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Articles 1 - 11 of 11
Full-Text Articles in Physical Sciences and Mathematics
Testing The Use Of Anisotropy Of Magnetic Susceptibility (Ams) In Determining Genetic Origins Of Paleoproterozoic Diamictites, Miles A. Harbury
Testing The Use Of Anisotropy Of Magnetic Susceptibility (Ams) In Determining Genetic Origins Of Paleoproterozoic Diamictites, Miles A. Harbury
Theses and Dissertations
The Huronian Supergroup (2.4-2.1 Ga) in Ontario, Canada is widely accepted as an important stratigraphic interval for interpreting Paleoproterozoic climate. This is because it contains some of the oldest glaciogenic rocks on the planet. However, massive and poorly-stratified diamictites in the Gowganda Formation of the Huronian Supergroup have varying depositional interpretations among sedimentologists (subglacial, rainout, sediment gravity flow etc.). Diamictites can occur from a variety of processes and, therefore, proper depositional interpretation is essential for unraveling detailed environmental conditions at the time of deposition. Anisotropy of magnetic susceptibility (AMS) looks at the orientation of magnetic particles within a rock and …
Entangled Conquest: A Study Of Cultural Hybridization And Change In Norman Ireland, Sean Mcconnel
Entangled Conquest: A Study Of Cultural Hybridization And Change In Norman Ireland, Sean Mcconnel
Theses and Dissertations
This thesis employs entanglement theory and new geophysical macro-analytical methods to
examine the spread of Norman culture in late medieval Ireland. The traditional theories of
Anglo-Norman conquest by mass migration, by military conquest, and by political conquest are
reviewed and compared to a more nuanced theory of Normanization, which suggests that
genetically Irish people, who spoke Irish, practiced Irish law, and pursued Irish interests were
primarily responsible for what is considered "Norman" material culture on the Island. This
dissertation presents the idea that adherence to the English king was a necessary and expedient
action on the part of Irish lords …
Using Anisotropy Of Magnetic Susceptibility (Ams) To Identify A Tectonic Lineation In The Pulo Do Lobo Formation In The Southern Iberian Shear Zone Near Aracena, Spain, Devin Levang
Theses and Dissertations
The Southern Iberian Shear Zone (SISZ) is a Variscan-aged suture representing the closure of a small ocean basin during the Carboniferous. The SISZ is bounded on either side by the well-studied, relatively homogeneous Beja-Acebuches Metabasites (BAM) and the complex and heterogeneous accretionary metasedimentary rocks of the Pulo do Lobo (PdL). The SISZ underwent a combination of shortening and lateral shearing known as transpression. Despite a very well-developed tectonic foliation, kinematic interpretation in the PdL is made difficult by a lack of easily identifiable lineations. Anisotropy of magnetic susceptibility (AMS), a geophysical technique measuring the relative anisotropy of magnetic susceptibility axes …
Characterization Of Quaternary Stratigraphy In The Mississippi Sound To Evaluate The Influence Of Geologic Heterogeneity On Submarine Groundwater Transport And Discharge, Zachary Peoples
Theses and Dissertations
Submarine Groundwater Discharge (SGD) through seafloor sediments is gaining recognition as an important component of coastal water quality. Stratigraphic features creating geologic heterogeneity, such as incised paleochannels, may influence preferential pathways for SGD. The central Mississippi Sound is underlain by paleochannels that were incised into Pleistocene sediments while the area was subaerially exposed during the last glacial maximum and are now buried by transgressive Holocene deposits. In this thesis, newly collected chirp, previously published seismic reflection, and sediment core data are used to characterize the three-dimensional structure of the Holocene-Pleistocene contact. Results indicate that Pleistocene paleochannels cross-cut the study area, …
Evaluating Hydration And Artificial Aging Effects On The Paleointensity In Natural Glass, Sebastian Fearn
Evaluating Hydration And Artificial Aging Effects On The Paleointensity In Natural Glass, Sebastian Fearn
Theses and Dissertations
Young natural volcanic glasses have been successfully used to recover Earth’s geomagnetic field intensity (paleointensity). However, the magnetic stability and reliability of volcanic glass as a paleomagnetic recorder over geologic time is unclear. Paleointensity estimates may be influenced by natural processes that alter magnetic mineralogy. Previous results from paleointensity and rock magnetic experiments suggest that post-emplacement hydrothermal alteration can alter the magnetic remanence and can possibly cause paleointensity experiments to fail. Low-temperature hydration and natural relaxation of the glass structure over time may also adversely impact paleointensity results. In this study, rhyolitic and basaltic glass specimens underwent artificial aging and …
Neural Network Models For Nuclear Treaty Monitoring: Enhancing The Seismic Signal Pipeline With Deep Temporal Convolution, Joshua T. Dickey
Neural Network Models For Nuclear Treaty Monitoring: Enhancing The Seismic Signal Pipeline With Deep Temporal Convolution, Joshua T. Dickey
Theses and Dissertations
