Rozprawy doktorskie na temat „Stable Strontium isotopes”

The work reported in this thesis applies a new isotope tracer, stable strontium isotopes (δ^88/86Sr), to address questions concerning changes in global climate that occur in response to continental weathering processes, and to constrain the modern marine geochemical Sr cycle. Stable Sr isotopes are a relatively new geochemical proxy, and as such their behavior needs to be understood in differing forms of marine calcium carbonate, the archives from which records of past stable Sr variability in the oceans can be constructed. Foraminifera, coccoliths and corals (both aragonite and high Mg calcite) acquire δ^88/86Sr values lighter than that of modern day seawater, (approximately 0.11, 0.05, 0.2 and 0.19 ‰ lighter than seawater at ~25°C respectively) providing a measureable offset which can be used to constrain the modern Sr outputs from the ocean and provide a better understanding of the modern Sr cycle. Using foraminifera as a sedimentary archive the first marine δ^88/86Sr record of seawater over the last two glacial cycles has been constructed, and used to investigate changing carbonate input and output over this 145 kyr period. Modelling of the large excursion of δ^88/86Sr to heavier values during Marine Isotope Stage (MIS) 3, reveals that this is more likely to be due to local changes in seawater or post-depositional alteration, rather then whole ocean changes. In the terrestrial environment δδ88/86^Sr has been measured in the dissolved load of rivers from the Himalaya. It is found that, in general, rivers draining carbonate catchments possess lighter isotopic δ^88/86Sr values than those from rivers draining silicates. Covariations of either δ88/86Sr vs. δ30Si or δ^88/86Sr vs. 1/[Sr] can be used to distinguish between rivers draining different catchment areas.

The work presented in this dissertation explores the nature of agro-pastoral strategies developed by Neolithic farmers as a way to understand how early food production was inter-twined with environmental and socio-economic opportunities and constraints. Towards this end, a multi-isotope approach is used to address questions of scale and intensity of crop cultivation and animal management at the archaeological sites of Kouphovouno, southern Greece, Makriyalos, northern Greece, and Çatalhöyük, south-central Turkey. Measurements of stable carbon, nitrogen, oxygen and strontium isotope values of carbonized plant remains, human and animal bone collagen and animal tooth enamel are used to examine the similarities and differences in the types of treatments that individual species of plants and animals received during the agricultural cycle at the distinct locations. The results show that farmers at the three sites developed variable methods for exploiting the arable and pastoral landscape and catering to their economic and culinary needs. The discussion considers the implications of these findings to our understanding of the complexity and adaptability of early farming systems.

This thesis concerns the application of a new technique for measuring the stable isotopes of Sr, specifically pertaining to mass dependent fractionation in high temperature processes on the Earth and Moon. Processes such as mantle melting and differentiation on Earth and the formation of the Lunar Magma Ocean are investigated by the application of a double-spike TIMS method to terrestrial and lunar material to obtain high-precision ⁸⁷Sr/⁸⁶Sr, ⁸⁸Sr/⁸⁶Sr and ⁸⁴Sr/⁸⁶Sr data. Measurements of mantle-derived mafic material provide insights into the ⁸⁸Sr/⁸⁶Sr composition of the silicate mantle. Ocean Island Basalts possess restricted δ⁸⁸Sr compositions, whilst Mid-Ocean Ridge Basalts from the Pacific, Atlantic and Indian ridges reveal variations in δ⁸⁸Sr, the majority of which is seen within the FAMOUS section of the Mid-Atlantic Ridge. These variations are attributed partly due to the effects of plagioclase crystallisation and partly due to mantle source heterogeneity. Analyses of mineral separates from three different igneous systems provide an understanding of δ⁸⁸Sr fractionation at a mineral-scale. The possibility of δ⁸⁸Sr fractionation as a result of magmatic differentiation has also been assessed, and found to occur between the basalt and rhyolitic end-members of the Icelandic Hekla suite. Variations in the ⁸⁷Sr/⁸⁶Sr ratios of these rocks are also found, and considered most likely to be due to contamination. Analyses of lunar rocks indicate that the highland suite appears to be relatively uniform in δ⁸⁸Sr, whilst significant fractionation to light δ⁸⁸Sr compositions occurs in the mare basalts. Such variations are thought to be associated with the crystallisation of plagioclase during the differentiation of the lunar magma ocean. Lastly, precise ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr data yield a model age for the Moon of 4.523 ± 0.019 Ga.

We test the fidelity of shallow-water gastropod skeletons as multi-proxy archives of seasonal paleo-environmental change by performing isotopic and trace-metal analyses on specimens of Conus ermineus from the Gulf of Mexico. Four adult specimens were collected from Stetson Bank in the Flower Garden Banks National Marine Sanctuary during the summer of 2002. Shell samples were milled along axes of growth to produce time-series profiles spanning up to eight years. We corrected the profiles for growth rate effects and compared the tuned results with in situ temperature and salinity records at the reef surface and temperature profiles from nearby surface buoys. Examination of sample densities in δ18O cycles shows that shell growth is faster during summers and slower during winters. Tuning the profiles versus time yields δ18O values that co-vary closely with seasonal temperatures to a high degree of coherency (R2 = 0.84). The δ13C profiles show cyclic variation modified by ontogenetic decreases in δ13C. These ontogenetic trends are attributable to decreasing metabolic efficiency, while seasonal cycles reflect hydrographic changes in the gastropods’ habitat. Salinity and δ13C of dissolved inorganic carbon show a strong correlation at Stetson Bank (R2 = 0.80), and early summer shell δ13C minima coincide with local salinity minima during times of peak river discharge. The terminations of these δ13C minima occur during annual upcoast reversals of shelf currents in this area. These effects are augmented by summer stratification and productivity minima that further decrease seawater δ13C. Sr/Ca ratios increase through ontogeny, most likely due to decreasing metabolic efficiency. However, seasonal variations in Sr/Ca profiles show strong similarity with δ18O profiles, confirming the temperature dependence of Sr/Ca and minimal influence of salinity on shell δ18O at Stetson Bank. The results of this study show that tuned δ18O and Sr/Ca profiles can be used to reconstruct seasonal paleotemperatures. Carbon isotope profiles and environmental data also demonstrate the utility of Conus δ13C as a proxy for freshwater flux and shelf circulation.

In this work, I present a multi-isotopic study (carbon, nitrogen, sulfur, strontium and lead) and Re-Os geochronology in rocks and crude oils of the Sonda de Campeche Petroleum System (SCPS). Since crude oils are complicated chemical systems easily disturbed, the Re-Os isotopic system could be affected if secondary processes perturb crude oils. Therefore, the multi stable isotopic study allows the identification of the presence and grade of these secondary processes in crude oils. The δ13C values of crude oils from the SCPS distinguish between: 1) crude oils with the fingerprint of source rocks of hydrocarbons (-28.3 to -26.7 ‰), and 2) crude oils with the fingerprint of the reservoir rocks (-25.5 to -24.9 ‰). Similarly, the δ15N values reveal that crude oils, during migration or trapping processes mimic the isotopic composition of the reservoir rocks of the Ek-Balam Formation. Furthermore, the δ34S values of crude oils from the SCPS (-8.0 to -2.5 ‰) show an absence of a thermal sulfate reduction (TSR) signature, which likely means that the use of Re-Os systematics in crude oils and rocks in the SCPS is appropriate. Strontium and lead measurements show crude oils have an isotopic composition different from rocks from the Edzna Formation but similar to rocks of the Akimpech and Ek-Balam formations, indicating that crude oils received Sr and Pb from the trapping rocks during migration or trapping processes, producing a isotopic mixing trend with rocks of these formations. Specifically, the lead isotope composition allows the identification of a source of lead never recorded before, the Guichicovi Complex. The isotopic data suggest that this Grenville Complex has been feeding with detrital material to the sedimentary rocks from Bacab, Ek-Balam and Akimpech formations in the SCPS, and in consequence contributing to the final isotopic composition of crude oils as well. Re-Os geochronology of rocks from the Edzna and Akimpech formations (152 ± 4 Ma; and 158.6 ± 5.5 Ma, respectively) provides precise ages of deposition that coincide with the ages proposed in previous studies based on the fossil record. Re-Os geochronology in crude oils yield ages with low uncertainty and moderate MSWD values, reflecting a rapid formation and migration process that occurred during evolution of the SCPS. The age of crude oils (28.3 ± 5.5 Ma) broadly agrees with petroleum generation models proposed by PEMEX.

