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ASU Electronic Theses and Dissertations


This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.


Subject
Date Range
2010 2019


East African extensional basins have played a crucial role in revealing the evolution and characteristics of the early stages of continental rifting and for providing the geological context of hominin evolution and innovation. The numerous volcanic eruptions, rapid sedimentation and burial, and subsequent exposure through faulting and erosion, provide excellent conditions for the preservation of tectonic history, paleoenvironment data, and vertebrate fossils. The reconstruction of depositional environments and provision of geochronologic frameworks for hominin sites have been largely provided by geologic investigations in conjunction with paleontological studies, like the Ledi-Geraru Research Project (LGRP). High-resolution paleoclimate records that can be directly …

Contributors
Garello, Dominique Ines, Arrowsmith, Ramon, Campisano, Chris J, et al.
Created Date
2019

Ethnogeology is the scientific study of human relationships with the Earth as a system, typically conducted within the context of a specific culture. Indigenous or historically resident people may perceive local places differently from outside observers trained in the Western tradition. Ethnogeologic knowledge includes traditional indigenous knowledge (alternatively referred to as traditional ecological knowledge or TEK), which exceeds the boundaries of non-Indigenous ideas of physical characteristics of the world, tends to be more holistic, and is culturally framed. In this ethnogeological study, I have implemented several methods of participatory rapid assessment (PRA) from the discipline of field ethnography to collect …

Contributors
Garcia, Angel Antonio, Semken, Steven, Brandt, Elizabeth, et al.
Created Date
2018

Previous workers hypothesized that lunar Localized Pyroclastic Deposits (LPDs) represent products of vulcanian-style eruptions, since some have low proportions of juvenile material. The objective of the first study is to determine how juvenile composition, calculated using deposit and vent volumes, varies among LPDs. I used Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) digital terrain models (DTMs) to generate models of pre-eruption surfaces for 23 LPDs and subtracted them from the NAC DTMs to calculate deposit and vent volumes. Results show that LPDs have a wide range of juvenile compositions and thinning profiles, and that there is a positive …

Contributors
Keske, Amber, Christensen, Philip R, Robinson, Mark S, et al.
Created Date
2018

The movement between tectonic plates is accommodated through brittle (elastic) displacement on the plate boundary faults and ductile permanent deformation on the fault borderland. The elastic displacement along the fault can occur in the form of either large seismic events or aseismic slip, known as fault creep. Fault creep mainly occurs at the deep ductile portion of the crust, where the temperature is high. Nonetheless, aseismic creep can also occur on the shallow brittle portion of the fault segments that are characterized by frictionally weak material, elevated pore fluid pressure, or geometrical complexity. Creeping segments are assumed to safely release …

Contributors
Khoshmanesh, Mostafa, Shirzaei, Manoochehr, Arrowsmith, Ramon, et al.
Created Date
2018

The dynamic Earth involves feedbacks between the solid crust and both natural and anthropogenic fluid flows. Fluid-rock interactions drive many Earth phenomena, including volcanic unrest, seismic activities, and hydrological responses. Mitigating the hazards associated with these activities requires fundamental understanding of the underlying physical processes. Therefore, geophysical monitoring in combination with modeling provides valuable tools, suitable for hazard mitigation and risk management efforts. Magmatic activities and induced seismicity linked to fluid injection are two natural and anthropogenic processes discussed in this dissertation. Successful forecasting of the timing, style, and intensity of a volcanic eruption is made possible by improved understanding …

Contributors
Zhai, Guang, Shirzaei, Manoochehr, Garnero, Edward, et al.
Created Date
2018

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 …

Contributors
Wade, Adam Micahel, Arrowsmith, Ramon, Reynolds, Stephen, et al.
Created Date
2018

Remote sensing in visible to near-infrared wavelengths is an important tool for identifying and understanding compositional differences on planetary surfaces. Electronic transitions produce broad absorption bands that are often due to the presence of iron cations in crystalline mineral structures or amorphous phases. Mars’ iron-rich and variably oxidized surface provides an ideal environment for detecting spectral variations that can be related to differences in surface dust cover or the composition of the underlying bedrock. Several imaging cameras sent to Mars include the capability to selectively filter incoming light to discriminate between surface materials. At the coarse spatial resolution provided by …

Contributors
Wellington, Danika, Bell III, James F, Christensen, Philip R, et al.
Created Date
2018

An exhaustive parameter study involving 133 dynamic crystallization experiments was conducted, to investigate the validity of the planetary embryo bow shock model by testing whether the cooling rates predicted by this model are consistent with the most dominant chondrule texture, porphyritic. Results show that using coarse-grained precursors and heating durations ≤ 5 minutes at peak temperature, porphyritic textures can be reproduced at cooling rates ≤ 600 K/hr, rates consistent with planetary embryo bow shocks. Porphyritic textures were found to be commonly associated with skeletal growth, which compares favorably to features in natural chondrules from Queen Alexandra Range 97008 analyzed, which …

Contributors
Perez, Alexandra Marie, Desch, Steven J, Till, Christy B, et al.
Created Date
2018

There is a growing body of evidence that the evolving redox structure of the oceans has been an important influence on the evolutionary trajectory of animals. However, current understanding of connections between marine redox conditions and marine extinctions and recoveries is hampered by limited detailed knowledge of the timing, duration, and extent of marine redox changes. The recent development of U isotopes (δ238U) in carbonates as a global ocean redox proxy has provided new insight into this problem. Reliable application and interpretation of the δ238U paleoproxy in geological records requires a thorough understanding of the reliability of δ238U recorded by …

Contributors
Zhang, Feifei, Anbar, Ariel, Gordon, Gwyneth, et al.
Created Date
2018

Education through field exploration is fundamental in geoscience. But not all students enjoy equal access to field-based learning because of time, cost, distance, ability, and safety constraints. At the same time, technological advances afford ever more immersive, rich, and student-centered virtual field experiences. Virtual field trips may be the only practical options for most students to explore pedagogically rich but inaccessible places. A mixed-methods research project was conducted on an introductory and an advanced geology class to explore the implications of learning outcomes of in-person and virtual field-based instruction at Grand Canyon National Park. The study incorporated the Great Unconformity …

