Este trabalho visa contribuir ao estudo geotectônico relacionado à Bacia do Camaquã, no Estado do Rio Grande do Sul, a partir de dados gravimétricos provenientes do Rifte Guaritas. Com este intuito, foram propostos três modelos de um perfil que corta perpendicularmente o trend do Rifte Guaritas e suas unidades. O mapa Bouguer residual, com valores entre –36 e 29 mGal, permitiu de maneira geral, delimitar áreas que possuem diferentes profundidades de embasamento. Os altos valores de gravidade podem indicar porções onde o topo do embasamento possui baixas profundidades ou rochas de maior densidade, enquanto que baixos valores podem estar associados a grandes profundidades ou rochas de densidade inferior. Com base nos dados de gravimetria, de caráter local à regional, foi possível estabelecer e, em algumas situações, estimar, o comportamento do embasamento ao longo deste perfil. Convêm ressaltar que cada modelo proposto contou com valores diferenciados de densidades de rocha, o que resultou em pequenas diferenças, tais como estruturais e variações de profundidade do embasamento. Porém, de modo geral, os três modelos se comportam de maneira muito semelhante. Cada um dos modelos propostos pode ser separado em cinco diferentes compartimentações que refletem as variações gravimétricas ao longo do perfil. De acordo com os modelos propostos neste trabalho a profundidade máxima do embasamento está localizada na porção oeste do Rifte Guaritas, chegando próxima dos seis quilômetros e a porção leste possui uma extensa estrutura deposicional. / This dissertation aims to contribute to geotectonic study related to Camaqua Basin, from gravimetric data of the Guaritas Rift. For this was proposed three models of one perpendicular profile which cross the trend of the Guaritas Rift. The residual Bouguer map, with values between -36 to 29 mGal, let, in general, to delimit areas with different depth of basement. The values of gravity may show areas where the top of the basement has low depths or rocks of major density while low values could be associated to great depth or rocks of minor density. Based on the gravimetric data of regional and local character, was possible to establish or at least estimate the variations of the depth basement along to this profile. It was proposed three models and each one of them used different combinations of rock densities, what resulted in few minor differences as structural differences and few minor variations of depth of the basement. However, in a general way, the three models behaved similarly. Each one of the models proposed could be fragmented in five different compartments which reflect the gravimetric variations across the profile. According to the models proposed in this paper, the maximum depth of the basement is located at the West portion of Rift Guaritas, almost six kilometers, and the East portion has an extensive depositional structure.

abstract: Sedimentary basins in the Afar Depression, Ethiopia archive the progression of continental breakup, record regional changes in east African climate and volcanism, and host what are arguably the most important fossiliferous strata for studying early human evolution and innovation. Significant changes in rift tectonics, climate, and faunal assemblages occur between 3-2.5 million years ago (Ma), but sediments spanning this time period are sparse. In this dissertation, I present the results of a geologic investigation targeting sediments between 3-2.5 Ma in the central and eastern Ledi Geraru (CLG and ELG) field areas in the lower Awash Valley, using a combination of geologic mapping, stratigraphy, and tephra chemistry and dating. At Gulfaytu in CLG, I mapped the northern-most outcrops of the hominin-bearing Hadar Formation (3.8-2.9 Ma), a 20 m-thick section of flat-lying lacustrine sediments containing 8 new tephras that directly overlie the widespread BKT-2 marker beds (2.95 Ma). Paleolake Hadar persisted after 2.95 Ma, and the presence and characteristics of the Busidima Formation (2.7-0.016 Ma) indicates Gulfaytu was affected by