Glaciohydraulic supercooling: a freeze-on mechanism to create stratified, debris-rich basal ice: I. Field evidence

Debris-laden ice accretes to the base of Matanuska Glacier, Alaska, U.S.A., from water that supercools while flowing in a distributed drainage system up the adverse slope of an overdeepening. Frazil ice grows in the water col umn and forms aggregates, while other ice grows on the glacier sole or on s ubstrate materials. Sediment is trapped by, this growing ice, forming strat ified debris-laden basal ice. Growth rates of >0.1 m a(-1) of debris-rich b asal ice are possible. The large sediment fluxes that this mechanism allows may have implications fair interpretation of the widespread deposits from ice that flowed through other overdeepenings, including Heinrich events and the till sheets south of the Laurentian Great Lakes.