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University of Arkansas, Fayetteville

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Articles 31 - 60 of 250

Full-Text Articles in Geology

Diet Specialization Mediates Drivers Of Cucurbita Herbivory In A Semi-Arid Agroecosystem, Hannah L. Gray, Nicholas A. Ivers, Elizabeth Lopez, Brad G. Peter, Scott D. Longing, Magarita M. Lopez-Uribe, Shalene Jha Jun 2024

Diet Specialization Mediates Drivers Of Cucurbita Herbivory In A Semi-Arid Agroecosystem, Hannah L. Gray, Nicholas A. Ivers, Elizabeth Lopez, Brad G. Peter, Scott D. Longing, Magarita M. Lopez-Uribe, Shalene Jha

Geosciences Faculty Publications and Presentations

Herbivory is a major fitness pressure for plants and a key driver of crop losses in agroecosystems. Dense monocultures are expected to favor specialist herbivorous insects, particularly those who primarily consume crop species; yet, levels and types of herbivory are not uniform within regional cropping systems. It is essential to determine which local and regional ecological factors drive variation in herbivory in order to support functional agroecosystems that rely less on chemical inputs. Crops in the genus Cucurbita host a suite of both generalist and specialist herbivores that inflict significant damage, yet little is known about the relative contribution of …

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Remote, Rugged Field Scenarios For Archaeology And The Field Sciences: Object Avoidance And 3d Flight Planning With Suas Photogrammetry, Carla Klehm, Malcolm D. Williamson, Leland C. Bement, Brandi Bethke Apr 2024

Remote, Rugged Field Scenarios For Archaeology And The Field Sciences: Object Avoidance And 3d Flight Planning With Suas Photogrammetry, Carla Klehm, Malcolm D. Williamson, Leland C. Bement, Brandi Bethke

Center for Advanced Spatial Technologies Publications and Presentations

Advances built into recent sUASs (drones) offer a compelling possibility for field-based data collection in logistically challenging and GPS-denied environments. sUASs-based photogrammetry generates 3D models of features and landscapes, used extensively in archaeology as well as other field sciences. Until recently, navigation has been limited by the expertise of the pilot, as objects, like trees, and vertical or complex environments, such as cliffs, create significant risks to successful documentation. This article assesses sUASs’ capability for autonomous obstacle avoidance and 3D flight planning using data collection scenarios carried out in Black Mesa, Oklahoma. Imagery processed using commercial software confirmed that the …

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Modeling Apparent Pb Loss In Zircon U-Pb Geochronology, Glenn R. Sharman, Matthew A. Malkowski Jan 2024

Modeling Apparent Pb Loss In Zircon U-Pb Geochronology, Glenn R. Sharman, Matthew A. Malkowski

Geosciences Faculty Publications and Presentations

The loss of radiogenic Pb from zircon is known to be a major factor that can cause inaccuracy in the U–Pb geochronological system; hence, there is a need to better characterize the distribution of Pb loss in natural samples. Treatment of zircon by chemical abrasion (CA) has become standard practice in isotope dilution–thermal ionization mass spectrometry (ID-TIMS), but CA is much less commonly employed prior to in situ analysis via laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) or secondary ionization mass spectrometry (SIMS). Differentiating the effects of low levels of Pb loss in Phanerozoic zircon with relatively low-precision in situ U–Pb …

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Observational Uncertainty For Global Drought-Pluvial Volatility, Yichan Li, Linyin Cheng, Chiyuan Miao, Zhiyong Liu Dec 2023

Observational Uncertainty For Global Drought-Pluvial Volatility, Yichan Li, Linyin Cheng, Chiyuan Miao, Zhiyong Liu

Geosciences Faculty Publications and Presentations

Droughts and pluvials have occurred in most regions in the past. However, what calls growing attention is the additive effects of these two opposite extreme events occurring in spatial-temporal proximity to one another, sometimes beyond either of the hazards individually. This study examines the likelihood of global drought-pluvial volatility which involves both meteorological drought-to-pluvial (DTP) and pluvial-to-meteorological drought transitions; meanwhile, identifies discrepancies and agreements among the widely used observations for such events, an aspect that remains currently overlooked. Globally, we find that the observation-based data sets including Global Precipitation Climatology Center (GPCC), Climate Research Unit (CRU) and ERA5 reach a …

