Browsing by Author "Licht, Kathy"
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Item A Glacier through a Grain of Sand: Sediment Micromorphology from a Land-Terminating Glacier in West Greenland(2024-10) Woodie, Kayla Pearl; Licht, Kathy; Gilhooly, William P., III; Graly, JosephIsunnguata Sermia is a land terminating glacier in West Greenland with prominent upwellings of subglacial water in the outwash plain. Sediment that is suspended in the upwelling water is preserved in ice, creating a window into the subglacial environment. The presence of certain established microtextures, such as those caused by fluvial or high-stress processes, is indicative of a grain’s impact and transport history. Scanning electron microscopy (SEM) imaging of quartz sand grains is used to analyze this micromorphology. Across sand grains collected from different glacial depositional environments and the frozen subglacial water of Isunnguata Sermia, the microtexture distributions are extremely similar despite their different transport processes. While this may represent the limitations of microtexture analysis, it also suggests a high degree of sediment recycling in a basin that includes both the subglacial and the proglacial environment.Item Characterization of lunar crust with moon mineralogy mapper data(2015-06-09) Sun, Ying; Lin, Li; Bird, Broxton; Johnson, Daniel; Licht, Kathy; Gilhooly, William P.This dissertation has three main focuses: (1) identify the distribution of a new rock type (Mg-spinel lithology) on the Moon and explore the likely petrogenesis of Mg-spinel; (2) investigate the presence of olivine in the crater central peaks and analyze the sources of olivine; (3) determine the compositional variations of lunar crust with depth, and establish a new model to describe the structure of the lunar crust.Item Developing Levitation Laser-Fused Glasses as Proxies for Lower Mantle Experiments: a Methodological Approach(2019-06) zur Loye, Thomas Edwards; Macris, Catherine; Barth, Andrew; Licht, KathyObservations of heterogeneities in Earth’s mantle motivate studies of mantle phase assemblages with variable composition. As samples cannot be directly collected from these regions, synthetic glasses can act as analogues for mantle melt and starting materials for high-pressure synthesis of stable mantle minerals in experiments. Here, I develop a specific methodology to produce homogeneous glasses that accurately span the composition space from enstatite (MgSiO3) to forsterite (Mg2SiO4), as well as Fe-bearing enstatite ((Mg0.1Fe0.9)SiO3 and ((Mg0.95Fe0.05)(Si0.95Fe0.05)O3) with variable oxidation states. This study systematically tests and iterates upon glass synthesis methods using an aerodynamic levitation laser furnace, in which a spherical glass sample levitates on a gas stream flowing vertically through a conical nozzle, while being heated from above with a 400 W CO2 laser. With sample diameters of 0.6-2.0 mm, shutting off the laser results in supercooling of levitated spheres at rates between 350 and 1350 °C/s. Sample preparation begins with grinding and mixing pure oxide powders in an agate mortar and pestle, followed by heating in a high temperature oven to devolatilize the mixture. Powders (0.5-7 mg aliquots) are fused into spheres in a copper hearth plate. To tune Fe valency and vitrify each sphere, samples are then levitated on flows of Ar, O2, 5% CO in Ar, 5% CO2 in Ar, or combinations of two of these gases, while being heated with the laser to temperatures above the liquidus for each composition for ~10 s before quenching. After x-ray diffraction (XRD) analyses confirm vitrification, a dual polish is applied, exposing parallel flat polished surfaces for scanning electron microscope (SEM) and electron probe microanalyzer analyses (EPMA). Back-scattered electron images and energy-dispersive x-ray spectroscopy (EDS) analyses of the spheres are obtained first on the SEM to gauge compositional accuracy and homogeneity, then EPMA analyses determine quantitatively the samples’ compositions. Once fully characterized, these glasses can be used in diamond anvil cell experiments, where they can act as proxies for an otherwise inaccessible area of the Earth. In addition to the development of this methodology, two web applications produced during this research aid in visualization of both data logs and analytical results.Item A High-Resolution Study of Local Diagenetic Effects on the Geochemistry of the Late Ordovician Kope Formation(2022-09) Becerra, Evelyn S.; Gilhooly, William P., III; Licht, Kathy; Filippelli, GabrielThe Ordovician (485-444 Ma) was a highly dynamic period, characterized by significant evolutionary and climatic change. Paleozoic fauna which evolved during the Great Ordovician Biodiversification Event (GOBE) populated extensive epicontinental seaways. Major sea level fluctuations during The Hirnantian glaciation are believed to have led to a mass extinction event at the End Ordovician. However, a reassessment of Early Paleozoic fossil assemblages suggests the onset of extinctions began in the mid-Katian, ~3 million years before the Hirnantian. The Kope formation, within the North American succession of the Katian, was deposited during the peak biodiversification of the GOBE at the point which a biological crisis begins. The well-studied series of interbedded shale and fossiliferous limestone beds, deposited within a shallow epeiric sea, provide ideal sedimentological and paleontological context to