Geology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2774
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Item Integrated Geochemical Studies of the Shuram Excursion in Siberia and South China(2024) Pedersen, Matthew; Kaufman, Alan J; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Ediacaran Period Shuram Excursion (SE) is a globally-distributed and highly controversial phenomenon where over millions of years, sedimentary carbonates record δ13C values of -10‰ and lower. This carbon cycle anomaly may reflect disequilibrium in the world’s oceans, driven by the oxidation of a large pool of dissolved organic carbon (DOC), with the oxidants sourced from the intense weathering of the continents, forcing major changes to ocean chemistry through the ventilation of the deep ocean, evidenced by a positive shift in carbonate uranium isotope values, and invoking the onset of early animal biomineralization. This study utilizes high-resolution carbonate Li isotopes from two SE-successions, U isotopes, REE abundances and Ce anomalies which reveal the dynamic interplay between intensified continental weathering associated with tectonic reconfiguration and the subsequent environmental and ecological response that may have been amplified by the ecosystem-engineering abilities of a newly discovered sponge-grade animal.Item LONGITUDINAL STREAM SYNOPTIC (LSS) MONITORING TO EVALUATE WATER QUALITY IN RESTORED STREAMS(2023) Malin, Joseph Thomas; Kaushal, Sujay S; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many kilometers of streams are being restored in the Chesapeake Bay watershed and elsewhere in efforts to stabilize streambanks, protect infrastructure, and improve water quality. Urban development and impervious surface cover increase peak flows, which degrade streams. Restoration strategies often employ engineering approaches to enhance stream-floodplain reconnection, dissipate erosive forces from urban runoff, and enhance contaminant retention. In this study, longitudinal stream synoptic (LSS) monitoring (sampling multiple points along flowpaths across both space and time) was conducted to assess the effectiveness of different forms of stream restoration in attenuating pollutants downstream. Spatial and temporal monitoring of carbon, nutrients, salt ions, and metals were conducted across five watersheds experiencing varying levels of stream-floodplain reconnection and stormwater management within the Chesapeake Bay region. Study sites included Sligo Creek (minimal floodplain reconnection), Paint Branch (streambank stabilization without significant reconnection), Scotts Level Branch (engineered stream-floodplain reconnection), Little Paint Branch (natural floodplain reconnection from sedimentation), and Campus Creek (regenerative stormwater conveyance with engineered floodplain reconnection). We investigated: (1) whether changes in water chemistry can be detected along longitudinal flowpaths in response to stream-floodplain reconnection, and (2) which monitoring scales across space and time can provide useful information regarding the effectiveness of restoration. Results from this work suggest that longitudinal synoptic monitoring can track the fate and transport of multiple contaminants and evaluate restoration strategies across high spatial-resolution scales. Along all five watersheds, stream water chemistry varied substantially across finer spatial scales (sometimes within hundreds of meters) in response to changes in landscapes, restoration features, or local hydrology. There were significant declining concentrations (p<0.05) or stable concentrations of nutrients, salts, and metals as streams flowed through restoration features. There were significant increasing trends in chemical concentrations (e.g. Na+, Ca2+, K+) in unrestored stream reaches with increasing impervious surface cover. Principal component analysis (PCA) also indicated that there were changes in the chemical compositions of mixtures of salts, metals, and nutrients in response to restoration projects, storm events, and seasons. Interestingly, dissolved Fe and Mn concentrations showed significant increasing trends along some stream reaches with hydrologically connected floodplains. Fe and Mn also showed significant decreasing trends along some unrestored stream reaches surrounded by increasing impervious surfaces. Increased concentrations of dissolved Fe and Mn may have been an indicator of increased hydrologic connectivity between groundwater and surface water and decreased redox potentials. Overall, longitudinal water quality changes over meters and kilometers can be useful in detecting effects of stream restoration on water quality at the watershed scale. Results suggest that water quality in urban streams can change locally in response to restoration projects for multiple chemicals, but the incremental changes associated with different forms of stream restoration and riparian conservation can also be overwhelmed across broader watershed spatial scales and during storm events.Item MOBILIZATION OF CHEMICAL