Oxygen Isotope

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John W Valley - One of the best experts on this subject based on the ideXlab platform.

  • Oxygen Isotope variability within nautilus shell growth bands
    PLOS ONE, 2016
    Co-Authors: Benjamin J Linzmeier, Shanan E Peters, Reinhard Kozdon, John W Valley
    Abstract:

    Nautilus is often used as an analogue for the ecology and behavior of extinct externally shelled cephalopods. Nautilus shell grows quickly, has internal growth banding, and is widely believed to precipitate aragonite in Oxygen Isotope equilibrium with seawater. Pieces of shell from a wild-caught Nautilus macromphalus from New Caledonia and from a Nautilus belauensis reared in an aquarium were cast in epoxy, polished, and then imaged. Growth bands were visible in the outer prismatic layer of both shells. The thicknesses of the bands are consistent with previously reported daily growth rates measured in aquarium reared individuals. In situ analysis of Oxygen Isotope ratios using secondary ion mass spectrometry (SIMS) with 10 μm beam-spot size reveals inter- and intra-band δ18O variation. In the wild-caught sample, a traverse crosscutting 45 growth bands yielded δ18O values ranging 2.5‰, from +0.9 to -1.6 ‰ (VPDB), a range that is larger than that observed in many serial sampling of entire shells by conventional methods. The maximum range within a single band (~32 μm) was 1.5‰, and 27 out of 41 bands had a range larger than instrumental precision (±2 SD = 0.6‰). The results from the wild individual suggest depth migration is recorded by themore » shell, but are not consistent with a simple sinusoidal, diurnal depth change pattern. In addition, to create the observed range of δ18O, however, this Nautilus must have traversed a temperature gradient of at least ~12°C, corresponding to approximately 400 m depth change. Isotopic variation was also measured in the aquarium-reared sample, but the pattern within and between bands likely reflects evaporative enrichment arising from a weekly cycle of refill and replacement of the aquarium water. Overall, this work suggests that depth migration behavior in ancient nektonic mollusks could be elucidated by SIMS analysis across individual growth bands.« less

  • primordial Oxygen Isotope reservoirs of the solar nebula recorded in chondrules in acfer 094 carbonaceous chondrite
    Geochimica et Cosmochimica Acta, 2012
    Co-Authors: Takayuki Ushikubo, Noriko T Kita, Makoto Kimura, John W Valley
    Abstract:

    Abstract Highly precise and accurate ion microprobe analyses of Oxygen three-Isotope ratios in chondrules from the Acfer 094, one of the most primitive carbonaceous chondrites, show that chondrules preserve evidence for Oxygen Isotope heterogeneity in chondrule-forming regions of the solar nebula. Identical Δ 17 O values in most minerals and glass within each chondrule indicate that the Oxygen Isotope ratio in chondrule melt did not change during or after crystallization. Nearly half of the chondrules studied contain small amounts of olivine grains that have an Oxygen Isotope anomaly relative to other minerals and glass in the same chondrule. Most chondrules in Acfer 094 can be classified into two Oxygen Isotope groups (Δ 17 O ∼ −2‰ and Δ 17 O ∼ −5‰) indicating that the final melting of chondrules occurred within two distinct Oxygen Isotope reservoirs, probably representing the local protoplanetary disk immediately before planetesimal formation. One of these reservoirs (Δ 17 O ∼ −2‰) is observed from chondrules in other carbonaceous chondrites and from crystalline silicates in comet Wild 2, suggesting that crystalline silicates formed in an Oxygen Isotope reservoir of Δ 17 O ∼ −2‰ were widely distributed in the outer asteroid belt and throughout the outer solar nebula. Oxygen three-Isotope ratios of minerals in chondrules from Acfer 094 are distributed along a newly defined Primitive Chondrule Minerals (PCM) line, which has slope ∼1 [δ 17 O = (0.987 ± 0.013) × δ 18 O − (2.70 ± 0.11)] and intersects the terrestrial fractionation line at δ 18 O = 5.8 ± 0.4‰. These data are distinct from, and plot between, the CCAM, and Young and Russell lines. The PCM line is interpreted to represent the mixing trend of extreme Oxygen Isotope reservoirs in the early solar system that were the primary Oxygen Isotope reservoir of solids that accreted to form planets including the Earth.