Contributors
Ruberto, Thomas, Semken, Steve, Anbar, Ariel, et al.
Created Date
2018

Interpreting the petrogenesis of materials exposed on the surface of planets and asteroids is fundamental to understanding the origins and evolution of the inner Solar System. Temperature, pressure, fO2, and bulk composition directly influence the petrogenetic history of planetary surfaces and constraining these variables with remote sensing techniques is challenging. The integration of remote sensing data with analytical investigations of natural samples, lab-based spectroscopy, and thermodynamic modelling improves our ability to interpret the petrogenesis of planetary materials. A suite of naturally heated carbonaceous chondrite material was studied with lab-based spectroscopic techniques, including visible near-infrared and Fourier transform infrared reflectance spectroscopy. …

Contributors
Haberle, Christopher William, Christensen, Philip R., Garvie, Laurence A. J., et al.
Created Date
2018

Explosive mafic (basaltic) volcanism is not easily explained by current eruption models, which predict low energy eruptions from low viscosity magma due to decoupling of volatiles (gases). Sunset Crater volcano provides an example of an alkali basalt magma that produced a highly explosive sub-Plinian eruption. I investigate the possible role of magmatic volatiles in the Sunset Crater eruption through study of natural samples of trapped volatiles (melt inclusions) and experiments on mixed-volatile (H2O-CO2) solubility in alkali-rich mafic magmas. I conducted volatile-saturated experiments in six mafic magma compositions at pressures between 400 MPa and 600 MPa to investigate the influence of …

Contributors
Allison, Chelsea M, Clarke, Amanda B, Hervig, Richard L, et al.
Created Date
2018

Impact cratering and volcanism are two fundamental processes that alter the surfaces of the terrestrial planets. Though well studied through laboratory experiments and terrestrial analogs, many questions remain regarding how these processes operate across the Solar System. Little is known about the formation of large impact basins (>300 km in diameter) and the degree to which they modify planetary surfaces. On the Moon, large impact basins dominate the terrain and are relatively well preserved. Because the lunar geologic timescale is largely derived from basin stratigraphic relations, it is crucial that we are able to identify and characterize materials emplaced as …

Contributors
Meyer, Heather, Robinson, Mark S, Bell, Jim, et al.
Created Date
2018

Carboxylic acids are an abundant and reactive species present throughout our solar system. The reactions of carboxylic acids can shape the organic abundances within oil field brines, carbonaceous chondrites, and different ranks of coal. I have performed hydrothermal experiments with model aromatic carboxylic acids in the presences of different oxide minerals to investigate the reactions available to carboxylic acids in the presence of mineral surfaces. By performing experiments containing one organic compound and one mineral surface, I can begin to unravel the different reactions that can occur in the presence of different minerals. I performed experiments with phenylacetic acid (PAA), …

Contributors
Johnson, Kristin Nicole, Shock, Everett, Hartnett, Hilairy, et al.
Created Date
2017

Water is a critical resource for future human missions, and is necessary for understanding the evolution of the Solar System. The Moon and Mars have water in various forms and are therefore high-priority targets in the search for accessible extraterrestrial water. Complementary remote sensing analyses coupled with laboratory and field studies are necessary to provide a scientific context for future lunar and Mars exploration. In this thesis, I use multiple techniques to investigate the presence of water-ice at the lunar poles and the properties of martian chloride minerals, whose evolution is intricately linked with liquid water. Permanently shadowed regions (PSRs) …

Contributors
Mitchell, Julie Leeanne, Christensen, Philip R, Bell III, James F, et al.
Created Date
2017

Impact cratering has played a key role in the evolution of the solid surfaces of Solar System bodies. While much of Earth’s impact record has been erased, its Moon preserves an extensive history of bombardment. Quantifying the timing of lunar impact events is crucial to understanding how impacts have shaped the evolution of early Earth, and provides the basis for estimating the ages of other cratered surfaces in the Solar System. Many lunar impact melt rocks are complex mixtures of glassy and crystalline “melt” materials and inherited clasts of pre-impact minerals and rocks. If analyzed in bulk, these samples can …

Contributors
Mercer, Cameron Mark, Hodges, Kip V, Robinson, Mark S, et al.
Created Date
2017

The collision of India and Eurasia constructed the Himalayan Mountains. Questions remain regarding how subsequent exhumation by climatic and tectonic processes shaped the landscape throughout the Late Cenozoic to create the complex architecture observed today. The Mount Everest region underwent tectonic denudation by extension and bestrides one of the world’s most significant rain shadows. Also, glacial and fluvial processes eroded the Everest massif over shorter timescales. In this work, I review new bedrock and detrital thermochronological and geochronological data and both one- and two-dimensional thermal-mechanical modeling that provides insights on the age range and rates of tectonic and erosional processes …

Contributors
Schultz, Mary Hannah, Hodges, Kip V, Whipple, Kelin X, et al.
Created Date
2017

Banded iron formations (BIFs) are among the earliest possible indicators for oxidation of the Archean biosphere. However, the origin of BIFs remains debated. Proposed formation mechanisms include oxidation of Fe(II) by O2 (Cloud, 1973), photoferrotrophy (Konhauser et al., 2002), and abiotic UV photooxidation (Braterman et al., 1983; Konhauser et al., 2007). Resolving this debate could help determine whether BIFs are really indicators of O2, biological activity, or neither. To examine the viability of abiotic UV photooxidation of Fe, laboratory experiments were conducted in which Fe-bearing solutions were irradiated with different regions of the ultraviolet (UV) spectrum and Fe oxidation and …

Contributors
Castleberry, Parker, Anbar, Ariel D, Herckes, Pierre, et al.
Created Date
2017

