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- Genre: Masters Thesis
- Member of: Theses and Dissertations
Description
Growth of the Phoenix metropolitan area led to exposures of the internal bedrock structure of surrounding semi-arid mountain ranges as housing platforms or road cuts. Such exposures in the Sonoran and Mojave deserts reveal the presence of sedimentary calcium carbonate infilling the pre-existing fracture matrix of the bedrock. Field surveys of bedrock fractures filled with carbonate (BFFC) reveal an average of 0.079 +/- 0.024 mT C/m2 stored in the upper 2 m of analyzed bedrock exposures. Back-scattered electron microscopy images indicate the presence of carbonate at the micron scale, not included in this estimation. Analysis of the spatial extent of bedrock landforms in arid and semi-arid regions worldwide suggests that ~1485 GtC could potentially be stored in the upper 2 m horizon of BFFCs. Radiocarbon dating obtained at one of the sites indicates it is likely that some of the carbonate was flushed into the bedrock system during glacial wet pulses, and is stored on Pleistocene timescales or longer. Strontium isotope analysis at the same site suggest the potential for a substantial cation contribution from weathering of the local bedrock, indicating the potential exists for sequestration of atmospheric carbon in BFFCs. Rates of carbon release from BFFCs are tied to rates of erosion of bedrock ranges in desert climates.
ContributorsHarrison, Emma (Author) / Dorn, Ronald (Thesis advisor) / Reynolds, Stephen (Committee member) / Schmeeckle, Mark (Committee member) / Arizona State University (Publisher)
Created2013
Description
The Kinsley Mountain gold deposit of northeastern Nevada, located ~70 km south of Wendover, Nevada, contains seven sediment-hosted, disseminated-gold deposits, in Cambrian limestones and shales. Mining ceased in 1999, with 138,000 ounces of gold mined at an average grade between 1.5-2.0 g/t. Resource estimates vary between 15,000 and 150,000 ounces of gold remaining in several mineralized pods. Although exploration programs have been completed within the study area, the structural history and timing of precious-metal mineralization are still poorly understood. This study aims to better understand the relation between stratigraphy, structural setting, and style of gold mineralization. In order to accomplish these goals, geological mapping at a scale of 1:5,000 was conducted over the property as well as analysis of soil and rock chip samples for multi-element geochemistry. Using cross-cutting relationships, the structural history of Kinsley Mountain has been determined. The deformation can broadly be categorized as an early stage of compressional tectonics including folding, attenuation of the stratigraphy, and thrust faulting. This early stage was followed by a series of extensional deformation events, the youngest of which is an ongoing process. The structural history determined from this study fits well into a regional context and when viewed in conjunction with the mineralization event, can be used to bracket the timing of gold mineralization. The northwest oriented structure responsible for concentrating decalcification, silicification, and mineralization has two generations of cave fill breccias that both pre- and post-date the gold event. The statistical analysis of multi-element geochemistry for rock chip and soil samples has determined that Au is most strongly associated with Te, while weaker correlations exist between Au and Ag, As, Hg, Mo, Sb, Tl, and W. This suite of elements is associated with an intrusion driven system and is atypical of Carlin-type gold systems. From these elemental associations the gold mineralization event is thought to be controlled by the emplacement of a felsic intrusion. The responsible intrusion may be an exposed quartz monzonite to the south of the study area, as suggested by possible zonation of Cu, Pb, and Zn, which decrease in concentration with increasing distance from the outcropping stock. Alternatively, an unexposed intrusion at depth cannot be ruled out as the driver of the mineralizing system.
ContributorsMacFarlane, Bryan (Author) / Reynolds, Stephen (Thesis advisor) / Hervig, Richard (Committee member) / Burt, Donald (Committee member) / Arizona State University (Publisher)
Created2012
Description
Increasing rates of sea-level rise (SLR) pose a major threat to coastal communities around the world. Evidence of these impacts is found in increased rates of extreme weather, erosion, coastal flooding, high water levels and wave height, altered geomorphology, and more. Coastal dunes act as a buffer for neighboring ecosystems and protect inland communities from increased rates of SLR. The Eureka Littoral Cell (ELC) in Humboldt County, California, which extends from Trinidad Head in the north to Cape Mendocino in the south, experiences extreme wave conditions and higher rates of SLR in comparison to the rest of the Pacific Northwest. This study focuses on assessing the vulnerability of the outer-barrier system of the ELC to SLR and complements previous vulnerability assessments of the inner Humboldt Bay. The study area was partitioned into thirteen (13) representative study reaches based on shoreline change rates and geomorphology. Twenty-two (22) environmental and socio-economic variables were identified to characterize the broader human-environmental connections and exposures that define coastal vulnerability beyond basic physical forcing and exposures. The study first compiled and examined a range of physical, biological, hazardous, socio-cultural, and infrastructure attributes of the outer barrier region of the study site for their inherent vulnerabilities. Second, individual vulnerability scores, based on geographic attributes of each variable, were determined by modifying existing methodologies (e.g., USGS), spanning variable data ranges, and/or with feedback from local representatives and a research advisory team. Aggregations of individual variables were used to provide variable category groupings (e.g., physical, biological, hazards, socio-cultural, and infrastructure). Finally, aggregated values were normalized on a one-to-ten scale to determine two sub-categories of vulnerability (environmental, socio-economic) and an overall comprehensive vulnerability for each study reach. The resulting vulnerability assessments identify which reaches are likely to experience low, moderate, and high levels of vulnerability and, based on variable and sub-grouping values, what factors contribute to this vulnerability. As such, this study addresses the significance of including both environmental and socio-economic variables to examine and characterize vulnerability to SLR and it is anticipated that the results will help inform future adaptation and resilience planning in the region.