  • optically continuous silcrete quartz cements of the st peter sandstone high precision Oxygen Isotope analysis by ion microprobe
    Geochimica et Cosmochimica Acta, 2007
    Co-Authors: Jacque L Kelly, Bin Fu, N T Kita, John W Valley
    Abstract:

    A detailed Oxygen Isotope study of detrital quartz and authigenic quartz overgrowths from shallowly buried (<1 km) quartz arenites of the St. Peter Sandstone (in SW Wisconsin) constrains temperature and fluid sources during diagenesis. Quartz overgrowths are syntaxial (optically continuous) and show complex luminescent zonation by cathodoluminescence. Detrital quartz grains were separated from 53 rocks and analyzed for Oxygen Isotope ratio by laser fluorination, resulting

  • extreme crustal Oxygen Isotope signatures preserved in coesite in diamond
    Nature, 2003
    Co-Authors: Daniel J Schulze, John W Valley, Ben Harte, James M Brenan, D Der M Channer
    Abstract:

    The anomalously high and low Oxygen Isotope values observed in eclogite xenoliths from the upper mantle beneath cratons have been interpreted as indicating that the parent rock of the eclogites experienced alteration on the ancient sea floor1. Recognition of this genetic lineage has provided the foundation for a model of the evolution of the continents whereby imbricated slabs of oceanic lithosphere underpin and promote stabilization of early cratons2. Early crustal growth is thought to have been enhanced by the addition of slab-derived magmas, leaving an eclogite residuum in the upper mantle beneath the cratons3. But the Oxygen Isotope anomalies observed in eclogite xenoliths are small relative to those in altered ocean-floor basalt and intermediate-stage subduction-zone eclogites, and this has hindered acceptance of the hypothesis that the eclogite xenoliths represent subducted and metamorphosed ocean-floor basalts. We present here the Oxygen Isotope composition of eclogitic mineral inclusions, analysed in situ in diamonds using an ion microprobe/secondary ion mass spectrometer. The Oxygen Isotope values of coesite (a polymorph of SiO2) inclusions are substantially higher than previously reported for xenoliths from the subcratonic mantle, but are typical of subduction-zone meta-basalts, and accordingly provide strong support for the link between altered ocean-floor basalts and mantle eclogite xenoliths.

  • Oxygen Isotope compositions and magmatic epidote from two contrasting metaluminous granitoids ne brazil
    Contributions to Mineralogy and Petrology, 2003
    Co-Authors: Valderez P Ferreira, John W Valley, Alcides N Sial, M J Spicuzza
    Abstract:

    Oxygen Isotope compositions of mineral separates were determined from two metaluminous granitoids (Emas and Sao Rafael plutons) from northeastern Brazil. The I-type Emas pluton has high δ18O (WR) values (11.5–11.8‰), whereas the Sao Rafael pluton has low δ18O (WR) values (7.5–8.1‰), but Sr and Nd are characteristics of S-type granitoids. Measured mineral–mineral fractionations suggest continuous sub-solidus inter-mineral Isotope exchange among all minerals except zircon. There is a large and consistent quartz–epidote fractionation that gives apparent temperatures that are much lower than anticipated closure temperatures for epidote. Oxygen Isotope fractionation between natural zircon and magmatic epidote is opposite to that predicted from theoretical determinations, as δ18O (epidote) <δ18O (zircon). An empirical calibration based on these results would suggests a closure T for Oxygen in epidote of ~500 °C and Δ(qtz–epi) ~5.19 at 500 °C.

Andreas Pack - One of the best experts on this subject based on the ideXlab platform.

  • triple Oxygen Isotope exchange between chondrule melt and water vapor an experimental study
    Geochimica et Cosmochimica Acta, 2015
    Co-Authors: Tommaso Di Rocco, Andreas Pack
    Abstract:

    Abstract We have conducted time and ƒO2-dependent Oxygen Isotope exchange experiments between chondrule analogue melts and H2O in the phase. The aim of our study is to address the question whether the Oxygen Isotope composition of chondrules is the result of exchange with the ambient nebular gas or has been inherited from the precursor material. The silicate melt-H2O vapor exchange experiments were carried out in a vertical gas-mixing furnace using the metal loop technique at 1500 °C. The duration ranged from 5 to 1440 min and ƒO2 was set between IW − 3.8 and IW − 1.3 using the H2O/H2 buffer. Our experiments show that 50% exchange between H2O gas and silicate melt occurs in ∼4 h at ƒO2 = IW − 3.8 and in ∼1 h at ƒO2 = IW − 1.3. At solar nebula conditions, significant exchange occurs only if chondrule-melting times were several hours.

