Dissertations / Theses on the topic 'Mesozoic sediments'

This thesis represents the results of a study concerned with the various chemical and thermal processes which produce remagnetizations in continental sediments. Information has been gathered from a number of disciplines; palaeomagnetism, petrography, diagenesis, thermal history modelling. These techniques have been combined to produce a model of the processes by which sediments in particular areas of the United Kingdom have been remagnetized. In southwest Dyfed (South Wales), the Old Red Sandstone (Silurian to Devonian in age) has been remagnetized both chemically and thermally in the Late Carboniferous by fluids precipitated during the Variscan Orogeny. This can be concluded from the palaeomagnetic data which indicate that the remagnetization occurred approximately half-way through the Variscan folding event. In Anglesey (North Wales), the Old Red Sandstone (Lower Devonian) was folded by an earlier event, the Acadian Orogeny (Middle Devonian) and was not greatly affected by the Variscan event which was terminated over 100km to the south. However, the uplift associated with the Variscan event brought the Old Red Sandstone of Anglesey into the realm of oxidising fluids and chemically-precipitated haematite produced a remagnetization which is Permian in age. Fold tests clearly show that the remagnetization post-dates folding in this area. In the southern North Sea, the Barren Red Measures (Westphalian C, Carboniferous) contain chemically-precipitated haematite which was also produced as a result of Permian uplift in the wake of the Variscan Orogeny. However, the main remagnetization is associated with Triassic haematite precipitation produced by lateral flow of fluids along permeable channel sandstone units. The fact that some of the sandstones are remagnetized at this time whilst others are not is perhaps indicative of the interconnectivity of the sandbodies. In southwest Birmingham (Central England) the Keele Formation (Westphalian D, Carboniferous) provides an onshore analogue (in terms of age) to the southern North Sea samples. In this area there is a similar Permian age of remagnetization as that seen in Anglesey, produced as a result of uplift in the Variscan foreland. However, unlike Anglesey, these rocks also contain a primary magnetization which can be isolated from thermal demagnetization experiments. Present day weathering of the Keele Formation has imposed a weak magnetization (probably held within grains of goethite) on those rocks which lie within 10m of the surface, particularly in the more permeable sandstone units. The other effect of the present day weathering is that it tends to remove the finer grains of haematite which tend to be associated with Permian remagnetization. On the Isle of Arran (West Scotland) the New Red Sandstone (Permian and Triassic) has been remagnetized by a number of igneous intrusions which were produced as a result of Lower Tertiary hot spot activity beneath the British Isles. Palaeomagnetic experiments have been compared with computer models of heat flow around a small dyke to show that the remagnetization associated with the intrusions is a product of both thermal and chemical processes. The thermal processes are a product of direct heat flow from the intrusions which thermally remagnetizes pre-existing magnetic grains. However, the chemical processes are driven by convectional flow of fluids through the permeable Permian and Triassic sandstones to precipitate new magnetite and haematite grains. Despite the high level of thermal and chemical activity in this region in the Lower Tertiary, many of the rocks still retain a primary component of magnetization associated with deposition or early post-depositional processes. In summary, the pre-Permian sediments studied in this thesis appear to be particularly prone to remagnetization as a result of Variscan movements and the resulting uplift of southern Britain. On the Isle of Arran Permian and Triassic sediments which post-date the Variscan event are affected by a combined thermal and chemical remagnetization associated with Early Tertiary hot spot activity. The results of this thesis have shown the value of using palaeomagnetic techniques to time remagnetizations in continental sediments. In addition, the results have outlined a number of key geological events since the Devonian which are likely to be responsible for a number of the remagnetizations seen in the rocks of the United Kingdom. Therefore, these results can be used in a predictive manner for future palaeomagnetic studies in the rocks of this country and perhaps even further afield. For example, the effects of the Variscan Orogeny have produced remagnetizations in the rocks of Europe, Africa and north America. It is considered essential that all future work in this field should include the study of the burial history for the sedimentary basins covered as the remagnetizations explained in this work have all been intimately related to particular burial or uplift episodes. In addition, petrographic analysis helps to distinguish the textural phases of the magnetic grains which are responsible for the remagnetizations and are thus also essential elements in the study of remagnetizations in sedimentary basins.

