A core of hard, sandy till is present beneath the clayey till of the Wabash and Fort Wayne Moraines in Allen County, Indiana. The buried surface of this till is relatively easy to determine through the use of surface exposures, engineering boring logs, and water well records. Knowledge of the configuration of this surface is significant to ground-water and engineering studies.
The last ice to invade the area, that of the Erie Lobe, overrode this surface, which is a subdued image of the present surface. The present-day Wabash and Fort Wayne Moraines may be more probably inherited moraines than classical recessional moraines. These ridges and similar ridges in surrounding states and Canada may have formed the margins of an ancestral glacial Lake Maumee, through which the last ice advanced and from which the ice derived its high content of clay.