Constraints on ocean carbonate chemistry and pCO2 in the Archaean and Palaeoproterozoic

Blättler, Clara L.; Kump, Lee R.; Fischer, Woodward W.; Paris, Guillaume; Kasbohm, Jennifer; Higgins, John A.

doi:10.1038/ngeo2844

Cited by 47 publications

(42 citation statements)

References 40 publications

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“…Hence, Mono Lake is not a suitable analog for the Tumbiana Formation in terms of Ca chemistry. Most importantly, carbonate precipitates in Mono Lake actually show a very narrow spread in δ 44/40 Ca-much narrower than the isotopic spread in dissolved Ca (Nielsen & DePaolo, 2013) and roughly identical to that reported from Tumbiana carbonates (Blättler et al, 2017). Hence, carbonates may not necessarily capture the Rayleigh effect observed in the aqueous phase, which makes the δ 44/40 Ca proxy problematic for tracking alkalinity in deep time.…”

Section: Nh 3 Volatilization From Alkaline Lakesmentioning

confidence: 74%

“…Another argument against high pH has been raised based on a relatively small spread of δ 44/40 Ca values in Tumbiana carbonates compared to waters of modern alkaline Mono Lake (Blättler et al, 2017),…”

Section: Nh 3 Volatilization From Alkaline Lakesmentioning

confidence: 99%

“…However, there are no known examples of chemical sediments from bona fide alkaline lakes that capture the extreme LREE depletion seen in the water column. Hence, REE patterns may not be a straightforward proxy for alkaline conditions in the ancient carbonate rock record.Another argument against high pH has been raised based on a relatively small spread of δ 44/40 Ca values in Tumbiana carbonates compared to waters of modern alkaline Mono Lake(Blättler et al, 2017), where high [HCO 3 -]/[Ca 2+ ] ratios induce a Rayleigh effect during carbonate precipitation, leading to a larger spread in δ 44/40 Ca (Nielsen & DePaolo, 2013). Hence, REE patterns may not be a straightforward proxy for alkaline conditions in the ancient carbonate rock record.Another argument against high pH has been raised based on a relatively small spread of δ 44/40 Ca values in Tumbiana carbonates compared to waters of modern alkaline Mono Lake(Blättler et al, 2017), where high [HCO 3 -]/[Ca 2+ ] ratios induce a Rayleigh effect during carbonate precipitation, leading to a larger spread in δ 44/40 Ca (Nielsen & DePaolo, 2013).…”

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Environmental niches and metabolic diversity in Neoarchean lakes

et al. 2017

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The diversification of macro-organisms over the last 500 million years often coincided with the development of new environmental niches. Microbial diversification over the last 4 billion years likely followed similar patterns. However, linkages between environmental settings and microbial ecology have so far not been described from the ancient rock record. In this study, we investigated carbon, nitrogen, and molybdenum isotopes, and iron speciation in five non-marine stratigraphic units of the Neoarchean Fortescue Group, Western Australia, that are similar in age (2.78-2.72 Ga) but differ in their hydro-geologic setting. Our data suggest that the felsic-dominated and hydrologically open lakes of the Bellary and Hardey formations were probably dominated by methanogenesis (δ C = -38.7 ± 4.2‰) and biologic N fixation (δ N =-0.6 ± 1.0‰), whereas the Mt. Roe, Tumbiana and Kylena Formations, with more mafic siliciclastic sediments, preserve evidence of methanotrophy (δ C as low as -57.4‰, δ C as low as -9.2‰) and NH loss under alkaline conditions. Evidence of oxygenic photosynthesis is recorded only in the closed evaporitic Tumbiana lakes marked by abundant stromatolites, limited evidence of Fe and S cycling, fractionated Mo isotopes (δ Mo = +0.4 ± 0.4‰), and the widest range in δ C (-57‰ to -15‰), suggesting oxidative processes and multiple carbon fixation pathways. Methanotrophy in the three mafic settings was probably coupled to a combination of oxidants, including O and SO . Overall, our results may indicate that early microbial evolution on the Precambrian Earth was in part influenced by geological parameters. We speculate that expanding habitats, such as those linked to continental growth, may have been an important factor in the evolution of life.

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Section: Nh 3 Volatilization From Alkaline Lakesmentioning

confidence: 74%

Section: Nh 3 Volatilization From Alkaline Lakesmentioning

confidence: 99%

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Environmental niches and metabolic diversity in Neoarchean lakes

et al. 2017

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“…The same calcium isotope distillation effect occurs with the precipitation of calcium carbonate, as previously shown in the Mono Lake system, where when there is a low ratio of calcium‐to‐alkalinity and there is a higher range in δ 44 Ca in the precipitated carbonate minerals (Nielsen & DePaolo, ). It has been suggested that when the calcium‐to‐alkalinity ratio is 0.75 or less, the calcium isotope distillation effect should be observed (Blättler et al, ). In Lake Lisan, we find a range of δ 44 Ca in aragonite of 0.7‰ with a lower range in δ 44 Ca if shorter time periods are taken into account (Figure ).…”

Section: Discussionmentioning

confidence: 99%

The Calcium Isotope Systematics of the Late Quaternary Dead Sea Basin Lakes

Bradbury

Torfstein

Wong

et al. 2018

Geochem Geophys Geosyst

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We report the calcium isotopic composition (δ44Ca) of primary aragonite laminae, primary gypsum, and secondary gypsum in sediments deposited from Lake Lisan, the last glacial cycle of the Dead Sea (70–14.5 ka). The δ44Ca of primary gypsum varies between 0.17‰ and 0.71‰ versus bulk silicate earth, with an average of 0.29‰, whereas the aragonite δ44Ca varies between −0.68‰ and −0.16‰ with an average of −0.4‰. The secondary gypsum δ44Ca is close to the calcium isotope composition of the aragonite, averaging at −0.3‰. The aragonite δ44Ca shows small variations temporally in sync with lake level fluctuations, suggesting the aragonite δ44Ca reflects changes in the lake calcium balance, which in turn reflects changes in the local hydrological cycle. The secondary gypsum calcium isotope composition (−0.3‰) overlaps with that of coeval aragonite, suggesting the calcium for secondary gypsum was derived from the aragonite through quantitative, or near‐isotopic equilibrium, recrystallization of the aragonite to gypsum after the lake desiccation and exposure of sediments during the Holocene. A numerical box model is used to explore the effect of changing lake water levels on the calcium isotope composition of the aragonite and gypsum in the lake. The relatively low variability in the δ44Ca over the lake's history suggests that a high‐concentration calcium‐rich brine buffers the calcium cycle.

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“…A nominal assumption of pH of 7 would give around 30,000 ppmv CO 2 . However, if another carobonate system parameter can be determined independently, then an actual constraint on pCO 2 will be available [Blattler et al, 2017].…”

Section: Proxy Constraints On and History Of Atmospheric Comentioning

confidence: 99%