Les propriétés pétrophysiques des réservoirs silicoclastiques sont influencées par de nombreux facteurs sédimentaires et diagénétiques. Les principaux phénomènes diagénétiques affectant les réservoirs sont généralement la cimentation de quartz et les compactions mécanique et chimique. Des réservoirs gréseux ayant des contextes géologiques différents ont été considérés dans cette étude ; les réservoirs carbonifères d’origine deltaïque-marine du bassin des Palmyrides-Sud en Syrie et les réservoirs cambro-ordoviciens du bassin de Sbaa en Algérie. Cette thèse consiste à établir l’histoire diagénétique, déterminer les contrôles sédimentaires et structuraux influençant l’évolution des phénomènes diagénétiques, caractériser l’habitus des cristaux authigènes de quartz formés autour les grains détritiques et aussi mettre en relation les différentes contrôles sédimentaires et diagénétiques sur les caractéristiques des pores et ainsi que sur la variation de la perméabilité. L’histoire diagénétique entre le réservoir du bassin de Sbaa se caractérise par une forte cimentation de quartz composée de trois phases Q1, Q2 /et Q3, par tapissage illitique et ainsi par une importante compaction chimique liée à certains faciès glaciaires et également une cimentation d’argiles principalement en illite mais surtout dans les champs d’Oued Zine et de Bou Hadid. A l’exception du champ de Hassi Ilatou, où une faible cimentation de quartz composée de Q1 a eu lieu. Alors que la diagenèse des réservoirs gréseux du bassin des Palmyrides-Sud est représentée par une faible cimentation de quartz composée d’une seule phase Q1, une absence de compaction chimique, ainsi qu’une cimentation d’argiles dominée par la chlorite et les kaolins. Les analyses microthermométriques des inclusions fluides dans les surcroissances de quartz mettent en évidence une silicification se déroulant principalement entre 100 et 160°C dans les deux bassins. D’après la reconstitution de l’histoire thermique de bassin, cet intervalle de température a été atteint entre le Viséen et la fin du Namurien dans le bassin de Sbaa et au Crétacé supérieur-Paléocène dans le bassin des Palmyrides-Sud. Les analyses isotopiques indiquent une eau originelle météorique et marine, progressivement réchauffée lors de l’enfouissement, et s’enrichissant au fur et à mesure en ¹⁸O dans les pores intergranulaires et des fluides évolués et chauds à l’origine des filonnets. L’habitus des cristaux authigènes de quartz et la forme de croissance montrent une relation avec les phases de ciment de quartz, son taux et la présence/absence de gaz. En effet, des cristaux à prisme court, tronqués par des facettes additionnelles, et des cristaux trapus caractérisent les grès cimentés par une seule phase de quartz authigène, et une fréquence importante des cristaux de quartz à multiples nucléas est constatée dans ces grès. Des cristaux à prisme développé et rarement des cristaux à prisme court caractérisent les grès contenant deux phases du ciment de quartz. Des cristaux peu développés et limités à quelques faces sont présents dans les grès cimentés par trois phases du ciment de quartz dans la paléozone à eau du réservoir dans le champ ODZ. Une forme de croissance en escalier est présente uniquement dans ces derniers grès. La présence des inclusions à hydrocarbures dans les surcroissances de quartz dans la partie supérieure du réservoir ordovicien du champ de Oued Zine indique que la mise en place des hydrocarbures dans le réservoir a été contemporaine à la cimentation de quartz à des températures 100-140°C en raison de la paléostructure anticlinale dans ce champ. Un deuxième épisode a eu lieu suite à la fracturation hercynienne à des températures comprises entre 117-185°C qui augmente vers le nord-ouest du bassin. La composition du gaz dans les inclusions monophasées (92 ± 5 mole %) est comparable à la composition actuelle du gaz dans le réservoir. / Petrophysic properties of siliciclastic reservoirs are influenced by many sedimentary and diagenetic factors. The main diagenetic processes affecting the reservoir quality are quartz cementation and mechanical and chemical compaction. The cementing of quartz plays a role in reducing the porosity as it precipitates occupying intergranular porosity. However, its influence on the evolution of permeability is not well known because the morphology of authigenic quartz crystals and controls responsible for this morphology remain poorly understood. Sandstone reservoirs with different geological settings were considered in this study; Carboniferous reservoirs of deltaic-marine Palmyrides South Basin (fields: Arak, Debayate South, and Sukhneh) in Syria and the Cambro-Ordovician reservoirs Sbaa Basin (fields : Hassi Ilatou , Hassi Ilatou NE, Bou