Sistemas estuarinos são locais de transição entre ambientes marinhos e fluviais, cujas forçantes influenciam a dinâmica e a distribuição das propriedades químicas, biológicas e sedimentares. Aproximadamente 60 % de todas as grandes cidades se desenvolveram ao redor de estuários que, por serem ambientes abrigados, favorecem a navegação e instalação de portos. O objetivo geral do trabalho foi de identificar os processos sedimentares atuantes em um trecho do canal de acesso ao Porto de Santos (Trecho 1 do Porto organizado), compreendendo 12 km de comprimento desde a embocadura da baía de Santos até a entrada no Canal do Porto, utilizando um conjunto de dados de diferentes períodos (entre 2010 e 2016), provenientes de diferentes fontes acústicas, visando contribuir para a melhor compreensão da dinâmica sedimentar do Sistema Estuarino de Santos. Foram utilizados dados obtidos com um duplo chirp (frequências entre 2-8 kHz e 10-20 kHz) e dados de batimetria multifeixe. A metodologia consistiu na comparação de levantamentos batimétricos (executados em diferentes períodos) e de forma complementar foram utilizados os dados obtidos com a fonte acústica chirp. As análises proporcionaram a identificação de indícios de erosão e de assoreamento no Trecho 1 do canal do Porto de Santos. Em alguns locais, foi possível relacionar os padrões de erosão e de assoreamento com a hidrodinâmica local e, assim, sugerir tendências nos processos sedimentares atuantes na área de estudo. Sem dragagem a tendência do Trecho 1 do Porto de Santos é de assoreamento. O Trecho 1 foi divido em 2 setores com comportamento distintos. O setor A (próximo à embocadura do canal) é, naturalmente, mais profundo, o sedimento de fundo não é depositado em grande quantidade nesse local devido à intensidade da velocidade das correntes que ocorrem no setor. Há indícios de instabilidade das encostas no trecho mais estreito do canal, da ocorrência de lama fluida e de gás raso nesse local. O setor B era, naturalmente, mais raso em 1960, período em que o canal passou a ter a sua configuração atual, sugerindo a formação de um delta de maré vazante no setor, onde a velocidade das correntes são mais lentas, quando comparadas com o setor A. / Estuarine systems are sites of transition between marine and fluvial environments, whose forcing influences the dynamics and distribution of chemical, biological and sedimentary properties. Approximately 60% of all large cities have developed around estuaries because they are sheltered environments, allowed the navigation and harbors installation. The objective of the study was to identify the sedimentary processes in a section of Santos Harbor channel, comprising 12 km in length from the mouth of the bay to the entrance in the Port Channel. It was used a data set from different periods (2010-2016), from different acoustic sources, aiming to contribute to a better understanding the sedimentary dynamics in the Santos Estuary System. It was used a double chirp data with frequencies between 2-8 kHz and 10-20 kHz and multibeam bathymetry data. The methodology consisted in the comparison of bathymetric surveys performed in different periods and in a complementary way used the data obtained from a double chirp. The analyzes allowed an identification of erosion and silting in Section 1 of Santos Port Channel. It was possible to relate erosion and silting patterns to local hydrodynamics and to suggest trends in sedimentary processes in the study region. Without dredging, the trend of Section 1 from the Santos Harbor was of silting. The Section 1 it was divided into 2 sectors with different behavior. Sector A is naturally deeper; the sediment is not deposited in large quantities at this location because of the currents velocities that occurring there. In this site there is evidence of instability of the slopes in the channel\'s narrowest section, the occurrence of fluid mud and shallow gas. Sector B was naturally shallower in 1960, when the canal became its current configuration, suggesting the formation in this site of an ebb tide delta, where the currents velocities are slower when compared to sector A.

