Matching Items (115)

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Detrital-Zircon and Paleontological Constraints on Correlations of Pennsylvanian-Permian Rocks Near Sedona, Arizona

Description

This research focuses on a geologic controversy regarding the stratigraphic position of the Hermit Formation outside of the Grand Canyon, specifically in Sedona, Arizona. The goal of this research is

This research focuses on a geologic controversy regarding the stratigraphic position of the Hermit Formation outside of the Grand Canyon, specifically in Sedona, Arizona. The goal of this research is to provide additional constraints on this dispute by pinpointing the transition to the Hermit Formation in Sedona, if possible. To accomplish this, we use field observations and detrital zircon dating techniques to compare data we collected in Sedona with data previously published for the Grand Canyon. Fossil evidence in Sedona and near Payson, Arizona is also used to aid correlation. Starting from the Grand Canyon, the Hermit Formation pinches out to the southeast and, hypothetically obstructed by the Sedona Arch, does not reach Sedona. Detrital zircon data show similar age distributions between the Grand Canyon and Sedona rock units, but the results are not strong enough to confidently correlate units between these two localities. The data collected for this study suggest that if the Hermit Formation is present in Sedona, it is limited to higher up in the section as opposed to occupying the middle portion of the section as is currently interpreted. To determine with greater accuracy whether the Hermit Formation does exist higher in the section of Sedona, more detrital zircons should be collected and analyzed from the part of the section that yielded a relative increase in young zircons aged 200-600 Ma.

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  • 2017-05

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Dating and Characterizing the Piedmont Fault in the North Virgin Mountains of Arizona

Description

Faults found in the arid to semi-arid Basin and Range Physiographic province of the southwestern US are given broad age definitions in terms of which features appear to be the

Faults found in the arid to semi-arid Basin and Range Physiographic province of the southwestern US are given broad age definitions in terms of which features appear to be the oldest. Particularly in the northwestern corner of Arizona, detailed geomorphic studies on the tectonic history and timing of faulting are not widespread. At the base of the Virgin Mountains in northwestern Arizona is a fault scarp along the Piedmont Fault line. This normal fault crosses a series of alluvial fans that are filled with sediments of ambiguous ages. Previous studies that were done in this region find a broad, Miocene age for the exhumation and uplift of these surfaces, with some indications of Laramide faulting history. However, specific fault characteristics and a time constraint of the tectonic history of the Piedmont Fault scarp has yet to be established. Here, we aim to determine the age, fault-slip rate, seismic history, and potential hazard of the fault scarp near Scenic and Littlefield, Arizona through structure from motion (SfM) modeling, which is a form of photogrammetry using a drone. In addition, we distinguish the climatic and tectonic influences on the geomorphology observed along the scarp through analysis along the fault line. With data collected from a ~500 m section of the fault, we present results from a digital elevation model (DEM) and orthophotos derived through the SfM modelling. Based on field observations and morphologic dating, we determine that the Piedmont Fault experiences an approximately continuous fault-slip and an earthquake recurrence interval in the range of 7,000 years. The approximate age of the scarp is 16.0 ka ± 5 kyr. Therefore, we conclude that the earthquake hazard posed to nearby cities is minimal but not nonexistent. Future work includes further analysis of fault profiles due to uncertainty in the present one and Terrestrial Cosmogenic Nuclide (TCN) dating of samples taken from the tops of boulders in a residual debris flow sitting on faulted and unfaulted alluvia. Determining the ages for these boulder surfaces can hopefully further inform our knowledge of the tectonic activity present in the North Virgin Mountains.

