Lacustrine sedimentation in a proglacial environment, Caribou River Valley, Yukon, Canada

Abstract

Proglacial Quaternary lacustrine sediments deposited along the Caribou River Valley, Yukon, Canada, formed in a lake impounded by glacial ice that was retreating downslope. Sedimentation in the lake was dominated by turbid sediment underflows generated from the upslope, previously deglaciated region. The base of the sedimentary succession indicates a gradual transition from sporadic low‐density distal flows to higher density proximal flows. Continued sediment accumulation resulted in the construction of a subaqueous clay and silt bank. Sedimentation was dominated by deposition of suspension load clay carried by subseasonal bottom countercurrents induced by katabatic winds. This sedimentation pattern prevailed until the subaqueous bank was disturbed by mass movement. Removal of the sediment bank increased the depth of the nearshore area sufficiently to allow turbid underflows to dominate sedimentation once more. The changing sedimentation patterns reflect events in the areas away from the ice front, rather than changes in the activity of the impounding glacier. Similar successions could be developed in other glacial lakes impounded by glaciers which moved up topographical slopes, either pre‐existing or generated by glacioisostatic depression.