The effect of eucalyptus forests in hidrossedimentologic processes has been little explored by the scientific community, which results in a database containing information related to these incipient effects, especially at the watershed scale. The monitoring and the mathematical modeling are recognized as effective tools of science to supply the lack of information, particularly in natural resource management, in the representation and prediction of these processes. In this sense, the aim of this study was to describe the monitoring data to assess effects of eucalyptus cultivation in the hidrossedimentological processes, to calibrate the input parameters and to verify the potential application of the Limburg Soil Erosion Model (LISEM) in the representation of watershed hydrological processes embedded with forest cover. The study was conducted in two forest watersheds located in Eldorado do Sul - RS, and the watershed has an area of 94.46 ha and drainage sub-watershed, which is embedded in the amount and terms of the watershed, has a drainage area of 38.86 ha. The hidrossedimentometrical monitoring began in February 2011 and was conducted within the limits of the watershed in two automatic sections, composed of linigraph, turbidimeters and pluviographs. This work has included monitoring over a period of six months from 02/16/2011 to 08/15/2011. The sediment yield was determined by multiplying the data of sediment concentration and flow. The model LISEM was calibrated from six different rain events. The model input parameters were obtained through surveys conducted in the watershed and literature data. To evaluate the model ability in representing the hydrological processes hydrographs measured in the watershed exutory were used. The monitoring results demonstrated that periods with higher rainfall volume presented a significant increase in peak flows in relation to the driest intervals, as well as an increase in the suspended sediments concentration in the watershed and in the sub-watershed. The events with greater rainfall intensity demonstrated that the smallest drainage area of the subwatershed generated faster answers in flow and sediment concentration. For the watershed, in most events occurred flood wave attenuation with least steeply sloping and lowest hydrograph peaks than the sub-watershed. Specifically, the sediment yield was 38.41 and 33.65 t km-2, during the six months of monitoring for the watershed and for the subwatershed, respectively. The magnitude of sediment yield was 0.77 t ha-1 yr-1 for the watershed and 0.67 t ha-1 yr-1 for the sub-watershed. The LISEM model was able to reproduce adequately the peak flow and direct runoff for the six events used for calibration. On the other hand, the peak time and shape of the hydrograph did not have adequate fit. / O efeito das florestas de eucalipto nos processos hidrossedimentológicos tem sido pouco explorado pela comunidade científica, o que resulta em banco de dados contendo informações incipientes relacionadas a esses efeitos, principalmente na escala de bacias. O monitoramento e a modelagem matemática são reconhecidos como eficientes ferramentas científicas para suprir a carência de informações, principalmente na gestão dos recursos naturais, na representação e na predição desses processos. Nesse sentido, objetivou-se com este estudo, descrever os dados do monitoramento, avaliar os efeitos dos cultivos de eucalipto nos processos hidrossedimentológicos, calibrar os parâmetros de entrada e verificar o potencial de aplicação do modelo Limburg Soil Erosion Model (LISEM) na representação dos processos hidrológicos de bacias hidrográficas embutidas, com cobertura florestal. O estudo foi desenvolvido em duas bacias hidrográficas florestais situadas em Eldorado do Sul RS, sendo que a bacia possui área de drenagem de 94,46 ha e a sub-bacia, que se encontra à montante e embutida em relação à bacia, possui área de drenagem de 38,86 ha. O monitoramento hidrossedimentométrico teve início em fevereiro de 2011 e foi realizado no exutório das bacias, em duas seções automáticas, compostas de linígrafos, turbidímetros e pluviógrafos. O presente trabalho contemplou o monitoramento durante um período de seis meses, de 16/02/2011 a 15/08/2011. Os resultados do monitoramento demonstram que os períodos com maior volume de precipitação apresentaram aumento significativo nos picos de vazão em relação aos intervalos mais secos, assim como aumento na concentração de sedimentos em suspensão, para a bacia e para a subbacia. Os eventos com maior intensidade máxima de precipitação demonstraram que a pequena área de drenagem e o relevo mais acentuado da sub-bacia geraram respostas rápidas na vazão e concentração de sedimentos. Para a bacia hidrográfica, na maioria dos eventos, ocorreu amortização da onda de cheia com hidrogramas menos íngremes e ocorrência após o pico de vazão da sub-bacia. A produção de sedimentos foi de 38,41 e 33,65 Mg km-2, durante os seis meses de monitoramento para a bacia e para a sub-bacia, respectivamente. O modelo LISEM foi calibrado a partir de seis eventos de chuva. Os parâmetros de entrada utilizados para o modelo foram obtidos por meio de levantamentos realizados na bacia e de dados da literatura. Para avaliar a capacidade do modelo em representar os processos hidrológicos, foram utilizados hidrogramas medidos no exutório da bacia. A análise estatística aplicada foi o teste BIAS (Erro (%)) para os parâmetros vazão de pico, escoamento superficial direto e tempo de pico. Para avaliar a eficiência do modelo em reproduzir adequadamente o formato dos hidrogramas, foi utilizado o Coeficiente de eficiência Nash-Sutcliffe (COE) para os seis eventos utilizados na calibração. O modelo LISEM foi capaz de reproduzir adequadamente a vazão de pico e o escoamento superficial direto para os seis eventos utilizados na calibração, indicado pelos baixos erros percentuais. Por outro lado, o tempo de pico e a forma do hidrograma não apresentaram ajuste adequado, indicado pelos elevados erros e valores negativos para o erro e para o COE, respectivamente.