The geochemical analysis of bioapatite in vertebrate skeletal tissues is an important tool used to obtain ecological information from fossil animals. An important consideration when conducting stable isotope and trace element analyses is obtaining biogenic information that has been unaffected by diagenetic processes. A two-step pretreatment procedure is commonly used remove diagenetically altered material by removing organic material, via an oxidation reaction with H2O2 or NaOCl, and secondary carbonate, via dissolution in dilute acetic acid, from bioapatite. While much work has been done to determine the efficacy of the pretreatment process, little research has been conducted to determine the potential effects of this process on the oxygen isotope composition of enamel bioapatite. A comparison between δ18O values of fossil enamel treated with 18O-depleted (δ18O = -10.0 / V-SMOW) and 18O-enriched solutions (δ18O = +16.4 / V-SMOW). On average, samples treated with 18O-enriched solutions had δ18O values at least 0.4 / V-PDB more positive than samples treated with 18O-depleted solutions. These results suggest that the isotopic composition of solutions used in the pretreatment process can significantly affect the δ18O values of fossil enamel prior to isotopic analysis. Diagenetic alteration can potentially be assessed using the linear relationship between δ18O values of the carbonate and phosphate components of bioapatite, as any deviation from a slope of 1 suggests alteration. Comparing the relationship between δ18Op and δ18Oc for fossil mammals from the Hadar Formation suggests that this method is successful at identifying samples that are significantly different from the remaining samples due to diagenetic alteration. The relationship between δ18Oc and δ18Op for the majority of sampled fossils from the Hadar Formation has a slope very close to 1 with an average offset, and apparent fractionation factor, between δ18Oc and δ18Op consistent with modern mammals. Therefore, it is likely that many of the fossil mammals sampled from the Hadar Formation retain in vivo δ18O values relating to the δ18O value of the water they consumed. The reliability of paleodietary reconstructions using trace element ratios (notably Sr/Ca and Ba/Ca) is strongly dependent on the preservation of biogenic trace element concentrations. Although most trace element ratio research relies on bone bioapatite, enamel has a better preservation potential and may successfully preserve biogenic trace element relationships. An analysis of Sr/Ca, Ba/Ca, and Zn/Ca ratios indicates that, despite rare earth element concentrations greater than the 1ppm observed in modern enamel, mammals from the Hadar and Busidima formations potentially reflect feeding strategies observed in modern counterparts, i.e. grazers have higher Sr/Ca and Ba/Ca ratios than browsers and omnivores

Regions of surface water and groundwater exchange are major sites for the transfer and transformation of solutes and nutrients between stream and subsurface environments. Conventional stream and groundwater exchange investigations are limited by methodologies that require intensive field investigations and/or the set-up of expensive infrastructure. These difficulties are exacerbated where hydraulic gradients are very low and stream discharge highly variable. This thesis uses a suite of environmental tracers (Cl-, Rn-222, H-2 & O-18, Sr-87/Sr-86) to characterise the extent of stream and groundwater exchange between a sand bed stream and adjacent alluvial aquifer in a subtropical catchment (the Wollombi Brook) of eastern Australia. The aims were to identify sources and relative contributions of different sources of groundwater to stream discharge and specifically to improve the methodology of using Rn-222 to obtain quantitative estimate of groundwater fluxes. The sensitivity of the Rn-222 technique for identifying groundwater discharge based on the Rn-222 concentration in stream water was improved via an iterative numerical approach to account for Rn-222 loss from stream water via turbulent gas exchange and radioactive decay. Optimal distances between stream sampling points for defining the magnitude of groundwater discharge to stream flow based on Rn-222 concentrations in stream water is a function of average stream velocity and water depth. The maximum allowable distance between sampling points for determining the magnitude of groundwater discharge to the Wollombi Brook was 2 km. This work showed that groundwater discharged to all reaches of the Wollombi Brook during baseflow and flood recession conditions. Alluvial groundwater contributed less than 30% of water to stream flow in the mid Wollombi Brook catchment. Dilution of steady-state Rn-222 concentrations measured in transects from the stream to the alluvial sediments showed that significant surface water and groundwater exchange occurs even when gradients between surface water and groundwater are low. Lateral stream water influx to the adjacent alluvial aquifer was more extensive in the lowland areas of the Wollombi Catchment during low flow than flood recession conditions. Extensive stream water influx to the adjacent alluvial aquifer occurs contrary to the net direction of surface water and groundwater flux (as indicated by hydraulic gradients toward the stream channel). The rate of stream and groundwater exchange within the adjacent alluvial aquifer appears to be greatest during baseflow conditions. Fresh alluvial groundwater appeared to provide a buffer against higher salinity regional groundwater discharge to the alluvial aquifer in some reaches of the Wollombi Brook catchment. Pumping of the alluvial aquifer and diversions of surface water may jeopardise the water quality and volume of the alluvial aquifer and induce water flow from the regional aquifer toward the stream, potentially salinising the fresh alluvial aquifer and subsequently the stream. The change in the Cl- concentration and the variation in slope of the deuterium � oxygen-18 line between consecutive stream sampling points could be used to differentiate between regional and alluvial groundwater discharge to stream flow. Incorporating this information with three-component end-member mixing using [Sr2+] and Sr-87/Sr-86 showed that stream and alluvial groundwater exchange within the stream channel was highest in the lowland floodplains during low flow conditions. The least stream and alluvial groundwater exchange occurred in the low streambed gradient mid reaches of the Wollombi Brook regardless of stream stage. The greatest difference in the degree of stream and alluvial groundwater exchange between high and low stream stages occurred in the lowland floodplains of the Wollombi Brook.

The importance of marine versus terrestrial foods in prehistoric Pacific and New Zealand diets, and the adaptation of the Polynesian diet to new enviroments, is examined through the analysis of the ratios in human bone of the stable isotopes of carbon, nitrogen and sulphur. In particular, this study seeks to obtain quantitative information which could provide answers to five main questions, relating to the subsistence focus of the early Lapita colonists in the Pacific, the significance of suger cane in the diets of early Pacific populations, the proportions of reef versus open ocean and terrestrial versus marine foods in these diets, and the identification of populations with pronounced marine or pronounced terrestrial diets. One hundred and nineteen samples of human bone from 13 sites throughtout the Pacific and New Zealand were processed. Nitrogen values were obtained directly from bone powder, while carbon values were determined from collagen produced by digesting bone powder in phosphoric acid. Sulphur evaluations were determined from a BaSo⁴ precipitate, produced after combustion of the collagen samples in a Parr bomb. Interpretation of results is approached from a comparative point of view, which enables the proportions of marine and terrestrial foods in the diets of each study group to be assessed in relation to the diets of all the other groups. Additional information on the composition of the diets is gained by comparing the stable isotope values obtained in this study with published values of other human populations, and of marine and terrrestrial plants and animals. The potential of stable isotope analysis to identify the composition of prehistoric New Zealand and Pacific diets is confirmed. A unique marine adaptation is revealed from the analysis of the Chatham Islands Moriori who appear to have focused almost exclusively on marine resources. In contrast, a highly terrestrial diet is suggested for groups from Nebira in Papua New Guinea and Lake Rotoiti in New Zealand.

