Abstract: The Yukon Geological Survey and Kluane First Nation intend to drill a temperature gradient well near Burwash Landing, YT, to evaluate the geothermal energy potential of the area. The preferred drill site is located immediately southwest of the Eastern Denali fault (EDF), which has ruptured multiple times in the Holocene. The kinematics and recent activity of the fault are important factors to consider when developing a geothermal resource, for two purposes: 1. identifying zones of enhanced permeability due to local fault geometry and 2. assessing the seismic hazard of drilling and developing a geothermal system along an active fault. Here, we present new lidar data collected from a drone platform, which enabled the production of 30 cm spatial resolution bare-earth Digital Terrain Models (DTMs) over several segments of the EDF. These products offer a considerable increase in both spatial resolution and canopy penetration compared to existing spaceborne and airborne photogrammetric Digital Surface Models (DSMs) and DTMs of the area. We use hillshades to map segments of the EDF surface trace in detail, and we make preliminary interpretations about the structure and kinematics of the fault. Offset stream channels and hill slopes that cross the fault at high angles indicate dextral offsets ranging between 5 and 75 m. Vertical separation ranges between 0 and 20 m, varying between northeast and southwest-side up. We confirm previous interpretations that the geothermal drill site is located at a minor releasing bend in the fault. Previous fault maps based on ArcticDEM data showed multiple fault splays parallel to the EDF at the geothermal drill site, whereas the lidar data indicate strain is concentrated to a singular fault plane in this area. The EDF is characterized by a series of sediment mounds that we interpret to be positive flower structures. The higher spatial resolution achieved by the drone reveals possible compressional structures (fault tips or folds) consistent with dextral transpression on the surface of these mounds. We recommend additional drone lidar acquisition, field studies, geophysical analysis, and kinematic modeling to be carried out over the coming year.

Authors: Finley, T., Salomon, G., Stephen, R., Nissen, E., Cassidy, J. and Menounos, B.

NTS Mapsheet(s): 115G01, 115G02, 115G05, 115G06, 115G07

Citation: Finley, T., Salomon, G., Stephen, R., Nissen, E., Cassidy, J. and Menounos, B., 2022. Preliminary results and structural interpretations from drone lidar surveys over the Eastern Denali fault, Yukon. In: Yukon Exploration and Geology 2021, K.E. MacFarlane (ed.), Yukon Geological Survey, p. 83–105.

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