ENGLISH SUMMARY Ammonite assemblage from the Upper Cenomanian of the Bohemian Cretaceous Basin realtively poorly known. Some species have been described herein for the first time: Thomelites cf. sornayi (Thomel) Euomphaloceras septemseriatum (Cragin) Eucalycoceras pentagonum (Gragin) and Allocrioceras annulatum (Shumard.). These records predominantly come from the M. geslinianum zone sediments developed in the higher parts of the Pecinov member (Uličný et al., 1998) of the Peruc - Korycany Formation. The sediments yielding ammonite assemblage represents the Late Cenomanian transgressive tract, accompanied by anoxic event OAE II = Oceanic anoxic Event II, CTBE) worldwide recorded in sediments and showing an increased content of stable isotope δ13 C. The OAE II is suggested to be connected to marine biota crisis and also the mass extinctionas well. The most affected organisms were benthic forms, due to high anoxic conditions at the bottom of the water column. Morphological features of the shells may, depending on the quality preservation shells (or cores) can be used to paleobathymetric interpretations. Most described species lived at depths of 50-80 m (up to 100m). Pelagic ammonites (i.e. Sciponoceras) lived at depths of up to 50 m. Heteromorphic taxa (Allocrioceras) have occurred at a depth of up to 100 m.

Nas últimas décadas, os Lagerstätten estiveram no centro das discussões relativas à história paleobiológica e geológica da Terra. Em particular, o Membro Crato da Formação Santana (Bacia do Araripe, Nordeste do Brasil) é um dos mais significantes Lagerstätten do Cretáceo já que registra invertebrados, vertebrados e plantas excepcionalmente preservados em sedimentos carbonáticos de um palaeolago. O principal objetivo desta dissertação é lançar luz sobre os processos de preservação responsáveis pela fossilização de insetos e peixes com tecidos moles em 3D. Lâminas petrográficas e diversas técnicas paleométricas - micro-Espectroscopia Raman, Fluorescência de raios-X (FRX) convencional, micro-FRX com fonte de luz sincrotron (RS-µFRX), emissão de Raios-X induzida por partículas (PIXE), microscopia eletrônica de varredura (MEV) e espectroscopia de energia dispersiva de Raios-X (EDS) - foram empregadas para caracterizar a rocha matriz, a morfologia e fidelidade de preservação dos tecidos moles e as composições elementares e moleculares dos fósseis em escala de centímetros e mícron. Os resultados revelam que, enquanto insetos e tecidos moles de peixes encontrados nos denominados calcários beges (BL) são substituídos por pseudomorfos de pirita framboidal (após oxidação da pirita), os quais ocorrem juntamente com possíveis substâncias poliméricas extracelulares secretadas por bactérias (EPS), tecidos de peixes dos calcários cinza (GL) são querogenizados. Em insetos, existe variação de tamanho dos framboides para dentro dos fósseis, que é aqui interpretada como produto do equilíbrio entre as taxas de difusão e de nucleação dos minerais. Além disso, a distribuição preferencial de Zn e Cu em estruturas piritizadas de insetos e peixes em comparação com a sua matriz é aqui considerada como sendo o resultado da fixação de elementos químicos em biofilmes bacterianos. Zn concentrado nos ossos de peixes com querogenizados e Fe/Cu observados em seus tecidos moles são considerados como tendo sido incorporados durante a vida dos peixes. No caso particular de peixes, modelo originalmente proposto para a preservação de metazoários do Pré-cambriano é aqui aplicado para explicar a variação de fossilização entre as fácies BL e GL. Lâminas petrográficas revelam que os GL têm geralmente teor de argila/matéria orgânica maior do que os BL, implicando que as taxas de soterramento poderiam ter sido mais intensas nos GL. Isto teria colocado carcaças em decomposição mais rapidamente na zona sedimentar de metanogênese, sendo formado o querogênio. Por outro lado, carcaças depositadas na fácies BL poderiam ter passado período mais longo na zona de redução de sulfato, o que teria levado à piritização generalizada. Além disso, a baixa porosidade do microespato, o cimento e a argila poderiam