Physical Sciences and Mathematics Commons^™

Assessing The Drivers Of Legacy Phosphorus Loading And Distribution In Shallow Eutrophic Lake Sediments And The Impacts Of Intervention, Ashton P. Kirol

Graduate College Dissertations and Theses

The eutrophication of freshwater lakes from excessive nutrient runoff leads to decreased water quality and worsening cyanobacteria blooms. Water quality improvements in shallow eutrophic lakes can be delayed by decades due to the seasonal recycling of legacy phosphorus (P) enriched lake sediments, even when external nutrient loads are addressed. It is critical to understand the drivers of internal P loading to suppress this source of P through intervention to meet water quality goals. This study contrasts two shallow eutrophic systems, Lake Carmi and Missisquoi Bay in Lake Champlain, impacted by legacy P loading driven by the occurrence of low dissolved …

Relationships Between Deformation, Magmatism, And Sedimentary Geology Along The Mongol-Okhotsk Suture Zone: Ulz Gol Region, Mongolia, Jarret William Pidgeon

Graduate College Dissertations and Theses

The Mongol-Okhotsk Suture Zone (MOSZ) is a continental-scale structure that signifies the closure of a Paleozoic ocean basin. Though suturing of the Siberian Craton and southern Mongolian terranes is thought to have occurred in the Mesozoic Era, the exact timing and mechanisms remain debated. This prolonged period of orogenic activity is believed to be responsible for forming much of the Central Asian Orogenic Belt (CAOB) that encompasses essentially all of Mongolia, part of China, Siberia, and Kazakhstan. Also permeated throughout the CAOB are intra-continental, post-suturing structures. In the Late Jurassic–Early Cretaceous, a significant, crustal-scale extensional episode affected central and eastern …

In-Situ Weathering Of Calcium Bearing Minerals In Forested Ecosystems, Victoria Treto

Graduate College Dissertations and Theses

Timber harvests in the northeastern United States are integral to its economy but shifts in land management, biotic stresses, and nutrient limitations are diminishing forest productivity levels. The effects of harvesting severity and repeated harvests result in net losses of base cation nutrients which decreases woody biomass, potentially as much as 20%. Calcium (Ca) serves to regulate critical processes linked to tree growth and ecosystem health, but it is the quickest depleting base cation from northeastern forest soils. As a result, the quantification of nutrient-bearing minerals in forest soils is fundamental in predicting long-term sustainability of wood production. Further, the …

Examining The Relationship Between The Ereendavaa Metamorphic Core Complex And Duch Gol Basin In Northeast Mongolia In The Context Of The Mongol-Okhotsk Suture, Gavin Pirrie

Graduate College Dissertations and Theses

The Mongol-Okhotsk suture is integral in understanding the closure of the Mongol-Okhotsk Ocean, an ocean basin that once separated the Siberian craton from terranes of the Central Asian Orogenic Belt in southern Mongolia. However, the timing of closure and exact location of the suture are poorly known. This study examines two areas in northeastern Mongolia adjacent to the suture, the Ereendavaa Metamorphic Core Complex (EMCC) and the Duch Gol Basin, to aid in this understanding. The EMCC is an Early Cretaceous metamorphic core complex with an associated top-to-the-NW extensional detachment fault. Two sets of mineral lineations have previously been documented …

Trace Metal Contamination In Urban Soils: A Field To Laboratory Methodological Framework For Characterization And Education, Sandra Leighanne Walser

Graduate College Dissertations and Theses

Urban soils around the world have been found to possess elevated concentrations of toxic trace metals such as As, Cd, Cu, Pb, Mn, Hg, Zn known to pose human health risks. Tightening environmental legislation and further elucidation of the detrimental health impacts from trace metals has necessitated more efficient means of contamination assessment, as well as greater public awareness. Within this thesis, I sought to develop an array of tools to holistically approach the socially relevant environmental challenges derived from heavy metal soil contamination. These tools consist in providing means to simplify Pb, Zn and Cu analysis in-situ, develop strategies …

