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Full-Text Articles in Physical Sciences and Mathematics
Magma Chamber Processes At Mutnovsky Volcano, Russia, Kelly L. Robertson
Magma Chamber Processes At Mutnovsky Volcano, Russia, Kelly L. Robertson
UNLV Theses, Dissertations, Professional Papers, and Capstones
This dissertation is composed of two manuscripts about the evolution of Mutnovsky Volcano in Kamchatka, Russia. Mutnovsky has been active for the past approximately 80,000 years, during which there was the formation and subsequent eruption of four major stratocones. These four eruptive centers, named Mutnovsky I, II, III, and IV from oldest to youngest, have a range of erupted product compositions from basalt to dacite. The first major goal of this project was to investigate the melt source for Mutnovsky. Whole rock trace element and Nd, Sr, and Pb isotopic data were used to determine that the melt source was …
Nitrogen Retention And Denitrification In Reservoirs, Erin Grantz
Nitrogen Retention And Denitrification In Reservoirs, Erin Grantz
Graduate Theses and Dissertations
Studies coupling direct measurements of micro-scale nitrogen (N) cycle processes with ecosystem-scale flux estimates are needed to determine N retention hotspots within river networks, where up to 50% of terrestrial loading to aquatic systems is retained. This study examined the role of denitrification, a microbially-mediated reactive N removal pathway, in ecosystem-scale N retention in 3 small (< 1 km2), shallow flood-control reservoirs. Annual reservoir N retention was estimated through mass balance modeling of system inputs and outputs. Annual denitrification rates were estimated by combining multiple measurements of seasonal, habitat-specific dinitrogen gas (N2) fluxes. Annual reservoir N retention ranged from 14 - 19 g m-2 in the reservoirs, while reactive N removal through denitrification was 13 - 25 g m-2. Denitrification efficiency, or the portion of the retained N load that was denitrified, was high relative to other lentic systems and was > 100% at 2 sites. Previous lentic denitrification studies may have underestimated denitrification efficiency by not considering water column denitrification, which was 50% of total denitrification at one study reservoir. However, not all potential inputs, most importantly biological N2 fixation, were included in this …
Field-Based Constraints On The Origin Of The Benton Uplift, Ouachita Mountains, Rachel Victoria Keng
Field-Based Constraints On The Origin Of The Benton Uplift, Ouachita Mountains, Rachel Victoria Keng
Graduate Theses and Dissertations
The Ouachita Mountains are an east-west trending fold-and-thrust belt exposed in west central Arkansas and southeastern Oklahoma. The Mississippian-Pennsylvanian Ouachita orogeny occurred when the Sabine arc terrane collided during south-facing subduction, during closure of the Cambrian passive margin of the North American plate. Deep-water Paleozoic strata were incorporated into an accretionary wedge as the Sabine terrane approached the North American plate. Folds and thrust faults in the Ouachita Mountains generally verge north due to tectonic transport of an accretionary wedge from south to north. Structures in the Benton and Broken Bow Uplifts (located in the core of the wedge) locally …
Paired Positive Carbonate Carbon Isotope, Organic Carbon Isotope, And Oxygen Isotope Composition Study Across The Lower Mississippian Positive Carbon Isotope Excursion, Southeastern Nevada, Usa, Robert Alan Henry
UNLV Theses, Dissertations, Professional Papers, and Capstones
A prominent positive carbonate carbon isotope (delta13Ccarb) excursion of Early Mississippian age (ca 351 Ma) has been documented by previous studies from numerous sites globally. This delta13Ccarb excursion has been interpreted as resulting from enhanced organic carbon burial that removed 13C-depleted carbon from the ocean and atmosphere. Anticipated outcomes from enhanced organic carbon burial would include a similar positive excursion in organic carbon isotopes (delta13Corg) and a global cooling event resulting from reduced CO2 in the atmosphere and ocean. These predictions, however, were not tested sufficiently in previous studies. This research has tested these predictions through an integrated study of …
Effects Of High-Impedance-Contrast Boundary Upon Multi-Modal Seismic Surface Wave Data, Prajwol Tamrakar
Effects Of High-Impedance-Contrast Boundary Upon Multi-Modal Seismic Surface Wave Data, Prajwol Tamrakar
UNLV Theses, Dissertations, Professional Papers, and Capstones
