Graduate Thesis Or Dissertation
 

JohnsonJoelE2005.pdf

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9880vt726

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  • During the last 15 years, numerous geophysical surveys and geological sampling and coring expeditions have helped to characterize the tectonic setting, subsurface stratigraphy, and gas hydrate occurrence and abundance within the region of the accretionary wedge surrounding Hydrate Ridge. Because of these investigations, Hydrate Ridge has developed as an international site of active margin gas hydrate research. The manuscripts presented in this dissertation are focused on the geologic setting hosting the gas hydrate system on Hydrate Ridge. These papers examine how active margin tectonic processes influence both the spatial and temporal behavior of the gas hydrate system at Hydrate Ridge and likely across the margin. From a high resolution sidescan sonar survey (Chapter II) collected across the region, the distribution of high backscatter, as well as the locations of mud volcanoes and pockmarks indicates variations in the intensity and activity of fluid flow across the Hydrate Ridge region. Coupled with subsurface structural mapping, the origins for many of these features as well the locations of abundant gas hydrates can be linked to folds within the subsurface. Continued structural mapping, coupled with age constraints of the subsurface stratigraphy from ODP drilling, resulted in a model for the construction of the accretionary wedge within the Hydrate Ridge region (Chapter III). This model suggests the wedge advanced in three phases of growth since the late Pliocene and was significantly influenced by the deposition of the Astoria fan on the abyssal plain and left lateral strike slip faulting. Changes in structural vergence, documented here, also help explain the variability in bathymetric relief across the region. Determination of the occurrence and timing of Holocene slope failures derived from Hydrate Ridge (Chapter IV) and comparison with a Holocene marine record of Cascadia subduction zone earthquakes suggests earthquake induced slope failure within the gas hydrate stability zone does occur at Hydrate Ridge and thus, may represent a high frequency mechanism for the mobilization of seafloor and subseafloor gas hydrates across the margin.
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file details JohnsonJoelE2005.pdf 2017-08-14 Pubblico Scaricare