Orientador: Antonio José Ranalli Nardy / Banca: Leila Soares Marques / Banca: Marcos Aurélio Farias de Oliveira / Banca: Evandro Fernandes de Lima / Banca: Antonio Carlos Artur / Acompanha 2 mapas anexos / Resumo: Os basaltos da Formação Serra Geral nos estados de Mato Grasso do Sul e Mato Grosso ocupam uma área aproximada de 180.000 km2 e estão sobrepostos aos arenitos desérticos da Formação Botucatu e sotopostos pelos sedimentos neocretácicos dos Grupos Bauru e Caiuá. Apresentam mineralogia primária constituída de plagioclásio (40% - 55%; An42-67), clinopiroxênios (19% - 40%; augita Wo30-40En34-46Fs35-39), minerais opacos (2% - 10%) e olivina (até 1,5%; Fo31-50). Dados geotermométricos revelam temperaturas de cristalização dos clinopiroxênios em ~1100ºC. A geoquímica dessas rochas mostram tratar-se de basaltos dos tipos Pitanga (ATi; 2,6%<TiO2<4,2%, 396ppm<Sr<438ppm) e Ribeira (BTi;1,7%TiO2<2,4%, 246ppm<Sr<286ppm), onde observam-se diferenças marcantes na distribuição de elementos traços, as quais parecem consistentes com um processo de cristalização fracionada. Processos de contaminação crustal que poderiam interferir na interpretação dos resultados analíticos foram descartados pelos baixos valores de Sri sempre menores de 0,706 e também Rb/Ba < 1,0. O empobrecimento dos basaltos Pitanga e Ribeira em Pbi, (206Pb/204Pbi<17,747; 207Pb/204Pbi<15,522 e 208Pb/204Pbi<38,174), Ndm (0,51235 - 0,51239) e Sri, (0,70549 - 0,70586) são semelhantes com as rochas básicas do sítio 525A da Cadeia Walvis e com o componente mantélico EMI, e ainda, os valores de eNd (-5,21 a - 6,00) sugerem tratar-se de rochas submetidas à fusão parcial pré-cambrianas. Os LILEs possuem padrões de abundância inconsistentes com aqueles de Tristão da Cunha (OIB) e NMORB, e ficam fora da linha de mistura destes. Assim, as razões (La/Yb)n: (4,17-7,70); e (La/Sm)n: (2,15-2,54) e isótopos das amostras representativas dos magmas, em conjunto com aquelas publicadas na literatura, indicam a contribuição do manto litosférico subcontinental na geração da Província Magmática do Paraná... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Paraná Magmatic Province (PMP) represents one of the greatest volcanic event of our planet, covering more than 70% of the Paraná Basin as flows, sills and dykes. In the Mato Grosso do Sul and Mato Grosso states, the study of basalts has geologic importance because of the absence of published works. In those regions, basaltic rocks occupy 180,000 km2, and are re-covered by the sediments of Bauru Basin, and are associated to sandstones of Botucatu Formation. The mineralogy of basalt is represented by plagioclase (An 42-67; 40% - 55%), pyroxene (augite: Wo30-40En34-46Fs35-39; 19-40%), magnetite (2-10%) and olivine (Fo31-50; <1,5%). Based on rheologic calculations the temperature of crystallization of the pyroxenes is estimated 1100ºC. Also geochemical analyses show that the investigated basalts are of Pitanga (ATi) and Ribeira (BTi) types: ATi: 2,6%<TiO2<4,2%; 396ppm<Sr<438ppm and BTi: 1,7%TiO2<2,4%, 246ppm<Sr<286ppm. LILE abundance for the studied flows evidence differences that are consistent with process of fractional crystallization. Processes of crustal contamination can be discarded considering the values of Sri < 0,70586 e Rb/Ba < 1,0. Moreover, the values of LILE show values that are not consistent with those of OIB - Tristão da Cunha and N-MORB and are outside of the line of mixture of these. In relation to isotopic ratio, the magmas are depleted in Pbi, ,(206Pb/204Pbi<17,747; 207Pb/204Pbi<15,522 e 208Pb/204Pbi<38,174); Ndm (0,51235 - 0,51239) e Sri, (0,70549 - 0,70586) if compared with BTi basalts occurring in southern PMP. These ratios are also similar with that of the basic rocks of the small site 525A of the Walvis Chain and of the mantle component EMI. The values of εNd (-5,21 a -6,00) and of 87Sr/86Sri indicate that the magma types Pitanga and Ribeira were submitted to partial melting in Precambrian times. The ratios (La/Yb)n: (4,17- 7,70); and (La/Sm)... (Complete abstract click electronic access below) / Doutor