The Taimyr Peninsula is a key element in the circum-Arctic region and represents the northern margin of the Siberian Craton. The Taimyr Peninsula preserves late Paleozoic through Mesozoic clasitic sedimentary successions in its Mesozoic fold belt, providing an ideal location to investigate the Mesozoic tectonic evolution associated with the opening of Amerasia Basin within a circum-Arctic framework. This thesis aims to establish the tectonic setting in which the late Paleozoic through Mesozoic sediments of Taimyr were deposited, in order to correlate Taimyr with other Arctic terranes utilizing provenance investigations. Multiple methods are adopted, including petrography, heavy mineral analysis and detrital zircon U-Pb geochronology.  The preliminary results of this work indicate that the late Paleozoic sediments of southern Taimyr were deposited in a foreland basin of the Uralian orogen during Uralian orogeny. The final collision between Baltica and Siberia in the last stage of Uralian orogenesis occurred between Early and Late Permian. Early Cretaceous sediments in northern Taimyr were mainly derived from Siberian Trap-related magmatism in Taimyr. Cretaceous sediment deposition is unrelated to Jurassic to Cretaceous rifting associated with the Verkhoyansk fold belt and instead relates to a rifting or post-rifting passive margin setting.

L'utilisation d'analyses isotopiques (nd et pb) et des teneurs en elements-trace a permis d'aborder plusieurs aspects de la geochimie des roches sedimentaires. On s'interesse a l'aspect temporel enregistre par les sediments avec la caracterisation de la croissance de la croute continentale et l'etude de son evolution chimique au cours du temps (afrique du sud et canada). L'autre aspect etudie concerne l'individualisation des contributions respectives des sources de particules sedimentaires (etude isotopique de la limite cretace-tertiaire, evolution geochimique du bassin oceanique marocain), les concentrations secondaires ou les phenomenes de circulation

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A região de Franca situa-se na borda nordeste da Bacia do Paraná, sendo margeada a nordeste por um soerguimento regional contemporâneo à individualização da Placa Sul-Americana e abertura do Oceano Atlântico Sul, o Soerguimento do Alto Paranaíba. A área é caracterizada por rochas do Grupo Araxá-Canastra (Pré-Cambriano) sobrepostas discordantemente por, da base para o topo, arenitos e conglomerados glaciogênicos da Formação Aquidauana (Permo-Carbonífero), arenitos eólicos e conglomerados eólico-fluviais da Formação Botucatu (Jurássico-Cretáceo) intercalados por rochas basálticas (derrames e sills) da Formação Serra Geral (Cretáceo), e rochas siliciclásticas do Grupo Bauru (Cretáceo Superior). Estas rochas encontram-se recobertas por sedimentos inconsolidados (Cenozóico), freqüentemente lateritizados. A história geológica mesozóico-cenozóica da região de Franca foi determinada por mecanismos tectono-sedimentares controlando a distribuição da sedimentação detrítica e formação de pláceres diamantíferos. O estudo de fácies sedimentares das unidades mesozóico-cenozóicas permitiu a caracterização das assembléias mineralógicas presentes, sob o enfoque de sedimentação fortemente vinculada a eventos de desnudação continental, com o preenchimento sedimentar de bacias, associado à elaboração de superfícies de aplanamento. O comportamento morfoestrutural e morfotectônico, ao qual as unidades aflorantes foram submetidas, condicionando a morfologia do relevo e a instalação da rede de drenagem num quadro estrutural, permitiu a caracterização da evolução tectono-sedimentar da região, sob um enfoque neotectônico. No Cenozóico, a morfologia do relevo e a instalação da rede de drenagem parecem fortemente controladas por um quadro de estruturas tectônicas...