This work was conducted to help understand a premature and irregular water breakthrough which resulted from a waterflooding project in the increment II region of Haradh oilfield in Saudi Arabia using different geophysical methods. Oil wells cannot sustain the targeted oil production rates and they die much sooner than expected when water enters the wells. The study attempted to identify fracture systems and their role in the irregular water sweep. Single-well acoustic migration imaging (SWI), walkaround vertical seismic profiling (VSP) and cross-dipole shear wave measurements were used to detect anisotropy caused by fractures near and far from the borehole. The results from all the different methods were analyzed to understand the possible causes of water fingering in the field and determine the reasons for discrepancies and similarities of results of the different methods. The study was done in wells located in the area of the irregular water encroachment in Haradh II oilfield. Waterflooding was performed, where water was injected in the water injector wells drilled at the flanks of Harahd II toward the oil producer wells. Unexpected water coning was noticed in the west flank of the field. While cross-dipole and SWI measurements of a small-scale clearly identify a fracture oriented N60E in the upper tight zone of the reservoir, the VSP measurements of a large-scale showed a dominating fracture system to the NS direction in the upper highpermeability zone of the same reservoir. These results are consistent with the directions of the three main fracture sets in the field at N130E, N80E and N20E, and the direction of the maximum horizontal stress in the field varies between N50E and N90E. Results suggested that the fracture which is detected by cross-dipole at 2 to 4 ft from the borehole is the same fracture detected by SWI 65 ft away from the borehole. This fracture was described using the SWI as being 110 ft from top to bottom, having an orientation of N60E and having an angle of dip of 12° relative to the vertical borehole axis. The detected fracture is located in the tight zone of the reservoir makes a path for water to enter the well from that zone. On the Other hand, the fractures detected by the large-scale VSP measurements in the NS direction are responsible for the high-permeability in the upper zone of the reservoir.

Volcanic rifting environments, such as in Iceland, are challenging for conventional seismic reflection methods using active surface seismic sources. This study demonstrates the potential of a novel technique, called Virtual Reflection Seismic Profiling (VRSP) for imaging reflections in geothermal regions, like Hverahlíð, where a dense seismic array recorded a number of local microearthquakes for cross-correlation. Uppsala University, in collaboration with Reykjavik Energy, recorded seismicity in Hverahlíð using both seismometers and geophones. Acquired data were processed using the VRSP method, which applies seismic interferometry only to selected events, in this thesis local microearthquakes. Cross-correlation of the signal from a microearthquake recorded at one of the stations, which acts as a virtual source, with a ghost reflection recorded by the remaining receivers, produces a virtual shot gather. Stacking each station’s result, for all available events, and following a conventional multichannel processing sequence resulted in two stacked seismic images. Potential reflections observed in the obtained sections could be associated with major feed zones identified in the area by the borehole measurements. Eight dynamite explosions were processed with a conventional seismic reflection method, as a complementary source to the microearthquakes. In the produced stacked seismic section two potential reflections could be observed. Results from both passive and active datasets were 3D visualised to verify whether the reflections correspond to each other between sections. Two horizons were traced throughout all three stacked sections. One more interface appeared on two images obtained from processing the passive data. This study shows promising results for using natural sources to image the subsurface in a challenging environment.

A constante pressão exercida sobre os ambientes costeiros por parte das diferentes atividades humanas, em conjunto com novas necessidades relacionadas a estudos ambientais particularmente no que diz respeito à geração de gases de efeito estufa em sedimentos marinhos, têm gerado uma crescente demanda por conhecimento dos processos de geração, acúmulo e liberação desses gases. Dado esse desafio, torna-se necessário o desenvolvimento de novas aplicações de ferramentas geofísicas que forneçam informações além das propriedades acústicas do meio. Dessa forma, o presente trabalho tem como objetivo a avaliação do método eletrorresistivo no mapeamento estratigráfico e na detecção de feições geoelétricas indicativas da presença de gás em sedimentos rasos. Para isso, foram analisadas seções geoelétricas adquiridas no Saco do Mamanguá e na Enseada de Paraty-Mirim por meio da comparação com perfis sísmicos de alta resolução e da medição de resistividade em amostras de sedimentos. Nessas amostras foi simulada a presença de bolhas de gás e analisada a variação da resistividade com a diminuição da salinidade da água intersticial. Observou-se que um volume de bolhas de 0,20% do volume total é suficiente para aumentar em um fator de 1,8 a resistividade de uma amostra saturada em água do mar. Também verificou-se que a resistividade medida é dependente da resistividade da água intersticial. Medidas de susceptibilidade magnética mostraram, neste local, que a variação da resistividade não é devida a variações mineralógicas. As seções geoelétricas mostraram boa correlação com os perfis sísmicos até 9 m de profundidade a partir da superfície