Aspectos referentes à tectônica rúptil mesozóico-cenozóica da Serra dos Órgãos, nome local dado a Serra do Mar na porção correspondente ao Parque Nacional da Serra dos Órgãos - PARNASO (municípios de Petrópolis, Teresópolis e Magé, Estado do Rio de Janeiro), foram investigados por meio da análise morfoestrutural e de levantamentos de campo. A área estudada compreende elevações que ultrapassam 2.200m de altitude e está incluída no Terreno Oriental do setor central da Faixa Ribeira, de idade neoproterozóica-cambriana, onde afloram rochas metassedimentares intrudidas por várias gerações de rochas granitóides. A análise conjunta dos resultados provenientes dos modelos digitais de elevação, mapas morfométricos, lineamentos, estruturas rúpteis e litotipos, associada ao quadro tectônico regional do sudeste do país, permitiu admitir que a formação das principais feições rúpteis verificadas no PARNASO pode estar relacionada a seis regimes tectônicos superpostos. O primeiro regime remontaria ao Neoproterozóico-Cambriano e seria caracterizado por transcorrência sinistral, com binário de direção geral E-W (compressão de direção NE-SW e distensão NW-SE). Regimes semelhantes foram ativos durante o Eocretáceo e Neocretáceo-Paleoceno, reponsáveis, respectivamente, pela colocação do enxame de diques básicos que ocorre na porção centro ocidental do Estado do Rio de Janeiro, e pelos centros intrusivos e diques de rochas alcalinas dispostos ao longo do Alinhamento Magmático de Cabo Frio. Estes regimes ocasionaram intenso fraturamento de orientação NE-SW distribuído por todo o PARNASO. Novo regime tectônico teria operado no Eoceno, caracterizado por distensão de direção NW-SE, considerado como gerador do Rift Continental do Sudeste do Brasil. Embora as feições rúpteis associadas a esta fase tectônica não estejam muito evidentes, sua principal conseqüência no PARNASO seria a compartimentação do relevo da sua porção sul-sudeste em blocos alongados e escalonados abatidos para sudeste. Concomitantemente a este abatimento, deu-se a deformação de uma antiga superfície de aplainamento, que teria nivelado a cimeira da Serra dos Órgãos em torno de 2.000 m. O regime tectônico seguinte, caracterizado por cisalhamento dextral com binário de direção E-W (compressão de direção NW-SE e distensão NE-SW), de idade pleistocena a holocena, teria reativado fraturas de orientação NW-SE, hoje realçadas pelas facetas trapezoidais observadas ao longo do vale do Rio do Bonfim. O último regime tectônico registrado encontra correspondência com uma compressão de direção E-W, de idade holocena. / Mezosoic-Cenozoic brittle tectonics of the Serra dos Órgãos range in the Rio de Janeiro State, southeastern Brazil, was investigated using morphostructural analysis and field surveys. The study area is a sector of the Serra do Mar coastal range, with summits over 2.200 m a.s.l., and is included in the central segment of the Neoproterozoic-Cambrian Ribeira Belt, where metassedimentary and several generations of granitoid rocks occur. Integrated analysis of digital elevation models, morphometric maps, lineaments, brittle structures and distribution of lithotypes, and comparison with the regional tectonic context of Southeastern Brazil, allowed us to admit that the main brittle features observed in the region are related to six superimposed brittle tectonic regimes. The first tectonic regime, of Neoproterozoic-Cambrian age, was characterized by left-lateral E-W-trending strike-slip, with NE-SW compression and NW-SE extension. Similar regimes were active during Early Cretaceous and Late Cretaceous to Paleocene, when they were responsible, respectively, for the emplacement of basic dykes swarm of the central-western portion of Rio de Janeiro State, and of the intrusive centers and alkaline dykes along the Cabo Frio Magmatic Lineament. This regime caused intense and widespread NE-SW-trending fracturing throughout the study area. During the Eocene, a NW-SE-trending extensional regime, considered as generator of the Continental Rift of Southeastern Brazil, operated in the region. It was responsible for the relief segmentation in the south-southeast part of the area, where NE-SW-trending elongated blocks in a step-like array descending to the southeast are observed. At the same time occurred the deformation of an old erosion surface, which had previously leveled the summit of the Serra dos Órgãos range at around 2.000 m a.s.l. The next tectonic regime is related to a NW-SE Late Pleistocene-Holocene compression which have reactivated NW-SE-trending fractures as normal faults, partially preserved as trapezoidal facets in the landscape. The last tectonic regime recorded in the region finds correspondence with an E-W Holocene compression.