Hadid, Oued Zine, and Bou Hadid W) in Algeria. They have widely varying porosities both laterally and vertically and permeabilities. Thus, this thesis is to establish the diagenetic history, determine the sedimentary and structural controls influencing the evolution of diagenesis, characterize crystallographic habits of authigenic quartz formed around the detrital grains and to relate the different sedimentary controls and diagenetic on pore characteristics and as well as the variation of the permeability. In the Sbaa Basin, the presence of inclusions hydrocarbons allowed to reconstruct the history of gas migration. The diagenetic history of the Sbaa Basin is characterized by strong cementing quartz composed of three phases Q1, Q2 / Q3, illite coatings, significant chemical compaction, and also by illite cements, especially in the fields of Oued Zine and Bou Hadid. However, Hassi Ilatou field shows low quartz cementation (Q1). In addition, reservoir sandstones of the Palmyrides-South Basin show low quartz cementation composed of a single phase Q1, an absence of chemical compaction, as well as clay cementation dominated by chlorite and kaolin characterize the diagenesis history. Microthermometric analyzes of fluid inclusions located in quartz overgrowths show that the silicification occurred mainly between 100 and 160 °C in both basins. According to the reconstruction of the thermal history, these temperatures have been reached between the end of the Visean and Namurian for the Sbaa Basin and Upper Cretaceous-Paéocène for the Palmyrides-South Basin. Isotope analyzes indicate marine/meteoric water gradually heated during burial, and enriched in ¹⁸O in intergranular pores and evolved hot fluids are responsible for vein precipitation. The habits of quartz overgrowth crystals and growth forms observed in the studied sandstones show a relation with the number of quartz cement phases. Effectively, crystals with short prisms, truncated by supplementary faces, and large crystals characterize one-phased (Q1) cemented sandstones. In addition, quartz crystals of multiple nucleations are frequent in these sandstones. However, crystals with long prisms and rarely crystals with short prisms characterize two-phased (Q1 and Q2) cemented sandstones. Crystals of poorly developed faces are present in three-phased (Q1, Q2, and Q3) cemented sandstones. Step-like striation present only in these sandstones. Methane inclusions in the quartz overgrowths of the upper part of Ordovician reservoir of Oued Zine indicate that the gas emplacement into the reservoir occurred synchronically with early quartz cementation in the sandstones located near the contact with the Silurian gas-source rocks at 100-140°C during the Late Carboniferous period and the late Hercynian episode fracturing at temperatures between 117 and 185°C. Microthermometric data on gas inclusions reveal the presence of an average of 92 ± 5 mole % of CH4, which is similar to the present-day gas composition in the reservoirs.

Ce manuscrit présente la dynamique des dépôts évaporitiques du bassin de Sivas en Turquie et évalue l’impact diagénétique de ces évaporites sur les analogues de réservoirs gréseux. Cette étude s’effectue dans un bassin d’avant-pays ayant la spécificité d’avoir enregistré une intense tectonique salifère, marquée notamment par la présence de mini-bassins oligo-miocènes. Les résultats présentés s’appuient sur des relevés cartographiques de terrain, des descriptions sédimentaires ainsi que sur des analyses pétrographiques et géochimiques.Les premières évaporites du bassin se forment à l’Eocène supérieur lorsque l’avant-pays perd progressivement sa connexion avec le domaine marin, en conséquence de la propagation de la chaine de plis et de chevauchements. La fermeture océanique s’accompagne d’une diminution drastique des apports clastiques. Les faciès turbiditiques évoluent alors vers des dépôts argilo-carbonatés propres à un bassin affamé et anoxique. Les évaporites commencent par précipiter dans des bassins en piggy-back précocement isolés du reste de l’avant-pays. Par surrection tectonique, ces dépôts subissent un démantèlement gravitaire qui induit des accumulations de gypses détritiques au front de la chaîne. Avec l’augmentation des conditions de salinité de l’ensemble du bassin, des plateformes évaporitiques s’établissent ensuite sur les domaines peu profonds et nourrissent en fond de bassin des turbidites de gypse. Enfin, dans un plan d’eau devenu peu profond, l’essentiel de l’avant pays est comblé par de la halite aujourd’hui lessivée en surface. Tout au long de l’Oligo-Miocène, les évaporites éocènes induisent des déformations halocinétiques. Les sels diapiriques sont alors dissous et recyclés sous forme de dépôts gypsifères qui