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Shallow Groundwater Distributions And Changes With Sea Level Rise In Seattle, Washington, Taylor L. Watson Dec 2023

Shallow Groundwater Distributions And Changes With Sea Level Rise In Seattle, Washington, Taylor L. Watson

Graduate Theses and Dissertations

Sea level rise (SLR) associated hazards, such as coastal flooding and erosion, are pressing issues of great concern for coastal communities across the globe. Shallow and emergent groundwater can contribute to groundwater hazards such as flooding, landslides, or damage to shallow infrastructure. This study investigates the shallow groundwater within Seattle, Washington, and projects how it will respond to SLR using interpolation and numerical groundwater modeling methods. Then, a geologic modeling method is presented as a preliminary investigation of heterogeneity and anisotropy within the aquifer system. In the results for the present-day interpolation, ~6 % of the coastal buffer –the total …

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Geochemistry Of Metal-Rich Black Shales And Their Genetic Relationship To Mississippi Valley-Type Pb-Zn Ore Deposits, Midcontinent U.S., Noah S. Morris Dec 2023

Geochemistry Of Metal-Rich Black Shales And Their Genetic Relationship To Mississippi Valley-Type Pb-Zn Ore Deposits, Midcontinent U.S., Noah S. Morris

Graduate Theses and Dissertations

The formation of Mississippi Valley-type (MVT) lead-zinc (Pb-Zn) ores is complex, involving an interaction of tectonic compression, hydrothermal fluid migration, and geochemical processes within the subsurface. Fundamental questions regarding this interaction remain unclear, including the source(s) of the Pb and Zn ions that make up the ores. A genetic link between black shales and MVT ores has been thought to exist because of (1) the presence of mature hydrocarbon and brine fluid inclusions within many MVT ores, (2) the association of the hydrothermal fluids that are linked to MVT ore formation with organic compounds and oil-like droplets, and (3) the …

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Modeling The Peak Ground Acceleration And Assessing The Economic Loss And Casualty Due To Potential Earthquakes Of Various Magnitudes In The New Madrid Seismic Zone, Mahmud Afroz Dec 2023

Modeling The Peak Ground Acceleration And Assessing The Economic Loss And Casualty Due To Potential Earthquakes Of Various Magnitudes In The New Madrid Seismic Zone, Mahmud Afroz

Graduate Theses and Dissertations

The New Madrid Seismic Zone (NMSZ) is one of the active tectonic zones capable of producing big earthquakes in the southcentral USA. The objective of this study was to assess the economic losses and casualties that might be caused by various magnitudes of seismic events in the NMSZ. The manifestation is the estimation for each magnitude which is using the Peak Ground Acceleration (PGA) that might occur during an earthquake. It is calculated using an attenuation function that correlates the intensity of local ground movement, the earthquake magnitude, and the distance from its epicenter. The assessment of casualties was conducted …

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Geospatial Analysis Of Weathering And Recession On Architectural Limestone At The 1891 Powerhouse/Icehouse In Eureka Springs, Arkansas, Stuart Bruce Wright Dec 2023

Geospatial Analysis Of Weathering And Recession On Architectural Limestone At The 1891 Powerhouse/Icehouse In Eureka Springs, Arkansas, Stuart Bruce Wright

Graduate Theses and Dissertations

The objective of this study of the architectural limestone of the 1891 Powerhouse/Icehouse in Eureka Springs, Arkansas was to analyze the environmental factors that influenced the deterioration and surface recession of this historical stone structure. The focus of this research was to examine and establish a baseline study that may assist in future monitoring and documentation of this historic limestone structure on stone weathering. A replicable methodology was specifically created toward this baseline research in hopes that it represented a solid baseline study. Observations and data analyses revealed the relationship between the architectural limestone building structure and the dominating recession …

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Tree-Ring Reconstruction Of Ouachita River Streamflow, Keaton Cade Jenkins-Joyce Dec 2023

