Senior Theses (School of Earth Sciences)

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Submission Instructions

During the senior year or with senior ranking, students pursuing the BS degree in Earth Sciences are required to undertake a senior research project with faculty supervision and to submit a letter-graded senior thesis report of professional quality to the Earth Sciences 4999.01 senior thesis faculty supervisor before graduation. Honors majors theses are also submitted to the honors program as Earth Sciences 4999.01H honors theses. Students pursuing the BA degree in Earth Sciences may also do a senior thesis, following the same procedures. A faculty committee reviews all submitted theses to select the Undergraduate Senior Research Award for that year. A bound paper copy of each submitted and graded thesis is deposited in the Orton Memorial Library of Geology.


Recent Submissions

Now showing 1 - 20 of 940
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    The Use of Diatoms as a Proxy for Environmental Variation in Ohio's Inland Lakes
    (The Ohio State University, 2024-05) Shirk, Trinity; Leonard-Pingel, Jill
    Globally, lacustrine environments are negatively impacted by anthropogenic nutrient input. In Ohio, many inland lakes have been particularly impacted via agricultural runoff. Determining past water quality and nutrient levels in nutrient-enriched lakes can help inform lake restoration efforts seeking to alleviate the negative effects of nutrient enrichment by providing valuable baseline data. Diatoms, photosynthetic microalgae, can serve as indicators of aquatic ecosystems' health. This project employs diatoms as a proxy for nutrient (e.g., phosphorus) enrichment in seven lakes in the Eastern Corn Belt Plains ecoregion of Ohio, focusing on diatom relative abundances (RAs) to understand which taxa are associated with nutrient-enriched waters. Using this proxy to better understand changes in nutrient concentration in Ohio’s lakes can help us understand how and why aquatic systems change throughout time because, while understanding modern water quality is important, establishing water quality baselines is necessary for effective restoration. This data will serve as the framework for the creation of a statistical model that will be employed to reconstruct total phosphorus concentrations in one of Ohio’s oldest reservoirs, Buckeye Lake. The results of this study will be shared with environmental agencies and local community organizations to help inform future restoration projects.
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    (The Ohio State University, 2024-05) Kachmar, Nolan; Griffith, Elizabeth
    Water chemistry of lakes and ponds on San Salvador Island in The Bahamas are influenced by the geological make-up of the island as well as seawater intrusions and the presence of conduits connecting the surface waters to seawater. Evaporation rates are also important for lakes and ponds in The Bahamas. The chemistry of water samples collected on the island were compared to their calcium isotopic composition (δ44/40Ca) to determine how similar the water bodies are to seawater. Seven different water samples were collected and analyzed for δ44/40Ca and elemental concentrations of calcium (Ca), magnesium (Mg), and strontium (Sr). The δ44/40Ca values and elemental concentrations (Ca, Mg, and Sr) were used to determine factors that may affect water chemistry such as evaporation, sea spray, presence of a conduit (connection to the ocean), and carbonate rock dissolution by freshwater infiltration. From my results, all samples excluding Inkwell Blue Hole, Salt Pond and the shallow groundwater sample from the Gerace Research Centre (GRC) well, look similar to seawater based on δ44/40Ca compositions. Inkwell Blue Hole and the GRC well both had δ44/40Ca values that were lower than seawater and resembled carbonate rocks. The hypersaline Salt Pond had high concentration of Ca but a lower δ44/40Ca than seawater suggesting that the water chemistry may be influenced by other processes such as elevated evaporation rates and carbonate rock dissolution or mineral precipitation.
