Matching Items (9)
Description
Tempe Terra, Mars, has a complex history marked by volcanism and tectonism. Investigation results presented here build on previous work to better determine the volcanic history of the Tempe volcanic province by identifying and mapping previously undetected vents, characterizing all vents, identifying spatial and temporal trends in eruptive styles, comparing vent density to similar provinces such as the Snake River Plains of Idaho and Syria Planum and determining absolute age relationships among the volcanic features. Crater size-frequency distribution model ages of 120 Ma to 2.4 Ga indicate the province has been active for over half of the planet's history. During that time, age decreases from southwest to northeast, a trend that parallels the dominant orientation of faulting in the region, providing further evidence that volcanic activity in the region is tectonically controlled (or the tectonics is magmatically controlled). Morphological variation with age hints at an evolving magma source (increasing viscosity) or changing eruption conditions (decreasing eruption rate or eruption through thicker lithosphere).
ContributorsManfredi, Leon (Author) / Clarke, Amanda B (Thesis advisor) / Williams, David A. (Thesis advisor) / Reynolds, Stephen J. (Committee member) / Arizona State University (Publisher)
Created2012
Description
A thorough understanding of Europa's geology through the synergy of science and technology, by combining geologic mapping with autonomous onboard processing methods, enhances the science potential of future outer solar system missions. Mapping outlines the current state of knowledge of Europa's surface and near sub-surface, indicates the prevalence of distinctive geologic features, and enables a uniform perspective of formation mechanisms responsible for generating those features. I have produced a global geologic map of Europa at 1:15 million scale and appraised formation scenarios with respect to conditions necessary to produce observed morphologies and variability of those conditions over Europa's visible geologic history. Mapping identifies areas of interest relevant for autonomous study; it serves as an index for change detection and classification and aids pre-encounter targeting. Therefore, determining the detectability of geophysical activity is essential. Activity is evident by the presence of volcanic plumes or outgassing, disrupted surface morphologies, or changes in morphology, color, temperature, or composition; these characteristics reflect important constraints on the interior dynamics and evolutions of planetary bodies. By adapting machine learning and data mining techniques to signatures of plumes, morphology, and spectra, I have successfully demonstrated autonomous rule-based response and detection, identification, and classification of known events and features on outer planetary bodies using the following methods: 1. Edge-detection, which identifies the planetary horizon and highlights features extending beyond the limb; 2. Spectral matching using a superpixel endmember detection algorithm that identifies mean spectral signatures; and 3. Scale invariant feature transforms combined with supervised classification, which examines brightness gradients throughout an image, highlights extreme gradient regions, and classifies those regions based on a manually selected library of features. I have demonstrated autonomous: detection of volcanic plumes or jets at Io, Enceladus, and several comets, correlation between spectral signatures and morphological appearances of Europa's individual tectonic features, detection of ≤94% of known transient events on multiple planetary bodies, and classification of similar geologic features. Applying these results to conditions expected for Europa enables a prediction of the potential for detection and recommendations for mission concepts to increase the science return and efficiency of future missions to observe Europa.
ContributorsBunte, Melissa K (Author) / Bell, Iii, James F. (Thesis advisor) / Williams, David A. (Committee member) / Saripalli, Srikanth (Committee member) / Clarke, Amanda B. (Committee member) / Reynolds, Stephen J. (Committee member) / Christensen, Phillip R. (Committee member) / Arizona State University (Publisher)
Created2013
Description
The goal of this study is to gain a better understanding of earthquake distribution and regional tectonic structure across Arizona. To achieve this objective, I utilized seismic data from EarthScope's USArray Transportable Array (TA), which was deployed in Arizona from April 2006 to March 2009. With station spacing of approximately 70 km and ~3 years of continuous three-component broadband seismic data, the TA provided an unprecedented opportunity to develop the first seismicity catalog for Arizona without spatial sampling bias. In this study I developed a new data analysis workflow to detect smaller scale seismicity across a regional study area, which serves as a template for future regional analyses of TA data and similar datasets. The final event catalog produced for this study increased the total number of earthquakes documented in Arizona by more than 50% compared to the historical catalog, despite being generated from less than three years of continuous waveform data. I combined this new TA catalog with existing earthquake catalogs to construct a comprehensive historical earthquake catalog for Arizona. These results enabled the identification of several previously unidentified areas of seismic activity within the state, as well as two regions characterized by seismicity in the deeper (>20 km) crust. The catalog also includes 16 event clusters, 10 of which exhibited clear temporal clustering and swarm-like behavior. These swarms were distributed throughout all three physiographic provinces, suggesting that earthquake swarms occur regardless of tectonic or physiographic setting. I also conducted a case study for an earthquake swarm in June of 2007 near Theodore Roosevelt Lake, approximately 80 miles northeast of Phoenix. Families of events showed very similar character, suggesting a nearly identical source location and focal mechanism. We obtained focal mechanisms for the largest of these events, and found that they are consistent with normal faulting, expected in this area of the Arizona Transition Zone. Further, I observed no notable correlation between reservoir water level and seismicity. The occurrence of multiple historical earthquakes in the areas surrounding the reservoir indicates that this swarm was likely the result of tectonic strain release, and not reservoir induced seismicity.