Le Bassin de Valence, situé à l’est de l’Ibérie et séparé du Bassin Algérien par le Promontoire Baléares, résulte d’une évolution polyphasée dans l’espace et dans le temps. Son histoire cénozoïque, celle d’un bassin d’arrière-arc Oligo-Miocène, est à présent reconnue. Toutefois cette extension se surimpose à plusieurs phases de rift observées à terre du Permien au Crétacé inférieur. Cette histoire plus ancienne demeure méconnue en mer malgré son importance dans l’héritage structural du bassin. Au sud du Bassin de Valence, le Bassin de Columbrets en témoigne en révélant d’épaisses séquences mésozoïques jusqu’alors incluses dans un « socle acoustique » indifférencié. Ce domaine permet donc le déchiffrage du mécanisme des évènements tectoniques qui se sont succédé du Mésozoïque à l’Est de l’Ibérie d’une part, au Cénozoïque en Méditerranée occidentale d’autre part.Basé sur une stratégie d’étude terre-mer, ce travail vise une meilleure compréhension (1) des processus tectoniques tertiaires modelant le sud du Bassin de Valence et la Méditerranée occidentale (2) de la réponse sédimentaire à des processus d’extension et d’hyper-extension au Mésozoïque (3) de l’importance de l’halocinèse lors la mise en place des structures sédimentaires et tectoniques.L’étude structurale d’Ibiza, l’île la plus méridionale du Promontoire Baléare, reconsidère le calendrier tectonique de la région ainsi que son intégration dans l’histoire géodynamique de la Méditerranée occidentale. Le rift Oligo-Miocène décrit dans le Bassin de Valence et initié par le Système de Rifts Cénozoïques Européens a été observé sur Ibiza. Cet évènement est suivi au Miocène Moyen d’une déformation compressive localisée par les failles normales précédemment formées. La comparaison avec le calendrier tectonique des Kabylies en Algérie montre que cette déformation compressive, qui épargne le Bassin Algérien, résulte de la convergence Europe-Afrique. Des cartes rétro-tectoniques intègrent ces évènements dans le contexte géodynamique de la Méditerranée occidentale depuis l’Oligocène.L’étude des séries Mésozoïques effectuées à terre et en mer (grâce à l’interprétation de données sismiques et de forages) révèle plusieurs phases de rifting du Permien au Crétacé inférieur. Un épisode majeur Jurassique supérieur à Crétacé inférieur est à l’origine de l’épaisse séquence sédimentaire du Bassin de Columbrets. Documentée à terre, cette phase ayant conduit à l’ouverture de la partie sud de l’Atlantique Nord est à l’origine de bassins ibériques ou péri-ibériques tels Maestrat, Caméros ou Parentis.Un amincissement majeur de la croûte est visible sous l’épaisse séquence mésozoïque, la réduisant à 5km. Le mécanisme d’extension voire d’hyper-extension proposé invoque une faille de détachement à pendage NW qui s’enracine dans la croûte inférieure litée. Une représentation des structures en 3D a été réalisée afin de comprendre l’évolution du Bassin de Columbrets.L’architecture sédimentaire du Bassin de Columbrets est également contrôlée par le mouvement des séries salifères depuis leur dépôt au Trias supérieur jusqu’à l’actuel. La partie septentrionale du bassin se caractérise par une halocinèse surtout lié aux déformations extensives de la région. En revanche au sud du front chevauchant des Bétiques, le sel est aussi remobilisé en compression. La géométrie et la répartition des structures salifères décrites à terre et en mer dépendent fortement de l’épaisseur initiale de la couche de sel dans le bassin; cette observation apporte des éléments de réponse sur la paléogéographie des séries du Keuper au sud du Bassin de Valence.Au final cette étude aborde d’une part des thèmes liés au mécanisme de formation des bassins intracontinentaux et plus particulièrement la relation entre hyper-extension, signature sédimentaire et halocinèse. D’autre, elle permet une meilleure intégration du sud du Promontoire Baléare et du Bassin de Valence dans la géodynamique Ouest- Méditerranéenne. / The Valencia Basin, located east of Iberia and separated from the Algerian Basin by the Balearic promontory, underwent a poly-phased tectonic evolution in space and time. The Cenozoic evolution of the basin has been widely discussed, the most classical interpretation being an Oligo-Miocene aborted back-arc basin. However, this extensional tectonic regime postdated several rifting events from the Permian to the Lower Cretaceous. This older evolution remains poorly understood offshore, despite its influence on the tectonic inheritance of the basin. The Columbrets Basin, in the southernmost part of the Valencia Basin, exhibits a thick Mesozoic sequence that was considered to belong to an undifferentiated “acoustic basement”. Hence, the Columbrets