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Zhang J. Oxygen Isotope Fractionation between Carbonate Minerals and Carbonic Acid Systems and Constraints for Environmental Science and Geological Processes. Molecules 2024; 29:698. [PMID: 38338441 PMCID: PMC10856116 DOI: 10.3390/molecules29030698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/25/2024] [Accepted: 01/30/2024] [Indexed: 02/12/2024] Open
Abstract
The equilibrium oxygen isotope fractionation factor is widely used in geological thermometry. However, under most natural conditions, the oxygen isotope exchange is rare to reach equilibrium. Especially for the complex water-rock interaction process, the contribution of the H2CO3 solution, CO32- solution, Ca(HCO3)2 solution, and CaCO3 solution to the equilibrium oxygen isotope fractionation factor of this process is poorly understood. In view of this predicament, these key parameters are obtained by ab initio calculations. The results showed that the contributions of different carbonate minerals and different aqueous solutions to the equilibrium oxygen isotope fractionation factor were different. Among all nine carbonate minerals (dolomite, calcite, aragonite, magnesite, siderite, otavite, smithsonite, ankerite, and strontianite), the minerals with the highest and lowest reduced partition function ratios (RPFR) were siderite and strontianite, respectively. At the same time, the RPFR of nitratine, which has the same structure as carbonate, was studied. The RPFRs of the three most widely distributed carbonates in nature (dolomite, calcite, and aragonite) were dolomite > calcite > aragonite. Among the H2CO3 solution, CO32- solution, Ca(HCO3)2 solution, and CaCO3 solution, the H2CO3 solution had the strongest ability to enrich 18O. In addition, the equilibrium oxygen isotope fractionation factors between aqueous solutions and gas phase species (CO2(g), H2O(g), and O2(g), etc.) were calculated systematically. The results showed that the oxygen isotope fractionation factors between solutions and gas phases were often inconsistent with the temperature change direction and that the kinetic effects played a key role. These theoretical parameters obtained in this study will provide key equilibrium oxygen isotope constraints for water-rock interaction processes.
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Affiliation(s)
- Jixi Zhang
- School of Geography and Environmental Science, Guizhou Normal University/State Engineering Technology Institute for Karst Desertification, Guiyang 550001, China;
- School of Karst Science, Guizhou Normal University/State Engineering Technology Institute for Karst Desertification, Guiyang 550001, China
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2
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Kaskes P, Marchegiano M, Peral M, Goderis S, Claeys P. Hot carbonates deep within the Chicxulub impact structure. PNAS NEXUS 2024; 3:pgad414. [PMID: 38213614 PMCID: PMC10783646 DOI: 10.1093/pnasnexus/pgad414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 11/21/2023] [Indexed: 01/13/2024]
Abstract
Constraining the thermodynamic conditions within an impact structure during and after hypervelocity impacts is extremely challenging due to the transient thermal regimes. This work uses carbonate clumped-isotope thermometry to reconstruct absolute temperatures of impact lithologies within and close to the ∼66 Myr old Chicxulub crater (Yucatán, México). We present stable oxygen (δ18O), carbon (δ13C), and clumped-isotope (Δ47) data for carbonate-bearing impact breccias, impact melt rock, and target lithologies from four drill cores on a transect through the Chicxulub structure from the northern peak ring to the southern proximal ejecta blanket. Clumped isotope-derived temperatures (T(Δ47)) are consistently higher than maximum Late Cretaceous sea surface temperatures (35.5°C), except in the case of Paleogene limestones and melt-poor impact breccias outside of the crater, confirming the influence of burial diagenesis and a widespread and long-lived hydrothermal system. The melt-poor breccia unit outside the crater is overlain by melt-rich impact breccia yielding a much higher T(Δ47) of 111 ± 10°C (1 standard error [SE]), which likely traces the thermal processing of carbonate material during ejection. Finally, T(Δ47) up to 327 ± 33°C (1 SE) is determined for the lower suevite and impact melt rock intervals within the crater. The highest temperatures are related to distinct petrological features associated with decarbonation and rapid back-reaction, in which highly reactive CaO recombines with impact-released CO2 to form secondary CaCO3 phases. These observations have important climatic implications for the Cretaceous-Paleogene mass extinction event, as current numerical models likely overestimate the release of CO2 from the Chicxulub impact event.
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Affiliation(s)
- Pim Kaskes
- Research Unit: Archaeology, Environmental Changes and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, 1050 Brussels, Belgium
- Laboratoire G-Time, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Marta Marchegiano
- Research Unit: Archaeology, Environmental Changes and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, 1050 Brussels, Belgium
- Department of Stratigraphy and Paleontology, University of Granada, 18071 Granada, Spain
| | - Marion Peral
- Research Unit: Archaeology, Environmental Changes and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, 1050 Brussels, Belgium
- CNRS, Bordeaux INP, EPOC, UMR 5805, Université de Bordeaux, F-33600 Pessac, France
| | - Steven Goderis
- Research Unit: Archaeology, Environmental Changes and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Philippe Claeys
- Research Unit: Archaeology, Environmental Changes and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, 1050 Brussels, Belgium
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Zhang H, Huang Y, Wijker R, Cacho I, Torner J, Santos M, Kost O, Wei B, Stoll H. Iberian Margin surface ocean cooling led freshening during Marine Isotope Stage 6 abrupt cooling events. Nat Commun 2023; 14:5390. [PMID: 37666864 PMCID: PMC10477208 DOI: 10.1038/s41467-023-41142-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 08/23/2023] [Indexed: 09/06/2023] Open
Abstract
The high-resolution paleoclimate records on the Iberian Margin provide an excellent archive to study the mechanism of abrupt climate events. Previous studies on the Iberian Margin proposed that the surface cooling reconstructed by the alkenone-unsaturation index coincided with surface water freshening inferred from an elevated percentage of tetra-unsaturated alkenones, C37:4%. However, recent data indicate that marine alkenone producers, coccolithophores, do not produce more C37:4 in culture as salinity decreases. Hence, the causes for high C37:4 are still unclear. Here we provide detailed alkenone measurements to trace the producers of alkenones in combination with foraminiferal Mg/Ca and oxygen isotope ratios to trace salinity variations. The results indicate that all alkenones were produced by coccolithophores and the high C37:4% reflects decrease in SST instead of freshening. Furthermore, during the millennial climate changes, a surface freshening did not always trigger a cooling, but sometimes happened in the middle of multiple-stage cooling events and likely amplified the temperature decrease.
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Affiliation(s)
- Hongrui Zhang
- Geological Institute, ETH Zürich, 8092, Zürich, Switzerland.
| | - Yongsong Huang
- Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
| | - Reto Wijker
- Geological Institute, ETH Zürich, 8092, Zürich, Switzerland
| | - Isabel Cacho
- Grup de Recerca Consolidat en Geociències Marines, Department de Dinàmica de la Terra i de l'Oceà, Universitat de Barcelona, Barcelona, Spain
| | - Judit Torner
- Grup de Recerca Consolidat en Geociències Marines, Department de Dinàmica de la Terra i de l'Oceà, Universitat de Barcelona, Barcelona, Spain
| | | | - Oliver Kost
- Geological Institute, ETH Zürich, 8092, Zürich, Switzerland
| | - Bingbing Wei
- Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Bremerhaven, 27570, Germany
| | - Heather Stoll
- Geological Institute, ETH Zürich, 8092, Zürich, Switzerland
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4
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U-Pb dating and geochemical dataset of fracture-filling calcite veins from the Bóixols-Sant Corneli anticline (Southern Pyrenees). Data Brief 2022; 45:108636. [PMID: 36425981 PMCID: PMC9679491 DOI: 10.1016/j.dib.2022.108636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/15/2022] [Accepted: 09/20/2022] [Indexed: 11/29/2022] Open
Abstract
U-Pb dating and geochemical analyzes (δ18O, δ13C, Δ47, 87Sr/86Sr and elemental composition) have been applied to fracture-filling calcite veins and host carbonates from the Bóixols-Sant Corneli anticline, which developed along the front of the Bóixols thrust sheet in the Southern Pyrenees. This robust dataset is used to determine: (i) the absolute timing of fracturing and mineralization from fluid flow; (ii) the age and duration of fold evolution; and (iii) the variations and implications of fluid behavior across the anticline, as has been described in the article “Spatio-temporal variation of fluid flow behavior along a fold: The Bóixols-Sant Corneli anticline (Southern Pyrenees) from U–Pb dating and structural, petrographic, and geochemical constraints – Marine and Petroleum Geology (2022) (Muñoz-López et al., 2022). In this new contribution, we present the raw data that have been analyzed and discussed in the related research article and, also, the whole elemental and REE composition of calcite veins and host carbonates that has not been published yet. These data may be used to unravel the age and origin of veins, to understand their sequential evolution in orogenic belts and to compare our results with those obtained in similar settings worldwide.
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Sources of Hydrothermal Fluids Inferred from Oxygen and Carbon Isotope Composition of Calcite, Keweenaw Peninsula Native Copper District, Michigan, USA. MINERALS 2022. [DOI: 10.3390/min12040474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
The Mesoproterozoic North American Midcontinent Rift hosts the world’s largest accumulation of native copper in Michigan’s Keweenaw Peninsula. During a regional metamorphogenic-hydrothermal event, native copper was deposited along with spatially zoned main-stage minerals in a thermal high. This was followed by deposition of late-stage minerals including minor copper sulfide. Inferences from the oxygen and carbon isotopic composition of main-stage hydrothermal fluids, as calculated from 296 new and compiled isotopic measurements on calcite, are consistent with existing models that low-sulfur saline native copper ore-forming fluids were dominantly derived by burial metamorphic processes from the very low sulfur basalt-dominated rift fill at depth below the native copper deposits. Co-variation of oxygen and carbon isotopic compositions are consistent with mixing of metamorphic-derived fluids with two additional isotopically different fluids. One of these is proposed to be evolved seawater that provided an outside source of salinity. This fluid mixed at depth and participated in the formation of a well-mixed hybrid metamorphic-dominated ore-forming fluid. Secondary Ion Mass Spectrometry in-situ isotopic analyses of calcite demonstrate a high degree of variability within samples that is attributed to variable degrees of shallow mixing of the hybrid ore-forming fluid with sulfur-poor, reduced evolved meteoric water in the zone of precipitation. The oxygen and carbon isotopic compositions of 100 new and compiled measurements on late-stage calcite are mostly isotopically different than the main-stage hydrothermal fluids. The late-stage hydrothermal fluids are interpreted as various proportions of mixing of evolved meteoric water, main-stage hybrid ore-forming fluid, and shallow, evolved seawater in the relatively shallow zone of precipitation.
