http://hdl.handle.net/1957/7889 Search the Channel search http://ir.library.oregonstate.edu/dspace/simple-search http://hdl.handle.net/1957/9075 Title: Temporal and spatial variability of methane emissions from Alaskan Arctic tundra <br/> <br/>Abstract: Methane flux was measured from northern Alaska Arctic Coastal Plain wetlands to assess the spatial and temporal variability of Arctic tundra emissions during the summers of 1987 through 1990. Initially, the role of vegetation in the release of methane from substrate to atmosphere was assessed. Methane emissions were shown to be proportional to the foliage surface area and release of methane from plants controlled by the stomata. Daily values of methane emissions and leaf conductance were correlated (r = 0.95). A satellite-derived regional methane flux estimate had 3 to 5 times greater precision than estimates based on direct expansion. Methane emissions from the tundra exhibit high temporal variability at hourly, daily, seasonal, and annual scales of observation. Daily variability in methane emissions was low near the summer solstice and increased through the growing season. Strong seasonal variation in emissions was related to the position of the local water table, the amount of leaf area above the water, and plant phenological development. An interannual comparison of emissions provided insight into the local and regional scale responses of Arctic tundra to potential climatic warming. Methane emissions in 1989, a warm year, were over three fold greater than in 1987, a "normal" year. Temperaturedependent increases in methane emissions expected as a result of climatic warming are projected to exceed increases due to a longer growing season. The potential for strong positive biological feedback exists whereby the enhanced emissions of methane, a greenhouse gas, to the atmosphere may further accelerate rates of regional and global climatic warming. <br/> <br/>Description: Graduation date: 1992 Wed, 05 Feb 1992 22:58:59 GMT http://hdl.handle.net/1957/9066 Title: Geology and structural history of the Butte district, Montana <br/> <br/>Abstract: Ore deposits of the Butte district formed at ca. 66 to 62 Ma within a host rock of Butte Quartz Monzonite (ca. 76 Ma). Deposition of the Lowland Creek Volcanics Formation (ca. 53 to 50 Ma) on top of the Butte Quartz Monzonite and its ores, followed a period of extensive uplift, erosion, and unroofing. The amount of post-mineral tilting related to Cenozoic normal faults has been controversial. In the northwest part of the district, the Lowland Creek Volcanics dip 10 to 50 degrees northwestward. From which data, Proffett (1973, 1979) inferred that the underlying ore deposit is similarly tilted. Paleomagnetic studies of the Butte Quartz Monzonite in the central and western part of the district suggest lesser tilts of 5 to 17 degrees north to northwest (Geissman et al., 1980z, b). In an effort to resolve the question to the amount of post-mineralization tilting, the structural geology of the Butte district was remapped at 1:12,000 scale. Structural attitudes (n=407) were collected on originally subhorizontal sill-like bodies of aplite that are cogenetic with the Butte Quartz Monzonite. Examination of these data supports a hypothesis that the amount of tilting related to Cenozoic normal fault block rotation varies spatially across the district. Sheeted sill-like bodies of aplite in the northwest part of the district are tilted 34 degrees northwestward. West of Big Butte, sill-like bodies of aplite are gently tilted 16 degrees northwestward. Sill-like bodies of aplite in the northern and eastern parts of the district are tilted 10 to 15 degrees north to northeastward. In the southern part of the district, sill-like bodies of aplite on Timber Butte are tilted 20 to 25 degrees northeastward. In the northwest part of the district, the Lowland Creek Volcanics and underlying Butte Quartz Monzonite are tilted 10 to 50 degrees northwestward by closely spaced (0.3 to 0.6 km) northeast-striking, southeast dipping normal faults that exhibit moderate displacements (less than 0.8 km). These northeast striking normal faults exhibit diminishing amounts of offset and northwest tilting southwestward along the faults and successively decreasing amounts of offset and tilting southeastward, perpendicular to the faults. The northeast striking normal faults include some moderate northwest dipping faults. Large north south striking, widely spaced (~9.5 km) Basin-and Range type normal faults cut northeast striking faults. These faults localized deposits of early Miocene and younger clastic sedimentary rocks in their hanging walls. The largest is the Continental-Klepper-East Ridge fault system which shows increased displacement (from ca. 1.5 to >2 km) and eastward tilting of the hanging wall southward along the fault system. By restoring the orientation of the sill-like bodies of aplite in the northwest part of the district, prior to moderate (10 to 50 degrees) northwest tilting, the sill-like bodies of aplite become gently tilted 10 to 15 degrees northeastward. The restored orientation of the sill-like bodies of aplite is similar to the orientation of the sill-like