Basin is a key study area to unravel the successive Mesozoic to Cenozoic tectonic events in Eastern Iberia and Western Mediterranean.Our study integrates onshore and offshore data to better constrain (1) the Cenozoic tectonic processes that led to the current morphology of the southern Valencia Basin and the Western Mediterranean (2) the sedimentary records Mesozoic extensional to hyper-extensional processes and (3) the importance of the halokinesis in the sedimentary and tectonic architectures.Ibiza Island, located on the southernmost part of the Balearic Promontory, questions the standard tectonic agenda of the area and its integration in the Western Mediterranean geodynamic frame. The Oligo-Miocene rifting phase described in the Valencia basin is initiated by the European Cenozoic Rift System (ECRIS) and has been observed in Ibiza. This event is followed by a Middle Miocene contractional phase reactivating the inherited normal faults. The comparison with the tectonic history of the Kabylies in Algeria shows that this stage that does not affect the Algeria basin, results from the convergence between Europe and Africa. A set of retro-tectonic maps integrates these events in the geodynamic context of West Mediterranean.The Mesozoic units were studied onshore and offshore (using drilling and seismic data); it reveals several rifting phases from the Permian to the Lower Cretaceous. A major Upper Jurassic to Lower Cretaceous event was responsible for the deposition of the thick sequence present in the Columbrets Basin. This tectonic event led to the opening of the southern part of the north Atlantic but is also at the origin of several Iberian or peri-iberian basins such as Maestrat, Cameros, or Parentis basins.A major crustal thinning has been observed underneath the thick Mesozoic sequence, reducing the crustal thickness to 5 km. The proposed extensional and even hyper-extensional mechanism used a NW dipping detachment fault rooting deeply into the layered lower crust. A 3D geometrical model of the structures illustrates the evolution of the Columbrets Basin.The sedimentary architecture of this basin is also controlled by salt movements from their deposition during the Late Triassic to current times. The northern part of the Basin is characterized by salt movements mainly linked to the extensional deformations of the area. South of the Betics Front, the salt is remobilized by compressional deformations. The geometry and the location of the salt structures described onshore and offshore depend on the initial thickness of the salt in the basin; this observation gives evidence for the paleogeography of the Keuper sequences in the south of Valencia Basin.Finally, this study documents the mechanisms leading to the formation of intracontinental basins and especially the relationships between hyperextension, sedimentary filling and halokinesis. On the other hand, our study allows a better integration of the southern part of the Balearic Promontory and Valencia Basin in the geodynamic frame of the West Mediterranean.

Heteromorph ammonites and dinoflagellate cysts from the Upper Cretaceous Northumberland Formation on Hornby Island, British Columbia, Canada are examined. The collection and preparation of new material has enabled the recognition of eleven species of which only three have been reported from the locality. Of these taxa represented from three heteromorph ammonite families in the study area, five are new occurrences and three are new to science. This expansion of the Hornby Island ammonite fauna is presented alongside a pioneering taxonomic survey of dinoflagellate cysts from the same rocks. Together, these macro- and microfossils reinforce a late Campanian age for the Northumberland Formation with the upper extent of the section approaching the Campanian-Maastrichtian boundary (CMB) interval. The palaeoecology and evolutionary relationships of these heteromorph ammonoids are considered with new insights into their ontogenetic development and neritic palaeoenvironmental circumstances. The dinoflagellate cysts and associated terrestrial palynomorphs have also allowed for enhanced palaeoenvironmental reconstruction and depositional setting inference. The scope of the studied material, and the presence of key index taxa, enables refined biostratigraphy and a stronger basis for correlation of the Hornby Island succession with neighboring coeval biotic provinces. / Graduate / 2018-08-10

