The level of organic maturation, thermal history, and source rock potential of Mesozoic and Tertiary strata in the Queen Charlotte Islands have been investigated with vitrinite reflectance measurements (%Ro rand)> numerical modelling (modified Arrhenius and Lopatin models), and Rock-Eval pyrolysis (source rock potential). The level of organic maturation increases from north to south and is primarily controlled by high heat flow associated with plutonism on Moresby Island. Upper Triassic-Lower Jurassic strata are overmature on Moresby Island with vitrinite reflectance values ranging from 2.40 to 5.80 %Ro rand Jurassic, Cretaceous, and Tertiary strata are immature to overmature on Graham Island with values ranging from 0.15 %Ro rand (Skonun Formation) to 2.43 % Ro rand (Haida Formation). Constant and variable geothermal gradient thermal regimes were numerically modelled with modified Arrhenius and Lopatin methods. Numerical modelling (assuming constant geothermal gradients) predicts high paleogeothermal gradients (45 to 90 °C/km) for up to 180 million years from the Late Triassic to the Tertiary. Variable paleogeothermal gradient modelling (utilizing a 30 °C/km background geothermal gradient) predicts peak geothermal gradients ranging up to 150 °C/km during Yakoun (183-178 Ma) and Masset (35-10 Ma) volcanism. The timing of hydrocarbon generation was estimated with numerical modelling. The levels of organic maturation for Mesozoic and Tertiary strata reflect the timing of plutonism and associated high heat flow. Triassic strata from west Graham Island and Cretaceous strata from north and south Graham Island entered the oil window during the Early Miocene and are still in the oil window. Jurassic strata in central Graham Island and north Moresby Island entered the oil window during the Bajocian and remain within the oil window. The Skonun Formation is generally immature except for strata at west Graham Island (Port Louis well) and at northeast Graham Island (basal strata in the Tow Hill well) which entered the oil window during the Late Miocene. Mean total organic carbon (TOC) contents are generally low (0.06 %) to moderately high (3.6 %) for Mesozoic and Tertiary strata. Some organic-rich horizons with TOC values up to 11.2 % occur in Upper Triassic (black limestone member of the Kunga Group) and Lower Jurassic (Sandilands and Ghost Creek Formations) source strata. Mesozoic and Tertiary strata generally contain gas prone Type III organic matter except for the Lower Jurassic Ghost Creek Formation and the Upper Triassic-Lower Jurassic Kunga Group which contain oil and gas prone Type II organic matter and significant amounts of oil prone Type I organic matter. Lateral variations in TOC and the quality of organic matter (QOM) for Triassic and Jurassic strata are primarily related to the level of organic maturation. The strata have poor to good hydrocarbon source potential on Graham Island. High heat flow associated with plutonism on Moresby Island has overmatured the strata resulting in poor source potential on Moresby Island. Hydrocarbon source potential for Cretaceous and Tertiary strata is primarily controlled by the level of organic maturation and depositional patterns. The Cretaceous Haida and Honna Formation generally contain terrestrially derived Type III organic matter with poor to fair gas source potential. The Skidegate Formation contains a mixture of Types II and III organic matter with decreased (terrestrial) Type III organic matter input and increased Type II (marine) organic matter input relative to the Haida Formation. Cretaceous strata from Moresby Island are generally overmature and have poor source potential whereas equivalent strata from Graham Island are immature to overmature and have fair to moderate gas source potential. Generally immature coal and lignite from the Tertiary Skonun Formation have poor to fair gas source potential. Resinite horizons containing hydrogen-rich organic matter have good oil and gas source potential where mature. Siltstone and shale facies of the Skonun Formation contain moderate amounts of Type II organic matter and have good hydrocarbon source potential. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Cette étude est basée sur une approche multidisciplinaire qui vise à expliquer les différents aspects de la tectonique du nord de l'Égée. Pour cela, nous avons choisi d'étudier le bloc Chalkidiki en utilisant diverses méthodes géologiques. 1) Nous avons réalisé plusieurs campagnes de cartographie sur le terrain afin de mesurer la géométrie des structures tectoniques. Un aperçu de la géométrie structurale est donnée au travers d'une synthèse faite à partir de cartes régionales qui présente la géométrie des éléments plans et linéaires de la déformation. 