Дисертації з теми "Ca isotope"
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Chang, Veronica Tzu-Chun. "Mg and Ca isotope fractionation during CaCO₃ biomineralisation." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269953.
Повний текст джерелаThériault, Réginald J. "Evolution of the ca. 1.9 gallium Taltson magmatic zone, Northwest Territories: A neodymium isotope perspective." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5788.
Повний текст джерелаMacDonald, Cody J. "Hydrothermal Circulation During Slip on the Mohave Wash Fault, ChemehueviMountains, SE CA: Oxygen Isotope Constraints." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1405810104.
Повний текст джерелаFeasby, Rebecca Susanne Godkin. "Stable isotope evidence for dietary patterns and environmental conditions at Tell Leilan, Syria, ca. 1900-2900 B.C." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28891.pdf.
Повний текст джерелаMarriott, Caedmon. "Lithium and calcium isotope fractionation and Li/Ca ratio incorporation into calcium carbonate as potential geochemical proxies." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418477.
Повний текст джерелаDu, Vivier Alice Diana Charlotte. "Global evaluation of Os and Ca marine isotope stratigraphy and U-Pb geochronology of the OAE 2." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10649/.
Повний текст джерелаWogsland, Brittan Valhalla. "Organomineralization of Microbialites from Storr’s Lake, San Salvador Island, Bahamas: Calcium Stable Isotope Analysis using TIMS and a 42Ca-43Ca double spike." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587723502946554.
Повний текст джерелаHorowitz, Michael (Michael Joshua) 1962. "Western South Atlantic holocene and glacial deepwater hydrography derived from benthic foraminiferal Cd/Ca and stable carbon isotope data." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/69183.
Повний текст джерелаIncludes bibliographical references (leaves 16-21).
Today, deep waters produced in the North Atlantic are exported through the western South Atlantic. Antarctic intermediate water (AAIW) also enters the Atlantic in this region. Circumpolar deep water (CDW) fills the depths below AAIW and above and below northern source waters. A depth transect of cores from 1567-3909 m water depth in the western South Atlantic are ideally located to monitor inter-ocean exchange of deep water, and variations in the relative strength of northern versus southern source water production. Last glacial maximum (LGM) Cd/Ca and 813C data indicate a nutrient-depleted intermediate-depth water mass. In the mid-depth western South Atlantic, a simple conversion of LGM 813C data suggests significantly less nutrient enrichment than LGM Cd/Ca ratios, but Cd/Ca and 613C data can be reconciled when plotted in CdW/ 13C space. Paired LGM Cd/Ca and S13C data from mid-depth cores suggest increasingly nutrient rich waters below 2000 m, but do not require an increase in Southern Ocean water contribution relative to today. Cd/Ca data suggest no glacial-interglacial change in the hydrography of the deepest waters of the region. To maintain relatively low Cd/Ca ratios (low nutrients) in the deepest western South Atlantic waters, and in CDW in general, during the LGM requires an increased supply of nutrient-depleted glacial North Atlantic intermediate water (GNAIW) and/or nutrient-depleted glacial Subantarctic surface waters to CDW to balance reduced NADW contribution to CDW. LGM Cd/Ca and 513C data suggest strong GNAIW influence in the western South Atlantic which in turn implies export of GNAIW from the Atlantic, and entrainment of GNAIW into the Antarctic Circumpolar current.
by Michael Horowitz.
S.M.
Perez, Fernandez Andrea. "Etude expérimentale sur l'échange isotopique dans le système eau-roches carbonatées." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30398.
Повний текст джерелаThe isotopic signatures of carbonate minerals have been applied to illuminate a plethora of natural geochemical processes. This thesis is aimed to assess the rates and or conditions at which such isotope signatures might be altered by fluid-mineral interaction through a series of systematic experimental studies performed with dolomite (CaMg(CO3)2) magnesite (MgCO3) and calcite (Ca-CO3). Ca and Mg isotopic compositions were measured as a function of time during closed-system stoichiometric dolomite dissolution experiments at 50 to 126°C. Although identical to that of the original dolomite at low temperatures, at temperatures >120 °C, the calcium isotopic signature of fluid phase (delta(44/42)Ca fluid) became 0.6±0.1‰ higher than that of the dissolving dolomite over a 4-week period. In contrast, the delta(26/24)Mg fluid, remained equal to that of the dolo-mite both at low and high temperatures. This set of experiments evidences the two-way transfer of calcium in and out of the dolomite structure at elevated temperatures. The results suggest that the inhability of dolomite to precipitate at these conditions is due to the difficulty of Mg to be reincorporated in the dolomite structure. In a follow-up study, magnesite was dissolved at 25°C in the presence of fluids with distinct pH and CO2 pressures. The isotopic compositions of the fluid differed from that of the solid at near-to chemical equilibrium indicating the two-way transfer of magnesium into this mineral at ambient temperatures. A single fractionation mechanism cannot explain the distinct Mg isotope behaviors observed. Further work on carbon isotope exchanges in the calcite water system shows a slow by steady evolution of the carbon isotopic composition towards the accepted equilibrium fractionation factor over the course of nearly year-long experiments after the system had attained bulk chemical equilibrium. Carbon isotope reequilibration rates were found to be approximately four orders of magnitude slower than that of bulk calcite dissolution, suggesting that the rate limiting step to the carbon isotope reequilibration process is the transport of carbon into and out of the bulk mineral after it has exchanged on the surface. The results of this thesis suggest that the Mg, Ca and C isotopic signatures in carbonate minerals are not invariant over geological time-frames and can be readily altered by water-mineral interaction. Such results indicate that the preservation of carbonate mineral signatures require low permeability rock formations or some inhibitory mechanism limiting metal and carbon exchange
Bright, Jordon, and Jordon Bright. "Multi-Disciplinary Paleoenvironmental Context for the Integration of the Lower Colorado River Corridor, Bouse Formation, CA-AZ, USA, and Middle to Late Pleistocene Human Evolution, the Koora Plain, Southern Kenya." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625880.