précipitent en domaine continental, au sein d’environnements sebkhaïques à lacustres peu profonds. Ces évaporites de seconde génération ont pu connecter différents émissaires diapiriques pour constituer ce que nous nommons « une canopée resédimentée ». Les sulfates recyclés se sont également accumulés sur des émissaires diapiriques en cours de déflation pour ainsi former de véritables mini-bassins évaporitiques secondaires encapsulés. Sur toute la bordure nord du bassin, et en continuité latérale d’une canopée salifère, les évaporites recyclées ont formé des accumulations majeures de gypse sélénitique lacustre.L’étude diagénétique des grès continentaux de mini-bassins montre une paragenèse ayant été contrôlée au premier ordre par la composition minéralogique des grains détritiques. Ainsi, dans les grès fortement polygéniques, des fluides salins et alcalins probablement dérivés du lessivage des émissaires diapiriques ont interagi avec les grains réactifs pour induire la précipitation précoce de ciments analcitiques. Ces derniers paraissent également avoir été favorisés dans les mini-bassins isolés hydrographiquement par des reliefs diapiriques. Plus localement, des phénomènes de gypsification se sont produits au niveau de dépôts faillés ou fracturés et positionnés à proximité immédiate de structures salifères. Les fluides salins impliqués circulaient par l’intermédiaire de la porosité créée par l’endommagement tectonique.L’ensemble des résultats présentés trouvent des analogies avec d’autres bassins salifères, actuels ou anciens, affectés par des déformations halocinétiques en contexte continental (e.g. le bassin Précaspien, le bassin du Zechstein ou le Great Kavir en Iran). / This manuscript focuses on the various evaporitic systems of the Sivas Basin (Turkey) and assesses the diagenetic impact of saline fluid flow on silicoclastic reservoir analogues. This study takes place in a foreland basin that has the peculiarity of having recorded halokinetic deformations, as evidenced by outcropping Oligo-Miocene mini-basins structures. The results are based on geological field mapping and sedimentary descriptions complemented by petrographic and geochemical analyses.The first evaporites of the basin precipitated during the Late Eocene when the foreland progressively lost its connection with the oceanic domain, as a result of the northward propagation of the fold-and-thrust-belt. Such event first resulted in sediment-starved conditions, with siliciclastic turbidites grading to muddy- and organic-rich facies. The evaporites then formed in early isolated piggy-back basins and were subsequently reworked in the foredeep by tectonically-induced gravitational collapses. With increasing saline conditions, evaporitic platforms developed in shallow-water domains of the foreland, and fed gypsum turbidites in the deep-water setting. Finally, after the general establishment of shallow-water hypersaline conditions, most of the available space was filled by halite deposits, nowadays entirely dissolved at the surface.During the Oligo-Miocene, Eocene evaporites induced halokinetic deformations. The diapiric salts were then recycled as gypsiferous deposits precipitated in sabkha to shallow-water lacustrine setting within salt-walled mini-basins. Such evaporitic deposits of second-generation were able to connect different diapiric structures, forming what we define as a “resedimented canopy”. The recycled evaporites also accumulated in depleting diapiric stems, resulting in the development of peculiar encased evaporitic mini-basins. Finally, along the northern border of the basin, the recycled evaporites formed massive accumulations of lacustrine selenitic gypsum southward connected to a spreading salt canopy.The diagenetic study of Oligocene continental sandstones emplaced within mini-basins highlights a paragenesis controlled at first order by the detrital composition. For instance, in the less sorted sandstones, saline-alkaline fluids, probably resulting from the leaching of diapiric salts, interacted with reactive grains to produce analcitic cements at shallow burial. These cements also seem to have been favored in mini-basins that were hydrographically isolated by diapiric reliefs. More locally, in fractured to faulted sandstones close from a diapiric structures, the porosity has been early to lately occluded by gypsum cements. The saline fluids inducing such cementation were fed by the diapiric evaporites, and reached the reservoirs through the fracture or fault-related porosity.All of these results may find relevant analogies with other ancient or present-day evaporitic basins affected by halokinetic deformation in continental setting (e.g. the Precaspian Basin, the Zechstein Basin or the Great Kavir in Iran).