As relações entre tectônica e sedimentação são fatores primordiais na compreensão geológica de sucessões sedimentares. Por sua vez, o estudo de depósitos fluviais pré-silurianos representa um desafio a esta área do conhecimento em consequência da ausência de interação entre rios e plantas terrestres que ocorre nos depósitos fluviais recentes. A Bacia do Camaquã (Ediacarano a Eocambriano) apresenta extensas exposições que possibilitam neste presente trabalho a discussão da sedimentação sob o ponto de vista de um modelo tectônico definido. Através da análise de fácies sedimentares e arquitetura deposicional, a caracterização da unidade estratigráfica basal do Grupo Guaritas (Eocambriano), a Formação Guarda Velha, um espesso pacote sedimentar de depósitos fluviais, levou à reconstituição das características do ambiente de sedimentação, considerando-se a influência da tectônica sin-deposicional e de fatores climáticos. É interpretado um estilo fluvial entrelaçado com grande variação de vazão, alta taxa de aporte sedimentar e grandes dimensões. Diversas estruturas de deformação sinsedimentares de reologia dúctil originadas por sismos são investigadas como indicadores da atividade tectônica sin-sedimentar e correlacionadas às informações de fácies sedimentares e elementos arquiteturais para caracterização do ambiente deposicional, revelando uma bacia com intensa atividade sísmica penecontemporânea. A caracterização dessas estruturas leva ao questionamento sobre o caráter efêmero do sistema fluvial proposto em trabalhos anteriores para a Formação Guarda Velha. Um importante evento reconhecido através da análise de estruturas rúpteis e responsável pela discordância angular entre os Grupos Santa Bárbara e Guaritas, é caracterizado por falhas transcorrentes e oblíquas geradas por compressão NE-SW. As evidências da intensa atividade sísmica sin-deposicional são correlacionadas ao evento regional distensivo com 3 NW-SE e posterior à compressão NE-SW, atribuído ao evento de subisidência responsável pela deposição do Grupo Guaritas. A Bacia do Camaquã apresentou também intensa atividade tectônica após a deposição do Supergrupo Camaquã, notadamente com eventos transcorrentes deformacionais, distintos dos eventos distensionais formadores da bacia. Notadamente foi reconhecido um evento de deformação transcorrente principal na região com direção principal de esforços WNW, estruturas de direção E-W com cinemática destral e estruturas de direção NNE apresentando cinemática sinistral. Este evento foi seguido então por uma distensão NW, que por sua vez precedeu um evento compressivo com direção principal de esforços NNE a N-S, responsável por estruturas com cinemática contrária à do evento transcorrente principal. Finalmente, foi reconhecido um evento de deformação com falhas predominantemente normais geradas por distensão NE, interpretado como de idade cretácea. Desta forma, as evidências coletadas no presente estudo da Formação Guarda Velha revelam intensa atividade sísmica sin-deposicional relacionada ao evento regional distensivo com 3 NW-SE e concomitante a deposição em planícies aluviais com predomínio de carga de fundo e grande variação de vazão, durante a subsidência inicial do rift continental eocambriano do Rio Grande do Sul. / The relationship between tectonics and sedimentation plays a primordial role in the understanding of sedimentary successions. On the other hand, the study of pre-Silurian fluvial deposits represents a challenge due to the lack of interaction between land plants and river systems which characterizes post-Silurian environments. The Camaquã Basin (Ediacaran to Eocambrian) presents extensive exposures allowing investigations of sedimentary environments under a well defined tectonic model. Through the analysis of sedimentary facies and depositional architecture, the geological characterization of the basal stratigraphic unit of the Guaritas Group (Eocambrian), the Guarda Velha Formation, a thick sedimentary strata composed of fluvial deposits, provided the recognition of the sedimentation environment, considering the influence of sin-depositional tectonics and climatic factors. A braided fluvial style with great discharge variation, high sedimentary load and large dimensions was identified. Many seismically triggered ductile sin-sedimentary deformation structures found in the area bring information about the tectonic activity during sedimentation and were correlated using sedimentary facies and architectural elements analysis in order to describe the depositional environment, revealing a basin system dominated by an intense contemporaneous seismic activity. The characterization of these structures lead to a questioning about the until now accepted model of ephemerous channels for this fluvial system. An important event recognized by means of brittle structures analysis was identified as the origin of the angular unconformity between the Santa Bárbara Group and the Guaritas Group which is characterized by strike-slip and oblique faults generated by a NE-SW compression. The intense sin-depositional seismic activity evidences are correlated to an extensional event with 3 direction NW-SE, which post-dates the compression and was responsible for the subsidence of the Guaritas Group. The Camaquã Basin also records an intense tectonic activity that occurred after the deposition of the Camaquã Supergroup, markedly deformational strike-slip events. The most important event recognized on the studied region had a mean WNW stress direction, with E-W structures showing right-slip kinematics and NNE structures presenting left-slip kinematics. Following this event a NW extension followed by a NNE to N-S compression were recognized, the late showing structures with reverse kinematics to the mean strike-slip event. At last, a NE extension event originated normal faults dated of Cretaceous age. Conclusively, the Guarda Velha Formation here collected data reveals an intense seismic activity related to an extension event showing 3 NW-SE concomitantly to a bed load-dominated aluvial plain deposition and great discharge variability, during the initial subsidence of the Guaritas rift (Eocambrian) in southern Brazil.