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Medina Ferrer F, Rosen MR, Feyhl-Buska J, Russell VV, Sønderholm F, Loyd S, Shapiro R, Stamps BW, Petryshyn V, Demirel-Floyd C, Bailey JV, Johnson HA, Spear JR, Corsetti FA. Potential role for microbial ureolysis in the rapid formation of carbonate tufa mounds. GEOBIOLOGY 2022; 20:79-97. [PMID: 34337850 DOI: 10.1111/gbi.12467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 07/10/2021] [Indexed: 06/13/2023]
Abstract
Modern carbonate tufa towers in the alkaline (~pH 9.5) Big Soda Lake (BSL), Nevada, exhibit rapid precipitation rates (exceeding 3 cm/year) and host diverse microbial communities. Geochemical indicators reveal that carbonate precipitation is, in part, promoted by the mixing of calcium-rich groundwater and carbonate-rich lake water, such that a microbial role for carbonate precipitation is unknown. Here, we characterize the BSL microbial communities and evaluate their potential effects on carbonate precipitation that may influence fast carbonate precipitation rates of the active tufa mounds of BSL. Small subunit rRNA gene surveys indicate a diverse microbial community living endolithically, in interior voids, and on tufa surfaces. Metagenomic DNA sequencing shows that genes associated with metabolisms that are capable of increasing carbonate saturation (e.g., photosynthesis, ureolysis, and bicarbonate transport) are abundant. Enzyme activity assays revealed that urease and carbonic anhydrase, two microbial enzymes that promote carbonate precipitation, are active in situ in BSL tufa biofilms, and urease also increased calcium carbonate precipitation rates in laboratory incubation analyses. We propose that, although BSL tufas form partially as a result of water mixing, tufa-inhabiting microbiota promote rapid carbonate authigenesis via ureolysis, and potentially via bicarbonate dehydration and CO2 outgassing by carbonic anhydrase. Microbially induced calcium carbonate precipitation in BSL tufas may generate signatures preserved in the carbonate microfabric, such as stromatolitic layers, which could serve as models for developing potential biosignatures on Earth and elsewhere.
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Affiliation(s)
- Fernando Medina Ferrer
- Department of Earth & Environmental Sciences, University of Minnesota, Twin Cities, Minneapolis, Minnesota, USA
| | - Michael R Rosen
- US Geological Survey, California Water Science Center, Carson City, Nevada, USA
| | - Jayme Feyhl-Buska
- Department of Earth Sciences, University of Southern California, Los Angeles, California, USA
| | - Virginia V Russell
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Fredrik Sønderholm
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark
| | - Sean Loyd
- Department of Geological Sciences, California State University Fullerton, Fullerton, California, USA
| | | | - Blake W Stamps
- 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio, USA
- UES, Inc., Dayton, Ohio, USA
| | - Victoria Petryshyn
- Environmental Studies Program, University of Southern California, Los Angeles, California, USA
| | | | - Jake V Bailey
- Department of Earth & Environmental Sciences, University of Minnesota, Twin Cities, Minneapolis, Minnesota, USA
| | - Hope A Johnson
- Department of Biological Science, California State University Fullerton, Fullerton, California, USA
| | - John R Spear
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado, USA
| | - Frank A Corsetti
- Department of Earth Sciences, University of Southern California, Los Angeles, California, USA
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Ternieten L, Früh‐Green GL, Bernasconi SM. Carbon Geochemistry of the Active Serpentinization Site at the Wadi Tayin Massif: Insights From the ICDP Oman Drilling Project: Phase II. JOURNAL OF GEOPHYSICAL RESEARCH. SOLID EARTH 2021; 126:e2021JB022712. [PMID: 35859726 PMCID: PMC9285459 DOI: 10.1029/2021jb022712] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 11/08/2021] [Accepted: 11/26/2021] [Indexed: 06/15/2023]
Abstract
A large part of the hydrated oceanic lithosphere consists of serpentinites exposed in ophiolites. Serpentinites constitute reactive chemical and thermal systems and potentially represent an effective sink for CO2. Understanding carbonation mechanisms within ophiolites are almost exclusively based on studies of outcrops, which can limit the interpretation of fossil hydrothermal systems. We present stable and radiogenic carbon isotope data that provide insights into the isotopic trends and fluid evolution of peridotite carbonation in ICDP Oman Drilling Project drill holes BA1B (400-m deep) and BA3A (300-m deep). Geochemical investigations of the carbonates in serpentinites indicate formation in the last 50 kyr, implying a distinctly different phase of alteration than the initial oceanic hydration and serpentinization of the Samail Ophiolite. The oldest carbonates (∼31 to >50 kyr) are localized calcite, dolomite, and aragonite veins, formed between 26°C and 43°C and related to focused fluid flow. Subsequent pervasive small amounts of dispersed carbonate precipitated in the last 1,000 years. Macroscopic brecciation and veining of the peridotite indicate that carbonation is influenced by tectonic features allowing infiltration of fluids over extended periods and at different structural levels such as along fracture planes and micro-fractures and grain boundaries, causing large-scale hydration of the ophiolite. The formation of dispersed carbonate is related to percolating fluids with δ 18O lower than modern ground and meteoric water. Our study shows that radiocarbon investigations are an essential tool to interpret the carbonation history and that stable oxygen and carbon isotopes alone can result in ambiguous interpretations.
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Vickers ML, Bernasconi SM, Ullmann CV, Lode S, Looser N, Morales LG, Price GD, Wilby PR, Hougård IW, Hesselbo SP, Korte C. Marine temperatures underestimated for past greenhouse climate. Sci Rep 2021; 11:19109. [PMID: 34580353 PMCID: PMC8476565 DOI: 10.1038/s41598-021-98528-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 09/09/2021] [Indexed: 02/08/2023] Open
Abstract
Understanding the Earth's climate system during past periods of high atmospheric CO2 is crucial for forecasting climate change under anthropogenically-elevated CO2. The Mesozoic Era is believed to have coincided with a long-term Greenhouse climate, and many of our temperature reconstructions come from stable isotopes of marine biotic calcite, in particular from belemnites, an extinct group of molluscs with carbonate hard-parts. Yet, temperatures reconstructed from the oxygen isotope composition of belemnites are consistently colder than those derived from other temperature proxies, leading to large uncertainties around Mesozoic sea temperatures. Here we apply clumped isotope palaeothermometry to two distinct carbonate phases from exceptionally well-preserved belemnites in order to constrain their living habitat, and improve temperature reconstructions based on stable oxygen isotopes. We show that belemnites precipitated both aragonite and calcite in warm, open ocean surface waters, and demonstrate how previous low estimates of belemnite calcification temperatures has led to widespread underestimation of Mesozoic sea temperatures by ca. 12 °C, raising estimates of some of the lowest temperature estimates for the Jurassic period to values which approach modern mid-latitude sea surface temperatures. Our findings enable accurate recalculation of global Mesozoic belemnite temperatures, and will thus improve our understanding of Greenhouse climate dynamics.
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Affiliation(s)
- Madeleine L. Vickers
- grid.5254.60000 0001 0674 042XFaculty of Science, Geology Section, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark
| | - Stefano M. Bernasconi
- grid.5801.c0000 0001 2156 2780Geologisches Institut, Dep. Erdwissenschaften, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland
| | - Clemens V. Ullmann
- grid.4991.50000 0004 1936 8948Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN UK ,grid.8391.30000 0004 1936 8024Camborne School of Mines, University of Exeter, Penryn Campus, Penryn, TR10 9FE Cornwall UK
| | - Stefanie Lode
- grid.13508.3f0000 0001 1017 5662Department of Petrology and Economic Geology, Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350 Copenhagen K, Denmark
| | - Nathan Looser
- grid.5801.c0000 0001 2156 2780Geologisches Institut, Dep. Erdwissenschaften, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland
| | - Luiz Grafulha Morales
- grid.5801.c0000 0001 2156 2780Geologisches Institut, Dep. Erdwissenschaften, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland ,grid.5801.c0000 0001 2156 2780Scientific Centre for Optical and Electron Microscopy (ScopeM), ETH Zürich, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
| | - Gregory D. Price
- grid.11201.330000 0001 2219 0747School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA UK
| | - Philip R. Wilby
- grid.474329.f0000 0001 1956 5915British Geological Survey, Keyworth, Nottingham, NG12 5GG UK ,grid.9918.90000 0004 1936 8411School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester, LE1 7RH UK
| | - Iben Winther Hougård
- grid.5254.60000 0001 0674 042XFaculty of Science, Geology Section, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark
| | - Stephen P. Hesselbo
- grid.8391.30000 0004 1936 8024Camborne School of Mines, University of Exeter, Penryn Campus, Penryn, TR10 9FE Cornwall UK
| | - Christoph Korte
- grid.5254.60000 0001 0674 042XFaculty of Science, Geology Section, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark
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Swart PK, Lu C, Moore EW, Smith ME, Murray ST, Staudigel PT. A calibration equation between Δ 48 values of carbonate and temperature. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2021; 35:e9147. [PMID: 34145645 DOI: 10.1002/rcm.9147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 06/14/2021] [Accepted: 06/16/2021] [Indexed: 06/12/2023]
Abstract
RATIONALE Information on the temperature of formation or alteration of carbonate minerals can be obtained by measuring the abundance of the isotopologues 47 and 48 (Δ47 and Δ48 values) of CO2 released during acid dissolution. The combination of these two proxies can potentially provide a greater insight into the temperature of formation, particularly if the carbonate minerals form by non-equilibrium processes. METHODS We have precipitated calcium carbonates at seven temperatures between 5 and 65°C and measured their δ48 values using a Thermo-253 plus isotope ratio mass spectrometer. The values were transformed to Δ48 values in the conventional manner and then converted to the carbon dioxide equilibrium scale. RESULTS Using the Δ48 values, we have established an empirical calibration between temperature and Δ48 values: [Formula: see text] CONCLUSIONS: The calibration line produced allows the determination of the temperature of natural carbonates using the Δ48 values and agrees with the measurements of the Δ47 and Δ48 values of some carbonates assumed to have formed under equilibrium conditions.