The region of Franca is located in the northeastern limits of the Paraná Basin, aside the Alto Paranaíba Uplift, with associated kimbelitic bodies. Its evolution is contemporaneous to the individualization of the South America Plate and by the opening of South Atlantic Ocean. The Mesozoic-Cenozoic geology of the Franca region is characterized by basement rocks of Araxá Group (Pré-Cambrian) overlaid, from bottom to top, by glaciogenic sandstones and conglomerates of the Aquidauana Formation (Permo- Carboniferous), eolic sandstone and fluvial-eolic conglomerates of the Botucatu Formation (Jurassic-Cretaceous), basaltic rocks of the Serra Geral Formation (Cretaceous), and by siliciclastic rocks of the Bauru Group (Late Cretaceous). All these rocks are covered unconformably, by lateritizated eluvial-coluvial cenozoic sediments. The area was conditioned by tectono-sedimentary events, wich controlled the detritic sedimentary distribution and the diamontiferous placers. The sedimentary facies study was done to characterize the mineralogical assemblage, under the light of a sedimentation associated with continental denudation, and planation surface elaboration. The morphotectonic and morphostructural pattern determine the relief features and the instalation of the drainage network on a structural frame, and allow to interpret the tectono-sedimentary evolution of the region in a neotectonic context. During the Cenozoic, the relief and drainage network instalation were controlled by tectonic structures associated with transtensive (NW-SE and E-W) and transpressive (NE-SW) features. The sequence of different tectono-sedimentary cycles resulted, probably, in erosion of kimberlitic of the Alto Paranaíba Uplift, provinding selection and progressive enrichment of resistent material, stable and ultra-stable rocks and minerals in to the Cretaceous (Bauru Group) and Cenozoic... (Complete abstract, access undermentioned electronic address)

Orientador: Sebastião Gomes de Carvalho
Banca: Nicolau Ladislau Ervin Haralyi
Banca: Yociteru Hasui
Banca: João Batista Moreschi
Banca: Rainer Aloys Schultz-Guttler
Resumo: A região de Franca situa-se na borda nordeste da Bacia do Paraná, sendo margeada a nordeste por um soerguimento regional contemporâneo à individualização da Placa Sul-Americana e abertura do Oceano Atlântico Sul, o Soerguimento do Alto Paranaíba. A área é caracterizada por rochas do Grupo Araxá-Canastra (Pré-Cambriano) sobrepostas discordantemente por, da base para o topo, arenitos e conglomerados glaciogênicos da Formação Aquidauana (Permo-Carbonífero), arenitos eólicos e conglomerados eólico-fluviais da Formação Botucatu (Jurássico-Cretáceo) intercalados por rochas basálticas (derrames e sills) da Formação Serra Geral (Cretáceo), e rochas siliciclásticas do Grupo Bauru (Cretáceo Superior). Estas rochas encontram-se recobertas por sedimentos inconsolidados (Cenozóico), freqüentemente lateritizados. A história geológica mesozóico-cenozóica da região de Franca foi determinada por mecanismos tectono-sedimentares controlando a distribuição da sedimentação detrítica e formação de pláceres diamantíferos. O estudo de fácies sedimentares das unidades mesozóico-cenozóicas permitiu a caracterização das assembléias mineralógicas presentes, sob o enfoque de sedimentação fortemente vinculada a eventos de desnudação continental, com o preenchimento sedimentar de bacias, associado à elaboração de superfícies de aplanamento. O comportamento morfoestrutural e morfotectônico, ao qual as unidades aflorantes foram submetidas, condicionando a morfologia do relevo e a instalação da rede de drenagem num quadro estrutural, permitiu a caracterização da evolução tectono-sedimentar da região, sob um enfoque neotectônico. No Cenozóico, a morfologia do relevo e a instalação da rede de drenagem parecem fortemente controladas por um quadro de estruturas tectônicas... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The region of Franca is located in the northeastern limits of the Paraná Basin, aside the Alto Paranaíba Uplift, with associated kimbelitic bodies. Its evolution is contemporaneous to the individualization of the South America Plate and by the opening of South Atlantic Ocean. The Mesozoic-Cenozoic geology of the Franca region is characterized by basement rocks of Araxá Group (Pré-Cambrian) overlaid, from bottom to top, by glaciogenic sandstones and conglomerates of the Aquidauana Formation (Permo- Carboniferous), eolic sandstone and fluvial-eolic conglomerates of the Botucatu Formation (Jurassic-Cretaceous), basaltic rocks of the Serra Geral Formation (Cretaceous), and by siliciclastic rocks of the Bauru Group (Late Cretaceous). All these rocks are covered unconformably, by lateritizated eluvial-coluvial cenozoic sediments. The area was conditioned by tectono-sedimentary events, wich controlled the detritic sedimentary distribution and the diamontiferous placers. The sedimentary facies study was done to characterize the mineralogical assemblage, under the light of a sedimentation associated with continental denudation, and planation surface elaboration. The morphotectonic and morphostructural pattern determine the relief features and the instalation of the drainage network on a structural frame, and allow to interpret the tectono-sedimentary evolution of the region in a neotectonic context. During the Cenozoic, the relief and drainage network instalation were controlled by tectonic structures associated with transtensive (NW-SE and E-W) and transpressive (NE-SW) features. The sequence of different tectono-sedimentary cycles resulted, probably, in erosion of kimberlitic of the Alto Paranaíba Uplift, provinding selection and progressive enrichment of resistent material, stable and ultra-stable rocks and minerals in to the Cretaceous (Bauru Group) and Cenozoic... (Complete abstract, access undermentioned electronic address)
Doutor

Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2017.