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    Searching for the 1867 Tsunami in the Greater and Lesser Antilles Islands
    (The Ohio State University, 2024-05) Schmetzer, Nicholas; Sawyer, Derek
    The Greater and Lesser Antilles form a chain of islands in the Caribbean Sea which lie on an active plate margin. This area is known for experiencing devastating hurricanes, earthquakes, and tsunamigenic events. Earthquakes and tsunamis are important natural disasters to study because of their destruction to coastal areas and to those who live in those areas. Earthquakes and subsequently tsunamis create extensive damage to infrastructure, landscapes, ecosystems, and amass countless casualties. Studying tsunamis and understanding how and why they form, allows us to prepare better for the future by setting up risk assessment protocols in the event they should occur. Retrieving sediment cores from undisturbed areas affected by tsunamis allows us to analyze the sediment deposition and observe any disruptions without disturbances from living organisms. Coastal salt ponds make excellent traps for tsunamiites, due to their high salinity and lack of life within the ponds. Tsunamiites are sections of the sediment record which are noted by disrupted sediment deposition, preserving evidence of a tsunami inundation events. Outlined in this paper are the steps taken to discover salt ponds and decide systematically which salt ponds are the likeliest to contain tsunami deposits. Further studies of higher ranked salt ponds may find evidence of this tsunamigenic event, which will further assist in understanding tsunami frequency and to plan better for the future
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    Developing Algorithms to Infer Mineralogy of Particles in Taylor Glacier Ice Cores from Elemental Composition Data Measured by spICP-TOFMS and TEM-EDXS
    (The Ohio State University, 2024-05) Smith, Andrew; Olesik, John
    The mineralogy of atmospheric particles affects the amount of light scattered and absorbed by these particles as they pass through the atmosphere. A classification system described in this thesis was developed to automatically infer mineralogy of particles based on their measured elemental chemical composition and the elemental chemical composition of known minerals. When comparing the particle's elemental composition to preset ranges for each mineral, if a particle falls within that range, it is marked as elementally similar to that mineral. When each ratio is converted to python code and applied to elemental composition output files, each particle can be labeled as any chemically similar mineral. The elemental chemical composition of hundreds of thousands to millions of particles atmospheric particles entrapped in glacial ice samples can be measured using single particle Inductively Coupled Plasma-Time of Flight Mass Spectrometry (spICP-TOFMS) in about 2 hours (consuming only about 4 mL of melted ice). A spICP-TOFMS can measure the total number of particles per mL, elemental composition of each particle, and the particle size (mass equivalent diameter). This system of inferring mineralogy was assessed by comparison to Transmission Electron Microscope-Energy Dispersive X-ray Spectroscopy (TEM-EDXS) analysis of a limited (50) number of particles from Taylor Glacier samples with manual inference of mineralogy. The system described in this thesis was also used to infer mineralogy of mineral standards whose elemental composition was measured using spICP-TOFMS. After comparisons to multiple methods of inferring mineralogy, the system within this thesis was used to analyze samples of Taylor glacier measured by spICP-TOFMS.
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    (The Ohio State University, 2024-05) Stalla, John; Barton, Michael
    Volcán de Pacaya is a volcanic complex that lies within the Central American Volcano Arc, formed by the subduction of the Cocos plate beneath the Caribbean Plate. In 1961, it began erupting following a 76-year dormancy. The dominant lithology of the lavas erupted during this time has been olivine-bearing basalt. Noble gas isotope ratios can provide chemical signatures for the source of magma, whether it be a subducting plate causing flux melting or mantle upwelling and decompression melting caused by crustal thinning. The 3He/4He ratio from this study indicated that mantle input has been occurring into Pacaya’s magma system since at least 1961. Helium isotope signatures of back-arc volcanism and midocean ridge basalts occur within these lavas. The argon isotopes indicate that the magma has been enriched with mantle material and that the magma did not fractionate before eruption. Lastly, the neon isotopes indicate that some crustal material is present within Pacaya’s magma, but it is dominated by a mantle signal.
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    Coupling GIPL Permafrost and Plant Hydraulics Model to Estimate Ecohydrological Responses to Climate Warming in Boreal Forests
    (The Ohio State University, 2024-05) McNeal, Briana; Liu, Yanlan
    In Arctic and Sub-Arctic regions, the existence of permafrost, a layer of soil below the earth’s surface that stays below the freezing point of 0°C for two consecutive years, depends largely on air surface temperatures. Therefore, with the occurrence of climate warming, permafrost extent and depth is changing throughout vulnerable regions located within and near the Arctic. With these regions heating up at more than twice the speed of the global average, it is becoming increasingly important to understand the dynamics of permafrost thaw and freeze cycles, as active layer thickness (ALT), which is defined as the height of the subsurface layer that freezes and thaws above the permafrost on an annual basis, affects infrastructure, methane, and carbon emissions. The vegetation that exists in permafrost regions is expected to play a large role in the progression of permafrost degradation, as plant hydraulics interact with the soil moisture, affecting characteristics such as thermal conductivity. Here, we analyze these predicted interactions between plant hydraulics and permafrost depth by coupling the GIPL soil temperature model and a plant hydraulics model. Using a robust soil, atmospheric, and plant hydraulic dataset collected at a site near Fairbanks, Alaska, independent and coupled real-world scenarios were tested. With plant hydraulics, we find that frozen soil depth has an impact on plant water stress. For frozen soil depth, we find that soil moisture impacts soil temperatures. However, sensitivity tests suggest that the thermo-physical properties of organic soils are not accurately captured by the GIPL model without further calibration.
