Stratigraphy and Paleoecology of the Saluda Formation (Cincinnatian) in Indiana, Ohio, and Kentucky

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Abstract
The Saluda Formation (Cincinnatian) was studied at 27 localities in southeastern Indiana, southwestern Ohio, and north-central Kentucky. The formation is a lens-shaped lithostratigraphic unit consisting essentially of calcitic dolomite interbedded with a small proportion of fossiliferous limestone and shale. A thin, laterally persistent, isochronous unit of clay shale in the lower half of the Saluda is used to demonstrate the diachronous nature of the upper and lower formational contacts. At most localities examined, a zone of large colonial corals lies near the base of the Saluda, and a coral-stromatoporoid zone lies near the top of the formation. Virtual circumscription of the Saluda Formation by these coralline zones, and the thinly laminated, micritic character of Saluda rocks suggest that the formation was deposited in a quiet-water lagoon that was isolated from the surrounding open sea by encompassing banks of corals and stromatoporoids. Random orientation of coral colonies within the coralline zone denotes turbulence in the sea that encircled the lagoon. Centripetal decrease in calcite/dolomite ratio and in number of fossil individuals and species reflects conditions of greater salinity in the center of the ancient lagoon and greater salinity during the middle period of Saluda deposition than earlier or later. Association of Saluda dolomite with original features such as laminae and rock layers which lack fossils indicates that the dolomite was deposited from lagoon waters as a primary precipitate or was formed during early diagenesis by recrystallization of magnesian calcite or by reaction of unconsolidated calcite mud with penesaline water. Desiccation cracks and very small, trochoidal, long-crested ripple marks scattered throughout the Saluda Formation suggest that the lagoonal sediments were deposited in water of only a few inches to a few feet in depth and were intermittently exposed subaerially owing to evaporation of lagoon waters or to filling of the lagoon to sea level. Gradual waning of restricted conditions and return of normal marine waters to the lagoon area may have resulted from subsidence greater than that with which growth of corals could keep pace or from destruction of part of the coralline bank.

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