Oxygen isotope evolution of Phanerozoic seawater

Veizer, Ján; Bruckschen, Peter; Pawellek, Frank; Diener, Andreas; Podlaha, Olaf G.; Carden, Giles A.F; Jasper, Torsten; Korte, Christoph; Strauß, Harald; Azmy, Karem; Ala, Davin

doi:10.1016/s0031-0182(97)00052-7

Cited by 200 publications

(78 citation statements)

References 63 publications

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“…The other possible explanation for the depleted δ 18 O values of the calcite, assuming the concretions precipitated from waters similar to Permo-Carboniferous seawater of −2‰ (SMOW) (Veizer et al, 1997), is recrystallisation of the calcite at a temperature of approximately 170°C. Temperatures of 170°C may have been reached in the Dwyka Group considering the proximity of the study area to the Cape Fold Belt (Daly et al, 1992) and the maximum burial depths of the Dwyka Group (Rubidge, 1995).…”

Section: Origin and Depositional Environment Of The Concretionsmentioning

confidence: 99%

Depositional environments of the lower Permian Dwyka diamictite and Prince Albert shale inferred from the geochemistry of early diagenetic concretions, southwest Karoo Basin, South Africa

Herbert

Compton

2007

Sedimentary Geology

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The upper Dwyka and lower Ecca Groups in the Karoo Basin of South Africa document the climatic and palaeoenvironmental changes associated with the final Permo-Carboniferous deglaciation of the Gondwana supercontinent. The depositional environments of these groups have, until recently, been interpreted on the basis of sedimentological and palaeontological evidence. Here we use the geochemistry of early diagenetic concretions -septarian calcite concretions from the upper Dwyka Group and phosphatic chert concretions and beds from the lower Ecca Group -to infer the depositional environment of these rocks in the southwestern Karoo Basin. δ 18 O values (7.8 to 8.9‰ SMOW) suggest that the calcite concretions precipitated from a mixture of meteoric and glacial melt waters rather than Permian seawater. δ 13 C values (−15 to − 3‰ PDB) indicate that the carbon was derived from a mixture of craton-derived calcareous material and organic matter, bacterially degraded in the lower sulphatereduction to upper methanogenesis zones during early burial diagenesis. The rare-earth element (REE) patterns, Sr concentrations and 87 Sr/ 86 Sr ratios (0.716-0.737) significantly greater than Permian seawater (0.708), together also support the interpretation that calcite and phosphatic concretions formed in glacial, fresh water sediments.

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Section: Origin and Depositional Environment Of The Concretionsmentioning

confidence: 99%

Depositional environments of the lower Permian Dwyka diamictite and Prince Albert shale inferred from the geochemistry of early diagenetic concretions, southwest Karoo Basin, South Africa

Herbert

Compton

2007

Sedimentary Geology

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“…The selected samples are low-Mg calcite shells of brachiopods, belemnites, and some carbonate matrices, mostly originating from 30°S to 30°N paleolatitudes . The investigation method and the preservation state of the samples are discussed in Diener et al (1996), Veizer et al (1997a), Veizer et al (1997b), Azmy et al (1998), Bruckschen et al (1999), andVeizer et al (1999). For this study we selected the best available samples from this database, with low Mg, Mn, and (for belemnites) Fe concentrations and with well clustered δ 18 O and 87 Sr/ 86 Sr ratios for coeval samples from the database; all indicating little diagenetic overprint (Bruhn et al, 1995;Veizer et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…For brachiopods, we sampled the "secondary" (or interior) layer, which is characterized by the highest degree of preservation (Veizer et al, 1997a).…”

Section: Introductionmentioning

confidence: 99%

The Phanerozoic δ88/86Sr record of seawater: New constraints on past changes in oceanic carbonate fluxes

Vollstaedt

Eisenhauer

Wallmann

et al. 2014

Geochimica et Cosmochimica Acta

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107

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The isotopic composition of Phanerozoic marine sediments provides important information about changes in seawater chemistry. In particular, the radiogenic strontium isotope ( 87 Sr/ 86 Sr) system is a powerful tool for constraining plate tectonic processes and their influence on atmospheric CO 2 concentrations. However, the 87 Sr/ 86 Sr isotope ratio of seawater is not sensitive to temporal changes in the marine strontium (Sr) output flux, which is primarily controlled by the burial of calcium carbonate (CaCO 3 ) at the ocean floor. The Sr budget of the Phanerozoic ocean, including the associated changes in the amount of CaCO 3 burial, is therefore only poorly constrained. Here, we present the first stable isotope record of Sr for Phanerozoic skeletal carbonates, and by inference for Phanerozoic seawater (δ 88/86 Sr sw ), which we find to be sensitive to imbalances in the Sr input and output fluxes. This δ 88/86 Sr sw record varies from ~0.25‰ to ~0.60‰ (vs. SRM987) with a mean of ~0.37‰. The fractionation factor between modern seawater and skeletal The oceanic net carbonate flux of Sr (F(Sr) carb ) varied between an output of -4.7x10 10 mol/Myr and an input of +2.3x10 10 mol/Myr with a mean of -1.6x10 10 mol/Myr.On time scales in excess of 100Myrs the F(Sr) carb is proposed to have been controlled by the relative importance of calcium carbonate precipitates during the "aragonite" and "calcite" sea episodes. On time scales less than 20Myrs the F(Sr) carb seems to be controlled by variable combinations of carbonate burial rate, shelf carbonate weathering and recrystallization, ocean acidification, and ocean anoxia. In particular, the Permian/Triassic transition is marked by a prominent positive δ 88/86 Sr sw -peak that reflects a significantly enhanced burial flux of Sr and carbonate, likely driven by bacterial sulfate reduction (BSR) and the related alkalinity production in deeper anoxic waters. We also argue that the residence time of Sr in the Phanerozoic ocean ranged from ~1Myrs to ~20Myrs.