There is a need to understand spatio-temporal variation of slip in active fault zones, both for the advancement of physics-based earthquake simulation and for improved probabilistic seismic hazard assessments. One challenge in the study of seismic hazards is producing a viable earthquake rupture forecast—a model that specifies the expected frequency and magnitude of events for a fault system. Time-independent earthquake forecasts can produce a mismatch among observed earthquake recurrence intervals, slip-per-event estimates, and implied slip rates. In this thesis, I developed an approach to refine several key geologic inputs to rupture forecasts by focusing on the San Andreas Fault in …

Contributors
Salisbury, James Barrett, Arrowsmith, Ramon, Shirzaei, Manoochehr, et al.
Created Date
2016

For this dissertation, three separate papers explore the study areas of the western Grand Canyon, the Grand Staircase (as related to Grand Canyon) and Desolation Canyon on the Green River in Utah. In western Grand Canyon, I use comparative geomorphology between the Grand Canyon and the Grand Wash Cliffs (GWC). We propose the onset of erosion of the GWC is caused by slip on the Grand Wash Fault that formed between 18 and 12 million years ago. Hillslope angle and channel steepness are higher in Grand Canyon than along the Grand Wash Cliffs despite similar rock types, climate and base …

Contributors
Darling, Andy Darling, Whipple, Kelin, Semken, Steven, et al.
Created Date
2016

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 …

Contributors
Adams, Mark Andrew, Whipple, Kelin, Heimsath, Arjun, et al.
Created Date
2016

The search for life on Mars is a major NASA priority. A Mars Sample Return (MSR) mission, Mars 2020, will be NASA's next step towards this goal, carrying an instrument suite that can identify samples containing potential biosignatures. Those samples will be later returned to Earth for detailed analysis. This dissertation is intended to inform strategies for fossil biosignature detection in Mars analog samples targeted for their high biosignature preservation potential (BPP) using in situ rover-based instruments. In chapter 2, I assessed the diagenesis and BPP of one relevant analog habitable Martian environment: a playa evaporite sequence within the Verde …

Contributors
Shkolyar, Svetlana, Farmer, Jack, Semken, Steven, et al.
Created Date
2016

Silicic volcanoes produce many styles of activity over a range of timescales. Eruptions vary from slow effusion of viscous lava over many years to violent explosions lasting several hours. Hazards from these eruptions can be far-reaching and persistent, and are compounded by the dense populations often surrounding active volcanoes. I apply and develop satellite and ground-based remote sensing techniques to document eruptions at Merapi and Sinabung Volcanoes in Indonesia. I use numerical models of volcanic activity in combination with my observational data to describe the processes driving different eruption styles, including lava dome growth and collapse, lava flow emplacement, and …

Contributors
Carr, Brett Brady, Clarke, Amanda B, Arrowsmith, Ramón, et al.
Created Date
2016

ABSTRACT The Spirit landing site in Gusev Crater has been imaged by the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE) camera more than thirty times since 2006. The breadth of this image set allowed a study of changes to surface features, covering four Mars years. Small fields of bedforms comprised of dark material, and dark dust devil tracks are among the features revealed in the images. The bedforms are constrained within craters on the plains, and unconstrained in depressions less than 200m wide within the topography of the Columbia Hills, a ~120m-high structure in center of Gusev. Dust …

Contributors
Pendleton-Hoffer, Mary C., Christensen, Philip, Whipple, Kelin, et al.
Created Date
2016

On Mars, sedimentary deposits reveal a complex history of water- and wind-related geologic processes. Central mounds – kilometer-scale stacks of sediment located within craters – occur across Mars, but the specific processes responsible for mound formation and subsequent modification are still uncertain. A survey of central mounds within large craters was conducted. Mound locations, mound offsets within their host craters, and relative mound heights were used to address various mound formation hypotheses. The results suggest that mound sediments once filled their host craters and were later eroded into the features observed today. Mounds offsets from the center of their host …

Contributors
Bennett, Kristen Alicia, Bell, James F, Christensen, Phillip, et al.
Created Date
2016

Amorphous phases are detected over large regions of the Martian surface from orbit and in more localized deposits by rovers on the surface. Amorphous silicates can be primary or secondary in origin, both having formed through very different processes, so the unambiguous identification of these phases is important for understanding the geologic history of Mars. Secondary amorphous silicates are poorly understood and underrepresented in spectral libraries because they lack the long-range structural order that makes their crystalline counterparts identifiable in most analytical techniques. Fortunately, even amorphous materials have some degree of short-range order so that distinctions can be made with …

Contributors
Smith, Rebecca Jean, Christensen, Philip, Shock, Everett, et al.
Created Date
2016

Amazonia, inhabited and investigated for millennia, continues to astonish scientists with its cultural and natural diversity. Although Amazonia is rapidly changing, its vast and varied landscape still contains a complex natural pharmacopeia. The Amazonian tribes have accrued valuable environmental and geological knowledge that can be studied. This dissertation demonstrates that Indigenous Knowledge considered alongside Western Science can enhance our understanding of the relationship of people to geological materials and hydrological resources, and reveal mineral medicines with practical applications. I used methods from anthropology and geology to explore the geological knowledge of the Uitoto, a tribe of the Colombian Amazon. The …

Contributors
Londono, Sandra, Williams, Lynda B, Semken, Steven, et al.
Created Date
2016

I investigate the Black Canyon City landslide (BCC landslide), a prominent deep-seated landslide located northeast of Black Canyon City, Arizona. Although the landslide does not appear to pose a significant hazard to structures, its prominent features and high topographic relief make it an excellent site to study the geologic setting under which such features develop. This study has the potential to contribute toward understanding the landscape evolution in similar geologic and topographic settings, and for characterizing the underlying structural processes of this deep-seated feature. We use field and remotely-based surface geology and geomorphological mapping to characterize the landslide geometry and …

Contributors
Helmi, Hurien, Arrowsmith, J Ramón, DeVecchio, Duane, et al.
Created Date
2016

Understanding the structural evolution of planetary surfaces provides key insights to their physical properties and processes. On the Moon, large-scale tectonism was thought to have ended over a billion years ago. However, new Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) high resolution images show the Moon’s surface in unprecedented detail and show many previously unidentified tectonic landforms, forcing a re-assessment of our views of lunar tectonism. I mapped lobate scarps, wrinkle ridges, and graben across Mare Frigoris – selected as a type area due to its excellent imaging conditions, abundance of tectonic landforms, and range of inferred structural …

