Matching Items (2)
Description
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 have integrated to the Pacific Ocean. In northern Chile, rates of landscape evolution are some of the slowest on Earth due to the region's hyperarid climate. While the magnitude of upland erosion driven by extensional tectonics is largely recorded in the stratigraphy of the structural basins, the landscape's response to post-tectonic forcings is unknown.
I employ the full suite of modern geomorphic tools provided by terrestrial cosmogenic nuclides - surface exposure dating, conventional burial dating, isochron burial dating, quantifying millennial-scale upland erosion rates using detrital TCN, quantifying paleo-erosion rates using multiple TCN such as Ne-21/Be-10 and Al-26l/Be-10, and assessing sediment recycling and complex exposure using multiple TCN - to quantify the rates of landscape evolution in southeastern Arizona and northern Chile during the Late Cenozoic. In Arizona, I also use modern remnants of the pre-incision landscape and digital terrain analyses to reconstruct the landscape, allowing the quantification of incision and erosion rates that supplement detrital TCN-derived erosion rates. A new chronology for key basin high stand remnants (Frye Mesa) and a flight of Gila River terraces in Safford basin provides a record of incision rates from the Pliocene through the Quaternary, and I assess how significantly regional incision is driving erosion rates. Paired nuclide analyses in the Atacama Desert of northern Chile reveal complex exposure histories resulting from several rounds of transport and burial by fluvial systems. These results support a growing understanding that geomorphic processes in the Atacama Desert are more active than previously thought despite the region's hyperarid climate.
I employ the full suite of modern geomorphic tools provided by terrestrial cosmogenic nuclides - surface exposure dating, conventional burial dating, isochron burial dating, quantifying millennial-scale upland erosion rates using detrital TCN, quantifying paleo-erosion rates using multiple TCN such as Ne-21/Be-10 and Al-26l/Be-10, and assessing sediment recycling and complex exposure using multiple TCN - to quantify the rates of landscape evolution in southeastern Arizona and northern Chile during the Late Cenozoic. In Arizona, I also use modern remnants of the pre-incision landscape and digital terrain analyses to reconstruct the landscape, allowing the quantification of incision and erosion rates that supplement detrital TCN-derived erosion rates. A new chronology for key basin high stand remnants (Frye Mesa) and a flight of Gila River terraces in Safford basin provides a record of incision rates from the Pliocene through the Quaternary, and I assess how significantly regional incision is driving erosion rates. Paired nuclide analyses in the Atacama Desert of northern Chile reveal complex exposure histories resulting from several rounds of transport and burial by fluvial systems. These results support a growing understanding that geomorphic processes in the Atacama Desert are more active than previously thought despite the region's hyperarid climate.
ContributorsJungers, Matthew Cross (Author) / Heimsath, Arjun M (Thesis advisor) / Whipple, Kelin (Committee member) / Arrowsmith, Ramon (Committee member) / Vivoni, Enrique (Committee member) / DeVecchio, Duane (Committee member) / Arizona State University (Publisher)
Created2014
Description
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 serves as a template for future regional analyses of TA data and similar datasets. The final event catalog produced for this study increased the total number of earthquakes documented in Arizona by more than 50% compared to the historical catalog, despite being generated from less than three years of continuous waveform data. I combined this new TA catalog with existing earthquake catalogs to construct a comprehensive historical earthquake catalog for Arizona. These results enabled the identification of several previously unidentified areas of seismic activity within the state, as well as two regions characterized by seismicity in the deeper (>20 km) crust. The catalog also includes 16 event clusters, 10 of which exhibited clear temporal clustering and swarm-like behavior. These swarms were distributed throughout all three physiographic provinces, suggesting that earthquake swarms occur regardless of tectonic or physiographic setting. I also conducted a case study for an earthquake swarm in June of 2007 near Theodore Roosevelt Lake, approximately 80 miles northeast of Phoenix. Families of events showed very similar character, suggesting a nearly identical source location and focal mechanism. We obtained focal mechanisms for the largest of these events, and found that they are consistent with normal faulting, expected in this area of the Arizona Transition Zone. Further, I observed no notable correlation between reservoir water level and seismicity. The occurrence of multiple historical earthquakes in the areas surrounding the reservoir indicates that this swarm was likely the result of tectonic strain release, and not reservoir induced seismicity.
ContributorsLockridge, Jeffrey Steven (Author) / Fouch, Matthew J (Thesis advisor) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen J. (Committee member) / Arizona State University (Publisher)
Created2011