Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-03-02T12:45:01Z No. of bitstreams: 1 arleilucasdesouzarosa.pdf: 827143 bytes, checksum: 9b9df97bf2f2804c9287dcee04958895 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-03-06T19:38:30Z (GMT) No. of bitstreams: 1 arleilucasdesouzarosa.pdf: 827143 bytes, checksum: 9b9df97bf2f2804c9287dcee04958895 (MD5) / Made available in DSpace on 2017-03-06T19:38:30Z (GMT). No. of bitstreams: 1 arleilucasdesouzarosa.pdf: 827143 bytes, checksum: 9b9df97bf2f2804c9287dcee04958895 (MD5) Previous issue date: 2009-05-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Durante décadas, problemas relacionados à estabilidade de tensão ou, segurança de tensão, têm despertada a atenção crescente de pesquisadores do setor elétrico. O crescimento da economia e o aumento do consumo de energia elétrica, aliados à falta de investimentos nos setores de geração e transmissão, têm levado o sistema elétrico de potência a operar muito próximo de seus limites. Desta forma, a habilidade do sistema em manter um nível operacional satisfatório, após a ocorrência de alguma contingência, pode ficar comprometida. Este trabalho avalia a segurança de tensão através de um método simples, eficiente e rápido computacionalmente, além de propor ações de reforço para melhorar a margem de carregamento do sistema elétrico. A análise da rede é função dos caminhos de transmissão de potência ativa e um modelo matemático muito simples é utilizado. Quanto às ações de reforço, a análise de sensibilidade fornece as barras mais adequadas ao redespacho de potência ativa e reativa. Um processo iterativo é estabelecido com o intuito de recomendar ações de controle e fornecer condições de segurança de tensão menos severas. Os resultados apresentados para um sistema real de 34 barras demonstram a eficácia da metodologia desenvolvida. / Voltage stability or voltage security analysis has motivated an expressive attention of power systems researchers. The economy growth and the increased electric energy consumption, allied to the lack of investments in generation and transmission areas, have led electrical power systems to operate very close to their limits. Therefore, they cannot be able to operate in a secure way after some contingencies. In this work, a simple and fast method evaluates voltage security and proposes conditions to improve the loading margin. System analysis is carried out in terms of active power transmission path. Sensitivity analysis provides the most adequate buses to active and reactive power redispatch. A sequential iterative methodology to reinforce system conditions is presented. The results for a real 34-bus system demonstrate the efficiency of proposed methodology.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-10-23T16:35:51Z No. of bitstreams: 1 marceloladeiramarques.pdf: 721811 bytes, checksum: 747d74835ffaa88383924f9f6783667b (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-11-09T13:52:02Z (GMT) No. of bitstreams: 1 marceloladeiramarques.pdf: 721811 bytes, checksum: 747d74835ffaa88383924f9f6783667b (MD5) / Made available in DSpace on 2017-11-09T13:52:02Z (GMT). No. of bitstreams: 1 marceloladeiramarques.pdf: 721811 bytes, checksum: 747d74835ffaa88383924f9f6783667b (MD5) Previous issue date: 2017-09-01 / O presente trabalho tem como proposta o desenvolvimento de uma abordagem capaz de melhorar os resultados obtidos por algoritmos de classificação quando aplicados em bases desbalanceadas. O método, denominado Algoritmo de Balanceamento Sintético In-cremental (Incremental Synthetic Balancing Algorithm – ISBA), realiza um procedimento iterativo baseado em classificadores de larga margem, visando gerar amostras sintéticas com o intuito de reduzir o nível de desbalanceamento. No processo são utilizados vetores suporte como referência para a geração das novas instâncias, permitindo posicioná-las em regiões com uma maior representatividade. Além disso, a estratégia permite que as novas amostras ultrapassem os limites das amostras utilizadas como referência para sua geração, o que possibilita uma extrapolação dos limites da classe minoritária, objetivando, assim, alcançar um maior reconhecimento dessa classe de interesse. São apresentados experimentos comparativos com demais técnicas, entre elas o Synthetic Minority Over-sampling Technique (SMOTE), os quais fornecem fortes evidências da aplicabilidade da abordagem proposta. / In this work we propose the development of an approach capable of improving the results obtained by classification algorithms when applied to unbalanced datasets. The method, called Incremental Synthetic Balancing Algorithm (ISBA), performs an iterative procedure based on large margin classifiers, aiming to generate synthetic samples in order to reduce the level of unbalance. In the process, we use the support vectors as reference for the generation of new instances, allowing them to be positioned in regions with greater representativeness. Furthermore, the strategy allows the new samples to exceed the limits of the samples used as reference for their generation, which allows an extrapolation of the limits of the minority class, in order to achieve greater recognition of this class of interest. We present comparative experiments with other techniques, among them the Synthetic Minority Over-sampling Technique (SMOTE), which provide strong evidence of the applicability of the proposed approach.