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    Reconstruction of Coral Reef Ecosystem Health in Lagoon Cay, Belize Using Invertebrate Assemblages in a Reef Matrix Core
    (The Ohio State University, 2024-05) Manross, Miranda; Leonard-Pingel, Jill
    Coral abundance is declining worldwide due to anthropogenic factors such as overfishing, agricultural advancements, and human driven climate change. While we have abundant data on reef coverage from underwater surveys completed in recent decades, there remains significant gaps in reef ecosystem data predating the 1970s. Reef matrix cores can help fill this knowledge gap by providing long-term records of reef community change prior to global-scale anthropogenic disturbance. We analyzed subfossil invertebrate assemblages preserved in lagoonal reef-matrix cores from Lagoon Cay, Belize. Bivalves, gastropods, coral, and echinoderm spines were sorted from sieve residue at 5-cm increments. Bivalves and gastropods were identified and counted. Echinoderm spines and coral were identified and weighed to obtain proportional abundance. All were identified to the lowest taxonomic level, typically to genus. Observed in this core is pre-colonial stability amongst the represented taxa. These stability patterns signal the abundance of available hard substrate (i.e., reef building corals). Herbivorous gastropods dominated the gastropod assemblage throughout the core, which is likely due to the abundance of benthic algae accessible to graze on over hard substrate. Despite its role as a keystone herbivore within Caribbean reefs, Diadema antillarum was not the dominant urchin anywhere in the core. Instead, Echinometra spp., the dominant urchin on these reefs today, was the most abundant urchin in all sections. The trends in available taxa show a healthy reef in the represented time. This contrasts other Caribbean cores as well as other cores from Belize. This could be due to the core not extending far enough into the present with the most recent date being 1867. Investigating long-term changes in coral reef invertebrate communities can reveal the ecosystem-level effects of recent declines in Caribbean reef-building corals.
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    A Physical Analysis of Icelandic Lavas: What Clinopyroxenes Reveal About the Southwest Reykjanes Peninsula
    (The Ohio State University, 2024-05) Wiksell, Cameron; Barton, Michael
    The geology of Iceland’s Southwest Reykjanes Peninsula is unique and not fully understood, and volcanic activity persists into modern times. It is a special location where a plate boundary is pulling apart, creating rift volcanism. To get a better foothold in understanding this complex geology, petrographic analyses were performed. Samples were collected from areas of high volcanism, namely Midfell, Litla Sandfell, and to a lesser degree Fagradalsfjall, Geitafell, and the southwestern tip of the Reykjanes Peninsula. Most of these samples were basaltic lavas or glasses erupted from nearby volcanic features. Detailed visual analyses were conducted on thin sections made from these igneous samples. Mineral makeup and volcanic textures present in these minerals were documented. Clinopyroxenes were studied in more detail, due to their common occurrence and ideal textures such as zoning that can tell a lot about magmatic processes. Due to the distribution of clinopyroxenes at these locations, Midfell and Sandfell were able to be analyzed in more depth than the other three localities.
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    Mineralogical Analysis and Material Source Interpretation of a Gravity Core from Marsili Seamount (Tyrrhenian Sea)
    (The Ohio State University, 2024-05) Bzdafka, Jacob; Sawyer , Derek
    Marsili Seamount (MS) is the largest volcano in the Mediterranean Sea with a peak at about 3000 m above the seafloor and -500 m below sea level. MS has been labeled as a potential geohazard due to measured 3He/4He anomalies indicating gases are being released by an active magma chamber. The core location is 328 m below the summit and possibly provides a view of the recent activity of MS. Physical characteristics data was collected from the core by a multi sensor core logger (MSCL) and grain size data was acquired via laser diffraction (LD). Smear slides were created, and XRD data was collected from the samples analyzed in this paper. The gravity core is comprised of a 13 cm clayed silt upper zone and a lower 25 cm thick volcanic zone made of lapilli and ash tephra layers. This volcanic zone is composed of high amounts of glass implying the source is that of an underwater eruption and it can be described as a tephra bearing unit. Additionally, plagioclase, muscovite, and augite are major minerals in the lower zone and further imply an igneous source. The loose nature of the volcanic zone, as well as its moderate grain sorting and an irregular upper contact, are consistent with near-source flows. These characteristics are similar to those of other cores taken from MS. However, without additional chemical composition data, it is difficult to confidently determine an exact source for the volcanic material.
