Lacustrine record of high energy geomorphic events in the Sawtooth Range, Ellesmere Island, Canadian High Arctic

Six sediment cores were retrieved from a 2.9 km(2), 140 m deep lake in west -central, Ellesmere Island. Non-laminated, low-organic clayey silts constit uted 63-99% of the sequences obtained. Stratigraphic correlation among five of the cores was made possible by the presence of a horizon with an elevat ed clay content. Based on this correlation and a single AMS C-14 date, the clayey silts accumulated at average rates of 0.13 mm yr(-1) to 0.22 mm yr(- 1) during the Holocene. Coarse facies present in the cores were (1) randoml y positioned angular drop stones, attributed to dirty snow avalanche and sl ushflow deposition onto lake ice, as well as incorporation during shoreline freezing; (2) thick clast rich diamict sequences, thought to have originat ed as sub-aqueous debris flows; and (3) thin distinct sandy layers, regarde d as indicators of debris flow on the slopes surrounding the lake. The freq uency of sandy horizons, and hence mass movement activity, is greater at co re sites which are shore proximal, have steep bottom-slopes, and are adjace nt to ACVTIVE sub-aerial slopes. The temporal distribution of these sandy l ayers does not support a model of simultaneous response of the geomorphic s ystem to climatic change. Instead, sedimentation is governed by processes a cting at the local slope scale, and intrinsic geomorphic thresholds.