Samples of sediments from just above the bedrock of the valley bottom of the ancient Teays and Mahomet rivers were taken in unglaciated regions of West Virginia and Ohio, and from beneath glacial drift in Ohio and Illinois and analyzed for heavy mineral content. Analysis of the West Virginia samples showed a mature suite of minerals characterized by rounded grains of tourmaline and zircon, some epidote, a high muscovite content, and the absence of pyroxenes. The Ohio samples contained abundant angular grains of hornblende, a few pyroxene grains, as well as much angular zircon and tourmaline. Analysis of the Illinois samples showed an abundant garnet content with much hornblende, epidote, a small amount of pyroxene, and in general displayed mineralogy typical of the Pleistocene tills. The mature mineralogy of the sediments in the unglaciated area of West Virginia indicates derivation of these sediments from the Paleozoics of the folded Appalachians rather than from the Piedmont. Mineralogy of the sediments in the valley bottom beneath the glacial drift suggests that the Teays-Mahomet alluvium has been scoured from these locations and has been replaced by glacial drift.