This vegetation occupies rolling to hilly outwash, drumlins on till plain, or end moraine with more fire protection than the flat to rolling sites occupied by tallgrass prairie, but less fire protection than sites occupied by sugar maple-basswood forest. Cambrian sandstone, with some dolomite and shale, is along the western edge of the sub-subsection.
Ground moraine predominates, often containing extensive drumlin fields.
There are also numerous end moraines. Outwash features occur, often as narrow channels between drumlins. Large lakes and streams are not common in those parts of the subsection dominated by oak savanna or forest. The loess cap is typically about 2 feet thick. It also occurred on some steep end moraines, where soils were excessively drained and no major wetlands served as fire breaks.