Повний текст джерелаSkinner, Luke Cameron. "Millennial climate change in the Northeast Atlantic : the role of surface- and deep hydrographic change determined by stable isotope geochemistry and MG/CA palaeothermometry." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615838.
Повний текст джерелаCourt, Mélanie. "Étude des cycles du Ca et Mg dans cinq hêtraies du nord de la France et des modifications induites par un amendement calco-magnésien : utilisation combinée des approches élémentaires et isotopiques (δ26/24Mg, δ44/40Ca et 87Sr/86Sr)". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0248/document.
Повний текст джерелаIn France, many forest ecosystems grow on acidic and nutrient poor soils. In numerous cases, the chemical fertility of forest soils is slowly degrading due to increasing external pressures (e.g. decreasing atmospheric inputs, increasing biomass exportations) and is a growing concern in the international forest community. Forest management often must resort to restauration/remediation practices to ensure the sustainability of the ecosystem. Forest liming with a carbonate product is a known practice to reduce soil acidity, globally improve the ecosystem functioning and compensate nutrient losses caused by biomass harvest and exportation. However, our understanding of the effects of liming on magnesium and calcium biogeochemical processes and cycling in forest ecosystems is still incomplete. This study focuses on the fate of magnesium and calcium originating from the dissolution of liming products in the soils and trees of five beech forests located in Northern France over a period up to 45 years. In order to do so, “conventional” total-element approaches were combined with a multi-isotopic approach (26/24Mg, 44/40Ca et 87/86Sr). At all five sites, the data measured in control plots throughout the study period suggest that the exchangeable pools of nutrient cations in the soil has decreased over the last several decades and that this trend, together with the low chemical fertility level of the soil, was reflected in foliar nutrition (Ca, Mg, K, P). Compared to the control plots, soil exchangeable pools of Mg and Ca in the 0-40cm layer in the limed plots increased during the first decade after liming but differences were no longer observable in soil pools after 20 to 30 years. However, the effect of liming on tree nutrition was still observed after 40 years, most probably because the biological cycling of these elements was enhanced by the lime input. The ecosystem response to the lime input varied between sites depending on the nature of the liming product (CaCO3 or Ca-MgCO3) and the initial chemical fertility level of the soil, the poorest sites showing the strongest responses. The natural variations of Mg, Ca and Sr isotopic ratios combined with conventional approaches highlight the importance of the BIO component of the biogeochemical cycling of Mg and Ca in the studied low chemical fertility beech forests. These isotopic tools also enabled to show the long-lasting incorporation of the Mg and Ca released from the liming product in the biological cycle and highlight the changes in the biogeochemical functioning of these forest ecosystems after the liming operation
Perretti, Adriana Rodrigues. "Avaliação da aplicação associada dos dados de δ18O e da razão Mg/Ca de foraminíferos como uma ferramenta paleoceanográfica." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/21/21133/tde-07062011-142829/.
Повний текст джерелаThe goal of this study is to evaluate the associated use of the proxies ?18O and Mg/Ca, both analyzed in foraminifera tests. ?18O and trace metals analyses were performed in order to achieve this purpose on samples of planktonic (G. ruber and G. sacculifer) and benthic (Cibicidoides spp., C. corpulentus, Uvigerina spp. and H. elegans) species of foraminifera from two cores from South Atlantic. Despite of the fact that the proxies used on this study present distinct fits within the species they correlate very well, being possible to estimate the values of temperature, ?18OSW and ?18OLocal. Based on the temperature estimated by Mg/Ca it was possible to identify a negative anomaly of -1,5 ± 0,2 °C between the LGM and HL, meanwhile a positive anomaly of 1,7 ± 0,4 °C was observed in the deep waters for the same period. The ?18OSW data estimated by temperature and ?18O indicate an oscilation of 1,0 ± 0,1 ? and 2,0 ± 0,2 ? for planktonic and benthic species between the LGM and the HL. Based on the literature value for the ice volume signal (~1,2 ?) the superficial waters of the study area indicated a very low salinity oscilation, opposite to the high salinity oscillation in the deep waters. The ?18OLocal estimatives exhibited a very weak salinity oscillation between LGM and HL in the superficial waters (~0,1 ?), providing a much more strong oscilation in the deep waters (1,0 ± 0,3 ?). The salinity increase during the LGM in the deep waters establish the validity of the positive temperature anomaly observed in this study, since the density of the deep water needs to be adequate to maintain the water column stratification.