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Date Created
  • 2020-12

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VOLUME APPROXIMATIONS OF LASER PIT ABLATIONS

Description

Radiometric dating estimates the age of rocks by comparing the concentration of a decaying radioactive isotope to the concentrations of the decay byproducts. Radiometric dating has been instrumental in the

Radiometric dating estimates the age of rocks by comparing the concentration of a decaying radioactive isotope to the concentrations of the decay byproducts. Radiometric dating has been instrumental in the calculation of the Earth's age, the Moon's age, and the age of our solar system. Geochronologists in the School of Earth and Space Exploration at ASU use radiometric dating extensively in their research, and have very specific procedures, hardware, and software to perform the dating calculations. Researchers use lasers to drill small holes, or ablations, in rock faces, collect the masses of various isotopes using a mass spectrometer, and scan the pit with an interferometer, which records the z heights of the pit on an x-y grid. This scan is then processed by custom-made software to determine the volume of the pit, which then is used along with the isotope masses and known decay rates to determine the age of the rock. My research has been focused on improving this volume calculation through computational geometry methods of surface reconstruction. During the process, I created an web application that reads interferometer scans, reconstructs a surface from those scans with Poisson reconstruction, renders the surface in the browser, and calculates the volume of the pit based on parameters provided by the researcher. The scans are stored in a central cloud datastore for future analysis, allowing the researchers in the geochronology community to collaborate together on scans from various rocks in their individual labs. The result of the project has been a complete and functioning application that is accessible to any researcher and reproducible from any computer. The 3D representation of the scan data allows researchers to easily understand the topology of the pit ablation and determine early on whether the measurements of the interferometer are trustworthy for the particular ablation. The volume calculation by the new software also reduces the variability in the volume calculation, which hopefully indicates the process is removing noise from the scan data and performing volume calculations on a more realistic representation of the actual ablation. In the future, this research will be used as the groundwork for more robust testing and closer approximations through implementation of different reconstruction algorithms. As the project grows and becomes more usable, hopefully there will be adoption in the community and it will become a reproducible standard for geochronologists performing radiometric dating.

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Date Created
  • 2016-05

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Modeling the Effects of Flow Conditions and Rheology on Lava Flows with Polyethylene Glycol

Description

This study explores the relationship between three physics-based predictive models defined by Castruccio et al. (2013), and four different distinct experimental morphologies of lava flows produced in a series of

This study explores the relationship between three physics-based predictive models defined by Castruccio et al. (2013), and four different distinct experimental morphologies of lava flows produced in a series of laboratory simulations where polyethylene glycol 600 (PEG) was pumped into an inclined chilled bath of water. The length of the experimental flow was recorded over time to create an experimental model to later be compared to the physics-based predictive models. The experimental morphologies are pillowed, rifted, folded, and leveed flows which can be characterized by a dimensionless parameter 𝛹, which scales natural lava flows to experimental lava flows and is a ratio of timescales, the characteristic timescale of thermal flux from the vent and the characteristic timescale of crust formation caused by surface cooling (Fink and Griffiths 1990). The three physics-based models are presented such that the downslope gravitational acceleration drives the flow, while either the Newtonian viscosity of the flow, the Yield Strength of the core (YS), or the Yield Strength of the growing crust (YSC) is the primary retarding factor in flow propagation. This study concluded that low 𝛹-value flows (low flux, low temperature, extensive crust formation) are better captured by the YSC model. And although the Newtonian model did not perfectly capture the behavior of any experimental flows in this study, high 𝛹-value flows (high flux, high temperature, little crust formation) that formed levees exhibited the most Newtonian behavior.

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Date Created
  • 2020-05

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Tecolote Cinder Cone Ballistics: Volcanic Bomb Formation and Dynamics

Description

Cinder cones are common volcanic structures that occur in fields, and on the flanks of shield volcanoes, stratovolcanoes, and calderas. Because they are common structures, they have a significant possibility

