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Alves, Luizemara Soares. "Estudo da margem continental ibérica ocidental com base em dados gravimétricos e magnetométricos regionais." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=6240.
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Os métodos potenciais são conhecidos como uma ferramenta útil para estudos regionais. Na Ibéria Ocidental, a gravimetria e a magnetometria podem ser
utilizadas para auxiliar no entendimento de algumas questões sobre a estruturação tectônica offshore. Nesta região, tanto as estruturas geradas pela quebra continental, quanto às herdadas do embasamento variscano, tem uma importante contribuição para a resposta geofísica regional observada com estes métodos. Este trabalho tem como objetivo correlacionar as feições geofísicas observadas com alguns modelos geológicos do arcabouço tectônico da Ibéria Ocidental já publicados na literatura. Mapas filtrados foram usados para auxiliar no reconhecimento de diferentes assinaturas geofísicas, os quais foram calculados a partir dos mapas de gravidade Bouguer e do campo magnético total tais como o gradiente horizontal total, derivada tilt, derivada vertical, e integral vertical. O domínio crustal continental foi definido a partir da interpretação dos dados gravimétricos, utilizando gradiente de
gravidade horizontal total da Anomalia Bouguer. Os dados magnéticos, originais e filtrados, foram utilizados para identificar mais três domínios regionais offshore, que sugerem a existência de três tipos de crosta não-siálica. Dois deles são propostos como domínios de transição. A região da crosta de transição mais próxima do continente tem uma fraca resposta regional magnética, e a porção mais distal é um domínio de anomalia de alta amplitude, semelhante à resposta magnética oceânica. O limite crustal oceânico não pôde ser confirmado, mas um terceiro domínio offshore, a oeste da isócrona C34, poderia ser considerado como crosta oceânica, devido ao padrão magnético que apresenta. Alguns lineamentos do embasamento
foram indicados na crosta continental offshore. As feições gravimétricas e magnéticas interpretadas coincidem, em termos de direção e posição, com zonas de sutura variscanas, mapeados em terra. Assim, esses contatos podem corresponder à continuação offshore destas feições paleozoicas, como o contato entre as zonas de Ossa Morena-Zona Centro-Ibérica. Nesta interpretação, sugere-se que a crosta continental offshore pode ser composta por unidades do Sudoeste da Península Ibérica. Isto permite considerar que a Falha de Porto-Tomar pertence a uma faixa de deformação strike-slip, onde parte das bacias mesozoicas da margem continental está localizada.Potential field methods are known as a very useful tool to regional studies. On Western Iberia, gravimetric and magnetometric data could be helpful to understand some questions about the offshore tectonic framework. In this area, both continental break-up features and inherited continental basement structures have a strong contribution to compose the regional geophysical response on gravimetric and magnetometric maps. This work aims to correlate observed geophysical features of the Iberian margin with some geological models about the tectonic framework of Western Iberia, already published on literature. Filtered maps were used to recognize different geophysical signatures, which were computed from both calculated Bouguer gravity and total magnetic field, such as total horizontal gradient, tilt derivative, vertical derivative, and vertical integration. The continental crustal domain was defined from gravity data interpretation using an enhanced total horizontal gradient of Bouguer Anomaly maps. Magnetic data was used to identify three more regional offshore domains that could indicate three types of non-sialic crust. Two of them are proposed as transitional domains. The landward transitional crust has a very weak regional magnetic response, and the seaward one is a high amplitude anomaly domain, similar to oceanic magnetic response. The oceanic crustal boundary was not confirmed, but a third offshore domain, seaward from C34 isochron, could be considered as oceanic crust by its magnetic pattern. Some basement lineaments were indicated in the offshore continental crust. Gravimetric and magnetic features coincide in terms of their direction and position with Variscan suture zones mapped onshore. Therefore these contacts could correspond the offshore continuation of these Paleozoic features, such as the Ossa-Morena Zone and Centro-Ibérica Zone suture zone. In this interpretation, offshore continental crust could be formed by units from Southwest Iberia. It allows considering the Porto-Tomar fault as a part of a swath of strike-slip deformation, where mesozoic basins are located.
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Bouton, Anthony. "Facteurs de contrôle extrinsèques des dépôts microbiens récents en domaine de transition continental-marin." Thesis, Dijon, 2016. http://www.theses.fr/2016DIJOS012/document.
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Les microbialites, dépôts lithifiés d’origine microbienne, sont des structures organosédimentaires documentées depuis plus de 3,5 milliards d’années. La compréhension de ces structures, des conditions et des modalités de leur mise en place, nous apporte des informations précieuses sur l’origine de la vie sur Terre. Cette thématique de recherche est également en plein essor du fait de ses implications économiques majeures concernant les hydrocarbures. La reconstitution des environnements associés aux structures microbiennes fossiles reste incertaine, notamment entre milieux de dépôts marins ou continentaux. Ces deux environnements contrastés ont été étudiés à travers deux exemples modernes, Cayo Coco (Cuba) en domaine marin lagunaire et le Grand Lac Salé (Utah, USA) en domaine lacustre continental dans le but d’identifier des critères diagnostiques pour discriminer ces environnements dans le registre fossile.La formation des microbialites résulte de la minéralisation et de la lithification d’un tapis microbien sous l’influence d’une composante métabolique (intrinsèque) liée à l’activité du tapis microbien, et d’une composante environnementale (extrinsèque). L’objectif de ce travail était de replacer à différentes échelles les dépôts microbiens dans leur contexte environnemental et de comprendre les influences directes des paramètres extrinsèques sur : (1) les processus de minéralisation des tapis microbiens et la formation de microbialites, (2) la morphologie des structures microbiennes, (3) la distribution spatio-temporelle des microbialites et des sédiments associés, et enfin (4) les relations entre les tapis microbiens et microbialites et leur environnementLithified microbial deposits, considered as microbialites, are organosedimentary structures observed since 3.5 billion years. Understanding the mechanisms and environmental conditions leading to their formation may provide valuable information about the origin of life on Earth. Our interest on this research topic has increased owing to the economic implications of these deposits, especially concerning the hydrocarbons. The reconstruction of the environments associated with microbial structures remains uncertain in the fossil record, especially between marine and continental domains. These two contrasting environments were studied through two modern examples: (1) a marine-fed lagoon area in Cayo Coco (Cuba), and the continental lake of the Great Salt Lake (Utah, USA) in order to identify diagnostic criteria allowing to distinguish both environments in the fossil record.Microbialite result from mineralization and lithification of microbial mats under the influence of metabolic chemical reactions (intrinsic) related to the activity of the microbial biomass and environmental (extrinsic) conditions. The objective of this PhD is to replace microbial deposits, at different scales, in their context of formation to highlight the significance of extrinsic parameters on: (1) the mineralization processes and the formation of microbialites, (2) the morphologies of observed microbial structures, (3) their spatial distribution, and (4) the relationship between microbial mats and microbialite and their environment
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Nunez, del Prado Hernando. "Systèmes de dépôts et évolution sédimentaire des séries de transition marin-continental dans le synclinorium de Guarga (bassin sud-pyrénéen) : (Province de Huesca N-Espagne)." Pau, 1986. http://www.theses.fr/1986PAUU300X.
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MAGALHÃES, José Ricardo Gonçalves. "Compartimentação tectono-sedimentar da Bacia da Paraíba, a partir da integração de métodos potenciais e interpretação sísmica de dados OFFSHORE." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17212.
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Vários trabalhos têm tentado abordar a evolução das margens conjugadas do Atlântico, incluindo o nordeste do Brasil e o oeste da África. Entretanto, o avanço de pesquisas anteriores tem sido dificultado em razão da falta de dados na região marginal da porção oriental do nordeste do Brasil, principalmente na área inserida entre a Zona de Cisalhamento de Pernambuco e o Alto de Touros. Este fato tem imposto limitações ao desenvolvimento de modelos regionais sobre a evolução geotectônica e paleogeográfica desta região, assim como na correlação com sua contraparte na África. Nesta dissertação é apresentada uma investigação realizada com base em dados gravimétricos, magnéticos e sísmicos regionais. Os resultados mostraram que esta região representa um alto do embasamento com a orientação regional das principais estruturas tectônicas (ENE-WSW), ortogonais as estruturas desenvolvidas durante o processo de abertura das bacias da Paraíba e da Plataforma de Natal (NNE-SSW e NNW-SSE). Sobre o embasamento continental formou-se uma plataforma estreita com uma cobertura sedimentar pouco espessa (0,8-2,5 km) e uma quebra abrupta da plataforma, criando uma vasta zona de bypass através do talude. A análise de uma seção sísmica profunda revelou que a crosta continental afinada (crosta transicional) representa uma estreita zona e que o limite crosta continental-oceânica (COB) está localizado a aproximadamente 100 km a leste da atual linha de costa, na Bacia da Paraíba, e a 70 km, na Bacia da Plataforma de Natal. A modelagem geofísica, integrada com a interpretação sísmica, indica que esta região é caracterizada por um afinamento abrupto da crosta continental, com a consequente ascensão súbita da Moho. Também há evidências da existência de uma zona de crosta continental extremamente afinada, a qual foi interpretada como crosta proto-oceânica. Estes novos dados demonstram que esta área apresenta fortes similaridades com margens rifteadas não vulcânicas ou pobres em magma.
Several studies have tried to address the evolution of the Atlantic conjugate margins, including Northeast Brazil and West Africa. However, past research advances has been hindered by a lack of data for the marginal region in the eastern portion of northeastern Brazil, extending from the Pernambuco Shear Zone to the Touros High. This situation has imposed serious limitations on the development of a regional view of the geotectonic and paleogeographic evolution of this area and on correlations with regional counterparts in Africa. Here, we present an investigation using regional gravimetric, magnetic and seismic data. The results show that this region represents a basement high with regional orientation of tectonic structures (ENE-WSW) orthogonal at structures developed during the open processes of the Paraíba and Natal Platform Basins (NNE-SSW and NNW-SSE). The continental basement forming a narrow platform with a thin sedimentary cover (0.8-2.5 km) and an abrupt shelf break, which created a large bypass zone towards the slope. The analysis of a deep seismic section revealed that thinned continental crust (transitional crust) occupies a narrow zone and that the continental-oceanic boundary (COB) is located approximately 100 km to the east of the present coastline, at Paraíba Basin, and 70 km, at Natal Platform Basin. Geophysical modeling integrated with interpretation of the seismic data suggests that this region is characterized by an abrupt thinning of continental crust, with an accompanying sudden rise of the Moho. There are also indications for the existence of a zone of extremely thinned continental crust, which was interpreted as protooceanic crust. Our findings suggest that the study area shows strong similarities to nonvolcanic or magma-poor rifted margins.
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Brionne, Charles. "Signatures morphosédimentaires de la dynamique juxta-glaciaire à la transition de fronts glaciaires marins à terrestres : le cas de la Côte-Nord du Québec (estuaire et golfe du St Laurent)." Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAH005.
