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- All Subjects: tectonics
- All Subjects: collision
- Creators: Whipple, Kelin
Description
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 complexity to the study of timing of collision by offsetting the Indus and Yarlung sutures. Recent work has used the complexities introduced by the Karakoram Fault to suggest that the more northerly Shyok suture, not the Indus suture, represents the India-Eurasia collision zone. Estimates for timing of the India-Eurasia collision fall into one of three groups: 40-34 Ma, 55-50 Ma, and 66-60 Ma. Attempts to reconcile these models have thus far been unsuccessful. In order to provide additional data that might further clarify the timing and location of collision, studies have been performed along the Shyok suture in India and along the Yarlung suture in Tibet at Sangsang. A study along the Shyok suture argues that the suture formed between 92-85 Ma. This timing precludes an interpretation that the Shyok suture marks the location of the India-Eurasia collision. A second study demonstrates the utility of two new geochronometers, (U-Th)/Pb joaquinite and 40Ar/39Ar neptunite, that play an important role in unraveling the tectonic history of the Yarlung suture. A third study is an investigation of the structure and geochronology of the Sangsang ophiolite complex. Here, multiple (U-Th)/Pb and 40Ar/39Ar systems record magmatism and metamorphism spanning ca. 125-52 Ma. By tying these chronometers to tectonic process, a history is reconstructed of the southern margin of Tibet that includes Early Cretaceous to Late Cretaceous forearc rifting associated with mid ocean ridge subduction, Paleocene accretionary wedge uplift and erosion, and finally Eocene metasomatism and collision.
ContributorsBorneman, Nathaniel (Author) / Hodges, Kip (Thesis advisor) / Reynolds, Stephen (Committee member) / Whipple, Kelin (Committee member) / Sharp, Thomas (Committee member) / Tyburczy, James (Committee member) / Arizona State University (Publisher)
Created2016
Description
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 and collision affects deformation in this part of the overriding plate. The majority of the upper plate deformation studies have been focused on the deformation in the main thrusts of the fore-arc region. Study of deformation within volcanic arc is limited despite the associated earthquake hazards. In this study, I use maps of active upper-plate structures, earthquake moment tensor data and stress orientation deduced from volcano morphology analysis to characterize the strain field of Java arc. In addition, I use sandbox analog modeling to evaluate the mechanical factors that may be important in controlling deformation. My field- and remotely-based mapping of active faults and folds, supplemented by results from my paleoseismic studies and physical models of the system, suggest that Java’s deformation is distributed over broad areas along small-scale structures. Java is segmented into three main zones based on their distinctive structural patterns and stress orientation. East Java is characterized by NW-SE normal and strike-slip faults, Central Java has E-W folds and thrust faults, and NE-SW strike-slip faults dominate West Java. The sandbox analog models indicate that the strain in response to collision is partitioned into thrusting and strike-slip faulting, with the dominance of margin-normal thrust faulting. My models test the effects of convergence obliquity, geometry, preexisting weaknesses, asperities, and lateral strength contrast. The result suggest that slight variations in convergence obliquity do not affect the deformation pattern significantly, while the margin shape, lateral strength contrast, and perturbation of deformation from asperities each have a greater impact on deformation.
ContributorsMarliyani, Gayatri Indah (Author) / Arrowsmith, J Ramon (Thesis advisor) / Clarke, Amanda B (Committee member) / Hartnett, Hilairy (Committee member) / Whipple, Kelin (Committee member) / Garnero, Edward (Committee member) / Arizona State University (Publisher)
Created2016
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
The South Tibetan Detachment System (STDS) marks a major decoupling horizon in the Himalaya, separating the highly metamorphosed infrastructure in the footwall from the weakly to unmetamorphosed superstructure in the hanging wall. The STDS stretches the entire range and is likely one of the most significant deformational features of the orogen, but its spatial and temporal evolution remain relatively unconstrained. As its name suggests, the STDS is a system of faults which occur at slightly different structural levels and are often diachronous. Detailed studies on the different strands are needed to understand the slip history of the system as a whole, which in turn will improve understanding of Himalayan orogenesis, thus informing tectonic models for continental orogenesis in general. I focus on some of the best exposed strands of the STDS which are located in the Annapurna region of Nepal. Outcrops within the shear zones of basal structures in the Kali Gandaki and Marsyandi valleys – the Annapurna and Chame detachments – contain leucogranites that are variably deformed via ductile slip on the detachments. I used U/Pb zircon and Th/Pb monazite geochronology to constrain emplacement ages of these leucogranites, which suggest ductile slip ceased prior to 14.95 ± 0.78 Ma and 16.0 ± 1.1 Ma on the Annapurna and Chame detachments respectively. 40Ar/ 39Ar muscovite and biotite, (U-Th)/He zircon and apatite thermochronology data and resulting thermal-kinematic models for samples I collected in the shear zones and footwalls of these detachments suggest further slip was ongoing on both detachments until ca. 12 Ma, although the majority of slip on the Chame detachment likely ceased by ca. 15-14 Ma. I also collected samples in the footwall of a structurally higher detachment in the Marsyandi and the resulting cooling ages and thermal-kinematic models suggest slip was contemporaneous with that on the lower Chame detachment. The new constraints on N-S extension on the STDS in the Annapurna region presented in this dissertation call into question the popular idea of a geodynamic change from N-S to E-W extension in the central Himalaya during the early Miocene, and emphasize the importance of the STDS as a major decoupling horizon.
ContributorsPye, Alexandra Eleanor (Author) / Hodges, Kip (Thesis advisor) / Whipple, Kelin (Committee member) / Barboni, Melanie (Committee member) / van Soest, Matthijs (Committee member) / McDonald, Christopher (Committee member) / Arizona State University (Publisher)
Created2022
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 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.
ContributorsApel, Emily Virginia (Author) / Heimsath, Arjun (Thesis director) / Arrowsmith, Ramon (Committee member) / Whipple, Kelin (Committee member) / School of Molecular Sciences (Contributor) / School of International Letters and Cultures (Contributor) / Barrett, The Honors College (Contributor)
Created2020-12