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Affiliation(s)
- Peter K Swart
- Department of Marine Geosciences, RSMAS, University of Miami, Miami, Florida
| | - Chaojin Lu
- Department of Marine Geosciences, RSMAS, University of Miami, Miami, Florida
| | - Evan W Moore
- Department of Marine Geosciences, RSMAS, University of Miami, Miami, Florida
| | - Megan E Smith
- Department of Marine Geosciences, RSMAS, University of Miami, Miami, Florida
| | - Sean T Murray
- Department of Marine Geosciences, RSMAS, University of Miami, Miami, Florida
- Department of the Environment, Macquarie University, Sydney, NSW, Australia
| | - Philip T Staudigel
- Department of Marine Geosciences, RSMAS, University of Miami, Miami, Florida
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, UK
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Titus AL, Knoll K, Sertich JJW, Yamamura D, Suarez CA, Glasspool IJ, Ginouves JE, Lukacic AK, Roberts EM. Geology and taphonomy of a unique tyrannosaurid bonebed from the upper Campanian Kaiparowits Formation of southern Utah: implications for tyrannosaurid gregariousness. PeerJ 2021; 9:e11013. [PMID: 33976955 PMCID: PMC8061582 DOI: 10.7717/peerj.11013] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 02/05/2021] [Indexed: 11/20/2022] Open
Abstract
Tyrannosaurids are hypothesized to be gregarious, possibly parasocial carnivores engaging in cooperative hunting and extended parental care. A tyrannosaurid (cf. Teratophoneus curriei) bonebed in the late Campanian age Kaiparowits Formation of southern Utah, nicknamed the Rainbows and Unicorns Quarry (RUQ), provides the first opportunity to investigate possible tyrannosaurid gregariousness in a taxon unique to southern Laramidia. Analyses of the site's sedimentology, fauna, flora, stable isotopes, rare earth elements (REE), charcoal content and taphonomy suggest a complex history starting with the deaths and transport of tyrannosaurids into a peri-fluvial, low-energy lacustrine setting. Isotopic and REE analyses of the fossil material yields a relatively homogeneous signature indicating the assemblage was derived from the same source and represents a fauna living in a single ecospace. Subsequent drying of the lake and fluctuating water tables simultaneously overprinted the bones with pedogenic carbonate and structurally weakened them through wet-dry cycling. Abundant charcoal recovered from the primary bone layer indicate a low temperature fire played a role in the site history, possibly triggering an avulsion that exhumed and reburied skeletal material on the margin of a new channel with minimal transport. Possible causes of mortality and concentration of the tyrannosaurids include cyanobacterial toxicosis, fire, and flooding, the latter being the preferred hypothesis. Comparisons of the RUQ site with other North American tyrannosaur bonebeds (Dry Island-Alberta; Daspletosaurus horneri-Montana) suggest all formed through similar processes. Combined with ichnological evidence, these tyrannosaur mass-burial sites could be part of an emerging pattern throughout Laramidia reflecting innate tyrannosaurid behavior such as habitual gregariousness.
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Affiliation(s)
- Alan L Titus
- Paria River District, US Bureau of Land Management, Kanab, UT, USA
| | - Katja Knoll
- Paria River District, US Bureau of Land Management, Kanab, UT, USA
| | - Joseph J W Sertich
- Department of Earth Sciences, Denver Museum of Nature and Science, Denver, CO, USA
| | - Daigo Yamamura
- Department of Geosciences, University of Arkansas at Fayetteville, Fayetteville, AR, USA
| | - Celina A Suarez
- Department of Geosciences, University of Arkansas at Fayetteville, Fayetteville, AR, USA
| | | | | | | | - Eric M Roberts
- Department of Earth and Environmental Sciences, James Cook University of North Queensland, Townsville, QLD, Australia
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12
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He C, Liu Z, Otto-Bliesner BL, Brady EC, Zhu C, Tomas R, Clark PU, Zhu J, Jahn A, Gu S, Zhang J, Nusbaumer J, Noone D, Cheng H, Wang Y, Yan M, Bao Y. Hydroclimate footprint of pan-Asian monsoon water isotope during the last deglaciation. SCIENCE ADVANCES 2021; 7:eabe2611. [PMID: 33523950 DOI: 10.1126/sciadv.abe2611] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 12/04/2020] [Indexed: 05/05/2023]
Abstract
Oxygen isotope speleothem records exhibit coherent variability over the pan-Asian summer monsoon (AM) region. The hydroclimatic representation of these oxygen isotope records for the AM, however, has remained poorly understood. Here, combining an isotope-enabled Earth system model in transient experiments with proxy records, we show that the widespread AM δ18Oc signal during the last deglaciation (20 to 11 thousand years ago) is accompanied by a continental-scale, coherent hydroclimate footprint, with spatially opposite signs in rainfall. This footprint is generated as a dynamically coherent response of the AM system primarily to meltwater forcing and secondarily to insolation forcing and is further reinforced by atmospheric teleconnection. Hence, widespread δ18Op depletion in the AM region is accompanied by a northward migration of the westerly jet and enhanced southwesterly monsoon wind, as well as increased rainfall from South Asia (India) to northern China but decreased rainfall in southeast China.
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Affiliation(s)
- C He
- College of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing, China
- Department of Geography, The Ohio State University, Columbus, OH, USA
- Open Studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Z Liu
- College of Geography Science, Nanjing Normal University, Nanjing, China.
- Department of Geography, The Ohio State University, Columbus, OH, USA
| | - B L Otto-Bliesner
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - E C Brady
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - C Zhu
- Open Studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
- Department of Geography, The Ohio State University, Columbus, OH, USA
| | - R Tomas
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - P U Clark
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
- School of Geography and Environmental Sciences, University of Ulster, Coleraine, Northern Ireland BT52 1SA, UK
| | - J Zhu
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - A Jahn
- Department for Atmospheric and Oceanic Sciences and Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA
| | - S Gu
- School of Oceanography, Shanghai Jiao Tong University, Shanghai, China
- Department of Geography, The Ohio State University, Columbus, OH, USA
| | - J Zhang
- Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington, Seattle, WA, USA
- NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, USA
| | - J Nusbaumer
- College of Geography Science, Nanjing Normal University, Nanjing, China
| | - D Noone
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - H Cheng
- Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an, China
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China
- Department of Earth Sciences, University of Minnesota, Minneapolis, MN, USA
| | - Y Wang
- College of Geography Science, Nanjing Normal University, Nanjing, China
| | - M Yan
- College of Geography Science, Nanjing Normal University, Nanjing, China
- Open Studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Y Bao
- Department of Geography, The Ohio State University, Columbus, OH, USA
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13
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Faria DJ, Moreira Dos Santos L, Bernard FL, Selbacch Pinto I, Carmona da Motta Resende MA, Einloft S. Dehydrating agent effect on the synthesis of dimethyl carbonate (DMC) directly from methanol and carbon dioxide. RSC Adv 2020; 10:34895-34902. [PMID: 35514376 PMCID: PMC9056860 DOI: 10.1039/d0ra06034h] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 09/15/2020] [Indexed: 11/21/2022] Open
Abstract
CO2 emissions and global warming have increased with the growth of the world economy and industrialization. Direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol (CH3OH) has been considered a promising route from a green chemistry point of view due to global warming mitigation by CO2 emission reduction. However, DMC yield, when obtained by direct synthesis, is limited due to unfavorable thermodynamics and catalyst deactivation by water formation in the reaction process. This problem motivated us to investigate the effect of dehydration on DMC production by direct synthesis. Herein, different dehydrating agents (2,2-dimethoxypropane, sodium sulfate, magnesium oxide and butylene oxide) were combined with molecular sieves to remove the water and minimize the reverse reaction. A new reactor presenting a compartment to accommodate molecular sieves in the gas phase was developed as well. The chemical/product analysis was carried out by gas chromatography and the results were used to calculate methanol conversion and DMC selectivity. The highest methanol conversion value was found for the combination of molecular sieves in the gas phase with 2,2-dimethoxypropane in the reaction liquid phase (methanol conversion = 48.6% and 88% selectivity). The results showed that dehydration systems may promote increased yield in direct DMC synthesis under mild conditions. The dehydration systems tested in this work exhibited excellent conversion and yield as compared to other reported studies. DMC was obtained from methanol and carbon dioxide and a new reactor was proposed for water removal from reaction medium.![]()
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Affiliation(s)
- Douglas José Faria
- Post-Graduation Program in Materials Engineering and Technology, Pontifical Catholic University of Rio Grande do Sul - PUCRS Brazil
| | | | | | - Ingrid Selbacch Pinto
- School of Technology, Pontifical Catholic University of Rio Grande do Sul PUCRS Brazil
| | | | - Sandra Einloft
- Post-Graduation Program in Materials Engineering and Technology, Pontifical Catholic University of Rio Grande do Sul - PUCRS Brazil .,School of Technology, Pontifical Catholic University of Rio Grande do Sul PUCRS Brazil
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14
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Ingalls M, Frantz CM, Snell KE, Trower EJ. Carbonate facies-specific stable isotope data record climate, hydrology, and microbial communities in Great Salt Lake, UT. GEOBIOLOGY 2020; 18:566-593. [PMID: 32196875 DOI: 10.1111/gbi.12386] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 01/17/2020] [Accepted: 02/27/2020] [Indexed: 06/10/2023]
Abstract
Organic and inorganic stable isotopes of lacustrine carbonate sediments are commonly used in reconstructions of ancient terrestrial ecosystems and environments. Microbial activity and local hydrological inputs can alter porewater chemistry (e.g., pH, alkalinity) and isotopic composition (e.g., δ18 Owater , δ13 CDIC ), which in turn has the potential to impact the stable isotopic compositions recorded and preserved in lithified carbonate. The fingerprint these syngenetic processes have on lacustrine carbonate facies is yet unknown, however, and thus, reconstructions based on stable isotopes may misinterpret diagenetic records as broader climate signals. Here, we characterize geochemical and stable isotopic variability of carbonate minerals, organic matter, and water within one modern lake that has known microbial influences (e.g., microbial mats and microbialite carbonate) and combine these data with the context provided by 16S rRNA amplicon sequencing community profiles. Specifically, we measure oxygen, carbon, and clumped isotopic compositions of carbonate sediments (δ18 Ocarb , δ13 Ccarb , ∆47 ), as well as carbon isotopic compositions of bulk organic matter (δ13 Corg ) and dissolved inorganic carbon (DIC; δ13 CDIC ) of lake and porewater in Great Salt Lake, Utah from five sites and three seasons. We find that facies equivalent to ooid grainstones provide time-averaged records of lake chemistry that reflect minimal alteration by microbial activity, whereas microbialite, intraclasts, and carbonate mud show greater alteration by local microbial influence and hydrology. Further, we find at least one occurrence of ∆47 isotopic disequilibrium likely driven by local microbial metabolism during authigenic carbonate precipitation. The remainder of the carbonate materials (primarily ooids, grain coatings, mud, and intraclasts) yield clumped isotope temperatures (T(∆47 )), δ18 Ocarb , and calculated δ18 Owater in isotopic equilibrium with ambient water and temperature at the time and site of carbonate precipitation. Our findings suggest that it is possible and necessary to leverage diverse carbonate facies across one sedimentary horizon to reconstruct regional hydroclimate and evaporation-precipitation balance, as well as identify microbially mediated carbonate formation.
