Este projeto teve como objetivo investigar a variação isotópica do oxigênio (?18O) e do hidrogênio (?D) de aqüíferos subterrâneos rasos (não confinados) em quatro regiões onde foram definidas transecções, partindo do canal principal em direção ao topo da vertente. As transecções foram estabelecidas no gradiente topográfico encontrado, em quatro sub-bacias ao longo da bacia hidrográfica do rio Piracicaba. Esta região possui uma população de aproximadamente 3,5 milhões de habitantes e uma economia baseada na agricultura e na indústria. Baseando-se em estudos anteriores sobre a variação isotópica do ?18O e ?D das águas das chuvas e dos rios (Martinelli et al. 2004), onde foi identificada uma sazonalidade nos dados e variações possivelmente associadas à utilização da água em áreas urbanas (uso industrial), os estudos foram estendidos para as fontes de águas subterrâneas (fluxo de base) para o canal principal (rio Piracicaba). A sazonalidade definida por um verão chuvoso (novembro - abril) e inverno seco (maio - outubro) foi coberta com amostragens mensais (final do período seco de 2005; período chuvoso de 2005-2006 e seco de 2006) e quinzenais (período chuvoso 2006-2007) das águas da chuva, de poços rasos, nascentes e rios que drenam as sub-bacias estudadas. Os valores do ?18O e do ?D encontrados na precipitação acumulada entre coletas nas sub-áreas apresentaram maiores variações (extremos; ?18O médio de -0,4 a -13,0? ) quando comparados aos valores das águas superficiais (?18O médio de -5,1 a -9,2? ) e subterrâneas (?18O médio de -6,9 a -7,1? ), sendo que as últimas (poços rasos e nascentes) apresentaram variações ainda menores ao longo do período estudado. A precipitação e o escoamento de base possuem composição isotópica do ?18O relativamente distintas, uma vez que a média ponderada da precipitação (-8,6? observada para o período estudado) foi diferente dos valores médios encontrados nas águas subterrâneas não confinadas (-7,0? em média). O escoamento superficial para o canal principal (rio Piracicaba) teve seu valor isotópico influenciado pela precipitação no período das chuvas (podendo apresentar variações dentro deste período), caso contrário, os sinais isotópicos das águas superficiais seriam mais semelhantes aos sinais isotópicos encontrados no fluxo de base, caracterizando a contribuição deste na manutenção das menores vazões. Contudo, observou-se que o valor médio do ?18O de todos os rios e ribeirões estudados (-5,7? ) foi cerca de 1,2? mais enriquecido do que o valor médio dos poços e nascentes (-6,9? ), no período seco. As amplitudes do ?18O encontradas nxa precipitação e água subterrânea não confinada foram utilizadas em estimativas do tempo de residência médio da água no aqüífero lívre como uma primeira aproximação. / This project had the objective to investigate the oxygen (?18O) and hydrogen (?D) isotopic variation of shallow unconfined aquifers in four regions, in transects defined from the river to the limit of the drainage area. The transects were established within a topographical gradient in four sub-catchments of the Piracicaba river hydrographic basin. The population in this basin is almost three and a half millions inhabitants and an economy based on agriculture and industry is responsible for about 10% of the total Brazilian gross production. Based on a well documented isotopic variation of rainwater and river water done previously (Martinelli et al. 2004), where data seasonality and a possible variation related to water use in urban areas were identified, the studies were extended to the groundwater (baseflow) sources to the major channel (Piracicaba river) of the basin. The seasonality defined by a wet summer (november - april) and a dry winter (may - september) was covered with monthly (end of dry season of 2005; rainy season of 2005-2006 and dry season of 2006) and every two weeks sampling (rainy season 2006-2007) of rain water, shallow wells, springs and surface water (rivers) that drain the studied sub-basins. The ?18O and ?D individual values of composite precipitation in the studied sub-areas presented higher variation (extreme values; mean ?18O from -0,4 to -13,0? ) when compared to the values found for surface water (mean ?18O from -5,1 to -9,2? ) and groundwater (wells and springs; mean ?18O from -6,9 a -7,1? ), being the values of groundwater almost constant within the studied period. Precipitation and baseflow have relative different isotopic composition of ?18O, once the weighted average of precipitation (-8,6? observed for the whole studied period) is different from the average values found for unconfined groundwater (-7,0? in average). Values of surface runoff to the main channel (Piracicaba river) were similar to those found in precipitation in the rainy season (presenting variations within this period), otherwise, the isotopic signals of surface water were rather more similar to those found in baseflow, characterizing the contribution of baseflow in the lower flows. However, average value of ?18O of all rivers and streams studied (-5,7? ) were about 1,2? more enriched than the average value of wells and springs (-6,9? ) in the dry season. The amplitudes of ?18O found in precipitation and groundwater were used as a first aproximation to estimate mean residence time of unconfined groundwater.

