-Neoproterozoic boundary: C and Sr isotopic evidence from Siberia, Precambrian Res., 111, 165–202, 2001. [C, O]

Bau, M., R. L. Romer, V. Lüders, and N. J. Beukes, Pb, O, and C isotopes in silicified Mooidraai dolomite (Transvaal Supergroup, South Africa): Implications for the composition of Paleoproterozoic seawater and “dating” the increase of oxygen in the Precambrian atmosphere, Earth Planet. Sci. Lett., 174, 43–57, 1999. [C, O]

Baur, M. E., J. M. Hayes, S. A. Studley, and M. R. Walter, Millimeter-scale variations of stable isotope abundances in carbonates from banded iron-formations in the Hamersley Group of Western Australia, Econ. Geol., 80, 270–282, 1985. [C]

Becker, R. H., and R. N. Clayton, Carbon isotopic evidence for the origin of banded iron formation in Western Australia, Geochim. Cosmochim. Acta, 36, 577–595, 1972. [C, O]

Becker, R. H., and R. N. Clayton, Oxygen isotope study of a Precambrian banded iron-formation, Hammersley Range, Western Australia, Geochim. Cosmochim. Acta, 40, 1153–1165, 1976. [C]

Beeunas, M. A., and L. P. Knauth, Preserved stable isotopic signature of subaerial diagenesis in the 1.2 b.y. Mescal Limestone, central Arizona: Implications for the timing and development of a terrestrial plant cover, Geol. Soc. Am. Bull., 96, 737–745, 1985. [C]

Bekker, A., A. J. Kaufman, J. A. Karhu, N. J. Beukes, Q. D. Swart, L. L. Coetzee, and K. A. Eriksson, Chemostratigraphy of the Paleoproterozoic Duitschland Formation, South Africa: Implications for coupled climate change and carbon cycling, Am. J. Sci., 301, 261–285, 2001. [Sr. C, O]

Bose, P. K., S. Sarkar, and S. K. Bhattacharyya, Dissolution seams: Some observations from the Proterozoic Chanda Limestone, Adilabad, India, Carbonates Evaporites, 11, 70–76, 1996. [C, O]

Brasier, M. D., and G. Shields, Neoproterozoic chemostratigraphy and correlation of the Port Askaig glaciation, Dalradian Supergroup of Scotland, J. Geol. Soc. London, 157, 909–914, 2000. [Sr, C, O]

Brasier, M. D., and S. S. Sukhov, The falling amplitude of carbon isotopic oscillations through the Lower to Middle Cambrian: Northern Siberian data, Can. J. Earth Sci., 35, 353–373, 1998. [C, O]

Brasier, M. D., G. Shields, V. N. Kuleshov, and E. A. Zhegallo, Integrated chemo- and biostratigraphic calibration of early animal evolution: Neoproterozoic-early Cambrian of southwest Mongolia, Geol. Mag., 133, 445–485, 1996. [Sr, C, O]

Buick, R., D. J. Des Marais, and A. H. Knoll, Stable isotopic compositions of carbonates from the Mesoproterozoic Bangemall Group, northwestern Australia, Chem. Geol., 123, 153–171, 1995. [C, O]

Buick, I. S., R. Uken, R. L. Gibson, and T. Wallmach, High-delta 13C Paleoproterozoic carbonates from the Transvaal Supergroup, South Africa, Geology, 26, 875–878, 1998. [C, O]

Burdett, J. W., J. P. Grotzinger, and M. A. Arthur, Did major changes in the stable-isotope composition of Proterozoic seawater occur?, Geology, 18, 227–230, 1990. [C, O; no data table]

Burns, S. J., U. Haudenschild, and A. Matter, The strontium isotopic composition of carbonates from the Late Precambrian (∼560–540 Ma) Huqf Group of Oman, Chem. Geol., 111, 269–282, 1994. [Sr, C, O]

Calver, C. R., Isotope stratigraphy of the Neoproterozoic Togari Group, Tasmania, Aust. J. Earth Sci., 45, 865–874, 1998. [Sr, C, O]

Calver, C. R., Isotope stratigraphy of the Ediacarian (Neoproterozoic III) of the Adelaide Rift Complex, Australia, and the overprint of water column stratification, Precambrian Res., 100, 121–150, 2000. [C, O, Corg]

Calver, C. R., and J. F. Lindsay, Ediacarian sequence and isotope stratigraphy of the Officer Basin, South Australia, Aust. J. Earth Sci., 45, 513–532, 1998. [Sr, Corg.]

