Earth Sciences Department Theses and Dissertations
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About the Program
The IUPUI graduate program in Geology leads to a Master of Science degree from Indiana University. Our terminal degree at the IUPUI campus is the Master of Science. As a result, our faculty are able to focus their attention on our Masters program student research. We offer a thesis and non-thesis option; however, typically only thesis-option students are considered for funding. Our thesis option requires 24 credit hours of graduate level courses and 6 credit hours of a research thesis. We have between 8-12 full-time graduate students per year.
Interested students should contact us prior to applying. If applicable, an appointment/visit can be set up for you to see our facilities and meet a few of our faculty. Students can apply with an interest in a specific faculty member or a group of faculty members. Admission decisions are decided by our graduate committee and not individual faculty members. Once you enter the program, you will take a majority of your courses in your first year. Also, you will choose your research advisor and submit your thesis (research) proposal. Your second year (including the summer) is focused on completing your research project and writing your thesis while finishing your course work.
For more information: http://www.geology.iupui.edu/Degree_Programs/Graduate_Studies/index.htm
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Item Common Era Midcontinental Hydroclimate Variability Inferred from Iowan Lake Sediments, Usa(2024-02) Goswami, Anusuya; Bird, Broxton; Filippelli, Gabriel; Jacinthe, Pierre-AndréGlobal climate change manifests diverse consequences across the United States, creating distinct challenges in different regions. For example: The Western United States grapples with a notable surge in wildfires and drought events, indicating reduced effective moisture. In contrast, the Eastern part faces severe and frequent flooding events, reflecting higher effective moisture conditions and suggesting an East-West dipole-like climatic pattern. While the current East-West dividing hinge-line sits at 96°W, questions linger about its persistence throughout the late Holocene or whether it has undergone changes over time. Understanding the evolution and stability of this hinge-line is crucial for predicting the impacts of ongoing global warming on various U.S. regions. To address this issue, it is essential to develop additional paleoclimate records from the U.S. Midcontinent, especially those in close proximity to the modern hydroclimate hinge-line. This research focuses on understanding the common era (CE; last 2000 years) hydroclimate variability and its driving mechanisms using lake sediment archives from two hydrologically restricted Iowan kettle lakes, West Lake Okoboji (~1800 years long) and Clear Lake (~2000 years long). The results of multiproxy sedimentological, geochemical, and isotopic analyses reveal a wetter period during the Medieval Climate Anomaly (MCA; 950-1250 CE) and a drier phase during the Little Ice Age (LIA; 1350-1850 CE), aligning with regional patterns in the upper Midwest. Comparisons with regional paleoclimate records suggest that pluvial conditions during the MCA were linked to mean state atmospheric circulation conditions resembling the negative phase of the Pacific-North American (-PNA) teleconnection pattern when Pacific Ocean-atmosphere conditions similarly resembled the negative phase of the Pacific Decadal Oscillation (-PDO). Conversely, drier conditions during the LIA occurred when +PNA-like atmospheric circulation patterns predominated under +PDO-like conditions in the North Pacific Ocean. Comparison with records near the modern hydroclimate hinge-line indicates in-phase relationships with records east of 96˚ W and anti-phased relationships with records west of 96˚ W. This supports idea of the stable hinge line position during the Common Era.Item Indicators of Euro-American land-use change as geochronologic markers in Midwest floodplain lake sediment archives(2024-02) LaRoche, Kierstin Marie; Bird, Broxton W.; Licht, Kathy J.; Gilhooly, William P., IIIIn association with predicted rising global average temperatures, spring and winter precipitation in the Midwest is projected to increase by up to 30% by the end of this century. Enhanced by the alteration of natural environments, this increase will likely result in more frequent extreme flood events. To best prepare for these circumstances, interest has risen in reconstructing the dynamics between changing climate, altered landscapes, and fluvial systems with age-depth modeling, often using radiocarbon (14C) and 210Pb dating and multi-proxy evidence from floodplain lake sediment archives. Age- depth modeling over the last 300 years can be difficult, however, due to a large plateau in the radiocarbon calibration curve, and 210Pb dating is not reliable