Os reservatórios lacustres do Grupo Lagoa Feia, seção rift da Bacia de Campos, margem Leste brasileira, tem mantido há décadas uma expressiva produção a partir de campos localizados em águas rasas. A descoberta de grandes acumulações na seção rift e sag (pré-sal) da Bacia de Santos reativou a exploração por reservatórios análogos na Bacia de Campos e em outras bacias marginais. Um estudo petrográfico e petrofísico sistemático foi executado sobre os reservatórios rift da Formação Coqueiros e sag da Formação Macabu do Norte da Bacia de Campos, com objetivo de caracterizar os principais controles sobre a gênese e evolução daqueles reservatórios não-convencionais e seus sistemas porosos. As principais petrofácies de reservatório reconhecidas foram grainstones e rudstones bioclásticos, arenitos ooidais argilosos e dolomitos na Formação Coqueiros, e crostas coalescentes e não-coalescentes de calcita fascicular, rudstones e grainstones intraclásticos e dolomitos na Formação Macabu. A evolução dos reservatórios bioclásticos foi controlada pelo balanço entre dissolução ou neomorfismo dos bioclastos aragoníticos de bivalves, favorecendo a geração de porosidade móldica pouco conectada, ou a preservação da porosidade interpartícula bem conectada, controlando a permeabilidade dos reservatórios. Os arenitos de oóides de argilas magnesianas sofreram dissolução e substituição por dolomita e sílica, o que gerou sistemas porosos altamente heterogêneos, compostos por poros móldicos, intercristalinos, vugulares e microcristalinos. O crescimento de agregados cristalinos arborescentes nas crostas coalescentes de calcita gerou porosidade de crescimento do arcabouço primária, que foi reduzida principalmente por cimentação dolomítica, ou alargada por dissolução, o que ampliou sua permeabilidade. Crostas nãocoalescentes de calcita mostram forte interação com argilominerais magnesianos, que preenchem interstícios, e/ou estão intercalados com as crostas. Sua porosidade está relacionada com a dissolução das argilas, o que produziu baixa permeabilidade. Rochas intraclásticas comumente mostram matriz argilosa, ou estão compactadas e cimentadas. Onde exibem porosidade interpartícula primária ou dissolução da matriz, podem ter boas porosidades e permeabilidades. A dolomitização heterogênea de ambas as Formações em alguns casos destruiu a porosidade primária ou eodiagenética, ou em outros gerou altos valores de porosidade e permeabilidade nos dolomitos. Relações de substituição e de compactação indicam que muitos dos processos diagenéticos ocorreram durante a eodiagênese, controlados principalmente pela instabilidade da aragonita nos reservatórios bioclásticos da Formação Coqueiros, e dos argilominerais magnesianos na Formação Macabu. Este estudo representa a primeira caracterização petrográfica publicada dos reservatórios carbonáticos não-convencionais do sag, e salienta a importância crucial dos estudos petrográficos sistemáticos para a compreensão e previsão da qualidade de reservatórios complexos. / Lacustrine carbonate reservoirs from the Lagoa Feia Group, rift section of Campos Basin, offshore eastern Brazil, have sustained for decades a significant production from shallow water oil fields. The discovery of giant accumulations in the rift and sag (pre-salt) section of the adjacent Santos Basin has reactivated the exploration for equivalent reservoirs in the Campos Basin and in other marginal basins. A systematic petrographic and petrophysical study was performed on the rift Coqueiros Formation and the sag Macabu Formation carbonates from the Lagoa Feia Group in northern Campos Basin, in order to characterize the main controls on the origin and evolution of those unconventional reservoirs and their pore systems. The main types of reservoir petrofacies recognized were grainstones and bioclastic rudstones, magnesian clay ooidal arenites and dolostones from the Coqueiros Formation; coalescent and non-coalescent crusts of fascicular calcite, intraclastic rudstones and grainstones, and dolostones from the Macabu Formation. The evolution of bioclastic reservoirs was controlled by the balance between dissolution and neomorphism of the aragonitic bivalve bioclasts, favoring the generation of poorly-connected moldic porosity or the preservation of well-connected interparticle porosity, which controlled the permeability of the reservoirs. The magnesian clay (stevensite) ooidal arenites suffered dissolution and replacement by dolomite and silica, what generated highly heterogeneous pore systems, composed by moldic, intercrystalline, vugular and microcrystalline pores. The growth of crystal shrubs in coalescent calcite crusts generated growth-framework primary porosity, which was reduced mostly by dolomite cementation, or enlarged by dissolution, what enhanced their permeability. Non-coalescent calcite crusts usually show strong interaction with syngenetic magnesian clay minerals, which fill interstices and/or are interbedded with the crusts. Their porosity is related to dissolution of the clays, what generated poor permeability. Intraclastic rocks usually display clay matrix, or are compacted and cemented. Where they show interparticle primary porosity or matrix dissolution, they may have good porosities and permeabilities. The heterogeneous dolomitization of both formations, either destroyed the primary or early diagenetic porosity, or generated high porosity and permeability values in the dolostones. Relationships of replacement and compaction indicate that most of the diagenetic processes occurred during eodiagenesis, controlled mostly by the instability of the aragonite in the bioclastic Coqueiros reservoirs, and of the magnesian clay minerals in the Macabu Formation. This study represents the first published petrographic characterization of the unconventional sag carbonate reservoirs, and stresses the crucial importance of systematic petrographic studies for the understanding and prediction of the quality of complex reservoirs.