ter diminuído a migração de aceptores de elétrons dos processos de respiração bacteriana anaeróbia - particularmente redução de sulfato (RS) e metanogênese - e de seus produtos biogeoquímicos, estreitando a zona de RS, o que teria reduzido a influência da piritização em alguns níveis. Enquanto que a piritização resultou na preservação de fibras musculares em 3D, sarcolema, possíveis núcleos celulares, tendões e olhos, a querogenização preservou tecidos conjuntivos, tegumento e fibras musculares distorcidas e compactadas. Em conclusão, é aqui proposto que fácies influenciadas por processos paleoambientais e geobiológicos produziram fósseis com gradiente diferencial de fidelidade de preservação de acordo com cada via tafonômica seguida. / Over the past decades, the so-called Fossil Lagerstätten have been in the core of discussions concerning the palaeobiological and geological history of the Earth. In particular, the Crato Member from the Santana Formation (Araripe Basin, north-east Brazil) is one of the most significant Cretaceous Lagerstätten since it records exceptionally well-preserved fossil invertebrates, vertebrates, and plants, deposited in palaeolake carbonate beds. The main aim of this dissertation is to shed light on the preservational processes responsible for the fossilization of insects and fishes still retaining 3D soft tissues. Petrographic thin sections and several palaeometric techniques - micro-Raman Spectroscopy, conventional X-ray Fluorescence (XRF), Synchrotron micro-XRF (SR-µXRF), Particle-Induced X-ray Emission (PIXE), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS) - have been employed to characterize the host rock, soft-tissue morphology and preservational fidelity, and fossil elemental and molecular compositions in centimetre to micrometre scale. The results reveal that while insects and fish soft-tissues found in the so called beige limestones (BL) are replaced by framboidal pyrite pseudomorphs (after pyrite oxidation) occurring together with putative bacterially-secreted extracellular polymeric substances (EPS), labile tissues of fishes from the grey limestones (GL) are kerogenized. In insects, there is a variation of framboid size inward the fossils, which is here interpreted as a product of the balance between diffusion and mineral nucleation rates. Moreover, the preferential distribution of Zn and Cu in pyritized insect/fish labile structures in comparison to their rock matrix is here considered as being the result of element fixation in bacterial biofilms. Zn concentrated in bones of kerogenized fishes and Fe/Cu occurring in their soft tissues are considered to have been incorporated during fish life. In the particular case of fishes, a model originally proposed for metazoan preservation in the Precambrian is here applied to explain the variation of fossilization between the BL and GL facies. Petrographic thin sections reveal that GL have generally higher clay/organic matter contents than BL, thus implying that burial rates might have been more intense in the former. This could have placed decaying carcasses more quickly in the methanogenesis sedimentary zone, in that way being kerogenized. On the other hand, carcasses deposited in the BL facies could have spent a longer period in the sulphate-reduction zone, which would have accounted for pervasive pyritization. Additionally, microspar low porosity, cement and clay could have diminished both downward migrations of electron acceptors for anaerobic bacterial respiration processes - particularly sulphate-reduction (SR) and methanogenesis - and of their biogeochemical products, narrowing the SR zone, which would have lowered the impact of pyritization in some levels. While pyritization has recorded 3D muscle fibres, sarcolemma, putative cell nuclei, tendons and eyes, kerogenization has yielded connective tissues, integument and compressed/distorted muscle fibres. In conclusion, it is here proposed that palaeoenvironmental/geobiological-influenced facies have yielded fossils with a variable preservational-fidelity gradient, accordingly to each taphonomic pathway followed.

