Geology Commons^™

Explosion Structures In Grande Ronde Basalt Of The Columbia River Basalt Group, Near Troy, Oregon, Leonard Lee Orzol

Dissertations and Theses

Explosion structures occur in flows of Grande Ronde Basalt in the study area near Troy, Oregon. Data from nineteen stratigraphic sites indicate that the maximum number of flows that contain explosion structures at any one site is six. In the informally named Troy flow, explosion structures are widespread.

Each flow that contains explosion structures can be divided into two cooling units. The first cooling units occupy troughs in the pre-eruption topography and are up to 10 meters thick. The second cooling units contain the explosion structures and are up to 100 meters thick. The thickness of flows that contain explosion …

An Analysis Of The Eastern Margin Of The Portland Basin Using Gravity Surveys, Steven Allen Davis

Dissertations and Theses

The recent contributions of several investigators has indicated the Portland basin may be a pull-apart structure associated with wrench tectonism. Because of the large density contrast between sedimentary and volcanic units and because of their reasonably uniform and continuous nature, gravity survey methods can be used to identify covered structures with considerable success. The study utilized gravity modeling techniques to investigate the structure and genesis of the Portland basin's eastern margin.

Geomorphic Character, Age And Distribution Of Rock Glaciers In The Olympic Mountains, Washington, Steven Paul Welter

Dissertations and Theses

Rock glaciers are tongue-shaped or lobate masses of rock debris which occur below cliffs and talus in many alpine regions. They are best developed in continental alpine climates where it is cold enough to preserve a core or matrix of ice within the rock mass but insufficiently snowy to produce true glaciers. Previous reports have identified and briefly described several rock glaciers in the Olympic Mountains, Washington {Long 1975a, pp. 39-41; Nebert 1984), but no detailed integrative study has been made regarding the geomorphic character, age,and distribution of these features.

Stratigraphic And Geochemical Evolution Of The Glass Buttes Complex, Oregon, Richard Louis Roche

Dissertations and Theses

Glass Buttes complex lies at the northern margin of the Basin and Range province in central Oregon and is cut by the northwest-trending Brothers fault zone. An older acrystalline volcanic sequence of high-silica rhyolites (>75% SiO₂) forms a broad platform composed of domes and flows with minor pyroclastic deposits. The high-silica rhyolite sequence is divided on the basis of texture into 1) zoned flows and domes, 2) obsidian flows, 3) felsite flows, and 4) biotite-phyric flows and domes.

A Seismic Refraction Study Of A Portion Of The Northeastern Margin Of The Tualatin Valley, Oregon, David John Nazy

Dissertations and Theses

The Tualatin Valley is a well defined elliptical basin centered at Hillsboro, with a major axis trending roughly N65°W. The valley is bordered on the northeast by the Tualatin Mountains (Portland Hills) which are a faulted, northwest-trending asymmetrical anticline. Topographic and geophysical evidence have defined the Portland Hills fault, which occurs along the northeast side of the Tualatin Mountains. The possibility that a fault or fault zone occurs along the southwest side of the Tualatin Mountains was investigated in this study.

Stratigraphic Model Of The Southern Portion Of The Jim Bridger Coal Field, Sweetwater County, Wyoming, Paul S. Maywood

Dissertations and Theses

Uppermost Lance and lowermost Fort Union Formation sediments are found in outcrop in the southern portion of the Jim Bridger coal field, located on the northeast flank of the Rock Springs Uplift in Sweetwater County, Wyoming. Twenty-nine surface sections and 581 subsurface (borehole) sections were evaluated and used to construct a stratigraphic model.

Stratigraphic correlations with economically mineable coal seams in the Fort Union Formation north and south of the study area combined with definition of questionable local formational boundary locations are significant objectives in this investigation.

Stratigraphy Of The Ohanapecosh Formation North Of Hamilton Buttes, Southcentral Washington, Cynthia Marie Stine

Dissertations and Theses

Over 1055 m of early Oligocene andesitic-dacitic volcaniclastic rocks and minor interbedded andesitic lava flows of the Ohanapecosh Formation are exposed in a dissected structural high in the southern Washington Cascade Range, about 22 km southwest of Packwood, Washington.

The exposed sequence of rocks in the study area are located approximately 250 m above the base of the Ohanapecosh Formation. A lower sequence of deposits, about 350 m in thickness, are dominated by primary and reworked lithic lapilli-tuff and epiclastic channelized volcanic sandstone and conglomerate. These sediments are interpreted as pyroclastic flows and stream deposits, respectively. The upper sequence, about …

Textural And Mineralogical Characteristics Of Altered Grande Ronde Basalt, Northeastern Oregon : A Natural Analog For A Nuclear Waste Repository In Basalt, Paul M. Trone

Dissertations and Theses

Altered flows that are low-MgO chemical types of the Grande Ronde Basalt crop out in the steep walls of the Grande Ronde River canyon near Troy, Wallowa County, Oregon. The alteration effects in these flows are being investigated as a natural analog system to a high level nuclear waste repository in basalt. The flows within the study are referred to as the analog flow, in which the alteration effects are the strongest, and the superjacent flow. The analog flow crops out at Grande Ronde River level and a roadcut-outcrop is developed in the flow-top breccia of this flow. The two …

Development And Application Of Some Quantitative Stratigraphic Techniques To The Coos Bay Coalfield, A Tertiary Fluvio-Deltaic Complex In Southwestern Oregon, Willard Sidney Titus Iii

Dissertations and Theses

A computer technique for interpreting geophysical logs of drill-holes in quantitative lithologic terms has been developed and tested on the deposits of the late Eocene Coaledo Formation, a well-studied fluvio-deltaic complex in southwestern Oregon. The technique involves the use of induced and natural gamma logs for separation of coal and claystone from coarse-grained detrital rocks and the use of the ratio of resistivity and natural gamma responses (defined here as the "grain size index") to divide the coarse elastic rocks into a series of textural classes corresponding to the Wentworth-Odden particle size scale.