La croûte de granitoïdes de la Terre Primitive la plus ancienne qui ait été préservée remonte au Paleoarchéen et se compose principalement de granitoïdes sodiques tonalite-trondhjémite-granodiorite (TTG) qui se sont formés par fusion partielle de métabasaltes hydratés. En revanche, les granites (stricto sensu) sont en général postérieurs aux TTG et apparaissent tardivement dans les cratons anciens.Cependant, l’existence de zircons Hadéens préservant des suites d’inclusions minérales qui sont compatibles avec la cristallisation à partir d’un magma granitique peralumineux, indique que les roches granitiques faisaient aussi partie de la croûte felsique de la Terre Primitive; même si nous n’avons pas de preuves directes et que cette dernière n’ait pas conservée. Dans cette thèse, je présente une variété inhabituelle de granites et rhyolites peralumineux qui sont marqués par un forte teneur en K2O et une faible teneur en CaO et qui possèdent du rutile. Ces roches sont situées dans le conglomérat basal du Groupe du Moodies (Afrique du Sud). Elles défient la vision commune que l’on a de l’évolution des cratons Archéens puisqu’elles ont été produites en même temps que des magmas TTG, pendant trois cycles magmatiques qui ont affectés la ceinture de roches vertes de Barberton (CRVB). Ces roches ont été par la suite mises en place, comme galets, dans un conglomérat plus jeune.L’étude des inclusions minérales localisées dans des zircons présents dans les granites et les rhyolites qui font le sujet de cette étude, montre que les inclusions de feldspaths alcalins sont plus abondantes que les inclusions de plagioclases et démontre que les principales caractéristiques de ces granites, c’est à dire qu’ils sont riches en K et pauvres en Ca, ont une signature magmatique. La signature isotopique de l’oxygène de ces zircons révèle que ceux-ci ont conservé la valeur du δ18O du magma à partir duquel les granites se sont formés. De plus ceci montre que la valeur du δ18O de la source des granites etait proche de celle de TTG contemporains. La poursuite de l’étude des zircons montre que leur système isotopique Lu-Hf reflète la signature crustale du magma dans lequel ils ont cru. L’étude Sm-Nd des granites et rhyolites indique que l’âge minimum du protolithe de leur source est de près de 3,9 milliards d’années, ce qui est en accord avec la signature Lu-Hf des zircons. De plus, je montre dans cette thèse que le caractère peralumineux des granites et des rhyolites, avec leur forte teneur en Sr et basse teneur en Ca associés à leurs Eu / Eu * ~ 1, est une conséquence de la fusion partielle de phengite dans une source métagrauwacke à des pressions supérieures a celle de la stabilité du plagioclase. Mon travail montre donc que des granites peralumineux riches en K et pauvres en Ca ont été générés durant le Paléo et Méso-Archéen, aux côtés des TTG sodiques, par la fusion partielle de sédiments, à haute pression. Non seulement ce processus a démontré la capacité de la Terre Primitive à recycler du matériel relativement jeune et ce, dès 3,9 milliards d’années; mais il a également contribué à chaque épisode de croissance crustale à travers le Paleo- et Méso-Archéen dans la CRVB, malgré l’absence de pluton mis en place à des profondeurs identiques à celles des TTG. / Earth’s oldest preserved granitoid crust dates back to the Paleoarchean and consists predominantly of sodic tonalite-trondhjemite-granodiorite (TTG) granitoids that arose through the partial melting of hydrated metabasalts. In contrast, granites (sensu stricto) typically postdate the TTG and appear late in the plutonic record of the old cratons. However, the existence of Hadean zircons with mineral inclusion suites that are consistent with crystallization from peraluminous granitic magmas indicates that granitic rocks formed part of the earliest felsic crust; although we have direct evidence, this earliest felsic crust is not preserved. In this PhD I present an unusual variety of markedly CaO-poor, K2O-rich, rutile-bearing, peraluminous granite and rhyolite that are located in the basal conglomerate of the Moodies Group (South Africa). These rocks challenge the common view of the Archean craton evolution as they were produced concurrently with TTG magmas during three magmatic cycles in the Barberton Greenstone Belt (BGB) and were later emplaced, as clasts, in a younger conglomerate. The study of mineral inclusions located in the zircons present within the granites and rhyolites, shows that alkali feldspar inclusions are abundant relative to plagioclase inclusions and demonstrates that the main characteristics of these granites, i.e. they are K-rich and Ca-poor, are a magmatic signature. The oxygen isotope signature of these zircon grains reveals that the zircons have preserved the δ18O value of the magma from which the granites originated and that the source of the granites had a magmatic oxygen isotope value close to the one of the regional coeval TTG. Further study of the zircons shows that their Lu-Hf isotopic system reflects the crustal signature of the magma into which they grew. Sm-Nd study of the granites and rhyolites whole rock indicates that the minimum age of the source’s protolith of the