Made available in DSpace on 2015-03-13T17:08:17Z (GMT). No. of bitstreams: 1 EduardoVQ.pdf: 3502040 bytes, checksum: cedac0b69deb4f4ec6d96c08f23f3160 (MD5) Previous issue date: 2008-12-15 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The study carried out in the environment of Maracaja? reef an S?o Roque channel, had as main objective to analyze the characteristics of sediments active locally expressed in the grains, through collections of sediments in the field, technical processing and data analyzes of sediments. Data processing were made on three main aspects: biotic composition, concentration of calcium carbonate and particle size of the sediment. Differences between the sediments of the reefs and channel were observed. It was emphasized the contribution of algae limestone in the production of carbonate, with some influence of foraminifera near the coast. The particle size distribution presented significant results for the understanding of locally sedimentary deposits. The results showed an environment of carbonate, with predominance of algae limestone, associated to unconsolidated sediments with gross granularity, besides the presence of rhodoliths in all samples.The fragmentation of biotic components and the prevalence of elliptical rhodoliths with little or no branch, indicate an environment of high energy hydrodynamics. This work is a further contribution to the understanding of sedimentology active locally in reef environments, in particular the of Maracaja? reef, by virtue of their complex ecosystem composed of a diversity of wild fauna and flora that still little studied in Brazil comparing to accelerated growth of teeth extractions and usufructs of natural resources causing often irreversible impacts to the environment / O estudo realizado teve como principal objetivo analisar as caracter?sticas dos sedimentos superficiais de fundo, atuantes localmente, no complexo recifal de Maracaja? e no canal de S?o R?que, sob diferentes aspectos: composi??o biog?nica, concentra??o de carbonato de c?lcio e granulometria do sedimento. Os resultados apresentaram as varia??es no sedimento superf?cial do fundo marinho quanto ? Biof?cies, An?lise Granulom?trica, Classifica??o Faciol?gica e Classifica??o de Rod?litos. Observou-se claramente diferentes padr?es sedimentol?gicos existentes nos recifes e no canal localizado entre os recifes e a costa, refletido em todos os par?metros levantados, revelando um ambiente carbon?tico, com predom?nio de algas calc?rias, associadas a um substrato inconsolidado com granula??o grossa. Enfatiza-se a contribui??o das algas calc?rias na produ??o de sedimentos carbon?ticos, com alguma influ?ncia de foramin?feros pr?ximos ? costa. A distribui??o granulom?trica apresentou resultados importantes na classifica??o dos sedimentos. Os sedimentos de tamanho m?dio se restringiram no canal numa ?rea protegida pelos recifes, enquanto que o sedimento com granula??o grossa se distribuiu no restante da ?rea, cobrindo parte da crista e toda regi?o frontal do recife, al?m de uma regi?o mais ao sul do canal. Rod?litos el?pticos se distribuiram em quase toda ?rea, excluindo apenas uma regi?o ao sul do canal e protegido pelos recifes com predom?nio de rod?litos discoidais. O predom?nio de rod?litos el?pticos com pouca ou nenhuma ramifica??o permite inferir um ambiente de alta energia hidrodin?mica, e a presen?a de rod?litos discoidais exclusivamente nos pontos ao norte do canal de S?o Roque e protegidos pelos Recifes possivelmente delimita uma ?rea de menor hidrodin?mica. O presente trabalho constitui mais uma contribui??o para o entendimento das caracter?sticas sedimentol?gicas atuantes localmente nos ambientes recifais, em especial os Parrachos de Maracaja?, em virtude de seu complexo ecossistema composto por uma diversidade de fauna e flora, ainda pouco estudadas no Brasil, contrapondo ao crescimento acelerado de extra??es e usufrutos dos recursos naturais causando impactos muitas vezes irrevers?veis ao meio ambiente