2) Nous avons évalué l'intensité des conditions métamorphiques à l'aide de diagrammes de phases isochimiques calculés par minimisation de l'énergie libre de Gibbs. Sur la base de ces résultats, nous avons déduit l'existence d'un événement en faciès éclogitique, qui précède le faciès amphibolitique régional. 3) Nous avons alors effectué des datations haute- (U/Pb sur zircon et monazite) et moyenne-température (40Ar/39Ar sur micas). Ces ages ont ensuite été couplés avec des ages issus de la thermochronologie à basse température qui nous a permis de modéliser l'histoire thermique en utilisant un système d'inversion bayésienne. Les résultats de la modélisation ont permis de contraindre l'histoire thermique complète (T-t) de la zone d'étude depuis des hautes températures Crétacé jusqu'à la mise à l'affleurement à l'Eocène. 4) Nous avons modélisé l'évolution géologique Tertiaire du nord de la mer Égée par rapport à l'exhumation de la croûte inférieure pendant l'extension de type core complexe. À partir d'expériences analogiques nous avons testé si la dispersion gravitaire d'un prisme orogenique qui subit extension est un processus approprié pour le développement des core complexes dans le Rhodope lors de l'ouverture de la mer Égée. Notre analyse suggère que la localisation de déformation et le développement des core complexes à l'arrière de la zone touchée par l'extension est étroitement liée à la géométrie pré-effondrement du prisme orogénique. / This study is based around a multidisciplinary approach that aims to unravel different aspects of the tectonics of North Aegean. For that purpose we have selected to study the Chalkidiki block using a variety of geological methods. 1) We carried out several field mapping campaigns measuring the geometry of structural fabrics. An overview of the regional geometry is given in the compiled regional maps that illustrate the attitude of the measured planar and linear structural fabrics. 2) We evaluated the intensity of the metamorphic conditions using isochemical phase diagram sections calculated by minimisation of the Gibbs free energy. Based on our model results, we inferred the existence of an early eclogite-facies event before the regional amphibolite-facies overprint. 3) We performed high- (U/Pb in zircon and monazite) and medium-temperature (40Ar/39Ar on micas) geochronology coupled with low-temperature thermochronology and inverse thermal history modelling using a Bayesian transdimensional inversion scheme. The modelling results delineated the complete thermal path (T-t) of the study area from Cretaceous heating to Eocene near surface exposure. 4) We modelled the Tertiary geological evolution of the North Aegean with reference to the exhumation of the lower crust during core complex formation. Using scaled laboratory experiments we tested whether the gravity spreading of a crustal-scale thrust wedge that undergoes extension is a suitable process for the development of the Rhodopean core complexes during the early opening of the Aegean. Our analysis suggests that strain localisation and core complex development near the backstop of the area affected by extension is intrinsic to the pre-collapse geometry of the orogenic wedge.

Studies of Vibroseis reflection profiles over the exposed Triassic-Jurassic Culpeper, Richmond, and Scottsville Basins, and another profile over a probable early Mesozoic basin (Toano) beneath the Atlantic Coastal Plain sediments, in Virginia indicate that resolution of the geometry of the basins is inhibited by small impedance contrasts between the rock units within the basin and those bordering the basin. None of the seismic sections exhibit reflections which can be directly attributed to a Triassic-pre-Triassic interface. Resolution of the geometry of the basin sediments depends upon the presence of anomalously high or low velocity/density rock units within the basin, and similarly the presence of large amplitude reflections from within these and possibly other basins may imply the presence of these units, which include basalt and lignite. A method of analyzing the refracted waves in the seismic reflection data with large receiver offsets for determination of apparent velocities and the geometry of the refraction interface is presented. The Culpeper seismic lines indicate a basin with a maximum thickness of 2500 m along the western side and approximately 1750 m along the eastern side of the basin. The maximum thickness of the Richmond Basin below the seismic line is approximately 2700 m. The Scottsville Basin contains sedimentary strata with a thickness of 1750 m and the seismic data from the Toano Basin indicate a thickness of 3000 m. The compressional wave velocity of the strata within these basins has a range of 4000-5300 m/sec. / M.S.

No description available.

No description available.