Impaktite des Chicxulubkraters wurden petrographisch (Polarisationsmikroskopie, REM, KL) und chemisch (RFA, TRFA, PGE, EMS) untersucht, um das Verhalten von Ejekta während des atmosphärischen Transports zu erforschen. Die proximalen Impaktite der UNAM-7 Bohrung bestehen aus einer suevitischen Brekzie (222.2 bis 384.4 m) und einer basalen, polymikten Brekzie mit geringem Silikatschmelzanteil. Letztere beinhaltet Evaporit-Megablöcke und Karbonatschmelzpartikel; Zersetzung von Kalzit und Anhydrit ist durch Entgasungsbläschen indiziert. An der distalen Kreide-Paläogen Grenze von El Guayal (520 km SW vom Kraterzentrum) beinhaltet eine 10 m mächtige suevitische Abfolge in einer oberen Untereinheit akkretionäre Lapilli und darüber eine Toneinheit. Das Auftreten von Karbonatschmelzen mit der PGE-angereicherten Impaktorkomponente in der Toneinheit belegt den Zusammenhang der K-P Grenze mit dem Chicxulub-Impakt. Die folgenden Stadien können für die Ablagerung und Alteration der Ejekta unterschieden werden: (1) Ein Hochgeschwindigkeitsauswurf beschleunigte Zersetzungsprodukte und initiierte einen Gasstrom. (2) Karbonatschmelzen wurden mit Anhydrit-Megablöcken ausgeworfen und initiierten einen lateral ausbreitenden Ejektavorhang. Kalzitrückreaktionen erhitzte das Material während des Transports. (3) Die Ejektionswolke kollabierte teilweise, wobei der zurückfallende Suevit vom Impaktormaterial, das in die Stratosphäre verteilt wurde, fraktioniert wurde. Die Kombination von Silikatschmelze mit Kalzit initiierte einen heißen, gas-angetriebenen Strom. In einer oberen, moderat temperierten, turbulenten Aschewolke kondensierte Wasserdampf, und durch Akkretion von Asche entstanden akkretionäre Lapilli. (4) Die Impaktorkomponente wurde mit den feinsten Ejektamassen für Wochen bis Jahre abgelagert. (5) Der Transport von Ejekta in der heißen Ejektionswolke induzierte Alterationsprozesse in den Ablagerungen. Es kann geschlussfolgert werden, dass ein gewisser Anteil des CO2 zu Kalzit zurückreagierte, währenddessen SOX Gase vollständig in die Atmosphäre freigesetzt wurden. Diese Beobachtungen inklusive des Auftretens von Karbonatschmelzen unterstützen die Aussage, dass der freigesetzte Anteil von CO2 in die Atmosphäre in der Vergangenheit überbewertet wurde. / Impactites of the Chicxulub crater were studied petrographically (polarisation microscopy, SEM, CL) and chemically (XRF, TXRF, PGE, EMPA) to investigate the evolution of ejecta during transit through the atmosphere. At the proximal UNAM-7 borehole, the sequence of impactites consists of a suevitic breccia (222.2 to 348.4 m) on top of a polymict silicate melt-poor breccia. The latter is intercalated with evaporite megablocks representing an analogue to the Bunte Breccia of the Nördlinger Ries crater. It contains carbonate melt particles; calcite and anhydrite decomposition is indicated by degassing vesicles. At the distal Cretaceous-Palaeogene site of El Guayal (~520 km SW of the crater centre), a ~10 m thick suevitic succession contains at its upper subunit accretionary lapilli and on top a clay unit. Intermixing of calcite with hot silicate melt resulted in recrystallisation and decomposition of calcite. In the clay unit, the presence of carbonate melt spheroids together with the PGE-enriched impactor component links the Chicxulub impact with the K-P boundary. The following stages can be distinguished for the deposition and alteration of the ejecta: (1) Jetting accelerated decomposition products and initiated a vapour flow. (2) Carbonate melts were excavated with anhydrite megablocks and initiated a lateral extending ejecta curtain. Calcite reformations heated the material during transport. (3) The expanding ejecta plume partially collapsed separating the falling suevite from impactor material that had been lifted into the stratosphere. The combination of silicate melt with calcite initiated a hot, gas-driven, basal flow. In an upper, moderately tempered, turbulent ash cloud, steam condensed and accretion of ash-sized material formed accretionary lapilli. (4) The impactor component was deposited with the finest ejecta for weeks to years. (5) The prolonged transport of ejecta in the hot ejecta plume induced alteration processes observed in the deposits. It can be concluded that a certain amount of CO2 has back-reacted to calcite, whereas SOX gases were completely liberated. These observations including the abundant presence of carbonate melts support that the amount of CO2 released to the atmosphere during the Chicxulub impact was overestimated previously.