Seismic signal processing at the IDC is critical to global security, facilitating the detection and identification of covert nuclear tests in near-real time. This dissertation details three research studies providing substantial enhancements to this pipeline. Study 1 focuses on signal detection, employing a TCN architecture directly against raw real-time data streams and effecting a 4 dB increase in detector sensitivity over the latest operational methods. Study 2 focuses on both event association and source discrimination, utilizing a TCN-based triplet network to extract source-specific features from three-component seismograms, and providing both a complimentary validation measure for event association and a one-shot …
A Feasibility Study Of Microbialites As Paleomagnetic Recorders, Ji-In Jung
A Feasibility Study Of Microbialites As Paleomagnetic Recorders, Ji-In Jung
Theses and Dissertations
Microbialites are carbonate organosedimentary deposits formed by benthic microbial communities that trap and bind detrital sediments, and/or inorganic and biologically influenced calcification. Any ferromagnetic particles incorporated into the microbialite structure have the potential to preserve variations in Earth’s magnetic field. A paleomagnetic record in microbialites would be useful for reconstructing the geomagnetic field because it may record at a high temporal resolution based on estimated growth rates, thus preserving relatively short-period variations of the Earth’s magnetic field. In addition, microbialites can be found in the geologic record going back ~3.5 Ga, hence potentially providing information on very ancient variations in …
Using Ams To Help Interpret Glaciogenic Deposits Of The Late Paleozoic Ice Age In The Paraná Basin, Brazil, James Anthony Amato
Using Ams To Help Interpret Glaciogenic Deposits Of The Late Paleozoic Ice Age In The Paraná Basin, Brazil, James Anthony Amato
Theses and Dissertations
The term ‘diamictite’ is used as a lithologic descriptive term without assigning a particular origin to a rock unit as either glacial deposits (till), proglacial, glacially influenced deposits (resulting from meltwater plumes and ice rafted debris), or mass transport deposits (glacial or non-glacial related). While in some cases, it is possible to delineate between the origins of diamictites, in other instances, weathering and lack of exposures make it difficult to determine. In general, the occurrence of diamictites within the Gondwana succession has been traditionally used to indicate the occurrence of subglacial deposition despite the potential occurrence of other depositional modes. …
An Evaluation Of Paleomagnetic Techniques To Determine Emplacement Temperatures Of Pyroclastic Density Currents At Mount St. Helens, Devin Gerzich
An Evaluation Of Paleomagnetic Techniques To Determine Emplacement Temperatures Of Pyroclastic Density Currents At Mount St. Helens, Devin Gerzich
Theses and Dissertations
During a volcanic eruption, pyroclastic density currents (PDCs) deposit new pumice and ash and rip out and transport lithic fragments from past eruptions. Magnetic minerals in the lithic fragments, such as titanomagnetite, may be partially or completely remagnetized, depending on their emplacement temperature with respect to their Curie and blocking temperatures. By finding the temperature at which this remagnetized overprint is removed, the emplacement temperature of the pyroclastic flow is estimated. This method assumes that the rock magnetic properties that govern magnetic unblocking are constant given a specific magnetic mineral composition, but recent studies demonstrate that Curie temperatures (Tc) in …
The Great Lakes' Regional Climate Regimes, Noriyuki Sugiyama
The Great Lakes' Regional Climate Regimes, Noriyuki Sugiyama
Theses and Dissertations
For the last couple of decades, the Great Lakes have undergone rapid surface warming. In particular, the magnitude of the summer surface-warming trends of the Great Lakes have been much greater than those of surrounding land (Austin and Colman, 2007). Among the Great Lakes, the deepest Lake Superior exhibited the strongest warming trend in its annual, as well as summer surface water temperature. We find that many aspects of this behavior can be explained in terms of the tendency of deep lakes to exhibit multiple regimes characterized, under the same seasonally varying forcing, by the warmer and colder seasonal cycles …
Sensitivity Analysis Of Empirical Parameters In The Ionosphere-Plasmasphere Model, Janelle V. Jenniges
Sensitivity Analysis Of Empirical Parameters In The Ionosphere-Plasmasphere Model, Janelle V. Jenniges
Theses and Dissertations
A sensitivity analysis of empirical parameters used in physics-based models was completed in this study to determine their effect on electron densities and total electron content (TEC) in the ionosphere. The model used was the Ionosphere-Plasmasphere Model (IPM) developed by Utah State University. The empirical parameters studied include the O+/O collision frequency, zonal wind, secondary electron production, nighttime ExB drifts, and tidal structure. The sensitivity analysis was completed by comparing a default run of the IPM to a run with the parameter adjusted for three geophysical cases. Many of the comparisons resulted in nonlinear changes to the model …