The upper Tanglewood Member is the final member of the Lexington Limestone and is well-known for its soft-sediment deformation. This study has confirmed the carbonate-shoal-complex origin of the unit, and detailed study shows that its development took place during five small-scale, sequence-like, fining-upward cycles related to eustasy and tectonics. Four lithofacies are represented in the unit. Facies analysis of each cycle shows that the thickest and coarsest part of each cycle corresponds to previously uplifted basement-fault blocks; the occurrence of thick, coarse facies on the same fault blocks suggests that the blocks continued to experience uplift due to Taconian far-field forces generated on the eastern margin of Laurentia. The upper Tanglewood Member includes six deformed horizons that can be traced into equivalent parts of the Clays Ferry and Point Pleasant formations. Concurrence of four lines of evidence, suggested by Ettensohn et al. (2002d) for interpretation of seismites, indicates that the widespread horizons of deformation are seismogenic in origin. Reactivation of basement structures due to Taconian far-field forces probably induced seismicity on the intra-platform carbonate complex so as to produce soft-sediment deformation. Petrographic investigation indicates that most of the cements in the upper Tanglewood limestones appear to be late diagenetic, fresh-water phreatic cements. Comparing the petrography of deformed and undeformed portions of the same horizon showed no significant differences in terms of cementation, indicating that cementation occurred primarily after deformation. The primary impact of deformation on the microstructure of the unit was the randomization of grain fabric and the increased presence of broken intraclasts.

Precambrian metamorphic rocks in the Beaver Dam Mountains display asymmetric, isoclinal folds with consistent fold axes plunging to the NW. These folds are parasitic and have a recursive nature that occurs on wavelengths from centimeters to perhaps kilometers as part of a NW-SE striking shear zone. The vergence of the folds indicates oblique shearing with a transport direction plunging 29° to the south. This shear zone may be associated with the collision of Yavapai Province island arcs with Laurentia. Structurally overlying, and adjacent to the metamorphic rocks are allochthonous and attenuated Mississippian limestone blocks and other strata debated to be either the result of mega-landsliding or fragments of the hanging wall rocks above a low-angle normal fault. We document previously unreported cataclastic damage zones tens of meters thick, an anastomosing zone of greenschist facies alteration hundreds of meters thick, and polished low-angle fault surfaces beneath these blocks. Other observations previously used to support a mega-landslide hypothesis are blocks of Redwall Limestone structurally overlying what was interpreted as Tertiary conglomerate. However, this contact is depositional, and the conglomerate is likely a sedimentary breccia facies of the Mississippian Redwall Limestone which is documented in several locations within the region. Additionally, some of the deformation and attenuation that was wrongly attributed to mega-landsliding or low-angle normal faulting is due to previously undocumented soft-sediment deformation. This deformation was gravity driven and accommodated by ductile granular flow, resulting in recumbent folds within the Mississippian Redwall Limestone and a prominent non-brittle detachment surface between the Redwall Limestone and the Cambrian Bonanza King Formation at Castle Cliff. This detachment was previously interpreted as the Castle Cliff Detachment, a low-angle normal fault, or as the slip surface of a landslide.