Les écosystèmes côtiers méditerranéens sont soumis à de multiples sources de contamination (activités agricoles, industrielles et touristiques) impactant à des degrés divers les compartiments environnementaux (colonne d'eau, sédiments, biota, ...). En particulier, des études précédentes ont démontré que les sédiments de la Rade de Toulon présentent un niveau de multi-contamination très important, qui pourrait avoir des conséquences non-négligeables sur l'écosystème côtier, ce qui nécessite la réalisation de différentes études complémentaires visant à mieux comprendre les processus régissant le transfert potentiel des polluants vers le milieu environnant. Dans ce contexte, les objectifs de cette thèse consistent à étudier les processus contrôlant la dynamique des polluants inorganiques dans la colonne sédimentaire et à l'interface eau/sédiment et à évaluer leur remobilisation potentielle vers la colonne d'eau. Trois modes principaux de dispersion peuvent conduire à une remobilisation des contaminants: (1) la diagénèse précoce mobilisant des éléments nutritifs et des éléments traces métalliques et métalloïdes, (2) la remobilisation des contaminants lors de remises en suspension sédimentaire, et (3) le flux diffusif à l'interface eau/sédiment en lien avec la mobilité des contaminants dans la colonne sédimentaire. Pour atteindre ses objectifs, ce projet de thèse combine des approches in-situ (carottage d'interface, extraction de l'eau interstitielle, traitement/analyse des eaux interstitielles et des fractions solides, …), des expériences en laboratoire (suivi cinétique de la remobilisation des contaminants lors des mélanges eau/sédiment, extractions séquentielles…), des outils de modélisation (calcul de la spéciation chimique, simulation de la partition dissous/particulaire, simulation des profils sédimentaires, réactivité de la matière organique, …) ainsi que le traçage des sources de contamination et de leur transfert entre différents compartiments environnements à l'aide des isotopes stables du Pb. Ces travaux ont été réalisés en étroite collaboration avec le LASEM et avec la contribution de différents partenaires (EPOC/Université de Bordeaux, Ruđer Bošković Institut/Croatie, CAM/Université de Lausanne/Suisse, IFREMER, IRSN, …). / Mediterranean coastal ecosystems are exposed to several contamination sources (agricultural, industrial and touristic activities) impacting the environmental compartments (water column, sediment, biota ...) at various scales. Some previous studies showed, in particular, that the sediments of Toulon Bay present important contents of several contaminants, which may have non-negligible impacts on the coastal ecosystem, and which require further studies to better understand the processes governing the potential pollutants transfer to the surrounding environment. In this context, the objectives of this PhD are to study the processes controlling the inorganic pollutants dynamic in the sediment column and at the sediment/water interface and to assess their potential remobilization to the water column. Three main modes of dispersion can lead to contaminants remobilization : (1) the early diagenesis mobilizing nutrients, trace metals and metalloids, (2) the contaminants remobilization during sediment resuspension events, and (3) the diffusive flux from the sediment/water interface due to the sedimentary mobility of contaminants. To achieve its goals, this PhD project combines in-situ approaches (interface coring, extraction, treatment and analysis of porewater and solid fractions, ...), laboratory experiments (kinetic monitoring of contaminants remobilization during sediment resuspension, sequential extractions, ...), modeling tools (chemical speciation calculation, dissolved/particulate partition simulation, depth profiles simulation, organic matter reactivity, …) and contamination sources tracking and transfer between various environmental compartments using Pb stable isotopes. These studies were performed in close cooperation with the LASEM and with the contribution of different partners (EPOC/University of Bordeaux, Ruđer Bošković Institute/Croatia, CAM/University of Lausanne/Suisse, IFREMER, IRSN, …).