Contributors
Williams, Nathan Robert, Bell, James, Robinson, Mark, et al.
Created Date
2016

Volcanic devolatilization is one of the major processes in the global nitrogen cycle. Past studies have often estimated the magnitude of this flux using volcanic emission measurements, which are limited to currently active systems and sensitive to atmospheric contamination. A different methodological approach requires appropriate analytical parameters for nitrogen analysis in silicate glasses by secondary ion mass spectrometry (SIMS), which have not yet been established. To this end, we analyze various ion implanted basaltic and rhyolitic glasses by SIMS. We demonstrate that water content significantly affects the ion yields of 14N+ and 14N16O−, as well as the background intensity of …

Contributors
Regier, Margo Regier, Hervig, Richard L, Roggensack, Kurt, et al.
Created Date
2016

Shallow earthquakes in the upper part of the overriding plate of subduction zones can be devastating due to their proximity to population centers despite the smaller rupture extents than commonly occur on subduction megathrusts that produce the largest earthquakes. Damaging effects can be greater in volcanic arcs like Java because ground shaking is amplified by surficial deposits of uncompacted volcaniclastic sediments. Identifying the upper-plate structures and their potential hazards is key for minimizing the dangers they pose. In particular, the knowledge of the regional stress field and deformation pattern in this region will help us to better understand how subduction …

Contributors
Marliyani, Gayatri Indah, Arrowsmith, J Ramon, Clarke, Amanda B, et al.
Created Date
2016

The collision between the Indian and Eurasian tectonic plates marked the onset of the rise of the Himalayan-Tibetan orogen, but also brought about profound changes to the Earth's oceans and climate. The exact sequence of events that occurred during this collision is poorly understood, leading to a wide range of estimates of its age. The Indus and Yarlung sutures are generally considered to represent the final collision between India and Eurasia, and together form a mostly continuous belt that can be traced over 2000 km along strike. In the western portions of the orogen the Karakoram Fault introduces a key …

Contributors
Borneman, Nathaniel, Hodges, Kip, Reynolds, Stephen, et al.
Created Date
2016

Scientific and Cultural Interpretations of Volcanoes, 1766-1901 analyzes nineteenth-century conceptions of volcanoes through interdisciplinary literature and science studies. The project considers how people in the nineteenth century used science, aesthetics, and other ways of knowing to understand volcanoes and their operations. In the mid-eighteenth century, volcanoes were seen as singular, unique features of the planet that lacked temporal and terrestrial reach. By the end of the nineteenth century, volcanoes were seen as networked, environmental phenomena that stretched through geological time and geographic space. Scientific and Cultural Interpretations of Volcanoes, 1766-1901 offers a new historical understanding of volcanoes and their environmental …

Contributors
Linthicum, Kent, Lussier, Mark, Bivona, Daniel, et al.
Created Date
2016

Understanding topography developed above an active blind thrust fault is critical to quantifying the along-strike variability of the timing, magnitude, and rate of fault slip at depth. Hillslope and fluvial processes respond to growing topography such that the existing landscape is an indicator of constructional and destruction processes. Light detection and ranging (lidar) data provide a necessary tool for fine-scale quantitative understanding of the topography to understand the tectonic evolution of blind thrust faulting. In this thesis, lidar topographic data collected in 2014 are applied to a well-studied laterally propagating anticline developed above a blind thrust fault in order to …

Contributors
Kleber, Emily, Arrowsmith, Ramón, DeVecchio, Duane E, et al.
Created Date
2015

Olympus Mons is the largest volcano on Mars. Previous studies have focused on large scale features on Olympus Mons, such as the basal escarpment, summit caldera complex and aureole deposits. My objective was to identify and characterize previously unrecognized and unmapped small scale features to understand the volcanotectonic evolution of this enormous volcano. For this study I investigated flank vents and arcuate graben. Flank vents are a common feature on composite volcanoes on Earth. They provide information on the volatile content of magmas, the propagation of magma in the subsurface and the tectonic stresses acting on the volcano. Graben are …

Contributors
Peters, Sean I., Christensen, Philip R, Clarke, Amanda B, et al.
Created Date
2015

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 …

Contributors
Severson, Allison, Reynolds, Stephen J, Semken, Steven, et al.
Created Date
2015

Among volcanic gases, sulfur dioxide (SO2) is by far the most commonly measured. More than a monitoring proxy for volcanic degassing, SO2 has the potential to alter climate patterns. Persistently active explosive volcanoes are characterized by short explosive bursts, which often occur at periodic intervals numerous times per day, spanning years to decades. SO2 emissions at those volcanoes are poorly constrained, in large part because the current satellite monitoring techniques are unable to detect or quantify plumes of low concentration in the troposphere. Eruption plumes also often show high concentrations of ash and/or aerosols, which further inhibit the detection methods. …

Contributors
Smekens, Jean-Francois, Clarke, Amanda, Christensen, Philip, et al.
Created Date
2015

ABSTRACT The Sentinel-Arlington Volcanic Field (SAVF) is the Sentinel Plains lava field and associated volcanic edifices of late Cenozoic alkali olivine basaltic lava flows and minor tephra deposits near the Gila Bend and Painted Rock Mountains, 65 km-100km southwest of Phoenix, Arizona. The SAVF covers ~600 km2 and consists of 21+ volcanic centers, primarily low shield volcanoes ranging from 4-6 km in diameter and 30-200 m in height. The SAVF represents plains-style volcanism, an emplacement style and effusion rate intermediate between flood volcanism and large shield-building volcanism. Because of these characteristics, SAVF is a good analogue to small-volume effusive volcanic …

Contributors
Cave, Shelby, Clarke, Amanda, Burt, Donald, et al.
Created Date
2015