Les mécanismes extensifs, matérialisés physiquement sous la forme de rifts ou de marges passives, impliquent des interactions entre les processus tectoniques, sédimentaires et métamorphiques, particulièrement quand ils sont associés à un métamorphisme de haute température. L'étude de ces mécanismes ne peut donc se faire correctement que par une approche triple afin de cerner ces différents aspects et de contraindre les interactions qui les relient. Une telle étude est difficile du fait de la profondeur à laquelle ont lieu ces mécanismes et donc de l'absence d'observation directe des objets géologiques qu'ils produisent. L'alternative consiste à étudier une paléo marge passive portée à l'affleurement. Dans le cadre de cette thèse, notre choix s'est porté sur la Zone Nord Pyrénéenne qui correspond à une paléo-marge passive mésozoïque qui a été mise à l'affleurement lors de la compression pyrénéenne à l'Éocène/Oligocène (40-20 Ma). Cette marge a subi une métamorphise HT/BP et constitue donc un bon analogue pour notre étude. Nous nous sommes concentrés en particulier sur la partie Est de la ZNP, dans la région du massif de l'Agly qui rassemble les bassins de Saint Paul-de-Fenouillet, du Bas-Agly et de Boucheville qui ont enregistré différentes intensités du métamorphisme. Le bassin de Boucheville étant le moins bien documenté mais ayant enregistré le métamorphisme le plus important, nous nous sommes attachés à le caractériser en détail. Nous avons effectué une étude structurale, stratigraphique et sédimentaire de ces trois bassins afin de bien contraindre leur géométrie et leur histoire. Nous avons couplé cette étude avec des analyses du métamorphisme, principalement par des mesures par spectrométrie Raman des températures maximum enregistrées lors de l'extension crétacée. Enfin, nous avons combiné ces résultats afin de produire des coupes restaurées de l'ensemble de notre zone d'étude. Ces coupes restaurées nous ont permis de proposer un modèle de la mise en place des bassins sédimentaires mésozoïques dans la partie orientale de la ZNP. Il apparaît au premier ordre que la zone est constituée, sur une coupe N-S, par un haut fond topographique constitué du futur massif de l'Agly, limité au nord par un détachement à vergence nord et au sud par un détachement à vergence sud. De part et d'autre de ce haut fond se mettent en place des bassins sédimentaires présentant une augmentation de l'épaisseur des dépôts au droit de ces détachements. Au seconde ordre, il faut considérer que le système n'est pas cylindrique et que le massif de l'Agly se comporte comme une zone de transfert entre une subsidence forte au nord-est dans le bassin du Bas-Agly et une subsidence forte au sud-ouest dans le bassin de Boucheville. / Extensive mechanisms induce interactions between tectonic, sedimentary and metamorphic processes, especially when they are associated with a high temperature metamorphism. Therefore, the study of these mechanisms requires a threefold approach in order to identify these processes and understand the interactions between them. Such study is hardened because of the depth of these mechanisms and the lack of direct observation. To overcome such difficulties we chose to study a paleo passive margin now visible thanks to many outcrops. For this thesis, we focused on the North Pyrenean Zone (NPZ) which happens to be a Mesozoic passive margin which outcroped during Eocene / Oligocene (40-20 Ma) Pyrenean compression. This margin recorded HT / LP metamorphism which makes it a good analogue for our study. We focused on the eastern part of the NPZ, in the Agly Massif area where are located the Saint Paul-de-Fenouillet basin, the bas-Agly basin and the Boucheville basin all of which recorded different intensity of metamorphism. The Boucheville basin is the worst documented but recorded the most metamorphism which is why we decided to study it in detail. We undergone a structural, stratigraphic and sedimentary analysis of these three basins in order to better understand their geometry and geological history. We combined this study with metamorphism analyzes mainly provided by Raman spectrometry on maximum temperatures recorded during Cretaceous extension. Finally, we synthetised these results to produce restored cross sections of our study area. Those cross sections allowed us to suggest a model for Mesozoic sedimentary basin formation in the eastern part of the NPZ. Considering first order analysis, on a N-S cross section, the area made of a shoal,the future Agly Massif. It is bordered on its northern side by a north verging detachment fault and on its southern by a south verging detachment fault. On both sides of this shoal are sedimentary basins much thicker towards these detachment faults. However, we must consider the system is not cylindrical. The Agly Massif acts as a transfer zone between two highly subsident basins, the Bas-Agly basin at its north-east and the Boucheville basin at its south-west.