O Bloco São Gabriel, localizado na zona central do embasamento cristalino do Rio Grande Sul, apresenta extensos registros do Neoproterozóico do Ciclo Brasiliano, contidos em complexos ígneos e metamórficos. Esses complexos também guardam registros sedimentares, com sequências carbonáticas metamorfisadas, cuja evolução tectônica é pouco conhecida. Essas sequências são observadas na Formação Passo Feio (Caçapava do Sul), no Complexo Cambaí (Vila Nova do Sul) e no Complexo Metavulcano-sedimentar Coxilha do Batovi (São Gabriel). As rochas carbonáticas da Formação Passo Feio compreendem dolomita mármores impuros. As amostras do Complexo Cambaí são classificadas como calcita mármores impuros. Os mármores do Complexo Coxilha do Batovi compreendem litotipos calcíticos e cálcio-silicáticos, cuja assembleia mineral é composta predominantemente por calcita em alguns exemplares e por grafita em outros, com percentuais de até 10% de quartzo, demonstrando contribuição siliciclástica no protólito. Idades de zircões de rochas associadas com os mármores, de trabalhos anteriores, indicam um intervalo entre 770 – 700 Ma para a deposição dos carbonatos do Bloco São Gabriel. Os carbonatos da Formação Passo Feio sofreram dolomitização durante ou logo após a deposição, enquanto os carbonatos do Complexo Cambaí não foram afetados pela dolomitização. A geoquímica dos elementos traços e terras raras indica que os mármores analisados preservaram as assinaturas originais do protólito nos diferentes graus metamórficos: Coxiha do Batovi (grau baixo), Formação Passo Feio e Complexo Cambaí (grau médio). A análise integrada dos isotópicos de Sr, 13C e 18O da Formação Passo Feio e do Complexo Cambaí revelou a preservação de assinaturas isotópicas primárias. Na Formação Passo Feio essas assinaturas são: 0,7074 (Sr87/Sr86), -0,26‰ e 2,44‰ (δ13CPDB) e -5,68‰ (δ18OPDB). Quando comparadas com a variação desses isótopos na água do mar ao longo do Neoproterozóico, verifica-se que os mármores da Formação Passo Feio e do Complexo Cambaí estão situados no intervalo entre 740 e 730 Ma. O período sugerido para a deposição das rochas carbonáticas da Formação Passo Feio é de 770 a 730 Ma, e entre 740-730 para o Complexo Cambaí. / The São Gabriel Block, located in the central zone of the crystalline basement of Rio Grande do Sul has extensive Neoproterozoic records of the Brasiliano Cycle, contained in igneous and metamorphic complexes. These complexes also keep sedimentary records with metamorphosed carbonate sequences whose tectonic evolution is poorly understood. These sequences are found in Passo Feio Formation, located in Caçapava do Sul region, in Complex Cambaí, at Vila Nova do Sul region and in Coxilha do Batovi metavolcanosedimentary Complex, in the São Gabriel region. The Passo Feio Formation carbonate rocks consist of impure dolomite marbles. The Cambaí Complex samples are classified as impure calcite marbles. Coxilha do Batovi Complex samples include calcite and calc-silicate marbles whose mineral assemblage are composed predominantly of calcite in some samples and graphite in others, with quartz rates up to 10% showing the siliciclastic contribution to the protolith. Zircon ages of associated rocks from previous works indicate an interval between 770-700 Ma for carbonate deposition in S. Gabriel Block. The carbonates from Passo Feio Formation were affected by dolomitization process during or early after its deposition, while the carbonates from Cambaí Complex were not affected by dolomitization. Trace elements and REE geochemistry of marbles indicate preservation of original signature of carbonate protoliths along different metamorphic grades; Coxilha do Batovi (low grade), Passo Feio Formation and Cambaí Complex (medium grade). The integrated analysis of Sr isotope, 13C and 18O from Passo Feio Formation and Cambaí Complex revealed the preservation of primary isotopic signatures. The Passo Feio Formation signatures are: 0,7074 (Sr87/Sr86), -0,26‰ and 2,44‰ (δ13CPDB) and -5,68 (δ18OPDB). In Cambaí Complex, the primary signatures are: 0,7069 (Sr87/Sr86), 5,75 (δ13CPDB) and -11,64 (δ18OPDB). When compared with the variation of these isotopes in seawater along the Neoproterozoic it appears that Passo Feio Formation and Cambaí Complex are situated in the range between 740 and 730 Ma. Based on these data it is suggested that the São Gabriel Block depositional event occurred between 770-700 Ma. The period suggested for the carbonate rocks depositional event of Passo Feio Formation is between 770-730 Ma, and specifically between 740-730 for Cambaí Complex.