Les illites et les chlorites sont des minéraux ubiquistes dans la plupart des roches diagénétiques. Leurs compositions chimiques dépendent des conditions physiques subies (pression, P ; température, T) et de la composition de l’encaissant (e.g. Vidal et al., 1999 ; Parra et al., 2002a, 2002b). Ces minéraux peuvent donc potentiellement être de très bons marqueurs de l’histoire de l’enfouissement, et sont à la base de nombreuses méthodes empiriques ou thermodynamiques d’estimation des conditions P-T.Une compilation de données naturelles et la comparaison des thermobaromètres existants ont permis d’établir leurs limitations respectives. Pour s’en affranchir, un nouveau modèle ordonné de solution solide pour les chlorites a été développé, qui rend compte des forts contenus en silicium observés dans les chlorites naturelles de basses températures. La calibration de ce nouveau thermobaromètre sur des domaines géologiques variés de BT-BP a été testée sur des analyses de chlorites naturelles de la Gulf Coast (Texas) au pic de température (où les données P-T ont été mesurées in situ) et montre d’excellents résultats. Concernant les illites, le modèle thermodynamique le plus abouti (Dubacq et al., 2010) a également été testé de manière à estimer sa précision. L’étude a été complétée par la quantification de l’influence du fer ferrique. Les analyses chimiques utilisées ont été obtenues grâce à un protocole analytique à haute résolution spatiale. Alliant FIB et MET-EDS, ce protocole a permis une étude microtexturale et chimique fine des chlorites et des illites. Il en ressort que ces minéraux possèdent une diversité intracristalline dans leurs compositions et que la zonation chimique résultante apparaît comme une potentielle source d’erreurs dans la calibration des thermobaromètres, tout en permettant d’envisager la notion d’équilibre à l’échelle locale.Cette approche a été utilisée pour quantifier les trajets P-T d’unités géologiques des Alpes de Glarus. Ces résultats, comparés à ceux obtenus avec des méthodes thermobarométriques conventionnelles, donnent une bonne image des processus d’enfouissement et d’exhumation des roches de basse température. Ainsi, il apparaît que chaque composition enregistre une portion du chemin P-T rétrograde. D’une manière générale, chaque zone d’un même cristal renvoie à une partie de l’histoire de la roche. / Illite and chlorite are ubiquitous in most diagenetic rocks. Their chemical compositions are sensitive to thermobarometric conditions (pressure, P; temperature, T) and the bulk composition (e.g. Vidal et al., 1999; Parra et al., 2002a, 2002b). These minerals can be good indicators of burial history, and are the basis of several empiric or thermodynamic methods to estimate P-T conditions. A compilation of natural data and the comparison of existing thermobarometers allowed to establish their limitations. To circumvent it, an ordered model of solid solution for chlorites was developed which considers Si-rich low-T compositions. The calibration of this new thermobarometer on various LT-LP geologic fields was tested on natural chlorites analysis of Gulf Coast (Texas) at metamorphic peak, and gives accurate results. Concerning illites, the thermodynamic model of Dubacq et al. (2010) was also tested to estimate its precision. The study was completed by the quantification of the Fe3+ effects. Chemical analyses were obtained by an analytical protocol with high spatial resolution. Combining FIB and EDX-TEM, this protocol allowed an accurate microstructural study of chlorites and illites. These minerals have an intracristalline diversity of their chemical composition. The resulting chemical zonation is a potential error in calibration of thermometers, but allowed consideration of local equilibrium.This approach was used to quantify the P-T path of geologic units in Alps (near Glarus). These results, compared to results of conventional thermobarometers, give a good representation of burial and exhumation process for low-T rocks. Thus, the chemistry records a part of retrograde P-T path and each part of a crystal zoning corresponds to a part of rocks history.

The Greater Aneth Buildup (GAB) is comprised of the 3rd-order middle Pennsylvanian (Desmoinesian) Desert Creek sequence of the Paradox Formation. A hierarchy of 4th- and 5th order, carbonate-dominated cycles comprise the Upper Desert Creek (UDC) 4th-order sequence. A SE to NW trending transect line, utilizing core and petrophysical data from six oil and gas wells (from SE to NW wells R-19, Q-16, O-16, J-15, K-430, E-313), revealed deposition of seven carbonate facies within four 5th-order parasequences in the UDC. While each of the seven carbonate facies are present across the transect line, the UDC parasequences are dominated by a shallow-water oolite facies. Laterally and vertically, a general facies transition is evident in each of the four parasequences from a dominantly deeper-water succession of facies in the SE, to a more shallow-water, open marine to restricted lagoon, succession of facies to the NW. Parasequence UDC-3 contains the best representation of this facies transition with the SE wells (R-19, Q-16, and O-16) displaying the deeper-water/mixed algal facies grades into the shoaling oolite facies in the NW wells (J-15, K-430, and E-313). Within UDC strata, porosity and permeability correlate well to each other, but poorly to facies type. Porosity and permeability are predominantly controlled by diagenesis. Minor appearances of fibrous isopachus rim cements, and more common micritization (both whole grain and envelope) suggest that early-marine diagenesis occurred within the oolite facies. Meteoric diagenesis is demonstrated by abundant calcite spar, and drusy dogtooth cements within oomoldic pores, intraparticle pores, and interparticle pores, in addition to neomorphism of early marine diagenetic fabrics. Spastolithic ooids, stylolitization, and grain brecciation are representative of burial diagenesis within these strata. Dolomitization is present in each of the six studied core, but only in minor amounts. The Upper Desert Creek 3rd-order sequence has preserved laminamoldic diagenetic fabric that is the oldest known example of selective leaching in a meteoric vadose environment. Lithofacies trends along transect line A to A' demonstrate an increase in ooid-rich grainstone NSCF both vertically and laterally from the SE to the NW. Lithofacies type, combined with diagenesis, are the major drivers for porosity and permeability creation and destruction within Upper Desert Creek strata. NSCF, specifically ooid grainstones, have the greatest diagenetic potential of the seven UDC lithofacies.