for all sediment records. Here, indicators of land-use change, magnetic susceptibility, Rb/Sr, Pb/Zr, and d15N values, were used to create age-depth control for Shannon Lake, IN, a difficult-to-date 600-year-old oxbow lake of the White River near Indianapolis. Age control for Shannon Lake was completed by correlating the timing in the rise of the same proxies from a previously well-dated lake record from Half Moon Pond, an oxbow lake of the White River near Petersburg, IN. The Shannon and Half Moon records were compared to those of three floodplain lake records of the Ohio River floodplain: Avery Lake, IL, Goose Pond, IN, and Grassy Pond, KY to investigate how these proxies varied in floodplain lake sediment from the lower Ohio River. The land-use indicators provided age-control for Shannon Lake, and the indicators of land-use change for the White River records resembled those of the Ohio River records over the last 600 years, where the onset of Euro-American land-use changes were detected at or around 1750 CE. MS, Rb/Sr, and d15N values displayed the greatest resemblance, while greater variations in Rb/Sr values were observed across the five lake records, potentially due to differences in regional setting or differences in the scale of the White River and Ohio River watersheds.Item A Combined Molecular and Isotopic Study of Sulfur Bacteria in Meromictic Lakes of the Pacific Northwest(2023-12) Harris, James H., IV; Gilhooly, William P., III; Druschel, Gregory K.; Bird, Broxton W.The isotope effects that result from the activity of modern sulfur metabolizing bacteria serve as analogs to interpreting the sulfur isotope values preserved in the geologic record. This biogenic signal is vital to reconstructing the history of Earth’s ancient oceans and atmosphere. However, the isotope compositions imprinted by these bacteria were influenced by multiple factors that must be considered when using these values to make interpretations about environmental change. These factors include: (1) sulfate availability, (2) the rapid and quantitative reoxidation of sulfide (i.e., cryptic sulfur cycling), (3) the initial oxygen isotope compositions of sulfate and water, and (4) the taxonomic structure of sulfur-metabolizing bacterial communities. To address these questions, this project studied four permanently stratified, anoxic and sulfidic (euxinic), lakes in southern British Columbia, Canada, and northern Washington, USA, that have a wide range of sulfate concentrations, from 0.15 – 120 mM. This project resulted in six key findings – (1) the measurement of large Δ34SSO4-H2S values at micromolar sulfate concentrations, (2) the consistent occurrence of δ18OSO4 minima at the chemocline that may be imparted during cryptic sulfur cycling, (3) that subsequent δ18OSO4 enrichments consistently preceded sulfide accumulation and δ34SSO4 enrichment in the suboxic zone of the water column, (4) that initial epilimnion Δ18OSO4-H2O values placed constraints on the maximum extent of δ18OSO4 evolution that occurred beneath the chemocline, (5) that observable changes in the metabolic composition of sulfur bacterial communities accompanied key inflections in the sulfur and oxygen isotope profiles of sulfate and sulfide within the water column, and (6) that, despite large overall differences in community structure, Δ34SSO4-H2S and Δ18OSO4-H2O values ultimately reached similar magnitudes in each lake.Item Midcontinental Hydroclimate Variability from a 1,500-yr Wisconsin Lake Sediment Record(2023-12) Nealy, Cameron Alexander; Bird, Braxton; Gilhooly, William, III; Licht, KathyLacustrine sediment archives preserve continuous records of changes in basin- to regional-scale processes that reflect broader variability in climatic conditions. Here, we present a 1,500-yr sediment record of inferred effective moisture (P/E) that spans the Current Warm Period (CWP; last 150 years), Medieval Climate Anomaly (MCA; ca. 950–1250 CE), and Little Ice Age (LIA; ca. 1300–1800 CE) from glacially-formed Pope Lake in central Wisconsin. A suite of sediment proxies constrained by 14C and 210Pb ages was developed at decadal resolution to investigate Common Era changes in Upper Midwest effective moisture in response to temperature and synoptic scale atmospheric variability, such as the Pacific North American (PNA) pattern. Lake water isotopes reconstructed with authigenic carbonate oxygen isotopes (d18Ocal) from Pope Lake compare favorably with other Midwestern closed-basin lakes, indicating that evaporation was a significant control on the isotopic composition of lake water. Relatively lower d18Ocal values during the MCA suggest that the moisture availability was greater during the MCA than LIA, despite increased air temperatures. This is supported by low carbon/nitrogen (C/N) ratios and low terrestrial lithic contributions that reflect increased lake levels during the MCA. Reversals of these trends during the cooler LIA were observed. Comparisons