Quaternary Landscape Evolution and the Surface Expression of Plume-Lithosphere Interactions in the Greater Yellowstone Area Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/z603r2948

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  • Numerous investigations demonstrate that mantle convective processes such as upwelling affect the surface topography of the overriding plate. The surface expression of mantle flow has been coined ‘transient topography’. Transient topography in the North American plate is thought to result from a mantle thermal anomaly beneath the Yellowstone volcanic center, the so-called Yellowstone hotspot. This work explores the sensitivity of the surface of Western North America by testing the hypothesis that advection of a transient topographic wave through the North American plate drove the post-Pliocene landscape evolution of the greater Yellowstone region. This study presents results from three approaches to assessing the expression of dynamic topography in continental lithosphere. First, analysis of digital elevation data reveals an asymmetric topographic swell that has an amplitude of 400-1200 m and a wavelength of ~600 km which was disentangled from overlapping signals preserved in the topography that result from other processes that shape the Earth’s surface. The transient topography swell data is then used to parameterize a model of advection of dynamic topography to estimate deformation rates and patterns that may be expected in the Yellowstone area. Second, analysis of stream channel morphology extracted from digital elevation data is used to identify crustal deformation, changes in streambed lithology, and erosional patterns throughout the Yellowstone area. Forcing of landscapes by dynamic topography in continental landscapes is below the detection limit of channel steepness indices (k[subscript sn]). The final chapter in this study presents an updated geochronology of erosion of the Bighorn Basin of Wyoming and Montana. The geochronology is the result of geomorphic mapping and paleodrainage interpretations of fluvial terraces preserved throughout the Bighorn basin that record the post-Pliocene erosional story in the basin. A new interpretation of the Basin’s erosion story is presented, and conclude that the change from a south to north drainage to a west to east drainage pattern and lateral migration of the Bighorn river away from Yellowstone coincides with the model of advection of dynamic topography.
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