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National Geologic Map Database

Geologic Unit: St. Peter

Usage:

St. Peter Sandstone (AR*,IL*,IN*,IA*,KY*,MI*,MN*,MO*,NE*,OH*,OK*,SD,WV,WI*)
St. Peter Sandstone of Ancell Group (IL,IN,IA,WI)
St. Peter Sandstone of Simpson Group (KS*-subsurface)


Subunits:

(alphabetical): Glenwood Member (MI,WI), Kingdom Member (MO), Kress Member (IL*,MO*,WI), Readstown Member (IA,WI), Starved Rock Member (IA,IL,MO), Tonti Member (IA,IL,MO,WI).


Geologic age:

Middle to Late Ordovician (Whiterockian to Mohawkian)*


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

Type section: bluff where Minnesota River (formerly called St. Peter's River) joins Mississippi River, Hennepin Co., southern MN (Stauffer, 1934).
Reference sections in MO: (1) roadcut on U.S. Interstate Highway I-55, beginning in NW/4 NW/4 SW/4 sec. 34, and continuing into SE/4 NE/4 sec. 33, T. 40 N., R. 6 E., Selma 7.5-min quadrangle, Jefferson Co.; and (2) roadcut on east side of I-55, in center of west line of NW/4 sec. 11, T. 38 N., R. 7 E., Bloomsdale 7.5-min quadrangle, Ste. Genevieve Co. (Thompson, 1991).


AAPG geologic province:

Appalachian basin*
Arkoma basin*
Cincinnati arch*
Forest City basin*
Illinois basin*
Iowa shelf*
Nemaha anticline*
Ozark uplift*
Salina basin*
Sioux uplift*
Upper Mississippi embayment*
Williston basin*
Wisconsin arch*


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 ([ ]).