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- Genre: Masters Thesis
Description
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 along-fault displacement patterns? (2) Do orographic climate patterns induced by rift topography affect rift-flank uplift or morphology? (3) How do uplift patterns along rift flanks vary over geologic timescales? In Malawi, 100-km-long border faults of alternating polarity bound half-graben sedimentary basins containing up to 4km of basin fill and water depths up to 700m. Orographically driven precipitation produces climatic gradients along footwall escarpments resulting in mean annual rainfall that varies spatially from 800 to 2500 mm. Temporal oscillations in climate have also resulted in lake lowstands 500 m below the modern shoreline. I examine bedrock river profiles crossing the Livingstone and Usisya Border Faults in northern Malawi using the channel steepness index (Ksn) to assess importance of these conditions on rift flank evolution. River profiles reveal a consistent transient pattern that likely preserves a temporal record of slip and erosion along the entire border fault system. These profiles and other topographic observations, along with known modern and paleoenvironmental conditions, can be used to interpret a complete history of rift flank development from the onset of rifting to present. I interpret the morphology of the upland landscape to preserve the onset of extensional faulting across a relict erosion surface. The linkages of individual faults and acceleration of slip during the development of a continuous border fault is suggested by an analysis of knickpoint elevations and Ksn. Finally, these results suggest that the modern observed climate gradient only began to significantly affect denudation patterns once a high relief rift flank was established.
ContributorsRobinson, Scott M (Author) / Heimsath, Arjun M (Thesis advisor) / Whipple, Kelin X (Thesis advisor) / Arrowsmith, Ramon J (Committee member) / Arizona State University (Publisher)
Created2014
Description
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 Byrd Glacier fault, to measure the timing of exhumation, and to gain a better overall understanding of the structural architecture of the TAM. Apatites and zircons separated from rock samples collected from various locations north and south of Byrd Glacier were dated using single-crystal (U- Th)/He analysis. Similar cooling histories were revealed with comparable exhumation rates of 0.03 ± 0.003 and 0.04 ± 0.03 mm/yr north and south of Byrd Glacier from apatite data and somewhat similar rates of 0.06 ± 0.008 and 0.04 ± 0.01 mm/yr north and south of Byrd Glacier from zircon data. Age vs. elevation regressions indicate a vertical offset of 1379 ± 159 m and 4000 ± 3466 m from apatite and zircon data. To assess differential movement, the Kukri Peneplain (a regional unconformity) was utilized as a datum. On-site photographs, Landsat imagery, and Aster Global DEM data were combined to map Kukri Peneplain elevation points north and south of Byrd Glacier. The difference in elevation of the peneplain as projected across Byrd Glacier shows an offset of 1122 ± 4.7 m. This study suggests a model of relatively uniform exhumation followed by fault displacement that uplifted the south side of Byrd Glacier relative to the north side. Combining apatite and zircon (U-Th)/He analysis along with remote geomorphologic analysis has provided an understanding of the differential movement and exhumation history of crustal blocks in the Byrd Glacier region. The results complement thermochronologic and geomorphologic studies elsewhere within the TAM providing more information and a new approach.
ContributorsFoley, Daniel Joseph (Author) / Stump, Edmund (Thesis advisor) / Whipple, Kelin X (Committee member) / Hodges, Kip (Committee member) / Arizona State University (Publisher)
Created2011
Description
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 assess the geomorphic response of along-strike variations in tectonic deformation. Wheeler Ridge is an asymmetric east-propagating anticline (10 km axis, 330 m topographic relief) above a north-vergent blind thrust fault at the northern front of the Transverse Ranges, Southern San Joaquin Valley, California. Wheeler Ridge is part of a thrust system initiating in the late Miocene and is known to have significant historic earthquakes occur (e.g., 1952 Mw 7.3 Kern County earthquake). Analysis of the lidar data enables quantitative assessment of four key geomorphic relationships that may be indicative of relative variation in local rock uplift. First, I observe remnant landforms in the youngest, easternmost section of Wheeler Ridge that indicate the erosional history of older deposits to the west. Second, I examine the central portion of Wheeler Ridge where drainages and hillslopes are closely tied to uplift rates. Third, I observe the major wind gap within which a series of knickpoints are aligned at a similar elevation and tie into the local depositional and uplift history. Finally, I survey the western section and specifically, the fold backlimb where high-resolution topography and field mapping indicate long ridgelines that may preserve the uplifted and tilted alluvial fan morphology. I address changing landforms along the fold axis to test whether backlimb interfluves are paleosurfaces or the result of post-tectonic erosional hillslope processes. This work will be paired with future geochronology to update the ages of uplifted alluvial fan deposits and better constrain the timing of along-strike uplift of Wheeler Ridge.