Mid-Late Triassic-age alkali-basalt dikes were emplaced along the coast of New England between 240-200 Ma. Known as the Coastal New England (CNE) magmatic province, this dike swarm is the immediate magmatic predecessor to the formation of the Central Atlantic Magmatic Province large igneous province at 201 Ma and the breakup of Pangea. The intent of this study is to determine the melt source and mechanisms for melting which produced the Triassic coastal dikes. To achieve this goal, major and trace element compositions were analyzed for 53 CNE dikes from Maine and Nova Scotia. Radiogenic Nd-Sr-Pb-Hf ratios, representing some of the first 176Hf/177Hf data for CNE, are reported for 12 of the dikes. Taken together, the compositional data implicate melting of a deep mantle source that is relatively enriched in incompatible elements, such as a mantle-plume similar to those hypothesized as the source of melting in modern ocean-island basalts (i.e. Hawaii). Dike compositions are inconsistent with melts generated at typical spreading-center ridges (i.e. MORB). Modeling suggests that CNE melts ascended through thick continental crust, consistent with the incipient stages of rifting of Pangea, as evidenced by a heterogeneous mix of melting and crystallization depths, between 0-70km, with no clear geographic pattern. Radiogenic isotope data are relatively consistent and represent a mixture between HIMU, EMI and DMM mantle reservoirs, implying component consisting of relict subducted oceanic crust (or other similarly evolved material). CNE magmatism may have contributed to the breakup of Pangea by destabilizing the lower crust in the limited local area where it erupted, but its true relationship with the breakup of Pangea and later CAMP event requires more study. / Master of Science / Approximately 200-250 million years ago, hundreds of sheets of lava, called dikes, erupted along what is today the coast of New England. As these volcanic dikes rose up from the Earth’s mantle, they traveled along cracks and weak areas of the Earth’s crust. Today, these dikes are found along the New England coast as far south as Rhode Island and as far north as Nova Scotia, Canada. Based on the similarity of their geochemistry and petrology, as well as their geologic age and geography of their eruption, geologists group these dikes and similar volcanics together as a single, related magmatic event. This magmatic event produced the Coastal New England (CNE) magmatic province. 250 million years ago, the coast of New England was actually an interior part of the supercontinent known as Pangea. Around 250 m.yr. ago, Pangea slowly began rifting apart, which is when CNE volcanism began. By 200 m.yr. ago, Pangea had broken up, and CNE volcanism had ended. Further complicating the story, a large-igneous province (LIP) also erupted 200 m.yr. ago. Known as the Central Atlantic Magmatic Province (CAMP), this volcanism consisted of enormous volumes of lava that flooded over the entire east coast of the United States. The intent of this study is to determine what geological conditions led to the CNE volcanism. By learning which part of the Earth melted and why, CNE volcanism’s role in the breakup of Pangea, and the much larger CAMP eruptions that coincided with it, will become clearer. For instance, did the geologic events that resulted in CNE volcanism contribute to the breakup of Pangea, or did the breakup of Pangea cause CNE volcanism followed by CAMP volcanism? To achieve this goal, the geochemical compositions of 53 CNE dikes from Maine and Nova Scotia were analyzed. Radiogenic Nd-Sr-Pb-Hf ratios for a subset of the dikes (12) were also analyzed. This study presents some of the first radiogenic hafnium data for rocks from CNE. The data indicate that the melting which produced the CNE dikes began in the deep mantle, similar to the melting of mantle plumes beneath modern ocean-islands such as Hawaii. In contrast, shallow mantle melting, like the melting at mid-ocean ridges where oceanic crust is produced, is not consistent with the geochemical evidence presented for CNE in this study. Modeling suggests that CNE magmas rose through thick continental crust, which caused them to begin forming crystals at relatively high depths. Radiogenic isotope data suggests that part of the mantle that melted was old, recycled oceanic crust or similar mantle material. CNE magmatism may have contributed to the breakup of Pangea by destabilizing the lower crust in the limited local area where it erupted, but its true relationship with the breakup of Pangea and later CAMP event requires more study.

In the Paria Plateau area of northern Arizona and southern Utah the Chinle formation of Upper Triassic age consists of a thick series of Ienticular sandstone, siltstone, claystone, and limestone. The series thins northwestward from about 900 feet at Lees Ferry, Ariz., to about 800 feet at Paria, Utah. Four members of the Chinle formation are recognized—1) the basal Shinarump member composed of conglomeratic sandstone and subordinate shale, 2) a unit, herein named the Lowery Spring member, composed of sandstone and mudstone, 3) the Petrified Forest member composed of bentonitic siltstone and claystone and thin sandstone, and 4) the Owl Rock member composed of cherty limestone and calcareous siltstone. Only the Petrified Forest member is present at all localities in the Paria Plateau area. The Shinarump member was deposited in topographic low areas on an erosion surface and its distribution is irregular. The Lowery Spring and Owl Rock members grade and pinch-out toward the northwest and are not present at Paria, Utah. The upper contact of the Chinle formation is locally unconformable. The three lowermost members were deposited on a broad, flat plain between the Cordilleran geosyncline and highlands to the southeast. In Owl Rock time the rising Cordilleran geanticline cut off the north-westward drainage of Chinle streams and a depositional basin trending southwest was formed.