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Affiliation(s)
- Miquela Ingalls
- Department of Geological Sciences, University of Colorado, Boulder, CO, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Carie M Frantz
- Department of Earth & Environmental Sciences, Weber State University, Ogden, UT, USA
| | - Kathryn E Snell
- Department of Geological Sciences, University of Colorado, Boulder, CO, USA
| | - Elizabeth J Trower
- Department of Geological Sciences, University of Colorado, Boulder, CO, USA
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15
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Miller KG, Browning JV, Schmelz WJ, Kopp RE, Mountain GS, Wright JD. Cenozoic sea-level and cryospheric evolution from deep-sea geochemical and continental margin records. SCIENCE ADVANCES 2020; 6:eaaz1346. [PMID: 32440543 PMCID: PMC7228749 DOI: 10.1126/sciadv.aaz1346] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 03/16/2020] [Indexed: 05/14/2023]
Abstract
Using Pacific benthic foraminiferal δ18O and Mg/Ca records, we derive a Cenozoic (66 Ma) global mean sea level (GMSL) estimate that records evolution from an ice-free Early Eocene to Quaternary bipolar ice sheets. These GMSL estimates are statistically similar to "backstripped" estimates from continental margins accounting for compaction, loading, and thermal subsidence. Peak warmth, elevated GMSL, high CO2, and ice-free "Hothouse" conditions (56 to 48 Ma) were followed by "Cool Greenhouse" (48 to 34 Ma) ice sheets (10 to 30 m changes). Continental-scale ice sheets ("Icehouse") began ~34 Ma (>50 m changes), permanent East Antarctic ice sheets at 12.8 Ma, and bipolar glaciation at 2.5 Ma. The largest GMSL fall (27 to 20 ka; ~130 m) was followed by a >40 mm/yr rise (19 to 10 ka), a slowing (10 to 2 ka), and a stillstand until ~1900 CE, when rates began to rise. High long-term CO2 caused warm climates and high sea levels, with sea-level variability dominated by periodic Milankovitch cycles.
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Affiliation(s)
- Kenneth G. Miller
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
- Corresponding author.
| | - James V. Browning
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - W. John Schmelz
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - Robert E. Kopp
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - Gregory S. Mountain
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - James D. Wright
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
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16
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Exceptional Multi Stage Mineralization of Secondary Minerals in Cavities of Flood Basalts from the Deccan Volcanic Province, India. MINERALS 2019. [DOI: 10.3390/min9060351] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Flood basalts of the Deccan Volcanic Province erupted between about 67.5 to 60.5 Ma ago and reached a thickness of up to 3500 m. The main part consists of compound and simple lava flows with a tholeiitic composition erupted within 500,000 years at about 65 Ma. Within the compound lava flows, vesicles and cavities are frequent. They are filled by secondary minerals partly of well development and large size. This study presents data on the secondary mineralization including detailed field descriptions, optical, cathodoluminescence and SEM microscopy, X-ray diffractometry, fluid inclusions, C and O isotope analyses, and Rb-Sr and K-Ar geochronology. The investigations indicate a multistage precipitation sequence with three main stages. During stage I clay minerals and subsurface filamentous fabrics (SFFs), of probably biogenic origin, formed after the lava flows cooled down near to the Earth’s surface. In stage II, first an assemblage of calcite (I) and zeolite (I) (including mordenite, heulandite, and stilbite) as well as plagioclase was overgrown by chalcedony, and finally a second calcite (II) and zeolite (II) generation developed by burial metamorphism by subsequent lava flows. Stage III is characterized by precipitation of a third calcite (III) generation together with powellite and apophyllite from late hydrothermal fluids. Rb-Sr and K-Ar ages of apophyllite indicate a large time span for stage III. Apophyllite formed within different time intervals from the Paleogene to the early Miocene even within individual lava flows at certain localities. From the Savda/Jalgaon quarry complex, ages cluster at 44–48 Ma and 25–28 Ma, whereas those from the Nashik area are 55–58 Ma and 21–23 Ma, respectively.
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17
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Meyer-Dombard DR, Osburn MR, Cardace D, Arcilla CA. The Effect of a Tropical Climate on Available Nutrient Resources to Springs in Ophiolite-Hosted, Deep Biosphere Ecosystems in the Philippines. Front Microbiol 2019; 10:761. [PMID: 31118921 PMCID: PMC6504838 DOI: 10.3389/fmicb.2019.00761] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 03/26/2019] [Indexed: 11/13/2022] Open
Abstract
Springs hosted in ophiolites are often affected by serpentinization processes. The characteristically low DIC and high CH4 and H2 gas concentrations of serpentinizing ecosystems have led to interest in hydrogen based metabolisms in these subsurface biomes. However, a true subsurface signature can be difficult to identify in surface expressions such as serpentinizing springs. Here, we explore carbon and nitrogen resources in serpentinization impacted springs in the tropical climate of the Zambales and Palawan ophiolites in the Philippines, with a focus on surface vs. subsurface processes and exogenous vs. endogenous nutrient input. Isotopic signatures in spring fluids, biomass, and carbonates were examined to identify sources and sinks of carbon and nitrogen, carbonate geochemistry, and the effect of seasonal precipitation. Seasonality affected biomass production in both low flow and high flow spring systems. Changes in meteorological precipitation affected δ13CDIC and δ13CDOC values of the spring fluids, which reflected seasonal gain/loss of atmospheric influence and changes in exogenous DOC input. The primary carbon source in high flow systems was variable, with DOC contributing to biomass in many springs, and a mix of DIC and carbonates contributing to biomass in select locations. However, primary carbon resources in low flow systems may depend more on endogenous than exogenous carbon, even in high precipitation seasons. Isotopic evidence for nitrogen fixation was identified, with seasonal influence only seen in low flow systems. Carbonate formation was found to occur as a mixture of recrystallization/recycling of older carbonates and rapid mineral precipitation (depending on the system), with highly δ13C and δ18O depleted carbonates occurring in many locations. Subsurface signatures (e.g., low DOC influence on Cbiomass) were most apparent in the driest seasons and lowest flow systems, indicating locations where metabolic processes divorced from surface influences (including hydrogen based metabolisms) are most likely to be occurring.
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Affiliation(s)
- D'Arcy R Meyer-Dombard
- Department of Earth and Environmental Sciences, The University of Illinois at Chicago, Chicago, IL, United States
| | - Magdelena R Osburn
- Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL, United States
| | - Dawn Cardace
- Department of Geosciences, The University of Rhode Island, Kingston, RI, United States
| | - Carlo A Arcilla
- Director of Science and Technology-Philippine Nuclear Research Institute, Manilla, Philippines
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18
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Hausmann N, Prendergast AL, Lemonis A, Zech J, Roberts P, Siozos P, Anglos D. Extensive elemental mapping unlocks Mg/Ca ratios as climate proxy in seasonal records of Mediterranean limpets. Sci Rep 2019; 9:3698. [PMID: 30842602 PMCID: PMC6403426 DOI: 10.1038/s41598-019-39959-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 01/23/2019] [Indexed: 11/09/2022] Open
Abstract
Elemental analysis of biogeochemical archives is an established technique used to study climate in a range of applications, including ocean circulation, glacial/interglacial climates, and anthropogenic climate change. Data from mollusc archives are especially important because of their global abundance and sub-annual resolution. Despite this potential, they are underrepresented among palaeoclimate studies, due to enigmatic physiological influences skewing the elemental record. Understanding the patterns behind these influences will improve data interpretation and lead to the development of new climate proxies. Here, we show for the first time that extensive spatial mapping of multiple mollusc specimens using Laser Induced Breakdown Spectroscopy (LIBS) across a wider region can resolve enigmatic patterns within the elemental record caused by physiological influences. 2D elemental (Mg/Ca) maps of whole limpet shells (Patella caerulea) from across the Mediterranean revealed patterns of variability within individual mollusc records as well as within isochronous parts of specimens. By registering and quantifying these patterns, we established previously uninterpretable correlations with temperature (R2 > 0.8, p < 0.01). This outcome redefines the possibilities of accessing sub-annual climate proxies and presents the means to assess annual temperature ranges using oxygen isotope analysis requiring only 2 samples per shell.
