ABSTRACT: High-energy sedimentary processes in Kluane Lake, Yukon Territory.

CGRG Bibliography of Canadian Geomorphology
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Abstract

The Little Ice Age advance of the Kaskawulsh Glacier in the St. Elias Mountains raised the level of Kluane Lake, the largest lake in the Yukon, by as much as 30 m and reversed the outflow direction, creating the 18 km long Slims River sandur. In the twentieth century the delta has advanced 3.6 km, which is the highest rate of any glaciolacustrine delta in the Cordillera, decreasing from 74 m/a (1899-1914) to 18 m/a (1970-2006). Data from moored instruments, sediment traps, water column profiling, and high-resolution sub-bottom acoustic surveys document lacustrine sedimentary processes in this very dynamic environment. Suspended sediment concentrations in the river of up to 7 g/L generate continuous, diurnally fluctuating turbidity currents in Kluane Lake with peak velocities in excess of 0.5 m/s. The turbidity of the underflows also varies diurnally by up to 600 NTU. Seasonal and short-term water level fluctuations in Kluane Lake influence the sediment delivery to the lake basin. The turbidity currents have created a field of large sediment waves in fine-grained sediment on the prodelta slope that are analogous to those of marine systems, but previously not reported from lakes. These bedforms have mean wavelength of 130 m (range 16 – 440 m) and mean amplitude of 2.3 m (range 0.1 – 9.0 m). They are migrating up-slope and their internal architecture is consistent with a sedimentary record formed by turbidity currents having alternating supercritical and subcritical flow. Accumulation in the prodelta area of Kluane Lake has averaged 0.4 m/a between 1970 and 2006 based on acoustic surveys, and was 0.3 m in 2006 based on sediment trap results.

Bibliography of Canadian Geomorphology