The Avar were nomadic people from Central Asia who migrated into the Carpathian Basin in Central-Eastern Europe during the mid to late Migration Period (AD 568 - 895). Archaeological evaluation of grave goods and documentation of mortuary practices have been the primary means of understanding the Avar. However, this approach has largely neglected skeletal and biochemical analysis, in particular as these approaches relate to the biological variation, ancestry, and dietary patterns of the Avar. There remains debate as to whether disparities existed among the socially stratified Avar population of ancient Hungary. It is argued by some that these disparities existed and were the result of differential access to nutritional resources. This hypothesis was tested using the unique properties of isotopes and their chemical signatures. In so doing, the qualitative work on the grave goods was augmented by an additional, quantifiable line of evidence. To investigate social stratification among the Avar population, the techniques of chemical multi-isotope and osteological analysis were employed. Multi-isotopic analyses can be done on stable isotopes (carbon, nitrogen, and oxygen) and on the heavy isotopes (strontium and lead). The particular stable isotopes examined were carbon (δ13C), nitrogen (δ15 N), and oxygen (δ18O). The heavy isotopes analyzed were strontium (87Sr/86Sr) and lead (206Pb/204Pb). Stable isotope analysis as well as ratio analysis of the heavy isotopes strontium (87Sr/86Sr) and lead (206Pb/204Pb) are well-established analytical chemistry methods for examining diverse aspects of diet and mobility through specific geographic regions. The analysis was performed on samples derived from well-preserved tooth enamel and bones. Reconstructing migration and dietary patterns at the Sajópetri cemetery site has helped estimate variability among social groups and between sexes in this population at the time of the Migration Period. Results of the heavy isotope analysis revealed that the Avar population were non-locals to the region, and the stable isotope analysis demonstrated that there was little variation between social groups with slightly higher variation between sexes. This research provides an empirical and analytical framework for further research into migration patterns and social class dynamics of late prehistoric Hungry. This study also adds existing research possibilities to the on-going biogeochemical studies conducted throughout Europe.

Au début des temps modernes (16ème - 18ème siècles), la construction de grands navires était primordiale pour le développement des rencontres culturelles dans ce qui est devenu l'âge de la découverte et de l'expansion européenne. L’Espagne était une des grandes puissances de l’époque. Le projet européen « ForSEAdiscovery » cherche dans ce contexte à répondre aux questions clés suivantes : les ressources forestières ibériques de l’époque soutenaient-elles la demande croissante de bois, ou bien ce bois était-il importé d’autres pays ? Si ces bois ne provenaient pas de l’Espagne, comment les réseaux de commerce étaient-ils organisés ? Ce projet aborde ces questions à travers un programme de recherche multidisciplinaire et innovant pour améliorer la compréhension de notre passé historique et de notre patrimoine culturel, et développer notre connaissance sur l'utilisation passée des ressources en bois pour la construction navale. L'objectif de cette thèse, qui s’insère dans ce projet, est d’identifier la provenance des bois utilisés dans la construction navale ibérique en utilisant des traceurs géochimiques. L’hypothèse est que les arbres se développant sur des roches et des sols contrastés possèdent des signatures géochimiques spécifiques héritées des roches. Les signatures isotopiques en strontium (87Sr/86Sr) peuvent notamment être des indicateurs de provenance géographique. Dans ce contexte, la démarche suivie dans la thèse a consisté à caractériser la signature isotopique en Sr dans des bois d'épaves de bateaux et dans les bois d’arbres actuels, les sols et roches prélevés dans les principaux peuplements forestiers espagnols pointés comme lieux de production des bois entre le 16ème - 18ème siècles. Les signatures en δ88/86Sr, traceur peu connu encore, ont également été caractérisées dans les échantillons. Les types et les âges des roches ont été caractérisés et les liens entre les rapports isotopiques 87Sr/86Sr et δ88/86Sr dans les roches, sols et arbres ont été étudiés sur les sites espagnols échantillonnés. La signature locale des sites espagnols potentiels de provenance de bois a été déterminée. Nos résultats mettent en évidence que le rapport isotopique 87Sr/86Sr dans les arbres reflète la signature de la fraction échangeable des sols sur lesquels ils croissent alors que le δ88/86Sr est affecté par le fractionnement, les isotopes légers (86Sr) étant préférentiellement incorporés dans les arbres laissant la fraction échangeable du sol enrichie avec les isotopes lourds (88Sr). Ce fractionnement observé pour les chênes, n’est pas marqué dans le bois des pins suggérant que le fractionnement isotopique durant le transfert du Sr entre le sol et l’arbre est dépendant de l’espèce. La contamination des bois d’épaves par les éléments marins a été identifiée. Le Sr marin se retrouve notamment sous forme adsorbée ou dans la structure des minéraux précipités dans les bois immergés. Différentes expériences d’extractions ont été testées et un protocole adapté a été développé pour extraire les éléments marins et retrouver la signature originelle du bois archéologique. Nous avons réussi à valider un protocole d’extraction et retrouver la signature originelle d’un échantillon de bois d’épave. Ce résultat souligne le potentiel et l’importance d’une nouvelle méthode combinant 87Sr/86Sr et δ88/86Sr pour des futures études de provenance de bois ou autres matériaux. Cependant, nos résultats indiquent également que beaucoup de nos échantillons de bois archéologiques n’ont pas conservé leur Sr originel. Partant de ce constat, des préconisations sont proposées pour améliorer la possibilité d’utilisation de ce traceur dans les études futures de provenance de bois archéologiques sous-marins
In the Early Modern Age (16th - 18th centuries), the construction of ocean-going ships was paramount to the development of cultural encounters in what became the Age of Discovery and European expansion. Spain was one of the biggest forces of that time. The European project “ForSEAdiscovery” seeks answers in this context to the following key questions: Could Spanish forest resources sustain the increasing demand of timber, or were the wood imported from elsewhere? If Spanish forests were not the only wood supplier, how were the trade networks organized? This project will address these questions through a multidisciplinary and innovative training research program to improve the understanding of our historical past, our cultural heritage, and our knowledge of the use of resources for shipbuilding. The objective of this PhD thesis, taking part of this project, is to identify the provenance of the Iberian shipbuilding wood using geochemical tracers. The hypothesis is that trees growing on contrasted rocks and soils have specific geochemical signatures, which can be an indicator of geographic provenance. In this context, the Sr isotopic signature (87Sr/86Sr) was characterized in shipwreck wood samples and wood from living trees, soils and rocks collected from the Spanish forest stands indicated as potential source of wood between the 16th - 18th centuries. The δ88/86Sr signatures were also characterized in the samples. The rock types and ages were characterized at the selected sites and the link between the 87Sr/86Sr and δ88/86Sr in rocks, soils and trees was studied on the sampled Spanish sites. The local signature of Spanish potential sites was determined for provenance of wood. Our results indicate that 87Sr/86Sr isotope ratios in trees reflect the signature of the corresponding soil exchangeable pool while δ88/86Sr was shown to be affected by mass-dependent fractionation with trees taking up lighter (86Sr) isotopes, leaving the soil exchangeable pool enriched with the heavier isotopes (88Sr). This fractionation observed for oak trees, was not found in pines suggesting that the isotopic fractionation during tree uptake is species dependent. The contamination of wood from shipwrecks by seawater elements was identified. Marine Sr was found to be adsorbed on the wood or included in the precipitated minerals in the waterlogged wood. Several extraction experiments were tested and an adapted protocol was developed to extract the seawater elements and retrieve the original signature of the archaeological wood. We succeeded to validate an extraction protocol and retrieve the original signature of one wood sample. This result underline the potential and importance of a new method combining 87Sr/86Sr and δ88/86Sr values for future provenance studies on wood or other materials. However, our results also indicated that most of our shipwreck wood samples did not conserve their original Sr. Therefore, preconizations were suggested in order to extend the use of this tracer in future provenance studies on archaeological wood from shipwrecks