Chemical and physical interactions of flowing ice and rock have inexorably shaped planetary surfaces. Weathering in glacial environments is a significant link in biogeochemical cycles – carbon and strontium – on Earth, and may have once played an important role in altering Mars’ surface. Despite growing recognition of the importance of low-temperature chemical weathering, these processes are still not well understood. Debris-coated glaciers are also present on Mars, emphasizing the need to study ice-related processes in the evolution of planetary surfaces. During Earth’s history, subglacial environments are thought to have sheltered communities of microorganisms from extreme climate variations. On Amazonian …

Contributors
Rutledge, Alicia Marie, Christensen, Philip R, Shock, Everett, et al.
Created Date
2015

Hydrogen isotope compositions of the martian atmosphere and crustal materials can provide unique insights into the hydrological and geological evolution of Mars. While the present-day deuterium-to-hydrogen ratio (D/H) of the Mars atmosphere is well constrained (~6 times that of terrestrial ocean water), that of its deep silicate interior (specifically, the mantle) is less so. In fact, the hydrogen isotope composition of the primordial martian mantle is of great interest since it has implications for the origin and abundance of water on that planet. Martian meteorites could provide key constraints in this regard, since they crystallized from melts originating from the …

Contributors
Tucker, Kera, Wadhwa, Meenakshi, Hervig, Richard, et al.
Created Date
2015

Seismic observations have revealed two large low shear velocity provinces (LLSVPs) in the lowermost mantle beneath Pacific and Africa. One hypothesis for the origin of LLSVPs is that they are caused by accumulation of subducted oceanic crust on the core-mantle boundary (CMB). Here, I perform high resolution geodynamical calculations to test this hypothesis. The result shows that it is difficult for a thin (~ 6 km) subducted oceanic crust to accumulate on the CMB, and the major part of it is viscously stirred into the surrounding mantle. Another hypothesis for the origin of LLSVPs is that they are caused by …

Contributors
Li, Mingming, McNamara, Allen K, Garnero, Edward J, et al.
Created Date
2015

Much of Mars' surface is mantled by bright dust, which masks the spectral features used to interpret the mineralogy of the underlying bedrock. Despite the wealth of near-infrared (NIR) and thermal infrared data returned from orbiting spacecraft in recent decades, the detailed bedrock composition of approximately half of the martian surface remains relatively unknown due to dust cover. To address this issue, and to help gain a better understanding of the bedrock mineralogy in dusty regions, data from the Thermal Emission Spectrometer (TES) Dust Cover Index (DCI) and Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) were used to identify …

Contributors
Lai, Jason Chi-Shun, Bell, James, Christensen, Philip, et al.
Created Date
2014

Sedimentary basins are defined by extensional tectonics. Rugged mountain ranges stand in stark relief adjacent to muted structural basins filled with sediment. In simplest terms, this topography is the result of ranges uplifted along normal faults, and this uplift drives erosion within upland drainages, shedding sediment into subsiding basins. In southeastern Arizona's Basin and Range province extensional tectonics waned at approximately 3-5 Myr, and the region's structural basins began transitioning from internal to external drainage, forming the modern Gila River fluvial network. In the Atacama Desert of northern Chile, some basins of the Central Depression remain internally drained while others …

Contributors
Jungers, Matthew Cross, Heimsath, Arjun M, Whipple, Kelin, et al.
Created Date
2014

The taxonomic and metabolic profile of the microbial community inhabiting a natural system is largely determined by the physical and geochemical properties of the system. However, the influences of parameters beyond temperature, pH and salinity have been poorly analyzed with few studies incorporating the comprehensive suite of physical and geochemical measurements required to fully investigate the complex interactions known to exist between biology and the environment. Further, the techniques used to classify the taxonomic and functional composition of a microbial community are fragmented and unwieldy, resulting in unnecessarily complex and often non-consilient results. This dissertation integrates environmental metagenomes with extensive …

Contributors
Alsop, Eric Bennie, Raymond, Jason, Anbar, Ariel, et al.
Created Date
2014

Boron concentrations and isotopic composition of phlogopite mica, amphibole, and selected coexisting anhydrous phases in mantle-derived xenoliths from the Kaapvaal Craton were measured by secondary ion mass spectrometry in an effort to better understand the B isotope geochemistry of the subcontinental lithospheric mantle (SCLM) and its implications for the global geochemical cycle of B in the mantle. These samples display a wide, and previously unrecognized, range in their boron contents and isotopic compositions reflecting a complex history involving melt depletion and metasomatism by subduction- and plume-derived components, as well as late stage isotopic exchange related to kimberlite emplacements. Micas from …

Contributors
Guild, Meghan R., Hervig, Richard L, Bell, David R, et al.
Created Date
2014

Impact cratering has played a crucial role in the surface development of the inner planets. Constraining the timing of this bombardment history is important in understanding the origins of life and our planet's evolution. Plate tectonics, active volcanism, and vegetation hinder the preservation and identification of existing impact craters on Earth. Providing age constraints on these elusive structures will provide a deeper understanding of our planet's development. To do this, (U-Th)/He thermochronology and in situ 40Ar/39Ar laser microprobe geochronology are used to provide ages for the Haughton and Mistastin Lake impact structures, both located in northern Canada. While terrestrial impact …

Contributors
Young, Kelsey, Hodges, Kip V, Asphaug, Erik I, et al.
Created Date
2014

The Himalayan orogenic system is one of the youngest and most spectacular examples of a continent-continent collision on earth. Although the collision zone has been the subject of extensive research, fundamental questions remain concerning the architecture and evolution of the orogen. Of particular interest are the structures surrounding the 5 km high Tibetan Plateau, as these features record both the collisional and post-collisional evolution of the orogen. In this study we examine structures along the southwestern margin of the Tibetan Plateau, including the Karakoram (KFS) and Longmu Co (LCF) faults, and the Ladakh, Pangong and Karakoram Ranges. New low-temperature thermochronology …

Contributors
Bohon, Wendy, Arrowsmith, Ramon, Hodges, Kip V, et al.
Created Date
2014

