Dissertations / Theses on the topic 'Diagenesis models'

Development of a predictive model for the distribution of diagenetic alterations and related evolution of reservoir quality of sandstones was achieved by integrating the knowledge of diagenesis to sequence stratigraphy. This approach allows a better elucidation of the distribution of eogenetic alterations within sequence stratigraphy, because changes in the relative sea level induce changes to: (i) pore water chemistry, (ii) residence time of sediments under certain near-surface geochemical conditions, (iii) variations in the detrital composition, and (iv) amounts and type of organic matter.

This thesis revealed that eogenetic alterations, which are linked to sequence stratigraphy and have an impact on reservoir quality evolution, include formation of: (i) pseudomatrix and mechanically infiltrated clays in fluvial sandstones of the lowstand and highstand systems tracts (LST and HST, respectively), (ii) kaolinite in tide-dominated deltaic and foreshore-shoreface sandstones of HST, Gilbert-type deltaic sandstones of LST and fluvial deltaic sandstones of LST, (iii) kaolinite and mechanically infiltrated clays in sandstones lying below sequence boundary, (iv) K-feldspar overgrowths in fluvial deltaic LST, (v) glaucony towards the top of fluvial deltaic LST immediately below and at transgressive surface (TS) and in foreshore and shoreface transgressive systems tracts (TST) below parasequence boundaries (PB) and maximum flooding surface (MFS), (vi) framboidal pyrite and extensive cementation by calcite and dolomite in foreshore and shoreface and tide-dominated deltaic TST, and shoreface and tidal flat HST bioclastic-rich arenites particularly in the vicinity of PB, TS and MFS, (vii) pervasive cementation by iron oxide in shoreface-offshore and shoreface sandstones of TST immediately below the MFS, (viii) zeolites and palygroskite in shoreface sandstones of TST and HST, particularly above PB, and (ix) cementation by siderite in Gilbert-type deltaic sandstones of LST, tide-dominated deltaic and foreshore-shoreface sandstones of HST and in tide-dominated deltaic sandstones of TST, particularly at MFS. Moreover, this thesis revealed that the distribution of eogenetic alterations strongly control, and thus provide information for constraining the distribution patterns of mesogenetic alterations, such as illitization of mechanically infiltrated clays and dickitization of kaolinite, and hence of related reservoir quality evolution of sandstones during progressive burial.

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.

This thesis details the results of an integrated study of carbonate platform sedimentology, geometry, evolution and diagenesis within a sequence stratigraphic framework. This study has been based on the Upper Cretaceous carbonates within the Tremp basin of the Spanish Pyrenees, which, through the effects of minor tectonic deformation during the later parts of the Pyrenean orogeny, are exceptionally well exposed and can be studied in the form of a platform to basin cross-section upon a scale that is comparable to that of a seismic section. This study concentrates on the mid-Turonian to Coniacian-aged Congest platform and its associated basinal succession, whose sedimentology and geometrical features, in particular cyclic progradational cycles, and evidence of repeated flooding and exposure of the platform-top are interpreted in terms of . fluctuations in relative sea-level and associated variations in available accommodation space. These interpretations, together with evidence of subaerial exposure in the form of karst features, intensive dissolution and the presence of speleo-cements, are used to propose a dynamic 'forced regression' model for the evolution of the Congost platform, which involves two phases of platform development, separated by a period of forced regression. The primary and secondary porosity afforded by the abundant bi-mineralic rudists within the platform-top sediments allows for a detailed and comprehensive diagenetic study of these carbonates, in the form of a case study for a number of interesting diagenetic features. In addition to standard petrography, cathodoluminescence and stable isotope studies have been employed and have allowed the identification of such features as botryoidal calcitic marine cements, neomorphism which occurred in lagoonal waters and speleo-cements. This study also provides a detailed investigation of the diagenesis associated with subaerial exposure and the development of sequence boundaries. Differences in the early diagenesis of these carbonates from different parts of the Congost platform suggest that two separate phases of platform development experienced: 1) differing pore-fluid regimes; 2) differing frequencies and duration of subaerial exposure events; and 3) different magnitudes of relative sea-level fall. These features are considered in terms of variations in accommodation space during platform development and are used to develop the dynamic 'forced regression' model for the evolution of the Congost platform. A succession of Cenomanian to Santonian-aged basinal and slope sediments which can be correlated with the contemporaneous Santa Fe, Congost and Sant Comeli platforms and contain a large amount of allochthonous debris, much of which is derived from underiying units, are described and interpreted in terms of local tectonic activity and relative sea-level change. The final part of this thesis presents a new sequence stratigraphic model for the mid-Turonian to Coniacian-aged Congost platform which is compatible with the observations and conclusions of this study. This new sequence stratigraphic model suggests that the Congost platform developed within two separate depositional sequences, albeit with one being on a much larger scale than the other. Sequence boundaries are characterised by subaerial exposure on the platform top which can be correlated with hardgrounds and/or glauconite accumulations within the more basinal locations, overlain by deeper-water facies. The presence of submarine onlap surfaces and down-slope slide deposits immediately above the sequence boundaries suggests that the major transgressive events which followed sequence boundary development were brought about by local extensional tectonic activity, while the stratigraphic cyclicity within the sequences and major falls in sea-level which produced the sequence boundaries are interpreted to have resulted largely from eustatic processes.

La diagenese precoce des sediments marins profonds contribue au recyclage oceanique des debris biogeniques particulaires. Elle est aussi la premiere etape des transformations que cette matiere subit lors de son enfouissement. Cette etape conduit a des transformations biogeochimiques de la composition des particules qui constituent le sediment et fixe un enregistrement historique des conditions oceaniques. Pour y avoir acces, il est donc necessaire de comprendre et de quantifier les processus de diagenese precoce. Dans cette optique, nous avons developpe des modeles globaux quantitatifs de diagenese precoce qui representent les couplages chimiques et microbiologiques du milieu naturel. Ces modeles permettent de representer simultanement les distributions de carbone organique, oxygene, nitrate, phosphate et manganese solide et dissous dans les sediments. D'autre part, il est important de prevoir le comportement des sediments au cours de diverses perturbations, afin d'etre en mesure d'estimer les consequences sur les milieux aquatiques des futures variations de notre environnement. Dans ce but, nous avons mis au point des modeles qui rendent compte de la dynamique du sediment a la suite a differents evenements: perturbation par la megafaune benthique, depot de turbidite, ou deploiement de chambre benthique

