National Geologic Map Database

Geologic Unit: Keokuk


Keokuk Limestone (IL*,IA*,KS*,KY*,MO*,NE,OK,TN, and CO*-subsurface)
Keokuk Formation of Augusta Group (IA)
Also called /Burlington-Keokuk Limestone of Mammoth Cave Group (IL-notably southwestern part)

[The use of a hyphen between undifferentiated formations is not considered proper notation (CSN, 1933).]


(alphabetical): Grand Falls Chert Member (OK), Montrose Chert Member (IL,IA, Peerless Park Member (IL,MO), Short Creek Oolite Member (MO).

Geologic age:

Middle Mississippian (Visean; Osagean)*

Type section, locality, area and/or origin of name:

Named from exposures along the western bluffs of the Mississippi River, in the vicinity of Keokuk, Lee Co., IA (Owen, 1852).
Williman and others (1975) state that type locality is along Soap Creek in quarry in Mississippi River bluff near mouth of creek, Lee Co., southeastern IA.
Reference sections: (1) in Brown quarry, on south bank of Wilson Creek, 0.5 mi northwest of intersection of Sunshine St and Scenic Dr, western Springfield, in E/2 NW/4 SE/4 sec. 28, T. 29 N., R. 22 W., Springfield 7.5-min quadrangle, Greene Co., southwestern MO (Thompson and Fellows, 1970, section Z, p. 213; Thompson, 1986); (2) in Kirshmann-Jeffreis quarry, in southwestern edge of Joplin, Newton Co., MO, in S/2 SE/4 SE/4 sec. 29, T. 27 N., R. 33 W., Joplin West 7.5-min quadrangle (Thompson and Fellows, 1970, section G, p. 166; Thompson, 1986).

AAPG geologic province:

Anadarko basin*
Illinois basin*
Iowa shelf*
Ozark uplift*

For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).