Corsetti, F. A., and A. J. Kaufman, Chemostratigraphy of Neoproterozoic-Cambrian units, White-Inyo region, eastern California: Implications for global correlation and faunal distribution, Palaios, 9, 211–219, 1994. [C, O]

Das Sharma, S., R. Srinivasan, S. M. Ahmad, and D. J. Patil, Carbon and oxygen isotopic compositions of the regionally metamorphosed Archaean carbonate rocks of the Dharwar craton: A preliminary appraisal, Curr. Sci., 66, 857–860, 1994. [C, O; no data table]

Deb, M., J. Hoefs, and A. Baumann, Isotopic composition of two Precambrian stratiform barite deposits from the Indian Shield, Geochim. Cosmochim. Acta, 55, 303–308, 1991. [Sr - barite]

Derry, L. A., L. S. Keto, S. B. Jacobsen, A. H. Knoll, and K. Swett, Sr isotopic variations in Upper Proterozoic carbonates from Svalbard and East Greenland, Geochim. Cosmochim. Acta, 53, 2331–2339, 1989. [Sr, C, O]

Derry, L. A., A. J. Kaufman, and S. B. Jacobsen, Sedimentary cycling and environmental change in the Late Proterozoic: Evidence from stable and radiogenic isotopes, Geochim. Cosmochim. Acta, 56, 1317–1329, 1992. [Sr, C, O]

Derry, L. A., M. D. Brasier, R. M. Corfield, A. Y. Rozanov, and A. Y. Zhuravlev, Sr and C isotopes in Lower Cambrian carbonates from the Siberian craton: A paleoenvironmental record during the “Cambrian explosion,” Earth Planet. Sci. Lett., 128, 671–681, 1994. [Sr, C, O]

Donnelly, T. H., J. H. Shergold, P. N. Southgate, and C. J. Barnes, Events leading to phosphogenesis around the Proterozoic/Cambrian boundary, Geol. Soc. Spec. Publ., 52, 273–287, 1990. [Sr]

Ebneth, S., G. A. Shields, J. Veizer, J. F. Miller, and J. H. Shergold, High-resolution strontium isotope stratigraphy across the Cambrian-Ordovician transition, Geochim. Cosmochim. Acta, 65, 2273–2292, 2001. [Sr]

Ebneth, S., G. A. Shields, D. Buhl, and J. Veizer, Sr and stable isotope data from the Cambrian-age Kuljumbe section, Siberia, unpublished data. [Sr, C, O]

Eichmann, R., and M. Schidlowski, Isotopic fractionation between coexisting Corg-Ccarb pairs in Precambrian sediments, Geochim. Cosmochim. Acta, 39, 585–595, 1975. [C]

Eglington, B. M., P. E. Matthews, J. P. G. Dixon, A. S. Talma, and S. Marais, Isotopic composition of Pongola Supergroup limestones from the Buffalo River gorge, South Africa: Constraints on their regional depositional setting, unpublished data in press. [Sr, C, O]

Fairchild, I. J., and B. Spiro, Petrological and isotopic implications of some contrasting Late Precambrian carbonates, NE Spitsbergen, Sedimentology, 34, 973–989, 1987. [C, O]

Fairchild, I. J., J. D. Marshall, and J. Bertrand-Sarfati, Stratigraphic shifts in carbon isotopes from Proterozoic stromatolitic carbonates (Mauritania): Influences of primary mineralogy and diagenesis, Am. J. Sci., 290A, 46–79, 1990. [C, O]

Fairchild, I. J., B. Spiro, P. Herrington, and T. Song, Geological controls on Sr and C isotope compositions on Neoproterozoic Sr-rich limestones of E. Greenland and N. China, in Carbonate Sedimentation and Diagenesis in the Evolving Precambrian World, edited by J. P. Grotzinger and N. P. James, SEPM Spec. Publ., 67, 297–313, 2000. [Sr, C, O]

Frank, T. D., T. W. Lyons, and K. C. Lohmann, Isotopic evidence for the paleoenvironmental evolution of the Mesoproterozoic Helena Formation, Belt Supergroup, Montana, USA, Geochim. Cosmochim. Acta, 61, 5023–5041, 1997. [C, O]

Friedman, G. M., C. Chakraborty, and M. M. Kolkas, δ13C excursion in the end-Proterozoic strata of the Vindhyan Basin (central India): Its chronostratigraphic significance, Carbonates Evaporites, 11, 206–212, 1993. [C, O]

Galimov, E. M., N. G. Kuznetsova, and V. S. Prokhorov, The composition of the former atmosphere of the Earth as indicated by isotope analysis of Precambrian carbonates, Geochem. Int., 5, 1126–1131, 1968. [C, O]

Gao, G., S. I. Dworkin, L. S. Land, and R. D. Elmore, Geochemistry of Late Ordovician Viola Limestone, Oklahoma: Implications for marine carbonate mineralogy and isotope compositions, J. Geol., 104, 359–367, 1996. [Sr, C, O]

Garde, A. A., Strontium geochemistry and carbon and oxygen isotopic compositions of lower Proterozoic dolomite and calcite marbles from the Marmorilik Formation, West Greenland, Precambrian Res., 8, 183–199, 1979. [C, O; no data table]