Les petroporphyrines sont des pigments presents, sous forme de melanges, dans la plupart des sediments contenant de la matiere organique. Ils sont en general les fossiles de chlorophylles. Leur purification chromatographique et l'identification de leurs structures sont souvent difficiles. L'acylation par reaction de friedel-crafts a ete reconsideree en tant qu'outil servant a faciliter la purification de ces melanges complexes et une nouvelle serie de porphyrines diacetylee a ete synthetisee dans ces conditions. Par ailleurs une nouvelle hemisynthese, de deux porphyrines fossiles, la deoxophylloerythroetioporphyrine (dpep) et la 15-methyl-dpep, a ete realisee a partir de la chlorophylle a. Cette preparation constitue une approche simple et rapide pour l'obtention de composes de reference. Nous avons egalement pu montrer que les porphyrines etaient facilement alkylees par l'alcool benzylique en presence d'une argile acide, la montmorillonite k10, ce qui constitue un premier pas vers la comprehension des phenomenes de transalkylation pouvant expliquer, en partie, la presence des porphyrines de haut poids moleculaires dans les melanges geochimiques. Dans une etude independante la preparation d'etioporphyrines par tetramerisation acido-catalysee d'un monopyrrole a permis d'obtenir une bonne selectivite en etioporphyrine i. La structure du monopyrrole de depart a, enfin, pu etre determinee avec exactitude et une serie de pyrroles reputes instables a ete preparee

Les porphyrines presentes dans la matiere organique sedimentaire (petroporphyrines) sont les fossiles moleculaires de chlorophylles ou d'hemes provenant essentiellement d'algues ou de bacteries. Ces precurseurs biologiques subissent, au cours de leur diagenese, de multiples transformations catalysees par la temperature ou leur environnement chimique (argiles, ions metalliques, soufre et ses derives, etc). Notre travail a consiste a etudier, sur des porphyrines synthetiques, certaines de ces reactions, en particulier les interactions porphyrines-soufre et certains aspects des reactions de metallation. La premiere partie du travail decrit la synthese des composes de depart tetra et octaalkylporphyrines et en particulier une optimisation de la synthese de l'octaethylporphyrine de meme que son marquage par #1#3c #1#5n. Dans une seconde partie nous montrons que des reactions thermiques soufre porphyrines ont lieu ce qui a permis d'isoler et de caracteriser une serie de composes originaux comme des thiapyrano- et thienylporphyrines. Nous avons observe des reactions d'incorporation de soufre, d'hydrogenation et deshydrogenation, de formation et de coupure de liaisons carbone-carbone, toutes reactions observees dans les milieux sedimentaires. Enfin la troisieme partie de la these decrit une serie d'experiences de metallation de porphyrines par le nickel et le vanadium. Les premiers resultats demontrent une forte correlation structure vitesse de metallation

Sedimentary basins form when water-borne sediments in shallow seas are deposited over periods of millions of years. Sediments compact under their own weight, causing the expulsion of pore water. If this expulsion is sufficiently slow, overpressuring can result, a phenomenon which is of concern in oil drilling operations. The competition between pore water expulsion and burial is complicated by a variety of factors, which include diagenesis (clay dewatering), and different modes (elastic or viscous) of rheological deformation via compaction and pressure solution, which may also include hysteresis in the constitutive behaviours. This thesis is concerned with models which can describe the evolution of porosity and pore pressure in sedimentary basins. We begin by analysing the simplest case of poroelastic compaction which in a 1-D case results in a nonlinear diffusion equation, controlled principally by a dimensionless parameter lambda, which is the ratio of the hydraulic conductivity to the sedimentation rate. We provide analytic and numerical results for both large and small lambda in Chapter 3 and Chapter 4. We then put a more realistic rheological relation with hysteresis into the model and investigate its effects during loading and unloading in Chapter 5. A discontinuous porosity profile may occur if the unloaded system is reloaded. We pursue the model further by considering diagenesis as a dehydration model in Chapter 6, then we extend it to a more realistic dissolution-precipitation reaction-transport model in Chapter 7 by including most of the known physics and chemistry derived from experimental studies. We eventually derive a viscous compaction model for pressure solution in sedimentary basins in Chapter 8, and show how the model suggests radically different behaviours in the distinct limits of slow and fast compaction. When lambda << 1, compaction is limited to a basal boundary layer. When lambda >> 1, compaction occurs throughout the basin, and the basic equilibrium solution near the surface is a near parabolic profile of porosity. But it is only valid to a finite depth where the permeability has decreased sufficiently, and a transition occurs, marking a switch from a normally pressured environment to one with high pore pressures.

Sandstone and shale samples were selected within the systems tracts for laboratory analyses. The sidewall and core samples were subjected to petrographic thin section analysis, mineralogical analyses which include x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and stable carbon and oxygen isotopes geochemistry to determine the diagenetic alteration at deposition and post deposition in the basin. The shale samples were subjected to Rock-Eval pyrolysis and accelerated solvent extraction (ASE) prior to gas chromatographic (GC) and gas chromatographic-mass spectrometric (GC-MS) analyses of the rock extracts, in order to determine the provenance, type and thermal maturity of organic matter present in sediments of the Orange Basin. The results revealed a complex diagenetic history of sandstones in this basin, which includes compaction, cementation/micritization, dissolution, silicification/overgrowth of quartz, and fracturing. The Eh-pH shows that the cements in the area of the basin under investigation were precipitated under weak acidic and slightly alkaline conditions. The &delta
18O isotope values range from -1.648 to 10.054 %, -1.574 to 13.134 %, and -2.644 to 16.180 % in the LST, TST, and HST, respectively. While &delta
13C isotope values range from -25.667 to -12.44 %, -27.862 to -6.954% and -27.407 to -19.935 % in the LST, TST, and HST, respectively. The plot of &delta
18O versus &delta
13C shows that the sediments were deposited in shallow marine temperate conditions.

