Morphology and Composition of Murtoos and Meltwater Corridors Associated with the Cordilleran Ice Sheet in South-Central British Columbia

Subglacial hydrology has been shown to significantly influence ice sheet dynamics in both Greenland and Antarctica.  Though direct observation and study of the subglacial hydrological network is limited by the presence of thick overlying ice, insights into subglacial hydraulics can be gained by studying landforms derived from meltwater in deglaciated landscapes.  Murtoos and meltwater corridors are examples of meltwater derived landforms, the former being triangular-shaped hills flanked by shallow troughs, and the latter being broad, shallow landforms with clear erosional boundaries and distinct internal morphologies.  While meltwater corridors have been previously identified in British Columbia, this study represents the first identification and study of murtoos associated with the Cordilleran Ice Sheet.  We identified a large network of murtoos and meltwater corridors in south-central British Columbia and studied both the morphology and internal composition of both landform groups using high resolution elevation data and near surface geophysical surveys. Electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) surveys on different murtoos reveal a homogeneous internal composition of sandy diamicton, while the troughs lateral to murtoos contain sorted sediment.  We interpret the murtoos as subglacial meltwater erosional remnants, their morphology determined by meltwater erosion of the lateral troughs.  The meltwater corridors studied contain two distinct morpho-stratigraphic relationships: channelized reaches exhibiting shallow intersecting and/or parallel troughs floored by sandy diamicton, the residuals resembling glacial curvilineations; and flat bed reaches with narrow eskers composed of fine sand and gravel.  We interpret the channelized and flat bed reaches as being formed by subglacial meltwater erosion and deposition, respectively, with the switch in process and form being determined by bed topography.  Together, these landforms suggest extremely wet-bed conditions during deglaciation of the Cordilleran Ice Sheet, with widespread subglacial meltwater erosion and deposition.  These observations provide insight into the likely conditions beneath portions of the Greenland and/or Antarctic ice sheets where widespread meltwater production has been reported, such as the western land terminating portion of the Greenland Ice Sheet.