Gauthier-Lafaye, F., and F. Weber, The Francevillian (Lower Proterozoic) uranium ore deposits of Gabon, Econ. Geol., 84, 2267–2285, 1989. [C, Corg]

Glumac, B., and K. R. Walker, A late Cambrian positive carbon-isotope excursion in the southern Appalachians: Relation to biostratigraphy, sequence stratigraphy, environments of deposition, and diagenesis, J. Sediment. Res., 68, 1212–1222, 1998. [C, O]

Gorokhov, I. M., M. A. Semikhatov, A. V. Baskakov, E. P. Kutyavin, N. N. Mel'nikov, A. V. Sochava, and T. L. Turchenko, Sr isotopic composition in Riphean, Vendian, and Lower Cambrian carbonates from Siberia, Stratigr. Geol. Correlation, 3, 1–28, 1995. [Sr]

Gorokhov, I. M., A. B. Kuznetsov, V. A. Melezhik, G. V. Konstantinova, and N. N. Mel'nikov, Sr isotopic composition in the Upper Jatulian (Early Paleo-Proterozoic) dolomites of the Tulomozero Formation, southeastern Karelia, Dokl. Acad. Sci. USSR, Earth Sci. Ser., Engl. Trans., 360, 609–612, 1998. [Sr]

Gutzmer, J., and N. J. Beukes, The Manganese Formation of the Neoproterozoic Penganga Group, India-Revision of an enigma, Econ. Geol., 93, 1091–1102, 1998. [C, O, Corg]

Hall, S. M., and J. Veizer, Geochemistry of Precambrian carbonates, VII, Belt supergroup, Montana and Idaho, U.S.A, Geochim. Cosmochim. Acta, 60, 667–677, 1996. [Sr, C, O]

Hill, A. C., and M. R. Walter, Mid-Neoproterozoic (∼830–750 Ma) isotope stratigraphy of Australia and global correlation, Precambrian Res., 100, 181–211, 2000. [Sr, C, O]

Hoering, T. C., The stable isotopes of carbon in the carbonate and reduced carbon of Precambrian sediments, in Annu. Rep. Dir. Geophys. Lab. 1961–62, pp. 190–191, Carnegie Inst. of Wash., Washington, D. C., 1962. [C]

Hofmann, H. J., and A. Davidson, Paleoproterozoic stromatolites, Hurwitz Group, Quartzite Lake area, Northwest Territories, Canada, Can. J. Earth Sci., 35, 280–289, 1998. [C, O]

Iyer, S. S., M. Babinski, H. R. Krouse, and F. Chemale Jr., Highly 13C-enriched carbonate and organic matter in the Neoproterozoic sediments of the Bambuí Group, Brazil, Precambrian Res., 73, 271–282, 1995. [C, O, Corg, S]

Johnson, W. J., and R. H. Goldstein, Cambrian sea water preserved as inclusions in marine low-magnesium calcite cement, Nature, 362, 335–337, 1993. [Sr, C, O; no data table]

Kah, L. C., A. G. Sherman, G. M. Narbonne, A. H. Knoll, and A. J. Kaufman, δ13C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: Implications for regional lithostratigraphic correlations, Can. J. Earth Sci., 36, 313–332. [C, O]

Kah, L. C., T. W. Lyons, and J. T. Chesley, Geochemistry of a 1.2 Ga carbonate-evaporite succession, northern Baffin and Bylot Islands: Implications for Mesoproterozoic marine evolution, Precambrian Res., 111, 203–234, 2001. [Sr, C, O, S]

Kamber, B. S., and G. E. Webb, The geochemistry of late Archean microbial carbonate: Implications for ocean chemistry and continental erosion history, Geochim. Cosmochim. Acta, 65, 2509–2525, 2001. [Sr, Nd]

Karhu, J. A., Paleoproterozoic evolution of the carbon isotope ratios of sedimentary carbonates in the Fennoscandian Shield, Bull. Geol. Surv. Finl., [volume?], 87 p., 1993. [C, O, Corg]

Kaufman, A. J., Geochemical and mineralogic effects of contact metamorphism on banded-iron formations: An example from the Transvaal Basin, South Africa, Precambrian Res., 79, 171–194, 1996. [C, O]

Kaufman, A. J., and A. H. Knoll, Neoproterozoic variations in the C-isotopic composition of seawater: Stratigraphic and biogeochemical implications, Precambrian Res., 73, 27–49,1995. [C; no data table]

Kaufman, A. J., J. M. Hayes, and C. Klein, Primary and diagenetic controls and isotopic compositions of iron-formation carbonate, Geochim. Cosmochim. Acta, 54, 3164–3473, 1990. [C, O]

Kaufman, A. J., J. M. Hayes, A. H. Knoll, and G. J. B. Germs, Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia: Stratigraphic variation and the effects of diagenesis and metamorphism, Precambrian Res., 49, 301–327, 1991. [C, O, Corg]