granites and rhyolites is close to 3.9 billion years, which is in agreement with the zircons’ Lu-Hf signature. Additionally I show in this thesis that the peraluminous character of the granites and rhyolites, along with their high Sr and low Ca content associated to their Eu/ Eu* ~ 1 is a consequence of phengite melting in a metagreywacke source at pressures in excess of plagioclase stability. My work therefore illustrates that K-rich, Ca-poor peraluminous granites were generated in the Paleo and Meso Archean, alongside with the sodic TTG, through partial melting of sediments at high pressures. Not only has this process demonstrated the ability of the early Earth to recycle relatively young material since 3.9 billions years ago, but it has also contributed to each episode of continental crustal growth through the Paleoarchean to Mesoarchean in the BGB, despite leaving no plutonic record at the typical mid-crustal level of exposure that the TTG plutons around the belt represent.

The carbonate storm-dominated sedimentary succession superbly exposed on Anticosti Island in Eastern Canada represents one of the most complete and well-preserved paleotropical stratigraphic records spanning the Ordovician-Silurian (O-S) boundary. We sampled the nearly continuous coastal outcrop exposed at low tide along the west coast of Anticosti Island for high-resolution δ13C and δ18O chemostratigraphy. These new isotopic curves comprise more than 500 data points spaced at ~0.6 m intervals; for a total of 320 m of strata across the O-S boundary. The δ13C curve displays two distinctive positive excursions in the Hirnantian Ellis Bay Formation; a small lower excursion (+2.5‰) and an upper larger excursion (+4.5‰). These two positive isotopic carbon excursions provide a distinctive chemostratigraphic signature for regional and global correlations with other Hirnantian sections. The continuing descending δ13C trend, at least 30 m above the currently interpreted O-S boundary, suggests a readjustment of that boundary on the Anticosti succession. The δ18O curve, similarly to the Quaternary δ18O marine curve, is tightly coupled with multi-order cyclic facies changes. Our tightly coupled lithological and oxygen isotopic data suggest that the Anticosti succession was influenced by glacio-eustatic fluctuations during the end-Ordovician. Furthermore, the estimated duration of these multi-order cycles supports an astronomical forcing. A primary isotopic signal record is also supported by the lack of significant covariance between δ13C and δ18O, by the excellent microfabric preservation of both macro and microfossils in petrographic, cathodoluminescence, and SEM microscopy, and by little or no diagenetic resetting as suggested by the trace element geochemistry, which is unusual in the deep geological time.

Plant carbon isotopes were used to track assimilation of riparian resources by small mammals. Voles and shrews derived significant portions of their carbon from riparian vegetation. Deer and harvest mice were abundant in riparian habitat but assimilated little riparian vegetation indicating that the riparian corridor provided resources other than food. This is first use of stable carbon isotopes to trace riparian resources into a vertebrate community. Conifer encroachment in sagebrush ecosystems negatively affects many wildlife populations. Conifer removal is recommended across millions of hectares in the Great Basin. However the effects of conifer encroachment and conifer removal are unknown for most wildlife species. We show that the consequences of conifer encroachment, a press impact, far outweigh the pulse impact of sagebrush restoration, on small mammal diversity. Lack of demographic data limit the development of effective management, conservation and recovery goals for rattlesnakes. We used a long-term dataset and capture mark recapture models to quantify demography of four rattlesnake populations. Mean population growth indicated an overall stable population across the study, with two of the four sites declining. Survival overwhelmingly contributed to population growth relative to recruitment. No small mammals drank stream water even during periods of environmentally high water stress and high aridity, extension of the linear regression equation for small mammal body water towards the meteoric waterline, captures stream water, the weighted mean average for regional meteoric waters. Similar regression of fossilized small mammal tissues would also capture local meteoric waters. Even in arid regions, small mammal fossils are a suitable proxy for climate reconstructions. In the Great Basin, snowmelt overwhelmingly contributes to local precipitation, plant production, and stream flows. Snowmelt supports riparian and upland plants, and small mammals. Rattlesnakes prey primarily on small mammals, indirectly depending on snow melt for survival and reproduction. Climate models and rattlesnake emergence strongly indicate an earlier onset of spring and reduced ratio of snow to rain. Declining snowpack will have major impacts on biodiversity and management such as riparian vegetation, native plant restoration, trophic interactions, and ecological goods and services.