Le manteau lithosphérique subcontinental est exhumé au pied des marges passives distales non-volcaniques en réponse à l’amincissement extrême de la croûte continentale. Ce processus d’amincissement peut être étudié à pied sec sur les témoins de la paléo-marge passive nord Ibérique affleurant aujourd’hui au nord de la chaîne des Pyrénées dans les Chaînons Béarnais (Zone Nord-Pyrénéenne : ZNP). La ZNP résulte de l’inversion de bassins ouverts entre les plaques Ibérique et Europe pendant l’Albo-Cénomanien. Dans les Chaînons Béarnais, la couverture mésozoïque pré-rift est intimement associée aux roches du manteau subcontinental et à de fines lentilles tectoniques de croûte continentale. L’hyper amincissement crustal s’est déroulé dans des conditions thermiques relativement chaudes, comme le montrent les déformations ductiles syn-métamorphiques crétacées affectant la croûte continentale et la couverture mésozoïque allochtone, localement en contact tectonique sur le manteau exhumé. Dans cette thèse, nous présentons des données structurales et géochimiques apportant de nouvelles contraintes pour la connaissance du processus d’amincissement extrême de la croûte continentale et pour la reconstruction de l’évolution de la paléo-marge nord-Ibérique. La couverture pré-rift a été désolidarisée de son socle paléozoïque au niveau des évaporites du Keuper et mise en contact direct avec le manteau pendant son exhumation dans le fond des bassins. Le détachement croûte/manteau est une discontinuité majeure caractérisée par des bandes de cisaillements anastomosées définissant une fabrique lenticulaire (« phacoidal fabric ») d’épaisseur pluri-métrique au sommet du manteau serpentinisé. La croûte continentale se réduit à de minces écailles elles-mêmes anastomosées, séparée par des bandes de cisaillement dans le faciès schistes verts et évoluant vers des cataclasites plus froides. Les analyses par spectrométrie Raman sur la matière carbonée (RSCM) montrent que l’ensemble de la couverture mésozoïque a été soumis à des températures maximales comprises entre 200°C et 480°C. Elle est sujette à d’intenses circulations de fluides. Les interactions fluides/roches ont eu lieu lors de tous les stades de l’extension, depuis les contextes profonds durant la déformation ductile, jusqu’au domaine superficiel durant la déformation cassante. Le détachement manteau/Mésozoïque est marqué par une couche de roches métasomatiques, riches en talc, chlorite et pyrite, mises en place dans les conditions du faciès schistes verts, impliquant en partie des fluides issus de la serpentinisation du manteau. De plus, la géochimie isotopique (O, C, Sr) et les inclusions fluides présentes dans des veines de carbonates des sédiments mésozoïques, témoignent d’une circulation de saumures chaudes (~200°C), à travers toute la couverture sédimentaire pendant l’exhumation du manteau. Ces saumures sont issues de la dissolution des évaporites du Keuper, très rarement conservées dans les Chaînons Béarnais. Nous développons un modèle conceptuel basé sur la géologie des Chaînons Béarnais dans lequel la croûte continentale moyenne est déformée ductilement. Le fonctionnement de détachements contre-régionaux (à pendage vers le continent) est associé à l’individualisation de fines lentilles tectoniques de croûte continentale moyenne qui sont extraites et exhumées avec le manteau dans le fond des bassins albo-cénomaniens, laissant en arrière la croûte continentale supérieure et inférieure. Ces lentilles crustales collées au manteau forment alors une large zone de croûte extrêmement amincie. Des fenêtres ouvertes au sein de cette mince pellicule crustale permettent au manteau de venir en contact direct avec les sédiments pré-rifts (Saraillé, Turon de la Técouère). Des ouvertures au sein de la couverture pré-rift permettent au manteau de venir directement à l’affleurement (Urdach-Les Pernes). / Sub-continental lithospheric mantle rocks are exhumed at the foot of magma-poor distal passive margins as a response to extreme stretching of the continental crust. Remnants of the Northern Iberian paleo-passive margin are now exposed in the Northern Pyrenees in the Chaînons Béarnais (North Pyrenean Zone: NPZ) and represent field analogues to study the processes of continental crust thinning and subcontinental mantle exhumation. The NPZ results from the inversion of basins opened between the Iberia and Europa plates during Albo-Cenomanian times. In the Chaînons Béarnais ranges the pre-rift Mesozoic sedimentary cover is associated with peridotite bodies in tectonic contact with small size