Marine sediments are a key component of the global carbon cycle and climate system. They host one of the largest carbon reservoirs on Earth, provide the only long-term sink for atmospheric CO2, recycle nutrients and represent the most important climate archive. Early diagenetic pro- cesses in marine sediments are thus central to our understanding of past, present and future biogeochemical cycling and climate. Because all early diagenetic processes can be directly or indirectly linked back to the degradation of organic matter (OM), advancing this understand- ing requires disentangling the different factors that control the fate of OM (sedimentation, degradation and burial) on different spatial and temporal scales. In general, the heterotrophic degradation of OM in marine sediments is controlled by the quantity and, in particular, by the ap- parent reactivity of OM that settles onto marine sediments. While the potential ((micro)biological, chemical and physical) controls on OM reactivity are increasingly well understood, their relative significance remains difficult to quantify. Traditionally, integrated data-model approaches are used to quantify apparent OM reactivity (i.e. OM degradation rate constants) at well-studied drill-sites. These approaches rely on Reaction-Transport Models (RTMs) that typically account for transport (advection, molecular diffusion, bioturbation, and bioirrigation) and reaction (pro- duction, consumption, equilibrium) processes, but vary in complexity. Apparent OM reactivity (i.e. the OM degradation rate constant) is generally considered as a free parameter that is used to fit observed depth-profiles, reaction rates or benthic-pelagic exchange fluxes. Currently, no quantitative framework exists to predict apparent OM reactivity in areas where comprehensive benthic data sets are not available.To evaluate the impact of this knowledge gap, the sensitivity of benthic biogeochemical reaction rates, as well as benthic-pelagic exchange fluxes to variations in apparent OM reactivity (i.e. reactive continuum model parameters a and ν) is explored by means of a complex, numerical diagenetic model for shelf, slope and deep sea depositional environments. Model results show that apparent OM reactivity exerts a dominant control on the magnitude of biogeochemical reaction rates and benthic-pelagic exchange fluxes across different environments. The lack of a general framework to quantify OM reactivity thus complicates the parametrization of regional and global scale diagenetic models and, thus, compromises our ability to quantify global benthic-pelagic coupling in general and OM degradation dynamics in particular.To make a first step towards an improved systematic and quantitative knowledge of OM reac- tivity, apparent OM reactivity (i.e. reactive continuum model parameters a and ν) is quantified by inverse modelling of organic carbon, sulfate (and methane) sediment profiles, as well as the location of the sulfate-methane transition zone using a complex, numerical diagenetic model for 14 individual sites across different depositional environments. Model results highlight again the dominant control of OM reactivity on biogeochemical reaction rates and benthic exchange fluxes. In addition, results show that, inversely determined ν-values fall within a narrow range (0.1 < ν < 0.2). In contrast, determined a-values span ten orders of magnitude (1 · 10−3 < a < 1·107) and are, thus, the main driver of the global variability in OM reactivity. Exploring these trends in their environmental context reveals that apparent OM reactivity is determined by a dynamic set of environmental controls rather than traditionally proposed single environmental controls (e.g. water depth, sedimentation rate, OM fluxes). However, the high computational demand associated with such a multi-species inverse model approach, as well as the limited availability of comprehensive pore water data, limits the number of apparent OM reactivity estimates. Therefore, while providing important primers for a quantification of OM reactivity on the global scale, inverse model results fall short of providing a predictive framework.To overcome the computational limitations and expand the inverse modelling of apparent OM reactivity to the global scale, the analytical model OMEN-SED is extended by integrating a nG- approximation of the reactive continuum model that is fully consistent with the general structure of OMEN-SED. The new version OMEN-SED-RCM thus provides the computational efficiency required for the inverse determination of apparent OM reactivity (i.e. reactive continuum model parameters a and ν) on the global scale. The abilities of the new model OMEN-SED-RCM in capturing observed local, as well as global patterns of diagenetic dynamics are rigorously tested by model-data, as well as model-model comparison.OMEN-SED-RCM is then used to inversely determine apparent OM reactivity by inverse modelling of 394 individual dissolved oxygen utilisation (DOU) rate measurements. DOU is commonly used as a proxy for OM reactivity, it is more widely available than comprehensive porewater data sets and global/regional benthic maps of dissolved oxygen utilisation rates (DOU) have been derived based on the growing DOU data set. Sensitivity test show that, while inverse modelling of DOU rates fails to provide a robust estimate of RCM parameter ν, it is a good indicator for RCM parameter a. Based on previous findings, parameter ν was thus assumed to be globally constant. Inversely determined a-values vary over order of magnitudes from a = 0.6 years in the South Polar region to a = 5.6 · 106 in the oligotrophic, central South Pacific. Despite a high intra- as well as interregional heterogeneity in apparent benthic OM reactivity, a number of clear regional patterns that broadly agree with previous observations emerge. High apparent OM reactivities are generally observed in regions dominated by marine OM sources and characterized by efficient sinking of OM and a limited degradation during sinking. In contrast, the lowest apparent OM reactivities are observed for regions characterized by low marine primary production rates, in combination with a great distance to the continental shelf and slope, as well as deep water columns. Yet, results also highlight the importance of lateral transport processes for apparent OM reactivity. In particular, deep sea sediments in the vicinity of dynamic continental margin environments or under the influence of strong ocean currents can receive comparably reactive OM inputs from more productive environments and, thus, reveal OM reactivities that are higher than traditionally expected. Finally, based on the observed strong link between apparent OM reactivity (i.e. RCM parameters a) and DOU rate, a transfer function that predicts the order of magnitude of RCM parameter a as a function of DOU is used to derive, to our knowledge, the first global map of apparent OM reactivity.Finally, we use the new global map of apparent OM reactivity to quantify biogeochemical dynamics and benthic-pelagic coupling across 22 benthic provinces that cover the entire global ocean. To this end, the numerical diagenetic model BRNS model is set-up for each province and forced with regionally averaged boundary conditions derived from global data sets, as well as apparent OM reactivities informed by the global OM reactivity map. The 22 regional model set-ups were then used to quantify biogeochemical process rates, as well as benthic carbon and nutrient fluxes in each province and on the global scale. Model results of regional and global fluxes and rates fall well within the range of observed values and also agree with general globally observed patterns. Results also highlight the role of the deeper ocean for benthic-pelagic cycling and indicate towards a large regional variability in benthic cycling at great depth. This is a first step towards a more refined global estimate of benthic biogeochemical cycling that accounts for the global heterogeneity of the seafloor environment. This aspect is critical to improve our understanding of benthic feedbacks on benthic-pelagic coupling and on the carbon-climate system, which can then be incorporated in benthic processes in Earth System Models.
