Master of Science (MS), Ohio University, 2024, Geological Sciences

Blueschists are an important petrogenetic indicator of subduction and the first appearance of blueschists in the geologic record is commonly taken as evidence for the start of modern-style plate tectonics on Earth. The oldest known blueschists are Neoproterozoic in age, so studies of these blueschists may provide information about the processes and conditions associated with the initiation of plate tectonics on Earth. Of the known Neoproterozoic blueschist localities, the Anglesey (Wales, UK) blueschists are of particular importance because they contain the mineral lawsonite and are thought to be the oldest known lawsonite-bearing rocks in the geologic record. Petrographic, bulk-rock geochemical, and mineral composition and zoning data were acquired to better understand the protolith of the Anglesey blueschists, the conditions (P-T) under which they formed, and their metamorphic evolution. The bulk-rock major and trace element compositions of the metamafic rocks in the Anglesey blueschist belt are generally consistent with a mid-ocean ridge basalt (MORB) protolith, although some samples display variable enrichments in the large ion lithophile elements (LILEs; Cs, Ba, Rb), as well as Sr, Pb, and U. Incompatible trace element systematics suggest most samples underwent seafloor alteration prior to subduction. The most common amphiboles in the Anglesey blueschist belt are glaucophane, winchite, actinolite, riebeckite, and magnesio-riebeckite. Amphiboles in the blueschist facies rocks have core-to-rim zoning and record a transition from calcic/sodic-calcic amphiboles (winchite and/or actinolite cores) to sodic amphiboles (glaucophane rims). Riebeckite and magnesio-riebeckite are most common in greenschist and transitional greenschist-blueschist facies rocks, where they display patchy zoning and compositional variations in Fe3+ and Al. Differences between the amphiboles developed in the greenschist and blueschist facies rocks likely reflect variations in the pressure- (open full item for complete abstract)

Committee: Katherine Fornash (Advisor) Subjects: Geochemistry; Geological; Geology; Plate Tectonics

Doctor of Philosophy, The Ohio State University, 2024, Earth Sciences

Knowledge of the distribution of Fe2+ and Mg between olivine and melt (the distribution coefficient, KD) is crucial to understand the origin and evolution of magmas. However, there is disagreement regarding which variables (temperature, melt composition, and oxygen fugacity – fO2) influence the value of KD, as well as the magnitude of their effects. To evaluate the dependence of KD on these variables, data were compiled from literature consisting of equilibrium olivine-melt pairs in experiments at controlled temperature, fO2, and 1 atm pressure. The results confirm that KD is essentially independent of temperature and fO2. However, it is strongly dependent on melt composition (particularly the concentration of silica and alkalis). An evaluation of different published formulations for KD using these data demonstrates that the expression of Gee and Sack (1988) is the most accurate and precise. Furthermore, a new and simpler model based on variation of KD with silica and alkalis has been fit to the olivine-melt database. This reproduces KD with the same accuracy and precision as the Gee and Sack (1988) formulation. The olivine-melt database also illustrates that KD can be used to calculate the proportion of the different valence states of iron in the melt (the Fe3+/ΣFe ratio), which cannot be measured using routine analytical techniques. The melt Fe3+/ΣFe can then be related to fO2 using empirical relationships. This method, referred to as the Olivine-Melt Equilibrium (OME) method, reproduces the fO2 imposed on the experiments within ±0.3 log units. This method was applied to compiled data for natural samples from literature from mid-ocean ridges, ocean islands, back-arc basin spreading centers, and volcanic arcs. Olivine-melt calculated values of fO2 for each location investigated agree with the results of independent techniques. These include compiled measurements of Fe3+/ΣFe ratios using Fe K-edge μ-X-ray Absorption Near Edge Structure (XANES) spectroscopy, as we (open full item for complete abstract)

Committee: Michael Barton (Advisor); Berry Lyons (Committee Member); Daniel Kelley (Committee Member); Derek Sawyer (Committee Member); David Cole (Committee Member) Subjects: Earth; Geochemistry; Geological; Geology; Petrology; Plate Tectonics

Master of Science, University of Akron, 2024, Geology

Partial melting of hydrous phases such as amphibole, biotite, and muscovite occurs in orogens where distributed ductile thinning is causing exhumation of mid- to lower-crustal rocks. The partial melting of these hydrous phases contributes significantly to the physical and chemical evolution of the crust, as well as affecting the crust's strength. The Si-rich melts generated from partial melting reactions of mid- to lower-crustal assemblages migrate toward the upper crust leaving a more mafic restite. Previous laboratory experiments conducted on amphibole-, biotite-, or muscovite-bearing rocks performed at rapid strain rates (10-4/s to 10-5/s) result in brittle deformation due to high local pore pressures. These rapid experiments suggest this brittle behavior is the likely mechanism causing melt segregation in the crust. However, field evidence and slower strain rate experiments (10-6/s to 10-7/s) suggest that crystal plastic processes may be dominant during syndeformational partial melting. To investigate grain-scale melt segregation mechanisms in a common lower crustal protolith, I performed a suite of axial compression and general shear experiments on an amphibole-bearing source rock during syndeformational partial melting at T = 800-975°C, Pc = 1.5 GPa, at a strain rate (ε) of 1.6 x 10-6/s. I also performed axial compression experiments on a biotite-bearing gneiss and a muscovite-bearing quartzite at T = 950°C, Pc = 1.5 GPa, at a strain rate (ε) of 1.6 x 10-6/s to compare the differences in melt development depending on which hydrous phase is partially melting. The Nemo Amphibolite (d = 140 ± 85 μm) is composed of 62 vol% amphibole (Fe-hornblende), 27 vol% plagioclase (andesine; An30Ab69Or1), 8 vol% quartz, and 3 vol% titanite. The biotite-bearing gneiss (d = 80 +/- 40 microns) consists of quartz (43 vol%), plagioclase (andesine (An22Ab77Or1); 40 vol%), biotite (16 vol%), and ~1 vol% muscovite/Fe-Ti oxides. The muscovite-bearing quartzite is composed of 90 vol% q (open full item for complete abstract)