ContributorsShinsato, Lara Miyori (Author) / Dorn, Ron I (Thesis advisor) / Walker, Ian J (Thesis advisor) / Schmeeckle, Mark (Committee member) / Arizona State University (Publisher)
Created2023
Description
This combined research provides in-depth insights into both the tectonic evolution of the Bradshaw Mountain region in Arizona and the effective use of Structure-from-Motion (SfM) photogrammetry in remote geological education. The first study focuses on deciphering paleostress fields in the Bradshaw Mountains region, which helps unravel Earth's past tectonic activities and lithospheric evolution. By examining fractures in plutonic stocks, ranging in age from 73 to 64 million years, crucial insights into the area's tectonic history were obtained. Fracture properties such as size, frequency, orientation, and location were diligently recorded. Further examination in a regional context revealed a complex stress regime during the Laramide orogeny, underpinned by diverse fracture and aplite dike orientations. The findings hint at potential influences of stress reversal during Laramide pluton emplacement and crystallization on regional principal stress, which deviated from previous regional tectonic studies. Factors like crustal dilation, local uplift, tensile stress cycle, and topographic stress could explain the lack of predicted mineralized orientations. The implications of these findings are vital for reconstructing Laramide tectonic and magmatic activities in the region, although further research is required to fully understand the causative mechanisms.
The second study centers on the use of SfM photogrammetry in geological education, with a focus on remote learning environments. This involves creating 3D models of hand samples and outcrops with exceptional resolution for detail recognition. Detailed guidance on hardware and software specifications, image capture conditions, file management, and 3D model creation using Metashape is provided. The study emphasizes the dual-masking technique for optimum texture quality and the role of SketchFab in the analysis and viewing of the final product. This integration of SfM photogrammetry into geological education supplements traditional hands-on learning and enhances students' grasp of geological concepts. The technique provides an immersive, interactive experience, especially beneficial for students unable to physically access geological samples, and fosters critical thinking through a hands-on digital interface.
ContributorsHurst, Joseph Gregory (Author) / Reynolds, Stephen (Thesis advisor) / Semken, Steven (Committee member) / Johnson, Julia (Committee member) / Arizona State University (Publisher)
Created2023
Description
The study of fault zones is a critical component to understanding earthquake mechanics and seismic hazard evaluations. Models or simulations of potential earthquakes, based on fault zone properties, are a first step in mitigating the hazard. Theoretical models of earthquake ruptures along a bi-material interface result in asymmetrical damage and preferred rupture propagation direction. Results include greater damage intensity within stiffer material and preferred slip in the direction of the more compliant side of the fault. Data from a dense seismic array along the Clark strand of the SJFZ at Sage Brush Flat (SGB) near Anza, CA, allows for analysis and characterization of shallow (<1km depth) seismic structure and fault zone properties. Results indicate potential asymmetric rock damage at SGB, similar to findings elsewhere along the SJFZ suggesting an NW preferred rupture propagation.
In this study, analysis of high resolution topography suggests asymmetric morphology of the SGB basin slopes are partially attributed to structural growth and fault zone damage. Spatial distributions of rock damage, from site mapping and fault perpendicular transects within SGB and Alkali Wash, are seemingly asymmetric with pulverization dominantly between fault strands or in the NE fault block. Remapping of the SJFZ through Alkali Wash indicates the fault is not isolated to a single strand along the main geologic boundary as previously mapped. Displacement measurements within SGB are analogous to those from the most recent large earthquake on the Clark fault. Geologic models from both a 3D shear wave velocity model (a product from the dense seismic array analysis) and lithologic and structural mapping from this study indicate surface observations and shallow seismic data compare well. A synthetic three-dimensional fault zone model illustrates the complexity of the structure at SGB for comparison with dense array seismic wave products. Results of this study generally agree with findings from seismic wave interpretations suggesting damage asymmetry is controlled by a NW preferred rupture propagation.