Uma série de pesquisas realizadas em depósitos de sistemas fluviais, desenvolvidos anterior e concomitantemente à colonização dos continentes por vegetação, são aqui apresentadas com o intuito de investigar as principais características deposicionais destes sistemas, particularmente suas assembléias de fácies e elementos arquitetônicos preservados. Esta pesquisa busca, desta maneira, propor modelos deposicionais para sucessões fluviais pré-vegetação e contribuir para o avanço do conhecimento sobre as mudanças seculares em padrões de sedimentação, principalmente em relação à evolução dos rios através do tempo geológico. Estudos sedimentológicos foram realizados em depósitos fluviais da Formação Applecross do Grupo Torridon (Toniano, Escócia), Formação Guarda Velha do Grupo Guaritas (Cambriano, Brasil) e no Old Red Sandstone do Midland Valley (Siluriano-Carbonífero, Escócia). Foram empregadas análises de associações de fácies e arquitetura deposicional por meio de estudos de alto detalhe em afloramentos, combinadas a análises de paleocorrentes, de proveniência, e de estruturas de deformação sinsedimentar. Depósitos de canais fluviais meandrantes pré-vegetação com espessos depósitos de planícies de inundação ricos em sedimentos de granulação fina são pela primeira vez descritos em detalhe nos estudos aqui apresentados sobre depósitos da Formação Applecross. Diversas estruturas de deformação sinsedimentar encontradas na unidade acima referida são analisadas, revelando que seus estilos podem ser relacionados a diferentes regiões de uma planície fluvial. Nos depósitos da Formação Guarda Velha, é registrada a inter-relação entre dois sistemas fluviais coevos, cuja arquitetura deposicional contrastante resultou da diferente localização destes sistemas em relação à estrutura da bacia, assim como de diferentes áreas de captação. São relatados os efeitos de distintos controles deposicionais, como ambiente tectônico e regimes hidráulicos, sobre a arquitetura deposicional preservada em sistemas fluviais pré-vegetação. Esses dados demonstram que o estilo entrelaçado-em-lençol, apontado como o estilo pré-vegetação predominante, engloba na verdade uma variedade de diferentes estilos fluviais. Estudos em depósitos do Siluriano ao Carbonífero do Old Red Sandstone revelam o crescente impacto da vegetação sobre depósitos fluviais, particularmente o aumento exponencial de formação de paleosolos, além de mostrar semelhanças entre alguns destes sistemas com os sistemas pré-silurianos. A integração desses estudos revela que sistemas fluviais pré-vegetação são relativamente mais complexos do que previsto pelos modelos atualmente disponíveis. Importantemente, sugere que a escassez de sedimentos de granulção fina, preservados em depósitos fluviais pré-silurianos, está mais relacionada à baixa competência destes sistemas em preservar tais sedimentos do que à sua suposta ausência em ambientes pré-vegetação. Foi também desenvolvida uma metodologia específica para o uso de estruturas de deformação em sedimentos inconsolidados como ferramentas na reconstrução de paleoambientes, através das relações entre diferentes estilos deformacionais e ambientes deposicionais, possibilitando a indicação de regimes hidráulicos em depósitos fluviais e a informação indireta de taxas de atividades tectônicas em bacias. A integração de dados de sedimentologia com estudos específicos de deformação sinsedimentar é uma ferramenta útil na reconstrução paleoambiental de sistemas fluviais. / A series of studies were undertaken on fluvial systems deposits which developed prior to land-plant colonization, in order to investigate the main depositional characteristics of those systems, particularly their main facies assemblages and preserved depositional architecture. Main objectives are the proposal of depositional models for pre-vegetation fluvial systems, and the understanding of main secular changes in sedimentation processes and its influence on the evolution of rivers through geological times. Sedimentologic studies were undertaken in fluvial deposits from the Applecoss Formation of the Torridon Group (Tonian, NW Scotland), the Guarda Velha Formation (Cambrian, southern Brazil), and the Old Red Sandstone in the Midland Valley (Silurian-Carboniferous, NE Scotland). Highly-detailed sedimentary facies and depositional architecture analyses in outcrop scale were integrated with palaeocurrent and provenance studies, and soft-sediment deformation analysis. Pre-vegetation meandering channel deposits with relatively thick, fine-grained floodplain deposits from the Applecross Formation and here described for the first time. Analyses on sinsedimentary deformation structures preserved in the Applecross Formation reveal different styles which can be related to different parts of the fluvial plain. Studies on the Guarda Velha Formation revealed the inter-relationship between two coeval fluvial systems with markedly contrasting preserved depositional architecture, which developed as a result of the different location of the systems in relation to basin structure and different caption areas. The effects of different depositional controls on preserved pre-vegetation fluvial system architecture, such as tectonic environment and hydraulic regime, are recorded and interpreted. The present data demonstrate that the sheet-braided style, which is regarded as the prevailing fluvial style before the Silurian, in fact encompasses a varied number of different pre-vegetation fluvial styles. Studies on the Silurian to Early Carboniferous Old Red Sandstones in the Midland Valley of Scotland reveal the progressive impact of land plants on fluvial sedimentation, particularly the exponential increasing rates of soil production. Integration of the here presented data reveal that pre-vegetation fluvial styles. Studies on the Silurian to Early Carboniferous Old Red Sandstone in the Midland Valley of Scotland reveal the progressive impact of land plants on fluvial sedimentation, particularly the exponential increasing rates of soil production. Integration of the here presented data reveal that pre-vegetation fluvial systems are relatively more complex than previously described in the literature. Importantly, it suggests that the paucity of fine-grained sediments in pre-Silurian fluvial deposits is most likely related to various preservation issues than to the lack of such sediments. A particular methodology for the use of soft-sediment deformation structures as palaeoenvironmental tool was developed, allowing the interpretation of hydraulic regimes in fluvial deposits, indication of the basin\'s tectonic activity, and the relationship between different deformation styles and distinct depositional environments. The combined analyses of soft-sediment deformation structures and sedimentologic data is a powerful tool with which fluvial systems palaeoenvironmental can be reconstructed.

