The North Wales Platform, UK, represents a lower Carboniferous carbonate platform that developed during back-arc extension on the northern margin of the Wales-Brabant Massif. This succession was faulted and folded during the Late Carboniferous Variscan Orogeny and again during the Late Jurassic extension-Tertiary Alpine Orogeny, resulting in multiple reactivations of Caledonian structural trends (N-S, NE-SW and NW-SE) and basin inversion. The platform underwent deformation, several episodes of fluid-flow, and multiple phases of diagenetic overprinting. The products of fluid circulation in this area consist of the Mississippi Valley-type (MVT) mineralisation and dolomitisation, mostly affecting the carbonates of the lower Carboniferous (Dinantian) succession. This study presents a combined regional sedimentological, diagenetic and structural framework through multiscale, interdisciplinary techniques. Techniques include field observation, transmitted light and cathodoluminescence analysis, in-situ and bulk major and trace element analysis including rare earth elements, stable isotope (oxygen/carbon), and strontium isotope analysis. The North Wales Dinantian (Asbian-Brigantian) succession developed from a ramp to rimmed platform geometry and records a range of depositional and non depositional environments including platform margin, subtidal, peritidal and emergent. Early diagenesis comprises a series of marine and meteoric calcite cements. These are volumetrically the most important cements and occlude nearly all primary interparticle porosity on the North Wales Platform. Consequently, burial calcite cements and MVT mineralisation was precipitated within fractures and dissolution-enhanced secondary porosity. Dolomitisation on the North Wales Platform occur as pods along the current day coastline/palaeo platform margin and eight dolomite phases have been identified. These are present as matrix replacive and cement phases that are spatially and temporally related to deep seated structural lineaments. It is proposed that early diagenesis resulted from the establishment of meteoric aquifers, influenced by tectono-eustatic fluctuations. Subsequently, small volumes of fluid were released following compaction and during the waning stages of lower Carboniferous extension. The onset of the Variscan compression during the mid – Late Carboniferous led to the main stage of basin de-watering on to the platform via faults/fracture systems and the development of pockets of overpressuring. Circulating marine pore-waters provided the necessary magnesium required for dolomitisation within select fault/fracture systems. A second phase of tectonic deformation with associated copper mineralisation occurred during the Triassic-Jurassic extension and Alpine uplift. Fluids and metals for the copper mineralisation were derived from the adjacent siliciclastic Permo-Triassic and Jurassic East Irish Sea Basin succession. Compared to the adjacent and time equivalent Derbyshire and Askrigg Platforms, the North Wales Platform displays a more complex paragenesis as a result of differing burial histories and fluid sources. This study highlights the importance of understanding palaeo-fluid flow and diagenesis in platform carbonates and is directly relevant to hydrocarbon production, mining and resource containment in reservoirs.

Global carbon cycle dynamics and fluxes of CO2 between biosphere and atmosphere have been progressed through the use of Keeling Plots. Processes that control and effect the isotopic composition of soil-respired CO2, soil CO2, and equilibrated soil carbonate are specifically addressed in this study through the use of Keeling Plots. Replicate grassland soil profiles containing either C3 or C4 homogenized organic matter were constructed and maintained under controlled settings to encourage the production of soil-respired CO2 and the precipitation of pedogenic carbonate. Soil CO2 was sampled over five months and analyzed with IRMS. Keeling Plots illustrated source CO2 affected by mixing with atmospheric CO2 near the surface and equilibration with ¹³C-depleted CO2 at depth in the zone of likely carbonate precipitation. The δ13C Keeling Plot intercepts for the surface horizons (~ -24.7 per mil for C3 profiles and ~ -11.1 per mil for C4 profiles) follow the diffusion-production model when corrected with a constant 4.4 per mil diffusional fractionation, but the Keeling Plot intercepts for developing Bk horizons were curved towards depleted values (~ -36.2 per mil for C3 profiles and ~ -18.4 per mil for C4 profiles). This change in isotopic composition with depth deviates from the usual interpretations of Keeling Plots (steady-state, source to background diffusional mixing). δ13C Keeling Plot intercepts indicated evaporative enrichment in the surface horizons of C3 and C4 profiles). This study uses Keeling Plots as a measure of mixing to assess the efficacy of steady-state diffusion-production models of soil CO2 equilibration with soil carbonate.