The Hirnantian mass extinction was the second largest of the Phanerozoic. A global sea level fall resulting from a glaciation on Gondwanaland caused significant changes in ocean circulation patterns and nutrient cycling that is recorded as a worldwide positive δ13C excursion.<p> In chapter 2, carbon and nitrogen isotope profiles were reconstructed from two North American carbonate platforms in Nevada and one in the Yukon with the purpose of gaining a better understanding of proximal to proximal gradients in δ13C values from Hirnantian epeiric seaway sediment. Positive δ13C excursions are recorded in bulk inorganic and organic carbon fractions from all three sections, and in graptolite periderms from one section. A larger positive excursion is recorded in the proximal sediment (7) compared to proximal sediment (3-4). This gradient appears to reflect differences in surface water dissolved inorganic carbon δ13C values across epeiric seas. These findings are consistent with the carbonate weathering hypothesis, that predicts larger positive δ13C shifts in proximal settings of tropical epeiric seas resulting from changes in the local carbon weathering flux caused by the exposure of vast areas of carbonate sediment during glacioeustatic sea level fall and restricted shelf circulation. A 2 positive excursion in δ15N is interpreted to result from increased ocean ventilation, greater partitioning of atmospheric oxygen into downwelling surface waters, oxygen minimum zone shrinkage, and declining denitrification rates. This allowed for upwelling of recycled nitrogen with high 15N values into the photic zone that forced exported organic matter from the photic zone to higher 15N values, consistent with the observed positive shift in 15N during the Hirnantian glaciation. This study presents a conceptual model to explain secular changes in δ13C and δ15N during the transition from a greenhouse to icehouse climate.<p> The second focus of this research, presented in chapter 3, was on improving the chemical and analytical methods for δ18O analysis of biogenic apatites. The technique applies cation exchange chromatography that allows for small sample sizes of apatite (200 µg) to be used for chemical conversion to Ag3PO4. The precision (0.15, 1) of δ18O analysis obtained using a Thermal Conversion Elemental Analyser Continuous Flow Isotope Ratio Mass Spectrometer (TC/EA CF-IRMS), and the ability to collect multipe isotopes (O, Ca, Sr, REE) using a cation exchange column, makes this technique valuable for high-resolution, multi-isotope studies of biogenic apatites.

In recent decades, there has been increased global concern about observed climate change; however for future climatic impacts and anthropogenic forcings of climate change to be realistically predicted, natural climate variability in the past needs to be better understood. The aim of this research is to develop quantifiable proxy records of past climate change through the calibration of isotope values in modern surface waters and tree ring cellulose with meteorological and atmospheric records. Terrestrial proxy records that utilize oxygen and hydrogen isotope values to reconstruct paleoclimatic and paleohydrologic conditions are limited by a paucity of data on the modification of surface water isotope values prior to sequestration into proxy material. To address this gap in our knowledge and determine the most appropriate study sites, this research focuses on isotopic records preserved in surface water reservoirs, precipitation, and tree-ring cellulose. In the first study, δD, δ18O, and deuterium-excess values were determined for lakes and rivers from Tasmania, southeastern Australia. <p> The second focus of this research was to calibrate the δ18O, δD, and δ13C values of tree-ring cellulose from North America with instrumental records. A new high-resolution sampling procedure that uses a robotic micromilling device to very precisely map and sample along growth rings in trees is discussed. Additionally, a seasonally resolved (early/late wood) 110-year record of δ18O values from tree-ring α-cellulose from spruce species (<i>Picea mariana</i> and <i>P. glauca</i>) from east-central Saskatchewan, Canada is compared to growing season precipitation δ18O values, temperature, and relative humidity. The δ18O time series from α-cellulose display a high correlation with growing season precipitation isotope values (r = 0.86). δ18O α-cellulose time series from a white spruce (<i>Picea glauca</i>) also records seasonal changes in atmospheric circulation associated with the position of the circumpolar vortex and dominate modes of atmospheric variability such as the North Atlantic Oscillation and Pacific Decadal Oscillation.