Quantifying the temporal and spatial evolution of active continental rifts contributes to our understanding of fault system evolution and seismic hazards. Rift systems also preserve robust paleoenvironmental records and are often characterized by strong climatic gradients that can be used to examine feedbacks between climate and tectonics. In this thesis, I quantify the spatial and temporal history of rift flank uplift by analyzing bedrock river channel profiles along footwall escarpments in the Malawi segment of the East Africa Rift. This work addresses questions that are widely applicable to continental rift settings: (1) Is rift-flank uplift sufficiently described by theoretical elliptical …

Contributors
Robinson, Scott Michael, Heimsath, Arjun M, Whipple, Kelin X, et al.
Created Date
2014

The Himalaya are the archetypal example of a continental collision belt, formed by the ongoing convergence between India and Eurasia. Boasting some of the highest and most rugged topography on Earth, there is currently no consensus on how climatic and tectonic processes have combined to shape its topographic evolution. The Kingdom of Bhutan in the eastern Himalaya provides a unique opportunity to study the interconnections among Himalayan climate, topography, erosion, and tectonics. The eastern Himalaya are remarkably different from the rest of the orogen, most strikingly due to the presence of the Shillong Plateau to the south of the Himalayan …

Contributors
Adams, Byron Allen, Whipple, Kelin X, Hodges, Kip V, et al.
Created Date
2014

Earth's topographic surface forms an interface across which the geodynamic and geomorphic engines interact. This interaction is best observed along crustal margins where topography is created by active faulting and sculpted by geomorphic processes. Crustal deformation manifests as earthquakes at centennial to millennial timescales. Given that nearly half of Earth's human population lives along active fault zones, a quantitative understanding of the mechanics of earthquakes and faulting is necessary to build accurate earthquake forecasts. My research relies on the quantitative documentation of the geomorphic expression of large earthquakes and the physical processes that control their spatiotemporal distributions. The first part …

Contributors
Haddad, David, Arrowsmith, Ramon, Reynolds, Stephen, et al.
Created Date
2014

Science, Technology, Engineering & Mathematics (STEM) careers have been touted as critical to the success of our nation and also provide important opportunities for access and equity of underrepresented minorities (URM's). Community colleges serve a diverse population and a large number of undergraduates currently enrolled in college, they are well situated to help address the increasing STEM workforce demands. Geoscience is a discipline that draws great interest, but has very low representation of URM's as majors. What factors influence a student's decision to major in the geosciences and are community college students different from research universities in what factors influence …

Contributors
Kraft, Katrien Van Der Hoeven, Husman, Jenefer, Semken, Steven, et al.
Created Date
2014

Impact craters are ubiquitous throughout the Solar System, formed by one of the principal processes responsible for surface modification of terrestrial planets and solid bodies (i.e., asteroids, icy moons). The impact cratering process is well studied, particularly on the Moon and Mercury, where the results remain uncomplicated by atmospheric effects, plate tectonics, or interactions with water and ices. Crater measurements, used to determine relative and absolute ages for geologic units by relating the cumulative crater frequency per unit area to radiometrically-determined ages from returned samples, are sensitive to the solar incidence angle of images used for counts. Earlier work is …

Contributors
Ostrach, Lillian Rose, Robinson, Mark S, Bell Iii, James F, et al.
Created Date
2013

Lunar Reconnaissance Orbiter (LRO) and MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft missions provide new data for investigating the youngest impact craters on Mercury and the Moon, along with lunar volcanic end-members: ancient silicic and young basaltic volcanism. The LRO Wide Angle Camera (WAC) and Narrow Angle Camera (NAC) in-flight absolute radiometric calibration used ground-based Robotic Lunar Observatory and Hubble Space Telescope data as standards. In-flight radiometric calibration is a small aspect of the entire calibration process but an important improvement upon the pre-flight measurements. Calibrated reflectance data are essential for comparing images from LRO to missions like …

Contributors
Braden, Sarah Elizabeth, Robinson, Mark S, Bell, James F, et al.
Created Date
2013

Sedimentary basins in the Afar Depression, Ethiopia archive the progression of continental breakup, record regional changes in east African climate and volcanism, and host what are arguably the most important fossiliferous strata for studying early human evolution and innovation. Significant changes in rift tectonics, climate, and faunal assemblages occur between 3-2.5 million years ago (Ma), but sediments spanning this time period are sparse. In this dissertation, I present the results of a geologic investigation targeting sediments between 3-2.5 Ma in the central and eastern Ledi Geraru (CLG and ELG) field areas in the lower Awash Valley, using a combination of …

Contributors
Dimaggio, Erin Nicole, Arrowsmith, J Ramon, Whipple, Kelin X, et al.
Created Date
2013

A fundamental gap in geomorphic scholarship regards fluvial terraces in small desert drainages and those terraces associated with integrating drainages. This dissertation analyzes four field-based case studies within the Sonoran Desert, south-central Arizona, with the overriding purpose of developing a theory to explain the formative processes and spatial distribution of fluvial terraces in the region. Strath terraces are a common form (Chapters 2, 3, 4) and are created at the expense of bounding pediments that occur on the margins of constraining mountainous drainage boundaries (Chapters 1, 2, 3). Base-level fluctuations of the major drainages cause the formation of new straths …

Contributors
Larson, Phillip Herman, Dorn, Ron I, Schmeeckle, Mark, et al.
Created Date
2013

The temperature of a planet's surface depends on numerous physical factors, including thermal inertia, albedo and the degree of insolation. Mars is a good target for thermal measurements because the low atmospheric pressure combined with the extreme dryness results in a surface dominated by large differences in thermal inertia, minimizing the effect of other physical properties. Since heat is propagated into the surface during the day and re-radiated at night, surface temperatures are affected by sub-surface properties down to several thermal skin depths. Because of this, orbital surface temperature measurements combined with a computational thermal model can be used to …

Contributors
Heath, Simon Nicholas, Christensen, Philip, Bel, James, et al.
Created Date
2013

Assessments for the threats posed by volcanic eruptions rely in large part on the accurate prediction of volcanic plume motion over time. That predictive capacity is currently hindered by a limited understanding of volcanic plume dynamics. While eruption rate is considered a dominant control on volcanic plume dynamics, the effects of variable eruption rates on plume rise and evolution are not well understood. To address this aspect of plume dynamics, I conducted an experimental investigation wherein I quantified the relationship between laboratory jet development and highly-variable discharge rates under conditions analogous to those which may prevail in unsteady, short-lived explosive …