Tree-Ring Reconstruction Of Ouachita River Streamflow, Keaton Cade Jenkins-Joyce

Graduate Theses and Dissertations

The Ouachita River drains the Ouachita Mountains and Upper Coastal Plain in Arkansas and Louisiana. The Ouachita River is used for navigation, power generation, recreation, water supply, and wastewater treatment. The river has been prone to low flows during drought and extreme flooding, which were principal justifications for the construction of three large multipurpose dams on the stream. It is likely that the use of the Ouachita River will be stressed by future population growth, economic expansion, and climate change. For this study, tree-ring chronologies from various locations in and near the Ouachita River drainage basin were used to reconstruct …

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Maximum Depositional Age Analysis Using Paired La-Icp-Ms And Ca-Id-Tims Detrital Zircon U-Pb Geochronology, Benjamin L. Howard Dec 2023

Maximum Depositional Age Analysis Using Paired La-Icp-Ms And Ca-Id-Tims Detrital Zircon U-Pb Geochronology, Benjamin L. Howard

Graduate Theses and Dissertations

The “law of detrital zircons” states that a sedimentary unit cannot be older than its youngest detrital zircon. The youngest U-Pb date(s) from detrital zircon may thus be used to infer a given sedimentary deposit’s maximum depositional age (MDA). MDAs may be calculated in various ways using dates from zircon U-Pb geochronology. Common dating methods used for U-Pb geochronology are laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS), a low- and high-resolution instrument type, respectively. Chapter 2 will systematically compare paired LA-ICP-MS and CA-ID-TIMS dates from the same zircon grains to assess the agreement …

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Observed And Modeled Moulin Heads In The Pâkitsoq Region Of Greenland Suggest Subglacial Channel Network Effects, Celia Trunz, Kristin Poinar, Lauren C. Andrews, Matthew D. Covington, Jessica Mejia, Jason Gulley, Victoria Siegel Nov 2023

Observed And Modeled Moulin Heads In The Pâkitsoq Region Of Greenland Suggest Subglacial Channel Network Effects, Celia Trunz, Kristin Poinar, Lauren C. Andrews, Matthew D. Covington, Jessica Mejia, Jason Gulley, Victoria Siegel

Geosciences Faculty Publications and Presentations

In the ablation zone of land-terminating areas of the Greenland Ice Sheet, water pressures at the bed control seasonal and daily ice motion variability. During the melt season, large amounts of surface meltwater access the bed through moulins, which sustain an efficient channelized subglacial system. Water pressure within these subglacial channels can be inferred by measuring the hydraulic head within moulins. However, moulin head data are rare, and subglacial hydrology models that simulate water pressure fluctuations require water storage in moulins or subglacial channels. Neither the volume nor the location of such water storage is currently well constrained. Here, we …

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Carbon Isotope Chemostratigraphy, Geochemistry, And Biostratigraphy Of The Paleocene–Eocene Thermal Maximum, Deepwater Wilcox Group, Gulf Of Mexico (Usa), Glenn R. Sharman, Eugene Szymanski, Rebecca A. Hackworth, Alicia C.M. Kahn, Lawrence A. Febo, Jordan Oefinger, Gunnar M. Gregory Sep 2023

Carbon Isotope Chemostratigraphy, Geochemistry, And Biostratigraphy Of The Paleocene–Eocene Thermal Maximum, Deepwater Wilcox Group, Gulf Of Mexico (Usa), Glenn R. Sharman, Eugene Szymanski, Rebecca A. Hackworth, Alicia C.M. Kahn, Lawrence A. Febo, Jordan Oefinger, Gunnar M. Gregory

Geosciences Faculty Publications and Presentations

The Paleocene–Eocene Thermal Maximum (PETM) represents the most pronounced hyperthermal of the Cenozoic era and is hypothesized to have resulted in an intensification of the paleohydrologic cycle, including enhanced seasonality and increased sediment discharge to the coastal ocean. Although the PETM has been widely documented, there are few records from deposits that form the distal, deepwater components of large sediment-routing systems. This study presents new constraints on the stratigraphic placement of the PETM in the deepwater Gulf of Mexico basin through analysis of geochemical, carbon isotopic, and biostratigraphic data within a ∼124 m cored interval of the Wilcox Group. Biostratigraphic …

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Constraining High Temperature Deformation And Metamorphism In The Southern Wet Mountains, Colorado, Usa: Implications For The Regional Extent Of The Picuris Orogeny, Sarah Morse Aug 2023