  • triple Oxygen Isotope analysis of bioapatite as tracer for diagenetic alteration of bones and teeth
    Palaeogeography Palaeoclimatology Palaeoecology, 2011
    Co-Authors: Alexander Gehler, Thomas Tutken, Andreas Pack
    Abstract:

    Abstract The detection of diagenetic alteration is critical for palaeoclimate reconstruction that is based on the Oxygen Isotope composition of fossil bones and teeth. So far, no direct chemical proxy has been found to track diagenetic modification of the Oxygen Isotope ratios. Here, a new approach to identify diagenetic changes of δ18OPO4 values in skeletal apatite of small mammals by means of triple Oxygen Isotope analysis (16O, 17O and18O) is presented. Our method is based on the fact that inhaled air Oxygen (O2) has an Isotope anomaly on its rare Isotope 17O. Inhaled air O2 is a major source of Oxygen in small land-living mammals. A fraction of the anomaly is transferred via body water to skeletal apatite, where it can be detected by means of δ17O and δ18O analyses. The approach, considering the current analytical uncertainty, is restricted to small mammals with body masses ≤ 1 kg. This is due to the low specific metabolic rates of large mammals, resulting in a lower fraction of Oxygen inhaled via breathing relative to Oxygen from other sources in their body water. Remnant negative 17O anomalies derived from in vivo inhaled O2 have been detected in enamel bioapatite of Eocene to Miocene rodent teeth while dentine of the same teeth lacks significant 17O anomalies. This suggests preservation of the original phosphate Oxygen Isotope composition in enamel of these small mammal teeth. In contrast, 17O anomalies in dentine have been erased due to diagenetic alteration with isotopically normal diagenetic fluids. Triple Oxygen Isotope analysis of bioapatite thus seems to be a useful new proxy to directly detect diagenetic alterations of the δ18OPO4 values of small mammal teeth.

  • technique for high precision analysis of triple Oxygen Isotope ratios in carbon dioxide
    Analytical Chemistry, 2010
    Co-Authors: Magdalena Hofmann, Andreas Pack
    Abstract:

    Since the discovery of mass-independent Isotope effects in stratospheric and tropospheric gases, the analysis of triple Oxygen Isotope abundance in carbon dioxide gained in importance. However, precise triple Oxygen Isotope determination in carbon dioxide is a challenging task due to mass-interference of 17O and 13C variations. Here, we present a novel analytical technique that allows us to determine slight deviations of CO2 from the terrestrial fractionation line [TFL]. Our approach is based on isotopic equilibration between CO2 gas and CeO2 powder at 685 °C and subsequent mass spectrometric analysis of ceria powder by infrared-laser fluorination. We found that βCO2-CeO2, the exponent in the relation α17/16 = (α18/16)β, amounts to 0.5240 ± 0.0011 at 685 °C. The Oxygen Isotope anomaly of CO2 (Δ17O) can be determined for a single analysis of CeO2 with a precision of ±0.05 ‰ (1σ). Our CO2−CeO2 equilibration procedure is performed with an excess of CO2 so that one analysis of Δ17O on CO2 requires at least 3....

Melanie J. Leng - One of the best experts on this subject based on the ideXlab platform.

  • pliocene diatom and sponge spicule Oxygen Isotope ratios from the bering sea isotopic offsets and future directions
    Climate of The Past, 2014
    Co-Authors: Andrea M Snelling, Melanie J. Leng, George E A Swann, Jennifer Pike
    Abstract:

    Oxygen Isotope analyses of different size fractions of Pliocene diatoms (δ18Odiatom) from the Bering Sea show no evidence of an Isotope offset and support the use of bulk diatom species samples for palaeoceanographic reconstructions. Additional samples containing concentrations of sponge spicules produce δ18O values several per mille (‰) lower than δ18Odiatom with a calculated mean offset of 3.9‰ ± 1.5. This difference is significantly greater than modern-day variations in water δ18O through the regional water column. Despite the potential for Oxygen Isotope disequilibrium within δ18Osponge, there appears to be some similarity between δ18Osponge and a global stacked benthic δ18Oforam record. This highlights the potential for δ18Osponge in palaeoenvironmental research at sites where carbonates are not readily preserved.