L'augmentation du pouvoir électrocatalytique d'une pile à combustible fonctionnant à haute température (SOFC, Solid Oxide Fuel Cell) passe notamment par l'amélioration des performances de la cathode. A cet effet, notre objectif a été de créer puis mesurer une conductivité mixte (électronique ou ionique) au sein de nouveaux oxydes de structure perovskite ABO3-d. Une étude fondamentale a été menée sur des composés choisis en fonction de l'état de valence et de la taille du cation B et du taux de lacunes d. La caractérisation des propriétés de transport (électronique et ionique) a été réalisée à l'aide de techniques nouvelles au laboratoire (meusure de la diffusion de 18O). Par la suite une corrélation entre les deux types de conductivité et les propriétés physico-chimiques des matériaux (paramètres de maille, polarisabilité des ions, ...) a été proposée.

Une approche a plusieurs echelles a été développé afin de vérifier si les différences de Δ13C entre les genotypes de peuplier représentaient les différences d'efficience de transpiration à l'échelle des feuilles et la plante entière. Nous avons également vérifié la stabilité des différences génotypiques pour Δ13C dans le temps. Nous avons constaté que les différences génotypiques pour Δ13C pouvaient etre traduites comme la difference d efficience de transpiration a l echelle des feuilles ainsi qu au niveau de la plante entière. L amplitude de la variabilité de l efficience de transpiration a l echelle du plant etait plus grand par rapport à la variabilite a l echelle de la feuille, demontrant le rôle de la perte du carbone lors de la respiration diurne et nocturne (Φc) ainsi que l'eau perdue pendant la transpiration nocturne (Φw). La productivité génotypique augmentait avec l efficience de transpiration chez Populus deltoides × nigra, mais restait stable chez Populus nigra. Les valeurs absolues de l efficience de transpiration observees lors de cette etude etaient plus elevees que chez les autres especes. L enrichissement en 18O de la matiere organique (Δ18Olb) et de l eau (Δ18Olw) des feuilles correlait avec la variation de la conductance stomatique (gs) soit au niveau de l individu ou au niveau génotypique. Lors d une premiere experience nous avons montre que les valeurs de Δ13C restaient stables pour les genotypes Populus deltoides × nigra ages de 5 a 15 ans, avec un classement génotypique particulierement conservé pendant l etude. Toutefois, une seconde experience nous a permis de demontre que des arbres ages de 4 a 7 ans presentaient des valeurs de Δ13C significativement plus faibles que celles observees lors de la premiere experimentation, avec une augmentation progressive de ces valeurs avec l age. Nous concluons que, chez le peuplier, le Δ13C peut etre considere comme un estimateur fiable de l efficience de transpiration a l echelle du plant entier, et le classement genotypique établi chez de jeunes arbres pour Δ13C reste stable avec l'âge.