Les sédiments marins sont un élément clé du cycle mondial du carbone et du système climatique. Ils abritent l’un des plus grands réservoirs de carbone sur Terre, fournissent le seul puits à long terme pour le CO2 atmosphérique, recyclent les nutriments et constituent les archives climatiques les plus importantes. Les processus de la diagénèse précoce dans les sédiments marins sont donc au cœur de notre compréhension des cycles et du climat biogéochimiques passés, présents et futurs. Étant donné que tous les processus diagénétiques précoces peuvent être directement ou indirectement liés à la dégradation de la matière organique (MO), faire progresser cette compréhension nécessite de démêler les différents facteurs qui contrôlent le devenir de la MO (sédimentation, dégradation et enfouissement) à différentes échelles spatiales et temporelles. En général, la dégradation hétérotrophique de la MO dans les sédiments marins est contrôlée par la quantité et, en particulier, la réactivité apparente de la MO qui se dépose sur les sédiments marins. Bien que les contrôles potentiels ((micro) biologiques, chimiques et physiques) de la réactivité de la MO soient de mieux en mieux compris, leur importance relative reste difficile à quantifier. Traditionnellement, des approches de modèle de données intégrées sont utilisées pour quantifier la réactivité apparente de la MO (c’est-à-dire les constantes de vitesse de dégradation de la MO) sur des sites de forage bien étudiés. Ces approches reposent sur des modèles de réaction-transport (RTM) qui tiennent généralement compte des processus de transport (advection, diffusion moléculaire, bioturbation et bio-irrigation) et de réaction (production, consommation, équilibre), mais leur complexité varie. La réactivité apparente de la MO est généralement considérée comme un paramètre libre qui est utilisé pour ajuster les profils de profondeur, les taux de réaction ou les flux d’échange benthique-pélagique observés. À l’heure actuelle, aucun cadre quantitatif n’existe pour prédire la réactivité apparente de la MO dans les zones où aucun ensemble complet de données benthiques n’est disponible.Pour évaluer l’impact de ce manque de connaissance, nous avons exploré la sensibilité des taux de réaction biogéochimiques benthiques, ainsi que des flux d’échange benthique-pélagique aux variations de la réactivité apparente de la MO (c.-à-d. les paramètres du modèle de con- tinuum réactif a et ν) au moyen d’un modèle diagénétique numérique complexe appliqué aux zones de dépôts sur les plateaux, les talus et en haute mer. Les résultats du modèle montrent que la réactivité apparente de la MO exerce un contrôle dominant sur l’ampleur des taux de réaction biogéochimiques et des flux d’échange benthique-pélagique dans différents environ- nements. L’absence d’un cadre général pour quantifier la réactivité de la MO complique donc la paramétrisation des modèles diagénétiques à l’échelle régionale et mondiale et, ainsi, compromet notre capacité à quantifier le couplage benthique-pélagique global en général et la dynamique de dégradation de la MO en particulier.Pour tendre à meilleure connaissance systématique et quantitative de la réactivité de la MO, la réactivité apparente OM (c.-à-d. les paramètres du modèle de continuum réactif a et ν) est quantifiée par modélisation inverse des profils de sédiments organiques de carbone, de sulfate (et de méthane), ainsi que localisation de la zone de transition sulfate-méthane à l’aide d’un modèle diagénétique numérique complexe pour 14 sites individuels à travers différents environnements de dépôt. Les résultats du modèle mettent à nouveau en évidence le contrôle dominant de la réactivité de l’OM sur les taux de réaction biogéochimiques et les flux d’échanges benthiques. De plus, les résultats montrent que les valeurs déterminées inversement déterminées se situent dans une plage étroite (0,1 <ν<0,2). En revanche, les valeurs déterminées s’étendent sur dix ordres de grandeur (1 ·10−3 <ν< 1·107) et sont donc le principal moteur de la variabilité globale de la réactivité OM. L’exploration de ces tendances dans leur contexte environnemental révèle que la réactivité apparente de l’OM est déterminée par un ensemble dynamique de contrôles environnementaux plutôt que par des contrôles environnementaux uniques traditionnellement proposés (par exemple, la profondeur de l’eau, le taux de sédimentation, les flux OM). Cependant, la forte demande de calcul associée à une telle approche de modèle inverse multi-espèces, ainsi que la disponibilité limitée de données complètes sur l’eau interstitielle, limitent le nombre d’estimations apparentes de la réactivité OM. Par conséquent, tout en fournissant des amorces importantes pour une quantification de la réactivité de l’OM à l’échelle mondiale, les résultats du modèle inverse sont loin de fournir un cadre prédictif.Pour surmonter les limites de calcul et étendre la modélisation inverse de la réactivité apparente de l’OM à l’échelle mondiale, le modèle analytique OMEN-SED est étendu en intégrant une approximation nG du modèle de continuum réactif qui est pleinement cohérente avec la structure générale d’OMEN-SED. La nouvelle version OMEN-SED-RCM fournit ainsi l’efficacité de calcul requise pour la détermination inverse de la réactivité apparente de l’OM (c’est-à-dire les paramètres du modèle de continuum réactif a et ν) à l’échelle mondiale. Les capacités du nouveau modèle OMEN-SED-RCM à capturer les modèles locaux et globaux de dynamique diagénétique observés sont rigoureusement testés par les données du modèle, ainsi que la comparaison modèle- modèle.OMEN-SED-RCM est ensuite utilisé pour déterminer inversement la réactivité apparente de l’OM par modélisation inverse de 394 mesures individuelles du taux d’utilisation de l’oxygène dissous (DOU). Le DOU est couramment utilisé comme indicateur de la réactivité de l’OM, il est plus largement disponible que les ensembles de données exhaustifs sur l’eau interstitielle et les cartes benthiques mondiales/régionales des taux d’utilisation de l’oxygène dissous (DOU) ont été dérivées sur la base de l’ensemble de données DOU croissant. Le test de sensibilité montre que, bien que la modélisation inverse des taux de DOU ne fournisse pas une estimation robuste du paramètre RCM ν, c’est un bon indicateur pour le paramètre RCM a. Sur la base des résultats précédents, le paramètre ν a donc été supposé être globalement constant. Les valeurs a déterminées à l’inverse varient selon l’ordre de grandeur, de a = 0,6 an dans la région polaire sud à a = 5, 6 · 106 dans le Pacifique sud oligotrophique central. Malgré une forte hétérogénéité intra et interrégionale dans la réactivité apparente de la MO benthique, un certain nombre de schémas régionaux clairs qui correspondent largement aux observations précédentes émergent. Des réactivités apparentes élevées de l’OM sont généralement observées dans les régions dominées par des sources marines de MO et caractérisées par un naufrage efficace de l’OM et une dégradation limitée pendant le naufrage. En revanche, les réactivités MO apparentes les plus faibles sont observées pour les régions caractérisées par de faibles taux de production primaire marine, en combinaison avec une grande distance du plateau continental et de la pente, ainsi que des colonnes d’eau profonde. Pourtant, les résultats mettent également en évidence l’importance des processus de transport latéral pour la réactivité apparente de l’OM.En particulier, les sédiments des mers profondes au voisinage d’environnements de marge continentale dynamiques ou sous l’influence de forts courants océaniques peuvent recevoir des apports OM de réactivité comparable provenant d’environnements plus productifs et, ainsi, révéler des réactivités OM plus élevées que ce qui était traditionnellement prévu. Enfin, sur la base du lien fort observé entre la réactivité apparente de l’OM (c’est-à-dire le paramètre RCM a) et le taux DOU, une fonction de transfert qui prédit l’ordre de grandeur du paramètre RCM a en fonction de DOU est utilisée pour dériver, pour nos connaissances, la première carte mondiale de la réactivité apparente de l’OM. Les résultats du modèle des flux et des taux régionaux et mondiaux se situent bien dans la gamme des valeurs observées et également d’accord avec les tendances générales observées au niveau mondial. Les résultats mettent également en évidence le rôle de l’océan profond pour le cycle benthique-pélagique et indiquent une grande variabilité régionale du cycle benthique à grande profondeur. Il s’agit d’une première étape vers une estimation mondiale plus précise du cycle biogéochimique benthique qui tient compte de l’hétérogénéité mondiale du milieu marin. Cet aspect est essentiel pour améliorer notre compréhension des rétroactions benthiques sur le couplage benthique-pélagique et sur le système carbone-climat, qui peuvent ensuite être incorporées aux processus benthiques dans les modèles du système terrestre.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Thesis (MSc)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: This study presents an outcrop characterisation and modelling of the excellently exposed Permian Kookfontein Formation of the Ecca Group in the Tanqua-Karoo sub-Basin. The sedimentary modelling (i.e. facies architecture and geometry) and petrophysical characterisation followed a hierarchical and deterministic approach. Quantitative outcrop data were based on the thirteen sedimentary cycles that characterise this stratigraphic succession at the Pienaarsfontein se Berg locality; and these data were analysed using a combination of detailed sedimentary log, gamma ray log and photopanel analysis, as well as petrographic thin-section and grain size-based petrophysical analysis. Based on texture and sedimentary structures, twelve depofacies are recognised which are broadly grouped into four lithofacies associations i.e. sandstone facies, heterolithic facies, mudstone facies and soft-sediment deformation facies; these depofacies and lithofacies form the basic building blocks for the flooding surface-bounded facies succession (i.e. cycle). Also, based on sediment stacking and cycle thickness patterns as well as relative position to the shelf break, the succession is sub-divided into: (1) the lower Kookfontein member (i.e. cycles 1 to 5) exhibiting overall upward thickening and coarsening succession with progradational stacking pattern; representing deposition of mid-slope to top-slope/shelf-margin succession, and (2) the upper Kookfontein member (i.e. cycles 6 to 13) exhibiting overall upward thickening and coarsening succession with aggradational stacking pattern; representing deposition of top-slope/shelf-margin to outer shelf succession. Lateral juxtaposition of observed vertical facies variations across each cycle in an inferably basinwards direction exhibits upward change in features, i.e. decrease in gravity effects, increase in waves and decrease in slope gradient of subsequent cycles. This systematic upward transition in features, grading vertically