Theses and Dissertations - Department of Geological Sciences

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    Investigating Rare Biomineralization Structures in Trilobites
    (University of Alabama Libraries, 2020) Greenberger, Raya; Perez-Huerta, Alberto; University of Alabama Tuscaloosa
    Trilobites, a diverse class of arthropods, inhabited a range of marine environments from Early Cambrian to Permian time, and their abundance and various morphologies are significant in the interpretation of evolution, paleoenvironments and biostratigraphy. Their preservation is due to their calcitic structures formed by biomineralization. Investigating biomineralization processes in trilobite can enhance our understanding of the evolution of trilobites. This thesis presents two rare biomineralization structures in trilobites; the Asaphus trilobites, displaying stalk eyes, varying in length and width, and the Eldredgeops rana trilobites, displaying patterns on their shells that may have served as an additional visual system or amorphous calcium carbonate reservoirs. The eyes of Asaphus kowalewski, Asaphus cornutus and Asaphus punctatus and the spots on the Eldredgeops rana were characterized using a scanning electron microscope for imaging, energy dispersive x-ray spectroscopy and electron backscattered diffraction mapping to obtain elemental composition and crystallographic orientation and to observe microstructural arrangements. Further analyses were done on the Eldredgeops rana trilobites using atomic force microscopy and Raman spectroscopy to study the surface of the spots and their chemical bonding, respectively. This study reveals the stalked eyes main features are lenses and fibers. Asaphus kowalewski has lenses shaped as a truncated prism. Asaphus cornutus and Asaphus punctatus have lenses that are shaped as either a cone or an elongated prism. The cone shaped lens resembles ommatidium in the compound eyes of modern arthropods. The variation in lens shape within a specie could be explained by sexual dimorphism, which has been reported in modern arthropods. These findings suggest a stronger evolutionary link between trilobites and modern arthropods. Analysis of the spots on the Eldredgeops rana trilobite show that they cannot be lenses; there is no pathway connecting the spots to the exterior of the trilobite and no uniform orientation in the crystalline structures. Atomic force microscopy and Raman analyses of the spots show inconsistency with amorphous calcium carbonate. Overall, the results of this study demonstrate that by applying new concepts from the study of modern organisms and using advanced analytical techniques, we can enhance our understanding of the diversification of trilobites.
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    Multiproxy Analysis of Paleoenvironments in the Norphlet Formation: Conecuh Sub-Basin, Escambia County, Alabama
    (University of Alabama Libraries, 2020) Olsen, Kyle Anthony; Totten Minzoni, Rebecca; University of Alabama Tuscaloosa
    Reservoirs in the Jurassic Norphlet Formation have been major hydrocarbon targets for decades in the Gulf Coastal Plain, and recent discoveries offshore in the eastern Gulf of Mexico have spurred renewed interest in this extensive aeolian unit. Focusing on the Flomaton Field within the Conecuh Sub-basin of southern Alabama, core lithofacies and well petrofacies are characterized to investigate dryland-fluvial environments from sedimentary facies in eight cores. Sedimentary facies are related to multi-proxy datasets, including well logs, pseudo-gamma logs from scintillometer core measurements, elemental composition from handheld X-ray Fluorescence and Laser-Induction Breakdown Spectroscopy devices, particle size, microfabrics from thin sections, and porosity and permeability from core plugs. The lithofacies-petrofacies relationships developed in this study allows for sedimentary facies to be interpreted from petrophysical data in wells without cores, which has implications for reservoir quality. The sedimentary facies of the Conecuh Sub-basin include alluvial, aeolian sheetsand (avalanche and wind ripple facies), fluvial/wadi environments, and reworked sand that only occurs in the top of the Norphlet Formation lithostratographic unit. In the Conecuh Sub-basin, alluvial deposits are prevalent updip with greater proximity to the Appalachians. Deposits from aeolian and reworked aeolian sands, which are favorable to higher reservoir quality (up to 110 mD in permeability and 15-20% porosity in aeolian facies and >25mD in permeability and >15% porosity in reworked sand facies), are found throughout the study area, but are thickest (up to 52 ft for reworked sand and up to 84 feet for aeolian deposits) and most prevalent downdip. Reworked sand is prevalent in the top of the Norphlet Formation and thickens (from < 1 ft up to 52 ft) to the southeast and southwest of the study area. Aeolian petrofacies can be found where there are moderate gamma ray (~25 to 75 API), low neutron porosity (~0 to 25), slightly negative to low density porosity (~-10 to 25), spontaneous potential concentrated around ~45 to 20, and variable from~-100 to150 mV, and moderate resistivity (~100 or range from ~10 to ~1000). Elemental composition analysis may aid in the identification of aeolian facies, as aeolian facies can be found where both marine (Ca, and Mn, and Mg) and terrestrial (K, Cr, Rb, Ti, V, and Y) elemental concentrations are relatively low. This study determines the dryland-fluvial facies and reservoir quality distribution in an onshore Norphlet play, which should improve predictive modeling of reservoir distribution in areas of frontier exploration, including deepwater plays of the Gulf of Mexico and greenfield areas of the recently opened Campeche margin.