Sea-level change during the Quaternary has had significant impacts on the geology of the Bahamas and the global carbon budget. During periods of low sea-level position conduit caves form in the Bahamas as a function of their respective water budgets. These conduit caves can then collapse and if this collapse reaches the surface a progradational collapse blue hole can be made. Upon subsequent sea-level rise these blue holes can become sediment inilled. Tidal pumping through these sedimentilled blue holes can result in the formation of whitings. Whitings are formed when the tidally pushed water warms and degasses CO2, driving the precipitation of CaCO3. Whitings are also formed on the shallow banks by resuspension by fish. As sea-level fluctuates the amount of land in the Bahamas and other carbonate regions increases or decreases with sea-level fall or rise, respectively. As the amount of land increases in the Bahamas and other carbonate regions, there is a decrease of carbonate rock exposure at high latitudes due to glaciation. The loss of high latitude carbonates is made up for in the gain of low latitude carbonates in terms of rates of inorganic carbon drawdown associated with karst processes. Additionally, this inorganic carbon draw down from karst processes represents approximately 16% of the unknown carbon sink as reported by the IPCC. This study is significant in that it contributes to the understanding of sea-level fluctuations in relation to the geology of the Bahamas and the global carbon budget.

Evidence of three glaciations in Paleoproterozoic successions of North America and at least one on three other continents, suggests that these glaciations were of global extent. In common with the Neoproterozoic record, carbonates cap the glacials. However, the relationship between biogeochemical cycling of carbon and ice ages has not been fully appreciated. This research involved the sedimentology and isotope stratigraphy of carbonates and shales in Paleoproterozoic glacially-influenced successions of Wyoming and South Africa. Carbonates of the Vagner Formation cap the middle of three diamictites in the Snowy Pass Supergroup, Medicine Bow Mountains, WY. The Duitschland Formation occurs between two glacial horizons in South Africa. Limestones retain negative d13C values for over 60 m in the Vagner Formation, and for over 100 m in the lower part of the Duitschland Formation. Isotope compositions of TOC from the lower part of the Duitschland Formation reveal pronounced enrichment resulting in significantly lower fractionation between organic and inorganic carbon. This is similar to enrichment noted in Neoproterozoic cap carbonates. Combined with strongly positive carbon isotope compositions in upper Duitschland carbonates, the data from the Vagner Formation underscores strongly positive-to-negative carbon isotope trends bracketing Paleoproterozoic glaciations. These trends mimic those noted in Neoproterozoic glacial successions and possibly indicate a recurrence of global glaciations. The Slaughterhouse and Nash Fork formations significantly postdate the glacial epoch. Both the lower part of the Nash Fork Formation, Medicine Bow Mountains and the Slaughterhouse Formation, Sierra Madre contains carbonates with 13C-enrichment >+6â ° and locally up to +28%, whereas carbonates higher in the Nash Fork Formation have d13C values between 0 and 2.5%. This dramatic change in the composition of the Paleoproterozoic ocean is constrained at ca. 2.1 Ga (Karhu, 1993). Carbonates in the Rawhide Canyon section of the Whalen Group in the Hartville Uplift (the easternmost exposure of the Wyoming Craton) display δ13C values up to +8.2% suggesting correlation with the Slaughterhouse and Nash Fork formations and their deposition on continuous carbonate platform along the margin of the Wyoming Craton. These data support an open-marine, and therefore a global origin for the ca. 2.2-2.1 Ga carbon isotope excursion. / Ph. D.