Cette thèse concerne l’étude du message magnétique de la lithosphère océanique. Nous nous sommes, dans un premier temps, intéressés à l’évolution du signal magnétique à travers une section de croûte océanique complète et continue des basaltes jusqu’aux gabbros. Le but était de comprendre comment les propriétés magnétiques des roches peuvent nous renseigner sur les conditions d’altération dans la croûte océanique. Nous avons donc établi un jeu de données magnétiques (température de Curie, paramètres d’hystérésis, mesures magnétiques basse température) sur l’ensemble de la section de croûte océanique forée au site IODP 1256D, dans l’océan Pacifique. Ces données sont confrontées aux températures d’altération, établies par thermo barométrie et mettent en évidence une étroite relation entre l’altération des phases magnétiques et les températures d’altération. De plus, des analyses semi-quantitatives et des observations microscopiques (optique, MEB et MET) mettent en évidence un changement de structure cristalline, associée à une perte de titane, permettant la formation d’une phase secondaire, l’hydroschorlomite, dans un intervalle de forte altération des phases magnétiques (entre 670 et 1028 mbsf (meters below sea floor)). Dans un second temps, l’acquisition de profils d’anomalies magnétiques marines de surface et d’un profil d’anomalies de fond « deep tow » à travers le superchron du Crétacé (entre 83 et 120 Ma) nous a permis de tester la stabilité de polarité du champ géomagnétique durant cette période. Nous mettons en évidence la présence d’anomalies magnétiques : des anomalies de courtes longueurs d’onde ou « tiny-wiggles » à travers l’ensemble du superchron et des anomalies magnétiques de plus grande longueur d’onde, assimilables à de courts intervalles de polarité inverse. Nos mesures montrent que le comportement du champ magnétique durant le superchron n’est pas différent des périodes qui le précèdent (chrons M0-M1-M2) et le suivent (chrons 33n et 33r). La définition de superchron doit être remise en question. / So we, in a first part, studied the evolution of the magnetic signal through a section of a, complete and continuous, oceanic crust, from basalts to gabbros. In order to understand how the magnetic properties of rocks can tell us about the conditions of alteration in the oceanic lithosphere, we established a set of magnetic data (Curie temperature, hysteresis parameters, low temperature magnetic measurements) through the entire section of the oceanic crust, drilled at IODP Site 1256D, in the Equatorial Pacific Ocean. These magnetic data are compared to alteration temperatures, determined by thermobarometry (Alt et al., 2010) and show a close relationship between the alteration of the magnetic phases and the alteration temperatures, including the identification of an interval of strong alteration of the titanomagnetites (between 670 and 1028 mbsf (meters below sea floor). In addition, semi quantitative chemical analysis and microscopic observations (optical, SEM and TEM), performed on titanomagnetites, show a change in crystalline structure and a loss of titanium element (Ti4 +) in titanomagnetites to form a secondary phase rich in titanium, in this same interval of strong alteration. In a second part, the acquisition of numerous sea-surface magnetic profiles and a high resolution magnetic profile ("deep tow") through the Cretaceous Normal Superchron (83-120 Ma), allowed us to test the stability of the geomagnetic polarity of the superchron and to highlight the presence of numerous magnetic anomalies: anomalies of short wavelength or "tiny-wiggles” through the entire period and magnetic anomalies of greater length wave, similar to short intervals of reverse polarity. Our measurements show that the behavior of the magnetic field during the superchron is no different from previous periods (chrons M0-M1-M2) and the following magnetic period (chrons 33n and 33R) and the definition of ‘superchron’, long geomagnetic event without inversions, must be questioned

Στην εργασία αυτή αξιολογούνται οι πετρογραφικές και φυσικομηχανικές ιδιότητες που καθορίζουν την καταλληλότητα των ανθρακικών σχηματισμών του Νομού Αιτωλοακαρνανίας Δυτικής Ελλάδας,που ανήκουν στη ζώνη Ωλονού-Πίνδου ηλικίας Άνω Κρητιδικού.Σκοπός είναι να συσχετισθούν οι ιδιότητες αυτές,να προσδιοριστεί η συμπεριφορά των αργιλικών προσμίξεων και να καθορισθεί η καταλληλότητας τους,για χρήση τους ως αδρανή σε έργα οδοποιϊας.Δυο από τις δοκιμές που προσδιορίζουν την καθαρότητα των αδρανών είναι η δοκιμή ισοδύναμου άμμου και η δοκιμή μπλε του μεθυλενίου,τα αποτελέσματα των οποίων συσχετίστηκαν με τις πετρογραφικές και φυσικομηχανικές παραμέτρους των πετρωμάτων. / In this paper we evaluate the petrographic and physicomechanical properties which determine the suitability of carbonate formations of Aitoloakarnania Western Greece , in Olonos - Pindos unit Cretaceous age.The objective is to relate these properties to determine the behavior of clay impurities and determine the suitability for use as aggregates in road construction.Two of the tests that used to determine the purity of the aggregates is the sand equivalent and methylene blue, the results of which were associated with the petrographic and physico-mechanical parameters of rocks .

