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 24 for “"Earth history"”.
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Quantifying spatial association between mineral deposits and geology across three African crustal segments of different age, with implication for secular change in mineralization during earth history
Variations in enrichment of mineralization, expressed in ore deposits, in the continental crust may be one way to test for secular changes in crustal genesis. This study collates and analyses fundamental information about mineral deposits with which to 'fingerprint' the metal endowment of African …
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Avian Diversification in the Andes: Understanding Endemism Patterns and Historical Biogeography
… of the tribe Thripophagini--can be linked to Earth history. The results show that the origin of these Andean taxa can be explained through vicariance from their lowland sister-groups, mediated by the uplift of the Andes. Thus, this thesis proposes that geological events are directly …
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Dolomite as a paleoenvironmental archive
… environment. Alternatively, seas on ancient Earth may have supported dolomite formation in depositional settings, making dolomite an exciting and useful paleoenvironmental proxy. The questions of how ancient dolomite formed — the longstanding “dolomite problem” — therefore has broad …
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Cyanobacterial evolution and interactions with the Proterozoic world
… biosphere and how it interacted with the early Earth. Cyanobacteria are thought to have evolved early in Earth history and played a large part in shaping the ancient biosphere and geosphere, but questions remain about their evolution and the ways in which cyanobacterial communities interacted …
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Cyclostratigraphy and sequence stratigraphy of the Solent Group (Eocene-Oligocene) of the Isle of Wight, UK
… forcing at this critical period in Earth history, when the change from a greenhouse world to an icehouse world took place. This has also allowed uncertainty surrounding the location of the Eocene-Oligocene boundary within the Solent Group to be cleared up. A major incision event …
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Multi-Proxy Records of Climate and Carbon Cycle Perturbations in the Paleozoic: Integrating Isotope Geochemistry and Sedimentology
… sediment pile during certain intervals of Earth history. Chapters 2 and 3 calibrate the clumped isotope paleothermometer for calcite, dolomite, and apatite, resolving significant discrepancies in calculated paleotemperatures. Chapter 4 applies clumped isotope thermometry to Early …
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Bridging the gap between microbial and metazoan evolutionary history
While microbial life originated early in Earth history and continues to underpin most modern ecosystems, its evolutionary trajectory remains murky. This is predominantly due to the dearth of diagnostic microbial fossils and biomarkers. Conversely, metazoans (animals) emerged relatively recently and …
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Linking sill morphology to emplacement mechanisms
… and to have a role in mass extinction events in Earth history. Most of the current models of sill emplacement assume that brittle fracture operates at all points of sill emplacement. Within this thesis, a series of observations are presented from sheet intrusions in South Africa, USA and the UK …
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Geological bodies: Form and process in romantic poetry and geology
… called attention to humans’ connection to the earth’s processes through death and decay. It argues that the poetry of the period confronted contemporary anxieties about mortality and human experience by dramatizing the difficulty of situating oneself in relation to an unstable earth. The new …
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Pre-vegetation alluvium: Geological evidence for river behaviour in the absence of land plants
… such rivers were the norm for the first 90% of Earth history and so a better understanding of their sedimentary product enables insight into both the fundamental underlying mechanisms of river behaviour and the ways in which fluvial processes operated on ancient Earth and other rocky planets. …
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Weathering Pathways and Limitations in Biogeochemical Models: Application to Earth System Evolution
… of climate following a Neoproterozoic snowball Earth should take more than 10(7) years, due to long-term geological limitation of global weathering rates. The timescale matches the observed gaps between extreme glaciations at this time, suggesting that the late Neoproterozoic system was …
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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
… and the intensity of its impact on the Earth's surface. In the second chapter of this dissertation, I investigate the changing chemical conditions of ocean waters following both the Marinoan glaciation and potentially one of the most intense disruptions to the carbon cycle in Earth …
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New Constraints For Convergent Margin Plate Tectonic Reconstructions From Imaged And Predicted Mantle Structure
… time, such that approximately one-third of the Earth surface lacks sufficient plate tectonic constraints by the early Cenozoic ~50 Ma, increasing to >60% uncertainty by the Late Jurassic. The most significant global plate model uncertainties can be traced to convergent margins, where tectonic …
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Deep-marine depositional systems of the western North Atlantic: Insights into climate and passive-margin evolution
… repository for signals pertaining to the history and evolution of Earth. Whereas the specific processes reflected by the stratigraphic record differ with respect to a given depositional environment, deposits in deep-marine settings, particularly passive margins, provide a unique, long-term …
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The influence of developmental patterns on vertebrate evolution, with the evolution of the sacrum and pelvis as a case study
… observations of changes in morphology through Earth history) and observations of extant clades (comparative patterns of pre- and postnatal development) is required to study the evolution of form across deep time. The pelvic complex plays a central role in tetrapod locomotion with the exception …
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Constraining the Ediacaran-Cambrian boundary in South China using acanthomorphic acritarchs and Palaeopascichnus fossils
… is arguably the most critical transition in Earth history. This boundary is currently defined by the GSSP (Global Stratotype Section and Point) at Fortune Head (Newfoundland, Canada) at a point that was once regarded as the first appearance of the branching trace fossil Treptichnus pedum. …
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Evaluating redox cycling across the Toarcian Oceanic Anoxic Event with implications for paleo-environmental reconstructions and organic matter sulfurization
Understanding oxygenation throughout Earth history, particularly intervals where marine deoxygenation occurred, are crucial to investigating the changes in habitability on Earth. Marine deoxygenation events, in particular, can result in changes in the carbon, sulfur, and iron cycles on our planet. …
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Changes in morphological disparity in eutherian mammals across the K-Pg boundary and Palaeocene-Eocene Thermal Maximum using discrete morphofunctional characters
… plus their stem relatives. A major event in Earth history that had a profound influence on Eutheria was the Cretaceous–Paleogene (K–Pg) extinction event, ~66 million years ago. Prior to this extinction event, during the Mesozoic, known eutherians were small and apparently predominantly …
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Sedimentology, provenance, and salt-sediment interaction in the Ediacaran Pound subgroup, Flinders Ranges, South Australia
… subcontinent during the Ediacaran, a key time in Earth history just prior to the development of multicellular life. Field investigations reveal that the Bonney Sandstone is primarily comprised of sands and shales, often in progradational parasequences that become progressively sand-dominated …
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Climate, uncertainty, and the slippery measurement of Antarctic ice
This thesis presents a history of scientific uncertainty as told through several key episodes in the mapping, measuring, and modeling of Antarctica's ice sheets. Throughout, I trace the scientific practices constraining uncertainty—and the ways in which uncertainty has repeatedly escaped …
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