Assessing The Impact Of Changes In Acid Deposition On Dissolved Organic Carbon Mobilization From Two Forested Headwater Catchments: A Combined Lab And Field Study, Caitlin Bristol

Graduate College Dissertations and Theses

Over the past few decades, dissolved organic carbon (DOC) concentrations in headwater streams in the northern hemisphere changed. Because these changes in DOC coincided with decreased acid deposition, a potential link was proposed early on. More recent research indicated that catchment attributes, especially soil characteristics and the presence of Ca-bearing minerals, play an important role in modulating DOC release from watersheds, but further research is necessary.

To investigate the role of catchment characteristics on DOC dynamics, I use several watersheds in the Northeastern United States with similar attributes and well-constrained differences. Sleepers River Research Watershed (SRRW) has naturally occurring Calcium …

Distinguishing Different Styles Of Transpressional Deformation At An Obliquely Convergent Plate Margin, Fiordland, New Zealand, Emily Sarah Lincoln

Graduate College Dissertations and Theses

Fiordland, New Zealand provides one of the best-known and deepest (to 65 km) exposures of an Early Cretaceous magmatic arc root known to geologists. These exposures allow for us to study tectonic deformational processes at varying crustal depths, including the role of pre-existing structures on later reactivation. The well-preserved Grebe shear zone (GSZ) marks the boundary between major basement terranes in southern Fiordland and has undergone multiple episodes of deformation during the Cretaceous and Cenozoic time periods. The primary focus of this study is to recognize and characterize the differing phases of deformation that occurred along this shear zone. To …

The Architecture Of A Lower-Crustal Shear Zone And Evidence For Along-Strike Variations In Strain Localization And Partitioning, Fiordland, New Zealand, Peter Carl Lindquist

Graduate College Dissertations and Theses

Rocks exposed in Fiordland, New Zealand provide a record of magmatic and tectonic processes that were active in the middle to lower crust of a magmatic arc during the Early Cretaceous. The George Sound shear zone (GSSZ) is one expression of those processes, and is a steep, lower-crustal shear zone that accommodated oblique sinistral motion within the continental margin of Gondwana. I have compiled structural and petrologic observations from five field areas that span the 50 km length of the exposed GSSZ. Directional and orientation statistics allow me to compare the orientation of fabrics at each field area to characterize …

Evidence For Polyphase Deformation In The Shear Zones Bounding The Chester And Athens Domes, Southeastern Vermont, From 40ar/39ar Geochronology, Kristin Schnalzer

Graduate College Dissertations and Theses

The Chester and Athens Domes are a composite mantled gneiss dome in southeast Vermont. While debate persists regarding the mechanisms of dome formation, most workers consider the domes to have formed during the Acadian Orogeny. This study integrates the results of 40Ar/39Ar step-heating of single mineral grains, or small multigrain aliquots, with data from microstructural analyses from samples collected in multiple transects across the dome-bounding shear zone(s) in order to understand the relationship between metamorphism and deformation. Results from the sheared units along the north and south transects are presented from west to east. In the north, hornblende from the …

Assessing The Biogeochemical Drivers Of Dissolved Organic Carbon (Doc) In Forested Headwater Catchments: A Multi-Scaled Approach, Thomas Adler

Graduate College Dissertations and Theses

Variability in export of dissolved organic carbon (DOC) from forested headwater catchments has been attributed to an array of hydrologic, biotic and geochemical drivers. In the Northeast United States specifically, one of the most commonly cited drivers is recovery from acid rain. A major challenge in understanding DOC dynamics has been relating long-term regional trends and patterns to catchment-scale processes and we address this challenge by integrating data driven and experimental methods to analyze trends and processes across spatial scales. On the regional scale, we quantify long-term trends of stream DOC concentrations in USGS headwater catchments with flow adjusted Seasonal …

