Geology Commons^™

Tales In The Teeth: Using Isotopic Analysis To Understand The Paleoecology And Social Behavior Of Brontotheres Of The Intermountain Basins During The Middle Eocene, John Michael Michalski

All Graduate Reports and Creative Projects, Fall 2023 to Present

Isotopic analysis has been a common practice used in paleontology to study ancient ecosystems, and the lives of animals therein. Oxygen isotopic analysis is of particular importance not only because of its use in studying paleoecology, diet, and migration, but also its use in studying mountain elevation, and its impact on ancient ecosystems. I use stable oxygen isotopic analysis to study the habits and ecology of brontotheres from intermountain basins surrounding the Uinta Mountains of Utah and Wyoming, USA. I studied the oxygen isotopes from 16 fossil specimens of teeth, most of which belonged to brontotheres, including the genera Palaeosyops …

Exploring Overbank Sediment Deposition Variation In Heavily Modified Floodplains Of The Lower Mississippi River: A Sedimentological And Geophysical Analysis, Seth Fradella

Master's Theses

Since the 1930s, the Lower Mississippi River (LMR) has experienced large-scale modifications to the channel profile and surrounding floodplains through dams, dikes, revetments, dredging, and channel cutoffs. Although these changes have improved navigation and reduced flood risk, unanticipated changes to the major flood return period, individual flood severity and duration, and sediment regime have become increasingly apparent and sometimes problematic, such as the 2011 and 2018-2020 floods. Flood control levees along the LMR have reduced the natural floodplain area by 70-90%, resulting in heavily restricted overbank storage capacity of water and sediment. For the same flood events in recent history, …

Accretion Of Warm Chondrules In Weakly Metamorphosed Ordinary Chondrites And Their Subsequent Reprocessing, Alex M. Ruzicka, Richard C. Hugo, Jon M. Friedrich, Michael T. Ream

Geology Faculty Publications and Presentations

To better understand chondrite accretion and subsequent processes, the textures, crystallography, deformation, and compositions of some chondrite constituents in ten lithologies of different cluster texture strength were studied in seven weakly metamorphosed (Type 3) and variably shocked ordinary chondrites (Ragland—LL3 S1, Tieschitz—H/L3 S1, NWA 5421—LL3 S2, NWA 5205—LL3 S2, NWA 11905—LL3-5 S3, NWA 5781—LL3 S3, NWA 11351—LL3-6 S4) using optical and electron microscopy and microtomography techniques.

Results support a four-stage model for chondrite formation. This includes 1) limited annealing following collisions during chondrule crystallization and rapid cooling in space prior to accretion, as evidenced by olivine microstructures consistent with dislocation …

Characterizing Groundwater Flow Across The Barrier Island-High Marsh Interface, Dean Michael Wrobel

Electronic Theses and Dissertations

The freshwater resources of barrier islands are influenced by a variety of hydrogeologic factors, which create unique regions of groundwater composition. Factors including evapotranspiration, geologic constraints, tidal forcing, and meteoric inputs influence subterranean flow creating a groundwater salinity gradient throughout the island-marsh setting which directly influences the spatial distribution of dominant vegetation on the island. Rising sea levels and variation in local climate may alter the hydrologic balance on barrier islands, potentially shifting salinity gradients and ecological baselines on short timescales. The intrusion of saltwater into the barrier island freshwater system could result in the shifting of ecotones and potential …

Exploring Intraplate Seismicity In The Midwest, Alexa Fernández

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Intraplate seismicity represents a notable occurrence within the stable North American Craton. This research explores the potential sources of stresses that could reactivate older faults and influence seismic activity within this region. Among these sources, the enduring impact of the last glacial period is considered, which includes continued glacial isostatic adjustments (GIA). During GIA the lithosphere rebounds due to the retreating ice, and the forebulge caused by far-field flexure in response to the glacial load, collapses. This results in significant faulting, fracturing, and seismic activity associated with the deglaciation phase. The adjustment of the lithosphere manifests as both near surface …

Sensitivity Of Present And Future Seasonal Precipitation Over Central United States To The Representation Of Rocky Mountain Topography, Ranasinghe Disanayakalage Sherly Shelton Ranathunga

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Precipitation change across the Central United States (USA) is of great interest to the research community. Studies using global climate simulations suggest that the “100^th-Meridian”, which separates the “dry west” from the “moist east” will shift to the east as the climate responds to future emissions pathways. However, these simulations are run at relatively coarse resolutions, which do not accurately represent topography. Here, we perform regional simulations using the Weather Research and Forecasting (WRF) model to explore the sensitivity of present and future precipitation patterns across the central USA to the representation of the Rocky Mountains (RM). We …

Upscaling Sapflow Measurements To Footprint Transpiration Estimations In The Jornada Experimental Range, New Mexico, Usa, Habibur R. Howlider