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    Seismic interpretation and structural restoration of a seismic profile through the Southern Appalachian thrust belt under Gulf Coastal Plain sediments
    (University of Alabama Libraries, 2007) Bailey, Ryan Michael; University of Alabama Tuscaloosa
    In the southern part of the Appalachian thrust belt, the thrust system is buried by Gulf Coastal Plain sediments; thus, directly studying this Paleozoic thrust belt is impossible. However, multi-channel seismic data and well log data are used to explore this thrust belt. In this region, Gulf Coastal Plain sediments cover the Paleozoic thrust belt that formed during the Ouachita and Alleghenian orogeny. Due to a lack of well control and limited availability of proprietary quality seismic reflection profiles, only a few other studies interpret subsurface structures beneath the Gulf Coastal Plain (Thomas, 1973; Thomas, 1989; Bally, 1983; Hale-Erlich and Coleman, 1993). Stratigraphic thicknesses in the thrust belt were derived from the Ethel M. Koch #1 well and in the Black Warrior Basin from the James W. Sterling 17-14 well. Two additional wells, the Willis #1 and Dollarhide #1 were used to identify the depth to formation tops within the interpretation. An 84 kilometer long seismic profile was depth-converted using a sonic log from the Koch well and then projected onto a straight line perpendicular to the Appalachian thrust belt which shortened the length of the line to 78 kilometers. Five main horizons were interpreted in two way travel time and depth-converted using interval velocities derived from synthetic seismograms and the sonic log in the Koch well. A 14 kilometer zone of poorly imaged seismic data within line segment 691-1 A may be the result of high velocity material juxtaposed with the base of the Coastal Plain sediments. Two interpretations, both incorporating forward-propagating sequences, were made. The depth of the upper detachment altered the structural style of the ramp anticline on thrust 1 from a fault bend fold in interpretation #1 to a fault propagation fold in interpretation #2. Consequently, the depth of the detachment along with the fault trace of thrust 2 effected the thickness of units incorporated in thrust 2 and the thickness and number of units incorporated in thrust 3. The lengths of the units are quantitative, while the actual positions are speculative. The flexural slip method and line length balancing was used to balance the cross sections. Shortening estimates range from 23 kilometers or 29% shortening in interpretation # 1 to 19 kilometers or 26% shortening in interpretation #2.
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    Watershed Export of Dissolved Organic Matter in Response to Anthropogenic and Hydroclimatic Drivers in Subtropical Streams and Rivers
    (University of Alabama Libraries, 2021) Chen, Shuo; Lu, Yuehan; University of Alabama Tuscaloosa
    Dissolved organic matter (DOM) is an assemblage of heterogeneous organic compounds that play important roles in terrestrial and aquatic ecosystems. In this dissertation, I investigated changes in the amount, source, composition, lability, and ecological functions of stream water DOM in response to agricultural land use, hydrological events, and downstream transport and transformation in the southeastern United States. The dissertation includes three stand-alone studies presented in Chapters 2, 3 and 4, respectively. In Chapter 2, I evaluated the effects of hurricane-induced storm events on the quantity and quality of DOM exported from ten watersheds of various physical and land-use characteristics within five Gulf and South Atlantic states. We found that large storms can significantly enhance the concentrations and yields of terrestrially-derived dissolved organic carbon (DOC) and nutrients in streams and rivers but decrease the percentage bioreactive DOC. This study demonstrates that extreme weather and climate events can lead to rapid, ecosystem-level disturbances that significantly shift energy and nutrient availability within drainage networks. The objective of Chapter 3 was to quantify the relative importance of agricultural land use and natural hydroclimatic drivers in affecting the quality and quantity of DOM in a group of 15 streams draining watersheds of a gradient of agricultural land use. The partial least square path modeling (PLS-PM) identified that agricultural land use increased stream water DOM quantity primarily through increasing allochthonous carbon sources. This study demonstrates that structural equation modeling is a powerful tool that should be more widely adopted to distinguish among multiple drivers and mechanisms regulating freshwater biogeochemistry. Chapter 4 investigated the longitudinal transformations of DOM in relation to ecosystem metabolism along a fluvial section including 3rd order, 7th and 8th order streams. From upstream to downstream, DOC concentrations and the relative contributions of freshly-produced DOM increased. The gross primary productivity was positively correlated with the contributions of autochthonous DOM, yet the ecosystem respiration did not vary with the quantity or quality of DOM. This study highlights the complexity of DOM transformations in relation to stream metabolism along the river continuum. Collectively, the three independent but connected studies reveal the complexity and sensitivity of inland water DOM in response to hydroclimatic and anthropogenic drivers. The findings provide new insights into potential shifts in energy and substrates exported across the terrestrial-aquatic boundary due to human activities and climate change and how these shifts can alter water quality and fluvial biogeochemical functions.