The Greater Aneth Buildup (GAB) is comprised of the 3rd-order middle Pennsylvanian (Desmoinesian) Desert Creek sequence of the Paradox Formation. A hierarchy of 4th- and 5th order, carbonate-dominated cycles comprise the Upper Desert Creek (UDC) 4th-order sequence. A SE to NW trending transect line, utilizing core and petrophysical data from six oil and gas wells (from SE to NW wells R-19, Q-16, O-16, J-15, K-430, E-313), revealed deposition of seven carbonate facies within four 5th-order parasequences in the UDC. While each of the seven carbonate facies are present across the transect line, the UDC parasequences are dominated by a shallow-water oolite facies. Laterally and vertically, a general facies transition is evident in each of the four parasequences from a dominantly deeper-water succession of facies in the SE, to a more shallow-water, open marine to restricted lagoon, succession of facies to the NW. Parasequence UDC-3 contains the best representation of this facies transition with the SE wells (R-19, Q-16, and O-16) displaying the deeper-water/mixed algal facies grades into the shoaling oolite facies in the NW wells (J-15, K-430, and E-313). Within UDC strata, porosity and permeability correlate well to each other, but poorly to facies type. Porosity and permeability are predominantly controlled by diagenesis. Minor appearances of fibrous isopachus rim cements, and more common micritization (both whole grain and envelope) suggest that early-marine diagenesis occurred within the oolite facies. Meteoric diagenesis is demonstrated by abundant calcite spar, and drusy dogtooth cements within oomoldic pores, intraparticle pores, and interparticle pores, in addition to neomorphism of early marine diagenetic fabrics. Spastolithic ooids, stylolitization, and grain brecciation are representative of burial diagenesis within these strata. Dolomitization is present in each of the six studied core, but only in minor amounts. The Upper Desert Creek 3rd-order sequence has preserved laminamoldic diagenetic fabric that is the oldest known example of selective leaching in a meteoric vadose environment. Lithofacies trends along transect line A to A<&trade> demonstrate an increase in ooid-rich grainstone NSCF both vertically and laterally from the SE to the NW. Lithofacies type, combined with diagenesis, are the major drivers for porosity and permeability creation and destruction within Upper Desert Creek strata. NSCF, specifically ooid grainstones, have the greatest diagenetic potential of the seven UDC lithofacies.

The Late Pennsylvanian was a time of frequent, rapid glacioeustatic sea-level changes. These changes were recorded in the Wolfcamp D Formation of the Midland Basin as a series of cyclothems similar to those studied in the Midcontinent region (e.g., Algeo and Heckel, 2008). This study focuses on identifying the mechanisms and controls on carbonate deposition and diagenesis through the Upper Pennsylvanian Wolfcamp D Formation and evaluating the potential for these layers to be stratigraphically significant. A stepwise progression of diagenetic processes was identified through the use of δ13Ccarb and δ18Ocarb, bulk geochemical and petrographic analysis, and scanning electron microscopy. Carbonate deposition and early-burial diagenesis appears to be strongly influenced by frequent changes in sea-level and benthic redox conditions. The transition to deep-burial diagenesis was controlled by the thermal gradient in the basin and the extent of diagenesis by the amount of clays and organic matter in the surrounding mudrocks. Further diagenesis was induced through interactions with a brine following clay diagenesis. The presence of multiple phases of diagenesis in this system further highlights the need for several lines of inquiry when evaluating the post-depositional evolution of carbonates in a mud-rich setting.

