Abstract

Stratigraphic and sedimentological analyses of exposures through a glacilacustrine sedimentary sequence along the south shore of Barrier Lake, Kananaskis Country, reveal evidence of glacitectonic disturbance, relating to a readvance of the Bow Valley glacier at the end of the last glaciation. Prior to disturbance, palaeocurrent measurements in gravel and sand foreset beds record the deposition of subaqueous fans-deltas from a glacier lobe retreating eastwards along the Barrier Lake depression. The fan-delta sediments fine upwards into ripple- and cross-bedded sands and laminated muds with dropstones, documenting progressively distal sedimentation. Palaeostress directions measured from large-scale folds, shear zones and glacitectonites, and deformation tills indicate that glacier ice readvanced southwards from a glacier lobe located over the Barrier Lake depression. These stress directions are used to reconstruct the flow lines within the southern margin of a low-profile glacier lobe that terminated halfway up lower Barrier Lake, a more extensive readvance than previously envisaged in the area for this period. Comparisons of diamicton and glacitectonite fabric shapes with similar sediments elsewhere indicate that the subglacially deformed material that caps some of the sections is immature and has undergone short travel distances. Although the exact age of the readvance is unknown, it probably represents the Canmore Readvance of the Late Wisconsinan glaciation.

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