ContributorsLockridge, Jeffrey Steven (Author) / Fouch, Matthew J (Thesis advisor) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen J. (Committee member) / Arizona State University (Publisher)
Created2011
Description
Meter-resolution topography gathered by LiDAR (Light Detection and Ranging) has become an indispensable tool for better understanding of many surface processes including those sculpting landscapes that record information about earthquake hazards for example. For this reason, and because of the spectacular representation of the phenomena that these data provide, it is appropriate to integrate these data into Earth science educational materials. I seek to answer the following research question: "will using the LiDAR topography data instead of, or alongside, traditional visualizations and teaching methods enhance a student's ability to understand geologic concepts such as plate tectonics, the earthquake cycle, strike-slip faults, and geomorphology?" In order to answer this question, a ten-minute introductory video on LiDAR and its uses for the study of earthquakes entitled "LiDAR: Illuminating Earthquake Hazards" was produced. Additionally, LiDAR topography was integrated into the development of an undergraduate-level educational activity, the San Andreas fault (SAF) earthquake cycle activity, designed to teach introductory Earth science students about the earthquake cycle. Both the LiDAR video and the SAF activity were tested in undergraduate classrooms in order to determine their effectiveness. A pretest and posttest were administered to introductory geology lab students. The results of these tests show a notable increase in understanding LiDAR topography and its uses for studying earthquakes from pretest to posttest after watching the video on LiDAR, and a notable increase in understanding the earthquake cycle from pretest to posttest using the San Andreas Fault earthquake cycle exercise. These results suggest that the use of LiDAR topography within these educational tools is beneficial for students when learning about the earthquake cycle and earthquake hazards.
ContributorsRobinson, Sarah Elizabeth (Author) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen J. (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2011
Description
New quadrangle-scale geologic mapping of the western part of the Date Creek Mountains (DCM) in west-central Arizona has revealed new insights into the geologic units, structures, and geologic history. Three U-Pb dates also provide surprising new information about the age and spatial relationships of the DCM as well as implications for the tectonics of the area. Paleoproterozoic metamorphic rocks in the central part of the DCM are presumably correlative with the Yavapai schist exposed in other parts of the Arizona Transition Zone. A granite formerly assigned to the Paleoproterozoic was subdivided into megacrystic and fine-grained units and hosts a set of previously undescribed subvertical felsic dikes. A new U-Pb date of the fine-grained phase has shown that unit to be Jurassic. The Mesoproterozoic Granite of Joshua Tree Parkway (Bryant, 1995), which also has fine-grained and megacrystic phases, displays a subhorizontal interunit contact suggestive of vertical stacking of individual intrusions. The age of another granitic pluton previously thought to be Laramide has been revised to Jurassic with the new U-Pb dates. Multiple noncontinuous sections of Tertiary volcanic rocks cover parts of the western end of the range with a combined thickness of at least 500 m. Tertiary basin fill abuts the northern and western edges of the range and perched remnants of the fill in the mountains suggest a former thickness of at least 100 m more than today. Quaternary alluvium is present in the drainages and covers the slopes south of the mountains. In addition to the felsic dikes, mafic and pegmatite dikes are also present. Two major structures are exposed in the study area: a roughly north-trending graben at the western end of the range and a probable normal fault which cuts northwest-southeast across the DCM and displays a zone of brittle deformation up to a few hundred meters wide. The orientation of the normal fault mirrors that of other similar faults in the area and is considered to be the result of regional tectonics activity, while the graben may owe its existence to movement on an underlying low-angle detachment fault.
ContributorsEddy, David (Author) / Reynolds, Stephen J. (Thesis advisor) / Arrowsmith, J R (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2012
Description
The Santa Gertrudis Mining District of Sonora, Mexico contains more than a dozen purported Carlin-like, sedimentary-hosted, disseminated-gold deposits. A series of near-surface, mostly oxidized gold deposits were open-pit mined from the calcareous and clastic units of the Cretaceous Bisbee Group. Gold occurs as finely disseminated, sub-micron coatings on sulfides, associated with argillization and silicification of calcareous, carbonaceous, and siliciclastic sedimentary rocks in structural settings. Gold occurs with elevated levels of As, Hg, Sb, Pb, and Zn. Downhole drill data within distal disseminated gold zones reveal a 5:1 ratio of Ag:Au and strong correlations of Au to Pb and Zn. This study explores the timing and structural control of mineralization utilizing field mapping, geochemical studies, drilling, core logging, and structural analysis. Most field evidence indicates that mineralization is related to a single pulse of moderately differentiated, Eocene intrusives described as Mo-Cu-Au skarn with structurally controlled distal disseminated As-Ag-Au.