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A margem ocidental de América do Sul é comumente considerada como um exemplo de margem oceano - continental convergente, constituindo a antigo Oeste do Gondwana antes de sua dispersão no Cretáceo. O segmento norte de América do Sul experimento a mudanças drásticas desde o desenvolvimento como bacia de trás-arco no Triássico-Jurássico até formar uma retro-bacia de ante-país no contexto atual andino. Uma maneira para determinar essas mudanças nos eventos geodinâmicos que afetam o segmento norte da América do Sul é estudando a proveniência das rochas sedimentares e reconstruir a evolução do paleodrenagem. Este estudo analisa a proveniência das rochas sedimentares que compõem o intervalo Triássico-Mioceno depositados na Bacia do Huallaga. Foram utilizados os métodos de U-Pb em zircão detrítico e isotopia de Nd-Sr. Os resultados mostram quatro mudanças da proveniência associados a eventos locais e regionais que afetam a bacia de ante-pais do norte de Peru. As rochas sedimentares do Triássico-Jurássico foram depositadas em um contexto de bacia de back-arc. Os valores de εNd (0) são de - 7,9 a -10 associada com um arco juvenil junto com idades U-Pb em zircão detritico que representam as províncias de Greenville- Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Maroni-Itacaiúnas (2-2.2 Ga). Estes resultados sugerem uma fonte de proveniência mista vindo do Arco Vulcânico Mesozoico (Arco Misahuallí-Colán) e rochas Pré-cambrianas da Cordilheira Oriental do Peru e Cordilheira Real do Equador. As rochas sedimentares do Cretáceo (Albiano-Maastrichtiano) têm valores de εNd (0) entre -16 a -18 com picos de idades U-Pb em zircão detritico representando as províncias de Rondônia-San Ignácio (1.3-1.54 Ga), Rio Negro-Juruena (1.54-1.82 Ga) e Ventuari Tapajós (1.82-2 Ga). Estes resultados sugerem uma fonte das áreas do Cráton Amazonico onde o transporte de sedimentos foi realizado no sentido Oeste para Leste durante o Albiano-Maastrichtiano e dominou todo o segmento norte de América do Sul. As rochas sedimentares do Paleoceno Inferior- Eoceno têm valores εNd (0) de - 5,58 a -10,35 com picos de idades U-Pb em zircão detritico que representam as províncias de Greenville-Sunsás (1.3- 0.9 Ga), Brasiliano (0.5-0.7 Ga) e Rio Negro-Juruena (1.54-1.82 Ga) junto com as primeiras populações de zircões com idades mais jovens que 120 Ma. Essas idades representam os primeiros zircões da região dos Andes e corresponde ao segmento da Cordilheira Ocidental. As rochas sedimentares do Oligoceno têm valores de εNd (0) entre -7,7 a -9,9 junto com um pico principal de idades U-Pb entre 23-29 Ma (Oligoceno). Estes resultados mostram uma predominância de fonte de arco vulcânico Paleógeno-Neógeno (Arco Vulcânico Calipuy- Saraguro) que se desenvolve na Cordilheira Ocidental do Equador e do Peru. As rochas sedimentares do Miocene apresentam valores de εNd (0) entre -5,8 a -12,6 junto com idades U-Pb em zircão detritico principais pertencem às províncias Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga), Arco Magmático Paleozóico (0.4-0.26 Ga) e Rift Permo-Triassico (0.25-0.15 Ga). Estas rochas apresentam uma fonte mista vindo dos segmentos da Cordilheira Ocidental e Oriental dos Andes Centrais. O desenvolvimento da Cordilheira Oriental gera uma barreira evita o transporte dos sedimentos que veim da Cordilheira Ocidental.
