Named for Clays Ferry, a village on the north bank of the Kentucky River, Fayette Co., KY. Gray, thinly bedded limestone, shale, and lesser siltstone; limestone commonly very fossiliferous. 190 ft thick at type section; ranges from 120 to 220 ft thick in nearby region. Basal contact with Lexington Limestone sharp to gradational through tens of ft; upper contact with Garrard Siltstone gradational and placed at top of highest persistent limestone bed. Northward, lower part becomes Point Pleasant Formation or Point Pleasant Tongue of Clays Ferry Formation. Replaces Cynthiana Formation and Million Shale.

Source: GNU records (USGS DDS-6; Reston GNULEX).

The Geological Survey of Ohio recognizes the Cincinnati Group proposed by Meek and Worthen (1865), but at this time retains it as an informal term. The unit will be formally reinstated as a lithostratigraphic term after revision of its lower boundary and minor lithologic redescription of its units are completed. The ten formations included in the group are the (ascending) Clays Ferry Formation, the Kope Formation, the Fairview Formation, the Miamitown Shale, the Grant Lake Limestone, the Arnheim Formation, the Waynesville Formation, the Liberty Formation, the Whitewater Formation, and the Drakes Formation. Six members have been identified in the course of field mapping: the Point Pleasant Tongue of the Clays Ferry, the informal Bellevue, Corryville, Mount Auburn, and Straight Creek members of the Grant Lake Limestone, and the Preachersville Member of the Drakes Formation. The Backbone Creek and Elk Creek beds are recognized as excellent stratigraphic marker beds.

Source: GNU records (USGS DDS-6; Reston GNULEX).

The Clays Ferry Formation in south-central KY consists of medium- to dark-gray, argillaceous, brachiopodal limestone, medium-gray crinoidal calcarenite, and greenish to olive gray shale. Thickness is 120 to 220 feet. Overlies the Lexington Limestone and underlies the Garrard Siltstone. In southwest OH, the Clays Ferry Formation is represented by it Point Pleasant Tongue which overlies the Lexington Limestone and underlies the Kope Formation. The Clays Ferry is of Middle and Late Ordovician (Shermanian and Edenian) age.

Source: GNU records (USGS DDS-6; Reston GNULEX).

The Cincinnatian Series is divided into five depositional sequences in this report, which correspond to lithostratigraphic units. The following stratigraphic names in KY should be abandoned as they have been applied to bodies of rock already named in downramp areas of OH and IN: Bardstown (=Lower Whitewater), Reba (=Oregonia), Stingy Creek (=Mount Auburn), Calloway Creek (=Bellevue), and Clays Ferry (=Fairview). The following units in KY, OH, and IN lump dissimilar facies and straddle sequence boundaries and therefore should be abandoned: Drakes, Ashlock, Dillsboro, Tanners Creek, and Bull Fork. Grant Lake has been defined in several different ways and consequently should be abandoned. Several units will be redefined at a later date, including the Upper Whitewater and the "Sunset" of OH and IN. Formal naming of new lithostratigraphic units will follow further study.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Nautiloid fauna of Clays Ferry Formation in KY and Kope Formation in OH and IN are most similar to fauna of coeval Utica Shale of NY and Whitby Formation in southern Ontario.

Source: GNU records (USGS DDS-6; Reston GNULEX).