Usage:
Defiance Member of Joachim Dolomite (IL*,MO*)
Defiance Member of Joachim Dolomite of Ancell Group (IL)
Geologic age:
Late Ordovician (Mohawkian; Turinian)*
Type section, locality, area and/or origin of name:
Type section (= type section of Boles Member): quarry in bluffs on north side of Missouri River, 1 mi southwest of village of Matson, in northeast corner SE/4 NE/4 SW/4 sec. 4, T. 44 N., R. 2 E., [Labadie 7.5-min quadrangle], St. Charles Co., eastern MO. Named from village of Defiance, St. Charles Co., 3 mi northeast of type section (Templeton and Willman, 1963).
Reference sections in MO: (1) roadcut on north side of U.S. Interstate Highway I-44, immediately east of interchange at Pacific, in NE/4 NW/4 sec. 12 and SE/4 SE/4 sec. 1, T. 43 N., R. 2 E., Pacific 7.5-min quadrangle, St. Louis Co.; and (2) roadcut on St. Louis County Road W., 1 mi south of Eureka, in SW/4 SE/4 sec. 1, T. 43 N., R. 3 E., Pacific 7.5-min quadrangle, St. Louis Co. (Thompson, 1991).
AAPG geologic province:
Illinois basin*
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 conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).