Committee: Caleb Holyoke (Advisor); Molly Witter-Shelleman (Committee Member); David Steer (Committee Member) Subjects: Earth; Experiments; Geochemistry; Geological; Geology; Mineralogy; Petrology; Plate Tectonics

Doctor of Philosophy, The Ohio State University, 2017, EDU Teaching and Learning

The purpose of this qualitative study was to explore the use of 3-D printed models as an instructional tool in a middle school science classroom for students with visual impairments and compare their use to traditional tactile graphics for aiding conceptual understanding of geoscience concepts. Specifically, this study examined if the students' conceptual understanding of plate tectonics was different when 3-D printed objects were used versus traditional tactile graphics and explored the misconceptions held by students with visual impairments related to plate tectonics and associated geoscience concepts. Interview data was collected one week prior to instruction and one week after instruction and throughout the 3-week instructional period and additional ata sources included student journals, other student documents and audio taped instructional sessions. All students in the middle school classroom received instruction on plate tectonics using the same inquiry-based curriculum but during different time periods of the day. One group of students, the 3D group, had access to 3-D printed models illustrating specific geoscience concepts and the group of students, the TG group, had access to tactile graphics illustrating the same geoscience concepts. The videotaped pre and post interviews were transcribed, analyzed and coded for conceptual understanding using constant comparative analysis and to uncover student misconceptions. All student responses to the interview questions were categorized in terms of conceptual understanding. Analysis of student journals and classroom talk served to uncover student mental models and misconceptions about plate tectonics and associated geoscience concepts to measure conceptual understanding. A slight majority of the conceptual understanding before instruction was categorized as no understanding or alternative understanding and after instruction the larger majority of conceptual understanding was categorized as scientific or scie (open full item for complete abstract)

Committee: Tiffany Wild (Advisor); Mollie Blackburn (Committee Member); Lin Ding (Committee Member) Subjects: Education; Geology; Middle School Education; Plate Tectonics; Science Education; Teaching

Master of Science, Miami University, 2016, Geology and Environmental Earth Science

We examine the along-strike transition from flat to steeper subduction in Oaxaca, Mexico to provide a better understanding of what controls the slab morphology. Prior studies have suggested the slab tends to tear along the transitions in dip as the slab rolls back. We determine the slab geometry based on local seismicity, nonvolcanic tremor (NVT), and slow slip utilizing a deployment of broadband seismometers and continuous GPS receivers distributed in and around Oaxaca. We construct depth contours of the subducting slab surface down to 100 km, which illustrate that the transition from flat to steeper subduction occurs rapidly via a sharper flexure than previously recognized. The prior catalog of NVT in Oaxaca is extended using the same method and additional stations that extend further west. The band of NVT follows the new slab contours, widening towards the west with the downdip extent gradually moving inland. The amount of NVT also correlates with the strength of an ultra slow velocity layer. There are no gaps in seismicity, NVT, or slow slip across the rapid transition in slab dip, further supporting the notion that the slab is not currently torn in the updip region. We propose that the sharp flexure is possible in this region due to bending moment saturation that leads to greater curvature in both the down-dip and along-strike directions. A similar set of observations in southern Peru suggests this is a viable alternative to tearing that accommodates the large strains from variable rates of slab rollback.

Committee: Michael Brudzinski (Advisor); Brian Currie (Committee Member); Elisabeth Widom (Committee Member) Subjects: Geophysics; Plate Tectonics

Master of Environmental Science, Miami University, 2013, Geology and Environmental Earth Science

The E-W-trending Ulukisla basin (UB) in Turkey occurs between the Central Anatolian Crystalline Complex to the north and the Tauride carbonate platform to the south. It contains 5 km-thick, uppermost Cretaceous to Miocene-Pleistocene strata and Eocene magmatic rocks. The Cretaceous - Eocene sedimentary rocks comprise an upward shallowing sequence of clastics. The Eocene sequence includes marine turbidites and is transitional upwards into Oligocene rocks. The upward transition from Lower Oligocene shallow marine, deltaic deposits to Upper Oligocene-Miocene evaporate and terrestrial deposits indicates a record of a successor basin. The Upper Cretaceous and Lower Paleocene rocks and the Middle Eocene - Middle Miocene units are deformed by north- and south-vergent, upright and overturned folds and thrust, strike-slip faults. The E-W normal faults in the Middle Paleocene and Middle Eocene units represent extensional deformation coeval with slab breakoff and induced mafic magmatism. The Ulukisla depocenter initially developed as a successor basin in the latest Mesozoic-early Cenozoic and then evolved into a terrestrial basin in the late Tertiary.

Committee: Yildirim Dilek (Advisor) Subjects: Geology; Plate Tectonics; Sedimentary Geology

Master of Arts, Miami University, 2011, English

This thesis is a novel exploring the question of fate versus free will as well as how coping with the trauma and grief that accompany an unexpected death can lead a survivor to begin exploring the world around him in a new way. The protagonist, Sam Mastin, attempts to find answers that may not be available to him or anyone until he is given the freedom to create a new life, inspired by episodic dreams of a woman writing his life story. Mastin discovers that finding out the truth is a tricky feat and one that comes with its own pain.

Committee: Eric Goodman (Committee Chair); Joseph Bates (Committee Member); Susan Morgan (Committee Member) Subjects: Fish Production; Plate Tectonics; Remote Sensing; Robots; Textile Research; Urban Forestry