da água, onde ocorre uma camada geoelétrica de resistividade <0,35 Ohm.m. Nessa profundidade, observa-se uma interface entre camadas de resistividade elétrica possivelmente causada por uma mudança no teor de água ou de matéria orgânica. Essa interface coincide com o topo da turbidez acústica produzida pela presença de gás. / Given the constant pressure exerted over coastal environments by different human activities, in addition to the need for more knowledge concerning environmental issues, particularly with respect to greenhouse gases generation in marine sediments have generated an increasing demand for more information regarding the generation, accumulation and seepage of these gases. Faced with this challenge, there is a necessity to develop new applications to geophysical tools that provide more information than merely the acoustic properties of the medium. This work aims to the evaluation of the geoelectric method in stratigraphic mapping and the detection of geoelectric features of shallow gas. For that purpose, geoelectric sections acquired in the ria of Saco do Mamanguá and Paraty-Mirim were compared with high resolution seismic profiles and resistivity measurements in sediment samples. Presence of gas bubbles inside the sedimentary matrix was simulated and resistivity variation analyzed against the decrease of interstitial water salinity. It was observed that a bubble volume of 0.20% of the total volume is sufficient to increase the resistivity by a factor of 1.8. It was also confirmed that the sample resistivity is dependent on interstitial water resistivity. Magnetic susceptibility measurements showed that resistivity variation is not due to mineralogical variations. The geoelectric sections showed good correlation with the seismic profiles up to 9 m depth from the water surface, where occurs a geoelectric layer of resistivity <0.35 Ohm.m. At this depth, it is observed an interface between resistivity layers possibly caused by a change in water or organic matter content. This interface matches the top of the acoustic turbidity produced by shallow gas occurrences.

A constante pressão exercida sobre os ambientes costeiros por parte das diferentes atividades humanas, em conjunto com novas necessidades relacionadas a estudos ambientais particularmente no que diz respeito à geração de gases de efeito estufa em sedimentos marinhos, têm gerado uma crescente demanda por conhecimento dos processos de geração, acúmulo e liberação desses gases. Dado esse desafio, torna-se necessário o desenvolvimento de novas aplicações de ferramentas geofísicas que forneçam informações além das propriedades acústicas do meio. Dessa forma, o presente trabalho tem como objetivo a avaliação do método eletrorresistivo no mapeamento estratigráfico e na detecção de feições geoelétricas indicativas da presença de gás em sedimentos rasos. Para isso, foram analisadas seções geoelétricas adquiridas no Saco do Mamanguá e na Enseada de Paraty-Mirim por meio da comparação com perfis sísmicos de alta resolução e da medição de resistividade em amostras de sedimentos. Nessas amostras foi simulada a presença de bolhas de gás e analisada a variação da resistividade com a diminuição da salinidade da água intersticial. Observou-se que um volume de bolhas de 0,20% do volume total é suficiente para aumentar em um fator de 1,8 a resistividade de uma amostra saturada em água do mar. Também verificou-se que a resistividade medida é dependente da resistividade da água intersticial. Medidas de susceptibilidade magnética mostraram, neste local, que a variação da resistividade não é devida a variações mineralógicas. As seções geoelétricas mostraram boa correlação com os perfis sísmicos até 9 m de profundidade a partir da superfície da água, onde ocorre uma camada geoelétrica de resistividade <0,35 Ohm.m. Nessa profundidade, observa-se uma interface entre camadas de resistividade elétrica possivelmente causada por uma mudança no teor de água ou de matéria orgânica. Essa interface coincide com o topo da turbidez acústica produzida pela presença de gás. / Given the constant pressure exerted over coastal environments by different human activities, in addition to the need for more knowledge concerning environmental issues, particularly with respect to greenhouse gases generation in marine sediments have generated an increasing demand for more information regarding the generation, accumulation and seepage of these gases. Faced with this challenge, there is a necessity to develop new applications to geophysical tools that provide more information than merely the acoustic properties of the medium. This work aims to the evaluation of the geoelectric method in stratigraphic mapping and the detection of geoelectric features of shallow gas. For that purpose, geoelectric sections acquired in the ria of Saco do Mamanguá and Paraty-Mirim were compared with high resolution seismic profiles and resistivity measurements in sediment samples. Presence of gas bubbles inside the sedimentary matrix was simulated and resistivity variation analyzed against the decrease of interstitial water salinity. It was observed that a bubble volume of 0.20% of the total volume is sufficient to increase the resistivity by a factor of 1.8. It was also confirmed that the sample resistivity is dependent on interstitial water resistivity. Magnetic susceptibility measurements showed that resistivity variation is not due to mineralogical variations. The geoelectric sections showed good correlation with the seismic profiles up to 9 m depth from the water surface, where occurs a geoelectric layer of resistivity <0.35 Ohm.m. At this depth, it is observed an interface between resistivity layers possibly caused by a change in water or organic matter content. This interface matches the top of the acoustic turbidity produced by shallow gas occurrences.