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    First Report of Carbonate Mudbanks in Cuba: a Geospatial Comparison with Florida Bay, USA, and Implications on Underlying Controls
    (University of Alabama Libraries, 2021) Nibert, Lucas Allen; Minzoni, Marcello; University of Alabama Tuscaloosa
    Carbonate mudbanks and associated islands of Florida Bay are shallow-water to intertidal, linear Holocene sedimentary accumulations forming basins 1.5-3 m deep. The resulting reticulate-patterned banks and basins have only been documented in Florida Bay, where they developed landward of the shelf margin, protected by the Pleistocene ridge of the Florida Keys. Although extensively studied, the origin of mudbanks is unclear. Apparently similar depositional features occur south of Florida Bay in Bahia de Santa Clara, Cayo Santa Maria, and Cayería de Diego Pérez along the northern and southern coasts of Cuba. Comparative geospatial analysis of these sites establishes potentially novel localities for shallow-water carbonate mudbanks. The shallow lagoons of Florida and Cuba vary in size and are dissected into smaller basins or “lakes” by linear or arcuate sediment accumulations. Banks, keys, and platform-margin archipelagos were mapped using satellite images at each site to quantify and compare relative abundance and physical attributes of these major depositional environments. Florida Bay mudbanks cover at least twice the relative area as banks at the other sites. There is no clear relationship between the degree of open-ocean exchange and relative area of shelf elements. Banks are generally oriented perpendicular to winter storm winds in Florida Bay, Cayo Santa Maria, and Cayería de Diego Pérez in the Gulf of Batabano, but not in Bahia de Santa Clara. We conclude that there is not sufficient evidence to determine the processes responsible for bank genesis, but the initial configuration of banks was likely re-oriented by winter storm winds and other physical sedimentation processes. Mudbank-dominated lagoons may serve as modern analogues for transgressive carbonate strata in shallow, protected, land-attached shelf systems. Physical sampling in Cuba, when possible, and comparative stratigraphic analysis with Florida Bay will yield additional insight into Holocene evolution of carbonate shelf environments.
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    Revealing the Nanoscale Geochemistry of an Antarctic Micrometeorite with Atom Probe Tomography
    (University of Alabama Libraries, 2021) Boyd, Mark Robert; Cartwright, Julia A; University of Alabama Tuscaloosa
    Micrometeorites (MMs) retrieved from the Earth’s surface commonly undergo frictional heating as they enter the atmosphere. The compositional and textural effects of this heat-processing have been well documented and can be observed on the micrometre (μm)-scale, including the formation of iron-rich shells or the depletion of volatile elements, such as zinc. Atom probe tomography (APT) is a technique that has the capability to explore nanometre (nm)-scale features within such materials by producing three-dimensional (3D) compositional maps, displaying trends that may have been undetectable at lower resolutions. Here, we present the successful application of APT to an Antarctic MM, which we believe to be the first use of this technique on cosmic dust. From our MM sample, 11 tips were analysed from 2 sites, displaying nm-scale trends from the core to the rim. Many of the tips show interesting features, for example, one tip (A-M5) has a compositional boundary highlighted by clear elemental differences, consistent with core-rim partitioning, while a second tip (B-M1) shows evidence for a grain boundary adjacent to a carbon-rich region. We discuss our findings in the context of previously described processes, such as the presence of temperature gradients, which occur during atmospheric entry. We find evidence of thermal processing that we believe has caused nm-scale features along a textural boundary and heterogeneous elemental distributions, which may indicate unmelted material. These features may represent atmospheric entry indicators, which would suggest that entry processing affects MMs on the nm-scale. This could have implications for the delivery of sub-μm phases to planetary bodies via cosmic dust, and their survival during atmospheric entry.
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    Investigation of K-Pg Boundary Sand Bodies At Moscow Landing Alabama, Via U-Pb Geochronology: Implications for End-Cretaceous Paleodrainage and the Chicxulub Impact
    (University of Alabama Libraries, 2021) Culp, Ryan Patrick; Wielicki, Matthew; University of Alabama Tuscaloosa
    Moscow Landing is a well-known Cretaceous-Paleogene (K-Pg) boundary site located in eastern Sumter County Alabama USA and serves as a natural laboratory to study the end-Cretaceous mass extinction given its proximity to the Chicxulub impact. Unique, discontinuous, sand bodies, commonly known as the Clayton sands, mark the contact between Cretaceous and Paleogene rocks. Megawaves generated by the Chicxulub impact and incised valley filling have been cited as the possible mechanisms behind Clayton sand deposition. To further investigate the source of the sediment in the Clayton sands, a multidisciplinary approach is used that involves microscopy (SEM analysis), geochemistry (trace element and major oxides), and detrital zircon U-Pb geochronology. This work represents the first wherein U-Pb geochronological tools have been applied to a K-Pg site in Alabama. Zircon ages reveal an Appalachian-derived sediment signature, with four grains of ~550 Ma possibly indicating a Chicxulub impact-derived source (i.e. Pan-African in age). Shock features within the zircons were not observed, possibly indicating that the ejecta blanket at Moscow Landing was erased or diluted by the subsequent megawave surge as previous research suggests. In addition, the detrital zircon data presented corroborate previous studies in suggesting that the ancestral Mississippi River system was draining large portions of North America at the end-Cretaceous into the Gulf of Mexico as it does today.