The Andean margin of South America is considered as the type example of an ocean - continental convergent margin, located along the west margin of Gondwana prior to its dispersion during to Cretaceous. The north segment of South America undergoes severe changes from the passage of a back-arc basin during the Triassic-Jurassic to a retro-foreland basin in the current Andean context. One way to constraint the changes of these geodynamical proccesses and the way it affected the northern part of South America is to study the sedimentary provenance and reconstruct its paleodrainage evolution. This study analyzes the sedimentary rocks of the Triassic-Miocene interval deposited in the Huallaga basin that has part of the northern Peruvian Amazonian basin. We performed sedimentary analyzes using the methods of, U-Pb in detrital zircon and Sr-Nd isotopes. The results show 4 changes in provenance associated with regional and local events that affect the northern Peruvian Amazonian basin. The Triassic-Jurassic is characterized by deposition of sediments in back-arc basin context. The Triassic-Jurassic sediments present εNd (0) values of -7.9 to - 10 associated with a young arc along with zircon population age from the representing the provinces of Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Maroni-Itacaiúnas (2- 2.2 Ga). These results suggest a mixed source between volcanic arc (Misahuallí-Colán Arc) and Pre-cambrian rocks of the Eastern Cordillera of Peru and Cordillera Real of Ecuador. The sedimentary rocks of the Cretaceous (Albian-Maastrichtian) present εNd (0) values of - 16 to -18 along with zircon population age from the representing the provinces of Rondonia- San Ignácio (1.3-1.54 Ga), Rio Negro-Juruena (1.54-1.82 Ga) e Ventuari-Tapajós (1.82-2 Ga). These results suggest a source of Amazon Craton, where the transport of sediments developed westward from the drainage systems during the Albian-Maastrichtian and dominated the entire northern segment of South America. The Early Paleocene to Eocene sedimentary rocks presents εNd (0) values of – 5.58 to -10.35 with zircon population age from the representing the provinces of Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Rio Negro-Juruena (1.54-1.82 Ga) with population age younger than 120 Ma. These ages represent the first zircons from the Andean mountains and correspond to the segment of the Western Cordillera. The Oligocene sedimentary rocks present εNd (0) values of -7.7 to - 9.9 with a main peak of zircon population ages between 23-29 Ma (Oligocene). These results show a predominance of the Paleogene-Neogene volcanic arc (Calipuy-Saraguro Volcanic Arc) source that is developed in the Western Cordillera of Peru and Ecuador. The Miocene sediments present εNd (0) values of -5.8 to -12.6 located in the sediments area of the Altiplano-Eastern Cordillera associated to a mixture sources of volcanic arc and recycled sediments of Phanerozoic and Pre-cambrian rocks. The main peaks of U-Pb ages belong to the Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga), Arco Magmático Paleozóico (0.4-0.26 Ga) e Rift Permo-Triassico (0.25-0.15 Ga). These sediments present a mixed source from the segments of the Western and Eastern Cordillera of the Central Andes. Te uplift of the Eastern Cordillera generates a barrier that avoids the transportation of the sediment that comes from the Western Cordillera.