Rocks of the Morenci-Metcalf district consist of Precambrian metaquartzite-schist, granodiorite, and granite overlain by Paleozoic and Mesozoic sediments. Intrusion of igneous rocks, emplacement of breccia masses, and associated hydrothermal activity occurred in Laramide time. Breccias of the district are associated with the youngest sialic intrusive complex. This sequence includes intrusion of the Older Granite Porphyry stock, main stage district hydrothermal alteration, quartz veining, breccia formation, main stage district hydrothermal mineralization, and intrusion of the Younger Granite Porphyry plug. Breccia formation in the Morenci-Metcalf district is similar to breccia descriptions reported in the literature for other porphyry copper deposits. Three breccia types, of separate and distinct origins, are herein described as the Morenci, Metcalf and King, and Candelaria Breccias. The Morenci Breccia is an intrusion breccia that has formed along a pre-existing structural feature during the ascent and emplacement of the Older Granite Porphyry stock. It exhibits an oblate lenticular shape with angular to subrounded fragments in a matrix of quartz, K-feldspar, biotite, and minor rock flour. The Metcalf-King Breccias and numerous smaller breccia masses are the remnants of an original Older Granite Porphyry mantle above the ascending Younger Granite Porphyry complex. The breccia masses occur as large 'xenoliths' floating within the Younger Granite Porphyry plug and were formed by surging and collapse during emplacement of this intrusive. Fragments in the Metcalf and King Breccias grade from angular in the central core to rounded at the contacts and occur in a matrix of sericite, K- feldspar, quartz, and rock flour. The Candelaria Breccia is an explosion pipe and is the largest continuous breccia mass in the district. It is oval with an inverted cone appearance consisting of angular to subangular equidimensional fragments in a matrix of sericite, quartz, specularite, and rock flour. All the breccia masses occur within and subsequent to the district phyllic (quartz-sericite-pyrite) alteration zone. Main stage district copper mineralization postdates emplacement of the Older Granite Porphyry stock and breccia formation, and is prior to the intrusion of the Younger Granite Porphyry plug. Late stage quartz-sericite-pyrite-chalcopyrite veinlets occur in the Metcalf-King Breccia group. Field mapping and laboratory studies indicate that the Older Granite Porphyry stock appears to have been the main district mineralizer.

As part of the wider European GTS Next project, I propose new constraints on the ages of the Late Cretaceous, derived from a multitude of geochronological techniques, and successful stratigraphic interpretations from Canada and Japan. In the Western Canada Sedimentary Basin, we propose a new constraint on the age of the K/Pg boundary in the Red Deer River section (Alberta, Canada). We were able to cyclostratigraphically tune sediments in a non-marine, fluvial environment utilising high-resolution proxy records suggesting a 11-12 precession related cyclicity. Assuming the 40Ar/39Ar method is inter-calibrated with the cyclostratigraphy, the apparent age for C29r suggests that the K/Pg boundary falls between eccentricity maxima and minima, yielding an age of the C29r between 65.89 ± 0.08 and 66.30 ± 0.08 Ma. Assuming that the bundle containing the coal horizon represents a precession cycle, the K/Pg boundary is within the analytical uncertainty of the youngest zircon population achieving a revised age for the K/Pg boundary as 65.75 ± 0.06 Ma. The Campanian - Maastrichtian boundary is preserved in the sedimentary succession of the Horseshoe Canyon Formation and has been placed ~8 m below Coal nr. 10. Cyclostratigraphic studies show that the formation of these depositional sequences (alternations) of all scales are influenced directly by sea-level changes due to precession but more dominated by eccentricity cycles proved in the cyclostratigraphic framework and is mainly controlled by sand horizons, which have been related by autocyclicity in a dynamic sedimentary setting. Our work shows that the Campanian - Maastrichtian boundary in the Western Canada Sedimentary Basin coincides with ~2.5 eccentricity cycles above the youngest zircon age population at the bottom of the section and ~4.9 Myr before the Cretaceous - Palaeogene boundary (K/Pg), and thus corresponds to an absolute age of 70.65 ± 0.09 Ma producing an ~1.4 Myr younger age than recent published ages. Finally, using advances with terrestrial carbon isotope and planktonic foraminifera records within central Hokkaido, Northwest Pacific, sections from the Cretaceous Yezo group were correlated to that of European and North American counterparts. Datable ash layers throughout the Kotanbetsu and Shumarinai section were analysed using both 40Ar/39Ar and U-Pb methods. We successfully dated two ash tuff layers falling either side of the Turonian - Coniacian boundary, yielding an age range for the boundary between 89.31 ± 0.11 Ma and 89.57 ± 0.11 Ma or a boundary age of 89.44 ± 0.24 Ma. Combining these U-Pb ages with recent published ages we are able to reduce the age limit once more and propose an age for the Turonian - Coniacian boundary as 89.62 ± 0.04 Ma.

