Cataclysmic erasure of mountain topography and major unrealized seismic hazards in the northern Basin and Range

University Of Kentucky Research Foundation, Lexington KY

Investigators

Abstract

This multidisciplinary project will investigate the extent to which progression of volcanism associated with the Yellowstone hot spot has truncated high-relief mountain ranges of the northern Rocky Mountains. As the hotspot has progressed northeastward through time, it has “erased” preexisting tectonic topography at rates significantly faster than natural erosional processes and by doing so, fundamentally reshape the topographic, fluvial, and climatic evolution of an entire region. The research will focus on the present-day southern Teton Range in northwest Wyoming, which is hypothesized to have extended farther south and was subsequently removed by the post-2 million-year eruptions of the Yellowstone caldera. In addition, the project will address the link between nascent faults and seismic activity that have formed during the actively migrating Yellowstone hotspot; thus, this project has the potential to greatly enhance the understanding of potential seismic hazards associated with the Teton fault. The Tetons and Yellowstone attract >7,000,000 visitors annually and by linking these two seemingly unrelated geologic features the investigators can provide the public with a new way of understanding one of the most unique and diverse natural landscapes in the world. The results of this research will be incorporated into new public awareness campaigns and informal public education, including visitor center exhibits, public talks, and development of a website and a series of mini-documentaries. The project will also advance desired societal outcomes by supporting advanced field and laboratory training for two doctoral students, research training and collaboration experience for at multiple undergraduate students, with an emphasis on including underrepresented minorities in STEM education. In the final year of the project, all results will be disseminated at a workshop that includes all regional stakeholders, including Teton County and Jackson city representatives, university researchers, National Park Service, U.S. Geological Survey, and the U.S. Bureau of Reclamation. Traditionally, the active Teton normal fault is interpreted to follow the topographic break between the range front and the adjacent Jackson Valley and this has been confirmed by recent LiDAR studies. The commonly held belief is that the fault must always be present near the topographic break at the range front, and thus slip on the northern extent of the fault is often interpreted to diminish as the topography recedes in the northern Teton Range. However; two key datasets indicate that the relict topography preserved today may not reflect the northern extent of the Teton fault, including: new data documenting the long-term fault slip and range uplift history suggests that the Teton fault may have originally extended much farther north than previously thought; and, recently acquired LiDAR imagery reveals multiple candidate fault scarps that may represent the active northern extent of the Teton fault. To test the hypothesis that the Teton Range originally extended much farther north, the investigators are using thermochronology combined with inverse thermal history and thermal-kinematic modeling to further refine the slip history along the main segment of the Teton fault and determine the possible lengths of a northern Teton fault projection. Second, the researchers will use a grid of high-resolution seismic reflection data acquired from Jackson Lake to define how the main Teton fault links with disparate fault scarps that display similar modern offset. This survey will also allow the investigators to develop footwall and hanging wall coring targets, the products of which will be used with radiocarbon geochronology to develop an episodic fault slip history that can be compared with previous trenching studies of other fault segments both south and north of the proposed study area. Linking the timing of slip events along the main Teton fault, the lake fault segments, and the northern segments will allow the researchers to determine whether or not all of these segments are seismogenically linked. The current catalog of fault slip events is based solely on trenching studies, but it is likely that the fine-grained lake sediments preserve a more complete seismogenic record, thus providing the possibility for identifying slip events that have not been previously identified. Finally, the investigators will acquire multiple onshore fault-normal seismic reflection lines to demonstrate a northern extension of the Teton fault. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.