Paleozoic basement lenses. Continental extension developed under hot thermal conditions, as demonstrated by the syn-metamorphic Cretaceous ductile deformation affecting both the crustal basement and the allochtonous Mesozoic cover locally in direct contact with exhumed mantle rocks. In this study, we present structural and geochemical data providing new constraints to the knowledge of extreme crustal thinning processes and to reconstruct the evolution of the northern Iberia paleo-margin. The pre-rift cover was detached from its Paleozoic bedrock at the Keuper evaporites level and was welded to mantle rocks during their exhumation in the bottom of the basins. The crust/mantle detachment fault is a major shear zone characterized by anastomosed shear bands defining a plurimetric phacoidal fabric at the top of the serpentinized mantle. Raman Spectroscopy on Carbonaceous Materials (RSCM), performed on the Mesozoic cover reveals that the entire sedimentary pile underwent temperatures ranging between 200°C and 480°C. This sedimentary pile displays numerous evidence of infiltration by geological fluids. The fluid/rock interactions went on during the entire extensional events, since early deep phases characterized by ductile deformation, to late shallower stages characterized by brittle deformation. The detachment is marked by a layer of metasomatic rocks, locally up to 20 meters thick, made of talc-chlorite-pyrite-rich rocks that developed under greenschist facies conditions, including fluids derived from mantle rocks serpentinisation. Moreover, isotopes geochemistry (O, C, Sr) and microthermometry/Raman spectrometry of fluid inclusions in a network of calcitic veins (with quartz locally) in the overlying sediments reveal moderate temperatures (~220°C) brines circulation through the whole sedimentary cover during mantle exhumation. These brines likely derived from the dissolution of the local Triassic evaporites, rarely preserved in the Chaînons Béarnais. We developed a conceptual model based on geological evidence from the Chaînons Béarnais. Implying ductile deformation of the middle crust. Counter-regional detachments (dipping toward the continent) are associated to the individualization of mid-crustal thin tectonic lenses which remain welded on the mantle rocks and are exhumed at the floor of the Albian-Cenomanian basins, leaving behind the upper and the lower crust. These crustal lenses welded on mantle rocks then form a large zone of extremely thinned continental crust. Breaking points in this thin crustal sheet allow mantle rocks to come in direct contact with the pre-rift sediments (Saraillé, Turon de la Técouère). Breaking points in the pre-rift cover allow mantle rocks to be completely exhumed to the seafloor (Urdach-Les Pernes).

Cette étude se concentre sur la caractérisation des blocs-H préservés dans les marges de type « upper plate ». L’approche terre-mer a permis de diviser l’architecture crustale d’une « upper plate » en trois terrasses et deux zones d’escarpement, possédant leurs propres architectures crustales et stratigraphiques. Les limites de terrasses sont liées à des changements dans les modes d’extensions et définissent des points majeurs. Dans les Alpes il apparait que les principales structures Alpines correspondent à la réactivation des zones d’escarpements ou des failles de détachement. La collision finale est contrôlée par la présence des butoirs pouvant coïncider avec la zone de necking et le point de couplage de la marge de rift. La comparaison entre les observations de terrain et l’imagerie à l’échelle crustale, a permis d’intégrer plus de détails géologiques dans les observations sismique. / This study focused on the characterization of so called “H-blocks” recorded in upper plate. The onshore-offshore approach used in this study enabled to characterize and divide the crustal architecture of upper plate margins in three terraces and two ramps, characterized by diagnostic structural and stratigraphic features. Limits of terraces and location of ramps are considered to coincide with changes in the mode of extension and to define major limits/points. It appears that major Alpine structures result from the reactivation of former ramps or extensional detachment faults. Final collision appears to be controlled by the presence of strong buttresses that may coincide with the necking zone/coupling point of the former margin. The comparison of the different datasets ranging from field outcrops to seismic sections enables integrate more detailed geological observations in seismic observations.

