Quaternary, structural and engineering geology of the Aishihik River landslide, Cracker Creek area (NTS 115A/15), Yukon

The Aishihik River landslide is a prehistoric slope failure located on a southwest-facing slope of the Ruby Range along the Alaska Highway. The failed mass consists of gneissic material from the Kluane metamorphic assemblage. Shoreline sediments from glacial lake Champagne were deposited on top of the landslide debris, suggesting that the slope failure occurred after the ice retreat but before the Dezadeash valley drained. Three dominant discontinuity sets were recognized and correlated to the fracturing associated with the formation of the Ruby Range antiform. Rock engineering classification and laboratory tests suggest that the rock mass present in the headscarp of the failure is of lower quality than on its sidescarps. This rock mass degradation was attributed to two intersecting fault sets at the headscarp. Tension cracks and trenches are present on all sides of the slope failure. Exposed soil and disturbed vegetation observed in trenches suggest continued instability.