El margen occidental andino sudamericano es comúnmente considerado como un ejemplo de margen océano - continental convergente, constituyendo el antiguo margen Oeste de Gondwana antes a su dispersión en el Cretáceo. El segmento norte de América del Sur experimenta cambios desde el desarrollo de una cuenca de tras-arco durante el Triásico- Jurásico hasta formar una retro-cuenca de ante-país en el actual contexto andino. Una manera para determinar estos cambios en la geodinámica que afectan el segmento norte de Sudamérica es estudiando la procedencia de los sedimentos y reconstruir la evolución de paleodrenaje. El presente estudio de procedencia analiza las rocas sedimentarias que componen el intervalo Triásico-Mioceno depositado en la Cuenca Huallaga que forma parte de la Cuenca Amazónica Norte del Perú. Para este estudio fueron utilizados dataciones U-Pb en circón detrítico e isotopia de Sr-Nd. Los resultados muestran cuatro cambios de procedencia asociados con eventos regionales y locales que afectan la retro-cuenca de antepaís al norte de Perú. Las rocas sedimentarias del Triásico-Jurásico fueron depositads en un contexto de cuenca tras-arco. Los valores de εNd (0) oscilan entre - 7.9 a -10 asociados a un arco juvenil junto con edades principales de U-Pb que representan las provincias Greenville- Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Maroni-Itacaiúnas (2-2.2 Ga). Estos resultados sugieren una fuente mixta entre arco volcánico (Arco Misahuallí-Colán) y rocas Precambrianas de la Cordillera Oriental de Perú y Cordillera Real de Ecuador. Las rocas sedimentarias del Cretáceo Superior (Albiano-Maastrichtiano) presentan valores de εNd (0) entre -16 a -18 junto con picos de edades U-Pb que representan las provincias de Rondônia- San Ignácio (1.3-1.54 Ga), Rio Negro-Juruena (1.54-1.82 Ga) e Ventuari-Tapajós (1.82-2 Ga). Estos resultados sugieren una fuente de Cratón Amazónico donde el transporte de sedimentos se desarrolló en dirección Este para el Oeste durante el Albiano-Maastrichtiano y dominó todo el segmento norte de América del Sur. Las rocas sedimentarias del Paleoceno Temprano-Eoceno presentan valores de εNd (0) entre – 5.58 a -10.35 con principales edades U-Pb que representan las provincias Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Rio Negro-Juruena (1.54-1.82 Ga) junto con las primeras poblaciones de edades menores a 120 Ma. Estas edades representan los primeros circones procedentes de la zona andina y corresponde al segmento de la Cordillera Occidental. Los rocas sedimentarias del Oligoceno son caracterizados por presentar valores εNd (0) entre -7.7 a -9.9 junto con un pico principal de edades de U-Pb entre 23-29 Ma (Oligoceno). Estos resultados muestran un predominio de fuente de arco volcánico Paleógeno-Neógeno (Arco Volcánico Calpiuy-Saraguro) que se desarrolla en la Cordillera Occidental de Perú y Ecuador. Las rocas sedimentarias del Mioceno presentan valores εNd (0) entre -5.8 a -12.6 junto con idades U-Pb principales que pertenecen a las provincias Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga), Arco Magmático Paleozóico (0.4-0.26 Ga) e Rift Permo-Triassico (0.25-0.15 Ga). Estos sedimentos presentan una fuente mixta procedente de los segmentos de la Cordillera Occidental y Cordillera Oriental de los Andes Centrales. Durante el desarrollo de a Cordillera Oriental genera una barrera que impide el transporte de sedimentos procedentes de la Cordillera Ocidental

L'etude des formations sableuses aux embouchures des oueds tensift, ksob et souss de l'atlas-atlantique (maroc) permet de mettre en evidence les processus de leur mise en place, ainsi que l'origine de leur materiel. Les oueds apportent jusqu'a l'ocean des elements terrigenes (quartz, feldspaths et mineraux lourds). Ces elements sont remanies et melanges aux depots marins. Le stock sedimentaire est redistribue par les actions marines, et principalement une forte derive littorale nord-sud. Ainsi, dans le systeme du tensift, le materiel dunaire evolue sous l'influence des alizes et des vents d'ouest, mais l'activite de ces derniers se revele plus efficace. Dans le systeme de ksob, le materiel dunaire evolue sous l'action principale des alizes. Dans le systeme du souss, la dynamique eolienne se fait sous l'action conjuguee des alizes et des vents d'ouest. Ces evolutions sedimentaires se traduisent par une amelioration du tri, une diminution progressive du grain moyen et des teneurs en carbonates et mineraux lourds, ainsi que par une eolisation croissante des grains quartz.