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    Distinctive Extinction Patterns of Late Cretaceous Hybodontiform and Lamniform Sharks in Northern Gulf of Mexico Controlled by Changing Marine Paleoenvironments
    (University of Alabama Libraries, 2021) Comans, Chelsea M; Lu, Yuehan; University of Alabama Tuscaloosa
    Abundant fossil occurrences of Late Cretaceous sharks (Chondrichthyes, Elasmobranchii), especially Hybodontiformes and Lamniformes, in the northern Gulf of Mexico offer an ideal opportunity to study shark diversity patterns leading up to the end-Cretaceous mass extinction. Here, we present a dataset representing 16 genera and 25 species (five hybodontiforms and 20 lamniforms). Species counts and extinction and origination rates are quantified across the Coniacian to Danian. Both groups display an overall increasing trend of extinctions that peak in the Campanian (e.g., the ‘Middle Campanian Crisis’: MCC) but show noticeable differences concerning the magnitude and relative timings. Hybodontiforms show increased diversity losses from the Santonian to middle Campanian before regionally disappearing during the entire Maastrichtian. Lamniforms declined in diversity in the early to middle Campanian (about half the magnitude of the hybodontiform losses) and the end-Maastrichtian. For both taxa, originations declined from the Santonian to middle Campanian and remained near zero toward the end-Cretaceous. Statistical analyses (correlation tests, principal component analysis) were used to determine the potential importance of marine environmental changes, such as sea level, sea surface temperature, marine productivity on the two different extinction trends of hybodontiforms and lamniforms. Lamniform diversity loss is negatively correlated with globally decreasing sea levels. Hybodontiform diversity loss is positively correlated with globally increasing sea levels. Sustained fluctuations in marine productivity and sea surface temperature in the Gulf of Mexico may have contributed to low origination rates for lamniforms following the MCC. Previously published occurrences in upper Campanian to upper Maastrichtian strata in the Northern Atlantic coast indicate that few species did not become extinct globally. This study suggests that changing marine paleoenvironments (esp., sea level changes) could have had a big impact on Cretaceous sharks (particularly benthic durophagous forms that lived in near-shore environments) due to newly emerged unsuitable habitats.
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    Seismic Stratigraphic Analysis of Nuiqsut Area, Central North Slope Alaska, USA
    (University of Alabama Libraries, 2021) Barin, Burcu; Zhang, Bo; University of Alabama Tuscaloosa
    This study focuses on the seismic stratigraphic analysis of the Nanuq South 3D seismic survey acquired over Nuiqsut, Central North Slope, Alaska to interpret the overall strata of the Ellesmerian, Beaufortian, and Brookian mega-sequences. Fourteen stratigraphic horizons were defined based on the seismic reflection patterns, and formation tops from the available well logs, and interpreted using a new semi-automatic horizon picking algorithm. The horizon tracking algorithm only needs interpreters manually picking 15% of the seismic vertical sections to generate horizons over the whole seismic survey. This result confirms that there is a significant decrease in interpretation effort with the automatic horizon picking algorithm.Four mega-sequences (Franklinian, Ellesmerian, Beaufortian, and Brookian) were identified based on interpreted horizons and well log tops. The thickness maps of mega-sequences were generated to analyze the depositional history and illustrate that four mega-sequences have different thickening directions. The Ellesmerian mega-sequence (Mississippian - Early Cretaceous) shows thickening northwestward with maximum thickness of 1.4 km. The Franklinian basement deepening towards the west caused Ellesmerian mega-sequence thickening in that direction. The Beaufortian (Early to Middle Jurassic and Early Cretaceous) and Brookian (Early Cretaceous to Cenozoic) mega-sequences both show thickening southwestward and the maximum thicknesses are 0.6 km and 2 km, respectively. The different thick patterns are believed related to the Brooks Range orogeny in the south, and the opening of the Canada Basin in the north during Jurassic–Early Cretaceous time. To further identify the potential reservoir, self-organizing map (SOM) was applied to multiple seismic attributes to analyze the seismic facies of Brookian mega-sequence. The results clearly highlight the west-east orientated incised valleys, moved sand to the basin floor fan delta in the southeast. Sand bodies along the shelf edge, slope, and basin floor could be a potential hydrocarbon production zone.
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    Provenance Analysis of Carboniferous Sandstone Units in the Black Warrior and Southern Appalachian Foreland Basins, USA
    (University of Alabama Libraries, 2021) Yates, Zachary T; Robinson, Delores M.; University of Alabama Tuscaloosa
    The Ouachita and Alleghanian orogenies occurred simultaneously as the collision of Laurentia and Gondwana progressed from Mississippian to Permian time. Juxtaposition of the two orogenic fronts in Alabama has led to differing interpretations of sediment provenance of the Carboniferous sedimentary rocks in the adjacent Black Warrior basin and Alleghanian fold-thrust belt. These rocks have been interpreted to be sourced from three disparate regions: 1) the Ouachita Orogen, 2) southern Appalachian Orogen, and 3) via a southward flowing fluvial system that delivered sediment from the mid-continent and northern Appalachians. The purpose of this study is to investigate the provenance of Carboniferous sandstone units in Mississippi and Alabama by quantifying the differences between their detrital zircon age distributions and that of potential sources.In this study, I examine the detrital zircon age distributions of 15 samples from the Mississippian aged Hartselle Sandstone, Pennington, and Parkwood Formations, and the Pennsylvanian Pottsville Formation. I use DZstats to quantify the differences between these formations as well as potential source rocks. Cross-correlation coefficient values for all Pottsville, Pennington, and Parkwood samples in Alabama indicate that they are within the range of expected variation for the same detrital zircon population. These samples are most similar to source rocks in the central and southern Appalachian, and Ouachita Mountains; however, these sources are highly similar to each other. The Parkwood Formation of Mississippi shows little similarity when compared to other Carboniferous samples in Alabama. The Mississippi Parkwood is most like northern Appalachian source rock distributions and is certainly not directly derived from the mid-continent. I interpret these data to suggest that the Parkwood Formation of Mississippi received sediment contributions from different sources than the Hartselle Sandstone, Parkwood, Pennington, and Pottsville Formations of Alabama, indicating two separate fluvial systems.