Constraining High Temperature Deformation And Metamorphism In The Southern Wet Mountains, Colorado, Usa: Implications For The Regional Extent Of The Picuris Orogeny, Sarah Morse

Graduate Theses and Dissertations

The Wet Mountains of Colorado are underlain by exhumed Proterozoic metamorphic rock that lies north of the recently identified 1.46 to 1.40 Ga Picuris orogen in northern New Mexico. The Picuris orogen is inferred to have formed in response to a Mesoproterozoic (ca. 1.49-1.40 Ga) contractional to transpressional event extrapolated to be regional in extent. It has been proposed that the Picuris orogen composes the westernmost tectonic segment of the Pinware-Baraboo-Picuris orogen that formed along an evolving convergent margin that becomes younger from northeast to southwest. This study is focused on the record of high temperature deformation, metamorphism, and plutonism …

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Chemostratigraphic And Paleoclimatic Studies Of Cloverly Formation, Northern Wyoming, U.S.A, Queen Amarachi Kalu Aug 2023

Chemostratigraphic And Paleoclimatic Studies Of Cloverly Formation, Northern Wyoming, U.S.A, Queen Amarachi Kalu

Graduate Theses and Dissertations

The Early – Late Cretaceous transition in Western North America recorded a period of rapid climatic and tectonic change in Earth’s history. Major climate events associated with large igneous province eruptions caused several instances of ocean anoxic events (OAE) and perturbations to the global carbon (C) – cycle. These perturbations to the global C-cycle are observed in the bulk organic C record of both marine and terrestrial deposits and can be used to correlate units across major depositional basins. Major efforts are being made to generate time-constrained palaeontologic and paleoclimate information from the North American Cordilleran foreland basin and C-isotope …

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Englacial Drainage Drives Positive Feedback Depression Growth On The Debris-Covered Ngozumpa Glacier, Nepal, R. M. Strickland, M. D. Covington, J. D. Gulley, R. B. Kayastha, J. M. Blackstock Aug 2023

Englacial Drainage Drives Positive Feedback Depression Growth On The Debris-Covered Ngozumpa Glacier, Nepal, R. M. Strickland, M. D. Covington, J. D. Gulley, R. B. Kayastha, J. M. Blackstock

Geosciences Faculty Publications and Presentations

The development of hummocky topography is a poorly understood aspect of down-wasting on debris-covered glaciers that is often attributed to variable debris thickness. Thousands of enclosed depressions pit the hummocky topography. To better understand depression growth, we examined the size distribution and geometry of depressions on the Ngozumpa Glacier, in the Everest Region of Nepal. The depressions exhibited a power-law size distribution, fractal perimeters, and power-law depth-area scaling, which suggest positive feedback growth. With a simple model, we showed that positive feedback growth produces similar power-law size distributions. Based on these findings, we propose a “sinkhole” hypothesis for the development …

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Hurricane Impacts On Land In The Central And Eastern Caribbean Since 1494 Ce From Written Records, Michael Chenoweth, Ian Howard Jul 2023

Hurricane Impacts On Land In The Central And Eastern Caribbean Since 1494 Ce From Written Records, Michael Chenoweth, Ian Howard

Geosciences Faculty Publications and Presentations

Written accounts of hurricanes and their impacts in the Caribbean region date back to 1494 CE We report a new compilation of hurricanes in the longest settled regions of the central and eastern Caribbean region (CECR) that is the most complete yet produced and present basic statistics. We assess likely undercounts of hurricanes due to incomplete documentary records in the earliest part of the record by using the most complete reporting from Puerto Rico relative to the remainder of the CECR. We compare our results with other documentary and proxy data from the region and demonstrate using wavelet analysis significant …

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Forecasting Sea Level Rise-Driven Inundation In Diked And Tidally Restricted Coastal Lowlands, K. M. Befus, A. P.D. Kurnizki, K. D. Kroeger, M. J. Eagle, T. P. Smith Jul 2023

Forecasting Sea Level Rise-Driven Inundation In Diked And Tidally Restricted Coastal Lowlands, K. M. Befus, A. P.D. Kurnizki, K. D. Kroeger, M. J. Eagle, T. P. Smith