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Affiliation(s)
- N Hausmann
- Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, Heraklion, Greece. .,BioArCh, Department of Archaeology, University of York, York, United Kingdom. .,Department of Archaeology, Max Planck Institute for the Science of Human History, Jena, Germany.
| | - A L Prendergast
- School of Geography, University of Melbourne, Melbourne, Australia
| | - A Lemonis
- Department of Chemistry, University of Crete, Heraklion, Greece
| | - J Zech
- Department of Archaeology, Max Planck Institute for the Science of Human History, Jena, Germany
| | - P Roberts
- Department of Archaeology, Max Planck Institute for the Science of Human History, Jena, Germany
| | - P Siozos
- Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, Heraklion, Greece
| | - D Anglos
- Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, Heraklion, Greece.,Department of Chemistry, University of Crete, Heraklion, Greece
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19
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Daëron M, Drysdale RN, Peral M, Huyghe D, Blamart D, Coplen TB, Lartaud F, Zanchetta G. Most Earth-surface calcites precipitate out of isotopic equilibrium. Nat Commun 2019; 10:429. [PMID: 30683869 PMCID: PMC6347637 DOI: 10.1038/s41467-019-08336-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 01/03/2019] [Indexed: 11/25/2022] Open
Abstract
Oxygen-isotope thermometry played a critical role in the rise of modern geochemistry and remains extensively used in (bio-)geoscience. Its theoretical foundations rest on the assumption that 18O/16O partitioning among water and carbonate minerals primarily reflects thermodynamic equilibrium. However, after decades of research, there is no consensus on the true equilibrium 18O/16O fractionation between calcite and water (18αcc/w). Here, we constrain the equilibrium relations linking temperature, 18αcc/w, and clumped isotopes (Δ47) based on the composition of extremely slow-growing calcites from Devils Hole and Laghetto Basso (Corchia Cave). Equilibrium 18αcc/w values are systematically ~1.5‰ greater than those in biogenic and synthetic calcite traditionally considered to approach oxygen-isotope equilibrium. We further demonstrate that subtle disequilibria also affect Δ47 in biogenic calcite. These observations provide evidence that most Earth-surface calcites fail to achieve isotopic equilibrium, highlighting the need to improve our quantitative understanding of non-equilibrium isotope fractionation effects instead of relying on phenomenological calibrations. Isotopic thermometry of carbonate minerals postulates that their composition reflects thermodynamic equilibrium constants. Here the authors constrain equilibrium relationships between temperature, 18O/16O and clumped isotopes and find that most natural calcites form out of isotopic equilibrium.
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Affiliation(s)
- M Daëron
- Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Orme des Merisiers, F-91191, Gif-sur-Yvette Cedex, France.
| | - R N Drysdale
- School of Geography, The University of Melbourne, 221 Bouverie Street, Carlton, VIC, 3053, Australia.,EDYTEM UMR CNRS 5204, Bâtiment "Pôle Montagne", Université Savoie Mont Blanc, 5 bd de la Mer Caspienne, F-73376, Le Bourget du Lac Cedex, France
| | - M Peral
- Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Orme des Merisiers, F-91191, Gif-sur-Yvette Cedex, France
| | - D Huyghe
- Laboratoire d'Ecogéochimie des Environnements Benthiques, LECOB, Sorbonne Université, CNRS, F-66650, Banyuls-sur-mer, France.,Géosciences Environnement Toulouse, UMR 5563 CNRS, UR 234 IRD, UM 97 UPS, Observatoire Midi-Pyrénées, CNES, 14 avenue Édouard Belin, 31400, Toulouse, France.,Centre de Géosciences, MINES ParisTech, PSL University, 35 rue St Honoré, 77305, Fontainebleau Cedex, France
| | - D Blamart
- Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Orme des Merisiers, F-91191, Gif-sur-Yvette Cedex, France
| | - T B Coplen
- U.S. Geological Survey, 12201 Sunrise Valley Drive, Reston, VA, 20192, USA
| | - F Lartaud
- Laboratoire d'Ecogéochimie des Environnements Benthiques, LECOB, Sorbonne Université, CNRS, F-66650, Banyuls-sur-mer, France
| | - G Zanchetta
- Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126, Pisa, Italy
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20
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Enhanced climate instability in the North Atlantic and southern Europe during the Last Interglacial. Nat Commun 2018; 9:4235. [PMID: 30315157 PMCID: PMC6185935 DOI: 10.1038/s41467-018-06683-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 09/19/2018] [Indexed: 11/11/2022] Open
Abstract
Considerable ambiguity remains over the extent and nature of millennial/centennial-scale climate instability during the Last Interglacial (LIG). Here we analyse marine and terrestrial proxies from a deep-sea sediment sequence on the Portuguese Margin and combine results with an intensively dated Italian speleothem record and climate-model experiments. The strongest expression of climate variability occurred during the transitions into and out of the LIG. Our records also document a series of multi-centennial intra-interglacial arid events in southern Europe, coherent with cold water-mass expansions in the North Atlantic. The spatial and temporal fingerprints of these changes indicate a reorganization of ocean surface circulation, consistent with low-intensity disruptions of the Atlantic meridional overturning circulation (AMOC). The amplitude of this LIG variability is greater than that observed in Holocene records. Episodic Greenland ice melt and runoff as a result of excess warmth may have contributed to AMOC weakening and increased climate instability throughout the LIG. It is important to establish a baseline for natural climate variability under relatively warm conditions. Here we show that the Last Interglacial in the North Atlantic and southern Europe was characterized by enhanced climate instability relative to the pre-industrial Holocene.
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21
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Abstract
There is a fundamental ecologic differentiation between zooxanthellate and non-zooxanthellate corals. This paper reviews factors which govern the stable carbon and oxygen isotopic composition of these groups of corals. Although the stable carbon and oxygen isotope compositions of coral skeletons are strongly influenced by environmental and physiological factors, the precise mechanisms remain a matter of debate. In particular the oxygen isotopic composition is known to be governed by the temperature and the oxygen isotopic composition of the water and perhaps also by kinetic factors. In contrast the carbon isotopic composition is controlled by a combination of photosynthesis, respiration, autotrophy, heterotrophy, and the isotopic composition of dissolved inorganic carbon. Using a combination of carbon and oxygen isotopes it is possible to distinguish zooxanthellate from non-zooxanthellate corals.
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Abstract
Clumped isotopes geochemistry measures the thermodynamic preference of two heavy, rare, isotopes to bind with each other. This preference is temperature dependent, and is more pronounced at low temperatures. Carbonate clumped isotope values are independent of the carbonate δ13C and δ18O, making them independent of the carbon or oxygen composition of the solution from which the carbonate precipitated. At equilibrium, it is therefore a direct proxy for the temperature in which the carbonate mineral formed. In most cases, carbonate clumped isotopes record the temperature of carbonate formation, irrespective of the mineral form (calcite, aragonite, or bioapatite) or the organism making it. The carbonate formation temperatures obtained from carbonate clumped isotope analysis can be used in conjunction with the δ18O of the same carbonate, to constrain the oxygen isotope composition of the water from which the carbonate has precipitated. There are, however, cases of deviation from thermodynamic equilibrium, where both clumped and oxygen isotopes are offset from the expected values. Such carbonates must be characterized and calibrated separately. For deep-time applications, special care must be paid to the preservation of the original signal, in particular with respect to diagenetic alteration associated with atomic scale diffusion that may be undetectable by common tests for diagenesis.
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Abstract
Foraminiferal tests are a common component of many marine sediments. The oxygen isotope ratio (δ18O) of test calcite is frequently used to reconstruct aspects of their life environment. The δ18O depends mainly on the isotope ratio of the water it is precipitated from, the temperature of calcification, and, to a lesser extent, the carbonate ion concentration. Foraminifera and other organisms can potentially preserve their original isotope ratio for many millions of years, although diagenetic processes can alter the ratios. Work on oxygen isotope ratios of foraminifera was instrumental in the discovery of the orbital theory of the ice ages and continues to be widely used in the study of rapid climate change. Compilations of deep sea benthic foraminifer oxygen isotopes have revealed the long history of global climate change over the past 100 million years. Planktonic foraminifer oxygen isotopes are used to investigate the history of past sea surface temperatures, revealing the extent of past ‘greenhouse’ warming and global sea surface temperatures.
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Abstract
Oxygen isotope paleotemperature studies of the Mesozoic and Paleozoic are based mainly on conodonts, belemnite guards, and brachiopod shells—material resistant to diagenesis and generally precipitated in oxygen isotope equilibrium with ambient water. The greatest obstacle to accurate oxygen isotope paleothermometry in deep time is uncertainty in the oxygen isotopic composition of the ambient seawater. The second greatest obstacle is fossil diagenesis. Useful application of the oxygen isotope method to brachiopod shells requires extreme care in sample screening and analyses, and is best done with scanning-electron microscopy, and petrographic and cathodoluminescence microscopy, and trace-element analysis. Correct interpretation of oxygen isotope data is greatly aided by thorough understanding of the paleolatitude, paleoecology, and depositional environment of the samples. The oxygen isotope record for the Triassic, based on brachiopod shells, is too sparse to show any distinct isotopic features. Jurassic and Early Cretaceous δ18O records, based on belemnites, show a Toarcian (Jurassic) decline (warming), a Callovian-Oxfordian acme, and an Early Cretaceous increase (cooling) to a Valanginian-Hauterivian maximum, followed by a decline (warming) to a middle Barremian minimum. Deep-time applications to oxygen isotope thermometry provide evidence for cooling and glaciation in the Ordovician, Carboniferous, and Permian. The δ18O values from Silurian and Devonian brachiopod shells and conodonts average lower than those of the remaining Phanerozoic because of the absence of continental glaciers and possibly higher temperatures (~37°?), although slightly lower (≤2%o) seawater δ18O cannot be ruled out. The hypothesis of high temperatures in the early Paleozoic implies a relatively constant hydrospheric δ18O, which is supported by clumped isotope paleotemperatures. However, more research is needed to develop methods for evaluating clumped isotope reordering in fossils. Ongoing and future research in oxygen isotope and clumped isotope thermometry hold the promise of resolving deep-time temperatures, seawater δ18O, and salinity with heretofore unavailable accuracy (±2°, ±0.4%o, and ±2 psu), providing the environmental setting for the evolution of metazoan life on Earth.