Strain Accommodation, Metamorphic Evolution, And 3d Kinematics Of Transpressional Flow Within The Lower Crust Of A Cretaceous Magmatic Arc In Fiordland, New Zealand, Griffin Amoss Moyer

Graduate College Dissertations and Theses

The George Sound Shear Zone (GSSZ) exposed in Bligh Sound within Fiordland, New Zealand allowed us to reconstruct the kinematics of transpressive flow in >100 km2 of exhumed Cretaceous lower crust. We compare the three-dimensional characteristics of the deformation to theoretical models of transpression that assume steady-state flow in a homogeneous medium. This assumption is rarely the case for shear zones that experience metamorphism during deformation. We determined the three-dimensional kinematics of the GSSZ and evaluated the effects of metamorphism on strain accommodation and structural fabric evolution in the GSSZ to determine if metamorphism is an important parameter that transpressional …

Application Of Geophysical And Geochronological Methods To Sedimentologic And Stratigraphic Problems In The Lower Cambrian Monkton Formation: Northwestern Vermont, Henry C. Maguire

Graduate College Dissertations and Theses

The Monkton Formation of the western shelf stratigraphic sequence in Vermont (VT) is identified as a Lower Cambrian regressive sandstone unit containing parasequences recording tidal flat progradation. Previous workers identified cycles believed to represent parasequences in a portion of a 1034' deep geothermal well drilled at Champlain College in Burlington, Vermont. For this study, both outcrop and well geophysical surveys were completed to better identify gamma emission curves and relative values for parasequences and select lithologies that are indicators of bathymetry and sea level. After using physical stratigraphic techniques to assemble a composite stratigraphic section for the Monkton Formation, analysis …

Soil Aggregates: The Mechanistic Link To Increased Dissolved Organic Carbon In Surface Waters?, Malayika Cincotta

Graduate College Dissertations and Theses

Dissolved organic carbon (DOC) plays an important role in the global carbon (C) cycle because increases in aqueous C potentially contribute to rising atmospheric CO2 levels. Over the past few decades, headwater streams of the northern hemisphere have shown increased amounts of DOC coinciding with decreased acid deposition. Although the issue is widely discussed in the literature, a mechanistic link between precipitation composition and stream water DOC has not yet been proposed.

In this study, the breakup of soil aggregates is hypothesized as the mechanistic link between reduced acid deposition and DOC increases in surface waters. Specific hypotheses state that …

From Sea To Lake: The Depositional History Of Saint Albans Bay, Vt, Usa, Matthew Kraft

Graduate College Dissertations and Theses

Sediment accumulated in lakes stores valuable information about past environments and paleoclimatological conditions. Cores previously obtained from Saint Albans Bay, located in the Northeast Arm of Lake Champlain, VT record the transition from the Champlain Sea to Lake Champlain. Belrose (2015) documented the presence of a peat horizon separating the sediments of the Champlain Sea from those of Lake Champlain. Initially, this layer was thought to comprise the transition from the marine environment of the Champlain Sea to a freshwater wetland. However, based on the results from this study, the transition between marine and freshwater conditions is thought to be …

Geochronological Constraints On The Timing Of Deformation: An Examination Of The Prospect Rock Fault Footwall In North-Central Vermont, Evan Tam

Graduate College Dissertations and Theses

The Prospect Rock Fault (PRF) is key to our understanding of the regional tectonic evolution of Vermont during the Taconic, Salinic, and Acadian Orogenies, and may have played an important role in the exhumation of blueschist and eclogite-facies rocks in the Tillotson Peak Complex (TPC) during the Taconic Orogeny. The TPC is in the footwall of the PRF in the eastern limb of the Green Mountain Anticlinorium. In the TPC, the dominant foliation is S2 and E-W trending F2 folds parallel L2 stretching lineations, which trend orthogonal to regional N-S trending folds associated with the Taconic Orogeny. The PRF itself …

