Geological Sciences electronic theses and dissertations (MU)
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The items in this collection are the theses and dissertations written by students of the Department of Geological Sciences. Some items may be viewed only by members of the University of Missouri System and/or University of Missouri-Columbia. Click on one of the browse buttons above for a complete listing of the works.
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Item Digital spaces and Cambrian facies : terminological analyses and case studies in geoscience virtual fieldwork & paleoenvironments and taphonomic windows of Australian lower Cambrian deposits(University of Missouri--Columbia, 2025) Speir, Eury; Jacquet, Sarah[EMBARGOED UNTIL 08/01/2026] This dissertation is divided into two volumes, each encapsulating two stand-alone projects. Volume One examines virtual field education within the geosciences, including the pedagogical and experiential considerations in naming virtual field opportunities, and documents the implementation of a virtual field trip within the University of Missouri's introductory geology curriculum. Volume Two examines the sedimentological, geochemical, and environmental factors that influence fossil distribution and preservation through an analysis of the lower Cambrian deposits in South Australia. Virtual field opportunities provide a digital means for geoscience students to explore sites of interest, and their usage has increased in popularity in recent years. This rise in popularity has led to the use of varying terminology to describe similar experiences. We conducted a qualitative content analysis on 97 unique publications related to virtual field opportunities in the geosciences, followed by a series of multiple correspondence analyses to investigate the relationships between pedagogical and experiential factors and their impact on naming convention. We constructed a new lexicon to guide naming selection for future virtual field opportunities: virtual tour, virtual field trip, virtual field experience, and generated field environment. Using the newly developed lexicon, we developed a virtual field trip of Rock Bridge Memorial State Park for the introductory geology program at the University of Missouri. We employed an iterative design process that utilized student feedback to improve the functionality of the virtual field trip. Our findings suggest that providing students with both physical and virtual methods of interacting with a field site results in higher academic achievement, particularly when encountering the virtual medium first. The lower Cambrian deposits of the Arrowie Basin, South Australia, are host to well-documented small shelly fauna assemblages, with a large component often preserved through secondary mineralization. Understanding the sedimentological, environmental, and geochemical factors that enhance preservation potential, either through mobilization of phosphorus-rich waters or through primary distribution, can provide insight into the biostratigraphic utility of these faunas. We documented a condensed interval of repeated phosphatic hardgrounds in the Elder Range, Arrowie Basin, and employed sedimentological, compositional, and geochemical techniques to investigate the relationship between faunal preservation and hardground development. Additionally, we applied a suite of geochemical proxies to contrasting fossil-rich and fossil-poor localities to determine whether primary distribution or secondary alteration was the cause of an unusual absence of fauna in the Chace Range. Results show that phosphatic hardgrounds formed over multiple phosphogenic cycles, thereby enhancing the preservation potential of calcareous faunas through secondary mineralization; however, the hardgrounds themselves hinder recovery. These phosphogenic cycles foreshadow a regional unconformity and subsequent sea level rise. Results from carbon and sulfur isotopic records suggest the development of anoxic deep waters in the Chace Range while shallower environments remained oxygenated. This stratification of the water column discouraged the distribution of faunas in deeper, anoxic waters, which ultimately resulted in the paucity of fauna observed in the Chace Range.Item Seismic anisotropy, attenuation, and site amplification study of Southeast Asia and northern Los Angeles Basin(University of Missouri--Columbia, 2025) Islam, Md Mohimanul; Sandvol, Eric A.[EMBARGOED UNTIL 08/01/2026] Understanding the structure and dynamics of the Earth's crust and upper mantle is fundamental to advancing our understanding of plate tectonics and seismic hazard assessment. This dissertation presents four integrated studies focused on high-resolution imaging of the upper mantle, lithosphere, and near-surface effects of ground amplification, using seismic anisotropy, attenuation, and site amplification analyses. Together, these four chapters span diverse tectonic environments, from the highly oblique Indo-Burma subduction system in Southeast Asia to the sediment-filled basins of northern Los Angeles, providing critical insights into mantle deformation, crustal rheology, and seismic ground motion amplification. First, shear wave splitting analysis of teleseismic phases (SKS, SKKS, and PKS) is used to characterize mantle flow and deformation beneath the Indo-Burma subduction zone and the eastern Indochina Peninsula. Results reveal trench-parallel N-S mantle flow beneath the forearc region, induced by prolonged northward motion of the Indian plate and preserved lithospheric fabric due to ongoing convergence, as well as E-W fabric in the east of the Sagaing Fault, likely associated with asthenospheric flow from the Hainan Plume. Second, lithospheric-scale attenuation structures are investigated across Southeast Asia by seismic quality factor (Q) tomography of regional seismic phases. Using both the two-station method and reverse two-station method applied to regional Lg and Sn phases, this study uncovers a heterogeneous attenuation structure that correlates strongly with crustal thickness, volcanic centers, and tectonic boundaries. Particularly notable is the low Q and frequency-dependent attenuation beneath the Tengchong volcanic arc and Indo-Burman Ranges, indicating the presence of partial melt and pervasive crustal scattering. Third, a novel site response mapping is conducted in Yangon, Myanmar, using a dense nodal seismic array, demonstrating that dense small-aperture arrays can resolve site amplification variability at city-block scales, crucial for improving urban seismic hazard models. Finally, reverse two-station analysis is used to map crustal attenuation and site response across the northern Los Angeles Basin, revealing complex amplification patterns tied to basin depth, geometry, and fault proximity. Collectively, this work addresses critical observational gaps in tectonically complex and urbanized