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    Terrestrial Lidar Imaging and Fracture Analysis of the Woodford Shale; Western Arkoma Basin, Oklahoma
    (University of Alabama Libraries, 2021) Wencel, Robert; Çemen, İbrahim; University of Alabama Tuscaloosa
    Since the late 1990s horizontal drilling and hydraulic fracturing of Devonian shales in the mid-continent region, such as the Woodford Shale, has revolutionized gas exploration in the United States. These two methods are reliant on robust predictive reservoir models, particularly addressing the geometry, spacing, and density of complex natural fracture networks within the otherwise tight shale. However, the natural fractures within the Woodford Shale have not been rigorously studied despite their importance to fluid flow and ultimately recovery of hydrocarbons. Most of the subsurface fracture mapping of the Woodford has been done using 3D seismic data and seismic attribute analysis. This study applies terrestrial Light Detection and Ranging (LiDAR) to study natural fracture patterns of two Woodford outcrops located in the Arkoma Basin, southeastern Oklahoma. One outcrop is located south of the town Wapanucka, and the other outcrop is east of the town Atoka. The high-resolution images obtained from terrestrial LiDAR reveal fracture spacing and fracture density allowing the quantitative assessment of how these fractures vary in different sections of the Woodford Shale where bedding thickness, mineralogy, and degree of deformation (folding) differ significantly. In this study we evaluate whether a statistical relationship exists between bedding thickness and the mineralogy (i.e., silica content vs organic content), fracture spacing, and fracture density of shale beds. Preliminary results suggest that thicker beds contain larger fracture spacing and smaller fracture density. The results of this study will help us to 1) better understand geometry, origin, and distribution of natural fractures in the Devonian Woodford shale in the Mid-Continent region of the United States and in other parts of the world; and 2) develop more realistic reservoir models for improved hydraulic fracturing methods.
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    Geochemistry, Thermochronometry, Petrogenesis, and Geometry of Igneous Dikes in Central Arkansas: Implications for Mississippi Embayment Evolution
    (University of Alabama Libraries, 2021) Walker, Samuel; Çemen, İbrahim; Wielicki, Matthew; University of Alabama Tuscaloosa
    The Mississippi Embayment (ME) is a south-plunging sedimentary basin which unconformably overlies the Cambrian Mississippi Valley Graben (MVG) and serves as a natural laboratory for extensional tectonics. The Arkansas Alkaline Province (AAP) lies along the ME’s western border in central Arkansas and was emplaced in the mid-Cretaceous Period as a suite of intrusive bodies. The relationship between the ME and AAP, and a mechanism which generated both, remain unclear. To investigate this relationship and identify a petrogenetic mechanism, a multidisciplinary approach was used that involves geochemistry (major oxide and trace element, Nd isotopes), thermochronometry (U-Th/He), and geometry of 11 igneous dikes from the AAP. These data reveal that dikes are potassic-ultrapotassic and extremely enriched in incompatible elements relevant to OIBs and MORBs. Combined with data from other studies, the Nd isotopic ratio values demonstrate that lamprophyres were derived from asthenospheric magma unlike other intrusions. Despite depleted Nd isotope ratios, lamprophyres and every other sample reveal enrichment in incompatible elements and high Sr and Nb contents (indicative of carbonatite metasomatism). This decoupling between isotope ratios and trace element contents could represent low degrees of partial melting of a depleted asthenospheric source. The remaining samples show similar trace element slopes on normalized diagrams and were likely derived from a similar source with varying degrees of crustal contamination. Despite geochemical similarities between samples and average OIB values, I propose a non-plume evolution for the AAP and ME related to edge-driven convection (EDC) associated with regional tectonics. At the time of the AAP’s emplacement (106-89 Ma), EDC was at its highest velocity (80-100 Ma after the Atlantic Ocean and GOM started rifting). At this time, the proto-ME region was uplifted, and melt was guided along pre-existing weaknesses. This is corroborated by rose diagrams, which indicate strong similarities between dike trends and thrust plane trends. Results and interpretations from this study clarify a potential mechanism for alkaline magmatism during a pulse of volcanism in the Cretaceous. Moreover, this study places the ME and AAP within the framework of global tectonics in the Cretaceous Period and emphasizes the influence of regional processes on nearby lithospheric weaknesses.
