Physical Sciences and Mathematics Commons^™

Distribution, Geochronology, And Petrogenesis Of The Picture Gorge Basalt With Special Focus On Petrological Relationships To The Main Columbia River Basalt Group, Emily Bogdan Cahoon

Dissertations and Theses

The Columbia River Basalt Group (CRBG) is the youngest and volumetrically smallest continental flood basalt exposed across the Pacific Northwest, USA. Similar to other large igneous provinces, the majority of material erupted during the initial 1 million years of activity, these lavas are subdivided into four main-phase units. The Picture Gorge Basalt (PGB) is the only main-phase unit of the CRBG whose age is not precisely known and understanding of PGB petrogenesis is largely based on a limited number of samples when compared with other main-phase units. It is suggested that a time gap of over 0.5 myr existed between …

An Investigation And Comparison Of Stable Isotopes In Meteoric Waters And Groundwaters From Southern Washington, Emily E. Smoot

University Honors Theses

A main source of freshwater in the Pacific Northwest is the Columbia River Basalt Group aquifer system. The semi-arid region of eastern Washington has undergone heavy groundwater depletion in recent decades due to increasing population and expanding agricultural use. Aggressive mining has resulted in drawdowns of up to 30 meters. By using stable isotopes oxygen-eighteen (¹⁸O) and deuterium (D), this study confines the timing of groundwater precipitation and proposes an explanation for why drawdowns are so significant. The isotopic composition of meteoric water is compared to groundwaters from southeast Washington. The two populations are statistically different (p < 0.001, alpha = 0.05). The isotopic composition of groundwaters from the deepest wells (< -150 m msl) are isotopically lighter than meteoric waters and not achievable by recharge under the current climate. These deep groundwaters are interpreted to have precipitated during the Last Glacial Maximum in the late Pleistocene and finished precipitating roughly 5 ka. Thus, replenishment of the aquifer cannot be expected to keep pace with extraction. Additionally, this research examines the elevation response in the stable isotope signature of meteoric water along the 47° N latitude by computing three lapse rates for ^{18 …}

Archaeological Feature Identification Through Geochemical Analysis Of Arctic Sediments From The Cape Krusenstern National Monument, Northwest Alaska, Patrick William Reed

Dissertations and Theses

Identification and interpretation of archaeological phenomena is typically based on visual cues and the physical presence of "something archaeological," such as a diagnostic artifact, landscape modification, or structural element. Yet many archaeological features, i.e. the discrete archaeological deposits related to past human behavior, lack clear indicators of human activity that provides clues to the feature's origin. At the Cape Krusenstern beach ridge complex, located in northwest Alaska, ambiguous features, that could be natural or anthropogenic (vegetation anomalies), or are of unknown cultural function (indeterminate), comprise 60% of the identified features at the complex. These ambiguous features represent a large gap …

Geochemical Response To Thermal Energy Storage In The Columbia River Basalt Aquifer System Beneath The Portland Basin, Oregon, Ellen Elizabeth Svadlenak

Dissertations and Theses

Deep direct use thermal energy storage (TES) is a low carbon emission method of geothermal energy storage and supply for large-scale residential, commercial, and manufacturing heating and cooling. The process entails repeated cycles of hot- or cold-water injection, storage, and extraction from slow groundwater flow zones within the deeper layers of an aquifer system. Though a promising technology, TES cycles may increase mineral dissolution and precipitation reactions, particularly at elevated temperatures. The ensuing mass transfer can form scale in heat exchange systems and alter aquifer porosity and permeability, processes that can reduce the operational efficiency of a TES system.

Within …