Geosciences Faculty Publications and Presentations

Diked and drained coastal lowlands rely on hydraulic and protective infrastructure that may not function as designed in areas with relative sea-level rise. The slow and incremental loss of the hydraulic conditions required for a well-drained system make it difficult to identify if and when the flow structures no longer discharge enough water, especially in tidal settings where two-way flows occur through the dike. We developed and applied a hydraulic mass-balance model to quantify how water levels in the diked and tidally restricted coastal wetlands and water bodies dynamically respond to sea-level rise, specifically applied to the Herring River Estuary …

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Diverged Landscape Of Restaurant Recovery From The Covid-19 Pandemic In The United States, Siqin Wang, Xiao Huang, Bing She, Zhenlong Li Jun 2023

Diverged Landscape Of Restaurant Recovery From The Covid-19 Pandemic In The United States, Siqin Wang, Xiao Huang, Bing She, Zhenlong Li

Geosciences Faculty Publications and Presentations

The COVID-19 pandemic has imposed catastrophic impacts on the restaurant industry as a crucial socioeconomic sector that contributes to the global economy. However, the understanding of how the restaurant industry was recovered from COVID-19 remains underexplored. This study constructs a spatially explicit evaluation of the effect of COVID-19 on the restaurant industry in the US, drawing on the attributes of +200,000 restaurants from Yelp and +600 million individual-level restaurant visitations provided by SafeGraph from 1st January 2019 to 31st December 2021. We produce quantitative evidence of lost restaurant visitations and revenue amid the pandemic, the changes in the customers’ origins, …

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Evaluating Snow And Ice Cover In Tierra Del Fuego, Argentina, Zoe Pitman May 2023

Evaluating Snow And Ice Cover In Tierra Del Fuego, Argentina, Zoe Pitman

Geosciences Undergraduate Honors Theses

Evaluating changes in snow and ice cover is an important field for studying climate change and its impacts. This evaluation is commonly done using remote sensing because of its ability to evaluate large areas. The purpose of this study is to determine the reliability of one remote sensing technology, the Moderate Resolution Imaging Spectroradiometer (MODIS), by comparing it to in-situ snow and climate data from the weather station at the Austral Center for Scientific Research (CADIC). Data was converted from daily to monthly averages and was sorted into a series of graphs to compare the two data sets. Correlations were …

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An Age, Size, And Climate Response Study Of Old Growth Shortleaf Pine In The Mccurtain County Wilderness Area, Oklahoma, Nicholas Cancalosi-Dean May 2023

An Age, Size, And Climate Response Study Of Old Growth Shortleaf Pine In The Mccurtain County Wilderness Area, Oklahoma, Nicholas Cancalosi-Dean

Graduate Theses and Dissertations

Increment cores were extracted from 483 trees distributed over 21 semi-randomly sampled 0.1-hectare plots on three distinct landscape positions in the McCurtain County Wilderness Area (MCWA), a 57 square kilometer tract of uncut shortleaf pine in southeastern Oklahoma. Forty additional cores were taken off plot from older-appearing trees. All sampled trees were shortleaf pine (Pinus echinata) with a diameter at breast height (DBH) of at least 10 cm. Hardwoods were not included in the size and age analyses. The study site chosen for the sampling was made up of four parallel east-west trending ridges near North Linson Creek, making up …

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The Use And Challenges Of Spatial Data In Archaeology, Carla Klehm Feb 2023

The Use And Challenges Of Spatial Data In Archaeology, Carla Klehm

Anthropology Faculty Publications and Presentations

Spatial data, under the broader umbrella of digital data, is becoming increasingly integral to all stages of archaeological research design and dissemination. As archaeologists lean toward reuse and interoperability, with ethics on their minds, how to treat spatial data is of particular importance. This is because of the complexities involved at every life-cycle stage, from collection to publication, including black box issues that may be taken for granted, and because the size of spatial data can lead to archiving difficulties. Here, the “DIY” momentum of increasingly accessible spatial methods such as photogrammetry and handheld lidar is examined alongside forthcoming changes …

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Carbonates In The Critical Zone, M. D. Covington, J. B. Martin, L. E. Toran, J. L. Macalady, N. Sekhon, P. L. Sullivan, Á. A. García Jr., J. B. Heffernan, W. D. Graham Jan 2023

