Les rapports isotopiques en Sr et Pb dans la fraction terrigène de sédiments marins nous permettent d'identifier les variations spatiales actuelles des apports sédimentaires autour de Taiwan : nous mettons en évidence l'augmentation progressive des apports de Taiwan (de 60% au Sud à 100% à la hauteur de Taiwan). Ces apports sont ensuite, au Nord-Est de l'île, dilués (50-60%) par du matériel de type Loess et particulaire du Fleuve Yangtze. De plus, les analyses des isotopes du Zn effectuées sur des échantillons représentatifs de Taiwan indiquent un enrichissement en isotopes lourds, qui est également observé dans la fraction silicatée de sédiments marins identifiés par les signatures isotopiques Sr-Pb comme provenant essentiellement de l'érosion de cette Chaîne.<br />A l'échelle des derniers 35ka, d'importantes variations isotopiques en Sr-Pb (terrigène) et en Cu-Zn (carbonate) sont enregistrées dans les échantillons du forage ODP 1202D (Bassin d'Okinawa). Les isotopes du Sr et du Pb mettent en évidence une augmentation des apports lœssiques durant la période du Younger Dryas : cette augmentation est reliée à une intensification de la mousson d'hiver, engendrant des vents plus forts provenant du continent asiatique. Parallèlement, les fractionnements isotopiques importants du Cu et du Zn enregistrés depuis 6.9ka seraient liés à l'incorporation préférentielle des isotopes légers par l'activité biologique dans la zone euphotique. Ainsi, les faibles fractionnements isotopiques mesurés dans les échantillons du Younger Dryas seraient dus à un mélange entre les eaux de surfaces et les eaux plus profondes du fait de l'intensification des vents, provoquant ainsi une homogénéisation isotopique.

Ce travail de thèse est une étude des relations entre les fluides et les déformations dans le prisme d'accrétion de Nankai. Ce travail s'appuie entre autres sur les résultats des deux campagnes de forage récentes Leg Ocean Drilling Program 190 et 196. L'étude des relations entre la mise en place de déformations et les circulations de fluides est plus particulièrement centrée sur le décollement, au front du prisme. Nous présentons d'abord une estimation de la surpression de fluides dans les formations sédimentaires autour du décollement à partir de l'étude des profils de porosité. Ceci nous permet de montrer que le décollement n'est pas une barrière pour les surpressions de fluides et de proposer que le saut de porosité au niveau du décollement résulte d'une discontinuité de l'état de contrainte au travers du décollement. Nous étudions ensuite l'anomalie de chlorinité présente dans les fluides interstitiels de la formation dans laquelle se développe le décollement. Nous montrons que l'on peut rendre compte de cette anomalie en ne considérant que les processus de compaction des argiles et de transformation des smectites en illites. Par ailleurs, nous avons mesuré la perméabilité d'échantillons du prisme sous contraintes avec une presse triaxiale, nécessaire pour la réalisation de simulations numériques de circulation de fluides dans le prisme. Les perméabilités mesurées sont comprises entre 10-18 et 10-19 m2. La rupture des échantillons entraîne une augmentation de la perméabilité à faible pression de confinement mais pas de modification de la perméabilité à une pression de confinement correspondant à la contrainte verticale de l'échantillon en place. Dans une autre partie, nous comparons les mesures de porosité des échantillons et la porosité calculée dans la formation in situ à partir d'un log de résistivité. Cela nous permet de montrer que la zone de décollement présente à la fois des déformations compactantes et dilatantes. Nous estimons la dilatance de fracture du décollement entre 2 et 8 %, et nous proposons un modèle incrémentiel de propagation du décollement par couplage entre des transferts transitoires de surpression de fluides et la déformation mécanique en tête de décollement. Enfin, nous présentons une étude numérique en 2D de la propagation d'ondes de surpression de fluide le long du décollement en supposant que la perméabilité dépend de la pression effective. Les ondes peuvent se propager rapidement le long du décollement. Le couplage hydromécanique entre l'état de contrainte dans la séquence subduite et la pression de fluide dans le décollement est proposés comme un mécanisme possible d'initiation et d'entretien de l'onde de pression.