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Cette thèse combine une double approche géomorphologique et sédimentologique associée à l’utilisation de données LiDAR, bathymétriques, photogrammétrie drone et de datations radiocarbones. Elle a permis de reconstituer les paléos dynamiques glaciaires en contexte de déglaciation pour l’Inlandsis Laurentidien depuis le dernier maximum glaciaire, il y a environ 20 000 ans, et plus précisément au passage d’une marge glaciaire ancrée en mer à une marge glaciaire continentale Deux études ont été menées conjointement, soit : (1) la cartographie, la synthèse et la proposition d’un modèle concernant les mégacannelures de la Côte-Nord du Saint-Laurent, une première pour ces morphologies et (2) la reconstruction de l’enregistrement géomorphologique et morphosédimentaire du complexe sédimentaire de Pentecôte, mimant précisément cette transition. D’une manière générale, cette thèse démontre l’importance de l’héritage structural et de la physiographie du plancher au marge glaciaire dans la reconstruction de la dynamique glaciaire de retrait de la marge du LIS orientalThis thesis combines a dual geomorphological and sedimentological approach with the use of LiDAR data, bathymetry, drone photogrammetry and radiocarbon dating. It has enabled us to reconstruct the glacial paleodynamics in a deglaciation context for the Laurentide ice sheet since the last glacial maximum, around 20,000 years ago, and more specifically during the transition from an ice margin anchored at sea to a continental ice margin: (1) mapping, synthesising and proposing a model for the megagrooves of the North Shore of the St Lawrence, a first study for these morphologies, and (2) reconstructing the geomorphological and morphosedimentary record of the Pentecôte sedimentary complex, which precisely represents this transition. Overall, this thesis demonstrates the importance of the structural heritage and physiography of the floor at the glacial margin in the reconstruction of the glacial retreat dynamics of the eastern LIS margin
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Hamai, Lamine. "Étude thermomécanique de la zone de transition mer-continent de la marge algérienne : implication géodynamique." Thesis, Nice, 2016. http://www.theses.fr/2016NICE4021/document.
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Comprendre comment s’initie une subduction au niveau d’une marge passive est un problème géodynamique majeur, mais il reste très débattu en raison des forces nécessaires pour provoquer la flexion de la plaque plongeante, et dépasser la résistance frictionnelle de la lithosphère pour localiser cette subduction. Formant la bordure sud de la Méditerranée Occidentale, la marge algérienne subit des conditions aux limites en compression en raison de la convergence Afrique-Eurasie à un taux de moins de 1 cm/an. Ce contexte favorise l’inversion de cette marge nord-africaine et possiblement le début d’une subduction. En effet, des données géophysiques récentes acquises dans le bassin algérien (campagnes de MARADJA, 2003, 2005 (MARge Active d’el Djazaïr) et SPIRAL 2009 (Sismique Profonde et Investigations Régionales en ALgérie) ont montré des indices de déformation compressive récente. Nous avons utilisé les profils SPIRAL afin de calculer l’état isostatique de la lithosphère au voisinage de la limite océan-continent. Ceci nous a permis d'imager un Moho trop profond dans le domaine océanique, et plus superficiel dans le domaine continental, de part et d'autre d'une limite située vers le pied de pente de cette marge, donc un déséquilibre isostatique général de la marge. Nos résultats indiquent que la marge algérienne montre les mêmes anomalies isostatiques qu’au niveau d'une marge active, avec une zone de découplage océan/continent située en pied de marge. Ces anomalies peuvent être interprétées par un mécanisme de flexure des deux lithosphères en présence, que l’on peut simuler ensuite par une modélisation en éléments finis d’une plaque mince élastiqueUnderstanding how subduction initiates at a passive margin is a major geodynamic question, which remains debatted because of the forces necessary to overcome bending and frictional resistance of the lithosphere and initiate this subduction. Along the southern shore of the Western Mediterranean Sea, the Algerian margin undergoes ~NS compression due to the African-Eurasian convergence at a rate of less than ~ 1 cm / year. This setting causes tectonic inversion of this North African passive margin and possibly incipient subduction. Indeed, recent geophysical marine data acquired in the Algerian Basin (MARADJA, 2003, 2005MARge Active d’el Djazaïr) and SPIRAL 2009 (Deep Seismic and Regional Investigations in Algeria campaigns) showed evidence of recent compressive deformation. We used SPIRAL wide-angle seismic profiles to determine the state of isostatic equilibrium at the vicinity of the continent-ocean boundary. This allowed us to image a too deep Moho in the oceanic part, and a too shallow one in the continental domain, with a boundary between both domains located at the margin toe. These results indicate that the Algerian margin display the same isostatic anomalies as an active margin. This isostatic disiquilibrium may be simulated by the flexural bending of two lithospheric plates that can be modelled by a finite element procedure. This modeling shows larger vertical deflection in the central part of the study area (6-7 km) compared to the earsternmost and westernmost profiles (3 km)
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Walsh, John Patrick. "Continental-margin sedimentation : a wet-tropical perspective from New Guinea /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/11017.
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Prescott, Clifford Neill. "Marine geophysical investigation of the Hatton Bank volcanic passive continental margin." Thesis, Durham University, 1988. http://etheses.dur.ac.uk/6660/.
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The Durham/Cambridge/Birmingham Universities two-ship marine geophysical cruise to the Hatton Bank continental margin took place in May/June 1985, during which single- and two-ship seismic reflection/refraction data, together with under way gravity and magnetic anomaly, and bathymetric data were collected within a 200 km by 150 km area straddling the continent-ocean transition. The processing, modelling and interpretation of four two-ship synthetic aperture profiles (SAP) and the gravity and magnetic anomaly data is presented. Gravity models show that a density model based on the crustal velocity structure defined by synthetic seismogram modelling of the two-ship expanding spread profiles is insufficient to reproduce the observed gravity profile across the margin. This requires additional contributions in the form of density gradients in the underlying sub-crustal part of the lithosphere and asthenosphere, and this is investigated by thermal modelling. Analysis of the magnetic anomaly data shows that oceanic magnetic anomalies 21 and 22 are developed in the north-west of the 1985 survey area. Anomalies 23 and 24 cannot be recognised due to post-rift igneous activity and/or subaerial seafloor spreading. The positions of anomalies 23 and 24B are reconstructed within the survey area, and the theoretical anomaly 24B position is used to determine the position of the continent-ocean boundary. Analysis of the anomalies recorded on the upper continental slope shows that the acoustic basement in this area is volcanic. Interpretation of the SAP profiles shows that the margin can be described in terms of three distinct volcanic sequences. The continental sequence is composed of lavas extruded onto continental crust during a period of continental volcanism which occurred before the onset of seafloor spreading just prior to anomaly 24B.The sequence thickens to the north-west, to form a set of seaward-dipping reflectors. The oceanic sequence comprises oceanic crust within which structurally different seaward-dipping dipping reflectors are developed. This sequence is associated with the reconstructed positions of anomalies 23 and 24B, and is interpreted as having formed during a period of subaerial seafloor spreading. The late sequence separates, and in part overlies the continental and oceanic sequences. Magnetic anomalies associated with the late sequence are arcuate, and have high amplitudes, implying an origin other than simple seafloor spreading. The late sequence is interpreted as originating from post-rift igneous activity in the Eocene.
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Hemer, Mark A. "The oceanographic influence of sedimentation on the continental shelf : a numerical comparison between tropical and Antarctic environments /." Connect to this title online, 2003. http://adt.lib.utas.edu.au/public/adt-TU20051223.102442.
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Close, David Ian. "A marine geophysical study of the Wilkes Land rifted continental margin, Antarctica." Thesis, University of Oxford, 2005. http://ora.ox.ac.uk/objects/uuid:bfc7eee9-de28-4934-8f79-82b300a5f706.
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The Wilkes Land margin of East Antarctica, conjugate to the southern Australian margin, is a non-volcanic rifted margin that formed during the Late Cretaceous. During 2000-01 and 2001-02, Geoscience Australia (GA) acquired ~10,000 line km of seismic reflection, magnetic anomaly, and gravity anomaly data, on the Wilkes Land margin. Seismic reflection and sonobuoy refraction data provide the first constraints on sediment thickness and images of the deep crustal structure for the extent of the Wilkes Land margin. Two major post-rift seismic-stratigraphic sequences are recognised, separated by a regionally correlatable unconformity. The unconformity is interpreted as Early- to Middle-Eocene (~50 Ma). This unconformity has previously been interpreted to represent the onset of continent-wide glaciation at ~34 Ma. A major unconformity at the base of post-rift sediments is interpreted as a breakup unconformity, of approximately Turonian (85-90 Ma) age. Timing the onset of seafloor spreading using lineated magnetic anomalies within the Australia-Antarctic Basin (AAB) is extremely difficult due to uncertainties in correlating anomalies to the geomagnetic reversal time scale. Modelling indicates that the anomaly commonly correlated to Chron 34y may, in some cases, be associated with high level intrusions and/or serpentinisation of exhumed upper-mantle peridotites. Process-oriented gravity modelling indicates that the Wilkes Land margin lithosphere is characterised by a relatively high effective elastic thickness (Te). Isostatic anomalies are most effectively reduced for models utilising Te = 30 km. Although the margin is broadly characterised by a high Te, zones of low Te are inferred from modelling. Spectral analysis of isostatic anomalies indicates that the power of the flexural isostatic anomalies is lower than the free air gravity anomalies. The margin does not appear to be segmented, at least in regard to its long-term strength. However, a change in initial, zero-elevation crustal thickness (Tc) is inferred from west to east. A Tc of ~35 km is inferred for western Wilkes Land, whereas eastern Wilkes Land is characterised by Tc = 29 to 31 km. Limited seismic refraction data from the conjugate margin indicates a similar trend from southwest to southeast Australia.
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Rodger, Matthew. "A marine geophysical study of the Amazon continental margin, North-Eastern Brazil." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504519.
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Schrodt, Franziska Irmela. "Multi-continental biogeochemical comparisons of tropical forest-savanna zones of transition." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545713.
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Nowicki, Sophie Marie Jeanne. "Modelling the transition zone of marine ice sheets." Thesis, University College London (University of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499076.
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Wren, Patricia Ansley. "Sediment transport measurements on the mid-continental shelf in Onslow Bay, NC." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-03152004-100655/.