Estudos de acumulações de gás raso e os efeitos destes fenômenos nas ondas sísmicas são objeto de trabalho de diversos pesquisadores em diferentes partes do planeta. As respostas das acumulações de gás nas ondas sísmicas se diferenciam pelas diversas frequências dos equipamentos sísmicos e trazem informações importantes no que concerne à formação e evolução dos ambientes em questão. O Canal da Bertioga se situa no litoral Sul do Estado de São Paulo, Brasil, e consiste em um ambiente de características estuarinas que conecta a plataforma continental, em sua desembocadura oceânica, e a Baixada Santista em sua desembocadura continental. Trata-se de um sistema de baixa hidrodinâmica, com profundidades máximas de 18m, e sofre influência de seus afluentes oriundos da serra do mar. Na presente pesquisa, foram utilizadas as fontes Pinger (24 kHz), Chirp (2 - 8 kHz) e Boomer (0,5 - 2 kHz) operando simultaneamente para o levantamento de dados geofísicos e amostragens superficiais com um amostrador de mandíbulas do tipo Van Veen. Foram também obtidos cinco testemunhos sedimentares, dos quais foram obtidos dados de taxa de sedimentação. O levantamento sísmico permitiu a identificação de diversas fácies acústicas de gás nos sedimentos assim como padrões de escape. Em função da identificação dos padrões de ocorrência destas formações de gás se pôde dividir o Canal da Bertioga em três setores: Estreito, Largo do Candinho e Canal Leste. No trecho denominado de Estreito as Coberturas acústicas foram predominantes com pouca variação de cota (± 3 m), os escapes de gás foram menos ocorrentes se comparados às outras áreas e se deu especialmente em forma de Pináculos de Turbidez. No Largo do Candinho predominaram as Sombras Negras e Coberturas Acústicas muito rasas, em torno de 1 a 2 m do substrato, com grande ocorrência de escape de gás do tipo Plumas Acústicas. Por fim, O Canal Leste apresentou as maiores variações nas cotas das Coberturas Acústicas, com ocorrências mais profundas (8 m em média) e escapes de gás em forma de Plumas Intrassedimentares. Foram definidas unidades estratigráficas deposicionais que contribuíram para a proposição de uma compartimentação do canal, em função dos padrões de ocorrência de gás. A fonte boomer permitiu identificar quatro unidades estratigráficas No Canal Leste, duas no Largo do Candinho e apenas uma no Estreito, neste último trecho a penetração do sinal foi especialmente comprometida em função da constante ocorrência das Coberturas Acústicas. Diante destas evidências pôde-se concluir que o Canal da Bertioga evoluiu como dois sistemas distintos, os quais foram separados durante as regressões marinhas e conectados novamente em trato de mar alto. A mudança brusca das cotas de ocorrência das Coberturas Acústicas entre o Canal Leste e o Largo do Candinho, além de evidências de falhamentos neotectônicos do Pleistoceno tardio sugerem que a conexão destes ambientes (Estreito + Largo do Candinho e Canal Leste) pode ter sido abrupta. / Studies of shallow gas accumulations and the effects of these components in the seismic waves are studied by several researchers in different parts of the world. The responses of the gas accumulations in the seismic waves are distinguished by different frequencies of seismic equipment and provide important information regarding the formation and evolution of the environments. The Channel of Bertioga is located on the southern coast of São Paulo, Brazil, and it\'s an environment with estuarine characteristics that connects the Sea of Bertioga to its oceanic mouth, and the city of Santos to it\'s continental mouth. This is a low hydrodynamic system with maximum depths of 18m, and is influenced by its tributaries from the Serra do Mar mountains. The present study was conducted with the sources Pinger (24kHz), Chirp (2 - 8 