A review of all available surface and subsurface data on Triassic and Lower Jurassic rocks in northeastern Arizona has revealed the following information. The Moenkopi Formation, the Chinle Formation, and the Glen Canyon Group of Triassic and Early Jurassic age are present throughout most of the study area. These units form a sequence of continental and transitional marine origin that shows notable vertical and lateral facies changes. The Moenkopi Formation thickening west and northwestward with a maximum thickness of 134 meters. The unit comprises sandstone and shale, and shows more shaley facies westward. The Chinle Formation shows minimum thickness to the north and thickens toward east and south with a maximum thickness toward west. This unit dominantly consists of sandy shale, but contains more sandstone westward and north westward. The unit contains some limestone in north and northern region. The Chinle Formation is overlain by the Glen Canyon Group, which in ascending order comprises the Wingate Sandstone, the Moenave Formation, the Kayenta Formation, and the Navajo Sandstone. The Wingate Sandstone shows its maximum thickness in the central and southcentral region of the study area and thins west and eastward. This unit mainly comprises sandstone, particularly in its upper part. The Moenave Formation displays its zero thickness, in the eastern region and shows its maximum thickness, 198 meters, in the west-central part. The unit mainly consist of sandstone. The Kayenta Formation attains its greatest thickness, 204 meters, in the southwestern part of the region and thins east and northward. This formation contains high percentages of sandstone. Within the area of this study, the Navajo Sandstone is the thickest formation in the Glen Canyon Group. This unit almost entirely consist of sandstone pinches out toward the south and east, and displays its maximum thickness, 300 meters, northward.

The coal-bearing Dakota Sandstone at Coal Canyon, Arizona, which is located in the western portion of the Black Mesa basin, has yielded abundant, diverse, and generally well-preserved spores, pollen, and microplankton. The formation is characterized by high frequencies of fern spores, especially striate spores belonging to the Schizaeaceae, and angiospermous pollen consisting primarily of simple tricolpate and tricolporate grains. Gymnospermous pollen is comparatively uncommon. The microflora assemblage contains many exclusively Cretaceous species previously reported from Australia, western Europe, Siberia, and other localities of North America. A microflora which compares closely with the Dakota assemblage occurs in the Woodbine strata of Oklahoma. On the basis of palynologic evidence, the age of the Dakota Sandstone at Coal Canyon, is interpreted as lowermost Upper Cretaceous (Cenomanian).

This work is focused on characterising and evaluating the intensity and selectivity of the marine fauna during the Tr/J mass extinction and recovery of the ecosystem in different localities throughout Pangaea. To address this, four localities were studied: St. Audrie’s Bay, Larne and Pinhay Bay in the UK, and Portezuelo Providencia in Chile. From each locality, samples were taken at approximately 1m intervals throughout the Tr/J sections. Species abundance per sample was estimated and each species was classified according to autoecological information derived from the literature. In order to assess changes in the structure and composition of the assemblages, NMDS and beta diversity index were performed, dominance and richness were estimated and the data were tested against five rank abundance (RAD) models. Ecospace modelling was used to estimate the loss in ecological diversity. Measures of the body size of bivalves and ichno-parameters were recorded on each section. Through the UK sections, the richness, dominance and the composition rate shifted abruptly during the extinction event. A geometric model shows the best fit during extinction events and, in contrast, a log-normal model best fits the pre-extinction and recovery event. The body size of the bivalves did not decrease during the Tr/J, while the coverage, richness and body size of ichnofossils increased during the recovery. The Chile Tr/J section records low richness, but the ecological complexity and richness decreases through the interval and composition records high turnover, while the dominance increases. The results indicate that the Tr/J disruption changed species composition in a relatively short time period, which decreased the ecological functionality of the invertebrate marine assemblage. In spatial terms, the UK fauna show a clear response to the extinction effect, but the diversity response of the Chilean assemblage is not clear at all, which may be related to taphonomical bias. Alternatively, this work analysed stage-by-stage occupation of ecospace of 3181 genera recorded from Sepkoski`s compendium for the marine fauna from the Late Permian to Early Jurassic. The ecospace can be represented as a combination of the three axes of tiering, motility and feeding, each divided into six subcategories. From the Cambrian to Recent, ecospace utilisation has tripled, however the trend through the Phanerozoic remains unclear. This result indicates that from the Guadalupian to Sinemurian the number of modes of life did not increase significantly, but the ecospace packing does. There was a significant positive correlation between abundance of predators and both infaunalisation and motility. However, the ecospace utilisation decreased 35% and 16% at the end of Permian and Triassic, respectively. During the extinction events, non-motile animals, organisms with little physiological control of biocalcification and the epifaunal forms, were heavily affected. This indicates that the mass extinction had a particular ecological effect on the biota and is an important episode of ecological changes due to ecological selectivity. Parallel, the appearance of adaptations to new trophic niches during the Triassic, like durophagy, presumably increased predation pressure and drove the increase in benthic infaunalisation. This series of adaptation could be potentially associated with the Marine Mesozoic Revolution.