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Long-term in situ measurements have been made on the mid-continental shelf in Onslow Bay, NC to determine the frequency and direction of bottom sediment movement and the processes responsible for bottom sediment motion. As part of the Coastal Ocean Research and Monitoring Program (CORMP) at the University of North Carolina at Wilmington, a quadrapod frame with a downward looking Pulse-Coherent Acoustic Doppler Profiler (PC-ADP) and an upward looking Acoustic Doppler Current Profiler (ADCP) has been maintained on the continental shelf at approximately 30 m depth since May of 2000. The instruments are moored 27 nautical miles off the coast of Wilmington, North Carolina in Onslow Bay, adjacent to a productive marine hardbottom. Simultaneous measurements of flow velocities from the surface to the seabed, along with acoustic backscatter measurements, have been obtained. Measurements of seabed elevation, temperature, conductivity, and pressure were also collected at the site. Bed stresses due to wave-current interactions are calculated using a bottom boundary layer model (Styles and Glenn, 2002). Wave-current interactions resulted in shear stresses at the sediment-water interface that exceeded the critical threshold for sediment movement over 50% of the time during a climatological average year. Sediment transport was been shown to occur during four different types of events at the site: 1) small to moderate northerly wind events 2) Gulf Stream Intrusion events 3) strong southerly wind events associated with the passage of frontal systems 4) the passage of tropical storm systems. Over the course of a year the total net suspended sediment flux at 1 mab was in the positive along-shelf direction (southwest) and in the negative across-shelf direction (onshore), where there was several times more net transport in the onshore direction than the along-shelf direction. Three mechanisms leading to significant sediment transport on the mid-continental shelf have been indentified: 1) wave-current interactions 2) subtidal currents associated with sustained wind-driven flows and the intrusion of Gulf Stream water on the shelf 3) infragravity waves. Subtidal currents played a key role in the sediment transport during all types of events. Wind driven subtidal currents were important in determining the magnitude and direction of sediment transport during storm events, while subtidal currents associated with a Gulf Stream intrusion event combined with fair-weather swell resulted in accretion at the site of 3 cm over a three week period. The results show that a moderate northeasterly wind event with sufficient duration to generate wind driven subtidal flows resulted in an order of magnitude more sediment transport (20,237 g cm?2) than a similar northerly wind event and the southerly wind event without developed wind?driven flows. These two events resulted in similar amounts of sediment transport of 3,600 g cm?2 and 3,061 g cm?2, respectively. The passage of a hurricane resulted in an order of magnitude more sediment transport than the moderate northeasterly wind event, on the order of 240,000 g cm?2. Shear velocities during the passage of Hurricane Isabel resulted in the largest bed shear stresses (~300 dynes cm?2) on record. Field measurements in the bottom boundary layer were compared with the bblm generated current profiles during moderate wind events and Hurricane Isabel. In addition, the suspended sediment concentration profiles from the model were compared with the ABS profile measurements to verify shape and magnitude as the storms increased and waned. In general, there was good agreement between the measured and model derived current profiles, and between suspended sediment measurements and the model concentration profiles for both large and small-scale events that occurred at the site.
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Nuwer, Jonathan Mark. "Organic matter preservation along a dynamic continental margin : form and fates of sedimentary organic matter /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/10999.
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Régnier, Damien. "Modélisation physique et numérique de la dynamique d’un pergélisol au cours d’un cycle climatique : implications pour le site de Meuse - Haute-Marne." Rennes 1, 2012. http://www.theses.fr/2012REN1S054.
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Ce mémoire présente les travaux réalisés sur la modélisation de la dynamique d’un pergélisol (sol dont la température est inférieure à 0°C durant 2 ans consécutifs) et de son impact sur les circulations hydrogéologiques. Ils contribuent aux études de l’Andra sur le stockage des déchets radioactifs et sur l’étude environnementale du site Meuse/Haute-Marne. Lors d’un cycle climatique, les périodes froides peuvent générer l’installation d’un pergélisol. Cette structure périglaciaire se propage vers les horizons géologiques profonds, et de par sa très faible perméabilité, peut immobiliser des masses d’eau importantes dans les aquifères. Ce travail présente l’élaboration de deux modèles numériques à l’aide du code Cast3M (CEA) : (i) un modèle thermique conductif pur, adaptation d’une procédure existante, pour l’étude de la propagation d’ondes de froid en milieu poreux avec transition de phase eau-glace ; (ii) un modèle élaboré, gérant le couplage thermo-hydraulique des processus du sous-sol (conduction, convection et transition de phase). Validés, ces deux modèles offrent ici trois axes de valorisation : (i) proposition d’un benchmark par l’étude de deux cas tests génériques ; (ii) étude du signal de température imposé en surface : importance des variations climatiques haute fréquence (échelle centennale) sur la propagation et la stabilité d’un pergélisol ; (iii) étude de la dynamique d’une discontinuité thermique dans un système hydrologique type rivière-plaine : temps de fermeture du système par le pergélisol selon différents paramètres (températures, flux géothermique, sens des flux hydrologiques…). Ces points étant directement reliés aux problématiques du site AndraThis manuscript deals about works realized on the permafrost modelling in porous media and its impact on the hydrogeological circulations. These are parts of the Andra’s studies on the nuclear waste storage and, on the environmental studies of the Meuse/Haute-Marne (MHM) site. During a climatic cycle, cold periods can generate permafrost (ground with temperature lower than 0°C for 2 consecutive years). This periglacial structure propagates towards deep geological layers, and, due to its very low permeability, can stop the flow of water bodies like aquifers. This work presents the elaboration of two numerical models (with Cast3M code (CEA)): (i) a model with thermal conduction, used for the study of a cold wave propagation in porous media with phase transition (water-ice); (ii) a more complex model, managing the thermo-hydraulic coupling of ground phenomenon (conduction, convection and transition of phase). After validation, these two models offer three axes of development: (i) benchmark proposition by the study of two generic test-cases; (ii) study of the local air temperature signal on MHM site : importance of high frequency temperature variations (centennial scale) for permafrost depth and stability ; (iii) study of the dynamics of a thermal discontinuity in a typical hydrological system river-plain: closure time of the system by the permafrost according to various parameters (temperatures, geothermal flow, hydrological flow directions). These points are directly linked with the problems of the MHM site
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Couzens, Timothy John. "The rift to drift transition and sequence stratigraphy at passive continental margins." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333509.
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Most passive margins display a prominent breakup unconformity coinciding with the rift to drift transition. The unconformity, as defined by Falvey, (1974) is of broad regional extent affecting both basins and highs and is easily recognised on seismic sections. Criteria for the recognition of the breakup unconformity include an inflection in the subsidence curve, fault terminations and volcanic strata (and/or evaporites) at the level of the unconformity. Falvey considered that it was caused by "erosion during the final uplift pulse associated with pre-breakup upwelling in the mantle". It is more likely that the uplift is caused by magmatic underplating in response to the passive upwelling of the mantle and the flexural isostatic effects of erosion throughout the syn-rift phase. The primary objective has been to quantify the amount of uplift and erosion associated with the breakup unconformity / breakup megasequence boundary. This is of particular importance in hydrocarbon exploration as it quantifies the potential loss of old reservoirs and predicts the provenance of new reservoir clastics. Two data sets, from the Grand Banks and the Northwest Shelf of Australia, have been studied. In both cases there are multiple breakup events and breakup megasequence boundaries form part of a complex tectono-stratigraphy. Regional seismic lines have been interpreted, depth converted and modelled using a new technique of combined reverse post-rift and forward syn-rift modelling. The results of this process, together with seismic megasequence analysis, show that the morphology of the breakup megasequence boundary varies systematically across a passive margin. It is strongly erosional at about 70 km landward of the continentocean boundary, where regional "breakup" uplift outweighs extensionally controlled subsidence, but may be depositional on either side of this zone. A coupled, quantitative magmatic-tectonic model has been constructed by combining the Bickle-McKenzie melt generation model with the flexural cantilever model for continental extension. The magnitude of underplating can be estimated using the Bickle-McKenzie model, in which the amount of melt produced is controlled by the extension factor, ß, and the proximity of a mantle plume convection cell.
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Juby, Paul Robert. "Hydrographic conditions of a continental shelf region in the Northwest African Upwelling System from in-situ data." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/19971.
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This study investigates the hydrographic and dynamic properties of the continental shelf region between Cape Juby (28.5 °N) and Agadir (30.4 °N) within the Moroccan Sub-region of the North West African Upwelling System. Data came from two cruises conducted in June (beginning of summer) and November (end of autumn) 2013. Coastal upwelling was obvious in both cruises in the in-situ temperature and salinity data as well as in remotely sensed sea surface temperature maps. ADCP data showed the presence of a strong jet like current associated with enhanced upwelling off Cape Juby. This strong quasi-permanent upwelling center was observed during both cruises. It results from the orientation of this portion of coast which is aligned with the dominant wind direction, as well as a wind intensification near the cape. The presence of a secondary upwelling front was also observed near the shelf break. It was accompanied by an intense baroclinic jet. The EK60 data showed evidence of internal waves as well as small and mesoscale turbulence that were probably strongly interacting with the mean upwelling circulation and made a straightforward interpretation of the data quite challenging. However, this study revealed the main physical processes of this poorly studied region, as well as their seasonal variability.
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McNeill, Gavin William. "The geochemical palaeo-oceanography and mineralogy of marine sediments from the Peruvian Continental Margin." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/15360.
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A comprehensive study of marine sediments collected during the R.R.S. Charles Darwin Leg 38 cruise from the Peruvian continental margin, has been carried out using a wide range of geochemical analysis technqiues. The prime objective of the study has been to determine the strength and down-core variation of many oceanographic processes during the glacial/interglacial stages of the Late Quaternary by means of geochemical palaeo-environmental indicators. Coastal upwelling is a physical movement of cold, nutrient-rich water to replace surface water which has been blown off-shore by Ekman transport, as a result of along-shore winds. This results in high marine productivity levels within the Peruvian coastal upwelling zone, and is recorded by enrichments of organic carbon and other biogenic-remains in the sediments accumulating below. Particular metals, which have a capacity to be scavenged from sea-water as organic matter falls through it, are also enriched in the sedimentary record. Organic matter and fish-remains supply a continuous source of phosphorus to the surface sediment. Upon bacterial decomposition of this biogenic debris, phosphate can become enriched in the pore-waters until precipitation of carbonate fluorapatite occurs to form the diagenetic mineral known as phosphorite. Within the Peru margin cores, the presence of disseminated phosphorite pellets and zones of nodular hardgrounds has been determined using pore-water modelling and geochemical partitioning equations. Many trace elements can be incorported into the phosphorite mineral structure. Quantitative analysis of the uranium, strontium and yttrium concentrations within phosphorite zones has allowed for the partitioning of these elements into the organic, carbonate and terrigenous phases respectively. Y-series radiochemical age dating of a phosphorite nodule yielded a 'maximum' age of about 114,000 years for the phosphatic material. This age corresponds to an initial pellet growth on the continental margin during an interglacial period and supports the hypothesis of nodule diagenesis during the last glacial period as a result of heavy mineral concentration by bottom-water currents during a eustatic drop in sea-level.
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Colvocoresses, James Alden. "Abundance, seasonality and community structure of fishes on the Mid-Atlantic Bight continental shelf." W&M ScholarWorks, 1985. https://scholarworks.wm.edu/etd/1539616615.
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Cluster analyses of seasonal (spring and fall) National Marine Fisheries Service Groundfish Survey bottom trawl catches on the Middle Atlantic Bight continental shelf revealed consistent species associations and faunal zones over a nine year period during. Boundaries between faunal zones tended to follow isotherms on the inner portions of the shelf and isobaths along the outer shelf. During the late winter/early spring, four faunal zones were identified: a northern inner and middle shelf zone extending from Cape Cod southward to about Delaware Bay, a northern middle and outer shelf zone offshore of the first zone, a southern middle and outer shelf zone, and a fourth zone on the shelf break and upper slope. The southern inner shelf was a transition zone between the first and third zones. Five species groups were identified: a small cryophilic group restricted to the first zone, a cold-water boreal group found in the first two zones, a ubiquitous boreal/resident group containing the major dominants, a warm-temperate group confined to the warmer southern and outer shelf waters, and a group of slope residents confined to the deepest zone. During the fall, five faunal zones were identified: a southern inner and middle shelf zone, a northern inner shelf zone, a northern mid-shelf zone, an outer shelf zone and a shelf break/upper slope zone. The five species associations recognized were largely analogous to those in the spring, with the following exceptions: the cryophilic group was absent, the ubiquitous group contained mixed boreal and warm-temperate elements, and a second outer shelf group was recognized. The most notable change in the distribution of groups from the spring was a general northward shift in the distributions of the boreal species and a sharply defined inshore movement of the warm temperate group. Analyses of a single summer cruise showed patterns of distribution intermediate to those seen during the spring and fall. Absolute abundances, both of individual species and the total fish community, were highly variable between areas, seasons and years. Species diversity and its components appear to be of little utility in describing the fish communities of the open continental shelves.