Kaufman, A. J., A. H. Knoll, and S. M. Awramik, Biostratigraphic and chemostratigraphic correlation of Neoproterozoic sedimentary successions: Upper Tindir Group, northwestern Canada, as a test case, Geology, 20, 181–185, 1992. [Sr, C, O]

Kaufman, A. J., S. B. Jacobsen, and A. H. Knoll, The Vendian record of Sr and C isotopic variations in seawater: Implications for tectonics and paleoclimate, Earth Planet. Sci. Lett., 120, 409–430, 1993. [Sr, C, O]

Kaufman, A. J., A. H. Knoll, M. A. Semikhatov, J. P. Grotzinger, S. B. Jacobsen, and W. Adams, Integrated chronostratigraphy of Proterozoic-Cambrian boundary beds in the western Anabar region, northern Siberia, Geol. Mag., 133, 509–533, 1996. [Sr, C, O]

Kennedy, M. J., Stratigraphy, sedimentology, and isotopic geochemistry of Australian Neoproterozoic postglacial cap dolostones: Deglaciation, δ13C excursions, and carbonate precipitation, J. Sediment. Res., 66, 1050–1064, 1996. [Sr, C, O]

Kennedy, M. J., B. Runnegar, A. R. Prave, K.-H. Hoffmann, and M. Arthur, Two or four Neoproterozoic glaciations?, Geology, 26, 1059–1063, 1998. [Sr, C, O]

Knoll, A. H., J. M. Hayes, A. J. Kaufman, K. Swett, and I. B. Lambert, Secular variations in carbon isotope ratios from Upper Proterozoic successions of Svalbard and East Greenland, Nature, 321, 832–838, 1986. [C, Corg]

Knoll, A. H., A. J. Kaufman, and M. A. Semikhatov, The carbon-isotopic composition of Proterozoic carbonates: Riphean successions from northwestern Siberia (Anabar Massif, Turukhansk Uplift), Am. J. Sci., 295, 823–850, 1995a. [C, O, Corg]

Knoll, A. H., J. P. Grotzinger, A. J. Kaufman, and P. Kolosov, Integrated approaches to terminal Proterozoic stratigraphy: An example from the Olenek Uplift, northeastern Siberia, Precambrian Res., 73, 251–270, 1995b. [C, O, Corg]

Kumar, B., V. S. Venkatasubramanian, and R. Saxena, Carbon and oxygen isotopic composition of the carbonates from greenstone belts of Dharwar Craton, India, Mem. Geol. Soc. India, 4, 260–266, 1983. [C, O]

Kuznetsov, A. B., I. M. Gorokhov, M. A. Semikhatov, N. N. Mel'nikov, and V. I. Koslov, Strontium isotopic composition in the limestones of the Inzer Formation, Upper Riphean type section, southern Urals, Trans. Russ. Acad. Sci. Earth Sci. Sect., 353, 319–324, 1997. [Sr]

Lambert, I. B., T. H. Donnelly, H. Etminan, and N. J. Rowlands, Genesis of late Proterozoic copper mineralization, Copper Claim, South Australia, Econ. Geol., 79, 461–475, 1984. [C]

Lambert, I. B., M. R. Walter, W. Zang, S. Lu, and G. Ma, Palaeoenvironment and carbon isotope stratigraphy of Upper Proterozoic carbonates of the Yangtze Platform, Nature, 325, 140–142, 1987. [C]

Lange, I. M., J. N. Moore, and H. R. Krouse, Diagenesis and copper mineralization in carbonates in the Spokane Formation, Belt Supergroup at Wolf Creek, Montana, Econ. Geol., 82, 1334–1347, 1987. [C]

Lindsay, J. F., and M. D. Brasier, A carbon isotope reference curve for ca. 1700–1575 Ma, McArthur and Mount Isa Basins, Northern Australia, Precambrian Res., 99, 271–308, 2000. (personal communication, J. F. Lindsay, 1999) [C, O]

Magaritz, M., W. T. Holser, and J. L. Kirschvink, Carbon-isotope events across the Precambrian/Cambrian boundary on the Siberian Platform, Nature, 320, 258–259, 1986. [C]

Maheshwari, A., A. N. Sial, and V. K. Chittora, High-δ13C Paleoproterozoic carbonates from the Aravalli Supergroup, Western India, Int. Geol. Rev., 41, 949–954, 1999. [C, O]

McCulloch, M. T., Primitive 87Sr/86Sr from an Archean barite and conjecture on the Earth's age and origin, Earth Planet. Sci. Lett., 126, 1–13, 1994. [Sr - barite]

McKirdy, D. M., J. M. Burgess, N. M. Lemon, X. Yu, A. M. Cooper, V. M. Gostin, R. J. F. Jenkins, and R. A. Both, A chemostratigraphic overview of the late Cryogenian interglacial sequence in the Adelaide Fold-Thrust Belt, South Australia, Precambrian Res., 106, 149–186, 2001. [Sr, C, O]