A sequential extraction method was used to determine which dominant sedimentary mineral phase was involved in phosphorus retention in the sediments of Lake Rotorua and to verify the importance of iron phases in the role as a phosphorus sink. The observed influence of the experimental conditions upon the extent of phosphate adsorption to various iron phases shows a considerable quantity of phosphorus is present in the reducible phase and in the residual mineral phase. The phosphorus associated with iron(III) oxide phases was released into solution under reducing conditions when ferric iron oxide/oxyhydroxides, including amorphous and poorly crystalline Fe(III) phases, were solubilized. The residual primary and secondary mineral phases remained stable in the sediments until they were exposed to extremely acidic media analogous to strongly reducing conditions. Manganese is not involved in phosphorus retention to the same extent as iron. Aluminium phases present were released from surface complexes with relative ease and also from mineral structures under the prevailing conditions. The results show a strong agreement between aluminium and phosphorus suggesting it is associated with various aluminium phases to some extent. The sediments of Lake Rotorua are rich in organic-bound P which is released when organic material is oxidized under conditions analogous to anaerobic degradation. The degradation of refractory organic material represents a significant source of phosphorus for incorporation into diagenetic minerals forming in oxic and anoxic layers of the sediment. Heavy liquid separation of the sediments concentrated the small quantities of dense minerals into a separate fraction and the presence of iron sulfides could be verified. Three density fractions obtained by this method separated the diatoms (d less than 2.6 g cm-3), the silicates (d greater than 2.6 less than 3.7 g cm-3) and the heavy minerals (d greater than 3.7 g cm-3) present in the sediment sample. In the heavy mineral phase spherulitic framboidal pyrite and rhombohedrial siderite were observed by scanning electron microscopy (SEM). Energy dispersive x-ray fluorescence (XRF) analysis of the framboidal pyrite detected significant fluorescence's for sulphur and iron. The elemental analysis of siderite characterised it as an iron-rich, non-sulfidic particle with no phosphorus fluorescence. Particles were also observed that had a variable morphology to the framboidal pyrite minerals but similar ratio of Fe to S in the XRF spectrum. It is likely they are other stable forms of iron sulfides or pyrites in various stages of diagenetic dissolution. Digestion of the three density fractions shows the heavy mineral phase is significantly enriched in sulfur and in iron confirming the presence of sulfides. The sulfide-forming trace metals are concentrating in the heavy mineral phase but a progressive enrichment of trace metals down core is not found in the results. Many of the trace elements show maximum concentrations in the Tarawera tephra. There is a good agreement between iron and phosphorus in both treatments that implies iron phases are the predominant phosphorus fixers in the sediments of Lake Rotorua. However the identity of the phosphorus sink could not be confirmed by SEM or XRF analysis of the heavy minerals. The most likely explanations for the observed concentrations of iron and phosphorus and enrichment in the heavy mineral fraction are the persistence of the highly insoluble crystalline iron oxyhydroxides (goethite) in reducing sediments or the formation of the reduced iron mineral vivianite. Considering the density of vivianite it would have being taken into the heavy fraction by default which would account for the enrichment demonstrated by the solution analysis.

Aquatic sediments are the recipients of a continual rain of organic debris from the water column. The decomposition reactions within the sediment and the rates of material exchange between the sediment and water column are critically moderated by the transport processes within the sediment. The sediment and solute movement induced by burrowing animals – bioturbation and bioirrigation – far exceed abiotic transport processes such as sedimentation burial and molecular diffusion. Thalassinidean shrimp are particularly abundant burrowing animals. Living in high density populations along coastlines around the world, these shrimp build complex burrow networks which they actively maintain and irrigate.¶ I used a laser scanner to map thalassinidean shrimp (Trypaea australiensis) mound formation. These experiments measured rapid two-way exchange between the sediment and depth. Subduction from the sediment surface proved to be just as important as sediment expulsion from depth, yet this is not detected by conventional direct entrapment techniques. The experiments demonstrated that a daily sampling frequency was needed to capture the extent of the two-way exchange.¶ I derived a one-dimensional non-local model accounting for the excavation, infill and collapse (EIC) of burrows. Maximum likelihood analyses were used to test the model against 210Pb and 228Th profiles taken from sediment cores in Port Phillip Bay, Melbourne. The maximum likelihood approach proved to be a useful technique for quantifying parameter confidence bounds and allowing formal comparison with a comparable biodiffusion model. The EIC model generally outperformed the biodiffusion model, and in all cases best EIC model parameter estimates required some level of burrow infill with surface material. The EIC model was expanded to two and three dimensions, which allowed the representation of lateral heterogeneity resulting from the excavation, infill and collapse of burrow structures. A synthetic dataset generated by the two-dimensional model was used to demonstrate the effects of heterogeneity and core sampling on the mixing information that can be extracted from one-dimensional sediment core data.¶ Burrow irrigation brings oxygenated water into burrow depths, and can affect the nitrogen cycle by increasing the rates of coupled nitrification and denitrification reactions. I modelled the nitrogen chemistry in the annulus of sediment surrounding an irrigated burrow using a radially-symmetrical diffusion model. The model was applied to three published case studies involving thalassinidean shrimp experiments and to field data from Port Phillip Bay. The results highlighted divergences between current theoretical understanding and laboratory and field measurements. The model further demonstrated potential limitations of measurements of burrow characteristics and animal behaviour in narrow laboratory tanks. Activities of burrowing animals had been hypothesised to contribute to high denitrification rates within Port Phillip Bay. Modelling work in this thesis suggests that the model burrow density required to explain these high denitrification rates is not consistent with the sampled density of thalassinidean shrimp in the Bay, although dense burrows of other animals are likely to be important. Limitations of one-dimensional representations of nitrogen diagenesis were explored via comparisons between one-dimensional models and the full cylinder model.