bodies of aplite southeastward across the district. These observations support the interpretation that the district was gently tilted 10 to 15 degrees northeastward prior to the deposition of the Lowland Creek Volcanics Formation. Analysis of these data identified three episodes of tilting that has tilted different parts of the district in differing amounts supporting both Proffett's (1973, 1979) and Geissman et al.'s (1980a & b) geologic data. The first episode gently tilted the district 10 to 15 degrees northeastward and occurred between 62 Ma (post Main-Stage mineralization) and 59 Ma (pre granite porphyry dike emplacement). The second episode moderately tilted the district 10 to 50 degrees northwest tilting in the northwest part of the district and occurred between 51 Ma (deposition of the Lowland Creek Volcanic Formation) and Basin and Range type normal faulting. Moderate northwest tilting is related to deformation and accommodation along northeast striking normal faults that cut the northwest part of the district. The final episode gently tilted the hanging wall of the Continental fault ~14 degrees eastward and occurred during the middle Miocene related to Basin and Range type normal faulting. By restoring the district prior to the three episodes of tilting, the orientations of quartz porphyry dikes, Pre-Main Stage veinlets, and zonal patterns related to ca. 66 to 62 Ma mineralization-hydrothermal alteration become vertical and symmetrical. This vertical orientation is consistent with most hypotheses of porphyry copper emplacement. Additionally, the two conjugate fault systems occupied by Main Stage veins (ca. 62 Ma) also restore to become normal oblique-slip faults. <br/> <br/>Description: Graduation date: 2002 Tue, 28 Aug 2001 22:58:59 GMT http://hdl.handle.net/1957/9061 Title: Stratigraphy, structure, and natural gas potential of tertiary sedimentary and volcanic units, Clatskanie 7.5 minute quadrangle, Northwest Oregon <br/> <br/>Abstract: The geology and natural gas potential of the Clatskanie 7.5-minute quadrangle in Columbia County, Oregon was studied utilizing a combination of geologic mapping, measuring of stratigraphic sections, diatom and molluscan fossil identifications, with subsurface geophysical data and petrographic and geochemical analyses. The stratigraphy of the study area consists of two Tertiary volcanic units (Grays River Volcanics and Columbia River Basalt Group) and four sedimentary units (Cowlitz (subsurface) Keasey, Pittsburg Bluff, and Scappoose formations) that were deposited in the Nehalem forearc basin. The major structure of the area is defined by the oblique-slip Scappoose-Clatskanie fault with both normal and dextral motion. In the east-central part of the study area, this post-Miocene fault zone, formed by a right step over in a right-lateral strike-slip system, created an extensional zone with abundant normal faulting (horsts and grabens). The faulting uplifted an isolated block of middle Eocene Grays River Volcanics subaerial flows against downdropped Miocene Columbia River Basalt in the northwestern part of the map area near the town of Clatskanie along Highway 30. This block was part of a major Grays River Volcanics paleohigh (herein named the Clatskanie High) and forms part of a regional gravity/magnetic high beneath the Columbia river. The Clatskanie High and the Windy Ridge High (subsurfance paleohigh also composed of Grays River Volcanics) in the central to southern part of the study area, restricted deposition and caused onlapping of the Cowlitz, Keasey, and Pittsburg Bluff formations. The Clatskanie High shield volcano defines the northern boundary of the Mist Gas Field. In addition, local unconformities at the base of the Keasey and Pittsburg Bluff formations progressively truncate the Cowlitz C&W sandstone reservoir and upper mudstone seal to the north. The largely unexplored central and northeastern parts of the study area near the Scappoose-Clatskanie fault zone with horst and grabens and stratigraphic pinchouts represent some of the most promising untested exploration plays in the quadrangle. Associated wtih the Clatskanie High are two new (informal) members of the Oligocene Pittsburg Bluff Formation that are defined and mapped by this study. The Conyers Creek member (informal) is a shallow-marine mollusk-bearing pebbly-basaltic litharenite (a poorly sorted nearshore to shoreface sandstone) with an interbedded fossiliferous fine pebble conglomerate of Grays River volcanic clasts. The lens-like nearshore unit was deposited on the margins of the uplifted Grays River basaltic oceanic island and, thus, restricted to an area around the paleohigh. Locally overlying the Conyers Creek member and interbedded with the East Fork member (Pittsburg Bluff Formation) is the Clatskanie Conglomerate member (the second informal member defined by this study). The 180 feet (55 meter) thick member consists of a basal, clast-supported 110 feet (33 meter) thick polymict conglomerate and upper well-consolidated 70 feet (21 meter) think micaceous arkosic sandstone. The Clatskanie Conglomerate is a lens-like fluvial deposit in the northwestern part of the study area, possibly syndepositional and