Carbonates In The Critical Zone, M. D. Covington, J. B. Martin, L. E. Toran, J. L. Macalady, N. Sekhon, P. L. Sullivan, Á. A. García Jr., J. B. Heffernan, W. D. Graham

Geosciences Faculty Publications and Presentations

Earth's Critical Zone (CZ), the near-surface layer where rock is weathered and landscapes co-evolve with life, is profoundly influenced by the type of underlying bedrock. Previous studies employing the CZ framework have focused primarily on landscapes dominated by silicate rocks. However, carbonate rocks crop out on approximately 15% of Earth's ice-free continental surface and provide important water resources and ecosystem services to ∼1.2 billion people. Unlike silicates, carbonate minerals weather congruently and have high solubilities and rapid dissolution kinetics, enabling the development of large, interconnected pore spaces and preferential flow paths that restructure the CZ. Here we review the state …

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Flood Hazard And Risk Analyses In The Republic Of Panama: A Case Study From The Juan Diaz River Watershed In Panama City, Virgilio De Jesus Quintero Dec 2022

Flood Hazard And Risk Analyses In The Republic Of Panama: A Case Study From The Juan Diaz River Watershed In Panama City, Virgilio De Jesus Quintero

Graduate Theses and Dissertations

Flooding is the natural hazard with most occurrences in Panama. Its frequency and magnitude have increased over the years. This dissertation analyzes Panama’s flood activity in order to better understand flood hazards, the current evolution of Panamanian perceptions of flood risk, and the incorporation of indigenous knowledge used to mitigate flood hazards. The first chapter developed a baseline of past and current flood inventory in Panama, which required the use of flood historical data, thematic cartography, and Geographic Information Science (GIS). This chapter shows Panama has experienced floods in varying degrees. Through the spatial and temporal distribution of floods from …

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Orbital Mapping Of Seasonal And Yearly Changes In Co2 And Water Ice On The Southern Polar Cap Of Mars, Victoria Michell Ann Karnes Dec 2022

Orbital Mapping Of Seasonal And Yearly Changes In Co2 And Water Ice On The Southern Polar Cap Of Mars, Victoria Michell Ann Karnes

Graduate Theses and Dissertations

This research exhibits a new foundation for the rates of change in CO2 and water ice on the southern polar cap of Mars, where the annual precipitation cycles are known to fluctuate seasonally between the north and south pole, based on observations from the Compact Reconnaissance Imaging Spectrometer (CRISM). The conventional belief is that both CO2 ice and water ice on the southern polar cap condenses and evaporates over the course of a Martian year (MY), condensing during the Martian spring and summer and evaporating during the Martian fall and winter. With this theory in mind, CO2 and water ice …

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Evaluation Of Carbon Isotopic Chemostratigraphy Of The Cedar Mountain Formation Of Utah, Clayton Forster Aug 2022

Evaluation Of Carbon Isotopic Chemostratigraphy Of The Cedar Mountain Formation Of Utah, Clayton Forster

Graduate Theses and Dissertations

The Lower Cretaceous rocks of Utah preserve the origin of a multitude of dinosaur taxa, spread of angiosperms on the North American continent, and evolution of marsupial and eutherian mammals. However, the timing of deposition of these rocks is not well understood and must be determined to understand climatic controls on these biological events. Estimates of the age of the Cedar Mountain Formation and its constituent members range from Late Jurassic to early Late Cretaceous. Understanding the timing of deposition of the Cedar Mountain Formation is critical to dinosaurian and associated taxa studies as well as paleoclimate reconstructions from within …

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Examining The Expression Patterns Of Desulfotalea Psychrophila Dsrab Operon And Pit At Subfreezing Temperatures And Different Concentrations Of Sulfate Salts As A Model For Mars And Icy Worlds Survival And Colonization, Sergio Luis Mosquera Mora Aug 2022

Examining The Expression Patterns Of Desulfotalea Psychrophila Dsrab Operon And Pit At Subfreezing Temperatures And Different Concentrations Of Sulfate Salts As A Model For Mars And Icy Worlds Survival And Colonization, Sergio Luis Mosquera Mora

