Geochronology of landslides in the Kluane Lake Region, Southwest Yukon

Landslides are dangerous, expensive, and ubiquitous hazards that affect people globally. The Kluane Lake region of southwest Yukon is prone to landsliding owing to its relatively high relief, seismic activity, and climate conditions conducive to slope failure. The purpose of this research is to determine the ages of rock slides in Kluane Lake region to contribute to a regional landslide frequency and help establish triggering mechanisms and causal conditions. Five rock slides (Sheep Mountain, Gladstone-1 and -2, Aishihik, and Generc) were dated using terrestrial cosmogenic nuclides, radiocarbon dating, and dendrochronology. The resulting ages were: Sheep Mountain ca., 2.0 cal kyr BP; Gladstone-1, 10.5 ± 0.3 cal kyr BP; Gladstone-2, 11.2 ± 0.3 cal kyr BP; Aishihik, ca. 5.7 ± 0.4 cal kyr BP; Generc, 1996-1997 CE. Regional paleoseismic records suggest Sheep Mountain may have been triggered by a seismic event 2.2 cal kyr BP. While seismicity may have triggered all five events, Gladstone-1 and -2 were potentially conditioned by glacial debuttressing following deglaciation around 11 kyr ago and possibly concomitant permafrost thaw. Aishihik may have been triggered by a paleoseismic event dated at 6.1 ± 0.1 cal kyr BP. Generc may have been conditioned by tectonic fracturing due to its proximity to the Denali Fault and ultimately failed due to weakened bedrock. The new chronological results will provide an important foundation for future landslide hazard assessment studies related to seismicity and climate change in a region undergoing rapid development with expensive infrastructure and rapid landscape change.