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Measured D 47 versus temperature for corals measured during this study. Data shown are the averages of all subsamples for each coral. Also shown are cold-water and warm-water coral data from Thiagarajan et al. (2011) and Saenger et al. (2012) after conversion to the absolute reference frame (Section 2.4). In addition, the inorganic calibration lines of Ghosh et al. (2006) and Dennis and Schrag (2010) as recalculated in Dennis et al. (2011), the Ghosh line recalculated by Eagle et al. (2013) and the calibration line of Zaarur et al. (2013) are also shown. The light and dark grey envelopes represent the 2 S.E. and 1 S.E. respectively of the Ghosh line recalculated by Dennis et al. (2011). Errors bars are 1 S.E. in all cases.
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The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes ‘clumping’ into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonat...
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Porites corals are valuable geological archives for reconstructing past sea surface temperature (SST) in tropical oceans. Their clumped isotope compositions (indicated by Δ47 values) provide a potential proxy for SST. The Δ47 value in Porites coral usually departs from thermodynamic equilibrium due to vital effects. To explore the temperature depen...
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... Organisms such as foraminifera and marine molluscs are not affected by it Grauel et al., 2013;Huyghe et al., 2022;Meinicke et al., 2020;Peral et al., 2018;Tripati et al., 2010). However, certain corals, echinoderms, brachiopods and terrestrial snails are (Bajnai et al., 2018;Davies & John, 2019;Dong et al., 2021;Spooner et al., 2016;Zhai et al., 2019). Bernasconi et al. (2021) describe the efforts of the clumped-isotope community to establish an international standardization (ETH 1-4, IAEA-C1&2 and MERCK; Meckler et al., 2014;Bernasconi et al., 2018Bernasconi et al., , 2021, and a uniform method for measuring and processing data, aimed at a robust and accurate comparison between Δ 47 measurements carried out in different laboratories. ...
... Thus, the number of analyzed samples (six different genera and species and five different temperatures, plus three coming from fossils record) is sufficient to demonstrate that the ostracods-Δ 47 signal records the temperature at which the organisms precipitated their shells. Previous calibration studies conducted on different organisms (i.e., corals, echinoderms, and terrestrial snails) used a comparable sample number to detect the presence (or not) of a vital effect for the entire class or phylum (Davies & John, 2019;Dong et al., 2021;Guo et al., 2019;Spooner et al., 2016). ...
This study presents a methodological advancement in the field of clumped‐isotope (∆47) thermometry, specifically tailored for application to freshwater ostracods. The novel ostracod clumped isotope approach enables quantitative temperature and hydrological reconstruction in lacustrine records. The relationship between ∆47 and the temperature at which ostracod shell mineralized is determined by measuring ∆47 on different species grown under controlled temperatures, ranging from 4 ± 0.8 to 23 ± 0.5ºC. The excellent agreement between the presented ∆47 ostracod data and the monitored temperatures confirms that ∆47 can be applied to ostracod shells and that a vital effect is absent outside the uncertainty of measurements. Results are consistent with the carbonate clumped‐isotope unified calibration (Anderson et al., 2021, https://doi.org/10.1029/2020gl092069), therefore, an ostracod‐specific calibration is not needed. The ostracod clumped‐isotope thermometer represents a powerful tool for terrestrial paleoclimate studies all around the world, as lakes and ostracods are found in all climatic belts.
... Disequilibrium clumped isotope values have been measured in most Earth-surface carbonate minerals (Daeron et al., 2019). Biominerals such as brachiopod shells (Carpenter and Lohmann, 1995;Bajnai et al., 2018;Rollion-Bard et al., 2019) and coral skeletons (McConnaughey, 1988;Cohen and McConnaughey, 2003;Rollion-Bard et al., 2010;Thiagarajan et al., 2011;Saenger et al., 2012b;Kimball et al., 2016;Spooner et al., 2016) are hypothesized to have biological effects that cause disequilibrium fractionation. In abiotic carbonate minerals, KIEs associated with (de)hydration and (de)hydroxylation reactions can cause departures from isotopic equilibrium (Ghosh et al., 2006;Guo, 2009;Saenger et al., 2012;Falk et al., 2016;Spooner et al., 2016;Parvez et al., 2023). ...