from distal to proximal, with an overall upward thickening and coarsening progradational to aggradational stacking pattern indicates a normal regressive prograding delta. However, in detail, cycles 1-3 show some anomalies from a purely thickening and coarsening upward succession. Deposition of each cycle is believed to result from: (1) primary deposition by periodic and probably sporadic mouthbar events governed by stream flow dynamics, and (2) secondary remobilisation of sediments under gravity. The facies distribution, architecture and geometry which governs the sedimentary heterogeneity within the deltaic succession is therefore mainly a consequence of the series of mouthbar flooding events governed by sediment supply and base-level changes. These series of flooding events resulted in the delineation of the studied stratigraphic interval into two main parasequence sets, i.e. transgressive sequence set and the overlying regressive sequence set. This delineation was aided through the identification of a maximum flooding surface (i.e. maximum landwards shift in facies) above Cycle 3 in the field. The architecture and geometry of the ensuing deposystem is interpreted to have been a river-dominated, gravitationally reworked and waveinfluenced shelf edge Gilbert-type delta. Widespread distribution of soft-sediment deformation structures, their growth-style and morphology within the studied succession are empirically related to progradation of Gilbert-type mouthbars over the shelf break as well as the slope gradients of the Kookfontein deltaic clinoformal geometry. Analysis of hypothetical facies stacking and geometrical models suggests that the Kookfontein sedimentary cyclicity might not be accommodation-driven but rather sediment supply-driven. The workflow employed for petrophysical evaluation reveals that the distribution of reservoir properties within the Kookfontein deltaic sandbody geometries is strongly influenced both by depositional processes and by diagenetic factors, the latter being more important with increased burial depth. The reservoir quality of the studied sandstones decreases from proximal mouthbar sands, intermediate delta front to distal delta front facies. The major diagenetic factors influencing the reservoir quality of the studied sandstones are mechanical compaction, chemical compaction (pressure solution) and authigenic pore-filling cements (quartz cement, feldspar alteration and replacement, calcite cement, chlorite and illite). Mechanical compaction was a significant porosity reducing agent while cementation by authigenic quartz and clay minerals (i.e. illite and chlorite) might play a major role in permeability distribution. The porosity-permeability relationship trends obtained for the studied sandstones show that there is a linear relationship between porosity and permeability. The relative timing of diagenetic events as well as the percentages of porosity reduction by compaction and cementation indicates that compaction is much more responsible for porosity reduction than cementation. The described internal heterogeneity in this work is below the resolution (i.e. mm-scale) of most conventional well-logs, and therefore could supplement well-log data especially where there is no borehole image and core data. The combination of ‗descriptive‘ facies model and schematic geological model for this specific delta, and petrophysical characterisation make the results of this study applicable to any other similar ancient deposystem and particularly subsurface reservoir analogue.
AFRIKAANSE OPSOMMING: Hierdie studie bied ‘n dagsoomkarakterisering en -modellering van die duidelik blootgelegde Permiese Kookfontein-formasie van die Ecca-groep in die Tankwa-Karoo-subkom. Wat die sedimentêre modellering (d.w.s. fasiesargitektuur en -geometrie) en petrofisiese karakterisering betref is ‘n hiërargiese en deterministiese benadering gevolg. Kwantitatiewe dagsoomdata is gebaseer op dertien sedimentêre siklusse wat hierdie stratigrafiese opeenvolging in die Pienaarsfontein se Berg-lokaliteit kenmerk; en die data is geanaliseer met behulp van ‘n kombinasie van gedetailleerde sedimentêre seksie, gammastraal-profiel en fotopaneelanalises, asook petrografiese slypplaatjie- en korrelgrootte-gebaseerde petrofisiese analises. Op grond van tekstuur en sedimentêre strukture is twaalf afsettingsfasies onderskei wat rofweg in vier assosiasies van litofasies gegroepeer kan word: sandsteenfasies, heterolitiese fasies, moddersteenfasies en sagtesediment-deformasiefasies. Hierdie afsettingsfasies en litofasies vorm die basiese boustene vir die fasiesopeenvolging (d.w.s. siklus) wat oorstromingsoppervlakgebonde is. Verder word die opeenvolging aan die hand van sedimentstapeling en skilusdiktepatrone, asook relatiewe posisie tot die rakbreuk, in die volgende onderverdeel: (1) die benede-Kookfontein-deel (d.w.s. siklus 1 tot 5), wat in die geheel ‘n opwaartse verdikkings- en vergrowwingsopeenvolging met ‘n progradasiestapelpatroon vertoon en die afsetting van middelhelling-tot-boonstehelling- of rakrand-opeenvolging verteenwoordig, en (2) die benede-Kookfontein-deel (d.w.s. siklus 6 tot 13) wat in die geheel ‘n opwaartse verdikkings- en vergrowwingsopeenvolging met ‘n aggradasiestapelpatroon vertoon en die afsetting van boonste helling- of rakrand-tot-buiterakopeenvolging verteenwoordig. Die laterale jukstaposisie van waargenome vertikale fasiesvariasies oor elke siklus heen, in ‘n afleibare komwaartse rigting, vertoon opwaartse verandering wat kenmerke betref, naamlik afname in gravitasiegevolge, toename in golwe en afname in die hellinggradiënt van daaropvolgende siklusse. Hierdie stelselmatige opwaartse oorgang van kenmerke, wat vertikaal van distaal tot proksimaal gradiënteer en in die geheel opwaartse verdikking en vergrowwing in ‘n progradasie-tot-aggradasie-stapelpatroon vertoon, dui op ‘n normale regressiewe progradasiedelta. Van naby beskou, vertoon siklus 1-3 egter bepaalde afwykings van ‘n suiwer opwaartse verdikkings- en vergrowwingsopeenvolging. Die afsettings van elke siklus is vermoedelik die gevolg van: (1) primêre afsetting deur periodieke en waarskynlik sporadiese mondversperringsgebeure wat deur stroomvloeidinamika beheer word, en (2) sekondêre hermobilisering van sedimente deur gravitasie. Die fasiesverspreiding, -argitektuur en -geometrie wat die sedimentêre heterogeniteit in die deltaïese opeenvolging beheer, is dus hoofsaaklik ‘n gevolg van die reeks oorstromingsgebeure by die mondversperring, wat deur sedimentvoorsiening en basisvlakveranderings beheer word. Hierdie reeks oorstromingsgebeure het gelei tot die delineasie van die bestudeerde stratigrafiese interval volgens twee hoofparasekwensie stelle, naamlik die transgressiewe opeenvolgings- en die oordekkende, regressiewe opeenvolgingsgroep. Dié delineasie word ondersteun deur die feit dat ‘n maksimum oorstromingsoppervlak (d.w.s. maksimum landwaartse verskuiwing in fasies) bo siklus 3 in die veld uitgeken is. Die argitektuur en geometrie van die daaropvolgende afsettingstelsel word geïnterpreteer as behorende tot ‘n Gilbert-rakranddelta wat deur ‘n rivier gedomineer, deur gravitasie herbewerk en deur golfwerking beïnvloed is. Die wye verspreiding van sagtesediment-deformasiestrukture, en die groeiwyse en morfologie daarvan binne die bestudeerde opeenvolging, is empiries verwant aan die progradasie van Gilbertmondversperrings oor die rakbreuk heen, asook aan die hellinggradiënte van die Kookfontein-deltaïese, klinoformele geometrie. Die analise van hipotetiese fasiesstapeling en geometriese modelle dui daarop dat die Kookfontein-sedimentêre siklisiteit dalk nie deur akkommodasieruimte gedryf word nie, maar deur sedimentvoorsiening. Die werkvloei wat vir petrofisiese evaluering gebruik is dui daarop dat die verspreiding van reservoir-eienskappe in die Kookfontein- deltaïese sandliggaam geometries sterk beïnvloed word deur afsettingsprosesse en diagenetiese faktore. Die diagenetiese faktore word belangriker op groter begrawing diepte. Die reservoir-aard van die bestudeerde sandgesteentes neem algaande af van proksimale mondversperring-sandsoorte tot intermediêre deltafront tot distale deltafrontfasies. Die hoof-diagenetiese faktore wat die reservoir-kenmerke van die bestudeerde sandsteensoorte beïnvloed is meganiese verdigting, chemiese verdigting (oplossingsdruk) en outigeniese porievullingsement (kwartssement, veldspaatomsetting en -vervanging, kalsietsement, chloriet en illiet). Meganiese verdigting is ‘n beduidende poreusheidreduseermiddel, terwyl sementering deur outigeniese kwarts- en kleiminerale (d.w.s. illiet en chloriet) moontlik ‘n belangrike rol by permeabiliteitsverspreiding kan speel. Die poreusheid-permeabiliteit-verhoudingstendense wat bekom is vir die bestudeerde sandsteensoorte dui daarop dat daar ‘n lineêre verhouding tussen poreusheid en permeabiliteit bestaan. Die relatiewe tydberekening van diagenetiese gebeure, asook die persentasie poreusheidvermindering deur verdigting en sementering, dui daarop dat verdigting baie meer as sementering tot poreusheidvermindering bydra. Die interne heterogeniteit wat in hierdie werk beskryf word, is onder die resolusie (d.w.s. mm-skaal) van die meeste konvensionele boorgatopnames, en kan dus boorgatopnamedata aanvul, veral waar daar geen boorgatafbeelding en kerndata bestaan nie. Die kombinasie van die 'deskriptiewe‘ fasiesmodel en skematiese geologiese model vir hierdie spesifieke delta, asook petrofisiese karakterisering, beteken dat die resultate van hierdie studie op enige ander soortgelyke antieke afsettingstelsels toegepas kan word, maar veral op suboppervlakreservoir-analoogstelsels.