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25
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The Hydrothermal Fluid Evolution of Vein Sets at the Pipeline Gold Mine, Nevada. MINERALS 2017. [DOI: 10.3390/min7060100] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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26
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Demény A, Németh P, Czuppon G, Leél-Őssy S, Szabó M, Judik K, Németh T, Stieber J. Formation of amorphous calcium carbonate in caves and its implications for speleothem research. Sci Rep 2016; 6:39602. [PMID: 28004767 PMCID: PMC5177889 DOI: 10.1038/srep39602] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 11/24/2016] [Indexed: 11/13/2022] Open
Abstract
Speleothem deposits are among the most valuable continental formations in paleoclimate research, as they can be dated using absolute dating methods, and they also provide valuable climate proxies. However, alteration processes such as post-depositional mineralogical transformations can significantly influence the paleoclimatic application of their geochemical data. An innovative sampling and measurement protocol combined with scanning and transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy is presented, demonstrating that carbonate precipitating from drip water in caves at ~10 °C contains amorphous calcium carbonate (ACC) that later transforms to nanocrystalline calcite. Stable oxygen isotope fractionations among calcite, ACC and water were also determined, proving that ACC is 18O-depleted (by >2.4 ± 0.8‰) relative to calcite. This, in turn, has serious consequences for speleothem-based fluid inclusion research as closed system transformation of ACC to calcite may induce a negative oxygen isotope shift in fluid inclusion water, resulting in deterioration of the original compositions. ACC formation increases the speleothems' sensitivity to alteration as its interaction with external solutions may result in the partial loss of original proxy signals. Mineralogical analysis of freshly precipitating carbonate at the studied speleothem site is suggested in order to determine the potential influence of ACC formation.
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Affiliation(s)
- Attila Demény
- Institute for Geological and Geochemical Research, RCAES, Hungarian Academy of Sciences, Budaörsi út 45, Budapest, H-1112, Hungary
| | - Péter Németh
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2., Budapest, H- 1117, Hungary
| | - György Czuppon
- Institute for Geological and Geochemical Research, RCAES, Hungarian Academy of Sciences, Budaörsi út 45, Budapest, H-1112, Hungary
| | - Szabolcs Leél-Őssy
- Department of Physical and Applied Geology, Eötvös Loránd University, Pázmány Péter sétány. 1/C, Budapest, H-1117, Hungary
| | - Máté Szabó
- Institute for Geological and Geochemical Research, RCAES, Hungarian Academy of Sciences, Budaörsi út 45, Budapest, H-1112, Hungary
| | - Katalin Judik
- Institute for Geological and Geochemical Research, RCAES, Hungarian Academy of Sciences, Budaörsi út 45, Budapest, H-1112, Hungary
| | - Tibor Németh
- Institute for Geological and Geochemical Research, RCAES, Hungarian Academy of Sciences, Budaörsi út 45, Budapest, H-1112, Hungary
| | - József Stieber
- Stieber Environmental Ltd., Nyerges u. 6., Budapest, H-1181, Hungary
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Thin MM, Sacchi E, Setti M. Hydrological processes at Inle Lake (Southern Shan State, Myanmar) inferred from hydrochemical, mineralogical and isotopic data. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2016; 52:455-467. [PMID: 26999492 DOI: 10.1080/10256016.2015.1130038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 10/14/2015] [Indexed: 06/05/2023]
Abstract
A one-year hydrochemical and isotopic monitoring was conducted at the Inle Lake, the second largest lake in Myanmar, also considering sediment samples. Lake waters are characterised by low electrical conductivities (236-489 μS/cm), neutral to alkaline pH (7.36-9.26), oxidising Eh (329-457 mV) and Ca-Mg-HCO3 facies. Stable isotopes indicate that lake waters are only slightly affected by evaporation, are fully flushed yearly and are not stratified. Carbonate equilibria dominate the lake water hydrochemistry. In summer, photosynthetic activity and temperature increase induce calcite precipitation, as testified by its high content in the sediments, up to 97 %, and by its isotopic composition. The short residence time and endogenic calcite precipitation likely prevent the accumulation of contaminants and nutrients in lake waters. This study suggests a high resilience of the system to anthropogenic disturbances and demonstrates the sediment potential for the reconstruction of the environmental evolution in time and for the anthropogenic impact assessment.
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Affiliation(s)
- Myat Mon Thin
- a Department of Physics , University of Mandalay , Mandalay , Myanmar
| | - Elisa Sacchi
- b Department of Earth and Environmental Sciences , University of Pavia , Pavia , Italy
| | - Massimo Setti
- b Department of Earth and Environmental Sciences , University of Pavia , Pavia , Italy
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Rasmussen CMØ, Ullmann CV, Jakobsen KG, Lindskog A, Hansen J, Hansen T, Eriksson ME, Dronov A, Frei R, Korte C, Nielsen AT, Harper DAT. Onset of main Phanerozoic marine radiation sparked by emerging Mid Ordovician icehouse. Sci Rep 2016; 6:18884. [PMID: 26733399 PMCID: PMC4702064 DOI: 10.1038/srep18884] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 11/30/2015] [Indexed: 11/21/2022] Open
Abstract
The Great Ordovician Biodiversification Event (GOBE) was the most rapid and sustained increase in marine Phanerozoic biodiversity. What generated this biotic response across Palaeozoic seascapes is a matter of debate; several intrinsic and extrinsic drivers have been suggested. One is Ordovician climate, which in recent years has undergone a paradigm shift from a text-book example of an extended greenhouse to an interval with transient cooling intervals – at least during the Late Ordovician. Here, we show the first unambiguous evidence for a sudden Mid Ordovician icehouse, comparable in magnitude to the Quaternary glaciations. We further demonstrate the initiation of this icehouse to coincide with the onset of the GOBE. This finding is based on both abiotic and biotic proxies obtained from the most comprehensive geochemical and palaeobiological dataset yet collected through this interval. We argue that the icehouse conditions increased latitudinal and bathymetrical temperature and oxygen gradients initiating an Early Palaeozoic Great Ocean Conveyor Belt. This fuelled the GOBE, as upwelling zones created new ecospace for the primary producers. A subsequent rise in δ13C ratios known as the Middle Darriwilian Isotopic Carbon Excursion (MDICE) may reflect a global response to increased bioproductivity encouraged by the onset of the GOBE.
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Affiliation(s)
- Christian M Ø Rasmussen
- Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark.,Department of Geology, Lund University, Sölvegatan 12, S-223 62 Lund, Sweden.,Center for Macroecology, Evolution and Climate, University of Copenhagen
| | - Clemens V Ullmann
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark.,Camborne School of Mines, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE, U.K
| | - Kristian G Jakobsen
- Ministry of Mineral Resources, Maneq 1A, 201, P.O. Box 930, 3900 Nuuk, Greenland
| | - Anders Lindskog
- Department of Geology, Lund University, Sölvegatan 12, S-223 62 Lund, Sweden
| | - Jesper Hansen
- Akvaplan-Niva, High North Research Centre 9296 Tromsø, Norway
| | - Thomas Hansen
- Akvaplan-Niva, High North Research Centre 9296 Tromsø, Norway
| | - Mats E Eriksson
- Department of Geology, Lund University, Sölvegatan 12, S-223 62 Lund, Sweden
| | - Andrei Dronov
- Geological Institute of the Russian Academy of Sciences, Moscow, Russian Federation
| | - Robert Frei
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark.,Nordic Center for Earth Evolution (NordCEE), University of Copenhagen
| | - Christoph Korte
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark
| | - Arne T Nielsen
- Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark
| | - David A T Harper
- Palaeoecosystems Group, Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
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Korte C, Hesselbo SP, Ullmann CV, Dietl G, Ruhl M, Schweigert G, Thibault N. Jurassic climate mode governed by ocean gateway. Nat Commun 2015; 6:10015. [PMID: 26658694 PMCID: PMC4682040 DOI: 10.1038/ncomms10015] [Citation(s) in RCA: 138] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Accepted: 10/26/2015] [Indexed: 11/30/2022] Open
Abstract
The Jurassic (∼201–145 Myr ago) was long considered a warm ‘greenhouse' period; more recently cool, even ‘icehouse' episodes have been postulated. However, the mechanisms governing transition between so-called Warm Modes and Cool Modes are poorly known. Here we present a new large high-quality oxygen-isotope dataset from an interval that includes previously suggested mode transitions. Our results show an especially abrupt earliest Middle Jurassic (∼174 Ma) mid-latitude cooling of seawater by as much as 10 °C in the north–south Laurasian Seaway, a marine passage that connected the equatorial Tethys Ocean to the Boreal Sea. Coincidence in timing with large-scale regional lithospheric updoming of the North Sea region is striking, and we hypothesize that northward oceanic heat transport was impeded by uplift, triggering Cool Mode conditions more widely. This extreme climate-mode transition provides a counter-example to other Mesozoic transitions linked to quantitative change in atmospheric greenhouse gas content. Dynamics of the Laurasian Seaway are thought to have had wide effects on oceanography and climate in the mid-Mesozoic. Here, the authors show evidence for seawater temperature change, ascribed to tectonic uplift that impeded poleward oceanic heat transport and triggered a cool climate mode in the earliest Middle Jurassic.
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Affiliation(s)
- Christoph Korte
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen-K, Denmark
| | - Stephen P Hesselbo
- Camborne School of Mines and Environment and Sustainability Institute, University of Exeter, Penryn Campus, Treliever Road, Penryn, Cornwall TR10 9FE, UK
| | - Clemens V Ullmann
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen-K, Denmark.,Camborne School of Mines and Environment and Sustainability Institute, University of Exeter, Penryn Campus, Treliever Road, Penryn, Cornwall TR10 9FE, UK
| | - Gerd Dietl
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany
| | - Micha Ruhl
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - Günter Schweigert
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany
| | - Nicolas Thibault
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen-K, Denmark
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30
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Linking megathrust earthquakes to brittle deformation in a fossil accretionary complex. Nat Commun 2015; 6:7504. [PMID: 26105966 PMCID: PMC4491836 DOI: 10.1038/ncomms8504] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 05/13/2015] [Indexed: 11/08/2022] Open
Abstract
Seismological data from recent subduction earthquakes suggest that megathrust earthquakes induce transient stress changes in the upper plate that shift accretionary wedges into an unstable state. These stress changes have, however, never been linked to geological structures preserved in fossil accretionary complexes. The importance of coseismically induced wedge failure has therefore remained largely elusive. Here we show that brittle faulting and vein formation in the palaeo-accretionary complex of the European Alps record stress changes generated by subduction-related earthquakes. Early veins formed at shallow levels by bedding-parallel shear during coseismic compression of the outer wedge. In contrast, subsequent vein formation occurred by normal faulting and extensional fracturing at deeper levels in response to coseismic extension of the inner wedge. Our study demonstrates how mineral veins can be used to reveal the dynamics of outer and inner wedges, which respond in opposite ways to megathrust earthquakes by compressional and extensional faulting, respectively.
