Channel and sheet sandstones are common in the uppermost Pennsylvanian and lowermost Permian shales of eastern Kansas. These sandstone bodies characterize the nonmarine phase of a typical Wabaunsee cyclothem and locally are presumed to be related either directly or indirectly to each other because of their textural, mineralogic, and other diagnostic features. Near Wamego, Kansas, a channel sandstone cuts sheet sandstone of the Willard Shale (Upper Pennsylvanian). K-Ar dates on muscovite separated from both sandstones are 377 ± 11 m.y. for the channel sandstone and 389 ± 8 m.y. for the sheet sandstone. Rb-Sr dates on muscovite are 368 ± 20 m.y. for the channel sandstone and 401 ± 20 m.y. for the sheet sandstone. These ages agree within the limits of err r and indicate a common provenance area for the two sandstones, which is consistent with their similarities in particle sizes, clay mineralogy, and heavy-mineral suites. However, the ages indicate either direct or indirect derivation from a Middle to Lower Devonian source, none of which is known to have supplied clastic material to eastern Kansas.