kHz) and Boomer (0.5 - 2 kHz) operating simultaneously for the geophysical survey data, surficial sediment sampling was made with a Van Veen grab. Five cores were also acquired, of which the sedimentation rate was obtained. The seismic survey allowed the identification of several buried gas facies and seepages. Regarding the patterns in the occurrence of gas formations the Bertioga Channel could be split into three sectors: The Narrow Sector, Candinho and Eastern Sector. In the Narrow part, the Acoustic Blankings were predominant with little variation in elevation (± 3 m), seepages occurred less compared to other areas and were mostly consisting of Turbidity Pinnacles. In the Candinho sector, Black Shadows and Acoustic Blankets about 1 to 2m of the substrate prevailed, with high occurrence of seepages in the form of Acoustic Plumes. Finally, the Eastern Sector had the highest changes in the levels of Acoustic Blankets, with the deepest occurrences (8m on average) and seepages in the form of Intrasedimentary Plumes. Some stratigraphic units were defined, which contributed to the previous division by the gas occurrences. The Booomer source allowed the identification of four Stratigraphic Units inthe Eastern Channel, two in the Candinho sector and only one Stratigraphic Unit in the Narrow Sector. In the last sector signal penetration was particularly compromised due to the constant occurrence of Acoustic Blankets. Given this evidence, it was concluded that the Bertioga Channel evolved as two distinct systems, which were separated during the marine regressions and re-connected during marine transgressions. The sudden change in the depths of occurrence in Acoustic Blankets between the Eastern Channel and Candinho, and evidence of neotectonic faulting in the Late Pleistocene suggest that the connection of these environments (Narrow Sector + Candinho and Canal East) may have been abrupt.

Estudos de acumulações de gás raso e os efeitos destes fenômenos nas ondas sísmicas são objeto de trabalho de diversos pesquisadores em diferentes partes do planeta. As respostas das acumulações de gás nas ondas sísmicas se diferenciam pelas diversas frequências dos equipamentos sísmicos e trazem informações importantes no que concerne à formação e evolução dos ambientes em questão. O Canal da Bertioga se situa no litoral Sul do Estado de São Paulo, Brasil, e consiste em um ambiente de características estuarinas que conecta a plataforma continental, em sua desembocadura oceânica, e a Baixada Santista em sua desembocadura continental. Trata-se de um sistema de baixa hidrodinâmica, com profundidades máximas de 18m, e sofre influência de seus afluentes oriundos da serra do mar. Na presente pesquisa, foram utilizadas as fontes Pinger (24 kHz), Chirp (2 - 8 kHz) e Boomer (0,5 - 2 kHz) operando simultaneamente para o levantamento de dados geofísicos e amostragens superficiais com um amostrador de mandíbulas do tipo Van Veen. Foram também obtidos cinco testemunhos sedimentares, dos quais foram obtidos dados de taxa de sedimentação. O levantamento sísmico permitiu a identificação de diversas fácies acústicas de gás nos sedimentos assim como padrões de escape. Em função da identificação dos padrões de ocorrência destas formações de gás se pôde dividir o Canal da Bertioga em três setores: Estreito, Largo do Candinho e Canal Leste. No trecho denominado de Estreito as Coberturas acústicas foram predominantes com pouca variação de cota (± 3 m), os escapes de gás foram menos ocorrentes se comparados às outras áreas e se deu especialmente em forma de Pináculos de Turbidez. No Largo do Candinho predominaram as Sombras Negras e Coberturas Acústicas muito rasas, em torno de 1 a 2 m do substrato, com grande ocorrência de escape de gás do tipo Plumas Acústicas. Por fim, O Canal Leste apresentou as