Stephensport Group
  

(HHG)

Chesterian Series,

Mississippian System


Type locality and description: The name Stephensport, though having some earlier mention (see Swann, 1963, p. 83), was formally proposed in a group sense by Gray, Jenkins, and Weidman (1960, p. 37), who redefined it to consist in descending order of the Glen Dean Limestone, the Hardinsburg Formation, the Golconda (now Haney) Limestone, the Big Clifty Formation, and the Beech Creek Limestone. The group, named for Stephensport, Breckinridge County, Ky., consists of about equal parts of limestone, shale, and cliff-forming sandstone (Gray, 1962, table 2 and fig. 4).

The total thickness of the Stephensport Group is 130 to 230 feet (40 to 70 m). The Stephensport conformably overlies the West Baden Group (Chesterian) and is overlain conformably by the Buffalo Wallow Group (Chesterian) or disconformably by the Mansfield Formation (Morrowan). It is recognized on the outcrop from central Owen County southward to the Ohio River. In the subsurface it extends from Clay County southwestward .

Correlation: The Stephensport Group is exactly correlative with the Okaw Group of southwestern Illinois (Swann, 1963, p. 53) but is distinct in usage by including prominent clastic formations the Okaw is dominantly limestone (Swann, 1963, p. 45-46). On the basis of their conodont faunas, formations of the group represent the Gnathodus bilineatus-Cavusgnathus altus and Gnathodus bilineatus-Kladognathus mehli Assemblage Zones of the North American standard (Collinson, Rexroad, and Thompson, 1971). The group spans the Visean-Namurian boundary of European usage and correlates with rocks within North American foraminiferal Zones 16s and 17 of Mamet and Skipp (1971).

(See also the discussion "Naming of groups in upper part of Mississippian System in Indiana" under "West Baden Group.")






 
 
 
Your session for the Indiana Geological Survey is about to expire in 30 minutes. Please refresh your broswer or click here to restart your session timer.