Thesis (MS)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: William Wyckoff. Includes bibliographical references (leaves 457-499).

Thesis (PhD)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Billie L. Kerans. Includes bibliographical references.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Andrew J. Hansen. Includes bibliographical references (leaves 128-140).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 95-99). Also available via the Internet.

The last several years have seen renewed interest in the origin of silicic magmas thanks to the developments of new microanalytical techniques allowing the measurement of the isotopic and trace element compositions of erupted magmas on sub-crystal length scales. Concurrently, there has been rapid improvement in the sophistication of computer modeling of igneous systems. This dissertation is an interdisciplinary study of the rhyolites of the Yellowstone hotspot track using both techniques. Chapters II-IV, which have all been published in existing journals, are a detailed study of the O and Hf isotopic compositions of zircon phenocrysts from large rhyolitic eruptions in the central Snake River Plain, and from rhyolites which erupted in Oregon, Idaho, and Nevada coeval with the Columbia River flood basalts. They show that rhyolites are derived from combinations of fractionates of mantle-derived basalts and of different crustal end-members which are identifiable by their distinct isotopic end-member compositions. In the Snake River Plain and Yellowstone, they recognize a common trend where early erupted rhyolites have a strong signature of melting of ancient Precambrian crust, whereas later erupted rhyolites more closely resemble the mantle in their radiogenic isotopes and are more likely to be depleted in oxygen isotopes. Diversity in zircon grain compositions also documents a batch mixing process in which multiple compositionally distinct magma bodies are assembled into a larger common magma body prior to eruption. In Chapters V and VI, the former of which has been published with the latter in preparation, a new series of magmatic-thermomechanical models is presented which assume that melts rising through the crust are arrested by strong rheological contrasts. The strongest such contrast occurs at the brittle-ductile transition at 5-10 km depth, leading to the formation of a 10-15 km thick mafic mid-crustal sill, which separates upper and lower-crustal zones of partial melt, corroborating previous geophysical imaging studies. In Chapter VI, the above isotopic trends are replicated in the modeling scheme, which shows that the source depth of crustal melts tends to shallow with time through a combination of crustal heating and repeated caldera collapses. This dissertation includes both previously published co-authored material.

Yellowstone National Park hosts over 10,000 thermal features (e.g. geysers, fumaroles, mud pots, and hot springs), yet little is known about the hydrothermally active zones hundreds of meters beneath the features. Transient electromagnetic (TEM) soundings and 2D direct current (DC) resistivity profiles show that hydrothermal alteration at active sites have a higher electrical conductivity than the surrounding hydrothermally inactive areas. For that reason, airborne TEM is an effective method to characterize large areas and identify hydrothermally active and inactive zones using electrical conductivity. Here we present results from an airborne TEM survey acquired jointly by the U.S. Geological Survey and the University of Wyoming in November, 2016. We integrate resistivity from the airborne electromagnetic (EM) survey with research drillhole data and rock physics models to investigate the controls on electrical conductivity in the upper few hundreds of meters of the Yellowstone hydrothermal system. Resistivities in Yellowstone are the product of complex variations of lithology, temperature, salinity, clay content, and hydrothermal fluids. Results show that the main drivers in lowering the high resistivitiy of volcanic rocks are water saturation and hydrothermal alteration. Salinities are not significantly elevated in Yellowstone and temperature is not a first order affect. / Master of Science / Yellowstone National Park is a popular scientific and tourist destination because of it’s vast amount of thermal features including hot springs like Grand Prismatic, geysers like Old Faithful, and many more. But what is happening beneath those features and how can we use geophysics to find out? In November 2016, the U.S. Geological Survey and University of Wyoming conducted an airborne geophysical survey that measures how conductive the rock is beneath Yellowstone. Using this data, we map fluids and hydrothermal activity, and relate them to the local geology. The goal of this thesis is to understand the geologic factors that make the rock beneath Yellowstone’s features conductive. We have shown that the main factors that contribute to the high conductivities in thermal areas of Yellowstone are hydrothermal alteration of the rocks and the high amount of fluids filling space inside the rocks.

