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Articles 1051 - 1080 of 59555
Full-Text Articles in Entire DC Network
Exhumation Of The Pelona-Orocopia-Rand Schist And Fault Kinematic Constraints On Evolution Of The Eastern California Shear Zone, James Boyette Barker
Exhumation Of The Pelona-Orocopia-Rand Schist And Fault Kinematic Constraints On Evolution Of The Eastern California Shear Zone, James Boyette Barker
Open Access Theses & Dissertations
Southeastern California has experienced a complex recent geologic history as it continues to evolve from a convergent boundary to a period of NE-directed extension and evolution of the Eastern California Shear Zone (ECSZ). This transition is recorded in exhumed bodies of Pelona-Orocopia-Rand (POR) schist and in changing styles of fault deformation. This thesis has two interrelated goals. First, I aim to refine the timing of transition from NE extension to NS contraction in the ECSZ of southeastern California by integrating (U-Th)/He thermochronology with field-based structural analysis. The second prong of this study is to constrain broader patterns of POR schist …
Exploring Connectivity And Element Distribution In The Critical Zone Using Deep Cores Below Agricultural And Natural Drylands In The American Southwest, Angie Lynette Cano
Exploring Connectivity And Element Distribution In The Critical Zone Using Deep Cores Below Agricultural And Natural Drylands In The American Southwest, Angie Lynette Cano
Open Access Theses & Dissertations
Water movement controls how solutes are transported and stored in arid Critical Zone (CZ) systems. In natural drylands, low precipitation and high evapotranspiration lead to long term salt accumulation in the CZ, whereas irrigation increases water input and increases downward solute transport. This study investigates how agricultural practices alter subsurface hydrology and geochemistry by comparing two deep CZ cores from the southwestern United States: a 50 m deep core beneath a flood irrigated pecan farm named 5R farm, in the Rio Grande Valley in Tornillo, Texas, and a 97.5 m deep core from the Red Lake Playa in the Jornada …
Geothermal Gradient And Lithium Co-Generation Power Potential In Lafayette County, Arkansas, Juan Agustin Falquez
Geothermal Gradient And Lithium Co-Generation Power Potential In Lafayette County, Arkansas, Juan Agustin Falquez
Graduate Theses and Dissertations
The Smackover formation in south Arkansas is a known reservoir for brines with high temperature and salinity. Recently, Smackover formation brines in Lafayette County, Arkansas are a target for lithium extraction. A county-wide dataset of Bottomhole Temperatures (BHT) is used to estimate a lower bound geothermal gradient of 36 C/km and a reservoir temperature of 116 C at an approximate depth of 2725 m. The high temperatures make the brines a candidate for geothermal power co-generation. Geothermal power co-generation can be achieved by implementing an Organic Rankine Cycle (ORC) power plant. The Southwest Arkansas Lithium project anticipates a total of …
Grazed Pasture Effects On Greenhouse Gas Emissions In The Ozark Highlands, Tyler Buchanan
Grazed Pasture Effects On Greenhouse Gas Emissions In The Ozark Highlands, Tyler Buchanan
Graduate Theses and Dissertations
In the United States (US), grazinglands serve as the main foundation for the livestock industry, and, in Arkansas specifically, pastures are essential for rotational grazing and dairy operations. Climate change is increasingly becoming a concern in the agriculture industry, largely caused by anthropogenic activities increasing greenhouse gas (GHG) concentrations in the atmosphere, at least partly due to the nutrient recycling that occurs from animal manure additions in grazinglands. Therefore, quantifying GHG emissions from pastures is essential to better understanding the impacts of grazing on the environment. The objective of this study was to quantify and evaluate the potential effects of …
Estimating Body Size And Biogeography In The Genus Alligator, Madelyn M. Turala
Estimating Body Size And Biogeography In The Genus Alligator, Madelyn M. Turala
Electronic Theses and Dissertations
Several studies have examined correlations between total body length (TL) and skeletal measurements in the American alligator (Alligator mississippiensis), with some measurements serving as stronger predictors of TL than others. Femur length (FL) has been found to be tightly correlated with TL in A. mississippiensis, and this relationship has been used to estimate body size of extinct crocodilians. This thesis demonstrates that the humerus, radius, ulna, and tibia are also strongly correlated with TL and useful for body size estimation in A. mississippiensis, and thus, can be applied to related extinct crocodilians. Additionally, species distribution modeling …
