Usage:
Tunnel City Group (IA,MN,WI)
Tunnel City Formation (WI-recognized locally in Sauk Co.)
Subunits:
GROUP STATUS (alphabetical): Lone Rock Formation (IA,MN,WI), Mazomanie Formation (MN,WI).
FORMATION STATUS (alphabetical) --recognized locally in Sauk Co., WI: Lone Rock Member, Mazomanie Member.
Geologic age:
Late Cambrian (Franconian)
Type section, locality, area and/or origin of name:
Named from village of Tunnel City, Monroe Co., west-central WI, in and near which the rocks are exposed in railroad cuts, roadcuts, quarries, and natural outcrops (Ostrom, 1966, 1967).
AAPG geologic province:
Sioux uplift
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 conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).