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    Investigating Tectonic Structures in East Antarctica Using Full Waveform Ambient Noise Tomography
    (University of Alabama Libraries, 2021) Kumar, Ashish; Hansen, Samantha; University of Alabama Tuscaloosa
    Previous investigations have proposed multiple origin models to explain the formation of major tectonic structures, such as the Gamburtsev Subglacial Mountains (GSMs), the Wilkes Subglacial Basin (WSB), the Aurora Subglacial Basin (ASB), and the Transantarctic Mountains (TAMs) in East Antarctica. However, existing tomographic images lack resolution and consistency given the sparse seismic coverage across the continent, particularly in East Antarctica. In this thesis, I use full-waveform ambient noise tomography to model the shear-wave velocity structure beneath East Antarctica to further investigate these tectonic features and to provide new insights into existing origin models. This technique has been shown to provide improved resolution of the seismic structure in geographic regions with limited station coverage compared to more traditional tomographic approaches. Rayleigh-wave Empirical Green’s Functions are extracted from ambient noise using a frequency-time normalization technique. Synthetic waveforms are simulated with a lateral grid spacing of 0.025º (~2.25 km) and are cross-correlated with the EGFs to measure phase delays. The shear-wave velocity model is computed by inverting the phase delays using a sparse, damped least-squares inversion method. The new tomographic model shows fast velocities beneath the GSMs that extend to ~250 km depth, suggesting Archean or Proterozoic lithosphere beneath the mountain range. The perseverance of thick ancient crust beneath the GSMs support the high topography of the mountain range. Slow upper mantle velocities are observed beneath the TAMs, likely associated with hot upper mantle material that provides a thermal load beneath the mountain range, consistent with a flexural uplift model. Beneath the WSB, fast seismic velocities are attributed to thick, stable lithosphere, also consistent with a flexural origin model. Slow velocities beneath the ASB, which is an area of particular interest since it has not been studied extensively, may reflect a zone of lithospheric weakness, associated with the reactivation of a major fault system. By providing new evidence that further constrains the origin models for tectonic structures in East Antarctica, my full-waveform ambient noise model helps to elucidate the geologic history of this remote continent. These seismic constraints could also inform cryospheric models, which require lithospheric and mantle characteristics to assess ice-sheet evolution.
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    The Pressure, Temperature, and Timing of Magmatism and Metamorphism, George Sound, Fiordland, New Zealand
    (University of Alabama Libraries, 2021) Anderson, Ian Robert; Stowell, Harold H.; University of Alabama Tuscaloosa
    Fiordland, New Zealand provides an opportunity to study the complex relationship between magmatism and metamorphism in the lower crust of a magmatic arc. The Eastern McKerr Intrusives, which are well exposed along George Sound, are a constituent of the Western Fiordland Orthogneiss magmatic suite. They they lack the extensive metamorphic recrystallization observed in neighboring Western Fiordland Orthogneiss plutons. This thesis presents pressure, temperature, and a Sm-Nd garnet age to better understand intrusion of the Eastern McKerr Intrusives, metamorphism of the adjacent George Sound Paragneiss, and the tectonic history. Results from amphibole thermometry and barometry indicate amphibole crystallization at 915-850°C and 8-11 kbar. Petrography, mineral compositions, and psuedosection models indicate that amphibole from the Eastern McKerr Intrusives are igneous and crystallized near solidus temperatures. Metamorphic garnet from the George Sound Paragneiss records pressure and temperature estimates of equilibration at ~720°C and 6 kbar for garnet cores. The garnet rims record lower temperature and higher pressure conditions of 680-600°C and 8-12 kbar. The overlap between magmatic and metamorphic pressure estimates is compatible with contact metamorphism in the George Sound Paragneiss. One new garnet Sm-Nd age of 108 ± 7 Ma is indistinguishable from the age of post magmatic garnet granulite metamorphism elsewhere in the Western Fiordland Orthogneiss. However, the imprecision of this age is likely two different age populations of garnet. The garnet Sm-Nd age indicates the Eastern McKerr Intrusives, either remained, or were reheated to amphibolite facies conditions after emplacement. The garnet age of ~108 Ma provides an estimate for the duration of amphibolite facies or the timing of reheating. Regardless, the igneous rocks did not significantly recrystallize to a metamorphic mineral assemblage. Based on the garnet age and the ca. 120 Ma pluton emplacement, the Eastern McKerr Intrusives would have been subject to amphibolite facies or higher temperature conditions. Possible interpretations for the lack of significant recrystallization in the igneous rocks include: 1); incorrect garnet age; 2) insufficient heat flow into George Sound rocks; 3) kinetic barriers to recrystallization and; 4) fault juxtaposition of amphibolite facies and lower temperature rocks.
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    A Model of the Crust and Upper Mantle Structures in Central Anatolia, Turkey, Constrained by Gravity and Seismic Data
    (University of Alabama Libraries, 2021) Yilmaz, Yagmur; Plattner, Alain; University of Alabama Tuscaloosa
    The complex tectonic setting of the easternmost Mediterranean Sea and central Anatolia remains largely unresolved. Previous studies, mostly based on seismic investigations, presented results that conflicted with each other. The purpose of this study is to use gravity modeling to distinguish which aspects of previously published work is consistent with Earth’s gravity signal. For this purpose, I constructed gravity model profiles between longitudes 30°E and 38°E, each ranging from latitude 32°N to latitude 40°N. In these models, I incorporated structural boundaries published in previous work and compared to the satellite based EIGEN-6C4 gravity data product, what the gravity signal of the structures would be. Based on my gravity models, I identified that the crustal thickness is increasing in northern as well as in eastern direction. My gravity models show that the Cyprus slab subducts with an angle of 29 and 31 degrees along longitudes 31°E and 32°E, respectively. Even though the Cyprus slab is present between longitudes 33°E and 34°E, it has most likely experienced slab breakoff which might cause lithospheric removal farther to the north in central Anatolia. The last three profiles longitude 35°E, 36°E and 37°E do not have the Cyprus slab.The central Anatolian lithosphere is thinner than both the African and Arabian lithosphere. The average lithospheric thickness is 75-81 km in central Anatolia and approximately 97 and 105 km in the African and Arabian plates, respectively. When the densities were compared to the African and Arabian plates, I observed relatively low-density crust and uppermost mantle in central Anatolia. The thin lithosphere and low-density material may indicate thermal alteration associated with delamination, slab breakoff and/or drip tectonics in central Anatolia.
