Graduate Students

Thesis Research:

I plan to document quartz deformation fabrics across a quantified strain gradient during transpressional deformation. Quartz fabrics are widely studied in the field and lab, but previous studies have not been able to track fabric development in rocks that have deformed under natural strain rates and where strain may be quantified. I will document quartzite fabrics in rocks where finite strains have been measured in deformed conglomerate clasts, and develop a link between strain and crystallographic and grain shape orientations. The work will look at both quartzite clasts and quartz veins, which will cover the whole strain history and a later portion of the strain history, respectively. I am working in the Seine Metaconglomerates located in the Rainy Lake region in northwestern Ontario. The area has a wide variability of measured strain, which will allow me to document the evolution of quartz fabrics with increasing deformation. In order to examine quartz fabrics, I will use Electron Backscatter Diffraction (EBSD) analyses on polished thin sections. In doing so, crystallographic orientation, grain shape, and grain shape orientation will be documented across the strain gradient. By documenting the fabric evolution with strain, I will be able to consider whether the fabric forms in a smooth progression, in spurts, or once a critical threshold of strain is reached. The strain within the conglomerate has been measured using standard Rf/Phi method by Fissler (2006). In the first phase of this project, the strain that she measured will be used to gauge the fabric evolution. The Rf/Phi method is the standard strain analysis technique, but is best used when there is no competence contrast between the clasts and matrix. This assumption is rarely valid in deformed conglomerates, so one additional aspect of my research will be to calculate the strain using a modified Rf/Phi technique proposed by Lisle (1983) that accounts for competence contrast.

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My Thesis involves the Cary Mound granite, a pluton approximately 10 km south of Marshfield Wisconsin. The pluton was shallowly emplaced and may represent a caldera that was formed at or near the end of the Penokean Orogeny. Major and trace element analysis will be conducted to determine the tectonic setting of emplacement as well as to relate a geographically associated rhyolite to the granite. Oxygen isotope analysis may be performed to establish conduit pathways of hydrothermal meteoric water. Magnetic susceptibility orientations will also be obtained to determine the amount of deformation.

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Chemical variation between lava flows and scoria deposits in cinder cones is an untested idea.  While some investigations have collected multiple samples from a single cone, no study has analyzed the chemical variations throughout the evolution of a cinder cone.  There are two main stages in the life cycle of a cinder cone, the early explosive stage composed of pyroclastic scoria deposits and the later effusive stage consisting of lava flows.  Each stage can be examined geochemically to determine the composition of their mantle source.  Although stratovolcanoes in Guatemala are related to subduction of the Cocos plate beneath the Caribbean plate, cinder cones in southeastern Guatemala cluster in an extensional graben.  The primary purpose of the study is to determine detailed variations in the geochemistry of Guatemalan cinder cones throughout their lifespans and distinguish the explosive-effusive transition in a basaltic magmatic system.

Two Guatemalan cinder cones will be targeted for detailed examination. The cinder cones examined will be quarried with low and high MgO contents, a measure of evolution from its primary composition. Multiple geochemical techniques to assess whether different petrologic processes have operated will be used to examine the stratigraphic samples collected. X-ray fluorescence (XRF) will be used to determine the major and minor element chemistry of both the lava flows and the scoria deposits. Nine scoria deposits and one lava flow (two if there are notable differences in the field) at each cinder will be examined using X-ray fluorescence. Inductively coupled plasma mass spectrometry (ICP-MS) will be utilized to determine the complete trace element composition of the deposits. Trace elements can be analyzed to determine variations and provide insight into the role of critical magmatic processes such as partial melting, magma mixing or crystal fractionation.

Olivine that crystallizes at depth as magma ascends frequently traps melt as it grows. Pre-eruptive magma volatile content is recorded in olivine melts which quench into a glass upon eruption. The release of H₂O and CO₂ from the ascending magma drives explosive eruptions, yet correlating volatile content with eruptive style has been problematic. H₂O and CO₂ contents measured in olivines from scoria deposits through time may provide significant information about the early explosive stage of a cinder cone. S, Cl, and major element contents of the melt inclusions will be measured by electron microprobe analysis, whereas the H₂O and CO₂ concentration will be determined by Fourier transform infrared (FTIR) spectroscopy. FTIR examines the minimum volatile content of the melt required to sustain an explosive column (i.e. marking the transition from the explosive to effusive stage).

Detailed geochemical analysis of the two stages in the growth of a cinder cone yields fundamental information on its evolution.  The geochemical comparison of the early scoria deposits to the later lava flows might highlight a change in the mantle source.  Additionally, the diminishing explosivity of a cinder cone over time may be explained by volatile content measurements.  Important volcanic hazard implication revealed by volatile measurements will help predict the duration and eventual cessation of the explosive stage.

Thesis Research:

My thesis project focuses on the Agua de Jagüel formation within the Calingasta-Uspallata basin in northwest Argentina. The stratigraphy of the formation exhibits the transition from glacial to post-glacial conditions for the second of three glacial successions over Gondwana during the late Paleozoic Gondwanan ice age. For my field work, I will gather information to determine the style and dynamics of the glacial environment, as well as the nature of the change from a glacial to a post-glacial setting. Such research will help to decipher the climatic history of the region and provide an understanding of how the glaciation in Argentina correlates with the overall glaciation of Gondwana.

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I will be looking at a cinder cone field in Guatemala. I will be applying GIS, Remote Sensing, & Ar/Ar age dating to hopefully get a better understanding of the temporal & spatial phenomenon of a cinder cone field. Ultimately, hopefully a researcher will be able to apply a general classification system to cinder cone field of interest.

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As part of a regional research project to determine potential alternative water sources for Southeastern Wisconsin, my research is focused on the feasibility of utilizing treated wastewater from Waukesha and its surrounding communities to enhance recharge to the shallow aquifer system.  To this end, surveys of historic major ion chemistry in the Dolomite aquifer and the Sand and Gravel aquifer have been performed to analyze for existing geochemical trends.  Geochemical modeling will be performed in order to assess the impact, if any, on these systems with the introduction of treated wastewater.

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