Contributors
Chojnicki, Kirsten Noel, Clarke, Amanda, Williams, Stanley, et al.
Created Date
2012

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 …

Contributors
Manfredi, Leon, Clarke, Amanda B, Williams, David A, et al.
Created Date
2012

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 …

Contributors
Vance, Brad L., Reynolds, Stephen J., Semken, Steven, et al.
Created Date
2012

The presence of a number of extinct radionuclides in the early Solar System (SS) is known from geochemical and isotopic studies of meteorites and their components. The half-lives of these isotopes are short relative to the age of the SS, such that they have now decayed to undetectable levels. They can be inferred to exist in the early SS from the presence of their daughter nuclides in meteoritic materials that formed while they were still extant. The extinct radionuclides are particularly useful as fine-scale chronometers for events in the early SS. They can also be used to help constrain the …

Contributors
Spivak-Birndorf, Lev Jacob, Wadhwa, Meenakshi, Hervig, Richard, et al.
Created Date
2012

The present understanding of the formation and evolution of the earliest bodies in the Solar System is based in large part on geochemical and isotopic evidences contained within meteorites. The differentiated meteorites (meteorites originating from bodies that have experienced partial to complete melting) are particularly useful for deciphering magmatic processes occurring in the early Solar System. A rare group of differentiated meteorites, the angrites, are uniquely suited for such work. The angrites have ancient crystallization ages, lack secondary processing, and have been minimally affected by shock metamorphism, thus allowing them to retain their initial geochemical and isotopic characteristics at the …

Contributors
Sanborn, Matthew Edward, Wadhwa, Meenakshi, Hervig, Richard, et al.
Created Date
2012

Early spacecraft missions to Mars, including the Marnier and Viking orbiters and landers revealed a morphologically and compositionally diverse landscape that reshaped widely held views of Mars. More recent spacecraft including Mars Global Surveyor, Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, and the Mars Exploration Rovers have further refined, enhanced, and diversified our understanding of Mars. In this dissertation, I take a multiple-path approach to planetary and Mars science including data analysis and instrument development. First, I present several tools necessary to effectively use new, complex datasets by highlighting unique and innovative data processing techniques that allow for the regional …

Contributors
Edwards, Christopher Scott, Christensen, Philip R, Bell, James, et al.
Created Date
2012

Molybdenum and uranium isotope variations are potentially powerful tools for reconstructing the paleoredox history of seawater. Reliable application and interpretation of these proxies requires not only detailed knowledge about the fractionation factors that control the distribution of molybdenum and uranium isotopes in the marine system, but also a thorough understanding of the diagenetic processes that may affect molybdenum and uranium isotopes entering the rock record. Using samples from the Black Sea water column, the first water column profile of 238U/235U variations from a modern euxinic basin has been measured. This profile allows the direct determination of the 238U/235U fractionation factor …

Contributors
Romaniello, Stephen, Anbar, Ariel, Hartnett, Hilairy, et al.
Created Date
2012

The tectonic significance of the physiographic transition from the low-relief Tibetan plateau to the high peaks, rugged topography and deep gorges of the Himalaya is the source of much controversy. Some workers have suggested the transition may be structurally controlled (e.g. Hodges et al., 2001), and indeed, the sharp change in geomorphic character across the transition strongly suggests differential uplift between the Himalayan realm and the southernmost Tibetan Plateau. Most Himalayan researchers credit the South Tibetan fault system (STFS), a family of predominantly east-west trending, low-angle normal faults with a known trace of over 2,000 km along the Himalayan crest …

Contributors
Mcdermott, Jeni Amber, Hodges, Kip V, Whipple, Kelin X, et al.
Created Date
2012

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 …

Contributors
Eddy, David, Reynolds, Stephen J, Arrowsmith, J R, et al.
Created Date
2012

Geologic field trips are among the most beneficial learning experiences for students as they engage the topic of geology, but they are also difficult environments to maximize learning. This action research study explored one facet of the problems associated with teaching geology in the field by attempting to improve the transition of undergraduate students from a traditional laboratory setting to an authentic field environment. Utilizing an artificial outcrop, called the GeoScene, during an introductory college-level non-majors geology course, the transition was studied. The GeoScene was utilized in this study as an intermediary between laboratory and authentic field based experiences, allowing …

Contributors
Wilson, Meredith, Jimenez-Castellanos, Oscar, Gonzalez, Gustavo, et al.
Created Date
2012

Future robotic and human missions to the Moon and Mars will need in situ capabilities to characterize the mineralogy of rocks and soils within a microtextural context. Such spatially-correlated information is considered crucial for correct petrogenetic interpretations and will be key observations for assessing the potential for past habitability on Mars. These data will also enable the selection of the highest value samples for further analysis and potential caching for return to Earth. The Multispectral Microscopic Imager (MMI), similar to a geologist's hand lens, advances the capabilities of current microimagers by providing multispectral, microscale reflectance images of geological samples, where …

Contributors
Núñez, Jorge Ivan, Farmer, Jack D., Christensen, Philip R., et al.
Created Date
2012

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 …

Contributors
Macfarlane, Bryan John, Reynolds, Stephen, Hervig, Richard, et al.
Created Date
2012

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: …

Contributors
Walsh, Joe, Heimsath, Arjun M., Whipple, Kelin X., et al.
Created Date
2011

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 …

Contributors
Robinson, Sarah E., Arrowsmith, Ramon, Reynolds, Stephen J, et al.
Created Date
2011

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 …

Contributors
Lockridge, Jeffrey, Fouch, Matthew J, Arrowsmith, Ramon, et al.
Created Date
2011