The present study focuses on the Emsian-Eifelian (Lower-Middle Devonian) carbonate sequences of the Prague Basin. The Třebotov Limestone (Daleje-Třebotov Formation) and the Choteč Limestone (Choteč Formation) and their equivalents represent the stratigraphic units studied. The main goal of this study is to characterize environmental changes, known as Basal Choteč event, that were described from the boundary interval of the Třebotov and Choteč Limestone. In order to do so, sedimentological (microfacies analysis), geochemical (δ13 Ccarb, δ18 Oapatite) and paleontological (taxonomy of conodonts) studies were carried out. Eight microfacies types of carbonate rocks were described and interpreted in this study. Beside that, massive accumulations of calcispheres, peloids, prasinophytes and occurrences of blue-green algae (Girvanella) were recorded especially in the Choteč Limestone. The multidisciplinary approach mentioned resulted in characterization of the sedimentary environment of the studied units as well as their development in time. The main result of the present study is the model of the Basal Choteč event. A hypothesis of enhanced nutrient load is suggested here as a triggering mechanism for intense micritization and peloid formation and prasinophyte blooms, which were together with greater...

Rain-on-snow events represent one of the basic mechanisms causing floods. Rain falling on the snow cover causes enhanced melting and the resulting runoff often exceeds the runoff caused by rain. During the winter seasons 2018 and 2019, water samples from the stream, snowpack and precipitation were repeatedly taken in the the Ptačí Brook catchment in the Šumava mountains, and the concentrations of 2 H and 18 O were measured in the laboratory. Based on the observed isotope ratios 18 O/16 O and 2 H/1 H in combination with other variables measured in the catchment, the two ROS events from 2019 were reconstructed. The ratio of heavy isotopes increased in the snowpack due to ROS events. Using the end member mixing equation, a hydrograph separation was performed for both investigated events. For the first event, it was not possible to clearly separate groundwater from rainfall, and thus the range of snow in the total runoff was determined by its separation from rainfall and subsequent separation from groundwater. The second event examined was separated directly into three components: rainfall, groundwater and snow. According to the analyses, the total runoff during ROS events in both cases was mostly formed by event water (a combination of rainfall and melt water). The melting water from the snow cover...

Introduction Optimal nutrition is vital in the management of infants born preterm. Dietary fat in infancy is fundamental for the provision of energy for growth and development. Essential fatty acids, specifically Long Chain Polyunsaturated Fatty Acids (LC-PUFAs) such as docosahexaenoic acid (DHA), have been under investigation by several international research groups in the past decade. Essential fatty acids are critical in neurodevelopment as DHA is found in high proportions in structural lipids of cell membranes, particularly in the central nervous system (CNS). The accumulation of essential fatty acids and particularly DHA in the brain and retina occurs most rapidly during the perinatal period, therefore preterm infants are of particular concern (Singer, 2001). Current scientific consensus is that the optimum growth rate for preterm infants is equal to the in utero growth rate throughout the last trimester, however, failure to achieve the optimum intrauterine growth rate is common in preterm infants (Olhager and Forsum, 2003). Preterm infants require large amounts of energy and nutrients with which many infants are not provided or are not able to absorb, due to immature gastrointestinal and metabolic systems and other medical complications (Olhager and Forsum, 2003). There are a number of unresolved issues regarding optimal growth rate and total energy requirements (ER) for preterm infants. Hypotheses/Objectives This study is a “side study” to a double blind randomised controlled trial (RCT) of DHA supplementation in preterm infants. The hypothesis of this “side study” is that increased DHA during the neonatal period would increase total energy expenditure (TEE) and improve neurodevelopmental outcome. Specifically, at term postconceptual age (PCA) it was hypothesised that preterm infants receiving higher intake of DHA would have higher TEE’s due to the acceleration in brain maturation. Also, it was hypothesised that preterm infants receiving high levels of DHA would have TEE’s equivalent to term born infants due to their same brain maturation status. Other hypothesised effects of DHA supplementation include an accelerated maturation of the visual cortical pathways, and accelerated white matter (WM) tract development aiding in brain maturation. The first objective of this study was to measure TEE and ER in very preterm infants when they reached an age of 31-33 weeks post conceptional age (PCA). The effects of DHA supplementation on TEE, at simulated in utero levels, in very preterm infants (born < 33 