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- All Subjects: geomorphology
- Creators: Hodges, Kip
- Creators: Robinson, Mark S
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
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 a result of the formation of the basins, such as light plains. Using high-resolution images under consistent illumination conditions and topography from the Lunar Reconnaissance Orbiter Camera (LROC), a new global map of light plains is presented at an unprecedented scale, revealing critical details of lunar stratigraphy and providing insight into the erosive power of large impacts. This work demonstrates that large basins significantly alter the lunar surface out to at least 4 radii from the rim, two times farther than previously thought. Further, the effect of pre-existing topography on the degradation of impact craters is unclear, despite their use in the age dating of surfaces. Crater measurements made over large regions of consistent coverage using LROC images and slopes derived from LROC topography show that pre-existing topography affects crater abundances and absolute model ages for craters up to at least 4 km in diameter.
On Mars, small volcanic edifices can provide valuable insight into the evolution of the crust and interior, but a lack of superposed craters and heavy mantling by dust make them difficult to age date. On Earth, morphometry can be used to determine the ages of cinder cone volcanoes in the absence of dated samples. Comparisons of high-resolution topography from the Context Imager (CTX) and a two-dimensional nonlinear diffusion model show that the forms observed on Mars could have been created through Earth-like processes, and with future work, it may be possible to derive an age estimate for these features in the absence of superposed craters or samples.
On Mars, small volcanic edifices can provide valuable insight into the evolution of the crust and interior, but a lack of superposed craters and heavy mantling by dust make them difficult to age date. On Earth, morphometry can be used to determine the ages of cinder cone volcanoes in the absence of dated samples. Comparisons of high-resolution topography from the Context Imager (CTX) and a two-dimensional nonlinear diffusion model show that the forms observed on Mars could have been created through Earth-like processes, and with future work, it may be possible to derive an age estimate for these features in the absence of superposed craters or samples.
ContributorsMeyer, Heather (Author) / Robinson, Mark S (Thesis advisor) / Bell, Jim (Thesis advisor) / Denevi, Brett (Committee member) / Clarke, Amanda (Committee member) / Asphaug, Erik (Committee member) / Arizona State University (Publisher)
Created2018
Description
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 relationship between juvenile material proportion and deposit size. These findings indicate there is greater diversity among LPDs than previously understood, and that a simple vulcanian eruption model may only apply to the smallest deposits.
There is consensus that martian outflow channels were formed by catastrophic flooding events, yet many of these channels exhibit lava flow features issuing from the same source as the eroded channels, leading some authors to suggest that lava may have served as their sole agent of erosion. This debate is addressed in two studies that use Context Camera images for photogeologic analysis, geomorphic mapping, and cratering statistics: (1) A study of Mangala Valles showing that it underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian, consistent with alternating episodes of flooding and volcanism. (2) A study of Maja Valles finds that it is thinly draped in lava flows sourced from Lunae Planum to the west, rendering it analogous to the lava-coated Elysium outflow systems. However, the source of eroded channels in Maja Valles is not the source of the its lava flows, which instead issue from south Lunae Planum. The failure of these lava flows to generate any major channels along their path suggests that the channels of Maja Valles are not lava-eroded.
Finally, I describe a method of locating sharp edges in out-of-focus images for application to automated trajectory control systems that use images from fixed-focus cameras to determine proximity to a target.
There is consensus that martian outflow channels were formed by catastrophic flooding events, yet many of these channels exhibit lava flow features issuing from the same source as the eroded channels, leading some authors to suggest that lava may have served as their sole agent of erosion. This debate is addressed in two studies that use Context Camera images for photogeologic analysis, geomorphic mapping, and cratering statistics: (1) A study of Mangala Valles showing that it underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian, consistent with alternating episodes of flooding and volcanism. (2) A study of Maja Valles finds that it is thinly draped in lava flows sourced from Lunae Planum to the west, rendering it analogous to the lava-coated Elysium outflow systems. However, the source of eroded channels in Maja Valles is not the source of the its lava flows, which instead issue from south Lunae Planum. The failure of these lava flows to generate any major channels along their path suggests that the channels of Maja Valles are not lava-eroded.
Finally, I describe a method of locating sharp edges in out-of-focus images for application to automated trajectory control systems that use images from fixed-focus cameras to determine proximity to a target.