ContributorsKleber, Emily (Author) / Arrowsmith, Ramon (Thesis advisor) / DeVecchio, Duane E (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2015
Description
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 found at a variety of scales in close proximity to Martian volcanoes. They can indicate flexure of the lithosphere in response to the load of the volcano or gravitation spreading of the edifice. Using Context Camera (CTX), High Resolution Imaging Science Experiment (HiRISE), Thermal Emission Imaging System (THEMIS), High Resolution Stereo Camera Digital Terrain Model (HRSC DTM) and Mars Orbiter Laser Altimeter (MOLA) data, I have identified and characterized the morphology and distribution of 60 flank vents and 84 arcuate graben on Olympus Mons. Based on the observed vent morphologies, I conclude that effusive eruptions have dominated on Olympus Mons in the Late Amazonian, with flank vents playing a limited role. The spatial distribution of flank vents suggests shallow source depths and radial dike propagation. Arcuate graben, not previously observed in lower resolution datasets, occur on the lower flanks of Olympus Mons and indicate a recent extensional state of stress. Based on spatial and superposition relationships, I have constructed a developmental sequence for the construction of Olympus Mons: 1) Construction of the shield via effusive lava flows.; 2) Formation of the near summit thrust faults (flank terraces); 3) Flank failure leading to scarp formation and aureole deposition; 4) Late Amazonian effusive resurfacing and formation of flank vents; 5) Subsidence of the caldera, waning volcanism and graben formation. This volcanotectonic evolution closely resembles that proposed on Ascraeus Mons. Extensional tectonism may continue to affect the lower flanks of Olympus Mons today.
ContributorsPeters, Sean I. (Author) / Christensen, Philip R. (Thesis advisor) / Clarke, Amanda B (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2015
Description
In the southwestern United States, water is a precious resource that influences landscapes and their respective ecosystems. Ephemeral lakes, known as playas, are drainage points for closed or endorheic basins and serve as important locations for plant productivity, biogeochemical processes, and groundwater recharge. In this study, I explore the hydrologic dynamics of eighteen (18) instrumented playas in the Jornada Basin of the Chihuahuan Desert with respect to the drivers of playa inundation and how their behaviors vary in space and time. To this end, I combine water level observations in playas with gauge-corrected radar precipitation estimates to determine hydrologic dynamics over the more than 6-year period of June 2016 to October 2022. Results indicate that all playa inundation events are associated with precipitation and that 76% of events occur during the warm season from April to September that is characterized by the North American monsoon. Mean annual runoff ratios in the playa catchments range from 0.01% to 9.28%. I observe precipitation depth and 60-minute intensity thresholds for playa inundation ranging from 16.1 to 71.3 mm and 8.8 to 40.5 mm/hr, respectively. Although playa inundation is typically caused by high rainfall amounts and intensities, other factors such as antecedent wetness conditions and the spatial variability of rainfall within the playa catchment also play a role. The magnitudes, durations, and occurrence of inundation events vary among playas, but their responses to precipitation generally agree with groupings determined based on their geological origin. Logistic and linear regressions across all playas reveal the relative importance of catchment variables, such as area, sand fraction, slope, and the percentage of bare ground. It is shown that larger catchment areas are strongly associated with a lower likelihood of inundation and higher precipitation thresholds for inundation. An analysis of precipitation data from 1916 to 2015 leads to the estimation of historical playa inundation and suggests that an increase has occurred in the frequency of large rainfall events that may be associated with increasing frequency of playa inundation. This study highlights the complex nature of playa inundation in the Jornada Basin, which can change over time in an evolving climate and landscape.