weeks PCA), when assessed at term equivalent (40 weeks PCA) were studied. Another objective was to compare WM brain tissue volume at term PCA between two preterm groups and then with the term born infants. Visual latency was also compared between the two preterm infant groups and then with the term born infants. Methods TEE was measured using the doubly labelled water (DLW) method which is based on the differential elimination of 2H (deuterium) and 18O from the body subsequent to a loading dose of these isotopes. TEE was measured at the preterm age between 31-33 weeks PCA and again at term PCA. TEE measurements are made at term PCA in a term born control group. Brain assessment was by Magnetic Resonance Imaging and (MRI) and Visual Evoked Potential (VEP). Magnetic resonance imaging quantitatively measured brain volumes and WM. Visual evoked potential would provide information on visual latency and amplitude. Results The cohort consisted of 38 infants. The TEE of the very preterm infant group was measured at 31-33 weeks PCA. The mean (±standard deviation) (SD) TEE was calculated at 80(±27) kcal/kg/d, and using data in the literature for foetal energy accretion of 28kcal/kg/d, the mean ER was calculated to be 108(±27) kcal/kg/d. At term PCA TEE was calculated for the preterm DHA supplemented group to be 56(±19) kcal/kg/d and for the non-DHA supplemented group 70(±39) kcal/kg/d. These measurements were not statistically different. Flash VEP conducted on preterm given different amounts of DHA tested at term PCA found no statistically different measurements. When combining these results and comparing them to measurements of term born infants at term PCA, the right eye measurements showed that preterm infants had statistically greater latencies than term infants. When combining the left and right eye measurements the latencies no statistical significance was found. Amplitude was also not statistically significant between the groups. MRI measures at term PCA were not statistically different DHA supplemented and the non-DHA supplemented preterm infant group. When the preterm infant cohort was combined and compared to the term born infant group, the results showed that preterm infants imaged at term PCA had reduced WM development in a number of frontal lobe projections, and anterior and posterior commissarial pathways of the corpus callosum and corona radiata. Discussion The TEE and ER measurements in this study represent the largest preterm infant cohort to date. The ER values reported here are of value in allowing the calculation of appropriate feeding and nutritional strategies for preterm infants. Although no differences in TEE between the DHA and non DHA supplemented groups were found this may have been due to the small sample size. With regard to the latency outcomes, it can be speculated that if measurements were conducted at a later PCA the correlations may have been stronger and significant. Several other factors may have also affected the results, including alertness of the infant at the time of testing, thickness of the cranium, and other health factors could not be controlled for. This study contains the youngest cohort to be compared via Flash VEP. The MRI data did not find significant differences in brain volume and WM between the DHA supplemented and the non-DHA supplemented groups. The infant CNS is rapidly developing and there are multiple environmental factors which may have affected outcomes. The data did however find differences in WM development between the preterm and term infants. The reduced WM development found in the preterm infants compared to term born infants may provide some explanation for the correlation between preterm birth and poorer cognitive and functional outcomes. Larger studies which extend beyond the first months of life are recommended in order to investigate the long-term relationships between DHA supplementation, TEE and brain maturation.

Lebanon is situated in a Mediterranean semi-arid region rich in hydraulic resources but strongly under the impact of anthropogenic pressure, mainly after the industrial boost in the last 50 years. In this thesis our research is devoted to the study of water resources and the assessment of soil pollution in two contrasting watersheds that may resemble similar regions in the world. Rivers act as a collective funnel of contaminants derived from rock weathering, industrial, agricultural and urban practices. Thus we focus our study on the two main contrasting watersheds in Lebanon: an industrially dominated watershed located northwest of the country on the Mediterranean coast (Al Jouz basin), and a rural historically agricultural watershed that lies in the continental valley between the two mountainous chains (Litani basin). Geochemical analysis coupled to multi-isotopic applications was used as tools to investigate the collective influence of land-use cover, geomorphological processes, topography, soil type, geology, geography, orography, climate, and hydrological variability on drainage basin evolution. A two-year sampling strategy was followed (2011-2013) to collect not only water samples at various depths in the reservoir