Morphology and Sedimentology of Eskers in the Lac de Gras Area, Northwest Territories, Canada

An integrated dataset, including LiDAR, grain-size analysis, GPR, and augered boreholes, was used to perform a morphological and sedimentological analysis on 28 km of eskers in the Lac de Gras area, NWT. Esker segments were classified based on morphology and surficial grain size, and depositional environments were interpreted based on sedimentological data gathered from GPR and boreholes. Peaked ridges of cobbles and boulders (Type 1) were inferred to deposit subglacially, and flat topped ridges of finer sediment (Type 2, 3, 4) were inferred to deposited deltaically. Deltaic deposits are found overlying Type 1 subglacial deposits, and at the down esker extents of Type 1 ridges. Evidence points to a time transgressive depositional model, with maximum extent of subglacial feeding conduits not exceeding 3 km in the study area. These results have potential implications for mineral exploration. Transport distance within eskers may not substantially exceed that of the subglacial till.