a reversal in depositional basin polarity. Combined with regional and geophysical data, I show the Hadar Formation underlying CLG is >300 m thick, supporting the hypothesis that it was the lower Awash Pliocene depocenter. At ELG, I mapped >300 m of sediments spanning 3.0-2.45 Ma. These sediments coarsen upward and show a progression from fluctuating lake conditions to fluvial landscapes and widespread soil development. This is consistent with the temporal change in depositional environments observed elsewhere in the lower Awash Valley, and suggests that these strata are correlative with the Hadar Formation. Furthermore, the strata and basalts at ELG are highly faulted, and overprinted by shifting extension directions attributed to the northern migration of the Afar triple junction. The presence of fossiliferous beds and stone tools makes ELG a high-priority target for anthropological and archaeological research. This study provides a new temporally-calibrated and high-resolution record of deposition, volcanism, and faulting patterns during a period of significant change in the Afar. / Dissertation/Thesis / Ph.D. Geological Sciences 2013

Este trabalho visa contribuir ao estudo geotectônico relacionado à Bacia do Camaquã, no Estado do Rio Grande do Sul, a partir de dados gravimétricos provenientes do Rifte Guaritas. Com este intuito, foram propostos três modelos de um perfil que corta perpendicularmente o trend do Rifte Guaritas e suas unidades. O mapa Bouguer residual, com valores entre –36 e 29 mGal, permitiu de maneira geral, delimitar áreas que possuem diferentes profundidades de embasamento. Os altos valores de gravidade podem indicar porções onde o topo do embasamento possui baixas profundidades ou rochas de maior densidade, enquanto que baixos valores podem estar associados a grandes profundidades ou rochas de densidade inferior. Com base nos dados de gravimetria, de caráter local à regional, foi possível estabelecer e, em algumas situações, estimar, o comportamento do embasamento ao longo deste perfil. Convêm ressaltar que cada modelo proposto contou com valores diferenciados de densidades de rocha, o que resultou em pequenas diferenças, tais como estruturais e variações de profundidade do embasamento. Porém, de modo geral, os três modelos se comportam de maneira muito semelhante. Cada um dos modelos propostos pode ser separado em cinco diferentes compartimentações que refletem as variações gravimétricas ao longo do perfil. De acordo com os modelos propostos neste trabalho a profundidade máxima do embasamento está localizada na porção oeste do Rifte Guaritas, chegando próxima dos seis quilômetros e a porção leste possui uma extensa estrutura deposicional. / This dissertation aims to contribute to geotectonic study related to Camaqua Basin, from gravimetric data of the Guaritas Rift. For this was proposed three models of one perpendicular profile which cross the trend of the Guaritas Rift. The residual Bouguer map, with values between -36 to 29 mGal, let, in general, to delimit areas with different depth of basement. The values of gravity may show areas where the top of the basement has low depths or rocks of major density while low values could be associated to great depth or rocks of minor density. Based on the gravimetric data of regional and local character, was possible to establish or at least estimate the variations of the depth basement along to this profile. It was proposed three models and each one of them used different combinations of rock densities, what resulted in few minor differences as structural differences and few minor variations of depth of the basement. However, in a general way, the three models behaved similarly. Each one of the models proposed could be fragmented in five different compartments which reflect the gravimetric variations across the profile. According to the models proposed in this paper, the maximum depth of the basement is located at the West portion of Rift Guaritas, almost six kilometers, and the East portion has an extensive depositional structure.