In this study, analysis of high resolution topography suggests asymmetric morphology of the SGB basin slopes are partially attributed to structural growth and fault zone damage. Spatial distributions of rock damage, from site mapping and fault perpendicular transects within SGB and Alkali Wash, are seemingly asymmetric with pulverization dominantly between fault strands or in the NE fault block. Remapping of the SJFZ through Alkali Wash indicates the fault is not isolated to a single strand along the main geologic boundary as previously mapped. Displacement measurements within SGB are analogous to those from the most recent large earthquake on the Clark fault. Geologic models from both a 3D shear wave velocity model (a product from the dense seismic array analysis) and lithologic and structural mapping from this study indicate surface observations and shallow seismic data compare well. A synthetic three-dimensional fault zone model illustrates the complexity of the structure at SGB for comparison with dense array seismic wave products. Results of this study generally agree with findings from seismic wave interpretations suggesting damage asymmetry is controlled by a NW preferred rupture propagation.
ContributorsWade, Adam Micahel (Author) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen (Committee member) / DeVecchio, Duane (Committee member) / Arizona State University (Publisher)
Created2018
Description
The morphology of mountainous areas is strongly influenced by stream bed incision rates, but most studies of landscape evolution consider erosion at basin scales or larger. The research here attempts to understand the smaller-scale mechanics of erosion on exposed bedrock channels in the conceptual framework of an established saltation-abrasion model by Sklar and Dietrich [2004]. The recirculating flume used in this experiment allows independent control of bed slope, water discharge rate, sediment flux, and sediment grain size – all factors often bundled together in simple models of river incision and typically cross-correlated in natural settings. This study investigates the mechanics of erosion on exposed bedrock channels caused by abrasion of transported particles. Of particular interest are saltating particles, as well as sediment near the threshold between saltation and suspension - sediment vigorously transported but with significant interaction with the bed. The size of these erosive tools are varied over an order of magnitude in mean grain diameter, including a sand of D¬50 = 0.56 mm, and three gravel sizes of 3.39, 4.63, and 5.88 mm. Special consideration was taken to prevent any flow conditions that created a persistent alluvial cover. The erodible concrete substrate is fully exposed at all times during experiments reported here. Rates of erosion into the concrete substrate (a bedrock proxy) were measured by comparing topographic data before and after each experimental run, made possible by a precision laser mounted on a high speed computer-controlled cart. The experimental flume was able to produce flow discharge as high as 75 liters per second, sediment fluxes (of many varieties) up to 215 grams per second, and bed slopes up to 10%. I find a general positive correlation is found between erosion rate and bed slope, shear stress, grain size, and sediment flux.
ContributorsAdams, Mark (Author) / Whipple, Kelin (Thesis advisor) / Heimsath, Arjun (Committee member) / Schmeeckle, Mark (Committee member) / Arizona State University (Publisher)
Created2016
Description
The Hassayampa River Canyon, located near Wickenburg, Arizona, is a riparian ecosystem and a popular recreational area in the arid Sonoran Desert of central Arizona. The canyon hosts well-exposed middle Cenozoic volcanic and sedimentary sequences, an underlying crystalline basement, and the unconformity that separates the two packages of rocks. The crystalline basement includes Proterozoic metamorphic and granitic rocks, and a Cretaceous granodiorite intrusion. The area features extension-related normal faults, major associated tear faults, evidence for faulting during accumulation of the mid-Cenozoic sequence, and known mineral deposits, including those of manganese, gold, and copper. New geologic mapping provides the city of Wickenburg with scientific and societal information for future land-use and resource-management decisions, and improves the understanding of the geologic history of the region. New geologic mapping in the southern half of the Sam Powell Peak 7.5' Quadrangle highlights (1) mid-Cenozoic volcanism and extension that formed the main geologic features of the area, including Hassayampa River Canyon; (2) relationships between Neogene sedimentation and late Neogene basin-fill deposits, and (3) the development of the modern Hassayampa River system onto pre-existing bedrock topography. Geologic mapping was conducted under the joint State-Federal USGS National Cooperative Geologic Mapping program, and was jointly funded by the Arizona Geological Survey and USGS under EdMap award G18AC00230.
ContributorsBrown, Holly (Author) / Reynolds, Stephen (Thesis advisor) / Semken, Steve (Committee member) / Johnson, Julia (Committee member) / Arizona State University (Publisher)
Created2021