Des observations macroscopiques et microscopiques sur les plantes actuelles et fossiles ont été effectuées. Sur les plantes actuelles ont été effectué des observations relativement aux effets des gaz volcaniques sur l’ultrastructure des cuticules de Pinus halepensis et de Erica arborea récoltés dans l’aire volcanique des Campi Flegrei, Italie. Les observations conduites au TEM sur les cuticules de P. halepensis, influencé et non influencé par les gaz volcaniques, ont montré que : 1) l'épaisseur totale de la CM (cuticule) + CW (paroi pectocellulosique) ne subit pas de variations significatives d'épaisseur ; 2) la cuticule des aiguilles influencée par les gaz volcaniques montre une accumulation d’oxalate de calcium ainsi que 3) un réarrangement des fibrilles disposées parallèlement à la surface. Les observations conduites sur E. arborea ont permis de 1) constater que les épaisseurs totales des cuticules, influencées ou non par les gaz, sont significativement différentes ; 2) en présence de gaz volcaniques la couche externe A2 subit un accroissement d’épaisseur significatif. Par rapport aux macro-restes végétaux fossiles, les localités du Crétacé de Cusano Mutri et Pietraroja ont été étudiées. Le première site fossilifère a permis 1) d’identifier plusieurs taxa appartenant aux conifères; 2) de décrire une nouvelle espèce de conifère: Frenelopsis cusanensis; 3) de trouver l’angiosperme ancestrale Montsechia vidalii. L’étude taxonomique a permis de décrire des entités typiques de la Province Euro-Sinienne. L’étude sédimentologique et systématique montre un climat plutôt tropical-subtropical, des abondants fusains montrant des incendies naturels. / Macroscopical and microscopical observations on extant and fossil plants have been made. Observations on extant plants led to study the effects of volcanic gases on the cuticle ultrastructure of Pinus halepensis and Erica arborea sampled in the volcanic area of Phlegrean Italy. TEM observations on P. halepensis cuticles fumigated or not by volcanic gases revealed: 1) insignificant thickness variations of the cell wall plus cuticle among current- and first-year-old needles of both fumigated and not fumigated trees; 2) a calcium oxalate accumulation in fumigated leaves; 3) moreover, in respect to the cell surface, fibrils are disposed parallel to the surface of the cuticle. In specimens of E. arborea fumigated or not by volcanic gases, 1) the total thickness of cuticles varies significantly; 2) in plants experiencing chronic fumigation the A2 layer increases its thickness. As for fossil plants, the cuticles of Cretaceous Fossil-Lagertätten of Cusano Mutri and Pietraroja have been studied. In the former: 1) numerous taxa belonging to conifers have been identified; 2) the new species Frenelopsis cusanensis has been described; 3) Montsechia vidalii has been found outside of Spain. Taxonomical studies allowed the description of typical Euro-Sinian fossil plants. Sedimentological and taxonomical studies suggest semi-arid or arid conditions in a subtropical or tropical climate. It is worth noting as for Cusano Mutri locality, evidence of wildfire (fusain) suggests a periodic combination of arid periods, high temperatures and lightning strikes.