Geochronologic Constraints On The Timing Of Metamorphism And Exhumation Of The Tillotson Peak Complex In Northern Vermont, Cheyne Aiken

Graduate College Dissertations and Theses

The Tillotson Peak Complex (TPC) in northern Vermont records high-pressure (HP) subduction zone metamorphism that occurred during the Ordovician Taconic Orogeny, and subsequent retrograde metamorphism and deformation that occurred during the Silurian Salinic Orogeny. Previous studies have documented a polymetamorphic history, with peak metamorphic pressures possibly up to 2.5 GPa and temperatures of 550°C. Prior to this research, constraints on the timing of metamorphism in the TPC were limited to a single Middle Ordovician 40Ar/39Ar total fusion age for glaucophane. This study integrates 40Ar/39Ar step heating analyses of multiple mineral phases and U-Pb dating of titanite with field and microstructural …

Combining Observations Of Soils And Streams To Investigate Trends Caused By Reduced Acid Depositon In The Sleepers River Watershed, Jesse Armfield

Graduate College Dissertations and Theses

Acid deposition forms when emission-derived sulfur dioxide and nitrogen oxides interact with precipitation and was particularly severe in the northeastern US. Effects of acid deposition include declining soil quality due to low pH and base cation leaching, which subsequently altered the composition of soil solution, ground water (GW) and eventually stream water. Because of the high buffering capacity of carbonates, watersheds underlain by carbonate rich rocks have received limited attention in acid deposition studies, however, carbonate weathering by strong anthropogenic acids can increase atmospheric CO2 levels.

Emission reductions due to the Clean Air Act and Amendments has led to a …

Microscale Controls On Lead Speciation In Soils: A Framework For Sustainable Remediation, Grant Reeder

Graduate College Dissertations and Theses

The potential of a soil to immobilize heavy metal ions is dependent on the presence of adsorption sites, and the stability of metal species over the range of geochemical conditions present in the soil over time. Lead (Pb) is a cumulative toxin that is enriched in much of the urban pedosphere due to historical use of Pb-based paint and Pb-amended gasoline. Because in-situ remediation of Pb is possible if the bioavailable fraction can be rendered inert, understanding Pb-sorbent interactions is necessary to accurately and efficiently alter Pb speciation in soils. The objectives of this study are to 1) determine efficient …

The Progressive Evolution Of The Champlain Thrust Fault Zone: Insights From A Structural Analysis Of Its Architecture, Matthew Merson

Graduate College Dissertations and Theses

Near Burlington, Vermont, the Champlain Thrust fault placed massive Cambrian dolostones over calcareous shales of Ordovician age during the Ordovician Taconic Orogeny. Although the Champlain Thrust has been studied previously throughout the Champlain Valley, the architecture and structural evolution of its fault zone have never been systematically defined. To document these fault zone characteristics, a detailed structural analysis of multiple outcrops was completed along a 51 km transect between South Hero and Ferrisburgh, Vermont.

The Champlain Thrust fault zone is predominately within the footwall and preserves at least four distinct events that are heterogeneous is both style and slip direction. …

4d Strain Path Recorded In The Lower Crust During The Transition From Convergence To Continental Rifting, Doubtful Sound, Fiordland, New Zealand, Michael Ingram

Graduate College Dissertations and Theses

ABSTRACT

Doubtful Sound, in SW New Zealand, exposes an exhumed section of lower crust that represents the root of an Early Cretaceous magmatic arc. Here, the lower crust underwent a change from contraction to extension and these tectonic cycles are fundamental to the growth of continental crust. Mafic-intermediate granulite gneisses occur below the extensional Doubtful Sound shear zone (DSSZ) which records the retrogression and transposition of granulite fabrics at the upper amphibolite facies. I compared 3D rock fabrics, microstructures and textures within and below the DSSZ to determine the processes involved in the shift from contraction to extension and to …