Graduate Theses and Dissertations

Since ancient times, Humanity has been fascinated with the idea of what lies beyond the borders of our planet. Fortunately, the combined efforts of many nations have made it possible to send unmanned spacecraft to orbit planets located close to Earth. These missions have the principal goal to collect data that could help us understand the basic environmental conditions that persist on those planets, or for evidence of past or present life. Equally important, landers and rovers have been successfully deployed to start the in-situ exploration of many planets of the Solar System. Among them, Mars has been extensively studied …

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Structural Interpretation Of An Alkaline-Carbonatite Complex Using Gravity And Magnetic Methods At Magnet Cove, Arkansas, Chelsea Morgan Amaral Aug 2022

Structural Interpretation Of An Alkaline-Carbonatite Complex Using Gravity And Magnetic Methods At Magnet Cove, Arkansas, Chelsea Morgan Amaral

Graduate Theses and Dissertations

The Magnet Cove alkaline-carbonatite complex in the Ouachita Mountains of south-central Arkansas could be a valuable resource for rare earth elements, though it has not yet been thoroughly studied using geophysical methods, and existing geophysical models simplify its diverse nature. Prior to this study, the subsurface structure and extent of the Magnet Cove complex was poorly understood and, in general, the process of emplacement of alkaline carbonatite complexes worldwide is also not fully understood. The Magnet Cove complex hosts an extensive variety of rare rock types and mineral resources that contrast significantly to the sedimentary rocks into which they have …

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Understanding Martian Salts And Their Implications For Liquid Water, Rachel Slank Aug 2022

Understanding Martian Salts And Their Implications For Liquid Water, Rachel Slank

Graduate Theses and Dissertations

Water is one of the key components for life as we know it. The existence of salts on Mars has been a large contributing factor to the possibility of habitability, due to their ability to allow liquid water to remain stable at colder temperatures. Salts, including perchlorates, chlorates, and chlorides, have been detected by multiple landers, rovers, and orbiters, and are now believed to be ubiquitous on Mars. One of the pathways to liquid brine solutions is through deliquescence. Deliquescence is the transition from a solid salt crystal into an aqueous solution when exposed to a humid atmosphere. This research …

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Machine Learning Applied To A Modern-Pleistocene Petrographic Data Set: The Global Prediction Of Sand Modal Composition (Gloprsm) Model, J. Isaac Johnson, Glenn R. Sharman, Eugene Szymanski, Xiao Huang Jun 2022

Machine Learning Applied To A Modern-Pleistocene Petrographic Data Set: The Global Prediction Of Sand Modal Composition (Gloprsm) Model, J. Isaac Johnson, Glenn R. Sharman, Eugene Szymanski, Xiao Huang

Geosciences Faculty Publications and Presentations

Petrography has long been used as a tool to decipher the sedimentary provenance of sand and sandstone based on relative proportions of detrital grain types. However, there is not yet a predictive framework that constrains the relationship between sand grain composition and the factors that influence it, including bedrock lithology, elevation, slope, basin area, precipitation, and temperature. We used a globally extensive modal point-count data set of 3,522 Pleistocene to modern sand samples to train an inline series of random forest meta-estimators to predict relative abundances of quartz (Q), feldspar (F), and lithic (L) grain types and eight subcompositions. The …

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A Geochemical And Mineralogical Evaluation Of The Mona Lisa Turquoise Mine, Polk County, Arkansas, Alexander Arai Goodsuhm May 2022

A Geochemical And Mineralogical Evaluation Of The Mona Lisa Turquoise Mine, Polk County, Arkansas, Alexander Arai Goodsuhm

Graduate Theses and Dissertations

The presence of turquoise in Arkansas has long been disputed by geologists and gem collectors. Despite the prevalence of other phosphate minerals in Arkansas, such as planerite, wavellite, and variscite, the absence of an obvious copper (Cu) source required for turquoise formation was considered too great of an obstacle for turquoise mineralization. In this study, geologic, mineralogical, and geochemical techniques provide overwhelming evidence that the novaculite-hosted Mona Lisa Mine in Arkansas does produce turquoise. X-ray diffraction and Raman spectroscopy have confirmed the structural nature of the material and identified other phosphate minerals, such as crandallite, often found in assemblage with …

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