Submitted by Nara Lays Domingues Viana Oliveira (naradv) on 2015-08-31T18:46:24Z No. of bitstreams: 1 trevisan.pdf: 3804396 bytes, checksum: 1771246a3b96f23d318e661980a0c61f (MD5) / Made available in DSpace on 2015-08-31T18:46:24Z (GMT). No. of bitstreams: 1 trevisan.pdf: 3804396 bytes, checksum: 1771246a3b96f23d318e661980a0c61f (MD5) Previous issue date: 2011 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / PROSUP - Programa de Suporte à Pós-Gradução de Instituições de Ensino Particulares / Fósseis de pteridófitas são conhecidos para a Antártica desde o final da Era Paleozóica, mas se tornam mais abundantes nas áreas da península, onde se situam as ilhas King George e Nelson, foco deste trabalho, apenas a partir do Mesozóico. Compostas por litologias dominantemente vulcânicas (fluxos e queda de cinzas), ou geradas por seu retrabalhamento, os restos relacionados às Filicales são encontrados em níveis correspondentes ao final do Cretáceo e Paleógeno e se concentram na ilha King George, a mais bem conhecida, nas áreas mais ao sul (Península Fildes). O conjunto da tafoflora dos níveis mais antigos (Campaniano/Maastrichtiano) mostra muitas pteridófitas, acompanhadas de coníferas podocarpáceas e araucariáceas e angiospermas com características primitivas, dominadas por formas relacionadas com Nothofagus. Nas sucessões mais jovens, do Paleoceno Superior e Eoceno, embora a composição não se modifique qualitativamente, há uma modernização da flora, com o aparecimento de uma maior variedade de coníferas podocarpáceas e, entre as angiospermas, morfotipos foliares já comparáveis aos de famílias atuais (em especial, Sapindaceae, Aquifoliaceae, Lauraceae, Myrtaceae e, mais uma vez, uma grande abundância de representantes das Nothofagaceae). Para a ilha Nelson, onde uma única localidade fossilífera, o Rip Point, é aqui comunicada de modo inédito, o estudo das associações fósseis de plantas demonstrou uma deposição que se reveste de grande importância por sua correlação com aquela dos níveis mais antigos da ilha King George. Concentrada em dois níveis de tufos, entre lavas e conglomerados, a tafoflora do mais inferior contém, como macrorresto exclusivo, frondes com morfologias comparáveis àquelas descritas para o gênero Coniopteris (Brongniart) Harris, cuja presença entre os fósseis é praticamente restrita ao Mesozóico. A preservação das impressões de pinas e pínulas permitiram a identificação de uma nova espécie, C. antarctica. A análise do material palinológico mostrou, contudo, que a vegetação reunia também raras coníferas (podocarpáceas e araucariáceas) e tipos angiospérmicos primitivos, entre os quais, grupos polínicos ancestrais de Nothofagus. Este conjunto, além de apoiar uma idade entre o final do Campaniano e/ou Maastrichtiano basal para a deposição do Rip Point, sugere a presença de condições climáticas temperadas e úmidas para as áreas do norte da Península Antártica neste intervalo. Seus acompanhantes confirmam ainda o papel que a vegetação pretérita da Antártica teve na origem dos biomas que hoje se desenvolvem nas latitudes médias a altas e de clima oceânico do Hemisfério Sul. / Pteridophyta fossils from Antarctica known since the end of Paleozoic Era. During the Mesozoic they become more abundant in areas of the King George and Nelson islands, object of this study, located at the Antarctic Peninsula. On King George Island the volcanic rocks dominates the successions and the fossil assemblages concentrates in levels originated by ash flow and fall processes, or for its reworking, in a time span that includes the end of Cretaceous and Paleogene. There, the pteridophytic remains dominate at southern areas (Fildes Peninsula) and in the older Cretaceous levels. This older assemblages (Campanian / Maastrichtian) shows many and well preserved ferns, accompanied by araucaria and podocarp conifers, and primitive angiosperms dominated by Nothofagus. In the Upper Paleocene and Eocene successions, although the unchanged general composition, the flora shows more modern character with the appearance of many new