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Hartnett, Hilairy Ellen. "Organic carbon input, degradation, and preservation in continental margin sediments : an assessment of the role of a strong oxygen deficient zone /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/10961.
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Gugliotta, Marcello. "The fluvial to marine transition zone and its stratigraphic significance." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-fluvial-to-marine-transition-zone-and-its-stratigraphic-significance(c9a2baf3-7ba0-46fb-a589-77d4f0f48578).html.
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The seaward end of modern rivers is characterized by the interactions of marine and fluvial processes within a tract known as the fluvial to marine transition zone (FMTZ), which varies between systems due to the relative strength of fluvial, tidal and wave processes. River deltas also show a range of different morphologies and architectures linked to the balance between these depositional processes. However sedimentological interpretations of fluvial to shallow-marine deposits from the rock record commonly relate sedimentary structures to single depositional processes and give greater importance to facies-based observations rather than to architectural style. To better understand how fluvial and tidal process interactions are preserved and distributed in the rock record, deltaic deposits of the Middle Jurassic Lajas Formation (Neuquén Basin, Argentina) have been investigated in large-scale outcrops. The degree of tidal influence has been evaluated using both facies-scale observations and architecture analysis, and critically testing the application of the FMTZ concept in ancient deposits. The characteristics of the reconstructed FMTZ together with the architectural elements described from the Lajas Formation are consistent with an interpretation of a fluvial-dominated, tide-influenced delta, rather than a tide-dominated system, as previously proposed. The results presented herein suggest that highstand systems tract progradational deltas of the Lajas Fm. accumulated largely under microtidal conditions. Comparison of facies and architecture between modern tide dominated deltas and published examples from ancient successions shows a fundamental mismatch; modern systems are mud-dominated with laterally accreting tidal bars while ancient examples are sand-rich and dominated by forward accreting deposits. This thesis argues that the majority of ancient sand-rich successions interpreted as tide-dominated deltas might have formed in large parts in a fluvial-dominated, tide-influenced delta system and that tide-dominated deltas may have not been adequately described from the rock record yet. The improved identification of process interactions presented in this study is crucial to refining classifications of shallow-marine successions and to understanding the recorded spatial and temporal evolution of ancient depositional systems. This can have fundamental implications in refining reservoir models and predicting correct geometries in hydrocarbon-bearing successions.
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Cordero, Luisa Mariutti. "Estudo dos processos sedimentológicos na Margem Continental Sudeste do Brasil pelo uso de radionuclídeos naturais." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/21/21133/tde-03082011-154909/.
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A Oceanografia, recentemente, vem fazendo uso dos mais diferentes radionuclídeos os quais funcionam como traçadores e auxiliam em uma maior compreensão dos processos de dinâmica oceânica, movimentação e deposição do fundo marinho. No Brasil, porém, há pouca informação a respeito dos teores de radionuclídeos naturais para a região costeira e oceânica e poucos são os estudos que utilizam esses radionuclídeos como ferramentas de compreensão de processos oceânicos. Neste contexto, este trabalho determinou atividades de 238U, 232Th e 40K por espectrometria gama e realizou análises granulométricas em amostras de sedimentos marinhos da Margem Continental Sudeste do Brasil. Os níveis variaram de 1,48 a 52,76 Bq kg-1 para o 238U, 10,63 a 49,45 Bq kg-1 para o 232Th e 65,45 a 873,28 Bq kg-1 para o 40K. Os resultados mostraram afinidade entre as frações finas do sedimento com 40K e 232Th. A razão 238U/232Th mostrou ser bom indicador de condições redox dos sedimentos. Verificou-se uma diferença nos níveis dos três radionuclídeos entre os setores ao norte e ao sul da Ilha de São Sebastião, com valores mais elevados ao sul. Estas diferenças foram relacionadas aos processos sedimentares dominantes em cada setor e aos agentes hidrodinâmicos responsáveis por tais processos.Recently, Oceanography has been using a variety of radionuclides as tracers to understand ocean dynamic processes, handling and disposal of sediments in seabed. In Brazil, there is little information about the contents of natural radionuclides on the coast and deep ocean and few studies using radionuclides as tools to comprehend oceanic processes. In this context, this work determined grain size and activities of 238U, 232Th and 40K using gamma spectrometry in marine sediments from shelf and upper slope off Southeast Brazil. The levels ranged from 1,48 to 52,76 Bq kg-1 for 238U, from 10,63 to 49,45 Bq kg-1 for 232Th and, from 65,45 to 873,28 Bq kg-1 for 40K. 40K and 232Th showed good correlation with grain size (mud and clay content) and 238U/232Th ratios appeared to be good indicators of sediment redox conditions. There was a difference in levels of radionuclides between sectors northward and southward of São Sebastião Island, with higher values in south sector. These differences were related to differences in sedimentary processes in each sector and to the hydrodynamic agents responsible for these processes.
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Gontikaki, Evangelia. "Carbon cycling in continental slope sediments : the role of benthic communities." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=128351.
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Previous pulse-chase experiments have revealed a wide diversity of benthic response patterns to organic matter (OM) input depending on environmental setting, benthic community structure and experimental conditions i.e. quantity and quality of the added OM. However, the mechanisms and interaction of environmental and biological factors that produce an observed response pattern are poorly understood. The present thesis set out to improve our current understanding on the set of parameters that determine benthic response patterns. The core of this study was based on two pulse-chase experiments in two bathyal settings: the Faroe-Shetland Channel (FSC) and the SW Cretan slope in the E. Mediterranean (E. Med). The sub-zero temperatures in the FSC enabled the observation of the benthic response in “slow-motion” and showed that the response is not static but instead might go through various “phases”. In the warm E. Med, C processing rates were considerably lower compared to previous measurements in adjacent regions. The discrepancy was attributed to the particularly refractory sedimentary OM at the sampling station with apparent consequences for the physiological state of the bacterial community. Both experiments showed that bacterial metabolism and its regulation is a key factor determining the reaction of the benthic community to OM inputs. This thesis provided further understanding on the short-term fate of organic C in deep-sea sediments but also raised certain issues that could be addressed in future studies.
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Houghton, S. D. "Coccolith assemblages in recent marine and estuarine sediments from the continental shelf of northwest Europe." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375743.
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Motz, Gary J. "Mollusc Diversity in the Marine and Continental Realms: A Case Study of the Estuary Effect." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1275740740.
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PALIAGA, ENRICO MARIA. "Upper slope geomorphology of Sardinian southern continental margin, applications to habitat mapping supporting marine strategy." Doctoral thesis, Università degli Studi di Cagliari, 2016. http://hdl.handle.net/11584/266760.
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This work, framed within the Marine Strategy Framework Directive, is
focused on Sardinian southern continental margins marine habitat mapping. Aim of
this thesis is to produce predictive marine habitat mapping, starting from a detailed
geomorphologic study integrated with biological and oceanographic data coming
both from original direct surveys than from bibliographic data. Underwater remotely
operated vehicles (ROV), coupled with multibeam echo-sounder (MBES), enabled to
perform interpretative hypothesis validation, controlled sampling and detailed
observation of specific mesophotic habitats with noninvasive protocols, which are
particularly relevant for habitats of conservation interest. Marine habitat mapping
represents the best estimation of the distribution of habitats in a place and at a
particular time, this goal have been focused on target biocoenosis A4.26 –
“Mediterranean coralligenous communities moderately exposed to hydrodynamic
action” and A4.713 – “Caves and overhangs with Corallium rubrum”, as defined by
EUNIS classification (European Nature Information System), subsequently reunite
under the name of Coralligenous Biocoenosis for the mapping of which has been
reached a high level of confidence. Principal drivers for seabed habitat distributions
include the type of seabed substrate, depth, light availability and the energy of water
movements. For the very first time on Sardinian southern margin a multidisciplinary
approach has been used to study the relationship between biotic and abiotic
components of marine habitats and how seabed morphologic features influences
different benthic biocoenosis development styles, geomorphologic characteristics of
settlement for substrates could be important factors structuring benthic biodiversity,
by affecting sediment accumulation rates, bottom currents and, ultimately, the rates
of food supply. These biocoenosis hosts relevant commercially relevant species, as
the blue and the giant red shrimp which represent the most important demersal
resources for trawling fleet of Sardinia.
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Aguiar, Neto Antonio Borges de. "Ocorrências de minerais pesados na plataforma continental interna/média oeste do Ceará." reponame:Repositório Institucional da UFC, 2015. http://www.repositorio.ufc.br/handle/riufc/18577.
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AGUIAR NETO, Antonio Borges de. Ocorrências de minerais pesados na plataforma continental interna/média oeste do Ceará. 2015. 118 f. Tese (Doutorado em geologia)- Universidade Federal do Ceará, Fortaleza-CE, 2015.Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-06-07T18:46:57Z No. of bitstreams: 1 2015_tese_abaguiarneto.pdf: 6536743 bytes, checksum: f1d5a6c8613161b0544872699e2bf94b (MD5)
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This study embraces the west continental shelf of Ceará (147 samples of marine sediments) and two fluvial courses (4 sediment samples of Curu and São Gonçalo rivers) to determine heavy minerals distribution with their possible provenances and economic potential. Sedimentary facies on the continental shelf were distinguished through the particle size and calcium carbonate content. Heavy minerals were investigated for their total content (%), relative abundance (%) of each mineral species, concentration in Kg/ton of predominant species, mineralogical index (RZi and ZRT) and grains imaging by SEM-EDS. In geoprocessing obtained the spatial distribution of data by Arcgis 10.1 and Surfer 10 got informations about bottom morphology of the continental. Multivariate analysis were included using Statistica 7.0 to aid in the interpretation of results. Heavy minerals were concentrated in Fortaleza chart (contents reached to 4.54%) at depths until 20 m in the litoclastic and litobioclastic sands. Among the 18 mineral species identified, ilmenite and tourmaline were embracing most of the continental shelf and with epidote and monazite presented content > 1 Kg/ton near São Gongaço do Amarante coast. Paleochannels and ancient beach-ridge were identified. The occurrence of typical regional metamorphic mineral paragenesis of rocks rich in aluminum suggests the provenance of Ceará Complex rocks (primary source) that occur both near the coast and outcrops directly on the continental shelf. Reworked sediments of Barreiras Formation, beach black sands and longshore drift sediments (secondary sources) contribute regionally in heavy mineral supply.Curu river influences ilmenite, tourmaline and epidote supply. Multivariate analyzes and RZi/ZTR variations corroborated with the dual nature provenance (primary and secondary) of the continental shelf sediments and expose a mixture of recente sediments with older reworked ones.