restricted in deposition to the center of a growing syncline. The cobble to boulder sized clasts of quartzite, chert, metamorphics, and andesites/dacites indicate extrabasinal sources such as the Western Cascades arc and continental sources in eastern Oregon, Idaho, Montana, and eastern Washington via an ancestral Columbia River drainage system. The diatom-bearing tuffaceous clayey siltstone of the Keasey Formation and the mollusk-bearing sandy siltstone of the East Fork member (Pittsburg Bluff Formation) formed in continental slope and middle to outer shelf environments. Extensive explosive dacitic eruptions in the nearby Western Cascade arc contributed abundant ash, which washed into the forearc basin. Local Thyosira chemosynthetic pelecypods and calcareous concretionary beds indicate the local presence of either cold methane seeps or a gas hydrate system on the Pittsburg Bluff continental shelf. The Scappoose Formation consists predominantly of a basal basalt and siltstone rip-up conglomerate deposited in an incised valley during a low stand systems tract (LST). The conglomerate is overlain by a diatom-bearing shallow-marine tuffaceous siltstone of a transgressive and highstand systems tracts (TST & HST), and capped by a cross-bedded fluvial lithic arkosic sandstone of a second lowstand systems tract (LST). Chemical analysis of the basal basalt conglomerate clasts indicate that they were derived from erosion of high TiO2R2 Wapshilla Ridge flow unit of the Grande Ronde Basalt (16.5 to 15.6 Ma) of the lower to middle Miocene Columbia River Basalt Group. The Scappoose Formation also includes thin fluvial and lacustrine sandstones and tuffs interbedded with Columbia River Basalt flows. Capping these Tertiary units are three units of low-MgO Grande Ronde Basalt of the Columbia River Basalt Group. These include 1-2 basal aphyric flow(s) of the high-TiO2R2 Wapshilla Ridge flow unit, at least six flows (some invasive) of the R2 low-TiO2 Grouse Creek flow unit, and the upper sparsely glomerophyric flows of N2 Winter Water flow unit. The structural history of the region is characterized by two major tectonic events. A late Eocene extensional period prior to deposition of the Keasey Formation created normal faulting (horsts and grabens) throughout the Cowlitz Formation. These faults formed most of the structural traps in the Mist Gas Field including those drilled by producing wells in the southern part of the quadrangle near the Windy Ridge High. The post-Miocene episode was dominated by wrench fault tectonics that manifested as strike-slip oblique-slip motion on dominant northwest-trending and subordinate northeast-trending faults in the Columbia River Basalt Group flows. <br/> <br/>Description: Graduation date: 2003 Tue, 28 May 2002 22:58:59 GMT http://hdl.handle.net/1957/9051 Title: Evaluation of seismic hazards from the Median Tectonic Line, Japan and blind thrust faults in the Los Angeles metropolitan area, California <br/> <br/>Abstract: This thesis analyzes active geologic structures in densely populated areas in Japan and southern California based on geological, geophysical, and paleoseismological observations. Chapter 2 discusses segmentation and paleoseismology of the Median Tectonic Line, Japan. We identified 12 geometric segments along the Median Tectonic Line separated by discontinuities such as en echelon steps, bends, changes in strike, and gaps in the surface trace. The recurrence interval and surficial offset for surface-rupturing earthquakes at four individual sites on the Median Tectonic Line in Shikoku Island are 1000-3000 years and 5-8 in, respectively. Part of the fault zone ruptured most recently during or after the 16th century A.D.; this rupture may be correlated to the 1596 Keicho-Kinki earthquake. Chapter 3 discusses active and late Cenozoic tectonics of the northern Los Angeles fault system, California. We mapped the subsurface geology of the northern Los Angeles basin from the City of Santa Monica eastward to downtown Los Angeles, based on an extensive set of oil-well data. The northern Los Angeles fault system developed through an early to late Miocene extensional regime and a Plio-Pleistocene contractional regime. The uplift of the oxygen isotope substage 5e marine terrace at Pacific Palisades and an estimated dip greater than 45° suggest a dip-slip rate as large as 1.5 mm/yr for the Santa Monica Mountains blind thrust fault, a rate considerably smaller than a previous estimate. Chapter 4 discusses the geologic setting of the 1971 San Fernando and 1994 Northridge earthquakes, two of the most devastating earthquakes in southern California history. We mapped the subsurface geology of the northern San Fernando Valley that lies at the updip projection of the two earthquake faults. The San Fernando Valley is underlain by a series of north-dipping blind thrust faults. The thick accumulation of the Robert S. ''eats Plio-Pleistocene Saugus Formation in the Sylmar basin and Merrick syncline is a surface expression of the south-dipping 1994 Northridge thrust that is overlain by the northdipping 1971 San Fernando fault at a depth of -5 km. <br/> <br/>Description: Graduation date: 1996 Wed, 06 Mar 1996 22:58:59 GMT