Gangloff, Sophie. "Evaluation of the mechanisms of trace elements transport (Pb, Rare Earth Elements,... ) and the elemental and isotopic fractionation (Ca and Sr) at the interface water-soil-plant." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAH002/document.
Повний текст джерелаThis work is focused on the study of a profile of soil and soil solutions collected on an experimental plot covered with spruce. All these samples come from the watershed of the Strengbach (environment - OHGE Hydrogeochimique Observatory), were sampled at different depths (5, 10, 30 and 60 cm) and during the period between 2009 and 2013. Characterizations of soil extracts by infrared spectroscopy allowed to highlight changes in the organic functional groups with depth and that these changes have a significant impact on the behaviour of the cations (major and trace) in the soil. Ultrafiltration experiments helped to identify flows of colloidal and dissolved organic carbon as well as those of the major and trace-element present in soil solutions. The joint use of isotope tracers (87Sr / 86Sr and δ44 / 40 Ca) and chemical (Rare Earth Elements) have highlighted processes taking place at the water-soil-plant interface, as the uptake by root or soil alteration
Brazier, Jean-Michel. "Rôle des phases minérales des sols en tant que réservoirs de nutriments : approche expérimentale (abiotique), en milieu naturel et multi-isotopique (isotopes stables Ca-Sr)." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAH005/document.
Повний текст джерелаThis PhD thesis examined the mechanisms of storage and release, from and elementary and isotopically point of view, of calcium (Ca) and strontium (Sr) onto or into mineral phases commonly encountered within soils (primary minerals, clay minerals, oxy-hydroxides, pedogenic carbonate). A robust δ88Sr measurements method had to be developed in the laboratory and validated by the measurement of international reference materials, mostly never measured in the literature. The results of this work show that Ca adsorption onto phyllosilicate minerals generates a quantifiable isotopic fractionation by preferential uptake of the light isotope (40Ca) under our experimental conditions when the minerals have a significant structural charge and specific surface area and/or an interlayer space open to hydrated cations adsorption. A study on rhizoliths in natural environment has also highlighted that the combination of Ca and Sr isotopes allows an effective tracing of sources and mechanisms in the problematic related to the storage of these two elements within soils
Einloth, Sharon L. "Intrinsic Isotopic Tracers as Independent Evaluators for China Lake Basin, CA." Thesis, The University of Arizona, 2000. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0204_sip1_w.pdf&type=application/pdf.
Повний текст джерелаHeuser, Alexander. "Variations of calcium isotopes (d44Ca) [delta 44 Ca] in foraminifers over the past 24 Ma." [S.l.] : [s.n.], 2002. http://e-diss.uni-kiel.de/diss_713/d713.pdf.
Повний текст джерелаMontanari, D. "Reaction dynamics of neutron rich nuclei in Ca isotopes with heavy ions and gamma spectroscopy." Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/152526.
Повний текст джерелаDeLong, Kristine L. "Reconstructing 20th century SST variability in the southwest pacific : a replication study using multiple coral Sr/Ca records from New Caledonia." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001734.
Повний текст джерелаDenk, Eberhard. "Evaluation of ⁴¹Ca as a novel isotopic tool to assess the impact of diet on bone health /." Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16416.
Повний текст джерелаSans-Jofre, Pierre. "L' environnement post-marinoen (ca. 635 ma) : une étude multi-proxy de la plateforme carbonatée du Groupe d'Araras (Mato Grosso, Brésil)." Paris 7, 2011. http://www.theses.fr/2011PA077166.
