Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 43 for “"Early Jurassic"”.
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The Karoo sand sea in changing climates: Early Jurassic interdune lakes and erg dynamics in southern Africa
… known sand seas in Earth's history. The Lower Jurassic Clarens Formation in the main Karoo Basin of southern Africa has been interpreted as an aeolian succession that is dominated by massive sandstones in the lower and upper parts of the unit, whereas large-scale cross-bedded sandstones are …
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The impact of global environmental changes on exceptional preservation, extinction, and recovery in the early Jurassic (late Pliensbachian-Toarcian)
… similar climate crises in the past. During the Early Jurassic there were significant perturbations in environmental conditions around the globe, such as thermal stress, low oxygen levels, higher nutrient concentration, and acidification in some parts of the ocean. Of particular importance are …
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Unravelling the palaeobiology of the dinosaurian post crania and associated carnivore teeth from the early jurassic, Elliot formation in the Eastern Cape
… ranges in age from the Late Triassic to the Early Jurassic. This stratigraphic unit bears a varied dinosaur assemblage, among which sauropodomorph dinosaurs are the most abundant. Sauropodomorpha are particularly well documented in the Upper Elliot Formation and are morphologically and …
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Position of the Triassic-Jurassic boundary in South Africa and Lesotho : a multidisciplinary approach aimed at improving the chronostratigraphy and biostratigraphy of the Elliot Formation, Stormberg Group
… and global understanding of the Late Triassic - Early Jurassic evolution of terrestrial vertebrate faunas, however, the temporal resolution of its biostratigraphy is inadequate for detailed regional and global correlations. The main aim of this dissertation is to build a more comprehensive …
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Tectonic Setting, Structure, and Seismic Stratigraphy of the Apalachicola Rift and its Overlying Sag Basin in the Northeastern Gulf of Mexico
… clastic deposits inferred to be of late Triassic-early Jurassic age. Previous workers have interpreted pre-salt (Triassic-early Jurassic), basinward-dipping, seismic reflectors within the syn-rift half-graben of the AR as either: 1) volcanic layers or sills erupted and tilted within Mesozoic …
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Palaeoenvironmental change from the Hettangian to Toarcian in Moyeni (Quthing District), southwestern Lesotho
… of southern Africa encompasses the Late Triassic-Early Jurassic geological evolution of southern Gondwana. The environment is known to have shifted from wet swamps to a semi-arid fluvio-lacustrine and then to an aeolian system, preceding the outpouring of the Karoo continental flood basalts. The …
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Landscape evolution and equilibrium in Southern Africa : insights from cosmogenic noble gases in Karoo dolerites and geospatial analyses
… the topography and surface exposure history of early Jurassic (~183 Ma) Karoo dolerites.
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Geology of the Snip Mine, and its relationship to the magmatic and deformational history of the Johnny Mountain area, northwestern British Columbia
… Galena Pb-Pb isotopic signatures suggest an Early Jurassic age for the veins. Abundant shallow easterly-dipping quartz-calcite extension veins formed during a later, probably Tertiary, event. The Red Bluff porphyry, an elongate K-feldspar megacrystic plagioclase porphyritic quartz diorite to …
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NEARING THE END: REEF BUILDING CORALS AND BIVALVES IN THE LATE TRIASSIC AND COMPARING CORALS AND BIVALVES BEFORE AND AFTER THE END-TRIASSIC MASS EXTINCTION USING A TAXONOMIC DATABASE
… disappeared at the end of the Triassic. In the early Jurassic, very few surviving species of corals can be found, and almost no reefs. If this ‘reef gap’ was caused by a change in ocean chemistry, then how did these few species of corals survive? Were bivalves also affected by the changes? On …
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NEARING THE END: REEF BUILDING CORALS AND BIVALVES IN THE LATE TRIASSIC AND COMPARING CORALS AND BIVALVES BEFORE AND AFTER THE END-TRIASSIC MASS EXTINCTION USING A TAXONOMIC DATABASE
… disappeared at the end of the Triassic. In the early Jurassic, very few surviving species of corals can be found, and almost no reefs. If this ‘reef gap’ was caused by a change in ocean chemistry, then how did these few species of corals survive? Were bivalves also affected by the changes? On …
