Papers by MAXIMILIANO GABRIEL TRONCOSO RODRÍGUEZ
Chemical Geology
Abstract Trace elements of marine shells are important tools for reconstructing past ocean condit... more Abstract Trace elements of marine shells are important tools for reconstructing past ocean conditions, which are usually obtained through empirical calibrations with ocean parameters. For example, Mg/Ca ratios of ostracod shells have been linked to ocean temperature. However, some uncertainties usually arise from extraneous impacts, such as the selection of cleaning methods, specimen ontogenetic stage and shell preservation. Here, we present an evaluation of trace elements (Ca, Mg, Sr, Na, Al and Fe) in a shallow marine ostracod, Sinocytheridea impressa, and their potential utility as paleoceanographic proxies. We investigated single-shell variability of trace-element-to‑calcium ratios through Inductively Couple Plasma Mass Spectrometry (ICP-MS). In addition, the internal distribution of trace-elements was studied by Electron Probe Micro Analysis (EPMA) and Flow-Through Time-Resolved Analysis (FT-TRA). We conducted these analyses on ostracod specimens of different life stages and preservation conditions, subject to different cleaning methods, to resolve the suitability of this species as a new paleoenvironmental archive. Based on cleaning tests, we observe that clays stuck to the shells are the major contaminants in our specimens. We report an optimal cleaning procedure using sodium hypochlorite, which reduced the adherence of clays to the organism without significantly dissolving adult and juvenile calcite. We additionally find that the internal Mg distribution of S. impressa specimens is different for adults and the oldest stage of juveniles, namely A-1, with only the former having an enriched inner Mg layer. Therefore, precautions should be taken when combining life stages for trace-element analysis. While Sr and Mn are found to be mostly homogenous throughout all shells, the distribution of Na was found to be heterogeneous, which suggests that the incorporation of Na is controlled by a different mechanism than Mg, Sr and Mn. Finally, we report that transparent and opaque shells show similar Mg/Ca, Sr/Ca and Na/Ca ratios, unlike Mn/Ca and Fe/Ca, which suggests that opaque shells result from Mn- and Fe-enriched porewaters and Mn-enriched waters from the Pearl River. Our combined analysis suggests that Mg, Sr and Mn of adult S. impressa are incorporated into the carbonate matrix during calcification, and may therefore be suitable proxies of important environmental variables such as temperature and aqueous elemental concentrations.
Revista uruguaya de cardiología, Jan 11, 2017
La importancia de la plataforma continental argentina no esta solamente vinculada con su extensio... more La importancia de la plataforma continental argentina no esta solamente vinculada con su extension sino tambien con su elevada productividad, lo que hace que sea utilizada como area de alimentacion por un importante numero y biomasa de predadores tope marinos que se reproducen en la costa y en sectores insulares alejados del continente. Entre estos predadores tope, las aves pelagicas se destacan por sus extraordinarias habilidades de vuelo y sus extensos viajes de alimentacion o migratorios de varios miles de kilometros. La distribucion de estas aves (y otros predadores tope marinos) a lo largo de la plataforma no es uniforme, presentando mayores concentraciones en areas donde las caracteristicas oceanograficas promueven elevadas abundancias de presas. Generalmente se observa un mayor numero de individuos agregados cerca de frentes con gradientes de temperatura horizontales que sobre areas termicamente mas homogeneas. Si bien algunas poblaciones de aves pelagicas sufren actualmente ...
Goldschmidt Abstracts, 2020
Geochemistry, Geophysics, Geosystems, 2021
Reconstructing intermediate and bottom‐water temperature in the Arctic Ocean is key for understan... more Reconstructing intermediate and bottom‐water temperature in the Arctic Ocean is key for understanding paleoclimatic phenomena, such as the region's interactions with warm Atlantic waters, stratification, and sea‐ice dynamics. However, benthic proxy archives are sparse throughout the Arctic circle compared to lower latitudes. Trace‐element ratios (E/Ca) derived from ostracodes, a group of bivalved microscopic crustaceans, have shown promise in this regard. Samples for E/Ca measurements typically require rigorous cleaning prior to analysis, and signs of contamination are routinely monitored through the presence of other trace elements such as Al, Fe, and Mn, which are associated with suspected sources of overprinting. However, there has not yet been an intra‐valve investigation of all of these trace elements, which may hinder our ability to effectively identify geochemical overprinting. Here, we present several elemental concentration and E/Ca ratio measurements in two ostracode g...