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    Carbonation of flue gas desulfurization gypsum for CO2 sequestration
    (University of Alabama Libraries, 2021) Riddle, Jonathan B.; Donahoe, Rona J.; University of Alabama Tuscaloosa
    The IPCC asserts that to prevent a 2°C global temperature increase by the year 2050, CO2 must be removed from the atmosphere by sequestration. The goal of this study was to use FGD gypsum for CO2 mineralization and experimentally explore to find the optimal conditions for the highest conversation rates at ambient temperature while eliminating ammonia usage. While maintaining an alkaline solution using NaOH, a stirred reactor was utilized to study the effects of PCO2 (0.69, 2.07, 4.14, 6.89, and 17.24 bar), solution pH (12, 13, 13.5 and 14), solid-to-solution ratio (1:100, 1:80, 1:40, 1:100), and reaction time (10, 15, 30, and 120+ min) variation on the rate of conversion. The CaCO3 produced was calculated by Rietveld refinement of XRD patterns to determine the impact of each experimental variable.Experimental results showed solution pH was a primary control on mineralization, with nearly 100% conversion of FGD gypsum to CaCO3 occurring at initial pH = 13.5 and 14, for PCO2 > 2 bar and S:L = 1:100. At initial pH of 12, no gypsum conversion occurred. Reaction time also affected the amount of gypsum conversion to CaCO3. At initial pH = 13, S:L = 1:100 and PCO2 = 2.07 bar, 15 min was the optimum reaction time, achieving 75% conversion. However, with the same conditions at 360 min, a 61% conversion occurred, due to final pH’s below 7. Increasing S:L ratio resulted in increased gypsum-to-carbonate conversion. The optimal conditions for conversion of gypsum into calcite occurred at short reaction times of 15 min, low pressures at around PCO2 = 2.07 bar, and low solution ratios of S:L = 1:100, achieving 75% conversion. In contract, a reaction time of 360 min produced a result of only 61% conversion at the same PCO2 and S:L ratio, due to the pH dropping below 7. The results of this study demonstrate that FGD gypsum is a viable feedstock for CO2 mineralization, potentially offering a cheap and rapid method for carbon sequestration.
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    P-t-time paths for mid to lower crustal metamorphism in orogenic belts: linking metamorphism with plutonism and toward a better understanding of garnet sm-nd and lu-hf geochronology
    (University of Alabama Libraries, 2020-12) Bollen, Elizabeth Marie; Stowell, Harold H.; University of Alabama Tuscaloosa
    Garnet is an exceedingly useful mineral for interpretation and identification of magmatic and metamorphic processes because it records pressure, temperature, and time (P-T-t) as it grows during metamorphism. Temperatures >650°C, required for partial melting of metasedimentary rocks, can chemically and isotopically reset garnet grains by diffusion, obscuring the growth history and biasing interpretations. However, in rocks that reach temperatures >850°C, large garnet grains can preserve a protracted growth history. Garnet major and trace element zoning is often used to identify preserved growth zoning or diffusional re-equilibration. Trace element zoning of Lu and Sm are particularly useful for interpreting the meaning of garnet ages because the two chronometers used to date garnet are based on the decay of these two elements: Lu to Hf and Sm to Nd. However, these two chronometers seldom yield the same result, often differing by 10’s of millions of years or more, casting uncertainty on the meaning of ages. This dissertation utilizes three suites of rocks in order to better understand discrepancies between the two widely used isotopic systems in garnet and the use of garnet ages for tectonic interpretations. This work uses garnet-bearing metamorphic samples from a variety of tectonic settings and terranes, including the metasedimentary rocks exposed within the southern Coast Mountains batholith, British Columbia; Precambrian metasedimentary rocks in northern New Mexico; and lower-crustal granulites exposed in the exhumed Zealandia magmatic arc, Fiordland, New Zealand. The results of this study highlight the usefulness of garnet geochronometry when chemical zoning is known, permitting connection of garnet ages to P-T conditions and geological processes. The low to mid-amphibolite facies conditions recorded in northern New Mexico and the Coast Mountains of British Columbia facilitate the preservation of prograde zoning in garnet. Garnet in these two settings grew in response to crustal thickening via thrust faulting and plutonism. However, the granulite facies conditions recorded in New Zealand are in sharp contrast. Only the largest garnet grains record prograde growth conditions, while the smallest garnet re-equilibrated at lower temperatures.