Crustal Deformation During Arc-Flare Up Magmatism: Field And Microstructural Analysis Of A Mid-Crustal, Melt Enhanced Shear Zone, John Bennett Gilbert

Graduate College Dissertations and Theses

This study combines structural field data with microstructural observations in an analysis of a mid-crustal shear zone related to the emplacement of the Misty pluton during a high-flux magmatic event in Northern Fiordland, New Zealand. These high-flux magmatic events transport massive amounts of heat and material as they develop along accretionary continental margins, and represent a primary source of continental crust. Fiordland, New Zealand possesses, perhaps, the most extensive middle and lower crustal exposure of these systems on earth. Therefore, this study area provides a significant opportunity to understand processes of continental crust formation in the mid-crust and how these …

Speciation, Distribution, Prediction, And Mobility Of Lead In Urban Soils: A Multiscale Study, Jennifer Bower

Graduate College Dissertations and Theses

Lead (Pb), a trace metal notorious for its impacts on human health, has achieved worldwide environmental dispersal resulting from centuries of use by human society. The toxicity of Pb is governed largely by its mineral form, which is in turn controlled by pH, localized reactivity and soil processes that differ according to soil type, location and Pb source. Given the context of these localized dependencies, or site specificity, efforts to predict Pb toxicity and refine sustainable remediation techniques are most useful when Pb behavior is constrained and predicted within environments with homogeneous conditions, such as a single soil. I evaluated …

The Structural Evolution Of A Portion Of The Median Batholith And Its Host Rock In Central Fiordland, New Zealand: Examples Of Partitioned Transpression And Structural Reactivation, Hannah Jane Blatchford

Graduate College Dissertations and Theses

This thesis presents the results of structural analyses and detailed field mapping from a region near Adams Burn in central Fiordland, New Zealand. The region preserves assemblages of metasedimentary and metaigneous rocks deposited, intruded, and ultimately metamorphosed and deformed during the growth of a Gondwana-margin continental arc from Cambrian-Early Cretaceous. Evidence of arc growth is preserved in the Late Devonian-Early Cretaceous Median Batholith, a belt of intrusive rock whose growth culminated with the emplacement of the Western Fiordland Orthogneiss (WFO) into the middle-lower crust of the margin. Following this magmatic flare-up, the margin experienced Late Cretaceous extensional orogenic collapse and …

High Flow Events As Hot Moments Of Reactive Fe And P Export: Impacts Of Land Cover And Seasonality, Braden Rosenberg

Graduate College Dissertations and Theses

High flow events often comprise the majority of annual discharge and riverine geochemical flux of phosphorus (P) and metals such as iron (Fe) and manganese (Mn) due to glacial melt, snowmelt, and storm-driven sustained high flow. Aquatic ecosystem productivity in receiving water bodies such as Lake Champlain and the Gulf of Alaska (GoA) are impacted by the riverine import of nutrients. The magnitude of these high flow events can be a strong predictor of receiving water body conditions, and in some cases can contribute to eutrophication. We explore the intersection of high flow events and land cover in contrasting catchments …

Using Long- And Short-Lived Sediment-Associated Isotopes To Track Erosion And Sediment Movement Through Rivers In Yunnan, Sw China, Thomas Bundgaard Neilson

Graduate College Dissertations and Theses

This research aims to understand the natural and human influences on erosion in three tributary watersheds to the Mekong River, Yunnan Province, China and to assess the utility of a novel application of isotopic indicators of erosion. It explores how erosion varies through time and space as a function of physical characteristics of the landscape, tectonic forces, and human alteration of the landscape for forestry and agriculture. To accomplish these goals, I use four sediment-associated radionuclides: in situ 10Be, meteoric 10Be, 210Pbex, and 137Cs. These isotopes accumulate in or on sediment grains, and each accumulates to a different depth on …