Comprehensive knowledge and information about the static and dynamic behaviour of machine tools, cutting processes and their interaction is essential for machining system design, simulation, control and robust operation in safe conditions. The very complex system of a machine tool, fixture and cutting tools during the machining of a part is almost impossible to model analytically with sufficient accuracy. In combination with increasing demands for precision and efficiency in machining call for new control strategies for machining systems. These strategies need to be based on the identification of the static and dynamic stability under both the operational and off-operational conditions. To achieve this it is necessary to monitor and analyze the real system at the factory floor in full production. Design information and operational data can then be linked together to make a realistic digital model of a given machining system. Information from such a model can then be used as input in machining simulation software to find the root causes of instability. The work presented in this thesis deals with the static and dynamic capability of machining systems. The main focus is on the operational stability of the machining system and structural behaviour of only the machine tool, as well. When the accuracy of a machining system is measured by traditional techniques, effects from neither the static stiffness nor the cutting process are taken into account. This limits the applicability of these techniques for realistic evaluation of a machining system’s accuracy. The research presented in this thesis takes a different approach by introducing the concept of operational dynamic parameters. The concept of operational dynamic parameters entails an interaction between the structural elements of the machining systems and the process parameters. According to this concept, the absolute criterion of damping is used to evaluate the dynamic behaviour of a machining system. In contrast to the traditional theory, this methodology allows to determine the machining system's dynamic stability, in real time under operating conditions. This framework also includes an evaluation of the static deformations of a machine tool.  In this context, a novel concept of elastically linked system is introduced to account for the representation of the cutting force trough an elastic link that closes the force loop. In addition to the elastic link which behaves as a static element, a dynamic non-contact link has been introduced. The purpose is to study the non-linear effects introduced by variations of contact conditions in joints due to rotational speed. / QC 20111123

This study aims to unravel the ecological and evolutionary dynamics within the calcareous nannofossil communities at the Eocene/Oligocene (E/O) transition and during the Oligocene time when Cenozoic 'icehouse' conditions were established. The main question this study aims to answer is whether the changes in the nannofossil assemblages were controlled by intrinsic evolutionary trends or if the changes were controlled by environmental factors such as changes in temperature and nutrient availability in the surface water. These questions are addressed with detailed analyses of the taxonomy, biostratigraphy and fluctuations in abundance and diversity of calcareous nannofossil assemblages from a continuous latest Eocene through Oligocene sediment section from the ODP Site 1218 (8°53.38´N, 135°22.00´W), paleo-equatorial Pacific Ocean. An improved nannofossil taxonomy and biostratigraphy has been established. At the E/O transition, changes in the nannofossil preservation mimics changes in calcium carbonate content. A detailed investigation of late Eocene and Oligocene sediments yields age estimates for ten nannofossil bioevents. Morphometric studies of the Reticulofenestra umbilicus-R. hillae show that these cannot be subdivided into two different morphospecies. Based on different morphometry and stratigraphic ranges, the Oligocene Sphenolithus lineage appears to be the result of a combined anagenetic and cladogenetic evolution. A new nannolith species is described: Triquetrorhabdulus longus. High-resolution nannofossil data indicate changes in the composition, abundance and diversity of the mid-Oligocene assemblages. Intervals of high diversity index coincide with Oi-glaciation events. However, visual examination of the variations in abundance of nannofossil taxa do not appear to correlate with changes in either oxygen or carbon isotopes. This presumably indicates that a dynamic equilibrium did not exist between these Oligocene nannoplankton assemblages and changes in surface water temperature or productivity conditions. / Doctoral Thesis in Marine Geoscience at Stockholm University, Sweden 2009

