Kapcsolt izotopok (clumped isotopes) a földtudomanyi kutatasokban

Clumped isotope geochemistry is a new, dynamically developing field of research, which is based on the temperature-dependent clumping of the 13C and 18O isotopes within one molecule. Using the clumped isotope thermometer, the temperature of the carbonate precipitating fluids can be determined with high precision, based on solely the clumped isotope value (∆47) of carbonates. Besides palaeoclimatology, the method can be used in several research fields in geology, including palaeoceanography, atmospheric research, reservoir geology, geomorphology, structural geology, diagenesis, biogeochemistry, low temperature metamorphic processes, meteorite research, etc. Due to continuous developments, the number of applications is still significantly increasing. This paper briefly introduces the reader to the principles of clumped isotope geochemistry, reviewing its theoretical basis, its possible applications, available calibrations and reviews the current state of the art

Clumped isotope record of salinity variations in the Subboreal Province at the Middle–Late Jurassic transition

Results of clumped isotope, oxygen isotope and elemental (Mg/Ca, Sr/Ca) analyses of exceptionally well-preserved belemnite rostra and ammonite shells from the uppermost Callovian–Upper Kimmeridgian (Lamberti–Mutabilis zones) of the Russian Platform are presented. Despite a significant decrease in belemnite δ18O values across the Upper Oxfordian–Lower Kimmeridgian, the clumped isotope data show a constant seawater temperature (ca. 16 °C) in the studied interval. The decrease in belemnite δ18O values and lower δ18O values measured from ammonite shells are interpreted as a result of the salinity decline of the Middle Russian Sea of ca. 12‰, and salinity stratification of the water column, respectively. The postulated secular palaeoenvironmental changes are linked to the inflow of subtropical, saline waters from the Tethys Ocean during a sea-level highstand at the Middle–Late Jurassic transition, and progressive isolation and freshening of the Middle Russian Sea during the Late Oxfordian–Kimmeridgian. The obtained clumped isotope data demonstrate relative stability of the Late Jurassic climate and a paramount effect of local palaeoceanographic conditions on carbonate δ18O record of shallow epeiric seas belonging to the Subboreal Province. Variations in Mg/Ca and Sr/Ca ratios of cylindroteuthid belemnite rostra, which are regarded by some authors as temperature proxies, are, in turn, interpreted to be primarily dependent on global changes in seawater chemistry. The paleoenvironmental variations deduced from clumped and oxygen isotope records of the Russian Platform correspond well with changes in local cephalopod and microfossil faunas, which show increasing provincialism during the Late Oxfordian and the Early Kimmeridgian. Based on the review of literature data it is suggested that the observed salinity decrease and restriction of Subboreal basins during the Late Jurassic played a major role in the formation of periodic bottom water anoxia and sedimentation of organic rich facies

The clumped and oxygen isotope compositions of biogenic carbonate archives: kinetic effects and reconstruction of seawater temperatures and seawater δ18O

During my PhD, I was applying the clumped isotope technique to modern brachiopods and fossil belemnites, and I conducted methodological work. Carbonate clumped isotope thermometry is a tool to reconstruct carbonate precipitation temperatures. In contrast to oxygen isotope thermometry, i.e., the δ18O-thermometer, the carbonate clumped isotope thermometer does not require an estimate for the oxygen isotope composition of the seawater, as it considers the fractionation of isotopes exclusively amongst carbonate isotopologues. The ∆47 value of a carbonate expresses the abundance of the 13C–18O bond bearing carbonate isotopologue, within the carbonate, relative to its random distribution. In thermodynamic equilibrium, the ∆47 value of a given carbonate is solely a function of the carbonate precipitation temperature. However, kinetic isotope fractionations, i.e., vital effects, driven by diffusion, pH or incomplete oxygen isotope exchange between water and dissolved inorganic carbonate species can cause the carbonate to be precipitated with isotopic compositions that are offset from those predicted for thermodynamic equilibrium. Brachiopods serve as important geochemical archives of past climate conditions. To investigate the nature and significance of kinetic controls on brachiopod shell δ18O and ∆47 values, in collaboration with the BASE-LiNE Earth ITN, I analysed the bulk and clumped isotope compositions of eighteen modern brachiopod shells, collected from different geographic locations and water depths that cover a substantial range of growth temperatures. Growth temperatures and seawater δ18O values for each brachiopod were independently determined. Most of the analysed brachiopods exhibit combined offsets from clumped and oxygen isotope equilibrium, and there is a significant negative correlation between the offset values. The observed correlation slope between offset ∆47 and offset δ18O point to the importance of kinetic effects associated with Knudsen diffusion and incomplete hydration and hydroxylation of CO2 (aq), occurring during biomineralisation. The correlations between the growth rates of the analysed brachiopods and both the offset ∆47 and the offset δ18O values provide further arguments for the presence of kinetic effects. In conclusion, the oxygen and clumped isotope composition of modern brachiopod shells are affected by growth rate-induced kinetic effects that hinder their use for palaeoceanography