Повний текст джерелаThe occurrence of low latitude glacial deposits in the Neoproterozoic is the basis of the Snowball Earth hypothesis, which postulates the planet had been completely covered by ice. The recovery from such an extreme climatic state would occur through an extreme greenhouse event. In this thesis we have combined sedimentological studies, geochemistry, magnetic methods and isotopic studies to investigate the Neoproterozoic carbonate platform of Araras, which is correlated to the Marinoan post-glacial successions. Five sections were sampled across the platform. Our results show that the dolomitic succession in the inner shelf sections is deposited in a progressive context, being then covered by transgressive limestones. Redox conditions were deduced from an integrated study, combining trace elements, magnetic mineralogy and iron speciation, which indicate oxic conditions in the shallower facies and relatively more reduced conditions at deeper facies. Multi-isotopic analyses of sulfur and carbon suggest that the end of the glacial event and the post-glacial transgression is accompanied by depletion in the sulfur reservoir, due to the increase in both primary productivity and bacterial sulfate reduction. Carbon isotopic composition of carbonate and associated organic matter in the cap carbonates indicate a maximum CO2 atmospheric concentration of 3200 ppmv. This concentration is coherent with Oa concentrations for the Neoproterozoic and with the ocean pH necessary for the widespread deposition of carbonate successions by that time. Yet, it is significantly lower than that predicted by numerical models of deglaciation
Stephans, Christie L. "Assessing the Reproducibility of Coral-based Climate Records: A Multi-proxy Replication Test using Three Porites lutea Coral Heads from New Caledonia." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000165.
Повний текст джерелаSchimmelpfennig, Irene. "Cosmogenic [36]Cl in Ca and K rich minerals : analytical developments, production rate calibrations and cross calibration with [3]He and [21]Ne." Aix-Marseille 3, 2009. https://tel.archives-ouvertes.fr/tel-00468337.
Повний текст джерелаPublished cosmogenic [36]Cl SLHL production rates from Ca and K spallation differ by almost 50% (Gosse and Phillips, 2001). The main difficulty in calibrating [36]Cl production rates is to constrain the relative contribution of the various production pathways, which depend on the chemical composition of the rock, particularly on the Cl content. Whole rock [36]Cl exposure ages were compared with [36]Cl exposure ages evaluated in Ca-rich plagioclases in the same independently dated 10 ± 3 ka lava sample taken from Mt. Etna (Sicily, 38° N). Sequential dissolution experiments showed that high Cl concentrations in plagioclase-grains could be significantly reduced after 16% dissolution yielding [36]Cl exposure ages in agreement with the independent age. Stepwise dissolution of whole rock grains, on the other hand, is not as effective in reducing high Cl concentrations as it is for the plagioclase. 330 ppm Cl still remains after 85% dissolution. The [36]Cl exposure ages are systematically about 30% higher than the ages calculated from the plagioclase. We could exclude contamination by atmospheric or magmatic [36]Cl as an explanation for this overestimate. High Cl contents in the calibration samples used for several previous production rate studies are most probably the reason for overestimated spallation production rates from Ca and K. This is due to a poorly constrained nature of [36]Cl production from low-energy neutrons. We used separated minerals, very low in Cl, to calibrate the production rates from Ca and K. [36]Cl was measured in Ca-plagioclases collected from 4 lava flows at Mt. Etna (38° N, Italy, altitudes between 500 and 2000 m), and in K-feldspars from one flow at Payun Matru volcano (36° S, Argentina, altitudes 2300 and 2500 m). The flows were independently dated between 0. 4 and 32 ka. Scaling factors were calculated using five different published scaling models resulting in five calibration data sets. Using a Bayesian statistical model allowed including the major inherent uncertainties. The inferred SLHL spallation production rates from Ca and K are 42. 2 ± 4. 8 atoms [36]Cl (g Ca)-1 a-1 and 124. 9 ± 8. 1 atoms [36]Cl (g K)-1 a-1 scaled with Stone (2000). Using the other scaling methods results in very similar values. These results are in agreement with previous production rate estimations both for Ca and K calibrated with low Cl samples. Moreover, although the exposure durations of our samples are very different and the altitude range is large, the ages recalculated with our production rates are mostly in agreement, within uncertainties, with the independent ages no matter which scaling method is used. However, scaling factors derived from the various scaling methods differ significantly. Cosmic ray flux is sensitive to elevation and its energy spectrum increases considerably with increasing altitude and latitude. To evaluate whether various TCN production rates change differently with altitude and latitude and if nuclide-specific or even target-element-specific scaling factors are required, cosmogenic [36]Cl, [3]He and [21]Ne concentration were determined in pyroxenes over an altitude transect between 1000 and 4300 m at Kilimanjaro volcano (3° S). No altitude-dependency of the nuclide ratios could be observed, suggesting that no nuclide-specific scaling factors be needed for the studied nuclides
Yurco, Lyanne Nadine. "A Multi-Proxy Investigation of the Late Glacial "Mystery Interval" (17.5-14.5 ka)in the Cariaco Basin, Venezuela." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_theses/26.
Повний текст джерелаStair, Kristine L. "Assessing the reproducibility of skeletal geochemistry records in Atlantic corals using Montastraea annularis coral heads from the Dry Tortugas, Florida." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0001966.
Повний текст джерелаMaupin, Christopher Robert. "Extracting a Climate Signal from the Skeletal Geochemistry of the Caribbean Coral Siderastrea siderea." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002433.