Ce travail de thèse a appréhendé les mécanismes de stockage/libération, d’un point de vue élémentaire et isotopique, du calcium (Ca) et du strontium (Sr) sur ou dans des phases minérales communes des sols (minéraux primaires, minéraux argileux, oxy-hydroxydes, carbonate pédogénétiques). Une méthode de mesure robuste du δ88Sr a dû être développée et validée par la mesure de matériaux de références internationaux, pour la plupart jamais mesuré dans la littérature. Les résultats montrent que l’adsorption du Ca sur des minéraux phyllosilicatés génère un fractionnement isotopique par prélèvement préférentiel de l’isotope léger (40Ca) dans nos conditions expérimentales lorsque les minéraux possèdent une charge structurale et une surface spécifique importante et/ou un espace interfoliaire ouvert à l’adsorption de cations hydratés. Une étude sur des rhizolithes en milieu naturel a mis en avant que l’utilisation des isotopes du Ca et du Sr permet un traçage de source et de mécanismes efficaces dans les thématiques touchant au stockage de ces deux éléments dans les sols
This 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

The Laramide Rocky Mountains in western U.S.A is an important topographic feature in the continental interior, yet its formation and evolution are poorly constrained. This study uses the oxygen and strontium isotope geochemistry of freshwater bivalve fossils from six Laramide basins in order to reconstruct the spatial evolution of the paleotopography and Precambrian basement erosion in late Cretaceous-early Eocene. In addition it uses the sedimentology, detrital zircon U-Pb geochronology, and isotope paleoaltimetry of early Eocene sedimentary strata to constrain the tectonic setting, paleogeography and paleoclimate of the Wind River basin. Annual and seasonal variation in ancient riverwater δ¹⁸O reconstructed from shell fossils shows that the Canadian Rocky Mountains was 4.5±1.0 km high in late Cretaceous-early Paleocene, and the Laramide ranges in eastern Wyoming reached 4.5±1.3 km high, while the ranges in western Wyoming were 1-2 km high in late Paleocene. The ⁸⁷Sr/⁸⁶Sr ratios of riverwaters reconstructed from the same fossils show that Proterozoic metamorphic carbonates in the Belt-Purcell Supergroup were not exposed in the Canadian Rocky Mountains during Late Cretaceous-early Paleocene, but that Precambrian silicate basement rock was exposed and eroded in the Laramide ranges during late Paleocene-early Eocene. The sedimentary environment of the early Eocene Wind River basin changed from gravelly fluvial and/or stream-dominated alluvial fan to low-sinuosity fluvial systems. Tectonic uplift of the Washakie and Wind River Range in early Eocene formed the modern paleodrainage system, although the elevation of the basin floor was only ~500 m high at that time, and early Eocene paleoclimate is more humid than modern climate.

Depuis de nombreuses années, une approche a été mise en œuvre reposant sur l'identification de l'origine géographique d'un produit agro-alimentaire via la connaissance de ses isotopes du Sr, notamment via l'analyse du rapport 87Sr/86Sr. L'objectif de cette thèse est d'appliquer cette stratégie de reconnaissance aux huiles d'olive, en s'appuyant sur la production des huiles AOP de Nîmes dans le Sud de la France (Gard). La viscosité, la charge organique élevée, la teneur faible en Sr de cette matrice, rendent néanmoins inadaptés les protocoles de purification du Sr existants. La première approche de l'étude correspond donc à la définition et à la validation d'une méthode de traitement des huiles d'olive en vue de la purification du Sr afin de procéder à l'analyse de sa composition isotopique (CI). La seconde partie de l'étude est consacrée à la définition des processus d'assimilation et de transfert du Sr dans l'olivier. Cette approche, menée grâce à une étude détaillée d'un des moulins AOP de Nîmes, a permis de démontrer que le transfert du Sr des sols vers l'olivier et au sein des oliviers se fait sans fractionnement isotopique.La dernière partie de l'étude s'appuie sur la mesure et la caractérisation des rapports isotopiques 87Sr/86Sr des dix huiles d'olive AOP de Nîmes, et une comparaison de cette signature avec celle des formations géologiques sur lesquelles reposent les parcelles de culture. L'identité de la CI huile-territoire de culture a permis de conclure, dans le contexte de production de l'huile d'olive AOP de Nîmes, que les isotopes du Sr constituent un très bon outil de traçage de l'origine géographique des produits oléicoles
For many years, an approach based on the identification of the geographical origin for food product has been implemented through the knowledge of its Sr isotopes, particularly through the analysis of 87Sr / 86Sr ratio. The objective of this thesis is to develop a similar strategy for the olive oils, from the example of PDO Nimes (Gard), in southern France. A specific methodology is necessary since the existing purification protocols of Sr revealed themselves inadequate because of viscosity, high organic load, low Sr content of this matrix In order to proceed to the analysis of the isotopic composition (IC), the first part of the study highlights the definition and validation of a specific method for the treatment of olive oils and strontium purification. The second part of the study is dedicated to expose the processes of assimilation and transfer of strontium into the olive tree. This approach, conducted through a detailed study of one of Nîmes PDO mills, demonstrated that the transfer of strontium from soils to olive tree, and within the olive tree, occurs without isotope fractionation.The last part of the manuscript studies the isotopic ratios 87Sr / 86Sr of the ten PDO olive oils of Nimes and consists in a comparison of this signature with the geological formations underlying the cultivation soils. This approach allows discussing quality of Sr isotopic tool in the geographical recognition of the olive products. The observed similarity between th IC from oils and soil allow us to conclude that, in this context of production, the Sr isotopes are a efficient tool to trace and certify the geographical origin of the oil

