The Development of an Ice-Dammed Lake: The Contemporary and Older Sedimentary Record

An ice-dammed lake on the northern margin of the Kaskawulsh Glacier in the St. Elias Mountains has drained annually for at least 30 to 40 yr. Input to the lake is from three glacierized sub-basins and from the margin of the Kaskawulsh Glacier. The deltas of the streams from each of the sub-basins are constructed and destroyed in each filling and draining cycle. There is little sediment accumulation in the lake basin due to subglacial drainage of the high density underflow input through most of the filling sequence. Older lacustrine sediments and deltas demonstrate previous higher level lakes, which were semipermanent, during the early phases of deglaciation after the maximum of the Little Ice Age. One of the sub-basin glaciers is a surging glacier, and a sequence of old deltas indicate that the location of the discharge stream has changed during each surge. It is hypothesized that continuing downwasting of the Kaskawulsh Glacier will eventually remove the conditions for damming.