Currently, most of the giant fields of oil reservoirs consist of carbonate rocks, and these holds more than 50% of world reserves of this energy resource, thus becoming the target of major importance study the oil industry and consequently, to the academy, where are trained professionals to work in the sector. In Sergipe-Alagoas basin, Riachuelo Formation is characterized by mixed sedimentation, consisting of siliciclastics sediments, coming from the continent, and carbonate sediments of marine origin. These last are the constituents of Maruim Member and correspond to the object of study of this dissertation. In this study, we analyzed in detail four carbonate outcrops, located in the regions of Laranjeiras and Maruim where the sedimentological and stratigraphic analysis took place in order to characterize the vertical succession of the deposits within a stratigraphic framework generated in response to relative changes in sea level. Deposits present in outcrops correspond to a clastic carbonate sedimentation occurred in an environment of inner ramp, in a carbonate homoclinal ramp model. The sedimentary environments are dominated by "not skeletal" grains essentially peloids and oncoids with subordinated ooids and reworked bioclasts. The main bioclasts identified correspond to groups of molluscs, echinoderms and solenoporaceans .red algae In total, 28 lithofacies were defined for the studied outcrops, and the same were individualized by outcrop due to substantial differences in the components identified. By 1D stratigraphic analysis were identified 15 transgressive-regressive cycles throughout the studied section. The analysis of lithofacies characterized stacking patterns that show changes barriers systems over time as a result of variations in the relative sea level, where the two basal outcrops would constitute the top of a depositional sequence and the two top outcrops corresponds to another depositional sequence. It was possible to identify that the deposits of the lower sequence were deposited in a highstand system tract and the top sequence shows sediments deposited in a transgressive system tract, correspondig to the intermediate outcrop and, highstand system tract, which corresponds to the top outcrop. / Atualmente, a maioria dos campos gigantes de produção de hidrocarbonetos são constituídos por reservatórios de rochas carbonáticas, e estas detém mais de 50% das reservas mundiais desse recurso energético, tornando-se assim alvo de principal importância de estudo para a indústria do petróleo e, conseqüentemente, para a academia, onde são formados profissionais para atuar no setor. Na bacia Sergipe- Alagoas, a Formação Riachuelo é caracterizada por sedimentação mista, sendo composta por sedimentos siliclásticos, provenientes do continente, e sedimentos carbonáticos, de origem marinha. Estes ultimos, são constituintes do Membro Maruim e correspondem ao objeto de estudo desta dissertação de mestrado. Neste trabalho foram analisados detalhadamente quatro afloramentos de sedimentos carbonáticos, localizados nos municípios de Laranjeiras e Maruim, onde foram realizadas análises sedimentológicas e estratigráficas com o objetivo de caracterizar a sucessão vertical dos mesmos dentro de um arcabouço estratigráfico gerado como resposta a variações relativas do nível do mar. Os depósitos presentes nos afloramentos correspondem a uma sedimentação carbonática clástica que ocorreu em ambiente de rampa interna, no modelo de rampa carbonática homoclinal. Os ambientes sedimentares são dominados por grãos não esqueletais , essencialmente peloides e oncoides, com ooides subordinados e os bioclastos apresentam-se retrabalhados. Os principais bioclastos identificados correspondem aos grupos dos moluscos, equinodermes e algas vermelhas solenoporáceas. No total foram definidas 28 litofácies para os afloramentos estudados, sendo que as mesmas foram individualizadas por afloramento, devido a diferenças substânciais nos componentes identificados. Através da análise estratigráfica 1D foi possível identificar 15 ciclos trannsgressivo-regressivos em toda a seção estudada. A análise do empilhamento das litofácies caracterizadas mostram a evolução de sistemas barreiras ao longo do tempo, como resultado de variações do nível relativo do mar, onde os dois afloramentos basais estariam numa sequência deposicional inferior e os dois afloramentos de topo numa outra sequência deposicional. Foi possível identificar que os depósitos da sequência inferior foram depositados em trato de sistema de mar alto. A sequência superior apresenta já um trato de sistema transgressivo, correspondente ao afloramento intermediário, sobreposto por um trato de sistema de mar alto, o qual corresponde ao afloramento de topo.