O Sistema de Falhas Transbrasiliano é uma estrura complexa que se estende por mais de 7.400km, desde a região de Córdoba, Argentina, até a região central da Argélia, na África. O Sistema de Falhas Transbrasiliano e outras estruturas do embasamento exerceram grande influência na instalação e história deposicional das bacias sedimentares da Plataforma Sul-Americana, entre elas a Província Parnaíba e a Bacia Água Bonita, objetos de estudo desta tese. Zonas de fraqueza litosférica importantes, como o Sistema de Falhas Transbrasiliano, tendem a concentrar esforços remotos gerados na borda das placas, e dessa forma a ser foco de atividade tectônica e sismicidade intraplaca. Sismos intraplaca, embora pouco comuns, podem atingir magnitudes consideráveis e afetar grandes áreas. Tectônica e sismicidade intraplaca podem gerar diversos tipos de registro em bacias intracratônicas. Entre eles, se destacam os sismitos: estruturas de liquidificação produzidas em sedimentos inconsolidados submetidos a choque sísmico. Sismitos são ferramentas particularmente úteis para a reconstrução da história tectônica de bacias sedimentares; no entanto, sua caracterização e interpretação podem ser problemáticas, visto que processos não sísmicos podem induzir a formação de estruturas similares às produzidas por terremotos. Desta forma, foi elaborada uma metodologia visando a diagnose do agente desencadeador da deformação sinsedimentar, permitindo a distinção entre agentes de deformação autógenos e agentes de deformação alógenos, e entre estes identificar estruturas produzidas por abalos sísmicos. A partir de sua caracterização como possíveis sismitos, as estruturas foram analisadas, visando determinar intervalos de atividade tectônica sinsedimentar, que estruturas do embasamento foram reativadas e possíveis campos de paleotensões à época de sua formação. Para esta última finalidade, foi desenvolvida também uma metodologia para aquisição e tratamento estatístico de dados de orientação e espessura de diques clásticos. Foram identificados horizontes com sismitos no Grupo Serra Grande, nas formações Pimenteiras, Cabeças, Piauí, Pedra de Fogo, Pastos Bons e no Grupo Areado (Província Parnaíba) e nas formações Água Bonita e Vereda Verde, (Bacia Água Bonita). Estruturas descritas para a Formação Ipu do Grupo Serra Grande se revestem de especial importância, pois se constituem em registros da tectônica responsável pela instalação da Bacia do Parnaíba. O Sistema de Falhas Transbrasiliano está relacionado à maioria das fases de atividade tectônica identificadas, embora outras estruturas lineares, como os lineamentos Tocantins-Araguaia e de Senador Pompeu também possam ter sido responsáveis por parte desta atividade. / The Transbrasiliano Fault System is a complex structure with a lenght of more than 7.400km, from the region of Cordoba, Argentina, to central Algeria, in Africa. The Transbrasiliano Fault System and other basement structures played a major role on the formation and depositional history of the sedimentary basins of the South American Platform, such as the Parnaíba Province and Água Bonita Basin, which are studied in this thesis. Major zones of lithospheric weakness, such as the Transbrasiliano Fault System, may concentrate remote stresses originated on the edges of tectonic plates, and so may be focus of intraplate tectonics and seismicity. Intraplate earthquakes, although uncommon, can reach large magnitudes and affect large areas. Intraplate tectonics and seismicity may leave several types of records in intracratonic basins. Of great significance among them are seismites: liquidization structures produced in soft-sediments under seismical shock. Seismites are particularly useful in the reconstruction of the tectonic history of sedimentary basins. However, identifying and interpreting seismites can be troublesome, since non-seismical processes can generate structures similar to those produced by earthquakes. A method was developed for the diagnosis of the trigger of the soft-sediment deformation, allowing the distinction between autogenic and allogenic triggers, and among the alllogenic triggers the identification of structures produced by seismic shock. Structures interpreted as seismites were analised in order to identify intervals of sinsedimentary tectonic activity, which basement strutures were reactivated and possible paleostress fields at the time of their formation. For this end, a method for acquisition and statistical analysis of orientation and thickness data of clastic dikes was developed. Horizons with soft-sediment deformation structures were identified in the Serra Grande Group, Pimenteiras, Cabeças, Piauí, Pedra de Fogo and Pastos Bons formations and Areado Group (Parnaíba Province) and Água Bonita and Vereda Verde formations (Água Bonita Basin). Structures described in the Ipu Formation of Serra Grande Group are specially important, because they are records of the tectonics related to the origin of Parnaíba Basin. The Transbrasiliano Fault System is related to the majority of the tectonic reactivations identified, although the Tocantins-Araguaia and Senadour Pompeu lineaments may also have played some role on these deformations.