Microporous carbonates host a significant portion of the remaining oil-in-place in the giant carbonate reservoirs of the Middle East. Improved understanding of petrophysical and multi-phase flow properties at the pore-scale is essential for the development of better oil recovery processes. These properties strongly depend on the 3D geometry and connectivity of the pore space. In this study, we harnessed the unique capabilities of fluorescence confocal laser scanning microscopy (CLSM) to capture both macroporosity and microporosity, down to 0.1 µm, to provide a more representative 3D representation of pore space compared to traditional methods. The experimental procedure developed was specifically designed to enable highresolution confocal 3D imaging of the pore space of carbonate systems. The protocol aims to render carbonates more "transparent" to CLSM by imaging etched epoxy pore casts of the sample and minimizing CLSM signal scattering. The resulting highquality 3D images of the multi-scale pore space allow more reliable petrophysical interpretation and prediction of transport properties. Additionally, we present a robust pore imaging approach that correlates 2D images produced by scanning electron microscopy (SEM) with the 3D models produced by CLSM that cover a range of scales, from millimeters in 3D to micrometers in 2D. For the first time, multi-color fluorescence confocal imaging was employed to characterize the geometric attributes of a porous medium. We foresee that the protocol developed in this study could be used as a standard protocol for obtaining high-quality 3D images of epoxy pore casts using confocal microscopy, and could contribute to improved characterization of micritic carbonate reservoirs and oil recovery methods. We also demonstrate the advantages of multi-scale and multi-color confocal images in realizing more accurate evaluations of petrophysical properties. Finally, we demonstrate that micro 3D printing (two-photon polymerization) can potentially be used to fabricate micromodels with sufficient resolution to capture the geometric attributes of micritic carbonates and that can replicate the inherent 3D interconnectivity between macro- and micro-pores.

<p> Previous workers in the Hamilton area have pointed out the occurance of lead and zinc mineralization within the Mid-Silurian carbonate beds. They also mentioned the existance of bitumens in these rock units.</p> <p> Analysis of 30 dolomite samples and separated bitumens by atomic absorption for Cu, Pb, Zn showed that the localization of the metals in the carbonates was controlled by the concentration of the bitumens in the rocks.</p> <p> Analysis of 5 bitumens samples by atomic absorption for Cu, Pb, Zn suggested that the bitumens act merely as a reducing agent and are not preferred sites for base metal accumulation.</p> / Thesis / Bachelor of Science (BSc)

<p dir="ltr">This dissertation explores the history of water on Mars through the lens of the Mars 2020 Perseverance rover mission at Jezero crater. In particular, I use in-situ rover observations to characterize evidence of past surface alteration at Jezero crater. I also present investigations of a modern lake analog on Earth to contextualize potential past depositional processes within the Jezero paleolake system.</p>

The Elbrook-Conococheage Formations (Middle to Upper Cambrian) are a kilometer-thick sequence of cyclic, peritidal carbonates that formed an aggraded, rimmed shelf on a mature, passive continental margin. Sedimentation rates for peri tidal carbonate environments far exceeded long term subsidence of the platform (3 to 5 cm/1000 yrs.); thus, the shelf stayed filled to sea level (i.e., was aggraded). Relative sea level rise did exceed sedimentation for brief periods, causing cyclic transgressions (max. 3 m initial submergence). Average cycle duration was 60,000 years. Cycles (1-7 m thick) are composed of basal subtidal/intertidal limestone consisting of bioherms, grainstone and ribbon carbonate; and dolomitic laminite caps containing minor quartz arenite, shale and breccia. Cycle development was controlled by initial submergence increment and position relative to shelf edge. Large initial submergence produced thick subtidal-based cycles representing shelf lagoon and shoal conditions. Small events resulted in submergence within the intertidal zone, which deposited thick, mudcracked intertidal limestones in outerplatform settings, and thick sequences of laminite in inner platform settings. Slopes on the platform were low (less than 3 cm/km); thus, subtidal facies developed in a mosaic pattern of lagoons and shoals, rather than in shore-parallel belts. When low areas filled, tidal flat laminites prograded seaward over subtidal units. Cyclicity may reflect spasmodic subsidence of the shelf, or uniform subsidence overprinted by small-scale glacio-eustatic sea level changes related to shifting patterns of mountain glaciation. Interior areas of Quaternary carbonate shelves are characterized by incipiently drowned facies and are punctuated by soil/caliche horizons and karst surfaces, that reflect 100 rn glacio-eustatic sea 'level fluctuations. In contrast, many ancient shelves, including the Cambre-Ordovician shelf of the Appalachians, were dominated by cyclic peritidal sequences lacking evidence of major sea level events. Aggraded shelves may represent the typical state of mature carbonate continental shelves in the absence of large-scale sea level fluctuations. / M.S.