The San Andreas Fault (SAF) is the primary structure within a system of faults accommodating motion between the North American and Pacific plates. Physical models of faulting and characterizations of seismic hazard are informed by investigations of paleoseismology, slip distribution, and slip rate. The impact of earthquakes on people is due in large part to social vulnerability. This dissertation contributes an analysis about the relationships between earthquake hazard and social vulnerability in Los Angeles, CA and investigations of paleoseismology and fault scarp array complexity on the central SAF. Analysis of fault scarp array geometry and morphology using 0.5 m digital …

Contributors
Toke, Nathan A., Arrowsmith, J R, Boone, Christopher G, et al.
Created Date
2011

Chemical and mineralogical data from Mars shows that the surface has been chemically weathered on local to regional scales. Chemical trends and the types of chemical weathering products present on the surface and their abundances can elucidate information about past aqueous processes. Thermal-infrared (TIR) data and their respective models are essential for interpreting Martian mineralogy and geologic history. However, previous studies have shown that chemical weathering and the precipitation of fine-grained secondary silicates can adversely affect the accuracy of TIR spectral models. Furthermore, spectral libraries used to identify minerals on the Martian surface lack some important weathering products, including poorly-crystalline …

Contributors
Rampe, Elizabeth Barger, Sharp, Thomas G, Christensen, Phillip, et al.
Created Date
2011

A new analytical method is proposed for measuring the deuterium to hydrogen ratio (D/H) of non-stoichiometric water in hydrous minerals via pyrolysis facilitated gas-chromatography - isotope ratio mass spectrometry (GC-IRMS). Previously published analytical methods have reported a poorly understood nonlinear dependence of D/H on sample size, for which any accurate correction is difficult. This sample size effect been variously attributed to kinetic isotope fractionation within the mass spectrometer and peripheral instruments, ion source linearity issues, and an unstable H_3^+-factor or incorrect H_3^+-factor calculations. The cause of the sample size effect is here identified by examinations of individual chromatograms as well …

Contributors
Sheehan, Michael Robert, Knauth, Leroy P, Anbar, Ariel, et al.
Created Date
2011

Dust devils have proven to be commonplace on Mars, although their occurrence is unevenly distributed across the surface. They were imaged or inferred by all six successful landed spacecraft: the Viking 1 and 2 Landers (VL-1 and VL-2), Mars Pathfinder Lander, the Mars Exploration Rovers Spirit and Opportunity, and the Phoenix Mars Lander. Comparisons of dust devil parameters were based on results from optical and meteorological (MET) detection campaigns. Spatial variations were determined based on comparisons of their frequency, morphology, and behavior. The Spirit data spanning three consecutive martian years is used as the basis of comparison because it is …

Contributors
Waller, Devin Ashley, Greeley, Ronald, Christensen, Philip, et al.
Created Date
2011

The Byrd Glacier region of Antarctica is important for understanding the tectonic development and landscape evolution of the Transantarctic Mountains (TAM). This outlet glacier crossing the TAM marks a major discontinuity in the Neoproterozoic-early Paleozoic Ross orogen. The region has not been geologically mapped in detail, but previous studies have inferred a fault to exist beneath and parallel to the direction of flow of Byrd Glacier. Thermochronologic analysis has never been undertaken across Byrd Glacier, and little is known of the exhumation history of the region. The objectives of this study are to assess possible differential movement across the inferred …

Contributors
Foley, Daniel Joseph, Stump, Edmund, Whipple, Kelin X, et al.
Created Date
2011

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 …

Contributors
Geier, John Jeffrey, Reynolds, Stephen J, Burt, Donald, et al.
Created Date
2011

An array of north-striking, left-stepping, active normal faults is situated along the southwestern margin of the Gulf of California. This normal fault system is the marginal fault system of the oblique-divergent plate boundary within the Gulf of California. To better understand the role of upper-crustal processes during development of an obliquely rifted plate margin, gravity surveys were conducted across the normal-fault-bounded basins within the gulf-margin array and, along with optically stimulated luminescence dating of offset surfaces, fault-slip rates were estimated and fault patterns across basins were assessed, providing insight into sedimentary basin evolution. Additionally, detailed geologic and geomorphic maps were …

Contributors
Busch, Melanie Marie, Arrowsmith, Ramon, Reynolds, Stephen, et al.
Created Date
2011

Geoscience educators commonly teach geology by projecting a photograph in front of the class. Geologic photographs often contain animals, people, and inanimate objects that help convey the scale of features in the photograph. Although scale items seem innocuous to instructors and other experts, the presence of such items is distracting and has a profound effect on student learning behavior. To evaluate how students visually interact with distracting scale items in photographs and to determine if cueing or signaling is an effective means to direct students to pertinent information, students were eye tracked while looking at geologically-rich photographs. Eye-tracking data revealed …

Contributors
Coyan, Joshua Aaron, Reynolds, Stephen, Arrowsmith, Ramon, et al.
Created Date
2011

Many shallow craters near the Spirit Mars Exploration Rover landing site contain asymmetric deposits of windblown sediments which could indicate the predominant local wind direction at the time of deposition or redistribution. Wind tunnel simulations and field studies of terrestrial craters were used to determine trends in deposition as a function of crater morphometry and wind direction. Terrestrial analog field work at the Amboy lava field, Mojave Desert, California, included real-time wind measurements and assessments of active sediment deposition in four small (<100 m) craters. Preliminary results indicate that reverse flow or stagnant wind and deposition on the upwind side …

Contributors
Kienenberger, Rebekah L., Greeley, Ronald, Christensen, Philip, et al.
Created Date
2011

The Juglandaceae (walnuts, hickories, pecans) has one of the best-documented fossil records in the Northern Hemisphere. The oldest modern genus, Cyclocarya, today restricted to China, first appears in the late Paleocene (57 ma) of North Dakota, USA. Unlike walnuts and pecans that produce edible fruits dispersed by mammals, Cyclocarya fruits are small nutlets surrounded by a prominent circular wing, and are thought to be wind- or water-dispersed. The current study provides the first evidence that fossil fruits were different from modern forms in the number and organization of their attachment to reproductive branches, and in their anatomical structure. Unlike the …

Contributors
Taylor, Witt, Pigg, Kathleen B, Wojciechowski, Martin F, et al.
Created Date
2010