The interaction of numerous sedimentary processes at key transition points along the depositional profile results in a complex heterogeneity in ancient basin margin successions. This complexity is generally well studied along depositional dip sections, but lateral (strike) variability and consequent implications for sediment distribution and stratigraphic architecture is commonly less well constrained. In the Karoo Basin, continuous NW-SE-oriented exposure over 80 km has been characterized by 53 logs with 9910 m of cumulative thickness, >2500 palaeocurrent measurements, and ground-, drone- and helicopter-based photo panels. Palaeoflow indicators suggest dominant sediment transport was to the N-NE, with E-W and NE-SW bidirectional components. These are consistent with a strike orientation of the outcrop belt relative to the NE-N margin progradation direction and a NE-SW reworking by waves orientation. In the south of the study area, upper slope and shelf edge parasequences (50-75 m-thick), show current ripples and inverse-to-normal grading in micaceous and organic-rich siltstones and sandstones. They are interpreted as river-dominated prodelta and mouth bar deposits, locally incised by distributary channels (100 m-thick, 1.5 km-wide). Overlying shelf parasequences are thinner (15-50 m) with symmetrical ripple tops, HCS and low angle cross bedding, interpreted as wave-influenced deltaic or shoreface deposits. They transition upward into erosive-based, fining-up sandstones and isolated sharp-based tabular climbing-rippled sandstones, interpreted as channels and crevasse splays within delta plain mudstones. Along strike to the north, upper slope parasequences show more wave reworking indicators and no evidence of gullying or incision. Overlying shelf parasequences are sandier, more amalgamated and strongly influenced by wave action. They are interpreted as offshore, shoreface, foreshore and strandplain deposits. Southern nearshore environments were therefore more river-dominated with bypass and sediment delivery to deeper parts of the basin across a steep, more erosive margin. Wave and storm current redistribution along strike to the northern, lower gradient margin resulted in higher net-to-gross and sand connectivity on a wider shelf, without major incision, bypass and sand supply to the upper slope. No evidence of major avulsions in the upstream tributary and distributary systems are interpreted because the bypass and fluvial-dominated characteristics are persistent in the southern areas through time, whereas the northern margin maintained a sand-starved upper slope and a wave dominated shelf succession. The overall thicker and delta- dominated succession in the south, and the thinner, more condensed and wave dominated stratigraphy in the north are interpreted to be controlled by a combination of basement and basin configuration and differential basin margin physiography. However, relative sea level fluctuations controlled the stacking patterns, with an overall shallowing-upward profile that can be subdivided into two prograding phases, separated by a transgressive phase. At parasequence scale, climate, autocyclicity and coastal processes influenced the equilibrium between sediment input, redistribution and compensational stacking. This study demonstrates that although basin margin successions may be consistently progradational, the interaction of mixed coastal processes and differential spatial configuration can result in a complex along-strike sedimentary architecture, with major implications for sediment distribution through time and space.

