Dr. Deirdre Commins
Earth Institute Contact: Dr. Joerg Schaefer
Locations: United States of America
Canyon Lands, Utah
Understanding displacement accumulation rates and timing of fault events is crucial to constrain models of fault growth and seismic risk in active settings. Previous studies have attempted to unravel fault growth histories in a qualitative sense, but the lack of a suitable dating technique for natural fault systems has limited the models' ability to predict rates and variations in rate, of displacement accumulation during development of a fault array. This work unites the traditional disciplines of structural geology, geomorphology and geochemistry in a quantitative analysis of extensional fault array evolution and drainage response to deformation. In particular, the study involves detailed mapping of fault systems and associated drainages, in tandem with Surface Exposure Dating using in-situ cosmogenic nuclides, to determine chronology and rates of fault growth during the complete cycle of fault growth from initial propagation to physical linkage. The study area is located in the Canyonlands Graben of southeastern Utah, where extensional faulting has occurred in the last 0.5 m.y. and is ongoing. It is one of the finest areas for this type of investigation, as the faults are exceptionally well exposed in a variety of fault interaction orientations, drainage responses are readily observed, and the exposed lithology and time scale is very appropriate for Surface Exposure Dating. The research involves careful physical mapping on aerial photographs and a 5-meter Digital Elevation Model, followed by more detailed field mapping of fault linkage zones and associated deformed drainage systems. Combined with an extensive Surface Exposure Dating study using in-situ Berylium-10, Aluminum-26 and Carbon-14 extracted from quartz-rich bedrock samples along stream beds and fault scarps, this approach yields unique quantitative information about the timing and rates of faulting. In addition, fluvial deformation will be correlated to specific events of displacement accumulation and will be used to evaluate the mechanisms and rates of fault-related knickpoint retreat through the landscape. The results of this research will provide, for the first time, a complete, quantitative reconstruction of fault growth rates through the entire cycle of lateral fault propagation, through interaction and linkage. This, in turn, will significantly improve the understanding of the fundamental processes underlying fault array evolution and thus increase the reliability of seismic risk assessments and sedimentary basin analysis. The research will also have important implications for understanding erosion and mass sediment removal through bedrock channel erosion, which is considered a governing force in the tectonic evolution of mountainous terrains.
The study area is located in the Canyonlands Graben of southeastern Utah, where extensional faulting has occurred in the last 0.5 m.y. and is ongoing. It is one of the finest areas for the type of investigation proposed as the faults are exceptionally well exposed in a variety of fault interaction orientations, drainage responses are readily observed, and the exposed lithology and time scale is ideal for cosmogenic analysis.
We will combine careful physical mapping on aerial photographs and a 5 m DEM, with detailed field mapping and an extensive SED study on bedrock samples along stream beds and fault scarps. This approach will determine the structural and geomorphic characteristics of the study sites in order to produce unique quantitative information about the timing and rates of faulting.
The proposed work is expected to provide valuable constraints on the timing and rates of fault growth, which will have important implications for understanding the fundamental processes underlying fault array evolution. This, in turn, will help to improve the reliability of seismic risk assessments and sedimentary basin analysis. The work will also have important implications for understanding erosion and mass sediment removal, which is considered a governing force in the tectonic evolution of mountainous terrains. Bedrock channel erosion is a rate-limiting process in these settings, effectively forming the threshold for topography downwearing through hillslope processes. We attempt to gain insights into modes and rates of bedrock channel incision that can be fed directly into models of landscape evolution.
Better understanding of fault processes has potential application to earthquake hazard evaluation, which is of societal benefit. The work promotes strong links between the traditionally disparate subjects of structural geology, process geomorphology and geochemistry. While providing sound scientific contribution to these areas, results will be broadly disseminated through publication in peer-reviewed journals and presentation at major scientific conferences, as well as colloquial seminars to a non-technical audience at National Park headquarters. The proposed work will feed directly into several educational programs at Columbia University’s Earth and Environmental science Curriculum including PhD and undergraduate programs, and the web-based introductory course “The Earth System”, which is available beyond Columbia University. The lead-PI is female.
Cross Cutting Themes:
Hazards and Risk
National Science Foundation