DISCERNING POSSIBLE FAULT REACTIVATION OF POST LARAMIDE DEFORMATION AS WELL AS WARPING WITHIN QUATERNARY UNITS OF THE WIND RIVER BASIN, CENTRAL WYOMING

There is a fault that has been identified that clearly cuts through Tertiary bedrock (Twr) as well Quaternary gravels (Qg) just west of the Boysen Reservoir in the Wind River Basin. The deformation of the bedrock in the basin is post Laramide in age. However, since the fault trace can be seen through Quaternary gravel formations, it is suspected that the fault has become reactivated into a reverse sense of motion. The fault trends northwest toward the direction of the Boysen Dam, a structure responsible for holding the waters of the Boysen Reservoir with a storage capacity of just over 800,000 acre-feet. Dangers include structural damage of the dam, power loss to a local power plant, damage to structures and land in the downstream direction, and loss of a major water resource.

To begin, satellite imagery was used to identify additional faulted areas that coincide with the already identified main fault structure for field investigation. Surveying of the Quaternary gravel surfaces was done using Real Time Kinematic GPS with small UAS equipment at the field site. To confirm the reactivation of this fault, mesoscale structural measurements were taken in the Wind River Formation to get an idea of the sense of motion as well as testing to see if there is any warping of the bedrock in the area. Specific locations of Bird’s Eye Creek in the area have been investigated for possible past stream diversion due to tectonism. This could help explain reactivation of the fault. To help date the timing of this reactivation, a combination of weathering penetration through Schmidt hammer analysis and relative age relationships between the many gravel surfaces in the area were used.

Satellite imagery and structural data has identified additional faulted/folded areas that can be linked to the main fault structure and are clearly late Cenozoic in age. Schmidt hammer testing has been conducted at the site and analysis of the data is underway to get a relative sense of age of these events. With the data collected, my goal is to show reactivation of tectonic structures and warping of Quaternary surfaces within the Bird’s Eye Creek area.