Geology Theses and Dissertations
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- ItemFreshwater salinization syndrome limits management efforts to improve water quality(2022) Maas, Carly Marcella; Kaushal, Sujay S; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Freshwater Salinization Syndrome (FSS) refers to the interactive effects of salt ions on the degradation of the natural, built, and social systems. FSS can mobilize chemical mixtures, termed ‘chemical cocktails’, in watersheds. The formation of chemical cocktails across space and time depends on the amounts and types of salt pollution, the surrounding land use including conservation and restoration areas, and the location along the flowpath in the watershed. We investigated (1) the formation of chemical cocktails temporally and spatially and (2) the natural capacity of watersheds and streams to attenuate salt ions along flowpaths with conservation and restoration efforts. We monitored high-frequency temporal and longitudinal spatial chemical changes in stream water in response to different pollution events (i.e., road salt, stormwater runoff, wastewater effluent, and baseflow conditions) and several types of watershed management efforts (i.e., national parks, regional parks, and floodplain reconnection) in six urban watersheds in the Chesapeake Bay region. There were significant relationships between watershed impervious surface cover and mean concentrations of salt ions (Ca2+, K+, Mg2+), metals (Fe, Mn, Sr2+), and nutrients (total dissolved nitrogen) (p < 0.05). Principal component analysis (PCA) indicates that chemical cocktails which formed along flowpaths in response to winter road salt applications were enriched in salts and metals (e.g., Na+, Mn, and Cu). During most baseflow and stormflow conditions, chemical cocktails that were less enriched in salt ions and trace metals were attenuated downstream. There was also downstream attenuation of FSS ions during baseflow conditions through management efforts including a regional park, national park, and floodplain restoration. Conversely, chemical cocktails that formed in response to multiple road salt applications or prolonged road salt exposure did not show patterns of attenuation downstream. The spatial patterns were quite variable, with increasing, plateauing, or decreasing patterns based on the magnitude, timing, duration of road salt loading, and extent of management efforts. Our results suggest that FSS can mobilize multiple contaminants along watershed flowpaths, however, the capacity of current watershed management strategies such as restoration and conservation areas to attenuate FSS is limited.
- ItemGENETICS, AGES, AND CHEMICAL COMPOSITIONS OF THE GROUP IIIE IRON METEORITES AND THE IRON METEORITE LIEKSA(2022) Chiappe, Emily; Walker, Richard; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Siderophile element concentrations, genetic isotopic data, and chronological data for ten group IIIE iron meteorites and the recently found iron meteorite Lieksa were determined. The modeling of siderophile element abundances shows that the IIIE irons can be related to one another through a common fractional crystallization process. Highly siderophile element data, however, indicate that the anomalous IIIE iron meteorite Aletai does not sample the same crystallization sequence as the bona fide IIIE irons. The bulk chemical characteristics of Lieksa are distinct from that of the established iron meteorite groups, indicating that, if it is an iron meteorite, it should be classified as an ungrouped iron meteorite. Isotopic data shows that, while the IIIE iron meteorites, Lieksa, and Aletai exhibit different HSE abundances, they exhibit similar genetic characteristics, indicating that they likely originated from the same nebular reservoir. Additionally, isotopic data indicate that all irons analyzed here sample parent bodies that differentiated within the first ~2 Myr of solar system history, which is consistent with other NC-type bodies.
- ItemPressure-Temperature-time-Deformation (P-T-t-D) History of High-Grade Gneisses of the Port aux Basque Area, Southwest Newfoundland, Canada(1994) Burgess, Jerry Lee; Brown, Michael; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)A polyphase deformation history (D1-D4) and upper amphibolite facies metamorphism characterize the Port aux Basques Gneisses. Late-D1 to early D2 kyanite porphyroblasts each contain inclusion trails that preserve S1. Reaction out of muscovite, staurolite and kyanite in favor of sillimanite + garnet + alkali feldspar-bearing assemblages in the matapelitic gneisses record syn- to late- D2 peak metamorphic conditions. Isograd surfaces related to syn-D2 metamorphism were probably subhorizontal to inclined but not their metamorphism were probably subhorizontal to incline but now their map pattern reflects subsequent deformation by D3. Fluid-present melting initiated in the kyanite zone and continued into the sillimanite zone. Metamorphic conditions increase to the southeast with 'peak' temperatures of c. 700-750° at 8-9 kbar associated with the D2/M2 thermal regime. A Pb207/Pb206 date of c. 417 Ma was obtained from titanite in high-grade rocks of the Harbour le Cou Group. This date provides a minimum contraint for the M2 event. Hornblende from a nearby amphibolite yields an 40Ar/39Ar isotope correlation date of c. 419 Ma. Muscovite at the same locality records a 40Ar/39Ar plateau date of 391 Ma. Hornblende and muscovite separates from rocks of the Port aux Basques Complex yield similar 40Ar/39Ar dates. Calculations indicate that post- D3 cooling rates of approximately 8-1°C/Ma are required for the area. They kyanite to sillimanite transition and D2 structures suggest a clockwise trajectory in P-T space as a result of Silurian orogenesis.
- ItemDeciphering Core Records of Carbon and Nitrogen in Typha-Dominated Freshwater Wetlands(2022) Ravi, Rumya; Prestegaard, Karen; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)I conducted decomposition experiments and examined soil characteristics in restored and natural freshwater marsh platform sites to decipher core records of soil C and N. Carbon loss rates and changes in ẟ13C and ẟ15N were obtained from decomposition experiments. Core samples at each site were analyzed for bulk density, weight %C, %N, ẟ13C, and ẟ15N. Typha C loss rates were similar among sites, and there was little change in ẟ13C composition, suggesting that DOC leaching is significant. Core carbon storage is higher in natural wetland sites. Initial Typha %N and ẟ15N reflect local N concentrations and sources to each wetland. ẟ15N increases between decomposed vegetation and upper cores in the tidal wetlands, possibly indicating denitrification. In N-rich wetlands, core %N and ẟ15N reflect differences in N sources and changes in N sources over time. In a wetland limited by N transport, core %N and ẟ15N may reflect vegetation N uptake.
- ItemASSESSING FAULT SLIP HAZARD IN TAIWAN USING SPACE GEODESY(2022) Robbins, Kathryn Rose; Huang, Mong-Han; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Taiwan is a geologically complex region due to the continuous collision of the Eurasian Plate and the Philippine Sea Plate. This study aimed to quantify the interseismic crustal deformation of Taiwan and detail the island’s seismic hazard potential using space geodesy. Data were collected between 2016 and 2021 through C-band Copernicus Sentinel-1 synthetic aperture radar imagery and continuous GNSS data from Academia Sinica, Taiwan. I excluded major earthquake events within this time period and generated a dataset consisting of interferometric synthetic aperture radar ground motion velocities with GNSS corrections and interpolated GNSS ground motion velocities. Then, utilizing this dataset, I performed a deformation rate analysis and error analysis. Next, I explored block modeling and used a total variation regularization approach to determine the reference block model that best reduced velocity residuals and minimized the number of independently rotating blocks. Results suggested that the Taipei Basin, Ilan Basin, Western Foothills, and Longitudinal Valley were experiencing increased total strain rate accumulation and, therefore, posed increased seismic hazard.