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“…Con anterioridad a esta edad los valores observados son más negativos (~-27‰) (Strauss y Peters-Kottig, 2003). Esta variación observada en el δ 13 C de la paleoflora, llamativamente coincide con una variación, también hacia valores más positivos, en el δ 13 C observado en los nódulos carbonáticos de los paleosuelos (Ekart et al, 1999;Tanner et al, 2001) y en el de los carbonatos marinos (Veizer et al, 1999) (Tabla 3). Esta variación simultánea en los carbonatos marinos, en los paleosuelos y en la materia orgánica no puede indicar más que una perturbación en el ciclo del carbono ya sea por un evento geológico o un cambio paleoclimático acontecido alrededor de los 230 Ma, casi en el límite entre el Triásico Medio y Superior.…”

Section: Composición Isotópica De La Paleoflora Triásica E Implicanciunclassified

“…Veizer et al, 1999). En el caso de las plantas terrestres puede determinarse analizando las cutículas fósiles (e.g.…”

Section: Introduciónunclassified

Registro de la relación isotópica de carbono en la paleoflora de la Formación Ischigualasto (Triásico Superior), noroeste Argentino: implicaciones paleoatmosféricas

Colombi¹,

Montañez²,

Parrish³

2011

Rev. bras. paleontol.

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-FLORAL CARBON ISOTOPIC RECORD, ISCHIGUALASTO FORMATION (UPPER TRIASSIC), NORTHWEST OF ARGENTINA: PALEOATMOSPHERIC IMPLICATIONS. The Upper Triassic IschigualastoFormation carries a well-preserved flora in the mid-upper portion (~225 Ma Carnian). This contribution is the first detailed study of the isotopic ratios (i.e. 13 Carbon vs. Carbon 12 δ 13 C) and the ratio of carbon and nitrogen (C/N) applied to Argentinean Triassic flora. The aim of this study is to chemically characterize this Triassic flora and provide data for this portion of the Pangea to be used in chemostratigraphic correlation as well as to analyze changes in the global carbon cycle. A total of 97 samples were analyzed, mainly of cuticle. The isotopic values of the samples indicate minimal diagenetic or taphonomic alteration, validating the interpretations reached. A detailed analysis of the isotopic values of this paleoflora documents minor variation in δ 13 C characteristic of differences in levels of local water-stress and of floral composition variations. Discarding minor variations, a mean value of the carbon isotope ratio of paleoflora Ischigualasto Formation of -25.4‰ was obtained within a range from -27.4 to -23.7‰, according to the average values of C3 plants. This value is consistent with the δ 13 C values reported for terrestrial plant fossils from other Upper Triassic successions worldwide, however is enriched by about 3 ‰ with respect to the Middle Triassic plants. This migration towards more positive values of δ 13 C coincide with those observed in marine carbonates and paleosols during the same time-interval, indicating a possible disturbance in the carbon cycle during Early Mesozoic. Finally, a paleo-atmosphere isotopic composition of -6.1‰ was estimated, which differs by ~ 0.5 ‰ from that inferred using the marine carbonate proxy for the ocean-reservoir. This difference can be the response of the oxygen to carbon dioxide ratio in the paleo-atmosphere, which produces differences in the plant isotopic fractionation, diagenesis in the marine carbonates or hydric-stress alteration of the Ischigualasto flora.Key words: carbon, isotopes, Ischigualasto Formation, paleoatmosphere, paleoflora, Triassic.RESUMO -A Formação Ischigualasto (Triássico Superior) é portadora de uma paleoflora muito bem preservada na sua porção médio-superior (~225 Ma.). No presente trabalho são detalhados os primeiros estudos isotópicos (i.e. carbono 13 vs. Carbono 12 = δ 13 C) e a relação entre carbono e nitrogênio (C/N) aplicados à flora triássica argentina. Estes estudos foram direcionados para caracterizar quimicamente esta flora e fornecer dados para esta área do Pangea, a fim de permitir a correlação quimioestratigráfica e a análise das variações no ciclo do carbono. Foram estudadas 97 amostras, principalmente de cutículas. Os valores de δ 13 C dessas amostras não apresentam sinais de alteração diagenética nem tafonômica, fatos que validam as interpretações alcançadas. A análise detalhada dos valores das relações isotópicas desta paleoflora permiti...

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Oxygen isotope evolution of Phanerozoic seawater

Cited by 200 publications

References 63 publications

Depositional environments of the lower Permian Dwyka diamictite and Prince Albert shale inferred from the geochemistry of early diagenetic concretions, southwest Karoo Basin, South Africa

Depositional environments of the lower Permian Dwyka diamictite and Prince Albert shale inferred from the geochemistry of early diagenetic concretions, southwest Karoo Basin, South Africa

The Phanerozoic δ88/86Sr record of seawater: New constraints on past changes in oceanic carbonate fluxes

Registro de la relación isotópica de carbono en la paleoflora de la Formación Ischigualasto (Triásico Superior), noroeste Argentino: implicaciones paleoatmosféricas

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