Riedel shear zones are geometric fault patterns commonly associated with strike-slip fault systems. The progressive evolution of natural Riedel shear zones within the Navajo Sandstone of southern Utah is interpreted from the spatial evolution of small-scale, incipient Proto-Riedel Zones (PRZs) to better-developed Riedel shear zones using field mapping and three-dimensional digital modeling. PRZs nucleate as a tabular zone of localized shearing marked by en èchelon deformation bands, each of which is no more than a few mm wide and tens of cm long, and oriented at 55° - 85° to the trend of the zone. With increasing strain, deformation bands and sedimentary markers are sheared ductily through granular flow and assume a sigmoidal form. The temporal and spatial evolution of bands comprising a Riedel shear zone suggests that PRZs nucleate as transitional-compactional deformation bands under localized, supra-lithostatic fluid pressure. Subsequent bands develop under modified regional stresses as conjugate shear fractures within the strain- hardened axis of the PRZ. These antithetic driven systems are not compatible with traditional synthetic driven models of Riedel shear zones. Unlike most synthetic driven examples, these antithetic driven systems are not controlled by preexisting "basement" structures, thus their geometries reflect a primary propagation or secondary passive deformation mechanism.

The vast distribution and long duration of the Late Mesozoic magmatism in the eastern part of South China presents a unique case in the world. This offers a natural laboratory to study the process of magma genesis, the magma emplacement mode, the relationship between magmatism and tectonics, the geodynamic role on the magma emplacement and lithospheric evolution. Since 50's, particularly 90's of the last century, geoscientists have made important efforts in geological cartography and carried out numerous studies with remarkable scientific achievements, building a solid background to understand the tectonic evolution of the South China Block (SCB). However, certain fundamental questions mentioned above remain unsolved and/or are in hot debate. In order to make progress in these scientific issues, we have carried out in a multi-disciplinary study in the Late Mesozoic Qingyang-Jiuhua massif, Hengshan massif and Fujian coastal zone according to their distance with respect to the paleo subduction zone of the Paleo-Pacific plate, the ages of granitic massifs and related tectonics, including field observation on the structure geology, micro-observation on thin section, U-Pb dating on monazite, AMS, paleomagnetism, gravity modeling and P condition concern the granite emplacement. In the view of deformation in these granitic massifs and their country rocks, mode and influence of regional tectonics on the emplacement, though each studied zone reveals its distinguished characteristics, they show some intrinsic and common relationships between them. With our new results and integrating previous data, in this thesis, we discuss the tectonic context of emplacement of these Late Mesozoic magmatic massifs and the geodynamic evolution of the SCB., We propose a 3-step geodynamic model: (1) during 145-130 Ma period, the Paleo-Pacific plate subducted northwestwardly, the West Philippines micro-continent, approaching to SCB, important subduction-related arc volcanism was produced in the coastal areas of Southeast China coast (Zhejiang-Fujian-Guangdong), forming a back-arc extension tectonic system in SCB; (2) during 130-110 Ma period, due to the collision between the West Philippines microcontinent and SCB, the compressional tectonic structures were developed in the Changle-Na'ao coastal zone, producing ductile deformation zones. However, the inland of the eastern part of SCB was under a NW-SE extensional tectonic regime; (3) during 105-90 Ma period, a new subduction zone was developed in the SE flank of the West Philippines micro-continent, the subducting slab reached the Changle-Nan'ao tectonic belt, with the possible break-off of slab, the asthenospheric ascent was responsible for the important emplacement of plutonic massifs and dykes. The tectonics of the eastern part of SCB was characterized by a general extensional system in this period. This tectonic pattern has been significantly disturbed by the Oligocene-Eocene opening of the South China sea,and the Miocene shortening of the SCB margin in Taiwan. Of course, this model should be improved by more geological, geophysical and geochemical investigations.