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National Geologic Map Database

Geologic Unit: Ion

Usage:

Ion Dolomite Member of Decorah Formation of Galena Group (IL*,IA*,MN*,WI*)
Ion submember (informal) of Dunleith Member of Galena Dolomite of Sinnipee Group (WI)


Geologic age:

Late Ordovician (Mohawkian; Chatfieldian)*


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

Type locality: in ravine along road, in NW/4 sec. 35, T. 96 N., R. 4 W., [approx. Lat. 43 deg. 05 min. 36 sec. N., Long. 91 deg. 16 min. 42 sec. W., Giard 7.5-min quadrangle], Allamakee Co., northeastern IA (Kay, 1928; see Agnew and others, 1956).
Named from hamlet of Ion, along Yellow River, [Giard 7.5-min quadrangle], Allamakee Co., northeastern IA, about 1 mi northeast of type locality (Kay, 1928; see Agnew and others, 1956).
Notable exposures in Dixon-Oregon area, northern IL (Templeton and Willman, 1952).


AAPG geologic province:

Iowa shelf*
Wisconsin arch*


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 ([ ]).