Este estudo abrange a plataforma continental oeste do Ceará (147 amostras de sedimentos marinhos) e dois cursos fluviais (4 amostras de sedimentos dos rios Curu e São Gonçalo) para determinar a distribuição dos minerais pesados com suas possíveis proveniências e potencial econômico. Distinguiram-se as fácies sedimentares da plataforma continental pela granulometria e teor de carbonato de cálcio. Os minerais pesados foram investigados pelos seus teores totais (%), abundâncias relativas (%) de cada espécie mineral, teores em Kg/ton das espécies predominantes, índices mineralógicos (RZi e ZRT) e imageamento dos grãos por MEV-EDS. No geoprocessamento obteve-se a espacialização dos dados pelo Arcgis 10.1 e informações da morfologia de fundo da plataforma continental com o Surfer 10. Incluíram-se análises multivariadas por meio do Statistica 7.0 para auxiliar na interpretação dos resultados. Os minerais pesados se concentraram na folha Fortaleza (teores de até 4,54%) em até 20 m de profundidade e nos domínios das areias litoclásticas e litobioclásticas. Dentre as 18 espécies minerais identificadas, a ilmenita e a turmalina foram as que abrangeram a maior parte da plataforma continental e juntamente com epídoto e monazita apresentaram teores > 1 Kg/ton próximo à costa de São Gonçalo do Amarante. Foram identificados paleocanais e antigas linhas de praia. A ocorrência da paragênese mineral típica de metamorfismo regional de rochas ricas em alumínio sugere a proveniência das rochas do Complexo Ceará (fonte primária) que ocorrem tanto próximo à costa como afloram diretamente na plataforma continental. Sedimentos retrabalhados da Formação Barreiras, areias pretas praiais e sedimentos de deriva litorânea (fontes secundárias) contribuem regionalmente no aporte de minerais pesados. O Rio Curu exerce influência no aporte de ilmenita, turmalina e epídoto. As análises multivariadas e as variações de RZi e ZTR corroboraram com a proveniência de natureza dual (primária e secundária) dos sedimentos plataformais, além de expor uma mistura de sedimentos recentes com sedimentos retrabalhados mais antigos.
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Hunter, William Ross. "Carbon and nitrogen cycling across the bathyal continental margins : oxygen availability and organic matter quality as controls upon sediment community activity." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=206993.
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The bathyal continental margins (200 – 3000 m) account for 7 % of global sea floor area, but are responsible for recycling 30 % of sedimentary organic matter (OM) within the oceans. Climate-change driven expansion of oxygen minimum zones and increasing frequency of extreme weather events (storms) may have implications for OM processing at the continental margins, resulting in decreased oxygen availability and increases in terrigenous OM inputs. The present thesis tests how changes in oxygen availability influence sea floor community structure and OM processing across the OMZ-impacted Indian continental margin. Megafaunal and macrofaunal assemblages exhibit a distinct zonation, with faunal distributions controlled by changes in oxygen availability and sediment OM content. In situ stable-isotope pulse-chase experiments reveal that, following phytodetritus deposition, macrofaunal feeding responses were influenced by oxygen availability through changes in macrofaunal assemblage structure. Macrofaunal feeding was governed at the organismal level, with fauna maximising organic nitrogen assimilation against an internal carbon-nitrogen budget. Bacterial feeding responses were not directly influenced by changes in oxygen availability and instead were regulated by the macrofaunal assemblage. This thesis proposes that the macrofauna may control the availability of labile organic matter in OMZ-sediments, limiting bacterial activity. The thesis also investigates the differential fates of marine and terrigenous phytodetritus in the sediments of the Whittard canyon (NE Atlantic). In situ pulse-chase experiments reveal nitrogen demand to control macrofaunal feeding responses, inhibiting the utilisation of the nitrogen-poor terrigenous phytodetritus. Bacteria exhibit similar feeding responses to the fauna, whilst bacterial biomass was negatively correlated to increasing faunal activity. This demonstrates that increased inputs of terrigenous organic matter may alter ecosystem-scale carbon cycling pathways and trophic interactions within continental margin sediments.
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Rao, Alexandra Mina Fernandes. "Carbon and nitrogen cycling in permeable continental shelf sediments and porewater solute exchange across the sediment-water interface." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-11152006-163727/.
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Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007.Martial Taillefert, Committee Member ; Jay Brandes, Committee Member ; Markus Huettel, Committee Member ; Philip Froelich, Committee Member ; Ellery Ingall, Committee Member ; Richard A. Jahnke, Committee Chair.
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Lashley, Justin Michael. "Reassessment of Geomorphic Features on the Continental Shelf off of Watch Hill, Fire Island National Sea Shore, NY." Thesis, State University of New York at Stony Brook, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10842942.
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The United States Bureau of Ocean Energy Management (BOEM)’s Sandy Needs Assessment collected geophysical and geotechnical data, related to beach nourishment activities, along the continental shelf south of Long Island between 2015–2017 in an area offshore the Fire Island National Sea Shore, near Watch Hill, NY. This new geological and geophysical data provides evidence of continuous and ongoing sand transport offshore of Fire Island National Sea Shore. New stratigraphic evidence shows the evolution, migration and erosion of shore-oblique sand ridges formed from the reworking of glacial outwash sand consistent with a conceptual process model. Three separate ridge features are related to each other with evidence of direct ridge migration in the region. Outwash fans and deltas likely provided the cores of mesoscale submarine ridges n the study area. Subsequent episodes of ridge erosion remobilized sand to feed the growth of ridges further west. The possibility of natural transport process actively delivering sand to the shore remains, but is not identified, and will require further work before these ridges can be sustainably utilized in nourishment activities.
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Popescu, Speranta Maria. "Continental and Marine Environmental changes in Europe induced by Global Climate variability and Regional Paleogeography Changes." Habilitation à diriger des recherches, Université Claude Bernard - Lyon I, 2008. http://tel.archives-ouvertes.fr/tel-00350116.
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My PhD and post-doctorate researches have focused on paleoclimatic, paleogeographical and paleoenvironmental reconstruction of the Mediterranean Basin and its adjacent seas (i.e. the residual former Paratethys) since 11 Ma. During this time-interval the Mediterranean marine and continental environments were affected by significant paleogeographic changes, forced by global climate and sea-level variability, plate tectonics and regional uplift of Alps s.l. and Carpathians. Two main important events characterize this period: the isolation and evolution of Paratethys and the almost complete desiccation of the Mediterranean Sea, an event known as the Messinian Salinity Crisis. I selected this region because it is very rich in long and continuous sediment archives, which document: (1) climate evolution of the Northern Hemisphere during the Late Cenozoic with respect to vegetation changes, and (2) progressive evolution of initially marine environments towards brackish and freshwater ones. The brackish to fresh environments had a profound effect on the marine organisms (especially dinoflagellates) that responded to the stress by developing a large variety of cyst morphologies, often described as new genera and/or species. Methods. The comparative analysis of pollen grains and dinoflagellate cysts from the same samples is rarely performed for such a long time-interval because it needs a deep knowledge in taxonomy and ecology of the both complementary proxies. I reached this parallel expertise, having the benefit of training in (1) botanical identification of pollen grains from the tropical to boreal zones and their ecological significance by Dr. J.-P. Suc, (2) taxonomy and ecology of dinoflagellate cysts by Pr. M. J. Head. To achieve an understanding of the primary factor inducing morphological variations of dinoflagellate cysts, I developed a biological approach (culturing and growing of present-day living dinoflagellates and inducing stress on microcultures experimentations) under supervision of Pr. J. Lewis (Westminster University, London, UK) and Drs. D. Anderson and D. Kulis (WHOI, USA) during my postdoc appointments. The simultaneous work on living and fossil (using biometry and associated statistical analyses) dinoflagellate cysts has allowed me to initiate the development of a transfer function, widely valid and able for the modelling of the physical parameters of sea-surface waters (salinity, temperature, nutrient contents). Such analyses were performed at high- to very high-chronological resolution, as resulting from the following approach: (1) independently established age-model, based on classical biostratigraphy or radiocarbon ages (for recent sediments), completed by magnetostratigraphy for deposits prior to Mid–Quaternary; (2) comprehensive counting of pollen grains (150 per sample, Pinus or any overabundant taxon excepted) and dinoflagellate cysts (200-300 per sample); (3) interpreting the resulting data with respect to ecological requirements. High- to very high-resolution analyses provides results directly comparable with classical oxygen isotope curves. These signals can therefore also be tuned to the frequency of eccentricity, obliquity and precession cycles. Although palynological proxies can be considered as standard, my integrated approach hoists them at the level of the most competitive methods. Another aspect consists in its present-day background, based on many surface samples from the Mediterranean, Marmara and Black seas, taken during several cruises and sampling parties at IFREMER-Brest and WHOI. To develop parallel analyses of pollen grains and dinoflagellate cysts offers additional considerable interests, such as (1) continuous records of climatic changes and sea-level variations independently from sediment types, and (2) quantifications (using transfer functions) of climate for both continental and marine (to brackish) realms as well as of physical oceanic parameters (SST, SSS, nutrient content etc.).Results and research in progress
Using pollen grains analysis, I developed investigations on vegetation dynamics and paleoclimate reconstructions for the whole Mediterranean region and Western Europe extended to the Late Cenozoic (Jiménez-Moreno et al., 2007; Fauquette et al., 2006). Thanks to the high-chronologic resolution:
a. I established the response of regional vegetation to eccentricity forcing in SW Romania (Dacic Basin) and Black Sea (DSDP Site380) whatever the sediment types (Popescu, 2001, 2006; Popescu et al., 2006a);
b. I was the first to demonstrate the precession forcing on regional vegetation (Popescu et al., 2006b) through the Lupoaia pollen record (SW Romania);
c. in the frame of two PhD theses that I co-supervise, pollen grain and dinoflagellate cyst records from DSDP Site 380 (7 - 4 Ma) were completed from 4 Ma to Present in order to evidence the impact of glacial-interglacial cycles over the regional vegetation and to reconstruct the climate variability for the last 7 Ma;
d. I was the first to demonstrate the solar cycles forcing (Hale and Gleissberg cycles) on the regional vegetation (through the “Thermophilous trees / Artemisia” ratio) since the Last Glacial Maximum were evidenced in cored sediments from the Black and Marmara seas (unpublished data), that is a unique outcome.
Using the biometric approach on the dinoflagellate cysts in association with statistical analyses, I demonstrated that fluctuations in salinity are partially responsible for modifying size, shape and ornamentation of the cysts, providing the first reliable paleoecological and paloebiogeographic reconstructions of the brackish Paratethyan basins (Popescu et al., palynology , in press).
Simultaneously, I performed experimental cultures on a living-dinoflagellate species (Scrippsiella trifida): suggested relationships between cyst morphological variations and stress under controlled salinity are confirmed by the preliminary results, while reproduction rate seems also modified (unpublished data).
The multi-proxy (palynology, sedimentology and geochemistry) study on the Aral Sea, done by the first PhD student that I co-supervised, allowed not only the reconstruction of the regional paleoclimate and paleoenvironments, but also permitted to understand the atmosphere dynamics of the last 2 ka over the high latitudes (Sorrel et al., 2006, 2007).
Hence, my palynological and biological expertise offers an exclusive tool for establishing a continuous high resolution chronology, paleoclimatic, paleobiogeographic and paleoenvironmental reconstructions. This is particularly important for the basins impacted by important environmental changes, such as the Mediterranean and Black seas, the sediments of the latter being precisely dated for the first time by this approach.
I do no want to close this Introduction Section without addressing my largest acknowledgements to those who supported my researches and expressed their interest in my project, providing personal grants and/or financial assistance for achieving my researches, and especially the PhD and master – graduation students that I appreciated so much to co-supervise.