Le phosphore (P) est un nutriment essentiel à la vie, suite à son rôle clé dans la régulation de la production primaire à l'interface fleuve-mer, et au lien étroit de son cycle avec les cycles du carbone et de l'azote. L'enfouissement du phosphore dans les sédiments de l'interface fleuve-mer se fait en association avec la matière organique et des minéraux. Cet enfouissement est la voie d'élimination du P à long terme. Cependant, le rôle des sédiments dans le recyclage du phosphore inorganique dissous (DIP) est mal quantifié dans les estuaires eutrophes. Cette thèse a pour objectif d'affiner la compréhension sur la réponse des sédiments au recyclage du DIP dans les sédiments des estuaires de l'Elorn et de l'Aulne (France). De plus, nous visons à la mettre en contraste avec les sédiments deltaïques (delta du Rhône) dans la mer Méditerranéenne oligotrophe. Deuxièmement, ces écosystèmes sont dynamiques, caractérisés par des charges intenses de matière organique et de nutriments (N, P), entraînant leur enfouissement sous l'interface eau-sédiment (IES) et leur minéralisation. Par conséquent, les processus biogéochimiques peuvent modifier en grande partie la chimie de la couche supérieure de ces sédiments. Nous visons à quantifier les processus diagénétiques, contrôlant le devenir de la matière organique, la transformation du phosphore et les flux de DIP vers l'eau de fond. Pour cela, nous avons utilisé des données de terrain couplées avec un modèle existant (OMEXDIA), étendu au cycle benthique du phosphore, pour évaluer aussi la capacité des sédiments à servir de puits ou de sources de P. Le modèle OMEXDIA-P a été adapté aux données d'eau interstitielle (oxygène, nitrate, ammonium, unités de demande en oxygène (Mn2+, Fe2+ et H2S; ODU) et de DIP) et de solides (P organique, P lié au fer et P lié au calcium) de quatre saisons en 2009 dans les stations amont, milieu et aval des deux estuaires. Ensuite, le modèle a été ajusté aux mêmes variables d'état, en plus des sulfates et carbone inorganique dissous (DIC) pour neuf stations dans l'exutoire du Rhône, son prodelta et son plateau continental adjacent, et échantillonnées en Mai 2018. Les deux applications du modèle ont montré une bonne concordance avec la distribution verticale des phases dissoutes et solides dans toutes les stations et les saisons. L'utilisation combinée de ces bases de données avec ce modèle a révélé que les flux de C organique à l’IES des estuaires de l'Elorn et de l'Aulne (23 à 98 mmol m-2 j-1) et dans le prodelta du Rhône (10 à 160 mmol m-2 j-1) étaient intenses, en particulier à l'exutoire du fleuve. Ainsi, la minéralisation en P organique a représenté la principale source de DIP produit dans les deux estuaires (77%) et dans le prodelta du Rhône (>90%). La contribution des voies de minéralisation a mis en évidence une augmentation de la contribution de la minéralisation anoxique due au gradient salin de l'amont vers l'aval des estuaires. Alors que ces voies ont montré une diminution de l'écoulement du Rhône vers le plateau continental, en fonction de la diminution des apports de matière organique avec la distance. Le calcul du bilan du P par le modèle a indiqué que le P lié au fer joue un rôle clé dans le cycle du P, en retenant le DIP dans les sédiments et en favorisant la précipitation de P lié au Ca. De plus, le P lié au fer représente une source supplémentaire de DIP dans les sédiments des deux estuaires. La plus grande proportion du DIP produit a été recyclée dans l'eau de fond de ces sédiments estuariens (85%) et deltaïques (72%), tandis que l'enfouissement sous forme de P lié au Ca était une fraction mineure. Dans l'ensemble, les résultats du modèle présentés ont démontré que ces sédiments estuariens et deltaïques jouaient un rôle essentiel dans le cycle benthique du P et constituaient des sources de DIP dans la colonne d'eau. De plus, les apports de DIP produits dans les sédiments de l'Elorn et de l'Aulne étaient plus élevés que les apports externes
Phosphorus (P) is an essential nutrient for life, playing a key role in the primary production regulation at the river-sea interface, and closely to carbon and nitrogen global cycles. The burial of phosphorus in sediments of the river-sea interface occurs in association with organic matter and mineral particles. This burial represents the long-term removal pathway for the phosphorus. However, sediments role in dissolved inorganic phosphorus (DIP) recycling, is poorly quantified in eutrophic estuaries. Therefore, the main purpose of this thesis is to refine our understanding about sediments response to DIP recycling in Elorn and Aulne estuarine sediments (Brittany, France). In addition, we aim to contrast it with deltaic sediments (Rhône River delta) in the oligotrophic Mediterranean Sea. Secondly, all these ecosystems are highly dynamic, characterized by intense loads of organic matter and nutrients (N, P), leading to their intense fall on the sea floor, burial below the sediment-water interface (SWI) and mineralization. Therefore, involved biogeochemical processes can change largely the chemistry of upper layer of these sediments. We aim to clarify and to quantify the depth sequences of diagenetic processes, controlling the fate of sedimentary organic matter, transformation of phosphorus and induced DIP fluxes to the overlying water. To this end, we used a coupled field data with an existing model (OMEXDIA), extended with phosphorus (P) benthic cycle, to study P dynamics and to evaluate the sediments capacity as sinks or sources of P in the eutrophic Elorn and Aulne estuaries and the Rhône River prodelta. First of all, the OMEXDIA-P model was fitted to the porewater (oxygen, nitrate, ammonium, Oxygen Demand Units (Mn2+, Fe2+ and H2S, reduced during the anoxic mineralization; ODU) and DIP) and solid (organic P, Fe-bound P and Ca-bound P) data from four seasons (February, May, July and October 2009) in upstream, midstream and downstream stations of Elorn and Aulne estuaries. Secondly, the model was fitted to the same state variables, in addition to sulfate and dissolved inorganic carbon (DIC) for nine stations located in Rhône River outlet, prodelta and its adjacent continental shelf and sampled in May 2018. Both model’s applications showed a good agreement with the vertical distribution of porewater and solid phases in all stations and seasons. The combined use of these two datasets with the present model revealed that organic C fluxes deposited in the SWI of Elorn and Aulne estuaries (23 to 98 mmol m-2 d-1) and Rhône River prodelta (10 to 160 mmol m-2 d-1) were intense, especially in the River outlet. Therefore, the organic P mineralization represented the main source of internally produced DIP in both estuaries (77% of total DIP production) and in Rhône River prodelta (>90%). The contribution of mineralization pathways highlighted an increase of anoxic mineralization contribution due to saline gradient from upstream to downstream estuaries. While this mineralization pathways showed a decrease from Rhône River outlet to the continental shelf, as a function of the decrease of organic matter inputs with distance. The model’s calculation of sedimentary P budget indicated also that Fe-bound P played a key role in the P cycle, by retaining DIP in sediments from diffusion to overlying water and promoting the Ca-bound P precipitation. Moreover, Fe-bound P represented an additional source of DIP in sediments, especially in Elorn and Aulne estuaries. The largest proportion of released DIP was recycled to overlying water in these estuarine (85%) and deltaic (72%) sediments, while the burial as an authigenic Ca-bound P was a minor fraction. Overall, the model’s results presented here also demonstrated that these estuarine and deltaic sediments played a key role in the benthic P cycle and acted as sources of DIP to the water column. Moreover, the internally produced DIP inputs in Elorn and Aulne sediments was higher the external inputs