ContributorsKeske, Amber (Author) / Christensen, Philip R. (Thesis advisor) / Robinson, Mark S (Committee member) / Clarke, Amanda B (Committee member) / Whipple, Kelin X (Committee member) / Bell, James F. (Committee member) / Arizona State University (Publisher)
Created2018
Description
Mountain landscapes reflect competition between tectonic processes acting to build topography and erosive processes acting to wear it down. In temperate mountain landscapes, bedrock rivers are the primary erosional agent, setting both the pace of landscape evolution and form of the surrounding topography. Theory predicts that river steepness is sensitive to climatic, tectonic, and lithologic factors, which dictate the rates and mechanics of erosional processes. Thus, encoded into topography is an archive of information about forces driving landscape evolution. Decoding this archive, however, is fraught and climate presents a particularly challenging conundrum: despite decades of research describing theoretically how climate should affect topography, unambiguous natural examples from tectonically active landscapes where variations in climate demonstrably influence topography are elusive. In this dissertation, I first present a theoretical framework describing how the spatially varied nature of orographic rainfall patterns, which are ubiquitous features of mountain climates, complicate expectations about how climate should influence river steepness and erosion. I then apply some of these ideas to the northern-central Andes. By analyzing river profiles spanning more than 1500 km across Peru and Bolivia, I show that the regional orographic rainfall pattern this landscape experiences systematically influences fluvial erosional efficiency and thus topography. I also show how common simplifying assumptions built into conventional topographic analysis techniques may introduce biases that undermine detection of climatic signatures in landscapes where climate, tectonics, and lithology all covary – a common condition in mountain landscapes where these techniques are often used. I continue by coupling this analysis with published erosion rates and a new dataset of 25 cosmogenic 10Be catchment average erosion rates. Once the influence of climate is accounted for, functional relationships emerge among channel steepness, erosion rate, and lithology. I then use these functional relationships to produce a calibrated erosion rate map that spans over 300 km of the southern Peruvian Andes. These results demonstrate that accounting for the effects of climate significantly enhances the ability to decode channel steepness patterns. Along with this comes the potential to better understand rates and patterns of tectonic processes, and identify seismic hazards associated with tectonic activity using topography.
ContributorsLeonard, Joel Scott (Author) / Whipple, Kelin (Thesis advisor) / Arrowsmith, Ramon (Committee member) / Christensen, Philip (Committee member) / Forte, Adam (Committee member) / Heimsath, Arjun (Committee member) / Hodges, Kip (Committee member) / Arizona State University (Publisher)
Created2022
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
Rock traits (grain size, shape, orientation) are fundamental indicators of geologic processes including geomorphology and active tectonics. Fault zone evolution, fault slip rates, and earthquake timing are informed by examinations of discontinuities in the displacements of the Earth surface at fault scarps. Fault scarps indicate the structure of fault zones fans, relay ramps, and double faults, as well as the surface process response to the deformation and can thus indicate the activity of the fault zone and its potential hazard. “Rocky” fault scarps are unusual because they share characteristics of bedrock and alluvial fault scarps. The Volcanic Tablelands in Bishop, CA offer a natural laboratory with an array of rocky fault scarps. Machine learning mask-Region Convolutional Neural Network segments an orthophoto to identify individual particles along a specific rocky fault scarp. The resulting rock traits for thousands of particles along the scarp are used to develop conceptual models for rocky scarp geomorphology and evolution. In addition to rocky scarp classification, these tools may be useful in many sedimentary and volcanological applications for particle mapping and characterization.
ContributorsScott, Tyler (Author) / Arrowsmith, Ramon (Thesis advisor) / Das, Jnaneshwar (Committee member) / DeVecchio, Duane (Committee member) / Arizona State University (Publisher)
Created2020
Description
The tectonism, volcanism, and sedimentation along the East African Rift System (EARS) produced a series of rift basins with a rich paleoanthropological record, including a Late Miocene–present record of hominin evolution. To better understand the relationship between Earth system history and human evolution within the EARS, the Hominin Sites and Paleolakes Drilling Project (HSPDP) collected paleolake sediments near key paleoanthropological sites in Ethiopia and Kenya, compiling a multi-proxy, high-resolution geological and environmental record. As part of the HSPDP, I studied the detrital mineral record of the basins and evaluated tectonic and climatic controls on East African landscapes during the Plio-Pleistocene using samples from three of the drill sites, Chew Bahir: (CHB, ~620–present; Ethiopia), Northern Awash (NA, ~3.3–2.9 Ma; Ethiopia,), and West Turkana (WTK, ~1.9–1.4 Ma; Kenya). I employed laser ablation U/Pb and (U-Th)/He double dating (LADD) of detrital zircons, which yields paired U/Pb and (U-Th)/He dates, and (U-Th)/He dating of detrital apatites to evaluate sediment provenance and the cooling history of the source rocks. In addition, I used in situ 10Be cosmogenic radionuclide analyses to determine paleoerosion rates. Two chapters of this dissertation focus on results from the NA and WTK drill sites. Source units for the NA and WTK drill sites are largely Cenozoic volcanic rocks, and the detrital zircon record yields an extensive record of the timing of various phases of volcanism within the EARS. Exceptionally young zircon (U-Th)/He dates reflect partial resetting associated with late mafic volcanism and/or hydrothermal activity. Erosion rates are consistent and relatively low across the Plio-Pleistocene, despite significant tectonic and geomorphic shifts in the landscape. Two other chapters of this dissertation cover results from the CHB drill site. The Chew Bahir basin has significant exposures of Neoproterozoic and Early Paleozoic crystalline basement units, and the detrital zircon record yields one singular phase of volcanism in the EARS. The CHB erosion rates show an overall decreasing trend over time, consistent with an aridifying climate, and increased environmental variability after ~200 ka.
ContributorsZawacki, Emily Elizabeth (Author) / Arrowsmith, J Ramon (Thesis advisor) / Campisano, Christopher (Thesis advisor) / Heimsath, Arjun (Committee member) / Hodges, Kip (Committee member) / Whipple, Kelin (Committee member) / Arizona State University (Publisher)
Created2021