Hydrology and Earth System Sciences Discussions, 2014
This paper presents a methodology for hydrograph separation in high elevation watersheds, which a... more This paper presents a methodology for hydrograph separation in high elevation watersheds, which aims at identifying individual flow sources such as snow- and ice melt, rainfall and soil water. Daily summer and bi-daily spring water samples from the outlet of the Juncal River were analyzed for all major ions as well as stable water isotopes, δ<sup>18</sup>O and δ<sup>2</sup>H. Additionally, various water sources such as rain, springs, snow- and glacial melt were sampled throughout the catchment. A principal component analysis (PCA) was performed in order to reduce the dimensionality of the problem. Potential sources were identified in a two-component <i>U</i> space that explains 77% of variability. Hydrograph separation (HS) was performed through three models: (i) Isotopic model, (ii) Mixing–PCA model, and (iii) Informative–Bayesian model, with very similar results in each case. At the Juncal River outlet, summer flows were composed by at lea...
Hydrology and Earth System Sciences, 2013
Central Chile is an economically important region for which water supply is dependent on snow-and... more Central Chile is an economically important region for which water supply is dependent on snow-and ice melt. Nevertheless, the relative contribution of water supplied by each of those two sources remains largely unknown. This study represents the first attempt to estimate the region's water balance using stable isotopes of water in streamflow and its sources. Isotopic ratios of both H and O were monitored during one year in a high-altitude basin with a moderate glacier cover (11.5 %). We found that the steep altitude gradient of the studied catchment caused a corresponding gradient in snowpack isotopic composition and that this spatial variation had a profound effect on the temporal evolution of streamflow isotopic composition during snowmelt. Glacier melt and snowmelt contributions to streamflow in the studied basin were determined using a quantitative analysis of the isotopic composition of streamflow and its sources, resulting in a glacier melt contribution of 50-90 % for the unusually dry melt year of 2011/2012. This suggests that in (La Niña) years with little precipitation, glacier melt is an important water source for central Chile. Predicted decreases in glacier melt due to global warming may therefore have a negative long-term impact on water availability in the Central Andes. The pronounced seasonal pattern in streamflow isotope composition and its close relation to the variability in snow cover and discharge presents a potentially powerful tool to relate discharge variability in mountainous, melt-dominated catchments with related factors such as contributions of sources to streamflow and snowmelt transit times.
Page 1. UFPR ASSINCRONIA E SINCRONIA DE ECLOSÃO: UM TESTE EXPERIMENTAL DE REPRODUÇÃO EM Furnarius... more Page 1. UFPR ASSINCRONIA E SINCRONIA DE ECLOSÃO: UM TESTE EXPERIMENTAL DE REPRODUÇÃO EM Furnarius rufus. Maximiliano Niedfeld Rodriguez, Aluno do Programa de Pós-Graduação em Ecologia e Conservação da UFPR Orientador: James J. Roper, PhD. ...
Revista Cubana de …, 2004
... de fractura más frecuente (57,9 %), seguido por el impacto contra un equipo o instrumento dej... more ... de fractura más frecuente (57,9 %), seguido por el impacto contra un equipo o instrumento dejuego (28,1 ... En las fracturas de mandíbula, la región más dañada fue el ángulo, asociada con terceros molares retenidos y fundamentalmente en ... Dr. José Manuel Díaz Fernández. ...
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Papers by MAXIMILIANO GABRIEL TRONCOSO RODRÍGUEZ