A Formação Candeias (PACK & ALMEIDA, 1945) pertencente ao Grupo Santo Amaro, consiste em arenitos e folhelhos do período Cretáceo e corresponde aos primeiros depósitos da abertura plena do rifte da Bacia do Recôncavo. A idade destes sedimentos varia do Berriasiano médio ao Valanginiano inferior (~143M. a.), com uma amplitude temporal de 4,5 M.a. e uma espessura média de 1000 m. Localiza-se no andar Rio da Serra, e os sedimentos são interpretados como lacustres e depósitos de corrente de turbidez, da fase de clímax do Rifte (PROSSER, 1993), possuindo um papel muito importante na historia do desenvolvimento da extração de petróleo e gás na Bacia do Recôncavo, pois os folhelhos desta formação são as rochas geradoras desta bacia, e os arenitos são importantes reservatórios de hidrocarbonetos. Entender os processos sedimentológicos desta formação, bem como sua evolução estratigráfica, ainda é um desafio, pois a maioria das informações provém de dados indiretos (sísmica, perfis elétricos e dados de produção de petróleo), já que os afloramentos são escassos. Assim, os estudos das rochas de testemunhos seriam os dados diretos principais e aqui explorados. A área de estudo está localizada no compartimento estrutural denominado Borda Nordeste da Bacia do Recôncavo, e abrange os campos de Rio Itariri, Fazenda Bálsamo e Riacho da Barra, que estão alinhados ao longo da Falha de Salvador (borda falhada do rifte) no Patamar de Patioba. O sistema deposicional é interpretado como lacustre com depósitos arenosos provenientes de corrente de turbidez, é composto principalmente por pelitos, heterolitos, arenitos arcoseanos (FOLK, 1968) e arenitos híbridos (ZUFFA, 1980). Os fluxos turbiditicos são interpretados como resultado da desestabilização do talude lacustre em período de atividade tectônica intensa. Durante o período de quiescência tectônica, a maior parte da sedimentação é atribuída a rochas pelíticas. Estes depósitos podem ser correlacionados em toda a borda nordeste e os pelitos possuem uma boa resposta em perfis elétricos e sísmica. A estratigrafia de sequências (ES) em bacias tipo rifte pode utilizar os mesmos critérios dos utilizados em bacias intracratônicas ou de margem passiva, porém deve-se levar em conta a intensa atividade tectônica atuante, como propõem Prosser, (1993) e Martins - Neto & Catuneanu (2010). A metodologia utilizada baseia-se identificar tendências Transgressiva – Regressiva (T-R) segundo Embry & Johannenessen (1992), de 3ª e 4ª ordens e, a partir destas, identificar as principais superfícies estratigráficas. Foram assim, identificadas cinco superfícies estratigráficas (duas superfícies de inundação máxima (SIM) e três limites de sequência (LS)) para as três sequências deposicionais, denominadas como Sequencia I, Sequencia II e Sequencia III. Estas superfícies permitiram correlacionar os depósitos arenosos, utilizando os perfis elétricos (Raios Gama, Resistividade e densidade-neutrão). Para isso, foram descritos 1430m de testemunhos, 54 lâminas petrográficas, feita a interpretação sísmica dos horizontes estratigráficos de duas sísmicas 3D, análises geoquímica de minerais pesados, análise de palinofácies e geoquímica orgânica, de seis poços dos três campos em estudo. A análise estratigráfica e sedimentológica baseou-se na correlação rocha x perfil destes poços, descrição granulométrica e interpretação das fácies, suas associações e petrofácies. As fácies arenosas são descritas como arenitos finos a grossos, com estratificação plana paralela a cruzada de baixo ângulo, muitas vezes com fluidização e carga e maciços. Estas fácies estão relacionadas à fácies de canais turbidíticos ou a lobos turbidíticos proximais. Heterolitos e arenitos muito finos com ripples de corrente e intensa fluidização e pelitos cinza laminados e maciços estão relacionados a lobos turbidíticos distais ou a depósitos de fundo de bacia. A análise petrográfica dos arenitos revelou que estes são essencialmente arcoseanos, e com presença abundante de bioclastos de ostracodes, oncolitos, além de pelóides e alguns aloquímicos indiferenciados, para sequencia I, e fragmentos de rocha metamórfica, ígnea e sedimentar, além de cristais de carbonato, fosfatos e intraclasto lamoso, para a sequência II. Calcita, calcita ferrosa, dolomita, dolomita ferrosa e são os principais cimentos encontrados