Evidence provided by surface morphology, exposures, cores, and the stratigraphic positions of Mazama (6600 years BP) and Bridge River (2500 years BP) ashes was used to interpret the origin and late Quaternary history of lacustrine and deltaic sediments in the Bow River valley near Banff, Alberta.There were three distinct stages of Lake Vermilion occupying the study area from Late Pleistocene to mid-Holocene times. The earliest stage was ice dammed, deposited beach gravel and nearshore sand, and drained along the present course of the Cascade River to the east. The second, proglacial stage is associated with thick subsurface deposits of non-organic clay and drained to the east along the course of the modern Bow River. The final stage is suggested by point bar and aeolian beach dune sediments.With the stabilization of the final stage of Lake Vermilion the low-energy, river-dominated Bow Delta prograded into the lake from the west. Progradation of the delta through three depositional zones produced the present Vermilion Lakes.