SEDIMENTOLOGICAL ANALYSIS OF SUBGLACIAL AND PROGLACIAL DEPOSITS AT SASKATCHEWAN GLACIER, BANFF NATIONAL PARK, ALBERTA

Recently deposited subglacial and proglacial sediments are well exposed in fluvially-eroded channels in front of Saskatchewan Glacier, a valley outlet glacier draining the Columbia Ice Field in Banff National Park, Alberta. Four main facies types can be identified within the exposures and record deposition under glaciofluvial, subglacial and supraglacial conditions. Two distinctive diamict facies (Facies 1 and Facies 4) are interpreted as subglacial tills. Facies 1 is exposed directly beneath the modern ice margin and overlies an irregular topography on poorly sorted gravels beneath. This diamict facies forms a relatively thin (less than 3 m), massive, clay-rich unit containing sparse, small clasts and is interpreted as a subglacial deformation till. Facies 2 consists of massive gravels that are relatively well sorted and record glaciofluvial outwash deposition in the ice marginal environment. Facies 3 forms a thin but extensive poorly sorted, gravel deposit, ranging in thickness from 15-25cm that covers large areas of the valley floor and is interpreted as supraglacial sediment derived from debris falls from the steep valley walls. Facies 4 is a poorly sorted, matrix supported silty-clay diamict that is exposed within a number of till terraces close to the modern ice margin along the northern valley wall. This diamict has similar characteristics to those of Facies 1 and is also interpreted as a subglacial deformation till. Individual till terraces in the valley probably record separate subglacial depositional episodes during the recent retreat of Saskatchewan Glacier. In several places on the valley floor, till has been streamlined into long, narrow flutes Erosion of previously deposited sediments by glaciofluvial activity is prevalent in the proglacial regions of Saskatchewan Glacier and the preservation potential for subglacial sediments within this glaciated valley is relatively low. Beyond the extent of the Little Ice Age maximum advance, gravels are the predominant surficial deposit and no subglacial landforms can be observed. Analysis of the characteristics and spatial distribution of sediments within the Saskatchewan Glacier Valley provides important information on which to base interpretation of ancient glaciated valley deposits.