Usage:
Thebes Sandstone (IL*,MO*)
Thebes Sandstone of Maquoketa Group (IL*,MO*)
Thebes Sandstone Member of Scales Formation (IL)
Geologic age:
Ordovician, Late*
Cincinnatian*
Type section, locality, area and/or origin of name:
Type section: outcrop below courthouse in town of Thebes, in SE/4 SW/4 SE/4 sec. 8, T. 15 S., R. 3 W., Thebes 7.5-min quadrangle, Alexander Co., southwestern IL (Thompson, 1991).
Reference sections in eastern MO: (1) exposure on east fork of Cape La Croix Creek, in N/2 SW/4 SW/4 SW/4 sec. 13., T. 31 N., R. 13 E., Cape Girardeau 7.5-min quadrangle, Cape Girardeau Co.; and (2) in upper part of type section for Cape Limestone, north of junction of Main St. and Broadway St. in city of Cape Girardeau, Cape Girardeau Co. (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 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 conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).