and in the piezometers, but also sediments (lacustrine, riverine and coastal) and soils (surficial and cores) to cover seasonal variations (rainy, first flush and dry seasons) in both studied areas. The results highlight the entire mechanism of characterization, origin, and partitioning between the dissolved and particulate phases of pollutants. Furthermore, the environmental implication of the Qaraaoun reservoir was assessed by emphasizing water hydrodynamics and its interaction with the watershed. Characterizing industrial and agricultural pollution allows the understanding of metal behavior and the prediction of its fate, in association with the environmental receiving media in semi-arid and Mediterranean areas. This work was the first to trace pollution sources and to reconstruct the metal fluxes in two of the most environmentally significant watersheds in the country. Stable and radioactive Pb isotopes were used in addition to 137Cs to study the geomorphological influence and the chronology of the environmental stress exerted by the factory and the dam on basin ecology. Moreover, the nature of the Qaraaoun reservoir and the internal hydrological dynamics were explored using stable hydrogen and oxygen isotopes to delineate the reservoir water layers and its fast response to meteorological and hydrodynamic changes in the watersheds, and to demonstrate its strong hydrological connectivity with groundwater. Reservoir water balance was made, indicating groundwater influx into the reservoir which was reported for the first time. The water hydrodynamics was also assessed using a box model, which in its role can be used to evaluate the reservoir water balance and hydro-project functionality and to establish the basis for water sustainability in the long term. This work has yielded a better understanding of biogeochemical processes under different environmental conditions. The treated issues in this thesis will provide a foundation for future hydropower projects and allow one to draw a road-map for national management plans, and to raise the alert for remediation processes and management methods to preserve the environment and resource sustainability, and ultimately the wellbeing of the local population.<p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

<p> Speleothems are calcium carbonate deposits, such as stalagmites, stalactites and flowstones, formed in a cave environment by loss of carbon dioxide from saturated groundwaters. Variations in the 18o/16o ratio of calcite are related to changes in depositional temperature provided that the speleothem formed in isotopic equilibrium with its seepage water (conditions characterised by slow coloss and no evaporation of seepage water). Variations in 18o/16o of the seepage water will also be reproduced in the calcite but allowance for this effect can be made if 18o/16o ratio of the source (ocean water) can be estimated (from deep sea sediment cores) and if the influence of temperature on 18o/16o ratio of precipitation at the site can be determined. Because cave temperatures closely approximate mean annual surface temperature, the axial 18o/16o record of a speleothem is therefore an indication of paleoclimate and of temperature change over the period of its growth. </p> <p> The frequency distribution of age measurements for several speleothems from an area may also be used as a paleoclimatic indicator because cold or glacial conditions above the cave will inhibit speleothem growth by freezing water at the surface and removing vegetation and soil cover, the main source of CO2 for the limestone dissolution-reprecipitation process. </p> <p> Pure, non-porous calcite speleothems from several limestone regions have been dated in this study by the 230Th/234U method, and in cases of uranium-rich speleothems, by the 231Pa/230Th method also. For ten such cases, examined, good agreement of ages determined by both dating methods was found. </p> <p> Relatively few deposits however, have shown deposition under isotopic equilibriwn conditions, due probably to the well-ventilated nature of the caves studied. </p> <p> The age distribution for speleothem from Cascade Cave on Vancouver Island, B.C., indicates growth during the mid-Wisconsin interstadial dated as 65 -30,000 yrs. B.P. Stable isotope profiles for two speleothems which grew over this period both show values of 18o/16o ratios of calcite which are significantly lower than calcite growing in the cave today. This is the first clearly-defined record of such an occurence (in previous work, 18o/16o of fossil speleothem was generally greater than modern). Using estimates of the change in 18o/16o of ocean water from a Pacific deep sea core, and the value determined by Dansgaard (1964) for the temperature dependence of 18o/16o of precipitation for oceanic sites, a realistic paleotemperature record is derived. The results indicate that temperatures at the Cascade Cave site were about 4.0°C , 64,000 yrs. ago· and gradually declined to 0°c by 35,000 yrs. ago. These data are consistent with the findings of Canadian workers from 14c and palynological studies of fossil organic matter in the area, and do not support the