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    Reservoir fluid-rock interactions during a co₂ eor/ccs pilot test at citronelle oil field, alabama
    (University of Alabama Libraries, 2020-12) Rheams, Erik; Donahoe, Rona; University of Alabama Tuscaloosa
    With the world’s expanding need for energy, new sources of petroleum or technologies to extend current petroleum reserves are required. However, concerns about global warming are increasing as atmospheric CO2 levels continue to rise worldwide due to the burning of fossil fuels. Enhanced oil recovery (EOR) provides a method for expanding existing petroleum reserves by prolonging the life of older oil fields where primary production methods have been exhausted. EOR also opens an avenue for using CO2 captured from point sources such as power plants for beneficial purpose, thus preventing its release into the atmosphere and sequestering the CO2 in deep geologic formations that also serve as petroleum reservoirs. Citronelle Oil Field, located in Mobile County, Alabama, was the site for a 2008-2012 SECARB pilot project funded by the U.S. Department of Energy (DOE) that was aimed at testing CO2 flood for enhanced oil recovery and carbon sequestration. Citronelle Field is the largest and oldest oil play in the state of Alabama with reserves originally estimated at about 500 million barrels in place, less than half of which had been produced between its discovery in 1955 and the start of the pilot project in 2008. The field’s primary producing units are the Upper and Lower Donovan Sands within the Rodessa Formation. The work performed for this study was funded by the DOE to examine the fluid-rock interactions induced in the reservoir by the injection of supercritical CO2. Water samples were collected from four production wells located around the CO2 injection well between June 2010 and February 2012, and water chemistry was analyzed by ICP-OES and IC. Temporal trends for water sample compositional variation are presented, and compositional similarities and differences between the water samples collected from the four wells are discussed. Geochemical modeling was employed to determine the fluid-rock interactions taking place within the reservoir and thus provide potential explanations for the observed water sample compositional trends. Finally, the impact of an over pressuring event that created preferred flow paths within the system and its impact on water chemistry and oil production is discussed.
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    Watershed-estuary dynamics in the mobile river watershed-mobile bay estuary (mr-mb) continuum examined by combined geochemical and satellite approaches
    (University of Alabama Libraries, 2020-12) Stewart, Jackson Buford; Dimova, Natasha T.; University of Alabama Tuscaloosa
    The Mobile River System acts as a vital economic, social, and cultural center for Alabama and the northern Gulf of Mexico region. With increasing levels of urbanization and land-use and development, the ecological integrity of this system becomes more vulnerable to imbalance due to pollution, anthropogenic alteration of stream course, and other land-use activities. This study focuses on tracking suspended sediment material transported by the Mobile River System, from upstream origin of erosion through the Mobile Estuary, and into Mobile Bay, by combining established geochemical and remote sensing methods and approaches. To accomplish this, I posed three research questions, (Q1) where in the upper reaches of the system are the suspended particulates originating? (Q2) what is the magnitude of flux for suspended sediment (SS) and associated major and trace metals from the river system? and (Q3) can the distribution of the suspended sediment material be effectively tracked within the Mobile Bay basin? The origin of sediment, i.e. identifying sources from the two major tributaries of the Mobile River, the Alabama and the Tombigbee Rivers (Q1) was determined using geochemical fingerprinting of radioisotopes and trace metals. The concatenation of fingerprinting properties of each tributary and of downstream suspended sediments in a geochemical mixing model resulted in 61% of suspended sediment material originating from the Tombigbee Basin, and 39% from the Alabama Basin. The flux of material out of the river system into Mobile Bay (Q2) was determined through compositional analysis of suspended sediment material collected by passive suspended sediment capture within the Mobile-Tensaw Delta. Using this sampling approach, SS flux entering the Delta varied between 981 g/s during low flow regime and 23,509 g/s during high flow. Associated trace metal fluxes were below EPA regulated limits. (Q3) Calibration of existing remote sensing algorithms with in-situ data from Mobile Bay proved successful in generating remote sensing algorithms which can track sediment movement in Mobile Bay across seasonal and hydrologic conditions.
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    New insights on porewater geochemistry in organic-rich coastal sediments
    (University of Alabama Libraries, 2020-12) Lamore, Alexander F.; Dimova, Natasha T.; University of Alabama Tuscaloosa
    Previous studies of groundwater nutrient dynamics in coastal Baldwin County, AL indicate that groundwater is contaminated with NO3-. However, recently, nutrient fluxes' mass-balance indicates positive fluxes of reduced nitrogen species, NH4+ and dissolved organic nitrogen (DON), while NO3- fluxes were negative. Further, it was suggested that geochemical transformations within an organic-rich layer comprising the subterranean estuary (STE) in Mobile Bay could be responsible for the observed changes in the groundwater-derived nitrogen fluxes. This study aims to examine the nitrogen geochemical transformations occurring in organic-rich shallow coastal sediments and to identify the quantity and quality of carbon exported by groundwater. In a laboratory-based study, sediment cores with identified organic-rich layers collected from a hypoxia-impacted shoreline of Mobile Bay were incubated with 400µM and 800µM NO3- solutions, natural groundwater (GW), and ultra-pure carbon-free water (UPCFW) to evaluate how the sediment reacts to different NO3- loading. Findings from the incubation studies show that the organic-rich sediments are indeed responsible for the NO3- loss in groundwater as all treatments with NO3- amendments experienced NO3- removal. Also, that the organic-rich sediments are a source of reduced N, in the form of DON and NH4+, evidenced by net-N production observed in three of four treatments and the N produced correlates with DON, and that higher NO3- loading promotes increased DON production. Additionally both DNRA and denitrification occurred, but the dominant pathway of NO3- removal was denitrification. Average NO3- removal rates increased with increases in NO3- loading, but complete NO3- removal was not observed. The STE sediment has the potential to denitrify significant amounts of anthropogenic NO3-, however, in the process producing NH4+, DON, DOC, and DIC.