Повний текст джерелаPerrot, Frédéric. "Etude spectroscopique des isotopes $^{51, 52, 53}$Ca par décroissance $\beta$ des noyaux riches en neutrons $^{51, 52, 52}$K et interaction effective dans la couche fp." Phd thesis, Université Louis Pasteur - Strasbourg I, 2004. http://tel.archives-ouvertes.fr/tel-00385423.
Повний текст джерелаAmsellem, Elsa. "Le fractionnement isotopique du Ca et du Sr à haute température : apport sur la formation et l’évolution de la Terre." Thesis, Université de Paris (2019-....), 2019. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=3979&f=25544.
Повний текст джерелаThe formation of the Solar System and its evolution remain poorly known despite the explosion of space exploration in the mid 20th century. Meteorites and terrestrial igneous rocks are particularly useful objects of study for gaining insights into the formation and evolution of the Earth: the former existed before the planets and the latter reflect the composition of the terrestrial mantle. For this thesis, we performed Ca, Sr and Rb isotopic analyses using MC-ICP-MS technique on a variety of terrestrial and extra-terrestrial rocks. The fractionation of Ca and Sr stable isotopes allows for tracing processes and source effects and Rb-Sr system enables us to date primordial events. Chondrules, a major component of chondrites, are analysed for Ca isotopic composition to test and confirm the pebble accretion model for the formation of the Earth. The timing of the heating event of thermally metamorphosed carbonaceous chondrites is estimated using Rb-Sr chronology and reveals the process of the event as impacts in the asteroid belt. From Earth, komatiites, OIBs and MORBs samples are analysed to estimate the Ca and Sr isotopic composition and evolution of the mantle. The stable isotopic composition of Sr in the mantle is homogenous through the evolution of the mantle while Ca isotopes reveal preservation of early heterogeneities. Carbonatites, rare igneous rocks containing 50 % of carbonate minerals, are studied for Ca isotopic composition in order to indicate their origin. We suggest that the enrichment in lighter Ca isotopes of the carbonatites compared to the bulk silicate Earth’s value derives from a contribution of recycled components through subduction in their mantle source. This thesis explores the wide applications of Ca and Sr isotopic fractionation in high temperature geochemistry
Hetzinger, Steffen [Verfasser]. "Stable oxygen isotopes and Sr-Ca-ratios in modern Diploria strigosa corals from different sites in the Caribbean Sea : evaluation of a new climate archive for the tropical Atlantic = Stabile Sauerstoffisotope und Sr-Ca-Elementverteilung in rezenten Diploria-strigosa-Korallen von verschiedenen Lokationen in der Karibik / Steffen Hetzinger." Kiel : Universitätsbibliothek Kiel, 2010. http://d-nb.info/1019952245/34.
Повний текст джерелаBowles, Rachel E. "The Use of the Ostracode Cyprideis Americana (Sharpe) as a Proxy for Salinity in Bahamian Lake Systems." TopSCHOLAR®, 2013. http://digitalcommons.wku.edu/theses/1272.
Повний текст джерелаHollstein, Martina Verfasser], Mahyar [Akademischer Betreuer] [Mohtadi, Dierk [Gutachter] Hebbeln, and Gerhard [Gutachter] Schmiedl. "Variations in surface and thermocline conditions of the Western Pacific Warm Pool : Insights from Mg/Ca and stable isotopes in foraminifera tests / Martina Hollstein ; Gutachter: Dierk Hebbeln, Gerhard Schmiedl ; Betreuer: Mahyar Mohtadi." Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1156710405/34.
Повний текст джерелаCampos, Marília de Carvalho. "Variabilidade milenar da Corrente do Brasil e do clima da América do Sul durante o último período glacial." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/100/100136/tde-27072016-113954/.
Повний текст джерелаThe Brazil Current (BC) represents the southern branch of the bifurcation of the South Equatorial Current that interacts with the southeastern Brazilian continental margin. Sea surface temperature at BC region plays an important role in controlling the intensity and position of the South Atlantic Convergence Zone, which represents one of the main componets of the South American Monsoon System (SAMS). This atmospheric system is responsible for summer precipitation in a large sector of South America, and, therefore, it is a natural feature of great importance for the national and international political-economic context. Moreover, the BC is markedly influenced by the Atlantic Meridional Overturning Circulation (AMOC) whose past oscillations generated marked global abrupt climatic changes. Presently, the few paleoceanographic records available from the western South Atlantic do not allow a detailed reconstruction of the changes that happened in the BC during the last glacial cycle. This MSc. dissertation aimed at reconstructing the variability of the BC around 32°S during the events Heinrich Stadial (HS) 3 and 2, as well as its impacts on the climate of southeastern South America. Therefore, we investigated one marine sediment core collected in the southern Brazilian continental margin, under the influence of the BC. For this core we produced an age model based on 14C ages, downcore records of carbon and oxygen stable isotopes and Mg/Ca, both in tests of planktonic foraminifera, and X-ray fluorescence in bulk sediment samples. During HSs (notably during HS2), the records show marked increases in sedimentation rate as well as in ln(Ti/Ca) and ln(Fe/Ca), and decrease in the stable carbon isotopic composition as well as sea surface temperature and salinity. Such changes were releted to the weakening of the AMOC, the intensification of the Southern Ocean upwelling, and the strengthening of the SAMS. The occurrence a w-structure in our HS records as well as in North Atlantic and South American records, suggest that such structure is a pervasive feature of HS2, and possibly also HS3
Romahn, Sarah [Verfasser], Andreas [Akademischer Betreuer] Mackensen, and Gerold [Akademischer Betreuer] Wefer. "Western Indian Ocean circulation and climate variability on different time scales : a study based on stable oxygen and carbon isotopes, benthic foraminiferal assemblages and Mg/Ca paleothermometry / Sarah Romahn. Gutachter: Andreas Mackensen ; Gerold Wefer. Betreuer: Andreas Mackensen." Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/1072226677/34.