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    Investigation of Cobble Bar Morphology and Sediment Texture in an Arctic River
    (The Ohio State University, 2024-05) Shoen, Kyle; Sawyer, Audrey
    Different methods are widely used to map grain size distributions in rivers, and a comparison of these methods could give better insight into the fluvial geomorphology of Arctic rivers, which are inaccessible to sampling over much of the year. This study focuses on the Miella River near Abisko, Sweden (latitude 68N), which has ice break-up and flood events. I analyze grain size across six geomorphic zones that were identified along a characteristic cobble bar and adjacent riverbed. As part of this analysis, I compare manual Wolman pebble counts and ground-based photographic analysis of sediment textures. Ten evenly scattered ground-based photographs from each of the six zones were taken approximately 1 m from the surface level and were analyzed using BASEGRAIN, an automatic MATLAB-based object detection software. BASEGRAIN was rapid to implement compared to Wolman pebble counts but challenging to implement in submerged portions of the channel, leading to inaccuracies in grain size estimation underwater. Both BASEGRAIN and Wolman pebble counts identified distinct sediment texture differences between zones. This study contributes to a larger effort to shed new light on geomorphologic and sediment transport processes of the Miella River and will help guide the selection of different grain size analysis techniques in future Arctic river studies.
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    How Does Radar Interact with Forests: Quantifying Forest Impact on Snow Radar Remote Sensing
    (The Ohio State University, 2024-05) Boeing, Felix; Durand, Michael
    Snowpack stores winter precipitation allowing for sufficient streamflow to meet spring and summer demand. Snow is an essential water source and supplies water for drinking and irrigation throughout the year. Climate change has been impacting and will continue to impact snowpack which will have far reaching consequences for food, water, and energy security, the economy, human health, biodiversity, wildfires, and climate change itself. It is more important now than ever to understand snow extent, snow properties such as depth and snow-water equivalent (SWE), and snowmelt dynamics. Despite the need for this data, snow remote sensing is not yet in a place where the questions of how snow might melt and how much water is contained within the snow can be answered. The best idea is a dual frequency dual polarization synthetic aperture radar and radiometer (SWESARR) at X and Ku band frequency to maximize sensitivity to various snow and vegetation properties. SWE calculation is especially difficult in forested area with a biomass density of greater than 100 m3/ha or a cover fraction (Cf) of greater than 30%. Most studies look at the volume scattering extinction of radar by canopies and use radiative transfer models where SWESARR readings are insufficient but neglect signal enhancement before the trees. We examine both enhancement and extinction in forested areas and propose a conceptual model against which to compare our results. We find a geometric enhancement of about 4 dB, an extinction magnitude of around -16 dB, with enhancement occurring at a distance of half the height of the trees and a signal recovery occurring at a distance of two thirds the height of the trees. Algorithms should consider both extinction and enhancement when estimating SWE to maximize accuracy.
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    Strain Partitioning around Faults in the Lake District of the Southern Andes
    (The Ohio State University, 2024-05) Kras, Peter; Griffith, W. Ashley
    This study addresses the variation of principal strains throughout the Southern Andean Volcanic Zone (SVZ). The SVZ has two prominent fault structures known as the Liquiñe-Ofqui Fault System (LOFS) and Andean Transverse Faults (ATF). The LOFS is a major transverse fault structure that strikes parallel to the margin and the ATF are crustal scale faults that strike NW and NE. Both fault structures are seismically active, underly many of the volcanic edifices in the SVZ, and partition strain from the obliquely convergent margin. To understand the strain partitioning throughout the region, kinematic information like slip direction and slip sense of brittle fractures were collected at various localities. The analyses of the fractures were run as fault-slip data inversions at the local and regional scale. The regional scale strain analysis displayed kinematically heterogeneous faulting with the predominate dextral strike-slip NE-striking faults of the LOFS. The local scale strain analysis displayed either homogeneous or heterogeneous results based on the individual locality. I discuss the calculated principal strain directions for each locality in the context of the local fault structure. Principal strain orientations vary considerably from locality to locality and deviate from the regional strain tensor. This can be interpreted in terms of strong strain partitioning throughout the SVZ due to mechanical interactions between the LOFS and ATF.