L’étude de l’Ordovicien de l’Anti-Atlas oriental s’intègre dans un vaste projet celui de l’étude de la plate-forme nord-gondwanienne qui se caractérise par une sédimentation essentiellement silico-clastique avec une polarité globale qui est Sud-Nord. Cette étude, basée sur les principes de la stratigraphie séquentielle et de la sédimentologie, met en évidence l’existence de deux systèmes de dépôts sur la marge nord-ouest de la plate-forme nord-gondwanienne. A l’Ordovicien moyen et supérieur préglaciaire, à l’emplacement de l’Anti-Atlas oriental, coexistent un système deltaïque (lato sensu) et un système de plate-forme dominée par l’action de la houle et des tempêtes. Ces deux systèmes de dépôts ont une certaine répartition spatiale et temporelle. Le système deltaïque domine le nord-est de l’Anti-Atlas oriental où il prend naissance à l’Est du Tafilalt. Ce système deltaïque est à dominance fluviale, il est actif lors des périodes de régression. Pendant les maximums de régression, il incise le haut du plateau continental en créant d’importantes structures érosives dont le remplissage se fait par des faciès de haute énergie à composante unidirectionnelle. Le système de haute énergie influencé par l’action de la houle et des tempêtes domine le secteur sud de l’Anti-Atlas oriental et se répand au nord au cours des périodes transgressives. La sédimentation durant l’Ordovicien préglaciaire sur la marge nord-ouest du Gondwana a un contrôle tectonique et eustatique avec une polarité des systèmes, dans le Tafilalt-Maïder qui diffère de celle de la plate-forme nord-gondwanienne et est Nord Est-Sud-Ouest. Le profil de dépôt est quasi plat où les clinoformes sont de faible amplitudes et se dessinent à l’intérieur des séquences de 3ème ordre. Le Darriwillien se caractérise par des une subsidence différentielle entre le domaine nord et le domaine sud en raison d’une tectonique active. Alors que, le Sandbien-Katien montre un taux de subsidence faible (x 10m/Ma) en adéquation avec un contexte intracratonique. L’Hirnantien dans le Tafilalt, décrit comme étant discontinu voir absent, est très bien développé il se caractérise par la mise en place d’une sédimentation mixte gréso-carbonaté à bryozoaires de type littoral et ce à l’extrémité oriental de l’Anti-Atlas et d’une épaisse série conglomératique (conglomérat d’Amessoui et d’Imzizoui) et flyschoïde qui peut atteindre les 500m dans le Tafilalt. / The Ordovician Anti-Atlas study is part of a larger project of comprehension the sedimentary system of the north Gondwana platform. This sedimentary area is characterized by essentially terrigenous sediments that come from the south from de West African Craton. This study based on sequence stratigraphy and sedimentology principles highlights two systems juxtaposed during the preglacial Ordovician period (before hirnantian). These two deposits systems have a spatial and temporal distribution. One deltaic occurs on north-eastern Tafilalt (east Anti-Atlas) and widespread during regressive periods. The second is storm dominate system which is developed in the south-western part of eastern Anti-Atlas and transgressive periods. The deltaic system is river dominant, it incise the continental shelf by creating a significant erosive structure whose filling is done by high energy facies unidirectional component. During the Ordovician, the sedimentation was controlled by tectonic and eustatic variation. The polarity of the system in the Tafilalt-Maïder is different from that of the northern Gondwana platform and it is given North East- South West. The Darriwilian characterized by differential subsidence, between the north and the south of the oriental Anti-Atlas, due to active tectonics, while, Sandbian-Katian show a low subsidence rates (x10m/Ma) in the line of intracratonic basin. The Hirnantian, in Tafilalt, is largely well developed and characterized by huge conglomeratic series, flysch deposits and Bryozoan limestone at the northeastern.

Seagrass meadows offshore Ras Ghanada, as elsewhere, are an important component to the ecosystem providing numerous benefits to both aquatic and human life. This work focused on mapping the spatial and temporal distribution of seagrass meadows offshore Ras Ghanada using aerial photography acquired in 1996 and high-resolution satellite images captured in 2006 and 2012. The movements of sand shoals were also tracked, so as to further explain the dynamics of this ecosystem, as it is the area between the shoal crests that hosts the best developed seagrass meadows. The natural limiting factor for seagrass on the Ras Ghanada coastal shelf seems to be the fact that they cannot inhabit the (mobile) crests of the sand shoals, but rather, are restricted to the (more stable) sands of the shoal troughs. In the considered time period, both sand shoals and seagrass meadows migrated predominantly in a southeastern direction. The changes of seagrass that occurred in this study occurred on a fairly rapid timescale, in such that they were able to come back when there was disturbance as long as they had available habitat to move into. Furthermore, although seagrass cover declined by 3.4% from 1996 – 2012, there was a greater increase than decline in the areal coverage of seagrass post-Khalifa port construction in 2010. If sediments offshore Ras Ghanada can remain stable and the waters are not polluted by further construction, seagrasses should continue to thrive in the future.