The present work focused on the possible influence of the Pacific Decadal Oscillation (PDO) on the positioning and intensity of the Intertropical Convergence Zone (ITCZ) during its annual cycle over the Atlantic Ocean and its impact in the rainfall totals in the northern South American continent. For this purpose, the mean annual fields of outgoing longwave radiation (OLR), sea surface temperature (SST), omega (&#969;), meridional wind (V) and precipitation rate (P) of Reanalysis data sets (NCEP/NCAR) were analysed. In addition, observed rainfall monthly mean series (INMET and HIDROWEB), the University of Delawere (UDEL) rainfall, interpolated in a 0.5°x0.5° grid, and the PDO indices found in the NOAA/ESRL/PSD site were used to support the analyses. The results were visualized with applets available in the ESRL/PSD/NOAA s site as well as GrADS software. The records period 1948-2005 was divided into PDO cold phase (1948-1976), warm phase (1977- 1998) and current phase (1999-2005), which was used to verify the climate tendency of the last seven years. The results suggested that the ITCZ remained farther north of its mean position during the PDO cold phase. Apparently, the ascending branch of the Hadley Cell was displaced farther north and the descendent branch of the Walker Circulation positioned farther west of their normal positions. This pattern led to a rainfall reduction in parts of Amazonia. In the PDO cold phase, the normalized rainfall indices showed a more noticeable rainfall reduction (increase) western (eastern) of 52°W, in the State of Pará. In the PDO warm phase, opposite circulation patterns and higher climate variability were observed. The results suggested that the PDO, in general, modified the SST patterns in the Atlantic and, as a consequence, the positioning and intensity of the ITCZ. There are evidences that the PDO is experiencing a new cold phase. Thus, one expects that the ITCZ and the Amazonian rainfall present a similar behaviour of previous cold phase. Particular attention should be paid to the Brazilian States of Roraima and Maranhão, eastern Pará State and western Amazonas State, including Colombia, Venezuela e north-eastern Bolivia, that may experience a sensible rainfall reduction during the next 10 years. Another relevant result was relative to a possible enhancement of convection and rainfall over the southern Saharan region (Sahel), Africa, during the present PDO phase. It was noticed that it rained more in the region till 1975, when the SST anomalies of Equatorial Guinea Gulf were negative and the wind south component was stronger. These conditions seem to be returning. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / No presente trabalho dissertou-se sobre as possíveis influências da Oscilação Decadal do Pacífico (ODP) no posicionamento e intensidade da Zona de Convergência Intertropical (ZCIT) em seu ciclo anual sobre o Oceano Atlântico e seus impactos na precipitação do norte da América do Sul. Para tanto, foram utilizados os campos médios de radiação de ondas longas emergentes (ROLE), temperatura da superfície do mar (TSM), omega, vento meridional e precipitação, elaborados a partir do conjunto de dados de Reanalises do NCEP/NCAR, além de índices de ODP do ESRL/PSD/NOAA e séries temporais da precipitação média observada de postos pluviométricos (INMET and HIDROWEB) e a interpolada pela University of Delawere (UDEL) numa grade de 0,5°x0,5°. Os aplicativos disponíveis no site do ESRL/PSD/NOAA, bem como o GrADS, foram utilizados para visualizar os resultados das análises. O período de 1948 a 2005, correspondendo às fases fria (1948- 1976), quente (1977- 1998) e atual (1999- 2005) da ODP, foi tomado como base, este último tendo sido utilizado para verificar tendências climáticas contemporâneas. Os resultados indicaram que, durante a fase fria da ODP, a ZCIT esteve mais ao norte de sua posição climatológica. O ramo ascendente da célula de Hadley permaneceu mais deslocado para norte e o descendente da circulação de Walker mais deslocado para oeste. Essa configuração foi responsável pelo decréscimo da precipitação observado em parte da Amazônia. Os índices de precipitação padronizada (IPP) mostraram redução (aumento) mais acentuada da chuva a oeste (leste) de 52°W, no Estado do Pará. Durante a fase quente da ODP, foram observadas configurações opostas e maior variabilidade climática interanual. De maneira geral, as análises mostraram que a ODP mudou a configuração das TSM no Atlântico e influenciou o posicionamento e intensidade da ZCIT. Sugeriram, também, que a ODP parece estar experimentando sua nova fase fria. Com base nesses resultados, espera-se que a ZCIT e a precipitação, apresentem variabilidade semelhante à fase fria anterior. Dessa forma, particular atenção, deve ser atribuída a regiões dos Estados de Roraima, Oeste do Amazonas, leste do Pará e Maranhão, além da Colômbia, Venezuela e nordeste da Bolívia, que deverão sofrer redução em sua precipitação média nos próximos 10 a 15 anos. Outro resultado relevante diz respeito aumento da convecção e precipitação que poderá ocorrer no Sul do Deserto de Sahara (Sahel), África, ao longo da atual fase da ODP. Nessa região, foi notado que choveu mais até 1975, quando o Golfo da Guiné apresentou anomalias negativas de TSM e a componente sul do vento esteve mais forte.Aparentemente, essas condições estão retornando.