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The Gawler Craton, South Australia hosts the Olympic Dam Iron Oxide Copper Gold deposit as well as a number of other IOCG, copper, gold, and iron ore deposits. In the Stuart Shelf region (eastern Gawler Craton), primary mineralisation is generally hosted within basement granites and volcanics of the Hiltaba Suite. Basement rock, potentially containing mineralisation, on the Stuart Shelf is often overlain and concealed by Adelaidean sequences as well as highly weathered, altered and complex Mesozoic cover sequences. These sedimentary basin sediments can conceal mineralisation and are a major frontier for mineral explorers to overcome. Identification of key physical, chemical and biological interfaces, such as basal gravels, redox zones and palaeosols, within the cover sequences and understanding the processes which have led to their formation can be a useful tool in exploration. Andamooka, South Australia, lies on the Stuart Shelf near the southern margin of the Eromanga Basin. Exposed Mesozoic sediments of the Eromanga basin at Andamooka are in close proximity to the Olympic Dam IOCG deposit and are therefore important in understanding dispersion patterns within the cover sequences of elements and minerals associated with IOCG type mineral systems. This understanding can be used for further exploration in the area, where mineralisation may be concealed by Mesozoic sediments. The purpose of this paper is to describe the Mesozoic sediments around Andamooka, identifying any key interfaces and to devise a geochemical footprint of the Mesozoic sediments in this area, which can be used to aid exploration. Gold, nickel, zinc, lead and copper are found to be elevated in multiple regions within the Mesozoic stratigraphy. Several geochemical conceptual models are presented, including; a detrital source of gold and base metals in the basal region of the Algebuckina Sandstone, and a relationship between base metal accumulation and a major redox zone in the Cadna-owie Formation. Other outcomes of this study include; a proposed structural framework of the region, where extensional block faulting has impacted the landscape structure and the relative positions of Mesozoic sequences, and a revision of previous geological mapping. As well as, a possible mechanism for the formation and distribution of opals within the Bulldog Shale, as a direct result of oxidation of pyrite and organic material causing the breakup of aluminosilicates.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2011

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Regolith and sedimentary material overlying potentially enriched basement, is an ever-present obstacle in the highly prospective Olympic iron-oxide copper gold (IOCG) Province, South Australia. The Eromanga Basin, composed of Mesozoic sediments - Algebuckina Sandstone, Cadna-owie Formation and Bulldog Shale - overlies the northern extent of the Stuart Shelf, including the Olympic Dam IOCG province. The closest surface exposures of these sediments to Olympic Dam, is around the opal mining town of Andamooka. The formation and distribution of the precious opal has been previously linked to fluctuating water tables. However, oxidation of pyrite by fluctuating water table height, caused by intracontinental extensional faulting in the area, provides an enhanced interpretation linking opal distribution with the presence of jasper and silcrete lag. Extensional fault boundaries were identified through contrasting regolith and landform components observed from field mapping and remote sensing imagery. ASTER band ratios and relative absorption-band depth ratios complimented field observations with ratios primarily useful in distinguishing high reflectance homogenous mineral groups e.g. opal diggings and sand dunes. A regolith-landform map and digital elevation model over the area identifies the contrasting units, with opal diggings (digitised from ASTER imagery) strongly associated with higher elevations. The potential for secondary economic mineralisation is proposed for the Andamooka area. A source material (Olympic IOCG Province), transport mechanism (extensional duplex faulting), and potential trap rock (REDOX boundaries and varying permeability of Mesozoic units) all contributed to a prospective exploration model for the area.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2011

Dissertação mest., Biologia e Geologia, Universidade do Algarve, 2007
Os mecanismos de mudança climática incluem fenómenos cíclicos que ocorrem a escalas temporais variadas. Os fenómenos que derivam directa ou indirectamente da Tectónica Global actuam a uma escala temporal e espacial tão vasta que as mudanças climáticas por eles provocadas não podem ser evitadas. Desta forma, a Península Ibérica, ao longo da sua viagem para norte de cerca de 200 Ma durante a Era Mesozóica saiu da faixa bioclimática tropical húmida e passou para a faixa bioclimática intertropical árida. Através de uma análise algo exaustiva do registo sedimentar das sete grandes áreas da Península Ibérica onde afloram rochas sedimentares mesozóicas (Bacia Lusitânica, Bacia Algarvia, Pirinéus, Cordilheira Cantábrica, Cordilheira Ibérica, Cordilheira Catalã e Cordilheira Bética) obtida por revisão bibliográfica e do cruzamento dessas informações com os dados provenientes de reconstruções da paleogeografia e da paleotopografia mesozóicas, formulou-se uma reconstrução interpretativa da evolução paleoclimática da Península Ibérica durante o Mesozóico. Nesta reconstrução, as interpretações das variações climáticas não se basearam unicamente no simples efeito da deriva continental mas foram formuladas hipóteses que levaram em consideração o efeito da paleotopografia e da paleogeografia envolventes à microplaca ibérica. A hipótese reconstrutiva da evolução paleoclimática que daí resultou indica que a Península Ibérica terá passado de um clima monsónico marcadamente sazonal no Triásico inferior-médio para um clima árido mas não necessariamente quente no Triásico superior, ao qual se terá seguido um clima relativamente quente durante o Jurássico, acompanhado de eventos tempestíticos ao longo de todo o período e terminando, durante o Cretácico, com um clima que terá sido excepcionalmente quente e árido por vezes.