interpret sediment geochemistry recorded at the onset of a global mass extinction. For a high-resolution section of the Kope, δ34Spyrite show an extraordinary range of variability, up to 64.5‰, with systematic oscillations throughout the core. The isotope signal represents a mix of pyrite formed at the time of deposition and during diagenesis. As sea levels fluctuated, the amount of sediment delivery influenced the connection of sediment porewaters to overlying seawater sulfate and the location of the sulfate reduction zone, which in turn, masked the primary signal. Reactive iron data suggest low oxygen concentrations in the water column, however fossil assemblages found throughout the Kope suggest otherwise. Changes in sedimentation can mask the water column signal, so these data also capture an aggregate signal. δ15Nbulk show an upsection decrease of 4.4‰, followed by a 3.4‰ increase. Though this excursion can be interpreted as a switch to increased denitrification in a low oxygen environment, the fossil record suggests the data capture localized diagenetic reactions that occur below an oxic water column. Perturbations in the ocean-climate system is often based on the interpretation of stable isotope excursions, and although excursions are diagnostic of changes to biogeochemical cycles, they may not fully account for diagenetic reactions that mask primary signals. The results from the Kope demonstrate strong localized, not global, controls on the sediment geochemistry.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 Late Holocene Climate-Flood Relationships on the Lower Ohio River(2020-08) Pollard, Harvie Jason; Bird, Broxton W.; Licht, Kathy; Jacinthe, Pierre-AndreThe frequency and magnitude of flooding events on the Lower Ohio River and their relationship with climate are investigated using a ca. 2000-year-long sediment core collected from Goose Pond, Indiana. Using high-resolution radiocarbon dating (n = 25), late Holocene sedimentation rates were calculated for Goose Pond. Changes in sediment accumulation rates are attributed to variations in the frequency of flooding events on the lower Ohio River. Elevated sedimentation rates immediately following the formation of Goose Pond ca. 2000 years ago persisted until 680 CE, suggesting regular flooding during this interval. Between 680 and 1190 CE, sedimentation rates decreased dramatically and abruptly, indicating a reduction in flood frequencies. Sedimentation rates subsequently increased again at ca. 1190 CE and persisted at a similar level until 1850 CE, suggesting that flooding frequencies increased during a time that overlapped with the Little Ice Age (LIA; 1250-1850 CE). Sedimentation rates increased again at ca. 1850 CE, reaching a 2000-year high (3.33 cm/yr) at 1970 CE and indicating a period characterized by frequent flooding and landscape erosion. The flood record from Goose Pond shows similarities with other Lower Ohio River flood reconstructions from Avery Lake, IL, and Hovey Lake, IN, suggesting the Goose Pond record reflects the regional flooding history for the lower Ohio River. Comparison with paleoclimate records from the Midwest supports the idea that lower Ohio River flood frequencies prior to Euro American occupation in the 1800s increased during times when winter precipitation predominated as a result of atmospheric circulation changes resembling the Pacific North vii American mode (PNA) that appear to have been driven in part by the Pacific Decadal Oscillation (PDO). Following Euro-American land clearance, lower Ohio River flooding increased dramatically despite a decrease in winter precipitation. This likely reflects an increase in runoff and erosion as a result of deforestation and landscape conversion to intensive row crop agriculture. As climate continues to change and the Midwestern United States continues to see an increase in precipitation, both winter and summer, flood frequencies could be expected to increase still further.Item Late Holocene Climate-Flood Relationships on the White River, Indiana, USA(2022-05) Wright, Maxwell N.; Bird, Broxton; Licht, Kathy; Gilhooly, William, III.The frequency and magnitude of floods in the midcontinental United States have increased in recent decades due to changing precipitation patterns as global temperatures rise. These trends pose major social and economic risks to the region, which is home to tens of millions of Americans and a global agricultural center. It is therefore critical to understand if current fluvial dynamics are within the scope of past fluvial-climate relationships, or if they represent a novel response to recent climate and land-use changes. Presented is a 1600-year-long flood frequency record for the moderately sized (~29,400 km2 watershed) White River, Indiana. Flood frequencies were determined using 14C-based sediment accumulation rates at Half Moon Pond, an oxbow lake on the lower White River’s floodplain. Comparison with regional paleoclimate data shows that White River flooding was frequent when atmospheric circulation resembled the negative mode of the Pacific-North American (PNA) teleconnection, particularly during the Medieval Climate Anomaly (950-1250 CE) and the Current Warm Period (last ~150 years). During these times, the regional climate was dominated by warm-season precipitation originating from the Gulf of Mexico. Conversely, White River flooding was less frequent during the Little Ice Age (1250-1800 CE) when cold-season precipitation from the North