scholarly journals Oxygen isotope equilibrium in brachiopod shell fibres in the context of biological control

2008 ◽  
Vol 72 (1) ◽  
pp. 239-242 ◽  
Author(s):  
M. Cusack ◽  
A. Pérez-Huerta ◽  
P. Chung ◽  
D. Parkinson ◽  
Y. Dauphin ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Seawater Temperature ◽  
Environmental Data ◽  
Ambient Seawater ◽  
Secondary Layer ◽  
Vital Effect ◽  
Vital Effects ◽  
Stable Oxygen ◽  
Isotope Equilibrium

With their long geological history and stable low-Mg calcite shells, Rhynchonelliform brachiopods are attractive sources of environmental data such as past seawater temperature (Buening and Spero, 1996; Auclair et al., 2003; Brand et al., 2003; Parkinson et al., 2005). Concerns about the influence of vital effects on the stable isotope composition of brachiopod shells (Popp et al., 1986), led to isotope analyses of different parts of brachiopod shells in order to identify those parts of the shell that are influenced by any vital effect and those parts that may be suitable recorders of seawater temperature via stable oxygen isotope composition (Carpenter and Lohmann, 1995; Parkinson et al., 2005). Such detailed studies demonstrated that the outer primary layer of acicularcalcite is isotopically light in both δ18O and δ13C while the secondary layer, composed of calcite fibres, is in oxygen-isotope equilibrium with ambient seawater(Fig. 1) (Parkinson et al., 2005).

Relationship between δ18O and minor element composition of Terebratalia transversa

2007 ◽  
Vol 98 (3-4) ◽  
pp. 443-449 ◽  
Author(s):  
Maggie Cusack ◽  
David Parkinson ◽  
Alberto Pérez-Huerta ◽  
Jennifer England ◽  
Gordon B. Curry ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Seawater Temperature ◽  
Minor Element ◽  
Oxygen Isotope Composition ◽  
Secondary Layer ◽  
Vital Effects ◽  
Stable Oxygen ◽  
Temperature Proxy ◽  
Isotope Equilibrium

ABSTRACTWith their extensive fossil record and shells of stable low-Mg calcite, rhynchonelliform brachiopods are attractive sources of climate information via seawater temperature proxies such as stable oxygen isotope composition. In Terebratalia transversa (Sowerby) there is a progression towards oxygen isotope equilibrium in the calcite of the innermost secondary layer. This study confirms the lack of any vital effects influencing oxygen isotope composition of T. transversa, even in specialised areas of the innermost secondary layer. Calcite Mg/Ca ratio is another potential seawater temperature proxy, that has the advantage of not being influenced by salinity. Mg concentrations measured by electron microprobe analyses indicate that there is no concomitant decrease in Mg concentration towards the inner secondary layer, associated with the progressive shift towards oxygen isotope equilibrium. Mg distribution is heterogeneous throughout the shell and correlates with that of sulphur, which may be a proxy for organic components, suggesting that some of the Mg may not be in the calcite lattice. It is essential therefore, to determine the chemical environment of the magnesium ions to avoid any erroneous temperature extrapolations in brachiopods or any other calcite biomineral.

Oxygen isotope composition in Modiolus modiolus aragonite in the context of biological and crystallographic control

2008 ◽  
Vol 72 (2) ◽  
pp. 569-577 ◽  
Author(s):  
M. Cusack ◽  
D. Parkinson ◽  
A. Freer ◽  
A. Pérez-Huerta ◽  
A. E. Fallick ◽  
...  
Keyword(s):  
Biological Control ◽  
Oxygen Isotope ◽  
Environmental Influence ◽  
Isotope Composition ◽  
Seawater Temperature ◽  
Crystal Habit ◽  
Ambient Seawater ◽  
Oxygen Isotope Fractionation ◽  
Modiolus Modiolus ◽  
Horse Mussel