ContributorsGeier, John Jeffrey (Author) / Reynolds, Stephen J. (Thesis advisor) / Burt, Donald (Committee member) / Stump, Edmund (Committee member) / Arizona State University (Publisher)
Created2011
Description
The historic Cacachilas mining district is located in Baja California Sur, approximately 20 kilometers east of La Paz, and has a series of gold- and silver-hosted veins, faults, and shear zones within Cretaceous granodioritic plutons. The remote geographic location and past political events within Mexico left the district essentially unexplored after the late 1800s, when the Mexican Revolution began. More recent discovery of gold deposits along the Baja peninsula instigated a renewed interest in mineralization in the Sierra Cacachilas. The area lacks detailed previous geologic data, so this study focused on characterizing the controls of mineralization and the locations of mineralized trends of deposits within the northeastern Sierra Cacachilas, with a goal toward helping assess economic viability of the deposits. I mapped surficial geologic data, such as outcrop locations, alteration assemblages, limonite intensities, and structural measurements. I then synthesized these into geologic maps and cross sections. I combined field data with geochemical assays and structural plots to better characterize individual historic district trends and newly located trends to understand the distribution of mineralization at surface and at depth. Lastly, I synthesized geology of the Sierra Cacachilas with other gold and silver deposits located in the southern Baja peninsula to better characterize the mineralization and deposit style of the Cacachilas district.
Mineralization in the northeastern Sierra Cacachilas is mainly restricted to steeply dipping quartz veins, faults, and brittle-ductile shear zones that trend generally northeast. Some veins are en-echelon within the mineralized zones, implying some lateral movement along the zones. Veins are dominated by milky to clear quartz with trace sulfides, abundant limonite (after sulfides), and local open-space textures. Mineralization is interpreted to be intermediate between classic epithermal and mesothermal veins. Within mineralized trends and commonly associated with mineralization are greisen-like zones that are defined by intense sericitic to muscovitic overprint, trend northeast, and are with or without sulfides. The intensity of sulfide abundance and limonitic alteration after sulfides within and near mineralized zones is overall a good guide to mineralization. Based on past reports and on my recent studies, the Cacachilas district has very promising potential for relatively small, high-grade deposits.
Mineralization in the northeastern Sierra Cacachilas is mainly restricted to steeply dipping quartz veins, faults, and brittle-ductile shear zones that trend generally northeast. Some veins are en-echelon within the mineralized zones, implying some lateral movement along the zones. Veins are dominated by milky to clear quartz with trace sulfides, abundant limonite (after sulfides), and local open-space textures. Mineralization is interpreted to be intermediate between classic epithermal and mesothermal veins. Within mineralized trends and commonly associated with mineralization are greisen-like zones that are defined by intense sericitic to muscovitic overprint, trend northeast, and are with or without sulfides. The intensity of sulfide abundance and limonitic alteration after sulfides within and near mineralized zones is overall a good guide to mineralization. Based on past reports and on my recent studies, the Cacachilas district has very promising potential for relatively small, high-grade deposits.
ContributorsSeverson, Allison Rose (Author) / Reynolds, Stephen J. (Thesis advisor) / Semken, Steven (Committee member) / Burt, Donald (Committee member) / Arizona State University (Publisher)
Created2015
Description
ABSTRACT The accretion of juvenile island-arc lithosphere by convergent tectonism during the Paleoproterozoic, in conjunction with felsic volcanism, resulted in the assembly, ductile to partial brittle deformation, uplift, and northwest-directed thrusting of rocks in the McDowell Mountains region and adjacent areas in the Mazatzal Orogenic belt. Utilizing lithologic characteristics and petrographic analysis of the Proterozoic bedrock, a correlation to the Alder series was established, revising the stratigraphic sequences described by earlier works. The central fold belt, composed of an open, asymmetric syncline and an overturned, isoclinal anticline, is cut by an axial-plane parallel reactivated thrust zone that is intruded by a deformed Paleoproterozoic mafic dike. Finite strain analyses of fold geometries, shear fabrics, foliations, fold vergence, and strained clasts point to Paleoproterozoic northwest-directed thrusting associated with the Mazatzal orogen at approximately 1650 million years ago. Previous studies constrained the regional P-T conditions to at least the upper andalusite-kyanite boundary at peak metamorphic conditions, which ranged from 4-6 kilobars and 350-450⁰ Celsius, although the plasticity of deformation in a large anticlinal core suggests that this represents the low end of the P-T conditions. Subsequent to deformation, the rocks were intruded by several granitoid plutons, likely of Mesoproterozoic age (1300-1400 Ma). A detailed analysis of Proterozoic strain solidly places the structure of the McDowell Mountains within the confines of the Mazatzal Orogeny, pending any contradictory geochronological data.