maiores variações nas cotas das Coberturas Acústicas, com ocorrências mais profundas (8 m em média) e escapes de gás em forma de Plumas Intrassedimentares. Foram definidas unidades estratigráficas deposicionais que contribuíram para a proposição de uma compartimentação do canal, em função dos padrões de ocorrência de gás. A fonte boomer permitiu identificar quatro unidades estratigráficas No Canal Leste, duas no Largo do Candinho e apenas uma no Estreito, neste último trecho a penetração do sinal foi especialmente comprometida em função da constante ocorrência das Coberturas Acústicas. Diante destas evidências pôde-se concluir que o Canal da Bertioga evoluiu como dois sistemas distintos, os quais foram separados durante as regressões marinhas e conectados novamente em trato de mar alto. A mudança brusca das cotas de ocorrência das Coberturas Acústicas entre o Canal Leste e o Largo do Candinho, além de evidências de falhamentos neotectônicos do Pleistoceno tardio sugerem que a conexão destes ambientes (Estreito + Largo do Candinho e Canal Leste) pode ter sido abrupta. / Studies of shallow gas accumulations and the effects of these components in the seismic waves are studied by several researchers in different parts of the world. The responses of the gas accumulations in the seismic waves are distinguished by different frequencies of seismic equipment and provide important information regarding the formation and evolution of the environments. The Channel of Bertioga is located on the southern coast of São Paulo, Brazil, and it\'s an environment with estuarine characteristics that connects the Sea of Bertioga to its oceanic mouth, and the city of Santos to it\'s continental mouth. This is a low hydrodynamic system with maximum depths of 18m, and is influenced by its tributaries from the Serra do Mar mountains. The present study was conducted with the sources Pinger (24kHz), Chirp (2 - 8 kHz) and Boomer (0.5 - 2 kHz) operating simultaneously for the geophysical survey data, surficial sediment sampling was made with a Van Veen grab. Five cores were also acquired, of which the sedimentation rate was obtained. The seismic survey allowed the identification of several buried gas facies and seepages. Regarding the patterns in the occurrence of gas formations the Bertioga Channel could be split into three sectors: The Narrow Sector, Candinho and Eastern Sector. In the Narrow part, the Acoustic Blankings were predominant with little variation in elevation (± 3 m), seepages occurred less compared to other areas and were mostly consisting of Turbidity Pinnacles. In the Candinho sector, Black Shadows and Acoustic Blankets about 1 to 2m of the substrate prevailed, with high occurrence of seepages in the form of Acoustic Plumes. Finally, the Eastern Sector had the highest changes in the levels of Acoustic Blankets, with the deepest occurrences (8m on average) and seepages in the form of Intrasedimentary Plumes. Some stratigraphic units were defined, which contributed to the previous division by the gas occurrences. The Booomer source allowed the identification of four Stratigraphic Units inthe Eastern Channel, two in the Candinho sector and only one Stratigraphic Unit in the Narrow Sector. In the last sector signal penetration was particularly compromised due to the constant occurrence of Acoustic Blankets. Given this evidence, it was concluded that the Bertioga Channel evolved as two distinct systems, which were separated during the marine regressions and re-connected during marine transgressions. The sudden change in the depths of occurrence in Acoustic Blankets between the Eastern Channel and Candinho, and evidence of neotectonic faulting in the Late Pleistocene suggest that the connection of these environments (Narrow Sector + Candinho and Canal East) may have been abrupt.