La paléosismologie sous-marine est une discipline basée sur la reconnaissance et l’étude des séismes passés à partir d’archives sous-marines tels que les dépôts turbiditiques. Cette discipline, mise en place à partir des années 1990 au niveau de la zone des Cascades (côte Nord-Ouest des Etats-Unis) a, par la suite, été développée dans d’autres mers, océans et lacs.La mer Ionienne est un petit bassin étroit et profond localisé au centre de la mer Méditerranée bordé par deux prismes d’accrétions, la ride Méditerranéenne à l’Est et le prisme Calabrais à l’Ouest. L’Est de la Sicile et la région Calabre ont été soumises à plusieurs reprises, à des séismes historiques destructeurs, parfois suivit de tsunamis, comme par exemple le séisme de 1693 AD à Catane (magnitude 7,4) ou celui de 1908 à Messine (de magnitude 7,1). Ce dernier séisme a déclenché des glissements sous-marins et des courants de turbidités qui sont à l’origine de rupture de câbles sous-marins. Au niveau de la plaine abyssale Ionienne, un autre type de dépôt est décrit à partir des données sismiques, caractérisées par une couche transparente. Ces méga-dépôts de plusieurs mètres d'épaisseur, sont associés à de grands évènements extrêmes (séismes, tsunamis, éruptions volcaniques) et sont appelés mégaturbidites ou homogénites.Les études réalisées durant cette thèse, se focalisent sur l’interprétation des turbidites et des méga-dépôts observés grâce à un nouveau jeu de données localisé dans la partie Ouest du prisme Calabrais et récolté durant la mission CIRCEE en octobre 2013. La compréhension des sources et des origines de ces dépôts est primordiale pour l’interprétation de l’enregistrement paléosismologique de la région. L’objectif général étant d'améliorer notre compréhension de la chronologie et l'origine des grands événements catastrophiques qui ont affecté la région.Ces nouvelles données, qui incluent des carottes sédimentaires, de la bathymétrie et des profils sismiques (Chirp et HR), ont permis dans un premier temps de revisiter l’interprétation des processus sédimentaires et l’origine des mégadépôts et en particulier, du dépôt le plus récent appelé « dépôt d’Augias ». Ce dernier, dont l’épaisseur atteint les douze mètres en plaine abyssale Ionienne, serait lié au séisme et tsunami de Crête en 365 AD. A partir de sa description sédimentologique et des diverses mesures réalisées, trois types de faciès ont été identifiés (faciès « mégaturbidite », « homogénite » et « turbidite sableuse épaisse ») et qui sont les résultats de différents processus sédimentaires. La deuxième partie de cette thèse représente une étude paléosismologique des derniers 25 ka en mer Ionienne basée sur des modèles d’âges. La période de temps recouverte par les carottes englobe la fin de la dernière période glaciaire, la remontée du niveau marin et la période historique. Cela a permis de différencier les dépôts de la période historique où l’évènement déclencheur principal des courants de turbidités est le séisme. Par contre pour les dépôts antérieurs il a pu être démontré que les variations eustatiques et climatiques ont un fort impact sur la fréquence de turbidites. / Submarine paleoseismology is a discipline based on the recognition and study of past earthquakes from submarine records such as turbidite deposits. This discipline was initially developed in the 1990’s in the Cascadia region (north-west coast of the USA), and was subsequently, applied to other seas, oceans and lakes. The Ionian Sea is a small, narrow and deep basin located in the central Mediterranean Sea and bounded by two accretionary wedges, the Mediterranean Ridge to the east and the Calabrian wedge to the west. Eastern Sicily and Calabria region have been repeatedly struck by destructive historical earthquakes, sometime followed by tsunamis, such as the 1693 AD earthquake in Catania (magnitude to 7.4) or the 1908 AD earthquake in Messina (magnitude to 7.1).This latter earthquake triggered a submarine landslide and turbidity currents that ruptured submarine cables. In the Ionian abyssal plain, another type of deposit is observed in seismic data, expressed as successive transparent layers. These mega-deposits, several meters in thickness, are associated with large extreme events (earthquakes, volcanic eruptions, tsunamis) and are named megaturbidites or homogenites.The research conducted during this thesis focuses on the interpretation of turbidites and mega-deposits, observed by a new data set located in the western part of the Calabrian prism and acquired during the CIRCEE cruise, in October 2013. The understanding of the sources and the origin of these deposits is essential for the interpretation of paleoseismological record in the region. The general objective is to improve our understanding of the chronology and origin of major catastrophic events that have affected the region. These new data, include piston cores, bathymetry and seismic profiles (Chirp and HR), and allow us, for first time, to revisit the interpretation of sedimentary processes and origin of mega deposits and in particular the most recent deposit named "Augias deposit" This deposit, whose thickness reaches 12 meters in Ionian abyssal plain, can be linked to the 365 AD Crete earthquake and associated tsunami. Based on the sedimentological description and different measurements that were conducted, three type facies could be identified ("megaturbidite", "homogenite" and "thick sandy turbidite") that are the expressions of different sedimentary processes.The second part of this thesis represents a paleoseismological study of the last 25 ka in Ionian Sea based on age models. The time period covered by the cores includes the end of the last glacial period, the sea level rise and the historical period. This allowed identification of deposits from the historical period whose main trigger of turbidity currents are earthquakes. On the other hand for earlier deposits, eustatic and climatic variations are shown to have a stong effect on the frequency of turbidites.