of the Pope Lake record to synoptic scale forcings suggest that shifts in regional P/E were consistent with high amplitude PNA variability that likely affected the source and seasonality of precipitation. The general warm/wet and cool/dry relationship noted during the MCA and LIA underscores how global temperature anomalies may alter the balance of effective moisture in the Upper Midwest in relatively short succession. The Pope Lake sediment record presented here is an important step in establishing hydroclimatic history that may inform expectations of future climate for a region sparsely populated with similar high resolution late Holocene records.Item Attributes of Organic Phosphorus Exported from a Central Indiana Agricultural Watershed: Effects of Season and Hydrologic Flowpath(2023-05) Pitcock, Rebecca Jo; Jacinthe, Pierre-Andre; Filippelli, Gabriel; Wang, LixinThe export of phosphorus (P) from agricultural watersheds has been extensively investigated but monitoring efforts have generally focused on inorganic P (Pi or soluble reactive phosphorus [SRP]), the P fraction thought to be immediately available to algae. However, in settings where no-till management is implemented and organic matter accumulates on soil surface, the amount of organic P (Po) in agricultural drainage waters can be significant and may represent another important P source to fuel algal growth in receiving water bodies. From a 2018 monitoring study at a Central Indiana agricultural watershed, measured total P and SRP loss amounted to 1.22 and 0.17 kg P/ha/year, respectively, indicating that the bulk (84%) of P exported from that watershed was in organic form. Results also showed that tile drainage was the main pathway for P transport (96% of Po loss). In light of these observations, the bioavailability of Po in agricultural drainage waters was investigated in 2019, and the effect of hydrologic flow path (surface versus subsurface flow) on the biochemical attributes of Po was examined. In these assessments, the iron strip method and a suite of enzymatic assays were used to gain a better understanding of the chemical composition of the exported Po. Higher concentration of labile Po was consistently measured in tile discharge than in surface runoff (59% versus 38% of the total bioavailable P). Further, the concentration of EHP (enzymatically hydrolysable P), in the form of monoester, diester, and phytate compounds, was highest during the summer season, for both tile and surface pathways. This elevated bioavailability of Po during the summer is a concern because, in combination with favorable water temperature and solar radiation during that period, this could lead to enhanced Po mineralization and release of Pi, resulting in further algal proliferation and continued degradation of water quality. Considering the high prevalence of tile drainage in agricultural landscapes of the US Midwest, this finding underscores the need for further investigation of the impact of land management and climate on the speciation and bioavailability of Po in the region’s agricultural waters.Item Exploring Competing Theories of Viscous Emulsion and Fractional Crystallization of the Impact Melt that Formed the Sudbury Igneous Complex(2023-01) Horman, Alexandra Rose; Macris, Catherine A.; Barth, Andrew P.; Gilhooly, William P., III.The Sudbury Igneous Complex (SIC) in Sudbury, Canada is a remnant geologic structure from a meteor impact that occurred ~1.85 Ga. The impact produced ~30,000 km3 of superheated melt which reached >2200 °C. The existing SIC is composed of three compositionally distinct layers, norite, quartz gabbro, and granophyre, which stretch the entire lateral distance of the complex. The presentation of layers in the SIC is unusual for impact melts, and the crystallization path has been debated by scientists. The SIC differs from more common layered mafic complexes because of its intermediate composition, crustal isotopic signature, and large volume of granophyre. This thesis is an investigation of some of the main theories surrounding the SIC and how it crystallized to form such distinct layers. There are two main theories of how the SIC formed its compositionally distinct layers: (1) fractional crystallization and (2) separation by viscous emulsion. The viscous emulsion theory involves isolated droplets of melt separating from the surrounding melt body due to differences in viscosity and density, similar to an emulsion of oil and water. In this study, viscous emulsion theory was investigated experimentally by heating samples of rock from the SIC to the extreme temperatures associated with the Sudbury impact, and then analyzing the cooled experimental products using electron microscopy to determine if there was evidence of textures that would be consistent with expectations for a viscous emulsion. Fractional crystallization was investigated by modeling using the vii software EasyMELTS to evaluate compositions