Повний текст джерелаSantarosa, Ana Claudia Aoki. "Respostas dos foraminíferos planctônicos às variações da Célula de Revolvimento Meridional do Atlântico (AMOC) desde o Último Máximo Glacial na Bacia de Campos." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/21/21136/tde-17012019-180044/.
Повний текст джерелаThe objective of the present study was to investigate the response of the planktonic foraminiferaassemblage to the superficial paleoceanographic variations in the western South Atlantic, which plays a key role in the AMOC. For this purpose, a continuous marine sedimentary record was analyzed from the Late Glacial Maximum to the present, based on the planktonic foraminifera assemblage, oxygen isotopes and the Mg/Ca ratio. In addition, variations in the occurrence and geochemistry of the two morphotypes of G. ruber (white) were evaluated. This is the main species used in paleoceanographic studies of tropical and subtropical regions. The results showed that the geochemical and relative abundance differences between the G. ruber morphotypes show two ecologically distinct groups of specimens, confirming that the morphotype sensu stricto calcifies at lower depths with respect to the morphotype and sensu lato, and paleoceanographic and paleoceanographic reconstructions using non-selective mixture of morphotypescould potentially be biased. The Factorial Analysis identified four factors: Factor 1, represented by G. tenella, G. calida, and G. rubescens, is related to the subsurface temperature; Factor 2, represented by N. incompta, N. dutertrei and G. truncatulinoides is related to the depth of the thermocline; Factor 3, represented by G. bulloides, is related toupwelling; and Factor 4, represented by G. ruber and G. glutinata, is related to the intensity of the Brazil Current. The results showed that the most significant variations of paleotemperature and paleosalinity and the planktonic foraminifera assemblage are related to the abrupt climatic events of the Northern Hemisphere occurred during deglaciation and were modulated by variations in AMOC arrangement and intensity. During the cold events Heinrich 1 and Younger Dryas, related to a weakening of the AMOC, an increase of paleotemperature and paleosalinity and intensity of the Brazil Current (Factor 4) in the western portion of the South Atlantic was observed. Conversely, during the hot event Bolli-Allerod, paleotemperature and paleosalinity decreased expressively, as a response to AMOC resumption, with increased productivity and presence of a shallower thermocline (Factors 2 and 3). It is also suggested that between 26 and 15 ka there was a displacement to the north of the Brazil-Malvinas Confluence, possibly reaching the latitude of the study area (∼23°S), inferred by the presence of the G. inflata. Along the Holocene, there was also a significant variation in the intensity of the Brazil Current, indicated by the maximum values of Factor 4 around 7ka. The reappearance of G. menardii plexus occurred in 8ka, as well as the increase of the species of subsurface planktonic foraminifera, indicated by Factor 1. These changes in the Holocene were attributed to the effective entrance of the hot and saline waters from the Indian Ocean via the Agulhas Leakage, which were essential for the reestablishment of the modern AMOC.
Schimmelpfennig, Irene. "L'isotope cosmogénique Cl-36 dans les minéraux riches en Ca et en K : développements analytiques, calibrations des taux de production et inter-calibration avec le He-3 et le Ne-21." Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2009. http://tel.archives-ouvertes.fr/tel-00468337.
Повний текст джерелаChiang, Hong-Wei, and 姜宏偉. "Oxygen Isotope and Ba/Ca Ratio Records in Coral Skeletons and their Environmental Explanations from Southern Taiwan." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/17373667981244403999.