proposal by some American workers of a major glaciation occurring between 35 - 40,000 yrs. B.P. </p> <p> The age distribution for 140 analyses of 82 speleothems collected from caves in north-west England show abundant deposition during the periods 130 -90,000 yrs. B.P. and 13,000 yrs. B.P. to present, with limited growth over the periods > 350 -170,000 yrs. B.P. and 70 -35,000 yrs. B.P. No ages were found to lie within the periods 170 -140,000 yrs. B.P. and 35-15,000 yrs. B.P. These intervals are correlated to the Wolstonian and Devensian glaciations respectively. </p> <p> Only four speleothems were found to have grown in isotopic equilibrium with their seepage waters, and one of these showed periods of non-equilibrium deposition. In contrast to the Vancouver Island results, 18o/16o all ratios were found to be greater than or equal to modern, indicating that the apparent oceanic location of this site is not expressed in the on the value for temperature dependence of 18o/16o precipitation. </p> <p> An oxygen isotope profile for a flowstone dated between 126,000 and 109, 000 yrs. B.P. shows 18o/16o ratios commencing at values slightly lower than for modern calcite and shifting to still lower values at about 112, 000 yrs. B.P. This shift may indicate a cooling event perhaps carrelative with the isotope stage 5e-5d transition seen in the deep sea core record. A profile for a flowstone over the period 290 -190,000 yrs. B.P. shows excellent correlation to interglacial stages 9e and 7c seen in the deep sea core record, and a pronounced growth hiatus dated at about 250 210,000 yrs. B.P. correlates with glacial stage 8. These are the first speleothem results to show a climatic record beyond 200,000 yrs. B.P. </p> <p> The differences in 18o/16o behaviour for speleothems from the two locations (N .E. Pacific and ..E. Atlantic) are interpreted in terms of their relative proximity to the ocean, potential for exchange of water vapour and 'rainout' by airmasses moving towards the cave sites, and possibility of change in meteorological conditions (principally storm track) over the periods studied. </p> <p> In a subsidiary study, evidence for major sea level lowering during the Illinoian glaciation is recognised by age determinations on the calcite core of speleothems collected at 45m below present sea level from a 'blue hole' near Andros Island in the Bahamas. </p> <p> The possibility of applying the 234U/238U dating method to speleothem is also investigated in this work, by the analysis of modern calci tes and their seepage waters, using a new method for uranium extraction from groundwater. However the variations in 234U/238U ratios observed over short distances in the same cave demonstrate that estimation of initial fossil 234U/238U in the speleothem cannot simply be made by averaging modern ratios for the cave. </p> <p> Consideration is also given to the temperature dependent distribution of trace elements in calcite, particularly magnesium and strontium. Analyses of modern calcites and waters show that Mg incorporation is strongly temperature dependent whereas Sr is not. The possibility of using Mg variations in fossil speleothem as indication of temperature change is briefly examined but the results for one sample are found to be inconclusive. </p> / Thesis / Doctor of Philosophy (PhD)

O objetivo do presente estudo é avaliar o uso associado dos proxies ?18O e Mg/Ca obtidos em testas de foraminíferos. Para alcançar tal objetivo foram realizadas análises de ?18O e Elemento/Ca em amostras de foraminíferos planctônicos (G. ruber e G. sacculifer) e bentônicos (Cibicidoides spp., C. corpulentus, Uvigerina spp. e H. elegans) de dois testemunhos do Atlântico Sul. Os resultados demonstraram que apesar dos proxies ?18O e Mg/Ca apresentarem perfis distintos em relação às espécies os mesmos se correlacionam de forma apropriada, sendo possível estimar a temperatura e os sinais de ?18OSW e ?18OLocal a partir dos mesmos. A partir dos dados de temperatura estimados com base em Mg/Ca foi possível identificar uma anomalia negativa das águas superficias entre o LGM e o HL de -1,5 ± 0,2 °C, enquanto que nas águas profundas observou-se uma anomali positiva de 1,7 ± 0,4 °C para o mesmo período. Os dados de ?18OSW estimados com base nos dados de temperatura e ?18O indicaram uma oscilação de 1,0 ± 0,1 ? e 2,0 ± 0,2 ? para as espécies planctônicas e bentônicas durante o LGM e o HL. Segundo o valor esperado para a variação do volume de gelo (~1,2 ?) há uma oscilação muito baixa da salinidade nas águas superficias da região de estudo, em contraste com uma oscilação bem marcada da salinidade nas águas de fundo. As estimativas de ?18OLocal indicaram uma oscilação entre o LGM e o HL muito pequena da salinidade (~0,1 ?) nas águas superficiais, com uma oscilação maior nas águas de fundo (1,0 ± 0,3 ?). O aumento da salinidade das águas de fundo durante o LGM corrobora a anomalia positiva da temperatura observada neste estudo, visto que, para a ocorrência da mesma, é necessário que a densidade das águas de fundo seja suficiente para manter a estratificação da coluna de água. / The 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.