La dynamique des courants de turbidité est fortement contrôlée par la morphologie du fond marin. Les turbidites issues de ces courants constituent des réservoirs d’hydrocarbures très importants dans les bassins sédimentaires à travers le monde. L'objectif principal de ce travail est de comprendre comment le paleorelief a contrôlé la géométrie et l'architecture des réservoirs turbiditiques, en utilisant comme zone d'étude les réservoirs du Crétacé d'un champ pétrolier du bassin de Campos (offshore du Brésil), où la tectonique a été en partie dominée par l'halocinèse. La méthodologie utilisée dans cette thèse a couplé deux approches. La première a inclus à la fois la description des séquences sédimentaires, à partir de données de sismique-réflexion et de puits, et les restaurations structurales. Six horizons régionaux et quatre unités-réservoirs ont été identifiés et cartographiés afin de construire un modèle géologique multi-2D. Ces surfaces ont ensuite été aussi restaurées. Les résultats de cette étape suggèrent que les failles liées à l'halocinèse ont contraint la paléotopographie pour le dépôt des réservoirs plus anciens et que des structures tectoniques et un canyon ont formés les contraintes paléotopographiques pour la distribution des réservoirs plus jeunes. La seconde approche a été l'analyse du rôle des paramètres des écoulements en effectuant des simulations numériques du type stratigraphique (Dionisos) et des automates cellulaires (CATS). Une surface restaurée, considérée comme référence pour le dépôt des unités-réservoirs a été utilisée comme paléotopographie pour les simulations CATS. Le modèle numérique a été contraint par les données réservoirs. Cette utilisation inédite des simulations 3D avec des automates cellulaires dans une étude de cas réel concernant des dépôts marins anciens a produit des résultats réalistes par rapport aux exemples modernes connus. Elle a également fourni des résultats plus exploitables à l'échelle de réservoir que les modèles numériques de type "stratigraphique". Ce travail met en évidence l'importance des interactions tectonique-sédimentation et de la paléotopographie pour la distribution de réservoirs turbiditiques. / The dynamic of gravity-driven turbidity currents is strongly influenced by the morphology of the seafloor. The resulting turbidites constitute important hydrocarbon reservoirs in sedimentary basins throughout the world. The main objective of the present work is thus to understand the way the paleorelief controls turbidite reservoir architectures, with application in a specific study area with Cretaceous reservoirs in Campos Basin (Brazilian offshore). The tectonics in this Basin was partly controlled by halokinesis. The first approach was describing the local Cretaceous sedimentary sequence architecture, from seismic and well data, and performing structural restorations. Six regional horizons and four reservoir-scale units were identified and mapped in order to build a multi-2D geological model. Structural restorations highlighted the structural evolution and allowed the related horizon palaeotopography to be obtained. The results of this work step suggest that the halokinesis-related listric faults regulated the distribution of the basal reservoirs. Moreover, at the top of the Albian carbonates, a canyon was identified, which, in association with the tectonic structures, forms the palaeotopographic constraints for the upper reservoir geometry. The second approach was analyzing the role of flow controlling parameters by performing stratigraphic (Dionisos) and cellular automata-based (CATS) numerical simulations. The latter provided a more appropriate reservoir scale-simulation process than Dionisos. A restored surface, considered as reference for the deposition of the reservoir units, was used as the palaeotopography for CATS simulations, having as constraints the reservoir data. This pioneer use of cellular automata simulations in a real subsurface case study produced coherent results when compared with the actual reservoir distribution. This work sheds light on the importance of tectonic-sedimentation interactions and of palaeotopography for the distribution of turbidite reservoirs.

PhDENV (Geology) / Department of Mining and Environmental Geology / The Cretaceous period marked the breaking up of Gondwana, giving rise to the separation of the African and South American continents with the subsequent emergence of the South Atlantic Ocean. Most correlation studies between the two continents with respect to paleoenvironmental conditions and tectonic settings during the Cretaceous- Tertiary periods have been concentrated more on the use of flora and fauna as indicators with less application of kaolinite as paleoenviromental proxies, hence, this study. The research involved the evaluation of paleoenvironmental conditions and tectonic settings of four (4) selected Cretaceous-Tertiary kaolin deposits with two (2) each from the Eastern Dahomey (Eruku and Lakiri) and Niger Delta (Awo-Omama and Ubulu-Uku) Basins in Nigeria. Representative kaolin samples collected from the selected deposits were analysed for physico-chemical, mineralogical, geochemical, isotopic, and geochronological data. The geochemical data obtained by x-ray fluorescence (XRF) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LAICPMS) were used in unraveling the provenance and