AbstractLiving systems exert exquisite control on all aspects of biomineral production and organic components, including proteins, are essential to this biological control. The protein-rich extrapallial (EP) fluid of bivalve molluscs is a strong candidate for the source of such proteins. Differences in calcium carbonate polymorphs between Modiolus modiolus and Mytilus edulis are concurrent with differences in EP fluid protein profiles. In conjunction with this biological control is the environmental influence which is interpreted using proxies such as δ18O to determine the history of ambient seawater temperature. In the horse mussel, Modiolus modiolus, the difference in oxygen isotope fractionation in the nacreous aragonite and the prismatic aragonite layer results in respective δ18O values of 2.1±0.2% and 2.5±0.2%. These δ18O values result in estimates of ambient seawater of 12.1±0.6°C and 10.2±0.6°C for nacreous and prismatic aragonite, respectively. Electron backscatter diffraction is used here to determine the crystallographic orientation at high spatial resolution, allowing the measurements of stable isotopes to be accurately mapped in terms of shell architecture. These preliminary data suggest that it is essential to account for both polymorph and crystal habit when deciphering ambient seawater temperature using δ18O as a proxy.

scholarly journals Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign

2016 ◽  
Vol 16 (4) ◽  
pp. 2659-2673 ◽  
Author(s):  
Joël Savarino ◽  
William C. Vicars ◽  
Michel Legrand ◽  
Suzanne Preunkert ◽  
Bruno Jourdain ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Transfer Functions ◽  
Isotope Composition ◽  
Surface Ozone ◽  
Ice Core ◽  
Isotope Analysis ◽  
Austral Summer ◽  
Direct Observations ◽  
Atmospheric Nitrate ◽  
Stable Oxygen

Abstract. Variations in the stable oxygen isotope composition of atmospheric nitrate act as novel tools for studying oxidative processes taking place in the troposphere. They provide both qualitative and quantitative constraints on the pathways determining the fate of atmospheric nitrogen oxides (NO + NO2 = NOx). The unique and distinctive 17O excess (Δ17O = δ17O − 0.52 × δ18O) of ozone, which is transferred to NOx via oxidation, is a particularly useful isotopic fingerprint in studies of NOx transformations. Constraining the propagation of 17O excess within the NOx cycle is critical in polar areas, where there exists the possibility of extending atmospheric investigations to the glacial–interglacial timescale using deep ice core records of nitrate. Here we present measurements of the comprehensive isotopic composition of atmospheric nitrate collected at Dome C (East Antarctic Plateau) during the austral summer of 2011/2012. Nitrate isotope analysis has been here combined for the first time with key precursors involved in nitrate production (NOx, O3, OH, HO2, RO2, etc.) and direct observations of the transferrable Δ17O of surface ozone, which was measured at Dome C throughout 2012 using our recently developed analytical approach. Assuming that nitrate is mainly produced in Antarctica in summer through the OH + NO2 pathway and using concurrent measurements of OH and NO2, we calculated a Δ17O signature for nitrate on the order of (21–22 ± 3) ‰. These values are lower than the measured values that ranged between 27 and 31 ‰. This discrepancy between expected and observed Δ17O(NO3−) values suggests the existence of an unknown process that contributes significantly to the atmospheric nitrate budget over this East Antarctic region. However, systematic errors or false isotopic balance transfer functions are not totally excluded.

Crystallographic contribution to the vital effect in biogenic carbonates Mg/Ca thermometry

2011 ◽  
Vol 102 (1) ◽  
pp. 35-41 ◽  
Author(s):  
Alberto Pérez-Huerta ◽  
Maggie Cusack ◽  
Paul Dalbeck
Keyword(s):  
Seawater Temperature ◽  
Environmental Parameters ◽  
Magnesium Concentration ◽  
Chemical Information ◽  
Environmental Signals ◽  
Physico Chemical ◽  
Vital Effect ◽  
Vital Effects ◽  
Biogenic Carbonates ◽  
Insufficient Knowledge

ABSTRACTThe processes involved in vital effects, defined as biological processes overriding environmental signals, are not well understood and this hampers the interpretation of environmental parameters such as seawater temperature. Insufficient knowledge is available about changes in physico-chemical parameters, in particular those related to crystallography, associated with biomineral formation and emplacement. This paper assesses the influence of crystallography on Mg2+ concentration and distribution in calcite biominerals of bivalved marine organisms, mussels and rhynchonelliform brachiopods, and considers the implications for Mg/Ca thermometry. In the mussel Mytilus edulis, changes in Mg2+ are not associated with crystallography; but in the brachiopod Terebratulina retusa, increases in Mg2+ concentrations (∼0·5–0·6 wt. ) are associated with the {0001 planes of calcite biominerals. A comparison between mussels and brachiopods with avian eggshells, which form at constant ambient temperature, also reveals that there is at least a common 0·1 wt. variation in magnesium concentration in these calcite biomineral systems unrelated to temperature or crystallography. Results demonstrate that the integration of contextual crystallographic, biological and chemical information may be important to extract accurate environmental information from biominerals.

