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Compendium
  
Downeys Bluff Member

(DDC & HHG)

Paoli Limestone,

Mississippian System


Type section and use of name in Indiana: According to Atherton (1948, p. 129), the name Downeys Bluff was proposed in an unpublished manuscript by F. E. Tipple for a member of the Paint Creek Formation. The unit was later given formational status (Willman and others, 1975, p. 153). At its type section in the NW¼SE¼ sec. 5, T. 13 S., R. S E., Hardin County, Ill. (Atherton, 1948, fig. 8), the Downeys Bluff Limestone consists of limestone with minor amounts of shale and is 41 feet (12.5 m) thick.

Pinsak (1957, p. 17) and Swann (1963, p. 65), among others, recognized that the Downeys Bluff Limestone is represented by the upper part of the Renault Formation of subsurface usage and by the upper non-shaly part of the Paoli Limestone of Indiana. There is general agreement on this correlation, and the name Downeys Bluff is here adopted for use in Indiana for the uppermost member of the Paoli Limestone. The principal reference section for the Paoli Limestone, an abandoned quarry just north of the railroad tracks on the west side of Paoli, Ind. (SW¼SE¼SE¼ sec. 35, T. 2 N., R. 1 W.), is here designated as a reference section for the member, which at this locality consists of about 13 feet (4 m) of oolitic, skeletal, and micritic limestone. The Downeys Bluff overlies the Yankeetown Member of the Paoli Limestone and underlies the Bethel Formation.

Description: Along the outcrop in Indiana the Downeys Bluff Member is a few feet thick to absent, probably depositionally, north of Monroe County, but it thickens irregularly southward, generally ranging from 6 to 12 feet (1.8 to 3.7 m) and to as much as 19 feet (6 m) in southern Crawford County near the Ohio River. The Downeys Bluff is light-gray medium- to thick-bedded, relatively pure limestone composed of variable textural types, mainly skeletal, micritic, and oolitic. Echinoids are the dominant skeletal type, followed in decreasing abundance by bryozoans and brachiopods (Kissing, 1967, p. 83, 86). The Downeys Bluff is similar in composition and texture to other limestones in the Paoli and the Ste. Genevieve, but it can be distinguished easily where the overlying Bethel Formation is also exposed because shale and sandstone of the Bethel are not calcareous, whereas those of the Paoli and the Ste. Genevieve are.






 
 
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