Basin-edge sediments of the Gasperian Stage (Upper Mississippian) in southwestern Indiana consist of four limestone formations that alternate rhythmically with three terrigenous formations. Each formation exhibits an aggregate of supratidal to subtidal lithofacies having characteristic fossil assemblages and diagnostic parameters of depositional turbulence. Areal distribution patterns of lithofacies for each widely correlative stratigraphic unit have analogs in known lithotope patterns of modern inner shelf sediments. Certain Gasperian patterns were influenced by antecedent topography. Lithofacies succeed one another in predictable sequences representing distinctive regressive and transgressive lithotopes of seven principal cyclothems. Two successive, homotaxial cyclothem are represented wholly by carbonate facies. Other cyclothems maintain greater individuality and are partly or entirely terrigenous. Lithofacies of all but one cyclothem are arranged asymmetrically with either prolonged transgressive or prolonged regressive phases. Sudden lithotope shifts are discernible. Local influxes of terrigenous sediments coupled with progressive changes in strike of the contemporaneous shoreline from N25° W to N5° W effected disappearance of three cyclothems toward the north.

Although Gasperian formations maintain essentially the same sequential order throughout the Illinois basin, those exposed in Indiana differ fundamentally from equivalent strata near the structural axis of the basin in thicknesses, proportion of carbonates, strike of sedimentary bodies with respect to paleoslope, and magnitude of shoreline migrations. Gasperian sediments in Indiana accumulated in a relatively stable coastal region influenced by shoreline processes. This area differs from the basin center which other authors have shown to be the locus of terrigenous deposition in an unstable deltaic regime.

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