L'étude de la composition isotopique de l'oxygène de l'émail des dents de vertébrésconstitue une méthode fiable de reconstitution des paléotempératures, grâce àl'interdépendance entre le δ18O de l'apatite des dents, le δ18O des fluides corporels, del'eau ingérée et la température du milieu. L'amélioration et la miniaturisation des techniquesanalytiques a permis d'augmenter la résolution du signal reconstitué, depuis les variations detempérature sur de grandes échelles de temps jusqu'aux variations saisonnières durant laformation de la dent. Cependant, ces variations du δ18O de la dent ne sont pas uniquementdépendantes des variations de température du milieu, mais peuvent également êtreaffectées par d'autres paramètres climatiques, comme la répartition des précipitations aucours de l'année, ou biologique, comme le mode de minéralisation de la dent, l'alimentation,la physiologie de l'animal ou des migrations.Les paramètres biologiques peuvent être estimés dans le cas de taxons possédantdes parents proches dans la faune actuelle. Par exemple, la connaissance des processus deformation et de minéralisation des dents de bovinés actuels permet d'interpréter le signalisotopique de l'oxygène enregistré dans les dents de bovinés fossiles. Ainsi, l'analyse dedents de Bison priscus provenant de l'aven de Coudoulous (Lot, France) a permis dereconstituer les variations saisonnières de température au cours de l'avant-dernier épisodeglaciaire (MIS 6) au Pléistocène moyen, lorsque la région servait de terrain de chasse àHomo neanderthalensis. Le climat était à cette époque plus froid de 4°C en moyenne, maisavec des saisons nettement plus contrastées. Ainsi, si les températures estivales étaientidentiques aux valeurs actuelles, les températures hivernales étaient plus basses de 6-7°C.En milieu marin, les variations saisonnières de température affectent uniquement leseaux de surface. Les plaques dentaires de myliobatidés, un groupe de raies pélagiquesvivant principalement entre 0 et 100 mètres de profondeur, sont un outil potentiel pourreconstituer la paléosaisonnalité. L'étude de plaques dentaires de Myliobatis et deRhinoptera actuels montre que la composition isotopique des dents de ces animauxenregistre des variations de température et de δ18O des eaux de surface. Ainsi, il est doncpossible de reconstituer les caractéristiques des masses d'eau traversées par l'animal. Cetoutil a également un intérêt paléoécologique car il permet de mettre en évidence d'éventuelscomportements migratoires, comme chez certains myliobatidés actuels. L'étude despécimens d'Aetomylaeus provenant du Pliocène de Montpellier (Hérault, France) montredes températures 5°C plus élevées par rapport aux v aleurs actuelles.

In recent decades, there has been increased global concern about observed climate change; however for future climatic impacts and anthropogenic forcings of climate change to be realistically predicted, natural climate variability in the past needs to be better understood. The aim of this research is to develop quantifiable proxy records of past climate change through the calibration of isotope values in modern surface waters and tree ring cellulose with meteorological and atmospheric records. Terrestrial proxy records that utilize oxygen and hydrogen isotope values to reconstruct paleoclimatic and paleohydrologic conditions are limited by a paucity of data on the modification of surface water isotope values prior to sequestration into proxy material. To address this gap in our knowledge and determine the most appropriate study sites, this research focuses on isotopic records preserved in surface water reservoirs, precipitation, and tree-ring cellulose. In the first study, δD, δ18O, and deuterium-excess values were determined for lakes and rivers from Tasmania, southeastern Australia. <p> The second focus of this research was to calibrate the δ18O, δD, and δ13C values of tree-ring cellulose from North America with instrumental records. A new high-resolution sampling procedure that uses a robotic micromilling device to very precisely map and sample along growth rings in trees is discussed. Additionally, a seasonally resolved (early/late wood) 110-year record of δ18O values from tree-ring α-cellulose from spruce species (<i>Picea mariana</i> and <i>P. glauca</i>) from east-central Saskatchewan, Canada is compared to growing season precipitation δ18O values, temperature, and relative humidity. The δ18O time series from α-cellulose display a high correlation with growing season precipitation isotope values (r = 0.86). δ18O α-cellulose time series from a white spruce (<i>Picea glauca</i>) also records seasonal changes in atmospheric circulation associated with the position of the circumpolar vortex and dominate modes of atmospheric variability such as the North Atlantic Oscillation and Pacific Decadal Oscillation.