The aim of this study was to characterize the extreme events of rainfall in Eastern Amazon, to analyze on ocean-atmosphere conditions in global scale associated with intense occurrence periods of these events, to contribute for temporal variation comprehension of rainfall extreme events, as well as of determinant phenomena to its occurrence and to make further projections. For this purpose, Pluviometric Precipitation stations data from Brazilian National Institute for Meteorology (INMET) located in Belém, Breves, Altamira, Tucuruí and Marabá; and monthly data of precipitation from Delaware University (UDEL). In addition, available meteorological series at ESRL/PSD, particularly, sea surface temperature; u and v components; outgoing long wave radiation; atmospheric vertical movements; divergence fields; satellite images and oceanic and atmospheric climatic indices as Multidecadal Atlantic Oscillation, Pacific Decadal Oscillation (PDO), North Atlantic Oscillation, South Oscillation and Multivariated ENOS index. The methodology has included statistical techniques for rainfall analysis and behavior, as well as major phenomena that influence its annual regime, and events diagnostic as well. It was made class distribution of daily rainfall in Belém-PA, Eastern Amazon, and was clear that rainfall yearly total high values in that region were resulting from extreme events of rainfall that contributed, in average, with 37% from rain yearly total. These extreme events corresponded to 10% from total values of rainy days. There was a rising trend of these events in the last 10 years, attributed to upper troposphere cooling during that beginning of new PDO cold phase. Oceanic and atmospheric indices from Pacífic Ocean have shown to be a valuable tool for prediction of periods with extreme event occurrences. Trade winds, and mainly the sea surface temperature, were determinant factors for extreme events occurrence and development in Eastern Amazon, wavelets transform analysis has shown the energy and annual cycle present in precipitation regime of this region, as well as influence of high frequency phenomena as ENOS at rainy season of analyzed stations. Climate perspectives indicated that PDO is already in the new cold phase and its permanence is not known, much less its causes. However, if that new phase remain for more 15 to 20 years, certainly there will be rise in rainfall extreme events in Eastern Amazon, due to slowly cooling of upper troposphere, resulting in most vertical development of cumulonimbus clouds, responsible by high total values of rainfall. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo principal desse estudo foi fazer a caracterização dos eventos extremos de precipitação no leste da Amazônia, a análise das condições oceano-atmosfera em escala global associadas a períodos com intensa ocorrência desses eventos, contribuir para a compreensão da variação temporal dos eventos extremos de chuva, assim como dos fenômenos determinantes para a sua ocorrência e fazer projeções futuras. Para tal, foram utilizados dados de precipitação pluviométrica do Instituto Nacional de Meteorologia (INMET) das estações de Belém, Breves, Altamira, Tucuruí e Marabá e dados de precipitação mensal da Universidade de Delaware (UDEL). Em adição a isso, séries de variáveis meteorológicas disponíveis no ESRL/PSD, em especial, temperatura da superfície do mar, componentes u e v do vento, radiação de onda longa emergente, movimentos verticais atmosféricos, campos de divergência, imagens de satélite e índices climáticos oceânicos e atmosféricos, como a Oscilação Multidecadal do Atlântico, Oscilação Decadal do Pacifico (ODP), Oscilação do Atlântico Norte, Oscilação Sul e Índice Multivariado de ENOS. A metodologia