Cinder cones are common volcanic structures that occur in fields, and on the flanks of shield volcanoes, stratovolcanoes, and calderas. Because they are common structures, they have a significant possibility of impacting humans and human environments. As such, there is a need to analyze cinder cones to get a better understanding of their eruptions and associated hazards. I will approach this analysis by focusing on volcanic bombs and ballistics, which are large clots of lava that are launched from the volcanic vent, follow ballistic trajectories, and can travel meters to a few kilometers from their source (e.g. Fagents and Wilson 1993; Waitt et al. 1995).
Tecolote Volcano in the Pinacate Volcanic Field in Mexico contains multiple vents within a horseshoe-shaped crater that have all produced various ejecta (Zawacki et al. 2019). The objectives of this research are to map ballistic distribution to understand the relationship between the source vent or vents and the bombs and ballistics that litter the region around Tecolote, and interpret the eruption conditions that ejected those bombs by using their distributions, morphologies, and fine-scale textures.
The findings of this work are that these bombs are apparently from the last stages of the eruption, succeeding the final lava flows. The interiors and exteriors of the bombs display different cooling rates which can are indicated by the fabric found within. Using this, certain characteristics of the bombs during eruption were extrapolated. The ‘cow pie’ bombs were determined to be the least viscous or contained a higher gas content at the time of eruption. Whereas the ribbon/rope bombs were determined to be the most viscous or contained a lesser gas content. Looking at the Southern Bomb Field site, it is dominated by large bombs that were during flight were molded into aerodynamic shapes. The Eastern Rim site is dominated by smaller bombs that appeared to be more liquid during the eruption. This difference in the two sites is a probable indication of at least two different eruptive events of different degrees of explosivity. Overall, aerodynamic bombs are more common and extend to greater distances from the presumed vent (up to 800 m), while very fluidal bombs are uncommon beyond 500 meters. Fluidal bombs (‘cow pie’, ‘ribbon’, ‘rope/spindle’) show a clear trend in decreasing size with distance from vent, whereas the size-distance trend is less dramatic for the aerodynamic bombs.

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Date Created
  • 2020-05

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THE BLUE MOUND CHERT INVESTIGATING A TOPOGRAPHIC ANOMALY IN SOUTHERN WISCONSIN

Description

Blue Mound State Park, located in the state of Wisconsin (USA), is host to a topographic anomaly known as Blue Mound. This mound is the western of the two mounds

Blue Mound State Park, located in the state of Wisconsin (USA), is host to a topographic anomaly known as Blue Mound. This mound is the western of the two mounds that make up the park, and it marks the highest elevation in southern Wisconsin. Unlike its eastern sibling, Blue Mound possesses an unusual chert cap that may have protected it from erosion, thus preserving its stratigraphic integrity. Although Blue Mound's unique chert armor was noted in 1927 by the Wisconsin Geological and Natural History Survey, no published work has satisfactorily explained its origin. As little was known about the formation of cherts until the mid-to-late 1900s, the Blue Mound cap was classified merely as a Silurian dolostone into which chert had somehow become integrated (Steidtmann). However, the published observations of the Blue Mound chert do not necessarily match with the classification granted by the Wisconsin Geological and Natural History Survey, nor were any convincing interpretations offered regarding the presence of the chert. Since 1927, significant progress in the field of sedimentology has been achieved. There now exists knowledge that may fill the gaps between observation and interpretation in the Blue Mound survey. The observations in the 1927 bulletin correspond with modern notions of a paleokarst chert breccia, which forms a chert rubble or residuum. A chert breccia is formed when existing clasts, or pieces, of chert become cemented together by further chert deposition (Kolodny, Chaussidon and Katz). This can form large boulders of chert rubble that resist erosion. Accumulation of chert rubble has been documented to form along old weathering surfaces as an insoluble residue in environments similar to Blue Mound (Kolodny, Chaussidon and Katz). The purpose of this investigation was to verify the observations within the 1927 survey of the Blue Mound chert, and determine through field observations and sample study if the Blue Mound chert fits the model of a paleokarst chert breccia.