Les parties distales des marges passives pauvres en magma représentent la transition complexe entre les domaines continentaux et océaniques. Ces zones encore peu étudiées sont pourtant des endroits clefs pour comprendre les processus impliqués durant les premiers stades de l’accrétion océanique, et plus particulièrement ceux du magmatisme et du métasomatisme. Durant ces premiers stades, ces deux processus sont gouvernés par l’exhumation mantellique. L’interaction entre les liquides magmatiques, les roches du manteau et les fluides marins vont affecter le régime thermique de la marge. De par le monde, seulement deux Transitions Océan-Continent (TOC) ont pu bénéficier d’investigations scientifiques poussées et constituent naturellement les deux sites d’études de cette thèse, à savoir, les marges actuelles conjuguées d’Ibérie-Terre Neuve du sud de l’Atlantique Nord ainsi que les marges fossiles de la Platta et de Tasna, fragments de TOCs de la Téthys Alpine Jurassique. En combinant les études de terrain ainsi que les investigations minéralogiques, pétrologiques et géochimiques, nous avons pu contraindre trois processus clefs se déroulant dans les TOCs. (i) La percolation de liquide magmatique imprégnant le manteau sous-continental hérité dans les marges Ibérie-Terre Neuve permet une refertilisation de ces marges distales. (ii) La transition géochimique visible entre les basaltes des TOCs et les basaltes de dorsales océaniques peut s’appréhender par la fusion partielle du manteau sous-continental refertilisé. (iii) Le rôle des fluides hydrothermaux, ayant des températures comprises entre 60°C et 190°C, joue un rôle sur le métasomatisme de la lithosphère en produisant une intense serpentinisation et rodingitisation, respectivement du manteau sous-continental en exhumation et des dykes basaltiques. Ces températures étant cohérentes avec une exhumation mantellique au niveau du plancher océanique. / Distal parts of magma-poor rifted margins represent a complex transition between continental and oceanic domains. These areas remain poorly understood while being a key-place to unravel magmatic and metasomatic processes involved during the first stages of oceanization. At this time, these processes are enhanced by mantle exhumation, and the interaction between melts, mantle rocks and fluids affect the thermal regime of the margin. So far, only two Ocean-Continent Transitions (OCT) have been particularly investigated, namely the present-day Iberia Newfoundland conjugate margins and the fossil analog Platta-Tasna nappes, remnants of the Jurassic Alpine-Tethys OCTs. Studies presented in this Ph.D. thesis have been focused on these two margins. Here, by combining field-works, petrological, mineralogical and geochemical investigations, we have unraveled in OCTs three key-points: (i) The deep porous-flow melt percolation impregnating the long-lived inherited subcontinental mantle in Iberia-Newfoundland margins allow the refertilization of these distal domains; (ii) The geochemical transition depicted from OCT-basalts towards MOR-basalts can be explained by the partial melting of the refertilized subcontinental mantle; (iii) The role of active hydrothermal fluids, on both the exhumed mantle and basalt dikes, lead to the serpentinisation and the rodingitization respectively, at temperature ranging between 60°C and 190°C. These temperatures being consistent with the ongoing mantle exhumation towards near-seafloor conditions.