  • inter laboratory comparison of Oxygen Isotope compositions from biogenic silica
    Geochimica et Cosmochimica Acta, 2011
    Co-Authors: Bernhard Chapligin, Elizabeth A Webb, Akira Ijiri, Anne Alexandre, Andrea Abelmann, Andreas Lücke, Aldo Shemesh, Justin P Dodd, Melanie J. Leng, Ulrike Herzschuh
    Abstract:

    Several techniques have been introduced in the last decades for the dehydration and release of O2 from biogenic silica (opal-A) for Oxygen-Isotope analysis. However, only one silica standard is universally available: a quartz standard (NBS28) distributed by the IAEA, Vienna. Hence, there is a need for biogenic silica working standards. This paper compares the existing methods of Oxygen-Isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the δ18O values of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of δ18O values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by scanning electron microscopy (SEM) were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a standard deviation (SD) for δ18O values between 0.3‰ and 0.9‰ (1σ). Based on the results, we propose four additional biogenic silica working standards (PS1772-8: 42.8‰; BFC: 29.0‰; MSG60: 37.0‰; G95-25-CL leaves: 36.6‰) for δ18O analyses, available on request through the relevant laboratories.

  • Oxygen Isotope ratios of sedimentary biogenic silica reflect the european transcontinental climate gradient
    Journal of Quaternary Science, 2008
    Co-Authors: Jonathan J. Tyler, Hilary J. Sloane, Dirk Sachse, Melanie J. Leng, Gerd Gleixner
    Abstract:

    Oxygen Isotope ratios of biogenic silica offer considerable potential in tracing past climate change using both marine and lacustrine sediment records. Despite recent improvements and standardisation in preparatory and analytical methods, evidence for a systematic relationship between climate parameters and the Oxygen Isotope composition of sedimentary diatom silica (18Osilica) is contradictory. In particular, observed differences between the 18Osilica of living and sedimentary diatom silica in both lake and marine environments question the validity of applying Isotope fractionation models derived from living diatoms to reconstructing climate from sediment records. In order to address this issue, Oxygen Isotope ratios of biogenic silica (18Osilica) are examined from a suite of lake surface sediment samples which span a large climatic gradient across western Europe. 18Osilica values are strongly correlated with air temperature and the Isotope composition of precipitation (18OP). When evaporation of lake waters is accounted for, the time-averaged surface sediment data suggest a fractionation of 35 between water and biogenic silica. However, the effect of temperature appears less marked than that observed between contemporary diatoms and lake water over short timescales, suggesting that diagenetic processes may lead to a reduction in the temperature sensitivity of sediment 18Osilica records. Comparison of 18Osilica data with D analysed from n-alkanes of aquatic origin (n-C17, n-C21 and n-C23) demonstrates that the slope of the regional 18O:D water line is preserved within the sediment record, offering exciting potential for palaeoclimate research

  • a review of the Oxygen Isotope composition of lacustrine diatom silica for palaeoclimate reconstruction
    Earth-Science Reviews, 2006
    Co-Authors: Melanie J. Leng, Philip A Barker
    Abstract:

    Diatom silica (frustules) are a form of biogenic opal and contain Oxygen Isotopes that are being increasingly used in palaeoclimate studies. Frustules are comprised of an inner tetrahedrally bonded silica skeleton (Si–O–Si) with an outer, hydrous layer. The hydrous layer is freely exchangeable and must be removed prior to Oxygen Isotope measurement using oxidising reagents and/or high temperatures. Analysis of the Oxygen Isotope composition of diatom silica requires samples that are almost pure diatomite since extraction techniques will liberate Oxygen from all the components in the sediment. There is a generally acceptable protocol involving chemistry, sieving and settling techniques and more recently laminar flow separation. Recent studies of lacustrine diatoms have shown that even a small proportion of contaminant can have a significant influence on the Oxygen Isotope value. All lake sediments require their own specific procedure and every sample must be scrutinised by microscopy to check for the level of contamination prior to analysis. Where sediment cannot be purified sufficiently, a semi-quantitative assessment of the diatom content can facilitate mass balance techniques. When robust preparation methods are used, diatom silica offers an important palaeoclimate proxy, providing an additional complementary, rather than an alternative, host of Oxygen Isotopes in carbonates. In lacustrine Isotope studies it is often assumed, but rarely proven, that diatom silica form in Isotope equilibrium and hence empirically derived palaeotemperature equations, usually made in vitro, can be used. Most studies lack the detailed investigation of contemporaneous materials from natural waters of the region under study to test these equations. Further investigations need to be conducted in order to understand the systematic relationship between temperature, water Isotope composition and diatom Isotope composition to enable quantitative interpretation of the sediment record. Experiments to test for vital effects and inter-specific differences have so far revealed little variation. It is useful to know when and where the diatom silica is formed in the modern environment, so details of diatom ecology are important in the interpretation of Isotope data. Here we show that valuable palaeoclimate data can be gained from the Oxygen Isotope composition of diatom silica (δ18Odiatom), especially since diatoms are abundant in many lakes sensitive to climate variation where other hosts (e.g., carbonates) are absent. To date the most successful studies have been conducted in areas where the δ18Odiatom registers changes in the Oxygen Isotope composition of the lake water (rather than temperature) which is then related to other aspects of climate. In these studies, the range of values obtained is often greater than the error introduced by contaminating materials.

Anne Alexandre - One of the best experts on this subject based on the ideXlab platform.

  • inter laboratory comparison of Oxygen Isotope compositions from biogenic silica
    Geochimica et Cosmochimica Acta, 2011
    Co-Authors: Bernhard Chapligin, Elizabeth A Webb, Akira Ijiri, Anne Alexandre, Andrea Abelmann, Andreas Lücke, Aldo Shemesh, Justin P Dodd, Melanie J. Leng, Ulrike Herzschuh
    Abstract:

    Several techniques have been introduced in the last decades for the dehydration and release of O2 from biogenic silica (opal-A) for Oxygen-Isotope analysis. However, only one silica standard is universally available: a quartz standard (NBS28) distributed by the IAEA, Vienna. Hence, there is a need for biogenic silica working standards. This paper compares the existing methods of Oxygen-Isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the δ18O values of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of δ18O values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by scanning electron microscopy (SEM) were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a standard deviation (SD) for δ18O values between 0.3‰ and 0.9‰ (1σ). Based on the results, we propose four additional biogenic silica working standards (PS1772-8: 42.8‰; BFC: 29.0‰; MSG60: 37.0‰; G95-25-CL leaves: 36.6‰) for δ18O analyses, available on request through the relevant laboratories.

  • Identification of the parent bodies of micrometeorites with high-precision Oxygen Isotope ratios
    Earth and Planetary Science Letters, 2010
    Co-Authors: Clément Suavet, Luigi Folco, Anne Alexandre, Corinne Sonzogni, Ian A. Franchi, Jérôme Gattacceca, Richard C. Greenwood, Pierre Rochette
    Abstract:

    Oxygen isotopic compositions allow identification of potential parent bodies of extraterrestrial materials. We measured Oxygen Isotope ratios of 33 large (diameter >500 mu m) silicate melted micrometeorites (cosmic spherules) from Antarctica, using IR-laser fluorination coupled with mass spectrometry. It is the first time that this high-precision method is used on individual micrometeorites. The selected micrometeorites are representative of the influx of extraterrestrial materials to the Earth. Our results show that most micrometeorites are related to carbonaceous chondrites, which is consistent with previous studies. However, 20-50% of them seem to be related to CO/CV carbonaceous chondrites, whereas CM/CR carbonaceous chondrites were thought to be the main source for micrometeorites. Furthermore, similar to 30% of measured samples have Oxygen Isotope ratios lying above the terrestrial fractionation line, which relates them to ordinary chondrites or other, as yet, unsampled parent bodies

  • Oxygen Isotope analyses of fine silica grains using laser extraction technique comparison with Oxygen Isotope data obtained from ion microprobe analyses and application to quartzite and silcrete cement investigation
    Geochimica et Cosmochimica Acta, 2006
    Co-Authors: Anne Alexandre, Isabelle Basiledoelsch, Florence Sylvestre, Claude Parron, Jeandominique Meunier, Corinne Sonzogni, Fabrice Colin
    Abstract:

    The laser fluorination technique reported here for analyzing the Oxygen Isotope composition (d 18 O) of fine quartz size fractions 50-20, 20-10, 10-5, 5-2, 2-1 and <1 lm has been validated by comparison with the ion microprobe technique. It yields accurate d 18 O data with an external precision better than 0.15&. This is a significant methodological improvement for isotopic studies dealing with materials such as soil or biogenic oxides and silicates: particles are often too small and recovered in insufficient amount to be easily handled for ion microprobe analysis. Both techniques were used to investigate d 18 O composition of a Cretaceous quartzite and silcrete sequence from the SouthEast of France. Quartzite cements average 31.04 ± 1.93&. They formed from Mid-Cretaceous seawater. Higher in the series, silcretes cements average 26.66 ± 1.36&. They formed from Upper-or post-Upper-Cretaceous soil water and groundwater. Oxygen Isotope data show that the silicification steps from one mineralogical phase to another and from one layer to another (including from an upper pedogenic silcrete to a lower groundwater silcrete) occurred in a closed or weakly evaporating hydrological system.

David T Johnston - One of the best experts on this subject based on the ideXlab platform.

  • triple Oxygen Isotope insight into terrestrial pyrite oxidation
    Proceedings of the National Academy of Sciences of the United States of America, 2020
    Co-Authors: Jordon D Hemingway, Haley Olson, Alexandra V Turchyn, Edward T Tipper, M J Bickle, David T Johnston
    Abstract:

    The mass-independent minor Oxygen Isotope compositions (Δ′17O) of atmospheric O2 and C O 2 are primarily regulated by their relative partial pressures, p O 2 / p C O 2 . Pyrite oxidation during chemical weathering on land consumes O 2 and generates sulfate that is carried to the ocean by rivers. The Δ′17O values of marine sulfate deposits have thus been proposed to quantitatively track ancient atmospheric conditions. This proxy assumes direct O 2 incorporation into terrestrial pyrite oxidation-derived sulfate, but a mechanistic understanding of pyrite oxidation—including Oxygen sources—in weathering environments remains elusive. To address this issue, we present sulfate source estimates and Δ′17O measurements from modern rivers transecting the Annapurna Himalaya, Nepal. Sulfate in high-elevation headwaters is quantitatively sourced by pyrite oxidation, but resulting Δ′17O values imply no direct tropospheric O 2 incorporation. Rather, our results necessitate incorporation of Oxygen atoms from alternative, 17O-enriched sources such as reactive Oxygen species. Sulfate Δ′17O decreases significantly when moving into warm, low-elevation tributaries draining the same bedrock lithology. We interpret this to reflect overprinting of the pyrite oxidation-derived Δ′17O anomaly by microbial sulfate reduction and reoxidation, consistent with previously described major sulfur and Oxygen Isotope relationships. The geologic application of sulfate Δ′17O as a proxy for past p O 2 / p C O 2 should consider both 1) alternative Oxygen sources during pyrite oxidation and 2) secondary overprinting by microbial recycling.

  • determination and application of the equilibrium Oxygen Isotope effect between water and sulfite
    Geochimica et Cosmochimica Acta, 2014
    Co-Authors: Alexander S Bradley, Scott D Wankel, Daniel L Eldridge, David T Johnston
    Abstract:

    The information encoded by the two stable Isotope systems in sulfate (d 34 SSO4 and d 18 OSO4 ) has been widely applied to aid reconstructions of both modern and ancient environments. Interpretation of d 18 OSO4 records has been complicated by rapid Oxygen Isotope equilibration between sulfoxyanions and water. Specifically, the apparent relationship that develops between d 18 OSO4 and d 18 Owater during microbial sulfate reduction is thought to result from rapid Oxygen Isotope equilibrium between intracellular water and aqueous sulfite – a reactive intermediate of the sulfate reduction network that can back-react to produce sulfate. Here, we describe the Oxygen equilibrium Isotope effect between water and sulfite (referring to all the sum of all S(IV)-oxyanions including sulfite and both isomers and the dimer of bisulfite). Based on experiments conducted over a range

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