Les courants de turbidité dans les canyons sous-marins contribuent largement au transfert sédimentaire à travers des marges continentales. L’étude géologique des canyons sous-marins et des systèmes turbiditiques associés a permis des avancées fondamentales dans la compréhension de l’évolution des courants de turbidité.Ces études sont cependant limitées à des interprétations a posteriori, basées sur la répartition des dépôts et des évidences morphologiques. Cette thèse vise à l’application de la modélisation numérique des courants de turbidité, sur la base des processus physiques, à deux canyons sous-marins de la côte Méditerranée Occidentale.Des courants de turbidité liés au chalutage de fond sont modélisés dans le canyon de La Fonera. Les résultats du modèle permettent de spatialiser ce transport; ainsi le modèle peut être un point de départ pour l’identification de zones de pêche au chalut avec un moindre impact. L’absence d’un plateau continental au niveau de Nice a permis une alimentation continue du système turbiditique du Var indépendamment des variations du niveau marin. Ainsi ce système s’avère un laboratoire naturel pour l’étude du contrôle climatique sur l’activité turbiditique. L’influence des forces de Coriolis dans l’évolution spatiale des courants de turbidité et dans la construction de la Ride sédimentaire du Var est modélisée et mise en évidence pour la première fois.La modélisation numérique des courants de turbidité ne peut pas fournir à présent des résultats de qualité prédictive du fait de la quantité limitée d’information disponible pour établir les conditions initiales de l’écoulement qui impactent largement son évolution et dépôts. Malgré ce fait, la modélisation numérique permet d’élargir les interprétations du fonctionnement sédimentaire des canyons étudiés, d’identifier les chemins empruntés par les écoulements et leur dépôt final et de mieux préparer des cibles (mouillages et carottage) lors des campagnes à la mer. / Turbidity currents in submarine canyons are the main contribution for sediment transfer across the continental margins. Geological studies of submarine canyons and associated turbiditic systems for more than 30 years led to an extraordinary breakthrough in the understanding of how turbidite systems evolve. However, these studies remain limited to a posteriori interpretations, based on the distribution of deposits and morphological evidences. The overarching aim of this thesis is to apply a 2DH process-based model to simulate large-scale turbidity currents on two different submarine canyons in the western Mediterranean coast.The work in La Fonera canyon, in the Catalan margin, focuses on the modelling of sediment transport and accumulation resulting from trawling activities on the canyon flanks. The numerical process-based provides a 3D visualization of potential trawling impacts on sediment dynamics. The study represents a starting point for the assessment of the sedimentary impact of bottom trawling in deep continental margins. The present work can help in the identification of trawling areas with lesser impacts. The Var Sedimentary System, located in the vicinity of Nice (France), is connected to the Var River during both low and high-stands and it can be considered as a natural laboratory for the study of the climatic control on the turbiditic activity. The influence of Coriolis forces on the spatial evolution of the hyperpycnal flows and hence in the construction of the Var Sedimentary Ridge (VSR) is evidenced and supported for the first time.The major drawback is the limited amount of information for the necessary initial and boundary conditions; hence modelling results might not be of predictive quality. However, modelling results provide a full-scale vision of the system allowing the identification of sediment pathways and deposition areas on the basis of physical processes and enlarge the present knowledge of the canyons studied. The results obtained may help in the identification of strategic mooring and coring sites to further advance the state of our knowledge on sediment dynamics of the different cases studies.

The hallmark of oceanic anoxic event 1a (OAE1a) (early Aptian ~125 Ma) corresponds to worldwide deposition of black shales with total organic carbon (TOC) content > 2% and a d13C positive excursion up to ~5‰. OAE1a has been related to large igneous province volcanism and dissociation of methane hydrates during the Lower Cretaceous. However, the occurrence of atypical, coeval and diachronous organic-rich deposits associated with OAE1a, which are also characterized by positive spikes of the d13C in epicontinental to restricted marine environments of the Tethys Ocean, indicates localized responses decoupled from complex global forcing factors. The present research is a high-resolution, multiproxy approach to assess the paleoenvironmental conditions that led to enhanced carbon sequestration from the late Barremian to the middle Aptian in a restricted, Tethyan marginal basin prior to and during OAE1a. I studied the lower 240 m of the El Pui section, Organyà Basin, Spanish Pyrenees. The basin developed as the result of extensional tectonism linked to the opening of the Atlantic Ocean. At the field scale the section consists of a sequence of alternating beds of cm – m-scale, medium-gray to grayish-black limestones and marlstones with TOC up to ~4%. The results indicate that the lowest 85 m of the section, from latest Barremian –earliest Aptian, characterize a deepening phase of the basin concomitant with sustained riverine flux and intensified primary productivity. These changes induced a shift in the sedimentation pattern and decreased the oxygen levels in the water column through organic matter respiration and limited ventilation of the basin. The upper 155 m comprising the earliest – late-early Aptian document the occurrence of OAE1a and its associated geochemical signatures (TOC up to 3% and a positive shift in d13C of ~5‰). However, a low enrichment of redox-sensitive trace elements indicates that the basin did not achieve anoxic conditions. The results also suggest that a shallower-phase of the basin, coeval with platform progradation, may have increased ventilation of the basin at the same time that heightened sedimentation rates and additional input of organic matter from terrestrial sources increased the burial and preservation rate of TOC in the sediment.

