Surficial geology, Kwokullie Lake, British Columbia

Kwokullie Lake map area (NTS 94P/07) covers the northeast part of the Etsho Plateau whose northern boundary is defined by a large meltwater channel that is now occupied by Kimea lake and creek at about 460 m above sea level (asl). The Kimea meltwater channel was cut by an ancestral Petitot River that flowed westward during deglaciation when the retreating Laurentide Ice Sheet still covered the land to the north. Prior to this time (ca. 25 000-11 000 years ago), the Laurentide Ice Sheet covered the entire map area with a dominant ice flow from the northeast. Etsho Plateau gradually rises to 720 m asl in the southeast quadrant of the map area and, although it offers some relief, most of the area is underlain by poorly-drained clayey till that is mantled by extensive organic deposits. Hummocky organic deposits containing ground various amounts of ground ice are common on the upper plateau, especially around Kwokullie and Desan lakes, where recent disturbances have led to thermokarst terrain. Glacial flutings and drumlins concentrated on the upstream flank of the Etsho Plateau indicate that at least two distinct ice lobes emanated from the ice sheet at some time after the glacial maximum. A persistent northern lobe was responsible for the widespread northeast ice flow however, in the southeast quadrant of the map area, it was deflected by a second lobe flowing westward up the plateau. A southwest-trending moraine system appears to mark the interlobate boundary. Subsequent episodic retreat of the two lobes is marked by groups of recessional moraines to the north and east. There are at least two main concentrations of recessional moraines on the northern flank of the plateau. Within these moraine concentrations, cross-cutting relationships are common, indicating that many stillstands and minor readvances of the northern lobe occurred as it thinned and retreated to the north. In general the end moraines are thin and rise above the boggy terrain with only a few metres of relief. They are composed mainly of till but, in places, they also contain discontinuous deposits of stratified material, with minor amounts of ice-thrust glaciofluvial and glaciolacustrine sediment.

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