COCKTAILS BY FRESHWATER SALINIZATION SYNDROME IN THE CHESAPEAKE BAY WATERSHED(2023) Galella, Joseph George; Kaushal, Sujay S; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increasing trends in base cations, pH, and salinity of urbanizing freshwaters have been documented in U.S. streams for over 50 years. These patterns, collectively known as Freshwater Salinization Syndrome (FSS), are driven by multiple processes, including applications of road salt and human-accelerated weathering of impervious surfaces, reductions in acid rain, and other anthropogenic legacies of change. FSS mobilizes chemical cocktails of distinct elemental mixtures via ion exchange, and other biogeochemical processes. Urban streams in temperate areas experience chronic salinization throughout the year punctuated by acute salinization during winter storms with associated road salting. My research analyzed impacts of FSS on stream water chemistry in the field with routine bi-weekly and targeted high frequency sampling during road salting events. Field sites were proximal to USGS stream sensors using multiparameter datasondes, allowing for additional parameters to be monitored at 5-15 minute resolution. In the laboratory incubation analyses were also conducted using sediment and water samples to assess the function of stormwater best management practices (BMPs) during road salting events. Acute FSS associated with road salting was found to mobilize chemical cocktails of metals (Mn, Cu, Sr²⁺), base cations (Na+, Ca²⁺, Mg²⁺, K⁺), nutrients (TDN), and organic matter (NPOC). Regression relationships were developed among specific conductance and major ion and trace metal concentrations. These linear relationships were statistically significant in most of the urban streams studied (e.g., R2 = 0.62 and 0.43 for Mn and Cu, respectively), and showed that specific conductance could be used as a proxy to predict concentrations of major ions and trace metals. Principal component analysis (PCA) showed co-mobilization (i.e., correlations among combinations of specific conductance, Mn, Cu, Sr²⁺, and all base cations during certain times of year and hydrologic conditions). Co-mobilization of metals and base cations was strongest during peak snow events but could continue over 24 hours after specific conductance peaked, suggesting ongoing cation exchange in soils and stream sediments. Increased salt concentrations of all three major road salts (NaCl, CaCl₂, and MgCl₂) had profound effects on major and trace element mobilization, with all three salts showing significant positive relationships across nearly all elements analyzed. Salt type showed preferential mobilization of certain elements. NaCl mobilized Cu, a potent toxicant to aquatic biota, at rates over an order of magnitude greater than both CaCl₂ and MgCl₂. Hourly mass fluxes of TDN in streams were also found to be elevated during winter months with peaks coinciding with road salting events. Targeted winter snow event sampling and high-frequency sensor data suggested plateaus in NO₃⁻ / NO₂⁻ and TDN concentrations at the highest peak levels of SC during road salt events between 1,000 and 2,000 μS/cm, which possibly indicated source limitation of TDN after extraction and mobilization of watershed nitrogen reservoirs by road salt ions. My results may help guide future regulations on road salt usage as there are currently no federally enforceable limits. NaCl is the most commonly used deicer in the United States, largely because it is often the least expensive option. Other technologies such as brines and other more efficient deicers (CaCl₂ and MgCl₂) should be considered in order to lessen the deleterious effects of FSS.Item Freshwater 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.Item TREE TRADE-OFFS IN STREAM RESTORATION: IMPACTS ON RIPARIAN GROUNDWATER QUALITY(2020) Wood, Kelsey Lynn; Kaushal, Sujay; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Restoring urban degraded stream channels in efforts to improve water quality often includes substantial alteration of the riparian zone which can require the removal of mature trees. This study assessed the impact of tree removal on riparian groundwater quality over time and space using a chronosequence of restored sites ages 5-20 years and well transects along groundwater flow paths. The response of multiple elements through various hydrologic conditions was evaluated by monitoring dissolved concentrations of inorganic carbon, organic carbon, total nitrogen, boron, calcium, copper, iron, potassium, magnesium, manganese, sodium, and sulfur over a 2-year period. Results revealed that concentrations of most bioreactive and organically derived elements were significantly elevated and increase along flowpaths at recently restored sites.Item SULFUR ISOTOPE RECORDS IN NEOARCHEAN CARBONATES: IMPLICATIONS FOR THE EARLY PRECAMBRIAN SULFUR CYCLE(2017) Zhelezinskaia, Iadviga; Farquhar, James; Kaufman, Alan J; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mass-independent fractionation of sulfur isotopes found in Early