The Hirnantian mass extinction was the second largest of the Phanerozoic. A global sea level fall resulting from a glaciation on Gondwanaland caused significant changes in ocean circulation patterns and nutrient cycling that is recorded as a worldwide positive δ13C excursion.<p> In chapter 2, carbon and nitrogen isotope profiles were reconstructed from two North American carbonate platforms in Nevada and one in the Yukon with the purpose of gaining a better understanding of proximal to proximal gradients in δ13C values from Hirnantian epeiric seaway sediment. Positive δ13C excursions are recorded in bulk inorganic and organic carbon fractions from all three sections, and in graptolite periderms from one section. A larger positive excursion is recorded in the proximal sediment (7) compared to proximal sediment (3-4). This gradient appears to reflect differences in surface water dissolved inorganic carbon δ13C values across epeiric seas. These findings are consistent with the carbonate weathering hypothesis, that predicts larger positive δ13C shifts in proximal settings of tropical epeiric seas resulting from changes in the local carbon weathering flux caused by the exposure of vast areas of carbonate sediment during glacioeustatic sea level fall and restricted shelf circulation. A 2 positive excursion in δ15N is interpreted to result from increased ocean ventilation, greater partitioning of atmospheric oxygen into downwelling surface waters, oxygen minimum zone shrinkage, and declining denitrification rates. This allowed for upwelling of recycled nitrogen with high 15N values into the photic zone that forced exported organic matter from the photic zone to higher 15N values, consistent with the observed positive shift in 15N during the Hirnantian glaciation. This study presents a conceptual model to explain secular changes in δ13C and δ15N during the transition from a greenhouse to icehouse climate.<p> The second focus of this research, presented in chapter 3, was on improving the chemical and analytical methods for δ18O analysis of biogenic apatites. The technique applies cation exchange chromatography that allows for small sample sizes of apatite (200 µg) to be used for chemical conversion to Ag3PO4. The precision (0.15, 1) of δ18O analysis obtained using a Thermal Conversion Elemental Analyser Continuous Flow Isotope Ratio Mass Spectrometer (TC/EA CF-IRMS), and the ability to collect multipe isotopes (O, Ca, Sr, REE) using a cation exchange column, makes this technique valuable for high-resolution, multi-isotope studies of biogenic apatites.

Water is a valuable and crucial resource, the protection of which poses environmental, social and economic challenges. Fundamental to the sustainable use of water is effective management. In the Canterbury region of New Zealand, nitrate contamination has become a resource management issue due to changes in land use and intensification, which have placed pressure on the region’s groundwater and surface water systems. The purpose of this study was to assess and track nitrate concentrations on the Central Canterbury Plains with specific emphasis on a local point source of nitrate, the Ashburton Meat Processors plant. To make this assessment review of historical data was followed by the collection of 131 groundwater and 25 surface water samples to analyse the geochemical properties of the water and the stable isotopic composition of nitrate in the water. It was hypothesised that nitrate concentrations at a regional scale have increased since regular records began and that the stable isotopic composition of different nitrate sources are not discernable. Nitrate concentrations across the Canterbury region were found to have increased, prompting concerns about water quality. Concentrations are elevated above natural background levels across much of the Canterbury Plains and extreme concentrations are associated with local point sources of nitrate. Nitrate concentrations down gradient of the Ashburton Meat Processing plant are shown to have declined approximately 5% per year for the past ten years, which is in contrast to the rest of the region, where average concentrations have nearly doubled in 20 years. The reduction of contamination from the point source is most likely the result of the implementation of better wastewater management practices in the early 21st century. The δ18O and δ15N values of nitrate were found to be relatively homogenous over the Canterbury Plains. Therefore, it is suggested by this study that the dual-isotope approach alone, is not a viable tool for nitrate source identification in the region. The uniform nitrate stable isotopic composition in Canterbury could be attributed to a single, principle source of nitrate, such as clover, that overprints other isotopic compositions of nitrate source, or may also be the result of soil processes and the farming techniques used in the region. This research presents important findings for the future of identifying and managing nitrate sources in the Canterbury region. Better management practices are required for the diffuse source(s) of nitrate contributing to the widespread contamination. Critical thinking and the willingness of stakeholders to engage in the identifying, documenting and solving problems is necessary to ensure the effective management and sustainability of this precious resource.