tectonic settings of the kaolins. The kaolinite stable isotopic data for oxygen and hydrogen determined using a Finnigan Delta XP Mass Spectrometer were used to assess the paleoenvironmental and paleoclimatic conditions under which the kaolins were formed. The detrital zircon geochronological data acquired by laser ablation – single collector – magnetic sectorfield – inductively coupled plasma – mass spectrometry (LA-SFICP-MS) as well as kaolinite stable isotopic data were employed in constraining the probable timing of kaolinisation. The industrial applications of the kaolins were assessed based on the physico-chemical (Colour, particle size distribution (PSD), pH, electrical conductivity, and Atterberg limits), mineralogical, and geochemical data. The mineralogical data were obtained through x-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric analysis and differential scanning calorimetry, and scanning electron microscopy (SEM). Correlative studies between selected Cretaceous African and South American kaolins were conducted. The results showed that the dominant colour in the studied kaolins was pale red (39 %) followed by pinkish and light grey (35 %) as well as reddish yellow, light pink, light brown, vii reddish brown, and pinkish white. The pH and EC values generally ranged from 4.27 to 5.29 and 0.2 to 13.1 μS/cm, respectively. The kaolins predominantly have clay to sandy clay textures with plasticity indices between 10 and 22 wt %. Bulk mineralogical quantitative results indicated that the Cretaceous kaolins have kaolinite, quartz, and muscovite present in that decreasing order with anatase, goethite, and hematite in traces whereas Tertiary kaolins have kaolinite and quartz present in that decreasing order with anatase and goethite in traces. In the silt fractions, kaolinite and quartz were the dominant mineral constituents, whereas in the clay fractions, the dominant clay mineral was kaolinite accounting for 69 to 99 wt % with the non-clay minerals like quartz, anatase, hematite and goethite accounting for percentages between 1 to 28 wt % in the Cretaceous – Tertiary kaolins. Morphologically, the studied kaolins were characterised by pseudohexagonal stacks to books and thin platy kaolinite particles with moderate structural order. The chemical compositions of the Cretaceous-Tertiary kaolin deposits were identical to hydrated alumino-silicates based on the dominance of SiO2, Al2O3 and LOI. The chemical index of alteration (CIA) and chemical index of weathering (CIW) values varied between 96.98 to 99.39 % and 98.95 to 99.89 %, respectively. The clay fractions were enriched in Cr, Nb, Sc, Th, U, V, Zr, and LREE and depleted in Ba, Co, Rb, Sr, and HREE, respectively, relative to the average Upper Continental Crust (UCC). The Th/Sc, La/Sc, Th/Cr, and Eu/Eu* ratios were within the range of sediments derived from felsic rocks. The TiO2 versus Al2O3 and La-Th-Sc plots indicated source rocks with granitic – granodioritic - gabbroic compositions. Geochemical discrimination plots showed that the Cretaceous and Tertiary kaolins were deposited in passive margin tectonic settings. The stable isotopic results indicated that the values of the Cretaceous kaolins ranged from – 47 to – 57 ‰ and 19.1 to 19.8 ‰, respectively, with paleotemperatures between 29.0 and 32.2 ˚C, whereas the δD and δ18O corresponding values for the Tertiary kaolins ranged from – 54 to – 66 ‰ and 20 to 21.5 ‰, respectively, with paleotemperatures between 17.0 and 23.9 ˚C. viii The U-Pb dating of the detrital zircons showed that the Cretaceous - Tertiary kaolins have inputs from rocks of Eburnean (2500 – 2000 Ma) and Pan African (750 – 450 Ma) ages. The age of maximum deposition determined from the least to statistically robust approach corresponds to the Ediacaran Period (645 – 541 Ma) of the Neoproterozoic Era (1000 – 541 Ma). The Cretaceous – Tertiary kaolins were formed under intense anoxic chemical paleoweathering conditions of predominantly felsic rocks in addition to contributions from intermediate and mafic rocks in passive margin tectonic settings. The Cretaceous kaolins were formed under warmer conditions relative to the Tertiary kaolins. The West African Massif rocks were the main sediment sources for the Cretaceous kaolins, whereas both the West African and Northern Nigerian Massif rocks were the major sediment sources for the Tertiary kaolins. The most probable timing of kaolinisation for the Cretaceous – Tertiary kaolins occurred between the Ediacaran (645 – 541 Ma) and Early Cretaceous Periods for the Cretaceous kaolins and between the Ediacaran Period (645 – 541 Ma) and Oligo – Miocene age for the Tertiary kaolins. The Nigerian and Brazilian Cretaceous kaolins formed under similar warm tropical paleoclimate. The study corroborated the occurrence of the Eburnean (Transamazonian) and Pan African (Brasiliano) orogenic events across the African and South American continents. Beneficiation of the Cretaceous – Tertiary kaolins will allow large scale industrial applications in paper coating, ceramics, pharmaceutical, and cosmetics industries. The major contributions from this study have been: the better understanding of the past environmental conditions and tectonic settings, the dating of the possible timing of kaolinisation, and improvement on the potential industrial applications of the Cretaceous – Tertiary kaolins. / NRF