Ontogeny And The Effects Of Perinatal Stress In The First Immature Skeleton Of Teleoceras Aepysoma (Perissodactyla, Rhinocerotidae), Joe Gajewski
Electronic Theses and Dissertations
Recovery of an immature fossil rhinoceros (Teleoceras aepysoma) skeleton (ETMNH 32999) from the Gray Fossil Site in Tennessee offers the first insights into the ontogeny of the species. ETMNH 32999 is interpreted to be a subadult male in an age class equivalent to ~17-20% of potential lifespan. Comparative analyses support the hypothesis that subadults of related taxa are typically ~91% of average adult size in most dimensions. However, certain cranial dimensions are substantially lower than expected in ETMNH 32999, averaging only ~74% of the average conspecific adult. Such departure from typical growth rates is suggested to be attributable …
Machine-Learning Landslide Susceptibility And Runout Modeling In The Nolichucky River Gorge After Hurricane Helene, Grace Braver
Machine-Learning Landslide Susceptibility And Runout Modeling In The Nolichucky River Gorge After Hurricane Helene, Grace Braver
Electronic Theses and Dissertations
Extreme rainfall from Hurricane Helene (September 2024) triggered widespread landslides across the southern Appalachian region, highlighting the need for rapid landslide susceptibility assessments that capture both landslide initiation and downstream runout. Traditional susceptibility models often focus solely on initiation zones, limiting their ability to identify which slopes will generate destructive landslides or where material will travel. This study addresses that gap by (1) integrating Geographic Information System (GIS)-based machine learning susceptibility modeling using ArcGIS Pro: Maximum Entropy (MaxEnt) and Random Forest-Based and Boosted Classification and Regression (FBBC) and (2) the U.S. Geological Survey (USGS) Grfin (Growth, Flow, and Inundation) runout …
Integrated Geophysical, Geotechnical, And Mineralogical Characterization Of Expansive Weches Formation Soils In East Texas: Implications For Infrastructure Design, Samuel Annobil
Electronic Theses and Dissertations
This study investigates the geotechnical, geophysical, and mineralogical characteristics of soils derived from the Weches Formation in Nacogdoches County, East Texas, with emphasis on the relationships among electrical resistivity, moisture condition, compaction state, and mineralogical composition. The Weches Formation is well known for producing clay-rich, moisture-sensitive soils that pose challenges to subgrade performance because of their plasticity and swelling behavior. Representative soil samples were collected and subjected to laboratory testing, including particle size analysis, Atterberg limits, Standard Proctor compaction, free swell tests, electrical resistivity measurements, and X-ray diffraction (XRD) mineralogical analysis. The soils are predominantly fine-grained and clay-rich, with USCS …
Soil Property Responses To Push-Pull Cropping In East Africa, Grace Mercy Amboka, Mattias Jonsson, Celina Apel, David Meinhof, Adomas Liepa, Frank Chidawanyika, Andargachew Detebo, Felipe Librán-Embid, Emily A. Martin, Ingolf Steffan-Dewenter, Marcell K. Peters, Jie Zhang, Michael Thiel, Michael Otim, James Mugisha, Ghebremedhin Belay Bahta, Fredah Maina, Alice Murage, Benjamin Feit, A. Sigrun Dahlin
Soil Property Responses To Push-Pull Cropping In East Africa, Grace Mercy Amboka, Mattias Jonsson, Celina Apel, David Meinhof, Adomas Liepa, Frank Chidawanyika, Andargachew Detebo, Felipe Librán-Embid, Emily A. Martin, Ingolf Steffan-Dewenter, Marcell K. Peters, Jie Zhang, Michael Thiel, Michael Otim, James Mugisha, Ghebremedhin Belay Bahta, Fredah Maina, Alice Murage, Benjamin Feit, A. Sigrun Dahlin
All Peer-Reviewed Publications
Push-pull technology is increasingly promoted in sub-Saharan Africa, particularly for pest management and enhancing crop productivity. However, its influence on soil properties remains understudied, despite its potential implications for soil health and sustainable soil fertility management. This study examines soil properties in push-pull and conventional non-push-pull cropping systems. Soil samples were collected from push-pull and conventional plots in Ethiopia, Kenya, Rwanda, and Uganda. We examined the associations between soil physicochemical properties and cropping systems, along with key components of push-pull, namely Desmodium coverage and plot age, and manure and mineral fertiliser application. Overall, there were a few differences in soil …
Of Dunes And Ice: A Surface-Atmosphere Investigation Of Mars Co2 Sublimation Features And Titan Aeolian Fields, Racine D. Cleveland
Of Dunes And Ice: A Surface-Atmosphere Investigation Of Mars Co2 Sublimation Features And Titan Aeolian Fields, Racine D. Cleveland
Graduate Theses and Dissertations