Submitted by Isaac Francisco de Souza Dias (isaac.souzadias@ufpe.br) on 2016-03-30T17:49:45Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) taiana oliveira - DISSERTAÇÃO.pdf: 4036407 bytes, checksum: b4f85048cc1a642722cd6e2d3778433b (MD5) / Made available in DSpace on 2016-03-30T17:49:45Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) taiana oliveira - DISSERTAÇÃO.pdf: 4036407 bytes, checksum: b4f85048cc1a642722cd6e2d3778433b (MD5) Previous issue date: 2015-07-17 / CNPQ / Interferências antrópicas no estuário do rio Timbó (Paulista-PE) representaram forçantes que modificaram as características hidrodinâmicas e geoquímicas desta bacia hidrográfica. Nesta pesquisa, as mudanças ambientais são abordadas por estudos micropaleontológicos, através da assembleia de foraminíferos bentônicos, com apoio de estudos geoquímicos, inclusive isotópicos, ambos a partir de testemunhos de sondagem de fundo executada no estuário deste rio.A coleta do testemunho foi realizada em dezembro de 2012 e dezembro de 2013, utilizando um equipamento constituído de tubo de PVC com 50 mm de diâmetro, alcançando a profundidade de 87 cm e 90 cm para dados isotópicos.Este perfil cobriu cronologicamente o período desde fins do século XIX à primeira década do século XXI. Os resultados, apoiados em estudos estatísticos, indicaram que a espécieQuinqueloculina lamarckianaparece restrita a condições de maior hidrodinâmica, marcadas por quartzo > 20% em sedimento total. Ammonia tepidamostrou-se confiável espécie bioindicadora de degradação ambiental, acompanhando concentrações de Pb nos sedimentos.Discorbis floridanatambém se mostrou boa indicadora ambiental, em sedimentações mais recentes, acompanhando a degradação ambiental desde as últimas décadas. As modificações ambientais neste estuário, sobretudo resultantes de interferências antrópicas, se mostraram bem rastreáveis através do estudo de isótopos deδ13C e δ18O a partir dos carbonatos dos exoesqueletos dos foraminíferos bentônicos estudados. / Anthropogenic interference in the estuary of Timbó river (Paulista-PE) changed the hydrodynamic and geochemical characteristics of the watershed. In this study, we evaluated the environmental changes by micropaleontologicalstudies through the assemblagesof benthic foraminifera, supported by geochemical studies, including isotopic evaluation, both from bottom drill core executed in the estuary of the river. The collection of core was held in December 2012 and December 2013, using a device made of PVC pipe with50 mm diameter, reaching a depth of 87 cm and 90 cm for isotopic data.This core chronologically covered the period from late nineteenth century to the first decade of this century. The results, supported by statistical studies, indicated thatQuinqueloculina lamarckianaseems restricted to conditions of greater hydrodynamics, marked by quartz > 20% in total sediment.Ammonia tepidaseems to be a reliable bioindicator of environmental degradation, following Pb concentrations in sediments.Discorbis floridanawas also a good environmental indicator, in more recent sedimentation, following the environmental degradation in the last decades. The environmental changes in this estuary, especially resulting from anthropogenic interference were well traceable through the study of δ13C and δ18O isotopes from the carbonates of the exoskeletons of benthic foraminifera studied.