Precambrian records is the main evidence supporting an oxygen-poor atmosphere before ~2.4 Ga when ancient sulfur cycling was different than today. In previous studies, shale facies formed in deep-water environments have been the main target that were used to constraint the ancient sulfur cycle using sulfur isotopes, even though, among sedimentary Neoarchean strata, carbonate rocks are found to be more abundant. In order to follow previous observations and reveal processes operating in shallow water environments, I conducted a series of systematic studies of Neoarchean carbonate archives. Elemental and isotope measurements of sulfur and carbon in carbonate (and some shale) facies were obtained from multiple cores drilled through ~2.7 to 2.5 Ga successions of South Africa (GKF01, GKP01, and BH1-Sacha), Western Australia (AIDP-2, AIDP-3, BB, PR, RP, and RG) and Brazil (GDR-117). This study demonstrates that carbonate facies preserve distinctive MIF-S compositions relative to shale facies. Drilled pyrites in carbonate formations mostly preserved negative Δ33S values suggesting that the major sulfur source to shallow environments was atmospheric sulfate that also was isotopically redistributed through microbial sulfate reduction producing δ34S > 35‰ isotope fractionation. Atmospheric sulfate was the main source for seawater sulfate making its concentration in the Neoarchean ocean of less than 10µM/l. At this low concentration, reservoir effects would be pronounced leading to the formation of carbonate associated pyrites with highly positive δ34S compositions ranging to > +30‰. The bulk pyrites in most carbonate formations from South African and Western Australian cores possess small positive Δ33S signals (<+3.0‰) suggesting the incorporation of 20-35% of photolytic elemental sulfur. Photolytic sulfate with Δ36S/Δ33S deviations found in macroscopic pyrites with negative Δ33S from the Carawine Formation provide evidence for changes in atmospheric reactions during periods of an organic hazy atmosphere. My study of Δ36S/Δ33S in contemporaneous Jeerinah shale indicates the possible temporal decoupling of the MIF-S signal on a basinal scale implying heterogeneous haze structure. Integration of sulfur and carbon isotopes measured in carbonate facies suggests that sulfur-metabolizing microbes such as sulfur phototrophs and sulfate reducers were actively recycling these elements in shallow marine environments.Item HYDROLOGICAL, BIOLOGICAL, AND GEOCHEMICAL RELATIONSHIPS AMONG CARBON, NITROGEN, AND BASE CATIONS IN RESTORED AND UNRESTORED URBAN STREAMS(2017) Doody, Thomas Rossiter; Kaushal, Sujay S; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Urban infrastructure changes hydrologic flowpaths of water into streams and alters ecosystem function. Geomorphic stream restoration is commonly implemented to stabilize channels, while ecosystem function, and nutrient retention are of secondary concern. This research investigated whether restoration alone significantly influences N uptake in streams and if significant hydrological, biological, and geochemical relationships exist between coupled biogeochemical cycles that should be considered when evaluating restorations. Carbon, nitrogen, base cations, and stream metabolism dynamics were investigated in six urban streams in Baltimore,MD. Nitrate tracer injections were used to quantify nitrogen uptake dynamics. Results did not show significant differences in nitrogen uptake based on restoration. Organic carbon, inorganic carbon, and nitrogen each have distinct but interrelated hydrological, biological, and geochemical relationships across all sites. These dynamic relationships may also significantly affect nitrogen uptake, but more spatiotemporal data are needed to quantify and understand variability among restored and unrestored sites.Item DISSOLVED AND GASEOUS FLUXES OF CARBON AND NITROGEN FROM URBAN WATERSHEDS OF THE CHESAPEAKE BAY(2016) Smith, Rose Marie; Kaushal, Sujay S; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Carbon and nitrogen loading to streams and rivers contributes to eutrophication as well as greenhouse gas (GHG) production in streams, rivers and estuaries. My dissertation consists of three research chapters, which examine interactions and potential trade-offs between water quality and greenhouse gas production in urban streams of the Chesapeake Bay watershed. My first research project focused on drivers of carbon export and quality in an urbanized river. I found that watershed carbon sources (soils and leaves) contributed more than in-stream production to overall carbon export, but that periods of high in-stream productivity were important over seasonal and daily timescales. My second research chapter examined the influence of urban storm-water and sanitary infrastructure on dissolved and gaseous carbon and nitrogen concentrations in headwater streams. Gases (CO2, CH4, and N2O) were consistently super-saturated throughout the course of a year. N2O concentrations in streams draining septic systems were within the high range of previously