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Van, de Poel Hendrik M. "Messinian marginal-marine and continental facies and their stratigraphy in the Eastern Almeria Province : SE Spain /." Toulouse : Université Paul Sabatier, Laboratoire de géologie sédimentaire et paléontologie, 1994. http://catalogue.bnf.fr/ark:/12148/cb35734114t.
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Sierra, Jimenez Mara Johanna. "Parcs nationaux en transition vers des parcs nationaux naturels anthropisés (PNNa) ? Étude comparative de trois parcs nationaux naturels habités du Continent américain (Colombie, Guyane française, Québec)." Thesis, Pau, 2016. http://www.theses.fr/2016PAUU1010/document.
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L’évolution des politiques de gouvernance environnementale internationale et la transition des contextes nationaux et locaux de conservation favorisent de plus en plus l’intégration de la dimension anthropique au sein des parcs nationaux (catégorie II-UICN). Cette dimension s’adresse d’une part aux populations locales qui habitent de manière permanente les diverses zones de protection, et d’autre part, aux acteurs économiques (légaux et illégaux) qui exploitent le territoire protégé (tourisme, orpaillage, bois, etc.) ou qui participent de manière directe et indirecte aux processus de construction territoriale du parc national. L’intégration de la dimension anthropique au sein de ces territoires naturels de protection favorise en conséquence l’émergence de nouvelles dynamiques et stratégies de gestion et de gouvernance participatives.Avec une triple approche scientifique construite autour des regards croisés de la géographie politique, de la géographie socioculturelle et de la political ecology, cette thèse s’intéresse à l’analyse de trois cas d’études particuliers du continent américain afin de comprendre comment l’intégration de cette dimension anthropique (socioculturelle et économique) favorise la transition de certains espaces naturels protégés classiques vers une nouvelle configuration que nous proposons d’identifier ici sous le nom de « parcs nationaux naturels anthropisés - PNNa ». L’analyse systémique de la structure et du fonctionnement des macrostructures de gouvernance et des microstructures de gestion du Parc amazonien de la Guyane en France, du Parc marin du Saguenay-Saint-Laurent au Québec (Canada) et du Parc national naturel Amacayacu en Amazonie colombienne, nous ont permis ainsi de mettre en évidence quelques aspects de cette transition dans la gestion territoriale des espaces naturels protégés de catégorie II, ainsi que les conflits de pouvoir qui en résultentThe evolution of international environmental policies and national and local conservation contexts gives increasing importance to the anthropic dimension within the national parks (category II UICN). Not only does this dimension takes into account the local population that lives permanently in these various natural areas, but also the economic actors who, legally or illegally, benefit from those protected areas (tourism, gold-washing, wood, etc.) or participate directly or indirectly in the process of the territorial elaboration of a national park. The integration of the anthropic aspect definitely help the emergence of new dynamics and strategies of collaborative management and policies. Building on political geography, socio-cultural geography and political ecology, this thesis aims to shed light how that anthropic dimension (sociocultural as well as economical) entails the transition of some protected areas from a classical type to a new category we identify as the “Nature and Anthropic National Park” (PNNa). We focus on three specific study cases in the American continent: the Amazonian park of the French Guiana, the Sea Park of Saguenay-Saint-Laurent of Québec, Canada, and the Amazonian Amacayacu National Park of Colombia. The systemic analysis of their structure and their functioning, as far as macrostructure of policies and microstructures of management are concerned, has allowed us to bring out that transition in the territorial management of these category II protected natural areas and the deriving conflicts for power
La evolución de las políticas de gobernanza medioambiental internacional y la transición de los contextos nacionales y locales de conservación, favorecen cada vez más la integración de la dimensión antrópica al interior de los parques nacionales (categoría II-UICN). Esta dimensión corresponde de una parte, a las poblaciones locales que habitan de manera permanente las diversas zonas de protección dentro del parque nacional, y de otra parte, a los actores económicos (legales e ilegales) que explotan el territorio protegido (Turismo, explotación minera, explotación de madera, etc), o que participan de manera directa o indirecta en los procesos de construcción territorial del parque nacional. La integración de la dimensión antrópica dentro de estos territorios naturales de protección favorece en consecuencia la emergencia de nuevas dinámicas y estrategias participativas de gestión y de gobernanza. A través de un triple enfoque científico construido mediante el cruce de diversos puntos de vista de la geografía política, de la geografía sociocultural y de la political ecology, esta tesis se interesa en el análisis de tres casos de estudio particulares del Continente americano. El objetivo de esta contribución es el de intentar mostrar, cómo la integración de la dimensión antrópica (sociocultural y económica) influencia la transición de algunos espacios naturales protegidos hacia una nueva configuración que nosotros proponemos identificar aquí bajo el nombre de “parques nacionales naturales antropizados – PNNa”.El análisis sistémico de la estructura y del funcionamiento de las macroestructuras de gobernanza y de las microestructuras de gestión participativa del Parque amazónico de la Guayana, en Francia, del Parque marino del Saguenay-Saint-Laurent en Quebec, Canadá, y del Parque nacional natural Amacayacu en Amazonia colombiana, nos permitieron poner en evidencia este tipo de transición en la gestión territorial de los espacios naturales protegidos de categoría II, así que los conflictos de poder que resultan de esta transformación
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Xu, Weimu. "Carbon burial in continental and marine settings : lacustrine and marine records of major environmental change in deep time and their depositional and diagenetic consequences." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:8838eda2-67a4-4946-a64a-e060d71247a2.
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The Early Jurassic Toarcian Oceanic Anoxic Event (T-OAE; ~183 Ma) is recognized as possibly the most extreme oceanographic and global climatic change event of the Phanerozoic. The T-OAE was marked by massive carbon release into the ocean-atmosphere system, widespread oceanic de-oxygenation, global organic-matter burial, and a strongly perturbed global carbon cycle. Although effects of the T-OAE are extensively studied in the marine realm, the environmental and climatic response on the continents is effectively unknown. In this thesis, I identify the first lacustrine record of the T-OAE, in the Da'anzhai Member of the Sichuan Basin (China), and demonstrate that a major lake system developed contemporaneously with the T-OAE, likely due to enhanced hydrological cycling under elevated atmospheric pCO2. Increased lacustrine organic productivity from elevated fluvial nutrient supply resulted in ~460 Gt of organic carbon burial in the palaeo-Sichuan lake alone, representing a major, but hitherto overlooked, carbon sink and negative feedback in the T-OAE global carbon cycle, and likely other similar events. Algal dominated biomass, deposited under a stratified water column during lake level rise, marks the Da'anzhai Member as potential hydrocarbon source rock. Given the challenges associated with Mesozoic stratigraphic correlation, I further present the first integrated (marine) stratigraphic reference framework for the complete Toarcian Stage from the Llanbedr (Mochras Farm) Borehole (Cardigan Bay Basin, UK), which allows precise correlation between the T-OAE and coeval Karoo-volcanism. I also show that accelerated global weathering rates during the T-OAE resulted in widespread mass transport deposits at different palaeolatitudes and changes in ocean chemistry leading to pronounced marine siderite deposition. Periodic smaller-magnitude carbon cycle perturbations in the Hettangian and Sinemurian were possibly in phase with short (~100kyr) and long (~405kyr) eccentricity astronomical forcing, with the formation of organic-rich laminated black shales in the Bristol Channel Basin, similar to Mediterranean sapropels in the Pleistocene.
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Fattal, Paul. "Etude geomorphologique et sedimentologique du plateau continental sud-armoricain." Nantes, 1986. http://www.theses.fr/1986NANT3004.
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Apres l'analyse des resultats bathymetriques, sedimentologiques et geologiques des campagnes menees de 1966 a 1978, nous procedons a l'etude de la dynamique des formes du plateau continental median et externe. Ce travail fait la part des formes heritees et des formes vives, etudie les interactions et retroactions d'agents dus aux variations incessantes de la mer au cours du plio-quaternaire. Les formes heritees d'une morphogenese subaerienne, les formes littorales anciennes et les formes vives sont semble-t-il en equilibre avec les agents actuelsAfter the analysis of the bathymetrics, sedimental and geological results of the 1966 to 1978 campagns, we are about to proceed upon the study of the shapes of the dynamics of the median and external continental shelf. This work distinguishes the inherited and living shapes, studies the interaction or retroaction of agents due to the permanent variations of the sea level during the plion quaternery era. It seems that the shapes due to a subaerian morphogenesis, the former coastal shapes and the living ones, are balanced whit the current agents of the present day
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Neto, Antonio Borges de Aguiar. "Heavy minerals occurrences in the continental shelf inner/mean west of CearÃ." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13816.
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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorThis study embraces the west continental shelf of Cearà (147 samples of marine sediments) and two fluvial courses (4 sediment samples of Curu and SÃo GonÃalo rivers) to determine heavy minerals distribution with their possible provenances and economic potential. Sedimentary facies on the continental shelf were distinguished through the particle size and calcium carbonate content. Heavy minerals were investigated for their total content (%), relative abundance (%) of each mineral species, concentration in Kg/ton of predominant species, mineralogical index (RZi and ZRT) and grains imaging by SEM-EDS. In geoprocessing obtained the spatial distribution of data by Arcgis 10.1 and Surfer 10 got informations about bottom morphology of the continental. Multivariate analysis were included using Statistica 7.0 to aid in the interpretation of results. Heavy minerals were concentrated in Fortaleza chart (contents reached to 4.54%) at depths until 20 m in the litoclastic and litobioclastic sands. Among the 18 mineral species identified, ilmenite and tourmaline were embracing most of the continental shelf and with epidote and monazite presented content > 1 Kg/ton near SÃo GongaÃo do Amarante coast. Paleochannels and ancient beach-ridge were identified. The occurrence of typical regional metamorphic mineral paragenesis of rocks rich in aluminum suggests the provenance of Cearà Complex rocks (primary source) that occur both near the coast and outcrops directly on the continental shelf. Reworked sediments of Barreiras Formation, beach black sands and longshore drift sediments (secondary sources) contribute regionally in heavy mineral supply.Curu river influences ilmenite, tourmaline and epidote supply. Multivariate analyzes and RZi/ZTR variations corroborated with the dual nature provenance (primary and secondary) of the continental shelf sediments and expose a mixture of recente sediments with older reworked ones.