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Zheng YF. Oxygen isotope fractionation in phosphates: the role of dissolved complex anions in isotope exchange. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2015; 52:47-60. [PMID: 25587823 DOI: 10.1080/10256016.2014.999678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Oxygen isotope fractionation factors for phosphates were calculated by means of the increment method. The results suggest that Ag3PO4 and BiPO4 are enriched in (18)O relative to AgPO4, and the three phosphates are consistently depleted in (18)O relative to Ba3[PO4]2; fluorapatite and chlorapatite exhibit a similar behaviour of oxygen isotope fractionation with consistent enrichment of (18)O relative to hydroxyapatite. The valence, radii and coordination of metal cations play a quantitative role in dictating the (18)O/(16)O partitioning in these phosphates of different compositions. The calculated fractionation factors for the Ag3PO4-H2O system are in agreement with experimental determinations derived from enzyme-catalysed isotope exchange between dissolved inorganic phosphate and water at the longest reaction durations at low temperatures. This demonstrates that the precipitated Ag3PO4 has completely captured the oxygen isotope fractionation in the dissolved inorganic phosphate. The calculated fractionation factors for the F/Cl-apatite-water systems are in agreement with the enzyme-catalysed experimental fractionations for the dissolved phosphate-water system at the longest reaction durations but larger than fractionations derived from bacteria-facilitated exchange and inorganic precipitation experiments as well as natural observations. For the experimental calibrations of oxygen isotope fractionation involving the precipitation of dissolved phosphate species from aqueous solutions, the fractionation between precipitate and water is primarily dictated by the isotope equilibration between the dissolved complex anions and water prior to the precipitation. Therefore, the present results provide a quantitative means to interpret the temperature dependence of oxygen isotope fractionation in inorganic and biogenic phosphates.
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Affiliation(s)
- Yong-Fei Zheng
- a CAS Kay Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences , University of Science and Technology of China , Hefei , People's Republic of China
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32
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Kruta I, Landman NH, Cochran JK. A new approach for the determination of ammonite and nautilid habitats. PLoS One 2014; 9:e87479. [PMID: 24475295 PMCID: PMC3903699 DOI: 10.1371/journal.pone.0087479] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 12/22/2013] [Indexed: 11/18/2022] Open
Abstract
Externally shelled cephalopods were important elements in open marine habitats throughout Earth history. Paleotemperatures calculated on the basis of the oxygen isotope composition of their shells can provide insights into ancient marine systems as well as the ecology of this important group of organisms. In some sedimentary deposits, however, the aragonitic shell of the ammonite or nautilid is poorly or not preserved at all, while the calcitic structures belonging to the jaws are present. This study tests for the first time if the calcitic jaw structures in fossil cephalopods can be used as a proxy for paleotemperature. We first analyzed the calcitic structures on the jaws of Recent Nautilus and compared the calculated temperatures of precipitation with those from the aragonitic shell in the same individuals. Our results indicate that the jaws of Recent Nautilus are secreted in isotopic equilibrium, and the calculated temperatures approximately match those of the shell. We then extended our study to ammonites from the Upper Cretaceous (Campanian) Pierre Shale of the U.S. Western Interior and the age-equivalent Mooreville Chalk of the Gulf Coastal Plain. In the Pierre Shale, jaws occur in situ inside the body chambers of well-preserved Baculites while in the Mooreville Chalk, the jaw elements appear as isolated occurrences in the sediment and the aragonitic shell material is not preserved. For the Pierre Shale specimens, the calculated temperatures of well-preserved jaw material match those of well-preserved shell material in the same individual. Analyses of the jaw elements in the Mooreville Chalk permit a comparison of the paleotemperatures between the two sites, and show that the Western Interior is warmer than the Gulf Coast at that time. In summary, our data indicate that the calcitic jaw elements of cephalopods can provide a reliable geochemical archive of the habitat of fossil forms.
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Affiliation(s)
- Isabelle Kruta
- Division of Paleontology American Museum of Natural History, New York, New York, United States of America
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut, United States of America
- * E-mail:
| | - Neil H. Landman
- Division of Paleontology American Museum of Natural History, New York, New York, United States of America
| | - J. Kirk Cochran
- School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York, United States of America
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Miller KG, Wright JD, Fairbanks RG. Unlocking the Ice House: Oligocene-Miocene oxygen isotopes, eustasy, and margin erosion. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/90jb02015] [Citation(s) in RCA: 767] [Impact Index Per Article: 63.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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34
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O'Neil JR, Hanks TC. Geochemical evidence for water-rock interaction along the San Andreas and Garlock Faults of California. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/jb085ib11p06286] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lawrence JR, Drever JI. Evidence for cold water circulation at DSDP site 395: Isotopes and chemistry of alteration products. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/jb086ib06p05125] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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36
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37
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Zoheir BA. Microchemistry and stable isotope systematics of gold mineralization in a gabbro–diorite complex, SE Egypt. Microchem J 2012. [DOI: 10.1016/j.microc.2012.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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38
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Zavadlav S, Mazej D, Zavašnik J, Rečnik A, Dominguez-Víllar D, Cukrov N, Lojen S. C and O stable isotopic signatures of fast-growing dripstones on alkaline substrates: reflection of growth mechanism, carbonate sources and environmental conditions. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2012; 48:354-371. [PMID: 22316094 DOI: 10.1080/10256016.2012.645540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Secondary carbonate precipitates (dripstones) formed on concrete surfaces in four different environments--Mediterranean and continental open-space and indoor environments (inside a building and in a karstic cave)--were studied. The fabric of dripstones depends upon water supply, pH of mother solution and carbonate-resulting precipitation rate. Very low δ(13)C (average-28.2‰) and δ(18)O (average-18.4‰) values showed a strong positive correlation, typical for carbonate precipitated by rapid dissolution of CO(2) in a highly alkaline solution and consequent disequilibrium precipitation of CaCO(3). The main source of carbon is atmospheric or biogenic CO(2) in the poorly ventilated karstic cave, which is reflected in even lower δ(13)C values. Statistical analysis of δ(13)C and δ(18)O values of the four groups of samples showed that the governing factor of isotope fractionation is not the temperature, but rather the precipitation rate.
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Affiliation(s)
- Saša Zavadlav
- Department of Environmental Sciences, Jožef Stefan Institute, Ljubljana, Slovenia.
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Cramer BS, Miller KG, Barrett PJ, Wright JD. Late Cretaceous–Neogene trends in deep ocean temperature and continental ice volume: Reconciling records of benthic foraminiferal geochemistry (δ18O and Mg/Ca) with sea level history. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011jc007255] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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40
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Ice-shelf collapse from subsurface warming as a trigger for Heinrich events. Proc Natl Acad Sci U S A 2011; 108:13415-9. [PMID: 21808034 DOI: 10.1073/pnas.1104772108] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Episodic iceberg-discharge events from the Hudson Strait Ice Stream (HSIS) of the Laurentide Ice Sheet, referred to as Heinrich events, are commonly attributed to internal ice-sheet instabilities, but their systematic occurrence at the culmination of a large reduction in the Atlantic meridional overturning circulation (AMOC) indicates a climate control. We report Mg/Ca data on benthic foraminifera from an intermediate-depth site in the northwest Atlantic and results from a climate-model simulation that reveal basin-wide subsurface warming at the same time as large reductions in the AMOC, with temperature increasing by approximately 2 °C over a 1-2 kyr interval prior to a Heinrich event. In simulations with an ocean model coupled to a thermodynamically active ice shelf, the increase in subsurface temperature increases basal melt rate under an ice shelf fronting the HSIS by a factor of approximately 6. By analogy with recent observations in Antarctica, the resulting ice-shelf loss and attendant HSIS acceleration would produce a Heinrich event.
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Breitenbach SFM, Bernasconi SM. Carbon and oxygen isotope analysis of small carbonate samples (20 to 100 µg) with a GasBench II preparation device. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2011; 25:1910-1914. [PMID: 21638367 DOI: 10.1002/rcm.5052] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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42
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Pokrovskaya OB, Litvin KE, Pokrovsky BG. The isotope composition of carbon and oxygen in eggshell of barnacle goose Branta leucopsis. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2011; 437:124-7. [PMID: 21562962 DOI: 10.1134/s0012496611020165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Indexed: 11/23/2022]
Affiliation(s)
- O B Pokrovskaya
- Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 117071, Russia
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Wendeberg M, Richter JM, Rothe M, Brand WA. δ18O anchoring to VPDB: calcite digestion with 18O-adjusted ortho-phosphoric acid. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2011; 25:851-860. [PMID: 21416521 DOI: 10.1002/rcm.4933] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 01/11/2011] [Accepted: 01/11/2011] [Indexed: 05/30/2023]
Abstract
For anchoring CO(2) isotopic measurements on the δ(18)O(VPD-CO2) scale, the primary reference material (NBS 19 calcite) needs to be digested using concentrated ortho-phosphoric acid. During this procedure, great care must be taken to ensure that the isotopic composition of the liberated gas is accurate. Apart from controlling the reaction temperature to ±0.1 °C, the potential for oxygen isotope exchange between the produced CO(2) and water must be kept to a minimum. The water is usually assumed to reside on the walls in the headspace of the reaction vessel. We demonstrate here that a large fraction of the exchange may also occur with water inside the acid. Our results indicate that both exchange reactions have a significant impact on the results and may have largely been responsible for scale inconsistencies between laboratories in the past. The extent of CO(2)/H(2)O oxygen exchange depends on the concentration (amount of free water) in the acid. For acids with a nominal H(3)PO(4) mass fraction of less than 102%, oxygen isotope exchange can create a substantial isotopic bias during high-precision measurements with the degree of the alteration being proportional to the effective isotopic contrast between the acid and the CO(2) released from the calcite. Water evaporating from the acid at 25 °C has a δ(18)O value of -34.5‰ relative to the isotopic composition of the whole acid. This large fractionation is likely to occur in two steps; by exchange with phosphate, water inside the acid is decreased in oxygen-18 relative to the bulk acid by ∼ -22‰. This water is then fractionated further during evaporation. Oxygen exchange with both water inside the acid and water condensate in the headspace can contribute to the measured isotopic signature depending on the experimental parameters. The system employed for this study has been specifically designed to minimize oxygen exchange with water. However, the amount of altered CO(2) for a 95% H(3)PO(4) at 25 °C still accounts for about 3% of the total CO(2) produced from a 40 mg calcite sample, resulting in a δ(18) O range of about 0.8‰ when varying the δ(18)O value of the acid by 25‰. Least biased results for NBS19-CO(2) were obtained for an acid with a δ(18)O value close to +23‰ vs. VSMOW. In contrast, commercial acids from several sources had an average δ(18)O value of +13‰, amounting to a 10‰ offset from the optimal value. This observation suggests that the well-known scale incompatibilities between laboratories could arise from this difference with measurements that may have suffered systematically from non-optimal acid-δ(18)O values, thus producing variable offsets, depending on the experimental details. As a remedy, we suggest that the δ(18)O of phosphoric acid reacted with calcites for establishing a δ(18)O scale anchor be adjusted, and this should reduce the variability of the δ(18)O of CO(2) evolved in acid digestion to less than ±0.05‰. The adjustment should be made by taking into account the difference in δ(18)O between the calcite-CO(2) and the acid, with a target difference of 16‰. With this strategy, agreement between δ(18)O scales based on water, atmospheric CO(2) , and carbonates as well as data compatibility between laboratories may be substantially improved.
