Late Glacial and Holocene Environmental Change Inferred from Sedimentary Archives of Kusawa Lake, Boundary Range Mountains, Yukon Territory, Canada

Abstract

Modern Kusawa Lake (60° 19' 55” N, 136° 4' 48” W, 142 km2) of southwestern Yukon Territory drains a 4290 km2 catchment, 4.7 % of which is glacier covered. Sediment cores show variability both down-lake and within specific sub-basins of the lake. In Regions II -V of Kusawa Lake, sediments are mainly clastic with massive to weakly laminated silts and clays interrupted by fine sand units, which reflect distinct runoff events into Region IV from glacier sources. In Region I, massive silts, silt-clay couplets are interrupted by thick sand deposits derived from the Primrose River delta. Further up-lake, the sediment record is further interrupted by modern sediment delivery from the Kusawa Campground alluvial fan. The relatively small accumulation of lake glacial and Holocene sediment input in Kusawa Lake is similar to other large lakes of the Canadian Cordillera. These patterns reflect a particular style of deglaciation and Holocene sediment inputs.