Mineral-depositing hydrothermal ecosystems, such as the hot springs in Yellowstone National Park, provide an unparalleled opportunity to document how microbial biosignatures form and contribute to the body of evidence indicative of the microbial inhabitants of active hot springs. Mineralization of microbial communities in silica-depositing hot springs can result in the preservation of microbial biofacies in the geologic record. To determine the effects of prolonged aerial exposure on the preservation potential of mid-to-low temperature cyanobacteria dominated microbial communities that are typically permineralized in the siliceous sinter, modern biofacies samples of such communities were collected from the active and inactive parts of Queen's Laundry hot spring in Yellowstone National Park. The strategy of the research was to: (1) perform qualitative and quantitative characterization of structural and morphometric attributes of subaqueous and aerially exposed Calothrix biofacies samples collected from terraces; and (2) determine whether prolonged subaerial exposure affected the fidelity of morphological biosignatures (i.e., biofabrics and microbial cells) in the aerially exposed samples. To ensure that the permanently subaqueous and aerially exposed samples were comparable, a protocol developed to describe structural and morphological attributes of stromatolites was utilized to characterize the hot spring samples. Morphometric analysis of both types of Calothrix biofacies samples (i.e., partly silicified subaqueous and aerially exposed samples) revealed the presence of: distinct microbially influenced structures; thicker lamina at or near the base of the terraces; the greatest density of microorganisms in microbial structures; and increased microbial structure flatness as height of the microbial structures within the terrace proper increased. These characteristics were also used to provide a means to interpret the environmental conditions within which the terrace structures developed. To determine whether prolonged subaerial exposure affected the morphological fidelity of the biosignatures in the aerially exposed samples, the microstructure of these samples was studied in detail petrographically. A silica layer defined the boundary between laminae and was referred to as the "capping" silica deposit because it was found to "cap" all of the laminae in the Calothrix biofacies samples. The top most capping silica deposit of the aerially exposed Calothrix biofacies samples was found to be distinctly different from the capping silica deposits in the interior of the same sample and in the partly mineralized subaqueous Calothrix biofacies samples. The aerially exposed capping silica deposit was milky and glassy in appearance and contained fine laminations. The fine laminations were not found in any laminae of the biofacies samples. Another key finding of the project is a new evaluation of the preservation potential of the Calothrix terrace samples. Petrographic observations revealed that preservation of the morphological fidelity of the laminae and the microstructures within them was significantly higher within the microbial shrub and domical structures in both the partially silicified subaqueous and aerially exposed Calothrix biofacies samples than other microstructure types observed. In summary, a detailed morphometric characterization protocol confirmed that it is possible to identify similar features in Calothrix biofacies found inside the active part of the hot spring as well as beyond the perimeter (i.e., aerially exposed for ≥ 3 years) at multiple spatial scales; only the top-most capping silica deposit of the aerially exposed samples is altered by subaerial exposure; the preservation potential for Calothrix biofabrics is highest within shrub and domical structures; and morphometric analysis on a variety of Calothrix terraced structures could lend insight into the factor(s) responsible for terrace formation. This research lays the foundation for analyzing similar structures in geologically older rocks and for recognizing how microbial organisms can and likely have influenced terrace formation. The work also suggests that aerial processes can alter such samples and biosignatures within them. It is recommended that additional non-destructive and spatially correlated analytical methods be considered in the search for chemofossils in the sinter surrounding filaments past and present.

Potential policy decisions regarding fly fishing in the Yellowstone National Park Area could severely impact the enjoyment possibilities of many of its users. In order to determine the magnitude of the impact, this paper applies a form of the basic travel cost model developed by Bell and Leeworthy [JEEM. 18,189-205 (1990)] to fishing sites in the Yellowstone National Park Area. Bell and Leeworthy have argued that consumer demand for the time spent at a recreation site is inversely related to on-site cost per day, and may be positively related to travel cost per trip. The paper discusses relevant literature on the method, presents background information on the site, and generates a demand curve for users of the resource. A consumer surplus measurement is then derived from the resulting demand data, which gives an estimate for the value of the resource; the consumer surplus is determined to be roughly $751.88 per day spent at the site. The assumptions of the model are then discussed, and an assessment is made of the potential policy implications. / Graduation date: 1998

Prepared for The National Park Service, United States Department of Interior, Yellowstone, Wyoming / The goal of this investigation has been the reconstruction of past seasonal climate for the period 1750-1910 (161 years) in the Yellowstone National Park region based upon tree-ring data. Tree-ring series are useful in the reconstruction of past climate owing to the availability of large numbers of trees, the great longevity of trees, and the critical fact that the climatic information they contain is accumulated over specific years. In this project a number of tree-ring series from the region around Yellowstone National Park have been calibrated against short-term (1912-1971) seasonal temperature and precipitation data for Bozeman, Moran, Red Lodge, and Yellowstone Park. From these calibrations, long-term seasonal temperature and precipitation records have been reconstructed for each of the four stations. A major reason for these reconstructions has been the need for long-term climatic data that can be used to indicate potential variations in the climate of the park region. Knowledge of these climatic variations may facilitate estimates of natural food supplies or availability of forage in winter as related to snow depth. Previously such estimates have had to be based upon relatively short-term climatic data which undoubtedly do not encompass all possible climatic variations. With this in mind, a series of precipitation and temperature maps have been produced to indicate some of the seasonal extremes that have probably been experienced since 1750 within a given year or group of years as indicated by the tree -ring data. It is hoped that these maps will be useful to various types of researchers involved in planning within Yellowstone National Park.

Thesis (M.S.)--Montana State University, 2004. / Title from PDF title page (viewed Feb. 11, 2005). Includes bibliographical references (p. 54-60).