incluiu técnicas estatísticas para análise e comportamento da precipitação, assim como os fenômenos que mais influenciam em seu regime anual, além dos diagnósticos dos eventos. Foi elaborada a distribuição de classes da precipitação diária em Belém (PA), leste da Amazônia, e ficou claro que os altos totais anuais de chuva nessa região foram decorrentes de eventos extremos de precipitação, que contribuíram, em média, com 37% do total anual de chuva. Esses eventos extremos representaram 10% dos totais de dias chuvosos. Houve uma tendência de aumento desses eventos nos últimos 10 anos, o que foi atribuído ao resfriamento da troposfera superior durante esse início da nova fase fria da ODP. Os índices oceânicos e atmosféricos do Oceano Pacifico, mostraram ser uma ferramenta valiosa para a previsão de períodos com ocorrência de eventos extremos. Os ventos Alísios, e principalmente a temperatura da superfície do mar, foram fatores determinantes para o desenvolvimento e ocorrência de eventos extremos no leste da Amazônia, A análise da Transformada de Ondeleta (TO) mostrou a energia e o ciclo anual presente no regime de precipitação dessa região, assim como a influência de fenômenos de alta freqüência como o ENOS no período chuvoso das estações analisadas. As perspectivas climáticas indicaram que a ODP já está em sua nova fase fria. Não se sabe por quanto tempo a ODP irá permanecer em sua nova fase, muito menos as suas causas, porém, se ela perdurar por mais 15 a 20 anos, que é o esperado, certamente haverá um aumento nos eventos extremos de chuva na região Amazônica, devido ao paulatino resfriamento da troposfera superior, resultando em maior desenvolvimento vertical de nuvens tipo cumulonimbo, responsável pelos altos totais pluviométricos.

Esta tese objetiva propor uma metodologia de especificação de requisitos de usabilidade e segurança orientada para arquitetura (MERUSA) aplicável a sistemas digitais de automação distribuídos e abertos. A estratégia utilizada para atingir esse objetivo consiste no desenvolvimento de uma metodologia focalizada nos processos de elicitação e análise dos requisitos de usabilidade e segurança, sincronizada com a evolução da arquitetura do sistema computacional. O modelo de referência ODP (Open Distributed Process) é utilizado como uma referência básica desse processo, fornecendo conceitos, procedimentos e modelos adequados à especificação e ao desenvolvimento de sistemas distribuídos e abertos de automação (orientados a objeto ou não), permitindo obter uma infra-estrutura coerente e gerenciável, com exigentes requisitos de integração. A eficácia da metodologia é verificada com a sua aplicação a um meta-modelo de especificação de projeto para sistemas digitais de controle distribuído de transmissão de energia para o sistema elétrico brasileiro. / This thesis purposes one new architecture oriented safety and usability requirements specification methodology (MERUSA) applied to open and distributed automation digital systems. The strategy used to achieve this goal consists on the development of a methodology centered on safety and usability requirement elicitation and analysis processes, synchronized with computational system architectural evolution. The RM-ODP (Reference Model of Open Distributed Process) is used as basic reference of this process. This pattern. supplies concepts, procedures and models appropriated to open and distributed system specification and development (object oriented or not), providing one coherent and manageable framework, with strong integration requirements. The methodology effectiveness is verified with its application to a project specification meta-model for energy transmission distributed control digital systems of Brazilian electrical system.