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Date Created
  • 2013-05

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Landslide Blocks within Miocene Sedimentary Rocks of Papago Park

Description

Papago Park in Tempe, Arizona (USA) is host to several buttes composed of landslide breccias. The focus of this thesis is a butte called “Contact Hill,” which is composed of

Papago Park in Tempe, Arizona (USA) is host to several buttes composed of landslide breccias. The focus of this thesis is a butte called “Contact Hill,” which is composed of metarhyolitic debris flows, granitic debris flows, and Barnes Butte Breccia. The Barnes Butte Breccia can be broken down into several different compositional categories that can be dated based on their relative ages. The depositional timeline of these rocks is explored through their mineral and physical properties. The rhyolitic debris flow is massively bedded and dips at 26° to the southeast. The granitic debris flow is not bedded and exhibits a mixture of granite clasts of different grain sizes. In thin section analysis, five mineral types were identified: opaque inclusions, white quartz, anhedral and subhedral biotite, yellow stained K-feldspar, and gray plagioclase. It is hypothesized that regional stretching and compression of the crust, accompanied with magmatism, helped bring the metarhyolite and granite to the surface. Domino-like fault blocks caused large brecciation, and collapse of a nearby quartzite and granite mountain helped create the Barnes Butte Breccia: a combination of quartzite, metarhyolite, and granite clasts. Evidence of Papago Park’s ancient terrestrial history is seen in metarhyolite clasts containing sand grains. These geologic events, in addition to erosion, are responsible for Papago Park’s unique appearance today.

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Date Created
  • 2021-05

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The Effect of the IRIS REU Program on Student Retention in Geoscience

Description

For the geoscience community to continue to grow, students need to be attracted to the field. Here we examine the Incorporated Research Institutions for Seismology (IRIS) Research Experience for Undergraduates

For the geoscience community to continue to grow, students need to be attracted to the field. Here we examine the Incorporated Research Institutions for Seismology (IRIS) Research Experience for Undergraduates (REU) program to understand how the participants' experiences' affects their interest in geoscience and educational and career goals. Eleven interns over two years (2013-2014) were interviewed prior to the start of their internship, after their internship, and after presenting their research at the American Geophysical Union annual meeting. This internship program is of particular interest because many of the interns come into the REU with non-geoscience or geophysics backgrounds (e.g., physics, mathematics, chemistry, engineering). Both a priori and emergent codes are used to convert interview transcripts into quantitative data, which is analyzed alongside demographic information to understand how the REU influences their decisions. Increases in self-efficacy and exposure to multiple facets of geoscience research are expressed as primary factors that help shape their future educational and career goals. Other factors such as networking opportunities and connections during the REU also can play a role in their decision. Overall, REU participants who identified as geosciences majors solidified their decisions to pursue a career in geosciences, while participants who identified as non-geosciences majors were inclined to change majors, pursue geosciences in graduate school, or explore other job opportunities in the geosciences.

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Date Created
  • 2016-12

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Using InSAR to Investigate Injection-Induced Deformation and Seismicity in Timpson, Texas

Description

Hydraulic fracturing, or fracking, has become a common practice in United States oil fields for enhancing their productivity. Among the concerns regarding fracking, however, is the possibility that it could

Hydraulic fracturing, or fracking, has become a common practice in United States oil fields for enhancing their productivity. Among the concerns regarding fracking, however, is the possibility that it could trigger shallow earthquakes. The brine that results from fracking is injected into the subsurface for disposal. This brine causes a pore pressure gradient that is commonly believed to trigger failure along critically stressed subsurface faults. In Timpson, a small city in eastern Texas, earthquakes have become much more common since two injection wells were installed in 2007. 16 events of M_W > 2 have been detected since 2008 and are believed to be associated with failure along a subsurface fault. Applying interferometric synthetic aperture radar, we analyzed 3 sets of SAR images from the Advanced Land Observing Satellite (ALOS) from May 2007 to December 2010. Using these data sets, XX interferograms were generated. From these interferograms, it was possible to determine the spatial and temporal evolution of the crustal deformation in the line-of-sight of the satellite. The results show strong evidence of uplift in the region adjacent to the injection wells. While previous studies have established a strong connection between fluid injection and increased seismicity, this is to our knowledge the first observed case of crustal deformation that has been observed as a result of hydraulic fracturing fluid disposal.

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Date Created
  • 2014-05