O Sistema de Falhas Transbrasiliano é uma estrura complexa que se estende por mais de 7.400km, desde a região de Córdoba, Argentina, até a região central da Argélia, na África. O Sistema de Falhas Transbrasiliano e outras estruturas do embasamento exerceram grande influência na instalação e história deposicional das bacias sedimentares da Plataforma Sul-Americana, entre elas a Província Parnaíba e a Bacia Água Bonita, objetos de estudo desta tese. Zonas de fraqueza litosférica importantes, como o Sistema de Falhas Transbrasiliano, tendem a concentrar esforços remotos gerados na borda das placas, e dessa forma a ser foco de atividade tectônica e sismicidade intraplaca. Sismos intraplaca, embora pouco comuns, podem atingir magnitudes consideráveis e afetar grandes áreas. Tectônica e sismicidade intraplaca podem gerar diversos tipos de registro em bacias intracratônicas. Entre eles, se destacam os sismitos: estruturas de liquidificação produzidas em sedimentos inconsolidados submetidos a choque sísmico. Sismitos são ferramentas particularmente úteis para a reconstrução da história tectônica de bacias sedimentares; no entanto, sua caracterização e interpretação podem ser problemáticas, visto que processos não sísmicos podem induzir a formação de estruturas similares às produzidas por terremotos. Desta forma, foi elaborada uma metodologia visando a diagnose do agente desencadeador da deformação sinsedimentar, permitindo a distinção entre agentes de deformação autógenos e agentes de deformação alógenos, e entre estes identificar estruturas produzidas por abalos sísmicos. A partir de sua caracterização como possíveis sismitos, as estruturas foram analisadas, visando determinar intervalos de atividade tectônica sinsedimentar, que estruturas do embasamento foram reativadas e possíveis campos de paleotensões à época de sua formação. Para esta última finalidade, foi desenvolvida também uma metodologia para aquisição e tratamento estatístico de dados de orientação e espessura de diques clásticos. Foram identificados horizontes com sismitos no Grupo Serra Grande, nas formações Pimenteiras, Cabeças, Piauí, Pedra de Fogo, Pastos Bons e no Grupo Areado (Província Parnaíba) e nas formações Água Bonita e Vereda Verde, (Bacia Água Bonita). Estruturas descritas para a Formação Ipu do Grupo Serra Grande se revestem de especial importância, pois se constituem em registros da tectônica responsável pela instalação da Bacia do Parnaíba. O Sistema de Falhas Transbrasiliano está relacionado à maioria das fases de atividade tectônica identificadas, embora outras estruturas lineares, como os lineamentos Tocantins-Araguaia e de Senador Pompeu também possam ter sido responsáveis por parte desta atividade. / The Transbrasiliano Fault System is a complex structure with a lenght of more than 7.400km, from the region of Cordoba, Argentina, to central Algeria, in Africa. The Transbrasiliano Fault System and other basement structures played a major role on the formation and depositional history of the sedimentary basins of the South American Platform, such as the Parnaíba Province and Água Bonita Basin, which are studied in this thesis. Major zones of lithospheric weakness, such as the Transbrasiliano Fault System, may concentrate remote stresses originated on the edges of tectonic plates, and so may be focus of intraplate tectonics and seismicity. Intraplate earthquakes, although uncommon, can reach large magnitudes and affect large areas. Intraplate tectonics and seismicity may leave several types of records in intracratonic basins. Of great significance among them are seismites: liquidization structures produced in soft-sediments under seismical shock. Seismites are particularly useful in the reconstruction of the tectonic history of sedimentary basins. However, identifying and interpreting seismites can be troublesome, since non-seismical processes can generate structures similar to those produced by earthquakes. A method was developed for the diagnosis of the trigger of the soft-sediment deformation, allowing the distinction between autogenic and allogenic triggers, and among the alllogenic triggers the identification of structures produced by seismic shock. Structures interpreted as seismites were analised in order to identify intervals of sinsedimentary tectonic activity, which basement strutures were reactivated and possible paleostress fields at the time of their formation. For this end, a method for acquisition and statistical analysis of orientation and thickness data of clastic dikes was developed. Horizons with soft-sediment deformation structures were identified in the Serra Grande Group, Pimenteiras, Cabeças, Piauí, Pedra de Fogo and Pastos Bons formations and Areado Group (Parnaíba Province) and Água Bonita and Vereda Verde formations (Água Bonita Basin). Structures described in the Ipu Formation of Serra Grande Group are specially important, because they are records of the tectonics related to the origin of Parnaíba Basin. The Transbrasiliano Fault System is related to the majority of the tectonic reactivations identified, although the Tocantins-Araguaia and Senadour Pompeu lineaments may also have played some role on these deformations.