... Biominerals such as brachiopod shells (Carpenter and Lohmann, 1995;Bajnai et al., 2018;Rollion-Bard et al., 2019) and coral skeletons (McConnaughey, 1988;Cohen and McConnaughey, 2003;Rollion-Bard et al., 2010;Thiagarajan et al., 2011;Saenger et al., 2012b;Kimball et al., 2016;Spooner et al., 2016) are hypothesized to have biological effects that cause disequilibrium fractionation. In abiotic carbonate minerals, KIEs associated with (de)hydration and (de)hydroxylation reactions can cause departures from isotopic equilibrium (Ghosh et al., 2006;Guo, 2009;Saenger et al., 2012;Falk et al., 2016;Spooner et al., 2016;Parvez et al., 2023). At high pH, in lab experiments, Tang et al. (2014) observed Δ 47 values that were enriched relative to equilibrium in calcite (precipitated at pH ≥ 10). ...
... The main disadvantage is that this calibration is only based on abiogenic calcite, and biomineralization is a process which could deviate from the expected equilibrium 47 -temperature relationships (e.g. some corals; Fiebig et al., 2021;Spooner et al., 2016). ...
... However, two major uncertainties remain that hinder the further application of the carbonate Δ 47 thermometer: First, it is difficult to eliminate the influence of post-depositional processes such as diagenesis and metamorphism on the clumped isotope signal of carbonate minerals (Eiler, 2011;Huntington and Petersen, 2023), which calls for the application of more suitable geological archives that can avoid the interference of these processes. Second, although the clumped isotope equilibrium was observed in various types of inorganic carbonate Bonifacie et al., 2017;Kelson et al., 2017), and in modern foraminifera (Peral et al., 2018;Breitenbach et al., 2018;Meinicke et al., 2020b), coccoliths , and bivalves (Huyghe et al., 2022), several other studies showed that speleothems (Affek et al., 2008), corals (Saenger et al., 2012;Spooner et al., 2016;Davies et al., 2022), brachiopods (Bajnai et al., 2018;Letulle et al., 2023), echinoids (Davies and John, 2019), and cephalopod molluscs (Dennis et al., 2013;Davies et al., 2021) exhibit varying degrees of kinetically mediated disequilibrium, or vital effects, on their carbonate Δ 47 values, which complicates the calibration of carbonate paleotemperature proxies. Land snails often live in a spatially limited zone on the Earth's surface, and their shells, consisting of accretionary aragonitic carbonate, are buried in situ and are largely unaffected by post-depositional processes, thus preserving primary information about the environment of carbonate precipitation (Liu, 1985;Bao et al., 2023). ...
... Contrary to our results, most biogenic data, including data from foraminifera and bivalves (Meinicke et al., 2020aHuyghe et al., 2022;de Winter et al., 2022), are generally consistent with the universal calibration of Anderson et al. (2021), although, as in the case for our snails, they show a relatively large scatter around the organic calibration line (Fig. 6). Also, some biogenic carbonates, such as corals (Saenger et al., 2012;Spooner et al., 2016;Davies et al., 2022), brachiopods (Bajnai et al., 2018;Letulle et al., 2023), and echinoids (Davies and John, 2019) have a positive Δ 47 offset from the inorganic Δ 47temperature calibration. Only cephalopods (Dennis et al., 2013;Davies et al., 2021) were reported to show a consistent result with snail shells, both having a negative offset. ...
... Due to the heavy reliance on metabolic CO 2 for air-breathing land snails, shell isotopic compositions may exhibit kinetic fractionation associated with hydration/hydroxylation when the rate of calcification exceeds the DIC-H 2 O isotope exchange rate. However, results for corals and echinoids showed that this kinetic effect often causes the carbonate Δ 47 values to be more positive than that for the equilibrium precipitation (Spooner et al., 2016;Davies et al., 2022;Saenger et al., 2012;Davies and John, 2019). Thus, we suspect that a mechanism different from that of these biogenic carbonates should be proposed to explain the origin of vital effects in land snails. ...
The application of carbonate clumped isotopes (Δ47) as a temperature proxy has been widely investigated in many types of carbonate materials, including biogenic carbonates such as foraminifera and corals. However, their application to land snails is relatively rare and it remains controversial whether shell carbonate Δ47 is impacted by biologically-driven fractionation. These uncertainties may stem from the lack of precise temperature-controlled calibration samples in previous natural-environment-based studies. In this study we cultured two species of land snail with different environmental tolerances: the thermo-humidiphilous Achatina fulica (A. fulica), and the cold-aridiphilous Cathaica fasciola (C. fasciola), under strictly controlled temperature conditions, covering the growth temperature range of 15-33 ℃. The results show that the shell Δ47 values for both A. fulica and C. fasciola had statistically significant negative correlations with the culturing temperature within their respective optimum temperature ranges (A. fulica: 25-33 ℃, C. fasciola: 15-25 ℃). However, shell Δ47 values for A. fulica at lower temperatures (20 ℃ in this study) and those for C. fasciola showed a negative deviation from the expected equilibrium values. We attribute the lower-than-equilibrium values to the existence of a vital effect in individual snail species, and more specifically, to the CO2 degassing associated with dehydration/dehydroxylation during carbonate precipitation in the snail’s calcifying fluid.
