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 9 of 9 for “"euxinia"”.
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Testing the ancient marine redox record from oxygenic photosynthesis to photic zone euxina
… in the marine photic zone (i.e. photic zone euxinia; PZE) during mass extinctions and oceanic anoxic events. Here, the molecular fossil evidence for oxygenic photosynthesis and eukaryotes is reevaluated, where the results imply that currently existing lipid biomarkers are contaminants. Next, …
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Testing the ancient marine redox record from oxygenic photosynthesis to photic zone euxina
… in the marine photic zone (i.e. photic zone euxinia; PZE) during mass extinctions and oceanic anoxic events. Here, the molecular fossil evidence for oxygenic photosynthesis and eukaryotes is reevaluated, where the results imply that currently existing lipid biomarkers are contaminants. Next, …
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Geochemical and Paleontological investigations of the Neoproterozoic-Cambrian Transition: Case Studies on geochemical clast provenance, emerging paleo redox proxies, and ambiguous dubiofossils
… redox, such as the development of photic zone euxinia. In the third chapter, I investigate the identity of Brooksella alternata, a purportedly cnidarian fossil that was later suggested to be a hexactinellid sponge fossil. My morphological and compositional analysis reveals B. alternata to be a …
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Biogeochemical proxies for environmental and biotic conditions at the Permian-Triassic boundary
… by bacterial inputs in which photic zone euxinia was prevalent for extended time periods. Additional findings from compound-specific isotope data suggest that at isolated intervals, the chemocine may have extended even closer to the surface. The timing of these intervals implies that ocean …
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Marine Deoxygenation Predates the End-Triassic Mass Extinction Within the Equatorial Panthalassa and its Influence on Marine Ecosystems Before the Biotic Crisis
… show persistent anoxic conditions and occasional euxinia occurred in the local bottom waters. We propose that the positive δ15N and iron speciation data from Grotto Creek reflect a progressive deoxygenation of the upper water column with the expansion of the equatorial oxygen minimum zone (OMZ). …
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Contributions to late Ediacaran geobiology in South China and southern Namibia
… in oceanic chemical conditions (e.g. anoxia/euxinia/ferruginia) with emerging data suggesting that it is not until the late Ediacaran Period (551-542 Ma) when pervasive oxidation of the deep oceans occurred. In addition, the study of Ediacaran paleobiology involves numerous factors, including …
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Earth’s oceanic oxygen history from Phanerozoic to Pleistocene glacial cycles: insights from the carbonate iodine-to-calcium proxy
… i.e., at higher oxygen levels rather than euxinia (containing H2S) or anoxia (no O2). Four major projects in my dissertation are:</p> <p>1) Phanerozoic upper ocean oxygenation history and its coevolution with life.</p> <p>When and how oceanic oxygen had evolved to modern-like levels has …
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Biogeochemical Cycling and Paleoenvironmental Reconstructions of the Toarcian Oceanic Anoxic Event from Western North America
The Toarcian Oceanic Anoxic Event (T-OAE; ~183 million years ago) represents an interval during the Mesozoic when the emplacement of the Karoo-Ferrar Large Igneous Province (LIP) is thought to have resulted in significant environmental change. Associated with this interval was the widespread …