Pacific/Arctic dominated (+PNA-like conditions). The pre-1790 CE White River flood history was antiphased with reconstructed Ohio River flood frequencies from southern Illinois. This dynamic is consistent with discharge in small to moderate sized watersheds being sensitive to rainstorm runoff and large watersheds being sensitive to snowmelt runoff. After 1790 CE, flooding frequencies of both river systems increased to their highest levels, despite a shift to -PNA-like conditions. This change was likely due to extensive Euro-American land-clearance, which increased runoff/erosion by reducing evapotranspiration, interception, and infiltration. While the White River responded strongly to climatic conditions in the past that were similar to present conditions (-PNA-like conditions), recent land-use practices have amplified the effects of the current hydroclimate. Since a warming climate is expected to increase regional average precipitation and extreme rainfall events, and that landscape modifications have lowered surface resilience to hydroclimate events, flooding will likely become more frequent in the coming decades.Item Meteoric 10Be as a Tracer for Subglacial Chemical Weathering in East Antarctica(2021-12) Arnardóttir, Eiríka Ösp; Licht, Kathy; Graly, Joseph; Bird, Broxton; Gilhooly, WilliamSubglacial chemical processes in Antarctica are potentially significant contributors to global geochemical cycles, but current understanding of their scale and nature is limited. A sequential chemical extraction procedure was developed and tested to investigate the utility of meteoric 10Be as a tracer for chemical weathering processes beneath the East Antarctic Ice Sheet. Subglacial meltwater is widely available under the Antarctic Ice Sheet and chemical constituents within it have the potential to drive geochemical weathering processes in the subglacial environment. Meteoric 10Be is a cosmogenic nuclide with a half-life of 1.39×106 years that is incorporated into glacier ice, therefore its abundance in the subglacial environment in Antarctica is meltwater dependent. It is known to adsorb to fine-grained particles in aqueous solution, precipitate with amorphous oxides, and/or be incorporated into authigenic clay structures during chemical weathering. The presence of 10Be in weathering products derived from beneath the ice therefore indicates chemical weathering processes in the subglacial environment. Freshly emerging subglacial sediments from the Mt. Achernar blue ice moraine were subject to chemical extractions where these weathering phases were isolated and 10Be concentrations therein quantified. Optimization of the phase isolation was developed by examining the effects of each extraction on the sample mineralogy and chemical composition. Experiments on 10Be desorption revealed that pH 3.2-3.5 was optimal for the extraction of adsorbed 10Be. Vigorous disaggregation of the samples before grain size separations and acid extractions is crucial due to the preferential fractionation of the nuclide with clay-sized particles. 10Be concentrations of 2-22×107 atoms g-1 measured in oxides and clay minerals in freshly emerging sediments strongly indicate subglacial chemical weathering in the catchment of the Mt. Achernar moraine. Sediment-meltwater contact in the system was calculated to be on the order of thousands of years, based on total 10Be sample concentrations, local basal melt rates, and 10Be ice concentrations. Strong correlation (R = 0.96) between 10Be and smectite abundance in the sediments indicate authigenic clay formation in the subglacial environment. This study shows that meteoric 10Be is a useful tool to characterize subglacial geochemical weathering processes under the Antarctic Ice Sheet.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 Quantarctica, an integrated mapping environment for Antarctica, the Southern Ocean, and sub-Antarctic islands(Elsevier, 2021-06) Matsuoka, Kenichi; Skoglund, Anders; Roth, George; de Pomereu, Jean; Griffiths, Huw; Headland, Robert; Herried, Brad; Katsumata, Katsuro; Le Brocq, Anne; Licht, Kathy; Morgan, Fraser; Neff, Peter D.; Ritz, Catherine; Scheinert, Mirko; Tamura, Takeshi; Van de Putte, Anton; van den Broeke, Michiel; von Deschwanden, Angela; Deschamps-Berger, César; Van Liefferinge, Brice; Tronstad, Stein; Melvær, Yngve; Earth Sciences, School of ScienceQuantarctica (https://www.npolar.no/quantarctica) is a geospatial data package, analysis environment, and visualization platform for the Antarctic Continent, Southern Ocean (>40oS), and sub-Antarctic islands. Quantarctica works with the free, cross-platform Geographical Information System (GIS) software QGIS and can run without an Internet connection, making it a viable tool for fieldwork in remote areas. The data package includes basemaps, satellite imagery, terrain models, and scientific data in nine disciplines, including physical and biological sciences, environmental management, and social science. To provide a clear and responsive user experience, cartography and rendering settings are carefully prepared using colour sets that work well for typical data combinations and with consideration of users with common colour vision deficiencies. Metadata included in each dataset provides brief abstracts for non-specialists and references to the original data sources. Thus, Quantarctica provides an integrated environment to view and analyse multiple Antarctic datasets together conveniently and with a low entry barrier.