Cette thèse étudie les contrôles des processus gravitaires transférant la production carbonatée des plateformes vers les bassins. Ces travaux consistent en 1) une synthèse géologique de la sédimentation gravitaire dans les systèmes carbonatés et une typologie des configurations favorables pour le transfert distal de la production grossière 2) une méthodologie de modélisation numérique innovante combinant la modélisation stratigraphique forward et le calcul de la stratigraphie mécanique. Elle évalue les mécanismes d’instabilités au cours de l’évolution d’un système. Ces travaux s’appuient sur deux cas d’analogues Plio-Quaternaire: La pente occidentale sous-le-vent du Great Bahama Bank (GBB) et le système d’Exuma Sound/San Salvador, qui constitue une voie exceptionnelle de transport distal de sables carbonatés vers la plaine abyssale. Une caractérisation commune des processus de transferts gravitaires a été établie pour ces deux zones. Des essais œdométriques et de cisaillement triaxial ont été conduits pour obtenir les paramètres géomécaniques des sédiments. La méthodologie de modélisation numérique a été appliquée à un transect 2D de la pente occidentale du GBB sur l’intervalle 1,7-0 Ma. Elle précise le mécanisme de progradation de la marge sous-le-vent, liée au développement de prismes marginaux cimentés de bas-niveaux. La modélisation de la stratigraphie mécanique souligne le contrôle des instabilités gravitaires par la géométrie des dépôts et les surpressions de fluides. Celles-ci se développent sous l’effet des charges piézométriques transitoires dans la plate-forme émergée, favorisant la déstabilisation de la marge de la plate-forme. / This PhD thesis focuses on the controls of the gravitational processes transferring the carbonate production of the platform towards the basins. This work consists in 1) a geological synthesis of the gravity-driven sedimentation in carbonate systems and a typology of favorable configurations for the distal transfer of coarse material 2) an innovative numerical modeling workflow combining the forward stratigraphic modeling and the computation of the mechanical stratigraphy. It estimates the instability mechanisms during the evolution of the system. This work is based on two Plio-Quaternary analog cases: The Great Bahama Bank (GBB) Western leeward slope and the Exuma Sound/San Salvador deep basin and major canyon system, which constitutes an exceptional conduit of distal transport of carbonate sands to the abyssal plain. A common characterization of gravitational transfer processes was established for these two zones. Oedometer and triaxial tests were conducted for the determination of geomechanical parameters of the sediments. The numerical modeling workflow was applied to a 2D transect of the western slope of the GBB over the 1.7-0 Ma interval. It precises the progradation mechanism of the leeward margin related to the development of marginal cemented lowstand wedges. The modeling of the mechanical stratigraphy underlines the control of the gravitational instabilities by the geometry of the platform and fluid overpressures. The latter develop under the effect of transient piezometric head in the emerged platform, promoting the destabilization of the platform margin.