published values. Total dissolved nitrogen concentration was positively correlated with CO2 and N2O and negatively correlated with CH4. My third research chapter examined a long-term (15-year) record of GHG emissions from soils in rural forests, urban forest, and urban lawns in Baltimore, MD. CO2, CH4, and N2O emissions showed positive correlations with temperature at each site. Lawns were a net source of CH4 + N2O, whereas forests were net sinks. Gross CO2 fluxes were also highest in lawns, in part due to elevated growing-season temperatures. While land cover influences GHG emissions from soils, the overall role of land cover on this flux is very small (< 0.5%) compared with gases released from anthropogenic sources, according to a recent GHG budget of the Baltimore metropolitan area, where this study took place.Item Authigenesis, biomineralization, and carbon-sulfur cycling in the Ediacaran ocean(2015) Cui, Huan; Kaufman, Alan J.; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fossil record of the Ediacaran Period (635-541 Ma) reveals unprecedented rise of early animal life (metazoan) in Earth history. Coupled with this evolutionary milestone, the Earth’s atmosphere and hydrosphere experienced dramatic redox fluctuations. In order to better constrain the redox architecture of the Ediacaran ocean margin, an integrated chemostratigraphic correlation of the Doushantuo Formation in basin scale was conducted (see Chapter 2). The revised redox model suggests that euxinic conditions on the platforms were mainly restricted in lagoonal settings, which helps us to better understand Ediacaran fossil distributions and fluctuated δ13C records in the Ediacaran strata in South China. One of the most distinct features of the Ediacaran chemostratigraphy is the δ13C negative excursion (i.e. Shuram Excursion, or SE) reported globally, which is the largest known C cycle anomaly in Earth history. In order to understand the biogeochemical processes that gave rise to the SE expressed in the upper Doushantuo Formation, systematic petrographic and geochemical investigations were conducted for the outer shelf sections in the Yangtze block (see Chapter 3). Methane-derived authigenic calcite cements and nodules with extreme 13C-depletion were discovered and interpreted as the first empirical evidence of authigenic mineralization associated with the SE. In light of these novel observations, it is proposed that the globally distributed SE may be formed by widespread syndeposition of authigenic carbonates in a sulfate-methane transitional zone positioned at the sediment-water interface in response to a global seawater sulfate increase. Finally, to provide environmental context for the terminal Ediacaran biomineralization of animals, we conducted a high-resolution elemental and isotopic study of the richly fossiliferous Gaojiashan Member (see Chapter 4). Coincident with the first appearance of Cloudina are significant C-S-Ca-Sr cycle anomalies. It is proposed that the onset of calcarious biomineralization of animals may have coincided with an increase in terrestrial weathering fluxes of sulfate, alkalinity, and nutrients to the depositional basin. Enhanced concentration of Ca ion in seawater may have promoted the calcarious biomineralization of the early animals. Integrated chemo-, bio- and litho-stratigraphy of the Doushantuo and Dengying formations presented in this dissertation emphasized intimate co-evolution of Earth-life system during the Ediacaran Period.Item A Time-Series Geochemical Study of the ca. 2.5 Ga Batatal Formation in Brazil: Sulfur and Carbon Isotopic Insights into Environmental Conditions before the Great Oxidation Event(2013) Zhelezinskaia, Iadviga; Kaufman, Alan J; Farquhar, James; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Neoarchean metasedimentary rocks from the Batatal Formation, Brazil were studied using petrographic, elemental and stable isotopic techniques to provide a better understanding of coupling between the atmosphere-ocean system and biogeochemical cycles prior to the Great Oxidation Event. Multiple sulfur isotope data from both shale and carbonate lithofacies confirms global preservation of mass-independent fractionations, thought to be produced through photochemical reactions in an oxygen-free Neoarchean atmosphere. Isotopic differences between lithofacies within the shallow marine Batatal Formation, and beyond in deeper subtidal environments from correlative successions in Western Australia and South Africa, suggest a strong influence of environmental conditions on the preservation of distinct &Delta33S signatures. To explain the novel isotopic data, it is proposed the Batatal Formation was deposited in a shallow water evaporitic environment, which resulted in higher sulfate concentrations and greater sulfur isotope fractionation associated with the activity of sulfate-reducing bacteria. Higher temperatures associated with such environments may have also promoted carbon dioxide limitation resulting in lesser carbon isotopic fractionation by photoautotrophs.