Develops a depositional and diagnenetic model for effective oil exploration within the Tandalogoo Formation on the south-east-flank of the Fitzroy Trough.
Thesis (M.Sc.) -- University of Adelaide, Dept. of Geology and Geophysics, 1992

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 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.¶ ...

Middle Triassic Doig reservoirs in the Fireweed, Buick Creek, Cache Creek and West Stoddart fields (94-A-13 to Twp.86, Rge.18) of northeastern British Columbia consist of deltaic and shoreline sands encased in shelf and offshore mudstones and siltstones. The reservoirs comprise a series of northwest and northeast trending elongate sand bodies that lie along a south-southeast depositional trend analogous to the position of the original Doig shoreline. Sediments of the Doig Formation are divisible into two facies associations and ten lithofacies representing deposition in shelf to offshore, and deltaic and inter-deltaic environments. Hydrocarbon producing intervals consist of clean, very fine to fine grained, sub-lithic to quartz arenites, inter-bedded sandstones and bioclastic detritus, and disseminated bioclasts. Effective porosity is primarily inter-granular in the sandstone facies with significant moldic and intra-granular porosity developed in the coquina facies at the West Stoddart and Cache Creek fields. Average porosities range from 6.5 - 9.5% for sandstone lithofacies and 4.9 - 8.6% for coquina lithofacies. Pore occluding cements are mainly calcite in the northwest part of the reservoir trend to dolomite and anhydrite in the southeast. The sedimentology and facies architecture of recent discoveries at Cache Creek and West Stoddart contrast with those identified in previous studies of Doig reservoirs at Buick Creek in northeastern British Columbia and Sinclair in west central Alberta. A three-dimensional facies model of the Doig Formation at the Cache Creek, West Stoddart and Fireweed fields depicts sandstone deposition in a deltaic environment as distributary channel fills and slumped delta front deposits. Data for the Buick Creek field confirms and extends the incised shoreface model to include fluvial or tidal channels deposited laterally continuous in the same systems tract as the shoreface sands. Sand bodies for all four fields were deposited contemporaneously as the Doig shoreline prograded over mudstones and siltstones of the Doig shelf. Seismic and well data reveal tectonic control on the position and orientation of the Doig reservoir trend. Synsedimentary growth faults control the location and geometry of thick sand bodies along the reservoir trend in the Fireweed area. Diagenetic controls along the reservoir trend include the precipitation of calcite in the near surface and shallow burial realm, fracturing of cemented horizons prior to extensive burial and dissolution of cements and framework grains in three distinct episodes. Multiple dissolution phases created moldic, vuggy and inter-granular secondary porosity. Reservoir quality and production from Doig Formation sand bodies in the Peace River area of Western Canada are significantly impacted by the preservation of inter-granular porosity and fracturing related to the distribution of early calcite cements. The early calcite cements were sourced from bioclastic debris and calcareous mudstones distributed during sand body deposition. The formation of open fractures during early diagenesis enhanced both the secondary pore network and the permeability of the West Stoddart and Cache Creek Doig pools. Sand bodies with only minor interstitial calcite have extensive porosity loss by compaction and precipitation of authigenic quartz. A fairway for Doig sand body exploration is constrained by production and core analysis data, structural and depositional models, thermal maturity data and diagenesis.