Open Access Theses & Dissertations

This study proposes a new method for computing transpiration across an eddy covariance footprint using field observations of plant sap flow, phytomorphology sampling, uncrewed aerial system (UAS) digital image processing, and eddy covariance micrometeorological measurements. The method is applied to the Jornada Experimental Range, New Mexico where we address three key questions: (1) How do daily summer transpiration rates of Mesquite (Prosopis glandulosa) and Creosote (Larrea tridentate) individuals of different ages compare? (2) How can the contributions of plants of varying sizes and ages be integrated for terrain-wide transpiration estimates? (3) What is the contribution of transpiration to total evapotranspiration …

Investigating Styles Of Contraction And Overprinting By Rio Grande Rift Extension In The Southern Indio Mountains, Western Texas, David W. West

Open Access Theses & Dissertations

Laramide-style intracontinental deformation occurred throughout a large area in the western United States from the late Cretaceous through the Eocene. This event is largely investigated and viewed from classic exposures in Colorado and Wyoming, extending south to southern New Mexico. In this region the Laramide orogen merges with the Mexican fold and thrust belt (MFTB) and the northern limits of the Mexican orogen along a blurry boundary. In the Indio Mountain range in western Texas, Cretaceous sediments were deposited in the Jurassic-Cretaceous Chihuahua trough. They were inverted due to contraction and emplaced adjacent to the Diablo Plateau. This region lies …

Staying Fresh: Unconventional Approaches Towards Advancing Energy Sustainability, Water Resources, And Community Resiliency In The Southwestern United States, Judith Hoyt

Open Access Theses & Dissertations

This dissertation addresses critical challenges in urban heat management, sustainable energy resource utilization, and water quality communication through three studies. Study 1 investigates the impact of roof color on urban heat islands in Tucson, Arizona where approximately 70% of roofs display high albedo (i.e., light) colors. Energy consumption simulations conducted indicate that converting dark- to light-colored roofs could save Tucson approximately $1,400,000 annually in energy costs, highlighting the potential of cool roofs for energy savings and improved thermal comfort. Study 2 assesses the sources of lithium in subsurface waters in West Texas and South Central New Mexico. Water chemistry data …

Shedding Light On Past Ice-Free Intervals In Northwest Greenland: Luminescence Dating Of The Base Of The Camp Century Ice Core, Hawke Woznick

All Graduate Theses and Dissertations, Fall 2023 to Present

The goal of this thesis is to provide greater resolution on the age and character of the subglacial sediment recovered from the base of the Camp Century ice core, northwestern Greenland. Geochemical analysis indicated that the upper sub-ice sediments were geochemically different and experienced greater weathering than the basal unit underlying a one-meter silty ice lens. Analysis of feldspars within the very fine sand fraction indicates they are dominated by potassium feldspar. Sediment was dated using luminescence, which provides an age for the last time sediment was exposed to light. Luminescence analysis returned ages around 420 thousand years old, which …

Rock Wall Fracturing As A Potential Control On River Valley Width In The Buffalo National River, Arkansas, Kindle Hon

Graduate Theses and Dissertations

Quantifying bedrock properties that control the persistence of fallen rock material (talus) along bedrock walls bounding river valleys may be a key factor in understanding what controls the rate at which these river valleys widen. My work is a component of a collaborative research project focused on the overarching hypothesis that the persistence vs. erodibility of talus that buffers river valley walls can be a first-order control on valley widening rates. I hypothesize that the primary control for creating erodible or persistent talus is the fracture spacing of bedrock valley walls as it sets the maximum block size of collapsed …

Environments And Controls Of Erosional Bedforms In Soluble Channels, Ethan W. Oleson

Graduate Theses and Dissertations

Erosional bedforms, such as scallops, preserve valuable information on the paleohydrologic conditions forming soluble channels in karst systems. While these bedforms are commonly used to interpret past conditions, questions about their formation remain. Mathematical models of speleogenesis in turbulent flow predict that the conditions for forming scallops do not occur in natural carbonate systems. However, scallops are readily found in caves throughout the world. This conundrum has several possible resolutions, but each lacks field-based observations. We present a field-based study of the environments and controls of scallops in gypsum, limestone, and dolostone caves. Our results are based on field observation, …

Shaking Off The Rust: Unraveling The Depositional And Diagenetic History Of Enigmatic Ferroan Dolostones In The Cambrian Bright Angel Formation, Tonto Group, Grand Canyon, Joseph J. Clevenger

All Graduate Theses and Dissertations, Fall 2023 to Present

Within the siliciclastic-sediment-dominated Bright Angel Formation (BAF) of the iconic Cambrian sedimentary strata (Tonto Group) in Grand Canyon National Park, Arizona, workers have identified and named prominent reddish-brown cliffs breaking up the generally slope-forming unit near, but separated from, its upper contact with the limestone-dominated Muav Formation, the "Rusty Brown Dolostones" (RBDs). Previous hypotheses suggest that the RBDs are chemically and physically altered tongues of the Muav Formation intercalated with the BAF at increasingly higher stratigraphic positions from west to east within the Canyon. A genetic association between the Muav Formation and the RBDs, as well as between the RBDs …

New Insights Into The Diverse Intraplate Volcanism Present Within The Howland And Baker Island United States Exclusive Economic Zone, Nicholas Foresta

