Drumlins : are they stratified glacial features by size and lithology?
Moon Island, one of 180 drumlins in the Boston, Massachusetts area, is composed of a compact, clayey till with the southeastern slope of the drumlin forming a cliff caused by marine erosion. Samples of pebbles from the cliff-face and drumlin surface show horizontal stratification of till units that are differentiated by pebble size. The stratification is interpreted as evidence that the drumlin was formed in two stages: (1) one or more ice advances or surges which deposited the size-distinctive till layers. Stratigraphic variation of pebble lithologies in the till indicates that the till layers were probably deposited by at least two different ice lobes, and (2) an ice advance which carved the drumlin form without distorting or reshaping the horizontal till layers.Ball State UniversityMuncie, IN 47306