from the SIC to estimate how they would crystallize according to the temperature, pressure, and other properties of the melt. There was no textural evidence of a viscous emulsion found in the experimental products. The models produced compositions similar to what is seen in the SIC but had limited application to fractional crystallization theory.Item Quantifying the Biogeochemical Impact of Land Plant Expansion in the Mid Devonian and Implications in Marine Anoxic Events(2022-12) Smart, Matthew Stephen; Filippelli, Gabriel; Gilhooly, William III; Barth, Andrew; Wilson, JeffreyThe evolution of land plant root systems occurred stepwise throughout the Devonian, with the first evidence of complex root systems appearing in the mid-Givetian. This biological innovation provided an enhanced pathway for the transfer of terrestrial phosphorus (P) to the marine system via weathering and erosion. This enhancement is consistent with paleosol records and has led to hypotheses about the causes of marine eutrophication and mass extinctions during the Devonian. To gain insight into the transport of P between terrestrial and marine domains, presented here are geochemical records from a survey of Middle and Late Devonian lacustrine and near lacustrine sequences that span some of these key marine extinction intervals. Root innovation is hypothesized to have enhanced P delivery and results from multiple Devonian sequences from Euramerica show evidence of a net loss of P from terrestrial sources coincident with the appearance of early progymnosperms. Evidence from multiple Middle to Late Devonian sites (from Greenland and northern Scotland/Orkney), reveal a near-identical net loss of P. Nitrogen and Carbon isotopes from a subset of these lakes confirm elevated input of terrestrial plant material concurrent with P perturbations. Terrestrial P input appears to be episodic in nature, suggesting land plant expansion was driven by an external catalyst in the study region. All sites analyzed are temporally proximal to significant marine extinctions, including precise correlation with the Kačák extinction event and the two pulses associated with the Frasnian-Famennian (F/F) mass extinction. The episodic expansion of terrestrial plants appears to be tied to variations in regional and global climate, and in the case of the F/F extinction, also to atmospheric changes associated with large scale volcanism. Using P data presented here as an input into an Earth system model of the coupled C-N-P-O2-S biogeochemical cycles shows that globally scaled riverine phosphorus export during the Frasnian-Famennian mass extinction generates widespread marine anoxia consistent with the geologic record. While timing precludes land plants as an initiating mechanism in the F/F extinction, these results suggest they are implicated in every marine extinction event in the Mid to Late Devonian.Item Analysing Urban Air Pollution Using Low-Cost Methods and Community Science(2022-12) Heintzelman, Asrah; Filippelli, Gabriel; Moreno-Madriñan, Max J.; Wilson, Jeffrey S.; Wang, Lixin; Druschel, Gregory K.Rise in air pollution resulting in negative health externalities for humans has created an urgent need for cities and communities to monitor it regularly. At present we have insufficient ground passive and active monitoring networks in place which presents a huge challenge. Satellite imagery has been used extensively for such analysis, but its resolution and methodology present other challenges in estimating pollution burden. The objective of this study was to propose three low-cost methods to fill in the gaps that exist currently. First, EPA grade sensors were used in 11 cities across the U.S. to examine NO2. This is a simplistic way to assess the burden of air pollution in a region. However, this technique cannot be applied to fine scale analysis, which resulted in the next two components of this research study. Second, a citizen science network was established on the east side of Indianapolis, IN who hosted 32 Ogawa passive sensors to examine NO2 and O3 at a finer scale. These low-cost passive sensors, not requiring power, and very little maintenance, have historically tracked very closely with Federal Reference Monitors. Third, a low-cost PurpleAir PA-II-SD active sensors measuring PM2.5 were housed with the citizen scientists identified above. This data was uploaded via Wi-Fi and available via a crowd sourced site established by PurpleAir. These data sets were analyzed to examine the burden of air pollution. The second and third research studies enabled granular analyses utilizing citizen science, tree canopy data, and traffic data, thus accommodating some of the present limitations. Advancement in low-cost sensor technology, along with ease of use and maintenance, presents an opportunity for not just communities, but cities to take charge of some of these analyses to help them examine health equity impacts on their citizens because of