provavelmente devido à dissolução dos aloquímicos carbonáticos. Porém os processos diagenéticos mais frequentes são a autigênese de sílica gerando crescimento de quartzo e albita. Muitos destes processos diagenéticos podem contribuir para redução substancial da porosidade primária e permeabilidade, porém quando a principal porosidade (primária intergranular) está combinada com a secundária (dissolução de feldspatos ou bioclastos gerando porosidade móldica ou intragranular), pode melhorar consideravelmente a porosidade destes arenitos. As características permoporosas melhores estão localizadas na sequência II, porém os reservatórios mais extensos, e de boa correlação lateral estão na sequência I, isso de dá pelo fato da sequencia I ter sido depositada em um ambiente desconfinado, e a sequencia II estar numa região mais confinada. Além da sequencia I ter sofrido maior processo de diagênese que a sequencia II, resultado provavelmente da cimentação de carbonato abundante neste intervalo estratigráfico e autigênese de sílica nos grãos de quartzo. Porém a porosidade secundária gerada pela dissolução dos constituintes carbonáticos e feldspato, proporcionou um aumento desta porosidade. A análise de palinofácies e geoquímica orgânica revelaram um aumento de fitoclastos para o topo da formação, o que indica que estes ficam cada vez mais continentais e com influencia fluvial mais acentuada. A intensa concentração de matéria orgânica resultando em um COT alto corresponde as SIM, reconhecidas em perfil e sísmica, sendo estes os intervalos Geradores da Bacia. Os dados de geoquímica dos minerais pesados permitiu reconhecer a existência de duas proveniências diferentes para os arenitos da sequencia I e sequência II, com base na assembleia de minerais pesados e principalmente pelos índices de Ar e Titanio+Zr. Revela ainda que a sequência I corresponde a sedimentos de segundo ciclo, ou seja, a retrabalhamento de rochas sedimentares preexistentes, e a grande quantidade de granada em todo o poço revela que estas rochas sofreram pouco processo de intemperismo, com rápida erosão e deposição. A importância dos estudos sedimentológicos e estratigráficos em escala de campo é principalmente para a previsão das fácies e sistema deposicional e consequentemente do reservatório encontrado. Sob o ponto de vista da ocorrência de reservatórios, estas correlações são muito importantes, pois permitem realizar previsões destes depósitos, e das suas fácies. / Candeias Formation (PACK & ALMEIDA, 1945) is belonging to the Santo Amaro Group, and consisting in sandstones and shales of the Cretaceous period and corresponds to the first deposit of the Rift phase from Recôncavo Basin. The age of these sediments varies from Medium Berriasian to lower Valanginian (~ 143M.a.). With a time range from of 4.5 M.a. and an average thickness of 1000 m. Located in Rio da Serra stage and this sediments are interpreted as lacustrine shales and deposits of turbidity current. The Rift climax (PROSSER, 1993), or Candeias Formation had a very important role in the history of development of oil and gas extraction in the Recôncavo Basin, because the shales are the source rocks from this basin, and the sandstones are important hydrocarbon reservoirs. Understanding the sedimentological processes of this formation and their stratigraphic evolution, is still a challenge, because most of the information comes from indirect data (seismic, logs and oil production data), because the outcrops are scarce. Thus, studies of the cores are the main and direct data explored here. The study area is located in the structural compartment from Recôncavo Basin, called Borda Nordeste, and covers the Rio Itariri field, Fazenda Bálsamo field and Riacho da Barra field, which are aligned along the Salvador Fault in Patioba plateau. The depositional system is interpreted as lake with sandy deposits from turbidity current, and is mainly composed of shales, intercalation of shale and very fine sandstones, arkosean sandstones (FOLK, 1968) and sandstones hybrids (ZUFFA, 1980). The turbidite flows are interpreted as a result of destabilization of the lake platform in intense tectonic activity period. During the tectonic quiescence, most of shale sedimentation is assigned. These deposits can be correlated throughout the study area and the shale has a good response