Paper No. 34-7
Presentation Time: 10:30 AM
ASSESSING TECTONIC TILT OF THE TETON RANGE, WYOMING AND IDAHO, USING STREAM TOPOGRAPHIC ANALYSIS
Topographic indices for quantifying tectonic tilt are used to determine the extent and cause of possible range tilting of the Teton Mountain Range, WY and ID. The Teton Range is a young, asymmetric range on the eastern edge of the Basin and Range and the southern edge of the thermally uplifted Yellowstone region. The thermal uplift, attributed to the Yellowstone hot spot, has caused regional tilt north of the Yellowstone area, and it may also cause regional tilt south of Yellowstone. The Teton Range is ideally situated to test this hypothesis. To determine the magnitude and direction of possible tilt we analyzed the transverse topographic symmetry (TTS) in 25 major basins within the Teton Range (13 on the western side and 12 on the east). The basins and their major streams were identified using ArcGIS basin and stream order algorithms to 10 m USGS Digital Elevation Models (DEMs). The algorithms defined the basins based on drainage divides; the stream analysis defined water flow through the basins. The TTS equals Ds/Dm where Ds is the distance from the midpoint of the basin to the midpoint of the stream meander and Dm is the distance from the ridge to the basin midpoint. Dm was determined by drawing transects, with equal elevation start and end points, from ridge to ridge. The TTS is evaluated for each transect and a vector is used to visualize the magnitude and direction of TTS for each transect. TTS was determined at approximately 100 m intervals in the primary E-W trending basins. If tilting of a basin has occurred, the stream will show a general pattern of down-tilt migration. Thermal uplift of the Yellowstone hotspot, if it influences tilt of the Tetons, will cause a general north-south, down-tilt trend. Understanding tectonic tilt in the Teton Range and evaluating the influence of the Yellowstone hotspot on it will help determine, temporally and spatially, past interactions between passage of the hotspot and Basin and Range faulting.