Deux types de déchets salins ont été traités par la voie de la phytoremédiation : des effluents industriels et des sédiments marins. Le potentiel de trois espèces aquatiques, Phragmites australis, Typha latifolia et Juncus maritimus, pour traiter la charge en ions Cl- a été caractérisé pour différents stades de maturité au travers d’essais en laboratoire. Ces espèces ont montré d’excellentes capacités d’adaptation aux milieux chlorurés et en particulier pour un stade de croissance mature (plants âgés d’un an). La phytoremédiation des déchets considérés semble possible avec des abattements significatifs, que ce soit pour les effluents (50-95 % d’abattement en 40 jours) ou les matrices solides (5-30 % d’abattement en 80 jours). Les abattements mesurés sur les essais sur effluents s’expliquent principalement par des mécanismes de sorption des ions Cl-. Les végétaux ne jouant alors quant à eux qu’un rôle mineur via l’exportation de leur matière verte. Une expérimentation à plus grande échelle sur des sédiments marins dragués spécifiquement pour cette étude a été menée. Sur la période expérimentale étudiée, aucune croissance des végétaux n’a pu être observée ayant pour conséquence aucun effet de remédiation. Plusieurs causes ont été mises en évidence ou présupposées : la granulométrie des sédiments (vase), la canicule de 2019 ou encore la présence d’autres contaminants (SO42-, métaux/métalloïdes). Ces essais ont néanmoins permis de montrer que la phytoremédiation en procédé unique de gestion des sédiments marins fraichement dragués n’est pas adaptée. De nouveaux systèmes de phytoremédiation doivent donc être étudiés sur ces sédiments en combinaison avec différents procédés tels que le lessivage, l’osmose inverse ou l’évaporation. De plus, afin d’optimiser les capacités épuratoires des végétaux dans un procédé de phytoremédiation, il est nécessaire d’employer des espèces acclimatées et donc locales. Aucune méthode de traçage de l’origine géographique des végétaux aquacoles n’est aujourd’hui préconisée. Un outil de traçage basé sur le rapport isotopique du strontium (87Sr/86Sr) a été étudié vis-à-vis des différentes fraudes pouvant être observées dans ce secteur. La faisabilité de discriminer des aires géographiques a été évaluée par la comparaison de la signature isotopique de différentes productions à travers le monde (France, Allemagne, Hongrie, Chine). La caractérisation du cycle biogéochimique du Sr pour les plantes aquatiques a permis de mettre en évidence la contribution majeure de l’eau d’irrigation ainsi que celle des pratiques agricoles, justifiant des rapports isotopiques propres aux productions. La stabilité temporelle de cet outil a été confirmée au travers de la reculture de végétaux étrangers dans des conditions locales. Ainsi, les isotopes stables du strontium se révèlent être un outil précieux pour certifier l’origine géographique des végétaux aquatiques et mettre en évidence les fraudes communément observées dans ce domaine
Two types of saline waste were treated by phytoremediation: industrial effluents and marine sediments. The potential of three aquatic species, Phragmites australis, Typha latifolia and Juncus maritimus, to treat the Cl-ion contamination was characterised for different stages of maturity through laboratory tests. These species showed excellent adaptation to saline environments and in particular for a mature growth stage (one-year-old plants). Phytoremediation of the waste considered seems possible with significant reductions, both for effluents (50-95% reduction in 40 days) and solid matrices (5-30% reduction in 80 days). The remediation rates measured in the effluent tests are mainly explained by Cl- ion sorption mechanisms. Plants then play only a minor role via the export of their green matter. A larger scale experiment was carried out on marine sediments dredged specifically for this study. Over the experimental period studied, no plant growth was observed, resulting in no remedial effects. Several causes were identified or presupposed: the granulometry of the sediment (silt), the heat wave of 2019 or the presence of other contaminants (SO42-, metals/metalloids). Nevertheless, these tests have shown that phytoremediation as a single process for managing freshly dredged marine sediments is not suitable. New phytoremediation systems must therefore be studied on these sediments in combination with different processes such as leaching, reverse osmosis or evaporation. Moreover, in order to optimise the epuration capacities of plants in a phytoremediation process, it is necessary to use acclimatised and therefore local species. No method for tracing the geographical origin of aquaculture plants is currently recommended. A tracing tool based on the strontium isotopic ratio (87Sr/86Sr) has been studied in relation to the various frauds that can be observed in this sector. The feasibility of discriminating between geographical areas was assessed by comparing the isotopic signature of different productions throughout the world (France, Germany, Hungary, China). The characterisation of the biogeochemical cycle of Sr for aquatic plants highlighted the major contribution of irrigation water as well as that of agricultural practices, justifying the isotope ratios specific to the productions. The temporal stability of this tool was confirmed through the recultivation of foreign plants in local conditions. Thus, the stable isotopes of strontium are proving to be a valuable tool for certifying the geographical origin of aquatic plants and highlighting the frauds commonly observed in this field

L'authenticité et la traçabilité des aliments gagnent un intérêt croissant au cours de la dernière décennie puisque la connaissance de la provenance des aliments est considérée comme une garantie supplémentaire de leur qualité. Les consommateurs ont également des inquiétudes et des préoccupations par l'origine de la nourriture qu'ils consomment car divers produits sont sujets à l'adultération ou à la fausse dénomination. L'intérêt accru à l’égard de la protection des consommateurs et de la lutte antifraude ont entraîné un accroissement de la recherche scientifique appliquée et le développement d'outils efficaces pour contrôler l'authenticité des produits alimentaires. Entre techniques analytiques appliquées à l'authenticité et à la traçabilité des aliments, les méthodes les plus prometteuses sont basées sur les empreintes d'éléments lourds mesurées par la spectroscopie atomique. La spectrométrie de masse à multicollection à couplage à plasma induit (MC-ICP-MS) est reconnue comme la méthode optimale pour effectuer des mesures de haute précision de nombreux éléments du tableau périodique en contrôlant simultanément les rapports entre leurs isotopes stables. Cette étude présente une nouvelle stratégie analytique basée sur des isotopes stables non-traditionnels combinés avec des éléments traces déterminés par ICP-MS. Les avantages de combiner les informations de deux systèmes isotopiques, l'un traçant le sol (Sr), et l'autre traçant la pollution environnementale ambiante (Pb), ont permis d'obtenir de nouvelles informations exceptionnelles sur la traçabilité et l'authenticité des matrices alimentaires sélectionnées : vins de Bordeaux, jambons secs et thé. En utilisant des techniques analytiques complémentaires telles que les empreintes des élémentaires traditionnelles, la spécification régionale, ainsi que le traçage du processus de préparation des aliments sont possibles. Traitée par la chimiométrie, cette approche analytique constitue un nouvel outil efficace et prometteur pour détecter des fraudes alimentaires, y compris l’imitation de produits de grande valeur, l’étiquetage erroné et la substitution par des produits moins cher
Food authenticity and traceability have received an increasing interest during the last decade since the knowledge of food provenance is regarded as an additional warranty of its quality. The world's globalization brought to the consumers is more and more concerned with the origin of the food they eat because various products are subjected to adulteration or false denomination. The augmentative interest in anti-fraud and consumer protection has led to the extension of scientific research and development of effective tools of food authenticity control. Among the analytical technics applied to food authenticity and traceability, one of the most rapidly developing and promising method is based on fingerprinting of heavy elements detected by atomic spectroscopy. The multicollection inductively coupled plasma mass spectrometry (MC-ICP-MS) is recognized as a method of choice for the high precision measurement of numerous elements of the periodic table as well as ratios of their stable isotopes. This study present a new analytical strategy based on combined non-traditional stable isotopes and trace elements determination by ICP-MS. The benefits of combining information from two isotopic systems, one tracing the soil (Sr), and the other tracing environmental ambient pollution (Pb), allowed to obtain an exceptional new information about traceability and authenticity of selected food matrixes: prestigious Bordeaux wines, dry-cured hams and tea. Using complementary analytical techniques such as traditional elemental fingerprinting, the regional specification, as well as tracing of the food preparation process are possible. When combined with chemometrics, these analytical advances constitute an efficient and promising tool to detect food frauds, including adulteration of high value products with cheaper substitutes, forgery and falsification