Повний текст джерела國立臺灣大學
地質科學研究所
99
Coral has been one of the best marine archives to study climate change from weekly to decadal timescales. The abundant trace elements and stable oxygen isotopes in massive coral skeletons are affected by the environment condition prevailing at the time of skeleton deposition. In this study two coral heads were collected from the Nanwan Bay, southern Taiwan to test the capabilities of traditional d18O values and recent-developed Ba/Ca ratios, with seasonal to sub-decadal timescales. Firstly, during El Niño episodes the skeletal d18O–SST correlation showed a gentler slope of -0.12 ± 0.04‰ °C-1 rather than the value of -0.21 ± 0.04‰ °C-1 during normal year. The difference was likely caused by enhanced penetration of Kuroshio Current waters into the South China Sea during El Niño summers. Secondly, an annually distinct double-peak feature of Ba/Ca ratios in coral was identified. The earlier peak is not concordant with the time of major precipitation but regularly occurred before the Sr/Ca value reached the minimum. It was resulted from a biotic source and possibly related to Cyanophyta bloom in the early-spring. The later peak happened at the time of raining seasons. Two different linear correlations are presented between skeletal Ba/Ca and accumulated precipitation in July-October. Before 1999, the relationship was given by Ba/Ca=3.02+0.0024*P; while after 1999, the relationship is given by Ba/Ca=2.26+0.0011*P. The decreased Ba/Ca baseline from the end of 1999 to 2001 is believed to relate to the operating of two sewage treatment plants since 1999 and 2000. It also can explain the gentler slope value of Ba/Ca-precipitation regression and the decreased amplitude of Ba/Ca maxima after 1999. Thus, the skeletal Ba/Ca ratios can be applied as a quantitative proxy of the paleo-precipitation in southern Taiwan.
"Scarlet Macaws, Long-Distance Exchange, and Placemaking in the U.S. Southwest and Mexican Northwest, ca 900-1450 CE." Doctoral diss., 2020. http://hdl.handle.net/2286/R.I.57275.
Повний текст джерелаDissertation/Thesis
Doctoral Dissertation Anthropology 2020
Chen, Jang-Chung, and 陳建璋. "Surprising Ca isotopic anomalies in the early solar system." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/50491210936538337869.
Повний текст джерела臺灣大學
天文物理研究所
98
We have achieved higher precision for the measurement of Ca isotopic ratio by increasing the beam intensity to around 1.2nA. 42Ca/44Ca was normalized in order to correct the remaining ratios for fractionation. The two standard deviations in reproducibility for 40Ca/44Ca, 43Ca/44Ca, 46Ca/44Ca and 48Ca/44Ca were 1.5, 0.3, 7.5 and 0.7ε (ε ≡ 0.01%) respectively. The improved precision enabled us to not only confirm 48Ca anomalies up to 5.1ε in ordinary CAIs (Ca-Al-Inclusions) in meteorites but also search for Ca isotopic variation in bulk meteorites. Prior to this, 48Ca anomalies were only endemic to CAIs in carbonaceous chondrites. Surprisingly, our experiment revealed 48Ca deficit up to -2.3ε in achondrites relative to terrestrial samples. Because achondrites were presumably solidified from large scale melting on planetary bodies hundreds of km in size, they were not expected to present any detectable heterogeneities. On the other hand, the widespread 48Ca anomalies that correlate with 50Ti and 54Cr without large effects on the tiny 46Ca indicate that these nuclides originated from the rare neutron rich nuclear statistic equilibrium (n-rich NSE), not neutron capture. However, it remains unclear. As to how to keep this nucleosynthetic component made only in rare subset of type Ia supernovae from completely mixed in the solar system after the achondrites being solidified, it lends some support to the speculation that the solar system received some injected material from a nearby supernova that happened to explode after the solidification of achondrites but before the formation of terrestrial planets.
Camaiani, Alberto, Giovanni Casini, and Andrea Stefanini. "Complete isotopic characterization of projectile fragments in Ca+Ca reactions at Fermi energies with the FAZIA array." Doctoral thesis, 2020. http://hdl.handle.net/2158/1204443.
Повний текст джерелаLiu, Hou-Chun, and 劉厚均. "Precise Determination of Ca Isotopic Composition in Carbonate and Seawater." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/63224611853735991669.
Повний текст джерела國立成功大學
地球科學系碩博士班
97
The Ca isotope composition of synthetic carbonates and corals have been measured in order to evaluate the Ca isotope fractionation during the carbonate formation; and the δ44/42Ca of a seawater profile in South China Sea (SCS) has been performed as well to realize the oceanic Ca cycle in preliminary. A fast and high-precision analytical technique for the Ca isotopes has been developed using high-resolution multi-collector ICP-MS (Neptune, Thermo-Fisher) coupled with a desolvation system (APEX-IR, ESI). Two-steps separation technique has been successfully applied to separate matrix component from the analyzed compound to avoid potential spectral interferences. The external reproducibility for δ44/42Ca analysis is better than 0.11‰ (2σ) using a standard-sample-standard bracketing method. Calcium carbonates obtained from controlled inorganic precipitation were used for evaluating the Ca isotope fractionation during precipitation and display a rather small temperature-dependent fractionation at 5-40°C (0.002 and 0.001‰/°C for aragonite and calcite, respectively). The Ca isotope fractionation factor (α) in synthetic carbonates reveals a significant difference compared with previous studies, which was attributed to the difference in growth rate under various precipitation techniques. Furthermore, Ca isotopes in cultured and field corals, Porites sp., show also only minor temperature-dependent fractionation. Kinetic rather than the temperature effects would strongly affect the Ca isotope fractionation in carbonates. On the other hand, seawaters collected from SCS displays a small but significant δ44/42Ca vertical variation. The lowest value of δ44/42Ca in the SCS is detected in the bottom water which could be partly attributed to the intense partial dissolution on marine carbonates. Further studies are necessary to improve analytical precision and to understand the main controlling factors on seawater Ca isotopes.