McNaughton, N. J., and A. F. Wilson, 13C-rich marbles from the Proterozoic Einasleigh metamorphics, northern Queensland, J. Geol. Soc. Aust., 30, 175–178, 1983. [C, O]

Melezhik, V. A., A. E. Fallick, P. V. Medvedev, and V.V. Makarikhin, Extreme 13Ccarb enrichment in ca. 2.0 Ga magnesite-stromatolite-dolomite-“red beds” association in a global context: A case for the world-wide signal enhanced by a local environment, Earth Sci. Rev., 48, 71–120, 1999. [C, O]

Melezhik, V. A., A. E. Fallick, P. V. Medvedev, and V. V. Makarikhin, Palaeoproterozoic magnesite: Lithological and isotopic evidence for playa/sabkha environments, Sedimentology, 48, 379–397, 2001a. [C, O]

Melezhik, V. A., I. M. Gorokhov, A. E. Fallick, and S. Gjelle, Strontium and carbon isotope geochemistry applied to dating of carbonate sedimentation: An example from high-grade rocks of the Norwegian Caledonides, Precambrian Res., 108, 267–292, 2001b. [Sr, C, O]

Mirota, D. M., and J. Veizer, Geochemistry of Precambrian carbonates, VI, Aphebian Albanel Formation, Quebec, Canada, Geochim. Cosmochim. Acta, 58, 1735–1745, 1994. [Sr, C, O]

Misi, A., and J. Veizer, Neoproterozoic carbonate sequences of the Una Group, Irece Basin, Brazil: Chemostratigraphy, age and correlations, Precambrian Res., 89, 87–100, 1998. [Sr, C, O]

Montañez, I. P., J. L. Banner, D. A. Osleger, L. E. Borg, and P. J. Bosserman, Integrated Sr isotope variations and sea-level history of Middle to Upper Cambrian platform carbonates: Implications for the evolution of Cambrian seawater 87Sr/86Sr, Geology, 24, 917–920, 1996. [Sr]

Mukhopadhyay, J., S. K. Chanda, M. Fukuoka, and A. K. Chaudhuri, Deep-water dolomites from the Proterozoic Penganga Group in the Pranhita-Godavari Valley, Andhra Pradesh, India, J. Sediment. Res., 66, 223–230, 1996. [C, O]

Myrow, P. M., and A. J. Kaufman, A newly discovered cap carbonate above Varanger-age glacial deposits in Newfoundland, Canada, J. Sediment. Res., 69, 784–793, 1999. [C, O]

Narbonne, G. M., A. J. Kaufman, and A. H. Knoll, Integrated chemostratigraphy and biostratigraphy of the Windermere Supergroup, northwestern Canada: Implications for Neoproterozoic correlations and the early evolution of animals, Geol. Soc. Am. Bull., 106, 1281–1292, 1994. [Sr, C, O, Corg]

Nicholas, C. J., The Sr evolution of the oceans during the “Cambrian Explosion,” J. Geol. Soc. London, 153, 243–254, 1996. [Sr, C, O]

Pelechaty, S. M., Integrated chronostratigraphy of the Vendian System of Siberia: Implications for a global stratigraphy, J. Geol. Soc. London, 155, 957–973, 1998. [C, O]

Pelechaty, S., A. J. Kaufman, and J. P. Grotzinger, Evaluation of δ13C chemostratigraphy for intrabasinal correlation: Vendian strata of northeast Siberian, Geol. Soc. Am. Bull., 108, 992–1003, 1996. [C, O]

Perry, E. C., Jr., and S. N. Ahmad, Carbon isotope compositions of graphite and carbonate minerals from 3.8 Ga metamorphosed sediments, Isukasia, Greenland, Earth Planet. Sci. Lett., 36, 280–284, 1977. [C]

Perry, E. C., Jr., and S. N. Ahmad, Oxygen and carbon isotope geochemistry of the Krivoy Rog iron formation, Ukrainian SSR, Lithos, 14, 83–92, 1981. [C, O]

Peryt, T. M., A. Hoppe, T. Bechstädt, J. Köster, C. Pierre, and D. K. Richter, Late Proterozoic aragonitic cement crusts, Bambui Group, Minas Gerais, Brazil, Sedimentology, 37, 279–286, 1990. [C, O]

Podkovyrov, V. N., M. A. Semikhatov, A. B. Kuznetsov, D. P. Vinogradov, V. I. Kozlov, and I. V. Kislova, Carbonate carbon isotopic composition in the Upper Riphean stratotype, the Karatau Group, southern Urals (in Russian), Stratigr. Geol. Korrelyatsiya, 6, 3–19, 1998. (Stratigr. Geol. Correlation, Engl. Transl., 6, 319–335, 1998.) [C, O]