Esta tese objetiva propor uma metodologia de especificação de requisitos de usabilidade e segurança orientada para arquitetura (MERUSA) aplicável a sistemas digitais de automação distribuídos e abertos. A estratégia utilizada para atingir esse objetivo consiste no desenvolvimento de uma metodologia focalizada nos processos de elicitação e análise dos requisitos de usabilidade e segurança, sincronizada com a evolução da arquitetura do sistema computacional. O modelo de referência ODP (Open Distributed Process) é utilizado como uma referência básica desse processo, fornecendo conceitos, procedimentos e modelos adequados à especificação e ao desenvolvimento de sistemas distribuídos e abertos de automação (orientados a objeto ou não), permitindo obter uma infra-estrutura coerente e gerenciável, com exigentes requisitos de integração. A eficácia da metodologia é verificada com a sua aplicação a um meta-modelo de especificação de projeto para sistemas digitais de controle distribuído de transmissão de energia para o sistema elétrico brasileiro. / This thesis purposes one new architecture oriented safety and usability requirements specification methodology (MERUSA) applied to open and distributed automation digital systems. The strategy used to achieve this goal consists on the development of a methodology centered on safety and usability requirement elicitation and analysis processes, synchronized with computational system architectural evolution. The RM-ODP (Reference Model of Open Distributed Process) is used as basic reference of this process. This pattern. supplies concepts, procedures and models appropriated to open and distributed system specification and development (object oriented or not), providing one coherent and manageable framework, with strong integration requirements. The methodology effectiveness is verified with its application to a project specification meta-model for energy transmission distributed control digital systems of Brazilian electrical system.

Im Rahmen dieser Doktorarbeit wurden die Hangkarbonate von zwei miozänen heterozoischen Karbonatsystemen näher untersucht: die Malta Inselgruppe (zentrales Mittelmeer) und das Marion Plateau (Nordost Australien, ODP Leg 194). Die Auswirkungen der mittelmiozänen Abkühlung (Mi3), die auf 13.6 Ma datiert wird und starken Einfluß auf die Sauerstoffisotopenkurve hatte, in den oben genannten Flachwassersystemen stellten das Ziel dieser Arbeit dar. Dieses Abkühlungsereignis beeinflußte außerdem sehr stark die ozeanographischen und klimatischen Muster, die im weiteren Verlauf zum modernen Eishausklima führten. So steht insbesondere die Vereisung von Ostantarktika mit diesem Ereignis in Verbindung. Diese Arbeit untersucht den Einfluß dieses Ereignisses auf Flachwassersysteme, um vorliegende Untersuchungen in Tiefwassersystemen zu ergänzen und so zum globalen Verständnis des miozänen Klimawechsels beizutragen.<br /> <br /> Die Profile auf der Maltainselgruppe wurden mit Hilfe von Kohlenstoff- und Sauerstoffisotopen Auswertungen im Gesamtgestein, Gesamtgesteinmineralogie, Tonmineralanalyse und organischer Geochemie untersucht. Durch einen Wechsel von karbonatischeren zu tonigeren Sedimenten beeinflußte das mittelmiozäne Abkühlungsereignis die Sedimentation in diesem Gebiet sehr stark. Weiterhin wurde beobachtet, daß jede Phase der antarktischen Vereisung, nicht nur das mittelmiozäne Hauptereignis, zu einem erhöhten terrigenen Eintrag in den Hangsedimenten der Maltainselgruppe führte. Akkumulationsraten zeigen, daß dieser erhöhte terrigene Eintrag den einzelnen Vereisungsperioden zusammenhängt und die karbonatischen Sedimente durch tonreiche Sedimente &ldquo;verunreinigt&rdquo; wurden. Das daraufhin entwickelte Modell erklärt diesen erhöhten terrigenen Eintrag mit einer nordwärtigen Verlagerung der innertropischen Konvergenzzone durch die Bildung von kalten, dichten Luftmassen, die zu verstärkten Niederschlägen in Nordafrika führten. Diese verstärkten Niederschläge (oder verstärkter afrikanischer Monsun) beeinflußten die kontinentale Verwitterung und den Eintrag, mit der Folge, daß verstärkt terrigene Sedimente im Bereich der Hangsedimente der Maltainselgruppe abgelagert wurden. Die tonreichen Intervalle weisen Ähnlichkeiten zu sapropelischen Ablagerungen auf, was mit Hilfe der Spektral analyse des Karbonatgehalts und der geochemischen Analyse des organischen Materials