SEDIMENT CHARACTERISTICS OF DIFFERENT TYPES OF ICE-CORED MORAINES, MATANUSKA GLACIER, ALASKA

A large area along the northern margin of the Matanuska Glacier is composed of debris-covered and forested ice that has been cut off from active glacier flow. The ice-cored moraines that exist in this area are morphologically similar to ice-cored moraines elsewhere near the margin, although they apparently result from different genetic processes. I propose that a continuum of ice-cored moraines exists, with true end moraines as one end-member type, and cut-off stagnating ice as the other. Although these different types of ice-cored moraines have similar morphologies, the sediment on top of each must reflect different sources within the glacial system and thus different processes of deposition and reworking. Ice-cored end moraines should reflect significant contribution from the basal ice, with rounded, striated clasts and a high percentage of silt. In the area of cut-off ice, the moraines presumably received their debris primarily from supraglacial sources and should thus contain courser and more angular sediment. This project compares the characteristics of sediment from ice-cored moraines at several different sites in the terminus region. Each site has been analyzed for sediment thickness, grain size distribution, particle roundness, and debris flow characteristics. In addition, trees were cored in order to estimate how long ago a section of ice was cut off from the active glacier. The goal is to establish a model of sediment deposition at each site studied.