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High-precision U/Pb geochronology of large igneous provinces and mass extinctions : testing coincidence and causation
… and (2) the Karoo-Ferrar LIP and the early-Jurassic biotic crisis and global ocean anoxia. With these datasets, age-models for both mass extinction and LIP magmatism precise to a maximum of ~0.02% are developed, enabling, for the first time, resolution of the relative timing of …
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Tectogenesis and metamorphism of the Piedmont from Columbia to Westview, Virginia along the James River
During Late Precambrian or Early Cambrian (~550 m.y.) a sequence of interlayered graywackes and shales was intruded by the Columbia granite. At approximately 340 m.y. the granite and sediments were metamorphosed to at least amphibolite facies. During the peak and waning stages of metamorphism, …
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Terrestrial Impacts of the Central Atlantic Magmatic Province on western Pangea
… with a disputed age of either late Triassic or early Jurassic and currently no absolute dating techniques can be applied to estimate an exact age. Therefore, I propose that identification of the CAMP carbon cycle perturbation through carbon isotope chemostratigraphy of the Whitmore Point Member …
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Jurassic-Recent Structure, Stratigraphy, and Basin Modeling of the Rifted-Passive Margin of Southern Morocco
… in eastern Canada started at the Late Triassic-Early Jurassic by splitting of the northeast, structural grain inherited from the late Paleozoic, Appalachian-Atlas orogeny. A massive, 14-km-thick, reefal-carbonate platform was formed above the rifted margin during the Early Jurassic and was …
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Mesozoic Rift Evolution and Crustal Structure of the Gulf of Mexico Basin from Integration of Multiple Geological and Geophysical Datasets
… However, our understanding of the Triassic-Jurassic rift history and crustal structure of the GOM is limited. This dissertation integrates satellite free-air gravity data, full-tensor gravity gradient data, 104,000 line-kilometers of 2D reflection data, and publicly available refraction data …
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Recalibrating the breakup history of SW Gondwana: the first U-Pb chronostratigraphy for the Uitenhage Group, South Africa
… chronostratigraphic framework for the onshore Jurassic – Cretaceous in the southern Cape. To further improve precision and accuracy, a selection of crystals from four pyroclastic deposits in key stratigraphic positions were selected for single-zircon Chemical Abrasion – Thermal Ionisation Mass …
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Towards an understanding of the carbon isotopic changes across the Toarcian oceanic anoxic event
… and lower falciferum zones of the Toarcian (early Jurassic, 183 Ma) ocean anoxic event (OAE). In this study, we reveal that apparent negative isotopic excursions in bulk organic and carbonate carbon were the result of compositional changes of organic matter and diagenesis, respectively. …
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Evolution of tectonic and stratigraphic geometries in the Southern Outeniqua Basin
… during the Mesozoic break-up of Gondwana. Early Jurassic (170-150Ma) rifting between West and East Gondwana is proposed to have created weaknesses in the crust along the Southern African margin in a NNE-SSW orientation leading to the development of small rift basins and the deposition of …
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Forelimb and Pectoral Anatomy of Arcticodactylus cromptonellus, an Early Pterosaur from the Late Triassic, and the Origins of Pterosaurs
… preservation of the earliest (Triassic—Jurassic) pterosaur remains. An exceptional early pterosaur specimen that is preserved in three dimensions, the holotype and only known specimen of Arcticodactylus cromptonellus (Fleming Fjord Formation, Greenland) may help address these problems. …
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Critical assessment of a proposed biostratigraphic scheme for Late Triassic fissure sediments from South West England
… of changes in faunal composition at the Triassic/Jurassic boundary remain unanswered. Inquiries are hampered by a general paucity of sections containing correlatable Late Triassic/Early Jurassic strata. Vertebrate fossil material from Cromhall Quarry, recovered as part of an extended project …
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