in electrical and seismic profiles. The sequence stratigraphy (SE) in rift basins could be used with the same criteria from those used in intracratonic basins or passive margin basins, but always thinking that this kind of basin are constantly affected by tectonics, as proposed by Prosser (1993) and Martins - Neto & Catuneanu (2010). The methodology is based on identify tendencies Transgressive - Regressive (TR) as proposed for Embry & Johannenessen (1992), from 3rd and 4th orders of sequence and, identify key stratigraphic surfaces then. Have been interpreted five stratigraphic surfaces (two of maximum flood surfaces (MFS) and three sequence limit (SL)) for the three depositional sequences, referred to as Sequence I Sequence II and Sequence III. These surfaces allowed correlating the sandy deposits, using the electric logs (Gamma, Resistivity and neutron-density). Have been described 1430m core, 54 thin sections, seismic interpretation of the stratigraphic surfaces of two 3D seismic, geochemical analysis of heavy minerals, palynofacies analysis and organic geochemistry, of six wells from the three fields in study. The stratigraphic and sedimentological analysis was based on the rock x core correlation, size description and interpretation from facies, and their associations. The sandstones facies are described as fine and coarse sandstones, parallel stratification and cross low angle stratification, often fluidization and massive sandstones happens. These facies are related to facies of turbidite channels or proximal turbidite lobes. Very fine sandstones with intercalation of shales and sandstones with current ripples and intense fluidization and gray shales laminated and massive are related to distal turbidite lobes or the basin bottom deposits. The petrographic analysis of sandstones showed that they are essentially arkosean, and had presence abundant of ostracod bioclasts, oncolites, and peloids to sequence I, and metamorphic rock fragments, and plutonic, and carbonate crystals, phosphates to the sequence II. Calcite, ferrous calcite, dolomite, ferrous dolomite are the main cements probably found due to the dissolution of carbonate components. But the most common diagenetical processes are silica authentic growth of quartz and albite. Many of these diagenetic processes can contribute to substantial reduction of primary porosity and permeability, but when the main porosity (primary intergranular) is combined with secondary porosity (dissolution of feldspars or bioclasts) can greatly improve the porosity of these sandstones. Best permoporosity features are located in the sequence II, but the most extensive reservoirs and good lateral correlation are in sequence I. It happens because the sequence I was placed in a large environment and the sequence II is a region more confined. Sequence I have suffered larger process of diagenesis that the sequence II, probably as result of the carbonate cementation in this stratigraphic interval and authigenic silica in quartz grains. But the secondary porosity generated by dissolution of carbonate constituents and feldspar, provided an increase of this porosity. The palynofacies and geochemical organic analysis showed an increase of phytoclasts to the top of the Candeias Formation, showing increasingly more severe continental and river influences. The intense concentration of organic matter is resulting in a high organic total carbon matches the MFS recognized in profile and seismic, which are the generators of the Recôncavo Basin. The geochemical data of heavy minerals allowed to recognize the existence of two different sources for the sandstones of sequence I and II, based on the assembly of heavy minerals and especially the rates of ARi and Titanium + Zr. It also reveals that the sequence I is formed by the second cycle sediments, like an erosion of pre-existing sedimentary rocks, and the large amount of garnet around the well shows that the rocks have no significant intemperism process, with quickly erosion and deposition. The importance of sedimentological and stratigraphic studies in field scale is mainly for the prediction of facies and depositional system of the reservoir. From the point of view of the occurrence of reservoirs, these correlations are very important, since these allow to forecast deposits and their facies.