Coastal sediments continuously interact with the overlying water column, collecting and decomposing the incoming rain of organic detritus into inorganic nutrients, and consuming oxygen in the process. This thesis compares the ability of two qualitatively different sediment models, a two-layer and a multi-layer model, to quantify the biogeochemical transformations that occur when detritus is decomposed in the sediment. Using sediment flux observations from a mesocosm eutrophication experiment, selected model parameters and different parameterizations for depositional fluxes of organic matter have been optimized using an evolutionary algorithm and a gradient descent algorithm respectively. Simulations with constant depositional fluxes outperformed simulations where deposition was dependent on proxies of biomass concentration in the overlying water. With these constant inputs, both sediment models produced similar nutrient fluxes across the sediment-water interface, however the multi-layer model was better able to adapt to new environments.
Opimization of the Sediment Flux Model (DiToro 2001) and the multi-layer model described in Soetaert et al. (1996).

Węglanowe konkrecje żelaziste stanowią charakterystyczną cechę sekwencji skał ilasto-mułowych, należących do formacji częstochowskich iłów rudonośnych, na monoklinie śląsko-krakowskiej. Celem badań konkrecji była charakterystyka mineralogiczno-geochemiczna dla określenia genezy tych skupień mineralnych. Kompleksowa analiza wybranych parametrów geochemicznych (TOC, S/TOC, relacje TOC-Fe-S, Cu+Mo/Zn, Ni/Co, V/Cr, V/V+Ni, U/Th, Uaut) pozwoliła ustalić warunki paleośrodowiska depozycji oraz wczesnej diagenezy goszczących konkrecje skał. Zakres metod badawczych obejmował standardowe analizy mineralogiczne (mikroskopowe w świetle przechodzącym z uwzględnieniem katodoluminescencji i odbitym, a także analizy SEM EDS oraz XRD). Wykonano analizy geochemiczne (INAA, ICP-AES) skał ilasto-mułowych i występujących w nim węglanowych konkrecji żelazistych a także izotopowe: δ13Corg w iłach rudonośnych oraz δ13Cwęgl i δ18O w badanych konkrecjach. Węglanowe konkrecje żelaziste występują w poziomach w obrębie skał ilasto-mułowych. Konkrecje pochodzące z różnych horyzontów reprezentują ten sam typ genetyczny: w większości poziomów występują konkrecje syderytowe, w kilku stwierdzono konkrecje apatytowo-syderytowe. Preferencyjne występowanie poziomów z konkrecjami było związane z wolniejszą depozycją goszczących je iłów rudonośnych, intensywniejszym zbioturbowaniem tych skał oraz zwiększoną dostępnością reaktywnego żelaza w miejscach formowania się konkrecji. Przeprowadzone badania wskazują na wczesnodiagenetyczne pochodzenie badanych konkrecji w procesie mikrobialnej redukcji żelaza (FeR) w strefie subtlenowej. Model tzw. „rozproszonego” wzrostu (z ang. pervasive model growth) opisuje sposób formowania się węglanowych konkrecji żelazistych w iłach rudonośnych. Tworzenie się konkrecji syderytowych następowało na skutek jednoczesnej precypitacji syderytu w przestrzeniach porowych osadu ilasto-mułowego, w całej jego objętości, który stał się konkrecją. Konkrecje apatytowo-syderytowe wykazują podobny, aczkolwiek bardziej złożony model wzrostu. Powstawaniu tych konkrecji sprzyjało nagromadzenie fosforanowych i kalcytowych szkieletów skamieniałości w miejscach formowania się konkrecji. Tworzenie się konkrecji apatytowo-syderytowych zostało zainicjowane rozpuszczaniem elementów szkieletów (fosforanowych i kalcytowych), fosfatyzacją kalcytowych szkieletów i precypitacją apatytu a następnie syderytu w przestrzeniach porowych osadu. W końcowym etapie tworzenia się węglanowych konkrecji żelazistych nastąpiło ich spękanie w formie szczelin septariowych. Proces powstawania szczelin wraz z ich wypełnianiem (kalcytem, pirytem, sfalerytem lub barytem) przebiegał w kilku etapach w późnym stadium diagenezy.
Iron carbonate concretions are characteristic features of the Ore-bearing clays in the Kraków-Silesia Monocline. The aim of this study was to determine the origin of these concretions through the mineralogical and geochemical characteristics. Complex analysis of geochemical indices (TOC, S/TOC, relacje TOC-Fe-S, Cu+Mo/Zn, Ni/Co, V/Cr, V/V+Ni, U/Th, Uaut) allowed to determine paleoenvironmental conditions of deposition and early-diagenesis of the host sediment. The scope of research methods included standard mineralogical analysis (optical microscopic observations in transmitted light, also with cathodoluminescence and reflected light), X-ray diffraction and scanning electron microscopy with EDS). Geochemical analysis (INAA, ICP-AES) of silty-clay sediment and concretions; isotope study of δ13Corg of host sediment and δ13Cwęgl, δ18O of concretions were performed. Iron carbonate concretions occur in single levels. Concretions from different horizons represent the same genetic type: siderite concretions dominate and apatite-siderite concretions were also found in several levels. The preferential occurrence of the concretion horizons is associated with particular conditions of the deposition and early diagenesis of the host sediment, favored by a slower deposition rate, more intense bioturbation and greater availability of reactive iron in places of concretions formation. The results of this study suggest an early diagenetic origin of the concretions in the microbial iron reduction process in suboxic zone. Pervasive growth model describes the formation mode of the iron carbonate concretions in the ore-bearing clays. The siderite concretions were formed by simultaneous precipitation of siderite in pore spaces, in the whole volume of sediment, which became the concretion. The apatite-siderite concretions show similar, although more complex, model of concretion growth. The formation of these concretions was favored by the accumulation of phosphate and carbonate skeletal fossils in the formation place of concretions and was initiated by dissolution of these skeletons (phosphates and carbonates) and phosphatization of carbonate skelets, followed by apatite and subsequently siderite precipitation in pore spaces of host sediment. In the final stage, the iron carbonate concretion were cracked. The process of septarian fissures formation with their infillings (calcite, pyrite, sphalerite or barite) proceeded in several stages during later diagenesis.