Este estudo abrange a plataforma continental oeste do Cearà (147 amostras de sedimentos marinhos) e dois cursos fluviais (4 amostras de sedimentos dos rios Curu e SÃo GonÃalo) para determinar a distribuiÃÃo dos minerais pesados com suas possÃveis proveniÃncias e potencial econÃmico. Distinguiram-se as fÃcies sedimentares da plataforma continental pela granulometria e teor de carbonato de cÃlcio. Os minerais pesados foram investigados pelos seus teores totais (%), abundÃncias relativas (%) de cada espÃcie mineral, teores em Kg/ton das espÃcies predominantes, Ãndices mineralÃgicos (RZi e ZRT) e imageamento dos grÃos por MEV-EDS. No geoprocessamento obteve-se a espacializaÃÃo dos dados pelo Arcgis 10.1 e informaÃÃes da morfologia de fundo da plataforma continental com o Surfer 10. IncluÃram-se anÃlises multivariadas por meio do Statistica 7.0 para auxiliar na interpretaÃÃo dos resultados. Os minerais pesados se concentraram na folha Fortaleza (teores de atà 4,54%) em atà 20 m de profundidade e nos domÃnios das areias litoclÃsticas e litobioclÃsticas. Dentre as 18 espÃcies minerais identificadas, a ilmenita e a turmalina foram as que abrangeram a maior parte da plataforma continental e juntamente com epÃdoto e monazita apresentaram teores > 1 Kg/ton prÃximo à costa de SÃo GonÃalo do Amarante. Foram identificados paleocanais e antigas linhas de praia. A ocorrÃncia da paragÃnese mineral tÃpica de metamorfismo regional de rochas ricas em alumÃnio sugere a proveniÃncia das rochas do Complexo Cearà (fonte primÃria) que ocorrem tanto prÃximo à costa como afloram diretamente na plataforma continental. Sedimentos retrabalhados da FormaÃÃo Barreiras, areias pretas praiais e sedimentos de deriva litorÃnea (fontes secundÃrias) contribuem regionalmente no aporte de minerais pesados. O Rio Curu exerce influÃncia no aporte de ilmenita, turmalina e epÃdoto. As anÃlises multivariadas e as variaÃÃes de RZi e ZTR corroboraram com a proveniÃncia de natureza dual (primÃria e secundÃria) dos sedimentos plataformais, alÃm de expor uma mistura de sedimentos recentes com sedimentos retrabalhados mais antigos.
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Cussatlegras, Anne-Sophie. "Dynamique spatio-temporelle de la bioluminescence marine en mer d'Alboran et sur le plateau continental atlantique français." Brest, 2001. http://www.theses.fr/2001BRES2011.
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L'objectif de cette thèse était d'étudier les variations spatio-temporelles de la bioluminescence du plancton afin de pouvoir estimer les risques d'indiscrétion potentiels que représente pour la marine ce phénomène, responsable des sillages lumineux derrière les navires ou les sous-marins. Ce travail rassemble l'ensemble des connaissances sur les espèces bioluminescentes du plancton marin et définit les caractéristiques physiques de l'émission lumineuse. Suite à cette étude, un instrument a été conçu pour mesurer in situ les émissions lumineuses des organismes du plancton jusqu'à 3000 m de profondeur. Ce bathyphotomètre, couplé à une sonde CTD (" Conductivity-Temperature-Depth "), permet d'obtenir des profils verticaux de bioluminescence, simultanément à la température, la salinité et la fluorescence. Les mesures effectuées en mer d'Alboran montrent un accroissement de la bioluminescence au niveau du front géostrophique d'Almeria - Oran. En mer d'Iroise, la distribution spatiale et saisonnière de la bioluminescence reflète les différences de peuplements entre les différentes masses d'eau de part et d'autre des zones frontales, la zone homogène et la frange littorale étant généralement plus lumineuses. L'évolution saisonnière de la bioluminescence en zone côtière atlantique française est similaire aux variations d'abondance des dinoflagellés, indiquant l'importance majoritaire de ces organismes dans les émissions lumineuses enregistrées par l'appareil. La relation entre les concentrations en chlorophylle et la bioluminescence n'est pas systématique et traduit les changements de composition des populations planctoniques. En effet, certaines espèces chlorophylliennes comme les diatomées ne sont pas bioluminescentes et à l'inverse, certains dinoflagellés bioluminescents ne possèdent pas de chlorophylle. La corrélation significative de nuit entre les abondances de dinoflagelles et la bioluminescence, ainsi qu'une périodicité très marquée de l'émission lumineuse, en relation avec les heures de lever et coucher de soleil, traduit l'inhibition de la bioluminescence des dinoflagellés pendant le jour. La bioluminescence apparaît comme un outil d'étude prometteur de la dynamique du plancton. Des améliorations possibles de l'appareil de mesure et des perspectives de modélisation sont proposées à l'issue de ce travail.
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Guerra, Josefa Varela. "Interannual variability of nearbed sediment flux and associated physical processes on the Eel River shelf, Northern California, USA /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/11000.
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Braker, John M. "The Impact of Variability in Coastal Circulation on Plankton Distributions Along the Continental Shelf of Southeast Florida." NSUWorks, 1995. http://nsuworks.nova.edu/occ_stuetd/346.
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Time series of zooplankton concentrations and current velocities were collected with a bottom mounted (190 m) 307.2 kHz acoustic Doppler current profiler (ADCP) at the shelf break off Fort Lauderdale, Florida. Simultaneously, time series of temperature and salinity were collected with a moored CTD in the Port Everglades estuary approximately 4 km inshore of the ADCP mooring. Software was developed to extract acoustic volume scattering strength data (Vs) from the ADCP data stream. Vs is a relative measure of zooplankton concentration. In addition, eastward velocity and northward velocity data were collected from the ADCP. Data were recorded in two minute averages, with additional processing yielding hourly averages. Acoustic volume scattering strength and current velocity records from 176, 136, 95, and 56 m deep were isolated during post-processing for spectral analysis. The acoustic estimate of zooplankton concentration was found to be coherent with current velocity (both north and east components) at frequencies corresponding to the scales of Gulf Stream meanders (2-10 days per cycle) and diurnal and semi-diurnal tidal variability (24 and 12 hours per cycle, respectively). Estuarine salinity variations were also coherent with variability in circulation at the shelf break at the energetic periods of 24, 12, 8 and 6 hours per cycle. Estuarine salinity varied inversely with the distance of the Gulf Stream front from shore (0.5 - 6 week observation interval). Apparently, low frequency variability in the salinity of estuarine water is also associated with variability in the position of the Gulf Stream. It would appear that variability of Gulf Stream position and flow influences the cross-shelf transport of planktonic organisms, such as fish larvae, at a variety of temporal scales and thereby links offshore and estuarine ecosystems off southeast Florida.
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Jordan, Tom A. R. M. "Gravity anomalies, flexure, and the long-term rigidity of the continental lithosphere." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:9f803b42-522e-442b-9849-bb8e6c2a5494.
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The cause and distribution of spatial variations in the mechanical properties of the continental lithosphere are fundamental questions for modern geology. In this study variations in long-term lithospheric rigidity have been investigated. These investigations used profile- and grid-based flexural models of the lithosphere’s response to geologically imposed topographic, or buried, loads. These models were constrained by topographic and gravity data allowing recovery of best fitting rigidity values. In Oman a Cretaceous ophiolite acts as a significant load on the continental crust. Flexural models along profiles orthogonal to the ophiolite strike show that the observed gravity data can be best modelled by an elastic beam with standard thickness (Te) of 30 km. Along strike there is shown to be significant variation in the foreland shape and the observed gravity signal. This, it is proposed, relates to the complex tectonic processes which occurred as the ophiolite was obducted. The Himalayan foreland has been the focus of controversy over the recovered long-term rigidity of the continents, with recovered Te values ranging from 40 to over 90 km. Both profile- and grid-based techniques show that Te is high (>70 km) in the foreland region. Across the India-Eurasia collisional system as a whole Te values are variable. Beneath the Tibetan plateau recovered values are generally low (<10 km), while the plateau margins are marked by regions of higher rigidity. Recovered Te values across the Arabia-Eurasia collisional system range from over 60 km in the foreland region to close to zero beneath the high Zagros mountains. In the eastern part of the foreland, flexural models match the gravity data; however, they disagree with sediment thickness data for the material infilling the foreland. This discrepancy is interpreted in terms of de-coupling of the flexural lithosphere from the shallower crustal levels, caused by the presence of significant salt deposits in this region. Application of grid-based techniques to South America, North America and Europe recover a broad range of Te values from ∼0 to over 90 km. The low Te values are explained in active orogenic belts in terms of current processes acting to weaken the lithosphere, and in the continental interiors as the relics of past orogenic events. High Te values in the continental interiors correlate with ancient cratonic cores which have undergone little deformation since their formation in the Archean. This study shows that Te variations have a critical influence on the development of large compressional orogenic belts. In the Himalayan and Andean orogens there is a correlation between the over-thrusting of the orogenic belt and high Te foreland regions. Where lower Te regions are seen, less over thrusting is apparent, and in the case of the India-Eurasia collisional system out-flow of lower crustal material may be occurring.
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Marsh, Daniel L. "TRACE METALS IN SEDIMENTS ON THE CONTINENTAL MARGINOF THE NORTHWEST ATLANTIC OCEAN." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1389654019.
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Chauveau, Etienne. "Les marges continentales de Guinée et de Côte-d'Ivoire orientale : étude de géomorphologie sous-marine." Paris 4, 1994. http://www.theses.fr/1994PA040334.
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Les marges continentales de Guinée et de Cote d’Ivoire orientale associent dans un espace restreint des segments divergents et des segments transformants. Les caractères transformants ayant été acquis des l'ouverture de l'Atlantique équatorial, les marges ont conserve tout au long de leur histoire les traces de transferts sédimentaires contrôles dans un premier temps, par des environnements continentaux et un cloisonnement prononce du relief, et par une sédimentation marine dominante des le crétacé supérieur, mais toujours fortement contrainte par des barrières structurales ayant entraîne une différenciation prononcée dans l'étagement des processus morphogéniques de ces deux marges, jusqu'au quaternaire. La ou ces barrières structurales s'estompent, les caractères de marge divergente classique s'affirment, et avec eux la mise en place de transferts sédimentaires pris en charge par des canyons entaillant la totalité de la pente continentale. L'observation des marges américaines conjuguées montre que la trame structurale des marges transformantes n'est pas nécessairement le critère prépondérant dans l'élaboration morphologique de ce type de marge. Outre-atlantique en effet, les facteurs paléo-océanographiques et paléoclimatiques semblent avoir pesé d'un poids considérable. Les moyens d'investigation modernes permettent aujourd'hui d'appréhender certaines des caractéristiques environnementales des espaces tropicaux, a travers une approche globale ou les interactions entre l'hydrosphère marine, l'atmosphère et la biosphère continentale sont analysées de plus en plus finement. Les modélisations élaborées enrichissent ainsi continuellement celles qui s'efforcent de retracer les environnements du passe, cette connaissance des paléo-environnements constituant un élément fondamental pour dresser les contours d'une paléogéomorphologie des régions étudiéesThe continental margins of Guinea and east Ivory-Coast associate rifted and transform segments in short distances. The transform features have been created since the early strikeslip motion at the beginning of the equatorial Atlantic. Thus, the margins have kept during all their evolution the marks of sedimentary transfers controlled by continental settling and hummocky topography first and marine sedimentation since the upper cretaceous. Since the time, structural barriers of both margins always induced morphogenic processes differentiation in a vertical plane. The Americans conjugate margins show that the structural framework is not necessarily the predominant criterion for the morphologic characteristics of transform margins. There indeed, the paleoceanographic and paleoclimatologic factors seem to have been very important. Nowadays, the understanding of global environmental systems allows modelling of tropical areas. Hence, the results of such investigations afford a better comprehension of the paleoenvironments, and can finally authorise paleogeomorphologic reconstitutions
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DeCroix, David Scot. "Large-eddy Simulations of the Convective and Evening Transition Planetary Boundary Layers." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20010319-182404.