A Bacia de Campos está limitada pelo Alto de Vitória ao Norte e pelo Alto de Florianópolis ao sul, possuindo uma área de aproximadamente 100.000 km2. Sua seção rifte é composta pela porção basal a mediana do Grupo Lagoa Feia, e inclui a principal rocha geradora da bacia, reconhecidamente rica em matéria orgânica, sendo a maior produtora de hidrocarbonetos do Brasil, e rochas reservatório carbonáticas. O presente estudo foca sua análise no intervalo rifte, onde foi realizada uma interpretação e mapeamento sistemático de linhas sísmicas 2D em uma área chave da bacia. Esta análise é baseada em adaptações de modelos já existentes de evolução de bacias rifte, e nos conceitos de estratigrafia de sequências aplicados à sismoestratigrafia. Através da interpretação e mapeamento das seções sísmicas, foi possível elaborar um modelo evolutivo para a fase inicial da Bacia de Campos, com a elaboração de uma carta cronoestratigráfica e estabelecimento dos tratos de sistemas que distinguem as diferentes fases de evolução dos meio-grábens reconhecidos. O resultado foi a delimitação de três tratos de sistemas tectônicos, que permitiram uma compreensão detalhada da complexa evolução e desenvolvimento das calhas da Bacia de Campos durante a fase rifte. / The Campos Basin is limited northward by the Vitória High and southward by the Florianópolis High, with an area of approximately 100,000 km2. The rift section in the Campos Basin comprises the basal and median portions of the Lagoa Feia Group, and includes the main source rocks in the basin, which is known to be rich in organic matter and is the best hydrocarbon producer in Brazil, as well as carbonate reservoir rocks. The present study focuses its analysis on the rift section, where a systematic mapping and interpretation of 2D seismic lines in a key area of the basin was carried out. This analysis is based on adaptations of existing evolution models for rift basins, and the concepts of sequence stratigraphy applied to seismic stratigraphy. Through the interpretation and mapping of seismic sections, it was possible to propose an evolution model for the initial phase of the Campos Basin, with the construction of a chronostratigraphic chart and the establishment of systems tracts that distinguish different stages on the evolution of the recognized half-grabens. The result was the delimitation of three tectonic systems tracts that allowed the detailed understanding of the complex evolution and trough development of the Campos Basin during the rift phase.

Virtual reality is a concept that has existed for some time but the recent advances in the performance of commercial computers has led the development of different commercial head mounted displays, for example the Oculus Rift. With this growing interest in virtual reality, it is important to evaluate existing techniques used when designing user interfaces. In addition, it is also important to develop new techniques to be able to give the user the best experience when using virtual reality applications. This thesis investigates the design of a user interface for a virtual reality using Oculus Rift combined with the Razer Hydra and Leap Motion as input devices. A set of different graphical user interface components were developed and, together with the different input devices, evaluated with a user test to try to determine their advantages. During the implementation of the project the importance of giving the user feedback was shown. Adding both visual and aural feedback when interacting with the GUI increases the usability of the system. According to the conducted user test, people preferred using the Leap Motion even if it was not the easiest input device to use. It also showed that the current implementation of input devices was not precise enough to be able to draw conclusions about the different user interface components.

No description available.

Modern virtual reality is an ever growing subject in today’s society. I delved deeper into some key moments in the development of modern virtual reality. Oculus Rift has shown incredible potential. Some developments even seek to envelope the human senses in virtual reality as well.   With several different approaches to the same solution there are many ways that the experience can affect the overall immersion of a consumer into the product.  The tests I performed were primarily focused around the interaction between the human senses and immersion. The immersion can be increased or decreased by basic means of stimulating the human senses. This test was implemented by having volunteers participate in two phases in a supervised environment. In the first phase, the participants were subjected to an increase in immersion by stimulating senses other than their eyes and ears. The second phase involved reducing the participants’ sensory stimulation to see what the difference in immersion would be between the two phases.  The results of the investigation show that manipulating the human senses does have an impact on immersion when using virtual reality. Immersion can be affected by increasing or decreasing the stimuli for the human senses.