Pokrovskii, B. G., and Vinogradov, V. I., Isotopic composition of strontium, oxygen and carbon in Upper Precambrian carbonates of the Western Slope of the Anabar Rise (Kotuykan River Area), Trans. USSR Acad. Sci. Earth Sci. Sect., 321A, 175–182, 1991. [Sr, C, O]

Pokrovskii, B. G., and L. O. Pertsev, Upper Precambrian carbonates with abnormally light isotopic carbon compositions (southern central Siberia), Lithol. Mineral Resour. Engl. Transl., 28, 50–63, 1993. [C, O]

Ray, J. S., and J. Veizer, Isotope geochemistry of the Vindhayan Supergroup, India, unpublished data. [Sr, C, O]

Rye, D. M., and N. E. Williams, Studies of the base metal sulphide deposits at McArthur River, northern Territory, Australia, III, The stable isotope geochemistry of the H.Y.C. Ridge and Cooley deposits, Econ. Geol., 76, 1–26, 1981. [C]

Saltzmann, M. R., B. Runnegar, and K. C. Lohmann, Carbon isotope stratigraphy of Upper Cambrian (Steptoean Stage) sequences of the eastern Great Basin: Record of a global oceanographic event, Geol. Soc. Am. Bull., 110, 285–297, 1998. [C, O]

Santos, R. V., C. J. S. de Alvarenga, M. A. Dardenne, A. N. Sial, and V. P. Ferreira, Carbon and oxygen isotope profiles across Meso-Neoproterozoic limestones from central Brazil: Bambuí and Paranoá groups, Precambrian Res., 104, 107–122, 2000. [C, O]

Sarkar, S., P. P. Chakraborty, S. K. Bhattacharya, and S. Banerjee, C12 enrichment along intraformational unconformities within Proterozoic Bhander limestone, Son Valley, India and its implications, Carbonates Evaporites, 13, 108–114, 1998. [C, O]

Sathyanarayan, S., J. D. Arneth, and M. Schidlowski, Stable isotope geochemistry of sedimentary carbonates from the Proterozoic Kaladgi, Badami and Bhima Groups, Karnataka, India, Precambrian Res., 37, 147–156, 1987. [C]

Schidlowski, M., R. Eichmann, and C. Junge, Precambrian sedimentary carbonates: Carbon and oxygen isotopic geochemistry and implications for the terrestrial oxygen budget, Precambrian Res., 2, 1–69, 1975. [C, O]

Schidlowski, M., R. Eichmann, and C. E. Junge, Carbon isotope geochemistry of the Precambrian Lomagundi carbonate province, Rhodesia, Geochim. Cosmochim. Acta, 40, 449–455, 1976a. [C]

Schidlowski, M., R. Eichmann, and W. Fiebiger, Isotopic fractionation between organic carbon and carbonate carbon in Precambrian banded ironstone series from Brazil, Neues Jahrb. Mineral. Mitt., 8, 344–353, 1976b. [C, O]

Schidlowski, M., P. W. U. Appel, R. Eichmann, and C. E. Junge, Carbon isotope geochemistry of the 3.7 × 109-yr-old Isua sediments, West Greenland: Implications for the Archaean carbon and oxygen cycles, Geochim. Cosmochim. Acta, 43, 189–199, 1979. [C]

Schidlowski, M., J. M. Hayes, and I. R. Kaplan, Isotopic inferences of ancient biochemistries: Carbon, sulfur, hydrogen, and nitrogen, in Earth's Earliest Biosphere: Its Origin and Evolution, edited by J. W. Schopf, pp. 149–187, Princeton Univ. Press, Princeton, N. J., 1983. [C, O]

Schopf, J. W., and C. Klein (Eds.), The Proterozoic Biosphere: A Multidisciplinary Study, Cambridge Univ. Press, New York, 1992. [C, O]

Semikhatov, M. A., I. M. Gorokhov, A. B. Kuznetsov, N. N. Mel'nikov, V. N. Podkovyrov, and I. V. Kislova, The strontium isotopic composition in Early Late Riphean seawater: Limestones of the Lakhanda Group, the Uchur-Maya Region, Siberia (in Russian), Dokl. Akad. Nauk, 360, 236–240, 1998. (Dokl. Acad. Sci. USSR, Earth Sci. Ser., Engl. Transl., 360, 488–492, 1998.) [Sr]

Shen, Y., and [X] Schidlowski, New C isotope stratigraphy from southwest China: Implications for the placement of the Precambrian-Cambrian boundary on the Yangtze Platform and global correlations, Geology, 28, 623–626, 2000. [C, O]

Shields, G. A., Working towards a new stratigraphic calibration scheme for the Neoproterozoic-Cambrian, Eclogae Geol. Helv., 92, 221–233, 1999. [Sr, C, O]

Shields, G. A., P. Stille, M. D. Brasier, N.-V. Atudorei, and D. A. Dorjnamjaa, Late Neoproterozoc geochemical record from marine limestones of western Mongolia, Earth Planet. Sci. Lett., in press, 2002. [Sr, C, O]