Kinetic Oxygen Isotope Fractionation between Water and Aqueous OH- during Hydroxylation of CO2

The fractionation of stable oxygen isotopes between water and aqueous hydroxide ions (epsilon(18)(H2O/OH-)) is an integral parameter in chemical modeling. Quantum chemical calculations predict thermodynamic isotope equilibrium epsilon(18)(H2O/OH-) values that are ca. 24 parts per thousand lower than what laboratory experiments suggest. Here, we performed quantitative BaCO3 precipitation experiments across a wide range of temperatures (1-80 degrees C) to complement the limited set of existing experimental data. The known isotope compositions of the tank CO2 gas and the hyperalkaline Ba(OH)(2) solutions allowed us to calculate apparent isotope fractionations. Our data broadly agree with previous experimental epsilon(18)(H2O/OH-) estimates and show a temperature dependence similar to what theoretical models predict (N = 20; T is in degrees C): epsilon(18)(H2O/OH-) = -0.035(+/- 0.005) x T + 43.4(+/- 0.2). The small difference (-0.6 to 0 parts per thousand) between the delta C-13 values of the precipitates and the tank CO2 suggests that kinetic isotope effects (KIEs) related to the preferential adsorption of isotopically light CO2 are insignificant. Instead, we argue that the observed 24 parts per thousand offset between the experimental and theoretical values derives from KIEs related to the preferential reaction of isotopically light OH- during CO2(aq) hydroxylation (KIEOH-). In our experimental setup, dehydroxylation is posited to be slower than carbonate precipitation; therefore, we conclude that our KIEOH- estimate is close to its maximum value expected for a purely unidirectional reaction path. In natural systems, however, isotope equilibration between water and dissolved inorganic carbon species generally reduces the extent of KIEOH- inherited by the solid carbonate

Clumped isotope measurements of Middle to Late Jurassic belemnites and ammonites from the Subboreal Province, link to analysis sheet

Here, we provide the results of the clumped isotope analyses of 24 biogenic carbonate samples, along with the results of carbonate reference materials (ETH1–4, Carrara, MuStd, Strauss) and equilibrated gases (25 °C and 1000 °C). Carbonate digestion at 90 °C and subsequent CO2 purification was done on an automated line connected to a ThermoFisher MAT 253 isotope ratio mass spectrometer. We present the raw isotope values calculated using both the [Gonfiantini/Santrock] and the [Brand]/IUPAC isotopic parameters. The raw data is projected onto the carbon dioxide equilibrium scale using the equilibrated gases and without applying any fractionation factor to the final values. Preparation methods and mass spectrometry analytics are further detailed in the associated files and the linked article

Clumped isotope measurements of Mesozoic belemnites from southern high latitudes

Here, we present the results of the clumped isotope measurements of 11 latest Jurassic to Early Cretaceous belemnites from DSDP Site 511, along with the results of carbonate reference materials (ETH1-4, Carrara, MuStd) and equilibrated gases (25 °C and 1000 °C). Carbonate digestion at 90 °C and subsequent CO2 purification was done on an automated line connected to a ThermoFisher MAT 253 isotope ratio mass spectrometer. We present the raw isotope values calculated using both the [Gonfiantini/Santrock] and the [Brand]/IUPAC isotopic parameters. The raw data is projected onto the carbon dioxide equilibrium scale (CDES) using the equilibrated gases and without applying any acid fractionation factor to the final values. The origin of sample material, sample preparation methods, and mass spectrometry procedures are further detailed in the associated files and the linked article: Vickers et al. (2019)

Pasantía en el Teatro Colón

El teatro se ha constituido como la expresión artística que desarrolla la comunicación entre los diferentes pueblos para transmitir su cultura. Por otra parte, el teatro como espacio físico es el lugar propicio donde se logra establecer esa mágica comunicación entre los artistas y el espectador, donde ninguno puede existir sin el otro, por eso Silvio D´Amico crítico de talla, dice que al teatro constituye “la comunicación de un público con su espectáculo viviente”. El presente trabajo de grado sustenta mi pasantía en el Teatro Colón de Bogotá, realizada en el segundo semestre de 2017, con el fin de culminar los estudios universitarios y optar por el título de Maestra en música con énfasis en Ingeniería de sonido otorgado por la Pontificia Universidad Javeriana. A lo largo del texto se describen cuatro casos en los que se expone la experiencia vivida en diferentes espectáculos y la manera en que se abordaron explorando el rol que deben ejercer un músico e ingeniero de sonido en el ámbito teatral, como el sonido en vivo, la grabación, la edición, la mezcla, la producción y el trabajo en equipo don todos los departamentos que hacen posible el éxito de una puesta en escena