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O relevo da Serra da Bocaina revela o forte controle das estruturas dúcteis e rúpteis relacionadas à Faixa Ribeira gerada na Orogênese Brasiliana (ca. 790-480 Ma) e às reativações mesozóica-cenozóicas. As rochas são agrupadas em 4 terrenos tectônicos colados nas etapas colisionais brasilianas, que formaram as estruturas mais penetrativas: foliação com mergulho para NW, zonas de cisalhamento dúcteis NESW e dobras. Zonas de cisalhamento rúptil-dúcteis NW marcam o colapso orogênico. A abertura do Atlântico Sul (ca. 135-120 Ma) é registrada pelos enxames de diques toleíticos NNE e ENE, em parte condicionados pelas estruturas brasilianas. No Planalto da Bocaina uma idade de traço de fissão em apatita (TFA) de ca. 145 Ma data o resfriamento ainda da fase pré-rifte do Gondwana. O soerguimento da margem continental na fase rifte pode ter alçado este nível para fora da zona de apagamento parcial do TFA. A reativação neocretácea é datada pelo TFA (ca. 85 Ma) na costa e na escarpa atlântica, indicando novo pulso de denudação e soerguimento da margem continental. Isto também concorda com o extenso aporte de sedimentação siliciclástica na Bacia de Santos. No Paleógeno, a formação dos Riftes Continentais do Sudeste Brasileiro (RCSB) gerou a reativação das estruturas dúcteis NE da Faixa Ribeira, falhas e fraturas NW, E-W, além de fraturas NE na Baía da Ilha Grande. O contato tectônico entre os Terrenos Paraíba do Sul e Embu é a principal zona reativada na Serra da Bocaina. Idades TFA (ca. 55 Ma) registram o estágio inicial do RCSB, que provocou o rebaixamento do nível de base e a formação de uma escarpa no interior. A Serra da Bocaina parece constituir uma região elevada desde a formação da Cordilheira Ribeira, incrementada pelos soerguimentos das fases rifte e pós-rifte do Atlântico e do RCSB. Estes eventos tectônicos que elevaram a Serra da Bocaina, também geraram as estruturas que conduzem sua denudação. Neste contexto, destaca-se o par de estruturas NE (foliação e zonas de cisalhamento reativadas ou não) e NW (fraturas e falhas), as mais freqüentes, que orienta a rede de drenagem, os níveis de base locais (knickpoints) e as formas côncavas das encostas (cabeceiras de canais). Diques toleíticos também conduzem a dissecação dos vales fluviais. Por outro lado, granitos e ortognaisses que sustentam as elevações e segmentos de escarpas mostram o papel da erosão diferencial em rochas mais resistentes. A denudação do Planalto da Bocaina e o recuo de suas escarpas (atlântica e interior) são regulados por diferentes níveis de base (p.ex. nível do mar, rio Paraíba do Sul no RCSB, diversos knickpoints), sensíveis aos eventos de reativações tectônicas (soerguimento), variações eustáticas e à erosão diferencial. Os pulsos erosivos vêm dissecando de modo diferencial os vales suspensos do planalto, através da incisão fluvial e reativação das cabeceiras de canais, que avançam sobre as encostas promovendo a quebra dos divisores e capturas de drenagens. Este processo rebaixamento de relevo parece levar à formação das superfícies colinosas que ocorrem em diferentes níveis topográficos. As idades TFA antigas indicam baixas taxas de denudação na porção mais elevada do Planalto da Bocaina, o que contrasta com as altas taxas da região costeira. Este caráter diferencial da denudação condicionada pelo substrato geológico e pelos eventos de soerguimento, vem preservando antigas paisagens no Planalto da Bocaina. No outro extremo, a denudação propagada pelo recuo das duas escarpas vem degradando as bordas e introduzindo a dissecação no interior do planalto. As duas escarpas geradas por eventos riftes distintos vêm se ajustando ao controle das rochas e estruturas da Faixa Ribeira. / The Bocaina Ridge landscape is strongly controlled by both ductile and brittle structures related to the Ribeira Belt (Brasiliano Orogeny ca. 790-480Ma) and also to the mesozoic-cenozoic reactivations. The rocks were subdivided in four tectonic terrains accreted in the brasiliano collisional stages. The most prominent structures related to these collisions are: NW dipping foliation, NE-SW ductile shear zones, and folds. NW ductile-brittle shear zones represent the orogenic collapse stage. The South Atlantic opening (ca.135-120 Ma) is registered in NNE and ENE tholeitic dike swarms, partly conditioned by brasiliano structures. In the Bocaina Plateau one apatite fission track age (AFT) of ca.145Ma represents pre-rift Gondwana cooling. The continental margin uplift associated to the rift phase might have raised this level out of the AFT partial annealing zone. Neocretaceous reactivation (ca. 85Ma) was AFT dated both in the coast and the atlantic scarp, pointing out to a newer continental margin denudation and uplift pulse. This reactivation is in accordance with the Santos basin significant siliciclastic sedimentation. In paleogene times, the Southeastern Brazil Continental Rift System (SBCR) development was responsible for: the reactivation of the Ribeira Belt NE ductile structures, NW and E-W faulting and fracturing, and NE fracturing in Ilha Grande Bay. The tectonic boundary between Paraíba do Sul and Embu Terrains is the main reactivation zone in the Bocaina Ridge. AFT ages of ca. 55 Ma register the initial stage of the SBCR, which produced base level lowering and the formation of an inland scarp. The Bocaina Ridge seems to constitute an elevated region since the development of the Ribeira Cordillera, increased by the South Atlantic rift and post-rift uplifts and also by the SBCR.