Shields, G. A., P. Stille, M. Deynoux, F. Gauthier-Lafaye, and M. D. Brasier, Sr and C isotope stratigraphy of the Neoproterozoic Atar Group, Mauritania, unpublished data. [Sr, C, O]

Shields, G. A., J.-J. Alvaro, M. D. Brasier, D. Buhl, and J. Veizer, Sr and stable isotope data across the Lower-Middle Cambrian boundary in southern Europe, unpublished data. [Sr, C, O]

Smith, L.H., A. J. Kaufman, A. H. Knoll, and P. K. Link, Chemostratigraphy of predominantly siliciclastic Neoproterozoic successions: A case study of the Pocatello Formation and Lower Brigham Group, Idaho, USA, Geol. Mag., 131, 301–314, 1994. [Sr, C, O]

Sreenivas, B., S. Das Sharma, B. Kumar, D. J. Patil, A. B. Roy, and R. Srinivasan, Positive δ13C excursion in carbonate and organic fractions from the Paleoproterozoic Aravalli Supergroup, Northwestern India, Precambrian Res., 106, 277–290, 2001. [C, O, Corg]

Srikantappa, C., and J. W. Valley, Oxygen and carbon isotopic composition of Precambrian carbonates from Karnataka and Tamilnadu, India, J. Geol. Soc. India, 40, 341–346, 1992. [C, O]

Strauss, H., The sulfur isotopic record of Precambrian sulfates: New data and a critical evaluation of the existing record, Precambrian Res., 63, 225–246, 1993. [Sr, S]

Thode, H. G., and A. M. Goodwin, Further sulfur and carbon isotope studies of late Archean iron formations of the Canadian Shield and the rise of sulfate-reducing bacteria, Precambrian Res., 20, 337–356, 1983. [C, O, S]

Tikhomirova, M., and V. V. Makarikhin, Possible reasons for the δ13C anomaly of Lower Proterozoic sedimentary carbonates, Terra Nova, 5, 244–248, 1993. [C, O]

Torquato, J. R. F., and A. Misi, Medidas isotopicas de carbono e oxigenio em carbonatos do grupo Bambui na regiao centro-norto do estado da Bahia, Rev. Bras. Geocienc., 7, 14–24, 1977. [C]

Tucker, M. E., Precambrian dolomites: Petrographic and isotopic evidence that they differ from Phanerozoic dolomites, Geology, 10, 7–12, 1982. [C]

Tucker, M. E., Sedimentation of organic-rich limestones in the late Precambrian of southern Norway, Precambrian Res., 22, 295–315, 1983a. [C, O]

Tucker, M. E., Diagenesis, geochemistry, and origin of a Precambrian dolomite: The Beck Spring Dolomite of eastern California, J. Sediment. Petrol., 53, 1097–1119, 1983b. [C, O]

Tucker, M. E., Carbon isotope excursions in Precambrian/Cambrian boundary beds, Morocco, Nature, 319, 48–50, 1986a. [C]

Tucker, M. E., Formerly aragonitic limestones associated with tillites in the late Proterozoic of Death Valley, California, J. Sediment. Petrol., 56, 818–830, 1986b. [C, O]

Veizer, J. (Ed.), Geochemistry of carbonates and related topics: Databases, 426 pp. Inst. of Geol., Bochum, Germany, 1994. [Sr, C, O]

Veizer, J., and W. Compston, 87Sr/86Sr in Precambrian carbonates as an index of crustal evolution, Geochim. Cosmochim. Acta, 40, 905–914, 1976. [Sr]

Veizer, J., and J. Hoefs, The nature of O18/O16 and C13/C12 secular trends in sedimentary carbonate rocks, Geochim. Cosmochim. Acta, 40, 1387–1395, 1976. [C, O]

Veizer, J., W. Compston, N. Clauer, and M. Schidlowski, 87Sr/86Sr in Late Proterozoic carbonates: Evidence for a “mantle” event at ∼900 Ma ago, Geochim. Cosmochim. Acta, 47, 295–302, 1983. [Sr, C, O]

Veizer, J., J. Hoefs, R. H. Ridler, S. L. Jensen, and D. R. Lowe, Geochemistry of Precambrian carbonates, 1, Archean hydrothermal systems, Geochim. Cosmochim. Acta, 53, 845–857, 1989a. [Sr, C, O]

Veizer, J., J. Hoefs, D. R. Lowe, and P. C. Thurston, Geochemistry of Precambrian carbonates, 2, Archean greenstone belts and Archean sea water, Geochim. Cosmochim. Acta, 53, 859–871, 1989b. [Sr, C, O]

Veizer, J., R. N. Clayton, R. W. Hinton, V. Von Brunn, T. R. Mason, S. G. Buck, and J. Hoefs, Geochemistry of Precambrian carbonates, 3, Shelf seas and non-marine environments of the Archean, Geochim. Cosmochim. Acta, 54, 2717–2729, 1990. [Sr, C, O]