A l'Est du Bassin de Paris, la superposition de roches sédimentaires aux propriétés hydrauliques, thermiques et mécaniques contrastées forme un système géologique compartimenté. Les séries aquifères du Jurassique moyen et supérieur et du Trias (faciès Buntsandstein) sont séparées par des niveaux aquitards constitués d'évaporites et d'argiles, parmi lesquelles la succession callovo-oxfordienne épaisse de 150 m, sélectionnée par l'agence nationale pour la gestion des déchets radioactifs (Andra). Retracer l'histoire thermique des séries sédimentaires mésozoïques et lier cette histoire aux processus d'interactions fluides-roches ayant modifié les propriétés pétrophysiques des formations perméables constitue la problématique centrale de ce travail de thèse. Ce mémoire présente, dans une première partie, une synthèse de l'évolution thermique des séries mésozoïques, s'appuyant sur des données géothermométriques (réflectance de la vitrinite, isomérisation des biomarqueurs moléculaires, inclusions fluides) et sur la modélisation numérique du bassin. Dans une seconde partie, les propriétés physico-chimiques des paléo-fluides ayant percolé dans les aquifères carbonatés du Jurassique moyen et supérieur sont recherchées à l'aide des teneurs en éléments traces et de la composition isotopique (d18O, d13C, 87Sr/86Sr) des phases minérales authigènes, couplée aux mesures de chlorinité et des rapports D/H des eaux piégées en inclusions fluides. Dans les grès du Trias, les datations K-Ar de fractions granulométriques riches en illite documentent deux périodes de cristallisation à 179.4 ± 0.8 Ma et 149.4 ± 0.3 Ma, respectivement durant le Lias et à la période fini-Jurassique / début Crétacé
In the eastern Paris Basin, the succession of sedimentary rocks with variable hydro-thermo-mechanical properties leads to a compartmentalization of the system. Three aquifer units - the Middle and Upper Jurassic limestones and the Lower Triassic sandstones - are apart from each other by very low-permeable evaporites and clay-rich successions, among which the Callovian-Oxfordian claystones currently investigated by the French national radioactive waste management agency (Andra). This PhD thesis deals with the thermal history reconstruction and the fluid-rock interactions in the Mesozoic series through a multidisciplinary approach. In the first part of the manuscript, the P-T evolution of the Mesozoic series is documented based on thermal indicators (vitrinite reflectance, biomarker isomerization, fluid inclusions) and numerical modeling. In the second part, major and trace element concentrations (including REE) and isotopic compositions (d18O, d13C and 87Sr/86Sr) of authigenic minerals and fluid inclusions were used to estimate the origin of paleo-fluids and their evolution through water-rock interactions. In the Lower Triassic sandstones, K-Ar dating of authigenic illite documents two periods of crystallization at 179.4 ± 0.8 Ma and 149.4 ± 0.3 Ma

The aim in this thesis is to use carbon, nitrogen and sulfur isotope analysis on teeth and bone to track diet and mobility of the population as well as the individual level from the articulated and disarticulated individuals from the passage grave Frälsegården, situated in Gökhem parish in the region of Falbygden, western Sweden. 50 human samples were analyzed from tooth, mandibula and femur, together with 11 faunal samples from different bone elements of local wild and domestic animals. The results fall well in line with earlier stable isotope work done on passage grave individuals from Falbygden in stable isotopes: A homogenous group with a diet which was clearly terrestrial and lived on a pretty high trophic level. It also seems that the analyzed individuals deliberately focused their food intake to the cultural and natural, megalith and limestone landscape of Falbygden, and not to its surroundings, even if the passage grave is situated in the outermost areas of the region. A small study compares the sulfur results to with earlier work done on strontium isotopes. The results show that the different methods might provide a deeper understanding in the interpretation of the methods, and therefore suggesting that further work should be done to compare the methods.

Les travaux de recherche présentés dans ce mémoire ont pour ambition la mise au point d'une nouvelle méthode de traçage des lixiviats dans les eaux souterraines afin de détecter les fuites ou bien une contamination des eaux à longue distance. Dans un premier temps, nous avons évalué l'impact de la décharge municipale de la Ville de Marseille (C. T. B. R. U. ) sur les eaux souterraines et mis en évidence un panache de pollution en aval du site. Délimitée grâce aux conductivités et aux concentrations en ions chlorure, la zone contaminée a une longueur maximale de 4. 6 km. La géochimie du panache de pollution se caractérise par une zone réductrice pour le fer et une zone réductrice pour les nitrates. Il semble que les zones méthanogènes et réductrices des sulfates soient absentes. Dans un deuxième temps, le traçage des lixiviats par les isotopes du plomb et du strontium s'est révélé très performant dans un environnement multi-sources. Ces traceurs ont permis de mettre en évidence des transferts entre les réservoirs sol, aquifère et atmosphère, induits par des activités anthropiques. Les pôles " naturel " et " déchets " sont déterminés par la mesure des rapports isotopiques du strontium et du plomb sur un autre site. En l'absence de pollution, cette nouvelle méthode de traçage montre une contamination des eaux souterraines par les lixiviats de décharge
We are evaluating strontium and stable lead isotopes, anionic tensides and TBT as an alternative tracers of landfill leachate in groundwater. The municipal landfill studied here is located in south-eastern France. Based on the evaluation of chloride concentration, the plume extends a maximum of 4600 m. Strontium and lead isotopic composition characterizes two sources : natural groundwater and landfill leachate contamination. Evolution of mixing ratios obtained with strontium reveals a second source of groundwater contamination : fertilizers (87Sr/86Sr = 0. 707859). These results suggest that isotopic signatures can be used to provide useful information on sources of groundwater contamination where conventional water quality parameters may yield ambiguous results

Research Doctorate - Doctor of Philosophy (PhD)
Changes in geochemical and physical properties of speleothems are considered to be accurate proxies of climate variability. However, the climate signal is modified by the internal dynamics of the whole karst system. The aim of the research was to obtain reproducible data extracted by established and non-conventional techniques from two coeval speleothems removed at Grotta Savi cave (Italy), to gain information about regional climate responses across the Last Glacial Maximum to Holocene transition. Different past hydrological regimes for the two stalagmites’ drips were reconstructed on the basis of stalagmites’ physical characteristics and this helped to disentangle the global from the local phenomena. This non-conventional approach, was applied here for the first time on fossil sample, resulting in a benchmark for interpreting the chemical proxies, and enabling assessment of calcite formation environment, hitherto not possible. The interpretation of δ¹⁸O values as reflecting past hydrology was then validated by using the Hydrology Index. The Index, developed in this study, considers two independent proxies: the Mg concentrations and the fraction of Sr uptake that is not dictated by growth rates. The method allowed recognition of a non-hydrological component encapsulated in δ¹⁸O values, then interpreted as changes of air mass provenance and rainfall seasonality. The δ¹³C was chiefly driven by temperature-dependent soil respiration rate. However, a hydrological component was also detected in the δ¹³C by using dead carbon proportion (dcp) and ⁸⁷Sr/⁸⁶Sr ratios. Increases of ⁸⁷Sr/⁸⁶Sr ratios suggest increases of aeolian dust deflated from proximal subalpine periglacial regions facilitated by vegetation-cover reduction, soil destabilisation and windier conditions, which in turn enhanced drier conditions. Although, the dcp trend was likely related to a local, faster, soil organic matter turnover, enhanced by warmer conditions, episodes of high dcp values were possibly hydrologically induced, as a result of wetter conditions. Furthermore, the Hydrology Index and δ¹³C signal allowed reconstructing that wet conditions occurred during climate cooling, an improvement relative to the state of the art of δ¹³C interpretation, where more commonly wet conditions occurs during warming. The comparison of δ¹³C trend of Savi with another stalagmite with similar physical characteristics, but from a cave (Sofular) located in Turkey, revealed a common trend despite the impact of the last glaciation having been drastic at Savi (no speleothem growth). Such δ¹³C similarity could be related to global phenomena and point to an intriguing possibility, which needs future testing, that speleothems may encode information of the C cycle, similar to soil carbonates. The palaeoclimate interpretation extracted from the Savi records between 15 to 9 ka indicates that the Younger Dryas (YD) was a dramatic climate reversal. In the northern Adriatic, the YD is characterised by high hydrological variability, strong winds and a cooling, which resulted in a decrease of vegetation cover and increase of soil erosion. The wind regime was possibly orographically induced, with the Alps acting as a barrier, deviating westerly winds and causing increased windiness in the northern Adriatic region. The Savi records reveal a significant Early Holocene anomaly (10.4 ka), whose drier and colder conditions were probably amplified by a local synoptic framework.

