Thesis (M.S.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file and four media files (media file 1.pdf, media file 2.pdf, media file 3.pdf, and media file 4.pdf) Title from title screen of research.pdf file (viewed on August 25, 2008) Vita. Includes bibliographical references.

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 182-195).

Thesis (Ph.D.)--Memorial University of Newfoundland, 1993. / Typescript. Restricted until October 1994. Bibliography: l. 363-388. Also available online.

Thesis (M. Sc.)--Carleton University, 1997. / Accompanying material: 3 maps in pocket. Also available in electronic format on the Internet.

Uranium-lead (U-Pb) geochronology and Hafnium (Hf) isotope geochemistry of detrital zircons of the Harmony Formation of north central Nevada provide new insights into the tectonic evolution of the Late Paleozoic western Laurentian margin. Using laser-ablation inductively coupled plasma mass spectrometry, 10 arenite samples were analyzed for U-Pb ages, and 8 of these samples were further analyzed for Hf isotope ratios. Three of the sampled units have similar U-Pb age peaks and Hf isotope ratios, including a 1.0-1.4Ga peak with epsilon Hf values of +12 to -3 and a 2.5-2.7Ga peak with epsilon Hf values of +7 to -5. The remaining seven samples differ significantly from these three, but are similar to one another; having age peaks of 1.7-1.9Ga with epsilon Hf of +10 to -20 and age peaks of 2.3-2.7Ga with epsilon Hf of +6 to -8. The data confirm the subdivision of the Harmony Formation into two petrofacies: quartzose (Harmony A) and feldspathic (Harmony B). The three samples with 1.0-1.4 and 2.5-2.7Ga peaks are the Harmony A, which originated in the central Laurentian craton. The other seven samples are the Harmony B, which originated in eastern Alberta-western Saskatchewan, north of the Harmony A source. We propose that all Harmony Formation strata were deposited near eastern Alberta and subsequently tectonically interleaved with Roberts Mountains allochthon strata. We interpret that the entire package was tectonically transported south along the western Laurentian margin and then emplaced eastward onto the craton during the Late Devonian-Early Mississippian Antler orogeny.

The influence of erosion on uplifting orogens has been demonstrated to be a primary force in landscape development. An understanding of fluvial erosion in mountain belts is fairly well documented, but the impact of glacial erosion is yet to be fully recognized. The uplift of the Chugach-St. Elias Mountains over the last 5-6 Ma under the influence of intense glaciation provides a unique setting to study the impact of glacial erosion on landscape development. The range has been built by rapid convergence (~5 cm/yr) of the Yakutat terrane with North America. Climatic forcing of northward-driven storms has created a disproportionate glacier distribution across strike, where extensive piedmont glaciers (low equilibrium line altitudes) cover the windward side of the range and small isolated glaciers (high equilibrium line altitudes) occupy the leeward side. If glacial erosion is greatest at the equilibrium line altitude, then glaciers will act as "buzzsaws" there to limit topographic development. Exhumation would therefore be expected to increase towards the coast. If glacial erosion is not dominant, exhumation would be expected to increase away from the coast towards the core of the range, where fault dip angles are high and deep crustal rocks are exposed. To determine the impact of long-term glacial erosion on exhumation of the Chugach-St. Elias Mountains, samples were collected along and across the strike of the range and analyzed by the apatite radiogenic helium (AHE) technique. Samples previously dated using the apatite fission track (AFT) method and located adjacent to our field area were also included in the analyses. The low-temperature sensitivity of these thermochronometers allows exhumation rates to be determined for shallow crustal depths. Both glacial and tectonic processes have influenced exhumation of the range. Exhumation rates increase to the south and east towards the collision zone, but coastal rates (0.36-2.5 mm/yr) are significantly higher than inland samples (0.038-0.24 mm/yr). These rates indicate that coastal glaciation plays a dominant role in landscape development and suggest that short-term erosion rates inferred from sediment yields are exaggerated. Although the exhumation rates are lower than expected, the correlation of exhumation patterns, glacier distribution, and equilibrium line altitude supports the "glacial buzzsaw hypothesis". / Master of Science

Controlled source seismic methods were employed in this study to investigate the reflectivity and velocity structure of two Hercynian orogens – the Uralides and Variscides. Conventional common depth point (CDP) sections from five reflection seismic campaigns and a velocity model obtained from tomographic inversion of wide-angle observations were the main datasets studied from the Middle Urals. These were complemented with the near-vertical seismic sections and velocity models from the Southern Urals. In the Variscides, conventional CDP processing, along with non-standard processing and synthetic data modeling, were used to obtain and interpret reflection seismic images of the Southwestern Iberian crust. Although, the Uralian and Variscan belts were formed in Late Paleozoic time in apparently similar plate collisional settings, a comparison of the seismic results show that the crust of these two orogens looks quite different at depth. In the Urals, collision of Baltica with Asian terranes (Siberia and Kazakhstan) resulted in a highly diversely reflective crust of 40-45 km thickness. The axial zone of the orogen is characterized by a high velocity crustal root of diffuse reflectivity and an imbricated Moho, with a crustal thickness reaching 55-60 km. The Moho discontinuity is marked by a sharp decrease in reflectivity and is well imaged in most locations except in the crustal root zone. The Southwestern Iberian Variscan crust is 30-35 km thick and is characterized by a highly reflective two-layered structure that resulted from collision of Luarussia and Gondwana, including terranes in-between them. This type of crustal structure is very similar to those imaged in other regions of the Variscan belt in the Europe. The Moho discontinuity is flat and appears to be the deepest reflection. This thesis compares the deep structure of the two orogens and interprets mountain building processes related to late Paleozoic plate movements.

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 115-137). Also available for download via the World Wide Web; free to University of Oregon users.

No description available.