Uma série de pesquisas realizadas em depósitos de sistemas fluviais, desenvolvidos anterior e concomitantemente à colonização dos continentes por vegetação, são aqui apresentadas com o intuito de investigar as principais características deposicionais destes sistemas, particularmente suas assembléias de fácies e elementos arquitetônicos preservados. Esta pesquisa busca, desta maneira, propor modelos deposicionais para sucessões fluviais pré-vegetação e contribuir para o avanço do conhecimento sobre as mudanças seculares em padrões de sedimentação, principalmente em relação à evolução dos rios através do tempo geológico. Estudos sedimentológicos foram realizados em depósitos fluviais da Formação Applecross do Grupo Torridon (Toniano, Escócia), Formação Guarda Velha do Grupo Guaritas (Cambriano, Brasil) e no Old Red Sandstone do Midland Valley (Siluriano-Carbonífero, Escócia). Foram empregadas análises de associações de fácies e arquitetura deposicional por meio de estudos de alto detalhe em afloramentos, combinadas a análises de paleocorrentes, de proveniência, e de estruturas de deformação sinsedimentar. Depósitos de canais fluviais meandrantes pré-vegetação com espessos depósitos de planícies de inundação ricos em sedimentos de granulação fina são pela primeira vez descritos em detalhe nos estudos aqui apresentados sobre depósitos da Formação Applecross. Diversas estruturas de deformação sinsedimentar encontradas na unidade acima referida são analisadas, revelando que seus estilos podem ser relacionados a diferentes regiões de uma planície fluvial. Nos depósitos da Formação Guarda Velha, é registrada a inter-relação entre dois sistemas fluviais coevos, cuja arquitetura deposicional contrastante resultou da diferente localização destes sistemas em relação à estrutura da bacia, assim como de diferentes áreas de captação. São relatados os efeitos de distintos controles deposicionais, como ambiente tectônico e regimes hidráulicos, sobre a arquitetura deposicional preservada em sistemas fluviais pré-vegetação. Esses dados demonstram que o estilo entrelaçado-em-lençol, apontado como o estilo pré-vegetação predominante, engloba na verdade uma variedade de diferentes estilos fluviais. Estudos em depósitos do Siluriano ao Carbonífero do Old Red Sandstone revelam o crescente impacto da vegetação sobre depósitos fluviais, particularmente o aumento exponencial de formação de paleosolos, além de mostrar semelhanças entre alguns destes sistemas com os sistemas pré-silurianos. A integração desses estudos revela que sistemas fluviais pré-vegetação são relativamente mais complexos do que previsto pelos modelos atualmente disponíveis. Importantemente, sugere que a escassez de sedimentos de granulção fina, preservados em depósitos fluviais pré-silurianos, está mais relacionada à baixa competência destes sistemas em preservar tais sedimentos do que à sua suposta ausência em ambientes pré-vegetação. Foi também desenvolvida uma metodologia específica para o uso de estruturas de deformação em sedimentos inconsolidados como ferramentas na reconstrução de paleoambientes, através das relações entre diferentes estilos deformacionais e ambientes deposicionais, possibilitando a indicação de regimes hidráulicos em depósitos fluviais e a informação indireta de taxas de atividades tectônicas em bacias. A integração de dados de sedimentologia com estudos específicos de deformação sinsedimentar é uma ferramenta útil na reconstrução paleoambiental de sistemas fluviais. / A series of studies were undertaken on fluvial systems deposits which developed prior to land-plant colonization, in order to investigate the main depositional characteristics of those systems, particularly their main facies assemblages and preserved depositional architecture. Main objectives are the proposal of depositional models for pre-vegetation fluvial systems, and the understanding of main secular changes in sedimentation processes and its influence on the evolution of rivers through geological times. Sedimentologic studies were undertaken in fluvial deposits from the Applecoss Formation of the Torridon Group (Tonian, NW Scotland), the Guarda Velha Formation (Cambrian, southern Brazil), and the Old Red Sandstone in the Midland Valley (Silurian-Carboniferous, NE Scotland). Highly-detailed sedimentary facies and depositional architecture analyses in outcrop scale were integrated with palaeocurrent and provenance studies, and soft-sediment deformation analysis. Pre-vegetation meandering channel deposits with relatively thick, fine-grained floodplain deposits from the Applecross Formation and here described for the first time. Analyses on sinsedimentary deformation structures preserved in the Applecross Formation reveal different styles which can be related to different parts of the fluvial plain. Studies on the Guarda Velha Formation revealed the inter-relationship between two coeval fluvial systems with markedly contrasting preserved depositional architecture, which developed as a result of the different location of the systems in relation to basin structure and different caption areas. The effects of different depositional controls on preserved pre-vegetation fluvial system architecture, such as tectonic environment and hydraulic regime, are recorded and interpreted. The present data demonstrate that the sheet-braided style, which is regarded as the prevailing fluvial style before the Silurian, in fact encompasses a varied number of different pre-vegetation fluvial styles. Studies on the Silurian to Early Carboniferous Old Red Sandstones in the Midland Valley of Scotland reveal the progressive impact of land plants on fluvial sedimentation, particularly the exponential increasing rates of soil production. Integration of the here presented data reveal that pre-vegetation fluvial styles. Studies on the Silurian to Early Carboniferous Old Red Sandstone in the Midland Valley of Scotland reveal the progressive impact of land plants on fluvial sedimentation, particularly the exponential increasing rates of soil production. Integration of the here presented data reveal that pre-vegetation fluvial systems are relatively more complex than previously described in the literature. Importantly, it suggests that the paucity of fine-grained sediments in pre-Silurian fluvial deposits is most likely related to various preservation issues than to the lack of such sediments. A particular methodology for the use of soft-sediment deformation structures as palaeoenvironmental tool was developed, allowing the interpretation of hydraulic regimes in fluvial deposits, indication of the basin\'s tectonic activity, and the relationship between different deformation styles and distinct depositional environments. The combined analyses of soft-sediment deformation structures and sedimentologic data is a powerful tool with which fluvial systems palaeoenvironmental can be reconstructed.

