Abstract
In North America Pleistocene ice sheets entered the lowland now occupied in part by Lake Erie and expanded far southward in several lobes in the Interior Plains, but less far in two lobes in the Allegheny Plateau to the east in north-eastern Ohio, north-western Pennsylvania and western New York. This maturely dissected plateau, composed of essentially horizontal Carboniferous strata, has a summit level ranging from about 1200 ft in the west to about 1800 ft in the east.