... The origin of disequilibrium isotope values in carbonate minerals are not well understood, but the measurement of dual clumped isotopes has the potential to study processes that influence isotopic equilibration in DIC and carbonate minerals (Tripati et al., 2015;Guo, 2020;Bajnai et al., 2020;Fiebig et al., 2021;Lucarelli et al., 2023). Previous studies have found disequilibrium clumped isotope values in biogenic carbonate minerals from organisms that have been shown to produce ACC or ACMC, including warm and cold-water corals (Saenger et al., 2012;Atasoy, 2015;Spooner et al., 2016;Kimball et al., 2016;Mass et al., 2017;Bajnai et al., 2020), cephalopods (Dennis et al., 2013), mollusks (Addadi et al., 2006;Henkes et al., 2013;Eagle et al., 2013) and brachiopods (Griesshaber et al., 2009;Bajnai et al., 2018Bajnai et al., , 2020. It has also been shown that Mg incorporation in calcite can significantly affect the degree of oxygen isotope fractionation between the mineral and solution, with 18 O concentrating in HMC relative to pure calcite precipitated under the same conditions by 0.06‰ for each mol-percent of Mg in calcite (Tarutani et al., 1969;Mavromatis et al., 2012). ...
... However, in biominerals that are known to form from amorphous precursors, there is evidence for disequilibrium fractionations (eg. Ghosh et al., 2006;Spooner et al., 2016;Kimball et al., 2016;Davies and John, 2019). Here, we present evidence for a new mechanism where disequilibrium isotope effects could be generated. ...
... 2012) found enriched Δ 47 values in Porites, Siderastrea, Astrangia, and Caryophyllia corals from the Red Sea that resulted in a consistent offset of Δ 47 -temperature values by − 8 • C. They ruled out many mechanisms that may have resulted in the offset, including salinity, organic matter contamination, alteration, symbionts, and analytical error.Spooner et al. (2016) found increased Δ 47 values of Dasmosmilia and Javania corals which resulted in a − 8 • C temperature offset.Kimball et al. (2016) andThiagaragan et al. (2011) have observed disequilibrium δ 18 O carb values with equilibrium Δ 47 values in scleractinian corals including Enallopsammia, Desmophyllum, Enallopsammia, and Caryophyllia. These ...
... Such is required to apply known calibrations of the dependence of clumped-isotope compositions on temperature to new systems. Formation in isotopic equilibrium cannot be assumed as some natural materials, including biogenic materials, can form out of clumped isotopic equilibrium (e.g., corals and speleothems; Bajnai et al., 2020;Ghosh et al., 2006;Kluge & Affek, 2012;Spooner et al., 2016). As such, it is necessary to establish (if possible) that carbonate clumped isotopic compositions indeed reflect mineral formation temperatures at isotopic equilibrium in any new system, and this is the purpose of this study. ...
The genus Celtis includes widespread trees that produce drupes with aragonite endocarps, or “hackberries.” These carbonate endocarps are preserved in the fossil record, often in cave deposits or packrat middens, and thus are targets for paleoclimate reconstructions. Stable oxygen isotopes in Celtis endocarps have been used as proxies for oxygen isotopic composition of past stream water and for paleothermometry. Here, we explore the suitability of hackberry carbonates for paleoclimate reconstructions based on carbonate clumped‐isotope thermometry. We sampled modern hackberries grown at sites across North America (n = 37) for stable and clumped isotope analyses. Measured clumped‐isotope temperatures are found to be within the range of measured local modern growing season surface temperatures and typically in dual clumped‐isotope equilibrium. As such, we propose that hackberry clumped‐isotope measurements can be used to reconstruct past Earth‐surface air temperatures.
... The relationship between D 47 and temperature in cold-water coral carbonate was initially observed to be indistinguishable from the inorganic calibration of Ghosh et al. (2006) (Thiagarajan et al., 2011). Further analyses, covering a broader range of cold-water coral genera, however, yielded higher D 47 than inorganic calibrations, including significant inter-genus variation (Kimball et al., 2016;Spooner et al., 2016). Departures from clumped isotope equilibrium in corals, brachiopods, echinoids, cephalopod molluscs and speleothems have been linked with kinetic isotope effects during the slow conversion between CO 2(aq) and bicarbonate HCO 3 -(e.g. ...