L’objectif de la thèse s’inscrit dans le cadre de contribuer à l’estimation des paramètres du système des carbonates en Mer Méditerranée, en particulier la pression partielle du CO2 dans l’eau (pCO2sw), l’alcalinité totale (AT), le carbone inorganique total (CT) et le pH. En premier lieu, on a calculé à partir des données des campagnes Boum en 2008 et MedSeA en 2013 les coefficients de mélange des masses d’eau dans les bassins Ouest et Est. L’analyse de ces coefficients nous a permis d’étudier l’évolution des masses d’eau en Mer Méditerranée entre les années 2008 et 2013.En deuxième lieu, on a présenté à partir des données de la mission MedSeA en mai 2013, les résultats des mesures récentes de pCO2sw sur une section longitudinale assez étendue allant du détroit de Gibraltar jusqu’au sous-bassin Levantin. Les résultats ont indiqué que les bassins Ouest et Est sont gouvernés par deux régimes différents de pCO2sw. Ces deux régimes ont été influencés par les propriétés physico-chimiques assez distinctes des deux bassins. A partir des mesures directes de pCO2sw on a calculé les flux journaliers de CO2 à travers l’interface air-mer en mai 2013 et cela pour le trajet couvert par la mission MedSeA. Pour aboutir à une analyse plus globale on s’est référé dans une étude ultérieure, aux données des campagnes Thresholds et MedSeA. On a établit ainsi deux équations pour estimer en mai 2007 et 2013, la pCO2sw à partir des données satellites de température de surface, Chlorophylle_a et l’index de la couleur de la matière organique dissoute. Puis, on a calculé et cartographié les flux air-mer de CO2 en mai 2013 à l’échelle de toute la Mer Méditerranée et pour une résolution spatiale de 4 km.Ensuite, on a établi à partir des données de la mission MedSeA, des régressions linéaires pour estimer l’AT et le CT à partir de la salinité, et cela pour chaque sous-bassin de la Mer Méditerranée et pour plusieurs intervalles de profondeur. Ultérieurement, on s’est concentré aux données physico-chimiques dans les eaux de surface, compilées de plusieurs campagnes océanographiques entre 1998 et 2013. Les équations établies pour estimer l’AT et le CT dans les eaux de surface, ont indiqué que le meilleur polynôme inclue la salinité et la température. Ces polynômes ont été appliqués sur les cartes climatologiques de température et de salinité du World Ocean Atlas, pour cartographier les variabilités spatiales et saisonnières de l’AT et du CT sur une moyenne de 7 ans. En outre, à partir des données de la mission MedSeA, on a estimé les concentrations en carbone anthropique (CANT) et la variation de l’acidification (∆pH) en Mer Méditerranée. Les résultats ont indiqué que la Mer Méditerranée est fortement contaminée par le CANT avec des concentrations bien plus élevées que celles enregistrées dans l’océan Pacifique ou Indien. Le calcul du ∆pH a indiqué que la Mer Méditerranée est déjà acidifiée de la surface jusqu’en profondeur. Enfin, on a présenté un modèle pour prédire le ∆pH en fonction de concentrations théoriques de CANT. On a montré que le seuil en CANT pour lequel l’acidification va fortement s’intensifier en Mer Méditerranée est déjà atteint. Aussi, les eaux profondes des bassins Occidental et Oriental, deviendront très probablement sous saturées par rapport à la calcite et à l’aragonite d’ici la fin du siècle prochain. / The objective of the thesis is to contribute to the estimation of the carbonate system parameters in the Mediterranean Sea, in particular the partial pressure of CO2 in water (pCO2sw), total alkalinity (AT), total inorganic carbon (CT) and pH.The study was initiated by an adequate calculation of the water masses mixing coefficients in the Western and Eastern basins, using data from the Boum and MedSeA cruises in 2008 and 2013, respectively. The analysis of the mixing coefficients, allowed us to study the evolution of water masses in the Mediterranean Sea between the years 2008 and 2013.Subsequently, using data from the 2013 MedSeA cruise, we presented the results of recent measurements of pCO2sw on a wide longitudinal section from the Strait of Gibraltar to the Levantine sub-basin. The results indicated that the Western and Eastern basins were characterized by two different pCO2sw regimes. These regimes were mainly affected by the distinctive physico-chemical properties of each basin. From the direct measurements of pCO2sw we calculated along the track of the MedSeA cruise, the daily CO2 fluxes across the air-sea interface in May 2013. To achieve a more comprehensive analysis, we referred in a consecutive study to the data of the Thresholds and MedSeA cruises. From these data, we provided two equations to estimate in May 2007 and 2013; pCO2sw from satellite data of sea surface temperature, Chlorophyll_a and the chromophoric dissolved organic matter index. Furthermore, we calculated and mapped the air-sea CO2 fluxes in May 2013 across the whole Mediterranean Sea, with a spatial resolution of 4 km.Successively, we established from the MedSeA cruise data, linear regressions to estimate AT and CT from salinity, in each sub-basin of the Mediterranean Sea and for several depths. Later on, we focused on the physico-chemical data in surface waters, compiled from several oceanographic cruises between 1998 and 2013. The equations developed to estimate the AT and CT in surface waters, indicated that it is best to include in these polynomials both salinity and temperature. These polynomials were applied to the climatological fields of salinity and temperature of the World Ocean Atlas, in order to map the spatial and seasonal variability of AT and CT on a 7 years average.Moreover, we estimated from the MedSeA cruise data, the concentrations of anthropogenic carbon (CANT) and the variation of acidification (ΔpH) in the Mediterranean Sea. The results indicated that the Mediterranean Sea is heavily contaminated by CANT, with higher concentrations than those recorded in the Pacific or Indian Ocean. Also, the calculated ΔpH indicated that the Mediterranean Sea is already acidified from the surface to the deep waters. Finally, we presented a model to predict the ΔpH according to theoretical concentrations of CANT. Consequently, we showed that we already reached the tipping point of CANT, for which the acidification will strongly intensify in the Mediterranean Sea. Moreover, the deep waters of the Western and Eastern basins are very likely to become under saturated in calcite and aragonite by the end of the next century.