Strontium (Sr) is an alkaline earth element that has four naturally occurring stable isotopes, 84Sr, 86Sr, 87Sr and 88Sr. During measurements of the radiogenic Sr isotope ratio (87Sr/86Sr), which is a widely used tracer in Earth sciences, the instrumental mass dependent fractionation is corrected by assuming the 88Sr/86Sr ratio as 8.375209. However, with the recent advancements in mass spectrometry, it is now possible to resolve variations in the 88Sr/86Sr ratio (expressed as δ88/86Sr) in natural samples. In this study, a measurement protocol for stable Sr isotope ratio measurements was developed using a double spike thermal ionization mass spectrometry (DS-TIMS) technique and δ88/86Sr variability in depth-bound seawater, groundwater, and large rivers are investigated. The analytical technique for high precision TIMS measurements of δ88/86Sr was developed using a new Sr double spike (87Sr-84Sr); the single spikes used to prepare this double spike were less pure compared to the spikes reported in literature and hence the DS of this study is less expensive and differs in isotopic composition from DS used in previous studies. The robustness of the method was validated by measurements of multiple standards of different matrices (carbonate, silicate, seawater, and pure Sr) and the long-term external reproducibility of δ88/86Sr was less than ± 0.035 ‰ (2SD) which is comparable to, if not better than previous studies. The δ88/86Sr values are not affected by the nature of the loading filament (tantalum versus zone refined rhenium) or amount of Sr loaded on the filament; further, the δ88/86Sr values are invariant over a wide range of spike/sample ratios, consistent with modelling calculations for error propagations. The δ88/86Sr values, relative to the NIST SRM987 standard, are reported for an Alfa Aesar ICPMS Sr standard (0.101 ± 0.033 ‰), NASS-6 seawater (0.387 ± 0.034 ‰), JCp-1 coral carbonate (0.196 ± 0.006 ‰), JCt-1 clam shell (0.252 ± 0.004 ‰), BCR-2 basalt (0.264 ± 0.003 ‰), and NIST SRM987 (0 ± 0.023 ‰). The Bay of Bengal, which has crucial control on marine Sr budget, receives large influx of continental Sr through the Himalayan rivers in form of surface flow with additional contribution from groundwater discharge. The present study reports restricted variability in the δ88/86Sr values (0.373-0.411 ‰) of seawater samples collected from multiple depths (0-1500 m) in the Bay of Bengal with an average δ88/86Sr = 0.388 ± 0.025 ‰ (2SD), which overlaps with previous estimates of global seawater. The chemistry of coastal seawater can be significantly influenced by groundwater and interactions between Bengal Basin groundwater and the adjacent Bay of Bengal seawater are well documented. This thesis presents δ88/86Sr values, 87Sr/86Sr, as well as stable Ca isotope (δ44/40Ca) data for a set of groundwater samples collected from multiple depths (14-333 mbgl) from coastal aquifers in and around the Sundarbans delta, India. Significant variabilities were observed in 87Sr/86Sr, salinity, and cation concentrations across depths which indicate seawater incursion at shallower depths (14-42 mbgl) while deep aquifer samples (~333 mbgl) retained freshwater signature. A substantial variability in δ88/86Sr values (~0.542 ‰) was observed in these groundwater samples with shallow aquifer samples showing high δ88/86Sr (up to 0.666 ‰), which is higher than modern seawater (~0.388 ‰). These variations along with modelling results suggest appreciable amounts of precipitation of secondary carbonates in the saline groundwaters along with indications of seawater-freshwater mixing. The δ44/40Ca values of the same samples show similar trends as the δ88/86Sr values and are consistent with removal of solute Ca as aragonites or calcites (up to 45%). Rivers are major transport pathways of weathering-derived continental Sr to the oceans and play a major role in modulating the overall Sr budget among modern reservoirs. The δ88/86Sr values in seasonally and spatially resolved river water samples from the lower Ganges (Hooghly River) varied from -0.167 to 0.418 ‰ while those in seasonally distributed river water samples from the Brahmaputra, collected from Guwahati and Jorhat, range between 0.136-0.304 ‰. Spatially and seasonally resolved river water from the Mahanadi Basin display δ88/86Sr values between 0.263-0.638 ‰; few samples from coastal regions overlapped with Bay of Bengal δ88/86Sr values underscoring seawater intrusion. The Mahanadi Basin groundwater samples display δ88/86Sr values between 0.276-0.423 ‰, which overlap with compositions of the Mahanadi River water, consistent with riverwater-groundwater interactions. Seasonally resolved river water samples from the Godavari River, collected from Rajahmundry, showed δ88/86Sr variability between 0.174-0.640 ‰. Overall, the significant variability in δ88/86Sr values of these large rivers broadly overlap with global river water data and reflect varying sources, congruent versus incongruent chemical weathering, with implications for role of water mass mixing and secondary minerals, such as carbonates and clays in river waters.