The experiment was carried out with the objective of evaluating the gross margin, the productive and reproductive performance of beef heifers kept exclusively on ryegrass pasture (Lolium multiflorum Lam.) or ryegrass receiving 0.5 and 1.0% of body weight (BW) of whole rice bran as supplement, provided daily at at 2:00 p.m. The grazing method was the rotational and the interval between grazings was set by the thermal sum required for the appearing of 1.5 ryegrass leaf (187.5º C). The experimental design was completely randomized with repeated measures, three feeding systems and two and two area replications. Heifers in different feeding systems were kept in similar forage mass and canopy height when they came out of plots in all paddocks. The heifers average daily gain did not differ between the feeding systems. The stocking rate and weight gain per area were higher when heifers received 1.0% BW of whole rice bran. The provision of 0.5% BW of WRB allowed stocking rate and capacity gain for intermediate area between the other feeding systems. The higher gross margin was observed when heifers received 0.5% BW. The variable cost obtained for the different feeding systems showed increasing behavior depending on the WRB levels, surpassing the exclusive use of ryegrass in 37.2% and 60.6%. The final body weight, body condition score and reproductive tract score did not differ between the feeding systems. Considering an adult animal with an average body weight of 450 kg, the heifers at the beginning of the experiment showed 34% of mature body weight and final average body weight of 56% of adult weight. / O experimento foi conduzido com o objetivo de avaliar a margem bruta, o desempenho produtivo e reprodutivo de bezerras de corte mantidas exclusivamente em pastagem de azevém (Lolium multiflorum Lam.) ou em azevém recebendo 0,5 e 1,0% do peso corporal (PC) de farelo de arroz integral (FAI) como suplemento, fornecido diariamente às 14 horas. O método de pastejo foi o rotativo e o intervalo entre pastejos foi estabelecido considerando a soma térmica necessária para a emissão de 1,5 folha de azevém (187,5º C). O delineamento experimental foi o inteiramente casualizado, com medidas repetidas no tempo, três sistemas alimentares e duas repetições de área. As bezerras, nos diferentes sistemas alimentares, foram mantidas em similar massa de foragem e altura de dossel quando saíram das parcelas em todos os piquetes. O ganho médio diário das bezerras não diferiu entre os sistemas alimentares. A taxa de lotação e o ganho de peso por área foram maiores quando as bezerras receberam 1,0% do PC de farelo de arroz integral. O fornecimento de 0,5% do PC de FAI permitiu taxa de lotação e ganho por área intermediários entre os demais sistemas alimentares. A maior margem bruta foi observada quando as bezerras receberam 0,5% de FAI. O custo variável obtido para os diferentes sistemas alimentares apresentou comportamento crescente em função dos níveis de FAI, superando o uso exclusivo do azevém em 37,2% e 60,6%. O peso corporal final, o escore de condição corporal e o escore do trato reprodutivo não diferiram entre os sistemas alimentares. Considerando um animal adulto com peso corporal médio de 450 kg, as bezerras ao início do experimento apresentaram 34% do peso corporal adulto e peso corporal final médio de 56% do peso adulto.

The present paper studied the floristic composition, structure and volume of a forest with an area of 120.2 hectares, called Forest Secret Massif, located in the village of Figueira, Segredo s city, Rio Grande do Sul, in order to create the VCA indicator (expanded margin call), RNR indicator (natural regeneration relative) and IRF indicator (forest resilience rating) to describe the representativeness of species in the forest. Also evaluated the phenotypic aspects of the trees and the related of competition at the trees in order to propose a forest restructuring plan by removing mature trees and regenerating trees in order to improve the conditions of the forest and noble species. The three indicators, on a percentage scale, presented able to describe the representation of mature species (VCA), the regenerating species (RNR) and both the forest formation (IRF), which allowed understand the current situation of each species and will understand the changes that may be manifested in the implementation of management plans, obtaining a history. The restructuring plan has listed 13,139 mother trees, 31,820 normal trees and 10,210 trees subject to deletion (group 1), 2.095 noble trees (group 2), 2776 bagueiras (group 3), 4,538 important trees for the forest ecology maintenance (group 4) ; and 24,454 individuals subject to removal for strategic reasons, except the 7,365 needed to stand on environmental issues (group 5). The regenerating forest comes up with 18,430 trees future level 1, 56 415 trees future level 2 and 17,107 trees future level 3. / O presente trabalho estudou a composição florística, estrutural e volumétrica de uma floresta com área de 120,2 hectares, denominada de Maciço Florestal Segredo, situado na localidade de Figueira, no município de Segredo, Rio Grande do Sul, com o objetivo de criar o indicador (valor de cobertura ampliado), (regeneração natural relativa) e (índice de resiliência florestal) para descrever a representatividade das espécies na floresta. Também se avaliou os aspectos fenotípicos e relacionados à competição das árvores com o objetivo de propor um plano de reestruturação florestal por meio da supressão de árvores maduras e de regenerantes, a fim de melhorar as condições da floresta e de espécies nobres. Os três indicadores, em uma escala percentual, se apresentaram capazes de descrever a representatividade das espécies maduras ( ), das espécies regenerantes ( ) e de ambas na formação da floresta ( ), o que permitiu entender a atual situação de cada espécie e permitirá entender as alterações que poderão se manifestar com a aplicação de planos de manejo, obtendo-se um histórico. O plano de reestruturação elencou 13.139 árvores matrizes, 31.820 árvores normais e 10.210 árvores passíveis de supressão (grupo 1), 2.095 árvores nobres (grupo 2), 2.776 bagueiras (grupo 3), 4.538 árvores importantes para manutenção da ecologia florestal (grupo 4); e 24.454 indivíduos passíveis a supressão por motivos estratégicos, salvo os 7.365 necessários a se manter por questões ambientais (grupo 5). A floresta regenerante surge com 18.430 árvores futuro nível 1, 56.415 árvores futuro nível 2 e em 17.107 árvores futuro nível 3.

