Only formal morphostratigraphic units recognized in IL are units related to moraines that are called "drifts." Is named for St. Charles, Kane Co, IL; is based on the St. Charles Moraine (mapped on pl. 1). St. Charles Moraine is a weak and poorly defined morainic area that extends northeastward about 25 mi from front of Marseilles Moraine (west of Yorkville, Kendall Co, IL) almost to St. Charles, where it is overridden by Minooka Moraine. Its front is contact of medium- to dark-gray clayey till of the Yorkville Till Member (new) with the yellow-gray silty till of Malden Till Member (new), both of Wedron Formation. Moraine is broken into disconnected areas by channels filled with younger outwash, and it is traced largely on basis of character of the till. Is included in the Princeton Sublobe of Lake Michigan Lobe because of its position east of Elburn Complex, but it does not extend far enough southward to demonstrate that it had a lobate form like other moraines of Princeton Sublobe, and it perhaps could be as easily assigned to Peoria Sublobe. Assigned to Woodfordian Substage of Wisconsinan Stage in Pleistocene Series.

Source: GNU records (USGS DDS-6; Denver GNULEX).