ContributorsKimsal, Charles Robert (Author) / Vivoni, Enrique R (Thesis advisor) / Whipple, Kelin X (Committee member) / Li, Jiwei (Committee member) / Arizona State University (Publisher)
Created2023
Description
Western Utopia Planitia, located in the northern plains of Mars, is home to a myriad of possible periglacial landforms. One of these is scalloped depressions, defined primarily by their oval-shape and north-south asymmetry, including both pole-facing “steps” and an equator-facing slope. Scalloped depressions are thought to have formed through sublimation of ground ice in the Late Amazonian, consistent with the hypothesis that Mars is presently in an interglacial period marked by the poleward retreat of mid-latitudinal ice. The directional growth of scalloped depressions was mapped within the region and present a correlation between topography and scalloped depression development. It was determined that topography appears to play a role in scallop development, as noted by the most-densely scalloped region residing among a lower spatial density of craters previously mapped by Harrison et al. (2019). Within this region, scallops were also observed to be absent atop crater ejecta, but present atop crater ejecta in other regions of the study area. A large majority of scallops maintain a north-south asymmetry and observed changes in geomorphology that range from predominantly smoother terrain in the northern latitudes to very hummocky terrain dominated by possible periglacial features as latitude decreases. Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) images were primarily used, with a few images coming from the MRO High Resolution Imaging Science Experiment (HiRISE). Observations are consistent with previous studies showing the overall density of scalloped depressions decreases with increasing latitude, with the majority exhibiting steps facing in a poleward direction. The majority of scallops observed to have steps in a non-poleward direction occur within in ice-rich regions mapped by Stuurman et al. (2016). It was ultimately concluded that scallops demonstrating poleward-facing steps likely formed during periods of high obliquity on Mars in the Late Amazonian, while scallops within the ice-rich regions potentially formed at a greater range of obliquities.
ContributorsTognetti, Laurence (Author) / Bell Iii, James F (Thesis advisor) / Robinson, Mark S (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2019
Description
The American Southwest is one of the most rapidly growing regions of the United States, as are similar arid regions globally. Across these landscapes where surface water is intermittent and variable, groundwater aquifers recharged by surface waters become a keystone resource for communities and are consumed at rates disproportional to recharge. In this study, I focus on the controls of runoff generation and connectivity at both hillslope and watershed scales along a piedmont slope. I also investigate the effects of plant phenology on hydrologic connectivity and runoff response at the hillslope scale during the summer monsoon season. To carry out this work, I combine existing hydrologic instrumentation, a new set of runoff plots with high-resolution monitoring, near-field remote sensing techniques, and historical datasets. Key analyses show that a rainfall intensity (I30) of 10 mm/hr yields runoff production at three scales (8, 12700, and 46700 m2). Rainfall, runoff, and soil moisture observations indicate a Hortonian (infiltration-excess) dominated system with little control imposed by antecedent wetness. Hydrologic connectivity analyses revealed that <15% of total rainfall events generate runoff at the hillslope scale. Of the hillslope events, only 20% of the runoff production leads to discharge at the outlet. Vegetation was observed to effect individual plot runoff response to rainfall. The results of this study show that 1) rainfall intensity is a large control on runoff production at all three scales (8, 12700, and 46700 m2), 2) proportions between bare and vegetated space effect runoff production at the hillslope scale, and 3) runoff connectivity decreases, and channel losses increase as you move downstream on an individual storm basis and across a 30-year historical record. These findings indicate that connectivity from the hillslope to outlet scale can be an evolving process over thehistorical record, reliant on both rainfall intensity, plant and bare soil mosaics, and available channel storage.
ContributorsKeller, Zachary Theodore (Author) / Vivoni, Enrique R (Thesis advisor) / Whipple, Kelin X (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2021