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National Geologic Map Database

Geologic Unit: Orchard Creek

Usage:

Orchard Creek Shale (IL*,MO*)
Orchard Creek Shale of Maquoketa Group (IL*,MO*)
Orchard Creek Formation (MO)
Orchard Creek Shale Member of Scales Formation (IL)


Geologic age:

Ordovician, Late*
Cincinnatian*


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

Type section: along Orchard Creek (now covered), 2 mi south of Thebes, in sec. 21, T. 15 S., R. 3 W., Alexander Co., southern IL (Thompson, 1991).
Reference section: across Mississippi River from southern Cape Girardeau Co., on east bank of Mississippi River 1 mi north of Thebes, in SE/4 SE/4 sec. 5, T. 15 S., R. 3 W., Thebes 7.5-min quadrangle, Alexander Co., southern IL (Thompson, 1991).


AAPG geologic province:

Illinois basin*
Ozark uplift
Upper Mississippi embayment*


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

Asterisk (*) indicates usage by the U.S. Geological Survey. Other usages by state geological surveys.

"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 ([ ]).