Thesis (M.S. in geology)--Washington State University, May 2008. / Includes bibliographical references (p. 98-103).

Thesis (M.S.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed October 20, 2008) Includes bibliographical references (p. 61-64).

Thesis (M. S. in Earth and Environmental Sciences)--Vanderbilt University, Aug. 2009. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 32-34).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Abstracted in Dissertation abstracts, v. 16 (1956) no. 2, p. 204-205. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 180-190).

Öræfajökull is an ice-capped stratovolcano situated in the south east of Iceland which has developed throughout the mid to late Quaternary. It has erupted basaltic and rhyolitic lavas during interglacial and glacial periods, many of which display strong physical evidence of volcano-ice interaction. This makes Öræfajökull an ideal location to reconstruct terrestrial palaeo-environments. The area of Goðafjall and Hrútsfjall is one of a small number of rhyolitic depositional centres situated on the south west flanks of the volcano and is the first rhyolitic area of Öræfajökull to be mapped in detail.The relatively high K content of the rhyolitic units make them good candidates for 40Ar/39Ar dating, yielding eruption ages that provide a temporal constraint on the development of the stratovolcano. 40Ar/39Ar dating of young rocks (<1 My) is challenging and many of the samples were found to contain both excess and atmospheric argon. A small number exhibited a fractionated argon source with a sub-atmospheric 40Ar/36Ar ratio that could not be explained by a single episode of mass fractionation. Soret thermal diffusion has been suggested as a possible mechanism for fractionation, although further investigation is required.Two dominant rhyolite eruptions have been identified by detailed field mapping supported by the geochemical application of chemostratigraphy. The stratigraphically lower group of lavas outcrop between 100 to 380 m.a.s.l. and were erupted subaerially into a relatively ice-free environment at the base of the edifice. A 40Ar/39Ar age of 202 ± 9 ka implies that eruption occurred during the interglacial MIS 7. Conversely the upper group of lavas show strong evidence of volcano-ice interaction, suggesting that they were erupted subglacially and confined by ice with a minimum ice surface elevation of at least 800 m.a.s.l. These lavas yield a 40Ar/39Ar age of 116 ± 14 ka, which implies that eruption occurred during the transitional period between the MIS5e interglacial and colder sub-stages prior to MIS 4.At least two further glacial advances have occurred since the emplacement of the subglacial rhyolite unit. In addition, an ice confined trachydacite flow from the Vatnafjall ridge situated 20 km north east of Goðafjall has also been dated yielding a 40Ar/39Ar age of 95 ± 7 k. This lava was emplaced at an elevation of over 700 m in the presence of an adjacent valley fill glacier was at least 700 m thick.Ice thickness has varied dramatically throughout the evolution of Öræfajökull and glacial erosion has played an important role in its topographic development.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1941. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [85-87]).

Inaug.-Diss.--Mineralogie--Ruprecht-Karls-Universität Heidelberg, 1990. / Resumé en anglais, allemand, français et perse. Bibliogr. p. 219-246.

Master of Science / Department of Geology / Matthew E. Brueseke / The Jarbidge Rhyolite of Elko County, Nevada, is approximately 26 mapped bodies of porphyritic rhyolite. Several of the bodies are truncated by the Idaho or Utah border, and extend into the states for an unknown distance. This study focuses on five bodies, the Mahoganies, two near Wild Horse Reservoir, the outcrop enclosing the Jarbidge Mountains, and one outcrop south of Wells. The study’s focus is providing field, petrography, geochemistry, oxygen isotope, and geochronology information about the five previously mentioned bodies. Physical volcanology encountered during this study indicates the sampled Jarbidge Rhyolite are effusive lava flows and domes that coalesced over the life of the volcanic system. First order approximations indicate that erupted products cover ~1,289 km2 and erupted material totals ~509 km3. Petrography indicates primary anhydrous mineral assemblages, assimilation of granitoid, possible assimilation of metamorphic rock and magma mixing of mafic and silicic bodies. Collectively, the Jarbidge Rhyolite lava flows sampled are compositionally restricted from rhyolite to high silica rhyolite and all samples demonstrate A-type magma characteristics. Compositions from different bodies overlap on Harker diagrams, and trace element ratios distinguish few flows from the other samples. Rare earth element patterns mimic one another, and incompatible trace element ratios overlap between bodies, likely indicating the presence of one large magma body. Oxygen isotope values for selected samples range 6.61-8.95%oVSMOW are coincident with normal igneous values. New 40Ar/39Ar geochronology indicates Jarbidge Rhyolite volcanism initiated ca. 16.7 Ma near Wild Horse Reservoir and was active at Bear Creek Summit ca.15.8 Ma. Local Steens Basalt, geochemistry, and Au-Ag mineralization indicate Jarbidge Rhyolite is similar to Middle Miocene silicic volcanics (e.g. Santa Rosa-Calico volcanic field) further west in the Oregon-Idaho-Nevada tristate region.