Le Cénozoïque est marqué par une instabilité climatique et l’accélération des surrections continentales. Ces phénomènes engendrent une augmentation de la production sédimentaire, transférée par les fleuves vers le domaine marin profond. Les façades nord et ouest de l’océan Indien voient se mettre en place quatre des plus grands systèmes sédimentaires au monde : le Gange-Brahmapoutre, l’Indus, le Zambèze et le système tanzanien. Ce travail vise à comprendre les forçages agissant sur la sédimentation et l’architecture de deux des principaux systèmes turbiditiques de l’océan Indien (système tanzanien et du Gange-Brahmapoutre), pour ensuite les comparer avec leurs plus proches voisins (respectivement le Zambèze et l’Indus). Nos principaux résultats, basés sur une approche multiproxy dans les deux zones, mettent en évidence plusieurs points : (1) l’évolution tectono-sédimentaire de la marge tanzanienne au cours du Cénozoïque a mené au développement d’un système turbiditique majeur et atypique, dont la morphologie moderne atteste de l’importance de l’activité tectonique sur sa construction ; (2) le système du Gange-Brahmapoutre enregistre une activité sédimentaire polyphasée, en lien principalement avec les variations du niveau marin. Ce système est capable d’enregistrer les variations de nombreux forçages, influençant à la fois les bassins versants et le domaine marin. Le fonctionnement sédimentaire et l’architecture des systèmes turbiditiques ont révélé une grande diversité selon le contexte géodynamique et physiographique des façades étudiées. La nécessité d’intégrer l’ensemble des forçages (agissant depuis le bassin versant jusque dans le domaine marin profond) dans l’étude de l’activité sédimentaire d’un système turbiditique apparait essentielle de nos jours. / Cenozoic is marked by climatic instability and accelerating continental uplifts. Increasing sediment yield is generated, buffered and transferred by river to the deep sea. Four of the major turbidite systems in the world are located on the northern and the western margins of the Indian Ocean: the Ganges-Brahmaputra, the Indus, the Zambezi and the Tanzanian systems. This work aims to understand forcings affecting sedimentation and morphology of two main turbidite systems (Tanzanian system and Ganges-Brahmaputra system) and results have been compared with their nearest neighbors (respectively Zambezi and Indus). Based on a multiproxies approach in both area, our main results are as follows: (1) during Cenozoic, tectono-sedimentary evolution of the Tanzania margin led to the development of an atypical turbidite system wherein morphology attest of a strong structural control; (2) the Ganges-Brahmaputra system has a sedimentary activity mainly forced by sea level variations. This turbidite system records variations in many forcings impacting sedimentation from the catchment to the deep sea. Turbidite system activity and architecture revealed a strong variability mainly linked to the geodynamic and physiographic context of each studied margin. It appears necessary to integrate all forcings (affecting both the catchment and the deep sea) in the study and the understanding of sedimentary activity in a turbidite system.