Veizer, J., R. N. Clayton, and R. W. Hinton, Geochemistry of Precambrian carbonates, 4, Early Paleoproterozoic (2.25 ± 0.25 Ga) seawater, Geochim. Cosmochim. Acta, 56, 875–885, 1992. [Sr, C, O]

Veizer, J., K. A. Plumb, R. N. Clayton, R. W. Hinton, and J. Grotzinger, Geochemistry of Precambrian carbonates, 5, Late Paleoproterozoic (1.8 ± 0.2 Ga) seawater, Geochim. Cosmochim. Acta, 56, 2487–2501, 1992. [Sr, C, O]

Walter, M. R., J. J. Veevers, C. R. Calver, P. Gorjan, and A. C. Hill, Dating the 844–500 Ma Neoproterozoic interval by isotopes of strontium, carbon, and sulfur in seawater, and some interpretative methods, Precambrian Res., 100, 371–433, 2000. [Sr, C, O]

Wang, Z., J. Yang, and W. Sun, Carbon isotope record of Sinian seawater in Yangtze Platform (in Chinese), Geol. J. Univ., 2, 112–120, 1996. [C, O]

Whittaker, S. G., T. T. Sami, T. K. Kyser, and N. P. James, Petrogenesis of 1.9 Ga limestones and dolostones and their record of Paleoproterozoic environments, Precambrian Res., 90, 187–202, 1998. [Sr, C, O]

Wickham, S. M., and M. T. Peters, High δ13C Neoproterozoic carbonate rocks in western North America, Geology, 21, 165–168, 1993. [Sr, C, O; no data table]

Williams, G. E., Sedimentology, stable-isotope geochemistry and palaeoenvironment of dolostones capping late Precambrian glacial sequences in Australia, J. Geol. Soc. Aust., 26, 377–386, 1979. [C, O]

Winter, B. L., and L. P. Knauth, Stable isotope geochemistry of cherts and carbonates from the 2.0 Ga Gunflint Iron Formation: Implications for the depositional setting, and the effects of diagenesis and metamorphism, Precambrian Res., 59, 283–313, 1992. [C, O]

Xiao, S., A. H. Knoll, A. J. Kaufman, Y. Leming, and Z. Yun, Neoproterozoic fossils in Mesoproterozoic rocks? Chemostratigraphic resolution of a biostratigraphic conundrum from the North China Platform, Precambrian Res., 84, 197–220, 1997. [C, O]

Yang, J., W. Sun, Z. Wang, Y. Xue, and X. Tao, Variations in Sr and C isotopes and Ce anomalies in successions from China: Evidence for the oxygenation of Neoproterozoic seawater?, Precambrian Res., 93, 215–233, 1999. [Sr, C, O]

Yudovitch, Y. E., V. V. Makarikhin, P. V. Medvedev, and N. V. Sukhanov, Carbon-isotope anomalies in carbonates of the Karelian complex, Geokhimiya, Engl. Transl., 7, 972–978, 1990. [C, O]

Zachariah, J. K., A 3.1 billion year old marble and the 87Sr/86Sr of late-Archean seawater, Terra Nova, 10, 312–316, 1998. [Sr, C, O]

Zempolich, W. G., B. H. Wilkinson, and K. C. Lohmann, Diagenesis of late Proterozoic carbonates: The Beck Spring Dolomite of eastern California, J. Sediment. Petrol., 58, 656–672, 1988. [C, O]

Zhong, H., and J. Chen, Carbon isotope evidence for lower biomass about 1400 Ma ago, Sci. Geol. Sinica, 2, 160–168, 1992. [C]

Zhong, H., and Y. Ma, Carbon isotope stratigraphy of dolomites in the early Proterozoic succession, north China, Geol. Mag., 134, 763–770, 1997. [C]

Zhong, H., Y. Ma, W. Huo, and Y. Yao, Carbon isotope evolution of early Proterozoic dolomites of Wutai mountain area, North China, Sci. China Ser. B, 37, 1525–1528, 1994. [C]


[28] The authors gratefully acknowledge the technical assistance of Patricia Wickham in the compiling of this database and the generosity of the following who supplied help, advice or data over the last two years: A. Bekker (Harvard, USA); M. D. Brasier (Oxford, UK); J. F. Lindsay (Canberra, Australia); L. C. Kah (Tennessee, USA); V. Melezhik (Trondheim, Norway); A. N. Sial (Recife, Brazil). Additional thanks are due to all those who sent sets of reprints for cataloguing purposes. This study was supported financially by grants from the Natural Sciences and Engineering Research Council of Canada and from the “Earth System Chair” of J. Veizer sponsored by Noranda, The Canadian Institute for Advanced Research and G. G. Hatch and Associates.