air pollution.Item Investigating the Effects of Synoptic-Scale Climatic Processes on Local-Scale Hydrology by Combining Multi-Proxy Analyses of Lacustrine Sediments and Instrumental Records(2022-09) Gibson, Derek Keith; Bird, Broxton; Gilhooly, William, III; Jacinthe, Pierre-André; Licht, Kathy; Wang, XianzhongPaleoclimate records from North and South America were used to develop a holistic understanding of global paleo-hydroclimatic drivers across a range of boundary conditions. Here, geophysical analysis of lacustrine sediment stratigraphy at Lago de Tota, Boyaca, Colombia provided evidence for significant lake-level fluctuations through the late Quaternary and produced a record that potentially spans the last 60 ka. Seismic data revealed a series of off-lap and on-lap sequences in the upper ~20 m of sediments that indicated large amplitude changes in lake-level, driven by variability in the mean latitude of the Intertropical Convergence Zone as controlled by insolation- and ocean circulation-driven hemispheric temperature gradients during glacial/stadial and interglacial/interstadial events. In North America, late Holocene flood recurrence in the Midwest and Holocene changes in the mean latitude of the polar front jet stream were investigated through multi-proxy examinations of sediment cores collected from swale lakes in northern Kentucky and southern Indiana, and a glacially formed kettle lake in northern Indiana. These results showed that the midlatitude jet stream was displaced to the south during the late Holocene, which increased the amount of Midwestern precipitation sourced from the northern Pacific and Arctic, especially during prolonged cool conditions. During these cool periods, when atmospheric flow was meridional and a greater amount of precipitation was delivered from the northerly sources, Ohio River flooding increased. During warm conditions, when clockwise mean-state atmospheric circulation advected southerly moisture from the Gulf of Mexico into the Midwest, flooding on the Ohio River decreased. At present, streamflow in the Midwest is demonstrated here to be generally increasing, despite atmospheric conditions typically associated with reduced streamflow in the paleo-record, due in part to increasing precipitation and modern land-use dynamics. Together, these studies demonstrate the sensitivity and vulnerability of local-scale hydrological processes to synoptic climate change.Item Quantifying the Responses of Vegetation to Environmental Stresses(2022-09) Lanning, Matthew L.; Wang, Lixin; Wang, Xianzhong; Novick, Kimberly Ann; Jacinthe, Pierre-André; Gilhooly, William P.I examined interactions between plants and the environment they live in along the soil-plant-atmospheric continuum and addressed the effects of drought and acid deposition on plant water use. Using a novel stable isotope technique, I showed that plant water source utilization can be modulated in some species based on the soil and atmospheric conditions they experience, whereas others only access a single subsurface water source. By modeling cuticular conductance in multiple plant species, I showed that the variability of cuticular conductance across species is largely related to the changes in leaf water potentials between pre-dawn and midday measurements collected in field studies. I also assessed the individual and combined effects of soil water stress and atmospheric water stress on plant productivity by developing a new methodology, which can be used across scales. In doing so, I found that in deciduous broad-leaf forests, periods of high vapor pressure deficit caused sufficient hydraulic stress to reduce plant productivity more than low soil water content alone, and often reduced productivity to levels equal to periods of both low soil water stress and high vapor pressure deficit. Utilizing historical data from a whole forest acidification experiment, I was able to link the stress of nutrient deficiencies caused by acid deposition (specifically calcium) to increases in plant water utilization. This was the first observation of such an effect at the ecosystem scale and could have significant implications for understanding water availability in the future. Finally, I assessed a common method for extracting cellulose from tree rings for isotope analyses, which is often used to determine the historical water use efficiency of plants. I was able to determine chemical alteration to the cellulose molecule using stable isotope measurements and spectroscopy. The chemical modification seems to be systemic and therefore could be addressed through mathematical corrections to existing data. Having accurate values of plant water use efficiency is extremely important for understanding how different stressors in the past changed the way plants used their water resources. My series of studies provide new insights and tools to evaluate the plant-environment interactions in current and future environments.