Synthetic studies and analyses of an experimental dataset were conducted to address the use of Rayleigh-type surface waves for estimation of shear wave velocity (VS) profiles of shallow bedrock sites. The shallow bedrock presents a high impedance contrast boundary which causes surface wave energy to be partitioned to higher modes. Idealized studies of hypothetical datasets and root-mean-squared calculations of error surfaces showed that if reliable dispersion data are available over a broad frequency spectrum, the VS profile can be recovered using the fundamental mode alone. However, when dispersion data are limited to a relatively narrow frequency band representing what might …
Microstructural Characterization Of Kinked Germanate Olivine Grains, Alex Gregory Drue
Microstructural Characterization Of Kinked Germanate Olivine Grains, Alex Gregory Drue
UNLV Theses, Dissertations, Professional Papers, and Capstones
Olivine is the most common and the weakest mineral in the upper mantle. Thus the strength of olivine controls the rheology of the earth's upper mantle. The rheology of olivine in the upper mantle has important implications for mantle flow, mountain building, and rates of isostatic adjustment. Recent experimental measurements of the flow strength of deformed olivine polycrystals have assumed a homogeneous state of stress. X-ray synchrotron diffraction experiments have implied that this assumption is not always valid. Elastic Plastic Self Consistent (EPSC) modeling offers an approach to estimating the flow strength of olivine that does not assume a homogeneous …
Assessing Ageing At Beaver Reservoir, Northwest Arkansas: Limnological, Geochemical & Paleolimnological Approach, Byron Anthony Winston
Assessing Ageing At Beaver Reservoir, Northwest Arkansas: Limnological, Geochemical & Paleolimnological Approach, Byron Anthony Winston
Graduate Theses and Dissertations
Access to potable water has been arguably one of the most important requisites for the advancement of human civilization on earth. As a result, man in his infinite wisdom devised the dam and formed reservoirs, (man- made lakes), to exploit water resources at will. In all natural lakes and reservoirs changes occur in the water quality parameters as it relates to chemical nutrients, temperature and turbidity over time. These changes are collectively referred to as "Reservoir Ageing", of which sedimentation and eutrophication are primary. Reservoir Ageing has consequences which adversely affect and defeat many of the intended uses of the …
Geochemical Controls On Mercury Methylation In Backwaters Of A Gulf Coastal Plain River System, Implications For Water Column Processes, Liam N. Schenk
Geochemical Controls On Mercury Methylation In Backwaters Of A Gulf Coastal Plain River System, Implications For Water Column Processes, Liam N. Schenk
Graduate Theses and Dissertations
The abundance and distribution of mercury and methyl mercury were investigated at three sites in the lower Ouachita River in the summer of 2010 in an effort to provide the first characterization of the extent of mercury contamination in this river system, and to investigate the potential for mercury methylation in the water column of backwaters off of the main channel. Results showed that filtered methyl mercury was positively correlated to dissolved organic carbon (r2=0.76) for water samples taken from the bottom 1 ft of the water column at three sites, suggesting the importance of dissolved organic carbon in mercury …
Mesozoic Burial, Mesozoic And Cenozoic Exhumation Of The Funeral Mountains Core Complex, Death Valley, Southeastern California, Mengesha Assefa Beyene
Mesozoic Burial, Mesozoic And Cenozoic Exhumation Of The Funeral Mountains Core Complex, Death Valley, Southeastern California, Mengesha Assefa Beyene
UNLV Theses, Dissertations, Professional Papers, and Capstones
The Funeral Mountains of Death Valley National Park, CA, provide an opportunity to date metamorphism resulting from crustal shortening and subsequent episodic extensional events in the Sevier hinterland. It was not clear whether crustal shortening and thus peak temperature metamorphism in the hinterland of the Sevier-Laramide orogenic wedge have occurred whether in Late Jurassic, Early Cretaceous , Late Cretaceous or somewhere between. Particularly ambiguous is the timing of crustal shortening in the deep levels of the hinterland of the Sevier belt, now manifest in the metamorphic core complexes, and how and when these middle-to-lower crustal rocks were exhumed. A 6-point …