conifer types mainly within the Podocarpaceae, and the angiosperms remains are represented by leaf morphotypes comparable to those found in extant families (mainly Sapindaceae, Aquifoliaceae, Lauraceae, Myrtaceae, and once again, abundant Nothofagaceae). On Nelson island, is find a single known fossiliferous locality (Rip Point), presented for the first time in this study. The fossil plant deposition brings the attention of its correlation to the older levels from the neighbouring King George island. The plant fossils at Rip Point concentrate in two levels of tuffitic rocks, between lava and conglomerate deposits, the lower one exclusively by its macrofloristic remains and restricted to fern frond fragments, exhibiting morphologies comparable to Coniopteris (Brongniart) Harris, a genus largely confined to the Mesozoic. The well preserved impressions and morphology of pinnae and pinnules allows the description of a new species, C. antarctica. Instead, the pollen analysis made in the same beds showed that the associated vegetation contains rare conifers representatives (podocarps and araucaria) and primitive angiosperms that include ancestral type of pollen grains from Nothofagus. This fossil assemblage, besides supports the late Campanian and /or basal Maastrichtian age to the Point Rip basal levels, allows inferring a wet and temperate climatic condition to the northern areas of Antarctic Peninsula during this time interval. Its composition also help to confirm the role of ancient Antarctic biomes in the origin of the vegetation that grow today in the high and middle latitudes, under oceanic climates, of the South Hemisphere.

The oldest sedimentary and metasedimentary rocks exposed in the Himalayan foothills of Pakistan record a gradual transition seaward from the evaporites of the Salt Range Formation to pelitic sediments deposited in deeper water to the north. The Upper Proterozoic Tanawal Formation was derived from erosion of a northern highland produced during the early stages of Late Proterozoic to early Ordovician tectonism. Early Paleozoic tectonism is indicated by an angular unconformity at the base of the Paleozoic section, the intrusion of the Mansehra Granite, and the local removal of Cambrian strata. Paleozoic shallow-marine strata are preserved in half-grabens created during extensional tectonism that began during the Carboniferous and climaxed with rifting during the Permian. Paleozoic rocks were largely or completely eroded from northwest-trending highlands on the landward side of the rift shoulder. Thermal subsidence of the rifted margin resulted in transgression of the highlands and deposition of a Mesozoic section dominated by carbonates. Compressional tectonism related to the impending collision with Asia commenced in the Late Cretaceous. Rocks north of the Panjal-Khairabad fault were deformed and metamorphosed during Eocene subduction of northern India beneath the Kohistan arc terrane. Following their uplift and exhumation, rocks metamorphosed beneath Kohistan were thrust southward over unmetamorphosed rocks along the Panjal and Khairabad faults which are inferred to be connected beneath alluvium of the Haripur basin. Contrasts in stratigraphy and metamorphism on either side of the Panjal-Khairabad fault indicate that shortening on this structure exceeds that of any other fault in the foothills region. The migration of deformation towards the foreland produced south- or southeast-vergent folds and thrust faults in strata south of the Panjal-Khairabad fault and reactivated Late Cretaceous structures such as the Hissartang fault. The Hissartang fault is the westward continuation of the Nathia Gali fault, a major structure that thrusts Proterozoic rocks in the axis of a Late Paleozoic rift highland southward over Mesozoic strata. Fundamental differences in stratigraphy, metamorphism, and relative displacement preclude straightforward correlation of faults and tectonic subdivisions of the central Himalaya of India and Nepal with the northwestern Himalaya of Pakistan. / Graduation date: 1994