Coastal systems in semi-arid areas are characterised by complex physico-chemical processes involving mixing of marine and continental water sources as well as precipitation of evaporitic and carbonate minerals. The latter processes involving carbonate cycling also represent an important but currently poorly constrained component of the coastal carbon budget. This thesis fills important knowledge gaps in our understanding of water source mixing and local carbonate cycling in a semi-arid coastal system in South Australia – the Coorong, Lower Lakes and Murray Mouth (CLLMM) estuary, using selected alkaline earth metals (Ca and Sr) and their isotopes with the following research components: 1. Application of radiogenic Sr isotopes ((87)Sr/(86)Sr), stable Ca isotopes (δ(44/40)Ca) and elemental ratios, complemented by mineralogical analysis of top-sediment samples and geochemical (PHREEQC) modelling of carbonate saturations in the CLLMM waters to constrain the water source apportionment and local carbonate output in the Coorong lagoon. 2. Development and validation of high-precision stable Sr isotope analysis (δ(88/86)Sr) using thermal ionisation mass spectrometry (TIMS) and follow up calibration of δ(88/86)Sr in the CLLMM waters with respect to changing salinity and carbonate saturation states. 3. Application of (87)Sr/(86)Sr and δ(88/86)Sr tracers, along with elemental concentration data, to monitor seasonal variations (i.e., every 3 months) in water source mixing and carbonate dynamics (i.e., dissolution vs precipitation) in the CLLMM. 4. Reconstruction of palaeo-hydrology and salinity in the Coorong South Lagoon throughout the past ~2400 years, based on (87)Sr/(86)Sr, δ(88/86)Sr and Mg/Sr analysed in fossil bivalve shell species (Arthritica helmsi) collected from sediment cores. The above data were complemented by radiocarbon (14C) and pollen-based geochronological models. Overall, the results from the thesis showed that the modern North Lagoon waters are mainly sourced from the Southern Ocean, with transient freshwater inputs sourced from the River Murray and Lower Lakes and/or local groundwater discharge. In contrast, the hypersaline South Lagoon waters are basically highly evaporated ‘brackish waters’ with significant contribution of Sr from continental water sources. Importantly, stable Ca and Sr isotope tracers and water chemistry data indicate that the South Lagoon acts as a net sink for dissolved inorganic carbon (DIC) in the form of precipitated carbonate minerals (mostly aragonite). Both δ(44/40)Ca and δ(88/86)Sr in the CLLMM waters seem to be controlled by mass-dependent isotope fractionation, most likely related to carbonate dissolution and precipitation. Despite the current uncertainty regarding the role of local groundwater discharge on the chemistry of Coorong waters, the results indicate that an increased alkalinity supply (mainly from the Salt Creek) may locally promote CaCO3 precipitation and increase in δ(88/86)Sr of waters in the South Lagoon. Finally, the multi-proxy analysis ((87)Sr/(86)Sr, δ(88/86)Sr and Mg/Sr) of fossil shells revealed that over the past two millennia the South Lagoon waters were never purely marine but originally rather comprised brackish waters (estimated minimum salinities of ~6-23 PSU) with at least 60% contribution from continental water. Overall, the findings of this thesis improved our understanding of modern and past water source mixing and carbonate cycling in the CLLMM system and can hopefully benefit future water management strategies and plans.
Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2021

博士
國立成功大學
地球科學系
103
The relationship between global climate change and continental weathering is a cause-consequence feedback system. Global climate may be perturbed by any of processes controlling weathering through changing atmospheric CO2 abundance, and in turns to further affect the extent of weathering. In this iteration, the atmospheric CO2 fluctuation is controlled by the stoichiometric balance between the CO2 consumption by silicate mineral weathering and CO2 release by marine carbonate precipitation at long-term time scale. Thus, discriminating the terrestrial weathering sources from silicates and carbonates, and determining the extent of weathering are important and the fundamental knowledge for comprehending the long-term climatic evolution. In chapter 1, the application of newly triple Sr isotopes, 87Sr/86Sr and δ88/86Sr ratios, was introduced and suggested to serve as a powerful isotopic tracer, rather than the 87Sr/86Sr alone, for simultaneously determining the continental weathering fluxes to the ocean and quantifying the Sr burial flux by the carbonate precipitation in the marine system at glacial and interglacial climatic cycles. Given that rivers are the largest Sr source to the ocean, however, there were only few attempts available for studying relevant controls on δ88/86Sr fractionation in riverine waters. In order to have confidence in interpretation based on the recent developed isotopic proxy, the following questions should be therefore clarified by the first order: (1) The variability of δ88/86Sr for lithological specimens, i.e. silicates and carbonates. (2) Potential physicochemical processes that controlling the δ88/86Sr fractionation in terrestrial environments. (3) Lithology and/or fractionation control the variability of δ88/86Sr in riverine waters. To address those fundamental questions, the following chapters provide a comprehensive evaluation of stable Sr isotope fractionation during continental weathering processes by natural specimens and laboratory experimental works. In chapter 2, we demonstrated a highly precise and accurate δ88/86Sr determination by using multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with empirical external normalization and standard sample bracketing (EEN-SSB) method for mass bias correction. In this chapter, we evaluated the fractionation behaviors of Sr and Zr isotopes during MC-ICP-MS determinations and established a modified procedure to apply 92Zr/90Zr instead of currently available 91Zr/90Zr for Sr isotopic mass bias correction. A factor of 1.5 was improved in precision of our δ88/86Sr determination that is likely owing to the smallest instrumental mass-independent fractionation between the isotopic pair of 88Sr/86Sr and 92Zr/90Zr. This new method allows 87Sr/86Sr and δ88/86Sr ratios to be measured simultaneously with high throughput and comparable precision and reproducibility with double spike (DS) applied MC-ICP-MS δ88/86Sr determinations. In chapter 3, to evaluate the potential processes lead to δ88/86Sr fractionation during silicate mineral weathering, an intense pedogenic paleosol sequence was sampled in the Chinese Loess Plateau (CLP). Sequential extraction procedure was applied to isolate different geochemical phases of the soils to study the stable Sr isotopic distributions in the extracted exchangeable, reducible and silicate fractions. The results suggested that heavier δ88/86Sr was preferentially released during incongruent silicate mineral weathering. This is further evidenced by the acid leaching experiments using the soil silicate phase, primary silicate minerals and clay standards. In chapter 4, an annual time-series monitoring of chemical and Sr isotopic compositions on a carbonate-dominated catchment was performed to evaluate the influences of secondary calcite precipitation and silicate mineral weathering on water δ88/86Sr. A seasonal systematic of karst cave stream water δ88/86Sr was detected showing coherent heavier δ88/86Sr and radiogenic 87Sr/86Sr ratios detected in the warm and rainfall period reflecting enhanced biological activities and intensive silicate weathering at that time. On the other hand, at least 30% to 55% of Ca was removed by the secondary calcite precipitation and lead to 0.1‰ heavier in water δ88/86Sr. Those time-series data emphasizes the critical role of secondary calcite precipitation on the comprehensive heavy δ88/86Sr ratios in waters draining carbonate-dominated catchments, and peak of related heavy δ88/86Sr ratios by intensive silicate weathering in wet season and extreme rainfall events. In chapter 5 (conclusion), we compile all the currently published stable Sr isotope data from literature sources (2006 to early 2015) and this study for evaluating the potential mechanisms controlling the sensitivity and variability of δ88/86Sr of the continental weathering flux to the ocean and its implication for global Sr cycling. The data suggests that the variability of δ88/86Sr of the terrestrial silicate materials and carbonates are statistically lighter than that of riverine waters. In stead of lithology, fractionation of Sr stable isotopes during and post-weathering processes, such as secondary phase precipitated, incongruent silicate weathering, and vegetation uptake, might be more important factors and by the first order lead to the enrichment of heavy δ88/86Sr in the waters. The degree of δ88/86Sr fractionation in continental weathering environments may have significant implications to the oceanic Sr isotopic budget at glacial-interglacial time scales. The variability of δ88/86Sr in modern rivers will still need to be better constrained for studying the global Sr cycling at geological time scales.

In this thesis the enriched stable isotope marking technique was examined to determine its validity and effectiveness in marking of Lake Sturgeon fin rays. The enriched stable isotope marking technique uses stable isotopes of elements that replace calcium in boney tissue, which are fixed in nature, however in laboratory settings can be easily manipulated. Manipulated ratios of naturally occurring isotopes can be determined from a small sample of the fin ray, thus allowing for the discrimination of fish stocks. Further, the thesis examined the underlying assumptions for strontium and barium into the Lake Sturgeon. For the marking technique to work, strontium and barium must be taken up from the environment and accumulated long-term in boney tissue. Net flux and tissue retention of strontium is reported and the research has demonstrated that enriched stable isotopes can be successfully used to mark the fin ray of Lake Sturgeon for long-term stock discrimination.
October 2015