regions, enhances our understanding of deep and shallow Earth structures, and provides a framework for improving physics-based ground motion simulations and seismic hazard models.Item Gravitational instabilities in the lithosphere : numerical studies(University of Missouri--Columbia, 2025) Gou, Yiren; Liu, Mian[EMBARGOED UNTIL 08/01/2026] Gravitational instability is one of the fundamental mechanisms controlling the evolution of planets. It drives convection in the Earth's mantle and core, as well as in the atmosphere. However, being cold and stiff, the Earth's lithosphere is supposed to resist the growth of internal gravitational instability. In this dissertation, I integrate numerical experiments with geophysical observations and geological data to explore three Earth's lithospheric deformation processes where gravitational instability plays a major role: salt diapirism in sedimentary basins, Archean dome-and-keel structures, and small-scale removal of mantle lithosphere beneath the central Andes. In the study of salt diapirism, high-resolution thermomechanical models reveal that an interplay of salt buoyancy, differential loading, and tectonic stresses drives salt diapirs. Findings challenge the conventional dichotomy of active versus passive diapirism and underscore the importance of plastic deformation in allowing the piercement of salt rocks into stiff overburdens. For Archean dome-and-keel structures, numerical experiments indicate that their formation through partial convective overturn is more difficult than previously assumed. The favorable conditions for forming dome-and-keel structures are synchronous voluminous mafic-ultramafic magma eruption and TTG (Tonalite--Trondhjemite--Granodiorite) magma intrusion, possibly related to mantle plume activity. Therefore, dome-and-keel structures are products of localized thermal anomalies rather than evidence of a globally dominant vertical tectonic regime suggested in previous studies. To explore the formation of discrete low-velocity zones beneath the central Andes, numerical experiments highlight that composition-induced convective dripping can cause the small-scale removal of the mantle lithosphere, triggered by rheological weakening and lithospheric heterogeneity. The small-scale removal of the mantle lithosphere may account for the seismic low-velocity zones, magmatism, and topographic evolution in the central Andes. This dissertation highlights that the lithosphere can be locally weakened to permit the growth of gravitational instability. Gravitational instability plays a major role in lithosphere tectonics across diverse spatial scales and geological timeframes. By integrating numerical methods with geophysical and geological studies, this dissertation enhances our understanding of lithosphere evolution from the perspective of gravitational instability.Item Calamari through time : exploring antagonistic biotic interactions victimizing cephalopods throughout geologic history(University of Missouri--Columbia, 2025) Burman, Zachary; Huntley, John Warren[EMBARGOED UNTIL 05/01/2026] Cephalopods, a class of marine mollusks that include octopods, squids, and cuttlefish, have existed in Earth's oceans since the Cambrian period. During that time, they have played the roles of both predator and prey as they fill in key ecological roles within their communities. However, exploring those roles from fossil assemblages creates key challenges due to a combination of taphonomic challenges and sampling biases. In this study, we explore traces of biotic interactions -- those that occur while all organisms involved in the interaction are living -- victimizing cephalopods. Specifically, we conduct a statistical meta-analysis based upon peer-reviewed publications dating back over a century to identify the prevalence of traces of parasitism and predation upon cephalopods as well as influences on the number of fossil occurrences. We also review changes in the genus-level biodiversity of cephalopods throughout deep time. We ultimately find that environmental factors including temperature and carbon dioxide levels can substantially influence both the prevalence and preservation of these interactions. However, we also advise caution in interpretation of these results, hoping they inspire further collection and analysis of cephalopod fossils for traces of interactions.Item Mesocopic and geomorphic analysis assessment of cenozoic deformation in the northern Wind River Basin, central Wyoming(University of Missouri--Columbia, 2024) Owens, Ryan Keith; Gomez, FranciscoPregnancy-associated glycoproteins (PAGs) are aspartic proteinases produced by trophoblasts at the fetal-maternal interface. The exact functions of PAGs are unknown. This experiment aims to elucidate PAG function via the ablation of select porcine PAGs in embryos. PAG null embryos were generated via cytidine deaminase base editor. 2 guides targeting homology in 9 of the 12 PAGs were injected into zygotes via microinjection. Subsequent blastocysts were transferred to surrogates and then collected on various days of pregnancy (day 25, day 18). Day 25 yielded no pregnancies. On day 18, the conceptus was present, and PAGKO was confirmed. Histology showed aberrant vascular formation beneath the uterine epithelium. RNAseq analysis showed the down- regulation of several targets related to ECM remodeling. Porcine PAGs appear to affect proper ECM remodeling, though further research will be needed to elucidate the cellular mechanisms of these interactions.Within the northern Wind River Basin, just east of the Boysen Reservoir, the Stagner Creek Fault can be seen exposed within Quaternary gravel formations indicating that tectonic activity has occurred in the recent geologic history of the area. This is relative to the older tectonics of the region produced by Laramide age tectonism and responsible for the deeper tectonic structures such as the Shotgun Butte Thrust Fault. The local environment is sparsely populated. However, a threat to the dam of the Boysen reservoir as well as to the many oil and natural gas wells of the area exists which could have negative implications across the broader region. We used structure from motion (SFM) photography to develop DEMs and scarp profiles that show a 0.36m in the youngest surface that the fault cuts through and corresponds to a 6.3 magnitude quake. New and existing mesoscopic measurements show us that the region has experienced overall contraction. Schmidt hammer sampling helps confirm surface to age relationships in pre-Pinedale age surfaces but is not sensitive enough for post Pinedale age surfaces. The contraction explains the reverse sense of slip on the Stagner Creek Fault. From their relative positions, we also suggest that the Stagner Creek Fault at the surface and the Shotgun Butte Thrust at depth are most likely one in the same. This explains a reactivation of deeper, Laramide age structures