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    Analysis of Bottom Simulating Reflections in the Blake Ridge 2D Seismic Reflection Data
    (The Ohio State University, 2024-05) Krysova, Anastasiia; Cook, Ann
    During the summer of 2023 I participated in a 2D seismic cruise on Blake Ridge. In this thesis, I analyze seismic reflection Lines 1001 and 1003 that were processed during the cruise. My interpretation is focused on identifying evidence for natural gas hydrate in near seafloor sediments. Gas hydrate is an ice-like substance that contains a highly concentrated source of methane. In seismic data, I look for and map bottom simulating reflections, which serve as indicators for the presence of gas hydrate. These reflections appear at the bottom of the gas hydrate stability zone. Line 1001 contains a clear, continuous BSR. Using the TgradBSR, an application that estimates the depth of the BSR, I calculated the thermodynamic base of gas hydrate stability. This requires pressure, salinity, seafloor temperature data, and the geothermal gradient. Using two different geothermal gradients from Ocean Drilling Program Leg 164, Site 994 and 995, two estimates of the BSR depth were calculated. The observed BSR depth was shallower than the two estimates. The change in the seafloor temperature and the P-wave velocities may have affected the depth of the BSR to some extent, but the greatest factor affecting the depth of the BSR was the geothermal gradient. Using a higher geothermal gradient of 39.6 °C/km, compared to Sites 994 and 995, the estimated BSR depth matches the observed BSR depth.
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    (The Ohio State University, 2024-05) Nidy, Claire; Barton, Michael
    The Pacaya Volcanic Complex in Guatemala sits atop an active subduction zone. With the Cocos plate (sitting below the Pacific Plate) moving to the east and subducting under the Caribbean plate, active volcanism presents itself about 40 miles inland into Guatemala and surrounding Central American countries. Yet, this volcanism has a geochemical signature of back-arc basin volcanism rather than arc magmatism, as would be expected of this tectonic boundary as seen in other subduction zones around the world. From 17 samples of Pacaya lava flows dating from 2008-2021, 10 major oxides and 18 trace elements have been accounted for and analyzed. This data gives the necessary geochemical information to interpret the type of volcanism occurring within the complex. Additionally, the data gives vital information as to the state of the magma chamber and melt composition or the Pacaya complex over this 2008- 2021 time.
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    Multi-Decadal Recovery of Post-Wildfire Gross Primary Productivity in North-Central-Colorado
    (The Ohio State University, 2024-05) Sneed, Claire; Liu, Yanlan
    Wildfires abruptly reduce vegetation cover and gross primary productivity (GPP), a measure of photosynthesis, with the complete recovery process extending beyond a decade. Post-fire recovery of vegetation in mountainous ecosystems is particularly complex due to topography’s influence on local hydrology and climate. Most existing studies on post-fire vegetation recovery primarily focus on the short-term response while neglecting long-term legacy effects and use vegetation metrics other than GPP. Here, we address these gaps by using long-term records of remotely sensed burn area and GPP from the Landsat Burned Area Product and MODIS GPP in a space-for-time substitution approach to analyze the spatial-temporal patterns of recovery over multi-decadal periods in North-Central Colorado. We further examine how climate, environmental, and fire-related conditions contribute to the observed variation in recovery by running 17 such predictors in a Random Forest machine learning regression model. We find that GPP in burned areas within the study area recovers more slowly under conditions that are hotter, more arid, and that burned under higher severity fires, with maximum temperature anomalies being the most important predictor of post-fire GPP recovery. As post-fire climatic conditions are identified as the most important predictors of GPP recovery, these findings suggest that increasing temperatures under climate change are expected to inhibit post-fire GPP recovery, especially compounded with drought and severe burns, pointing to the value in considering post-fire climate to evaluate the impact of wildfires on terrestrial carbon budgets.