gezeigt wurde. <br /> <br /> Auf dem Marion Plateau wurden die Sauerstoff- und Kohlenstoffisotopenkurven anhand von Foraminiferen der Gattung Cibicidoides spp. rekonstruiert. Der Karbonatgehalt wurde mit Hilfe einer chemischen Methode (Coulometer) ermittelt. Genauso wie die Sedimente der Maltainselgruppe beeinflußte das mittelmiozäne Abkühlungsereignis (Mi3) auch die Sedimente auf dem Marion Plateau. So kam es bei 13,8 Ma, in etwa zur Zeit der Vereisung von Ostantarktika, zu einem Abfall der Karbonatakkumulationsraten. Weiterhin traten Änderungen in der Zusammensetzung der Sedimente auf, so nehmen neritische Karbonatfragmente ab, der planktische Foraminiferengehalt nimmt zu und es wurden verstärkt Quarz und Glaukonit abgelagert. Ein überraschendes Ergebnis ist die Tatsache, daß der große N12-N14 Meeresspiegelabfall um 11,5 Ma die Akkumulationsraten der Karbonate auf dem Hang nicht beeinflußte. Dieses Ergebnis ist umso erstaunlicher, da Karbonatplattformen normalerweise sehr sensitiv auf Meeresspiegeländerungen reagieren. Der Grund, warum sich die Karbonatakkumulationsraten schon um 13,6 Ma (Mi3) und nicht erst um 11,5 Ma (N12-N14) verringerten, liegt in der Tatsache, daß die ozeanischen Strömungen die Karbonatsedimentation auf dem Hang des Marion Plateau schon im Miozän kontrollierten. Das mittelmiozäne Ereignis (Mi3) erhöhte die Stärke diese Strömungen und als eine Ursache wurde die Karbonatakkumulation auf den Hängen reduziert. Die Amplitude des N12-N14 Meeresspiegelabfalls liegt bei 90 m unter der Berücksichtigung der Sauerstoffisotopendaten aus der Tiefsee und Berechnungen des Meeresspiegels anhand des &ldquo;coastal onlaps&rdquo;, die während Leg 194 gemacht wurden. Die Isotopendaten dieser Arbeit weisen hingegen auf einen verringerten Meeresspiegelabfall von 70 m hin.<br /> <br /> Als allgemeine Schlußfolgerung kann gesagt werden, daß der mittelmiozäne Klimaumschwung die Karbonatsysteme zumindest an den beiden untersuchten Lokalitäten beeinflußt hat. Allerdings waren die Auswirkungen sehr von den unterschiedlichen lokalen Gegebenheiten abhängig. Insbesondere wirkten sich die Anwesenheit einer Landmasse (Malta) und die Abwesenheit einer Barriere vor den Einflüssen des offenen Ozeans (Marion Plateau) stark auf die Ablagerung der Karbonate aus. / This study investigated the slope carbonates of two Miocene carbonate systems: the Maltese Islands (in the Central Mediterranean) and the Marion Plateau (Northeastern Australia, drilled during ODP Leg 194). The aim of the study was to trace the impact of the Miocene cooling steps (events Mi1-Mi6) in these carbonate systems, especially the Mi3 event, which took place around 13.6 Ma and deeply impacted the marine oxygen isotope record. This event also profoundly impacted oceanographic and climatic patterns, eventually leading to the establishment of the modern ice-house world. In particular, East Antarctica became ice covered at that period. The rational behind the present study was to investigate the impact that this event had on shallow water systems in order to complement the deep-sea record and hence acquire a more global perspective on Miocene climate change.<br /> <br /> The Maltese Islands were investigated for trends in bulk-rock carbon and oxygen isotopes, as well as bulk-rock mineralogy, clay minerals analysis and organic geochemisty. Results showed that the mid Miocene cooling event deeply impacted sedimentation at that location by changing sedimentation from carbonate to clay-rich sediments. Moreover, it was discovered that each phase of Antarctic glaciation, not just the major mid Miocene event, resulted in higher terrigenous input on Malta. Mass accumulation rates revealed that this was linked to increased runoff during periods when Antarctica was glaciated, and thus that the carbonate sediments were &ldquo;diluted&rdquo; by clay-rich sediments. The model subsequently developed to explain this implies feedback from Antarctic glaciations creating cold, dense air masses that push the ITCZ Northward, thus increasing precipitation on the North African subcontinent. Increased precipitation (or stronger African monsoon) accelerated continental weathering and runoff, thus bringing more terrigenous sediment to the paleo-location of the slope sediments of Malta. Spectral analysis of carbonate content and organic matter geochemical analysis furthermore suggest that the clay-rich intervals are similar to sapropelic deposits.