Brittney Thaxton, University of Utah
Physical Sciences
There are many undocumented shorelines seen in Utah. As many as 30+ shorelines have been identified along the edges of the basin throughout the state. The purpose of this study is to characterize undocumented shorelines and identify potential evidence for tsunamis that might have occurred in Lake Bonneville thousands of years ago in areas such as Little Mountain, Stansbury Island, and Promontory Point, Utah. Lake Bonneville existed 32-10K years ago and was influenced by the Wasatch fault which was active as early as the Miocene. Scarps of this age are common and range between 15-20 feet in height (Machette, Personius, Nelson, Schwartz, Lund 1991; Dinter, Pechman, 2004a and 2004b). Several faults beneath Lake Bonneville could have produced tsunamis. The more water that is displaced the greater the tsunami will become and leave a greater impact onshore (Dutykh and Dias 2009). The East Great Salt Lake fault cuts NS across Bear River Bay east of Promontory Range. This fault line is an excellent candidate for causing a tsunami during the Lake Bonneville highstand because it is beneath the Great Salt Lake meaning it would have uplifted the entire water column of Lake Bonneville and since it is also close to the Promontory Range, it is likely it would leave tsunamite evidence along the shore. The fault rupture interval is between 3,000 and 3,500 years meaning fault ruptures could produce a tsunami during the lake’s high stand. Tsunamite is the term used for deposits related to tsunamis. The tsunamite features found along the shorelines will be similar to sedimentary features such as normally graded sand, mudstone clasts, and other gravel deposits that are out of place with the known shorelines (Shanmugam 2006). This is a unique opportunity to discover ancient tsunami evidence in Utah, a topic that has yet to be pursued.