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Affiliation(s)
- Magnus Wendeberg
- MPI-BGC (Max-Planck-Institut für Biogeochemie), Postfach 10 01 64, D-07701 Jena, Germany
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MORISHITA Y. Research on the Genesis of Mineral Deposits - Significance of the Isotope Ratio Analysis and SIMS Analysis -. BUNSEKI KAGAKU 2011. [DOI: 10.2116/bunsekikagaku.60.921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Yuichi MORISHITA
- Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
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45
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Demény A, Kele S, Siklósy Z. Empirical equations for the temperature dependence of calcite-water oxygen isotope fractionation from 10 to 70°C. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:3521-3526. [PMID: 21080503 DOI: 10.1002/rcm.4799] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Although the temperature dependence of calcite-water oxygen isotope fractionation seems to have been well established by numerous empirical, experimental and theoretical studies, it is still being discussed, especially due to the demand for increased accuracy of paleotemperature calculations. Experimentally determined equations are available and have been verified by theoretical calculations (considered as representative of isotopic equilibrium); however, many natural formations do not seem to follow these relationships implying either that existing fractionation equations should be revised, or that carbonate deposits are seriously affected by kinetic and solution chemistry effects, or late-stage alterations. In order to test if existing fractionation-temperature relationships can be used for natural deposits, we have studied calcite formations precipitated in various environments by means of stable isotope mass spectrometry: travertines (freshwater limestones) precipitating from hot and warm waters in open-air or quasi-closed environments, as well as cave deposits formed in closed systems. Physical and chemical parameters as well as oxygen isotope composition of water were monitored for all the investigated sites. Measuring precipitation temperatures along with oxygen isotope compositions of waters and calcites yielded empirical environment-specific fractionation-temperature equations: [1] 1000 · lnα = 17599/T - 29.64 [for travertines with a temperature range of 30 to 70°C] and [2] 1000 · lnα = 17500/T - 29.89 [for cave deposits for the range 10 to 25°C]. Finally, based on the comparison of literature data and our results, the use of distinct calcite-water oxygen isotopic fractionation relationships and application strategies to obtain the most reliable paleoclimate information are evaluated.
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Affiliation(s)
- Attila Demény
- Institute for Geochemical Research, Hungarian Academy of Sciences, Budaörsi út 45, H-1112 Budapest, Hungary.
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Sahlstedt E, Karhu JA, Pitkanen P. Indications for the past redox environments in deep groundwaters from the isotopic composition of carbon and oxygen in fracture calcite, Olkiluoto, SW Finland. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2010; 46:370-391. [PMID: 20665300 DOI: 10.1080/10256016.2010.505981] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In paleohydrogeological studies, the geochemical and isotope geochemical composition of fracture calcites can be utilised to gain information about the evolution of the composition of deep groundwaters in crystalline bedrock. The aim of our study was to investigate the latest hydrogeochemical evolution of groundwaters in the crystalline bedrock at Olkiluoto, which is the planned site for deep geological disposal of spent nuclear fuel. Samples were collected from drill cores intercepting water-conducting fractures at the upper ~500 m of the bedrock. The latest fracture calcite generations were identified using optical microscopy and electron microprobe. They occur as thin ~10-200 μm crusts or small euhedral crystals on open fracture surfaces. These latest calcite fillings were carefully sampled and analysed for the isotopic composition on carbon and oxygen. In addition, fluid inclusion homogenisation temperatures were determined on selected calcite samples. Fluid inclusion data indicated a low temperature of formation for the latest fracture calcite fillings. The δ(18)O values of calcite in these fracture fillings vary only slightly, from-7.3 to-11.5 ‰ (Vienna Pee Dee Belemnite, VPDB), whereas the δ(13)C values fluctuate widely, from-30 to+31 ‰ (VPDB). The δ(13)C values of latest calcite fillings show a systematic pattern with depth, with high and variable δ(13)C values below 50 m. The high δ(13)C values indicate active methanogenesis during the formation of the latest calcite fillings. In contrast, the present-day methanic redox environment is restricted to depths below 200-300 m. It is possible that the shift in the redox environment at Olkiluoto has occurred during infiltration of SO2-(4)-rich marine waters, the latest of such events being the infiltration of brackish waters of the Littorina Sea stage of the Baltic Sea at ~8000-3000 BP.
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Affiliation(s)
- Elina Sahlstedt
- Department of Geosciences and Geography, University of Helsinki, Helsinki, Finland.
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Tanner LH. Chapter 4 Continental Carbonates as Indicators of Paleoclimate. DEVELOPMENTS IN SEDIMENTOLOGY 2010. [DOI: 10.1016/s0070-4571(09)06204-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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Siklósy Z, Demény A, Vennemann TW, Pilet S, Kramers J, Leél-Ossy S, Bondár M, Shen CC, Hegner E. Bronze Age volcanic event recorded in stalagmites by combined isotope and trace element studies. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2009; 23:801-808. [PMID: 19219896 DOI: 10.1002/rcm.3943] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Stable isotope analyses of speleothems (carbonate deposits formed in caves) have been widely used to reconstruct paleoenvironmental conditions. Recent improvements in geochemical techniques have enabled us to analyze climate-influenced deposits at high temporal resolution so that hitherto unrecognized environmental conditions may be identified. Stable H, C and O isotope analyses on carbonate and inclusion water have been combined with multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) age dating and laser-ablation ICP-MS trace element analyses on a stalagmite from southern Hungary. The study reveals significant changes in chemical and isotopic compositions of the speleothem between approx. 3800 and 3500 years BP ('Before Present') indicating coupled changes in the temperature and precipitation regime under which the speleothem formed. Stable isotopic and trace element correlations within this time period correlate with similar studies of stalagmites of comparable age from the Alpine-Mediterranean region. Our studies suggest that traces of deposition of volcanic dust, possibly related to the Thera eruption of Santorini (Greece) ca. 1650 BC (approximately 3650 BP), and environmental changes can be detected at a distance of several thousand kilometers.
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Affiliation(s)
- Zoltán Siklósy
- Institute for Geochemical Research, Hungarian Academy of Sciences, Budaörsi út 45, H-1112 Budapest, Hungary
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Williams M, Haywood AM, Harper EM, Johnson ALA, Knowles T, Leng MJ, Lunt DJ, Okamura B, Taylor PD, Zalasiewicz J. Pliocene climate and seasonality in North Atlantic shelf seas. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:85-108. [PMID: 18852093 DOI: 10.1098/rsta.2008.0224] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
This paper reviews North Atlantic shelf seas palaeoclimate during the interval 4-3Ma, prior to and incorporating the 'Mid-Pliocene warm period' (ca 3.29-2.97Ma). Fossil assemblages and stable isotope data demonstrate northwards extension of subtropical faunas along the coast of the Carolinas-Virginia (Yorktown and Duplin Formations) relative to the present day, suggesting a more vigorous Florida Current, with reduced seasonality and warm water extending north of Cape Hatteras (reconstructed annual range for Virginia 12-30 degrees C). This interpretation supports conceptual models of increased meridional heat transport for the Pliocene. Sea temperatures for Florida (Lower Pinecrest Beds) were similar to or slightly cooler than (summers 25-27 degrees C) today, and were probably influenced by seasonal upwelling of cold deep water. Reduced seasonality is also apparent in the Coralline Crag Formation of the southern North Sea, with ostracods suggesting winter sea temperatures of 10 degrees C (modern 4 degrees C). However, estimates from Pliocene bivalves (3.6-16.6 degrees C) are similar to or cooler than the present day. This 'mixed' signal is problematic given warmer seas in the Carolinas-Virginia, and climate model and oceanographic data that show warmer seas in the 'Mid-Pliocene' eastern North Atlantic. This may be because the Coralline Crag Formation was deposited prior to peak Mid-Pliocene warmth.
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Affiliation(s)
- Mark Williams
- Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
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Dwyer GS, Chandler MA. Mid-Pliocene sea level and continental ice volume based on coupled benthic Mg/Ca palaeotemperatures and oxygen isotopes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:157-168. [PMID: 18854304 DOI: 10.1098/rsta.2008.0222] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Ostracode magnesium/calcium (Mg/Ca)-based bottom-water temperatures were combined with benthic foraminiferal oxygen isotopes in order to quantify the oxygen isotopic composition of seawater, and estimate continental ice volume and sea-level variability during the Mid-Pliocene warm period, ca 3.3-3.0Ma. Results indicate that, following a low stand of approximately 65m below present at marine isotope stage (MIS) M2 (ca 3.3Ma), sea level generally fluctuated by 20-30m above and below a mean value similar to present-day sea level. In addition to the low-stand event at MIS M2, significant low stands occurred at MIS KM2 (-40 m), G22 (-40m) and G16 (-60m). Six high stands of +10m or more above present day were also observed; four events (+10, +25,+15 and +30 m) from MIS M1 to KM3, a high stand of +15m at MIS K1, and a high stand of +25m at MIS G17. These results indicate that continental ice volume varied significantly during the Mid-Pliocene warm period and that at times there were considerable reductions of Antarctic ice.
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Affiliation(s)
- Gary S Dwyer
- Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC 27708, USA.
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