Detailed information about the oceanic environment is essential for many applications in the field of marine geology, marine biology, coastal engineering, and marine operations. Especially, knowledge of the properties of the sediment body is often required. Acoustic remote sensing techniques have become highly attractive for classifying the sea bottom and for mapping the sediment properties, due to their high coverage capabilities and low costs compared to common sampling methods. In the last decades, a number of different acoustic devices and related techniques for analyzing their signals have evolved. Each sensor has its specific application due to limitations in the frequency range and resolution. In practice, often a single acoustic tool is chosen based on the current application, supported by other non-acoustic data where required. However, different acoustic remote sensing techniques can supplement each other, as shown in this thesis. Even more, a combination of complementary approaches can contribute to the proper understanding of sound propagation, which is essential when using sound for environmental classification purposes. This includes the knowledge of the relation between acoustics and sediment properties, the focus of this thesis. Providing a detailed three dimensional picture of the sea bottom sediments that allows for gaining maximum insight into this relation is aimed at.<p><p><p>Chapters 4 and 5 are adapted from published work, with permission:<p>DOI:10.1121/1.3569718 (link: http://asadl.org/jasa/resource/1/jasman/v129/i5/p2878_s1) and<p>DOI:10.1109/JOE.2010.2066711 (link: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=5618582&queryText%3Dsiemes)<p>In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of the Université libre de Bruxelles' products or services.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Cette thèse a pour objectif d’établir une vision globale et continue mer-terre-mer d’une barrière littorale paraglaciaire, en combinant une approche morphologique et architecturale. L’originalité de l’isthme de Miquelon-Langlade (NO Atlantique) entre les deux îles éponymes réside en sa diversité et complexité de systèmes (flèches, cordons littoraux, lagune) qui s’emboitent formant une barrière composite évoluant le long de deux façades ouvertes sur l’océan. Ce travail a été rendu possible grâce à l’association de données topographiques (GPS-RTK), de géophysique marine (sismique HR) et terrestre (géo-radar), sédimentaires (carottes, échantillons de surface) ainsi que des datations par OSL. L’étude de cette barrière a permis 1) d’identifier l’ensemble des dépôts d’une séquence paraglaciaire (dépôts de chute, bas niveau, augmentation et haut niveau marin); 2) de pointer l’importance de la géométrie des îles, du substratum rocheux ainsi que de la topographie héritée dans la formation de la barrière; 3) de définir l’architecture interne de beach ridges mixte sable-galet; et 4) de pointer le potentiel de ces systèmes en tant marqueur du paléo-niveau marin tout en proposant la première courbe de tendance de l’évolution du RSL pour l’Archipel de Saint-Pierre-et-Miquelon sur les derniers 3000 ans (+1mm/an). L’association de l’ensemble de ces informations a permis de proposer un schéma de mise en place de la barrière, depuis le retrait de la calotte (13 700 ans) jusqu’à sa forme actuelle, évoluant dans un contexte d’augmentation du RSL et de fort apport sédimentaire, tout en proposant une vision de détail de la formation de la plaine de beach ridges au cours des derniers 3000 ans. / The purpose of this PhD thesis was to define a complete and continuous sea-land-sea view of a paraglacial coastal barrier system, combining morphological and architectural approaches. Particularity of the Miquelon-Langlade isthmus (NO Atlantic) lies in its diversity and complexity of systems (spits, beach ridges, and lagoon) that fit together to form a composite barrier prograding along two open coasts. Investigations of this barrier included topographic (RTK-GPS), ground-penetrating radar (GPR) seismic, sedimentary (cores, augers, samples) and chronologic (OSL) data collections. This study of this paraglacial composite barrier make possible 1) to characterize all deposits of the paraglacial sequence (FSST, LST, TST, HST); 2) to emphasize the primary influence of islands geometry, bedrock and inherited topography on the coastal progradational pattern; 3) to provide a better understanding of the internal architecture of depositional processes and driving mechanisms of mixed sand-and-gravel beach ridges; 4) to examine the potential of these mixed beach-ridge systems to record and preserve paleo-sea-level information, to produce the first sea level trends for the Saint-Pierre-et-Miquelon archipelago over the last 3000 years. The combination of all these data provide a model of development of the barrier since the ice sheet retreat (13 700 yrs) to its present form, in a context of RSL rise and high local glaciogenic sediment supply, and a detailed view of the formation of the beach ridge plain over the last 3000 yrs.