Les structures de déformation pré-lithification s’enregistrent dans les sédiments meubles. Ces structures sont abondantes dans les domaines sous-glaciaires et marins profonds en raison du développement de surpressions de fluide. A partir de cas d’études choisis dans ces deux environnements, leurs implications sur les (1)reconstructions paléoenvironnementales, leurs impacts sur la (2) morphologie glaciaire, et sur les (3) propriétés pétrophysiques ont pu être définis.(1) L’analyse de ces structures de déformation a permis de mieux contraindre les paléoenvironnements sédimentaires. Ces structures de déformation ont été utilisées comme des «proxy » permettant d’estimer les variations de la vitesse d’écoulement, de l’épaisseur de glace, de la production d’eaux de fonte et de la position de la marge glaciaire.(2) Les séries sédimentaires des vallées tunnels ordoviciennes enregistrent la mise en place de nombreuses structures de déformation liées aux surpressions de fluides. L’analyse de ces structures a permis de proposer un nouveau modèle de creusement des vallées tunnels induits par des pressions de fluides élevées. Ce modèle de creusement, lié aux surpressions de fluide, est favorisé dans les zones d’inter ice-stream. A l’inverse, sous les ice-stream, l’écoulement des eaux de fonte se produit à l’interface glace-substrat et favorise d’autres modèles de formation des vallées tunnels.(3) Les processus de remobilisation sédimentaire ont un impact sur les propriétés pétrophysiques des réservoirs sableux. Les études pétrophysiques menées sur des grès déposés en environnements marins profonds et glaciaires ont permis de mettre en évidence l’impact des surpressions de fluides sur les propriétés réservoirs des sables. Les processus de fluidisation sont capable de créer de bons réservoirs, tandisque les processus d’élutriations ont tendance a réduire la porosité/perméabilité. / Soft-sediment deformation structures (SSDs) occur in unconsolidated sediments, during or shortly after deposition. SSDs are abundant in subglacial and deep-marine environments because of the development of fluid overpressure. Case studies of these two sedimentary environments were used (1) to reconstruct palaeoenvironments from SSDS, and (2) to define the impacts of SSDS on glacial morphologies and (3) petrophysical properties.(1) Analyses of strain regimes, deformation mechanisms, and chronologies in SSDs served to improve palaeoenvironmental reconstructions. These structures were used as proxys to estimate variations of ice flow velocities, ice thickness, meltwater production, and position of the ice margin.(2) The sedimentary series of ordovician tunnel valleys record numerous SSDs induced by fluid overpressure. A new model of tunnel valley formation controlled by the increase of porewater pressure in the bed is proposed. This model of formation occurs in inter-ice stream zones, where meltwater is transferred to the substratum. In ice-stream corridors, meltwater circulates at the ice-bed interface and promotes the formation of tunnel valleys controlled by meltwater processes.(3) Remobilisation processes triggered by the increase of fluid pressure have an impact on the granular framework and on the geometry of reservoirs. Petrophysical studies of subglacial and deep-marine sandstones demonstrated the impact of fluid overpressure on reservoir properties. Processes of fluidisation are responsible for the increase in porosity/permeability, while elutriation processes lead to a decrease in these petrophysical properties.