... Our data suggest ''equilibrium" or ''pH" effects are not a primary driver of clumped isotope disequilibrium in the coral carbonate analyzed in this study, as proposed by some earlier studies (Spooner et al., 2016;Thiagarajan et al., 2011). We observe correlated depletion in D 48 and enrichment in D 47 of both cold and warm-water coral aragonite (D 47 /D 48 À0.78 ± 0.05 and D 47 /D 48 À0.4 ± 0.03, respectively) (Fig. 2a). ...
The stable (δ¹⁸O and δ¹³C) and clumped (Δ47) isotope compositions of coral carbonate are valuable archives for paleoclimate reconstructions. However, the Δ47-temperature relationships of warm and cold-water corals deviate from that of inorganic carbonate precipitated at equilibrium. Dual clumped isotope thermometry of carbonates (i.e., simultaneous Δ47 and Δ48 measurements on a single carbonate) has the potential to achieve more accurate paleotemperature reconstruction, identifying and correcting for kinetically driven isotopic disequilibrium. Here we present the first extensive dual clumped isotope dataset of coral carbonate, spanning a broad range of cold and warm-water coral species. We confirm that corals are enriched in Δ47 and depleted in Δ48 relative to equilibrium, a pattern corresponding to the mixing of an equilibrium DIC pool with kinetically derived HCO3⁻ produced by hydration and hydroxylation of CO2. Dual clumped isotope measurements of cold-water corals fall on the initial linear portion of model (IsoDIC) predicted departure from equilibrium. The dual clumped isotope composition of cold-water corals, corrected by the model-predicted Δ47/Δ48 offset slope (-0.78), yield accurate reconstruction of coral growth temperature with a precision of <3°C at the 68% confidence level. In contrast, disequilibrium offsets in the Δ47 and Δ48 of warm-water corals correspond to precipitation from a more equilibrated DIC pool, which we attribute to the action of carbonic anhydrase in the calcifying fluid. It may be possible to correct warm-water coral growth temperatures, using an empirically derived correction (Δ47/ Δ48 offset slope of -0.4). Dual clumped isotope thermometry of coral carbonate opens new possibilities to reconstruct both sea surface temperatures and ocean dynamics of intermediate to deep water masses.
... As a consequence of such processes, termed "vital effects," biomineral compositions may depart from those observed in abiotically precipitated minerals under the same seawater conditions. These vital effects not only can hinder the reconstruction of paleoenvironmental conditions using fossils (41,57,65,107,109,(118)(119)(120)(121)(122)(123)(124)(125)(126) but can also test the CaCO 3 biomineralization model because isotopic and trace element concentrations are affected by factors such as ion sources, rates of transport, CA activity, and ICF or ECF fluid conditions. Although the relevant studies have not yet been performed, trace element and isotope signatures may also be affected by the relative contributions of PA and IA. ...
Calcium carbonate (CaCO3) biomineralizing organisms have played major roles in the history of life and the global carbon cycle during the past 541 Ma. Both marine diversification and mass extinctions reflect physiological responses to environmental changes through time. An integrated understanding of carbonate biomineralization is necessary to illuminate this evolutionary record and to understand how modern organisms will respond to 21st century global change. Biomineralization evolved independently but convergently across phyla, suggesting a unity of mechanism that transcends biological differences. In this review, we combine CaCO3 skeleton formation mechanisms with constraints from evolutionary history, omics, and a meta-analysis of isotopic data to develop a plausible model for CaCO3 biomineralization applicable to all phyla. The model provides a framework for understanding the environmental sensitivity of marine calcifiers, past mass extinctions, and resilience in 21st century acidifying oceans. Thus, it frames questions about the past, present, and future of CaCO3 biomineralizing organisms.
... [p. 594] need to remove ice volume effect; also sensitive to salinity (Zachos et al., 2001;Marchitto et al., 2014) Benthic foraminiferal Mg/Ca ratios potential additional carbonate ion influence (Lear et al., 2000;Elderfield et al., 2012) Clumped isotopes of oxygen and carbon (∆47) in carbonates independent of fluid composition, but need to consider speciesdependent vital effects in corals (Ghosh et al., 2006;Spooner et al., 2016) Sea surface temperature (SST) Planktonic foraminiferal oxygen isotopes (δ 18 O) need to remove ice volume effect; also sensitive to salinity (Emiliani, 1955;Pearson, 2012) Planktonic foraminiferal Mg/Ca ratios need species-and/or locationspecific calibrations; foraminifera cleaning method is important (Nürnberg et al., 1996;Elderfield and Ganssen, 2000;Barker et al., 2005;Vázquez Riveiros et al., 2016) Unsaturation index in alkenones derived from coccoliths (U k' 37 and variants) calibrations for different regions and temperature ranges; coccoliths can be absent near the poles; need to consider seasonality effects (Sikes and Volkman, 1993;Conte et al., 2006) Tetraether index in organic membrane lipids (TEX86 and variants) versions of the index exist for different latitudes; regional calibrations may be useful (Schouten et al., 2002;Ho et al., 2014) Long Chain Diol Index (LDI) wide distribution including high latitudes; calibration extends to cold temperatures; research needed on source of diols, mechanism, and seasonality effect (Rampen et al., 2012;Lopes dos Santos et al., 2013) Heterocyst diol and triol indices (HDIs and HTIs) developed in lakes; application in the ocean is in its infancy (Bauersachs et al., 2015) Salinity ...
