The elongate, lenticular, multistory sandstone body of the West Baden Group (Mississippian) that crops out in Owen and Greene Counties, Indiana, is an abandoned distributary finger of the late Paleozoic Michigan River system, a large river system that carried mud and sand from northeastern United States and Canada southwestward across the Illinois basin toward the Ouachita trough.

The sandstone body has two major parts: a lower, thin body probably of tidal origin, and an upper, much thicker body. Cross-bedding and ripple-bedding are the two principal bedding facies and define the reservoir units. The cross-bedded facies is very permeable, whereas the ripple-bedded facies has low permeability and inhibits vertical flow. Groundwater, flowing downward into the underlying limestone, produced permeability values near the surface that greatly exceed those of the subsurface.

A hypothetical example illustrates how permeability in a sandstone body in the subsurface, buried below an unconformity, might develop.