Preservation And Sediment Cycling Beneath "Ghost Glaciers": How Cold-Based Ice Dictates Arctic Landscape Evolution, Lee Corbett

Graduate College Dissertations and Theses

Constraining past episodes of climate change and glacial response is critical for understanding future impacts of climate change, especially in the high latitudes where warming is expected to be rapid and most of Earth's glaciers exist. Many studies of past glacier size utilize rare isotopes called cosmogenic nuclides to perform surface exposure dating. Since most areas of Earth's surface that were previously glaciated were covered by erosive ice, which stripped away pre-existing cosmogenic nuclides, surface exposure dating yields the timing of the most recent deglaciation. However, in some high latitude areas where glacial ice is cold-based and non-erosive (so-called 'ghost …

The Relationship Between Magmatism And Deformation During The Acadian Orogeny: A Case Study From Eastern-Central Vermont, Samuel William Lagor

Graduate College Dissertations and Theses

The Silurian-Devonian metasedimentary rocks of the Connecticut Valley-Gaspé trough (CVGT) were subjected to multiple deformational and metamorphic events during the Acadian orogeny in the Middle-Late Devonian. Plutons intruding the Devonian Waits River and Gile Mountain Formations have been considered post-tectonic, but microstructural studies of the intrusions and their metamorphic aureoles indicate some of these plutons intruded syntectonically. This study investigates the relationship between Acadian deformation and intrusion of the Knox Mountain pluton (KMP) of central Vermont. Structural and geochronological data were collected along a c. 15 km transect from the western limit of the CVGT, where the unconformable Richardson Memorial …

Comparing Meteoric 10be, In Situ 10be, And Native 9be Across A Diverse Set Of Watersheds, Emily Sophie Greene

Graduate College Dissertations and Theses

The cosmogenic nuclide 10Be is a tool for quantifying earth surface processes that occur on millennial timescales. 10Be is produced in the atmosphere (meteoric 10Be) or in mineral grains (in situ 10Be). Well-understood nuclear physics, physical mixing processes, and the denudation of regolith control concentrations of in situ 10Be; in contrast, a combination of geomorphic, pedogenic, geochemical, and biological processes influence meteoric 10Be concentrations. Some have hypothesized that meteoric 10Be can be used as a tracer of sediment movement if meteoric 10Be is normalized against the concentration of native 9Be in grain coatings. This study aims to better understand Be …

The Interplay Between Deformation And Metamorphism During Strain Localization In The Lower Crust: Insights From Fiordland, New Zealand, Kathryn Elise Dianiska

Graduate College Dissertations and Theses

In this thesis, I present field, microstructural, and Electron Backscatter Diffraction (EBSD) analyses of rock fabrics from high strain zones in exposures of lower crustal Cretaceous plutons at Breaksea Entrance, Fiordland, New Zealand. The interplay between deformation and metamorphism occurs across multiple scales at the root of a continental arc. I show a series of steps in which retrogressive metamorphism is linked to the accommodation of deformation.

I define three main phases of deformation and metamorphism at Breaksea Entrance. The first phase (D1) involved emplacement of dioritic to gabbroic plutons at depths up to 60 km. The second phase (D2) …

The Champlain Sea/Lake Champlain Transition Recorded In The Northeast Arm Of Lake Champlain, Usa-Canada, Ashliegh Theresa Belrose

Graduate College Dissertations and Theses

Sediment accumulated on a lakebed archives information about past climate and changes in the regional environment. Previous studies (Burgess, 2007; Koff, 2011; Palmer, 2012) in the Northeast Arm of Lake Champlain, specifically Missisquoi Bay and Saint Albans Bay, showed a period (~9,400 - 8,600 yBP) of elevated organic matter deposition in both bays, indicating a productive event that pre-dated any possible anthropogenic influence. However, the record was abruptly cut off and any documentation representing the span of time leading up to this event was not found. The elevated organic matter levels were explained as being the result of a warm, …