Contemporary frontal moraine formation in the Yoho Valley, British Columbia

The northern terminus of Emerald Glacier (51ﾟ31'N, 116ﾟ32'W) in the Yoho Valley, British Columbia was bordered by a small, actively forming frontal moraine during summer 1979. Stratigraphic and morphological contrasts existed round the ice front, which primarily resulted from a contrast in the distribution of supraglacial debris. -- Sedimentological and geotechnical techniques were utilised to determine the origin of stratigraphic units within the moraine ridge. -- Moraine A, at the margin of heavily debris covered ice, exhibited a complex stratigraphy. At most sites a lens of subglacially derived till was evident, between units of supraglacially derived material. It is proposed that the moraine forming process involved the initial development of an ice-front talus apron, which was subsequently pushed and over-ridden. A plastic subglacial till was squeezed from beneath the supra-morainal ice margin, and overlain by a sorted supraglacial unit during glacier retreat. The moraine was actively advancing during the field season due to the maintenance of glacier-moraine contact resulting from the retardation of ice-melt afforded by the supraglacial debris cover. -- Moraine B is located at the margin of debris-free ice. The stratigraphy is less complex, although an upper unit representing a younger depositional phase was observed. The process of formation involved the melt-out of subglacial deposits during the summer months (July to August), which were bull-dozed into a ridge during winter advance. Successive accretions of till onto the proximal moraine side, perhaps on a annual basis, are suggested. -- Deterioration of climate, resulting in positive mass balances is the main cause of glacier advance. Positive balances have been recorded from nearby glaciers between 1973 and 1976. This suggests that small glaciers are sensitive indicators of periods of climatic deterioration. -- The thesis concludes that more than one moraine forming process may be observed around a single ice margin, one of which may be 'annual' in nature; and that complex moraines may be formed by depositional processes operating at the margin of a temperate glacier. If complexities exist in presently forming moraines, then such a possibility must be considered when examining deposits of past glaciations