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    Ecological Correlates of the Morphology of the Auditory Bulla in Rodents: Applications to the Fossil Record
    (The Ohio State University, 2020-12) Scarpitti, Erica; Calede, Jonathan
    For rodents, hearing is essential to survival; it enables predator evasion, prey detection, and conspecific recognition. The hearing system of rodents is likely to be ecology-specific since hearing is constrained by the surrounding physical environment. Previous research on the middle ear of rodents shows this ecomorphological association. The link between tympanic bulla morphology and ecology has never been investigated across a broad array of rodent species before; such link may enable the determination of the ecological affinities of many fossil species only known from partial skulls. In this study, I use geometric morphometrics to quantify the shape of the auditory bulla of 197 specimens of extant rodents representing 91 species from 17 families across four different locomotory modes. I use landmarks and semi-landmarks on the ventral and lateral views of the skull to capture characteristics of bullar inflation and external auditory meatus extension. The results of my principal component analyses and canonical variate analyses demonstrate an association between bullar morphology and locomotion in rodents. The classification phase of my combined analysis of the two views enables the correct classification of 76% of the species in the training set. A phylogenetically-informed flexible discriminant analysis shows a weak phylogenetic effect on tympanic morphology. The application of this approach to select fossil rodents from the Oligo-Miocene shows broad agreements with prior studies and yields new locomotory inferences for 17 fossil species, including the first proposed locomotion for members of the family Florentiamyidae. Such results call for the timing of burrowing diversification in rodents to be reevaluated.
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    Carbon Export at Shatsky Rise During Maastrichtian from 67.776 to 67.704 Million years ago Using Marine Barite Accumulation Rate as Proxy
    (The Ohio State University, 2018-12) Ahmad Zulkifli, Siti Faizura; Griffith, Elizabeth
    The ocean regulates CO2 concentrations in the atmosphere through physical, biological and carbonate pumps. The biological pump sequesters CO2 in the form of organic carbon (organic carbon export) while the carbonate pump sequesters the CO2 in the form of inorganic carbon in marine sediments. In this study, carbonate content and barite accumulation rate (BAR) were used as carbon export proxies to reconstruct ocean conditions at Shatsky Rise in the Pacific Ocean over a ~70 kyr time interval during the Maastrichtian at ~67 million years ago (Ma). Since carbonate accumulation in deep sea sediments can be affected by temperature, pH, depth and productivity of phytoplankton, BAR was used to eliminate the possibility of low primary productivity and constrain interpretations of the carbonate proxy. Barite is a refractory mineral with high preservation rate (~30%) in deep sea sediments that are not sulfate reducing. Marine barite forms in the water column when the organic matter degrades. Eight consecutive samples (67.776 Ma to 67.704 Ma) from Ocean Drilling Program (ODP) Expedition 198 Site 1210B were processed through a sequential leaching method to obtain barite residue. BAR is the highest (5.0 mg/cm2.kyr) starting from 232.78 mbsf until 232.83 mbsf (10kyr) suggesting carbon export and primary production during this interval is the highest. The BAR results show negative correlation to the color reflectance used to estimate carbonate content in the core. The drop in carbonate content might be caused by decreasing bottom water temperature and more corrosive water dissolving carbonate resulting in the short term shoaling of the carbonate compensation depth (CCD). Based on previous work, the bottom water temperature and chemistry was changing due to variations in ocean circulation at this time.