ContributorsVance, Brad (Author) / Reynolds, Stephen J. (Thesis advisor) / Semken, Steven (Committee member) / Stump, Edmund (Committee member) / Arizona State University (Publisher)
Created2012
Description
Geochronology and thermochronology are valuable tools for investigating the synergy between the deformational and erosional processes that shape mountainous terrains. Though numerous techniques have been developed to probe the rate and timing of events within these settings, the research presented here explores how scientists can use fewer samples to produce richer data products with broader contextual importance.
The beginning of this compilation focuses on establishing laboratory techniques to facilitate this goal. I developed a novel laser ablation ‘double dating’ (LADD) technique that rapidly yields paired U/Pb and (U-Th)/He dates for the accessory minerals zircon, titanite, and apatite. The technique obviates the need for geometric corrections typically applied during (U-Th)/He data reduction, enables the analysis of a broader spectrum of detrital crystals, and provides the opportunity for additional mapping and isotopic analyses that are traditionally challenging to procure and/or fraught with assumptions. Despite the technique’s promise, I also found it essential to weigh several considerations of relevance when attempting to date young (≤ Miocene) accessory minerals with low concentrations of U + Th. Consequently, I discuss the impact that such variables have on the magnitude of analytical imprecision and the data’s flexibility for geologic interpretation.
Beyond the lab, I collected a suite of bedrock and detrital samples from small catchments draining the southeastern Sierra Nevada mountains of California. Using the techniques described above as well as conventional methods for (U-Th)/He zircon dating, I compared the utility of both bedrock and detrital approaches for extrapolating local exhumation histories. I additionally tested the ability to employ detrital datasets to extrapolate cooling histories that span from mineral crystallization to rock exhumation through the upper crust. Employing principal mode dates from a combination of zircon and apatite LADD dates and detrital hornblende 40Ar/39Ar dates, I was able to derive thermal models that demonstrate the existence of significant variability in the cooling histories of various intrusive units along the eastern Sierra Nevada. While these results only scratch the surface of what’s possible within the realm of detrital-based research, this contribution demonstrates the utility of expanding the temporal and spatial scope of traditional detrital methodologies.
The beginning of this compilation focuses on establishing laboratory techniques to facilitate this goal. I developed a novel laser ablation ‘double dating’ (LADD) technique that rapidly yields paired U/Pb and (U-Th)/He dates for the accessory minerals zircon, titanite, and apatite. The technique obviates the need for geometric corrections typically applied during (U-Th)/He data reduction, enables the analysis of a broader spectrum of detrital crystals, and provides the opportunity for additional mapping and isotopic analyses that are traditionally challenging to procure and/or fraught with assumptions. Despite the technique’s promise, I also found it essential to weigh several considerations of relevance when attempting to date young (≤ Miocene) accessory minerals with low concentrations of U + Th. Consequently, I discuss the impact that such variables have on the magnitude of analytical imprecision and the data’s flexibility for geologic interpretation.
Beyond the lab, I collected a suite of bedrock and detrital samples from small catchments draining the southeastern Sierra Nevada mountains of California. Using the techniques described above as well as conventional methods for (U-Th)/He zircon dating, I compared the utility of both bedrock and detrital approaches for extrapolating local exhumation histories. I additionally tested the ability to employ detrital datasets to extrapolate cooling histories that span from mineral crystallization to rock exhumation through the upper crust. Employing principal mode dates from a combination of zircon and apatite LADD dates and detrital hornblende 40Ar/39Ar dates, I was able to derive thermal models that demonstrate the existence of significant variability in the cooling histories of various intrusive units along the eastern Sierra Nevada. While these results only scratch the surface of what’s possible within the realm of detrital-based research, this contribution demonstrates the utility of expanding the temporal and spatial scope of traditional detrital methodologies.
ContributorsHorne, Alexandra Michelle (Author) / Hodges, Kip V. (Thesis advisor) / van Soest, Matthijs C. (Committee member) / Whipple, Kelin X (Committee member) / Heimsath, Arjun M. (Committee member) / Reynolds, Stephen J. (Committee member) / Arizona State University (Publisher)
Created2019