scholarly journals 14C Analyses of Groundwater From the Botucatu Aquifer System in Brazil

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 926-933 ◽  
Author(s):  
Annkarin Aurelia ◽  
Kimmelmann E Silva ◽  
Aldo da Cunha Rebouças ◽  
Maria Marlucia ◽  
Freitas Santiago
Keyword(s):  
Stable Isotope ◽  
Oxygen Isotope ◽  
Gradual Increase ◽  
Isotope Composition ◽  
Stable Isotope Composition ◽  
Stable Oxygen Isotope ◽  
Aquifer System ◽  
Groundwater Samples ◽  
Stable Oxygen ◽  
Different Origins

Measurements of 14C activity as well as determinations of the stable isotope composition (18O, 2H and 13C) of groundwater samples were made to investigate the flow path, origin, recharge and age of the Botucatu Aquifer System in Brazil, between 1984 and 1987. The stable oxygen isotope composition reflects infiltration during several climatic recharge conditions. Measured 14C activities range from 0.4 to 94.2% modern. δ13C values enable us to distinguish two groundwater types of different origins. There is a gradual increase of 14C ages from the outcrop area towards the central part of the basin, associated with a progression of the confining conditions. Anomalous fluoride contents seem to be correlated with high 14C ages of the groundwater. The reliability of the 14C data is discussed.

Interannual trends in stable oxygen isotope composition in precipitation of China during 1979–2007: Spatial incoherence

2017 ◽  
Vol 454 ◽  
pp. 25-37 ◽  
Author(s):  
Sen Yang ◽  
Mingjun Zhang ◽  
Shengjie Wang ◽  
Yangmin Liu ◽  
Fang Qiang ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Oxygen Isotope Composition ◽  
Stable Oxygen Isotope ◽  
Stable Oxygen

scholarly journals Oxygen isotope composition of waters recorded in carbonates in strong clumped and oxygen isotopic disequilibrium

2019 ◽  
Author(s):  
Caroline Thaler ◽  
Amandine Katz ◽  
Magali Bonifacie ◽  
Bénédicte Ménez ◽  
Magali Ader
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Isotopic Equilibrium ◽  
Oxygen Isotopic ◽  
Vital Effects ◽  
Biogenic Carbonates ◽  
Clumped Isotope ◽  
Interstitial Waters ◽  
Isotopic Disequilibrium ◽  
Paleoenvironmental Reconstructions

Abstract. Paleoenvironmental reconstructions, which are mainly retrieved from oxygen isotope (δ18O) and clumped isotope (Δ47) compositions of carbonate minerals, are compromised when carbonate crystallization occurs in isotopic disequilibrium. To date, knowledge of these common isotopic disequilibria, known as vital effects in biogenic carbonates, remains limited and the potential information recorded by δ18O and Δ47 offsets from isotopic equilibrium values is largely overlooked. Additionally, in carbonates formed in isotopic equilibrium, the use of the carbonate δ18O signature as a paleothermometer relies on our knowledge of the paleowaters' δ18O value, which is often assumed. Here, we report the largest Δ47 offsets observed to date (as much as −0.270 ‰), measured on microbial carbonates, that are strongly linked to carbonate δ18O offsets (−25 ‰) from equilibrium. These offsets are likely both related to the microorganism metabolic activity and yield identical erroneous temperature reconstructions. Unexpectedly, we show that the δ18O value of the water in which carbonates precipitated, as well as the water-carbonate δ18O fractionation dependence to temperature at equilibrium can be retrieved from these paired δ18O and Δ47 disequilibrium values measured in carbonates. The possibility to retrieve the δ18O value of paleowaters, sediments' interstitial waters or organisms' body water at the carbonate precipitation loci, even from carbonates formed in isotopic disequilibrium, opens long-awaited research avenues for both paleoenvironmental reconstructions and biomineralization studies.

Sign in / Sign up

Export Citation Format

Share Document