| Recent research in glaciology and glacial geology has focused on the debris entrainment and transport mechanisms of glaciers and ice sheets. A debris-rich basal ice zone characterizes Matanuska Glacier in Alaska, making it an appropriate subject for studies of debris entrainment and transport. The origin of the debris-rich ice has been hypothesized by Strasser et al., (1996), Lawson et al., (1998), and Alley et al., (1998) to be related to the process by which the water supercools while passing through portions of the glacier's drainage system. Research for this study extends the earlier entrainment and transport work in three ways. First, silt-rich laminated debris bands that contact the young, debris-rich basal ice and crosscut the older, englacial ice have been found to originate by a basal crevasse-fill mechanism. The crevasse-fill mechanism is also related to the glaciohydraulic conditions of the glacier and is not an effective sediment-transport mechanism. Second, the high debris content of the basal ice generates a thermodynamic condition that is responsible for the formation of a concentration of the coarse sediment fraction at the top of the basal ice zone. Third, because glaciohydraulic supercooling and its associated basal freeze-on process is potentially so important to our linkage of modern glaciers to ancient landforms, the geometry required for its occurrence has been modeled on the Superior, Rainy, Wadena, and Lobe of the Laurentide Ice Sheet. Conditions were found to be appropriate for glaciohydraulic supercooling and the associated basal freeze-on of debris-rich ice where the ice flowed out of Lake Superior. |