This dissertation investigates a central question: How do planetary boundary layer processes manifest in observable surface geomorphology, and how can planetary imagery be used to quantify those effects? The planetary boundary layer (PBL) governs near-surface exchanges of momentum, heat, and volatiles, yet direct atmospheric measurements remain spatially and temporally limited on most planetary bodies. By analyzing geomorphic features preserved in high-resolution imagery, this work quantifies how boundary-layer processes leave measurable signatures on planetary surfaces. For Mars, high-resolution images from the Mars Reconnaissance Orbiter (MRO) HiRISE instrument were used to map CO2 sublimation features, or Swiss Cheese Features (SCFs), on the …
From Phenology To Yield Zones: Functional Clustering Of Satellite Time Series For Crop Growth Monitoring, Ikram Morso
From Phenology To Yield Zones: Functional Clustering Of Satellite Time Series For Crop Growth Monitoring, Ikram Morso
Graduate Theses and Dissertations
Remote sensing and land surface phenology provide a strong basis for characterizing crop development, but their usefulness for within-field yield-zone delineation depends on whether crop development is analyzed as a phenological trajectory and whether the resulting zones are evaluated with spatially defensible statistics. These questions are especially relevant in soybean production because soybean is one of the most important row crops in the United States and the country’s dominant oilseed crop. This relevance is strong in Arkansas, where soybean is a major component of agricultural production. In soybean production, within-field yield variability reflects the combined influence of soil properties, stand …
From Infiltration Pathways To Aquifer Recharge: An Electrical Resistivity And Vadose-Zone Isotope Study In Pecan Agroforestry Systems, Jose Josue Cabral
From Infiltration Pathways To Aquifer Recharge: An Electrical Resistivity And Vadose-Zone Isotope Study In Pecan Agroforestry Systems, Jose Josue Cabral
Open Access Theses & Dissertations
Groundwater in arid or semi-arid regions is critical for agricultural production, yet the contribution of irrigation return flow to regional aquifer recharge remains poorly constrained. As is the case beneath flood-irrigated pecan orchards in the Rio Grande floodplain of Far West Texas. This study integrates time-lapse electrical resistivity tomography (ERT) with stable water isotopes (δ¹⁸O, δ²H) in vadose-zone soil-pore water to evaluate how irrigation water infiltrates. This study tracks how irrigation return is stored and may contribute to recharge of the Hueco Bolson aquifer. The objectives are to (1) relate observed resistivity variations to stratigraphic heterogeneity influencing infiltration, (2) characterize …
Characterization Of The Synhalokinetic Megaflap Lithofacies And Stratigraphy At Sinbad Valley, Paradox Basin, Western Colorado, Michael David Laase
Characterization Of The Synhalokinetic Megaflap Lithofacies And Stratigraphy At Sinbad Valley, Paradox Basin, Western Colorado, Michael David Laase
Open Access Theses & Dissertations
This study documents the halokinetic evolution of the Sinbad Valley salt wall and flanking megaflap through the characterization of its lithofacies, stratigraphy, and major structures. Sinbad Valley salt wall is in the northern Paradox Basin, in western Colorado, and is the most proximal salt diapir to the Uncompahgre Uplift, the clastic sediment source for the basin. Megaflaps are recently defined structures involving early minibasin strata that are folded up to form steeply dipping "stratal panels" along the sides of steep diapirs. The Sinbad Valley megaflap crops out as a ~7.5km long and 400m wide panel of folded and deformed Pennsylvanian- …
The Short Term Water Quality Impacts Of A Low-Head Dam Removal On Urban Stream Water Quality In Central Virginia, Usa: Is It The Dam Or The Urban Environment?, Lorraine L. Upton
The Short Term Water Quality Impacts Of A Low-Head Dam Removal On Urban Stream Water Quality In Central Virginia, Usa: Is It The Dam Or The Urban Environment?, Lorraine L. Upton
Undergraduate Theses and Capstone Projects
Dam removal in the United States has become a common practice for stream restoration and community safety. Studies have shown removals to restore an ecosystem to its natural flow, but in urban environments, dams can serve as a retention basin that help to mitigate increased amounts of stormwater and high pollution loads from increased percentages of impervious surfaces. A central Virginia watershed located in an urbanized community recently experienced a low-head dam removal and its conversion to a constructed wetland. This study assesses the short-term impacts of the dam removal through water quality sampling based on its chemical, biota, and …
Mgrre_Thinsections_Mgrre-150_10, Mgrre
Mgrre_Thinsections_Mgrre-95_15, Mgrre
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Mgrre_Thinsections_Mgrre-151_1, Mgrre
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