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    Use of noble gas and hydrocarbon geochemistry to determine the source of hydrocarbons in Gulf of Mexico gas hydrates
    (The Ohio State University, 2018-05) Lary, Brent; Darrah, Thomas
    Global gas hydrate deposits along continental slopes and below permafrost are estimated to contain between 1,000 and 22,000 gigatonnes of carbon. However, their role in the energy sector and the global carbon cycle remains uncertain. Integration of noble gas geochemistry with conventional hydrocarbon molecular and isotopic composition approaches offers an insight into how natural gas contained in hydrates was generated (e.g., biogenic, thermogenic, mixed) and/or the manner in which hydrocarbons contained in clathrates migrated. By integrating the above techniques, one can also help to improve exploration techniques for natural gas in clathrates and help better estimate their economic hydrocarbon extraction potential. Furthermore, the accumulation of 4He can be used to estimate the residence time of fluids associated with clathrate formation in gas hydrate reservoirs. Because the original noble gas composition of a fluid is preserved independent of microbial activity, chemical reactions, or changes in oxygen fugacity, the integration of noble gas data can provide both a geochemical fingerprint for the sources of fluids and an additional insight as to the uncertainty between effects of mixing versus post-genetic modification. Fluids from pressurized cores acquired from the UT-GOM2-01 drilling project in the GC955 block of the Green Canyon within the Gulf of Mexico were analyzed for hydrocarbon molecular composition (e.g., C1-C6), major gas abundances (e.g., H2, N2, CO2), and noble gas elemental and isotopic abundances (e.g., He, Ne, Ar). Clathrates acquired during this cruise were dominantly biogenic in origin and contained evidence of 2-phase migration with a range of residence times of 37,300 years to 575,000 years. The data collected in this study were compared with previously published data from 3 additional locations within the Gulf of Mexico. The additional data displayed gases from regions in the Gulf of Mexico that exhibited a purely biogenic endmember and a region that exhibited a mixture of biogenic and thermogenic sources.
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    (The Ohio State University, 2023-12) Courtright, Daniel; Sawyer, Derek; Alsdorf, Douglas
    Surficial deposits across the state of Ohio, created by glacial erosion and recession, as well as anthropogenic causes, lie on top of the bedrock throughout the state. The datasets that are available to be captured by the testing of these deposits could fill a void in the current information that is publicly available online. The variability among these deposits is useful information in a wide range of construction projects, from residential and commercial, to transportation and agriculture related. The goal of this thesis is to propose the expansion of the online database used by the state in order to create a more in depth ArcGIS map that would be easily accessible in order to have data points to refer to when planning new projects, or altering current structures? A total of 31 boreholes were sampled from 3 different sites across central Ohio. These samples were gathered using standard penetration test (SPT) using the hollow stem auger (HSA) method in 1 ½ foot increments, and all lab testing on moisture content and Atterberg limits was carried out at DHDC Engineering Consulting Services, located in Columbus, Ohio. These locations were selected randomly from the datasets available to DHDC in order to sample areas affected by glacial processes (2 of the sites) and one site that has not. These sites therefore are a representative subset available for this project. A key outcome or finding of this project is that there is a wide range of properties of deposit composition, including moisture content, grain size, color, liquid and plastic limits, and depth of bedrock, of the samples taken at these sites illustrates the possibility to formally collect and organize similar reports and datasets for a statewide surficial sediment database or a central information center in order to create a better understanding of the composition of different localities, and also a build platform where data can be visually observed, without entering the field, that can illustrate the variation across regions and time.
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    Carbon Delivery to Floodplain Aquifers in Response to Water Table Fluctuations: Observations from Soil Column Experiments
    (The Ohio State University, 2023-08) Scaccia, Maria; Sawyer, Audrey
    Water tables in floodplain aquifers rise and fall over a variety of timescales in response to changes in nearby surface water levels, precipitation, floods, and groundwater pumping. The associated change in saturation state and vertical movement of water through soil layers can profoundly influence dissolved organic matter (DOM) sources to shallow groundwater. To investigate the effects of water table fluctuations on DOM supply to groundwater, an experiment was conducted at two Mediterranean sites: a pristine forested stream and an urban coastal floodplain. Groundwater was pumped into and out of the bottom of a layered soil column at varying rates to simulate water table fluctuations within zones of more mineral or organic-rich soils over a period of 16 days. Flooding events were simulated by inundating the top of the column with local surface water. The effects of repeated wetting and drying events on carbon mobilization, DOM quality, and geochemical responses were measured. During initial water table fluctuations, redox potential near the soil-Mineral Interface was relatively stable but declined after subsequent wettings. DOC concentrations were consistently greater in shallow soil layers, and DOC-rich water moved downward into deeper layers after each wetting and draining cycle. As DOC concentrations in pore waters increased, SUVA at 254 nm also increased. Water table fluctuations had a measurable effect on the humification, fluorescence, and freshness indices of DOM. This study shows the influence of multiple saturation events on carbon mobilization and shallow groundwater biogeochemistry in unique floodplain soil sequences.