<br /> <br /> On the Marion Plateau, trends in oxygen and carbon isotopes were obtained by measuring Cibicidoides spp foraminifers. Moreover, carbonate content was reconstructed using a chemical method (coulometer). Results show that the mid Miocene cooling step profoundly affected this system: a major drop in accumulation rates of carbonates occurs precisely at 13.8 Ma, around the time of the East Antarctic ice sheet formation. Moreover, sedimentation changes occurred at that time, carbonate fragments coming from neritic environments becoming less abundant, planktonic foraminifer content increasing and quartz and reworked glauconite being deposited. Conversely, a surprising result is that the major N12-N14 sea-level fall occurring around 11.5 Ma did not impact the accumulation of carbonates on the slope. This was unexpected since carbonate platform are very sensitive to sea-level changes. The model developed to explain that mass accumulation rates of carbonates diminished around 13.6 Ma (Mi3 Event) instead of 11.5 Ma (N12-N14 event), suggests that oceanic currents were controlling slope carbonate deposition on the Marion Plateau prior to the mid-Miocene, and that the mid Miocene event considerably increase their strength, hence reducing the amount of carbonate being deposited on slope sites. Moreover, by combining results from deep-sea oxygen isotopes with sea-level estimates based on coastal onlaps made during Leg 194, we constrain the amplitude of the N12-N14 sea-level fall to 90 meters. When integrating isotopic results from this study, this amplitude is lowered to 70 meters.<br /> <br /> A general conclusion of this work is that the mid Miocene climatic shift did impact carbonate systems, at least at the two locations studied. However, the nature of this response was highly dependant on the regional settings, in particular the presence of land mass (Malta) and the absence of a barrier to shelter from the effects of open ocean (Marion Plateau).

Global climate is controlled by two factors, the amount of heat energy received from the sun (solar insolation) and the way that heat is distributed Earth's surface. Solar insolation varies on timescales of 10s to 100s of thousands of years due to changes in the path of Earth's orbit about the sun (Milankovitch cycles). Earth's internal boundary conditions, such as paleogeography, the presence/absence of polar icecaps, atmospheric/oceanic chemistry and sea level, provide distribution and feedback mechanisms for the incoming heat. Variations in these internal boundary conditions may happen abruptly or, as in the case of plate tectonics, take millions of years. We use geochemical and sedimentological techniques to investigate the response of ocean chemistry, regional aridity and atmospheric and oceanic circulation patterns to climate change during both greenhouse and icehouse climates. To explore the connection between orbitally-forced changes in solar insolation, continental aridity and wind, we generated a high-resolution dust record for ~58 Myr old deep-sea sediments from Shatsky Rise. Our data provide the first evidence of a correlation between dust flux to the deep sea and orbital cycles during the Early Paleogene, indicating dust supply (regional aridity) responded to orbital forcing during the last major interval of greenhouse climate. The change in dust flux was comparable to that during icehouse climates implying subtle variations in solar insolation have a similar impact on climate during intervals of over-all warmth as they do during glacial-interglacial states. The Carboniferous Period (359-299 Ma) marks a critical time in Earth's history when a series of tectonic and biological events caused a shift in the mean climate state from a global "greenhouse" to an "icehouse". Geochemical records extracted from sedimentary rocks deposited in shallow epicontinental seaways are increasingly being used to infer relationships between tectonism, carbon cycling and climate and therefore are assumed to reflect global ocean processes. We analyzed radiogenic isotopes in biogenic apatite along a North American transect to constrain the degree of geochemical coupling between the epicontinental seas and the open ocean. Our results argue strongly for decoupling of North American seaways from the open ocean by latest Mississippian time.