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Large-eddy simulation (LES) is a very useful tool in computationalfluid dynamics. The LES model allows one to solve a filtered set of theNavier-Stokes equations, thereby explicitly resolving scales of motionlarger than the discretization or grid size. Those motions smaller thanthe grid size are parameterized using a so-called subgrid scale model.
In this series of papers, we will use the TASS LES model, originallya cloud model, which has been modified to simulate planetary boundarylayer turbulence. We will first introduce the LES model and a newgrid-nesting method for the LES. Then we will present simulations ofthe convective planetary boundary layer, and then use the LES to studythe decay of convective planetary boundary layer turbulence to a stablystratified state.
The LES model has been modified to include a grid nesting capability.Grid meshes of higher resolution may be embedded within the LES enablingone to resolve smaller scales of motion (turbulence) than would bepossible by using a single grid mesh. The grid nesting methodology isdescribed in detail in Chapter 2.
In Chapter 3, the nested-grid LES will be applied to thesimulation of the convective planetary boundary layer. We will usea total of three grid meshes to increase the resolution in the surfacelayer, allowing a detailed analysis of the turbulence near the surface ofthe earth.
In Chapter 4, we will focus on applying Rayleigh Benardconvection criteria, using a linearized perturbation method,to the surface layer of a CBL produced by large-eddy simulation.Similarities and differences will be discussed between the LESproduced surface layer and classical Rayleigh-Benard convection theory.
In Chapter 5, using a large-eddy simulation model, we willexamine in detail the turbulent kinetic energy (TKE) budget during theevening transition. The simulation will be performed in order to compareto observations gathered at the Dallas-Fort Worth International Airport,Fort-Worth, TX. during September and October 1997.
In Chapter 6 the decay of planetary boundary layerturbulence during the evening transition will be studied. In previousstudies of the decay of turbulence, the effects of mean winds and shearsdue to pressure gradient on the turbulence decay was not considered.We propose to examine the effects of increasing geostrophic wind onthe convective boundary layer and its transition or decay to a stablecondition. Finally, the overall conclusions of each chapter will bepresented.
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Ali, Heba. "THE EFFECT OF DEPTH ON DEVELOPMENT AND SEXUAL DIMORPHISM OF THE SONIC SYSTEM IN DEEP SEA NEOBYTHITINE FISHES: THE UPPER CONTINENTAL SLOPE." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4095.
Full textAbstract:
Abstract
Background: Cusk-eels from the subfamily Neobythiitinae are one of the major groups of sound-producing fishes on the continental slope. Sounds have never been recorded from a member of this subfamily, and sonic anatomy is considered a proxy for sound production. As the first part of a study on the effects of depth on sonic anatomy, we examined three relatively shallow species from the upper continental slope.
Methods: Three species (Hoplobrotula armata, Neobythites longipes and Neobythites unimaculatus) were examined for sonic anatomy (skeleton, swimbladder and sonic muscles), and sonic and epaxial muscle fibers were measured for diameter. Regressions of dimensions and weights of sonic muscles and swimbladders against fish total length and weight were compared to determine sexual dimorphism and relative development between species.
Results: Four pairs of sonic muscles (two medial and two lateral) originate on the skull and insert on the medial swimbladder or on modified epineural ribs that attach to the lateral swimbladder. The medial and medial intermediate muscles are generally larger in males than females and are made of relatively small fibers (ca 10 um in diameter), and lateral muscles are generally larger in females and consist of larger fibers as in epaxial muscles. Medial muscles are considerably larger in Hoplobrotula armata than in the Neobythites species.
Conclusion: Neobythitines from the upper slope have relatively well-developed sexually-dimorphic sonic systems, suggesting that males produce advertisement calls for courtship. There are major quantitative differences between species. We suggest that sound production involves tonic contraction of the large-fibered lateral muscle pair and oscillatory contractions of the smaller medial fibers setting the swimbladder into vibration. Hoplobrotula armata is probably capable of making more intense sounds than the Neobythies spp.
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Billington, Tyler. "Sedimentologic and Petrographic Evidence of Flow Confinement In a Passive Continental Margin Slope Channel Complex, Isaac Formation, Windermere Supergroup, British Columbia, Canada." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39727.
Full textAbstract:
At the Castle Creek study area in east-central British Columbia a well-exposed section about 450 m wide and 30 m thick in the (Neoproterozoic) Isaac Formation was analyzed to document vertical and lateral changes in a succession of distinctively heterolithic strata. Strata are interpreted to have been deposited on a deep-marine levee that was sandwiched between its genetically related channel on one side and an erosional escarpment sculpted by an older (underlying) channel on the other. Flows that overspilled the channel (incident flow) eventually encountered the escarpment, which then set up a return flow oriented more or less opposite to the incident (from the channel) flow. This created an area of complex flow that became manifested in the sedimentary record as a highly tabular succession of intricately interstratified sand and mud overlain by an anomalously thick, plane-parallel interlaminated sand-mud unit capped finally by a claystone.
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Nameroff, Tamara J. "Suboxic trace metal geochemistry and paleo-record in continental margin sediments of the eastern tropical North Pacific /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/8514.
Full text
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Hightower, Gerald R. "Aviation proof of concept the transition of Marine Corps aviation maintenance computer assets and systems into the Navy Marine Corps Intranet /." Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Mar/10Mar%5FHightower.pdf.
Full textAbstract:
Thesis (M.S. in Information Technology Management)--Naval Postgraduate School, March 2010.Thesis Advisor(s): Cook, Glenn. Second Reader: Oros, Carl. "March 2010." Description based on title screen as viewed on April 28, 2010. Author(s) subject terms: DT, OT, APOC, NTCSS, NMCI. Includes bibliographical references (p. 69-70). Also available in print.
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Cowie, Leanne. "Determination of ocean continent transition structure, continent ocean boundary location and magmatic type at rifted continental margins." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2008044/.
Full textAbstract:
Knowledge of ocean continent transition (OCT) structure, continent ocean boundary (COB) location and magmatic type are of critical importance for understanding rifted continental margin formation and evolution, and in evaluating petroleum systems in deep-water frontier oil and gas exploration. A suite of quantitative analytical techniques have been developed in order to determine the structure of the OCT, the location of the COB and magmatic type at rifted continental margins; these techniques include the use of gravity anomaly inversion, residual depth anomaly (RDA) and subsidence analysis. Gravity anomaly inversion, incorporating a lithosphere thermal gravity anomaly correction, has been used to determine Moho depth, crustal basement thickness and continental lithosphere thinning. RDA analysis has been used to investigate OCT bathymetric anomalies with respect to expected oceanic bathymetries, and subsidence analysis has been used to determine the distribution of continental lithosphere thinning. These techniques have been applied to the Iberian, Gulf of Aden, northern Angolan, and south-eastern Brazilian rifted continental margins. Integrated quantitative analysis results have been validated using ODP well data and magnetic anomalies along the Iberian rifted continental margin. Results identify a clearly defined zone of exhumed mantle on the Iberian profiles, which is also observed in the ODP well data. In addition to the quantitative analysis techniques, a methodology for the joint inversion of deep long offset seismic data and gravity anomaly data has been developed in order to further constrain the OCT structure and COB location. The joint inversion method solves for coincident seismic and gravity Moho in the time domain and calculates the lateral variations in crustal basement densities and velocities along profile. Integrated quantitative analysis along the northern Angolan profile suggests that exhumed mantle, corresponding to a magma-poor margin, is absent beneath the allochthonous salt and that the thickness of earliest oceanic crust is approximately 7km. Integrated quantitative analysis along the south-eastern Brazilian profile predicts that the earliest oceanic crust is between 7km and 8km thick and that there is no evidence of exhumed mantle as suggested by Zalán et al. (2011). The results from the integrated quantitative analysis have also been used together with post-breakup subsidence modelling to determine the palaeo-bathymetry of the base Loeme salt along northern Angolan profiles. The proximal autochthonous base salt restores to near sea level, but not the distal allochthonous salt. Our interpretation is that the distal salt formed during the late syn-rift while the crust under it was being actively thinned, resulting in additional tectonic subsidence. Residual topography, which we attribute to mantle dynamic topography, has been determined using RDA analysis, with corrections for sediment loading and crustal basement thickness variations. Residual topography of -650m is measured along the Iberian Abyssal Plain; +400m in the Gulf of Aden, and +700m along the northern Angolan margin.
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Webster, John Ackroyd III. "Design and Analysis of Low Reynolds Number Marine Propellers with Computational Fluid Dynamics (CFD) Transition Modeling." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/93038.
Full textAbstract:
Small-scale marine propellers operate at low Reynolds numbers, where laminar-turbulent
transition of the boundary layer can impact the distributions of pressure and shear stress
on the blade surface. Marine propellers operating at low Reynolds numbers are subject to
laminar-turbulent transition of the boundary layer, which impacts the distributions of pressure
and shear stress on the blade surface. To design efficient propellers for operation at
low Reynolds numbers, transitional effects must be included in the evaluations of propeller
performance. In this work, transition modeling techniques in Reynolds Averaged Navier-
Stokes computational fluid dynamics (RANS CFD) are utilized to evaluate and design propellers
operating at low Reynolds numbers. The Galilean invariant γ transition model with
an extension for crossflow transition is coupled to the SSG (Speziale, Sarkar, Gatski) /LRR
(Launder, Reece, Rodi) -ω Reynolds stress transport turbulence model, with validation cases
performed for flate plate boundary layers, 2-dimensional airfoils, a 3-dimensional wing, and
6:1 prolate spheroids. The performance of the coupled SSG/LRR-ω-γ Reynolds stress transition
model for propellers with flow transition is then evaluated using experimental surface
streamline and force data from four model-scale marine propellers. A method for the design
of low Reynolds number marine propellers is presented using a transition-sensitive lifting line
method coupled with the panel method code XFOIL. Initial geometries generated using the
lifting-line method are then optimized in RANS CFD using the 2 equation γ-Reθ transition
model and an adjoint method to warp the propeller shape to improve the efficiency. Two
design studies are performed, including an open water propeller, and a propeller designed
for a small autonomous underwater vehicle.Doctor of Philosophy
Small-scale marine propellers exhibit transition from laminar to turbulent flow in the region near the surface of the blades. Regions of laminar and turbulent flow on the blade surface contribute differently to the overall thrust and torque on the propeller. Prediction of flow transition in the design process for small-scale marine propellers can improve the accuracy of the thrust and torque prediction compared to modeling the flow as purely laminar or turbulent. Propeller thrust and torque can be modeled using computational fluid dynamics (CFD) simulations, where transition modeling is accomplished by solving a transport equation for the intermittency γ, which represents the percentage of time the flow in a given location is turbulent. In this work, a transition model is coupled to a high-fidelity full Reynolds stress turbulence model, which solves 6 transport equations to solve for each component of the Reynolds stress tensor. The Reynolds stress tensor represents the turbulent velocity fluctuations in the governing equations solved in the CFD simulation. This coupled transition and turbulence model is then validated using experimental results of flows with a number of different transition mechanisms. The coupled model is then tested with a series of model-scale propellers, with results of the CFD simulations compared to the experimental results. A method for the design of propellers with flow transition is presented which incorporates transition effects. The designs generated by this method are then optimized in a CFD framework which morphs the blade geometry to improve the ratio of the thrust produced by the propeller to the torque, which corresponds to a higher efficiency. Two design cases are presented: a propeller designed for open water operation, and a propeller design for a small autonomous underwater vehicle.