Doctor of Philosophy / Department of Diagnostic Medicine/Pathobiology / A. Sally Davis / William Wilson / Rift Valley fever virus (RVFV) is a zoonotic arbovirus that is a significant threat to livestock and humans. It is listed as #3 for most dangerous animal threats and is in the top 10 pathogens needing urgent research in preventative and control measures. Although RVFV has never been reported in the US or Europe, outbreaks outside the African continent have sparked renewed interest in developing diagnostics and vaccines to protect both agriculture and public health. Having specific and versatile diagnostics is critical for vaccine development and application. For example, diagnostic tools that aid in identifying key immunogens and understanding the virus-host interaction directly contribute to developing protective vaccines. Additionally, vaccines that are used prophylactically or in response to an outbreak require diagnostic tests to differentiate infected from vaccinated animals (DIVA). This is critical for assessing the return to ‘disease free’ status after an outbreak. Unfortunately, there are limited RVFV diagnostic tests that are versatile and DIVA compatible with the newest RVFV vaccines. We describe the development of several diagnostic tools that are DIVA compatible for detecting RVFV nucleic acid, antibodies, and antigens. First, we evaluate a fluorescence microsphere immunoassay (FMIA) for the detection of antibodies against a RVFV surface glycoprotein and the nucleocapsid protein. The targets developed in this assay provide the basis for a DIVA-compatible serological assay with a candidate RVFV Gn/Gc subunit vaccine, as well as, offer a multiplexing platform that can simultaneously screen for several ruminant diseases. Second, we describe a novel chromogenic in situ hybridization (ISH) assay to detect RVFV in formalin-fixed, paraffin-embedded (FFPE) tissues. This molecular assay offers a highly sensitive, multiplexing platform that detects RVFV RNA on the cellular level of diagnostic tissue samples. Moreover, we demonstrate the first application of ISH as a DIVA-compatible assay for candidate RVFV gene-deletion vaccines. Third, we provide working protocols for western blot (WB), immunohistochemistry (IHC), and immunofluorescence (IF) that use monoclonal or polyclonal antibodies against key RVFV antigens. These tools can be applied to pathogenesis research and used in the development of vaccine and therapeutic countermeasures against RVFV. The RVFV diagnostic methods developed and evaluated in this dissertation can serve as a model for developing diagnostic strategies for other transboundary animal diseases.

Les marges passives volcaniques, qui représentent plus des trois-quarts des marges passives sur Terre, sont les témoins privilégiés des processus d'extension lithosphérique menant à l'ouverture de nouveaux bassins océaniques. Nous explorons les relations structurales et temporelles qui existent entre le développement des grandes structures qui accommodent l'extension et l'amincissement, et la production magmatique qui lui est associée pendant le développement d'une marge volcanique naissante, accessible à l'observation directe : le point triple Afar en Éthiopie. Nous produisons une nouvelle lecture de la province Afar en tant qu'analogue en devenir des marges volcaniques. L'approche combine (1) une étude de terrain et de datation du volcanisme pour caractériser le timing de la déformation crustale et le style structural du rift pendant les phases les plus précoces, (2) la détermination géochimique de l'évolution des régimes de fusion mantellique au cours de l'extension, (3) la construction d'un modèle régional qui traite de l'évolution des marges volcaniques en lien avec leur segmentation. Nous mettons en évidence un style structural de " magmatic wide rift " en Afar, associé au jeu de grands détachements. Des phases tectoniques ponctuelles alternent avec des périodes de magmatisme plus prolongées. La segmentation précoce syn-rift contrôle le style structural, la mise en place du magma et l'asymétrie des marges. Le break-up correspond à l'amincissement et le remplacement de la croûte initiale par du matériel mafique pour former la première croûte océanique. / Volcanic passive margins, that represent more than the three quarters of continental margins worldwide, are privileged witnesses of the lithospheric extension processes that form new oceanic basins. We explore the structural and temporal relationships that exist between the development of the major thinning and stretching structures and the magmatic production associated to them. To do so, we will focus our work on the Afar triple junction, Ethiopia, a nascent volcanic passive margin. The rationale of this work is threefold. First, we present fieldwork analysis with lavas geochronology to determine the timing and style of the rift formation, since the early syn-rift period to present days. Second, we determine how the melting regime evolved in response to the deformation of the crust, through a geochemical study of the pre- to syn-rift lavas. Third, we present a synthetic regional that describes the evolution of the volcanic margins in relationship with their segmentation. Central Afar deformed as a magmatic wide rift, associated with major detachment faults. Punctual tectonic phases alternate with protracted magmatic periods. Early syn-rift segmentation controls the structural style, magma emplacement and asymmetry of the margins. The break-up is reached when the initial crust is thinned and replaced by mafic material to form the first oceanic crust.