During the Pleistocene, Earth experienced high-amplitude fluctuations in global temperature, atmospheric composition, ice sheet extent and sea level that were forced by orbital variations in the seasonal distribution of solar energy across the planet. Subtle cyclical variations in forcing were greatly amplified by internal feedbacks in the Earth system, with processes in the polar regions influential for pole-to-equator temperature gradients and atmospheric carbon dioxide levels. Exploring the behaviour of the polar ice sheets and the Southern Ocean during this interval is crucial for understanding how the climate system operates and for constraining its sensitivity to future changes. Southern Ocean processes, including wind-driven upwelling, sea ice formation, deep water production and biological productivity, were instrumental in regulating Earth’s atmospheric carbon dioxide levels through Pleistocene glacial–interglacial cycles. On millennial timescales, rapid changes in ocean and atmospheric circulation were influenced by meltwater input from unstable ice sheet margins in both hemispheres, leading to highly variable regional and interhemispheric climate responses. This chapter provides an overview of the tools used in marine sediment and ice core archives to reconstruct Pleistocene changes in the Earth system. We discuss the mechanisms that controlled Earth’s climate over different timescales and review the latest evidence that is revealing how the Antarctic Ice Sheet has both influenced and responded to Pleistocene climate change, including during intervals when Earth’s climate was similar to near-future projections. Despite experiencing ice volume changes that were modest in comparison to the advance and retreat of large Northern Hemisphere ice sheets, Antarctica has been a very active player in the ice sheet–ocean–climate system of the past 2.6 million years, and evidence increasingly suggests that it could respond dramatically to anthropogenic warming.
... The origin of disequilibrium isotope values in carbonate minerals are not well understood, but the measurement of dual clumped isotopes has the potential to study processes that influence isotopic equilibration in DIC and carbonate minerals (Tripati et al., 2015;Guo, 2020;Bajnai et al., 2020;Fiebig et al., 2021;Lucarelli et al., 2023). Previous studies have found disequilibrium clumped isotope values in biogenic carbonate minerals from organisms that have been shown to produce ACC or ACMC, including warm and cold-water corals (Saenger et al., 2012;Atasoy, 2015;Spooner et al., 2016;Kimball et al., 2016;Mass et al., 2017;Bajnai et al., 2020), cephalopods (Dennis et al., 2013), mollusks (Addadi et al., 2006;Henkes et al., 2013;Eagle et al., 2013) and brachiopods (Griesshaber et al., 2009;Bajnai et al., 2018Bajnai et al., , 2020. It has also been shown that Mg incorporation in calcite can significantly affect the degree of oxygen isotope fractionation between the mineral and solution, with 18 O concentrating in HMC relative to pure calcite precipitated under the same conditions by 0.06‰ for each mol-percent of Mg in calcite (Tarutani et al., 1969;Mavromatis et al., 2012). ...
... However, in biominerals that are known to form from amorphous precursors, there is evidence for disequilibrium fractionations (eg. Ghosh et al., 2006;Spooner et al., 2016;Kimball et al., 2016;Davies and John, 2019). Here, we present evidence for a new mechanism where disequilibrium isotope effects could be generated. ...
... 2012) found enriched Δ 47 values in Porites, Siderastrea, Astrangia, and Caryophyllia corals from the Red Sea that resulted in a consistent offset of Δ 47 -temperature values by − 8 • C. They ruled out many mechanisms that may have resulted in the offset, including salinity, organic matter contamination, alteration, symbionts, and analytical error.Spooner et al. (2016) found increased Δ 47 values of Dasmosmilia and Javania corals which resulted in a − 8 • C temperature offset.Kimball et al. (2016) andThiagaragan et al. (2011) have observed disequilibrium δ 18 O carb values with equilibrium Δ 47 values in scleractinian corals including Enallopsammia, Desmophyllum, Enallopsammia, and Caryophyllia. These ...