Magister Scientiae - MSc / Many hydrocarbon reservoirs are situated in barren sequences that display poor stratigraphic control. Correlation between the wells can become extremely difficult and traditional correlation techniques can prove to be inadequate. Past studies have shown that trace and major element concentrations can be used as a correlation tool. This practice of using geochemical fingerprints to characterize between wells is called Chemostratigraphic analysis. (Pearce et al, 1999) Chemostratigraphy has been recognized as a very important correlation technique as it can be used for rocks of any age, in any geological setting as well as sequences that are traditionally defined as barren. Chemostratigraphic analyses can be used as a means of getting rid of ambiguities within data produced by traditional correlation methods such as Biostratigraphy, Lithostratigraphy and Geophysical Logging. In areas where stratigraphic data is not available it can be used to construct correlation frameworks for the sequences found in the area. The motivation behind this study is that the research is not only worthy of academic investigation, but can also provide the industry with new insights into areas that were previously misunderstood because traditional correlation methods were not adequate. The study area, the Orange basin, is located offshore South Africa and is largely underexplored. The basin, that hosts two gas field namely the Ibhubesi and the Kudu gas fields, has large potential but in the past has not been given due attention with only 34 wells being drilled in the area. The Orange basin has recently been the topic of investigation because of the belief that it may be hosts to more hydrocarbons. This study will utilise Chemostratigraphy to attempt to provide geological information on this relatively under-explored basin. The aim of this research study is to produce a chemostratigraphic framework -scheme for the Orange Basin in order to facilitate reservoir scale interwell correlation. The Objectives of this research study will be to identify chemostratigraphic units or indices, to prove the adequate use of chemostratigraphy as an independent correlation technique and to integrate the chemostratigraphy and petrophysical characteristics of the four wells to facilitate lithological identification. / South Africa

Comprendre comment s’initie une subduction au niveau d’une marge passive est un problème géodynamique majeur, mais il reste très débattu en raison des forces nécessaires pour provoquer la flexion de la plaque plongeante, et dépasser la résistance frictionnelle de la lithosphère pour localiser cette subduction. Formant la bordure sud de la Méditerranée Occidentale, la marge algérienne subit des conditions aux limites en compression en raison de la convergence Afrique-Eurasie à un taux de moins de 1 cm/an. Ce contexte favorise l’inversion de cette marge nord-africaine et possiblement le début d’une subduction. En effet, des données géophysiques récentes acquises dans le bassin algérien (campagnes de MARADJA, 2003, 2005 (MARge Active d’el Djazaïr) et SPIRAL 2009 (Sismique Profonde et Investigations Régionales en ALgérie) ont montré des indices de déformation compressive récente. Nous avons utilisé les profils SPIRAL afin de calculer l’état isostatique de la lithosphère au voisinage de la limite océan-continent. Ceci nous a permis d'imager un Moho trop profond dans le domaine océanique, et plus superficiel dans le domaine continental, de part et d'autre d'une limite située vers le pied de pente de cette marge, donc un déséquilibre isostatique général de la marge. Nos résultats indiquent que la marge algérienne montre les mêmes anomalies isostatiques qu’au niveau d'une marge active, avec une zone de découplage océan/continent située en pied de marge. Ces anomalies peuvent être interprétées par un mécanisme de flexure des deux lithosphères en présence, que l’on peut simuler ensuite par une modélisation en éléments finis d’une plaque mince élastique. / Understanding how subduction initiates at a passive margin is a major geodynamic question, which remains debatted because of the forces necessary to overcome bending and frictional resistance of the lithosphere and initiate this subduction. Along the southern shore of the Western Mediterranean Sea, the Algerian margin undergoes ~NS compression due to the African-Eurasian convergence at a rate of less than ~ 1 cm / year. This setting causes tectonic inversion of this North African passive margin and possibly incipient subduction. Indeed, recent geophysical marine data acquired in the Algerian Basin (MARADJA, 2003, 2005MARge Active d’el Djazaïr) and SPIRAL 2009 (Deep Seismic and Regional Investigations in Algeria campaigns) showed evidence of recent compressive deformation. We used SPIRAL wide-angle seismic profiles to determine the state of isostatic equilibrium at the vicinity of the continent-ocean boundary. This allowed us to image a too deep Moho in the oceanic part, and a too shallow one in the continental domain, with a boundary between both domains located at the margin toe. These results indicate that the Algerian margin display the same isostatic anomalies as an active margin. This isostatic disiquilibrium may be simulated by the flexural bending of two lithospheric plates that can be modelled by a finite element procedure. This modeling shows larger vertical deflection in the central part of the study area (6-7 km) compared to the earsternmost and westernmost profiles (3 km).