USING GROUND-BASED TERRESTRIAL LASER SCANNING TO MODEL ANTECEDENT TOPOGRAPHY: CORAL PINK SAND DUNES, KANE COUNTY, UTAH

The Coral Pink Sand Dunes (CPSD) comprise one of the largest active dune fields in the Great Basin–Colorado Plateau Transition Zone. The dune field is bisected by the Sevier Normal Fault, which also forms the eastern boundary of the lower dune field (LDF). Dunes are self-organizing systems that should approach system state uniformity over time but, like many dune fields, the CPSD do not show this uniformity. Recent studies of dune fields have shown that in addition to boundary conditions such as sediment supply and wind regime, antecedent topography may also be a factor in explaining the bedform complexity observed in dune fields. Geomorphic evidence in the CPSD suggests that underlying bedrock is topographically lower in the center of the LDF than along its margins, and several antithetic faults paralleling the Sevier have been mapped within a kilometer north of the dunes. We hypothesize that the antecedent topography at CPSD includes a buried graben structure, bounded by the Sevier to the east and an unmapped antithetic fault or faults, and that this structural control factors into antecedent boundary conditions that subsequently influence dune patterning. In order to estimate the trend surface of underlying topography and identify locations for investigation with other geophysical methods, high resolution elevation data were collected using a Riegl Terrestrial Laser Scanner (TLS) for a ~5 km² area containing the LDF. The point cloud from the TLS data was converted to a 1-meter resolution DEM, and ArcGIS was used to identify the points of lowest elevation in the lee of the dunes. The resulting topographic trend suggests several potential fault scarps or bedrock step structures that will be further imaged and verified using ground penetrating radar and physical sampling techniques.