Cette thèse propose une méthodologie pour caractériser et intégrer les distributions minéralogiques des dépôts de l’Eocène Inférieur du Bassin de Graus-Tremp-Ainsa dans un cadre séquentiel reconstruit à haute résolution. Le couplage des approches stratigraphiques et géochimiques/minéralogiques permet d’évaluer la part des forçages tectoniques, climatiques, eustatiques et diagénétiques sur l’enregistrement sédimentaire et minéralogique du bassin. La caractérisation de la minéralogie repose sur un calcul automatisé utilisant la géochimie multi-élémentaire et calibré ponctuellement par les outils d’analyse minéralogique conventionnels (pétrographie, DRX, Qemscan, microsonde). Elle a l’avantage de permettre de traiter les évolutions minéralogiques à l’échelle du bassin et sur l’ensemble des lithologies rencontrées. Après avoir évalué les effets de la diagenèse, du tri hydrodynamique et reconstitué la composition minéralogique primaire des sédiments, nous caractérisons les différentes sources.Nous précisons l’évolution de la tectonique (avec un pas de temps de l’ordre du million d’années) et ses effets sur l’architecture sédimentaire et la minéralogie des dépôts. Ceux-ci montrent un contrôle spatial de la diagenèse et des changements spatio-temporels des sources, liés à une compétition entre la tectonique intrabassinale (activité des chevauchements locaux) et régionale (surrection de l’orogène et subsidence flexurale). Nous montrons également que l’impact de la tectonique est modulé par des anomalies climatiques ponctuelles de l’ordre de la centaine de milliers d’années (PETM, ELMO, X-Event), que nous avons reconnues par un changement marqué des environnements de dépôt et des cortèges argileux.Deux grands épisodes régionaux caractérisent l’évolution du Bassin piggyback de Graus-Tremp-Ainsa. Le stade précoce, d’âge Ilerdien-Cuisien Inférieur, est marqué par le passage d’une rampe carbonatée mixte à des systèmes deltaïques alimentés depuis l’orogène pyrénéen par des contributions plutoniques. Cet ensemble passe ensuite à un vaste système fluvio-deltaïque au Cuisien Inférieur / Moyen, montrant l’apport de lithiques carbonatés et silicoclastiques qui coïncide avec l’émergence des nappes sédimentaires. La fin de cet épisode est marquée par la propagation du chevauchement du Montsec et de ses rampes latérales, provoquant un partitionnement du bassin, induisant la surrection du Bassin de Graus-Tremp et une forte subsidence du Bassin d’Ainsa. Ce contraste de subsidence est souligné par un partitionnement de la diagenèse, avec une kaolinisation des formations supérieures du Bassin de Graus-Tremp, liée à la percolation d’eaux météoriques, et, dans le Bassin d’Ainsa, une albitisation des grès couplée à une illitisation des smectites dans les lutites, liée à une diagenèse d’enfouissement plus marquée. / We develop here a methodology to integrate the mineralogical record into a high resolution sequence stratigraphic framework realized in the Early Eocene Graus-Tremp-Ainsa Basin. Coupling stratigraphic with geochemical and mineralogical approaches allows us to unravel the effects of tectonics, climate, eustasy and diagenesis on basin architecture and mineralogy. An automated computed mineralogy is derived from whole-rock geochemical data, and calibrated against direct mineral quantifications (petrography, DRX, Qemscan, microprobe). It provides a basinscale view of mineral distribution, irrespective of the lithology. Diagenetic overprint and hydrodynamic sorting effects are evaluated first, then primary mineral distributions are reconstructed and ascribed to different types of sediment sources.We show that, at the million-year timescale, tectonics shape the architecture and the mineralogy of the deposits. Spatially distributed diagenesis and temporal and spatial changes in sediment sources reflect the competing effects of intrabasinal tectonics (local thrust displacements) versus basinscale flexural subsidence linked to the orogen uplift and loading. Tectonically-driven changes are also sensitive to higher frequency (100 ky) anomalic climatic events (PETM, ELMO, X-EVENT) leaving a mineralogical signal in clay fractions and environment deposits succession.The basinscale evolution displays two contrasting stages. During the Ilerdian to the lower Cuisian, a mixed carbonate ramp evolves to a set of deltaic fans of Northern (Pyrenean orogen) provenance delivering plutonic-dominated materials. Then, during the lower/mid Cuisian, they are overprinted by a large fluvial and deltaic system bringing recycled carbonates and siliciclastics sourced in the emerging eastern to southern sedimentary thrust sheets. Later on, the propagation of the Montsec thrust and its lateral ramp decouples the uplifted Graus-Tremp basin from the strongly subsiding Ainsa basin. These different subsidizing schemes are underlined diagenetic overprints diverge, with an extensive kaolinisation of the uppermost units in the Graus-Tremp Basin driven by meteoric fluid circulations, and a severe albitisation of sandstones in the Ainsa basin, coupled with the illitisation of smectites in the lutites and caused by deep basinal fluids.