Bürger, Alexander [Verfasser]. "Nuclear structure of light Ca and heavy Cr isotopes / vorgelegt von Alexander Bürger." 2007. http://d-nb.info/987153021/34.
Повний текст джерелаProulx, Alexandre. "L'effet des amendements cationiques sur la photosynthèse : le cas des érables à sucre (Acer Saccharum)." Thèse, 2020. http://depot-e.uqtr.ca/id/eprint/9737/1/eprint9737.pdf.
Повний текст джерелаHeuser, Alexander [Verfasser]. "Variations of calcium isotopes (δ44Ca) [delta 44 Ca] in foraminifers over the past 24 Ma / vorgelegt von Alexander Heuser". 2002. http://d-nb.info/971995583/34.
Повний текст джерелаTeh, Ee-Ee, and 鄭郁豫. "Reconstruction of paleotemperature and paleosalinity of the South China Sea for the past 170kyrs using planktonic foraminiferal Mg/Ca ratio and oxygen isotopes." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/14866613111877671126.
Повний текст джерелаHennissen, Jan. "Late Pliocene–Early Pleistocene North Atlantic Circulation: Integrating Dinocyst Assemblages and Foraminiferal Geochemistry." Thesis, 2013. http://hdl.handle.net/1807/35845.
Повний текст джерелаKnott, Diane Clemens. "Geologic and isotopic investigations of the early Cretaceous Sierra Nevada Batholith, Tulare Co., CA, and the Ivrea Zone, NW Italian Alps: examples of interaction between mantle-derived magma and continental crust." Thesis, 1992. https://thesis.library.caltech.edu/6347/2/Knott_dc_1992.pdf.
Повний текст джерелаTwo igneous suites containing layered ultramafic-mafic cumulates were investigated with the intent to characterize the parental magma and to identify processes significant to the petrogenesis of these rocks. In both study areas, the early Cretaceous Sierra Nevada batholith and the Ivrea Zone, isotopic systematics of the cumulates were found to preserve the characteristics of the mantle-derived parental magma and to record the effects of fractional crystallization and assimilation. Modeling the relative importance of these processes and characterization of the material derived from the mantle are necessary to understanding the growth of the continental crust.
Geologic mapping of 110 mi2 of the 125 to 110 Ma Stokes Mountain region reveals the presence of layered cumulate megaxenoliths and two coeval ring dike complexes. Petrographic analysis and geochemical modeling of 125 dominantly mafic and intermediate samples demonstrate the comagmatic nature of this suite. Combined oxygen, strontium and neodymium analysis of 22 samples indicates, however, that each ring complex was fed by an isotopically distinct parental magma (εNd(115) = +6.1, Sri = 0.70338, δ18O = 6.6‰ ; (εNd(115) = +5.7, Sri = 0.70372, δ18O = 6.7‰) both of which were derived from a variably contaminated, depleted mantle source. Minor assimilation of continentally-derived metasediments and mafic-ultramafic material of the Kings-Kaweah ophiolite further affected the isotopic evolution of the two subsuites. Hydrothermal alteration in the subvolcanic environment is recorded only by rare stoped xenoliths of 120 Ma hypabyssal intrusives.
Late Hercynian (≈300 - 270 Ma) magmatism produced the 10 km thick Mafic Complex lying at the base of the Ivrea-Strona-Ceneri crustal cross section. δ18O analysis of 237 whole rock samples and 26 mineral separates reveals that presumably early intrusions into the cool crust preserve the depleted mantle signature of the modeled parental magma (εNd(115) = +7, Sri = 0.703, δ18O = 6.5‰) while later intrusions assimilated significant amounts of the 10 - 12‰ metapelite. Subsequent intrusion of voluminous basaltic magma fonned a large, convecting magma chamber in which assimilation was concentrated within boundary layers. Such lower crustal production of high-18O (δ18O = 8 - 10‰) mafic magmas is suggested as contributing to the petrogenesis of upper crustal Permian granites.
Zarrieß, Michelle [Verfasser]. "Primary productivity and ocean circulation changes on orbital and millennial timescales off Northwest Africa during the last glacial, interglacial cycle : evidence from benthic foraminiferal assemblages, stable carbon and oxygen isotopes and Mg, Ca paleothermometry / vorgelegt von Michelle Zarrieß." 2010. http://d-nb.info/1010641425/34.
Повний текст джерела