Matching Items (13)
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
Numerous studies have examined the interplay of climate, tectonics, biota and erosion and found that these variables are intertwined in a complicated system of feedbacks and as a result, some of these factors are often oversimplified or simply neglected. To understand the interplay of these factors one must understand the processes that transport or inhibit transport of soil. This study uses the short-lived, fallout-derived, radionuclides 137Cs and 210Pb to identify soil transport processes and to quantify soil transport using the profile distribution model for 137Cs. Using five field sites in the San Gabriel Mountains of California, I address four questions: (1) Is there a process transition between high and low gradient slopes observable with short-lived isotopes? (2) Do convex hilltops reflect short-term equilibrium erosion rates? (3) Do linear transects of pits accurately characterize hillslope averaged erosion rates? and (4) What role does fire play on short-term soil transport and isotope distribution? I find no evidence supporting a process transition from low gradient to high gradient slopes but also find that significant spatial variability of erosion rates exist. This spatial variability is the result of sensitivity of the method to small scale variations in isotopes and indicates that small scale processes may dominate broader scale trends. I find that short-term erosion rates are not at equilibrium on a convex hilltop and suggest the possibility of a headward incision signal. Data from a post-fire landscape indicates that fires may create complications in 137Cs and 210Pb distribution that current models for erosion calculation do not account for. I also find that across all my field sites soil transport processes can be identified and quantified using short-lived isotopes and I suggest high resolution grid sampling be used instead of linear transects so that small scale variability can be averaged out.
ContributorsWalsh, Joseph Robert (Author) / Heimsath, Arjun M. (Thesis advisor) / Whipple, Kelin X. (Committee member) / Zapata, Claudia E. (Committee member) / Arizona State University (Publisher)
Created2011
Description
The San Gabriel Mountains (SGM) of southern California provide the opportunity to study the topographic controls on erosion rate in a mountain range where climate and lithology are relatively constant. I use a combination of digital elevation model data, detailed channel survey data, decadal climate records, and catchment-averaged erosion rates quantified from 10Be concentrations in stream sands to investigate the style and rates of hillslope and channel processes across the transition from soil-mantled to rocky landscapes in the SGM. Specifically, I investigate (1) the interrelations among different topographic metrics and their variation with erosion rate, (2) how hillslopes respond to tectonic forcing in "threshold" landscapes, (3) the role of discharge variability and erosion thresholds in controlling the relationship between relief and erosion rate, and (4) the style and pace of transient adjustment in the western SGM to a recent increase in uplift rate. Millennial erosion rates in the SGM range from 0.03-1.1 mm/a, generally increasing from west to east. For low erosion rates (< 0.3 mm/a), hillslopes tend to be soil-mantled, and catchment-averaged erosion rates are positively correlated with catchment-averaged slope, channel steepness, and local relief. For erosion rates greater than 0.3 mm/a, hillslopes become increasingly rocky, catchment-mean hillslope angle becomes much less sensitive to erosion rate, and channels continue to steepen. I find that a non-linear relationship observed between channel steepness and erosion rate can be explained by a simple bedrock incision model that combines a threshold for erosion with a probability distribution of discharge events where large floods follow an inverse power-law. I also find that the timing of a two-staged increase in uplift rate in the western SGM based on stream profile analysis agrees with independent estimates. Field observations in the same region suggest that the relict topography that allows for this calculation has persisted for more than 7 Ma due to the stalling of migrating knickpoints by locally stronger bedrock and a lack of coarse sediment cover.
ContributorsDibiase, Roman Alexander (Author) / Whipple, Kelin X (Thesis advisor) / Heimsath, Arjun M. (Thesis advisor) / Arrowsmith, J Ramon (Committee member) / Garnero, Edward J. (Committee member) / Hodges, Kip V. (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
Ponderosa pine forests are a dominant land cover type in semiarid montane areas. Water supplies in major rivers of the southwestern United States depend on ponderosa pine forests since these ecosystems: (1) receive a significant amount of rainfall and snowfall, (2) intercept precipitation and transpire water, and (3) indirectly influence runoff by impacting the infiltration rate. However, the hydrologic patterns in these ecosystems with strong seasonality are poorly understood. In this study, we used a distributed hydrologic model evaluated against field observations to improve our understandings on spatial controls of hydrologic patterns, appropriate model resolution to simulate ponderosa pine ecosystems and hydrologic responses in the context of contrasting winter to summer transitions. Our modeling effort is focused on the hydrologic responses during the North American Monsoon (NAM), winter and spring periods. In Chapter 2, we utilized a distributed model explore the spatial controls on simulated soil moisture and temporal evolution of these spatial controls as a function of seasonal wetness. Our findings indicate that vegetation and topographic curvature are spatial controls. Vegetation controlled patterns during dry summer period switch to fine-scale terrain curvature controlled patterns during persistently wet NAM period. Thus, a climatic threshold involving rainfall and weather conditions during the NAM is identified when high rainfall amount (such as 146 mm rain in August, 1997) activates lateral flux of soil moisture and frequent cloudy cover (such as 42% cloud cover during daytime of August, 1997) lowers evapotranspiration. In Chapter 3, we investigate the impacts of model coarsening on simulated soil moisture patterns during the NAM. Results indicate that model aggregation quickly eradicates curvature features and its spatial control on hydrologic patterns. A threshold resolution of ~10% of the original terrain is identified through analyses of homogeneity indices, correlation coefficients and spatial errors beyond which the fidelity of simulated soil moisture is no longer reliable. Based on spatial error analyses, we detected that the concave areas (~28% of hillslope) are very sensitive to model coarsening and root mean square error (RMSE) is higher than residual soil moisture content (~0.07 m3/m3 soil moisture) for concave areas. Thus, concave areas need to be sampled for capturing appropriate hillslope response for this hillslope. In Chapter 4, we investigate the impacts of contrasting winter to summer transitions on hillslope hydrologic responses. We use a distributed hydrologic model to generate a consistent set of high-resolution hydrologic estimates. Our model is evaluated against the snow depth, soil moisture and runoff observations over two water years yielding reliable spatial distributions during the winter to summer transitions. We find that a wet winter followed by a dry summer promotes evapotranspiration losses (spatial averaged ~193 mm spring ET and ~ 600 mm summer ET) that dry the soil and disconnect lateral fluxes in the forested hillslope, leading to soil moisture patterns resembling vegetation patches. Conversely, a dry winter prior to a wet summer results in soil moisture increases due to high rainfall and low ET during the spring (spatially averaged 78 mm ET and 232 mm rainfall) and summer period (spatially averaged 147 mm ET and 247 mm rainfall) which promote lateral connectivity and soil moisture patterns with the signature of terrain curvature. An opposing temporal switch between infiltration and saturation excess runoff is also identified. These contrasting responses indicate that the inverse relation has significant consequences on hillslope water availability and its spatial distribution with implications on other ecohydrological processes including vegetation phenology, groundwater recharge and geomorphic development. Results from this work have implications on the design of hillslope experiments, the resolution of hillslope scale models, and the prediction of hydrologic conditions in ponderosa pine ecosystems. In addition, our findings can be used to select future hillslope sites for detailed ecohydrological investigations. Further, the proposed methodology can be useful for predicting responses to climate and land cover changes that are anticipated for the southwestern United States.
ContributorsMahmood, Taufique Hasan (Author) / Vivoni, Enrique R. (Thesis advisor) / Whipple, Kelin X. (Committee member) / Shock, Everett (Committee member) / Heimsath, Arjun M. (Committee member) / Ruddell, Benjamin (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