UNLV Theses, Dissertations, Professional Papers, and Capstones

The origin of oceanic volcanism has been attributed to various mechanisms, such as upwelling mantle plumes, lithospheric extension driven decompression melting, and small-scale convective cells in the asthenosphere. Discovering the range of magmatic drivers present in the ocean basins aids in understanding mantle geodynamics and tectonic processes. A recent seafloor exploration campaign within the Howland and Baker Island (HBI) U.S. Exclusive Economic Zone (EEZ; approximately near the equator and the International Date Line) resulted in the collection of multiple lava flow samples, which offer valuable insights into the complex origins and dynamics of intraplate seamounts. According to current absolute plate …

Phylogenetic And Biogeographic Patterns Of Devonian Proetid Trilobites, Katherine Jane Jordan

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Ecological disruption events such as mass extinctions can result in the permanent alteration in clades and ecosystems. A pivotal time of change during the history of life on Earth can be seen in the Devonian Period. During this time, major transitions in marine and terrestrial system resulted in a different world at the end of the period in comparison to the beginning. One such group most heavily impacted were trilobites. Trilobites were reduced to one order by the end of the Devonian: Proetida. My dissertation focuses on phylogenetic, biogeographic, and paleocommunity patterns of this group, known as the last of …

Dynamics Of Climate And Tectonics On Surface Processes And Their Sedimentary Archives In The Colorado Plateau And Basin And Range, Usa And The Calabrian Forearc, Sicily, Natalie M. Tanski

All Graduate Theses and Dissertations, Fall 2023 to Present

Landscapes change over time in response to movements of the Earth’s crust and the effects of climate. This dissertation examines how these factors shape different landscapes, focusing on erosion of river canyons in elevated plateaus, how the transport history in quartz sand may be encoded in its properties, and how a paleo-delta has formed in response to sea-level change and fault displacement. I use dating techniques, field methods, and topographic analyses to offer insight into erosional patterns and rates in different landscapes.

Rivers can take a long time to adjust to changes in boundary conditions, even after those changes have …

Hydrogen Stable Isotope Constraints On Hydration Of Colorado Plateau Lower Crust From Oligocene-Miocene Navajo Volcanic Field Xenoliths, Shelby Dianne Litton

All Graduate Theses and Dissertations, Fall 2023 to Present

Understanding flat-slab subduction is crucial as it involves the horizontal movement of an oceanic plate beneath a continental margin over a long distance. This tectonic process is widespread yet not fully understood, particularly regarding how it influences the chemical makeup of the continental plate and recycling in the hydrosphere. By analyzing isotopes, which are variations of certain elements found in minerals and water, we can gain insights into the sources of chemicals and geological processes at play. Our study area included six locations within the Navajo volcanic field (NVF), a region in the Colorado Plateau. We analyzed 23 lower crustal …

Silica Fault Mirror Development Along The Cordillera Blanca Detachment Fault, Peru, Kayla Michelle Chaudoir

All Graduate Theses and Dissertations, Fall 2023 to Present

Earthquakes occur along planes of geologic weakness called faults. Thin, light-reflective surfaces on faults are called fault mirrors and often considered signatures of previous earthquakes along these faults. The Cordillera Blanca mountain range in the Peruvian Andes provides a natural laboratory to explore meter scale exposures of fault mirrors. Three naturally formed fault mirror samples were collected from the Cordillera Blanca detachment fault which runs along the edge of the Cordillera Blanca mountain range. Prior work on this fault reveals that it is capable of destructive earthquakes every few thousand years and is a significant earthquake hazard to the surrounding …

Effects Of Climate Change On (Semi)-Arid Ecosystems In The Southwestern United States, Charlotte Van Der Nagel

UNLV Theses, Dissertations, Professional Papers, and Capstones

Climate change is considered amongst the most severe threats to terrestrial and aquatic ecosystems globally. Ecosystems in the southwestern United States have specifically been impacted by intense drought conditions since 2000. Higher temperatures combined with altered precipitation stresses many ecosystems; however, ecosystem specific responses to such stressors may vary. Here, the effects of climate change on semi-arid ecosystems are analyzed for some of the most vulnerable ecosystems in the southwestern United States: lacustrine, riparian, and dryland ecosystems.

Lakes and reservoirs in arid environments often serve as drinking water sources and recreational areas where high water quality is essential. Climate change …

Differential River Incision Due To Quaternary Faulting On The Río Jemez-Salado System At The Million-Year Timescale, Cameron Reed

Earth and Planetary Sciences ETDs

Analysis of long-term average bedrock incision rates along the Río Salado-Jemez system using fluvial terraces can be used to test and quantify the hypothesis that differential river incision reflects Quaternary fault slip during ongoing uplift of the Jemez and Nacimiento Mountains. Terrace flights were correlated from the Arroyo Peñasco to the Río Salado near the southern nose of the Nacimiento and along the Río Jemez. Using highest/oldest river terraces, resulting bedrock incision values average out glacial/interglacial cycles and are interpreted to reflect differential uplift. For previously mapped and correlated terraces, we applied lidar datasets to refine strath heights. We also …